Elizabeth Goodwin

The rotational spectrum of 15N-ammonium chloride vapour: characterisation of the hydrogen-bonded dimer H3N...HCl

Abstract The rotational spectra of associated species (15NH3, H35Cl) and 15NH3, H37Cl) have been detected in 15N-ammonium chloride vapour by pulsed-nozzle, Fourier-transform microwave spectroscopy. Values of the rotational constant B0, the centrifugal distortion constants DJ and DJK, and the Cl-nuclear quadrupole coupling constant χ(Cl) have been determined for both species. The spectroscopic constants are interpreted in terms of a hydrogen-bonded dimer H3N...HCl (rather than the ion-pair H4N+Cl−) having C3v symmetry, with r(N...Cl) = 3.1367 A and the hydrogen-bond stretching force constant kσ = 18.1 Nm−1.

The rotational spectrum and molecular geometry of an antihydrogen‐bonded dimer of sulfur dioxide and hydrogen cyanide

The ground‐state rotational spectra of the four isotopic species (32SO2,HC14N), (32SO2,DC14N), (32SO2,HC15N), and (34SO2,HC14N) of a weakly bound dimer of sulfur dioxide and hydrogen cyanide have been observed by means of pulsed‐nozzle, Fourier‐transform microwave spectroscopy. The 14N‐nuclear quadrupole coupling constants determined for the isotopomer (32SO2,HC14N) of this asymmetric rotor molecule are χaa =−2.876(3) MHz and χbb =2.025(4) MHz while the rotational and centrifugal distortion constants are (A0−ΔK) =8633.849(1) MHz, B0=1848.890(2) MHz, C0=1615.863(2) MHz, ΔJ =9.56(1) kHz, ΔJK =114.84(7) kHz, δJ =0.838(6) kHz, and δK =89(1) kHz. The spectroscopic constants have been interpreted in terms of a nonplanar, antihydrogen‐bonded geometry of Cs symmetry with S, H, C, and N nuclei lying in the symmetry plane. The HCN molecule is roughly perpendicular to the plane of the SO2 molecule with N lying between the SO2 plane and the H atom. The distance between the SO2 and HCN centers of mass is rc.m. =3.6542...

Effect of weakening the hydrogen bond on the angular geometry of H2CO...HX: evidence from the rotational spectrum of H2CO...HCN

The ground‐state rotational spectra of three isotopic species (H2CO⋅⋅⋅HC1 4N, H2CO⋅⋅⋅HC1 5N, and H2CO⋅⋅⋅DC1 4N) of the formaldehyde–hydrogen cyanide dimer have been observed by pulsed‐nozzle, Fourier‐transform microwave spectroscopy.Analysis of the spectra yielded rotational constants, centrifugal distortion constants, and 1 4N‐nuclear quadrupole coupling constants which for the species H2CO⋅⋅⋅HC1 4N have the following values: A 0=91.2(7.5) GHz, B 0=1785.6217(10), C 0=1749.7215(10) MHz, Δ J =4.76(2) kHz, Δ J K =−6.1181(7) MHz, δ J =2.58(1) kHz, χ a a =−4.381(3) MHz, and χ b b =2.141(4) MHz. The spectroscopic constants have been interpreted to establish a planar geometry for the dimer in which HCN forms a hydrogen bond to O in H2CO. The angle between the C=O bond and HCN symmetry axis is θ=138.1 deg, and the intermolecular distance from O to C is r(O⋅⋅⋅C)=3.271 A. The difference in the angle θ between H2CO⋅⋅⋅HCN and H2CO⋅⋅⋅HF is discussed on the basis of a simple model for the hydrogen bond in these dimers.

A Quality-Adjusted Life-Year Measure for Multiple Sclerosis: Developing a Patient-Reported Health State Classification System for a Multiple Sclerosis-Specific Preference-Based Measure

BACKGROUND Increasingly, generic preference-based measures of health-related quality of life (HRQOL) are used to estimate quality-adjusted life-years to inform resource allocation decisions. Evidence suggests that generic measures may not be appropriate for multiple sclerosis (MS). OBJECTIVES To report the first stage in the development of an MS-specific preference-based measure to quantify the impact of MS and its treatment: deriving a health state classification system, which is amenable to valuation, from the 29-item Multiple Sclerosis Impact Scale (MSIS-29), a widely used patient-reported outcome measure in MS. METHODS The dimensional structure of the MSIS-29 was determined using factor analysis and a conceptual framework of HRQOL in MS. Item performance was assessed, using Rasch analysis and psychometric criteria, to enable the selection of one item to represent each dimension of HRQOL covered by the MSIS-29. Analysis was undertaken using a sample (N = 529) from a longitudinal study of people with MS. Results were validated by repeating the analysis with a second sample (N = 528). RESULTS Factor analysis confirmed the two-subscale structure of the MSIS-29. Both subscales covered several conceptually independent dimensions of HRQOL. Following Rasch and psychometric analysis, an eight-dimensional classification system named the MSIS-8D was developed. Each dimension was represented by one item with four response levels. CONCLUSIONS Combining factor analysis with conceptual mapping, and Rasch analysis with psychometric criteria, provides a valid method of constructing a classification system for an MS-specific preference-based measure. The next stage is to obtain preference weights so that the measure can be used in studies investigating MS.

