Nano Silicon from Nano Silica Using Natural Resource (Rha) for Solar Cell Fabrication

Abstract

High purity (～99%) nano silica with an average particle size of ～100 nm was extracted at pH 3 at 650°C from a natural resource, rice husk, using alkaline extraction followed by acid precipitation method. Using nano silica as a precursor, silicon (Si) nanoparticles have been synthesized by high-temperature magnesiothermic reduction method. The prepared sample was characterized by X-ray diffraction, particle size analyzer, Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray fluorescence analyzer, and UV–Vis spectroscopy. The comprehensive characterization studies indicate the pure phase formation of Si and the variation of particle size from 70 nm to 100 nm for samples synthesized at different sintering temperatures. Moreover, the silicon nanoparticles produced at 850°C have pure phase formation, high purity, and good absorption peaks. The efficiency calculated through IV characteristics is found to be increasing in silicon and ruthenium combination (2.67%), which is better than that achieved from the conventional solar cells. The produced silicon nanoparticles could be applied as an anode material for solar cell fabrication.     

Polymicrobial Biofilm Inhibition Effects of Acetate‐Buffered Chitosan Sponge Delivery Device

Polymicrobial biofilm‐associated implant infections present a challenging clinical problem. Through modifications of lyophilized chitosan sponges, degradable drug delivery devices for antibiotic solution have been fabricated for prevention and treatment of contaminated musculoskeletal wounds. Elution of amikacin, vancomycin, or a combination of both follows a burst release pattern with vancomycin released above minimum inhibitory concentration for Staphylococcus aureus for 72 h and amikacin released above inhibitory concentrations for Pseudomonas aeruginosa for 3 h. Delivery of a vancomycin, amikacin, or a combination of both reduces biofilm formation on polytetrafluoroethylene catheters in an in vivo model of contamination. Release of dual antibiotics from sponges is more effective at preventing biofilm formation than single‐loaded chitosan sponges. Treatment of pre‐formed biofilm with high‐dose antibiotic release from chitosan sponges shows minimal reduction after 48 h. These results demonstrate infection‐preventive efficacy for antibiotic‐loaded sponges, as well as the need for modifications in the development of advanced materials to enhance treatment efficacy in removing established biofilm.

     

Relative effectiveness of pretreatments on performance of Rhizomucor miehei lipase in nonpolar reaction media

Enzymes can be used in nonpolar reaction media to modify waterinsoluble substrates. A variety of pretreatments, applied to the enzyme prior to introduction to the nonpolar media, can improve enzyme activity. However, the various pretreatments have not been studied using directly comparable conditions, nor have they been applied simultaneously to test for interactive effects. This work evaluates pretreatment of lipase with various classes of additives. The pretreated lipase is used to catalyze esterification between citronellol and acetic acid in a medium of n-hexane. The effectiveness of a particular pretreatment is presented in terms of relative performance (RP), which is equal to the number of times faster the pretreated lipase catalyzes the reaction relative to untreated lipase. The individual and interactive effects of the pretreatment factors were studied and compared. Buffer salts had a much stronger performance-enhancing effect than nonbuffer salts; pretreatment with 90% (w/w) sodium phosphate yielded lipase with an RP of approx 64. A strong interaction was found between the treatments with sodium phosphate and pH adjustment. These treatments may mitigate the inhibitory effect of acetic acid. Activating effects of phase interfaces and active-site protectants are shown to be complementary to other treatments, demonstrating that they likely act by distinct mechanisms.     

Physicochemical Differences in Dehydrated Saccharomyces Boulardii Yeast as a Function of the Dehydration Process

Measurements of the masses of incorporated water and of the heats of hydration have been performed at 310 K, under air atmosphere saturated with water vapour, on three differently dehydrated samples of the Saccharomyces boulardii yeast in order to evaluate differences in physicochemical properties related to the following dehydration processes: cryodesiccation (or lyophilization) and thermodesiccation (spray drying and in-fluidized-bed heating).Thermogravimetric (TG) experiments have shown that the lyophilized yeast contains less residual water than heat-treated yeasts and that it incorporates more water and more rapidly. Isothermal water sorption of a spherical yeast cell has been represented by a two-parameter equation able to take account of a maximum of the hydration rate when this is taken as a function of time. On the other hand, isothermal DSC experiments have shown that hydration-heat values are higher for the heat-treated yeasts than for the lyophilized one. The TG and DSC results have been shown to be consistent with the idea that the physicochemical properties of a dehydrated yeast are related to cell-wall behaviour during desiccation.This revised version was published online in November 2005 with corrections to the Cover Date.     

