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Fundamental molecules of life are pigments which arose and co-evolved as a response to the thermodynamic imperative of dissipating the prevailing solar spectrum
摘要： The driving force behind the origin and evolution of life has been the thermodynamic imperative of increasing the entropy production of the biosphere through increasing the global solar photon dissipation rate. In the upper atmosphere of today, oxygen and ozone derived from life processes are performing the short-wavelength UV-C and UV-B dissipation. On Earth’s surface, water and organic pigments in water facilitate the near-UV and visible photon dissipation. The first organic pigments probably formed, absorbed, and dissipated at those photochemically active wavelengths in the UV-C and UV-B that could have reached Earth’s surface during the Archean. Proliferation of these pigments can be understood as an autocatalytic photochemical process obeying non-equilibrium thermodynamic directives related to increasing solar photon dissipation rate. Under these directives, organic pigments would have evolved over time to increase the global photon dissipation rate by (1) increasing the ratio of their effective photon cross sections to their physical size, (2) decreasing their electronic excited state lifetimes, (3) quenching radiative de-excitation channels (e.g., fluorescence), (4) covering ever more completely the prevailing solar spectrum, and (5) proliferating and dispersing to cover an ever greater surface area of Earth. From knowledge of the evolution of the spectrum of G-type stars, and considering the most probable history of the transparency of Earth’s atmosphere, we construct the most probable Earth surface solar spectrum as a function of time and compare this with the history of molecular absorption maxima obtained from the available data in the literature. This comparison supports the conjecture that many fundamental molecules of life are pigments which arose, proliferated, and co-evolved as a response to dissipating the solar spectrum, supports the thermodynamic dissipation theory for the origin of life, constrains models for Earth’s early atmosphere, and sheds some new light on the origin of photosynthesis.
关键词： photosynthesis,thermodynamic dissipation,UV-C,solar spectrum,UV-B,Archean,organic pigments,origin of life
更新于2025-09-09 09:28:46
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Thermodynamic Properties of Negative Discharge Channels in a 1-m Air Gap Measured by Optical Interferometry
摘要： Lightning is a common natural phenomenon and is a typical air discharge on a large spatial scale. The stepping of lightning leaders and space stems of thunderstorms are similar to those of negative discharges in the laboratory. There have been extensive experimental observations and theoretical research on positive discharge but less research on the negative form. This paper conducts an experiment on a 1-m rod–plane gap under a negative impulse voltage. To observe the thermodynamics of the negative discharge, a Mach–Zehnder interferometer combined with a high-speed video camera was set up. The Abel inverse method was used to quantify the thermal parameters for negative channels. The space stem is of great interest, and its bidirectional propagation and connection with the electrode were captured. When a space stem formed, the gas temperature within the stem ranged 320–550 K. Two negative leaders connected in space and formed one negative channel. The connection region was about 800 K while the temperature on the two sides of the negative channel reached 1500–1800 K. After a negative channel formed, it expanded, and its thermal parameter distributions tended to be uniform owing to thermal conduction and convection losses. The gas density near the discharge center was about 20%–30% of the ambient density, and the corresponding temperature was 1000–1500 K. The experiments provide deep insight into the thermodynamic properties of a negative leader discharge.
关键词： Mach–Zehnder (M-Z) stem,discharge channel,Connection process,negative,space interferometry,thermodynamic properties
更新于2025-09-09 09:28:46
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Experimental framework for evaluation of the thermodynamic and kinetic parameters of metal-oxides for solar thermochemical fuel production
摘要： The two-step metal oxide redox cycle is a promising and thermodynamically attractive means of solar fuel production. In this work, we describe the development of a high-temperature tubular reactor in which the fundamental thermodynamic and kinetic behaviour of thermochemical materials can be readily assessed. This reactor system is capable of operating at temperatures up to 1873 K, total pressures ranging from vacuum to ambient, and oxygen partial pressures (pO2) as low as 10-29 atm. Compared to off-the-shelf systems like thermogravimetric analyzers (TGA) or indirect conductivity-based measurement systems, this system has three inherent benefits: (1) the flexibility to control the sample morphology (e.g. powder, packed bed, reticulated porous ceramic, or pellet), (2) the potential for a well-developed and characterized flow, and (3) the ability to readily customize the system on demand (e.g. easy integration with a steam generator to control and operate at very low pO2). The reactor system and experimental methods were validated by performing isothermal relaxation experiments with undoped ceria, wherein the sample environment was rapidly altered by stepwise changes in the delivered H2O vapor concentration, and comparing measured oxygen nonstoichiometries with accepted data available in the literature. Data was measured at temperatures from 1173-1473 K and pO2 from 4.54×10-18-1.02×10-9 atm. The measured equilibrium data displayed strong agreement with the literature and the expected trends were preserved. Kinetic data was extracted by first transforming reactant concentrations measured downstream of the reaction zone using a tanks-in-series mixing model to account for gas dispersion. Next, a mechanistic kinetic model distinguishing surface and bulk species concentrations was fit to the data to extract pertinent thermodynamic and kinetic parameters. The model assumed a two-step reaction mechanism mediated by the formation of an intermediate hydroxyl species on the surface. Activation energies and defect formation enthalpies and entropies for the forward and reverse reactions were found to be in good agreement with previous modelling efforts, providing further validation of the use of this system to explore thermodynamic and kinetic behaviour of emerging thermochemical materials.
