Artículos de revistas sobre el tema "Capillary bonds"
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Hou, Mingpeng, Qiuying Li y Yanchao Che. "Hydrophilic Modification of Polytetrafluoroethylene (PTFE) Capillary Membranes with Chemical Resistance by Constructing Three-Dimensional Hydrophilic Networks". Polymers 16, n.º 8 (19 de abril de 2024): 1154. http://dx.doi.org/10.3390/polym16081154.
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Polytetrafluoroethylene (PTFE) capillary membranes, known for the great chemical resistance and thermal stability, are commonly used in membrane separation technologies. However, the strong hydrophobic property of PTFE limits its application in water filtration. This study introduces a method whereby acrylamide (AM), N, N-methylene bisacrylamide (MBA), and vinyltriethoxysilane (VTES) undergo free radical copolymerization, followed by the hydrolysis-condensation of silane bonds, resulting in the formation of hydrophilic three-dimensional networks physically intertwined with the PTFE capillary membranes. The modified PTFE capillary membranes prepared through this method exhibit excellent hydrophilic properties, whose water contact angles are decreased by 24.3–61.2%, and increasing pure water flux from 0 to 1732.7–2666.0 L/m2·h. The enhancement in hydrophilicity of the modified PTFE capillary membranes is attributed to the introduction of hydrophilic groups such as amide bonds and siloxane bonds, along with an increase in surface roughness. Moreover, the modified PTFE capillary membranes exhibit chemical resistance, maintaining the hydrophilicity even after immersion in strong acidic (3 wt% HCl), alkaline (3 wt% NaOH), and oxidative (3 wt% NaClO) solutions for 2 weeks. In conclusion, this promising method yields modified PTFE capillary membranes with great hydrophilicity and chemical resistance, presenting substantial potential for applications in the field of water filtration.
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Bowden, Ned, Scott R. J. Oliver y George M. Whitesides. "Mesoscale Self-Assembly: Capillary Bonds and Negative Menisci". Journal of Physical Chemistry B 104, n.º 12 (marzo de 2000): 2714–24. http://dx.doi.org/10.1021/jp993118e.
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Wu, Hongkai, Ned Bowden y George M. Whitesides. "Selectivities among capillary bonds in mesoscale self-assembly". Applied Physics Letters 75, n.º 20 (15 de noviembre de 1999): 3222–24. http://dx.doi.org/10.1063/1.125284.
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Zulkifli, Muhammad Nubli, Fuaida Harun y Azman Jalar. "Effect of surface roughness and hardness of leadframe on the bondability of gold wedge bonds". Microelectronics International 36, n.º 2 (1 de abril de 2019): 62–67. http://dx.doi.org/10.1108/mi-08-2018-0053.
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Purpose This paper aims to analyze the effect of surface roughness and hardness of leadframe on the bondability of gold (Au) wedge bond using in situ inspection of laser interferometer and its relationship with the deformation and wire pull strength. Design/methodology/approach The in situ inspection of ultrasonic vibration waveform through the changes of vertical axis (y-axis) amplitude of wire bonder capillary was carried out using laser interferometer to analyze the formation of Au wedge bond. The relationship between the changes of ultrasonic waveform of capillary with the deformation and the pull strength was analyzed to evaluate the bondability of Au wedge bonds. Findings It was observed that the changes in vertical axis amplitude of ultrasonic vibration waveform of wire bonder capillary can be used to describe the process of bonding formation. The loss of ultrasonic energy was exhibited in ultrasonic vibration waveform of wire bonding on leadframe that has higher value of roughness (leadframe A) as compared to that of leadframe that has lower value of roughness (leadframe B). The lower pull strength obtained by Au wedge bond further confirms the reduction of bond formation because of the higher deformation on leadframe A as compared to that of leadframe B. Originality/value The relationship between in situ measurement using laser interferometer with the bondability or deformation and wire pull strength of Au wedge bonds on different surface roughness and hardness of leadframes is still lacking. These findings provide a valuable data in analyzing the bonding mechanisms that can be identified based on the in situ measurement of ultrasonic vibration and the bondability of Au wedge bonds.
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Rezvani, A., M. Mayer, I. Qin, J. Brunner y Bob Chylak. "Stitch Bond Process of Pd-Coated Cu Wire: Experimental and Numerical Studies of Process Parameters and Materials". International Symposium on Microelectronics 2013, n.º 1 (1 de enero de 2013): 000312–17. http://dx.doi.org/10.4071/isom-2013-tp42.
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Cost reduction is the main driver in the recent transition to Cu wire bonding from predominate Au wire bonding. Other cost reduction in packaging comes from new developments in substrates and lead frames, for example, Pre-Plated Frames (PPF) and uPPF for QFP and QFN reduce the plating and material cost. However, 2nd bonds (stitch bonds) can be more challenging on some of the new leadframe types due to the rough surface finish and thin plating thickness. Pd-coated Cu (PCC) wire has been recently introduced to improve the wire bonding process with bare Cu wire, mainly to improve reliability and enhance the stitch bond process. More fundamental studies are required to understand the influences of bonding parameters and bonding tools to improve stitch bondability. The stitch bond process of 0.7 mil diameter PCC wire on Au/Ni/Pd-plated quad flat-no lead (QFN) PPF substrate is investigated in this study. Two capillaries with the same geometry but different surface finishes are used to investigate the effect of capillary surface finish on the stitch bond process. The two capillary types are a polished finish type which is commonly used for Au wire bonding, and a granular finish capillary that has a much rougher surface finish. Process window between no stick on lead (NSOL) and short tail is compared. The effect of process parameters including bond force and table scrub amplitude is studied. The process window test results revealed that the granular capillary has larger process window and a lower chance of short tail occurrence. It has been shown that a higher scrub amplitude increases the chance of successful stitch bond formation. To further compare the capillary surface finishes, 3 sets of parameter settings with different bond force and scrub amplitude are tested. For all three parameter sets tested, the granular capillary showed better quality in bond strength. The granular capillary resulted in higher stitch pull strength compared to the polished type. A finite element model (FEM) of the process was developed to better understand the experimental observations. The amount of surface expansion (plastic deformation) of the wire at the wire and substrate interface was extracted from the model and attributed to the degree of adhesion (bonding). The model was used to confirm the experimental observation of adhesion (bonding) with different surface finish.
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Ivanek, Ondřej, Pavel Schmidt y Bohdan Schneider. "Infrared spectroscopic study of the hydration of porous glass". Collection of Czechoslovak Chemical Communications 54, n.º 4 (1989): 878–91. http://dx.doi.org/10.1135/cccc19890878.
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Infrared spectra of mesoporous and macroporous siliceous glasses were measured in the native state and after silylation, at various contents of H2O and D2O. By analysis of these spectra it was found that water is bound to the glass surface by strong hydrogen bonds between the water molecules and isolated Si-OH groups; capillary condensation was observed only in native mesoporous glasses.
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Radjai, Farhang y Vincent Richefeu. "Bond anisotropy and cohesion of wet granular materials". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 367, n.º 1909 (28 de diciembre de 2009): 5123–38. http://dx.doi.org/10.1098/rsta.2009.0185.
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We analyse the Coulomb cohesion of wet granular materials and its relationship with the distribution of capillary bonds between particles. We show that, within a harmonic representation of the bond and force states, the shear strength can be expressed as a state equation in terms of internal anisotropy parameters. This formulation involves a dependence of the shear strength on loading direction and leads to the fragile behaviour of granular materials. The contact dynamics simulations of a wet material, in which a capillary force law is prescribed, are in excellent agreement with the predictions of this model. We find that the fragile character decreases as the local adhesion is increased or the mean stress is decreased.
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Orlowski, M. y M. Lesser. "Lung lymph capillary injury-related protease". American Journal of Physiology-Lung Cellular and Molecular Physiology 257, n.º 4 (1 de octubre de 1989): L202—L208. http://dx.doi.org/10.1152/ajplung.1989.257.4.l202.
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Capillary damage induced in sheep by intravenous infusion of Escherichia coli endotoxin, oleic acid, or air emboli causes the appearance in lung lymph of a serine protease with trypsin-like activity. The time course of the appearance of the enzyme and the extent of its activity increase indicate a close association with capillary injury. The enzyme was isolated from active lymph after a 9,000-fold purification by affinity chromatography on Reactive Blue-agarose, aprotinin-agarose, and p-amino-benzamidine-agarose columns. The protein, molecular mass of 70-75 kDa, is composed of two polypeptide chains of 31 and 43 kDa linked by disulfide bonds. Studies with synthetic peptide and thioester substrates showed preferential cleavage of substrates having two or more basic amino acids and the importance for activity of secondary enzyme-substrate interactions at sites removed from the scissile bond. The specificity of the enzyme and its pattern of sensitivity to inhibition by a series of isocoumarin derivatives distinguish it from enzymes of the clotting and complement systems and also from tissue plasminogen activator and lung and skin tryptase. The origin of the enzyme, its role in capillary damage, and its physiological function remain to be established.
