Effects of temperature and impurities on the DC conductivity of snow

Several major parameters affecting the electrical behavior of natural snow, namely volume conductivity and density, liquid water content and conductivity of water melted from snow, are crucial for the characterization of the electrical performance of snow-covered HV insulators. However, little study has been devoted to this subject, despite of its importance. These parameters are found to vary significantly with snow composition and purity as well as with other parameters, such as temperature, airborne pollutants, electric field strength and polarity. From laboratory experiments carried out on a large number of snow samples, it was found that DC conductivity of snow shows a peak at about -2degC. This apparently curious behavior near the melting temperature is attributed to important changes to the microstructure of snow. A correlation between DC conductivity and snow temperature was established     

Influence of plasma treatment on CNT absorption of cotton fabric and its electrical conductivity and antibacterial activity

In this study, effect of plasma pretreatment on the absorption of carboxilated carbon nanotubes (CNTs) on the surface of cotton fabrics was investigated. Treated samples were characterised using a Raman spectrophotometer. Also, the morphological properties of samples were studied using a scanning electron microscope. Electrical resistance and interactions between CNTs and plasma-treated cotton functional groups at the surface were also evaluated. Antibacterial activity of cotton fabric when modified by low temperature plasma and stabilised with CNTs was also investigated. Results showed a uniform coating of CNTs on the plasma-treated cotton fabric and it was found that the plasma treatment is effective on improving CNTs absorption by cotton fabric. Generally, cotton fabric characterisation, such as antibacterial activity and electrical conductivity, after plasma treatment and loading CNT are improved.     

Critical moisture content for microbial growth in dried food‐processing residues

BACKGROUND: Food‐processing residues are good feedstocks for biofuel and biochemical production because they have high energy content and are abundant. Year‐round biofuel and biochemical production requires proper storage to prevent microbial decomposition and thermal runaway. In this study, microbial activity of tomato pomace (TP), grape pomace (GP), fermented grape pomace (FGP) and sugar beet pulp (SBP) was monitored at nine different moisture contents. RESULTS: Maximum and cumulative respirations for each feedstock with respect to moisture content followed a sigmoidal relationship. The critical moisture content below which no microbial activity was detected for SBP, TP, FGP and GP was 24–31, 16–21, 23–33 and 43–46% (dry basis) respectively. A logarithmic relationship was observed (R² = 0.94) between critical moisture content and initial water‐soluble carbohydrate (WSC) content of the processing residues. CONCLUSION: The critical moisture content below which no microbial activity was detected and the relationship between critical moisture content and initial WSC content were determined in this study for four food‐processing residues. Both parameters permit evaluation of the potential for deterioration of food‐processing residues during storage based on moisture content and WSC content. Copyright © 2010 Society of Chemical Industry     

N ‐acetylcysteine–PLGA nano‐conjugate: effects on cellular toxicity and uptake of gadopentate dimeglumine

Gadolinium as a contrast agent in MRI technique combined with DTPA causes contrast induced nephropathy (CIN) and nephrogenic systemic fibrosis (NSF) which can reduce by usage of antioxidants such as N‐acetyl cysteine by increasing the membrane''s permeability leads to lower cytotoxicity. In this study, N ‐acetyl cysteine‐PLGA Nano‐conjugate was synthesized according to stoichiometric rules of molar ratios andafter assessment by FTIR, NMR spectroscopy and Atomic Force Microscopy (AFM) imaging was combined with Magnevist® (gadopentetate dimeglumine) and its effects on the renal cells were evaluated. MTT [3‐(4,5‐Dimethylthiazol‐2‐yl)‐2,5‐Diphenyltetrazolium Bromide] and cellular uptake assays have indicated relatively significant toxicity of magnevist (P  < 0.05) on three cell lines including HEK293, MCF7 and L929 compared to other synthesized ligands that shown no toxicity. Moreover, systemic evaluation has shown no notable changes of blood urea nitrogen (BUN) and creatinine in kidney of mice. In consequence, antioxidant effect was increased as well as the renal toxicity of the contrast agent reduced at the cell level. As a result, PLGA‐NAC nano‐conjugate can be a promising choice for decreasing the magnevist toxicity for treatment and prevention of CIN and will be able to open a new horizon to research on reduction of toxicity of contrast agents by using nanoparticles.Inspec keywords: blood, toxicology, nanofabrication, cellular biophysics, biomedical materials, nanoparticles, chromatography, cancer, biodegradable materials, biomedical MRI, kidney, pH, nanomedicine, patient treatment, diseases, atomic force microscopy, Fourier transform infrared spectraOther keywords: cellular toxicity, gadopentate dimeglumine, contrast agent, magnetic resonance imaging technique, diethylenetriamine pentaacetate, contrast‐induced nephropathy, nephrogenic systemic fibrosis, stoichiometric rules, molar ratios, dimethyl sulphoxide solution, chromatography techniques, nuclear magnetic resonance spectroscopy, atomic force microscopy imaging, Magnevist®, gadopentetate dimeglumine, renal cells, MTT cytotoxicity, human embryonic kidney‐293, L929 cell lines, in vitro conditions, cellular uptake assays, Magnevist uptake, antioxidant effect, renal toxicity, cell level, PLGA nanocarrier, acetylcysteine nanoconjugate, Magnevist toxicity, N‐acetylcysteine–PLGA nano‐conjugate, N‐acetyl cysteine‐poly‐lactic‐co‐glycolic acid nanoconjugate     

