• BMB Reports
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• 제34권1호
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• pp.1-7
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• 2001

Structural and physical properties of type wild type and various selected mutants of the vnd/NK-2 homeodomain, the protein product of the homeobox, and the implication in genetic disease are reviewed. The structure, dynamics and thermodynamics have been Investigated by NMR and by calorimetry. The interactions responsible for the nucleotide sequence-specific binding of the homeodomain to its consensus DNA binding site have been identified. There is a strong correlation between significant structural alterations within the homeodomain or its DNA complex and the appearance of genetic disease. Mutations in positions known to be important in genetic disease have been examined carefully For example, mutation of position 52 of vnd/NK-2 results in a significant structural modification and mutation of position 54 alters the DNA binding specificity and amity The $^{15}N$ relaxation behavior and heteronuclear Overhauser effect data was used to characterize and describe the protein backbone dynamics. These studies were carried out on the wild type and the double mutant proteins both in the free and in the DNA bound states. Finally, the thermodynamic properties associated with DNA binding are described for the vnd/NK-2 homeodomain. These thermodynamic measurements reinforce the hypothesis that water structure around a protein and around DNA significantly contribute to the protein-DNA binding behavior. The results, taken together, demonstrate that structure and dynamic studies of proteins combined with thermodynamic measurements provide a significantly more complete picture of the solution behavior than the individual studies.

• International Journal of Naval Architecture and Ocean Engineering
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• 제5권4호
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• pp.529-545
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• 2013

Strong restrictions on emissions from marine power plants (particularly $SO_x$, $NO_x$) will probably be adopted in the near future. In this paper, a combined solid oxide fuel cell (SOFC) and gas turbine fuelled by natural gas is proposed as an attractive option to limit the environmental impact of the marine sector. It includes a study of a heat-recovery system for 18 MW SOFC fuelled by natural gas, to provide the electric power demand onboard commercial vessels. Feasible heat-recovery systems are investigated, taking into account different operating conditions of the combined system. Two types of SOFC are considered, tubular and planar SOFCs, operated with either natural gas or hydrogen fuels. This paper includes a detailed thermodynamic analysis for the combined system. Mass and energy balances are performed, not only for the whole plant but also for each individual component, in order to evaluate the thermal efficiency of the combined cycle. In addition, the effect of using natural gas as a fuel on the fuel cell voltage and performance is investigated. It is found that a high overall efficiency approaching 70% may be achieved with an optimum configuration using SOFC system under pressure. The hybrid system would also reduce emissions, fuel consumption, and improve the total system efficiency.

• 한국수소및신에너지학회논문집
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• 제22권2호
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• pp.223-231
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• 2011

The thermal efficiency of energy-to-power conversion becomes uneconomically low when the temperature of heat source drops below $370^{\circ}C$. ORC (Organic Rankine Cycle) has attracted much attention in last few years due to its potential in reducing consumption of fossil fuels and relaxing environmental problems, and its favorable characteristics to exploit low-temperature heat sources. In this work thermodynamic performance of ORC using nine working fluids is comparatively assessed. Special attention is paid to the effect of system parameters such as turbine inlet temperature and pressure on the characteristics of the system such as volumetric flow rate and quality at turbine exit, latent heat, net work as well as thermal efficiency. Results show that in selection of working fluid it is required to consider various criteria of performance characteristics as well as the thermal efficiency. Results also show that the system efficiencies become same irrespective of kind of working fluid when the temperature of heat source decreases to low range.

• Bulletin of the Korean Chemical Society
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• 제30권2호
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• pp.423-428
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• 2009

The comparative study of three calix[4]heterocycles (calix[4]pyrrole, calix[4]furan, and calix[4]thiophene) has been theoretically performed by using high-level density functional theory (DFT) at the MPWB1K/6-311G$^{**}$//B3LYP/6- 311G$^{**}$ level. The effect of different hetero-atoms (nitrogen, oxygen, and sulfur) placed in the heterocycles on the conformational flexibility, thermodynamic stability order, cavity sizes, charge distributions, and binding propensities are examined. The thermodynamic stability differences between the conformers are found to be much greater in calix[4]pyrrole compared to those in calix[4]furan and calix[4]thiophene. Relatively larger NH group and higher dipole of a pyrrole ring in calix[4]pyrrole contribute to the higher energy barrier for the conformational conversions and relatively rigid potential energy surface compared to the case of calix[4]furan and calix[4]thiophene. The computational results herein provide theoretical understanding of the conformational flexibility and the thermodynamic nature which can be applied to understand the complexation behavior of the three calix[4]heterocycles.

• Journal of Magnetics
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• 제22권2호
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• pp.244-249
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• 2017

To get deeper insight into the effect of intergranular additives in sintered Nd-Fe-B magnet and consequently improve the properties better, the interaction between additives (oxide, nitride, and carbide) and Nd-rich phase in the temperature range of 298.15-1400 K was analyzed thermodynamically. It can be found that the oxide additives became less stable than nitrides and carbides. Except for calcium oxide, almost all oxides could react with Nd from Nd-rich phase. To be different from oxide additives, the mechanism of nitrides and carbides was defined with various elements, either reaction with Nd from Nd-rich phase or not. The two different mechanisms would show different effects on the microstructure and hence properties of magnet. The thermodynamic analysis had a better agreement with the experimental information.

