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• An in-house adsorption test rig is designed and developed for CH 4 -AC pair. • Isotherm and kinetic constants are determined for subzero and high temperatures. • Physiochemical and thermophysical properties are experimentally estimated. • Heat of adsorption, adsorbed phase-specific heat, enthalpy, entropy are estimated. • 3D transient analysis of the ANG reactor is conducted. The current study investigates the equilibrium methane (CH 4) adsorption capacity and the adsorption kinetics of a locally produced coconut shell-derived activated carbon (AC CARB 6X12 60) for pressure and temperatures ranging from 0 to 55 bar and -20 to 70 °C, respectively. The adsorption isotherms and kinetics are determined using an in-house developed adsorption test rig. A maximum methane adsorption uptake of 0.140 kg/kg is obtained at -20 °C and 40 bar pressure. The adsorption equilibrium isotherm data are fitted using Toth, Dubinin-Astakhov (DA), and Modified-DA isotherm models. Afterwards, the kinetics study is done considering pseudo first order, second order, Elovich, and intra-particle diffusion models. In continuation, based on the DA isotherm model, Clausius Clapeyron relation, and Maxwell's relations, the expressions for the crucial thermodynamic parameter of adsorbed phase, i.e., isosteric heat of adsorption, specific heat capacity, enthalpy, and entropy is derived, and same is estimated using DA isotherm parameters. Additionally, the activated carbon's thermophysical properties (i.e., thermal conductivity, thermal diffusivity, and specific heat) are determined using the TPS 2500 S analyzer, which works on the hot-disk principle. Using the most suitable isotherm (DA) and kinetic model (pseudo second order), heat and mass transfer analysis is carried out on novel reactor configuration with an external cooling jacket, double row of cooling pipes with external longitudinal fins for methane storage using a 3D transient model in Comsol Multiphysics. The charge characteristics are studied for gas charging pressure varying from 1 to 50 bar and cooling fluid temperature of -20 to 70 °C. Iso-concentration contours are plotted to identify the pressure-temperature combination resulting in identical storage capacity (i.e., including both gaseous and adsorbed phases). Further simulations are carried out for constant pressure charging and constant flow discharge conditions to expound upon the effects of the dormancy period, gas charging pressure, and cooling/heating fluid temperature. 14% improvement in total discharge amount is obtained with a dormancy period between charging and discharging compared to no dormancy case. [ABSTRACT FROM AUTHOR]

A detailed performance evaluation of modified transcritical CO 2 adsorption refrigeration systems integrated with an ejector and a thermoelectric sub-cooler is carried out using simplified thermodynamic models. The simultaneous effect of subcooling and the lift produced by the ejector on system COP and the specific cooling effect (SCE) is expounded. It is observed that the proposed system yields an identical COP with that of heat and mass recovery systems with reduced design and operational complexity. However, the heat and mass recovery systems clubbed with ejector and thermoelectric sub-cooler yield the best system performance with a maximum increment of 126% in COP. The gas cooler pressure and subcooling temperature strongly affect the entrainment ratio; however, COP and SCE strongly depend on gas cooler pressure, evaporator and generator temperatures. The maximum COP attained (i.e., 0.353) using the novel adsorbent (M-AC C-500) in the modified system can be used as a benchmark. [Display omitted] • Thermodynamic study is done on a CO 2 -based transcritical adsorption cooling system. • Enhanced system performance is achieved by various cycle modifications. • different activated carbon-CO 2 pairs are compared for best cycle modification. • M-AC C-500 yields the maximum COP of 0.353 and SCE of 123.10 kJ/kg. • Effects of critical design and operating parameters are studied in detail. [ABSTRACT FROM AUTHOR]

Abstract: We present theoretical photoionization cross sections for He 1s2s 1S and He 1s2p 1P states in a Debye plasma environment by the complex coordinate rotation method, using a finite L 2 basis set constructed from one electron Laguerre orbitals. The plasma environment is found to appreciably influence the photoionization cross sections near the ionization threshold. In this regard, the photoionization cross sections of isolated He are compared with other theoretical and experimental results. Our results are in good agreement with the previous results. A new minimum appears in the photoionization cross section curve for the metastable 1s2s 1S state. Results are given for the S- and D-wave partial photoionization for the excited 1s2p 1P state. [Copyright &y& Elsevier]

