Academic literature on the topic 'MECHANISM AND FRAGMENT'
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Journal articles on the topic "MECHANISM AND FRAGMENT"
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NAKAOKA, YASUO, TOHRU KUROTANI, and HIROKAZU ITOH. "Ionic Mechanism of Thermoreception in Paramecium." Journal of Experimental Biology 127, no. 1 (January 1, 1987): 95–103. http://dx.doi.org/10.1242/jeb.127.1.95.
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The localization of thermoreceptors in Paramecium, and the ionic basis of thermoreception, was investigated in posterior and anterior fragments of cells. Transverse section of the animals was used to obtain these fragments, which sealed up and swam actively. In the anterior fragment, an increase in the frequency of directional changes in swimming and depolarization of the membrane was produced by cooling below the temperature of the culture. In the posterior fragment, these effects were produced by wanning above culture temperature. Reversal potentials of these effects were found by injection of constant current to change membrane potential. In the anterior fragment, the reversal potential of the response to cooling was more negative than the resting potential and was potassium-dependent (52 mV/log[K+]o). In the posterior fragment, the reversal potential of the warming response was above resting potential and was primarily calcium-dependent (28 mV/log[Ca2+]o). It is concluded that cooling results in changes in the frequency of directional changes in swimming of Paramecium by causing a transient change in the membrane conductance for potassium, whereas warming produces its effects by a transient change in calcium conductance.
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Zhang, Xiaoqian, and Hanshan Li. "A Target Damage Assessment Mathematical Model and Calculation Method Based on the Intersection of Warhead Fragment and Target Mechanism." Mathematics 10, no. 17 (August 29, 2022): 3101. http://dx.doi.org/10.3390/math10173101.
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This paper proposes a target damage calculation method based on the profit-loss value of a warhead fragment group. The group is discretized into a fan-shaped column warhead fragment dispersion arrangement model, and the angle of its intersection with the target is combined to establish the dynamic dispersion density model of the warhead fragment group. In addition, the function to calculate the number of warhead fragments hitting the target’s surface is devised. The capability matrix of the warhead fragment group is constructed according to the quality, quantity, and storage velocity of the warhead fragments, and then, the profit-loss value of the warhead fragment group is established. Combining the intersection probability of the target and the warhead fragment of the dispersion area, the model to calculate the probability of damage caused to the target by the warhead fragment group formation is deduced. The calculation and experimental analysis verifies that the dispersion angle of warhead fragments, the intersection angle of projectile and target, and the intersection distance of projectile and target significantly influence the impact of target damage.
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Khobragade, Shrutika, Rohini Bhosale, and Rahul Jiwahe. "High Security Mechanism: Fragmentation and Replication in the Cloud with Auto Update in the System." APTIKOM Journal on Computer Science and Information Technologies 5, no. 2 (April 22, 2020): 54–59. http://dx.doi.org/10.34306/csit.v5i2.138.
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Cloud Computing makes immense use of internet to store a huge amount of data. Cloud computing provides high quality service with low cost and scalability with less requirement of hardware and software management. Security plays a vital role in cloud as data is handled by third party hence security is the biggest concern to matter. This proposed mechanism focuses on the security issues on the cloud. As the file is stored at a particular location which might get affected due to attack and will lost the data. So, in this proposed work instead of storing a complete file at a particular location, the file is divided into fragments and each fragment is stored at various locations. Fragments are more secured by providing the hash key to each fragment. This mechanism will not reveal all the information regarding a particular file even after successful attack. Here, the replication of fragments is also generated with strong authentication process using key generation. The auto update of a fragment or any file is also done here. The concept of auto update of filles is done where a file or a fragment can be updated online. Instead of downloading the whole file, a fragment can be downloaded to update. More time is saved using this methodology.
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Khobragade, Shrutika, Rohini Bhosale, and Rahul Jiwane. "High security mechanism: fragmentation and replication in the cloud with auto update in the system." Computer Science and Information Technologies 1, no. 2 (July 1, 2020): 78–83. http://dx.doi.org/10.11591/csit.v1i2.p78-83.
Full textAbstract:
Cloud Computing makes immense use of internet to store a huge amount of data. Cloud computing provides high quality service with low cost and scalability with less requirement of hardware and software management. Security plays a vital role in cloud as data is handled by third party hence security is the biggest concern to matter. This proposed mechanism focuses on the security issues on the cloud. As the file is stored at a particular location which might get affected due to attack and will lost the data. So, in this proposed work instead of storing a complete file at a particular location, the file is divided into fragments and each fragment is stored at various locations. Fragments are more secured by providing the hash key to each fragment. This mechanism will not reveal all the information regarding a particular file even after successful attack. Here, the replication of fragments is also generated with strong authentication process using key generation. The auto update of a fragment or any file is also done here. The concept of auto update of filles is done where a file or a fragment can be updated online. Instead of downloading the whole file, a fragment can be downloaded to update. More time is saved using this methodology.
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Spiering, Michelle M., Philip Hanoian, Swathi Gannavaram, and Stephen J. Benkovic. "RNA primer–primase complexes serve as the signal for polymerase recycling and Okazaki fragment initiation in T4 phage DNA replication." Proceedings of the National Academy of Sciences 114, no. 22 (May 15, 2017): 5635–40. http://dx.doi.org/10.1073/pnas.1620459114.
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The opposite strand polarity of duplex DNA necessitates that the leading strand is replicated continuously whereas the lagging strand is replicated in discrete segments known as Okazaki fragments. The lagging-strand polymerase sometimes recycles to begin the synthesis of a new Okazaki fragment before finishing the previous fragment, creating a gap between the Okazaki fragments. The mechanism and signal that initiate this behavior—that is, the signaling mechanism—have not been definitively identified. We examined the role of RNA primer–primase complexes left on the lagging ssDNA from primer synthesis in initiating early lagging-strand polymerase recycling. We show for the T4 bacteriophage DNA replication system that primer–primase complexes have a residence time similar to the timescale of Okazaki fragment synthesis and the ability to block a holoenzyme synthesizing DNA and stimulate the dissociation of the holoenzyme to trigger polymerase recycling. The collision with primer–primase complexes triggering the early termination of Okazaki fragment synthesis has distinct advantages over those previously proposed because this signal requires no transmission to the lagging-strand polymerase through protein or DNA interactions, the mechanism for rapid dissociation of the holoenzyme is always collision, and no unique characteristics need to be assigned to either identical polymerase in the replisome. We have modeled repeated cycles of Okazaki fragment initiation using a collision with a completed Okazaki fragment or primer–primase complexes as the recycling mechanism. The results reproduce experimental data, providing insights into events related to Okazaki fragment initiation and the overall functioning of DNA replisomes.
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Dhote, KD, and RS Deodhar. "Effect of fragment dispersion on damage assessment of a directional fragment generator." International Journal of Damage Mechanics 27, no. 4 (January 24, 2017): 568–77. http://dx.doi.org/10.1177/1056789517690215.
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Effective neutralisation of an offensive target missile can be accomplished by a defensive missile system carrying a potential kill mechanism. A directional fragment generator warhead is one of the kill mechanisms for such an application. It projects fragments in a designed beam angle. Few researchers have attempted to quantify fragment dispersion on explosion, which revealed that the fragment projection angle follows a normal distribution with wide range in standard deviation value of 0.75° and 3°. In this paper, an attempt has been made to analyse the importance of knowing the standard deviation value for assessing damage in terms of fragment hit density and kill probability. By altering the standard deviation value between 0 and 3°, the fragment spray distribution for the fragment generator warhead is generated and compared with the distribution that corresponds to a standard deviation value of 0.75°. It is observed that the hit density variation varies by −51% to 40% from the actual. On comparing the effect of standard deviation on kill probability, it is observed that it depends on the proportionate area of vulnerable component in the fragment beam. For the vulnerable area of 0.5 times (50%) of annular fragment beam area, more than or equal to eight fragments can achieve kill probability close to 1. However, for vulnerable area of 0.02 (2%) and 0.1 times (10%) of annular fragment beam area, the kill probability depends on standard deviation value.
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Amano, Yasushi, Ichiji Namatame, Yukihiro Tateishi, Kazuya Honboh, Eiki Tanabe, Tatsuya Niimi, and Hitoshi Sakashita. "Structural insights into the novel inhibition mechanism ofTrypanosoma cruzispermidine synthase." Acta Crystallographica Section D Biological Crystallography 71, no. 9 (August 25, 2015): 1879–89. http://dx.doi.org/10.1107/s1399004715013048.
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Trypanosoma cruzicauses Chagas disease, a severe disease affecting 8–10 million people in Latin America. While nifurtimox and benznidazole are used to treat this disease, their efficacy is limited and adverse effects are observed. New therapeutic targets and novel drugs are therefore urgently required. Enzymes in the polyamine–trypanothione pathway are promising targets for the treatment of Chagas disease. Spermidine synthase is a key enzyme in this pathway that catalyzes the transfer of an aminopropyl group from decarboxylatedS-adenosylmethionine (dcSAM) to putrescine. Fragment-based drug discovery was therefore conducted to identify novel, potent inhibitors of spermidine synthase fromT. cruzi(TcSpdSyn). Here, crystal structures of TcSpdSyn in complex with dcSAM,trans-4-methylcyclohexylamine and hit compounds from fragment screening are reported. The structure of dcSAM complexed with TcSpdSyn indicates that dcSAM stabilizes the conformation of the `gatekeeping' loop to form the putrescine-binding pocket. The structures of fragments bound to TcSpdSyn revealed two fragment-binding sites: the putrescine-binding pocket and the dimer interface. The putrescine-binding pocket was extended by an induced-fit mechanism. The crystal structures indicate that the conformation of the dimer interface is required to stabilize the gatekeeping loop and that fragments binding to this interface inhibit TcSpdSyn by disrupting its conformation. These results suggest that utilizing the dynamic structural changes in TcSpdSyn that occur upon inhibitor binding will facilitate the development of more selective and potent inhibitors.
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Hui, Man-To, and David Jewitt. "Fragment Dynamics in Active Asteroid 331P/Gibbs." Astronomical Journal 164, no. 6 (November 3, 2022): 236. http://dx.doi.org/10.3847/1538-3881/ac978d.
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Abstract We present a dynamical analysis of the fragmented active asteroid 331P/Gibbs. Using archival images taken by the Hubble Space Telescope from 2015 to 2018, we measured the astrometry of the primary and the three brightest (presumably the largest) components. Conventional orbit determination revealed a high degree of orbital similarity between the components. We then applied a fragmentation model to fit the astrometry, obtaining key parameters including the fragmentation epochs and separation velocities. Our best-fit models show that Fragment B separated from the primary body at a speed of ∼1 cm s−1 between 2011 April and May, whereas two plausible scenarios were identified for Fragments A and C. The former split either from the primary or from Fragment B, in 2011 mid June at a speed of ∼8 cm s−1, and the latter split from Fragment B either in late 2011 or between late 2013 and early 2014, at a speed of ∼0.7–0.8 cm s−1. The results are consistent with rotational disruption as the mechanism causing the cascading fragmentation of the asteroid, as suggested by the rapid rotation of the primary. The fragments constitute the youngest known asteroid cluster, providing us with a great opportunity to study asteroid fragmentation and formation of asteroid clusters.
