Direct Evidence of Catalytic Role of Boron in Graphite‐to‐Diamond Solid‐Phase Conversion under High Pressure

2020 ◽  
Vol 14 (8) ◽  
pp. 2000247 ◽  
Author(s):  
Rustem Bagramov ◽  
Vladimir Filonenko ◽  
Igor Zibrov ◽  
Sergey Lyapin ◽  
Igor Vlasov
Keyword(s):  
High Pressure ◽  
Direct Evidence ◽  
Solid Phase ◽  
Phase Conversion ◽  
Catalytic Role

Effect of light on birnessite catalysis of the Maillard reaction and its implication in humification

2001 ◽  
Vol 81 (3) ◽  
pp. 277-283 ◽  
Author(s):  
A. Jokic ◽  
A I Frenkel ◽  
P M Huang
Keyword(s):  
Humic Substances ◽  
Maillard Reaction ◽  
Solid Phase ◽  
Natural Environments ◽  
Promoting Effect ◽  
Nitrogenous Compounds ◽  
Heterogeneous Catalytic ◽  
Catalytic Role ◽  
Effect Of Light

The Maillard reaction between carbohydrates and nitrogenous compounds originally investigated in 1912 has subsequently been proposed as a possible pathway for the formation of humic substances in natural environments. However, the role of mineral catalysis of the Maillard reaction is little understood and the promoting effect of light on such catalysis is not known. Birnessite (δ-MnO2), which is commonly present in soil environments, was investigated for its activity in promoting the Maillard reaction between glucose and glycine at a light intensity of 168 µE s–1 m–2 or in the dark. The presence of substantial quantities of Mn(II) was detected in both the supernatant and solid phase of the glucose-glycine-birnessite systems. The spectroscopic evidence indicates that birnessite, in the presence of light, is a very effective catalyst in abiotic browning of solutions of glucose and glycine. Furthermore, birnessite significantly promoted the reaction even in the absence of light. Therefore, the abiotic heterogeneous catalytic role of soil minerals such as birnessite in polycondensation of simple sugars and amino acids merits close attention in the formation of humic substances in natural environments. Key words: Maillard reaction, heterogeneous catalysis, light, birnessite, humic substance formation, XANES

Direct Evidence for the Role of Inhibition in Resolving Interference

2009 ◽  
Author(s):  
M. Karl Healey ◽  
Karen L. Campbell ◽  
Lynn Hasher ◽  
Lynn Ossher
Keyword(s):  
Direct Evidence

Introduction to geomicrobiology

2018 ◽  
Author(s):  
David L. Kirchman
Keyword(s):  
Fossil Fuels ◽  
Solid Phase ◽  
Direct Reduction ◽  
Iron Oxidation ◽  
Mineral Dissolution ◽  
Precipitation Process ◽  
Soluble Ions ◽  
Chemolithoautotrophic Bacteria ◽  
The Impact

Geomicrobiology, the marriage of geology and microbiology, is about the impact of microbes on Earth materials in terrestrial systems and sediments. Many geomicrobiological processes occur over long timescales. Even the slow growth and low activity of microbes, however, have big effects when added up over millennia. After reviewing the basics of bacteria–surface interactions, the chapter moves on to discussing biomineralization, which is the microbially mediated formation of solid minerals from soluble ions. The role of microbes can vary from merely providing passive surfaces for mineral formation, to active control of the entire precipitation process. The formation of carbonate-containing minerals by coccolithophorids and other marine organisms is especially important because of the role of these minerals in the carbon cycle. Iron minerals can be formed by chemolithoautotrophic bacteria, which gain a small amount of energy from iron oxidation. Similarly, manganese-rich minerals are formed during manganese oxidation, although how this reaction benefits microbes is unclear. These minerals and others give geologists and geomicrobiologists clues about early life on Earth. In addition to forming minerals, microbes help to dissolve them, a process called weathering. Microbes contribute to weathering and mineral dissolution through several mechanisms: production of protons (acidity) or hydroxides that dissolve minerals; production of ligands that chelate metals in minerals thereby breaking up the solid phase; and direct reduction of mineral-bound metals to more soluble forms. The chapter ends with some comments about the role of microbes in degrading oil and other fossil fuels.

scholarly journals CHOP-Dependent Stress-Inducible Expression of a Novel Form of Carbonic Anhydrase VI

1999 ◽  
Vol 19 (1) ◽  
pp. 495-504 ◽  
Author(s):  
John Sok ◽  
Xiao-Zhong Wang ◽  
Nikoleta Batchvarova ◽  
Masahiko Kuroda ◽  
Heather Harding ◽  
...  
Keyword(s):  
Carbonic Anhydrase ◽  
Target Gene ◽  
Target Genes ◽  
Direct Evidence ◽  
Nuclear Protein ◽  
Intracellular Form ◽  
Carbonic Anhydrase Vi ◽  
Responsive Element

ABSTRACT CHOP (also called GADD153) is a stress-inducible nuclear protein that dimerizes with members of the C/EBP family of transcription factors and was initially identified as an inhibitor of C/EBP binding to classic C/EBP target genes. Subsequent experiments suggested a role for CHOP-C/EBP heterodimers in positively regulating gene expression; however, direct evidence that this is the case has so far not been uncovered. Here we describe the identification of a positively regulated direct CHOP-C/EBP target gene, that encoding murine carbonic anhydrase VI (CA-VI). The stress-inducible form of the gene is expressed from an internal promoter and encodes a novel intracellular form of what is normally a secreted protein. Stress-induced expression of CA-VI is both CHOP and C/EBPβ dependent in that it does not occur in cells deficient in either gene. A CHOP-responsive element was mapped to the inducibleCA-VI promoter, and in vitro footprinting revealed binding of CHOP-C/EBP heterodimers to that site. Rescue of CA-VIexpression in c/ebpβ−/− cells by exogenous C/EBPβ and a shorter, normally inhibitory isoform of the protein known as LIP suggests that the role of the C/EBP partner is limited to targeting the CHOP-containing heterodimer to the response element and points to a preeminent role for CHOP in CA-VI induction during stress.

