Rheological Studies of NR/PVP Blends and Impact of Concentration and Speed Range on Their Properties

Natural Rubber Latex (NRL) and Polyvinyl pyrolidone (PVP) blends with different PVP concentrations were prepared and rheological properties of NRL/PVP blends have been investigated at different speed range. Significant changes of behaviors are found with increased PVP in blends. Yield stress increases with increased PVP in blends. The increasing trend of stress increases with PVP content in blend. Shear stress and yield stress increase with increased speed range. Change of nature of rheogram of NRL with PVP indicates the interaction between NRL and PVP. Increasing speed range, the decreasing trend of viscosity indicates the orderliness of molecular segments in blends.     

Theory of the negative anode drop in low-pressure discharges

A kinetic model of the anode region with a negative anode potential drop is proposed, which explicitly takes into account the ratio of the directed velocity of electrons in plasma v ₀ to their thermal speed v _T as a parameter of the electron velocity distribution function. A transcendent equation is derived for determination of the negative anode drop as a function of the ratio v ₀/v _T . It is shown that, unlike the known Langmuir formula, the anode drop remains negative for any value of v ₀/v _T . In the case of small values (v ₀/v _T ? 1), the derived expression asymptotically reduces to the Langmuir formula. It is shown that the dependence of electron concentration on the potential differs from the Boltzmann law. The anode regions of the short high-current vacuum-arc discharge and the classical low-pressure discharge are considered as examples. For the vacuum-arc discharge, the current density distribution and the anode drop distribution over the anode surface under strong current contraction are calculated. For the low-pressure discharge, potential drops are calculated across the region of the inhomogeneous near-anode plasma and the space charge layer.     

APPLICATION OF MULTICOLUMN VALVE SWITCHING GAS CHROMATOGRAPHY FOR THE ANALYSIS OF NAPHTHA AND KEROSENE FRACTIONS OF SAUDI ARABIAN LIGHT CRUDE OIL

Abstract

The straight run naphtha and kerosene fractions of Saudi Arabian Light crude oil were analyzed for paraffins, olefins, naphthenes and aromatics (PONA) using a gas chromatographic technique. This method is based upon group type separation according to carbon numbers using a programmed multiple valve switching sequence and employing multicolumn approach. The chromatographic operating conditions and carrier gas flow rates were selected to determine PONA contents of naphtha and kerosene fractions. These straight run fractions were produced by an automatic true boiling point (TBP) apparatus. Boiling range distributions of these fractions were determined using a standard ASTM method of simulated distillation. PONA results were compared with the literature. Total paraffins, naphthenes and aromatics agreed with each other.     

Graphite/rolled graphene oxide/carbon nanotube photoelectrode for water splitting of exhaust car solution

Graphite/rolled graphene oxide/ carbon nanotubes (G/R-GO/CNTs) was prepared and applied as a photoanode for water splitting from exhaust car solution. R-GO was prepared from graphene oxide (GO) using the modified Hummer method after settle down in solution for 2 months to roll out. The R-GO coated the graphite (G) electrode using the dip-coating method to form G/R-GO. Finally, CNTs were prepared on the G/R-GO electrode by using the chemical vapor deposition method to form G/R-GO/CNT electrode. The images of field emission scanning electron microscope show the formation of relatively homogenous and uniform R-GO with an average diameter of about 140 nm. Also, the high density of CNTs was observed with uniform diameters distribution and lengths of CNTs up to several micrometers. The values of the current density of G/R-GO/CNT electrode for water splitting are changed from 0.82 mA cm⁻² in dark to 1.50 mA cm⁻² in light. The value of incident photon-to-current efficiency was 8.4% at 470 nm. The thermodynamic parameters were calculated, in which the activation energy (E_a), enthalpy (ΔH*), and entropy (ΔS*) values were 8.1 kJ mol⁻¹, 29.9 J mol⁻¹, and 56.4 J K⁻¹ mol⁻¹, respectively.     

Upgrading of Low-grade Jute and Cuttings. Part II: Interaction between Jute Fibres and Microbial Enzymes

An investigation is reported in which two isolated strains, A. nigerand A. terreus, exhibited similar enzyme activity, but A. nigershowed the maximum pectinlyase activity (acidic). An enzyme extract of both the strains and commercial enzymes (Flaxzyme and Bioxylanase) softened jute cuttings within 24 hours. The physico-mechanical properties of jute cuttings after treatment with enzyme revealed that flaxzyme and A. terreusand a mixture of commercial enzymes had been found to be among the most effective in improving fibre separation, fineness, and stiffness.     

Modeling the effect of weave structure and fabric thread density on the barrier effectiveness of woven surgical gowns

Surgical gowns are the shielding cloths worn by the surgical team throughout a surgery to save them from blood pathogens of the patient being operated, and to avoid bacterial infections. Barrier effectiveness of a fabric depends upon the liquid penetration resistance and pathogen resistance of the fabric. The objective of this study was to analyze the effect of different weave structures and fabric thread densities on the barrier effectiveness of the woven surgical gowns. Twelve fabric samples were produced using three different weave structures, i.e. 1/1 plain, 2/2 z-twill, and 3/3 z-twill, and four different fabric constructions and then completed with a water repellent finish. Water repellency spray test and air permeability test were conducted on each of the 12 woven samples. The results of fabric samples were analyzed in Minitab statistical software. The coefficients of determinations (R² values) of the regression equations show good prediction ability of the developed statistical models. The findings of the study may be helpful in deciding appropriate manufacturing specifications of surgical gowns to attain maximum barrier effectiveness.     

Spatial distribution and temporal variability of arsenic in irrigated rice fields in Bangladesh. 2. Paddy soil

Arsenic-rich groundwater from shallow tube wells is widely used for the irrigation of boro rice in Bangladesh and West Bengal. In the long term this may lead to the accumulation of As in paddy soils and potentially have adverse effects on rice yield and quality. In the companion article in this issue, we have shown that As input into paddy fields with irrigation water is laterally heterogeneous. To assess the potential for As accumulation in soil, we investigated the lateral and vertical distribution of As in rice field soils near Sreenagar (Munshiganj, Bangladesh) and its changes over a 1 year cycle of irrigation and monsoon flooding. At the study site, 18 paddy fields are irrigated with water from a shallow tube well containing 397 +/- 7 microg L(-1) As. The analysis of soil samples collected before irrigation in December 2004 showed that soil As concentrations in paddy fields did not depend on the length of the irrigation channel between well and field inlet. Within individual fields, however, soil As contents decreased with increasing distance to the water inlet, leading to highly variable topsoil As contents (11-35 mg kg(-1), 0-10 cm). Soil As contents after irrigation (May 2005) showed that most As input occurred close to the water inlet and that most As was retained in the top few centimeters of soil. After monsoon flooding (December 2005), topsoil As contents were again close to levels measured before irrigation. Thus, As input during irrigation was at least partly counteracted by As mobilization during monsoon flooding. However, the persisting lateral As distribution suggests net arsenic accumulation over the past 15 years. More pronounced As accumulation may occur in regions with several rice crops per year, less intense monsoon flooding, or different irrigation schemes. The high lateral and vertical heterogeneity of soil As contents must be taken into account in future studies related to As accumulation in paddy soils and potential As transfer into rice.