The Rate of Recombination of H Atoms in the Presence of NH3

1973 ◽  
Vol 51 (22) ◽  
pp. 3771-3773 ◽  
Author(s):  
L. Teng ◽  
C. A. Winkler
Keyword(s):  
Rate Constant ◽  
Pressure Range ◽  
Flow System ◽  
Carrier Gas ◽  
A Value ◽  
Fast Flow

The rate constant for the homogeneous recombination of H atoms in the presence of NH3, with He as carrier gas, has been determined at 298°K in a fast flow system, over the pressure range 1.50 to 4.55 Torr, using e.s.r. technique. A value of either 4.00 × 1016 or 5.14 × 1016 cm6 mol−2 s−1 was calculated, depending upon the rate constant taken, or estimated, from the literature for the recombination in the presence of helium.

THE REACTION OF NITROGEN ATOMS WITH OXYGEN ATOMS IN THE ABSENCE OF OXYGEN MOLECULES

1961 ◽  
Vol 39 (8) ◽  
pp. 1601-1607 ◽  
Author(s):  
C. Mavroyannis ◽  
C. A. Winkler
Keyword(s):  
Nitric Oxide ◽  
Nitrogen Atom ◽  
Rate Constant ◽  
Rate Constants ◽  
Flow System ◽  
Titration Method ◽  
Active Nitrogen ◽  
Reaction Tube ◽  
Fast Flow ◽  
Oxygen Atoms

The reaction has been studied in a fast-flow system by introducing nitric oxide in the gas stream with excess active nitrogen. The nitrogen atom consumption was determined by titrating active nitrogen with nitric oxide at different positions along the reaction tube. The rate constant is found to be k1 = 1.83(± 0.2) × 1015 cc2 mole−2 sec−1 at pressures of 3, 3.5, and 4 mm, and with an unheated reaction tube.The homogeneous and surface decay of nitrogen atoms involved in the above system were studied using the nitric oxide titration method, and the rate constants were found to be k3 = 1.04 ± 0.17 × 1016 cc2 mole−2 sec−1, and k4 = 2.5 ± 0.2 sec−1 (γ = 7.5 ± 0.6 × 10–5), respectively, over the range of pressures from 0.5 to 4 mm with an unheated reaction tube.

Rates of elementary processes in the chain reaction between hydrogen and oxygen I. Reactions of oxygen atoms

1963 ◽  
Vol 275 (1363) ◽  
pp. 544-558 ◽  
Keyword(s):  
Rate Constant ◽  
Atomic Oxygen ◽  
Elevated Temperatures ◽  
Collision Frequency ◽  
Flow System ◽  
Chain Reaction ◽  
Elementary Processes ◽  
A Value ◽  
Good Agreement ◽  
Oxygen Atoms

The rates of reaction of 3 P oxygen atoms with hydroxyl and hydrogen have been measured in a flow system at pressures around 2 mmHg. The former reaction, O + OH -> H + O 2 , ( — 4) occurred in the products of the rapid reaction between H and NO 2 , and was followed by measurements of atomic oxygen concentrations. k -4 was found to be 5±2 x 10 -11 cm 3 molecule -1 s -1 at 265 and 293 °K. This result, when combined with data on the reverse reaction at elevated temperatures, gives a value of k -4 which is virtually independent of temperature and equal to about 1/20 of the bimolecular collision frequency. The reaction O + H 2 -> OH + H (3) was studied in the absence of molecular oxygen and found to have a rate constant of 6 x 10 -13 exp (-8900/ RT ) cm 3 molecule -1 s -1 in the range 409 to 733 °K. This is in good agreement with values obtained at higher temperatures. The rate constant for O + D 2 was significantly less than that for O + H 2 at temperatures between 491 and 671 °K.

The Reaction of CH2OH Radicals with O2 Studied by Laser Magnetic Resonance Technique

1985 ◽  
Vol 40 (12) ◽  
pp. 1289-1298 ◽  
Author(s):  
S. Dóbé ◽  
F. Temps ◽  
T. Böhland ◽  
H.Gg. Wagner
Keyword(s):  
Pressure Range ◽  
Rate Coefficient ◽  
Flow System ◽  
Isothermal Flow ◽  
Oh Radical ◽  
Complex Mechanism ◽  
Resonance Technique ◽  
A Value ◽  
Magnetic Resonance Technique ◽  
Laser Magnetic Resonance

The reaction of CH2OH with O2 was studied in an isothermal flow system at 296 K. A rate coefficient, K1(296 K) = (6.4 ± 1.5) x 1012 cm3 mol-1 s-1, has been determined for the overall reaction CH2OH + O2 → product(s) (1) by monitoring the decay of the LMR signal of the CH2OH radical. A value of (6.3 ± 2.8) x 1012 cm3 mol-1 s-1 has been obtained for the overall rate coefficient by following the formation of the product HO2 radicals in the specific reaction channel CH2OH + O2 -> HO2 + CH2O . (1a)No dependence on pressure of k1 observed in the pressure range 0.69≦ P/mbar ≦ 6.50 studied. A complex mechanism has been proposed for the formation of HO2 and CH2O in the reaction.

