The reaction of the hydroxyl radical (HO) with stable carbon isotopes methane has been studied as a function temperature from 273 to 353 K. measured ratio rate coefficients for 12 CH 4 relative 13 ( k / ) was 1.0054 (±0.0009 at 95% confidence interval), independent within precision measurement, over range studied. present value is much improved that previous studies, and this result provides important constraints on current understanding cycling through atmosphere use isotope measurements.

Absolute rate constants and their temperature dependencies for the deactivation of O(1D) by five important atmospheric gases are reported. atoms produced photolysis ozone at 266 nm directly observed in time resolved decay →O(3P) radiation 630 nm. Gases which only quench (O2, N2, CO2) to have a small negative dependence while O3 H2O, also reactive channel, display no dependence. Arrhenius expressions reactions measured (A units 10−10 cm3/molecule⋅ s, E cal/mole) O2(T=104–354 K) 0.29...

Absolute rate constants for the deactivation of O(1D) atoms by some atmospheric gases have been determined observing time resolved emission at 630 nm. were produced dissociation ozone via repetitive laser pulses 266 relaxation (×10−10 cm3 molecule−1⋅s−1) N2(0.30±0.01), O2(0.41±0.05), CO2(1.2±0.09), O3(2.4±0.1), H2(1.3±0.05), D2(1.3±0.05), CH4(1.3±0.3), HCl(1.4±0.3), NH3 (3.4±0.3), H2O(2.1±1.0), N2O(1.4±0.1), and Ne (<0.0013) are reported 298 K. The results obtained compared with...

To optimize the performance of total hip replacement, scientists and clinicians are seeking new materials noncemented, press-fit designs that cam improve load transfer to bone reduce incidence loosening thigh pain. Currently us

The micromechanics of ultra high molecular weight polyethylene (UHMWPE) wear in total hip replacement are very complex. Polyethylene from the metal head and debris formation two common types wear. There additional wear-related processes occurring at metal-bearing surfaces that not well-known, however. This study outlines these processes, including (1) surface wettability changes, (2) oxidative surfaces, (3) microabrasion oxide film damage, (4) abrasion three-body polymethylmethacrylate bone...

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTemperature-dependent formaldehyde cross sections in the near-ultraviolet spectral regionChris A. Cantrell, James Davidson, Anthony H. McDaniel, Richard E. Shetter, and Jack G. CalvertCite this: J. Phys. Chem. 1990, 94, 10, 3902–3908Publication Date (Print):May 1, 1990Publication History Published online1 May 2002Published inissue 1 1990https://pubs.acs.org/doi/10.1021/j100373a008https://doi.org/10.1021/j100373a008research-articleACS...

The reactions of N2O5 with CO3−, NO2−, and the halide ions, F−, Cl−, Br−, I−, have been found to be very fast (k∼10−9 cm3 s−1) at 300 K produce NO3− ion. It is inferred from thermochemistry that neutral products must XNO2. positive ions O2+ NO+ react NO2+, while H3O+ reacts form NO2+ H2NO3+. was observed not readily N2O5.

Abstract The equilibrium constant for the reaction equation image has been determined between 331 and 480°K using a variable‐temperature flowing afterglow. These data give Δ H °(1) = ‐1.03 ± 0.21 kcal/mol S —4.6 1.0 cal/mol°K. When combined with known thermochemical values HBr, Br − , HNO 3 this yields (NO ) ‐74.81 0.54 59.4 cal/mol·°K. In addition n ‐1, gas‐phase reactions were 2 3. implications of these measurements to negative ion chemistry are discussed.

Abstract An electron spin resonance (ESR) technique is employed to determine the free radical distribution in articulating surfaces of retrieved acetabular cups and knee‐joint plateaus (retrieved after more than 6 years implantation). Similar measurements made on samples prepared from cyclically stressed unstressed cups, following oxidations nitric acid intralipid solutions provided sufficient data gain knowledge about combined chemical mechanical effects PE radicals during implantation. In...

Absolute rate constants are reported for the deactivation of O(1D) by five trace atmospheric constituents temperature range 200–350 K. atoms produced photolyzing ozone with a frequency quadrupled pulse from Nd-YAG laser monitored directly means →O(3P) emission at 630 nm. All gases studied here thought to deactivate primarily through reactive channels. Their exhibit no detectable dependence. The (in units 10−10 cm3/molecule⋅s) N2O: 1.1,±0.2, H2: 0.99±0.3, HCl: 1.4±0.4, NH3: 2.5±0.5, CH4:...

