Synthesis of β-SiC powder from organic precursor and its sinterability

β-SiC powders were synthesized by the carbothermic reduction of SiC precursors which were derived from liquid silica and carbon sources. From the precursor materials in which the mixing condition of silica and carbon was improved, pure SiC powders were produced. The powders could be sintered by additions of carbon and small amounts of boron. No decarburization and no acid purification processes were required before sintering.     

Synthesis of β‘—SIALON Powder from Clay

The synthesis of β‘-sialon powder by carbothermic reduction of clay followed by nitridation has been carried out.The effect of charge mixture,temperature,holding time and nitrogen flow rate on synthesis was examined.The fired sample was identified by XRD and the nitrogen content of fired sample was measured.The synthesis process of sialon powder was described.     

Synthesis and characterization of polymers from β-propiolactone and poly(ethylene glycol)s

Uncatalysed polymerizations of β-propiolactone with low-molecular-weight poly(ethylene glycol)s were carried out in bulk, at temperatures in the range of 70 to 120°C. ¹H nuclear magnetic resonance (n.m.r.) and differential scanning calorimetry (d.s.c.) measurements on the resulting products indicated a block copolymer structure. Gel permeation chromatography (g.p.c.) and d.s.c. analyses showed that in some cases the copolymerization is accompanied by homopolymerization of β-propiolactone, probably due to the presence of residual water in the poly(ethylene glycol). N.m.r. and infra-red (i.r.) spectra of copolymers revealed the presence of hydroxyl and carboxyl end groups. The copolymerization reaction may be visualized as a two-step process, in which the ring opening of β-propiolactone takes place on both the hydroxyl groups of poly(ethylene glycol), followed by repetitive monomer addition forming an ester-ether-ester triblock copolymer.     

Synthesis and Characterization of the Inclusion Complex of β-cyclodextrin and Azomethine

A β-cyclodextrin (β-Cyd) inclusion complex containing azomethine as a guest was prepared by kneading method with aliquot addition of ethanol. The product was characterized by Fourier Transform Infrared (FTIR) spectrometer, ¹H Nuclear Magnetic Resonance (¹H NMR) and Thermogravimetric Analyzer (TGA), which proves the formation of the inclusion complex where the benzyl part of azomethine has been encapsulated by the hydrophobic cavity of β-Cyd. The interaction of β-Cyd and azomethine was also analyzed by means of spectrometry by UV-Vis spectrophotometer to determine the formation constant. The formation constant was calculated by using a modified Benesi-Hildebrand equation at 25 °C. The apparent formation constant obtained was 1.29 × 10⁴ L/mol. Besides that, the stoichiometry ratio was also determined to be 1:1 for the inclusion complex of β-Cyd with azomethine.     

Selective Synthesis of Perillyl Alcohol from β-Pinene Epoxide over Ti and Mo Supported Catalysts

Catalysis Letters - Isomerization of β-pinene epoxide to perillyl alcohol using several materials based on titanium and molybdenum is reported. The metals were incorporated on SBA-15, MCM-41...     

Nifedipine Protects INS-1 β-Cell from High Glucose-Induced ER Stress and Apoptosis

Sustained high concentration of glucose has been verified toxic to β-cells. Glucose augments Ca(2+)-stimulated insulin release in pancreatic β-cells, but chronic high concentration of glucose could induce a sustained level of Ca(2+) in β-cells, which leads to cell apoptosis. However, the mechanism of high glucose-induced β-cell apoptosis remains unclear. In this study, we use a calcium channel blocker, nifedipine, to investigate whether the inhibition of intracellular Ca(2+) concentration could protect β-cells from chronic high glucose-induced apoptosis. It was found that in a concentration of 33.3 mM, chronic stimulation of glucose could induce INS-1 β-cells apoptosis at least through the endoplasmic reticulum stress pathway and 10 μM nifedipine inhibited Ca(2+) release to protect β-cells from high glucose-induced endoplasmic reticulum stress and apoptosis. These results indicated that inhibition of Ca(2+) over-accumulation might provide benefit to attenuate islet β-cell decompensation in a high glucose environment.     

