Excimer Emission From Pulsed Microhollow Cathode Discharges

Microhollow cathode discharges (MHCDs) are direct current, high-pressure, non-equilibrium gas discharges. Direct current MHCDs in xenon and argon have shown to emit excimer radiation at 172 and 127 nm, respectively. Internal efficiency of excimer emission in DC MHCD was measured to be 6–9% in xenon, and 1–6%, depending on the gas flow rate in argon. This high efficiency is due to the high rate of rare gas excitation by electrons accelerated in the cathode fall and to subsequent three-body collisions in the high-pressure gas. The excimer power scales linearly with current; however, due to the increasing size of the source with increasing current, the radiant emittance and the current density stay constant at 1.5 W/cm2 and 0.3 A/cm 2, respectively, at 400 Torr xenon. In DC operation, the current was limited to 8 mA to avoid thermal damage of the electrodes. In order to explore the discharge physics and the excimer emission at higher currents, the discharge was pulsed with a duty cycle of 0.0007. This allowed us to increase the peak power and current without increasing the average power. A discharge behavior different from the DC and quasi DC (ms pulsed) was observed when the pulse was reduced to values in the order of the electron relaxation time. For argon this is in the order of 36 ns at atmospheric pressure. Pulsing the discharge with such short pulses allows for heating the electrons without heating the gas. Applying electrical pulses of 20 ns duration to direct current MHCDs in xenon increased the excimer emission exponentially with the pulse voltage by more than two orders of magnitude over the DC value. At 750 V pulse voltage, an output VUV optical power of 2.75 W and internal efficiency of 20% was measured. Pulsing MHCDs in argon with a 10 ns pulse increased the intensity by a factor of six but the efficiency was not increased beyond the DC value. Electron density measurements using the Stark effect showed that the increase in excimer intensity was due to the increase in electron density and the increased electron energy caused by pulsed electron heating

Excimer Emission From Cathode Boundary Layer Discharges

The excimer emission from direct current glow discharges between a planar cathode and a ring-shaped anode of 0.75 and 1.5 mm diameter, respectively, separated by a gap of 250 μm, was studied in xenon and argon in a pressure range from 75 to 760 Torr. The thickness of the “cathode boundary layer” plasma, in the 100 μm range, and a discharge sustaining voltage of approximately 200 V, indicates that the discharge is restricted to the cathode fall and the negative glow. The radiant excimer emittance at 172 nm increases with pressure and reaches a value of 4 W/cm2 for atmospheric pressure operation in xenon. The maximum internal efficiency, however, decreases with pressure having highest values of 5% for 75 Torr operation. When the discharge current is reduced below a critical value, the discharge in xenon changes from an abnormal glow into a mode showing self-organization of the plasma. Also, the excimer spectrum changes from one with about equal contributions from the first and second continuum to one that is dominated by the second continuum emission. The xenon excimer emission intensity peaks at this discharge mode transition. In the case of argon, self-organization of the plasma was not seen, but the emission of the excimer radiation (128 nm) again shows a maximum at the transition from abnormal to normal glow. As was observed with xenon, the radiant emittance of argon increases with pressure, and the efficiency decreases. The maximum radiant emittance is 1.6 W/cm2 for argon at 600 Torr. The maximum internal efficiency is 2.5% at 200 Torr. The positive slope of the current–voltage characteristics at maximum excimer emission in both cases indicates the possibility of generating intense, large area, flat excimer lamps

Argon excimer emission from high-pressure microdischarges in metal capillaries

We report on argon excimer emission from high-pressure microdischarges formed inside metal capillaries with or without gas flow. Excimer emission intensity from a single tube increases linearly with gas pressure between 400 and 1000 Torr. Higher discharge current also results in initial intensity gains until gas heating causes saturation or intensity drop. Argon flow through the discharge intensifies emission perhaps by gas cooling. Emission intensity was found to be additive in prealigned dual microdischarges, suggesting that an array of microdischarges could produce a high-intensity excimer source

The role of antibiotics metaphylaxis on developmental dynamics of fecal microbiota and persistence of antimicrobial resistome in piglets