A redetermination of the temperature dependence absorption cross section (σ) NO 2 in visible‐ultraviolet region (264–649 nm) has been made order to provide a more reliable data base for calculation photolysis rates atmosphere. Experiments over wide range temperatures (−40.6° 124°C) and concentrations (3.4×10 13 –7.3×10 14 molecules cm −3 ) were at relatively low high spectral resolutions, employing diode array Fourier transform spectrometers, respectively. There are three aspects which...

The reaction O−3+CO2?CO−3+O2 has been examined in the forward and reverse directions a variable-temperature flowing afterglow from 200 to 600 K flow-drift tube at mean relative kinetic energies 0.04 1 eV. direction is clearly established as exothermic direction. Furthermore, collisional dissociation of CO−3 O−3 ions high E/N form O− shows that more stable ion. All this implies D (CO2+O−) ≳D (O2+O−). Kinetic-equilibrium studies higher temperatures show rate constant less than 6×10−15 cm3 s−1...

The American Psychiatric Association (APA) issued a 2023 report on the future of psychiatry, focusing how organization should position itself in relation to coming developments over next 10 years. Here, we follow up with discussion psychiatrist's role needs evolve adapt changes ahead.

A long path cell has been designed and constructed for absorption measurements at temperatures ranging from 215 to 470 K pressures vacuum 10 atm. It enables us measure temperature pressure dependence of the spectra reaction rates gases atmospheric interest.

The carbon kinetic isotope effect in the CH 4 + HO reaction can enrich atmospheric methane 13 C relative to its sources. In only previous measurement of this reaction, a value k 12 / 1.003 was reported. present experimental determination we have found significantly larger 1.010±0.007 (95% confidence interval). This report discusses details and possible implications use result. Tropospheric is known C/ ratio −47‰ (parts per thousand) Peedee belemnite, most sources for which measurements...

The possibility of significant losses chlorofluoromethanes and their photochemical products in the troposphere or stratosphere has been examined. A number laboratory measurements have carried out involving possible ambient positive negative ions CFCL3, CF2Cl2 HCl. No reactions between expected to concentrations these species observed. It appears that which might important are fact endothermic. This is a result normal atmospheric chemistry leading very stable on short time scale. We conclude...

Fifty-seven patients had sixty-three total hip replacements, performed using a femoral stem with soft, low-modulus porous coating of Proplast and conventional acrylic-cemented acetabular component. Forty-seven the hips were followed for an average thirty-seven months. Seventeen (36 per cent) forty-seven judged to be clinical failures, five failures revised by inserting new component fixing it acrylic cement. The prostheses thought have failed because they inadequate support, due deficiencies...

To improve fuel economy, the automotive manufacturers have been gradually incorporating lighter gage, higher strength sheet steels. For same fatigue loads, operating stresses of these spot-welded lighter-gage sheets will be greater causing a concomitant reduction in life. This paper describes results program using fracture-mechanics concepts to determine life connections various stiffness. A model is developed which predicts life, and shows that increases with increasing joint Two types...

Abstract This work is concerned with the design of hip prostheses using advanced fiber reinforced composite materials. The major focus study to evaluate how stiffness and strength can be affected by variations in ply orientation stacking sequence for a selected manufacturing method. investigation involved both analytical experimental work. An model was developed which consists stress analysis failure analysis. A finite element program during course analyzing stresses, strains, deformations...

The rate constants for the deactivation of O(1D) by Xe, Kr, and Ar were measured over range 110–330 K. Only Xe had a significant temperature dependence. Its Arrhenius expression is { (8.5±1.7) ×10−11 exp[(−103±52)/RT] cm3/molecule⋅s} (E in cal/mole). Kr are (6.4±1.3) ×10−12 (5.0±1.5) ×10−13 cm3/molecule⋅s, respectively. observed trend efficiency, Xe≳Kr≳Ar, effects support results spin–orbit interaction mechanism given Husain co-workers.

Rate constants for the quenching of O2(1Σg+) to O2(1Δg) by nine diatomic molecules have been calculated on assumption that relaxation results from long-range interactions between transition quadrupole and dipole quenchers. The suggest in most cases this may be dominant mode which is induced. With assumption, major channels processes identified