Modified insulator semiconductor electrode with functionalized nanoparticles for Proteus mirabilis bacteria biosensor development

The development of enzymatic sensors for biological purposes such as biomedicine, pharmacy, food industry, and environmental toxicity requires the purification step of the enzyme. To prevent the loss of the enzyme activity, a new strategy is held in order to immobilize the bacteria. It will constitute the biological sensing element leading to a high operational stability and multiple adaptations to various conditions such as temperature, pH and ionic strength changes. In this work we describe the development of a urea biosensor by immobilizing Proteus mirabilis bacteria onto an insulator–semiconductor electrode on functionalized Fe₃O₄ nanoparticles (NPs), using cationic, Poly (allylamine hydrochloride) then anionic, Poly (sodium 4-styrenesulfonate) polyelectrolytes, BSA (serum bovin albumin), and glutaraldehyde as a cross-linking agent. The response of P. mirabilis to urea addition is evaluated in homogeneous and heterogeneous phases. Before the immobilization step, the activity of urease produced from the P. mirabilis bacteria was attempted using the ion ammonium selective electrodes (ISEs). Adhesion of the bacteria cells on IS electrodes have been studied using contact angle measurements.After immobilization of the bacteria, on the (Si/SiO₂/Si₃N₄) and (Si/SiO₂) substrates, the relationship between the evolution of the flat band potential ?V_FB and the urea concentration is found to be linear for values ranging from 10^? 2 M to 10^? 5 M.     

Unified model for assessing checkpointing protocols at extreme‐scale

In this paper, we present a unified model for several well‐known checkpoint/restart protocols. The proposed model is generic enough to encompass both extremes of the checkpoint/restart space, from coordinated approaches to a variety of uncoordinated checkpoint strategies (with message logging). We identify a set of crucial parameters, instantiate them, and compare the expected efficiency of the fault tolerant protocols, for a given application/platform pair. We then propose a detailed analysis of several scenarios, including some of the most powerful currently available high performance computing platforms, as well as anticipated Exascale designs. The results of this analytical comparison are corroborated by a comprehensive set of simulations. Altogether, they outline comparative behaviors of checkpoint strategies at very large scale, thereby providing insight that is hardly accessible to direct experimentation. Copyright © 2013 John Wiley & Sons, Ltd.     

Ultrafine Wool and Cotton Powder and Their Characteristics

Micro powders of recycled wool and cotton from textile waste is prepared and characterized. Wool and cotton waste fibers were frozen in liquid nitrogen and milled for various period times to produce fine powders. The powders sizes distribution depends on the milling time. Scanning electron microscopy micrographs confirm that, the fine cotton and wool powders have average size around 60 μm, and that, there are powder particle with size even less than 20 μm. Differential scanning calorimeter (DSC) and thermal gravimetrical analysis (TGA) results show that as the powder particle size decreases, its thermal stability increases slightly. Fourier transform infrared spectroscopy, Raman spectroscopy, and amino acid analysis confirm that, the freeze milling technique is a safe technique to produce ultrafine powder, with no effect on the chemical structure of cotton and wool.     

Numerical simulation of the effect of grain size on corrosion processes: Surface roughness oscillation and cluster detachment

This work reports on the numerical simulation results of the grain size effect on the corrosion processes using a cellular automata model. The material considered consists of domains and their edges. The domains represent the monocrystalline cores while their edges represent the intergranular defects. Either a periodic pattern or randomly generated domains of Voronoï tessellation are used. The model parameters, taking into account the polycrystalline aspect of corrosion, are the domain density and the corrosion probabilities of metal grain core and grain boundary sites. The corrosion probability for grain edge is taken as higher than for the grain core. A complicated surface structure appears with a high geometrical roughness if the density of defects is not too high. A strong correlation between the roughness evolution, the metal crystalline properties and the corrosion mechanism of the metal dissolution was established.     

