Surface and bulk properties of hot-pressed PbMo6S8 superconductor studied by Auger electron spectroscopy and calorimetry

A direct observation of the grain-boundary phases for several well-characterized hot-pressed PbMo₆S₈ samples were made by Auger electron spectroscopy. The surface elemental concentrations are completely different when compared to its bulk composition. The thickness of this altered composition is in the range 100–200 Å gradually increasing with increase in hotpressing temperature. Also, evidence of segregation of impurities, such as carbon and SiO_x, to the grain-boundaries were noticed for some of the samples. Calorimetric experiments show a continuous broadening and a reduction in amplitude of the specific heat anomaly atT _c . This in terms of superconducting volume fraction indicates aT _c distribution in the range 9–15 K. Such an observation can be related to the local inhomogeneities with respect to the ternary composition, i.e., a deviation from ideal stoichiometry, PbMo₆S₈. The results are discussed in conjunction with X-ray diffraction, scanning electron microscope, and energy dispersive X-ray analysis. By considering the grain-boundary phases and the calorimetric observation of inhomogeneities, a plausible explanation is given for the low critical current densities in these materials.     

磁性纳米颗粒固定化细菌纤维素酶的活性和稳定性

在氨水溶液中进行Fe+2和Fe+3离子共沉淀并水热处理后制得磁性纳米颗粒Fe3O4,通过戊二醛活化将纤维素酶固定于其上。采用基于响应面法的Box-Behnken法(BBD)优化了制备条件,如磁性纳米颗粒浓度、戊二醛浓度、酶浓度和交联时间。 BBD分析结果表明,用实验数据可合理调节二次模型。利用生成的基于统计数据的等高线评价了响应面的变化,以理解纳米颗粒和酶活性之间的关系。运用扫描电镜、X射线衍射和红外光谱表征了纳米颗粒上酶的尺寸、结构、形貌和结合情况。采用诸如pH值、温度、重复使用性和存储能力分析了固定化纤维素酶的活性和稳定性。发现固定后的纤维素酶表现出更好的稳定性和活性。     

Cell-Cell Communication Between Fibroblast and 3T3-L1 Cells Under Co-culturing in Oxidative Stress Condition Induced by H<Subscript>2</Subscript>O<Subscript>2</Subscript>

The present study was carried out to understand the interaction between fibroblast and 3T3-L1 preadipocyte cells under H₂O₂-induced oxidative stress condition. H₂O₂ (40 μM) was added in co-culture and monoculture of fibroblast and 3T3-L1 cell. The cells in the lower well were harvested for analysis and the process was carried out for both cells. The cell growth, oxidative stress markers, and antioxidant enzymes were analyzed. Additionally, the mRNA expressions of caspase-3 and caspase-7 were selected for analysis of apoptotic pathways and TNF-α and NF-κB were analyzed for inflammatory pathways. The adipogenic marker such as adiponectin and PPAR-γ and collagen synthesis markers such as LOX and BMP-1 were analyzed in the co-culture of fibroblast and 3T3-L1 cells. Cell viability and antioxidant enzymes were significantly increased in the co-culture compared to the monoculture under stress condition. The apoptotic, inflammatory, adipogenic, and collagen-synthesized markers were significantly altered in H₂O₂-induced co-culture of fibroblast and 3T3-L1 cells when compared with the monoculture of H₂O₂-induced fibroblast and 3T3-L1 cells. In addition, the confocal microscopical investigation indicated that the co-culture of H₂O₂-induced 3T3-L1 and fibroblast cells increases collagen type I and type III expression. From our results, we suggested that co-culture of fat cell (3T3-L1) and fibroblast cells may influence/regulate each other and made the cells able to withstand against oxidative stress and aging. It is conceivable that the same mechanism might have been occurring from cell to cell while animals are stressed by various environmental conditions.     

Synthesis of novel 1,3-thiazin-4-ones by acetylene diester cyclization and their anticancer activities

A novel series of 1,3-thiazin-4-one derivatives containing a piperidyl ring (7–16) were designed and synthesized efficiently by thioamide and acetylene diester cyclization reaction via aminolysis of the ester group and the elimination of an alcohol molecule. The structures of all the novel compounds were established by their FTIR, Mass, ¹H NMR, and ¹³C NMR spectral techniques. The newly synthesized compounds (7–16) were studied for their in vitro anticancer activity against human liver cancer cell lines Hep G2 using MTT assay. The IC₅₀ values of the tested compounds were ranging in between 7.48 ± 0.71 and 56.57 ± 1.37 µM. Further, the apoptosis evaluation by the mitochondrial membrane potential using JC-1 dye was carried out and the results are in good agreement with the cytotoxicity studies.     

