Spin Decay in a Quantum Dot Coupled to a Quantum Point Contact

We consider a mechanism of spin decay for an electron spin in a quantum dot due to coupling to a nearby quantum point contact (QPC) with and without an applied bias voltage. The coupling of spin to charge is induced by the spin-orbit interaction in the presence of a magnetic field. We perform a microscopic calculation of the effective Hamiltonian coupling constants to obtain the QPC-induced spin relaxation and decoherence rates in a realistic system. This rate is shown to be proportional to the shot noise of the QPC in the regime of large bias voltage and scales as $a^{-6}$ where $a$ is the distance between the quantum dot and the QPC. We find that, for some specific orientations of the setup with respect to the crystallographic axes, the QPC-induced spin relaxation and decoherence rates vanish, while the charge sensitivity of the QPC is not changed. This result can be used in experiments to minimize QPC-induced spin decay in read-out schemes.Comment: 10 pages, 2 figures, 2 table

Process modelling, validation and analysis of rotating packed bed stripper in the context of intensified CO2 capture with MEA

Rotating packed bed (RPB) system has applications in CO2 removal using chemical solvents which can reduce the size about ten times compared to common packed bed (PB) system. In this study, RPB stripper using monoethanolamine (MEA) solution is modelled in gPROMS® software. The model has been validated using experimental data from literature and show good agreement. In addition to stripper modelling and validation, the process analysis is accomplished in this study by assessing the influence of four parameters namely rotor speed, reboiler temperature, flow rate of rich liquid, and pressure on desorption efficiency and desorption energy

Analysis of solar energy development strategies for a successful energy transition in the UAE

© 2022 The Authors. Published by MDPI AG. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://www.mdpi.com/2227-9717/10/7/1338The United Arab Emirates (UAE) is making significant progress in improving its economy by attracting tourists and trade. In the short run, however, economic activity will continue to be more based on oil, natural gas, and related industries. Rising demand for natural gas for power plants and industrial users, such as petrochemicals and steelmakers, has made the UAE a net gas importer, prompting the country to launch multibillion-dollar investments in nuclear and renewable energy. This study addresses the trend of solar energy production and consumption in the UAE. The strengths, weaknesses, opportunities, and threats (SWOT) analysis was performed on the different types of solar energy in the UAE, and some strategies were developed based on it. The SWOT analysis reveals promising strategies for the UAE’s solar energy transition that would reduce fossil fuel demand, mitigate greenhouse gas emissions through solar energy production, and transform the UAE into the carbon market centre of the Gulf Cooperation Council countries.This research received no external funding.Published onlin

Environmental aspects of the combined cooling, heating, and power (CCHP) systems: a review

© 2022 The Authors. Published by MDPI AG. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.3390/pr10040711Expanding cities means increasing the need for energy in the residential sector. The supply of this energy must be in environmentally friendly ways; one method of meeting demand in the residential sector is the use of combined cooling, heating, and power (CCHP) systems. The current review paper shows that due to the high cost of gas and electricity, CCHP can be used in various sectors, such as hospitals and airports, to reduce energy consumption with lower environmental impacts by using renewable energy systems as the main driver. While CCHP systems are not feasible in tropical regions with high cooling demand, a solar hybrid system is a superior candidate for regions with sufficient radiation. CCHP can also be used in sectors such as wastewater treatment units, desalination systems, and hydrogen production units to improve performance and increase productivity. The carbon and water footprints of CCHP systems are discussed in detail. The main drivers for reducing carbon and water footprints are improving system components such as the combustion engine and increasing productivity by expanding the system to multi-generation systems. Finally, the carbon tax index can help reduce carbon emissions if properly used in the right context. Based on our best knowledge, there is no extensive review of the environmental aspects of CCHP systems in the literature.Published versio

Integration of solid-oxide fuel cells and absorption refrigeration for efficient combined cooling, heat and power production

Combined cooling, heating and power (CCHP) systems are characterized by a substantially higher energyutilization efficiency compared to standalone systems. In this study, an integrated system comprising a solidoxide fuel cell (SOFC), hot-water storage tank (HWST) and absorption refrigeration (AR) cycle is considered. The SOFC model was developed in Aspen Plus®. It was used to determine the thermodynamic properties of the exhaust gas that was then used to provide heat for the HWST and to drive the AR cycle. Thermodynamic models for the AR cycles were developed in Engineering Equation Solver, considering LiBr–H2 O and NH3 –H2 O as working fluids. The sensitivity analysis of a number of SOFC output parameters has been carried out. The most optimal case was characterized with the coefficient of performance (COP) and CCHP efficiency of 0.806 and 85.2% for the LiBr–H2 O system, and 0.649 and 83.6% for the NH3 –H2 O system, respectively. Under such optimal operating conditions, the SOFC was characterized by the net electrical efficiency of 57.5% and the net power output of 123.66 kW. Data from the optimal solution were used to perform the thermodynamic study and sensitivity analysis to assess the influence of different absorption cycle operating conditions and to identify possible applications for the considered integrated system

