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1
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.
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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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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.
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Boss, Alan P. "The Fragmentation Mechanism." International Astronomical Union Colloquium 135 (1992): 195–205. http://dx.doi.org/10.1017/s0252921100006370.
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AbstractBinary and multiple star systems may form by fragmentation, that is, through break-up of a dense molecular cloud core during the dynamical collapse phase that leads to the formation of protostellar objects. This review concentrates on theoretical models of fragmentation based on numerical hydrodynamical calculations in three spatial dimensions, using both finite-difference and smoothed particle hydrodynamics techniques. A variety of recent results are described, including calculations of the fragmentation of bar-like (prolate) clouds, fragmentation in clouds with initial power-law density and angular velocity distributions, tidally-induced fragmentation, fragmentation in cooling clouds, formation of hierarchical systems, and the dividing line between clouds that fragment and those that appear to form single protostars. A brief comparison of the predicted physical and dynamical properties of the theoretical fragments with the observed properties of main-sequence and pre-main-sequence binary stars lends supports to the hypothesis that fragmentation is the dominant formation mechanism for binary and multiple star systems. The major uncertainties regarding fragmentation are the extent to which precollapse clouds are susceptible to fragmentation, and the degree to which binary fragments undergo orbital decay and possibly mergers through interactions with the enveloping disk.
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Wang, Zhenning, Junhui Yang, Jianping Yin, Xudong Li, Rui Shi, and Jianya Yi. "Study on Joint Damage of Double Prefabricated Fragments Penetrating Finite Thickness Concrete." Shock and Vibration 2023 (April 3, 2023): 1–17. http://dx.doi.org/10.1155/2023/1528983.
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In order to study the joint damage mechanism of multiple prefabricated fragments to finite thickness concrete targets, experiments on the damaging effect of a single fragment on a 300 × 300 × 100 mm concrete target were carried out, and the reliability of the simulation calculation model of single fragment damage to concrete was verified. On this basis, according to the trajectory of two fragments penetrating concrete, the double fragment penetration is divided into two penetration situations, that is, coplanar and heterogeneous. The orthogonal optimization method is used to carry out the joint damage simulation calculation of the double fragments to the concrete target by changing the fragment velocity, penetration angle, fragment spacing, and other factors. The simulation results show that the relationship between joint damage and fragment spacing is the largest when the fragment trajectories are coplanar, and the partial least squares regression coefficients affecting the joint damage time and surface joint length are 0.70 and 0.68 respectively. When the trajectory is different, the joint damage mode is relatively complex. Based on this, the joint damage degree analysis method between fragments is established, and each variable can explain 73.8% of the joint damage degree. It is found that the joint damage of the front pit area is the largest when the fragment is in different planes, and the PLS regression coefficient is −0.44. The hypothesis that joint damage is easy to occur in the area of the intersection line on the back of the target is analyzed and verified.
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Xu, Chengcheng, Kun Yu, Xinghua Xu, Xianqiang Bao, Songbing Wu, and Baokang Zhao. "Offset-FA: A Uniform Method to Handle Both Unbounded and Bounded Repetitions in Regular Expression Matching." Sensors 22, no. 20 (October 13, 2022): 7781. http://dx.doi.org/10.3390/s22207781.
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With the exponential growth of cyber–physical systems (CPSs), security challenges have emerged; attacks on critical infrastructure could result in catastrophic consequences. Intrusion detection is the foundation for CPS security protection, and deep-packet inspection is the primary method for signature-matched mechanisms. This method usually employs regular expression matching (REM) to detect possible threats in the packet payload. State explosion is the critical challenge for REM applications, which originates primarily from features of large character sets with unbounded (closures) or bounded (counting) repetitions. In this work, we propose Offset-FA to handle these repetitions in a uniform mechanism. Offset-FA eliminates state explosion by extracting the repetitions from the nonexplosive string fragments. Then, these fragments are compiled into a fragment-DFA, while a fragment relation table and a reset table are constructed to preserve their connection and offset relationship. To our knowledge, Offset-FA is the first automaton to handle these two kinds of repetitions together with a uniform mechanism. Experiments demonstrate that Offset-FA outperforms state-of-the-art solutions in both space cost and matching speed on the premise of matching correctness, and achieves a comparable matching speed with that of DFA on practical rule sets.
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Vecchi, Manuela, and Graham Carpenter. "Constitutive Proteolysis of the ErbB-4 Receptor Tyrosine Kinase by a Unique, Sequential Mechanism." Journal of Cell Biology 139, no. 4 (November 17, 1997): 995–1003. http://dx.doi.org/10.1083/jcb.139.4.995.
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The heregulin receptor tyrosine kinase ErbB-4 is constitutively cleaved, in the presence or absence of ligand, by an exofacial proteolytic activity producing a membrane-anchored cytoplasmic domain fragment of 80 kD. Based on selective sensitivity to inhibitors, the proteolytic activity is identified as that of a metalloprotease. The 80-kD product is tyrosine phosphorylated and retains tyrosine kinase activity. Importantly, the levels of this fragment are controlled by proteasome function. When proteasome activity is inhibited for 6 h, the kinase-active 80-kD ErbB-4 fragment accumulates to a level equivalent to 60% of the initial amount of native ErbB-4 (∼106 receptors per cell). Hence, proteasome activity is essential to prevent the accumulation of a significant level of ligand-independent, active ErbB-4 tyrosine kinase generated by metalloprotease activity. Proteasome activity, however, does not act on the native ErbB-4 receptor before the metalloprotease-mediated cleavage, as no ErbB-4 fragments accumulate when metalloprotease activity is blocked. Although no ubiquitination of the native ErbB-4 is detected, the 80-kD fragment is polyubiquitinated. The data, therefore, describe a unique pathway for the processing of growth factor receptors, which involves the sequential function of an exofacial metalloprotease and the cytoplasmic proteasome.
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Ohana, Ravit, Renata Klein, Roni Shneck, and Jacob Bortman. "Experimental Investigation of the Spall Propagation Mechanism in Bearing Raceways." Materials 16, no. 1 (December 21, 2022): 68. http://dx.doi.org/10.3390/ma16010068.
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This article investigates the spall propagation mechanism for ball bearing raceways by focusing on an experimental investigation of cracks that evolve in the vicinity of the spall edge. Understanding the spall propagation mechanism is an important step towards developing a physics-based prognostic tool for ball bearings. This research reflects an investigation of different spall sizes that propagate naturally both in laboratory experiments and in the field. By using a combined model of a rigid body dynamic model and a finite element model that simulates the rolling element–spall edge interaction, our results shed light on the material behavior (displacements, strains, and stresses) that creates an environment for crack formation and propagation. With the support of the experimental results and the rolling element–spall edge interaction model results, three stages of the mechanism that control fragment release from the raceway were identified. In Stage one, sub-surface cracks appear underneath the spall trailing edge. In Stage two, cracks appear in front of the trailing edge of the spall and, in Stage three, the cracks propagate until a fragment is released from the raceway. These stages were observed in all the tested bearings. In addition, other phenomena that affect the propagation of the cracks and the geometry of the fragment were observed, such as blistering and plastic deformation. We include an explanation of what determines the shape of the fragments.
