46 research outputs found
Collisional kinetics of non-uniform electric field, low-pressure, direct-current discharges in H
A model of the collisional kinetics of energetic hydrogen atoms, molecules,
and ions in pure H discharges is used to predict H emission
profiles and spatial distributions of emission from the cathode regions of
low-pressure, weakly-ionized discharges for comparison with a wide variety of
experiments. Positive and negative ion energy distributions are also predicted.
The model developed for spatially uniform electric fields and current densities
less than A/m is extended to non-uniform electric fields, current
densities of A/m, and electric field to gas density ratios MTd at 0.002 to 5 Torr pressure. (1 Td = V m and 1 Torr =
133 Pa) The observed far-wing Doppler broadening and spatial distribution of
the H emission is consistent with reactions among H, H,
H, and H ions, fast H atoms, and fast H molecules, and with
reflection, excitation, and attachment to fast H atoms at surfaces. The
H excitation and H formation occur principally by collisions of
fast H, fast H, and H with H. Simplifications include using a
one-dimensional geometry, a multi-beam transport model, and the average
cathode-fall electric field. The H emission is linear with current
density over eight orders of magnitude. The calculated ion energy distributions
agree satisfactorily with experiment for H and H, but are only in
qualitative agreement for H and H. The experiments successfully modeled
range from short-gap, parallel-plane glow discharges to beam-like,
electrostatic-confinement discharges.Comment: Submitted to Plasmas Sources Science and Technology 8/18/201
Enhancing surface production of negative ions using nitrogen doped diamond in a deuterium plasma
The production of negative ions is of significant interest for applications
including mass spectrometry, particle acceleration, material surface
processing, and neutral beam injection for magnetic confinement fusion. Methods
to improve the efficiency of the surface production of negative ions, without
the use of low work function metals, are of interest for mitigating the complex
engineering challenges these materials introduce. In this study we investigate
the production of negative ions by doping diamond with nitrogen. Negatively
biased ( V or V), nitrogen doped micro-crystalline diamond films
are introduced to a low pressure deuterium plasma (helicon source operated in
capacitive mode, 2 Pa, 26 W) and negative ion energy distribution functions
(NIEDFs) are measured via mass spectrometry with respect to the surface
temperature (30C to 750C) and dopant concentration. The
results suggest that nitrogen doping has little influence on the yield when the
sample is biased at V, but when a relatively small bias voltage of
V is applied the yield is increased by a factor of 2 above that of un-doped
diamond when its temperature reaches 550C. The doping of diamond with
nitrogen is a new method for controlling the surface production of negative
ions, which continues to be of significant interest for a wide variety of
practical applications
A review of combined advanced oxidation technologies for the removal of organic pollutants from water
Water pollution through natural and anthropogenic activities has become a global problem causing short-and long-term impact on human and ecosystems. Substantial quantity of individual or mixtures of organic pollutants enter the surface water via point and nonpoint sources and thus affect the quality of freshwater. These pollutants are known to be toxic and difficult to remove by mere biological treatment. To date, most researches on the removal of organic pollutants from wastewater were based on the exploitation of individual treatment process. This single-treatment technology has inherent challenges and shortcomings with respect to efficiency and economics. Thus, application of two advanced treatment technologies characterized with high efficiency with respect to removal of primary and disinfection by-products in wastewater is desirable. This review article focuses on the application of integrated technologies such as electrohydraulic discharge with heterogeneous photocatalysts or sonophotocatalysis to remove target pollutants. The information gathered from more than 100 published articles, mostly laboratories studies, shows that process integration effectively remove and degrade recalcitrant toxic contaminants in wastewater better than single-technology processing. This review recommends an improvement on this technology (integrated electrohydraulic discharge with heterogeneous photocatalysts) viz-a-vis cost reduction in order to make it accessible and available in the rural and semi-urban settlement. Further recommendation includes development of an economic model to establish the cost implications of the combined technology. Proper monitoring, enforcement of the existing environmental regulations, and upgrading of current wastewater treatment plants with additional treatment steps such as photocatalysis and ozonation will greatly assist in the removal of environmental toxicants
The Effect of Yoga Practice on Lipid Profiles in Patients with Chronic Heart Failure
The aim of the present study was to assess the efficiency of yoga practice in addition to the standard medical therapy in patients with chronic heart failure (HF) and dyslipidemia. One hundred and two patients with chronic HF and dyslipidemia were divided into the control group (CG) – 54 patients and the yoga group (YG) – 48 patients. The CG was prescribed standard therapy for chronic HF (angiotensin converting enzyme inhibitors, β-blockers, aldosterone antagonists, digoxin, loop diuretics, statins, antiplatelet agents) and dyslipidemia. The YG additionally followed lifestyle modification in the form of 1 h daily practice of yoga for a period of 3 months. All patients completed the questionnaire reporting on their age, gender, medical history and treatment. The Fasting blood samples were analyzed for total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol, C-reactive protein, interleukin-8 and tumor necrosis factor -α on admission to the department and after 3 months of treatment. The pre-specified duration of the enrollment period was two years and during that time we interviewed 168 patients. Forty-two did not meet the inclusion criteria for the study, 24 patients refused to participate. A total of 102 patients were enrolled, of them, 54 were included into the control group and 48 into the yoga group. At baseline, there were no significant (p>0.05) differences between the groups in clinical characteristics of the patients. On admission to hospital the patients of both groups received standard therapy in comparable doses. By the end of the study, a significant (p<0.05) reduction in TC, TG and LDL-C levels was observed in both groups with a tendency to more considerable changes in YG. Correlation analysis revealed the positive correlation relationship between TC, LDL-C levels and cytokines. The present study has shown that the practice of yoga in addition to the standard therapy in patients with HF and dyslipidemia could be associated with lipid profile improvements
New putative phenol oxidase in ascidian blood cells
The phenol oxidase system is ancient and ubiquitously distributed in all living organisms. In various groups it serves for the biosynthesis of pigments and neurotransmitters (dopamine), defence reactions and tissue hardening. Ascidians belong to subphylum Tunicata, which is considered the closest living relative to Vertebrates. Two phenol oxidases previously described for ascidians are vertebrate-like and arthropod-like phenol oxidases. In our present study, we described a new ascidian protein, Tuphoxin, with putative phenol oxidase function, which bears no sequence similarity with two enzymes described previously. The closest related proteins to Tuphoxin are mollusc haemocyanins. Unlike haemocyanins, which are oxygen transporting plasma proteins, Tuphoxin is synthesised in ascidian blood cells and secreted in the extracellular matrix of the tunic—ascidian outer coverings. Single mature transcript coding for this phenol oxidase can give several protein products of different sizes. Thus limited proteolysis of the initial protein is suggested. A unique feature of Tuphoxins and their homologues among Tunicata is the presence of thrombospondin first type repeats (TSP1) domain in their sequence which is supposed to provide interaction with extracellular matrix. The finding of TSP1 in the structure of phenol oxidases is new and we consider this to be an innovation of Tunicata evolutionary lineage