980 research outputs found
Charge-ice dynamics in the negative thermal expansion material Cd(CN)
We use variable-temperature (150--300\,K) single-crystal X-ray diffraction to
re-examine the interplay between structure and dynamics in the ambient phase of
the isotropic negative thermal expansion (NTE) material Cd(CN). We find
strong experimental evidence for the existence of low-energy vibrational modes
that involve off-centering of Cd ions. These modes have the effect of
increasing network packing density---suggesting a mechanism for NTE that is
different to the generally-accepted picture of correlated Cd(C/N) rotation
modes. Strong local correlations in the displacement directions of neighbouring
cadmium centres are evident in the existence of highly-structured diffuse
scattering in the experimental X-ray diffraction patterns. Monte Carlo
simulations suggest these patterns might be interpreted in terms of a basic set
of `ice-rules' that establish a mapping between the dynamics of Cd(CN) and
proton ordering in cubic ice VII.Comment: 5 pages, 5 figures, submitted to PR
Measurement of the Hyperfine Structure and Isotope Shifts of the 3s23p2 3P2 to 3s3p3 3Do3 Transition in Silicon
The hyperfine structure and isotope shifts of the 3s23p2 3P2 to 3s3p3 3Do3
transition in silicon have been measured. The transition at 221.7 nm was
studied by laser induced fluorescence in an atomic Si beam. For 29Si, the
hyperfine A constant for the 3s23p2 3P2 level was determined to be -160.1+-1.3
MHz (1 sigma error), and the A constant for the 3s3p3 3Do3 level is -532.9+-0.6
MHz. This is the first time that these constants were measured. The isotope
shifts (relative to the abundant isotope 28Si) of the transition were
determined to be 1753.3+-1.1 MHz for 29Si and 3359.9+-0.6 MHz for 30Si. This is
an improvement by about two orders of magnitude over a previous measurement.
From these results we are able to predict the hyperfine structure and isotope
shift of the radioactive 31Si atom, which is of interest in building a scalable
quantum computer
Determination of the Oswestry Disability Index score equivalent to a "satisfactory symptom state" in patients undergoing surgery for degenerative disorders of the lumbar spine-a Spine Tango registry-based study.
BACKGROUND CONTEXT
The achievement of a given change score on a valid outcome instrument is commonly used to indicate whether a clinically relevant change has occurred after spine surgery. However, the achievement of such a change score can be dependent on baseline values and does not necessarily indicate whether the patient is satisfied with the current state. The achievement of an absolute score equivalent to a patient acceptable symptom state (PASS) may be a more stringent measure to indicate treatment success.
PURPOSE
This study aimed to estimate the score on the Oswestry Disability Index (ODI, version 2.1a; 0-100) corresponding to a PASS in patients who had undergone surgery for degenerative disorders of the lumbar spine.
STUDY DESIGN/SETTING
This is a cross-sectional study of diagnostic accuracy using follow-up data from an international spine surgery registry.
PATIENT SAMPLE
The sample includes 1,288 patients with degenerative lumbar spine disorders who had undergone elective spine surgery, registered in the EUROSPINE Spine Tango Spine Surgery Registry.
OUTCOME MEASURES
The main outcome measure was the ODI (version 2.1a).
METHODS
Surgical data and data from the ODI and Core Outcome Measures Index (COMI) were included to determine the ODI threshold equivalent to PASS at 1 year (±1.5 months; n=780) and 2 years (±2 months; n=508) postoperatively. The symptom-specific well-being item of the COMI was used as the external criterion in the receiver operating characteristic (ROC) analysis to determine the ODI threshold equivalent to PASS. Separate sensitivity analyses were performed based on the different definitions of an "acceptable state" and for subgroups of patients. JF is a copyright holder of the ODI.
RESULTS
The ODI threshold for PASS was 22, irrespective of the time of follow-up (area under the curve [AUC]: 0.89 [sensitivity {Se}: 78.3%, specificity {Sp}: 82.1%] and AUC: 0.91 [Se: 80.7%, Sp: 85.6] for the 1- and 2-year follow-ups, respectively). Sensitivity analyses showed that the absolute ODI-22 threshold for the two follow-up time-points were robust. A stricter definition of PASS resulted in lower ODI thresholds, varying from 16 (AUC=0.89; Se: 80.2%, Sp: 82.0%) to 18 (AUC=0.90; Se: 82.4%, Sp: 80.4%) depending on the time of follow-up.
CONCLUSIONS
An ODI score ≤22 indicates the achievement of an acceptable symptom state and can hence be used as a criterion of treatment success alongside the commonly used change score measures. At the individual level, the threshold could be used to indicate whether or not a patient with a lumbar spine disorder is a "responder" after elective surgery
Experiences of living with chronic back pain: The physical disabilities
Purpose. Back-related functional limitations are largely assessed using lists of activities, each scored on a yes/no basis and the scores then summed. This provides little information about how chronic back pain (CBP) patients live with their condition. This study describes the consequences of living day-to-day with CBP and documents the 'insider' accounts of its impact on daily life.