• Four different configurations of adsorption cooling cycles are studied for improved performance for subcritical and transcritical cycles. • Detailed thermodynamic analysis is carried out for 5 different adsorbent materials for all the configurations. • Effect of various parameters are studied on system performance. • Out of all the adsorbents used, Maxsorb III showed better system performance. • Various co-relations have been developed for various intermediate temperatures and COP. In the present investigation, thermodynamic analysis of four different adsorption cooling cycles; basic, internal heat recovery, mass recovery, and heat & mass recovery cycles are carried out employing CO 2 as the refrigerant. The said investigation is done for five different adsorbent materials i.e. a highly microporous activated carbon (Maxsorb III), Maxsorb III based composite, Activated carbon fibre (ACF) A-20, BPL activated carbon (AC), and Norit AC. The study stretches the analysis from subcritical to supercritical zone for evaporator temperature ranging from −5 °C to 15 °C. For subcritical cycle, generator and condenser temperatures are varied between 65 °C to 91 °C and 20 °C to 30 °C, and for transcritical cycle, generator and gas cooler exit temperatures are varied from 90 °C to 120 °C and 35 °C to 40 °C, respectively. The maximum COP and specific cooling effect (SCE) achieved by incorporating both heat and mass recovery to the basic cycle are 0.305 and 105 kJ/kg, respectively. The improvement in COP and 2nd law efficiency of the same cycle w.r.t. other cycles are in the range of 7% to 84% and 38% to 77%, respectively for subcritical cycles. Similarly, for transcritical cycles, improvements in COPs of HMRC are in range of 17% to 75%. Analysis showed better system performance for Maxsorb III and it's composite as compared to other adsorbents. Various regression equations are developed to predict the different intermediate temperatures and COP for the mentioned modified subcritical and transcritical cycles. [ABSTRACT FROM AUTHOR]

• 4-Bed CO 2 -based adsorption cooling system is analyzed with various sorbent reactors. • Variable aspect ratios of cylindrical reactors with longitudinal fins are explored. • The study is carried out for subcritical and transcritical cyclic operations. • Results show system performance is strongly dependent on reactor geometry. • 23–98 % COP improvement is achieved during transcritical and subcritical operations. The present investigation expounds on the effects of the reactor geometry, cycle time and heating/cooling fluid temperatures on the performance of a 4-bed CO 2 adsorption cooling system. Cylindrical adsorbent reactors of varying aspect ratios (AR) with an optimum number of internal longitudinal fins and non-finned reactors are compared. The study confirms the substantial effect of reactor configuration on the system COP, specific cooling effect (SCE) and power, energy interactions during various processes and the total cycle time (TCT), which the equilibrium or lumped system analysis fails to predict. An increment of 98 % and 189 % in system COP and SCE is attained by varying the aspect ratio of the reactor with fins under subcritical operations. In continuation, a reduction of 41 % in TCT is observed. The study confirms the optimum adsorption/desorption time for which the COP and SCE are maximum, especially for higher AR reactors. It is noteworthy that proper selection of reactor aspect ratio results in a better system COP, even at lower heating fluid temperatures. During the transcritical operations, an increment of 23 % in COP and 6 % in SCE is achieved for a gas cooler exit temperature of 35 °C. Moreover, the reactor configuration also affects the optimum gas cooler pressure for the transcritical cycle, like the gas cooler exit temperature. One of the crucial observations is that, for a given combination of reactor configuration, heating/cooling fluid temperatures, and operating pressures, there exists a minimum cycle time below which a cyclic steady-state condition is impossible to achieve. During the subcritical and transcritical operations, a maximum COP of 0.1 and 0.052 is achieved for the proposed adsorption chiller configuration, respectively. [ABSTRACT FROM AUTHOR]

