Monte Carlo simulation of charge transport in amorphous selenium photoconductors

The electronic properties of amorphous materials are greatly affected by the density of localized states in the mobility gap of these materials. The exact shape of the density of states (DOS) distribution in amorphous selenium (a-Se) is still unresolved despite decades of research. One of the most commonly employed methods to investigate charge transport properties in high resistivity materials is time-of-flight (TOF) transient photoconductivity experiment. The TOF transient photoconductivity technique is used to measure the induced photocurrent in the external circuit when the sample is photoexcited. Information pertaining to carrier mobility and other carrier parameters are deduced from the shape of the photocurrent. The investigation of the charge transport phenomenon is well known to be a complicated task. Monte Carlo (MC) simulation method has become a standard method for carrier transport studies in amorphous materials. The purpose of this research work is to develop a Monte Carlo simulation model for charge transport in typical TOF transient photoconductivity experiment to investigate the DOS distribution in a-Se. The MC simulations were first performed for relatively simpler models for which theoretical and analytical solutions were available. The MC model developed here is based on simulating the drift of carriers resulting from photogeneration, subject to the influence of an applied electric field and multiple trapping events. The free drift time of photocarriers and their dwell time in the traps are stochastic in nature, in accordance with the probabilities of these events. Electron time-of-flight transient photocurrents were calculated in amorphous selenium as a function of the electric field. The distribution of localized states (DOS) in a-Se has been investigated by comparing the experimentally measured and calculated transient photocurrents. The analysis of multiple-trapping transport has been done by the discretization of a continuous DOS. The DOS distribution has been optimized to produce the best agreement between the calculated and measured transient photocurrents. The resulting DOS has distinct features: A first peak at ~0.30 eV below Ec with an amplitude ~1017 eV–1 cm–3, a second small peak (or shoulder) at 0.45–0.50 eV below Ec with an amplitude 1014–1015 eV–1 cm–3, and deep states with an integral concentration 1011–1014 cm–3 lying below 0.65 eV, whose exact distribution could not be resolved because of the limitations of the available experimental data. The density of states (DOS) distribution in the vicinity of the valence band mobility edge in vacuum coated a-Se films has been investigated by calculating the MC hole transient photocurrents at different temperatures, and also the dependence of the drift mobility on the temperature and field. The calculated TOF transient photocurrents were compared with experimental data published elsewhere. It is shown that, analogous to electron transport in a-Si:H, the DOS near Ev is a featureless, monotonically decreasing distribution in energy up to Ev + 0.4 eV, without the 0.28 eV peak near the valence band which was thought to control the hole drift mobility. Such a DOS was able to account for hole TOF data reported previously by several authors to date

Screening for hen’s egg and chicken meat specific IgE antibodies in Saudi patients with allergic disorders

Background: Allergy to hen’s egg and meat contributes significantly to the manifestations of food allergy all over the world.Objectives: This study was performed to assess the presence of hen’s egg and meat specific IgE antibodies among patients investigated for various allergic disorders.Methods. This is a retrospective study performed at King Khalid University Hosptial, Riyadh. Data from 421 patients with allergic disorders screened for food specific IgE antibodies between January 2009 and March 2011 were analyzed. Sixty (14.25%) patients including 42 males and 18 females with the mean age (sd) of 7.5 (7.4) years were found to have specific IgE antibodies against hen’s egg and chicken meat. There were 56 (93.3%) children and 4 (6.7%) adult patients. Specific IgE antibodies were measured by radioallergosorbent test (RAST) using Pharmacia ImmunoCAP 250 analyzer.Results: Atopic dermatitis was the most common (55%) clinical condition. Out of the total 60 patients harboring hen’s egg and chicken meat specific IgE antibodies high levels of egg white, yolk and chicken meat specific IgEs were detected in 58 (96.6%), 37 (61.6%) and 6 (10%) patients respectively. Both the egg white and yolk antibodies coexisted in 35 (58.3%) patients.Conclusion: Sensitization against hen’s egg was higher compared to the chicken meat. Egg white sensitization higher than the egg yolk particularly in Saudi children with food related allergic disorders.Key words: Allergy, atopic dermatitis, chicken meat, hen’s egg, IgE antibodie

Cytokine gene polymorphisms and serum cytokine levels in patients with idiopathic pulmonary fibrosis

