Temperature Dependence of 207 Pb MAS Spectra of Solid Lead Nitrate. An Accurate, Sensitive Thermometer for Variable-Temperature MAS

1995 ◽  
Vol 116 (2) ◽  
pp. 215-220 ◽  
Author(s):  
ANTHONY BIELECKI ◽  
DOUGLAS P. BURUM
Keyword(s):  
Temperature Dependence ◽  
Variable Temperature ◽  
Lead Nitrate

Variable Temperature Nuclear Magnetic Resonance Studies of Some Five-Membered Ring Chelate Complexes

1975 ◽  
Vol 53 (7) ◽  
pp. 1038-1045 ◽  
Author(s):  
William R. Cullen ◽  
Laurance D. Hall ◽  
John E. H. Ward
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Temperature Dependence ◽  
Significant Variation ◽  
Conformational Equilibrium ◽  
Variable Temperature ◽  
Membered Ring ◽  
Coupling Constants ◽  
Chelate Complexes ◽  
Magnetic Resonance Studies

The temperature dependence of the n.m.r. spectra of nine ditertiary arsine chelate complexes of formula (CH3)2AsC(3)(3′)C(4) (4′)As(CH3)2M(CO)3X has been studied (M = Mo, Cr; X = CO; M = Mn; X = halogen; (3), (3′), (4), (4′) = H, F, Si(CH3)3, CN; but not all combinations ). Significant variation in coupling constants, indicating a shift in the conformer populations, was found only for the CHFCF2 bridged Mn(CO)3Cl complex, the CH2CF2 bridged Mn(CO)3Cl complex, and the CHFCHF bridged Mo(CO)4 complex. In the last case the 3JHH coupling constants were used to estimate ΔH ∼ 1 kcal/mol and ΔS ∼ 3 e.u for the conformational equilibrium.

TEMPERATURE-DEPENDENT MICROWAVE PERFORMANCE OF SB-HETEROSTRUCTURE BACKWARD DIODES FOR MILLIMETER-WAVE DETECTION

2007 ◽  
Vol 17 (01) ◽  
pp. 105-110
Author(s):  
N. SU ◽  
Z. ZHANG ◽  
P. FAY ◽  
H. P. MOYER ◽  
R. D. RAJAVEL ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Millimeter Wave ◽  
Variable Temperature ◽  
Device Performance ◽  
Material System ◽  
Temperature Dependent ◽  
Junction Resistance ◽  
Measured Voltage ◽  
Wave Detection ◽  
Self Consistent

The temperature dependence of heterostructure backward diodes based on the InAs/AlGaSb/GaSb material system for millimeter-wave detection has been investigated experimentally. Measured dc curvatures of 36 V-1 at 298 K and 74 V-1 at 4.2 K have been obtained. Variable-temperature on-wafer s-parameters to 110 GHz reveal that the junction capacitance of a typical 2×2 μ m 2 area device decreases from 18 fF at 298 K to 11 fF at 77 K, while the junction resistance decreases from 13.9 kΩ to 10.2 kΩ. Directly measured voltage sensitivities at 50 GHz of 3650 V/W and 7190 V/W were obtained at 298 K and 4.2 K, respectively, consistent with the expected value from measured dc curvature. A 1 dB compression point of 18.5 μW and 7.2 μW at 298 K and 77 K, respectively, was measured. A physical model based on self-consistent Poisson-Schrödinger equation solutions was obtained to explain the experimental observations, and suggests the ways to further improve the device performance.

scholarly journals The temperature dependence of C–H⋯F–C interactions in benzene : hexafluorobenzene

CrystEngComm ◽  
2018 ◽  
Vol 20 (42) ◽  
pp. 6677-6682 ◽  
Author(s):  
Jeremy K. Cockcroft ◽  
Alexander Rosu-Finsen ◽  
Andrew N. Fitch ◽  
Jeffrey H. Williams
Keyword(s):  
Solid State ◽  
Neutron Diffraction ◽  
Temperature Dependence ◽  
Variable Temperature ◽  
Intermolecular Forces ◽  
X Ray

Variable temperature X-ray and neutron diffraction and simple ideas of intermolecular forces permit a rationalization of the 4 phases observed for the solid-state adduct of benzene and hexafluorobenzene.

scholarly journals Hydrogen tunnelling in enzyme-catalysed H-transfer reactions: flavoprotein and quinoprotein systems

2006 ◽  
Vol 361 (1472) ◽  
pp. 1375-1386 ◽  
Author(s):  
Michael J Sutcliffe ◽  
Laura Masgrau ◽  
Anna Roujeinikova ◽  
Linus O Johannissen ◽  
Parvinder Hothi ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Variable Temperature ◽  
Isotope Effects ◽  
Experimental Studies ◽  
Zero Point ◽  
Reaction Rates ◽  
State Theory ◽  
Strong Temperature Dependence ◽  
Methylamine Dehydrogenase ◽  
Point Energy