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Li, Heng, Yuhang Liu, Ning Sun, Zhaohua Xu, Yibiao Li y Shaohua Jiang. "Unique viscosity mutation of multi-generation hyperbranched waterborne polyurethane". Journal of Polymer Engineering 34, n.º 7 (1 de septiembre de 2014): 605–9. http://dx.doi.org/10.1515/polyeng-2013-0312.
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Abstract Different generation hyperbranched polyurethanes (HBPUs) were synthesized through the A2+B’B2 strategy. The molecular structures and viscosity were characterized by nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography (GPC). The NMR results confirmed the formation of the branched units between the segments contained in the HBPU structure. The GPC with a four-capillary bridge design differential viscometer and the Ubbelohde viscometer showed a different viscosity. For the HBPUs, the viscosity first increased to higher values then decreased to lower values, and finally increased with increasing weight, which can be attributed to the spherical structure. The growth degree of HBPUs spherical structure depends on the forming hydrogen bonds; when the hydrogen bonds reach a certain degree, the spherical structure becomes compact.
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Lawrence, M. B. y T. A. Springer. "Neutrophils roll on E-selectin." Journal of Immunology 151, n.º 11 (1 de diciembre de 1993): 6338–46. http://dx.doi.org/10.4049/jimmunol.151.11.6338.
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Abstract Using flow conditions that simulate those in post capillary venules, we have found that neutrophils attach and roll on a substrate bearing purified E-selectin. E-selectin resembles P-selectin (CD62) with regard to the dependence of attachment efficiency on wall shear stress and selectin density. In contrast, once attached, neutrophils form rolling adhesions on E-selectin that are much stronger than those on P-selectin. Rolling velocities on E-selectin are slower and have less variance than on P-selectin. With increasing shear stress, rolling velocities reach a plateau level that is dependent on E-selectin density, suggesting that the number of receptor-ligand bonds and the bond dissociation rate limit rolling velocity, and that the bonds are not broken by the applied force.
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Psota, Boleslav, Martin Buršík y Ivan Szendiuch. "The Use of Computer Simulation in the Electronic Packaging Process". Key Engineering Materials 592-593 (noviembre de 2013): 201–4. http://dx.doi.org/10.4028/www.scientific.net/kem.592-593.201.
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This paper deals with the use of the computer simulation for semiconductor chip attach investigation, where the wire bonding is the mostly used process. The main focus lays on the correct definition of the capillary trace, which is essential for creation of a good bond contact as for chip, as well for package or substrate pad. Several simulations for different shapes of loops were created and compared with real bonds, which were done based on the settings from the analysis.
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Huang, Wei-Chi, Jian-Long Ruan, Yang-Kuao Kuo y Benjamin T. H. Lee. "Low Temperature Wafer Bonding of Silicon Carbide/Aluminum Nitride". ECS Meeting Abstracts MA2023-01, n.º 29 (28 de agosto de 2023): 1789. http://dx.doi.org/10.1149/ma2023-01291789mtgabs.
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Because of the wide energy gap material properties and high compatibility with existing silicon material processing, silicon carbide (SiC) has become the preferred material for power management chips that have been used in electric vehicles. On the other hand, aluminum nitride (AlN) material has become the first choice for carrying wafers due to its high strain-resistant mechanical properties, strong dielectric coefficient, excellent thermal conductivity, and high etching resistance. In this study, the surface chemistry of silicon carbide was changed into an AlN-based material to perform wafer bonding processing to develop low-temperature bonding technology for silicon carbide/aluminum nitride materials. We found through experiments that it is quite difficult for a SiC wafer to bond with an AlN wafer even if the surfaces ofthe SiC wafer and the AlN wafer are subjected to conventional surface activation treatment using oxygen plasma or argon plasma. The possible reason is that although the surface of the SiC wafer is bombarded by oxygen or argon plasmas to generate some dangling bonds, the chemical properties of Si-C and Al-N, such as electronegativity, make it difficult to generate chemical bonds between the matching surfaces of SiC/AlN. Through a material modification technology, a high-temperature sputtering method is used to make highly active AlN clusters sputtered from the target directly bond with SiC and finally form a thin AlN layer that strongly adheres to the surface of the SiC wafer. And then through the bonding of AlN/AlN homogeneous materials, although the surface roughness measurement (RMS) cannot satisfy the condition of being less than 5 angstroms for wafer bonding, the goal of low-temperature bonding can be achieved by capillary bonding. Therefore, the SiC surface is changed into an AlN-based thin layer by high-temperature sputtering, which can further chemically bond with the AlN wafer surface by capillary bonding to achieve the low-temperature bonding of SiC/AlN, as shown in Figure 1. Reference 1. Shao-Ming Nien, Jian-Long Ruan, Yang-Kuao Kuo, and Benjamin Tien-Hsi Lee, Low-temperature rough-surface wafer bonding with aluminum nitride ceramics implemented by capillary and oxidation actions, Ceramics International, Volume 48, Issue 6, 2022 Figure 1
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Набережнов, А. А., А. Е. Совестнов, Д. А. Курдюков, Э. В. Фомин y А. В. Фокин. "Влияние ультрадиспергирования на химические сдвиги рентгеновских K-линий в оксидах меди и марганца". Физика твердого тела 62, n.º 10 (2020): 1637. http://dx.doi.org/10.21883/ftt.2020.10.49912.118.
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The results of study of shifts of X-ray Kα and Kß lines of manganese and copper obtained for CuO, MnO, Mn3O4 and MnO2 oxide nanoparticles (relative to the corresponding massive materials) are presented. Oxide nanoparticles were synthesized in the pores of borosilicate glasses with an average pore diameter of 7±1 nm from the corresponding nitrates introduced into the pores by capillary impregnation. It was found, that for nanocomposites with CuO and Mn3O4 there is a small (about ~0.1 el./atom) increase in the role of 3d electrons in the chemical bonds. On the contrary, for nanocomposites with MnO2 the role of these electrons has an opposite trend.
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Beloti, Luiz, Luis Miranda y Maria Queiroz. "Butyl Methacrylate-Co-Ethylene Glycol Dimethacrylate Monolith for Online in-Tube SPME-UHPLC-MS/MS to Determine Chlopromazine, Clozapine, Quetiapine, Olanzapine, and Their Metabolites in Plasma Samples". Molecules 24, n.º 2 (16 de enero de 2019): 310. http://dx.doi.org/10.3390/molecules24020310.
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This manuscript describes a sensitive, selective, and online in-tube solid-phase microextraction coupled with an ultrahigh performance liquid chromatography-tandem mass spectrometry (in-tube SPME-UHPLC-MS/MS) method to determine chlopromazine, clozapine, quetiapine, olanzapine, and their metabolites in plasma samples from schizophrenic patients. Organic poly(butyl methacrylate-co-ethylene glycol dimethacrylate) monolith was synthesized on the internal surface of a fused silica capillary (covalent bonds) for in-tube SPME. Analyte extraction and analysis was conducted by connecting the monolithic capillary to an UHPLC-MS/MS system. The monolith was characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FTIR). The developed method presented adequate linearity for all the target antipsychotics: R2 was higher than 0.9975, lack-of-fit ranged from 0.115 to 0.955, precision had variation coefficients lower than 14.2%, and accuracy had relative standard error values ranging from −13.5% to 14.6%, with the exception of the lower limit of quantification (LLOQ). The LLOQ values in plasma samples were 10 ng mL−1 for all analytes. The developed method was successfully applied to determine antipsychotics and their metabolites in plasma samples from schizophrenic patients.
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Arafa Musa, Ehab M. Mostafa, Mohammad M. Al-Sanea, Shaimaa R. Ahmed, Gomaa Mostafa-Hedeab y Mohamed A. Abdelgawad. "Insights Studies for Certain Natural FDA Approved Polyphenolics and Repurposing for COVID-19". International Journal of Research in Pharmaceutical Sciences 11, SPL1 (8 de diciembre de 2020): 1390–95. http://dx.doi.org/10.26452/ijrps.v11ispl1.3667.
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Natural polyphenolic drugs were approved for treatment of various diseases. Diosmin, rutin, quercetin, aesculin, genistein, hesperidin and silybin are known for their safety and have been applied for several human disorders including cancer, cardiovascular disorders, atherosclerosis, oxidative stress, capillary fragility, liver and pancreatic disorders and others. As the structures of the selected polyphenolic compounds possess variable chemical moieties with diverse chemical and electronic characters, these properties have been employed for further insights studies to predict new applications concerning the newly occurred pandemic. COVID-19 is a terrible disease that attacked millions of human populations at the end of year 2019. As the number of death cases has increased to exceed one million of humans, the early discovery of new treatment from previously approved and safe drugs is the main target of this study. Employing the putative docking studies for the selected polyphenolic drugs were done and the results were promising, all tested drugs exhibited high affinity with the selected five proteins of protease enzyme, the docking score ranged from -8.4461 to -26.1691 kcal/mol with 3-7 variable interaction bonds. Among the tested drugs, diosmin appeared as the most promising drug as it exhibited the highest energy score and interaction bonds with the most of proteins.