BACKGROUND: Studies have demonstrated associations between cytokine gene polymorphisms and the risk of idiopathic pulmonary fibrosis (IPF). We therefore examined polymorphisms in the genes encoding interleukin (IL)-6, IL-10, interferon gamma (IFN-γ), tumor necrosis factor alpha (TNF-α), and transforming growth factor-beta 1 (TGF-β(1)), and compared the serum levels of these cytokines in IPF patients and healthy controls. Furthermore, we examined the association of the studied genotypes and serum cytokine levels with physiological parameters and the extent of parenchymal involvement determined by high-resolution computed tomography (HRCT). METHODS: Sixty patients with IPF and 150 healthy controls were included. Cytokine genotyping was performed using the polymerase chain reaction sequence specific primer (PCR-SSP) method. In a subset of patients and controls, serum cytokine levels were determined by enzyme-linked immunosorbent assay. RESULTS: There was no difference between IPF patients and controls in the genotype and allele distributions of polymorphisms in TNF-α, IFN-γ, IL-6, IL-10, and TGF-β(1) (all p > 0.05). The TNF-α (−308) GG, IL-6 (−174) GG and CG, and IL-10 (−1082, -819, -592) ACC ATA genotypes were significantly associated with HRCT scores (all p < 0.05). IL-10 (−1082, -819, -592) ACC haplotype was associated with the diffusion capacity of the lung for carbon monoxide, and ATA haplotype was associated with the partial pressure of oxygen (PaO(2)) (all p < 0.05). The TGF-β(1) (codons 10 and 25) TC GG, TC GC, CC GG and CC GC genotypes were significantly associated with the PaO(2) and HRCT scores (p < 0.05). The TGF-β(1) (codons 10 and 25) CC GG genotype (5 patients) was significantly associated with higher PaO(2) value and less parenchymal involvement (i.e., a lower total extent score) compared to the other TGF-β(1) genotypes (81.5 ± 11.8 mm Hg vs. 67.4 ± 11.1 mm Hg, p = 0.009 and 5.60 ± 1.3 vs. 8.51 ± 2.9, p = 0.037, respectively). Significant differences were noted between patients (n = 38) and controls (n = 36) in the serum levels of IL-6 and IL-10 (both, p < 0.0001), but not in the levels of TNF-α and TGF-β(1) (both, p > 0.05). CONCLUSION: The studied genotypes and alleles do not predispose to the development of IPF but appear to play an important role in disease severity. Our results suggest that the TGF-β(1) (codons 10 and 25) CC GG genotype could be a useful genetic marker for identifying a subset of IPF patients with a favorable prognosis; however, validation in a larger sample is required

Nickel challenge up regulates CD69 expression on T lymphocyte sub-sets from patients with nickel induced contact dermatitis

Background: Persistent antigenic stimulation due to repeated exposure to nickel may lead to chronic inflammation resulting in allergic contact dermatitis (ACD).Objectives: This study was performed to assess nickel induced immune activation among patients sensitized against nickel.Patients and Methods: A total of 35 patients (29 females and 6 males; mean age 36±9 years) with nickel contact dermatitis and 20 patch test negative healthy individuals  (14 females and 6 males; mean age 29±7 years) were included in this study. Peripheral blood of patients and controls was incubated with nickel sulfate for 24 hours. Immune activation was assessed by CD69 up-reg- ulation on T lymphocyte sub-sets by flow cytometry.Results: Base line expression of CD69 on CD8+ lymphocytes was higher among patients compared to controls (4.1±1.3%vs2.8±1.1%;p&lt;0.009). There was no difference in proportions of CD±CD69+ cells between patients and controls (3.2±0.9%vs2.3±0.8%). Exposure to nickel induced expression of CD69 on a significantly higher proportion of CD4+ lympho- cytes (22.1±6.2%) of the ACD patients compared to controls (2.8±2.5%;p&lt;0.0001). Similarly nickel induced CD69 expression on a higher proportion of CD8+ lymphocytes (18.2±5.3%) from ACD patients compared to the controls (1.9±1.8%;p&lt;0.0006).Conclusion: CD69 molecule appears to be an important regulator of immune response in nickel contact dermatitis.   Keywords: Nickel, CD4+, CD8+, CD69, contact dermatitis

Nickel challenge up regulates CD69 expression on T lymphocyte sub-sets from patients with nickel induced contact dermatitis

