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Simulation and electrochemical impedance spectroscopy of dye-sensitized solar cells
Subarna Rudra,서현우,수브라타사르카,김동민 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.97 No.-
Here, we report on simulating the steady-state j–V characteristics of dye-sensitized solar cells (DSSCs). First, a set of differential equations describing the kinetic processes involving the charge carriers –electron, iodide, triiodide, and dye cation – are derived. We consider non-linearity both in transport andin the recombination of electrons. Also, we consider that the charge transport occurs only by diffusion. Moreover, Boltzmann statistics relate electron density and Fermi level in TiO2, a quasi-static equilibriumholds between free and total electrons, and traps in the semiconductorfit to an exponential distributionof energies. Most importantly, we assume that electron transport occurs according to the multipletrappingmodel. The numerical solution provides j–V characteristics of the photoelectrode. To establish arelationship between the photovoltaic performance of the photoelectrode and that of the overall DSSCs,we consider the potential drops due to series-resistive elements according to the device physics of DSSCs. Finally, the model is applied to simulate the photovoltaic performance of real DSSCs with varying TiO2film thickness and electrolyte composition. The critical parameters of the model were extracted fromelectrochemical impedance spectroscopy (EIS) data of the DSSCs. The model successfully reproduced thej–V curves of the DSSCs.
Relationship between Perceived Bribery and Economic Growth: An Empirical Analysis
Subarna Samanta,Rajib Sanyal People&Global Business Association 2009 Global Business and Finance Review Vol.14 No.2
Examining measures of bribe taking and the real gross domestic product (GDP) of 26 countries over a twelve year period, it appears that higher incidences of bribery do adversely affect the rate of economic growth of nations. However, the rate of growth of real GDP does not have a similarly strong impact on reducing bribery levels. Furthermore, for individual countries, the relationship between these two variables varies considerably, indicating that country-specific factors explain both the prevalence of bribery and the pace of economic growth.
Subarnas, Anas,Herdiana, Yana,Sriwidodo, Sriwidodo,Dianti, Ajeng Kyung Hee Oriental Medicine Research Center 2004 Oriental pharmacy and experimental medicine Vol.4 No.4
A protective effect of the methanol extract of Shelliguea feei METT. roots on gastric lesions induced by stress in mice and HCl/ethanol in rats has been investigated. Animals were randomly divided into control and test groups and given the methanol extract orally at doses of 0.5, 1.0, and 2.0 g/kg of body weight. This investigation indicated that the methanol extract at doses of 1.0 and 2.0 g/kg significantly reduced stress-induced gastric lesions in mice at the percent protection of 38% and 62%, respectively, and decreased the number of HCI/ethanol-induced ulcers in rats significantly at the percent inhibition of 21.50% and 90.65%, respectively, and severity of ulcers at the score of 3.6 and 1.0 significantly different from the control. These results suggest that the methanol extract of S. feei may have a beneficial protective effect on the gastric ulcers.
The role of rural women in household food security and nutrition management in Bangladesh
Subarna GHOSH,Liton Chandra SEN,Sujan Kanti MALI,Md. Mozahidul ISLAM,Jhantu BAKCHI 이화여자대학교 한국여성연구원 2021 Asian Journal of Women's Studies(AJWS) Vol.27 No.3
Ensuring nutrition at the household level has been one of the greatest challenges for rural communities in Bangladesh. In this study, a coastal subdistrict in Barguna, Bangladesh was selected for data collection, where we undertook 20 focus group discussions, 10 key informant interviews, and dietary diversity scoring with 50 respondents to understand women’s involvement in decision-making and income-generating activity. Based on descriptive and thematic analyses, we found that women’s participation in various income-generating activities made them self-dependent in decisionmaking within their households, which in turn improved their roles in household food security and nutritional management. The pattern of family food distribution revealed that most women ate meals leftover by males, whereas 48 percent consumed food from less than four food groups. These findings should be useful for public health workers, activists, and national/ international stakeholders involved in improving the dietary quality and nutritional status of rural people.