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Capaldo, Clément, Mourad Cheddad El Aouni, Damien Laurelli, Cyril Leven y Jean-Luc Carré. "Detection of monoclonal protein by capillary zone electrophoresis can be challenged by iodinated contrast agent interference: a case report". Biochemia medica 31, n.º 2 (15 de junio de 2021): 359–62. http://dx.doi.org/10.11613/bm.2021.021001.
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The detection of monoclonal immunoglobulins is a key element in the diagnosis of monoclonal gammopathy. In clinical practice, screening and measurement of monoclonal proteins are commonly performed using capillary zone electrophoresis (CZE). Some exogenous substances, such as iodinated contrast agents, absorb incident UV light at the same wavelengths as the peptide bonds and may therefore interfere with the detection of proteins in CZE. We herein use the description of a case to illustrate that iodinated contrast agents can mask the presence of monoclonal immunoglobulins in CZE and we discuss the strategy needed to confirm this interference. Performing immunofixation, immunosubtraction, or a second CZE at a distance from the first blood sample is not only necessary to confirm the presence of an iodinated contrast media interference but also to ensure the absence of monoclonal proteins.
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Panarello, Andrew Philip, Corey Edward Seavey, Mona Doshi, Andrew K. Dickerson, Thomas J. Kean y Bradley Jay Willenberg. "Transforming Capillary Alginate Gel (Capgel) into New 3D-Printing Biomaterial Inks". Gels 8, n.º 6 (14 de junio de 2022): 376. http://dx.doi.org/10.3390/gels8060376.
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Three-dimensional (3D) printing has great potential for creating tissues and organs to meet shortfalls in transplant supply, and biomaterial inks are key components of many such approaches. There is a need for biomaterial inks that facilitate integration, infiltration, and vascularization of targeted 3D-printed structures. This study is therefore focused on creating new biomaterial inks from self-assembled capillary alginate gel (Capgel), which possesses a unique microstructure of uniform tubular channels with tunable diameters and densities. First, extrusions of Capgel through needles (0.1–0.8 mm inner diameter) were investigated. It was found that Capgel ink extrudes as slurries of fractured and entangled particles, each retaining capillary microstructures, and that extruded line widths W and particle sizes A were both functions of needle inner diameter D, specifically power-law relationships of W~D0.42 and A~D1.52, respectively. Next, various structures were successfully 3D-printed with Capgel ink, thus demonstrating that this biomaterial ink is stackable and self-supporting. To increase ink self-adherence, Capgel was coated with poly-L-lysine (PLL) to create a cationic “skin” prior to extrusion. It was hypothesized that, during extrusion of Capgel-PLL, the sheared particles fracture and thereby expose cryptic sites of negatively-charged biomaterial capable of forming new polyelectrolyte bonds with areas of the positively-charged PLL skin on neighboring entangled particles. This novel approach resulted in continuous, self-adherent extrusions that remained intact in solution. Human lung fibroblasts (HLFs) were then cultured on this ink to investigate biocompatibility. HLFs readily colonized Capgel-PLL ink and were strongly oriented by the capillary microstructures. This is the first description of successful 3D-printing with Capgel biomaterial ink as well as the first demonstration of the concept and formulation of a self-adherent Capgel-PLL biomaterial ink.
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Oztuna, A. y H. Nazir. "(A210) Chemical Sensor Trial for Nerve Agent Differentiation: Impact of Hydrogen Bonds on Detection". Prehospital and Disaster Medicine 26, S1 (mayo de 2011): s58. http://dx.doi.org/10.1017/s1049023x11002007.
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Chemical warfare agents (CWAs) are a growing concern for many countries. The uses of CWAs as they can be synthesized by simple chemical reactions, and often have an extremely high toxicity. Conventional, analytical techniques for the detection of nerve agents from environmental and biological samples include gas chromatography, liquid chromatography, gas chromatography– mass spectrometry, ion chromatography, atomic emission detection, capillary electrophoresis, etc. These methods have very high sensitivity, reliability, and precision. However, in spite of these advantages, these techniques require expensive instrumentation and highly trained personnel. They also are time-consuming and unsuitable for field analysis. To meet these prerequisites of rapid warning and field deployment, more compact, low-cost instruments are highly desirable for facilitating the task of on-site monitoring of nerve agents. a quartz crystal microbalance (QCM) sensors could be a reliable and promising alternative to routine methods because of their simplicity, ease of use and high sensitivity and selectivity.1,2 In this study, we prepared QCM sensors functionalized with –NH2 and –COOH groups for differentiate diethyl ester phosphonic acid (DEHP) from diethyl phthalate (DEP), which are known as G and VX agent stimulants respectively. Infrared spectroscopy (FT-IR) was performed in order to characterize the surface of the sensor after modification and the detection. Furthermore, impact of hydrogen bonds on detection will be discussed.
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Liu, Ruoting, Wenrui Chi, Qihao Zhu, Hailan Jin, Jian Li y Lijuan Wang. "Capillary-Assisted Monitoring of Milk Freshness via a Porous Cellulose-Based Label with High pH Sensitivity". Foods 12, n.º 9 (29 de abril de 2023): 1857. http://dx.doi.org/10.3390/foods12091857.
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A cellulose-based matrix for monitoring milk freshness (MF) was produced from rice straw particles (RSPs) in a 0.125–0.150 mm that was bis-quaternized to attach bromocresol purple (BP) as a sensor. Under alkali conditions, the obstinate structure of the rice straw had opened, thereby improving the accessibility of the cellulose. Bis-quaternization created more adsorption sites for BP. The maximum adsorption capacity was 97.68 mg/g. The sensors were interwoven with cellulosic fibers to form the cellulose-based label with a relatively loose three-dimensional structure via hydrogen bonds. As the proportion of BP-BCRPs was increased from 10% to 40%, the air permeability of the label increased from 3.76 to 15.01 mm/s, which increased the response to the tested gases (10.12 s for 1 mL of acetic acid). The intelligent label exhibited excellent sensitivity at pH values of 3–9 with highly saturated color changes. During the storage period, the label color shifted from blue-purple to yellow as acidity was increased from 17.24 to 19.8 °T due to capillarity action, providing a timely warning to consumers. The prepared colorimetric porous intelligent cellulose-based label is suitable for monitoring of MF.
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Pérez, Paloma, Carolina Simó, Christian Neusüss, Matthias Pelzing, Julio San Román, Alejandro Cifuentes y Alberto Gallardo. "New Pseudopeptidic Cross-Linker Containing Urea Bonds: Study of Its Degradation Routes in Aqueous Media Using Capillary Electrophoresis-Mass Spectrometry". Biomacromolecules 7, n.º 3 (marzo de 2006): 720–27. http://dx.doi.org/10.1021/bm050577e.
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Ge, Liangpeng y Shixuan Chen. "Recent Advances in Tissue Adhesives for Clinical Medicine". Polymers 12, n.º 4 (18 de abril de 2020): 939. http://dx.doi.org/10.3390/polym12040939.
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Tissue adhesives have attracted more attention to the applications of non-invasive wound closure. The purpose of this review article is to summarize the recent progress of developing tissue adhesives, which may inspire researchers to develop more outstanding tissue adhesives. It begins with a brief introduction to the emerging potential use of tissue adhesives in the clinic. Next, several critical mechanisms for adhesion are discussed, including van der Waals forces, capillary forces, hydrogen bonding, static electric forces, and chemical bonds. This article further details the measurement methods of adhesion and highlights the different types of adhesive, including natural or biological, synthetic and semisynthetic, and biomimetic adhesives. Finally, this review article concludes with remarks on the challenges and future directions for design, fabrication, and application of tissue adhesives in the clinic. This review article has promising potential to provide novel creative design principles for the generation of future tissue adhesives.
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Josell, Daniel y Frans Spaepen. "Surfaces, Interfaces, and Changing Shapes in Multilayered Films". MRS Bulletin 24, n.º 2 (febrero de 1999): 39–43. http://dx.doi.org/10.1557/s0883769400051538.