Synthesis and microwave absorption properties of bamboo-like β-SiC nanowires

Lightweight and strong microwave adsorption property have become the foremost crucial factors in the practical application of modern microwave absorbers. This study mainly dealt with synthesize of bamboo-like β-SiC nanowires with high-performance microwave absorption property via a polymer pyrolysis CVD (PPCVD) approach. The PPCVD process was conducted by cleverly placing the polymer powders into two temperature zones to produce reactant gases with alternating concentrations. The morphological study revealed that the nodes exhibited abundant stacking faults as compared to the stem segments, which was beneficial for the microwave losses. The optimal reflection loss value of −35.47 dB was gained at 18 GHz corresponding to 2.0-mm absorber thickness, and the corresponding −10 dB bandwidth (>90% absorption) was 3.22 GHz. It has turned out that the as-prepared nanowires could be applied at different frequencies by adjusting the thickness. Especially, it exhibits a good prospect in the fields of ultrathin absorbers. Furthermore, the microwave absorption mechanisms of the nanowires were explored. This present investigation has opened a high-efficient facile approach to develop ultrathin, lightweight, and high-performance microwave absorbers.     

Synthesis and drug-release properties of biodegradable hydrogels having β-cyclodextrin

A new β-cyclodextrin (β-CD) methacrylated monomer was synthesized from the reaction of β-CD, glycidyl methacrylate. Based on inclusion character of β-CD, a series of hydrogels were prepared by irradiating the mixtures of β-CD methacrylate monomer (β-CD-Met), poly(ethylene glycol) monoacrylate, poly(ethylene glycol)diacrylate, fumaric acid monoethyl ester-functionalized poly(lactic-co-glycolic) acid, 1-vinyl-2-pyrrolidone, N,N′-methylene bisacrylamide, and the photoinitiator. Gel percentages and equilibrium swelling ratios (%) of hydrogels were investigated. It was observed that equilibrium-swelling ratio increased with increasing β-CD-Met content in the hydrogel composition. SEM images demonstrated that β-CD-Met-based hydrogel have lots of voids on the fractured surface. In this study, ibuprofen (IBU) which is capable of forming inclusion complex with β-CD was chosen. For the hydrogel with maximum CD content, the IBU drug loading was found as 9 mg/g dry gel. It can be concluded that the inclusion complex-formation capability of β-CD moiety increases the drug release by improving the aqueous solubility of hydrophilic drugs.     

Synthesis of 3-oxalinolenic acid and β-oxidation-resistant 3-oxa-oxylipins

3-Oxalinolenic acid (3-oxa-9(Z), 12(Z), 15(Z)-octadecatrienoic acid or (6(Z), 9(Z), 12(Z)-pentadecatrienyloxy)acetic acid) was synthesized from 5(Z), 8(Z), 11(Z), 14(Z), 17(Z)-eicosapentaenoic acid by a sequence involving the C15 aldehyde 3(Z), 6(Z), 9(Z), 12(Z)-pentadecatetraenal as a key intermediate. Conversion of the aldehyde by isomerization and two steps of reduction afforded 6(Z), 9(Z), 12(Z)-pentadecatrienol, which was coupled to bromoacetate to afford after purification by HPLC >99%-pure 3-oxalinolenic acid in 10–15% overall yield. 3-Oxalinolenic acid was efficiently oxygenated by soybean lipoxygenase-1 into 3-oxa-13(S)-hydroperoxy-9(Z), 11(E), 15(Z)-octadecatrienoic acid, and this hydroperoxide could be further converted chemically into 3-oxa-13(S)-hydroxy-9(Z), 11(E), 15(Z)-octadecatrienoic acid and 3-oxa-13-oxo-9(Z), 11(E), 15(Z)-octadecatrienoic acid. The 3-oxa-hydroperoxide also served as the substrate for the plant enzymes allene oxide synthase, divinyl ether synthase, and hydroperoxide lyase to produce 3-oxa-12-oxo-10, 15(Z)-phytodienoic acid and other 3-oxa-oxylipins that were characterized by MS, 3-Oxalinolenic acid was not oxygenated by 9-lipoxygenase from tomato but was converted at a slow rate into 3-oxa-9(S)-hydroperoxy-10(E), 12(Z), 15(Z)-octadecatrienoic acid by recombinant maize 9-lipoxygenase. Recombinant α-dioxygenase-1 from Arabidopsis thaliana catalyzed the conversion of 3-oxalinolenic acid into a 2-hydroperoxide, which underwent spontaneous degradation into a mixture of 6,9,12-pentadecatrienol and 6,9,12-pentadecatrienyl formate. A novel α-dioxygenase from the moss Physcomitrella patens was cloned and expressed and was found to display the same activity with 3-oxalinolenic acid as Arabidopsis thaliana α-dioxygenase-1. Lipoxygenase-generated 3-oxa-oxylipins are resistant toward β-oxidation and have the potential for displaying enhanced biological activity in situations where activity is limited by metabolic degradation.     