Estimating a Preference-Based Index for an Eight-Dimensional Health State Classification System for Multiple Sclerosis

BACKGROUND Condition-specific measures are frequently used to assess the health-related quality of life of people with multiple sclerosis (MS). Such measures are unsuitable for use in economic evaluations that require estimates of cost per quality-adjusted life-year because they are not based on preferences. OBJECTIVES To report the estimation of a preference-based single index for an eight-dimensional instrument for MS, the Multiple Sclerosis Impact Scale - Eight Dimensions (MSIS-8D), derived from an MS-specific measure of health-related quality of life, the 29-item Multiple Sclerosis Impact Scale (MSIS-29). METHODS We elicited preferences for a sample of MSIS-8D states (n = 169) from a sample (n = 1702) of the UK general population. Preferences were elicited using the time trade-off technique via an Internet-based survey. We fitted regression models to these data to estimate values for all health states described by the MSIS-8D. Estimated values were assessed against MSIS-29 scores and values derived from generic preference-based measures in a large, representative sample of people with MS. RESULTS Participants reported that the time trade-off questions were easy to understand. Observed health state values ranged from 0.08 to 0.89. The best-performing model was a main effects, random effects model (mean absolute error = 0.04). Validation analyses support the performance of the MSIS-8D index: it correlated more strongly than did generic measures with MSIS-29 scores, and it discriminated effectively between subgroups of people with MS. CONCLUSIONS The MSIS-8D enables health state values to be estimated from the MSIS-29, adding to the methods available to assess health outcomes and to estimate quality-adjusted life-years for MS for use in health technology assessment and decision-making contexts.

The rotational spectrum and geometry of the heterodimer oxirane ⋅ ⋅ ⋅ hydrogen cyanide in the vibrational ground state and the vβ(0)=1 state

The rotational spectrum of the heterodimer formed by oxirane and hydrogen cyanide has been observed by pulsed‐nozzle, Fourier‐transform microwave spectroscopy. Two sets of rotational transitions of similar intensity have been identified for each of the isotopic species (CH2)2O ⋅⋅⋅ HC14N, (CH2)2O ⋅⋅⋅ HC15N, and (CH2)2O ⋅⋅⋅ DC14N. Each set of rotational transitions was fitted to give rotational constants B and C, centrifugal distortion constants ΔJ, ΔJK, δJ, and HJK, and, where appropriate, 14N–nuclear quadrupole coupling constants χaa and χbb. The rotational constants for each of the two states (labeled A and B) were interpreted in terms of a molecule of Cs symmetry, with a hydrogen bond O ⋅⋅⋅ HCN and a pyramidal geometry at the oxygen atom. For the species (CH2)2O ⋅⋅⋅ HC14N, the angle φ between the bisector of the COC angle and the HCN axis increases from 52.2(3)° in state A to 61.3(3)° in state B, while the distance r(O ⋅⋅⋅C) correspondingly increases from 3.035(4) to 3.130(4)A. Similar changes are obser...

The rotational spectrum, geometry, and intermolecular force constant of the heterodimer of hydrogen cyanide and fluoroform

The ground‐state rotational spectra of six isotopic species of an intermolecular complex formed by hydrogen cyanide and fluoroform have been measured using the pulsed‐nozzle, Fourier‐transform microwave technique. The rotational constant B0, the centrifugal distortion constants DJ,DJK,HJ, HJK, and HKJ, and, where appropriate, the nuclear quadrupole coupling constants χ(14N) and χ(D) have been determined for each of the species HC14N⋅⋅⋅HCF3, DC14N⋅⋅⋅HCF3, HC14⋅⋅⋅DCF3, HC15N⋅⋅⋅HCF3, HC15N⋅⋅⋅DCF3, and DC15N⋅⋅⋅HCF3. For HC14N⋅⋅⋅HCF3 the values are as follows: B0=1151.2991(4) MHz, DJ=1.91(1) kHz, DJK=282.75(6) kHz, HJ=−0.1(1) Hz, HJK=44.3(5) Hz, HKJ=53(5) Hz, and χ(14N)=3.948(8) MHz. The form of the spectra and magnitudes of the rotational constants allow the conclusion that the geometry of the complex is of C3V symmetry with the nuclei in the order HCN⋅⋅⋅HCF3 and lead to r(N⋅⋅⋅C)=3.489(2) A for HCF3 species but 3.483(1) A for DCF3 species. The intermolecular stretching force constant determined from DJ is kσ=...

