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J W Sutherland

Publications and source records attributed to J W Sutherland.

At least 19 recordsLinked to original sources
PubMed2005

Reflected shock tube studies of high-temperature rate constants for CH3 + O2, H2CO + O2, and OH + O2.

The reflected shock tube technique with multipass absorption spectrometric detection of OH-radicals at 308 nm, corresponding to a total path length of approximately 2.8 m, has been used to study the reaction CH3 + O2 CH2O + OH. Experiments were performed between 1303 and 2272 K, using ppm quantities of CH3I (methyl source) and 5-10% O2, diluted with Kr as the bath gas at test pressures less than 1 atm. We have also reanalyzed our earlier ARAS measurements for the atomic channel (CH3 + O2 --> CH3O + O) and have compared both these results with other earlier studies to derive a rate expression of the Arrhenius form. The derived expressions, in units of cm3 molecule(-1) s(-1), are k = 3.11 x 10(-13) exp(-4953 K/T) over the T-range 1237-2430 K, for the OH-channel, and k = 1.253 x 10(-11) exp(-14241 K/T) over the T-range 1250-2430 K, for the O-atom channel. Since CH2O is a major product in both reactions, reliable rates for the reaction CH2O + O2 --> HCO + HO2 could be derived from [OH]t and [O]t experiments over the T-range 1587-2109 K. The combined linear least-squares fit result, k = 1.34 x 10(-8) exp(-26883 K/T) cm3 molecule(-1) s(-1), and a recent VTST calculation clearly overlap within the uncertainties in both studies. Finally, a high sensitivity for the reaction OH + O2 --> HO2 + O was noted at high temperature in the O-atom data set simulations. The values for this obtained by fitting the O-atom data sets at later times (approximately 1.2 ms) again follow the Arrhenius form, k = 2.56 x 10(-10) exp(-24145 K/T) cm3 molecule(-1) s(-1), over the T-range, 1950-2100 K.

Journal Article↗
PubMed2005

Reflected shock tube studies of high-temperature rate constants for OH + CH4 --> CH3 + H2O and CH3 + NO2 --> CH3O + NO.

The reflected shock tube technique with multipass absorption spectrometric detection of OH radicals at 308 nm has been used to study the reactions OH + CH(4) --> CH(3) + H(2)O and CH(3) + NO(2) --> CH(3)O + NO. Over the temperature range 840-2025 K, the rate constants for the first reaction can be represented by the Arrhenius expression k = (9.52 +/- 1.62) x 10(-11) exp[(-4134 +/- 222 K)/T] cm(3) molecule(-1) s(-1). Since this reaction is important in both combustion and atmospheric chemistry, there have been many prior investigations with a variety of techniques. The present results extend the temperature range by 500 K and have been combined with the most accurate earlier studies to derive an evaluation over the extended temperature range 195-2025 K. A three-parameter expression describes the rate behavior over this temperature range, k = (1.66 x 10(-18))T(2.182) exp[(-1231 K)/T] cm(3) molecule(-1) s(-1). Previous theoretical studies are discussed, and the present evaluation is compared to earlier theoretical estimates. Since CH(3) radicals are a product of the reaction and could cause secondary perturbations in rate constant determinations, the second reaction was studied by OH radical production from the fast reactions CH(3)O --> CH(2)O + H and H + NO(2) --> OH + NO. The measured rate constant is 2.26 x 10(-11) cm(3) molecule(-1) s(-1) and is not dependent on temperature from 233 to 1700 K within experimental error.

Journal Article↗
PubMed2001

Streptococcal meningitis resulting from contact with an infected horse.

We report a case of group C streptococcal meningitis in a woman with a history of close animal contact as well as head trauma as a result of a kick by a horse. Blood and cerebrospinal fluid cultures grew Streptococcus equi subsp. zooepidemicus, as did a throat culture taken from the colt that had kicked her 2 weeks prior to admission.

Animals↗
PubMed1991

Stabilized procedure for the determination of urokinase fibrinolytic potency.

A stabilized procedure for the determination of urokinase (UK) fibrinolytic potency is described in which method response is dependent on urokinase concentration and independent of normal variation in assay parameters. The method is a selective stability-indicating procedure for UK active enzyme. It is suitable for evaluation of both high molecular weight as well as low molecular weight urokinase fractions and is calibrated against the World Health Organization International Reference Preparation for UK code 66/46 using a biological six-point parallel line log-log dose-response approach where sample and standard are compared under essentially identical conditions. High method stability and sensitivity are achieved through the use of appropriate levels of purified human plasminogen and human plasma (source of fibrinogen) as primary and secondary substrates, respectively. Method precision versus house reference standard (%RSD less than or equal to 2%) is suitable for research and pharmaceutical purposes. The absolute UK potency reference plane established in the calibrated procedure is equivalent to that established by other investigators in the fibrinolytic field.

Animals↗
PubMed1987

High-performance liquid chromatographic assay for thyrotropin releasing hormone and benzyl alcohol in injectable formulation.

A stability-indicating, high-performance liquid chromatographic method is presented for the determination of thyrotropin releasing hormone (TRH) and benzyl alcohol in a multidose injectable formulation. Separation is achieved on a microparticulate octadecylsilica column, with pH 2.2 ion-pair reagent (octanesulfonic acid, sodium salt) solution/methanol/acetonitrile/triethylamine (92:4:4:0.01), at a flow rate of 1.5 ml/min and a detection wavelength of 215 nm. p-Aminobenzoic acid is used as an internal standard. The relative standard deviations of the method are +/- 0.6% for TRH and +/- 0.7% for benzyl alcohol. Recoveries from standard additions to placebos ranged from 99.0 to 101.3 and 99.7 to 101.8% for TRH and benzyl alcohol, respectively.