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Bengtson, Hans, and Charles Giangarra. "Osteochondral Avulsion Fracture of the Anterior Cruciate Ligament Femoral Origin in a 10-Year-Old Child: A Case Report." Journal of Athletic Training 46, no. 4 (July 1, 2011): 451–55. http://dx.doi.org/10.4085/1062-6050-46.4.451.
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Objective: To describe the case of a 10-year-old football player who sustained a comminuted osteochondral avulsion fracture of the femoral origin of the anterior cruciate ligament (ACL) via a low-energy mechanism. Background: In children, both purely cartilaginous and osteochondral avulsion fractures have been described; most such ACL avulsions are from the tibial eminence. In the few previous case reports describing femoral osteochondral avulsion fractures, high-energy injury mechanisms were typically responsible and resulted in a single fracture fragment. Differential Diagnosis: Femoral osteochondral avulsion fracture at the ACL origin, femoral cartilaginous avulsion fracture at the ACL origin, midsubstance ACL tear, meniscal tear. Treatment: Sutures and a button were used to repair the comminuted fragments. Postoperatively, a modified ACL reconstruction rehabilitation program was instituted. Uniqueness: Most injuries of this nature in youngsters are caused by a high-energy mechanism of injury, result in an osteochondral avulsion fracture of the tibial eminence, and involve a single fracture fragment. Conclusions: Although they occur infrequently, ACL femoral avulsion fractures in children can result from a low-energy injury mechanism. Identifying the mechanism of injury, performing a thorough physical examination, and obtaining appropriate diagnostic studies will enable the correct treatment to be implemented, with the goal of safely returning the athlete to play.
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Liu, Han, Yao Zhao, Zhi-wei Guo, Guang-yan Huang, and Shun-shan Feng. "Influence and its Mechanism of Non-reactive Fillers on the Dispersion Characteristics of the Fragments from Charge Structures." Journal of Physics: Conference Series 2478, no. 7 (June 1, 2023): 072085. http://dx.doi.org/10.1088/1742-6596/2478/7/072085.
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Abstract With the diversified development of innovative warheads and the increasing threat of improvised explosive devices (IEDs), the charge structure filled with both explosives and non-reactive materials has attracted the attention of researchers, which is few studied. In order to obtain the fragmentation of the charge structure with part of the non-reactive filler, the X-ray radiography explosion experiment was carried out for an axisymmetric charge structure partially filled with nylon that serves as a typical non-reactive filler. The fragmentation and fragment dispersion characteristics of the charge structure were observed. Based on the results of X-ray experiments, the influence mechanism of shell breakage and fragment dispersion characteristics of the charge structure filled with non-reactive filler are analysed by using SPH numerical calculation method. The results show that the non-reactive filler will significantly affect the fragmentation of the shell and considerably reduce the fragment velocity of the fragments in the filling direction. However, the fragment dispersion direction of the charge structure is not affected by the non-reactive filler. The conclusions could be a foundation and reference for further research on new charge structures.
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Smirnova, O. A., O. N. Ivanova, F. Sh Mukhtarov, V. L. Tunitskaya, J. Jansons, M. G. Isaguliants, S. N. Kochetkov, and A. V. Ivanov. "Analysis of the Domains of Hepatitis C Virus Core and NS5A Proteins that Activate the Nrf2/ARE Cascade." Acta Naturae 8, no. 3 (September 15, 2016): 123–27. http://dx.doi.org/10.32607/20758251-2016-8-3-123-127.
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The hepatitis C virus (HCV) triggers a chronic disease that is often accompanied by a spectrum of liver pathologies and metabolic alterations. The oxidative stress that occurs in the infected cells is considered as one of the mechanisms of HCV pathogenesis. It is induced by the viral core and NS5A proteins. It is already known that both of these proteins activate the antioxidant defense system controlled by the Nrf2 transcription factor. Here, we show that this activation is mediated by domain 1 of the NS5A protein and two fragments of the core protein. In both cases, this activation is achieved through two mechanisms. One of them is mediated by reactive oxygen species (ROS) and protein kinase C, whereas the other is triggered through ROS-independent activation of casein kinase 2 and phosphoinositide 3-kinase. In the case of the HCV core, the ROS-dependent mechanism was assigned to the 37-191 a.a. fragment, while the ROS-independent mechanism was assigned to the 1-36 а.a. fragment. Such assignment of the mechanisms to different domains is the first evidence of their independence. In addition, our data revealed that intracellular localization of HCV proteins has no impact on the regulation of the antioxidant defense system.
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MacAyeal, Douglas R., Ted A. Scambos, Christina L. Hulbe, and Mark A. Fahnestock. "Catastrophic ice-shelf break-up by an ice-shelf-fragment-capsize mechanism." Journal of Glaciology 49, no. 164 (2003): 22–36. http://dx.doi.org/10.3189/172756503781830863.
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AbstractTwo disintegration events leading to the loss of Larsen A and B ice shelves, Antarctic Peninsula, in 1995 and 2002, respectively, proceeded with extreme rapidity (order of several days) and reduced an extensive, seemingly integrated ice shelf to ajumble of small fragments. These events strongly correlate with warming regional climate and accumulation of surface meltwater, supporting a hypothesis that meltwater-induced propagation of pre-existing surface crevasses may have initiated ice-shelf fragmentation.We address here an additional, subsequent mechanism that may sustain and accelerate the ice-shelf break-up once it begins. The proposed mechanism involves the coherent capsize of narrow (less than thickness) ice-shelf fragments by rolling 90° in a direction toward, or away from, the ice front. Fragment capsize liberates gravitational potential energy, forces open ice-shelf rifts and contributes to further fragmentation of the surrounding ice shelf.
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Yang, Rui, Xiaodi Wang, Hao Zha, Xiuzhang Yang, Yang Zhang, Gang Huang, and Yongjie Yang. "Classification and Fractal Characteristics of Limestone Fragments Obtained in Conventional Compression and Cyclic Loading Tests under Uniaxial and Triaxial Conditions." Advances in Materials Science and Engineering 2020 (April 24, 2020): 1–16. http://dx.doi.org/10.1155/2020/3802471.