• Membrane and Water Treatment
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• 제9권2호
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• pp.79-85
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• 2018

In this work, batch adsorption of anionic dye acid green-25 (AG-25) from aqueous solution has been carried out at room temperature using anion exchange membrane (DF-120B) as a noval adsorbent. The effect of various experimental parameters such as contact time, membrane dosage, ionic strength and temperature on the adsorption of dye were investigated. Kinetic models namely pseudo-first-order, pseudo-second-order, Elovich, liquid film diffusion, Bangham and modified freundlich models were employed to evaluate the experimental data. Parameters like adsorption capacities, rate constant and related correlation coefficients for every model are calculated and discussed. It showed that adsorption of AG-25 onto DF-120B followed pseudo-first-order rate expression. Thermodynamic study indicates that adsorption of AG-25 onto DF-120B is an exothermic and spontaneous process.

• 한국초전도ㆍ저온공학회논문지
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• 제11권1호
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• pp.55-59
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• 2009

Miniature Joule-Thomson refrigerators have been widely used for rapid cooling of infrared detectors, probes of cryosurgery, thermal cameras, missile homing head and guidance system, due to their special features of simple configuration, compact structure and rapid cool-down characteristics. The thermodynamic performance of J-T refrigerator highly depends on the hydraulic and heat transfer characteristics of the recuperative heat exchanger. The typical recuperative heat exchanger of the J-T refrigerator has the double helical tube and fin configuration. In this study, effectiveness-NTU approach was adopted to predict the thermodynamic behaviors of the heat exchanger for the J-T refrigerator. The thermodynamic properties from the REFPROP were used to account the real gas effects of the gas. The results show the effect of the operating conditions on the performance of the heat exchanger and refrigerator for the given heat exchanger. The influences of mass flow rate and the supply pressure on the effectiveness of heat exchanger and the ideal cooling capacity are discussed in details.

• 한국태양에너지학회 논문집
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• 제27권3호
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• pp.87-94
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• 2007

In this paper, with water-LiCl-$CaCl_2-Zn(NO_3)_2$ mixture which utilizes solar energy at the evaporator heat source, a thermodynamic analysis was performed to provide design data for a double-effect absorption heating system. A comparative study of the water-LiCl-$CaCl_2-Zn(NO_3)_2$ mixture against the water-LiBr pair was conducted by a computer simulation. The computer simulation is based on mass, material and heat balance equations for each part of the system. Coefficients of performance and flow ratios for effects of different operating temperatures are investigated. It is found that the heating COP is higher for the water-LiCl-$CaCl_2-Zn(NO_3)_2$ mixture than for the water-LiBr pair, and FR is lower for the former.

• Asian Journal of Atmospheric Environment
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• 제9권1호
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• pp.86-90
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• 2015

Temperature was considered to estimate the minimum detectable absorption coefficient of aerosol particles from photothermal spectroscopy. Light energy absorbed by subsequent emission from the aerosol results in the heating of the aerosol sample and consequently causes a temperature change as well as changes in thermodynamic parameters of the sample. This thermal effect is the basis of photothermal spectroscopy. Photothermal spectroscopy has several types of techniques depending on how the photothermal effects are detected. Photothermal interferometry traces the photothermal effect, refractive index, using an interferometer. Photoacoustic spectroscopy detects the photothermal effect, sound wave, using a microphone. In this study, it is suggested that the detection limit for photothermal spectroscopy can be influenced by the introduction of a slip correction factor when the light absorption is determined in a high temperature environment. The minimum detectable absorption coefficient depends on the density, the specific heat and the temperature, which are thermodynamic properties. Without considering the slip correction, when the temperature of the environment is 400 K, the minimum detectable absorption coefficient for photothermal interferometry increases approximately 0.3% compared to the case of 300 K. The minimum detectable absorption coefficient for photoacoustic spectroscopy decreases only 0.2% compared to the case of 300 K. Photothermal interferometry differs only 0.5% point from photoacoustic spectroscopy. Thus, it is believed that photothermal interferometry is reliably comparable to photoacoustic spectroscopy under 400 K.

• 한국응용과학기술학회지
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• 제14권3호
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• pp.39-46
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• 1997

Ultraviolet spectrophotometric investigation has been carried out on the rate constants for 1,3-dipolar cycloaddition of 4-substituted-3-phenyloxadiazole derivatives with dipolarophiles such as phenyl acetylene, propiolic acid methyl ester and dimethylacetylene dicarboxylate. From there, the rate constants for 1,3-dipolar cycloaddition were determined at 80, 100 and $120^{\circ}C$, and the reaction rates were increased with increasing temperature. From these rate constants, the values of the thermodynamic activation parameters were obtained. Some thermodynamic activation parameters such as $E_{\alpha}$, ${\Delta}H^{\ast}$, ${\Delta}S^{\ast}$ and ${\Delta}G^{\ast}$ from Arrhenius equation were also calculated for the electrophilic 1,3-dipolar cycloaddition of 3-phenyloxadiazole derivatives with dipolarophiles. In order to the proposal the mechanism and reactivity of 1,3-dipolar cycloaddition reaction, the effect of substituents having various kinds of electron withdrawing or releasing groups were examinated. Considering the effect of substituents, an electron withdrawing group attached at the 4-carbon position in 3-phenyloxadiazole derivatives decreases the reaction rate because of the lack of electron density in 3-phenyloxadiazole ring.