• 12 adsorbent composites are synthesized with enhanced thermophysical properties. • Composites are employed in post-combustion CO 2 capture applications. • 6–606% increment in thermal conductivity is achieved. • 5 isotherm models have been used to correlate the measured isotherm data. • Thermodynamic performance is investigated under different operation conditions. The present investigation aims at developing consolidated adsorbent composites with enhanced thermophysical and transport properties at the cost of a minimum sacrifice in equilibrium CO 2 uptake. Twelve samples are synthesized using a coconut shell-derived activated carbon (CSAC) as the parent material, graphite, graphene nanoplatelets, and CuO as the additives and PVA as the binder. All the synthesized had undergone a proper characterization using N 2 adsorption/ desorption and FE-SEM to highlight the changes in the BET surface area, pore volume, pore size distribution, and pore networking compared to the parent activated carbon and surface morphology. The thermophysical (specific heat capacity) and transport properties (thermal conductivity and thermal diffusivity) of all the composites of various mass fractions of the additives (10–40%) are measured using a TPS-2500 S transient hot disk method. The experimental results show that maximum thermal conductivity of 1.72 W/m K is achieved with graphite as the additive with a ratio of CSAC: graphite: PVA (Composite 4) of 50:40:10 wt%, corresponding to an increment of 606% compared to parent CSAC. The increment is comparable and better than the other consolidated adsorbent composites reported in the literature. All the constants of various isotherm models are obtained based on the experimentally obtained pressure-temperature and concentration data using the non-linear regression analysis. Based on the R2 values, the Toth model is identified as the best model for all the composites. A detailed thermodynamic analysis is further carried out, and important thermodynamic parameters, i.e., Enthalpy, Entropy, Gibbs free energy change associated with the adsorption process and the Isosteric heat of adsorption are obtained. The estimated thermodynamic parameters, isotherm and thermophysical data are crucial for the actual design and development of compact systems suitable for adsorption-based CO 2 capture applications. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Based on the hypothesis that highly expressed genes are often characterized by strong compositional bias in terms of codon usage, there are a number of measures currently in use that quantify codon usage bias in genes, and hence provide numerical indices to predict the expression levels of genes. With the recent advent of expression measure from the score of the relative codon usage bias (RCBS), we have explicitly tested the performance of this numerical measure to predict the gene expression level and illustrate this with an analysis of Yeast genomes. In contradiction with previous other studies, we observe a weak correlations between GC content and RCBS, but a selective pressure on the codon preferences in highly expressed genes. The assertion that the expression of a given gene depends on the score of relative codon usage bias (RCBS) is supported by the data. We further observe a strong correlation between RCBS and protein length indicating natural selection in favour of shorter genes to be expressed at higher level. We also attempt a statistical analysis to assess the strength of relative codon bias in genes as a guide to their likely expression level, suggesting a decrease of the informational entropy in the highly expressed genes. [Copyright &y& Elsevier]

• Expressions for the efficiency and effectiveness of a porous fin with prescribed tip temperature are developed. • Analytical expressions for fin temperature profile and performance parameters are obtained using Galerkin's method of weighted residual. • The critical value of fin parameter S H is identified and different behaviour of the fin in the two different zone S H < S H * & S H > S H * are expounded. • The non-operating zone for a porous fin with prescribed tip temperature is identified. • Four different fin profile are explored. The present investigation aims at estimating the efficiency and effectiveness of porous fins of various profiles in a natural convection environment with both the ends imposed at certain temperatures. Unlike the other boundary conditions (insulated tip, convective tip) the maximum heat transfer rate for the present case cannot be determined considering the whole fin being at the base temperature. The maximum heat transfer rate is calculated by first finding the temperature profile of the fin corresponds to a very high value of thermal conductivity (i.e. k eff → ∞). Using the local maximum temperature values the maximum heat transfer rate is calculated. The variation of the temperature as well as the performance parameters for the longitudinal porous fin as a function of fin parameter (S H), is presented for four different profiles (rectangular, trapezoidal, parabolic concave and cubic concave). The variation of the fin efficiency with S H for different values of fin tip to base temperature ratio (θ L / θ b), depicts that for certain value of θ L / θ b the fin behaves differently in the two different zones S H < S H * and S H > S H *. The results indicate that for θ L / θ b ≥ 0.45 there exists a range of S H for which the fin efficiency is reduced and there exist local maxima and minima. This range of S H is undesirable to operate and it should be avoided for the proper design of the fin. The nonlinear governing differential equations are solved using the finite difference method followed by an iterative solver. To get approximate analytical expressions for the temperature as well as the fin efficiency and effectiveness semi- analytical solutions are also presented using Galerkin's method of weighted residual. [ABSTRACT FROM AUTHOR]