关键词： thermodynamic and kinetic parameters,undoped ceria,solar fuel production,metal oxide redox cycle,high-temperature tubular reactor
更新于2025-09-09 09:28:46
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Preparation of Tin Dioxide Nanoparticles by the Reverse Micelle Method: Experiment and Preliminary Calculations
摘要： Synthetic and computational experiments were carried out to study the influence of the nature and structure of surfactants, and also of the reaction medium on the size of tin dioxide nanoparticles obtained by the reverse micelle method.
关键词： tin dioxide,microemulsions,nanoparticles,molecular-thermodynamic simulation,synthesis in inverted micelles
更新于2025-09-09 09:28:46
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Polarization-Direction Dependence of Thermodynamic Stability of Ferroelectric BiAlO <sub/>3</sub> (0001) Polar Surfaces
摘要： Polar surfaces of ferroelectric oxides are of great importance for both fundamental and practical interest. In this report, we present a theoretical study to determine the thermodynamic stability and electronic properties of ferroelectric BiAlO3(0001) surfaces. According to the calculated surface phase diagram, we predict that the equilibrium stoichiometries are distinct for the oppositely polarized BiAlO3 surfaces under the same chemical conditions. In addition to nonstoichiometry of the surface chemical compositions, we find that anomalous filling of the surface states can also result in surface metallization in order to compensate the remarkable surface polarity. Besides providing atomic-scale understanding of the BiAlO3(0001) surfaces, we also put forward the practical implications in novel magnetoelectric devices and advanced surface chemistry.
关键词： Magnetoelectric devices,Surface chemistry,Thermodynamic stability,Surface metallization,BiAlO3(0001) surfaces,Electronic properties,Ferroelectric oxides
更新于2025-09-09 09:28:46
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Elastic and thermophysical properties of BAs under high pressure and temperature
摘要： The pseudopotential plane-wave approach in the framework of the density functional theory, and the density functional perturbation theory with the generalized gradient approach for the exchange-correlation functional has been used to calculate the structural phase stability, elastic constants and thermodynamic properties of boron-arsenide (BAs) compound. The BAs compound transforms from the zincblende phase to rock-salt structure; the phase transition pressure was found to be 141.2 GPa with a volume contraction of around 8.2 %. The thermodynamic properties under high pressure and temperature up to 125 GPa and 1200 K respectively were also determined, analyzed and discussed in comparison with other data of the literature. The systematic errors in the static energy were corrected using the bpscal EEC method. Our results agree well with those reported in the literature, where for example, our calculated melting temperature (2116 K) deviates from the theoretical one (2132.83 K) with only 0.8 %, and the deviation between our result (1.86) of the Grüneisen parameter and the theoretical one (1.921) is only around 3.2 %.
关键词： Phase transition,Thermodynamic properties,High-pressure,High-temperature,Boron arsenide
更新于2025-09-09 09:28:46
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AIP Conference Proceedings [Author(s) OIL AND GAS ENGINEERING (OGE-2018) - Omsk, Russia (26 February–2 March 2018)] - Influence of the average daily outdoor air parameters on the efficiency of solar lithium bromide-water absorption refrigeration machine
摘要： In this research, the authors have investigated the influence of changes in the average daily temperature and humidity on the efficiency of solar lithium bromide-water absorption cooling system working on solar energy for the purposes of conditioning and condensing moisture from the air. The analysis of thermodynamic cycles at various schematic solutions of lithium bromide-water refrigeration machine has been made. Minimum temperature values of the heating source at which it is possible to receive fresh water for the cities of Dubai, Singapore and Chongqing have been obtained.
关键词： conditioning,fresh water,lithium bromide-water absorption refrigeration machine,thermodynamic cycles,solar energy
更新于2025-09-09 09:28:46
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Fluorescence Spectral Study on the Interaction Between Brilliant Blue and Trypsin
摘要： The interaction between brilliant blue and trypsin was studied by using fluorescent technique. The fluorescence quenching data were analyzed according to Stern-Volmer equation and Line weaver-Burk equation. The binding constants, thermodynamic parameters and binding sites were obtained. According to the thermodynamic parameters, the main binding force between brilliant blue and trypsin was ascertained as electrostatic interaction. The binding distance between brilliant blue and trypsin was also given based on the F?rster energy transfer theory.
关键词： Fluorescence spectrum,Thermodynamic parameters,Trypsin,Brilliant blue
更新于2025-09-09 09:28:46
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Thermodynamic conditions for cluster formation in supersaturated boundary layer during plasma spray-physical vapor deposition
摘要： Plasma spray-physical vapor deposition (PS-PVD) is used to produce columnar microstructure coatings for vapor materials under particular operating parameters. However, due to the particular conditions of PS-PVD, the state of vapor material transported in plasma jet is di?cult to predict by experimental method. Moreover, the properties of plasma jet changes sharply when the hot plasma jet approaches a relatively low temperature substrate. It is more di?cult to examine the behavior variation of vapor material by experiment. In this work, the thermodynamic condition for state variation of the vapor material along with methods to change this condition were studied. The distribution of plasma temperature near the substrate surface was obtained through simulation and the vapor pressure of vapor materials was calculated by the obtained temperature distribution. The supersaturated boundary layer was obtained from the distribution of the vapor pressure and partial pressure of the vapor atoms. The environment of this supersaturated boundary layer agreed with the thermodynamic conditions of the state variation of vapor materials. Further, this layer could be varied by changing the spraying distance and powder feed rate, thus allowing further control of the state variation of vapor materials. For PS-PVD process, especially for the deposition of columnar coating, it is very important to understand the properties of boundary layer and condensation conditions of vapor materials; this study provides the basis for future research on the transport of materials in the boundary layer.
关键词： Thermodynamic condition,Cluster,PS-PVD,Supersaturated boundary layer
更新于2025-09-04 15:30:14