Solution-phase deposition and nanopatterning of GeSbSe phase-change materials

Chalcogenide films with reversible amorphous-crystalline phase transitions have been commercialized as optically rewritable data-storage media, and intensive effort is now focused on integrating them into electrically addressed non-volatile memory devices (phase-change random-access memory or PCRAM). Although optical data storage is accomplished by laser-induced heating of continuous films, electronic memory requires integration of discrete nanoscale phase-change material features with read/write electronics. Currently, phase-change films are most commonly deposited by sputter deposition, and patterned by conventional lithography. Metal chalcogenide films for transistor applications have recently been deposited by a low-temperature, solution-phase route. Here, we extend this methodology to prepare thin films and nanostructures of GeSbSe phase-change materials. We report the ready tuneability of phase-change properties in GeSbSe films through composition variation achieved by combining novel precursors in solution. Rapid, submicrosecond phase switching is observed by laser-pulse annealing. We also demonstrate that prepatterned holes can be filled to fabricate phase-change nanostructures from hundreds down to tens of nanometres in size, offering enhanced flexibility in fabricating PCRAM devices with reduced current requirements.     

Sodium is not essential for high bioactivity of glasses

This study aims to demonstrate that excellent bioactivity of glass can be achieved without the presence of an alkali metal component in glass composition. In vitro bioactivity of two sodium-free glasses based on the quaternary system SiO₂-P₂O₅-CaO-CaF₂ with 0 and 4.5 mol% CaF₂ content was investigated and compared with the sodium-containing glasses with equivalent amount of CaF₂. The formation of apatite after immersion in Tris buffer was followed by Fourier-transform infrared spectroscopy, X-ray diffraction, ³¹P and ¹⁹F solid-state MAS-NMR. The dissolution study was completed by ion release measurements in Tris buffer. The results show that sodium-free bioactive glasses formed apatite at 3 h of immersion in Tris buffer, which is as fast as the corresponding sodium-containing composition. This signifies that sodium is not an essential component in bioactive glasses and it is possible to make equally degradable bioactive glasses with or without sodium. The results presented here also emphasize the central role of the glass compositions design which is based on understanding of structural role of components and/or predicting the network connectivity of glasses.     

Effect of chloride ions in Tris buffer solution on bioactive glass apatite mineralization

Degradation and apatite precipitation of Bioglass 45S5 were characterized in two different tris(hydroxymethyl)aminomethane (Tris) buffer solutions. In the conventional one, pH was adjusted to 7.4 using hydrochloric acid (Tris-HCl buffer). In the other one, acetic acid was used instead, thereby obtaining a Tris buffer solution, which was virtually free of chloride ions (Tris-HAc). EDX results showed that chloride ions present in Tris-HCl buffer solution were incorporated into the apatite formed during immersion experiments, forming a (partially) substituted chlorapatite. No chloride ions were detected in apatite precipitated in Tris-HAc. Although no significant differences in the rate of apatite formation were observed during the time points studied here (6 hours to 7 days), the presence of chloride ions may affect very early stages of apatite formation. It may therefore be advantageous to use modified Tris buffer solutions, which do not contain high concentrations of ions involved in apatite formation, when studying early time point release kinetics or apatite precipitation of bioactive glasses.     

A nickel tetra-coordinated complex as catalyst in heterogeneous hydrogenation

The [NiCl₂(NH₂(CH₂)₁₂CH₃)₂] complex supported on γ-Al₂O₃ produces a catalyst which is considerably more active and sulfur-resistant for the hydrogenation of cyclohexene carried out in mild conditions than a conventional catalyst obtained from acid solutions of NiCl₂ and even than the same complex unsupported. As determined by XPS, the active species is the complex itself, which is stable under the reaction conditions. The higher sulfur-resistance is attributed to electronic and geometrical effects. The catalyst system is considerably more resistant to poisoning with thiophene than with tetrahydrothiophene. © 1998 SCI     

Frequency and antimicrobial resistance of Salmonella serotypes on beef carcasses at small abattoirs in Jalisco State, Mexico