A Systematic Review of the Literature on the Development of Condition-Specific Preference-Based Measures of Health

BackgroundHealth state utility values (HSUVs) are required to calculate quality-adjusted life-years (QALYs). They are frequently derived from generic preference-based measures of health. However, such generic measures may not capture health attributes of relevance to specific conditions. In such cases, a condition-specific preference-based measure (CSPBM) may be more appropriate.ObjectiveThis systematic review aimed to identify all published accounts of developing CSPBMs to describe and appraise the methods used.MethodWe undertook a systematic search (of Embase, MEDLINE, PsycINFO, Web of Science, the Cochrane Library, CINAHL, EconLit, ASSIA and the Health Management Information Consortium database) to identify published accounts of CSPBM development up to July 2015. Studies were reviewed to investigate the methods used to design classification systems, estimate HSUVs, and validate the measures.ResultsA total of 86 publications were identified, describing 51 CSPBMs. Around two-thirds of these were QALY measures; the remainder were designed for clinical decision making only. Classification systems for 33 CSPBMs were derived from existing instruments; 18 were developed de novo. HSUVs for 34 instruments were estimated using a ‘composite’ approach, involving statistical modelling; the remainder used a ‘decomposed’ approach based on multi-attribute utility theory. Half of the papers that described the estimation of HSUVs did not report validating their measures.ConclusionVarious methods have been used at all stages of CSPBM development. The choice between developing a classification system de novo or from an existing instrument may depend on the availability of a suitable existing measure, while the choice between a decomposed or composite approach appears to be determined primarily by the purpose for which the instrument is designed. The validation of CSPBMs remains an area for further development.

“Naming and Framing”: The Impact of Labeling on Health State Values for Multiple Sclerosis:

Introduction. Health state valuation is a key input in many economic evaluations that inform resource allocation across competing healthcare interventions. Empirical evidence has shown that, in preference elicitation surveys, respondents may value a health state differently if they are aware of the condition causing it (‘labeling effects’). This study investigates the impact of including a multiple sclerosis (MS) label for valuation of MS health states. Methods. Health state values for MS were elicited using two internet-based surveys in representative samples of the UK population (n = 1702; n = 1788). In one survey respondents were not informed that health states were caused by MS. The second survey included a condition label for MS. Surveys were identical in all other ways. Health states were described using a MS-specific eight-dimensional classification system (MSIS-8D), and the time trade-off valuation technique was used. Differences between values for labeled and unlabeled states were assessed using descriptive statistics and multivariate regression methods. Results. Adding a MS condition label had a statistically significant effect on mean health state values, resulting in lower values for labeled MS states v. unlabeled states. The data suggest that the MS label had a more significant effect on values for less severe states, and no significant effect on values for the most severe states. The inclusion of the MS label had a differential impact across the dimensions of the MSIS-8D. Across the MSIS-8D, predicted values ranged from 0.079 to 0.883 for unlabeled states, and 0.066 to 0.861 for labeled states. Conclusion. Differences reported in health state values, using labeled and unlabeled states, demonstrate that condition labels affect the results of valuation studies, and can have important implications in decision-analytic modelling and in economic evaluations.

Health State Values Derived from People with Multiple Sclerosis for a Condition-Specific Preference-Based Measure: Multiple Sclerosis Impact Scale–Eight Dimensions–Patient Version (MSIS-8D-P)

OBJECTIVE In economic evaluation, health outcomes are commonly quantified using quality-adjusted life-years (QALYs) derived from the preferences of a sample of the general population. It can be argued that this approach ignores the preferences of people with experience of the condition, and that patient preferences have a place in the valuation of health outcomes. Here we report the estimation of a preference-based index for an existing condition-specific preference-based measure for multiple sclerosis (MS), the MSIS-8D, based on the preferences of people with MS. STUDY DESIGN Internet time trade-off (TTO) survey, eliciting preferences from people with MS. METHODS We elicited preferences from a sample of people with MS (N = 1635) across 169 MSIS-8D health states, using the TTO technique. We fitted ordinary least squares and random effects models to the survey data to estimate values for all health states described by the MSIS-8D. RESULTS The new patient-derived index (the MSIS-8D-P) provides values ranging from 0.893 for the best possible health state to 0.138 for the worst state. The MSIS-8D-P exhibits good discriminative validity, identifying expected significant differences between groups based on presence/absence of MS, type of MS, and duration since diagnosis. CONCLUSIONS The MSIS-8D-P index of values for MS-specific health states provides an opportunity to estimate QALYs based on patient preferences, for use in economic evaluations of treatments for MS. More broadly, it adds to the methods and data available to consider the health-related quality of life of people with MS to inform resource allocation and individual-level decisions regarding treatments for MS.