Method. Unstructured interviews, using the 'Framework' approach with topic guide, were recorded and transcribed verbatim. Subjects were sampled for age, sex, ethnicity and occupation from new referrals with back pain to a rheumatology outpatient clinic. Eleven subjects (5 male, 6 female) were interviewed either in English (n = 9) or their preferred language (n = 2). Interviews were read in-depth twice to identify the topics. Data were extracted in phrases and sentences using thematic content analysis.
Results. Four themes emerged: sleep/rest, mobility, independence and leisure. All subjects reported issues about sleep and rest, nine about mobility, seven about independence and six on leisure. Most descriptions concerned loss and limitation in daily life. Strategies for coping with sleep disruption and physical limitations were described.
Conclusions. Subjects provided graphic 'in-depth' descriptions of experiences living with CBP every day; expressed regret at the loss of capabilities and distress at the functional consequences of those losses. Facilitating 'adjustment' to 'loss' may be more helpful than inferring the potential for a life free of pain as a result of therapeutic endeavours
The Swedish Spine Register: development, design and utility
The Swedish Spine Register enables monitoring of surgical activities focusing on changes in trends over time, techniques utilized and outcome, when implemented in general clinical practice. Basic requirements for a prosperous register are unity within the profession, mainly patient-based documentation and a well functioning support system. This presentation focuses on the development and design of the register protocol, problems encountered and solutions found underway. Various examples on how the results can be presented and utilized are given as well as validation. Register data demonstrate significant gender differences in lumbar disc herniation surgery with females having more pain, lower quality of life and more pronounced disability preoperatively while improvement after surgery is similar between genders. Quality of life after surgery for degenerative disorders is significantly improved for disc herniation, stenosis, spondylolisthesis and disc degenerative disorders. Over the last 10 years, surgical treatment for spinal stenosis has increased gradually while disc herniation surgery decreases regarding yearly number of procedures. An added function to the register enables more complex prospective clinical studies to include register data together with data suitable for the individual study. A common core set of demographic, surgical and outcome parameters would enable comparisons of clinical studies within and between nations
A review of RCTs in four medical journals to assess the use of imputation to overcome missing data in quality of life outcomes
Background: Randomised controlled trials (RCTs) are perceived as the gold-standard method for evaluating healthcare interventions, and increasingly include quality of life (QoL) measures. The observed results are susceptible to bias if a substantial proportion of outcome data are missing. The review aimed to determine whether imputation was used to deal with missing QoL outcomes. Methods: A random selection of 285 RCTs published during 2005/6 in the British Medical Journal, Lancet, New England Journal of Medicine and Journal of American Medical Association were identified. Results: QoL outcomes were reported in 61 (21%) trials. Six (10%) reported having no missing data, 20 (33%) reported ≤ 10% missing, eleven (18%) 11%–20% missing, and eleven (18%) reported >20% missing. Missingness was unclear in 13 (21%). Missing data were imputed in 19 (31%) of the 61 trials. Imputation was part of the primary analysis in 13 trials, but a sensitivity analysis in six. Last value carried forward was used in 12 trials and multiple imputation in two. Following imputation, the most common analysis method was analysis of covariance (10 trials). Conclusion: The majority of studies did not impute missing data and carried out a complete-case analysis. For those studies that did impute missing data, researchers tended to prefer simpler methods of imputation, despite more sophisticated methods being available.The Health Services Research Unit is funded by the Chief Scientist Office of the Scottish Government Health Directorate. Shona Fielding is also currently funded by the Chief Scientist Office on a Research Training Fellowship (CZF/1/31)
Mobility of thorium ions in liquid xenon
We present a measurement of the Th ion mobility in LXe at 163.0 K and
0.9 bar. The result obtained, 0.2400.011 (stat) 0.011 (syst)
cm/(kV-s), is compared with a popular model of ion transport.Comment: 6.5 pages,
A review of RCTs in four medical journals to assess the use of imputation to overcome missing data in quality of life outcomes
Peer reviewedPublisher PD
Observation of single collisionally cooled trapped ions in a buffer gas
Individual Ba ions are trapped in a gas-filled linear ion trap and observed
with a high signal-to-noise ratio by resonance fluorescence. Single-ion storage
times of ~5 min (~1 min) are achieved using He (Ar) as a buffer gas at
pressures in the range 8e-5 - 4e-3 torr. Trap dynamics in buffer gases are
experimentally studied in the simple case of single ions. In particular, the
cooling effects of light gases such as He and Ar and the destabilizing
properties of heavier gases such as Xe are studied. A simple model is offered
to explain the observed phenomenology.Comment: 5 pages, 4 figures, accepted for publication in Phys. Rev. A. Minor
text and figure change
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