From Colloidal Dispersions of Zeolite Monolayers to Effective Solid Catalysts in Transformations of Bulky Organic Molecules: Role of Freeze-Drying and Dialysis

We investigated the properties and catalytic activity of zeolites with MWW topology obtained by unprecedented liquid exfoliation of the MCM-56 zeolite into solutions of monolayers and isolation/reassembly of the dispersed layers by various methods, with optional purification by dialysis or ammonium exchange. The layers were recovered by flocculation with alcohol or ammonium nitrate and freeze-drying. Flocculation alone, even with ammonium nitrate, did not ensure removal of residual sodium cations resulting in catalysts with low activity. Dialysis of the solutions with dispersed monolayers proved to be efficient in removing sodium cations and preserving microporosity. The monolayers were also isolated as solids by freeze-drying. The highest BET area and pore volume obtained with the freeze-dried sample confirmed lyophilization efficiency in preserving layer structure. The applied test reaction, Friedel–Crafts alkylation of mesitylene, showed high benzyl alcohol conversion due to increased concentration of accessible acid centers caused by the presence of secondary mesoporosity. The applied treatments did not change the acid strength of the external acid sites, which are the most important ones for converting bulky organic molecules. Zeolite acidity was not degraded in the course of exfoliation into monolayers, showing the potential of such colloid dispersions for the formation of active catalysts.     

New apparatus for the in-situ observation of a freeze drying process

This work presents the performances of a new apparatus developed for thein-situ observation of a freeze drying (lyophilization) phenomenon. The results obtained on the lyophilization kinetics performed on a standard mixture (aqueous saturated NaCl solution) are presented.     

Determination of lipid mediators in breast cancer cells using lyophilization‒supercritical fluid extraction online coupled with supercritical fluid chromatography‒quadrupole tandem mass spectrometry

A lyophilization?supercritical fluid extraction coupled with supercritical fluid chromatography?quadrupole tandem mass spectrometry online method was developed for the determination of lipid mediators in breast cancer cells. Supercritical fluid extraction was applied to the cell samples for the first time due to the use of lyophilization. The conditions of supercritical fluid extraction and supercritical fluid chromatography?quadrupole tandem mass spectrometry were investigated systematically. Under the optimized conditions, all the calibration curves for the lipid mediators showed good linearity (correlation coefficient > 0.99). The limits of detection and the limits of quantification were in the range of 0.190?5.36 pg and 0.560?16.2 pg, respectively. The recoveries were in the range of 70.3?125%. The relative standard deviations of the precision ranged from 1.49?18.7% and the accuracies were higher than 84%. Compared with liquid?liquid extraction coupled with liquid chromatography and tandem mass spectrometry method, the present approach reduced the manual labor and obtained higher sensitivity as well as higher extraction recoveries for all 15 lipid mediators. Finally, the online method was applied to the quantification of lipid mediators in breast cancer cells and normal mammary epithelial cells. On the basis of the results, this lyophilization?supercritical fluid extraction online coupled with supercritical fluid chromatography?quadrupole tandem mass spectrometry method showed great promise in the analysis of lipid mediators in complex biological samples.     

海蜇不同部位脂肪酸的组成研究

报道了黄海海域成熟海蜇不同部位脂肪酸的研究结果。利用GC-MS技术测定海蜇皮、海蜇头、海蜇生殖腺的脂肪酸组成。结果表明：海蜇含有30多种脂肪酸,3个部位的脂肪酸组成差别不大;海蜇中含有丰富的多不饱和脂肪酸,含量在36．2％～38．7％之间,其中二十二碳六烯酸(DHA)、二十碳四烯酸(AA)和二十碳五烯酸(EPA)含量较高。     

Application of design-of-experiments procedures to optimize efficiently pretreatment of lipase for use in a nonaqueous reaction

A variety of different pretreatments can improve the performance of enzymes in nonpolar reaction media. These pretreatments have primarily been studied in isolation; however, interactions between some pairs of pretreatments are known to exist. The presence of these interactions complicates the design of an optimum multifactor pretreatment. Modern design-of-experiments techniques allow the simultaneous optimization of two or more variables. To improve the performance of lipase in a model reaction, we used a technique called the method of steepest ascent to optimize three variables simultaneously: pretreatment pH and sodium phosphate concentration, and the concentration of acetic acid (one of the reactants) in the reaction mixture. In only 26 experimental runs, this optimization process determined a combination of variable settings that yielded a reaction product approx 180 times faster than achieved with untreated enzyme. Evidence is presented to demonstrate that locating this optimum with single-factor experiments would be inefficient. This article demonstrates the efficiency of the method of steepest ascent particularly for evaluation of enzymatic reaction conditions exhibiting significant interactions.     

A nondestructive and noninvasive method to determine water content in lyophilized proteins using low-field time-domain NMR

Determining the moisture content in lyophilized solids is a fundamental step towards predicting the quality and stability of lyophilized products, but conventional methods are time-consuming, invasive, and destructive. High levels of residual moisture in a lyophilized product can lead to cake collapse, product degradation, and reduced shelf life. The aim of this study was to develop a fast, noninvasive, nondestructive, and inexpensive method for determining the moisture content in a lyophilized monoclonal antibody (mAb) formulation using benchtop low-field time-domain nuclear magnetic resonance spectroscopy.