The prevalence and antimicrobial resistance of Salmonella serotypes on beef carcasses from four small abattoirs in Jalisco State, Mexico, were investigated during a 10-month period. Following U.S. Department of Agriculture Food Safety and Inspection Service protocols, Salmonella was isolated from 78 (15.4%) beef carcasses (n = 505) after the final carcass water wash. Isolation frequency differed by establishment (P < 0.05) and was higher (P < 0.05) during the wet season (May through September) for all establishments. Thirteen Salmonella serotypes and four serogroups (partially serotyped isolates) were identified. The most prevalent were Salmonella enterica Give (24.4%), Salmonella Typhimurium (17.9%), and Salmonella Group B (14.1%). Antimicrobial susceptibility was tested against 11 drugs, and results indicated that 46.2% of the isolates were resistant to tetracycline, 42.3% were resistant to streptomycin, 23.1% were resistant to chloramphenicol, 21.8% were resistant to trimethoprim-sulfamethoxazole, and 19.2% were resistant to gentamicin. No resistance to ceftriaxone or ciprofloxacin was observed, and 33% of the isolates were resistant to three or more antimicrobials. Although Salmonella Give was the most prevalent serotype, 95% of the isolates of this serotype were susceptible to all antimicrobials tested. Antimicrobial resistance was more common in Salmonella Typhimurium, and 93% (13 of 14) of the isolates of this serotype were resistant to at least five antimicrobials. The frequency of multidrug-resistant Salmonella isolates differed among establishments (P < 0.05) and may be related to the origin of the cattle presented for harvesting. These findings highlight the need for control measures to reduce Salmonella prevalence on beef carcasses in small abattoirs in Mexico and for strategies to ensure the cautious use of antimicrobials in animal production to prevent and control the spread of antimicrobial-resistant foodborne pathogens.     

Effects of nitrobenzene concentrations and hydraulic retention time on the treatment of nitrobenzene in sequential anaerobic baffled reactor and continuously stirred tank reactor system.

The effects of increasing nitrobenzene (NB) concentrations and hydraulic retention time (HRT) on the performance of anaerobic baffled reactor (ABR) and aerobic completely stirred tank reactor (CSTR) were studied. In the first step the NB concentration was increased from 30 to 700 mg/L at constant COD and flowrates. Maximum COD removal efficiencies in ABR varied between 88-92% as NB concentrations increased from 30 to 210 mg/L. After this dose, COD removal efficiency decreased to 85 and 79% at NB concentrations of 550 and 700 mg/L, respectively. Removal efficiencies of NB were nearly 100% for all NB concentrations in ABR reactor effluent. In the second step, COD and NB concentrations were kept constant while HRT decreased from 10.38 days to 1 day. As HRT decreased from 10.38 to 2.5 days the COD removal efficiencies in the anaerobic and anaerobic/aerobic reactor effluents were 92-94% and 97-98%, respectively. As HRT decreased from 2.5 days to 1 day COD removal efficiencies in the anaerobic and anaerobic/aerobic reactor effluents decreased to 83 and 95%, respectively. This study showed that HRT is a more important operation parameter than increasing NB concentration in ABR/CSTR sequential reactor system. Although ABR/CSTR system exhibited good COD and NB removal efficiencies, the lower HRTs slightly decreased the removal efficiencies compared to increasing NB concentration.     

Synthesis of Antibacterial Hybrid Hydroxyapatite/Collagen/Polysaccharide Bioactive Membranes and Their Effect on Osteoblast Culture

Inspired by the composition and confined environment provided by collagen fibrils during bone formation, this study aimed to compare two different strategies to synthesize bioactive hybrid membranes and to assess the role the organic matrix plays as physical confinement during mineral phase deposition. The hybrid membranes were prepared by (1) incorporating calcium phosphate in a biopolymeric membrane for in situ hydroxyapatite (HAp) precipitation in the interstices of the biopolymeric membrane as a confined environment (Methodology 1) or (2) adding synthetic HAp nanoparticles (SHAp) to the freshly prepared biopolymeric membrane (Methodology 2). The biopolymeric membranes were based on hydrolyzed collagen (HC) and chitosan (Cht) or κ-carrageenan (κ-carr). The hybrid membranes presented homogeneous and continuous dispersion of the mineral particles embedded in the biopolymeric membrane interstices and enhanced mechanical properties. The importance of the confined spaces in biomineralization was confirmed by controlled biomimetic HAp precipitation via Methodology 1. HAp precipitation after immersion in simulated body fluid attested that the hybrid membranes were bioactive. Hybrid membranes containing Cht were not toxic to the osteoblasts. Hybrid membranes added with silver nanoparticles (AgNPs) displayed antibacterial action against different clinically important pathogenic microorganisms. Overall, these results open simple and promising pathways to develop a new generation of bioactive hybrid membranes with controllable degradation rates and antimicrobial properties.     

