scholarly journals Decoupling the Arrhenius equation via mechanochemistry

2017 ◽  
Vol 8 (8) ◽  
pp. 5447-5453 ◽  
Author(s):  
Joel M. Andersen ◽  
James Mack
Keyword(s):  
Activation Energy ◽  
Oscillation Frequency ◽  
Arrhenius Equation ◽  
Region I ◽  
Forbidden Region ◽  
Region Ii ◽  
Mechanochemical Reactions

We identified three different energetic regions that we believe are defining characteristics of most, if not all mechanochemical reactions. For a given ball mill's region, activation energy determines whether a reaction is energetically easy (Region I), challenging (Region II), or forbidden (Region III). In Region II, yield depends exponentially on oscillation frequency. Modifications granted control of the locations of Regions I, II, and III.

A study of the mechanism of decay of alkyl macroradicals in isotactic polypropylene

1985 ◽  
Vol 50 (6) ◽  
pp. 1391-1401 ◽  
Author(s):  
Josef Bartoš ◽  
Jozef Tiňo
Keyword(s):  
Activation Energy ◽  
Isotactic Polypropylene ◽  
Kinetic Data ◽  
Molecular Mechanisms ◽  
Point Of View ◽  
Diffusion Limited ◽  
Region I ◽  
The Matrix ◽  
Region Ii ◽  
Two Temperature

The kinetic data of decay of alkyl macroradicals in two temperature regions in isotactic polypropylene exposed to gamma radiation at 77 K were interpreted in terms of the model of diffusion-limited reactions at the activation energy level. The potential molecular mechanisms of transfer of the radical centres were tested from the point of view of their physical and/or chemical migration. Two mechanisms are suggested for the mutual approach of the centres in macroradical decay regions I and II in the amorphous zones of the matrix. Both of them involve the contribution of segmental conformational motions, the mobility of the terminal segments being of importance in region I whereas in region II the mutual nearing of the reactants proceeds in a relay way via intermolecular H-abstraction in conjunction with crank and crankshaft motions of the end and inner segments of the chain.

Cr-Substituted Mesoporous Aluminophosphate Molecular Sieve: Synthesis, Characterization, Crystallization Kinetics and Catalytic Activity

2013 ◽  
Vol 316-317 ◽  
pp. 1018-1023
Author(s):  
Xin Zhu Li ◽  
Ji Shi Zhang
Keyword(s):  
Activation Energy ◽  
Catalytic Activity ◽  
Crystal Growth ◽  
Crystallization Kinetics ◽  
Molecular Sieve ◽  
Arrhenius Equation ◽  
Degree Of Crystallinity ◽  
Tert Butylhydroperoxide ◽  
Growth Activation ◽  
Cr Map

Cr-substituted mesoporous aluminophosphate molecular sieve (Cr-MAP) was synthesized and characterized. Crystallization kinetics curves measured as an index to the relative degree of crystallinity, according to the Arrhenius equation to calculate the apparent nucleation activation energy and crystal growth activation energy of Cr-MAP, which was 63.7 and 14.7 kJ• mol-1, respectively. Cr-MAP had highly catalytic activity for fabricating acetophenone by selectively oxizing ethylbenzene. Using tert-butylhydroperoxide as oxidant and chlorobenzene as solvent at 100 °C for 8 h, acetophenone selectivity, acetophenone yield and ethylbenzene conversion reaches 85.4, 62.2 and 72.8 %, respectively.

Diffusion Coefficients of Interest for the Simulation of Heat Treatment in Rare-Earth Transition Metal Magnets

2012 ◽  
Vol 727-728 ◽  
pp. 163-168 ◽  
Author(s):  
Marcos Flavio de Campos
Keyword(s):  
Experimental Data ◽  
Heat Treatment ◽  
Activation Energy ◽  
Rare Earth ◽  
Transition Metal ◽  
Impurity Atom ◽  
Diffusion Coefficients ◽  
Arrhenius Equation ◽  
Atom Diffusion ◽  
Essential Input

In the case of the modeling of sintering and heat treatments, the diffusion coefficients are an essential input. However, experimental data in the literature about diffusion coefficients for rare-earth transition metal intermetallics is scarce. In this study, the available data concerning diffusion coefficients relevant for rare-earth transition metal magnets are reviewed and commented. Some empirical rules are discussed, for example the activation energy is affected by the size of the diffusing impurity atom. Diffusion coefficients for Dy, Nd and Fe into Nd2Fe14B are given according an Arrhenius equation D=D0exp (-Q/RT). For Dy diffusion into Nd2Fe14B, Q 315 kJ/mol and D08 . 10-4m2/s.

