39 research outputs found
Comprehensive Review on Two-Step Thermochemical Water Splitting for Hydrogen Production in a Redox Cycle
No full textThe interest in and need for carbon-free fuels that do not rely on fossil fuels are constantly growing from both environmental and energetic perspectives. Green hydrogen production is at the core of the transition away from conventional fuels. Along with popularly investigated pathways for hydrogen production, thermochemical water splitting using redox materials is an interesting option for utilizing thermal energy, as this approach makes use of temperature looping over the material to produce hydrogen from water. Herein, two-step thermochemical water splitting processes are discussed and the key aspects are analyzed using the most relevant information present in the literature. Redox materials and their compositions, which have been proven to be efficient for this reaction, are reported. Attention is focused on non-volatile redox oxides, as the quenching step required for volatile redox materials is unnecessary. Reactors that could be used to conduct the reduction and oxidation reaction are discussed. The most promising materials are compared to each other using a multi-criteria analysis, providing a direction for future research. As evident, ferrite supported on yttrium-stabilized zirconia, ceria doped with zirconia or samarium and ferrite doped with nickel as the core and an yttrium (III) oxide shell are promising choices. Isothermal cycling and lowering of the reduction temperature are outlined as future directions towards increasing hydrogen yields and improving the cyclability.ChemE/Catalysis Engineerin
Computational Investigation of Microreactor Configurations for Hydrogen Production from Formic Acid Decomposition Using a Pd/C Catalyst
No full textThe need to replace fossil fuels with sustainable alternatives has been a critical issue in recent years. Hydrogen fuel is a promising alternative to fossil fuels because of its wide availability and high energy density. For the very first time, novel microreactor configurations for the formic acid decomposition have been studied using computational modeling methodologies. The decomposition of formic acid using a commercial 5 wt % Pd/C catalyst, under mild conditions, has been assessed in packed bed, coated wall, and membrane microreactors. Computational fluid dynamics (CFD) was utilized to develop the comprehensive heterogeneous microreactor models. The CFD modeling study begins with the development of a packed bed microreactor to validate the experimental work, subsequently followed by the theoretical development of novel microreactor configurations to perform further studies. Previous work using CFD modeling had predicted that the deactivation of the Pd/C catalyst was due to the production of the poisoning species CO during the reaction. The novel membrane microreactor facilitates the continuous removal of CO during the reaction, therefore prolonging the lifetime of the catalyst and enhancing the formic acid conversion by approximately 40% when compared to the other microreactor configurations. For all microreactors studied, the formic acid conversion increases as the temperature increases, and the liquid flow rate decreases. Further studies revealed that all microreactor configurations had negligible internal and external pore diffusion resistances. The detailed models developed in this work have provided an interesting insight into the intensification of the formic acid decomposition reaction over a Pd/C catalyst
Characterizing the emergence and persistence of drug resistant mutations in HIV-1 subtype C infections using 454 ultra deep pyrosequencing.
No full textBACKGROUND: The role of HIV-1 RNA in the emergence of resistance to antiretroviral therapies (ARTs) is well documented while less is known about the role of historical viruses stored in the proviral DNA. The primary focus of this work was to characterize the genetic diversity and evolution of HIV drug resistant variants in an individual's provirus during antiretroviral therapy using next generation sequencing. METHODS: Blood samples were collected prior to antiretroviral therapy exposure and during the course of treatment from five patients in whom drug resistance mutations had previously been identified using consensus sequencing. The spectrum of viral variants present in the provirus at each sampling time-point were characterized using 454 pyrosequencing from multiple combined PCR products. The prevalence of viral variants containing drug resistant mutations (DRMs) was characterized at each time-point. RESULTS: Low abundance drug resistant viruses were identified in 14 of 15 sampling time-points from the five patients. In all individuals DRMs against current therapy were identified at one or more of the sampling time-points. In two of the five individuals studied these DRMs were present prior to treatment exposure and were present at high prevalence within the amplified and sequenced viral population. DRMs to drugs other than those being currently used were identified in four of the five individuals. CONCLUSION: The presence of DRMs in the provirus, regardless of their observed prevalence did not appear to have an effect on clinical outcomes in the short term suggesting that the drug resistant viral variants present in the proviral DNA do not appear to play a role in the short term in facilitating the emergence of drug resistance
QTrim : a novel tool for the quality trimming of sequence reads generated using the Roche/454 sequencing platform
No full textBackground
Many high throughput sequencing (HTS) approaches, such as the Roche/454 platform, produce sequences in which the quality of the sequence (as measured by a Phred-like quality scores) decreases linearly across a sequence read. Undertaking quality trimming of this data is essential to enable confidence in the results of subsequent downstream analysis. Here, we have developed a novel, highly sensitive and accurate approach (QTrim) for the quality trimming of sequence reads generated using the Roche/454 sequencing platform (or any platform with long reads that outputs Phred-like quality scores).