Determination of the bond dissociation energy, D(CH3Hg—CH3), by the toluene carrier method

1969 ◽  
Vol 47 (6) ◽  
pp. 991-994 ◽  
Author(s):  
R. J. Kominar ◽  
S. J. Price
Keyword(s):  
Thermal Decomposition ◽  
Excellent Agreement ◽  
Rate Constant ◽  
Pressure Range ◽  
Arrhenius Equation ◽  
Flow System ◽  
Methyl Radicals ◽  
Exponential Factors ◽  
Pressure Independent

The thermal decomposition of Hg(CH3)2 has been studied in a toluene carrier flow system over the pressure range 4.5 to 323 mm at temperatures of 422 to 527 °C. The Arrhenius equation for the pressure independent region,[Formula: see text]is in excellent agreement with earlier work on the fully inhibited decomposition at lower temperatures. The region of fall off of the unimolecular rate constant is in agreement with a classical Kassel calculation using s = 16−18, but the rate of fall off requires the use of a curve with s = 3, displaced five log units to the left. This is consistent with the previous results for the dissociation of ethane into two methyl radicals and is further evidence of the inability of the classical Kassel equation to represent the behavior of systems with high pre-exponential factors.

THE REACTION OF NITROGEN ATOMS WITH HYDROGEN ATOMS

1962 ◽  
Vol 40 (2) ◽  
pp. 240-245 ◽  
Author(s):  
C. Mavroyannis ◽  
C. A. Winkler
Keyword(s):  
Atomic Hydrogen ◽  
Molecular Hydrogen ◽  
Pressure Range ◽  
Flow System ◽  
Hydrogen Bromide ◽  
Hydrogen Atoms ◽  
Active Nitrogen ◽  
Reaction Tube ◽  
Fast Flow ◽  
Hydrogen Stream

The reaction has been studied in a fast-flow system by the addition of atomic hydrogen to active nitrogen. Hydrogen atom concentrations were estimated from the maximum destruction of hydrogen bromide in the atomic hydrogen stream. The nitrogen atom consumption, in the reaction mixture, was determined by addition of nitric oxide at different positions along the reaction tube. A lower limit of 4.87 ± 0.8 × 1014 cc2mole−2sec−1 was derived for the rate constant of the reaction of nitrogen atoms with hydrogen atoms, over the pressure range 2.5 to 4.5 mm, in an unheated reaction tube, poisoned with phosphoric acid. No reaction between nitrogen atoms and molecular hydrogen was observed, even at 350 °C.

Quenching of the O2 (Aν=2 → Xν=5) Herzberg I band by O2(a) and O

1984 ◽  
Vol 62 (12) ◽  
pp. 1599-1602 ◽  
Author(s):  
R. D. Kenner ◽  
E. A. Ogryzlo
Keyword(s):  
Rate Constant ◽  
Electrical Discharge ◽  
Flow System ◽  
Nickel Surface ◽  
Quenching Rate ◽  
Vibrational Levels ◽  
Fast Flow ◽  
Oxygen Atoms

Data are presented that indicate that O2(a1Δg) is an effective quencher of [Formula: see text]. In a system where O and O2 are produced by an electrical discharge in a fast-flow system, O2(A) molecules were formed by allowing some of the oxygen atoms to recombine on a nickel surface. From the decay of O2(A) in the presence of O2(a), a rate constant of (8.1 ± 3) × 10−11 cm3 molec−1 s−1 was obtained for the interaction of these two species. A revised value of 1.3 × 10−11 cm3 molec−1 s−1 for the rate constant for the O2(A)ν = 2 quenching by O has been determined. The relative quenching rate of vibrational levels 0–4 have also been estimated.

Interaction between loop of Henle flow and arterial pressure as determinants of glomerular pressure

1989 ◽  
Vol 256 (3) ◽  
pp. F421-F429 ◽  
Author(s):  
J. Schnermann ◽  
J. P. Briggs
Keyword(s):  
Arterial Pressure ◽  
Pressure Range ◽  
Loop Of Henle ◽  
Half Maximum ◽  
Perfusion Rate ◽  
A Value ◽  
Regulatory Input ◽  
Flow Pressure ◽  
The Relationship ◽  
Stop Flow