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It is generally recognized that the capillary forces associated with internal and external interfaces affect both the shapes of liquid-vapor surfaces and wetting of a solid by a liquid. It is less commonly understood that the same phenomenology often applies equally well to solid-solid or solid-vapor interfaces.The fundamental quantity governing capillary phenomena is the excess free energy associated with a unit area of interface. The microscopic origin of this excess free energy is often intuitively simple to understand: the atoms at a free surface have “missing bonds”; a grain boundary contains “holes” and hence does not have the optimal electronic density; an incoherent interface contains dislocations that cost strain energy; and the ordering of a liquid near a solid-liquid interface causes a lowering of the entropy and hence an increase in the free energy. In what follows we shall show how this fundamental quantity determines the shape of increasingly complex bodies: spheres, wires, thin films, and multilayers composed of liquids or solids. Crystal anisotropy is not considered here; all interfaces and surfaces are assumed isotropic.Consideration of the equilibrium of a spherical drop of radius R with surface free energy γ shows that pressure inside the droplet is higher than outside. The difference is given by the well-known Laplace equation:This result can be obtained by equating work done against internal and external pressure during an infinitesimal change of radius with the work of creating a new surface.
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Jiao, Yunhao, Yujin Yao, Heping Qiu, Huaxin Chen y Yongchang Wu. "A Molecular Dynamics Analysis of the Thickness and Adhesion Characteristics of the Quasi-Liquid Layer at the Asphalt–Ice Interface". Materials 17, n.º 6 (17 de marzo de 2024): 1375. http://dx.doi.org/10.3390/ma17061375.
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The quasi-liquid layer (QLL), a microstructure located between ice and an adhering substrate, is critical in generating capillary pressure, which in turn influences ice adhesion behavior. This study employed molecular dynamics (MD) methods to obtain QLL thickness and utilized these measurements to estimate the adhesive strength between ice and asphalt. The research involved constructing an ice–QLL–asphalt MD model, encompassing four asphalt types and five temperature ranges from 250 K to 270 K. The QLL thickness was determined for various asphalts and temperatures using the tetrahedral order parameter gradient. Additionally, capillary pressure was calculated based on the QLL thickness and other geometric parameters obtained from the MD analysis. These findings were then compared with ice adhesion strength data acquired from pull-off tests. The results indicate that QLL thickness varies with different asphalt types and increases with temperature. At a constant temperature, the QLL thickness decreases in the order of the basal plane, primary prism plane, and secondary prism plane. Furthermore, the adhesion strength of the QLL diminishes as the temperature rises, attributed to the disruption of hydrogen bonds at lower temperatures. The greater the polarity of the asphalt’s interface molecules, the stronger the adhesion strength and binding free energy. The MD simulations of the asphalt–ice interface offer insights into the atomic-scale adhesive properties of this interface, contributing to the enhancement in QLL property prediction and calibration at larger scales.
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Kong, Zhengyang, Elvis K. Boahen, Hayoung Lim y Do Hwan Kim. "Autonomous Self-Healable, Ag Nanowire-Polymer Composite Flexible Electrode for Underwater Sensors". Journal of Flexible and Printed Electronics 2, n.º 2 (diciembre de 2023): 229–42. http://dx.doi.org/10.56767/jfpe.2023.2.2.229.
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The development of self-healing electrodes tailored for underwater wearable sensors is paramount to broaden their applications in aquatic environments. However, autonomous self-healing of flexible electrodes, which encompasses both mechanical and electrical performance, remains a formidable challenge. Here, we present the development of a self-healing flexible electrode (AgNW–FPU), incorporating Ag nanowires (AgNWs) and a fluorine functionalized polyurethane (FPU) substrate. The FPU polymer was designed by systematically adjusting the dynamic bonds and chain mobility to achieve fast self-healing speed and efficiency. Higher dynamic bond content and good chain mobility led to the highest self-healing speed, both in air and underwater. The introduction of a fluorinated side chain enhanced hydrophobicity, further improving underwater self-healing. The AgNW–FPU electrode demonstrated fast underwater self-healing, driven by capillary bridges and enhanced contact between fractured nanowires. The AgNW-FPU electrodes were employed in a capacitive pressure sensor, showcasing its potential for underwater sensing applications.
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Dobrzycki, Lukasz. "Towards clathrates. 2. The frozen states of hydration of tert-butanol". Zeitschrift für Kristallographie - Crystalline Materials 233, n.º 1 (26 de enero de 2018): 41–49. http://dx.doi.org/10.1515/zkri-2017-2074.
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AbstractA new crystal structure oftert-butanol and water crystallizing as the decahydrate is reported. The crystallization of the mixture in the desired molar ratio was performed in a capillary placed directly on a goniometer of a single crystal diffractometer at 200 K and ambient pressure using focused IR laser radiation. The crystals were grown while the melting zone formed by the IR laser was moved along the capillary. Usually the crystallization process should be long enough (hours) in order to obtain a good quality single crystal. However, in the case oftert-butanol decahydrate, such a long process led to separation of the ice and alcohol. Only fast crystallization taking tens of seconds allowed crystallization of the desired crystalline phase. In the decahydratetert-butanol molecules are located in channels formed by water molecules. Hydroxyl groups are anchored to the water framework via hydrogen bonds. All water molecules in the structure have hydrogen atoms disordered equally over two sites; the hydroxyl group is likewise disordered. This effect is observed at both, 200 K and 100 K. Raman spectra recorded for the crystalline phase suggest dynamic disorder at higher temperature, converting to static at lowerT. The decahydrate oftert-butanol, together with already known itsdi- andhepta-hydrates, display similar features to those observed for series oftert-butylamine hydrates. The latter structures behave as frozen steps of amine hydration observed as crystal structures leading, at maximum dilution, to hexagonal ice. Hydrates oftert-butanol nicely follow this tendency completing the relationship found for thetert-butylamine: water system.
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BOGDANOVA, Ekaterina V., Elena I. MELNIKOVA y Irina B. KOSHEVAROVA. "THE RESEARCH OF THE TYPES OF MOISTURE BONDS IN PROTEIN-CARBOHYDRATE CONCENTRATES OF CHEESE WHEY". Periódico Tchê Química 17, n.º 34 (20 de marzo de 2020): 33–44. http://dx.doi.org/10.52571/ptq.v17.n34.2020.51_p34_pgs_33_44.pdf.
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The purpose of the research is to improve the technology of producing cheese whey proteincarbohydrate concentrates, in terms of binding moisture with the main components. Objects of the research were natural cheese whey obtained in the production of Rossiyskii cheese and ultrafiltration cheese whey concentrates with protein dry matter percentage of 35 and 55%, produced with the use of MMS Swissflow UF industrial ultrafiltration unit with ceramic membranes. The chemical composition and Physico-chemical properties of raw materials and the finished product have been studied using standard methods. Three stages of sample dehydration have been identified. They conform to moisture release with different bonds and energy. Stage I is the production area where unbound moisture is heated and removed, and water molecules are held by weak capillary forces. Stage II is the production area for immobilized moisture removal. Stage III is the production area for chemically bound water removal, which conforms to the residual moisture after drying the sample. An increase in the least mobile water and a change in the ratio between different types of moisturebinding have been observed with an increase in the protein mass fraction in the dry matter of the samples. It has been found that the Maillard reaction occurred in cheese whey concentrates with protein dry matter percentage of 35 and 55% at the temperatures above 78 and 70 °C, respectively. The temperature range of the unbound moisture release was increasing during the drying process due to an increase of the protein content in concentrates as well as the rate of interaction between proteins and lactose leading to non-enzymatic browning of dry products. It has been established that drying cheese whey protein-carbohydrate concentrates with protein dry matter percentage of 35, and 55% is inexpedient at temperatures exciding 130 and 173 °C, respectively.
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Dziubek, Kamil F. y Andrzej Katrusiak. "Structure–melting relations in isomeric dibromobenzenes". Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials 70, n.º 3 (31 de mayo de 2014): 492–97. http://dx.doi.org/10.1107/s2052520614011445.
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1,4-Dibromobenzene melts at a considerably higher temperature than the 1,2- and 1,3-isomers. This melting-point difference is consistent with the molecular symmetry, as described by Carnelley's rule, and with the frequency of Br...Br halogen bonds. The lowest melting point of 1,3-dibromobenzene correlates with its two symmetry-independent molecules, indicating their inability to pack closely. Single crystals of 1,2- and 1,3-dibromobenzene have been grown under isochoric conditions in a diamond–anvil cell and at isobaric conditions in a glass capillary. Their structures have been determinedin situby X-ray diffraction. At 295 K 1,2-dibromobenzene crystallizes at 0.2 GPa as orthorhombic, space groupPbca,Z′ = 1, and 1,3-dibromobenzene at 0.3 GPa as orthorhombic, space groupP212121,Z′ = 2. The same crystal phases are formed at ambient pressure by freezing these liquids below 256.15 and 248.45 K, respectively. The third isomer, 1,4-dibromobenzene, is a solid at room temperature and crystallizes as monoclinic, space groupP21/a. Striking relations between the structures and melting points of the corresponding dibromobenzene and dichlorobenzene isomers have been discussed.
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Pongpilaipruet, Angkana y Rathanawan Magaraphan. "Ozonolysis by High Voltage Power Supply to the Melt-Extrudates of Admicelled Rubber and Natural Rubber". Advanced Materials Research 747 (agosto de 2013): 459–62. http://dx.doi.org/10.4028/www.scientific.net/amr.747.459.