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The mechanical response characteristics of rocks under cyclic loading conditions are crucial factors for evaluating and analyzing the stability of rock mass during underground excavation. In this study, based on fractal theory and a series of tests using the MTS815.02 rock mechanics test system, the classification and fractal characteristics of limestone specimen fragments are investigated. The results show that limestone specimens subjected to cyclic loading can generate more small-sized fragments than conventional compression, but the large-fragment-producing abilities of the two tests exhibit small difference. The mass fraction of the fragments in the cyclic loading test is obviously greater than that in the conventional test when the fragment size is less than 4.75 mm; however, only a small difference is observed between the cyclic loading tests with frequencies of 0.25 and 0.5 Hz. In the same type of test, a confining pressure is helpful in reducing the fragmentation of limestone specimen. As the size interval decreases, the shapes of limestone fragment transition from rectangular to long slice and then to square. The results also indicate that the confining pressure has a significant influence on the size-quantity and size-mass fractal dimensions of limestone fragments. The former has a positive correlation with the confining pressure, whereas the latter decreases with confining pressure. The conclusions obtained in this investigation can enrich the theoretical research on the failure response and mechanism of rock under cyclic loading conditions.
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Manna, S., T. K. Rana, C. Bhattacharya, S. Bhattacharya, S. Kundu, K. Banerjee, P. Roy, et al. "The effect of clusters on fragment emission mechanism." Journal of Physics: Conference Series 863 (June 2017): 012064. http://dx.doi.org/10.1088/1742-6596/863/1/012064.
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CHEN, YONG-JING, JING QIAN, TING-JIN LIU, ZHU-XIA LI, XI-ZHEN WU, and NENG-CHUAN SHU. "ENERGY PARTITION IN 235U FISSION REACTION INDUCED BY THERMAL NEUTRON." International Journal of Modern Physics E 21, no. 08 (August 2012): 1250073. http://dx.doi.org/10.1142/s0218301312500735.
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The partition of the total excitation energy between the fission fragments for the n th +235 U and n(En = 5.55 MeV)+235 U fission reactions are analyzed with the experimental data available. Our results show that the total excitation energy is not shared by the fragments in proportion of their masses but support the so-called energy sorting-mechanism. The temperature of the heavy fragment is generally lower than that of the light one when the shell effect does not play a strong role. As soon as the mass of heavy fragment closes to 132, its temperature becomes higher than the complementary light one because of strong shell effect. Our results also show that the heavy fragments gain more energy than the complementary light ones when the incident neutron energy increases.
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Goldsmith, Edie C., Wayne Carver, Alex McFadden, Jack G. Goldsmith, Robert L. Price, Mark Sussman, Beverly H. Lorell, Garth Cooper, and Thomas K. Borg. "Integrin shedding as a mechanism of cellular adaptation during cardiac growth." American Journal of Physiology-Heart and Circulatory Physiology 284, no. 6 (June 1, 2003): H2227—H2234. http://dx.doi.org/10.1152/ajpheart.00920.2002.
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Integrin-mediated cell-extracellular matrix (ECM) interactions are essential for multiple cellular processes; however, little is known regarding integrin turnover during these events. Recent studies have demonstrated shedding of cell surface molecules and suggested this as a potential mechanism for integrin turnover. Confocal microscopy of mouse hearts under different physiological conditions demonstrated the presence of β1-integrin-immunoreactive material in the interstitium. Culture media from neonatal rat cardiac myocytes and fibroblasts contained a 55-kDa fragment of β1-integrin. Attachment to ECM components, response to phorbol 12-myristate 13-acetate stimulation, and matrix metalloproteinase inhibition assays demonstrated that fibroblasts responded differently to the fragment compared with myocytes. The β1-integrin fragment stimulated myocyte attachment to collagen and the fragment itself bound a variety of ECM proteins. These studies indicate that as myocytes and fibroblasts change size and shape, cellular contacts with the ECM are altered, resulting in the liberation of a β1-integrin fragment from the cell surface. Integrin shedding may represent a novel mechanism of rapidly modifying cell-ECM contacts during various cellular processes.
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Kim, J. W., J. Won, S. Sohn, and C. O. Joe. "DNA-binding activity of the N-terminal cleavage product of poly(ADP-ribose) polymerase is required for UV mediated apoptosis." Journal of Cell Science 113, no. 6 (March 15, 2000): 955–61. http://dx.doi.org/10.1242/jcs.113.6.955.
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The role of the N-terminal cleavage product of poly(ADP-ribose) polymerase (PARP) on UV mediated apoptosis was investigated in cultured HeLa cells. Ultrastructural analysis of cells expressing caspase-resistant PARP (PARP(D214A)) revealed the typical features of necrosis following UV treatment. However, cells co-expressing PARP(D214A) with the N-terminal fragment of PARP containing the DNA-binding domain underwent apoptosis instead of necrosis. In this study, we have demonstrated that the DNA-binding activity of the N-terminal fragment of PARP is important for the execution of apoptosis. Point mutations were introduced in the DNA-binding sites of the N-terminal fragment. Cells co-expressing PARP(D214A) with the mutated N-terminal fragments neither stimulated apoptosis nor prevented necrosis in response to UV irradiation. The present study proposes that the DNA-binding activity of the N-terminal fragment of PARP in UV treated cells prevents cellular ATP depletion, a mechanism by which necrotic cell death is triggered.
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Gushchin, Ivan, Igor Melnikov, Vitaly Polovinkin, Andrii Ishchenko, and Valentin Gordeliy. "Crystal Structure of a Proteolytic Fragment of the Sensor Histidine Kinase NarQ." Crystals 10, no. 3 (February 27, 2020): 149. http://dx.doi.org/10.3390/cryst10030149.
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Two-component signaling systems (TCSs) are a large and important class of sensory systems in bacteria, archaea, and some eukaryotes, yet their mechanism of action is still not fully understood from the structural point of view. Many TCS receptors are elongated flexible proteins with transmembrane (TM) regions, and are difficult to work with. Consequently, truncated fragments of the receptors are often used in structural studies. However, it is not fully clear whether the structures of the fragments correspond well to their native structures in the context of full-length proteins. Recently, we crystallized a fragment of Escherichia coli nitrate/nitrite sensor histidine kinase, NarQ, encompassing the sensor, TM, and HAMP domains. Here we report that a smaller proteolytic fragment consisting of the sensor and TM domains can also be crystallized using the in meso approach. The structure of the fragment is similar to the previously determined one, with minor differences in the vicinity of the truncation site. The results show that the crystallization of such sensor–TM fragments can be accomplished and can provide information on the packing of transmembrane helices, albeit limited, and that the proteolysis may or may not be a problem during crystallization.
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Stack, M., Miriam Wahl, Salvatore Pizzo, and Tammy Moser. "The Mechanism of Action of Angiostatin: Can You Teach an Old Dog New Tricks?" Thrombosis and Haemostasis 87, no. 03 (2002): 394–401. http://dx.doi.org/10.1055/s-0037-1613016.
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SummaryWhat is angiostatin? In 1994, Folkman and colleagues published a landmark paper describing anti-tumor effects in mice with a purified fragment of plasminogen they named angiostatin (1). Although many papers have been published describing activities of cryptic polypeptides derived from plasminogen fragments, this was the first report which associated plasminogen kringles 1–4 as a suppressor of metastasis development. This review will describe what is known about the mechanism of action of angiostatin from the current literature.