Background: Persistent antigenic stimulation due to repeated exposure to nickel may lead to chronic inflammation resulting in allergic contact dermatitis (ACD). Objectives: This study was performed to assess nickel induced immune activation among patients sensitized against nickel. Patients and Methods: A total of 35 patients (29 females and 6 males; mean age 36\ub19 years) with nickel contact dermatitis and 20 patch test negative healthy individuals (14 females and 6 males; mean age 29\ub17 years) were included in this study. Peripheral blood of patients and controls was incubated with nickel sulfate for 24 hours. Immune activation was assessed by CD69 up-regulation on T lymphocyte sub-sets by flow cytometry. Results: Base line expression of CD69 on CD8+ lymphocytes was higher among patients compared to controls (4.1\ub11.3%vs2.8\ub11.1%;p&lt;0.009). There was no difference in proportions of CD\ub1CD69+ cells between patients and controls (3.2\ub10.9%vs2.3\ub10.8%). Exposure to nickel induced expression of CD69 on a significantly higher proportion of CD4+ lymphocytes (22.1\ub16.2%) of the ACD patients compared to controls (2.8\ub12.5%;p&lt;0.0001). Similarly nickel induced CD69 expression on a higher proportion of CD8+ lymphocytes (18.2\ub15.3%) from ACD patients compared to the controls (1.9\ub11.8%;p&lt;0.0006). Conclusion: CD69 molecule appears to be an important regulator of immune response in nickel contact dermatitis. DOI: https://dx.doi.org/10.4314/ahs.v19i1.19 Cite as: Zahid S, Mustafa A, Dina A, Sawsan B, Felwa A, Mohammed G, et al. Nickel challenge up regulates CD69 expression on T lymphocyte sub-sets from patients with nickel induced contact dermatitis. Afri Health Sci. 2019;19(1). 1460-1466. https://dx.doi. org/10.4314/ahs.v19i1.1

Investigation of input and output energy for wheat production : a comprehensive study for Tehsil Mailsi (Pakistan)

The global increasing food demand can be met by efficient energy utilization in mechanized agricultural productions. In this study, input–output energy flow along with CO2 emissions for different wheat production cases (C-I to C-V) were investigated to identify the one that is most energy-efficient and environment-friendly case. Data and information about input and output sources were collected from farmers through questionnaires and face-to-face interviews. Input and output sources were converted into energy units by energy equivalents while CO2 emissions were calculated by emission equivalents. Data envelopment analysis (DEA) was conducted to compare technical efficiencies of the developed cases for optimization of inputs in inefficient cases. Results revealed that case C-Ⅴ (higher inputs, larger fields, the tendency of higher fertilizer application and tillage operations) has the highest energy inputs and outputs than the rest of the cases. Moreover, it possesses the lowest energy use efficiency and energy productivity. The highest CO2 emissions (1548 kg-CO2/ha) referred to C-Ⅴ while lowest emissions per ton of grain yield were determined in C-Ⅳ (higher electricity water pumping, moderate energy input). The grain yield increases directly with input energy in most of the cases, but it does not guarantee the highest values for energy indices. C-Ⅲ (moderate irrigations, educated farmers, various fertilizer applications) was found as an optimum case because of higher energy indices like energy use efficiency of 4.4 and energy productivity of 153.94 kg/GJ. Optimum input and better management practices may enhance energy proficiency and limit the traditionally uncontrolled CO2 emissions from wheat production. Therefore, the agricultural practices performed in C-Ⅲ are recommended for efficient cultivation of wheat in the studied area.The global increasing food demand can be met by efficient energy utilization in mechanized agricultural productions. In this study, input–output energy flow along with CO2 emissions for different wheat production cases (C-I to C-V) were investigated to identify the one that is most energy-efficient and environment-friendly case. Data and information about input and output sources were collected from farmers through questionnaires and face-to-face interviews. Input and output sources were converted into energy units by energy equivalents while CO2 emissions were calculated by emission equivalents. Data envelopment analysis (DEA) was conducted to compare technical efficiencies of the developed cases for optimization of inputs in inefficient cases. Results revealed that case C-Ⅴ (higher inputs, larger fields, the tendency of higher fertilizer application and tillage operations) has the highest energy inputs and outputs than the rest of the cases. Moreover, it possesses the lowest energy use efficiency and energy productivity. The highest CO2 emissions (1548 kg-CO2/ha) referred to C-Ⅴ while lowest emissions per ton of grain yield were determined in C-Ⅳ (higher electricity water pumping, moderate energy input). The grain yield increases directly with input energy in most of the cases, but it does not guarantee the highest values for energy indices. C-Ⅲ (moderate irrigations, educated farmers, various fertilizer applications) was found as an optimum case because of higher energy indices like energy use efficiency of 4.4 and energy productivity of 153.94 kg/GJ. Optimum input and better management practices may enhance energy proficiency and limit the traditionally uncontrolled CO2 emissions from wheat production. Therefore, the agricultural practices performed in C-Ⅲ are recommended for efficient cultivation of wheat in the studied area.King Saud University, Riyadh, Saudi Arabi

Suboptimal Immune Reconstitution among HIV-Infected Saudi Patients following Successful Antiretroviral Treatment