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Ozone (O3) is created when diatomic oxygen (O2) is exposed to an electrical field or ultraviolet light. The reaction occurring between double bonds in the unsaturated elastomer chain of natural rubber (NR) and O3 is known as ozonolysis which in turn results in a variety of products. The end result of these reactions is polymer chain scission. In this study, NR was employed as a core substrate for admicellar polymerization of pyrrole (Py) and methyl methacrylate (MMA). Ozonolysis that was studied by using a high voltage power supply connected to a capillary rheometer. These melt extrudates were then subjected to the ozonolysis at a voltage of 9 kV. The effect of ozonolysis at extrude conditions on the chain scission of both extrudates was investigated by melt flow rate measurement (MFR) and Fourier transform infrared spectroscopy. The admicelled rubber showed smaller in percent change of MFR and intensity of changed structure from ozonolysis which suggesting better ozone resistance of the admicelled rubber. Moreover, PMMA-NR showed better ozone stability than PPy-NR.
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Myher, J. J., A. Kuksis y L. Y. Yang. "Stereospecific analysis of menhaden oil triacylglycerols and resolution of complex polyunsaturated diacylglycerols by gas–liquid chromatography on polar capillary columns". Biochemistry and Cell Biology 68, n.º 1 (1 de enero de 1990): 336–44. http://dx.doi.org/10.1139/o90-046.
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The sn-1,2-, sn-2,3-, and X-1,3-diacylglycerols derived by Grignard degradation of purified menhaden oil triacylglycerols were isolated by conventional thin-layer chromatography with boric acid complexing. The sn-1,2(2,3)-diacylglycerols were resolved into sn-1,2- and sn-2,3-diacylglycerols by stepwise digestion with phospholipase C of the corresponding phosphatidylcholines and the positional distribution of the fatty acids were determined. Diacylglycerols were converted into trimethylsilyl ethers and resolved on the basis of molecular weight and degree of unsaturation by gas–liquid chromatography using a polar capillary column and isothermal or programmed temperatures. The order of chromatographic elution was established for more than 70 major and minor species by reference to primary and secondary diacylglycerol standards and by calculation of relative retention times. The identified molecular species ranged in carbon number from 28 to 44 and in double bond number from 0 to 12 being made up of C14–C22 fatty acids with 0 to 6 double bonds each and representing the n – 9, n – 6, n – 4, n – 3, and n – 1 series. The gas–liquid chromatographic determinations yielded proportions of all major species that were consistent with those calculated from the knowledge of the stereospecific distribution of the fatty acids in the original triacylglycerol molecules.Key words: Grignard degradation, rac-phosphatidylcholines, phospholipase C, enantiomeric diacylglycerols, thin-layer chromatography, molecular species of diacylglycerols, composition of fatty acids.
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Abebe, Adane Muche, Gian Domenico Soraru, Ganesh Thothadri, Dinsefa Mensur Andoshe, Andrea Zambotti, Gulam Mohammed Sayeed Ahmed, Vineet Tirth y Ali Algahtani. "Synthesis and Characterization of High Surface Area Transparent SiOC Aerogels from Hybrid Silicon Alkoxide: A Comparison between Ambient Pressure and Supercritical Drying". Materials 15, n.º 4 (9 de febrero de 2022): 1277. http://dx.doi.org/10.3390/ma15041277.
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In this article, highly porous and transparent silicon oxycarbide (SiOC) gels are synthesized from Bis(Triethoxysilyl) methane (BTEM). The gels are synthesized by the sol-gel technique followed by both ambient pressure and supercritical drying. Then, the portion of wet gels have been pyrolyzed in a hydrogen atmosphere at 800 and 1100 °C. The FT-IR spectroscopy analysis and nitrogen sorption results indicate the successful synthesis of Si-O-Si bonds and the formation of mesopores. From a hysteresis loop, the SiOC ceramics showed the H1 type characteristic with well-defined cylindrical pore channels for the aerogel and the H2 type for the ambigel samples, indicating that the pores are distorted due to the capillary stress. The produced gels are mesoporous materials having high surface areas with a maximum of 1140 m2/g and pore volume of 2.522 cm3/g obtained from BTEM aerogels. The pyrolysis of BTEM aerogels at 800 °C results in the production of a bulk and transparent sample with a slightly pale white color, while BTEM xerogels are totally transparent and colorless at the same temperature. At 1100 °C, all the aerogels become opaque brown, confirming the formation of free carbon and crystalline silicon.
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Kanatieva, Anastasiia Yu, Dmitry A. Alentiev, Valeria E. Shiryaeva, Alexander A. Korolev y Alexander A. Kurganov. "Impact of the Polymer Backbone Structure on the Separation Properties of New Stationary Phases Based on Tricyclononenes". Polymers 14, n.º 23 (24 de noviembre de 2022): 5120. http://dx.doi.org/10.3390/polym14235120.
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The main purpose of this paper is to compare the chromatographic properties of capillary columns prepared with polymers with different backbone structures and to demonstrate the possibility of polymer differentiation via inverse gas chromatography. With the use of addition and metathesis types of polymerization of tricyclononenes, two new stationary phases were prepared. The metathesis polymer contained double bonds in the polymeric backbone while the backbone of the addition polymer was fully saturated and relatively mobile. A comparison of the separation and adsorption properties of new phases with conventional gas chromatography (GC) stationary phases clearly indicated their non-polar characteristics. However, the difference in the polymer structure appeared to have very little effect on the stationary phase separation properties, so other parameters were used for polymer characterization. The thermodynamic parameters of the sorption of alkanes and aromatic compounds in both polymeric stationary phases were also very similar; however, the entropy of sorption for hydrocarbons with seven or more carbon atoms was different for the two polymers. An evaluation of the specific surface energy of the stationary phases also allowed us to discriminate the two stationary phases.
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Pardridge, William M. "Drug Transport across the Blood–Brain Barrier". Journal of Cerebral Blood Flow & Metabolism 32, n.º 11 (29 de agosto de 2012): 1959–72. http://dx.doi.org/10.1038/jcbfm.2012.126.
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The blood–brain barrier (BBB) prevents the brain uptake of most pharmaceuticals. This property arises from the epithelial-like tight junctions within the brain capillary endothelium. The BBB is anatomically and functionally distinct from the blood–cerebrospinal fluid barrier at the choroid plexus. Certain small molecule drugs may cross the BBB via lipid-mediated free diffusion, providing the drug has a molecular weight <400 Da and forms <8 hydrogen bonds. These chemical properties are lacking in the majority of small molecule drugs, and all large molecule drugs. Nevertheless, drugs can be reengineered for BBB transport, based on the knowledge of the endogenous transport systems within the BBB. Small molecule drugs can be synthesized that access carrier-mediated transport (CMT) systems within the BBB. Large molecule drugs can be reengineered with molecular Trojan horse delivery systems to access receptor-mediated transport (RMT) systems within the BBB. Peptide and antisense radiopharmaceuticals are made brain-penetrating with the combined use of RMT-based delivery systems and avidin–biotin technology. Knowledge on the endogenous CMT and RMT systems expressed at the BBB enable new solutions to the problem of BBB drug transport.
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Azoulay, Jacob. "Memory features of water cyclically treated with magnetic field". World Journal of Engineering 13, n.º 2 (8 de abril de 2016): 120–23. http://dx.doi.org/10.1108/wje-04-2016-015.
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Purpose This paper aims to study the properties of cyclically treated pure water in magnetic fields and its comparison with pure untreated water. Design/methodology/approach The magnetic treatment was carried out using a static permanent magnetic field and alternating electromagnetic field. We have measured the magnetic effect on the rising level of the water in capillary tubes and the relaxation time for restoration after removing the magnetic field. The dependence on the magnetic field intensity and on the cyclical time treatments was investigated and discussed. The results of magnetization by static field and electromagnetic field were compared and discussed. It is well known that the clustering structure of hydrogen-bonded chains and polarization effects of water molecules are enhanced after magnetization. Therefore, each experimental series was followed by a “memory” test, the results of which enabled us to have some insights into the molecular and hydrogen bonds of water. Findings It was found that water remembers and keeps the impact of its passing through a magnetic field for several hours and also that many mechanical features were changed under cyclical treatment of a magnetic field.
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Aitzetmüller, K., Gisela Werner y Nansadyn Tsevegsüren. "Screening of seed lipids for γ-linolenic acid: Capillary gas-liquid chromatographic separation of 18:3 fatty acids with Δ5 and Δ6 double bonds". Phytochemical Analysis 4, n.º 6 (noviembre de 1993): 249–55. http://dx.doi.org/10.1002/pca.2800040602.