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Chen, Hong Bin, Ying Zhu, Jie Wu, and Di Wu. "The Way of Obtain C6H10O+ Fragments Laser-Induced by C7H12O+ Excited State." Applied Mechanics and Materials 152-154 (January 2012): 255–59. http://dx.doi.org/10.4028/www.scientific.net/amm.152-154.255.
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We issue the theoretical calculation of C7H12O+ excited state, the corresponding vibration mode is given by the Gaussian03 calculation; In the analysis of vibration mode, it gives the possibility of C7H12O+ dissociation into fragments and the corresponding fragment analysis. In order to obtain relevant data of the fragments dissociation mechanism, we take the way analysis of C6H10O+ ion fragmentation as an example, then the bridge of experiment and theoretical calculations will provide a reference basis.
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Wang, Yan, Aidong Wang, Jianhua Wang, Xiaoran Wu, Yijie Sun, and Yan Wu. "Me-Better Drug Design Based on Nevirapine and Mechanism of Molecular Interactions with Y188C Mutant HIV-1 Reverse Transcriptase." Molecules 27, no. 21 (October 29, 2022): 7348. http://dx.doi.org/10.3390/molecules27217348.
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In this paper, the Y188C mutant HIV-1 reverse transcriptase (Y188CM-RT) target protein was constructed by homology modeling, and new ligands based on nevirapine (NVP) skeleton were designed by means of fragment growth. The binding activity of new ligands to Y188CM-RT was evaluated by structural analysis, ADMET prediction, molecular docking, energy calculation and molecular dynamics. Results show that 10 new ligands had good absorbability, and their binding energies to Y188CM-RT were significantly higher than those of wild-type HIV-1 reverse transcriptase(wt). The binding mode explained that fragment growth contributed to larger ligands, leading to improved suitability at the docking pocket. In the way of fragment growth, the larger side chain with extensive contact at terminal is obviously better than substituted benzene ring. The enhancement of docking activity is mainly due to the new fragments such as alkyl chains and rings with amino groups at NVP terminal, resulting in a large increase in hydrophobic bonding and the new addition of hydrogen bonding or salt bonding. This study is expected to provide reference for the research on non-nucleoside reverse transcriptase inhibitors resistance and AIDS treatment.
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Horton, Maureen R., Steven Shapiro, Clare Bao, Charles J. Lowenstein, and Paul W. Noble. "Induction and Regulation of Macrophage Metalloelastase by Hyaluronan Fragments in Mouse Macrophages." Journal of Immunology 162, no. 7 (April 1, 1999): 4171–76. http://dx.doi.org/10.4049/jimmunol.162.7.4171.
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Abstract Although the metalloproteinase murine metalloelastase (MME) has been implicated in lung disorders such as emphysema and pulmonary fibrosis, the mechanisms regulating MME expression are unclear. Low m.w. fragments of the extracellular matrix component hyaluronan (HA) that accumulate at sites of lung inflammation are capable of inducing inflammatory gene expression in macrophages (Mφ). The purpose of this study was to examine the effect of HA fragments on the expression of MME in alveolar Mφ. The mouse alveolar Mφ cell line MH-S was stimulated with HA fragments over time, total RNA was isolated, and Northern blot analysis was performed. HA fragments induced MME mRNA in a time-dependent fashion, with maximal levels at 6 h. HA fragments also induced MME protein expression as well as enzyme activity. The induction of MME gene expression was specific for low m.w. HA fragments and dependent upon new protein synthesis; it occurred at the level of gene transcription. We also examined the effect of HA fragments on MME expression in inflammatory alveolar Mφ from bleomycin-injured rat lungs. Although normal rat alveolar Mφ did not express MME mRNA in response to HA fragments, alveolar Mφ from the bleomycin-treated rats responded to HA fragment stimulation by increasing MME mRNA levels. Furthermore, baseline and HA fragment-induced MME gene expression in alveolar Mφ from bleomycin-treated rats was inhibited by IFN-γ. These data suggest that HA fragments may be an important mechanism for the expression of MME by Mφ in inflammatory lung disorders.
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Bulgac, Aurel. "New developments in fission studies within the time-dependent density functional theory framework." EPJ Web of Conferences 284 (2023): 04001. http://dx.doi.org/10.1051/epjconf/202328404001.
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We have extended significantly the microscopic description of the fission process by examining a larger set of observables. We extract neutron and proton numbers of fission fragments, their spins and fission fragment relative orbital angular momentum and their correlations, investigate neutrons emitted at or shortly after scission, excitation energy sharing mechanism, total kinetic energy of fission fragments, and the entanglement entropy. I will present a short overview of our simulations obtained with two independent nuclear energy density functionals.
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Dhara, Asish K., C. Bhattacharya, S. Bhattacharya, and K. Krishan. "Mechanism of intermediate mass fragment emission at low energy." Physical Review C 48, no. 4 (October 1, 1993): 1910–14. http://dx.doi.org/10.1103/physrevc.48.1910.
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Álvarez-Rodríguez, R., A. S. Jensen, E. Garrido, D. V. Fedorov, H. O. U. Fynbo, and O. S. Kirsebom. "Three-Body Decays: Structure, Decay Mechanism and Fragment Properties." Few-Body Systems 45, no. 2-4 (February 11, 2009): 149–52. http://dx.doi.org/10.1007/s00601-009-0010-2.
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Zhang, Jiao, Qing Dong, Yong Bing Dai, Bao De Sun, and Hong Lan Xie. "Study of Fragment Behavior during Columnar-Equiaxed Transition of Hypoeutectic Alloy with Synchrotron Radiation." Materials Science Forum 706-709 (January 2012): 1743–48. http://dx.doi.org/10.4028/www.scientific.net/msf.706-709.1743.
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In the present work, solidification of hypoeutectic, eutectic and hypereutectic Al-Cu alloys was illustrated by synchrotron X ray imaging, and the CET of hypoeutectic alloy was picked out to thorough investigated. The mechanism of hypoeutectic dendrites fragment behaviors among the nucleation area was studied by in-situ imaging and first-principles computation. The results show that the density difference between the fragments and the enriched melt leads to the movement of the fragments. The ejected fragments contributed to the columnar-eutectic transition and expanded the breadth of mush zone in front of the solid/liquid interface.
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Li, Meng Yang, and Gui Cheng Huo. "Characterization of the Replicon Region of the Enterococcus faecium Plasmid pEV105 Potentially Used in the Construction of Cloning Vector." Advanced Materials Research 781-784 (September 2013): 1255–59. http://dx.doi.org/10.4028/www.scientific.net/amr.781-784.1255.