The addition of sugarcane bagasse and asparagus peel enhances the properties of sweet potato starch foams

The agro‐industrial wastes, sugarcane bagasse (SB) and asparagus peel (AP), were used to enhance the properties of biodegradable foam trays based on sweet potato starch‐based foam trays (starch/SB and starch/AP trays, respectively). Starch/SB and starch/AP trays containing different concentrations of SB and AP (0%‐40%, w/w) were prepared, and their microstructure and physical, thermal, and mechanical properties were characterized. The addition of fibers wastes allowed obtaining a yellowish foam tray with lower luminosity and higher porosity, mechanical resistance, deformability, and better ability to absorb water as compared with the sweet potato starch foam trays without fibers. The addition of SB yielded foam trays less porous, with lower water absorption capacity and greater tensile strength than the addition of AP. Higher concentrations of AP fibers (greater than 30%) generate more extendible foam trays. The addition of fibrous wastes improved the thermal stability of the sweet potato starch foam trays. The composite foam trays produced in this work could be used as substitutes for expanded polystyrene in dry food packaging.     

Increase of Circulating Monocyte–Platelet Conjugates in Rheumatoid Arthritis Responders to IL-6 Blockage

Platelets (PLT) bind to a significant percentage of circulating monocytes and this immunomodulatory interaction is increased in several inflammatory and autoimmune conditions. The therapeutic blockage of IL-6 with Tocilizumab (TCZ) alters PLT and the phenotype and function of monocytes in rheumatoid arthritis (RA). However, the relationship between monocyte–PLT conjugates (CD14+PLT+) and clinical and immunological variables and the regulation of this interaction by IL-6 blockage are still unknown. Here, we compared the presence of monocyte–PLT conjugates (CD14+PLT+) and membrane CD162 expression using flow cytometry, and, by ELISA, the markers of PLT activation (sCD62P and sCD40L) in healthy donors (HD) and patients with long-standing RA before TCZ (baseline). We found higher percentages and absolute counts of CD14+PLT+, and higher plasmatic levels of sCD62P and sCD40L but lower CD162 expression on monocytes from RA patients than those from HD. Additionally, the levels of CD14+PLT+ inversely correlated with inflammatory parameters. Interestingly, 95% of patients with lower percentages of CD14+PLT+ and only 63% of patients with higher percentages of CD14+PLT+ achieved a EULAR-defined response at four weeks (p = 0.036). After TCZ, the percentage of CD14+PLT+ increased in 92% of RA patients who achieved 12 w-remission (p < 0.001). Our results suggest that the binding of PLTs has a modulatory effect, accentuated by the increased binding of PLTs to monocytes in response to the therapeutic blockage of IL-6.     

Bupivacaine‐loaded chitosan hydrogels for topical anesthesia in dentistry

The paper describes the preparation of polymeric hydrogels, loaded with bupivacaine, which could represent a good alternative in clinical dentistry as local anesthetics. The hydrogels were prepared by condensation using an amidation reaction between a natural polymer (chitosan) and a synthetic one, poly[(maleic anhydride)‐alt‐(vinyl acetate)]. Infrared spectroscopy studies confirmed crosslinking through the presence of amide bonds, formed between the two types of polymer chains. Scanning electron microscopy results demonstrated that the hydrogels have a porous structure, the pore dimensions being non‐uniform with diameters between 200 and 600 μm. Hydrogels presented good bupivacaine inclusion and release capacity whereas theoretical analysis confirmed the validity of the generalized fractal model, reinforcing a csavi‐universal pattern of drug release. Cytotoxicity tests on human dermal fibroblasts revealed that the obtained hydrogels are not cytotoxic. In vivo, the bupivacaine‐loaded hydrogels presented anesthetic effects after 15 min and no side effects were observed. This system has the advantage of alleviating or eliminating pain associated with invasive procedures and avoiding direct contact of the drug with tissues, leading thus to the prevention of side effects. © 2020 Society of Chemical Industry