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Cukrowski, Ignacy, George Dhimba, and Darren L. Riley. "A reaction energy profile and fragment attributed molecular system energy change (FAMSEC)-based protocol designed to uncover reaction mechanisms: a case study of the proline-catalysed aldol reaction." Physical Chemistry Chemical Physics 21, no. 30 (2019): 16694–705. http://dx.doi.org/10.1039/c9cp03046h.
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Inchingolo, Alessio V., Samantha Beck Previs, Michael J. Previs, David M. Warshaw, and Neil M. Kad. "Revealing the mechanism of how cardiac myosin-binding protein C N-terminal fragments sensitize thin filaments for myosin binding." Proceedings of the National Academy of Sciences 116, no. 14 (March 15, 2019): 6828–35. http://dx.doi.org/10.1073/pnas.1816480116.
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Cardiac muscle contraction is triggered by calcium binding to troponin. The consequent movement of tropomyosin permits myosin binding to actin, generating force. Cardiac myosin-binding protein C (cMyBP-C) plays a modulatory role in this activation process. One potential mechanism for the N-terminal domains of cMyBP-C to achieve this is by binding directly to the actin-thin filament at low calcium levels to enhance the movement of tropomyosin. To determine the molecular mechanisms by which cMyBP-C enhances myosin recruitment to the actin-thin filament, we directly visualized fluorescently labeled cMyBP-C N-terminal fragments and GFP-labeled myosin molecules binding to suspended actin-thin filaments in a fluorescence-based single-molecule microscopy assay. Binding of the C0C3 N-terminal cMyBP-C fragment to the thin filament enhanced myosin association at low calcium levels. However, at high calcium levels, C0C3 bound in clusters, blocking myosin binding. Dynamic imaging of thin filament-bound Cy3-C0C3 molecules demonstrated that these fragments diffuse along the thin filament before statically binding, suggesting a mechanism that involves a weak-binding mode to search for access to the thin filament and a tight-binding mode to sensitize the thin filament to calcium, thus enhancing myosin binding. Although shorter N-terminal fragments (Cy3-C0C1 and Cy3-C0C1f) bound to the thin filaments and displayed modes of motion on the thin filament similar to that of the Cy3-C0C3 fragment, the shorter fragments were unable to sensitize the thin filament. Therefore, the longer N-terminal fragment (C0C3) must possess the requisite domains needed to bind specifically to the thin filament in order for the cMyBP-C N terminus to modulate cardiac contractility.
Dissertations / Theses on the topic "MECHANISM AND FRAGMENT"
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Buyens, Dominique. "Alkylation of adenine : a synthetic and computational study of the reaction mechanism." Diss., University of Pretoria, 2015. http://hdl.handle.net/2263/64255.
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This dissertation describes the benzylation of adenine under basic conditions, the unequivocal determination of the identity of the products of this reaction, an exploration of the effect of solvent on the reaction, a thorough computational study of the reaction mechanism and an investigation into the hydrogen-deuterium exchange reaction of the N-benzyladenine products and related compounds.
The preferential sites of alkylation of adenine under basic conditions in DMSO were proven to be the N9 and N3 positions. X-ray crystal structures were obtained for both compounds. Formation of the N9-benzyladenine product is the most favoured in polar aprotic solvents, such as DMSO, and as the proportion of polar protic solvents, such as water, increases, so does the formation of the N3-benzyladenine product. Characteristic 1H NMR chemical shifts of the purine ring protons and HMBC 1H-13C correlation NMR spectroscopy were useful tools to assign the 1H and 13C NMR spectra chemical shifts and confirm that the solution structures were the same as the isolated crystals.
Simulating the SN2 mechanism for the N1-, N3-, N7- and N9-pathways computationally, employing DMSO as the simulated solvent, resulted in ambiguous results when considering the electronic energies of initial, TS and final products alone. However, a novel approach was developed (employing IQA-defined energy terms) to study fragment interactions along the reaction paths. It provided a full explanation of the reaction mechanism and yielded results which supported the N3/N9 positions of alkylation over the N1/N7 sites. The preference for the sites of alkylation occurs after the transition state, in which the N1/N7 reaction paths fail to proceed favourably to the end product, N1- and N7-benzyladenine, respectively. The N9-pathway dominates the N3-pathway at the product formation step, which corresponds to the N9-
benzyladenine being the major product, as shown in Figure 1, and the N3-benzyladenine being
the minor product from the benzylation of adenine. The faster rate of deuteration at the C8 position of N9-benzyladenine as compared to the
deuteration rates at the C2 and the C8 of N3-benzyladenine, have shown support for a sp3
mediated mechanism and a carbene mediated mechanism of deuteration based on the “push” and
“pull” mechanisms proposed for the C8 proton transfer of ATP in kinase enzymes. The
deuteration of the C8 proton of 2,6-dichloropurine derivatives supports the existence of the
carbene mediated mechanism since these compounds lack the amine moiety necessary for the
sp3 mediated mechanism.
These results demonstrate how experimentation and computation have led to greater insights
into the reactivity of adenine and its derivatives. This strategy provides a useful platform for
future research into adenine reaction mechanisms and the role adenine plays in kinase catalysis.Dissertation (MSc)--University of Pretoria, 2015.
National Research Foundation (NRF)
Chemistry
MSc
Unrestricted
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KUMAR, ASHISH. "STUDY OF MULTI-CUE OBJECT TRACKING IN VIDEO SEQUENCES." Thesis, DELHI TECHNOLOGICAL UNIVERSITY, 2020. http://dspace.dtu.ac.in:8080/jspui/handle/repository/18764.
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Multi-cue object tracking is a challenging eld of computer vision. In particular,
the challenges originate from environmental variations such as occlusion, similar
background and illumination variations or due to variations in target's appearance
such as pose variations, deformation, fast motion, scale and rotational changes. In
order to address these variations, a lot of appearance model have been proposed but
developing a robust appearance model by fusing multi-cue information is tedious
and demands further investigation and research. It is essential to develop a multicue
object tracking solution with adaptive fusion of cues which can handle various
tracking challenges. The goal of this thesis is to propose robust multi-cue object
tracking frameworks by exploiting the complementary features and their adaptive
fusion in order to enhance tracker's performance and accuracy during tracking
failures.
A real-time tracker using particle lter under stochastic framework has been developed
for target estimation. The inherent problems of particle lter namely, sample
degeneracy and impoverishment have been addressed by proposing a resampling
method based upon meta-heuristic optimization. In addition, an outlier detection
mechanism is designed to reduce the computational complexity of the developed
tracker.
A robust tracking architecture has been proposed under deterministic framework.
Fragment-based tracker with a discriminative classi er has been designed that can
enhance tracker's performance during dynamic variations. Periodic and temporal
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update strategy is employed to make tracker adaptive to changing environment.
Extensive experimental analysis has been performed to prove the e ectiveness of
the developed tracking solution.
Multi-stage tracker based on adaptive fusion of multi-cue has been developed for
multi-cue object tracking. The rst stage of target rough localization improves
the accuracy of tracker during precise localization. In the appearance model complementary
cues are considered to handle illumination variations and occlusion.
Classi er mechanism and fragment based appearance model are proposed to improve
the tracker's accuracy during background clutters and fast motion. Experimental
validation on multiple datasets validates the performance and accuracy of
the proposed tracker.
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Hsieh, S. "Fragmentation mechanisms of doubly charged ions." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284502.
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Sun, Ang. "Anti-cancer Functions and Mechanisms of a pRb2/p130 Peptide Fragment." Diss., Temple University Libraries, 2009. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/58962.
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BiologyPh.D.
The spacer region of pRb2/p130 was reported to be able to inhibit the kinase activity of Cdk2. The region responsible for the inhibitory effect was further narrowed down to a 39-amino-acid sequence, which was named as Spa310. In this dissertation, the anti-cancer functions and mechanisms of Spa310 were studied. The synthesized Spa310 peptide was able to inhibit the kinase activities of Cdk2/Cyclin E/A complexes. In vitro kinase assays showed the inhibition occurred in a dose-dependent manner. The half maximal inhibition concentration of the Spa310 in the kinase assay was 1.67mM. In addition, it has been shown that Spa310 peptide is able to inhibit the kinase activities of both Cdk2/Cyclin E and Cdk2/Cyclin A. Intra-cellular distribution study using fluorescein-labeled Spa310 peptide showed that Spa310 was able to localize to the nuclei of A549 cancer cells. Some data indicated the endoplasmic reticulum might play a role in transporting Spa310 peptide from cytoplasm to the nucleus. At high concentration, the treatment of Spa310 peptide was able to arrest cells at the G0/G1 phase of the cell cycle and reduce the growth of xenografted tumors in nude mice. Further studies indicated Spa310 peptide is not a specific inhibitor for Cdk2/Cyclin E/A. It is also able to inhibit the kinase activities of Cdk1/Cyclin B, Cdk4/Cyclin D and Cdk9/Cyclin T/K. Result of a binding assay using GST-Spa310 and in vitro transcribed/translated Cdk2 did not support a direct binding between Spa310 and Cdk2. Additionally, GST-Spa310 was unable to bind to the in vitro transcribed/translated Cyclin E. At first, co-immunoprecipitation experiments indicated a weak binding between Spa310 peptide and Cdk2. However, later this weak binding was proven to be unspecific and only occurred when the concentration of Spa310 peptide was high. Thus, the hypothesized mechanism of the inhibitory effect of Spa310 was not supported. After noticing three classic Cdk phosphorylation sites present in Spa310, it was proven that Spa310 is a substrate for Cdk1, 2, 4 and 9. Results of kinase assays supported the inhibitory effect of Spa310 on the different Cyclin-dependent kinases was resulted from a substrate-competitive mechanism. Although the data generated from this study does not support Spa310 is a potent peptide inhibitor for the Cdks, knowledge gained from and the approach used in this research can be applied to design and develop more potent and specific Cdk2 peptide inhibitors, which have their potentials to work as powerful anti-cancer reagents.
Temple University--Theses
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Woodlock, David A. "Application of molecular mechanics polarization to fragment based drug design." Thesis, University of Essex, 2015. http://repository.essex.ac.uk/16774/.