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Luksha, O. V., N. Ch Belous, S. P. Rodtsevich y V. M. Chernetskaya. "Hydro-phobization of fine-grained portland cement concrete with spent filtering and bleaching powders". Proceedings of the National Academy of Sciences of Belarus, Chemical Series 60, n.º 1 (4 de marzo de 2024): 63–72. http://dx.doi.org/10.29235/1561-8331-2024-60-1-63-72.
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The results of studying the chemical and phase composition of oil and fat production wastes - used filtering and bleaching powders are presented. It has been established that the crystalline phase of the powders is represented mainly by silicon dioxide, as well as aluminum, iron and titanium oxides, sodium and potassium aluminosilicates. The organic part of the spent filtering powders consists of waxes, while the bleaching powder phase contains fats and free fatty acids with unsaturated bonds. The concentration of water-soluble organic compounds in filtering powders does not exceed 30 mg/dm3, and in spent bleaching powder reaches 700–900 mg/dm3, which explains the decrease in surface tension at the solution-air interface in its presence and contributes to an increase in the effectiveness of its hydrophobic action in Portland cement systems. Analysis of the results of the study of the hardening process, strength, hydrophysical and corrosion properties of fine-grained Portland cement concretes confirmed the maximum effect of increasing the draft of the cone and mobility, due to the air entrainment of Portland cement mortars and their saturation with air microbubbles when bleaching powder is introduced. At the same time, in the presence of spent filtering powders, additional air entrainment, and, consequently, plasticization, is not observed. As a result of the formation of a protective layer in Portland cement concrete, there is difficulty in the access of water molecules to the solid phase, which leads to a significant improvement in hydrophysical properties. There is a decrease in water absorption by 45–54 %, salt absorption – by an average of 55 %, as a result, an increase in the coefficient of salt resistance of materials is recorded. The maximum effect of reducing salt corrosion and increasing the salt resistance coefficient of materials is due to the peculiarities of the capillary-porous structure of concrete in the presence of bleaching powder, the kinetics of diffusion of salt solutions in them, and the decrease in capillary suction and crystallization pressure of salts in the pores of the material.
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Delvaux, Cédric, Philippe Massonnet, Christopher Kune, Jean R. N. Haler, Gregory Upert, Gilles Mourier, Nicolas Gilles, Loïc Quinton, Edwin De Pauw y Johann Far. "Combination of Capillary Zone Electrophoresis-Mass Spectrometry, Ion Mobility-Mass Spectrometry, and Theoretical Calculations for Cysteine Connectivity Identification in Peptides Bearing Two Intramolecular Disulfide Bonds". Analytical Chemistry 92, n.º 3 (29 de diciembre de 2019): 2425–34. http://dx.doi.org/10.1021/acs.analchem.9b03206.
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Lee, Changho, Q. Hung Truong y Jong-Sub Lee. "Cementation and bond degradation of rubber–sand mixtures". Canadian Geotechnical Journal 47, n.º 7 (julio de 2010): 763–74. http://dx.doi.org/10.1139/t09-139.
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Cementation influences the mechanical behavior of soils. The effects of cementation and bond degradation are investigated for lightly cemented rigid sand and soft rubber particle mixtures subjected to vertical loading under the K0 condition. Cemented and uncemented specimens were prepared with various sand volume fractions. The propagation velocity of small strain body waves was measured by piezo materials, incorporated within an oedometer. Cemented specimens exhibited a bilinear behavior in the semi-log plot (vertical strain versus log of vertical stress). Vertical strains of a cemented specimen normalized by an uncemented specimen show that the stress–strain behavior is controlled by several different mechanisms and forces: capillary force, cementation bonds, and interparticle contact stresses after bond degradation. The elastic wave velocities dramatically increase due to cementation hardening under fixed vertical stress, and are constant after curing even though vertical stress increases. Additional loading of the vertical effective stress decreases the elastic wave velocities due to bond degradation. The shear wave velocity presents three behavior regions as a function of the sand fraction for both uncemented and cemented specimens: rubber-like, sand-like, and transition behaviors. The vertical stress–strain response and the elastic wave velocities can serve as indicators of cementation and bond degradation.
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Zaafarany, Ishaq Abdullah. "Kinetics and mechanism of sol-gel transformation between some trivalent- and tetravalent-metal ions and Sodium alginate Anionic polyelectrolyte with formation of coordination Biopolymeric structure polymembranes Hydrogels of Capillary Structures Ex". JOURNAL OF ADVANCES IN CHEMISTRY 3, n.º 1 (9 de abril de 2007): 133–42. http://dx.doi.org/10.24297/jac.v3i1.914.
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Abstract The kinetics of sol-gel transformation between A13+, La 3+ and Th4+ metal ion electrolytes and sodium alginate sol have been studied complexometrically at various temperatures. In the presence of a large excess of sodium alginate sol concentration over that of metal ion electrolyte, the pseudo first–order plots of exchange showed sigmoidal curves with two distinct stages. The initial part was relatively fast and curved significantly at early times, followed by a slow decrease in the rates of exchange over longer time periods. The rate constants of gelation showed second-order overall kinetics which was first order in the concentration of both reactants. The thermodynamic parameters have been evaluated and tentative gelation mechanisms consistent with the kinetic results of gelation are suggested. The stability of these ionotropic metal-alginate complexes has been discussed in terms of the coordination geometry and strength of chelated bonds.
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Szalad, Horațiu, Natalia Candu, Bogdan Cojocaru, Traian D. Păsătoiu, Marius Andruh y Vasile I. Pârvulescu. "∞3[Cu2(mand)2(hmt)]–MOF: A Synergetic Effect between Cu(II) and Hexamethylenetetramine in the Henry Reaction". Chemistry 2, n.º 1 (13 de febrero de 2020): 50–62. http://dx.doi.org/10.3390/chemistry2010006.
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∞3[Cu2(mand)2(hmt)]·H2O (where mand is totally deprotonated mandelic acid (racemic mixture) and hmt is hexamethylenetetramine) proved to be a stable metal–organic framework (MOF) structure under thermal activation and catalytic conditions, as confirmed by both the in situ PXRD (Powder X-ray diffraction) and ATR–FTIR (Attenuated total reflection-Fourier-transform infrared spectroscopy) haracterization. The non-activated MOF was completely inert as catalyst for the Henry reaction, as the accessibility of the substrates to the channels was completely blocked by H-bonded water to the mand entities and CO2 adsorbed on the Lewis basic sites of the hmt. Heating at 140 °C removed these molecules. Only an insignificant change in the relative ratios of the XRD facets due to the capillary forces associated to the removal of the guest molecules from the network has been observed. This treatment afforded the accessibility of nitromethane and various aldehydes (4-bromobenzaldehyde, 4-nitrobenzaldehyde, and p-tolualdehyde) to the active catalytic sites, leading to conversions up to 48% and selectivities up to 98% for the desired nitroaldol products. The behavior of the catalyst is solvent-sensitive. Protic solvents completely inhibited the reaction due to the above-mentioned strong H-bonds. Accordingly, very good results were obtained only with aprotic solvents such as acetonitrile and 1,4-dioxane. The synthesized MOF is completely recyclable as demonstrated for five successive cycles.
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Yang, Lin, Ka Yiu Leung, Ying Cao, Yu Huang, W. M. N. Ratnayake y Zhen-Yu Chen. "α-Linolenic acid but not conjugated linolenic acid is hypocholesterolaemic in hamsters". British Journal of Nutrition 93, n.º 4 (abril de 2005): 433–38. http://dx.doi.org/10.1079/bjn20041365.
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Conjugated linolenic acid (CLN) refers to a group of octadecatrienoic acid isomers that have three double bonds in conjugation. Both pomegranate and tung seed oils are rich in CLN but the major isomer in the former iscis9,trans11,cis13 while in the latter it iscis9,trans11,trans13. The present study examined the effects of CLN, isolated from either pomegranate seed oil or tung seed oil, and α-linolenic acid (LN), isolated from flaxseed oil, on serum cholesterol levels in male hamsters (body weight 105 g; age 10 weeks) fed a 0.1 % cholesterol and 10 % lard diet, for a period of 6 weeks. All hamsters were allowed free access to food and fluid. The blood samples were taken by bleeding from the retro-orbital sinus into a heparinized capillary tube under light ether anaesthesia after overnight fasting at weeks 0, 2, 4 and 6. It was found that supplementation of CLN at levels of 12.2–12.7 g/kg diet exhibited no significant effect on serum cholesterol level while LN at a similar level of supplementation had serum cholesterol reduced by 17–21 % compared with the control diet containing no LN and CLN. Supplementation of CLN and LN significantly decreased hepatic cholesterol but no effect was observed on heart and kidney cholesterol levels. It was concluded that LN possessed hypocholesterolaemic activity while CLN had no effect on blood cholesterol, at least in hamsters.