Texturation of model clay materials using tape casting and freezing

The present work aimed to investigate the processing of textural clay based materials using tape casting together with freezing. Two model raw materials were used, namely: BIP kaolin from France and ABM montmorillonite from Mediterranean region. The mixtures of both clays were studied, whereby, the amount of montmorillonite was 0, 5, 10, 20 or 50 mass%. After tape casting, the as-obtained green bands were frozen into liquid nitrogen, lyophilized and then fired at 1050 °C or 1200 °C.The amount of montmorillonite appeared as a critical parameter that controls the cohesion of the dry products. For montmorillonite content ≥20 mass%, the products exhibited multiple cracks after lyophilisation. With lower montmorillonite content, the cohesion of the dry products was satisfactorily and a macroscopic cross-linked surface texturation was observed. After calcination at 1050 °C or 1200 °C, the texturation appeared well defined. Moreover, calcination at 1200 °C increased the densification of products and the occurrence of a glassy phase was noted.The combination of both tape casting and freezing (freeze tape casting) is a promising way to develop various clay-based and composites materials exhibiting unique microstructure organization and characteristics with potential application in the field sustainable and environmentally friendly filtration, adsorption or catalysis.     

Facile synthesis of hybrid nanocomposite based on chitosan binary metal oxides for high-performance supercapacitor

The advancement in materials for energy storage for supercapacitors has been supported by the current shortage of energy as well as the increasing availability of sources of clean energy. Consequently, two-dimensional materials based on metal oxide nanoparticles (copper oxide (CuO) and zinc oxide (ZnO), have great potential for the previously discussed utilization. A simple and affordable solid-state approach was employed to design hybrid nanocomposite based on chitosan (Cs) blended with ZnO and CuO; this nanocomposite was labeled with CZC. The structural, morphological investigation of CZC hybrid nanocomposites, and X-ray diffraction (XRD) of the prepared nanocomposites were characterized. Consequently, hybrid nanocomposites for application as electrodes for supercapacitor devices were developed. The hybrid nanocomposite (CZC-3) shows improved cycle stability, high energy density, and a specific capacitance in the electrochemical activity. Remaining at 97.8% of the initial capacitance even after 5000 cycles. These results imply that the hybrid nanocomposite based on Cs/ZnO/CuO has a promising future as a supercapacitor electrode material. Additionally, it provides superior performance to other nanocomposites with a high specific capacitance of 638.3 F/g and about 86.98% capacity retention after 5000 cycles at a current density of 1 A/g.     

Antibacterial activity of quaternary ammonium salt grafted cotton

Cotton having good antibacterial activity can be obtained without the need for a binding chemical as a cross linker or the need for chemically pre-treated antibacterial agent. The procedure of synthesis consists in grafting an alkali-cellulose fibre by a quaternary ammonium salt: Epoxy propyltrimethylammonium chloride (EPTMAC). The characterization of grafted cotton (EPTMAC-Cotton) has been targeted on the nitrogen and the methyl group in the ammonium graft structure, by using some analytical techniques, such as infrared, NMR spectroscopy, and volumetric measurement. The antibacterial activity of EPTMAC-Cotton has been studied using four kinds of bacterial stains (Escherichia coli 25922, Pseudomonas aeruginosa 27853, Staphylococcus aureus 259223 and Salmonella LT2DT104 typhimirium). An optimization of conditions of culture medium has been carried out for the bacterial strain for which the modified cotton presents the best antibacterial activity. This optimization is achieved while varying the most important parameters influencing the bacterial growth. We have chosen the pH and the sodium chloride concentration as variable parameters, and we have applied an experiment plant, in order to consider all possible combinations of experiments, and therefore, to estimate the effect of each factor, as well as the effect of their interaction. It has been noticed that a quaternary ammonium salt (EPTMAC) is an efficient antibacterial agent, especially against salmonella in alkaline medium slightly concentrated in salt, and its action depends, in some manner, on the whitening procedure of cotton.     