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A replication probe vector (pUB380) was constructed for detecting the replicon of LAB plasmid. A cryptic plasmid, pEV105, was isolated fromEnterococcus faeciumKLDS 6.0718. Multiple restriction endonuclease fragments of pEV105 were separately ligased to pUB380. After a series of subcloning and electrotransformation, the minimal replicon of pEV105 was isolated on a 2.5 kbPstI-XbalI fragment. Replicon based on this region followed a theta-type mechanism of replication inEnterococcus faeciumKLDS 6.0718. The minimal replicon DNA fragment was sequenced and the result shows that the gene sequence homology has 99.8 % compared with partial sequence of pCIZ2 fromEnterococcus faeciumL50. Five putative ORFs were concluded by software. The result of alignments indicated two ORFs, repAl05 and repBl05, encoding two putative proteins RepAl05 and RepBl05 of 245 and 178 amino acids respectively. The 2.5 kb fragment of minimal replicon as a stable replicon is feasible for constructing food-grade cloning and expressing vector of lactic acid bacteria.
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Kang, S., Z. Guo, F. Zhao, L. Song, L. Lu, C. Wang, Z. Liu, and J. Zhao. "Lanzhou Lily polysaccharide fragment protects human umbilical vein endothelial cells from radiation-induced DNA double-strand breaks." Human & Experimental Toxicology 41 (January 2022): 096032712211401. http://dx.doi.org/10.1177/09603271221140110.
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Background Radiotherapy is widely used in the treatment of tumors. However, while killing tumor cells, radiation may also cause damage to the surrounding normal tissues. Therefore, it is very important to find safe and effective radiation protection agents. Purpose To investgate the radiation protection effect of Lanzhou Lily polysaccharide fragments (LLP). Methods: The crude polysaccharides of Lanzhou Lily were extracted from the dried bulb powder of Lilium lilium by ultrasonic-assisted hot water method, and then five different fragments were separated from the polysaccharides by DEAE-52-cellulose column. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide assay, neutral comet and immunofluorescent staining were used to investigate the effect of LPe fragment on Human Umbilical Vein Endothelial Cells (HUVEC) survival and the possible radioprotective mechanism. Results The LPe fragment (composing of mannose and glucose, with a ratio of 5.5:2.9, and the average molecular weight is 8629.8 Da), significantly promoted the proliferation of HUVECs and protected cells from X-ray-induced double-strand breaks (DSBs) in DNA, in which pretreatment with the LPe fragment at 100 μg/mL showed the most pronounced protection. In addition, the occurrence of X-ray-induced γH2AX foci was significantly reduced by treatment with the LPe fragment at 50, 100, and 200 μg/mL. Furthermore, caffeine or wortmannin in combination with the LPe fragment at 25 μg/mL significantly reduced the number of X-ray-induced γH2AX foci, indicating phosphoinositide-3 kinases (PI3K) is involved in H2AX phosphorylation in HUVECs. Conclusion These results indicate the LPe fragment has a protective effect against radiation-induced DSBs and may be used as a natural antioxidant agent.
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REN, GUOWU, TIEGANG TANG, ZHAOLIANG GUO, YUANSHUAI YANG, and QINGZHONG LI. "BRITTLE FRAGMENTATION OF AN EXPANDING RING BY MOLECULAR DYNAMICS." International Journal of Computational Materials Science and Engineering 02, no. 02 (June 2013): 1350010. http://dx.doi.org/10.1142/s2047684113500103.
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In this paper, the brittle fragmentation of an expanding ring is numerically studied by a simple atomistic model. We investigate the statistical distribution of fragment spanned over a wide range of strain rates when damage related to broken bond reaches a steady state. It is shown that at low strain rate limited number of heavy fragments can be generated because of anisotropic behavior while for high strain rate fragment can be well fitted with Weibull distribution. The physical mechanism of fragmentation process reveals that damage accompanying with numerous microcracks is found to initiate in the inner regime of the expanding ring. Furthermore, we discuss the effect of random defect on the fragmentation process.
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Weir, A. N. C., A. Nesbitt, A. P. Chapman, A. G. Popplewell P. Antoniw, and A. D. G. Lawson. "Formatting antibody fragments to mediate specific therapeutic functions." Biochemical Society Transactions 30, no. 4 (August 1, 2002): 512–16. http://dx.doi.org/10.1042/bst0300512.
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Monoclonal antibodies are increasingly being used as therapeutic agents in a wide range of indications, including oncology, inflammation and infectious disease. In most cases the basis of the therapeutic function is the high degree of specificity and affinity the antibody-based drug has for its target antigen. However, the mechanism of action (MOA), the way the drug takes advantage of this specificity to mediate a therapeutic effect, varies considerably from drug to drug. Three basic potential categories of MOAs exist: antagonists, agonists and specific delivery mechanisms to target an active function to a particular cell type. The latter functions include selective cell killing, based on Fc-mediated events, recruitment of effector cells, and drug or radioisotope delivery. The majority of these mechanisms are not necessarily optimally mediated by an IgG structure; clearly, in the case of antibody-dependent cellular cytotoxicity or complement-mediated lysis, Fc is required. However, Fab fragments (the fragment comprising one antigen-binding arm of the Y-shaped IgG molecule) can be formatted to mediate most mechanisms and have the advantage that valency and half-life can be controlled to simplify the drug and address only the mechanism required. Moreover, Fab fragments can be produced in microbial expression systems which address manufacturing issues such as scale of supply and cost of goods.
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Stalmans, Giel, Anastasia V. Lilina, Pieter-Jan Vermeire, Jan Fiala, Petr Novák, and Sergei V. Strelkov. "Addressing the Molecular Mechanism of Longitudinal Lamin Assembly Using Chimeric Fusions." Cells 9, no. 7 (July 7, 2020): 1633. http://dx.doi.org/10.3390/cells9071633.
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The molecular architecture and assembly mechanism of intermediate filaments have been enigmatic for decades. Among those, lamin filaments are of particular interest due to their universal role in cell nucleus and numerous disease-related mutations. Filament assembly is driven by specific interactions of the elementary dimers, which consist of the central coiled-coil rod domain flanked by non-helical head and tail domains. We aimed to investigate the longitudinal ‘head-to-tail’ interaction of lamin dimers (the so-called ACN interaction), which is crucial for filament assembly. To this end, we prepared a series of recombinant fragments of human lamin A centred around the N- and C-termini of the rod. The fragments were stabilized by fusions to heterologous capping motifs which provide for a correct formation of parallel, in-register coiled-coil dimers. As a result, we established crystal structures of two N-terminal fragments one of which highlights the propensity of the coiled-coil to open up, and one C-terminal rod fragment. Additional studies highlighted the capacity of such N- and C-terminal fragments to form specific complexes in solution, which were further characterized using chemical cross-linking. These data yielded a molecular model of the ACN complex which features a 6.5 nm overlap of the rod ends.