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Dong, Lian-Jie, Cheng-Di Li, Jia Peng, Jia-Hong Luo y Yun Hong. "The Effect of Silica Sol on the Stain Resistance of Exterior Wall Latex Coatings through Natural Exposure to Sunlight". Coatings 13, n.º 12 (28 de noviembre de 2023): 2013. http://dx.doi.org/10.3390/coatings13122013.
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Stain resistance is one of the important characteristics of exterior wall latex coatings in cities. Adding silica sol to the coating can increase its stain resistance. However, there is currently limited research on the long-term natural exposure test of latex coatings. This paper first investigates the influence of different amounts of silica sol on the elongation, water absorption, and stain resistance of coatings and obtains a better percentage of silica sol addition. Then, heat storage tests were conducted to obtain the viscosity and pH changes of the coating. Afterwards, outdoor natural exposure tests were conducted for up to 12 months to obtain the stain resistance of the coating with the addition of silica sol. The results indicate that the stain resistance value of the coating with added silica sol was significantly better than that without added silica sol after 12 months of natural exposure to sunlight, increasing by 65.8%. The formation of a network structure of Si O-Si bonds in the silica sol enhances the hardness and rigidity of the coating while also allowing it to enter the capillary tubes of the coating caused by prolonged exposure to sunlight, avoiding cracking of the coating and preventing the entry of dust and impurities. Therefore, the stain resistance of the coating is improved. These research results will contribute to the better application of exterior wall latex coatings in architecture.
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Ganderton, Tim, Colin N. Chesterman, Michael C. Berndt y Philip Hogg. "Evidence for Control of von Willebrand Factor Multimer Size by Intramolecular Thiol-Disulfide Exchange." Blood 106, n.º 11 (16 de noviembre de 2005): 412. http://dx.doi.org/10.1182/blood.v106.11.412.412.
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Abstract Plasma von Willebrand factor (VWF) is a multimeric glycoprotein from endothelial cells and platelets that mediates adhesion of platelets to sites of vascular injury. In the shear force of flowing blood, however, only the very large VWF multimers are effective in capturing platelets. The multimeric size of VWF is controlled by proteolysis at the Tyr842-Met843 peptide bond by ADAMTS13. It is apparent, however, that VWF multimers are processed to a significant degree in the absence of ADAMTS13 in mice and humans. This finding implies that another mechanism of controlling VWF multimer size must exist. We noticed similarities between the structural control of α-keratin and VWF. Both are multimeric elongated proteins whose substrates are linked by disulfide-bonds and both proteins undergo shear-dependent conformational change. Keratin shape is controlled by thiol-mediated events and we have shown that the free thiol of thrombospondin-1 can facilitate cleavage of the disulfide-bonds that hold VWF multimers together. The structure of α-keratin is controlled by shear-dependent intramolecular thiol-disulfide exchange. Free thiols in keratin from unpaired cysteines exchange with nearby disulfides when the α-keratin fibre is exposed to shear. The thiol-disulfide exchange process continues until the shear across the fibre is resolved. We hypothesized that a similar mechanism may be operating in VWF. Intramolecular thiol-disulfide exchange is dependent on the presence of at least one unpaired cysteine thiol in the protein. Using a biotin-linked maleimde that specifically alkylates free thiols, we have shown that plasma VWF does contain unpaired cysteine residues. VWF was coated onto the interior of glass capillary tubes and exposed to shear using a precision syringe pump. VWF eluted from the tube when shear was stepped, but not when the shear was constant, and the eluted VWF was of smaller multimer size than that bound to the tube. These observations imply that VWF multimer size can be controlled by intramolecular thiol-disulfide exchange. We suggest that this mechanism may be responsible for the processing of VWF multimer size observed in the absence of ADAMTS13.
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Serikov, T. M. "The effect of electric transport properties of titanium dioxide nanostructures on their photocatalytic activity". Bulletin of the Karaganda University. "Physics" Series 99, n.º 3 (30 de septiembre de 2020): 13–21. http://dx.doi.org/10.31489/2020ph3/13-21.
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. Films formed by nanoparticles, nanorods and nanotubes of titanium dioxide with a thickness of 3.9, 4.0 and 4.1 μm, respectively, with an area of 2 cm2 were obtained by various methods. Nanostructures were characterized by X-ray phase analysis, scanning electron microscopy (SEM), BET (Brunauer–Emmett–Teller), BJH (Barrett–Joyner–Halenda). The electric transport properties of the films were studied by impedance pectroscopy. The photocatalytic activity of the samples was evaluated by the photocurrent and degradation of the methylene blue dye under xenon lamp illumination. The concentration of hydrogen released per unit time was determined by gas chromatography in a standard quartz cuvette using a platinum electrode. The study of texture characteristics showed that the obtained isotherms belong to type IV isotherms with a hysteresis loop, reflecting the process of capillary condensation in mesopores. The diffraction peaks for the films of nanoparticles and nanotubes of titanium dioxide are identical and correspond to the tetragonal phase of anatase, for films of nanorods to the tetragonal phase of rutile. When studying the electric transport properties of films, it was found that films of titanium dioxide nanoparticles have a higher resistance associated with unformed bonds between nanoparticles. Despite the low specific surface area, titanium dioxide nanorods showed higher photocatalytic activity than nanotubes and nanoparticles. The results are confirmed by measurements of photocurrent, dye decomposition and the splitting of water molecules into hydrogen gas and oxygen.
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Ghasemi-Mobarakeh, Laleh, Santiago Cano, Vahid Momeni, Dongyan Liu, Ivica Duretek, Gisbert Riess, Christian Kukla y Clemens Holzer. "Effect of Increased Powder–Binder Adhesion by Backbone Grafting on the Properties of Feedstocks for Ceramic Injection Molding". Polymers 14, n.º 17 (2 de septiembre de 2022): 3653. http://dx.doi.org/10.3390/polym14173653.
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The good interaction between the ceramic powder and the binder system is vital for ceramic injection molding and prevents the phase separation during processing. Due to the non-polar structure of polyolefins such as high-density polyethylene (HDPE) and the polar surface of ceramics such as zirconia, there is not appropriate adhesion between them. In this study, the effect of adding high-density polyethylene grafted with acrylic acid (AAHDPE), with high polarity and strong adhesion to the powder, on the rheological, thermal and chemical properties of polymer composites highly filled with zirconia and feedstocks was evaluated. To gain a deeper understanding of the effect of each component, formulations containing different amounts of HDPE and or AAHDPE, zirconia and paraffin wax (PW) were prepared. Attenuated total reflection spectroscopy (ATR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and rotational and capillary rheology were used for the characterization of the different formulations. The ATR analysis revealed the formation of hydrogen bonds between the hydroxyl groups on the zirconia surface and AAHDPE. The improved powder-binder adhesion in the formulations with more AAHDPE resulted in a better powder dispersion and homogeneous mixtures, as observed by SEM. DSC results revealed that the addition of AAHDPE, PW and zirconia effect the melting and crystallization temperature and crystallinity of the binder, the polymer-filled system and feedstocks. The better powder--binder adhesion and powder dispersion effectively decreased the viscosity of the highly filled polymer composites and feedstocks with AAHDPE; this showed the potential of grafted polymers as binders for ceramic injection molding.
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McLarney, Ellen. "The private is political: Women and family in intellectual Islam". Feminist Theory 11, n.º 2 (agosto de 2010): 129–48. http://dx.doi.org/10.1177/1464700110366805.
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In Hiba Ra’uf’s Woman and Political Work, she argues that the family is the basic political unit of the Islamic community or nation (the umma). Her thesis is both feminist and Islamist, as she argues that the ‘private is political’. By drawing analogies between family and umma, family and caliphate, the personal and the political, the private and public, Ra’uf seeks to dismantle the oppositions of secular society, to challenge the division of society into discrete spheres. This entails an implicit challenge to the secular state, but effected through the politics of the family. An Islamic family, she argues, is a powerful site for the transformation of socio-political institutions; a politics of the microcosmic with macrocosmic ramifications, effected through the very embodiment and practice of an Islamic ethos at a grassroots, capillary level. However, though Ra’uf contests liberal secularism’s division of spheres with feminist and Islamist critical methods, she reproduces some of its fundamental assumptions about the nature of the family: as the domain of religion, in opposition to the secular state; as rooting community, in opposition to the individualism of the citizen; as an ethics grounded in affect; and as an essentially feminine world. In making the family the sphere of Islamic politics, Ra’uf re-enacts secularism’s division of spheres, sacralizing the affective bonds of intimate relations and making the family the domain of religion. Furthermore, by emphasizing the family as the domain of women’s political work, she reinscribes the family as a feminine sphere, so that woman’s vocation is familial, as is her ethical disposition.
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Shvidia, V. O., S. P. Stepanenko, B. I. Kotov, A. V. Spirin y V. Yu Kucheruk. "Influence of vacuum on diffusion of moisture inside seeds of cereals". Bulletin of the Karaganda University. "Physics" Series 107, n.º 3 (30 de septiembre de 2022): 90–98. http://dx.doi.org/10.31489/2022ph3/90-98.