Experiments were performed in anesthetized rats to study the relationship between loop of Henle perfusion rate, arterial pressure, and stop-flow pressure (SFP) as an index of glomerular capillary pressure. In one set of experiments we measured the SFP feedback response to changes in loop perfusion at three levels of arterial pressure. The maximum SFP response fell significantly from 13.1 +/- 1.44 to 8.14 +/- 1.72 and 3.13 +/- 0.76 mmHg when arterial pressure was reduced from 118.1 +/- 1.27 to 98.8 +/- 0.51 and 78.8 +/- 1.72 mmHg. In other experiments arterial pressure was altered while loop perfusion rate was fixed at one of three levels. Without loop perfusion SFP changed with a slope of 0.27 +/- 0.04 mmHg/mmHg in the arterial pressure range between 80 and 130 mmHg. During perfusion at the flow rate at which response is half maximum, the slope was significantly reduced to 0.12 +/- 0.04. During perfusion at 45 nl/min, it was 0.03 +/- 0.05, a value not significantly different from zero. During dopamine administration (70 micrograms/kg min) SFP was pressure-dependent even during loop perfusion at 45 nl/min. These results show that arterial pressure determines TGF responsiveness and that the TGF signal determines the range of a regulatory input that is directly dependent on arterial pressure.

Rate constant for the reaction of the CFCl2 radical with oxygen in the pressure range 0.2–12 Torr at 298 K

1983 ◽  
Vol 102 (1) ◽  
pp. 54-58 ◽  
Author(s):  
F. Caralp ◽  
R. Lesclaux
Keyword(s):  
Rate Constant ◽  
Pressure Range

THE Hg 6(3P1)-PHOTOSENSITIZED DECOMPOSITION OF NITRIC OXIDE

1961 ◽  
Vol 39 (12) ◽  
pp. 2549-2555 ◽  
Author(s):  
Otto P. Strausz ◽  
Harry E. Gunning
Keyword(s):  
Nitric Oxide ◽  
Quantum Yield ◽  
Ground State ◽  
Pressure Range ◽  
Oxides Of Nitrogen ◽  
Total Rate ◽  
A Value ◽  
Electronically Excited ◽  
Static Conditions ◽  
Observed Behavior

The reaction of NO with Hg 6(3P1) atoms has been studied under static conditions at 30°, over the pressure range 1–286 mm. The products were found to be N2, N2O, and higher oxides of nitrogen. At NO pressures exceeding 4 mm, the total rate of formation of N2+N2O was constant, while the ratio N2O/N2 increased linearly with the substrate pressure. The rate was found to vary directly with the first power of the intensity at 2537 Å, and a value of 1.9 × 10−3 moles/einstein was established for the quantum yield of N2 + N2O production. In the proposed mechanism, reaction is attributed to the decomposition of an energy-rich dimer, (NO)2*, which is formed by the collision of electronically excited (4II) NO molecules with those in the ground state. The (NO)2* species is assumed to decompose by the steps: (NO)2* → N2 + O2 and (NO)2* + NO → N2O + NO2. The mechanism satisfactorily explains the observed behavior of the system.

Kinetic characterization of a cis- and trans-acting M2+-independent DNAzyme that depends on synthetic RNaseA-like functionality — Burst-phase kinetics from the coalescence of two active DNAzyme folds

2007 ◽  
Vol 85 (4) ◽  
pp. 313-329 ◽  
Author(s):  
Richard Ting ◽  
Jason M Thomas ◽  
David M Perrin
Keyword(s):  
Steady State ◽  
Rate Constant ◽  
Acid Catalyst ◽  
Initial Population ◽  
Substrate Complex ◽  
Single Turnover ◽  
A Value ◽  
Burst Phase ◽  
Cis And Trans

This work describes the kinetics of the DNAzyme 925-11, a combinatorially selected, M2+-independent ribophosphodiesterase that is covalently modified with both cationic amines and imidazoles. At 13 °C, cis- and trans-cleaving constructs of 925-11 demonstrate the highest rate constants reported to date for any M2+-independent nucleic acid catalyst, investigated at physiological ionic strength and pH 7.5 (0.3 min–1 for self cleavage and 0.2 min–1 for intermolecular cleavage). In contrast to the cis-cleaving species, single-turnover experiments with the trans-cleaving species exhibit biphasic cleavage data, suggesting the presence of two conformations of the catalyst–substrate complex. Pulse–chase experiments demonstrate that both complexes lead to substrate cleavage. Under multiple-turnover conditions, the higher rate constant appears in a burst phase that decays to a slower steady state exhibiting a rate constant of 0.0077 min–1, a value approximating that of the slow-cleaving phase seen in single-turnover experiments. Slow product release is excluded as the source of the burst phase. An integrated rate equation is derived to describe burst-phase kinetics based on the funneling of the initial population of fast-cleaving conformation into a steady-state population composed largely of the slow-cleaving conformation.Key words: RNase mimics, DNAzymes, ribozymes, kinetics, RNA cleavage.

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