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PAOLI, Paolo, Tania FIASCHI, Paolo CIRRI, Guido CAMICI, Giampaolo MANAO, Gianni CAPPUGI, Giovanni RAUGEI, Gloriano MONETI, and Giampietro RAMPONI. "Mechanism of acylphosphatase inactivation by Woodward's reagent K." Biochemical Journal 328, no. 3 (December 15, 1997): 855–61. http://dx.doi.org/10.1042/bj3280855.
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The organ common-type (CT) isoenzyme of acylphosphatase is inactivated by Woodward's reagent K (WRK) (N-ethyl-5-phenylisoxazolium-3ʹ-sulphonate) at pH 6.0. The inactivation reaction follows apparent pseudo first-order kinetics. The dependence of the reciprocal of the pseudo first-order kinetic constant (kobs) on the reciprocal WRK concentration reveals saturation kinetics, suggesting that the WRK forms a reversible complex with the enzyme before causing inactivation. Competitive inhibitors, such as inorganic phosphate and ATP, protect the enzyme from WRK inactivation, suggesting that this reagent acts at or near to the enzyme active site. The reagent-enzyme adduct, which elicits a strong absorption band with λmax at 346 nm, was separated from unreacted enzyme by reverse phase HPLC and the modified protein was cleaved with endoproteinase Glu-C to produce fragments. The HPLC fractionation gave two reagent-labelled peptides (peak 1 and peak 2) that were analysed by ion-spray MS and sequenced. The former is VFFRKHTQAE (residues 20-29 of human CT acylphosphatase) and the latter IFGKVQGVFFRKHTQAE (residues 13-29). MS demonstrated that both peptides are WRK adducts. A fragment ion with m/z of 1171, which is present in the mass spectrum of peak 1, has been identified as a WRK adduct of the peptide fragment 20-26. The λmax at 346 nm of WRK adduct suggests that the modified residue is His-25. Five recombinant enzymes mutated in residues included in the 20-29 polypeptide stretch have been produced. Analysis of their reactivities with WRK demonstrates that His-25 is the molecular target of the reagent as its modification causes the inactivation of the enzyme. Since both His-25 → Gln and His-25 → Phe mutants maintain high catalytic activity, we suggest that the observed enzyme inactivation is caused by the reagent (covalently bound to His-25), which shields the active site.
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Kraposhin, V. S., N. D. Simich-Lafitskiy, A. L. Talis, A. A. Everstov, and M. Yu Semenov. "Formation of the cementite crystal in austenite by transformation of triangulated polyhedra." Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 75, no. 3 (May 10, 2019): 325–32. http://dx.doi.org/10.1107/s205252061900324x.
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A mechanism is proposed for the nucleus formation at the mutual transformation of austenite and cementite crystals. The mechanism is founded on the interpretation of the considered structures as crystallographic tiling onto non-intersecting rods of triangulated polyhedra. A 15-vertex fragment of this linear substructure of austenite (cementite) can be transformed by diagonal flipping in a rhombus consisting of two adjacent triangular faces into a 15-vertex fragment of cementite (austenite). In the case of the mutual austenite–cementite transformation, the mutual orientation of the initial and final fragments coincides with the Thomson–Howell orientation relationships which are experimentally observed [Thompson & Howell (1988). Scr. Metall. 22, 229–233] in steels. The observed orientation relationship between f.c.c. austenite and cementite is determined by a crystallographic group–subgroup relationship between transformation participants and noncrystallographic symmetry which determines the transformation of triangulated clusters of transformation participants. Sequential fulfillment of diagonal flipping in the 15-vertex fragments of linear substructure (these fragments are equivalent by translation) ensures the austenite–cementite transformation in the whole infinite crystal. The energy barrier for diagonal flipping in the rhombus with iron atoms in its vertices has been calculated using the Morse interatomic potential and is found to be equal to 162 kJ mol−1 at the face-centered cubic–body-centered cubic transformation temperature in iron.
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Peng, Hong, Ning Kang, Jun Xu, Patric K. Stanton, and Jian Kang. "Two Distinct Modes of Exocytotic Fusion Pore Expansion in Large Astrocytic Vesicles." Journal of Biological Chemistry 288, no. 23 (April 25, 2013): 16872–81. http://dx.doi.org/10.1074/jbc.m113.468231.
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Formation of the fusion pore is a central question for regulated exocytosis by which secretory cells release neurotransmitters or hormones. Here, by dynamically monitoring exocytosis of large vesicles (2–7 μm) in astrocytes with two-photon microscopy imaging, we found that the exocytotic fusion pore was generated from the SNARE-dependent fusion at a ring shape of the docked plasma-vesicular membrane and the movement of a fusion-produced membrane fragment. We observed two modes of fragment movements, 1) a shift fragment that shifted to expand the fusion pore and 2) a fall-in fragment that fell into the collapsed vesicle to expand the fusion pore. Shift and fall-in modes are associated with full and partial collapses of large vesicles, respectively. The astrocytic marker, sulforhodamine 101, stained the fusion-produced membrane fragment more brightly than FM 1-43. Sulforhodamine 101 imaging showed that double fusion pores could simultaneously occur in a single vesicle (16% of large vesicles) to accelerate discharge of vesicular contents. Electron microscopy of large astrocytic vesicles showed shift and fall-in membrane fragments. Two modes of fusion pore formation demonstrate a novel mechanism underlying fusion pore expansion and provide a new explanation for full and partial collapses of large secretory vesicles.
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Wang, Zhejun, Hongfu Qiang, Biao Geng, and Tingjing Geng. "Numerical simulation of fragment impacting solid rocket motors." AIP Advances 12, no. 5 (May 1, 2022): 055204. http://dx.doi.org/10.1063/5.0088412.
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For the initiation characteristics of solid rocket motors (SRMs) filled with high-energy solid propellant under fragment impact, the related theoretical critical criterion for shock initiation was established based on the critical energy criterion and equivalent analysis method. Afterward, numerical simulation of fragment impacting SRM was carried out by using the ANSYS/LS-DYNA software and the nonlinear finite element method. Based on the calculated pressure and reactivity in the high-energy solid propellant grain, the shock critical initiation velocity of SRM and its variation with different forms of fragments and impact conditions were determined. It is found that the numerical simulation results under typical conditions are in good agreement with the data calculated with the developed theoretical critical criterion for shock initiation of SRM. However, the shock initiation mechanism becomes more complex when the case thickness of SRM increases to more than 5 mm; thus, the applicability of the developed theoretical critical criterion reduces. Moreover, it is found that all the case thickness, fragment shape, material properties of the fragment, and impact attitude can significantly affect the shock critical initiation velocity of SRM, even the initiation position and time. First, the critical velocity increases linearly with the increase in case thickness, and the increment rate is faster beyond the thickness of 6 mm. Second, the shock critical initiation velocity induced by fragments with different shapes is as follows: spherical fragment > cubic fragment > cylindrical fragment, while the initiation capacity of different fragment materials is ranked as follows: tungsten alloy > 45 steel > 2024 aluminum. Third, the effects of impact attitude on the shock critical initiation velocity, position and time are complex, and these effects are also influenced by fragment shape. When the impact angle is less than 60°, there is a higher shock critical initiation velocity of SRM under inclined impact than that under positive impact. In addition, the critical velocity induced by cubic fragment is the highest under the combination of vertex impact and positive impact. The variation of the critical velocity under this condition is approximately consistent with that by impacting with cylindrical fragment. Furthermore, when the impact angle is greater than 60°, the shock critical initiation velocity of SRM is less obviously influenced by impact attitude and fragment shape. Meanwhile, the critical velocity decreases sharply under this condition, which indicates that it is easier for SRM to detonate.