Molecular simulation techniques as applied to silica and carbon-based adsorbents for carbon capture

There has been ongoing interest in research to mitigate climate change through carbon capture (CC) by adsorption. This guideline is meant to introduce computational chemistry techniques in CC by applying them to mesoporous structures and disordered morphologies. The molecular simulation techniques presented here use examples of literature studies on silica and carbon-based adsorbents. An initial summary of molecular simulation techniques and concepts is first presented. This is followed by a section on molecular simulation applications in mesoporous amorphous silica, both functionalized and not. Novel strategies to validate and output useful results are discussed, specifically when modelling chemisorption. The use of computational chemistry to build upon experimental results is reviewed, and a similar summation is presented for carbon-based adsorbents. The final section provides a short review of computational chemistry methods in novel applications and highlights potential complications. Computational chemistry techniques provide a streamlined method of gathering data across a range of conditions. Alongside experimental studies, these techniques can provide valuable information on underlying molecular mechanisms. This paper aims to be a starting point for navigating these numerical methods by providing an initial understanding of how these techniques can be applied to carbon capture while clarifying the current and inherent limitations present

Hybrid QSPR models for the prediction of the free energy of solvation of organic solute/solvent pairs

© 2019 The Authors. Published by the Royal Society of Chemistry. This is an open access article available under a Creative Commons licence. The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.1039/C8CP07562JDue to the importance of the Gibbs free energy of solvation in understanding many physicochemical phenomena, including lipophilicity, phase equilibria and liquid-phase reaction equilibrium and kinetics, there is a need for predictive models that can be applied across large sets of solvents and solutes. In this paper, we propose two quantitative structure property relationships (QSPRs) to predict the Gibbs free energy of solvation, developed using partial least squares (PLS) and multivariate linear regression (MLR) methods for 295 solutes in 210 solvents with total number of data points of 1777. Unlike other QSPR models, the proposed models are not restricted to a specific solvent or solute. Furthermore, while most QSPR models include either experimental or quantum mechanical descriptors, the proposed models combine both, using experimental descriptors to represent the solvent and quantum mechanical descriptors to represent the solute. Up to twelve experimental descriptors and nine quantum mechanical descriptors are considered in the proposed models. Extensive internal and external validation is undertaken to assess model accuracy in predicting the Gibbs free energy of solvation for a large number of solute/solvent pairs. The best MLR model, which includes three solute descriptors and two solvent properties, yields a coefficient of determination (R2) of 0.88 and a root mean squared error (RMSE) of 0.59 kcal mol−1 for the training set. The best PLS model includes six latent variables, and has an R2 value of 0.91 and a RMSE of 0.52 kcal mol−1. The proposed models are compared to selected results based on continuum solvation quantum chemistry calculations. They enable the fast prediction of the Gibbs free energy of solvation of a wide range of solutes in different solvents.Financial support from Eli Lilly via the Lilly Research Award Program (LRAP) and from the UK Engineering and Physical Sciences Research Council (EPSRC) of the UK via a Leadership Fellowship (EP/J003840/1) is gratefully acknowledged.Published onlin

The effects of statin use on inflammatory markers among patients with metabolic syndrome and related disorders: A systematic review and meta-analysis of randomized controlled trials

Current evidence suggests that statin use decreases the incidence of cardiovascular diseases (CVD) through reducing LDL cholesterol and decreasing inflammation. Metabolic syndrome (MetS) is usually associated with increased inflammatory markers and increased risk of CVD. We conducted a systematic review and meta-analysis to determine the effect of statin use on inflammatory markers including C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1 (IL-1) among patients with MetS and related disorders. PubMed, EMBASE, Web of Science databases, and Cochrane Library were searched for randomized controlled trials (RCTs) through April 2018. Three independent investigators evaluated study eligibilities, extracted data, and assessed study quality using the Cochrane Collaboration risk of bias tool and Jadad's quality scales. Heterogeneity was determined using Cochran's Q statistic and I-square (I 2 ) test. Based on the heterogeneity results, we pooled data using random-effect or fixed effect models presented as standardized mean differences (SMD) and corresponding 95 confidence intervals (CI). One hundred thirteen RCTs (19,644 patients) were included in our meta-analysis. The pooled results using random effects model showed that statin use statistically significantly decreased CRP level (SMD= -0.97; 95 CI, -1.10, -0.85; P < 0.001; I 2 : 95.1), TNF-α (SMD= -1.88; 95 CI, -2.40, -1.38; P < 0.001; I 2 : 97.2), IL-6 (SMD= -1.67; 95 CI, -1.98, -1.34; P < 0.001; I 2 : 96.5), and IL-1 concentrations (SMD= -8.35; 95 CI, -10.49, -6.22; P < 0.001; I 2 : 98.4) among patients with MetS and related disorders. Our meta-analysis showed beneficial effects of statin use on reducing inflammatory markers in patients with MetS and related disorders. © 2018 Elsevier Lt