Synthesis,characterization, thermal and optical properties of soluble polyimides derived from an unsymmetrical diamine

A new unsymmetrical diamine monomer, 2,4‐diaminophenyl [4′‐(2′′,6′′‐diphenyl‐4′′‐pyridyl)phenyl]ether, was successfully synthesized by nucleophilic substitution of 1‐chloro‐2,4‐dinitrobenzene with 4‐(2′,6′‐diphenyl‐4′‐pyridyl) phenol. The diamine monomer was characterized by FTIR, ¹H and ¹³C NMR, and elemental analysis techniques and used for the preparation of novel polyimides (PIs) by reaction with commercially available tetracarboxylic dianhydrides such as pyromellitic dianhydride, 3,3′,4,4′‐benzophenone tetracarboxylic dianhydride, and bicyclo[2.2.2]‐oct‐7‐ene‐2,3,5,6‐tetracarboxylic dianhydride. These PIs with inherent viscosities ranged from 0.43 to 0.48 dL/g were readily soluble in many organic solvents and afforded tough and flexible films by solution casting. These polymers exhibited T_gs between 237 and 294°C, and 10% weight loss temperatures in excess of 500°C with up to 56% char yield at 600°C in air. Their maximum fluorescence emission in dilute (0.2 g/dL) NMP solution appeared at 450 nm. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Study of polyamide 12 crystallization behavior within rotational molding process

Our study is focused on the investigation of polyamide 12 (PA 12) grade behavior in rotational molding process. Hence, some rotational molding tests of polyamide 12 were conducted on a STP LAB 40 machine. To simulate the cooling stage within the rotational molding, the crystallization behavior of polyamide 12 was studied using differential scanning calorimetry technique and the obtained results for non-isothermal crystallization were fitted with Ozawa model. Furthermore, morphology survey has been carried out by a hot stage method using a microscope to investigate the spherulites evolution which depends on the temperature. The micro-tensile properties have been studied using micro-tensile bench (MVTV2) to explain the mechanical behavior of polyamide 12 during crystallization. As a result, the rotational molding of PA 12 was successfully carried out. The simulation of the melting and crystallization stages, by application of Ozawa model coupled with enthalpy method gave a good representation of experimental data on one hand. On the other hand, all characterization revealed useful information to understand the different phenomena that govern the rotational molding process.     

Synthesis and properties of fluorescent light‐emitting polyamide hybrids with reactive nanosilica by epoxide functionalization

A series of poly(carbazole‐quinoxaline‐amide)s (PCQAs) containing phenyl and long alkyl chain as pendants was synthesized from polycondensation between a new diamine with a synthesized and several commercial dicarboxylic acids using Yamazaki's method. PCQAs had inherent viscosities and weight average molecular weights ( ) in the range of 0.48–0.62 dL g^?1 and 51,600–58,500 g mol^?1, respectively. These luminescent polymers are readily soluble in a variety of organic solvents and formed low‐colored and tough thin films. In this study, silane modified SiO₂ (mSiO₂) nanoparticles were prepared, characterized and used with PCQAs in preparation of nanocomposites via solution blending method. The interfacial interaction strength between mSiO₂ and the polymer–matrix enhanced thermal stability (T_10%, from 463°C to 500°C) and mechanical strength (from 100 MPa to 150 MPa) for composite containing 30 wt % mSiO₂ in comparison with the pure polyamide. These materials showed good ability for extraction–elimination of metal ions such as Cr⁶⁺, Cr³⁺, Co²⁺, Zn²⁺, Pb²⁺, Cd²⁺, and Hg²⁺ from aqueous solutions either individually or in the mixture at various pH. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40219.     

Dielectric spectroscopy techniques as quality control tool: a feasibility study - [feature article]

In this article, the feasibility of using time- and frequency-domain dielectric spectroscopy measurements to monitor the condition of oil-impregnated paper (OIP) condenser bushings is discussed.     

Synthesis,characterization and immobilization of iron (III) pyridoxinato complex within Al-MCM-41 as catalyst for cycloalkanes oxidation

Biomimetic [Fe(pyridoxinato)₂OH·(H₂O)₃] non-hem complex designated as [Fe(L)₂OH·(H₂O)₃] was synthesized with basic solution of pyridoxine (Vitamin B₆) and FeCl₃ in methanol under reflux condition. It was then immobilized within the Al-MCM-41. Characterizations were carried out by powder X-ray diffraction, nitrogen adsorption desorption, FTIR and UV–Vis spectroscopy. It was found that pore volume, surface area, and pore diameter of Al-MCM-41 decreases after immobilization of iron complex. Density functional theory studies confirmed the experimental results of [Fe(L)₂OH·(H₂O)₃] complex. Fe-complex/Al-MCM-41 was found to successfully catalyze the oxidation of cyclohexane, cyclooctane and adamantane using H₂O₂ as oxidant with 45–90 % conversion toward the corresponding alcohols and ketones is considerable.