Synthesis and Characterization of the Inclusion Complex of Dicationic Ionic Liquid and β-Cyclodextrin

The supramolecular structure of the inclusion complex of β-cyclodextrin (β-CD) with 1,1',2,2'-tetramethyl-3,3'-(p-phenylenedimethylene) diimidazolium dibromide (TetraPhimBr), a dicationic ionic liquid, has been investigated. The inclusion complex with 1:1 molar ratio was prepared by a kneading method. Fourier transform infrared spectroscopy (FTIR), powder X-ray diffraction (XRD) analysis, (1)H NMR and thermogravimetric analysis (TGA) confirmed the formation of the inclusion complex. The results showed that the host-guest system is a fine crystalline powder. The decomposition temperature of the inclusion complex is lower than that of its parent molecules, TetraPhimBr and β-CD individually.     

Advance in the Polymerization Strategy for the Synthesis of β-Peptides and β-Peptoids

Peptide mimics, possessing excellent biocompatibility and protease stability, have attracted broad attention and research in the biomedical field. β-Peptides and β-peptoids, as two types of vital peptide mimics, have demonstrated great potential in the field of foldamers, antimicrobials and protein binding, etc. Currently, the main synthetic strategies for β-peptides and β-peptoids include solid-phase synthesis and polymerization. Among them, polymerization in one-pot can minimize the repeated separation and purification used in solid-phase synthesis, and has the advantages of high efficiency and low cost, and can synthesize β-peptides and β-peptoids with high molecular weight. This review summarizes the polymerization methods for β-peptides and β-peptoids. Moreover, future developments of the polymerization method for the synthesis of β-peptides and β-peptoids will be discussed.     

Synthesis and characterisation of β-TCP/bioglass/zirconia scaffolds

Tricalcium phosphate scaffolds reinforced with bioglass were characterised morphologically, physically, and mechanically. The scaffolds were fabricated through powder technology and the polymer foaming technique using 80?wt-% of β-TCP and 20?wt-% of phosphate-based bioglass doped with zirconia in various amounts (0, 0.25, 0.5, 0.75, and 1.0?wt-%). The foaming agent was varied (1, 1.5, 2, 2.5, and 3?wt-%) to determine the optimal amount that ensured an interconnected porosity and pore size suitable for increasing osteoconduction and cell attachment. Promising samples for tissue engineering applications showed a pore size ranging from 1.41 to 303?μm, total porosity of 50–53%, compressive strength values between 0.6 and 1?MPa, Young’s modulus from 357 to 574?MPa, and excellent interconnectivity.     

Synthesis and hydrolysis of β-cyanoethyl ether of poly(vinyl alcohol)

Poly(vinyl alcohol) (PVA) was cyanoethylated by reaction with acrylonitrile in the presence of sodium hydroxide and quaternary ammonium halide. Quaternary ammonium halide, acting as a phase transfer catalyst, increases the degree of substitution (DS) of PVA. The DS also increased with increasing acrylonitrile concentration. Cyanoethylation of PVA up to 98% can be achieved under optimum conditions. The hydrolysis of β-cyanoethyl ether of PVA (CN–PVA) was studied. The rate of hydrolysis was affected by the sodium hydroxide concentration and the reaction temperature. The rheological properties of aqueous solution of hydrolysis product of CN–PVA were determined at different temperatures, and the flow activation energy was calculated. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2771–2777, 1999     

High Temperature Alkaline Degradation of Phenyl β-D-Glucopyranoside

Reaction rates and product distributions have been determined for the degradation of phenyl β-D-glucopyranoside in aq. alkali under various conditions. The effects of a stronger nucleophile, variations in hydroxide ion concentration at constant ionic strength, changes in temperature, and the level of ¹⁸O incorporation from the solvent into the product phenol were investigated. The degradation rate decreased greatly for the 2-O-methyl analog. The results indicate that, at both 100 and 170°C, phenyl β-D-glucopyranoside degradation proceeded by an SNicB(2) reaction. At both temperatures the expected SNicB(2) product, levoglucosan, formed in less than quantitative yields because of competing reactions which occurred after the rate-determining step.     

