scholarly journals Oxide-based Composites: Application in Thermo-Photo Catalysis

2021 ◽  
Author(s):  
Irene Barba-Nieto ◽  
María N. Gómez-Cerezo ◽  
Anna Kubacka ◽  
Marcos Fernández-García
Keyword(s):  
Chemical Reactions ◽  
Energy Sources ◽  
Photo Catalysis ◽  
Photonic Energy

The combination of thermal and photonic energy sources to carry out catalyzed chemical reactions appears as a new avenue to optimize current industrial-oriented processes as well as to open new...

scholarly journals Possibilities of lightning-induced processes in gas-dusty atmosphere of water-containing bodies of Solar System

2008 ◽  
Vol 4 (S251) ◽  
pp. 331-332
Author(s):  
Yuriy Serozhkin
Keyword(s):  
Solar System ◽  
Chemical Reactions ◽  
Energy Sources ◽  
Biochemical Compounds ◽  
Satellites Of Jupiter ◽  
Experimental Researches

AbstractLightning is considered as one of energy sources for synthesis of biochemical compounds. Numerous theoretical and experimental researches of gas-grain chemistry show that chemical reactions on the gas - ice boundary play a considerable role in such synthesis. In this connection the greatest interest represents studying lightning in gas-dusty atmospheres of water-containing bodies (comets, ice satellites of Jupiter and Saturn).

scholarly journals Thermodynamic Discrimination Between Energy Sources for Chemical Reactions

2020 ◽  
Author(s):  
Zachary Schiffer ◽  
Aditya Limaye ◽  
Karthish Manthiram
Keyword(s):  
Energy Source ◽  
Equilibrium Constant ◽  
Chemical Reactions ◽  
Process Parameters ◽  
Energy Analysis ◽  
Energy Sources ◽  
Chemical Transformations ◽  
Universal Equation ◽  
Specific Data ◽  
Case Basis

Chemical transformations traverse large energy differences, yet the choice of energy source to drive a chemical reaction is often decided on a case-by-case basis; there is no fundamentally-driven, universal framework with which to analyze and compare the choice of energy source for chemical reactions. In this work, we present a reaction-independent expression for the equilibrium constant as a function of temperature, pressure, and voltage. With a specific set of axes, all reactions can be represented by a single (x,y) point and a quantitative divide between electrochemically and thermochemically driven reactions is visually evident. In addition, we show that our expression has a strong physical basis in work and energy fluxes to the system, although more specific data about reaction operation is necessary to provide a quantitative energy analysis. Overall, this universal equation and facile visualization of chemical reactions enables quick and informed justification for electrochemical versus thermochemical energy sources without knowledge of detailed process parameters.

Bioenergetics and Primitive Metabolic Pathways

2019 ◽  
Author(s):  
David W. Deamer
Keyword(s):  
Chemical Reactions ◽  
Solution Chemistry ◽  
Energy Sources ◽  
Feedback Systems ◽  
Cellular Life ◽  
Complex Process ◽  
Metabolic Systems ◽  
Metabolic Reactions ◽  
Visible Wavelengths ◽  
Main Ideas

It seems inescapable that at some point primitive cells incorporated chemical reactions related to what we now call metabolism. In all life today, metabolic reactions are driven by sources of chemical or photochemical energy, and each step is catalyzed by enzymes and regulated by feedback systems. There have been multiple proposals for the kinds of reactions that could have been incorporated into early life, but so far there is little consensus about a plausible way for metabolism to begin. This chapter will briefly review the main ideas that are familiar to chemists as solution chemistry but then ask a new question from the epigraph: how can reactions in bulk aqueous solutions be captured in membranous compartments? This question is still virtually unexplored, but I can offer some ideas in the hope of guiding potentially fruitful approaches. Because metabolism is such a complex process, it is helpful to use bullet points to help clarify the discussion. The first is a list of questions that guide the discussion, the second is list of facts to keep in mind, and the third is a list of assumptions that introduce the argument. Questions to be addressed: What are the primary metabolic reactions used by life today? What reactions can occur in prebiotic conditions that are related to metabolism? How can potential nutrient solutes cross membranes in order to support metabolism? How could metabolic systems become incorporated into primitive cellular life? Metabolism can be defined as the activity of catalyzed networks of intracellular chemical reactions that alter nutrient compounds available in the environment into a variety of compounds that are used by living systems. Most of the reactions are energetically downhill, so there is an intimate association between the energy sources available to life and the kinds of reactions that can occur. Here is a summary of energy sources used by life today: Light is by far the most abundant energy source, totaling 1360 watts per square meter as infrared and visible wavelengths. Chemical energy in the form of reduced carbon compounds is made available by photosynthesis.

scholarly journals Thermodynamic Discrimination between Energy Sources for Chemical Reactions

Joule ◽  
2021 ◽  
Vol 5 (1) ◽  
pp. 135-148
Author(s):  
Zachary J. Schiffer ◽  
Aditya M. Limaye ◽  
Karthish Manthiram
Keyword(s):  
Chemical Reactions ◽  
Energy Sources

Stability of α-ketoglutaric acid simulating an impact-generated hydrothermal system: implications for prebiotic chemistry studies

2020 ◽  
Vol 19 (3) ◽  
pp. 253-259
Author(s):  
L. Ramírez-Vázquez ◽  
A. Negrón-Mendoza
Keyword(s):  
Chemical Reactions ◽  
Chemical Evolution ◽  
Hydrothermal System ◽  
Krebs Cycle ◽  
Physicochemical Process ◽  
Energy Sources ◽  
Mineral Surfaces ◽  
The Past ◽  
The Stability