Microbial oxidation of mixtures of methylmercaptan and hydrogen sulfide

Refinery spent-sulfidic caustic, containing only inorganic sulfides, has previously been shown to be amenable to biotreatment withThiobacillus denitrificans strain F with complete oxidation of sulfides to sulfate. However, many spent caustics contain mercaptans that cannot be metabolized by this strict autotroph. An aerobic enrichment culture was developed from mixedThiobacilli and activated sludge that was capable of simultaneous oxidation of inorganic sulfide and mercaptans using hydrogen sulfide (H₂S) and methylmercaptan (MeSH) gas feeds used to simulate the inorganic and organic sulfur of a spent-sulfidic caustic. The enrichment culture was also capable of biotreatment of an actual mercaptancontaining, spent-sulfidic caustic but at lower rates than predicted by operation on MeSH and H₂S fed to the culture in the gas phase, indicating that the caustic contained other inhibitory components.     

Universality of the Sodium Ion Binding Mechanism in Class A G‐Protein‐Coupled Receptors

The allosteric modulation of G‐protein‐coupled receptors (GPCRs) by sodium ions has received significant attention as crystal structures of several receptors show Na⁺ ions bound to the inactive conformations at the conserved Asp^2.50. To date, structures from 24 families of GPCRs have been determined, though mechanistic insights into Na⁺ binding to the allosteric site are limited. We performed hundreds‐of‐microsecond long simulations of 18 GPCRs and elucidated their Na⁺ binding mechanism. In class A GPCRs, the Na⁺ ion binds to the conserved residue 2.50 whereas in class B receptors, it binds at 3.43b, 6.53b, and 7.49b. Using Markov state models, we obtained the free energy profiles and kinetics of Na⁺ binding to the allosteric site, which reveal a conserved mechanism of Na⁺ binding for GPCRs and show the residues that act as major barriers for ion diffusion. Furthermore, we also show that the Na⁺ ion can bind to GPCRs from the intracellular side when the allosteric site is inaccessible from the extracellular side.     

A theoretical study on the cyclopropane adsorption onto the copper surfaces by density functional theory and quantum chemical molecular dynamics methods

We report a theoretical study on the cyclopropane adsorption onto Cu(1 1 1) surfaces by density functional theory (DFT) and quantum chemical molecular dynamics methods. The equilibrium geometry of the physisorbed species was obtained using both periodic and cluster models by DFT methods that employ Cambridge serial total energy package (CASTEP), DMol ab initio quantum chemistry software of Accelrys’ materials studio (DMol), and Amsterdam density functional (ADF) program. It was found that the adsorbate molecule was tilted towards the metal surface with one C---C bond (upwards) parallel to the surface and that the physisorption occurred via a third carbon atom pointing (downwards) towards the surface. The electronic distribution and geometrical structure of physisorbed cyclopropane were slightly deviated from its gas phase molecule. The calculated vibrational frequencies and adsorption energies are close to experimental data, confirming the reliability of our DFT results. The adsorption process was simulated using our novel tight-binding quantum chemical molecular dynamics program, ‘Colors’. The calculation results indicated that both the adsorption and desorption processes of cyclopropane took place molecularly. The electron transfer and structural properties of equilibrium position obtained by ‘Colors’ are consistent with those by the first principles DFT methods.     

Density functional study of the insertion and ring-opening mechanism of MCP over Cp2LaH and Cp2LuH catalysts

The insertion and ring opening of methylenecyclopropane (MCP) catalyzed by Cp2LnH (Ln = La and Lu) was investigated using DFT method. Geometries and energies of the reactants, minima, and transition states for this reaction were obtained. The present study indicates the formation of Cp2LaH-MCP complex followed by 1,2-insertion through a tetrahedral transition state with subsequent ring opening at the proximal bond via hydrogen transfer transition state resulting in the formation of the final product.     

Synthesis, characterization and photocrosslinking properties of polyacrylamides having bromo substituted pendant cinnamoyl moieties

New 3- and 4-bromocinnamoyl aniline were synthesized condensing 4-aminoacetophenone and the respective bromobenzaldehydes in the presence of sodium hydroxide. The monomers, 4-(3′-bromocinnamoyl) phenyl acrylamide (4,3′-BCPA) and 4-(4′-bromocinnamoyl) phenyl acrylamide (4,4′-BCPA) were prepared by reacting the respective chalcones and acryloyl chloride in the presence of triethylamine at 0-5 °C. Homopolymers of 4,3′-BCPA and 4,4′-BCPA was carried out in methyl ethyl ketone using benzoyl peroxide (BPO) under nitrogen atmosphere at 70 °C. The prepared polymers were characterized by UV, IR, ¹H-NMR and ¹³C-NMR techniques. The molecular weights (M_w and M_n) of the polymers were determined by gel permeation chromatography. The thermogravimetric analysis (TGA) of the polymers in nitrogen atmosphere reveals that they possess very good thermal stability required of a negative type photoresist. The glass transition temperature of poly(4,3′-BCPA) and poly (4,4′-BCPA) were found to be 55 and 64 °C respectively. The solubility of the polymers was tested in various polar and non-polar solvents. Photocrosslinking nature of the polymer samples was carried out in the presence and absence of various triplet photosensitizers in solution phase using chloroform solvent under medium frequency UV light. For using the polymers as negative photoresist materials the rate of photocrosslinking of the polymers was measured under the influence of different solvents, concentrations and position of the substituent.