The swine gastrointestinal microbiota is comprised of a diverse and complex microbial population that coexists in a coordinated, complex mucosal ecosystem that contributes to host gastrointestinal and immunological development. While antimicrobial are cost-effective tools for prevention and treatment of infectious diseases, the impact of their use on potentially beneficent mucosal microbial communities has not been widely explored. Optimization of antimicrobial use in swine management systems requires full understanding of antimicrobial-induced changes on developmental dynamics of gut microbiota and prevalence of antimicrobial resistance genes (ARGs). While the antibiotic resistance profiles of pathogens have been characterized, the antimicrobial resistance bacteria and ARGs from the whole gut microbiota have received far less attention. The objective of this study was to characterize the impact of parenteral antibiotics administration on composition and diversity of the resident fecal microbiota in pigs. In commercial swine farm, five antimicrobial treatment groups, each consisting of four, eight-week old piglets, were administered one of the antimicrobial; Tulathromycin (TUL), Ceftiofur Crystalline free acid (CCFA), Ceftiofur hydrochloride (CHC), Oxytetracycline (OTC), and Procaine Penicillin G (PPG) at label dose and route. Individual fecal swabs were collected immediately before antimicrobial administration (control = day 0), and again on days 1, 3, 7, and 14 after dosing. Additionally, a randomized complete block design was used to study the impacts of early-life antimicrobial intervention on fecal microbiota structure, and their accompanying antimicrobial resistome in neonatal piglets. Forty-eight litters were blocked to one of six treatments; Control (CONT), TUL, CCFA, CHC, OTC and PPG. Two piglets per litter were individually identified and weights and deep fecal swabs were collected at days 0 (prior to treatment), 5, 10, 15 and 20. All fecal swabs were processed for DNA extraction. Sequencing analysis of the V3-V4 hypervariable region of 16S rRNA gene and the selected ARGs were performed using Illumina Miseq platform. Moreover, whole genome, metagenomics sequencing approach was performed on subset of samples from the CONT and TUL groups, to assess the fecal microbiota structure and their accompanying antimicrobial resistome. In growing piglets, the most abundant phyla were Firmicutes, Bacteroidetes, and Proteobacteria. Linear discriminant analysis, showed a pronounced, antimicrobial-dependent shift in the composition of fecal microbiota over time from day 0. By day 14, the fecal microbial compositions of the groups receiving CHC and TUL had returned to a distribution that closely resembled that observed on day 0, but differences were still evident. In contrast, animals that received PPG, OTC and CCFA, showed a tendency towards a normalized microbiota structure on day 7, but appeared to deviate away from the day 0 composition by day 14. In neonatal piglets, our results show that, while early-life antibiotics prophylaxis had no effect on individual weight gain, or mortality, it was associated with noticeable changes in the prevalence of selected ARGs, and minor shift in the composition of the fecal microbiota during this developmental stage. Relative to CONT, only TUL treated piglet exhibited significant decline in chao1 richness index at day 20. Compared to the CONT, the PPG treated piglets exhibited a significant increase in the prevalence of ermB and tetW at day 20 of life. Tulathromycin intervention was also resulted in significant increase in the abundance of tet W at days 10 and 20, and erm B at day 20. Using whole genome metagenomics sequencing on subset of samples from the CONT and TUL groups, a total of 127 antimicrobial resistome related to 19 different classes of antibiotics were identified across all samples. The majority of identified antimicrobial resistome were observed in both experimental groups and at all-time points. The magnitude and extent of differences in microbial composition, and antimicrobial resistome, between the TUL and CONT groups were statistically insignificant. However, both the fecal microbiota composition and antimicrobial resistome were changed significantly between the sampling days. Based on our results, the observed changes in fecal microbiota in growing piglets showed antimicrobial-specific variation in both duration and extent. While in the perinatal piglets, the shifts in fecal microbiota structure caused by perinatal antimicrobial intervention are modest and limited to particular groups of microbial taxa. However, early life PPG and TUL intervention could promote selection of ARGs in herds. While additional investigations are required to explore the consistency of these findings across larger populations, these results could open the door to new perspectives on the utility of early life antimicrobial administration to healthy neonates in swine management systems

GASTRO-PROTECTION OF ATORVASTATIN IN INDOMETHACIN-INDUCED ULCER: ROLE OF TUMOR NECROSIS FACTOR-ALPHA AND PROSTAGLANDINS

Using non-steroidal anti-inflammatory drugs as over-the-counter pain-killers may predispose to gastric ulcer as a side effect.The objective of this study is to investigate the possible benefit of a common statin used in hyperlipedemic patients;atorvastatin (AtoR), in ameliorating the ulcerogenic effect of indomethacin (IndoM), and to explore the possible mechanismsinvolved. AtoR (10 mg/kg/day) was administered orally for 7 days. At day 7, gastric ulcer was induced by a single dose ofIndoM (40 mg/kg i.p.), with or without AtoR pre-treatment. IndoM induced gastric ulcer as evident by notable gastriculceration in histopathological sections compared to normal control. Gastric tissue in rats receiving IndoM showedsignificantly higher oxidative stress markers as lipid peroxidation represented by increased malondialdehyde (MDA)content, with significant decrease in gastric tissue nitric oxide (NO) and prostaglandin E2 (PGE2) levels, as well as reductionin catalase and superoxide dismutase antioxidant enzymatic activities. In addition, IndoM induced inflammatory signs asshown by the significant increase in tumor necrosis factor-alpha (TNF-α) level assessed via ELISA. Pre-administration ofAtoR significantly decreased ulcer index (16±1) compared to that of IndoM alone (34±2). In addition, AtoR restored normalgastric histological structure and reverted oxidative and inflammatory markers tested. AtoR confers gastro-protection againstIndoM-induced ulceration via reducing gastric oxidative stress and increasing gastric NO and PGE2 levels, as well asdecreasing the inflammatory marker; TNF-α