Review on simulation of current–voltage characteristics of dye-sensitized solar cells
Subarna Rudra,수브라타사르카,김동민 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.80 No.-
Dye-sensitized solar cells (DSSCs) has become a promising technology because of its outstanding abilityto generate electricity, especially in diffuse light. Despite the rise of perovskite solar cells, intenseresearch activities on developing new materials forflexible, efficient, and stable DSSCs have been goingon. Understanding of the essential aspects of the device and their effect on overall performance is of greatimportance to upscale the device. Mathematical models and simulations help in quantitativeunderstanding of the critical aspects and their relation to the overall performance of the device atdesired operating conditions. Here, we review the mathematical models of DSSCs discussing the keyparameters: ideality factor, electron diffusion, and recombination. We have reconciled the concepts ofelectron generation, diffusion and recombination into a set of ordinary differential equations and solvedthose equations to simulate the photovoltaic performance of DSSCs. There is no conflict on the concept ofelectron diffusion via multiple trapping; however, the recombination of DSSCs is still under debate sincethe theory and experimental evidence often conflicts. The latter affects the photovoltage of DSSCs. Thereview should help the researchers understand the key parameters and their relation to the overall cellperformance.
Juvenile Polyps in Bangladeshi Children and Their Association with Fecal Calprotectin as a Biomarker
Subarna Rani Das,A S M Bazlul Karim,Md RukonUzzaman,Md Wahiduzzaman Mazumder,Rubaiyat Alam,Md Benzamin,Parisa Marjan,Mst. Naznin Sarker,Hazera Akther,Mohuya Mondal 대한소아소화기영양학회 2022 Pediatric gastroenterology, hepatology & nutrition Vol.25 No.1
Purpose: Colonoscopy is considered the most reliable method for the diagnosis of juvenile polyps. However, colonoscopic screening is an invasive and expensive procedure. Fecal calprotectin (FCP), a marker of intestinal inflammation, has been shown to be elevated in patients with polyps. Therefore, this study aimed to evaluate FCP as a screening biomarker for the diagnosis of juvenile polyps. Methods: This cross-sectional, observational study was conducted at the Pediatric Gastroenterology and Nutrition Department, Bangabandhu Sheikh Mujib Medical University, Dhaka, Bangladesh. For children with polyps, colonoscopic polypectomy and histopathology were performed. FCP levels were analyzed before and 4 weeks after polypectomy in all patients. Information was recorded in a datasheet and analyzed using the computer-based program SPSS. Results: The age of the children was between 2.5 and 12 years. Approximately 93% of the polyps were found in the rectosigmoid region. Children with juvenile polyps had elevated levels of FCP before polypectomy that subsequently normalized after polypectomy. The mean FCP levels before and after polypectomy were 277±247 μg/g (range, 80–1,000 μg/g) and 48.57±38.23 μg/g (range, 29–140 μg/g) (p<0.001), respectively. The FCP levels were significantly higher in patients with multiple polyps than in those with single polyps. Moreover, mean FCP levels in patients with single and multiple polyps were 207.6±172.4 μg/ g and 515.4±320.5 μg/g (p<0.001), respectively. Conclusion: Colonic juvenile polyps were found to be associated with elevated levels of FCP that normalized after polypectomy. Therefore, FCP may be recommended as a noninvasive screening biomarker for diagnosis of colonic juvenile polyps.
Shifting the Optimum pH of Bacillus circulans Xylanase towards Acidic Side by Introducing Arginine
Subarna Pokhrel,주정찬,유영제 한국생물공학회 2013 Biotechnology and Bioprocess Engineering Vol.18 No.1
Electrostatic interactions are important in protein folding, binding, flexibility, stability and function. The pH at which the enzyme is maximally active is determined by the pKas of the active site residues, which are modulated by several factors including the change in electrostatics in its vicinity. As the acidic xylanases are important in food and animal feed industries, electrostatic interactions are introduced in Bacillus circulans xylanase to shift their pH optima towards the acidic side. Arg substitutions are made to modulate the pKas of the active site residues. Neutral residues are substituted by Arg in such a way that the substituted residue can make direct interaction with the catalytic residues. However, the mutations with other titratable residues (Asp, Arg, Lys, His, Tyr, and Ser) present in between the catalytic sites and the substituted sites are avoided. Site directed mutagenesis was conducted to confirm the strategy. The results show the shift in pH optima of the mutants towards the acidic side by 0.5 - 1.5unit. Molecular dynamics simulation of the mutant V37R reveals that the decrease in activity is due to the increase in distance between the substrate oxygen atoms and catalytic glutamates.