A novel micro-mesoporous activated carbon (SBL AC-700) is synthesized from subabul (Leucaena leucocephala) sawdust waste by direct single-stage physical activation at 700 °C for 1 h for carbon capture applications. The synthesized AC is characterized to explore various physiochemical properties like elemental composition, surface morphology and crystallinity, presence of functional groups, surface area, pore size, and pore volume. Additionally, emphasis is given to exploring the thermophysical aspects of the novel AC, the literature regarding which is scarce in the open domain. The CO 2 adsorption study is carried out for a 0–1 bar pressure for temperatures ranging from 0 to 75 °C. The analysis revealed that the AC possesses a surface area of 590 m2/g and pore volume and width of 0.27 cm3/g and 1.85 nm, corresponding to a 70% microporosity with a well-developed porous structure. At 25 °C and 1 bar, a CO 2 uptake of 40.54 cm3/g is achieved, corresponding to an increment of 6–202% compared to other commercials, chemically and physically activated carbons. Moreover, SBL AC-700 has a thermal conductivity of 0.095 W/m K, 8–131% higher than other benchmarks ACs and much lower specific heat of 0.82 kJ/kg K corresponding to lesser regeneration energy requirements. Experimental data are fitted with various isotherm models, i.e., Langmuir, Freundlich, Sips, R–P, and Toth, out of which R–P and Toth models exhibit the best fit. In continuation, adsorption kinetics is studied to explore the dynamic performance of the SBL AC-700 by using Pseudo-first-order, Pseudo-second-order, Elovich, and intraparticle diffusion kinetic models. [Display omitted] • AC SBL AC-700 from subabul sawdust waste is synthesized successfully. • Novel AC is prepared by eco-friendly single-step direct CO 2 activation. • The ability of CO 2 uptake at 25 °C and 1 bar is 40.54 cm3/g. • SBL AC-700 has a thermal conductivity of 0.095 W/m K, 8–131% higher than other ACs. • Isotherm, kinetics, and thermodynamic modeling is done for the AC-CO 2 pair. [ABSTRACT FROM AUTHOR]

Abstract: The expression of functional proteins plays a crucial role in modern biotechnology. The free-living cynobacterium Synechocystis PCC 6803 is an interesting model organism to study oxygenic photosynthesis as well as other metabolic processes. Here we analyze a gene expression profiling methodology, RCBS (the scores of relative codon usage bias) to elucidate expression patterns of genes in the Synechocystis genome. To assess the predictive performance of the methodology, we propose a simple algorithm to calculate the threshold score to identify the highly expressed genes in a genome. Analysis of differential expression of the genes of this genome reveals that most of the genes in photosynthesis and respiration belong to the highly expressed category. The other genes with the higher predicted expression level include ribosomal proteins, translation processing factors and many hypothetical proteins. Only 9.5% genes are identified as highly expressed genes and we observe that highly expressed genes in Synechocystis genome often have strong compositional bias in terms of codon usage. An important application concerns the automatic detection of a set of impact codons and genes that are highly expressed tend to use this narrow set of preferred codons and display high codon bias .We further observe a strong correlation between RCBS and protein length indicating natural selection in favor of shorter genes to be expressed at higher level. The better correlations of RCBS with 2D electrophoresis and microarray data for heat shock proteins compared to the expression measure based on codon usage difference, E(g) and codon adaptive index, CAI indicate that the genomic expression profile available in our method can be applied in a meaningful way to study the mRNA expression patterns, which are by themselves necessary for the quantitative description of the biological states. [Copyright &y& Elsevier]