Fluorescence Spectrometric Determination of Drugs Containing α-Methylene Sulfone/Sulfonamide Functional Groups Using N1-Methylnicotinamide Chloride as a Fluorogenic Agent

A simple spectrofluorometric method has been developed, adapted, and validated for the quantitative estimation of drugs containing α-methylene sulfone/sulfonamide functional groups using N1-methylnicotinamide chloride (NMNCl) as fluorogenic agent. The proposed method has been applied successfully to the determination of methyl sulfonyl methane (MSM) (1), tinidazole (2), rofecoxib (3), and nimesulide (4) in pure forms, laboratory-prepared mixtures, pharmaceutical dosage forms, spiked human plasma samples, and in volunteer's blood. The method showed linearity over concentration ranging from 1 to 150 μg/mL, 10 to 1000 ng/mL, 1 to 1800 ng/mL, and 30 to 2100 ng/mL for standard solutions of 1, 2, 3, and 4, respectively, and over concentration ranging from 5 to 150 μg/mL, 10 to 1000 ng/mL, 10 to 1700 ng/mL, and 30 to 2350 ng/mL in spiked human plasma samples of 1, 2, 3, and 4, respectively. The method showed good accuracy, specificity, and precision in both laboratory-prepared mixtures and in spiked human plasma samples. The proposed method is simple, does not need sophisticated instruments, and is suitable for quality control application, bioavailability, and bioequivalency studies. Besides, its detection limits are comparable to other sophisticated chromatographic methods

Series Operation of Direct Current Xenon Chloride Excimer Sources

Stable, direct current microhollow cathode discharges in mixtures of hydrochloric acid, hydrogen, xenon, and neon have been generated in a pressure range of 200–1150 Torr. The cathode hole diameter was 250 μm. Sustaining voltages range from 180 to 250 V at current levels of up to 5 mA. The discharges are strong sources of xenon chloride excimer emission at a wavelength of 308 nm. Internal efficiencies of approximately 3% have been reached at a pressure of 1050 Torr. The spectral radiant power at this pressure was measured as 5 mW/nm at 308 nm for a 3 mA discharge. By using a sandwich electrode configuration, consisting of five perforated, alternate layers of metal and dielectric, a tandem discharge—two discharges in series—could be generated. For an anode–cathode–anode configuration the excimer irradiance, recorded on the axis of the discharge, was twice as large as that of a single discharge. The extension of this basic tandem electrode structure to a multiple electrode configuration allows the generation of high irradiance excimer sources. Placing such a structure with a string of microhollow cathode discharge into an optical resonator promises to lead to a direct current microexcimer laser

Microhollow Cathode Discharge Excimer Lamps

Microhollow cathode discharges are high-pressure, nonequilibrium gas discharges between a hollow cathode and a planar or hollow anode with electrode dimensions in the 100 μm range. The large concentration of high-energy electrons, in combination with the high-gas density favors excimer formation. Excimer emission was observed in xenon and argon, at wavelengths of 128 and 172 nm, respectively, and in argon fluoride and xenon chloride, at 193 and 308 nm. The radiant emittance of the excimer radiation was found to increase monotonically with pressure. However, due to the decrease in source size with pressure, the efficiency (ratio of excimer radiant power to input electrical power), has for xenon and argon fluoride a maximum at ∼400 Torr. The maximum efficiency is between 6% and 9% for xenon, and ∼2% for argon fluoride

Sensitivity, specificity of biochemical markers for early prediction of endothelial dysfunction in atherosclerotic obese subjects

Background: The obesity increased incidence of diabetes, hypertension and atherosclerosis and rate of morbidity and mortality. The main cause of atherosclerosis is endothelial dysfunction and formation of foam cells and macrophage that lead to unfavorable complications. This study evaluated specific biomarkers for endothelial dysfunction as sensitive indices for early predication of atherosclerosis in obese subjects. Study Design: One hundred fifty male age and sex matching were included in the current study divided into three groups according to body mass index (BMI): Control (BMI ≤ 22), obese (BMI> 28) and obese with atherosclerosis (BMI> 28). Fasting serum was subjected for determination of adhesion molecules, sICAM-1, sVCAM-1, E-selectin, oxo-LDL and 8-iso-PGF2α by ELISA technique. Results: Data obtained showed that, a significant elevation of serum inflammatory markers CRP, IL-6 and TNF-α and adhesion molecules sICAM-1 (p<0.001) with sensitivity 96%, sVCAM-1 (p <0.01) with sensitivity 92%, E-selectin (p<0.001) with sensitivity 94%, oxo-LDL (p <0.05) and 8-iso-PGF2α (p < 0.001) with sensitivity 97% in obese with atherosclerosis compared with obese and control. Conclusion: The levels of serum adhesion molecules contributed in the pathogenesis of endothelial dysfunction can be used as sensitive biomarkers for early prediction of atherosclerosis in obese subjects. Keywords: Obesity; atherosclerosis; endothelial dysfunction