scholarly journals The Role of Electric Pressure/Stress Suppressing Pinhole Defect on Coalescence Dynamics of Electrified Droplet

Coatings ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 503
Author(s):  
Jaehyun Lee ◽  
Ehsan Esmaili ◽  
Giho Kang ◽  
Baekhoon Seong ◽  
Hosung Kang ◽  
...  
Keyword(s):  
Solid Phase ◽  
Critical Factor ◽  
Air Pressure ◽  
Conical Shape ◽  
Electric Stress ◽  
Bottom Interface ◽  
Electric Pressure ◽  
Pressure Stress ◽  
Air Film

The dimple occurs by sudden pressure inversion at the droplet’s bottom interface when a droplet collides with the same liquid-phase or different solid-phase. The air film entrapped inside the dimple is a critical factor affecting the sequential dynamics after coalescence and causing defects like the pinhole. Meanwhile, in the coalescence dynamics of an electrified droplet, the droplet’s bottom interfaces change to a conical shape, and droplet contact the substrate directly without dimple formation. In this work, the mechanism for the dimple’s suppression (interfacial change to conical shape) was studied investigating the effect of electric pressure. The electric stress acting on a droplet interface shows the nonlinear electric pressure adding to the uniform droplet pressure. This electric stress locally deforms the droplet’s bottom interface to a conical shape and consequentially enables it to overcome the air pressure beneath the droplet. The electric pressure, calculated from numerical tracking for interface and electrostatic simulation, was at least 108 times bigger than the air pressure at the center of the coalescence. This work helps toward understanding the effect of electric stress on droplet coalescence and in the optimization of conditions in solution-based techniques like printing and coating.

High Pressure Studies of Quantum Well Emission and Deep Emission in GaInP(ordered)-GaAs Heterostructures

1997 ◽  
Vol 499 ◽  
Author(s):  
S. H. Kwok ◽  
P. Y. Yu ◽  
K. Uchida ◽  
T. Arai
Keyword(s):  
High Pressure ◽  
Quantum Well ◽  
Emission Band ◽  
Excitation Power ◽  
High Excitation ◽  
High Pressure Studies ◽  
Band Alignments ◽  
High Pressure Study

ABSTRACTWe report on a high pressure study of emission from a series of GaInP(ordered)/GaAs heterostructures. A so-called “deep emission” band at 1.46 eV is observed in all our samples. At high excitation power, quantum well emission emerges in only one structure where thin GaP layers are inserted on both sides of the GaAs well. From the pressure dependent emission in this sample we have determined its band alignments. The role of the GaP layers in suppressing the deep emission is elucidated.

scholarly journals Stoichiometric Analysis of Shifting in Subcellular Compartmentalization of HSP70 within Ischemic Penumbra

Molecules ◽  
2021 ◽  
Vol 26 (12) ◽  
pp. 3578
Author(s):  
Federica Mastroiacovo ◽  
Francesca Biagioni ◽  
Paola Lenzi ◽  
Larisa Ryskalin ◽  
Stefano Puglisi-Allegra ◽  
...  
Keyword(s):  
Direct Evidence ◽  
Neuronal Survival ◽  
Hsp 70 ◽  
Preclinical Models ◽  
Brain Areas ◽  
Cell Compartments ◽  
Control Brain ◽  
Disease Modifier ◽  
Subcellular Compartmentalization

The heat shock protein (HSP) 70 is considered the main hallmark in preclinical studies to stain the peri-infarct region defined area penumbra in preclinical models of brain ischemia. This protein is also considered as a potential disease modifier, which may improve the outcome of ischemic damage. In fact, the molecule HSP70 acts as a chaperonine being able to impact at several level the homeostasis of neurons. Despite being used routinely to stain area penumbra in light microscopy, the subcellular placement of this protein within area penumbra neurons, to our knowledge, remains undefined. This is key mostly when considering studies aimed at deciphering the functional role of this protein as a determinant of neuronal survival. The general subcellular placement of HSP70 was grossly reported in studies using confocal microscopy, although no direct visualization of this molecule at electron microscopy was carried out. The present study aims to provide a direct evidence of HSP70 within various subcellular compartments. In detail, by using ultrastructural morphometry to quantify HSP70 stoichiometrically detected by immuno-gold within specific organelles we could compare the compartmentalization of the molecule within area penumbra compared with control brain areas. The study indicates that two cell compartments in control conditions own a high density of HSP70, cytosolic vacuoles and mitochondria. In these organelles, HSP70 is present in amount exceeding several-fold the presence in the cytosol. Remarkably, within area penumbra a loss of such a specific polarization is documented. This leads to the depletion of HSP70 from mitochondria and mostly cell vacuoles. Such an effect is expected to lead to significant variations in the ability of HSP70 to exert its physiological roles. The present findings, beyond defining the neuronal compartmentalization of HSP70 within area penumbra may lead to a better comprehension of its beneficial/detrimental role in promoting neuronal survival.

Role of dislocations in the bcc-hcp transition under high pressure: A first-principles approach in beryllium

2020 ◽  
Vol 4 (6) ◽  
Author(s):  
Vanessa Riffet ◽  
Bernard Amadon ◽  
Nicolas Bruzy ◽  
Christophe Denoual
Keyword(s):  
High Pressure ◽  
First Principles
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