Extraction and Separation of α-lactalbumin and β-Lactoglobulin from Skim Milk by Microfiltration and Ultrafiltration at High Shear Rates: A Feasibility Study

Abstract

This paper presents a two-stage membrane filtration process for extracting and separating α-Lactalbumin (α-La) and β-Lactoglobulin (β-Lg), from UHT skim milk, using dynamic filtration. The 1st stage separates casein micelles in retentate from whey proteins in the permeate with rotating 0.2 µm pores ceramic membrane disks. Casein micelles rejection was excellent, while α-La and β-Lg transmissions remained between 80 and 90%. The permeate flux at 40°C ranged from 105 to 40 Lh^?1m^?2 at a volume reduction ratio of VRR = 4. The 2nd stage consisted of ultrafiltration of the previous permeate with a metal disk rotating at 2000 rpm near a fixed 50 kDa PES membrane, in order to concentrate β-Lg in retentate, while collecting α-La in the permeate. The flux dropped from 270 Lh^?1m^?2 at VRR = 1, and remained nearly constant at 200 Lh^?1m^?2 until a VRR of 3.3. α-La transmission increased with VRR to reach 23% at VRR = 3.3, while β-Lg transmission decayed at increasing VRR to 3%, to give a maximum selectivity of 8.     

Synthesis and Characterization of Silica–Polymer Nanocomposites Functionalized with Piperazine for the Synthesis of β-Nitro Alcohols

Abstract  

In order to compare the activity and selectivity for the synthesis of β-nitro alcohols, piperazine was functionalized directly and after surface modification into the ordered mesoporous SBA-15 framework. The materials were characterized by powder X-ray diffraction, N₂-adsorption–desorption isotherm, FT-IR, SS-NMR and scanning electron microscopy. The catalyst synthesized via surface modification under solvent free conditions showed very high activity and selectivity of β-nitro alcohols compared to the one synthesized by direct functionalization of SBA-15. Finally the possible reaction pathways were explained mechanistically.     

Synthesis of α-Ketoamide-Based Stereoselective Calpain-1 Inhibitors as Neuroprotective Agents

Calpain inhibitors have been proposed as drug candidates for neurodegenerative disorders, with ABT-957 entering clinical trials for Alzheimer's disease and mild cognitive impairment. The structure of ABT-957 was very recently disclosed, and trials were terminated owing to inadequate CNS concentrations to obtain a pharmacodynamic effect. The multistep synthesis of an α-ketoamide peptidomimetic inhibitor series potentially including ABT-957 was optimized to yield diastereomerically pure compounds that are potent and selective for calpain-1 over papain and cathepsins B and K. As the final oxidation step, with its optimized synthesis protocol, does not alter the configuration of the substrate, the synthesis of the diastereomeric pair (R)-1-benzyl-N-((S)-4-((4-fluorobenzyl)amino)-3,4-dioxo-1-phenylbutan-2-yl)-5-oxopyrrolidine-2-carboxamide ( 1 c ) and (R)-1-benzyl-N-((R)-4-((4-fluorobenzyl)amino)-3,4-dioxo-1-phenylbutan-2-yl)-5-oxopyrrolidine-2-carboxamide ( 1 g ) was feasible. This allowed the exploration of stereoselective inhibition of calpain-1, with 1 c (IC₅₀=78 nM) being significantly more potent than 1 g . Moreover, inhibitor 1 c restored cognitive function in amnestic mice.     

Synthesis and dissolution behavior of β-TCP and HA/β-TCP composite powders

Calcium phosphate powders, β-TCP and biphasic HA/β-TCP, were synthesized by calcining the powders obtained from the co-precipitation method using Ca(NO₃)₂·4H₂O and (NH₄)₂HPO₄. The effects of the initial Ca/P ratio and pH of the solution on the phase evolution and in vitro dissolution behavior of the powders in a Ringer's solution were investigated. The Ca/P ratio of the resulting powders was strongly dependent on the pH of the solution and weakly dependent on the initial Ca/P ratio. Single phase TCP powder was obtained at pH=7.4 and the initial Ca/P ratio had a little effect on the resulting Ca/P ratio. Biphasic composite powders were prepared at pH=8.0 and the Ca/P ratio of resulting powder was controllable by adjusting the initial Ca/P ratio. TCP powder showed the highest dissolution rate in the Ringer's solution and biphasic composite powder exhibited an intermediate dissolution behavior between that of HA and TCP.