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Polarization is a term that is often excluded from almost all virtual screening. Polarizability helps explain interactions between nonpolar atoms and electrically charged species. When studying fragments in FBDD these minor interactions could have large effect in changing how well a ligand will bind to its target. After including the polarizability terms in docking a validation set of ligands (Favia et al., 2011) with GLIDE, it improved the results the amount good docked poses (< 2 Å RMSD) by up to 12%. However some ligands were bound in incorrect poses. Further investigation was carried out with MD to observe if given enough time ligands bound in an incorrect pose would return to the binding site. In the first stages of investigating MD we ascertained if we could use GPUs to simulate larger systems and faster. After some performing some MD simulations in GROMACs we found that GPUs were an improved option and thus continued the simulation work with ACEMD which allowed multiple GPUs in tandem. After running the MD simulations for 200ns with atomic charges generated from the polarization the results we found were quite interesting. Some ligands would be trapped in their binding site but would fluctuate quite readily such as 2GVV. Some ligands showed that despite low RMSD they would be ejected from the binding site. In some cases the ligands would then attempt to return to their binding site. Ligands such as in 2CIX would show binding based on the breathing movement of the protein. Some ligands such as 1F5F or 1F8E bound tightly to their binding site during the MD, these ligands also enjoyed improved docking polarization with 0.1 – 1.0 Å improvement. These could be carried forward to become good candidates for experimental testing. Polarization is shown to have an overall positive effect improving binding data and if implemented with simple methods would have little opportunity cost to be added to modern FBDD methods.
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Verger, Denis. "Etude cristallographique préliminaire de la région globulaire de C1q et d'un fragment de C3 du complément humain : structures cristallines de complexes entre la subtilisine de Bacillus lentus et des inhibiteurs de type acide boronique." Université Joseph Fourier (Grenoble), 1996. http://www.theses.fr/1996GRE10097.
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C1q initie la voie classique du complement grace a sa region globulaire (gr). C3de correspond a la partie de c3b qui se fixe sur les cellules cibles. Nous avons cristallise ces proteines et enregistre un jeu de donnees a 3,2 a pour la gr, a 3,7 a pour c3de. Des problemes de reproductibilite et de taille des cristaux nous ont empeche de poursuivre l'etude. La subtilisine de bacillus lentus (savinase#t#m) est utilisee comme additif dans les detergents des lessives. Des inhibiteurs competitifs et reversibles (acides boroniques) sont ajoutes dans ces solutions pour eviter que la savinase#t#m ne degrade les autres enzymes presentes. Nous avons resolu la structure de 4 complexes a 2 a puis 1,7 a par remplacement moleculaire a partir d'une nouvelle forme cristalline. Les acides boroniques interagissent avec la proteine par une liaison covalente entre leur atome de bore et l'oxygene gamma de la serine active, et par des contacts hydrophobes entre leur groupement r et la poche de specificite s1. L'acide benzo furane 2 boronique (bf2ba) est l'inhibiteur le plus efficace parmi les 4 etudies. La reactivite entre le bore et la serine active depend de la nature du groupement r, du ph, de la concentration en inhibiteur. A partir du modele savinase#t#m/bf2ba, nous proposons des inhibiteurs potentiellement plus efficaces
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Hilton, D. W. "Elucidating the aggregation mechanisms of antibody fragments through biophysical analysis." Thesis, University College London (University of London), 2016. http://discovery.ucl.ac.uk/1492898/.
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The spontaneous formation of aggregates presents an obstacle in the developability, manufacturability and long term storage of numerous therapeutic proteins. These aggregates are a manifestation of the drug molecule's physical instability, potentially leading to reduced biological activity, differences in solution properties or increased immunogenic potential. Currently our understanding of the mechanisms behind aggregation and the role of a protein's extrinsic environment upon the molecule's aggregation propensity remains limited. In this study we investigated the aggregation behavior of a previously unstudied commercial biopharmaceutical, an α-TNF Fab' antibody fragment. Initially we mapped the differences in aggregation kinetics and product morphologies accompanying changes to the protein's aqueous environment, finding that the aggregation pathway adopted by the molecule depended upon the pH of the system. We then employed a combination of intrinsic and colloidal stability measurements to probe the causes of the behavioral differences seen. Together, these biophysical properties quantitatively captured the relative differences in aggregation rates observed. Furthermore, we were able to infer the existence of various partially folded intermediates whose populations govern the types and rates of aggregates formed. Finally, we sought to identify whether observable changes in the native state conformation precluded aggregate formation through low resolution structural analysis using small angle X-ray scattering. We showed that a drop in pH generated a conformationally expanded state which appeared to coincide with the titration of a key histidine residue within the protein's structure. We predict that an equivalent mechanism will lead to aggregation at low pH of other human derived antigen binding fragments.
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Ma, Ying. "Ballistic strength of multi-layer fabrics against fragment simulating projectiles." Diss., Kansas State University, 2017. http://hdl.handle.net/2097/35067.
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Doctor of PhilosophyDepartment of Mechanical and Nuclear Engineering
Youqi Wang
Ballistic performance of textile fabric is affected by numerous elements, such as fabric architecture, material property, and projectile characteristics. Near fiber-level microstructures of soft body armor composed of multi-layer Kevlar KM-2 fabrics are generated for numerical simulation. The modified digital element approach (DEA) is applied to determine the ballistic limit of textile fabrics against fragment simulating projectiles (FSP). Different from other numerical models, the DEA takes a considerable amount of fiber-level detail into consideration and models the fabric at filament-level. In this approach, fabric is an assembly of yarns weaved and relaxed into pre-arranged pattern; yarn is simulated as a bundle of digital fibers. When the number of digital fibers per yarn reaches the number of actual fibers per yarn, fiber-level simulation is achieved. The DEA model successfully simulates real scale multi-layer fabric impacted by spherical projectile and accurately predicted fabric displacement and failure mechanism. It was assumed that the digital fiber is fully flexible and its bending rigidity is negligible. Shear force was thus neglected. However, for projectiles with sharp edge(s), such as FSP, due to resultant shear force, fabric failure starts where it interacts with projectile edge. As a result, the numerical results derived from the previous DEA overestimated the impact strength of fabrics against projectiles with shape edges. Therefore, shear force and fiber bending rigidity must be considered. In the modified DEA approach, numerical tests are employed to determine the effective bending rigidity of digital fiber. A combined tension-shear failure model is then incorporated into the DEA in order to calculate the shear force applied to fibers. The 3-D microscope is applied to measure the radius of FSP along the edge. The surface of the FSP is meshed into triangle elements. A unique algorithm is developed and employed to search contacts between textile fabric and projectile of arbitrary shape. In this research, first, an overview of ballistic impact analysis is discussed; the previous DEA model used in simulating ballistic impact and penetration process is presented. Second, the modified DEA approach used in simulating arbitrary shape projectile perforation process is established and verified. The method of searching and calculating contacts between textile fabric and solid body projectile is explained. The convergence and accuracy of digital element mesh are investigated statistically using tension-shear failure model. Third, fabric shear force and fiber bending rigidity are investigated using tension-shear failure model. The effective digital fiber area moment of inertia is numerically determined. Fourth, standard ballistic tests of real scale multi-layer Kevlar KM2 fabrics are simulated using FSP. Numerical results are compared to high-resolution experimental test data. The modified DEA is validated.
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Lin, Hsin Hsin. "Mechanisms of Intravenous Immunoglobulin in the Treatment of Experimental Autoimmune Neuritis." University of Sydney, 2007. http://hdl.handle.net/2123/1696.
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PhDThe aims of this study were to test the efficacy of immunoglobulin and its Fab and Fc fragment in the treatment of experimental autoimmune neuritis (EAN) in Lewis rats, to investigate which portion of immunoglobulin is operative in the effect of IVIg, and to clarify the possible mechanisms by which immunoglobulin exerts its action in the treatment of rats EAN. EAN was induced by immunization with whole bovine peripheral nerve myelin. The immunized rats were randomized into groups, assessed clinically, electrophysiologically, and histologically, and intravenously injected with normal saline, albumin, human IVIg preparation, purified Fab or Fc fragments. The treatment efficacy was compared between normal saline and albumin groups, albumin and IVIg groups, albumin and Fab groups, albumin and Fc groups, Fab and Fc groups, Fab and IVIg groups, and Fc and IVIg groups. Methods of myelin isolation, antibody purification, and Western blot techniques were also applied. The results revealed that treatment with Fc fragment and IVIg at the onset of signs of disease effectively prevented further progression of disease, shortened disease duration, and facilitating recovery from illness as shown in clinical, electrophysiological and histological parameters. In the study which the efficacy of albumin and IVIg was compared, 5 out of 17 rats (29%) in the albumin group and 12 out of 17 (71%) in the IVIg group completely recovered from the clinical disease by day 30. The animals receiving IVIg treatment exhibited lower clinical scores, less prolongation of S wave latencies, better maintained S wave amplitudes, less reduction of distal motor NCVs, better maintained distal and proximal CMAP amplitudes, and lower histological grades. In the study which the efficacy of albumin, Fab fragment, Fc fragment, and IVIg was compared, 0 out of 8 (0%) in the albumin group, 1 out of 8 (13%) in the Fab group, 4 out of 8 (50%) in the Fc group, and 6 out of 9 (67%) rats in the IgG group completely recovered from the clinical disease by day 30. The animals receiving Fc fragment and IVIg treatment exhibited lower clinical scores, less prominent weight loss, less prolongation of S wave latencies, better maintained S wave amplitudes, less reduction of distal motor NCVs, better maintained distal and proximal CMAP amplitudes, and lower histological grades.
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Lin, Hsin Hsin. "Mechanisms of Intravenous Immunoglobulin in the Treatment of Experimental Autoimmune Neuritis." Thesis, The University of Sydney, 2006. http://hdl.handle.net/2123/1696.
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The aims of this study were to test the efficacy of immunoglobulin and its Fab and Fc fragment in the treatment of experimental autoimmune neuritis (EAN) in Lewis rats, to investigate which portion of immunoglobulin is operative in the effect of IVIg, and to clarify the possible mechanisms by which immunoglobulin exerts its action in the treatment of rats EAN. EAN was induced by immunization with whole bovine peripheral nerve myelin. The immunized rats were randomized into groups, assessed clinically, electrophysiologically, and histologically, and intravenously injected with normal saline, albumin, human IVIg preparation, purified Fab or Fc fragments. The treatment efficacy was compared between normal saline and albumin groups, albumin and IVIg groups, albumin and Fab groups, albumin and Fc groups, Fab and Fc groups, Fab and IVIg groups, and Fc and IVIg groups. Methods of myelin isolation, antibody purification, and Western blot techniques were also applied. The results revealed that treatment with Fc fragment and IVIg at the onset of signs of disease effectively prevented further progression of disease, shortened disease duration, and facilitating recovery from illness as shown in clinical, electrophysiological and histological parameters. In the study which the efficacy of albumin and IVIg was compared, 5 out of 17 rats (29%) in the albumin group and 12 out of 17 (71%) in the IVIg group completely recovered from the clinical disease by day 30. The animals receiving IVIg treatment exhibited lower clinical scores, less prolongation of S wave latencies, better maintained S wave amplitudes, less reduction of distal motor NCVs, better maintained distal and proximal CMAP amplitudes, and lower histological grades. In the study which the efficacy of albumin, Fab fragment, Fc fragment, and IVIg was compared, 0 out of 8 (0%) in the albumin group, 1 out of 8 (13%) in the Fab group, 4 out of 8 (50%) in the Fc group, and 6 out of 9 (67%) rats in the IgG group completely recovered from the clinical disease by day 30. The animals receiving Fc fragment and IVIg treatment exhibited lower clinical scores, less prominent weight loss, less prolongation of S wave latencies, better maintained S wave amplitudes, less reduction of distal motor NCVs, better maintained distal and proximal CMAP amplitudes, and lower histological grades.
