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The article briefly reviews literature on the modification of epoxy resins and their properties, which are used for its industrial applications. Experimental results on modified epoxy resins are collectively summarized, which focu...
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The article briefly reviews literature on the modification of epoxy resins and their properties, which are used for its industrial applications. Experimental results on modified epoxy resins are collectively summarized, which focus on the structure, curing, and alternate methods for modification of epoxy resins. The several properties such as thermal stability, adhesive, toughness, and electrical conductivity have been studied during the modifications of epoxy resins, which is useful in the field of electronic encapsulation, blending, composites, and nanocomposites, etc. The review concludes with a brief discussion on the most useful valuable modifications for industrial applications.
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This paper addresses an efficient modification method that eliminates the undesirable effects of strains due to various non-conforming modes so that the non-conforming element can pass the patch test unconditionally. The scheme is...
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This paper addresses an efficient modification method that eliminates the undesirable effects of strains due to various non-conforming modes so that the non-conforming element can pass the patch test unconditionally. The scheme is incorporated in the element formulation to establish new types of non- conforming hexahedral elements designated as NHx and NVHx for the regular element and variable node element, respectively. Non-conforming displacement modes are selectively behavior of the ordinary (conforming)element displacement assumptions to improve the bending behavior of the distorted solid element.
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A large array of posttranslational modifications can dramatically change the properties of proteins and influence different aspects of their biological function such as enzymatic activity, binding interactions, and proteostasis. D...
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A large array of posttranslational modifications can dramatically change the properties of proteins and influence different aspects of their biological function such as enzymatic activity, binding interactions, and proteostasis. Despite the significant knowledge that has been gained about the function of posttranslational modifications using traditional biological techniques, the analysis of the site-specific effects of a particular modification, the identification of the full complement of modified proteins in the proteome, and the detection of new types of modifications remains challenging. Over the years, chemical methods have contributed significantly in both of these areas of research. This review highlights several posttranslational modifications where chemistry-based approaches have made significant contributions to our ability to both prepare homogeneously modified proteins and identify and characterize particular modifications in complex biological settings. As the number and chemical diversity of documented posttranslational modifications continues to rise, we believe that chemical strategies will be essential to advance the field in years to come.
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Methods have been developed to synthesize tri- and pentapeptide thioesters containing one or more p-(hydroxyphenyl)glycine (pHPG) residues and l-serine, some where the latter is O-phosphorylated, O-acetylated, or exists as a β-la...
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Methods have been developed to synthesize tri- and pentapeptide thioesters containing one or more p-(hydroxyphenyl)glycine (pHPG) residues and l-serine, some where the latter is O-phosphorylated, O-acetylated, or exists as a β-lactam. Selection of orthogonal protection strategies and development of conditions to achieve seryl O-phosphorylation without β-elimination and to maintain stereochemical control, especially simultaneously at exceptionally base-labile pHPG α-carbons, are described. Intramolecular closure of a seryl peptide to a β-lactam-containing peptide and the syntheses of corresponding thioester analogues are also reported. Modification of classical Mitsunobu conditions is described in the synthesis of the β-lactam- containing products, and in a broadly useful observation, it was found that simple exclusion of light from the P(OEt)_3-mediated Mitsunobu ring closure afforded yields of >95%, presumably owing to reduced photodegradation of the azodicarboxylate used. These sensitive potential substrates and products will be used in mechanistic studies of the two nonribosomal peptide synthetases NocA and NocB that lie at the heart of nocardicin biosynthesis, a family of monocyclic β-lactam antibiotics.
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Surface force measurements between titania surfaces in electrolyte solutions have previously revealed an unexplained long-range repulsive force at high pH, not described by Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory. He...
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Surface force measurements between titania surfaces in electrolyte solutions have previously revealed an unexplained long-range repulsive force at high pH, not described by Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory. Here, the surface forces between titania surfaces produced by atomic layer deposition (ALD) and cleaned using a variety of methods have been measured to determine the influence of the cleaning protocol on the measured forces and test the hypothesis that water plasma cleaning of the surface results in non-DLVO forces at high pH. For argon plasma and water plasma cleaned surfaces, a diffuse double layer repulsion and van der Waals attraction is observed near the isoelectric point. At high pH, the force remained repulsive up until contact, and no van der Waals attraction or adhesion was observed. Differences in the measured forces are explained by modification of the surface chemistry during cleaning, which alters the density of charged groups on the surface, but this cannot explain the observed disagreement with DLVO theory at high pH.
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General and efficient methods for selective modification of macrocyclic oligomers are rare, mostly because restricting a reaction to a defined number of identical functional groups is difficult to achieve. This work describes a un...