AbstractLife originated on Earth possibly as a physicochemical process; thus, geological environments and their hypothetical characteristics on early Earth are essential for chemical evolution studies. Also, it is necessary to consider the energy sources that were available in the past and the components that could have contributed to promote chemical reactions. It has been proposed that the components could have been mineral surfaces. The aim of this work is to determine the possible role of mineral surfaces on chemical evolution, and to study of the stability of relevant molecules for metabolism, such as α-ketoglutaric acid (α-keto acid, Krebs cycle participant), using ionizing radiation and thermal energy as energy sources and mineral surfaces to promote chemical reactions. Preliminary results show α-ketoglutaric acid can be relatively stable at the simulated conditions of an impact-generated hydrothermal system; thus, those systems might have been plausible environments for chemical evolution on Earth.

scholarly journals Thermodynamic Discrimination Between Energy Sources for Chemical Reactions

2020 ◽  
Author(s):  
Zachary Schiffer ◽  
Aditya Limaye ◽  
Karthish Manthiram
Keyword(s):  
Energy Source ◽  
Equilibrium Constant ◽  
Chemical Reactions ◽  
Process Parameters ◽  
Energy Analysis ◽  
Energy Sources ◽  
Chemical Transformations ◽  
Universal Equation ◽  
Specific Data ◽  
Case Basis

Chemical transformations traverse large energy differences, yet the choice of energy source to drive a chemical reaction is often decided on a case-by-case basis; there is no fundamentally-driven, universal framework with which to analyze and compare the choice of energy source for chemical reactions. In this work, we present a reaction-independent expression for the equilibrium constant as a function of temperature, pressure, and voltage. With a specific set of axes, all reactions can be represented by a single (x,y) point and a quantitative divide between electrochemically and thermochemically driven reactions is visually evident. In addition, we show that our expression has a strong physical basis in work and energy fluxes to the system, although more specific data about reaction operation is necessary to provide a quantitative energy analysis. Overall, this universal equation and facile visualization of chemical reactions enables quick and informed justification for electrochemical versus thermochemical energy sources without knowledge of detailed process parameters.

Surface reactions observed by photoemission electron microscopy (PEEM)

1992 ◽  
Vol 50 (1) ◽  
pp. 286-287
Author(s):  
H.H. Rotermund
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Work Function ◽  
Chemical Reactions ◽  
Reaction Diffusion ◽  
Dynamic Processes ◽  
Clean Surface ◽  
Crystal Surfaces ◽  
Single Crystal Surfaces ◽  
Photoemission Electron

Chemical reactions at a surface will in most cases show a measurable influence on the work function of the clean surface. This change of the work function δφ can be used to image the local distributions of the investigated reaction,.if one of the reacting partners is adsorbed at the surface in form of islands of sufficient size (Δ>0.2μm). These can than be visualized via a photoemission electron microscope (PEEM). Changes of φ as low as 2 meV give already a change in the total intensity of a PEEM picture. To achieve reasonable contrast for an image several 10 meV of δφ are needed. Dynamic processes as surface diffusion of CO or O on single crystal surfaces as well as reaction / diffusion fronts have been observed in real time and space.

Microwaves: Application in Electron Microscopy

1990 ◽  
Vol 48 (3) ◽  
pp. 140-141
Author(s):  
Anthony S-Y Leong ◽  
David W Gove
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Chemical Reactions ◽  
Electromagnetic Waves ◽  
Tissue Fixation ◽  
Primary Method ◽  
Dipolar Molecules ◽  
Wide Range ◽  
Time Required ◽  
Cryostat Sections

Microwaves (MW) are electromagnetic waves which are commonly generated at a frequency of 2.45 GHz. When dipolar molecules such as water, the polar side chains of proteins and other molecules with an uneven distribution of electrical charge are exposed to such non-ionizing radiation, they oscillate through 180° at a rate of 2,450 million cycles/s. This rapid kinetic movement results in accelerated chemical reactions and produces instantaneous heat. MWs have recently been applied to a wide range of procedures for light microscopy. MWs generated by domestic ovens have been used as a primary method of tissue fixation, it has been applied to the various stages of tissue processing as well as to a wide variety of staining procedures. This use of MWs has not only resulted in drastic reductions in the time required for tissue fixation, processing and staining, but have also produced better cytologic images in cryostat sections, and more importantly, have resulted in better preservation of cellular antigens.

Fine structure and properties of defects in naturally occurring silicates and oxides

1990 ◽  
Vol 48 (4) ◽  
pp. 460-461
Author(s):  
David R. Veblen
Keyword(s):  
Chemical Reactions ◽  
High Resolution Electron Microscopy ◽  
Extended Defects ◽  
Single Chain ◽  
Naturally Occurring ◽  
Resolution Electron ◽  
Fine Structures ◽  
Image Simulations ◽  
Similar Crystal Structure

Extended defects and interfaces control many processes in rock-forming minerals, from chemical reactions to rock deformation. In many cases, it is not the average structure of a defect or interface that is most important, but rather the structure of defect terminations or offsets in an interface. One of the major thrusts of high-resolution electron microscopy in the earth sciences has been to identify the role of defect fine structures in reactions and to determine the structures of such features. This paper will review studies using HREM and image simulations to determine the structures of defects in silicate and oxide minerals and present several examples of the role of defects in mineral chemical reactions. In some cases, the geological occurrence can be used to constrain the diffusional properties of defects.The simplest reactions in minerals involve exsolution (precipitation) of one mineral from another with a similar crystal structure, and pyroxenes (single-chain silicates) provide a good example. Although conventional TEM studies have led to a basic understanding of this sort of phase separation in pyroxenes via spinodal decomposition or nucleation and growth, HREM has provided a much more detailed appreciation of the processes involved.

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