Books on the topic "MECHANISM AND FRAGMENT"
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Kulviecas, Liubomiras. Klasikinė mechanika: Vadovėlio fragmentai. Vilnius: Vilniaus Valstybinis pedagoginis universitetas, 1991.
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A fracture mechanics study of crack propagation mechanism in coal: The mechanics of fine fragment formation : fifth annual report (October 1, 1987-September 30, 1988). [University Park, Pa.]: College of Earth and Mineral Sciences, PennState, 1988.
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Eland, John H. D., and Raimund Feifel. Diatomic molecules. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198788980.003.0003.
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Double ionisation of most of the experimentally accessible diatomic molecules has been studied previously by several techniques, including Auger spectroscopy, double electron transfer, kinetic energy release, and high-level theory. New double photoionisation spectra of HBr, HI, N2, CO, NO, O2, Br2, ICl, and I2 are presented here with analysis to identify the electronic states of the doubly charged ions. A simple empirical model is introduced to estimate double ionisation energies on the basis of orbital energies. For CO, NO, and O2, an indirect double ionisation mechanism is found, involving dissociation of a singly charged molecular ion followed by atomic autoionisation of one fragment. Energies of the dication states are listed with distinction between adiabatic and vertical values.
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Exterior Ballistics with Applications: Skydiving, Parachute Fall, Flying Fragments. United States of America: Xlibris, 2008.
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Angel, Naomi. Fragments of Truth. Edited by Dylan Robinson and Jamie Berthe. Duke University Press, 2022. http://dx.doi.org/10.1215/9781478023173.
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In 2008, the Canadian government established a Truth and Reconciliation Commission (TRC) to review the history of the residential school system, a brutal colonial project that killed and injured many Indigenous children and left a legacy of trauma and pain. In Fragments of Truth Naomi Angel analyzes the visual culture of reconciliation and memory in relation to this complex and painful history. In her analyses of archival photographs from the residential school system, representations of the schools in popular media and literature, and testimonies from TRC proceedings, Angel traces how the TRC served as a mechanism through which memory, trauma, and visuality became apparent. She shows how many Indigenous communities were able to use the TRC process as a way to claim agency over their memories of the schools. Bringing to light the ongoing costs of transforming settler states into modern nations, Angel demonstrates how the TRC offers a unique optic through which to survey the long history of colonial oppression of Canada’s Indigenous populations.
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Svrakic, Dragan M., and Mirjana Divac Jovanovic. The Fragmented Personality. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780190884574.001.0001.
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This book pioneers a new model of personality disorder primarily intended to serve mental health professionals, those already in practice and equally those in training. In contrast to the static concepts of mental normalcy and pathology, the presented nosology is dynamic (accounts for the reversibility of mental functioning) and personalized, context- and time sensitive. In a 3D diagnostic cylinder, the coordinates cross match the person’s common level of mental functioning (vertical diagnosis) with his or her behavior style (horizontal diagnosis) at a point in space and a unit of time, giving the clinician precise milestones to monitor changes in diagnosis and progress in therapy. The central problem with persons suffering from personality disorder does not rest in their extreme behaviors but rather underneath the surface, in the fragmented substrate of personality (a core deficit sine qua non shared by all individual variants), while extreme behaviors merely represent variable compensatory strategies. Based on this model, mechanism-based treatments are outlined: reconstructive interpersonal psychotherapy (a novel, integrative, transtheoretical approach which relies on psychoanalytic and humanist traditions) and mechanism-based pharmacotherapy of neurobiological vulnerabilities associated with excessive temperament traits.
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Obinger, Herbert, Klaus Petersen, and Peter Starke. Introduction. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198779599.003.0001.
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The Introduction presents the overarching research question of the book, namely the question of whether and how war between nations has influenced the development of advanced welfare states. This question has received only scant attention from the welfare state literature so far. The Introduction reviews the fragmented literature in history and social science with a focus on national narratives and revisionist positions, and argues for a comparative angle which puts the various causal mechanisms linking mass war and welfare state development. These mechanisms are systematized, using a heuristic of supply- vs. demand-side mechanisms and three distinct phases of military conflict: war preparation, mobilization, and the post-war period.
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Marett, Douglas Michael *. Examination of the mechanisms of T cell activation by pertussis toxin using recombinant holotoxin mutants and purified toxin fragments. 1989.
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Wetzel, Ronald, and Rakesh Mishra. Structural Biology. Oxford University Press, 2014. http://dx.doi.org/10.1093/med/9780199929146.003.0012.
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The 3,144–amino acid huntingtin protein (HTT) folds in water into a structure consisting of compact, organized domains interspersed with intrinsically disordered protein (IDP) elements. The IDPs function as sites of post-translational modifications and proteolysis as well as in targeting, binding, and aggregation. Although the dominant structural motif of HTT is the α-helix–rich HEAT repeat, the expanded polyglutamine (polyQ) toxicity responsible for Huntington’s disease is most likely played out within intrinsically disordered HTT exon 1–like fragments consisting of the 16– to 17–amino acid N-terminal HTTNT segment, the polyQ segment, and a proline-rich segment. The physical behavior of HTT exon 1 fragments is dominated by interactive, polyQ repeat length–dependent structural transitions responsible for membrane and protein–protein interactions and the formation of tetramers, higher oligomers, amyloid fibrils, and inclusions. Understanding the basis of this solution behavior may be the key to disease mechanisms and molecular therapeutic strategies.
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Cordelia, Koch. Part 4 Constitutionalism and Separation of Powers, 4.3 The Separation of Powers in a Fragmented State: The Case of Lebanon. Oxford University Press, 2012. http://dx.doi.org/10.1093/acprof:osobl/9780199759880.003.0021.
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This chapter analyzes the Lebanese Constitution in the light of consociational democracy. It begins with an overview on the political system to highlight the formal consensus requirements based on affiliation with one of the main religious groups in the country. It examines the evolution of confessional power-sharing, which is supplemented by the traditional family-based feudal lord system. It then explores the historical interplay of state-building, civil wars, and existing political frictions which still contribute to what the Lebanese Constitution is about today. Next, the chapter outlines the constitutional development regarding consociational democracy, emphasizing the different consensus-mechanisms now incorporated in the written constitution. This shows how the Lebanese political system diverges from the classical Montesquieu system and creates its own separation of powers through consensus mechanisms.
Book chapters on the topic "MECHANISM AND FRAGMENT"
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Tsumoto, Kouhei, Hideki Watanabe, and Izumi Kumagai. "Open Sandwich Selection: Selection of Human Antibody Fragments Using the Mechanism of Fv Fragment Stabilization in the Presence of Antigen." In ACS Symposium Series, 285–95. Washington, DC: American Chemical Society, 2002. http://dx.doi.org/10.1021/bk-2002-0830.ch023.
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Toyoshima, Yoko Y. "How are Myosin Fragments Bound to Nitrocellulose Film ?" In Mechanism of Myofilament Sliding in Muscle Contraction, 259–65. Boston, MA: Springer US, 1993. http://dx.doi.org/10.1007/978-1-4615-2872-2_25.
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Curran, D. R., L. Seaman, J. W. Simons, and T. Cooper. "Modeling the Flow of Fragmented, Brittle Material." In Computational Mechanics ’95, 1879–85. Berlin, Heidelberg: Springer Berlin Heidelberg, 1995. http://dx.doi.org/10.1007/978-3-642-79654-8_314.
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Zattara, Eduardo E., and Fernando A. Fernández-Alvarez. "Collecting and Culturing Lineus sanguineus to Study Nemertea WBR." In Methods in Molecular Biology, 227–43. New York, NY: Springer US, 2022. http://dx.doi.org/10.1007/978-1-0716-2172-1_12.
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AbstractWhole-body regeneration, the ability to reconstruct complete individuals from small fragments, is rare among ribbon worms (phylum Nemertea) but present in the pilidiophoran species Lineus sanguineus. This species can regenerate complete individuals from a tiny midbody section, and even from a quarter of a piece, provided it retains a fragment of a lateral nerve cord. While a few other unrelated species of ribbon worms are also excellent regenerators, L. sanguineus is unique in having evolved its regenerative abilities quite recently and thus offers an exceptional opportunity to gain insight into the evolutionary mechanisms of regeneration enhancement. Interestingly, both its sister species Lineus lacteus and Lineus pseudolacteus, a third species derived from the recent hybridization of the other two, differ in their regeneration abilities: while L. lacteus is uncapable of regenerating a lost head, L. pseudolacteus is capable of anterior regeneration, albeit at a slower rate than L. sanguineus. L. sanguineus has a worldwide distribution in temperate shores of both hemispheres, is readily found at intertidal habitats, and can survive, feed and be bred through asexual replication with minimal effort in laboratory settings. All the above make this species a superb candidate for studies of regenerative biology. In this chapter, we present protocols to collect, identify and breed L. sanguineus to study the extraordinary whole-body regeneration abilities found in this species.
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Ptak, Arkadiusz, Mina Dudkowiak, and Danuta Frąckowiak. "Photopotential Generation in Green Bacteria Cells and Cell Fragments Located in an Electrochemical Cell." In Photosynthesis: Mechanisms and Effects, 4241–44. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-3953-3_982.
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Langer, A. M., R. P. Nolan, and J. Addison. "Distinguishing between Amphibole Asbestos Fibers and Elongate Cleavage Fragments of their Non-Asbestos Analogues." In Mechanisms in Fibre Carcinogenesis, 253–67. Boston, MA: Springer US, 1991. http://dx.doi.org/10.1007/978-1-4684-1363-2_22.
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Kaba, Ali B., and Jean-Claude Derniame. "Modelling processes for change: Basic mechanisms for evolving process fragments." In Software Process Technology, 99–107. Berlin, Heidelberg: Springer Berlin Heidelberg, 1996. http://dx.doi.org/10.1007/bfb0017736.
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Kurreck, J., and G. Renger. "Investigation of the Plastoquinone Pool Size and Fluorescence Quenching in Photosystem II (Ps II) Membrane Fragments." In Photosynthesis: Mechanisms and Effects, 1157–60. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-3953-3_276.