Results
The performance of QTrim was evaluated against all other available quality trimming approaches on both poor and high quality 454 sequence data. In all cases, QTrim appears to perform equally as well as the best other approach (PRINSEQ) with these two methods significantly outperforming all other methods. Further analysis of the trimmed data revealed that the novel trimming approach implemented in QTrim ensures that the prevalence of low quality bases in the resulting trimmed data is substantially lower than PRINSEQ or any of the other approaches tested.
Conclusions
QTrim is a novel, highly sensitive and accurate algorithm for the quality trimming of Roche/454 sequence reads. It is implemented both as an executable program that can be integrated with standalone sequence analysis pipelines and as a web-based application to enable individuals with little or no bioinformatics experience to quality trim their sequence data
An Ayurvedic management on Shushkakshipaka (dry eye syndrome) - A Case Report
No full textBackground: Shalakya Tantra is one of the eight branches of Ayurveda, which also includes ophthalmology. Shushkakshipaka (dry eye syndrome) is one of the diseases, involving all parts of eye (Sarvagata Netra Roga) characterized by Gharsha (gritty feeling), Toda (pricking type of pain), Kunita (photophobia), Avila Darshana (blurred vision), Daha (burning sensation) and Raktaraji (congestion in the eye). All these symptoms are like the symptoms of dry eye syndrome. Aims and Objective: To evaluate the effect of Triphala Ghrita Tarpana (therapeutic procedure done on the eye) in the management of Shushkakshipaka. Materials and Methods: A 26yr male patient having symptoms of Shushkakshipaka were selected OPD of Shalakyatantra department, Government Ayurved college, Nagpur. Clinical signs and symptoms were given suitable scores according to their severity, and assessment was based on the relief in these symptoms after the treatment. Patients of dry eye syndrome were allocated for Tarpana Kriyakalp was given for 7 consecutive days in afternoon with follow up after 15 days for 2 months. Results: Marked Relief in symptoms like Gharsha (74%), Avila Darshana (65%), Upadeha (80%), Daha (72%), Kunita (78%), Toda (59%) and Raktaraji (83%) was obtained after Triphala Ghrita Tarpana. Conclusion: Remarkable result observed after Triphala Ghrita Tarpana in the form of improvement in all the chief complaints of Shushkakshipaka and provides long lasting relief to the patient
CO<sub>2</sub> Capture and Reduction: Placing the process in an industrial framework
No full textCapturing and utilizing the emissions of CO2 has become a method to reduce the occurring emissions from industrial flue gases. One of the methodologies to capture and use the CO2 is through the CO2 capture and reduction (CCR) process. This process uses a bi-functional catalyst to capture CO2 from diluted gas streams and subsequently reduce it to CO in the presence of H2. The obtained product (syngas) can be further used as feedstock in for example the Fischer-Tropsch process. To implement a novel technology in industry, thetechnology itself should be economical feasible.To determine the feasibility of the process a technoeconomical analysis is executed. The analysis uses process parameters obtained by evaluating the catalytic activity of the bifunctional catalysts. Two catalyticsystems have been evaluated: Cu-K/𝛾-Al2O3 and FeCrCuK/PMG20. Effect on the synthesis conditions of Cu-K/𝛾-Al2O3 were also investigated. Cu-K/𝛾-Al2O3without additional drying steps during the synthesis shows a higher CO2 capacity and a faster CO production rate compared to the other catalysts. Furthermore, toestimate the H2 requirement in an industrialized process the consumption of H2 during the process has been quantified.To ensure a continuous process operation, a two reactor process has been proposed in the techno-economical analysis. The sizing and subsequent cost of the process equipment has been determined by utilizing the obtained process parameters. Besides the capital costs, the operating costs were also estimated to determine the profitability of the process. After the monetary benefit of selling the syngas was determined, it could be stated that the process is profitable under certain conditions. The process is profitable if the used H2 source has a buying price below 2.4 to ensure a profitable process.Applied Science
Hydrogen emissions from an electrolysis unit