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The article solves the problem of thermal injury of seeds of grain crops during drying, which are capillaryporous bodies. It is hypothesized that the use of a vacuum in the drying chamber reduces the risk of thermal stress. In this regard, the article studies the effect of a vacuum inside the drying chamber on the diffusion of moisture inside the seeds. Seeds are complex materials in which moisture has different bonds with dry matter. During the working process, the drying speed in the surface layers and inside the seeds occurs at different speeds. As a result, drying stresses occur, which cause cracks on the surface of the seeds. Based on the solution to the differential diffusion equation with an absorbing screen as a boundary condition, the condition for drying without thermal stresses is found. Experimental verification of theoretical studies is carried out on a specially made experimental setup on the example of corn seeds. The effect of thermal stress on seed viability is determined by laboratory germination. Experimental studies confirm the adequacy of theoretical statements. Thus, when drying the seeds of grain crops, which are capillary-porous bodies, there is a limit value of rarefaction, above which cracks appear on the surface of the seeds due to different drying rates on the surface and inside. For drying seeds of grain crops without thermal stresses, it is necessary to consider not only the heating temperature but also the rarefaction in the drying chamber, which should be close to the limit value.
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Mamonov, V. I. "Analysis of plasma effect on ultrahigh-molecular weight polyethylene fibers’ surface energy on strength of fibers and fiber reinforced composites". Perspektivnye Materialy 3 (2021): 42–54. http://dx.doi.org/10.30791/1028-978x-2021-3-42-54.
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Completely saturated chemical bonds in ultrahigh-molecular-weight polyethylene (UHMWPE) fibers — are a reason for their low surface energy (FSE), i.e. inert properties. Elongated crystal structure of UHMWPE molecules ensures high anisotropic tensile strength of the fibers. An inertness is a problem for utilization these fibers in high-strength composites production. Surface energy (SE) difference of the fibers and a binder in fiber/matrix system hinders chemical interaction at interphase boundary and worsens fiber wettability. Increase in their FSE is a topical task for this problem decision. Necessary condition of FSE increase is the integrity of molecule structure, lying under modified surface. Low temperature, nonequilibrium plasma (LTP) treatment in a medium of argon and argon/propane mixture, used in this work for plasma activation of fibers’ surface, permits to abide by this condition. However, plasma ion bombardment during a process of activation can modify interior crystal structure and, as a result, decrease their strength. The rovings SK75 (Holland) and D800 (China) were used for study of the properties of UHMWPE fibers after plasma treatment. Activation effect on FSE, strength, and fibers’ wetting by water and epoxy binder before and after ageing was studied. Capillary wetting of the fibers by distilled water used for FSE evaluation. The data of filaments surface structure and their diameter change at maximal load, obtained by optical microscope study, were used for the analysis of FSE and epoxy matrix effect on the strength of fiber/matrix systems. Essential distinction of SK75 and D800 fibers properties is ascertained. Negative effect of fibers’ and matrix’s stiffness, as well as increased FSE of stiff fibers on the strength of fiber/matrix system is revealed.
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Osicka, Tanya M. y Wayne D. Comper. "Characterization of Immunochemically Nonreactive Urinary Albumin". Clinical Chemistry 50, n.º 12 (1 de diciembre de 2004): 2286–91. http://dx.doi.org/10.1373/clinchem.2004.039743.
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Abstract Background: Conventional immunoassays underestimate the urinary albumin concentration because intact albumin in urine exists in two forms, immunoreactive and immunochemically nonreactive. Methods: Urinary albumin concentration measured by HPLC (which measures total albumin, i.e., the sum of immunoreactive albumin + immunochemically nonreactive albumin) or RIA was compared with densitometric analysis of albumin bands in diabetic urine samples separated by either native polyacrylamide gel electrophoresis (PAGE) or reducing sodium dodecyl sulfate (SDS)-PAGE. Immunochemically nonreactive albumin was also isolated from diabetic urine (relative amount detected, 70–80% of the expected) and was tested for contamination by common urinary proteins by native PAGE, ELISA, and capillary electrophoresis. Results: Urinary albumin concentrations measured by native PAGE and HPLC were better correlated (r2 = 0.83) than concentrations measured by native PAGE and RIA (r2 = 0.62) because under native conditions both native PAGE and HPLC detect total albumin and not only the immunoreactive albumin alone that is measured by RIA. Urinary albumin concentrations measured by reducing SDS-PAGE and RIA were better correlated (r2 = 0.84) than concentrations measured by reducing SDS-PAGE and HPLC (r2 = 0.65) because under reducing conditions immunochemically nonreactive albumin is unstable and fragments into many smaller peptides. The partially purified preparation was found to contain <1% contamination by common urinary proteins and is stable to freezing and frequent freeze/thaw cycles. Conclusions: The results are consistent with the interpretation that immunochemically nonreactive albumin has a limited number of polypeptide chain scissions and is held together by noncovalent intrachain bonding and disulfide bonds. Detection of this molecule is likely to be of clinical importance in diagnosing kidney disease as well as cardiovascular disease.
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Stepanova, Kseniya, Daria Lytkina, Rustam Sadykov, Kseniya Shalygina, Toir Khojazoda, Rashidjon Mahmadbegov y Irina Kurzina. "Composite Cement Materials Based on β-Tricalcium Phosphate, Calcium Sulfate, and a Mixture of Polyvinyl Alcohol and Polyvinylpyrrolidone Intended for Osteanagenesis". Polymers 15, n.º 1 (31 de diciembre de 2022): 210. http://dx.doi.org/10.3390/polym15010210.
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The primary purpose of the study, presented in this article, was to obtain a composite cement material intended for osteanagenesis. The β-tricalcium phosphate powder (β-TCP, β-Ca3(PO4)2) was obtained by the liquid-phase method. Setting and hardening of the cement system were achieved by adding calcium sulfate hemihydrate (CSH, CaSO4·1/2H2O). An aqueous solution of polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), and a PVA/PVP mixture were used as a polymer component. The methods of capillary viscometry and Fourier-transform infrared spectroscopy (FTIR) revealed the formation of intermolecular hydrogen bonds between polymer components, which determines the good miscibility of polymers. The physicochemical properties of the synthesized materials were characterized by X-ray diffraction (XRD) and FTIR methods, and the added amount of polymers does not significantly influence the processes of phase formation and crystallization of the system. The size of crystallites CSD remained in the range of 32–36 nm, regardless of the ratio of polymer components. The influence of the composition of composites on their solubility was investigated. In view of the lower solubility of pure β-TCP, as compared to calcium sulfate dihydrate (CSD, CaSO4·2H2O), the solubility of composite materials is determined to a greater degree by the CSD solubility. Complexometric titration showed that the interaction between PVA and PVP impeded the diffusion of calcium ions, and at a ratio of PVA to PVP of 1/1, the smallest exit of calcium ions from the system is observed. The cytotoxicity analysis results allowed us to establish the fact that the viability of human macrophages in the presence of the samples varied from 80% to 125% as compared to the control.
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Chervan, A. M., V. I. Melnik y V. M. Yatsukhno. "Assessment and intra-regional differences in the soil vulnerability of the agricultural lands of Belarussian Polesye to droughts under warming climate". Doklady of the National Academy of Sciences of Belarus 66, n.º 4 (8 de septiembre de 2022): 444–53. http://dx.doi.org/10.29235/1561-8323-2022-66-4-444-453.
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A quantitative assessment of the areas of vulnerable soils to droughts was presented for the first time and a series of maps was compiled to identify soils of agricultural lands in the zone of the most pronounced risk on the basis of the most complete agrometeorological information in comparison with other studies. The article presents the results of assessing the soil vulnerability (predisposition or susceptibility) of agricultural lands to droughts in the region of Belarusian Polesye. To determine the degree of its manifestation, it is proposed to use such soil-hydrological constants of soil moisture availability as maximum field capacity moisture, rupture of capillary bonds and dynamics of change in their indicators during the growing season (April–October) over a 30-year period (1989–2018). The series of digital maps of the vulnerability of agricultural land use soils to droughts at the level of the region, administrative districts and individual agricultural organizations was compiled using the GIS technologies. The grouping of the administrative regions of Belarusian Polesye according to the ratio of agricultural land areas with varying degrees of soil vulnerability to droughts was carried out in order to develop territorially differentiated measures for adaptation and mitigation of their negative impact on agroecosystems. The obtained research results have found practical application in the development of measures to mitigate the negative impact of soil droughts on agricultural production. It is concluded that in the context of an increase in the number and duration of atmospheric droughts in the region, the need to apply the results of assessing the vulnerability of soils to their adverse effects is mandatory when substantiating and applying measures to adapt agricultural activities to mitigate the negative effects of droughts.