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Huang, Jing, Qing Ming Zhang, Jin Qing Li, and Chuan Xiao. "The Experiment Study on the Shielded Charge Initiated by the High Speed Fragment." In Experimental Mechanics in Nano and Biotechnology, 1255–58. Stafa: Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/0-87849-415-4.1255.
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Hundal, Torill, Cornelia Spetea, Felix Lohmann, and Bertil Andersson. "ATP- and Zinc-Dependent Proteolysis of the D1 Protein Primary Fragments — Possible Involvement of the FtsH Protease." In Photosynthesis: Mechanisms and Effects, 2023–26. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-3953-3_473.
Full textConference papers on the topic "MECHANISM AND FRAGMENT"
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IMTIAZ, AZIZUDDIN, DHARMA TEJA KAMBAM, and MAHESH M. SUCHEENDRAN. "Mechanism of Multi-Layered Fragment Separation Due to High Explosive Loading." In 31st International Symposium on Ballistics. Lancaster, PA: DEStech Publications, Inc., 2019. http://dx.doi.org/10.12783/ballistics2019/33192.
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Bhattaram, Rohan, Ryan Reichert, and Victoria Marino. "Novel Hydrogel for Stone Fragment Control During Ureteroscopic Lithotripsy." In 2022 Design of Medical Devices Conference. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/dmd2022-1052.
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Abstract Surgical treatment of kidney stones commonly involves ureteroscopic lithotripsy with laser-assisted stone fragmentations. Particles that remain are considered “clinically insignificant” and are left behind, though these fragments are associated with downstream complications such as infection and stone reformation. The researchers aimed to develop a novel hydrogel that would prevent stone retropulsion intraoperatively and facilitate complete fragment removal. A novel inversely thermosensitive gel was developed which would theoretically stay solid to surround kidney stone, suspend stone fragments and would become liquid for gel removal. The aim of this study was to better understand the gel delivery mechanism considering its unique thermal properties. It was hypothesized that due to the gel’s thermal properties, an active cooling method, i.e. an intracatheter cooled guide wire, would be necessary to maintain gel fluidity to reach the intended destination. The researchers designed an experiment to test gel delivery through a 5 French, 70 cm long catheter surrounded by body temperature water with and without a cooled guide wire. We found there was no significant difference between both trial groups, indicating the gel does not require an active cooling method and can be administered directly. The lack of easy-to-use and cost-effective commercially available options to effectively reduce residual stone fragments presents a path for clinical adoption of the proposed hydrogel. Future trials will look into the fluid mechanics of gel administration and potential clinical outcomes such as stone free rates and rates of complications.
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Volkova, Tatiana Danilovna, Armine Vrezovna Avetisyan, Dmitry Otarovich Koroev, and Olga Volpina. "PROTECTIVE RAGE FRAGMENT INHIBITS AMYLOID BETA OLIGOMERIZATION." In NEW TECHNOLOGIES IN MEDICINE, BIOLOGY, PHARMACOLOGY AND ECOLOGY. Institute of information technology, 2021. http://dx.doi.org/10.47501/978-5-6044060-1-4.19.
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The article discusses the involvement of beta-amyloid in the mechanism of the protective action of the synthetic RAGE fragment. It was shown that the peptide is able to suppress the formation of oligomers and fibrils of beta-amyloid in solution. This confirms the hypothesis that the protective activity of the peptide is associated with its ability to inhibit the process of oligomerization of beta-amyloid.
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XIANG, JING-AN, TAO SUN, and HAIFU WANG. "ENHANCED DAMAGE EFFECT OF REACTIVE FRAGMENTS OBLIQUE PENETRATING TITANIUM ALLOY PLATES." In 32ND INTERNATIONAL SYMPOSIUM ON BALLISTICS. Destech Publications, Inc., 2022. http://dx.doi.org/10.12783/ballistics22/36166.
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Focusing on the reactive fragments oblique penetration behavior, a series of penetration experiments at velocity of 630-1040m/s at 0-60°were conducted. The results show that the area of perforation hole at 30° increase 143.53% compared with that of normal penetrations, ricochet occurs at 60°. The perforation size at critical velocity (v =705m/s) is much larger than that at higher velocity (v=734m/s) when both oblique penetrated at 30°. The damage zone of front titanium alloy plate was divided into 5 zones according to the morphology of damaged plate. The analytical mode considers both kinetic energy and chemical energy of reactive fragment is developed to reveal the mechanism of enhanced damage effect of reactive fragment oblique penetrating at critical velocity.
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Otsubo, Yuhei, Akira Otsuka, Mamoru Mimura, Takeshi Sakaki, and Hiroshi Ukegawa. "o-glassesX: Compiler Provenance Recovery with Attention Mechanism from a Short Code Fragment." In Workshop on Binary Analysis Research. Reston, VA: Internet Society, 2020. http://dx.doi.org/10.14722/bar.2020.23001.
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Heimbs, S., H. Lang, and T. Havar. "Rim release analysis: impact of aircraft wheel flange fragment on wing flap mechanism." In SUSI 2012. Southampton, UK: WIT Press, 2012. http://dx.doi.org/10.2495/su120171.
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Saito, Ryusuke, Yutaka Abe, Akiko Kaneko, Takayuki Suzuki, Hiroyuki Yoshida, and Fumihisa Nagase. "Development of Numerical Simulation for Jet Breakup Behavior in Complicated Structure of BWR Lower Plenum: (3) Influence by Complicated Structure on Jet Breakup and Fragmentation Behavior." In 2014 22nd International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/icone22-30037.
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To estimate the state of Reactor Pressure Vessel (RPV) of Fukushima Daiichi nuclear power plant, it is important to clarify the breakup and the fragmentation behavior of molten material jet in BWR lower plenum by a numerical simulation. To clarify the effects of complicated structures on jet breakup and fragmentation behavior experimentally and construct the benchmarks of the simulation code, we conduct the visualized experiments simulating the severe accident in the BWR. In this study, the jet breakup behavior, the fragmentation behavior and internal/external velocity profiles of the jet were observed by the backlight method and the particle image velocimetry (PIV). From experimental results, it is clarified that the complicated structures prolong the jet breakup length or make the fragments fallen together to the lower plenum similar to the bulk state. In addition, it is clarified that strong shearing stress occurs at the crest of interfacial waves at side of the jet when fragments are generated. Finally, the fragment diameters measured in the present study well agree with the theory suggested by Kataoka et al. (1983) by changing the coefficient term at each experimental condition. Thus, it is suggested that the fragmentation mechanism is mainly controlled by shearing stress and the fragment diameter can be estimated by adjusting the constant term.
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Bacon-Baguley, Theresa, Suzanne Kendra-Franczak, and Daniel Walz. "THROMBOSPONDIN SPECIFICALLY INTERACTS WITH AMINO ACID SEQUENCES WITHIN THE A α- AND B β- CHAINS OF FIBRINOGEN." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643822.
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Thrombospondin (TSP) is responsible for the secretion-dependent phase of platelet aggregation. The mechanism of this action is believed to be through the binding of TSP to fibrinogen, resulting in the stabilization of the platelet aggregate. It has been established that the binding of fibrinogen to the platelet surface is dependent upon peptide sequences present, respectively, in the Aa- and y-chains. We have hypothesized that the binding of TSP to fibrinogen is also dependent upon unique fibrinogen peptide sequences. To test this hypothesis we have examined the interaction of TSP and f.ih.r.inogen. using..a.-blat-b.inding assaLy of reduced fibrinogen, the separated fibrinogen chains, selected fibrinogen domains or peptides generated from cyanogen bromide cleaved chains. Iodinated TSP bound specifically to the Aα - and Bβ - chains. Binding to these chains was calcium independent, mutually exclusive and could be blocked either by preincubation of TSP with 9.4 μ M fibrinogen or by preincubation of fibrinogen with 1.1 nM thrombospondin. TSP bound to the D and DD plasmin fragment of fibrinogen; TSP interacted exclusively with the B-chain component of the DD fragment. The cyanogen bromide fragments of the separated Aα - and Bβ -chains were resolved through a combination of gel filtration and reverse-phase chromatography. TSP was found to bind to a single peptide within these fibrinogen chains. These studies demonstrate that thrombospondin interacts with at least two distinct sites on fibrinogen, and these sites differ from those already described for fibrinogen binding to platelets.
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Goldin, Graham, Zhuyin Ren, Yang Gao, Tianfeng Lu, Hai Wang, and Rui Xu. "HEEDS Optimized HyChem Mechanisms." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-64407.
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Transportation fuels consist of a large number of hydrocarbon components and combust through an even larger number of intermediates. Detailed chemical kinetic models of these fuels typically consist of hundreds of species, and are computationally expensive to include directly in 3D CFD simulations. HyChem (Hybrid Chemistry) is a recently proposed modeling approach for high-temperature fuel oxidation based on the assumptions that fuel pyrolysis is fast compared to the subsequent oxidation of the small fragments, and that, although their proportions may differ, all fuels pyrolyse to similar sets of these fragment species. Fuel pyrolysis is hence modeled with a small set of lumped reactions, and oxidation is described by a compact C0-4 foundation chemistry core. The stoichiometric coefficients of the global pyrolysis reactions are determined to match experimental or detailed mechanism computational data, such as shock-tube pyrolysis products, ignition delays and laminar flame speeds. The model is then validated against key combustion properties, including ignition delays, laminar flame speeds and extinction strain rates. The resulting HyChem model is relatively small and computationally tractable for 3D CFD simulations in complex geometries. This paper applies the HEEDS optimization tool to find optimal pyrolysis reaction stoichiometric coefficients for high-temperature combustion of two fuels, namely Jet-A and n-heptane, using a 47 species mechanism. It was found that optimizing on experimental ignition delay and laminar flame speed targets yield better agreement for ignition delay times and flame speeds than optimizing on pyrolysis yield targets alone. For Jet-A, good agreement for ignition delays and flame speeds were obtained by using both ignition delay and flame speeds as targets. For n-heptane, a trade-off between ignition delay and flame speed was found, where increased target weights for ignition delay resulted in worse flame speed predictions, and visa-versa.
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Mirshahi, M., J. Soria, C. Soria, S. Mirshaho, J. Y. Perrot, C. Boucheix, and A. Bernadou. "MODIFICATION OF FIBRIN POLYMERIZATION INDUCED BY MONOCLONAL ANTIBODIES AGAINST FRAGMENT D DOMAIN OF FIBRIN/OGEN DEGRADATION PRODUCTS." In XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643322.