Plasmodium falciparum EBA-175 kDa protein peptides which bind to human red blood cells

Parasitology ◽  
2000 ◽  
Vol 120 (3) ◽  
pp. 225-235 ◽  
Author(s):  
L. E. RODRIGUEZ ◽  
M. URQUIZA ◽  
M. OCAMPO ◽  
J. SUAREZ ◽  
H. CURTIDOR ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Binding Activity ◽  
Ligand Interaction ◽  
Merozoite Invasion ◽  
Human Red Blood Cells ◽  
Affinity Constants ◽  
Region I ◽  
Binding Peptides ◽  
V Region ◽  
Region Ii

Solid experimental evidence indicates that EBA-175 is used as a ligand by the Plasmodium falciparum merozoite to bind to human RBC, via different binding processing fragments. Using synthetic peptides and specific receptor-ligand interaction methodology, we have identified 6 high-activity binding sequences from the EBA-175 CAMP strain; peptide 1758 (KSYGTPDNIDKNMSLIHKHN), located in the so-called region I for which no binding activity has been reported before, peptides 1779 (NIDRIYDKNLLMIKEHILAI) and 1783 (HRNKKNDKLYRDEWWKVIKK), located in region II, in a sub-region known as 5′ Cys F2, previously reported as being a binding region, and peptides 1814 (DRNSNTLHLKDYRNEENERH), 1815 (YTNQNINISQERDLQKHGFH) and 1818 (NNNFNNIPSRYNLYDKKLDL), in region III–V where antibodies inhibit merozoite invasion of erythrocytes. The affinity constants were between 60 and 180 nM and the critical amino acids involved in the binding were identified. The binding of these peptides to enzyme-treated RBC was analysed; binding of peptide 1814, located in the III–V region, was found to be sialic acid dependent. Some of these high binding peptides were able to inhibit in vitro merozoite invasion and to block the binding of recombinant RII-EBA to RBC. Several of these peptides are located in regions recognized by protective immune clusters of merozoites (ICMs) eluted antibodies.

Viscosity Of Molten Rare Earth Metal Trichlorides I. Cecl3, Ndcl3, Smcl3, Dycl3 And Ercl3

2003 ◽  
Vol 58 (7-8) ◽  
pp. 457-463 ◽  
Author(s):  
A. Potapov ◽  
V. Khokhlov ◽  
Y. Satoa
Keyword(s):  
Activation Energy ◽  
Rare Earth ◽  
Viscous Flow ◽  
Rare Earth Metal ◽  
Dynamic Viscosity ◽  
Kinematic Viscosity ◽  
Arrhenius Equation ◽  
Earth Metal ◽  
Capillary Viscometer ◽  
Density Data

The kinematic viscosity of molten CeCl3, NdCl3, SmCl3, DyCl3 and ErCl3 has been measured by using a capillary viscometer. The dynamic viscosity was computed by using density data taken from the literature. The viscosity increases with going from CeCl3 to ErCl3. The activation energy of the viscous flow, calculated by the Arrhenius equation, rises in the same order.

Giant dielectric constant and high-temperature dielectric relaxation properties in La-doped SrTiO3 ceramics

2020 ◽  
pp. 2150046
Author(s):  
Tianyang Liu ◽  
Xiaofei Wang ◽  
Congcong Li ◽  
Bowen Shen ◽  
Mingyan Yao ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
High Temperature ◽  
Temperature Region ◽  
Relaxation Processes ◽  
Doping Amount ◽  
Solid State Method ◽  
Giant Dielectric ◽  
Region I ◽  
Giant Dielectric Constant ◽  
Region Ii

[Formula: see text] (SLTO) ceramics ([Formula: see text] = 0.05, 0.10, 0.15) were prepared with giant dielectric constant by the traditional solid-state method at 1350[Formula: see text]C. The temperature dependence of the dielectric constant was obtained at the temperature ranging from 29[Formula: see text]C to 500[Formula: see text]C and the frequency ranging from 2 kHz to 2 MHz. Two sets of relaxation peaks appear in the low temperature (region I) and the high temperature (region II), respectively. For region I, we conclude that the relaxation behavior is related to the oxygen vacancy migration. For region II, the two relaxation processes are caused by grain boundary for high frequency and Sr or Ti defects at grain interior for low frequency. With the doping amount reaching 0.15, the relaxation peaks disappear and become a common phase transition because of the aggravation of lattice distortion. These possible physical mechanisms of two sets of relaxation peaks are briefly discussed.