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KIEPE, DANIELA, DENNIS L. ANDRESS, SUBBURAMAN MOHAN, LUDGER STÄNDKER, TIM ULINSKI, RAINER HIMMELE, OTTO MEHLS, and BURKHARD TÖNSHOFF. "Intact IGF-Binding Protein-4 and -5 and Their Respective Fragments Isolated from Chronic Renal Failure Serum Differentially Modulate IGF-I Actions in Cultured Growth Plate Chondrocytes." Journal of the American Society of Nephrology 12, no. 11 (November 2001): 2400–2410. http://dx.doi.org/10.1681/asn.v12112400.
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Abstract. Impairment of longitudinal growth among children with chronic renal failure (CRF) may be partly attributable to the inhibition of insulin-like growth factor (IGF) activity by an excess amount of high-affinity IGF-binding proteins (IGFBP). Elevated levels of immunoreactive IGFBP-4 in CRF serum are inversely correlated with the standardized heights of these children, whereas levels of IGFBP-5, which circulates mainly as proteolyzed fragments, are positively correlated with growth parameters. To delineate the respective effects of these IGFBP on growth cartilage, the biologic effects of intact and fragmented forms of IGFBP-4 and IGFBP-5 on rat growth plate chondrocytes in primary cultures were characterized. Intact IGFBP-4 and IGFBP-5 and the amino-terminal fragment IGFBP-51-169 were recombinant proteins; the carboxy-terminal fragments IGFBP-5144-252 and IGFBP-4136-237 and the amino-terminal fragment IGFBP-41-122 were purified to homogeneity from CRF hemofiltrates. Intact IGFBP-4 and, to a lesser extent, IGFBP-41-122 inhibited IGF-I-induced cell proliferation. In contrast, intact IGFBP-5 was stimulatory in the absence or presence of exogenous IGF-I, whereas the amino-terminal fragment IGFBP-51-169 was inhibitory. Studies on the mechanism by which IGFBP-4 and IGFBP-5 exert opposite effects on chondrocyte proliferation demonstrated that intact IGFBP-4 prevented the binding of 125I-IGF-I to chondrocytes, whereas intact IGFBP-5 enhanced ligand binding and was able to bind specifically to the cell membrane. These data suggest that intact IGFBP-4 and, to a lesser extent, IGFBP-41-122 act exclusively as growth-inhibitory binding proteins in the growth cartilage. IGFBP-5, however, can either stimulate (if it remains intact) or inhibit (if amino-terminal forms predominate) IGF-I-stimulated chondrocyte proliferation.
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Osborne, Timothy, and Thomas Groß. "Answer fragments." Linguistic Review 35, no. 1 (January 26, 2018): 161–86. http://dx.doi.org/10.1515/tlr-2017-0020.
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Abstract This manuscript presents a dependency grammar (DG) theory of answer fragments. The ellipsis mechanism implicated in answer fragments is called fragment ellipsis. The potential of a DG account based on the catena unit is probed, but found to be insufficient because it fails to account for certain cases involving in-situ focusing, e.g. Institutional what is hindering progress? – Authority. Therefore, an alternative account is produced, one that identifies four constraints on answer fragments, two that pertain to the elided material and two that pertain to the remnants that survive ellipsis. These four constraints then predict the shape of answer fragments to a large extent.
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Fabricant, Peter D., Yi-Meng Yen, Dennis E. Kramer, Mininder S. Kocher, Lyle J. Micheli, J. Todd R. Lawrence, Theodore J. Ganley, and Benton E. Heyworth. "Fixation of Traumatic Chondral-Only Fragments of the Knee in Pediatric and Adolescent Athletes: A Retrospective Multicenter Report." Orthopaedic Journal of Sports Medicine 6, no. 2 (February 1, 2018): 232596711775314. http://dx.doi.org/10.1177/2325967117753140.
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Background: While traditional biological principles have suggested that fragments consisting of cartilage alone cannot be reaffixed to bone with expectable long-term healing, case reports of successful healing after fixation in younger patients indicate that this concept remains incompletely explored. Purpose: To evaluate the presenting features, techniques, healing rates, and clinical and radiological results in a cohort of pediatric and adolescent athletes who underwent fixation of traumatic chondral-only fragments in the knee. Study Design: Case series; Level of evidence, 4. Methods: Patient registries at 2 tertiary care children’s hospitals were reviewed to identify patients ≤18 years old who underwent fixation of a “chondral-only” fragment in the knee, defined as the inability to visualize the fragment on injury radiographs or discern bone on the articular portion of a fragment intraoperatively. The mechanism of injury, fragment features, fixation technique, and postoperative clinical course, including timing of sports clearance, healing on postoperative magnetic resonance imaging (MRI), and any complications or reoperations, were assessed. Results: Fifteen patients with a median age at surgery of 12.7 years (interquartile range [IQR], 11.7-14.2 years) and median follow-up of 12.0 months (IQR, 6.0-19.2 months) were analyzed. All patients sustained an acute knee injury before surgery. The injured sites, as assessed on MRI, were the patella (n = 6), trochlea (n = 5), and lateral femoral condyle (n = 4). The median fragment surface area was 492.0 mm2 (IQR, 400.0-787.5 mm2). Fixation with bioabsorbable implants was performed in all patients at a median of 1.6 weeks (IQR, 1.0-2.6 weeks) after the injury. One patient (7%) sustained a fall 8 weeks postoperatively, requiring secondary surgery for excision of a dislodged fragment, and 1 patient (7%) underwent unrelated patellar stabilization surgery 3.4 years postoperatively, at which time the fragment was found to be stable. MRI was performed in 9 of 14 patients with retained fragments (median, 12.0 months postoperatively), with 5 patients (56%) showing restoration of the cartilage contour and the resolution of subchondral edema; 2 patients showed thinning but intact cartilage, 1 had cartilage thickening, and 1 had subchondral edema, fissuring, and cystic changes. The median time to return to sports for all 15 patients was 26.0 weeks (IQR, 22.8-40.9 weeks), including 2 patients who required second surgery and returned to sports at 26.1 and 191.1 weeks. Conclusion: Fixation of traumatic chondral-only fragments using bioabsorbable implants may result in successful short-term healing in the majority of pediatric and adolescent athletes.