No full textHydrogen is expected to play a vital role as an energy carrier in the future decarbonized system. Currently, a large portion of the hydrogen produced comes from the steam reforming of methane present in natural gas, which produces significant amounts of carbon dioxide emissions. However, with the growing need to reduce greenhouse gas emissions, a shift from fossil fuels to renewable energy sources is required. As a result, there is a growing emphasis on green hydrogen, i.e., hydrogen generated using renewable power. Green hydrogen has been growing at an exponential rate since 2020 and is expected to account for the majority of hydrogen production by 2050. However, a few studies have recently suggested that hydrogen may indirectly contribute to global warming. It is believed that hydrogen delays the decomposition of methane, a strong greenhouse gas, and thus extends its lifetime in the atmosphere. If green hydrogen is to be the primary fuel in the energy transition, hydrogen emissions from an electrolysis unit should be investigated.This project focuses on identifying the sources of hydrogen emissions from an electrolysis unit. The goal is to comprehend the depth of this potential issue and investigate possible solutions. This project is carried out in collaboration with Worley, a market leader in the design, construction, and delivery of green H2 facilities. The leakage estimates for the green hydrogen alkaline electrolysis plant are based on Worley’s in-house data. Venting during startup and shutdowns when power is unavailable, as well as hydrogen crossover in the electrolyzer, have been identified as two major contributors to hydrogen emissions. Solutions such as flaring systems to combust the vented hydrogen and battery energy systems to reduce frequent shutdowns and startups are investigated. To reduce emissions from hydrogen crossover, a reactor is modeled to explore the catalytic recombination of hydrogen and oxygen. These solutions are subjected to a techno-economic analysis to determine their viability.Flare systems and battery energy systems are both deemed feasible. In the longrun, however, installing a battery energy system would be preferable to combusting the hydrogen product. In comparison to other battery technologies such as Li-ion and lead-acid batteries, vanadium redox flow battery systems have been found to provide the maximum incentives and highest optimal capacities at the lowest overall costs. To avoid emissions from hydrogen crossover in a low-pressure alkaline electrolysis unit, the most cost-effective design involves a single-stage compression followed by a scrubber, heater, and reactor. However, this design is still costly because the annualized costs are four times greater than the costs offset by emissions reductions per year. Governments can encourage the adoption of such solutions by providing financial incentives to businesses.Electrical Engineering | Sustainable Energy Technolog
Hydrogenation of carbon dioxide (CO₂) to fuels in microreactors: a review of set-ups and value-added chemicals production
No full textClimate change, the greenhouse effect and fossil fuel extraction have gained a growing interest in research and industrial circles to provide alternative chemicals and fuel synthesis technologies. Carbon dioxide (CO2) hydrogenation to value-added chemicals using hydrogen (H2) from renewable power (solar, wind) offers a unique solution. From this aspect this review describes the various products, namely methane (C1), methanol, ethanol, dimethyl ether (DME) and hydrocarbons (HCs) originating via CO2 hydrogenation reaction. In addition, conventional reactor units for the CO2 hydrogenation process are explained, as well as different types of microreactors with key pathways to determine catalyst activity and selectivity of the value-added chemicals. Finally, limitations between conventional units and microreactors and future directions for CO2 hydrogenation are detailed and discussed. The benefits of such set-ups in providing platforms that could be utilized in the future for major scale-up and industrial operation are also emphasized
In vitro Propagation of a Rare Medicinal Plant Abrus laevigatus E. May
No full textAbstractAn efficient protocol was developed for in vitro propagation of Abrus laevigatus E. May. through induction of Plantlets by indirect organogenesis in nodal segment derived callus tissues. Yellowish green, fragile, nodular callus was induced at the cut surface of the nodal segments cultured on MS fortified with 5.0 mg/1 BAP, 0.2 mg/l KIN and 0.1 mg/1 IBA. The callus differentiated into adventitious shoots when it was sub-cultured on to MS supplemented with 3.0 mg/l BAP + 0.5 mg/1 Kin + 0.5 mg/1 NAA. On an average 6.87 ± 0.26 shoots developed. These micro-shoots were rooted in half-strength MS containing 1.0 mg/1 IBA and the rooted plantlets were transferred to soil after acclimatization. Keywords: Abrus laevigatus E. May, In vitro propagation, Callu
