Enhancement of mechanical properties and chemical durability of Soda-lime silicate glasses treated by DC gas discharges

We report for the first time a study on non-contact thermal poling of soda lime silicate glasses using DC gas discharge. In this work, the formation of a glow discharge is evidenced during the thermal poling treatment (longer than 30 minutes). The hardness and the chemical durability of glasses poled under different conditions (contact or non-contact) and atmospheres (nitrogen or air) are measured and compared to that of un-poled reference glass. The results reveal enhanced mechanical and chemical properties for samples poled under nitrogen as compare to air poled or soda lime silicate glass samples. A structural and chemical analysis of surface of the glass using IR-reflectance measurement and ToF-SIMS is also presented. The formation of a “silica-like” layer on the surface of nitrogen poled glasses is observed, which is likely associated with the enhancement of surface properties. On the other hand, the introduction of protons beneath the surface of glasses poled under air leads to the formation of a hydrated alkaline earth silica layer. Based on the observations a mechanism behind the sustainability of the plasma under DC conditions is proposed.     

Influence of Lipid Saturation,Hydrophobic Length and Cholesterol on Double-Arginine-Containing Helical Peptides in Bilayer Membranes

Membrane proteins are essential for many cell processes yet are more difficult to investigate than soluble proteins. Charged residues often contribute significantly to membrane protein function. Model peptides such as GWALP23 (acetyl-GGALW⁵LAL⁸LALALAL¹⁶ALW¹⁹LAGA-amide) can be used to characterize the influence of specific residues on transmembrane protein domains. We have substituted R8 and R16 in GWALP23 in place of L8 and L16, equidistant from the peptide center, and incorporated specific ²H-labeled alanine residues within the central sequence for detection by solid-state ²H NMR spectroscopy. The resulting pattern of [²H]Ala quadrupolar splitting (Δν_q) magnitudes indicates the core helix for R^8,16GWALP23 is significantly tilted to give a similar transmembrane orientation in thinner bilayers with either saturated C12:0 or C14:0 acyl chains (1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) or 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC)) or unsaturated C16:1 Δ9 cis acyl chains. In bilayers of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC; C18:1 Δ9 cis) multiple orientations are indicated, whereas in longer, unsaturated 1,2-dieicosenoyl-sn-glycero-3-phosphocholine (DEiPC; C20:1 Δ11 cis) bilayers, the R^8,16GWALP23 helix adopts primarily a surface orientation. The inclusion of 10–20 mol % cholesterol in DOPC bilayers drives more of the R^8,16GWALP23 helix population to the membrane surface, thereby allowing both charged arginines access to the interfacial lipid head groups. The results suggest that hydrophobic thickness and cholesterol content are more important than lipid saturation for the arginine peptide dynamics and helix orientation in lipid membranes.     

Thermomechanical characterization of thermoplastic polyimide to improve the chain interaction via crystalline domains

In a previous study on polyimides, we incorporated an aromatic diamine monomer with a methylene linker, 4,4′‐methylenebis(2,6‐dimethylaniline), to make a robust main chain along with aliphatic polyetherdiamine backbone linkers to decrease rigidity. In this report, we explore the behavior of crystalline regions provided by the organized packing of polyethylene oxide into the formerly characterized polymers. The polymers were designed to exhibit thermal properties in between those of conventional aromatic polyimides and polymers with wholly aliphatic ether diamine links, with a target to improve the mechanical characteristics. Through dynamic mechanical analysis and differential scanning calorimetry, it is shown that the incorporation of polyethylene oxide diamine and the removal of methyl pending groups serve to improve the organized packing of the chains. All of this allows for a broader range in tenability of thermal and mechanical properties of the polyimide. Furthermore, the crystalline regions are an important component to maintain the temperature stability of polyimide while maintaining the processability. The polymers are characterized by Fourier‐transform infrared spectroscopy, thermomechanical and calorimetric analysis, microhardness measurements, tensile testing, and wide‐angle X‐ray scattering. POLYM. ENG. SCI., 59:1919–1932, 2019. © 2019 Society of Plastics Engineers     

Rehydration and Rehydroxylation in Ancient Ceramics: New Constraints from Mass Gain Analyses Versus Annealing Temperatures

We present a series of new mass‐gain data acquired on ancient pottery following heating at increasing temperatures from 60°C to 590°C to further constrain our understanding of the rehydration and rehydroxylation (RHX) processes acting within archeological fired‐clay artifacts. The ancient pottery, deliberately chosen for its low‐porosity, is second century ad Samian ware fragments originating from Lezoux in central France. The mass‐gain data, after each temperature step, adequately define a (time)^1/N power law. We demonstrate that values of the 1/N exponent vary systematically with heating temperature. These results suggest that the sorption of chemisorbed and rehydroxylated water into the clay matrix occurs simultaneously. The 1/N exponent values obtained are consistent with power law kinetics resulting from the combination of both one‐dimensional and Brownian diffusion processes. The balance between these two end‐member processes, in particular after heating at 500°C, may depend on the nature of the clay and on the manufacturing conditions of the studied ceramics. The results presented herein confirm previous claims that major complexities vitiate the RHX dating method proposed by Wilson et al. 1     

Effect of Particle Size on the Performance of an N95 Filtering Facepiece Respirator and a Surgical Mask at Various Breathing Conditions

