Threshold behavior of endothermic reactions: C+(2P) + H2 → CH+ + H

Journal ArticleThe reaction C+(2p) + H2 → CH+ + H (1) and its deuterium analog is a model system in ion-molecule chemistry. It is of interest due to its astrophysical significance, because it is an endothermic process, and because the interaction involves several potential energy surfaces. Experimental work has included determinations of the total reaction cross section,1-3 studies of the reaction dynamics,4 measurements of product internal energy distributions,5 and chemiluminescence studies of electronically excited products.

Translational energy dependence of Ar+ + XY → ArX+ + Y (XY = H2, D2, HD) from thermal to 30 eV c.m.

Journal ArticleCross sections for the reactions of Ar+ with H2, D2, and HD to form ArH + and ArD + are measured using a new guided ion beam tandem mass spectrometer which affords an experimental energy range from 0.05 to 500 eV laboratory. The apparatus and experimental techniques are described in detail. Cross sections for H2 and D2 are found to be nearly identical over this entire energy range when compared at the same barycentric energy

C+(2P) + H2(D2,HD)→CH+(CD+) + H(D). I. Reaction cross sections and kinetic isotope effects from threshold to 15 eV c.m.

Journal ArticleTotal cross sections for the reactions of carbon (1 + ) ions with isotopic molecular hydrogen (H2, D2 , and HD) to form methyliumylidene (CH+ and C D + ) have been measured using guided ion beam techniques. Cross sections are reported as a function of the translational energy of the reactants from the reaction threshold up to 15 eV cm

Spin-orbit state-selected reactions of Xe+(2P3/2 and 2P1/2) with H2, D2, and HD

Journal ArticleSpin-orbit state-selected reactions of X e + (2Pj ), j = 3/2 and 1/2, with isotopic molecular hydrogen (H2 , D2 , and HD) to form X e H + and XeD + are studied using guided ion beam mass spectrometry. Reaction cross sections are determined as a function of reactant kinetic energy from near thermal energy to 15 eV c m . Although the reaction of Xe + ( 2p 1/2 ) + H2 to form ground state products XeH+ + H is exothermic, no reaction is observed at low energies and the reaction cross section is zero or small at higher energies

The epidemiology of low back pain in primary care

This descriptive review provides a summary of the prevalence, activity limitation (disability), care-seeking, natural history and clinical course, treatment outcome, and costs of low back pain (LBP) in primary care. LBP is a common problem affecting both genders and most ages, for which about one in four adults seeks care in a six-month period. It results in considerable direct and indirect costs, and these costs are financial, workforce and social. Care-seeking behaviour varies depending on cultural factors, the intensity of the pain, the extent of activity limitation and the presence of co-morbidity. Care-seeking for LBP is a significant proportion of caseload for some primary-contact disciplines. Most recent-onset LBP episodes settle but only about one in three resolves completely over a 12-month period. About three in five will recur in an on-going relapsing pattern and about one in 10 do not resolve at all. The cases that do not resolve at all form a persistent LBP group that consume the bulk of LBP compensable care resources and for whom positive outcomes are possible but not frequent or substantial

Energy dependence, kinetic isotope effects, and thermochemistry of the nearly thermoneutral reactions of N+(3P) + H2(HD, D2) → NH+(ND+) + H(D)

Journal ArticleThe reactions of N + (3P) ions with H2 , HD, D2 are examined using guided ion beam tandem mass spectroscopy. Absolute reaction cross sections are measured from near thermal energies to 30 eV relative energy. The low energy cross section behavior is analyzed using empirical threshold models and phase space theory

C+(2P)+H2(D2,HD)→CH+(CD+)+H(D). I. Reaction cross sections and kinetic isotope effects from threshold to 15eV c.m.

Journal ArticleTotal cross sections for the reactions of carbon (1 + ) ions with isotopic molecular hydrogen (H2, D2, and HD) to form methyliumylidene (CH+ and CD+) have been measured using guided ion beam techniques. Cross sections are reported as a function of the translational energy of the reactants from the reaction threshold up to 15 eV c m . The true cross sections are shown to rise sharply from thresholds given by the thermochemical endothermicities. Inter- and intramolecular isotope effects in the threshold region can be attributed to the different endothermicities due to vibrational zero-point energies. At higher energies, an unexpected intermolecular isotope effect is found. Thermal reaction rates (300 K) derived from the data are 1.2X10-16 for H2 , 2.3 X 10 -17 for D2 , and 1.2X 10 -16 for HD (17% CH+, 83% CD+), all in units of cm3 s -1

Spin-orbit state-selected reactions of Kr+(2P3/2 and 2P1/2) with H2, D2, and HD from thermal energies to 20 eV c.m.

Journal ArticleSpin-orbit state-selected reactions of K r + (2Pj), J = 3/2 and / = 1/2, with isotopic molecular hydrogen (H2 , D2 , and HD) to form KrH+ and Kr D+ are investigated using guided ion beam techniques. Reaction cross sections for each spin-orbit state are measured as a function of the relative translational energy of the reactants from near thermal energies up to 20 eV cm. At low energies, the cross sections for reaction with H2 and D 2 are each about 2.6 times larger for the 2P3/2 ground spin-orbit state of krypton ion than for the 2Px12 excited state

Hydrogen atom transfer reactions of He+ and Ne+ with H2, D2, and HD

Journal ArticleThe hydrogen atom transfer reactions of helium (1 +) and neon(1+) ions with isotopic molecular hydrogen (H2 , D2 , and HD) are investigated using guided ion beam techniques. These reactions are exothermic, but are known to be extremely slow at thermal energies. The cross sections for formation of HeH+ (HeD+) and NeH+ (NeD+) exhibit thresholds at high relative translational energies, 8 to 12 eV c m . Unusual isotope effects are observed in the reaction with HD

Rasch analysis of the 23-item version of the Roland Morris Disability Questionnaire

Objective: To determine the psychometric properties of the 23-item version of the Roland Morris Disability Questionnaire (RMDQ-23) and to quantify their stability across 2 cultures/languages and 2 types of care-settings. Methods: Rasch analysis of data from 1,000 patients with low back pain from primary care (UK and Denmark) and secondary care (Denmark). Results: The RMDQ-23 is unidimensional if local item dependency issues are accommodated, but contains several misfitting or overdiscriminating items, some poor targeting of items, and the scoring of 4-5 items is differentially affected by common clinical characteristics (such as age, gender, pain intensity, pain duration and care setting), depending on the country. Conclusion: As similar results have been found for the RMDQ-24, we believe it is timely to reconsider whether: (i) the RMDQ should be reconstructed using an item-response theory-based approach that includes consideration of new items and response options; or (ii) the use of alternative questionnaires should be recommended, such as the Oswestry Disability Index, that have shown evidence of fitting the Rasch model; or (iii) a completely new condition-specific questionnaire should be developed, perhaps utilizing a computerized adaptive testing platform