Background and Objectives. Variations in immune reconstitution following antiretroviral treatment (ART) among HIV patients have previously been observed. This study aims at assessing immune reconstitution after successful ART among HIV-infected Saudi patients. Methods. This retrospective study of 240 HIV-infected patients was performed between May 2010 and June 2015 in the HIV center at King Saud Hospital, Riyadh. Data were extracted for CD4, CD8 cell, and CD3/HLA-DR counts along with the viral load from patient records before and after four years of successful ART. The inclusion criterion was patients with CD4 reconstitution of either equal to or more than 400 cells/mm3 with an undetectable HIV viral load following ART. Based on their presentation, the HIV patients were grouped into early treatment (ET) and delayed treatment (DT) groups with CD4 counts of 200–350 cells/mm3 and less than 200 cells/mm3, respectively. Findings. The pretreatment CD8+ counts of median 865 cells/mm3 (interquartile range (IQR) 774–1072) in the DT group declined to median 753 cells/mm3 (IQR 574–987; p<0.0001). Moreover, there was a decline in CD8 counts from 703 cells/mm3 (IQR 655–747) to 620 cells/mm3 (IQR 563–645; p<0.04) in the ET group after four years of successful ART. Pretreatment activation marker (CD3/HLA-DR+) expression of median 29% in the DT group declined to 22% and in the ET group from a median of 23% to 19% after treatment. The CD4/CD8 ratio in the DT group increased from 0.14 (IQR 0.09–0.88) to 0.71 (IQR 0.54–0.9) and from 0.42 (IQR 0.35–0.55) to 0.87 (IQR 0.71–0.98) in the ET group. Conclusion. Immune reconstitution after successful ART among HIV-infected Saudi patients was associated with a CD8 T-cell population expansion with a suboptimal CD4/CD8 ratio and persistent immune activation. Early initiation of ART appears to favorably influence the CD4/CD8 ratio

Critical Analysis and Application of Net-Metering Practice in MEPCO

The electrical infrastructure around the globe is expanding at a rapid rate for the sake of fulfilling power demands in the domestic, commercial and entertainment industries aiming to boost the living standards. In this regard, renewable energy sources (RES) are globally accepted potential candidates for maintaining inexhaustible, clean, and reliable electricity with a supplementary feature of economic prospect. The efficiency of power distribution at reduced cost to the consumers can be further enhanced by introducing a two-way billing system so-called net-metering which has the potential to overcome issues such as voltage regulation, power blackouts, overstressed grid and need for expensive storage systems thereby making it beneficial for the grid and the end user. This envisioning has encouraged the Government of Pakistan to install net-metering infrastructure at places which accommodate surplus renewable energy reserves. According to the Electric Power Act 1997, the National Electric Power Regulatory Authority (NEPRA) issued the net-metering rules and regulations in September 2015 by the endorsement of Federal Government which allowed the distribution companies in Pakistan to buy surplus electricity units generated by the consumers in order to partly reimburse the units imported from the utility grid. The aim behind this research work is to promote renewable energy utilization through net-metering mechanism in order to achieve maximum power. The export of units from consumer side to utility grid and vice versa can be made through bidirectional energy meter. In this paper, a solar net-metering analysis has been carried out on ETAP software to determine its benefits in a distribution network. Different scenarios have been investigated, and it is concluded that solar net-metering technique has multiple influential benefits, e.g., improvement in voltage regulation, reduction in transmission and distribution losses, increase in power availability, less billing to consumers, and reduction of loading on utility grid

Precision Nitrogen Management for Cotton Using (GreenSeeker) Handheld Crop Sensors

The precise monitoring of nitrogen (N) is an effective strategy for enhancing the crop yield per unit of land, but it involves field-level soil and crop data. The two years of experimental study were conducted during the cotton growing seasons of 2018 and 2019 at the Agriculture Research Farm of the Department of Agricultural Engineering, Bahauddin Zakariya University, Multan. The Nitrogen Fertilizer Optimization Algorithm (NFOA) was formulated based on the observed data for cotton lint yield (CLY) and GreenSeeker Normalized Difference Vegetation Index (GSNDVI) during the growing stages of cotton. The precision nitrogen application rate-based green seeker (PNAR) G.S for cotton was identified as 150-165 kg/ha. A linear relationship was observed between CLY (R2 = 0.80) for cotton with the GSNDVI. The average nitrogen requirement (Nreq) using (PNAR) G.S was determined through the nitrogen fertilizer optimization algorithm (NFOA). The Nreq was found to be 0.013 kg/kg for cotton. Precision N management originating from handheld crop sensors (GreenSeeker) may be helpful in decision-making for site-specific in-season N fertilizer management to enhance crop yield