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Monoclonal antibodies (McAb) are often used to detect the domains of a molecule involved in an important function of a biological system.In this work, the effect of 20 McAb directed against the D domain of fibrin/ogen degradation products (FbDP) were analyzed on fibrin polymerization. Two McAb which react with fragment D1 but not with fragment D3 inhibited both thrombin and reptilase-induced fibrin formation. It is therefore suggested that these 2 McAb recognize an epitope in the vicinity of the polymerization site "a" located in the JT 374-396 domain in fibrin/ogen molecule. (This sequence is only present in D1 and not in D3.An inhibitory effect on thrombin and reptilase-induced fibrin formation was also induced by 2 other anti D McAb which recognize an epitope present in both D1 and D3 fibrinogen-degradation products. Therefore, these 2 McAb do not react directly with the polymerizing site "a". A possible mechanism of this inhibition could be a conformational change induced by the binding of these McAb, leading to the masking of the polymerizing site "a". Another possible mechanism of the inhibitory effect is that thrombin and reptilase-induced fibrin formation may involve other sites on the fibrinogen molecule. It should therefore be suggested that unknown domains could be important for fibrin polymerization. These domains may act either directly or indirectly by inducing a three dimensional structure of the native molecule required for the expression of polymerizing domains.
Reports on the topic "MECHANISM AND FRAGMENT"
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Lers, Amnon, and Gan Susheng. Study of the regulatory mechanism involved in dark-induced Postharvest leaf senescence. United States Department of Agriculture, January 2009. http://dx.doi.org/10.32747/2009.7591734.bard.
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Postharvest leaf senescence contributes to quality losses in flowers and leafy vegetables. The general goal of this research project was to investigate the regulatory mechanisms involved in dark-induced leaf senescence. The regulatory system involved in senescence induction and control is highly complex and possibly involves a network of senescence promoting pathways responsible for activation of the senescence-associated genes. Pathways involving different internal signals and environmental factors may have distinctive importance in different leaf senescence systems. Darkness is known to have a role in enhancement of postharvest leaf senescence and for getting an insight into its regulatory mechanism/s we have applied molecular genetics and functional genomics approaches. The original objectives were: 1. Identification of dark-induced SAGs in Arabidopsis using enhancer/promoter trap lines and microarray approaches; 2. Molecular and functional characterization of the identified genes by analyzing their expression and examining the phenotypes in related knockout mutant plants; 3. Initial studies of promoter sequences for selected early dark-induced SAGs. Since genomic studies of senescence, with emphasis on dark-induced senescence, were early-on published which included information on potential regulatory genes we decided to use this new information. This is instead of using the uncharacterized enhancer/promoter trap lines as originally planned. We have also focused on specific relevant genes identified in the two laboratories. Based on the available genomic analyses of leaf senescence 10 candidate genes hypothesized to have a regulatory role in dark-induced senescence were subjected to both expression as well as functional analyses. For most of these genes senescence-specific regulation was confirmed, however, functional analyses using knock-out mutants indicated no consequence to senescence progression. The transcription factor WARK75 was found to be specifically expressed during natural and dark-induced leaf senescence. Functional analysis demonstrated that in detached leaves senescence under darkness was significantly delayed while no phenotypic consequences could be observed on growth and development, including no effect on natural leaf senescence,. Thus, WARKY75 is suggested to have a role in dark-induced senescence, but not in natural senescence. Another regulatory gene identified to have a role in senescence is MKK9 encoding for a Mitogen-Activated Protein Kinase Kinase 9 which is upregulated during senescence in harvested leaves as well as in naturally senescing leaves. MKK9 can specifically phosphorylate another kinase, MPK6. Both knockouts of MKK9 and MPK6 displayed a significantly senescence delay in harvested leaves and possibly function as a phosphorelay that regulates senescence. To our knowledge, this is the first report that clearly demonstrates the involvement of a MAP kinase pathway in senescence. This research not only revealed a new signal transduction pathway, but more important provided significant insights into the regulatory mechanisms underlying senescence in harvested leaves. In an additional line of research we have employed the promoter of the senescence-induced BFN1 gene as a handle for identifying components of the regulatory mechanism. This gene was shown to be activated during darkinduced senescence of detached leaves, as well as natural senescence. This was shown by following protein accumulation and promoter activity which demonstrated that this promoter is activated during dark-induced senescence. Analysis of the promoter established that, at least some of the regulatory sequences reside in an 80 bps long fragment of the promoter. Overall, progress was made in identification of components with a role in dark-induced senescence in this project. Further studies should be done in order to better understand the function of these components and develop approaches for modulating the progress of senescence in crop plants for the benefit of agriculture.
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Blum, Abraham, and Henry T. Nguyen. Molecular Tagging of Drought Resistance in Wheat: Osmotic Adjustment and Plant Productivity. United States Department of Agriculture, November 2002. http://dx.doi.org/10.32747/2002.7580672.bard.
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Drought stress is a major limitation to bread wheat (Triticumaestivum L.) productivity and its yield stability in arid and semi-arid regions of world including parts of Israel and the U.S. Currently, breeding for sustained yields under drought stress is totally dependent on the use of yield and several key physiological attributes as selection indices. The attempt to identify the optimal genotype by evaluating the phenotype is undermining progress in such breeding programs. Osmotic adjustment (OA) is an effective drought resistance mechanism in many crop plants. Evidence exists that there is a genetic variation for OA in wheat and that high OA capacity supports wheat yields under drought stress. The major objective of this research was to identify molecular markers (RFLPs, restriction fragment length polymorphisms; and AFLPs, amplified fragment length polymorph isms) linked to OA as a major attribute of drought resistance in wheat and thus to facilitate marker-assisted selection for drought resistance. We identified high and low OA lines of wheat and from their cross developed recombinant inbred lines (RILs) used in the molecular tagging of OA in relation to drought resistance in terms of plant production under stress. The significant positive co-segregation of OA, plant water status and yield under stress in this RIL population provided strong support for the important role of OA as a drought resistance mechanism sustaining wheat production under drought stress. This evidence was obtained in addition to the initial study of parental materials for constructing this RIL population, which also gave evidence for a strong correlation between OA and grain yield under stress. This research therefore provides conclusive evidence on the important role of OA in sustaining wheat yield under drought stress. The measurement of OA is difficult and the selection for drought resistance by the phenotypic expression of OA is practically impossible. This research provided information on the genetic basis of OA in wheat in relations to yield under stress. It provided the basic information to indicate that molecular marker assisted selection for OA in wheat is possible. The RIL population has been created by a cross between two agronomic spring wheat lines and the high OA recombinants in this population presented very high OA values, not commonly observed in wheat. These recombinants are therefore an immediate valuable genetic recourse for breeding well-adapted drought resistant wheat in Texas and Israel. We feel that this work taken as a whole eliminate the few previous speculated . doubts about the practical role of OA as an important mechanism of drought resistance in economic crop plants. As such it should open the way, in terms of both concept and the use of marker assisted selection, for improving drought resistance in wheat by deploying high osmotic adjustment.
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Snyder, Victor A., Dani Or, Amos Hadas, and S. Assouline. Characterization of Post-Tillage Soil Fragmentation and Rejoining Affecting Soil Pore Space Evolution and Transport Properties. United States Department of Agriculture, April 2002. http://dx.doi.org/10.32747/2002.7580670.bard.
Full textAbstract:
Tillage modifies soil structure, altering conditions for plant growth and transport processes through the soil. However, the resulting loose structure is unstable and susceptible to collapse due to aggregate fragmentation during wetting and drying cycles, and coalescense of moist aggregates by internal capillary forces and external compactive stresses. Presently, limited understanding of these complex processes often leads to consideration of the soil plow layer as a static porous medium. With the purpose of filling some of this knowledge gap, the objectives of this Project were to: 1) Identify and quantify the major factors causing breakdown of primary soil fragments produced by tillage into smaller secondary fragments; 2) Identify and quantify the. physical processes involved in the coalescence of primary and secondary fragments and surfaces of weakness; 3) Measure temporal changes in pore-size distributions and hydraulic properties of reconstructed aggregate beds as a function of specified initial conditions and wetting/drying events; and 4) Construct a process-based model of post-tillage changes in soil structural and hydraulic properties of the plow layer and validate it against field experiments. A dynamic theory of capillary-driven plastic deformation of adjoining aggregates was developed, where instantaneous rate of change in geometry of aggregates and inter-aggregate pores was related to current geometry of the solid-gas-liquid system and measured soil rheological functions. The theory and supporting data showed that consolidation of aggregate beds is largely an event-driven process, restricted to a fairly narrow range of soil water contents where capillary suction is great enough to generate coalescence but where soil mechanical strength is still low enough to allow plastic deforn1ation of aggregates. The theory was also used to explain effects of transient external loading on compaction of aggregate beds. A stochastic forInalism was developed for modeling soil pore space evolution, based on the Fokker Planck equation (FPE). Analytical solutions for the FPE were developed, with parameters which can be measured empirically or related to the mechanistic aggregate deformation model. Pre-existing results from field experiments were used to illustrate how the FPE formalism can be applied to field data. Fragmentation of soil clods after tillage was observed to be an event-driven (as opposed to continuous) process that occurred only during wetting, and only as clods approached the saturation point. The major mechanism of fragmentation of large aggregates seemed to be differential soil swelling behind the wetting front. Aggregate "explosion" due to air entrapment seemed limited to small aggregates wetted simultaneously over their entire surface. Breakdown of large aggregates from 11 clay soils during successive wetting and drying cycles produced fragment size distributions which differed primarily by a scale factor l (essentially equivalent to the Van Bavel mean weight diameter), so that evolution of fragment size distributions could be modeled in terms of changes in l. For a given number of wetting and drying cycles, l decreased systematically with increasing plasticity index. When air-dry soil clods were slightly weakened by a single wetting event, and then allowed to "age" for six weeks at constant high water content, drop-shatter resistance in aged relative to non-aged clods was found to increase in proportion to plasticity index. This seemed consistent with the rheological model, which predicts faster plastic coalescence around small voids and sharp cracks (with resulting soil strengthening) in soils with low resistance to plastic yield and flow. A new theory of crack growth in "idealized" elastoplastic materials was formulated, with potential application to soil fracture phenomena. The theory was preliminarily (and successfully) tested using carbon steel, a ductile material which closely approximates ideal elastoplastic behavior, and for which the necessary fracture data existed in the literature.
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Solovyanenko, Nina I. ЮРИДИЧЕСКИЕ СТРАТЕГИИ ЦИФРОВОЙ ТРАНСФОРМАЦИИ АГРАРНОГО БИЗНЕСА. DOI CODE, 2021. http://dx.doi.org/10.18411/0131-5226-2021-70004.
Full textAbstract:
t.The development of global agricultural production and food trade in recent decades implies a digital transformation and the transition to a new technological order, which is an essential factor for sustainable development. Digitalization of agriculture and the food sector is carried out on the basis of IT 2 platforms, the Internet of Things, cloud computing, big data, artificial intelligence, and blockchain technology. Fragmented and unclear legal mechanisms, slow updating of legal regulation hinder the introduction of digital solutions. A modern regulatory framework based on digital strategies should strengthen the confidence of farmers in "smart agriculture". In Russia, the legal mechanism of strategic planning covers the development of the national platform "Digital Agriculture". Digital strategies also include updating basic legislation.