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Piryatinska, Alexandra, and Boris Darkhovsky. "Retrospective technology of segmentation and classification for GARCH models based on the concept of the $ \epsilon $-complexity of continuous functions." Data Science in Finance and Economics 2, no. 3 (2022): 260–76. http://dx.doi.org/10.3934/dsfe.2022012.
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<abstract><p>We consider a retrospective segmentation and classification problem for GARCH models. Segmentation is the partition of a long time series into homogeneous fragments. A fragment is homogeneous if only one mechanism generates it. The points of "concatenation" of homogeneous segments we call (by analogy with the term used in the stochastic literature) points of disorder or change-points. We call classification the separation of two relatively short time series generated by different mechanisms. By classification, we mean the way in which two groups of time series with unknown generating mechanism (in particularly, generated by GARCH models) can be distinguished, and the new time series can be assigned to the class. Our model free technology is based on our concept of $ \epsilon $-complexity of individual continuous functions. This technology does not use information about the time series generation mechanism. We demonstrate our approach on time series generated by GARCH models. We present simulations and real data analysis results confirming the effectiveness of the methodology.</p></abstract>
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Iwan, Volker, and Jürgen Grotemeyer. "Elucidating the Fragmentation Mechanism of Protonated Lewis A Trisaccharide using MSn CID." European Journal of Mass Spectrometry 27, no. 6 (December 2021): 256–65. http://dx.doi.org/10.1177/14690667211069033.
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Lewis blood group antigens are a prominent example of isomeric oligosaccharides with biological activity. Understanding the fragmentation mechanism in the gas phase is essential for their identification and assignment by mass spectrometric methods such as ESI-MS. In this work, the [M + H]+ species of Lewis A trisaccharide and Lewis A trisaccharide methyl glycoside were studied by ESI-MS with FT-ICR as mass analyzer with respect to their fragmentation mechanism. The comparison between the underivatized and the methylated species has shown that the reducing end plays a key role in this mechanism. The results of this study question the existence of Z-type fragment ions after activation of the protonated species. The main product of the fragmentation are Y-type fragment ions and a combination of Y-type fragmentation and the loss of water at the reducing end instead of Z-type fragmentation. C-type fragment ions could not be detected. MS3 measurements also reveal that each fragment ion only occurs with the participation of a mobile proton and the possibility of glycosidic bond cleavage after fragmentation has already occurred at the reducing end as B2 fragment ion.
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Brosch, Roland, Wolfgang J. Philipp, Evangelos Stavropoulos, M. Joseph Colston, Stewart T. Cole, and Stephen V. Gordon. "Genomic Analysis Reveals Variation between Mycobacterium tuberculosis H37Rv and the AttenuatedM. tuberculosis H37Ra Strain." Infection and Immunity 67, no. 11 (November 1, 1999): 5768–74. http://dx.doi.org/10.1128/iai.67.11.5768-5774.1999.
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ABSTRACT Mycobacterium tuberculosis H37Ra is an attenuated tubercle bacillus closely related to the virulent type strain M. tuberculosis H37Rv. Despite extensive study, the reason for the decreased virulence of M. tuberculosis H37Ra has not been determined. A genomic approach was therefore initiated to identify genetic differences between M. tuberculosis H37Rv andM. tuberculosis H37Ra as a means of pinpointing the attenuating mutation(s). Digestion with the rare-cutting restriction endonuclease DraI revealed two polymorphisms between the strains: a 480-kb fragment in M. tuberculosis H37Rv was replaced by two fragments of 220 and 260 kb in M. tuberculosis H37Ra, while there was a ∼7.9-kb DraI fragment in M. tuberculosis H37Ra that had no counterpart in M. tuberculosis H37Rv. As the M. tuberculosis insertion sequence IS6110 contains a single DraI restriction site, it was considered possible that these polymorphisms were the result of IS6110transposition events in M. tuberculosis H37Ra, events that may have inactivated virulence genes. The 7.9-kb polymorphism was found to be due to the presence of the previously described H37Rv RvD2 deletion in M. tuberculosis H37Ra, with sequence analysis suggesting an IS6110-mediated deletion mechanism for loss of RvD2. Three other IS6110-catalyzed deletions from theM. tuberculosis H37Rv chromosome (RvD3 to RvD5) were also identified, suggesting that this mechanism plays an important role in genome plasticity in the tubercle bacilli. Comparative mapping and sequencing revealed that the 480-kb polymorphism was due to an IS6110 insertion in M. tuberculosis H37Ra nearoriC. Complementation of M. tuberculosis H37Ra with a 2.9-kb restriction fragment from M. tuberculosisH37Rv that encompassed the IS6110 insertion did not increase the survival of recombinant M. tuberculosis H37Ra in mice. In conclusion, this study describes the presence and mechanisms of genomic variation between M. tuberculosisH37Ra and M. tuberculosis H37Rv, although the role that they play in the attenuation of M. tuberculosis H37Ra is unclear.
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Duda, Taylor, Euan Zhang, and Kesava Reddy. "Craniocerebral gunshot injury bullet migration to the cardiac right ventricle." Surgical Neurology International 12 (September 30, 2021): 491. http://dx.doi.org/10.25259/sni_221_2021.
Full textAbstract:
Background: Missile embolism is the process of slow velocity projectiles penetrating into vascular spaces followed by arterial, venous, or paradoxical embolism of the fragments. This is a rare complication in craniocerebral gunshot injuries (CGI), with only five other cases previously published demonstrating pulmonary or arterial emboli from these injuries. There is a high rate of mortality from these injuries. Case Description: A patient presented with a CGI from an occipital trajectory, causing penetrating fragments into the venous sinus system. The weapon was a Glock Model 17M 9 mm with a hollow-point bullet, fired close range. Initial chest X-ray demonstrated only atelectasis. After stabilization, 18 min from the initial chest X-ray, subsequent computed tomography (CT) imaging demonstrated extensive intracranial injuries and fragmentation of the bullet with the expected devastating intracranial injuries. Unexpectedly, chest CT revealed metallic fragments in the right cardiac ventricle which was redemonstrated on follow-up chest X-ray. Unfortunately, his extensive intracranial injuries and poor clinical status were nonsurvivable, and thus the family elected to discontinue supportive measures. Conclusion: This case demonstrates radiographic imaging of a metallic intravascular fragment from CGI through presumed transvenous mechanisms. The imaging provides a consistent timeline demonstrating migration can occur in the acute phase. This study additionally supports the presumed mechanism for pulmonary of migration through the right heart. Fragment embolization should be considered in cases of acute deterioration in this patient population.
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Blok, Arno N. J., Peter H. M. Budzelaar, and Anton W. Gal. "Mechanism of Ethene Trimerization at anansa-(Arene)(cyclopentadienyl) Titanium Fragment." Organometallics 22, no. 13 (June 2003): 2564–70. http://dx.doi.org/10.1021/om030049o.
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