Benzyl Alcohols↗
PubMed1985

Recurrence after a single renal stone in a community practice.

The natural history of recurrence of kidney stones was studied in a community urology practice, in which treatment with agents such as thiazide, allopurinol or oral phosphate has not been consistent or widespread. Using life-table analysis, the mean interval to first recurrence was 8.8 +/- 1.2 years and was not influenced by gender, age at first occurrence, or family history of stones. The tempo of recurrence justifies an individual approach to evaluation and treatment.

Adult↗
PubMed1984

Evaluation of the thermal stability of clinically relevant enzymes at 37 degrees C.

The thermal stability at 37 degrees C of several clinically relevant enzymes and isoenzymes was assessed by measuring changes in enzyme activity as a function of time under incubation and reaction conditions. Selwyn plots were used in the reaction-condition assessments. Except for CK-1 (BB), all the enzymes investigated are stable enough at 37 degrees C to permit assay. These enzymes were LDH-1, LDH-5, s-AspAT, m-AspAT, apo-s-AspAT, apo-m-AspAT, ALP-liver, ALP-bone, ALP-intestine, ALT, apo-ALT, CK-2, and CK-3. CK-1 is stable at 37 degrees C under assay conditions but not under incubation conditions. We specifically avoided using Arrhenius plots to evaluate thermal stability and point out pitfalls inherent in their indiscriminate use.

Alanine Transaminase↗
PubMed1981

Residual postoperative upper urinary tract stone.

Of 175 patients operated on from 1925 to 1955 for upper urinary tract stones, in whom immediate postoperative x-rays were available for study, there were 38 instances of false recurrence (22 percent). Subsequent review of the x-rays in a further 130 patients showed no residual stones and no stone had passed during the intervening period. This finding adjusted the rate of 12.5 per cent (38 instances in a series of 305 patients). The incidence of residual stones afer nephrolithotomy was 30 per cent. Factors responsible for a continuing high incidence of residual stones are discussed, along with important radiographic and surgical adjuvant techniques in their prevention. Proper use of these techniques should reduce the incidence of false recurrence to less than 10 per cent. Accurate intraoperative localization of the stones is of paramount importance.

False Positive Reactions↗
PubMed1980

Observation of an exothermic process associated with the in vitro polymerization of brain tubulin.

The polymerization of tubulin has been studied with a high-sensitivity differential scanning microcalorimeter, with results which indicate that microtubule assembly can proceed via one or possibly two exothermic reactions. The amount of heat evolution has been found to be far in excess of GTP hydrolysis. The heat liberated has been observed to depend strongly upon the exact experimental conditions, varying from many hundreds of kilocalories per mole of tubulin dimer when dilute tubulin solutions are heated rapidly to a few kilocalories per mole of tubulin dimer when concentrated tubulin solutions are heated slowly. The results are tentatively interpreted in terms of the existence of at least two pathways for the formation of energetically distinct polymers. These findings indicate the importance of kinetic factors in studying tubulin polymerization.

Animals↗
PubMed1977

Disagreement between calorimetric and van't Hoff enthalpies of assembly of protein supramolecular structures.

The effect of temperature on the extent of association of self-assembling protein polymers is expressed mathematically in terms of the van't Hoff enthalpy of polymerization, deltaHV.H. This quantity has been experimentally defined in two ways--from the respective temperature derivatives of the critical polymerization concentration and of the fractional conversion of protein into polymer. These two definitions are shown not to be identical, except in certain limits. In terms of both definitions, it is shown that deltaHV.H. depends not only upon the enthalpy changes but also upon the corresponding equilibrium constants for the various equilibria involved in polymer formation. This has two consequences: (i) large deltaHV.H. values may result from reactions having small calorimetric enthalpy changes; and (ii) deltaHV.H. can depend strongly on temperature. These considerations are applied to two systems for which there exist considerable experimental data--namely, hemoglobin S and tubulin. The large discrepancy between the calorimetric and van't Hoff enthalpies for the polymerization of tubulin is shown to be explicable in terms of these considerations.

Calorimetry↗
PubMed1976

Calorimetric studies of the in vitro polymerization of brain tubulin.

The enthalpy change for chain propagation in the polymerization of bovine tubulin has been studied directly by stopped-flow microcalorimetry at 17 degrees and 25 degrees, and found to be 0 +/- 1 kcal per mol of 6S tubulin dimer at both temperatures. Substantial heat evolution with a half-time of decay of approximately 1 hr was observed w-en tubulin was injected into the calorimeter. This heat was shown to result from contamination of the tublin by small amounts of some material from the crude brain homogenate from which the tubulin was prepared, and to be totally unconnected with microtubule assembly. Model calculations of nucleated polymerization processes reveal that the van't Hoff enthalpy calculated from the temperature dependence of the critical polymerization concentration is a complicated function of the separate enthalpy changes for nucleation and chain propagation. The published values of this quantity for tubulin probably pertain primarily to the nucleation process. It is shown that our observation of a propagation enthalpy change of vanishingly small size is not necessarily inconsistent with the reported van't Hoff enthalpies.

Animals↗