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Sadka, Avi, Mikeal L. Roose, and Yair Erner. Molecular Genetic Analysis of Citric Acid Accumulation in Citrus Fruit. United States Department of Agriculture, March 2001. http://dx.doi.org/10.32747/2001.7573071.bard.
Full textAbstract:
The acid content of the juice sac cells is a major determinant of maturity and fruit quality in citrus. Many citrus varieties accumulate acid in concentrations that exceed market desires, reducing grower income and consumer satisfaction. Pulp acidity is thought to be dependent on two mechanisms: the accumulation of citric acid in the vacuoles of the juice sac cells, and acidification of the vacuole. The major aim of the project was to direct effort toward understanding the mechanism of citric acid accumulation in the fruit. The following objectives were suggested: Measure the activity of enzymes likely to be involved in acid accumulation and follow their pattern of expression in developing fruit (Sadka, Erner). Identify and clone genes which are associated with high and low acid phenotypes and with elevated acid level (Roose, Sadka, Erner). Convert RAPD markers that map near a gene that causes low acid phenotype to specific co dominant markers (Roose). Use genetic co segregation to test whether specific gene products are responsible for low acid phenotype (Roose and Sadka). Objective 1 was fully achieved. Most of the enzymes of organic acid metabolism were cloned from lemon pulp. Their expression was studied during fruit development in low and high acid varieties. The activity and expression of citrate synthase, aconitase and NADP-isocitrate dehydrogenase (IDH) were studied in detail. The role that each enzyme plays in acid accumulation and decline was evaluated. As a result, a better understanding of the metabolic changes that contribute to acid accumulation was achieved. It was found that the activity of the mitochondrial aconitase is greatly reduced early in high-acid fruits, but not in acidless ones, suggesting that this enzyme plays an important role in acid accumulation. In addition, it was demonstrated that increases in the cytosolic forms of aconitase and NADP-IDH towards fruit maturation play probably a major role in acid decline. Our studies also demonstrated that the two mechanisms that contribute to fruit acidity, vacuolar acidification and citric acid accumulation, are independent, although they are tightly co-regulated. Additional, we demonstrated that sodium arsenite, which reduce fruit acidity, causes a transient inhibition in the activity of citrate synthase, but an induction in the gene expression. This part of the work has resulted in 4 papers. Objective 3 was also fully achieved. Using bulked segregant analysis, three random amplified polymorphic DNA (RAPD) markers were identified as linked to acitric, a gene controlling the acidless phenotype of pummelo 2240. One of them, which mapped 1.2 cM from acitric was converted into sequence characterized amplified region (SCAR marker, and into co dominant restriction length polymorphism (RFLP) marker. These markers were highly polymorphic among 59 citrus accessions, and therefore, they should be useful for selecting seedling progeny heterozygous for acitric in nearly all crosses between pummelo 2240 and other citrus genotypes. This part of the project resulted in one paper. Objective 4 was also fully achieved. Clones isolated by the Israeli group were sent to the American laboratory for co segregation analysis. However, none of them seemed to co segregate with the low acid phenotype. Both laboratories invested much effort in achieving the goals of Objective 2, namely the isolation of genes that are elevated in expression in low and high acid phenotypes, and in tissue cultures treated with arsenite (a treatment which reduces fruit acidity). However, conventional differential display and restriction fragment differential display analyses could not identify any differentially expressed genes. The isolation of such genes was the major aim of a continuation project, which was recently submitted.
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Shomer, Ilan, Louise Wicker, Uzi Merin, and William L. Kerr. Interactions of Cloud Proteins, Pectins and Pectinesterases in Flocculation of Citrus Cloud. United States Department of Agriculture, February 2002. http://dx.doi.org/10.32747/2002.7580669.bard.
Full textAbstract:
The overall objective was to understand the cloud flocculation of citrus juice by characterization of the interactions between proteins and pectins, and to determine the role of PE isozymes in catalyzing this phenomenon. Specific objectives were to: 1. identify/characterize cloud-proteins in relation to their coagulable properties and affinity to pectins; 2. to determine structural changes of PME and other proteins induced by cation/pectin interactions; 3. localize cloud proteins, PME and bound protein/pectates in unheated and pasteurized juices; 4. to create "sensitized" pectins and determine their effect on clarification. The original objectives were not changed but the methods and approach were modified due to specific research requirements. Two i postulates were: 1. there is a specific interaction of cloud proteins with de-esterified regions of ! pectin and this contributes to cloud loss; 2. isozymes of pectin-methyl-esterase (PME) vary in efficiency to create sensitized pectins. The appearance of citrus fruit juice is an important quality factor and is determined by the color and turbidity that .are conferred by the suspended particles, i.e., by the cloud and its homogeneity. Under some circumstances the cloud tend to flocculate and the juice clarifies. The accepted approach to explain the clarification is based on pectin demethoxylation by PME that promotes formation of Ca-pectate. Therefore, the juice includes immediate heat-inactivation upon ~ squeezing. Protein coagulation also promotes cloud instability of citrus fruit extracts. However, the clarification mechanism is not fully understood. Information accumulated from several laboratories indicates that clarification is a more complex process than can be explained by a single mechanism. The increasing trend to consume natural-fresh juice emphasizing the importance of the knowledge to assure homogeneity of fresh juice. The research included complementary directions: Conditions that induce cloud-instability of natural- juice [IL]. Evaluate purification schemes of protein [USA]. Identifications of proteins, pectin and neutral sugars ([IL]; Structure of the cloud components using light and electron microscopy and immuno-labeling of PME, high-methoxyl-pectin (HMP) and low-methoxyl-pectin (LMP); Molecular weight of calcium sensitized pectins [US]; Evaluation of the products of PME activity [US]. Fractions and size distribution and cloud components [IL-US]. The optimal pH activity of PME is 7 and the flocculation pH of the cloud is 3-4. Thus, the c roles of PME, proteins and pectins in the cloud instability, were studied in pH ranges of 2- 7. The experiments led to establish firstly repeatable simulate conditions for cloud instability [IL]. Thermostable PME (TS-PE) known to induce cloud instability, but also thermolabile forms of PME (TL-PE) caused clarification, most likely due to the formation and dissolution of inactive :. PE-pectin complexes and displacement of a protective colloid from the cloud surface [US]. Furthermore, elimination of non-PME protein increases TS-PE activity, indicating that non-PME proteins moderate PME activity [US]. Other experiments Concomitantly with the study of the PME activity but promotes the association of cloud-proteins to pectin. Adjusting of the juice pH to f 7 retains the cloud stability and re-adjusting of the pH to 40% DE reacts to immuno-labeling in the cloud fragments, whereas
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McElwain, Terry F., Eugene Pipano, Guy H. Palmer, Varda Shkap, Stephn A. Hines, and Wendy C. Brown. Protection of Cattle against Babesiosis: Immunization against Babesia bovis with an Optimized RAP-1/Apical Complex Construct. United States Department of Agriculture, September 1999. http://dx.doi.org/10.32747/1999.7573063.bard.
Full textAbstract:
Previous research and current efforts at control of babesiosis fall short of meeting the needs of countries where the disease is endemic, such as Israel, as well as the needs of exporting countries and countries bordering on endemic areas, such as the U.S. Our long-term goal is to develop improved methods of immunization against bovine babesiosis based on an understanding of the molecular mechanisms of immune protection and parasite targets of a protective immune response. In our previous BARD project, we established the basis for focusing on rhoptry antigens as components of a subunit vaccine against bovine babesiosis, and for additional research to better characterize rhoptry associated protein-1 (RAP-1) as a target of protective immunity. In this continuation BARD project, our objectives were to [1] optimize the immune response against RAP-1, and [2] identify additional rhoptry candidate vaccine antigens. The entire locus encoding B. bovis RAP-1 was sequenced, and the rap-1 open reading frame compared among several strains. Unlike B. bigemina, in which multiple gene copies with variant domains encode RAP-1, the B. bovis RAP-1 locus contains only two identical genes which are conserved among strains. Through testing of multiple truncated constructs of rRAP-1, one or more immunodominant T cell epitopes were mapped to the amino terminal half of RAP-1. At least one linear and one conformational B cell epitope have been demonstrated in the same amino terminal construct, which in B. bigemina RAP-1 also contains an epitope recognized by neutralizing antibody. The amine terminal half of the molecule represents the most highly conserved part of the gene family and contains motifs conserved broadly among the apicomplexa. In contrast, the carboxy terminal half of B. bovis RAP-1 is less well conserved and contains multiple repeats encoding a linear B cell epitope potentially capable of inducing an ineffective, T cell independent, type 2 immune response. Therefore, we are testing an amino terminal fragment of RAP-1 (RAP-1N) in an immunization trial in cattle. Cattle have beer immunized with RAP-1N or control antigen, and IL-12 with Ribi adjuvant. Evaluation of the immune response is ongoing, and challenge with virulent B. bovis will occur in the near future. While no new rhoptry antigens were identified, our studies did identify and characterize a new spherical body antigen (SBP3), and several heat shock proteins (HSP's). The SBP3 and HSP21 antigens stimulate T cells from immune cattle and are considered new vaccine candidates worthy of further testing. Overall, we conclude that a single RAP-1 vaccine construct representing the conserved amino terminal region of the molecule should be sufficient for immunization against all strains of B. bovis. While results of the ongoing immunization trial will direct our next research steps, results at this time are consistent with our long term goal of designing a subunit vaccine which contains only the epitopes relevant to induction of protective immunity. Parallel studies are defining the mechanisms of protective immunity. Apicomplexan protozoa, including babesiosis and malaria, cause persistent diseases for which control is inadequate. The apical organelles are defining features of these complex protozoa, and have been conserved through the evolutionary process, Past and current BARD projects on babesiosis have established the validity and potential of exploiting these conserved organelles in developing improved control methods applicable to all apicomplexan diseases.
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Ohad, Itzhak, and Himadri Pakrasi. Role of Cytochrome B559 in Photoinhibition. United States Department of Agriculture, December 1995. http://dx.doi.org/10.32747/1995.7613031.bard.