It is now widely accepted that enzyme-catalysed C–H bond breakage occurs by quantum mechanical tunnelling. This paradigm shift in the conceptual framework for these reactions away from semi-classical transition state theory (TST, i.e. including zero-point energy, but with no tunnelling correction) has been driven over the recent years by experimental studies of the temperature dependence of kinetic isotope effects (KIEs) for these reactions in a range of enzymes, including the tryptophan tryptophylquinone-dependent enzymes such as methylamine dehydrogenase and aromatic amine dehydrogenase, and the flavoenzymes such as morphinone reductase and pentaerythritol tetranitrate reductase, which produced observations that are also inconsistent with the simple Bell-correction model of tunnelling. However, these data—especially, the strong temperature dependence of reaction rates and the variable temperature dependence of KIEs—are consistent with other tunnelling models (termed full tunnelling models), in which protein and/or substrate fluctuations generate a configuration compatible with tunnelling. These models accommodate substrate/protein (environment) fluctuations required to attain a configuration with degenerate nuclear quantum states and, when necessary, motion required to increase the probability of tunnelling in these states. Furthermore, tunnelling mechanisms in enzymes are supported by atomistic computational studies performed within the framework of modern TST, which incorporates quantum nuclear effects.

Direct measurements of N2 broadened linewidths in the CO fundamental at low temperatures

1983 ◽  
Vol 61 (2) ◽  
pp. 192-197 ◽  
Author(s):  
J.-P. Bouanich ◽  
R. Farrenq ◽  
C. Brodbeck
Keyword(s):  
High Resolution ◽  
Temperature Dependence ◽  
Low Temperatures ◽  
Variable Temperature ◽  
Absorption Cell ◽  
Fundamental Band ◽  
Direct Measurements ◽  
High Resolution Spectrometer ◽  
Vibration Rotation ◽  
Resolution Spectrometer

The halfwidths of CO vibration–rotation lines, pressure-broadened by N2 have been measured in the fundamental band at −83, −148, and −180 °C, using a variable temperature absorption cell and a high resolution spectrometer. The temperature dependence of linewidths has been calculated from the Anderson–Tsao–Curnutte theory and compared to the experimental determinations.

A Systematic Evaluation of Time-Temperature Indicators for Use as Consumer Tags

1991 ◽  
Vol 54 (11) ◽  
pp. 885-889 ◽  
Author(s):  
MAUREEN SHERLOCK ◽  
BIN FU ◽  
PETROS S. TAOUKIS ◽  
THEODORE P. LABUZA
Keyword(s):  
Activation Energy ◽  
Temperature Dependence ◽  
Shelf Life ◽  
Visual Recognition ◽  
Arrhenius Equation ◽  
Variable Temperature ◽  
Systematic Evaluation ◽  
End Point ◽  
Instrumental Measurement ◽  
Nonisothermal Conditions

The applicability of single end point, consumer readable Time-Temperature Indicators (TTIs) as monitors of the end of shelf life of refrigerated food products was examined. Two types of consumer TTIs, an enzymatic and a polymer based, were tested under isothermal and nonisothermal conditions. Their temperature dependence followed the Arrhenius equation (activation energy 11 to 24 kcal/mol), and except for one tag model, the response obtained under variable temperature conditions agreed well with that predicted from the Arrhenius equation. Evaluation showed satisfactory visual recognition of the end point as compared to an instrumental measurement. Consumer TTIs can be reliably used as end of shelf-life indicators for foods with a similar activation energy for deterioration.

Investigation of the Payne Effect and its Temperature Dependence on Silica-Filled Polydimethylsiloxane Networks. Part I: Experimental Results

2005 ◽  
Vol 78 (2) ◽  
pp. 211-231 ◽  
Author(s):  
F. Clément ◽  
L. Bokobza ◽  
L. Monnerie
Keyword(s):  
Elastic Modulus ◽  
Surface Treatment ◽  
Temperature Dependence ◽  
Shear Strain ◽  
Variable Temperature ◽  
Silica Particles ◽  
Experimental Results ◽  
Payne Effect ◽  
Low Shear

Abstract The Payne effect is studied in silica-filled polydimethylsiloxane networks, containing various silica loadings and at variable temperature. The effect of a permanent surface treatment of the silica particles, as well as the influence of the incorporation in the system of a processing aid agent, have been investigated. The amplitude of the Payne effect is reduced by introducing a permanent treatment of the silica or a processing aid. Contrary to the unfilled network which shows the typical entropic dependence of the elastic modulus, the low shear strain elastic modulus of filled networks decreases when temperature increases. When the shear strain increases, this temperature dependence becomes less and less pronounced, and reaches a plateau value at deformations above 100%.

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