Design and Implementation of a Site for a One-Ångstrom TEM

1997 ◽  
Vol 3 (S2) ◽  
pp. 1177-1178
Author(s):  
John H. Turner ◽  
M.A. O'Keefe ◽  
M.A. O'Keefe
Keyword(s):  
Field Emission ◽  
Acoustic Noise ◽  
Mechanical Vibration ◽  
Region I ◽  
Critical Requirement ◽  
The One ◽  
A Site ◽  
Region Ii ◽  
Critical Direction ◽  
Suitable Environment

The National Center for Electron Microscopy has recently acquired a field-emission TEM to form thebasis of a project to achieve a resolution of one Ångstrom. To reach this resolution, both instrumental and environmental factors need to be considered. We have designed and constructed a new building to provide a suitable environment for this instrument, with emphasis on providing isolation from external influences detrimental to the achievement of ultra-high resolution. Such influences include mechanical vibration, temperature fluctuations, acoustic noise, and stray electromagnetic fields.The microscope chosen for the one-Ångstrom project is a Philips CM300 Ultra-Twin equipped with a field-emission gun. Pre-installation specifications provided by Philips for this 1.7Å-resolution TEM specify maximum-allowable values for vibration levels in three mutually-perpendicular directions. In the most critical direction (console left to right), vibration is required to remain below 0.8)μm/sec in the frequency range from 1Hz to 5Hz, although allowed to rise to 6μm/sec above 10Hz (Region I in fig. 1). Even when resolution is not a critical requirement, vibration must be minimized at 2.5Hz (Region II in fig.1).

scholarly journals Regional Characteristics of Long-Term Variability of Summer Precipitation in the Poyang Lake Basin and Possible Links with Large-Scale Circulations

Atmosphere ◽  
2020 ◽  
Vol 11 (10) ◽  
pp. 1033
Author(s):  
Hua Zhu ◽  
Handan He ◽  
Hongxiang Fan ◽  
Ligang Xu ◽  
Jiahu Jiang ◽  
...  
Keyword(s):  
Large Scale ◽  
Poyang Lake ◽  
Summer Precipitation ◽  
Climate Indices ◽  
Lake Basin ◽  
Regional Characteristics ◽  
Poyang Lake Basin ◽  
Region I ◽  
Region Ii

Understanding the spatiotemporal regime of summer precipitation at local scales plays a key role in regional prevention and mitigation of floods disasters and water resources management. Previous works focused on spatiotemporal characteristics of a region as a whole but left the influence of associated physical factors on sub-regions unexplored. Based on the precipitation data of 77 meteorological stations in the Poyang Lake basin (PYLB) from 1959 to 2013, we have investigated regional characteristics of summer precipitation in the PYLB by integrating the rotated empirical orthogonal function (REOF) analysis with hierarchical clustering algorithm (HCA). Then the long-term variability of summer precipitation in sub-regions of the PYLB and possible links with large-scale circulations was investigated using multiple trend analyses, wavelet analysis and correlation analysis. The results indicate that summer precipitation variations in the PYLB were of very striking regional characteristics. The PYLB was divided into three independent sub-regions based on two leading REOF modes and silhouette coefficient (SC). These sub-regions were located in northern PYLB (sub-region I), central PYLB (sub-region II), and southern PYLB (sub-region III). The summer precipitation in different sub-regions exhibited distinct variation trends and periodicities, which was associated with different factors. All sub-regions show no trends over the whole period 1959–2013, rather they show trends in different periods. Trends per decade in annual summer precipitation in sub-region I and sub-region II were consistent for all periods with different start and end years. The oscillations periods with 2–3 years were found in summer precipitation of all the three sub-regions. Summer precipitation in sub-region I was significantly positively correlated with the previous Indian Ocean Dipole (IOD) event, but negatively correlated with East Asian Summer Monsoon (EASM). While summer precipitation in sub-region II and sub-region III showed weak teleconnections with climate indices. All of the results of this study are conducive to further understand both the regional climate variations in the PYLB and response to circulation patterns variations.

scholarly journals DNase I footprinting shows three protected regions in the promoter of the rRNA genes of Xenopus laevis.

1985 ◽  
Vol 5 (2) ◽  
pp. 313-319 ◽  
Author(s):  
M Dunaway ◽  
R H Reeder
Keyword(s):  
Xenopus Laevis ◽  
Base Pair ◽  
Transcription Initiation ◽  
Protein S ◽  
Dnase I ◽  
Rrna Genes ◽  
Xenopus Laevis Oocytes ◽  
Dnase I Footprinting ◽  
Region I ◽  
Region Ii

Extracts prepared from Xenopus laevis oocytes contain a protein(s) which specifically protects three discrete regions of the RNA polymerase I promoter from digestion by DNase I. Protected region I, from nucleotide +15 to nucleotide -10, spans the site of transcription initiation. Protected region II extends from nucleotide -70 to nucleotide -100 relative to initiation, falling within a 42-base-pair sequence which is homologous to the 60/81-base-pair repeated elements which occur outside of the promoter in the spacer. Protected region III is upstream of region II, from nucleotide -120 to nucleotide -140. All three regions correlate with sequences known from deletion studies to be important for promoter function. Deletion mutants which retain either region I or regions II and III together footprint normally. Deletion of region III, however, reduces but does not eliminate footprinting on region II, suggesting either that one protein binds to both regions or that the proteins which bind to these sites interact with each other.

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