Full textAbstract:
The aim of this research project was to obtain information on the role of the cytochrome b559 in the function of Photosystem-II (PSII) with special emphasis on the light induced photo inactivation of PSII and turnover of the photochemical reaction center II protein subunit RCII-D1. The major goals of this project were: 1) Isolation and sequencing of the Chlamydomonas chloroplast psbE and psbF genes encoding the cytochrome b559 a and b subunits respectively; 2) Generation of site directed mutants and testing the effect of such mutation on the function of PSII under various light conditions; 3) To obtain further information on the mechanism of the light induced degradation and replacement of the PSII core proteins. This information shall serve as a basis for the understanding of the role of the cytochrome b559 in the process of photoinhibition and recovery of photosynthetic activity as well as during low light induced turnover of the D1 protein. Unlike in other organisms in which the psbE and psbF genes encoding the a and b subunits of cytochrome b559, are part of an operon which also includes the psbL and psbJ genes, in Chlamydomonas these genes are transcribed from different regions of the chloroplast chromosome. The charge distribution of the derived amino-acid sequences of psbE and psbF gene products differs from that of the corresponding genes in other organisms as far as the rule of "positive charge in" is concerned relative to the process of the polypeptide insertion in the thylakoid membrane. However, the sum of the charges of both subunits corresponds to the above rule possibly indicating co-insertion of both subunits in the process of cytochrome b559 assembly. A plasmid designed for the introduction of site-specific mutations into the psbF gene of C. reinhardtii. was constructed. The vector consists of a DNA fragment from the chromosome of C. reinhardtii which spans the region of the psbF gene, upstream of which the spectinomycin-resistance-conferring aadA cassette was inserted. This vector was successfully used to transform wild type C. reinhardtii cells. The spectinomycin resistant strain thus obtained can grow autotrophically and does not show significant changes as compared to the wild-type strain in PSII activity. The following mutations have been introduced in the psbF gene: H23M; H23Y; W19L and W19. The replacement of H23 involved in the heme binding to M and Y was meant to permit heme binding but eventually alter some or all of the electron transport properties of the mutated cytochrome. Tryptophane W19, a strictly conserved residue, is proximal to the heme and may interact with the tetrapyrole ring. Therefore its replacement may effect the heme properties. A change to tyrosine may have a lesser affect on the potential or electron transfer rate while a replacement of W19 by leucine is meant to introduce a more prominent disturbance in these parameters. Two of the mutants, FW19L and FH23M have segregated already and are homoplasmic. The rest are still grown under selection conditions until complete segregation will be obtained. All mutants contain assembled and functional PSII exhibiting an increased sensitivity of PSII to the light. Work is still in progress for the detailed characterization of the mutants PSII properties. A tobacco mutant, S6, obtained by Maliga and coworkers harboring the F26S mutation in the b subunit was made available to us and was characterized. Measurements of PSII charge separation and recombination, polypeptide content and electron flow indicates that this mutation indeed results in light sensitivity. Presently further work is in progress in the detailed characterization of the properties of all the above mutants. Information was obtained demonstrating that photoinactivation of PSII in vivo initiates a series of progressive changes in the properties of RCII which result in an irreversible modification of the RCII-D1 protein leading to its degradation and replacement. The cleavage process of the modified RCII-D1 protein is regulated by the occupancy of the QB site of RCII by plastoquinone. Newly synthesized D1 protein is not accumulated in a stable form unless integrated in reassembled RCII. Thus the degradation of the irreversibly modified RCII-D1 protein is essential for the recovery process. The light induced degradation of the RCII-D1 protein is rapid in mutants lacking the pD1 processing protease such as in the LF-1 mutant of the unicellular alga Scenedesmus obliquus. In this case the Mn binding site of PSII is abolished, the water oxidation process is inhibited and harmful cation radicals are formed following light induced electron flow in PSII. In such mutants photo-inactivation of PSII is rapid, it is not protected by ligands binding at the QB site and the degradation of the inactivated RCII-D1 occurs rapidly also in the dark. Furthermore the degraded D1 protein can be replaced in the dark in absence of light driven redox controlled reactions. The replacement of the RCII-D1 protein involves the de novo synthesis of the precursor protein, pD1, and its processing at the C-terminus end by an unknown processing protease. In the frame of this work, a gene previously isolated and sequenced by Dr. Pakrasi's group has been identified as encoding the RCII-pD1 C-terminus processing protease in the cyanobacterium Synechocystis sp. PCC 6803. The deduced sequence of the ctpA protein shows significant similarity to the bovine, human and insect interphotoreceptor retinoid-binding proteins. Results obtained using C. reinhardtii cells exposes to low light or series of single turnover light flashes have been also obtained indicating that the process of RCII-D1 protein turnover under non-photoinactivating conditions (low light) may be related to charge recombination in RCII due to back electron flow from the semiquinone QB- to the oxidised S2,3 states of the Mn cluster involved in the water oxidation process.
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Nagabhatla, Nidhi, Panthea Pouramin, Rupal Brahmbhatt, Cameron Fioret, Talia Glickman, K. Bruce Newbold, and Vladimir Smakhtin. Migration and Water: A Global Overview. United Nations University Institute for Water, Environment and Health, May 2020. http://dx.doi.org/10.53328/lkzr3535.
Full textAbstract:
Global migration has been increasing since the 1990s. People are forced to leave their homes in search of safety, a better livelihood, or for more economic opportunities. Environmental drivers of migration, such as land degradation, water pollution, or changing climate, are acting as stronger phenomena with time. As millions of people are exposed to multiple water crises, daily needs related to water quality, lack of provisioning, excess or shortage of water become vital for survival as well for livelihood support. In turn, the crisis can transform into conflict and act as a trigger for migration, both voluntary and forced, depending on the conditions. Current interventions related to migration, including funding to manage migration remain focused on response mechanisms, whereas an understanding of drivers or so-called ‘push factors’ of migration is limited. Accurate and well-documented evidence, as well as quantitative information on these phenomena, are either missing or under-reflected in the literature and policy discourse. The report aims to start unpacking relationships between water and migration. The data used in this Report are collected from available public sources and reviewed in the context of water and climate. A three-dimensional (3D) framework is outlined for water-related migration assessment. The framework may be useful to aggerate water-related causes and consequences of migration and interpret them in various socioecological, socioeconomic, and sociopolitical settings. A case study approach is adopted to illustrate the various applications of the framework to dynamics of migration in various geographic and hydrological scenarios. The case studies reflect on well-known examples of environmental and water degradation, but with a focus on displacement /migration and socioeconomic challenges that apply. The relevance of proxy measures such as the Global Conflict Risk Index, which helps quantify water and migration interconnections, is discussed in relation to geographic, political, environmental, and economic parameters. The narratives presented in the Report also point to the existing governance mechanisms on migration, stating that they are fragmented. The report examines global agreements, institutions, and policies on migration to provide an aggerated outlook as to how international and inter-agency cooperation agreements and policies either reflected or are missing on water and climate crises as direct or indirect triggers to migration. Concerning this, the new directives related to migration governance, i.e., the New York Declaration and the Global Compact for Migration, are discussed. The Report recommends an enhanced focus on migration as an adaptation strategy to maximize the interconnectedness with the Sustainable Development Goals (SDGs). It calls for the migration discourse to look beyond from a preventative and problematic approach to a perspective emphasizing migration as a contributor towards achieving sustainable development, particularly SDGs 5, 6, 13, and 16 that aim strengthening capacities related to water, gender, climate, and institutions. Overall, the synthesis offers a global overview of water and migration for researchers and professionals engaged in migration-related work. For international agencies and government organizations and policymakers dealing with the assessment of and response to migration, the report aims to support the work on migration assessment and the implementation of the SDGs. The Report may serve as a public good towards understanding the drivers, impacts, and challenges of migration, for designing long-term solutions and for advancing migration management capabilities through improved knowledge and a pitch for consensus-building.
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Nilsson Lewis, Astrid, Kaidi Kaaret, Eileen Torres Morales, Evelin Piirsalu, and Katarina Axelsson. Accelerating green public procurement for decarbonization of the construction and road transport sectors in the EU. Stockholm Environment Institute, February 2023. http://dx.doi.org/10.51414/sei2023.007.
Full textAbstract:
Public procurement of goods and services contributes to about 15% of global greenhouse gas emissions. In the EU, public purchasing represents 15% of its GDP, acting as a major influencer on the market through the products and services acquired by governments from the local to national levels. The public sector has a role to play in leveraging this purchasing power to achieve the best societal value for money, particularly as we scramble to bend the curve of our planet’s warming. Globally, the construction and transport sectors each represent about 12% of government procurements’ GHG emissions. Furthermore, these sectors’ decarbonization efforts demand profound and disruptive technological shifts. Hence, prioritizing these sectors can make the greatest impact towards reducing the environmental footprint of the public sector and support faster decarbonization of key emitting industries. Meanwhile, the EU committed to achieving 55% reduction in GHG emissions by 2030 compared to 1990 levels. Drastic emissions reductions are needed at an unprecedented speed and scale to achieve this goal. Green Public Procurement (GPP) is the practice of purchasing goods and services using environmental requirements, with the aim of cutting carbon emissions and mitigating environmental harm throughout the life cycle of the product or service. While the EU and many of its Member States alike have recognized GPP as an important tool to meet climate goals, the formalization of GPP requirements at the EU level or among local and national governments has been fragmented. We call for harmonization to achieve the consistency, scale and focus required to make GPP practices a powerful decarbonization tool. We surveyed the landscape of GPP in the EU, with a focus on construction and road transport. Through interviews and policy research, we compiled case studies of eight Member States with different profiles: Sweden, the Netherlands, France, Germany, Estonia, Poland, Spain and Italy. We used this information to identify solutions and best practices, and to set forth recommendations on how the EU and its countries can harmonize and strengthen their GPP policies on the path toward cutting their contributions to climate change. What we found was a scattered approach to GPP across the board, with few binding requirements, little oversight and scant connective tissue from national to local practices or across different Member States, making it difficult to evaluate progress or compare practices. Interviewees, including policy makers, procurement experts and procurement officers from the featured Member States, highlighted the lack of time or resources to adopt progressive GPP practices, with no real incentive to pursue it. Furthermore, we found a need for more awareness and clear guidance on how to leverage GPP for impactful societal outcomes. Doing so requires better harmonized processes, data, and ways to track the impact and progress achieved. That is not to say it is entirely neglected. Most Member States studied highlight GPP in various national plans and have set targets accordingly. Countries, regions, and cities such as the Netherlands, Catalonia and Berlin serve as beacons of GPP with robust goals and higher ambition. They lead the way in showing how GPP can help mitigate climate change. For example, the Netherlands is one of the few countries that monitors the effects of GPP, and showed that public procurement for eight product groups in 2015 and 2016 led to at least 4.9 metric tons of avoided GHG emissions. Similarly, a monitoring report from 2017 showed that the State of Berlin managed to cut its GHG emissions by 47% through GPP in 15 product groups. Spain’s Catalonia region set a goal of 50% of procurements using GPP by 2025, an all-electric in public vehicle fleet and 100% renewable energy powering public buildings by 2030. Drawing from these findings, we developed recommendations on how to bolster GPP and scale it to its full potential. In governance, policies, monitoring, implementation and uptake, some common themes exist. The need for: • Better-coordinated policies • Common metrics for measuring progress and evaluating tenders • Increased resources such as time, funding and support mechanisms • Greater collaboration and knowledge exchange among procurers and businesses • Clearer incentives, binding requirements and enforcement mechanisms, covering operational and embedded emissions With a concerted and unified movement toward GPP, the EU and its Member States can send strong market signals to the companies that depend on them for business, accelerating the decarbonization process that our planet requires.