The effect of aerosol particle size on the performance of an N95 filtering facepiece respirator (FFR) and a surgical mask (SM) was evaluated under different breathing conditions, including breathing frequency and mean inspiratory flow (MIF) rate. The FFR and SM were sealed on a manikin headform and challenged with charge-equilibrated NaCl aerosol. Filter penetration (P _filter) was determined as the ratio of aerosol concentrations inside and outside the FFR/SM size-selectively (28 channels) within a range of 20 to 500 nm. In addition, the same models of the FFR and SM were donned, but not sealed, on an advanced manikin headform covered with skin-like material. Total inward leakage (TIL), which represents the total particle penetration, was measured under conditions identical to the filter penetration experiment. Testing was conducted at four mean MIFs (15, 30, 55, and 85 L/min) combined with five breathing frequencies (10, 15, 20, 25, and 30 breaths/min). The results show that SM produced much higher P _filter and TIL values, and thus provide little protection against aerosols in the size range tested. P _filter was significantly affected by particle size and breathing flow rate (p < 0.05) for the tested FFR and SM. Surprisingly, for both devices, P _filter as a function of the particle size exhibited more than one peak under all tested breathing conditions. The effect of breathing frequency on P _filter was generally less pronounced, especially for lower MIFs. For the FFR and SM, TIL increased with increasing particle size up to about 50 nm; for particles above 50 nm, the total penetration was not significantly affected by particle size and breathing frequency; however, the effect of MIF remained significant.

Copyright 2013 American Association for Aerosol Research     

竹制活性炭处理酸性染料废水吸附等温线模型的误差分析(英文)

High surface area activated carbons were produced by thermal activation of waste bamboo scaffolding with phosphoric acid.Single component equilibrium dye adsorption was conducted on the carbons produced and compared with a commercially available carbon.Two acid dyes with different molecular sizes,namely Acid Yellow 117(AY117) and Acid Blue 25(AB25),were used to evaluate the adsorption capacity of the produced carbons.It was found that the dye with smaller molecular size,AB 25,was readily adsorbed onto the produced carbon,nearly three times higher than a commercially available carbon,while the larger size dye,AY117,showed little adsorption.The experimental data were analyzed using isotherm equations including Langmuir,Freundlich,Tempkin,Toth,Redlich-Peterson and Sips equations.The equilibrium data were then analyzed using five different non-linear error analysis methods.     

Targeted Suppression of Lipoprotein Receptor LSR in Astrocytes Leads to Olfactory and Memory Deficits in Mice

Perturbations of cholesterol metabolism have been linked to neurodegenerative diseases. Glia–neuron crosstalk is essential to achieve a tight regulation of brain cholesterol trafficking. Adequate cholesterol supply from glia via apolipoprotein E-containing lipoproteins ensures neuronal development and function. The lipolysis-stimulated lipoprotein receptor (LSR), plays an important role in brain cholesterol homeostasis. Aged heterozygote Lsr+/− mice show altered brain cholesterol distribution and increased susceptibility to amyloid stress. Since LSR expression is higher in astroglia as compared to neurons, we sought to determine if astroglial LSR deficiency could lead to cognitive defects similar to those of Alzheimer’s disease (AD). Cre recombinase was activated in adult Glast-CreERT/lsrfl/fl mice by tamoxifen to induce astroglial Lsr deletion. Behavioral phenotyping of young and old astroglial Lsr KO animals revealed hyperactivity during the nocturnal period, deficits in olfactory function affecting social memory and causing possible apathy, as well as visual memory and short-term working memory problems, and deficits similar to those reported in neurodegenerative diseases, such as AD. Furthermore, GFAP staining revealed astroglial activation in the olfactory bulb. Therefore, astroglial LSR is important for working, spatial, and social memory related to sensory input, and represents a novel pathway for the study of brain aging and neurodegeneration.     

Chronic and acute effects of walnuts on antioxidant capacity and nutritional status in humans: a randomized,cross-over pilot study

Background  

Compared with other common plant foods, walnuts (Juglans regia) are consistently ranked among the highest in antioxidant capacity. In vitro, walnut polyphenols inhibit plasma and LDL oxidation, while in animal models they lower biomarkers of oxidative stress and raise antioxidant capacity. A limited number of human feeding trials indicate that walnuts improve some measures of antioxidant status, but not others.     

Simplified fixed bed column model for adsorption of organic pollutants using tapered activated carbon columns

The dynamic adsorption of organic pollutants (an acid dye and para-chlorophenol) has been investigated via tapered column adsorbers using activated carbon. Equilibrium sorption isotherm experiments were determined to provide a crucial parameter, the saturation capacity (q_e) of each pollutant by F 400 carbon, for operating continuous adsorption columns. The Redlich–Peterson isotherm gave the best fit model to describe the sorption process of these organic pollutants onto F 400 carbon. Adsorption studies of organic pollutants have been carried out in novel tapered fixed bed columns using activated carbon. A series of columns with different tapered angles, from one to five degrees, have been used. Experimental data obtained from the breakthrough curves have been analysed using the Bed Depth Service Time (BDST) model in this paper. However, the conventional BDST model has not been applied to tapered beds before, as the linear velocity of adsorbate is changing along the column. Therefore, some modifications have been developed to the original model. The extended-modified BDST model has proved to be successful in correlating the bed height and service time for tapered column adsorption.     

High efficiency UMG silicon solar cells: impact of compensation on cell parameters

High efficiency solar cells have been fabricated with wafers from an n‐type Czochralski grown (Cz) ingot using 100% Upgraded Metallurgical‐Grade (UMG) silicon feedstock. The UMG cells fabricated with a passivated emitter and rear totally diffused (PERT) structure have an independently confirmed cell efficiency of 19.8%. This is the highest efficiency reported for a cell based on 100% UMG silicon at the time of publication. The current and power losses are analysed as a function of measured material parameters, including carrier mobility, lifetime and the presence of the boron–oxygen defect. Dopant compensation is shown to reduce both the minority carrier lifetime and mobility, which significantly affects both the current and voltage of the device. Copyright © 2015 John Wiley & Sons, Ltd.