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General and efficient methods for selective modification of macrocyclic oligomers are rare, mostly because restricting a reaction to a defined number of identical functional groups is difficult to achieve. This work describes a unique, general, and rational methodology for the iteroselective functionalization of polyphenolic platforms by N-tert-butylaminocarbonyl (Bac) groups. The methodology consists of reacting the oligomeric platform with t-BuNCO and an inorganic base in an apolar solvent. This very simple one-step procedure has been applied to various calix[4, 5, 6, and 8]arenes, and in all cases, calixarenes with a single leftover phenolic moiety were isolated in high yields (>90%). Interestingly, this so-called "all-but-one" methodology gives a straightforward access to calixarenes displaying inherent chirality. It is also shown that the Bac group can be used as a protective group. Thus, the all-but-one methodology has been used for the efficient monofunctionalization of a key precursor platform, illustrating its huge potential for the tailored synthesis of sophisticated macrocyclic oligomers.
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Gasseparating membranes were obtained according to an original method of directed modifica tion of ultra filtration membranes having 50 nm pores by means of pyrocarbon nanosized crystallites (PNCs). For the first time, the size of...
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Gasseparating membranes were obtained according to an original method of directed modifica tion of ultra filtration membranes having 50 nm pores by means of pyrocarbon nanosized crystallites (PNCs). For the first time, the size of the pores was reduced not along the entire depth of the selective layer but only at the pore orifice, increasing their productivity by several orders of magnitude. PNC deposition was done at 800 and 650°C using methane and propane as a pyrolyzed gas at 90–100 kPa, respectively. The depth of PNC deposition was determined by scanning electron microscopy and energy dispersive spectrometry. It was demonstrated that at the used pressure, the depth of deposition was 1.5 μm, i.e., PNCs were deposited in the pore orifices. Gas permeability analysis for a membrane with rpore ~ 0.8 nm allowed us to estimate the Knudsen ratio and surface diffusion. The Knudsen and surface diffusion fluxes were estimated. The advantages and chal lenges of the proposed approach are discussed; these are mainly related to the thermal stability of the porous structure and the compatibility of the thermal expansion coefficients of the porous substrate and deposited PNCs. An analysis of the obtained results is presented, along with an outline for further studies.
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We propose a new modification of the Adomian decomposition method for Volterra integral equations of the second kind. By the Taylor expansion of the components apart from the zeroth term of the Adomian series solution, this new te...
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We propose a new modification of the Adomian decomposition method for Volterra integral equations of the second kind. By the Taylor expansion of the components apart from the zeroth term of the Adomian series solution, this new technology overcomes the problems arising from the previous decomposition method. The validity and applicability of the new technique are illustrated through several linear and nonlinear equations by comparing with the standard decomposition method and the modified decomposition method.The results obtained indicate that the new modification is effective and promising.
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Human-bear conflicts occur frequently in the Pasvik Valley, Norway. We used a variant of the hair-trapping method with higher densities of traps (2.5 × 2.5 km grid) to detect brown bears moving near human settlements and livestoc...
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Human-bear conflicts occur frequently in the Pasvik Valley, Norway. We used a variant of the hair-trapping method with higher densities of traps (2.5 × 2.5 km grid) to detect brown bears moving near human settlements and livestock. We distributed 20 hair traps for one month close to a farm with frequent observations of grazing bears. The study area consisted of one area close to the farm, and one adjacent area without settlements. We collected 85 hair samples and identified 13 different individuals by STR analysis. In the farm area, we detected 4 different males once, and a female that was detected in both areas. In comparison, nine bears (2 males and 7 females) were detected for more than one week in the area without settlements, suggesting lower roaming activity. Conclusively, hair trapping has the potential to survey bears at specific locations of importance to the wildlife management.
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The initiative for estimating glomerular filtration rate (GFR) derives from the limitations of interpreting plasma creatinine alone, the cost and complexities of determining a gold standard GFR with either inulin or radionuclides,...
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The initiative for estimating glomerular filtration rate (GFR) derives from the limitations of interpreting plasma creatinine alone, the cost and complexities of determining a gold standard GFR with either inulin or radionuclides, and the inaccuracies inherent in measuring a 24 h urine creatinine clearance. In August 2005, the Australasian Creatinine Consensus Working Group recommended that an eGFR based on the abbreviated MDRD (Modification of Diet in Renal Disease) formula shall be automatically calculated for every request for creatinine in people over 18 years. Uptake was almost universal, though with appropriate caveats in place regarding potential limitations. Updated recommendations in 2007 recognised uniform standardisation of the plasma creatinine assay. A recent development is the CKD-Epidemiology Collaboration (CKD-EPI) equation which confers less underestimation of GFR in subjects with normal renal function. Cystatin C and its derivative equations may have advantages in some situations.
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