Wavelet neural networks for modelling high pressure inactivation kinetics of Listeria monocytogenes in UHT whole milk

The aim of the present work was to investigate the applicability of a Wavelet Neural Network to describe the inactivation pattern of Listeria monocytogenes by high hydrostatic pressure in ultra high temperature (UHT) whole milk, and evaluate its performance against models used in predictive microbiology such as the re-parameterized Gompertz and modified Weibull equations. A comparative study with linear partial least squares regression (PLS-R) as well as neural network (NN) models demonstrated on the same dataset has been also considered. Milk was artificially inoculated with an initial population of the pathogen of ca. 10⁷ CFU/ml and exposed to a range of high pressures (350, 450, 550, 600 MPa) for up to 40 min at ambient temperature (ca. 25 °C). Typical survival curves were obtained including a shoulder, a log-linear and a tailing phase. Increasing the magnitude of the applied pressure resulted in increasing levels of inactivation. Modelling approaches provided good fit to experimental training data as inferred by the low values of the root mean squared error (RMSE) and the high values of regression coefficient (R²). Models were validated at 400 and 500 MPa with independent experimental data. First or second order polynomial models were employed to relate the inactivation parameters to pressure, whereas the wavelet network as well as the PLS and NN models were utilised as a one-step modelling approach. The prediction performance of the proposed learning-based network was better at both validation pressures. The development of accurate models to describe the survival curves of micro-organisms in high pressure treatment would be very important to the food industry for process optimisation, food safety and would eventually expand the applicability of this non-thermal process.     

Tryptophan: From Diet to Cardiovascular Diseases

Cardiovascular disease (CVD) is one of the major causes of mortality worldwide. Inflammation is the underlying common mechanism involved in CVD. It has been recently related to amino acid metabolism, which acts as a critical regulator of innate and adaptive immune responses. Among different metabolites that have emerged as important regulators of immune and inflammatory responses, tryptophan (Trp) metabolites have been shown to play a pivotal role in CVD. Here, we provide an overview of the fundamental aspects of Trp metabolism and the interplay between the dysregulation of the main actors involved in Trp metabolism such as indoleamine 2, 3-dioxygenase 1 (IDO) and CVD, including atherosclerosis and myocardial infarction. IDO has a prominent and complex role. Its activity, impacting on several biological pathways, complicates our understanding of its function, particularly in CVD, where it is still under debate. The discrepancy of the observed IDO effects could be potentially explained by its specific cell and tissue contribution, encouraging further investigations regarding the role of this enzyme. Thus, improving our understanding of the function of Trp as well as its derived metabolites will help to move one step closer towards tailored therapies aiming to treat CVD.     

Liberal and conservative political ideology, experiences of harassment, and perceptions of campus climate.

The purpose of this study was to examine the relations among racial-ethnic group membership, political ideology (i.e., conservative and liberal), and perceptions of general campus climate (GCC) and of campus climate for racial-ethnic minorities (RECC). One hundred and thirty-six (136) undergraduate, graduate, and professional students participated in this study at a large public Midwestern university. A series of multivariate analyses of variance, hierarchical regressions, and mediation analyses were conducted. Findings indicated that Whites endorsed more positive perceptions of campus climate, reported fewer experiences of racial-ethnic harassment, and endorsed less liberal political ideological beliefs than people of color. No racial differences in conservative ideology emerged. After controlling for racial-ethnic group membership, results showed that experiences of racial-ethnic harassment predicted both GCC and RECC, whereas conservative ideology only predicted RECC. Post hoc analyses demonstrated that experiences of racial-ethnic harassment fully mediated the relationship between racial-ethnic group membership and GCC, but only partially mediated the relationship between racial-ethnic group membership and RECC. Neither conservative nor liberal ideologies were significant mediators. Implications for future research and practice are provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved)