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Source: Teaching Stats Circle: Feb 21, 2008, A

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Area/lipid of bilayers from NMR.: Biophys J, Vol. 64, No. 5. (May 1993), pp. 1476-1481.Valu es of area per lipid A ranging from 56 to 72 A 2 have been reported from essentially the same SCD data from DPPC in the L alpha phase. The differences are due primarily to three separate binary choices in interpretation . It is argued that one particular combination is best; this yields A = 62 +/- 2 A 2 for DPPC at 50 degrees C. Each preceding interpretation agrees with at least one of the three present choices and disagrees with at least one.

Source: Biophys J, Vol. 64, No. 5. (May 1993), pp. 1476-1481.
On the calculation of the topographic wetness index: evaluation of different methods based on field observations: Hydrology and Earth System Sciences, Vol. 10 (February 2006), pp. 101-112.The topographic wetness index (TWI, ln(a/tanbeta)) , which combines local upslope contributing area and slope, is commonly used to quantify topographic control on hydrological processes. Methods of computing this index differ primarily in the way the upslope contributing area is calculated. In this study we compared a number of calculation methods for TWI and evaluated them in terms of their correlation with the following measured variables: vascular plant species richness, soil pH, groundwater level, soil moisture, and a constructed wetness degree. The TWI was calculated by varying six parameters affecting the distribution of accumulated area among downslope cells and by varying the way the slope was calculated. All possible combinations of these parameters were calculated for two separate boreal forest sites in northern Sweden. We did not find a calculation method that performed best for all measured variables; rather the best methods seemed to be variable and site specific. However, we were able to identify some general characteristic s of the best methods for different groups of measured variables. The results provide guiding principles for choosing the best method for estimating species richness, soil pH, groundwater level, and soil moisture by the TWI derived from digital elevation models.

Source: Hydrology and Earth System Sciences, Vol. 10 (February 2006), pp. 101-112.
Recent progress of avalanche photodiodes in high-resolutio n X-rays and Gamma-rays detection: (17 Feb 2006)We have studied the performance of large area avalanche photodiodes (APDs) recently developed by Hamamatsu Photonics K.K, in high-resolutio n X-rays and Gamma-rays detections. We show that reach-through APD can be an excellent soft X-ray detector operating at room temperature or moderately cooled environment. We obtain the best energy resolution ever achieved with APDs, 6.4 % for 5.9 keV X-rays, and obtain the energy threshold as low as 0.5 keV measured at -20deg. Thanks to its fast timing response, signal carriers in the APD device are collected within a short time interval of 1.9 nsec (FWHM). This type of APDs can therefore be used as a low-energy, high-counting particle monitor onboard the forthcoming Pico-satellite Cute1.7. As a scintillation photon detector, reverse-type APDs have a good advantage of reducing the dark noise significantly. The best FWHM energy resolutions of 9.4+-0.3 % and 4.9+-0.2 % were obtained for 59.5 keV and 662 keV Gamma-rays, respectively, as measured with a CsI(Tl) crystal. Combination of APDs with various other scintillators (BGO, GSO, and YAP) also showed better results than that obtained with a photomultiplie r tube (PMT). These results suggest that APD could be a promising device for replacing traditional PMT usage in some applications. In particular 2-dim APD array, which we present in this paper, will be a promising device for a wide-band X-ray and Gamma-ray imaging detector in future space research and nuclear medicine.

Source: (17 Feb 2006)
Socioeconomic variations in the use of common surgical operations.: British medical journal (Clinical research ed.), Vol. 291, No. 6489. (20 July 1985), pp. 183-187.The surgical experience of a sample of people aged 40-64 randomly selected from general practice lists was elicited by means of a postal questionnaire and the results examined in relation to two indicators of socioeconomic status. Eighty per cent of the sample had had one or more surgical operations and women had a higher mean number of operations than men. Those in the more advantaged groups had a higher mean number of operations than those in the less advantaged groups. This difference was, however, mainly accounted for by operations carried out in childhood before the establishment of the National Health Service and by private sector surgery.

Source: British medical journal (Clinical research ed.), Vol. 291, No. 6489. (20 July 1985), pp. 183-187.
Small area analysis of surgery for low-back pain.: Spine, Vol. 17, No. 5. (May 1992), pp. 575-581.Rates of spine surgery (discectomy, laminectomy, fusion) vary several-fold among "small areas" such as counties or hospital market areas. To ascertain why this is so, an analysis was conducted of variability in rates among counties in the State of Washington (N = 39). Since, unlike previous published reports, this study excluded patients with cancer, major trauma, and infection, as well as those with cervical and thoracic procedures, rates in this study pertain specifically to the problem of low-back pain. Six classes of variables to explain variability among county rates were defined: I) percentage of the labor force in heavy labor and transportation occupations; II) socioeconomic conditions; III) neurologic and orthopedic surgeon density; IV) occupancy rate of back surgery hospitals; V) primary payer and VI) health care availability. In all, the effect of 28 explanatory variables was tested. In doing so, the authors took into account the possibility of spurious correlation. The rate of surgery for low-back pain varied nearly 15-fold among counties. The explanatory variables that were tested, however, accounted for only a minor part of the variability. The hypothesis that "physician practice style factor" accounts for the major part is explored; potential properties of practice style factor are specified for further testing.

Source: Spine, Vol. 17, No. 5. (May 1992), pp. 575-581.
Multilevel and Clustering Analysis of Health Outcomes in Small Areas: European Journal of Population/Rev ue européenne de Démographie, Vol. 13, No. 4. (1 December 1997), pp. 305-338.This paper considers models of the variable incidence of health outcomes in geographical areas and of variable regression effects of socio-economic variables on such outcomes. It adopts a Bayesian approach to variation in relative risk and regression effects, and assesses different prior specifications of risk (e.g. a latent class structure versus a spatially correlated structure). Implications are considered for smoothing and mapping rare health outcomes. The analysis is for electoral wards in London, with the health-depriva tion link forming the focus for regression effects. Implications for inferences about risk factors and for health-need ratings (before and after smoothing) are also considered.

Source: European Journal of Population/Revue européenne de Démographie, Vol. 13, No. 4. (1 December 1997), pp. 305-338.
Exploring the spatial pattern in hospital admissions: Health Policy, Vol. In Press, Corrected ProofThe determinants for the number of inpatient hospital admissions across Danish municipalities are analysed using balanced panel data from the period 1998-2004. The determinants include socio-demograp hic variables, home help service, residential homes capacity, proxy variables for morbidity, utilisation of primary care services, accessibility of hospitals and a number of other factors. Panel effects in the form of intra-municipa l correlation and heterogeneity across years are controlled for. Spatial spillover effects across municipalities will be investigated in order to disclose the spatial dynamics of hospital admissions. Reverse causalities among the number of hospital admissions and certain health systems characteristic s are further controlled for. The results are shown to be highly sensitive to such adjustments, as the effects of determinants - including those over which the municipalities exert some control - are seriously overestimated if such features are ignored.

Source: Health Policy, Vol. In Press, Corrected Proof
Small area variation analysis. Methods for comparing several diagnosis-rela ted groups.: Med Care, Vol. 31, No. 5 Suppl. (May 1993)In small-area variation analysis, the variation of health care utilization rates, e.g., admission rates, among small areas is calculated. Frequently, the variation of one diagnosis, diagnosis-rela ted group (DRG), or procedure is compared with the variation of another. Unfortunately, the methods generally used to make these comparisons are not consistent. They differ on whether they 1) adjust for the prevalence of the DRGs, 2) distinguish between variation among areas and variation within areas, 3) weight all areas equally, and 4) adjust for multiple admissions per person. None has an associated confidence interval. These discrepancies occur in part because there is no statistical model of small area variation. Without such a model, it is not known how to measure variation, and thus, it is not known how to compare different DRGs. Here, the authors use data on 473 DRGs from 28 counties in Washington state to study the nature of variability. The variation was higher for the more prevalent DRGs, suggesting that adjusting for prevalence may be reasonable. The true coefficient of variation appears to be a "natural" measure of variation, but the usual small area variation statistics do not provide good estimates of the true coefficient of variation. A new estimate is proposed that can be used to compare and test the variability of several DRGs.

Source: Med Care, Vol. 31, No. 5 Suppl. (May 1993)
Seasonal variation in orthopedic health services utilization in Switzerland: the impact of winter sport tourism.: BMC Health Serv Res, Vol. 6 (2006)BACKGROU ND: Climate- or holiday-relate d seasonality in hospital admission rates is well known for many diseases. However, little research has addressed the impact of tourism on seasonality in admission rates. We therefore investigated the influence of tourism on emergency admission rates in Switzerland, where winter and summer leisure sport activities in large mountain regions can generate orthopedic injuries. METHODS: Using small area analysis, orthopedic hospital service areas (HSAo) were evaluated for seasonality in emergency admission rates. Winter sport areas were defined using guest bed accommodation rate patterns of guest houses and hotels located above 1000 meters altitude that show clear winter and summer peak seasons. Emergency admissions (years 2000-2002, n = 135'460) of local and nonlocal HSAo residents were evaluated. HSAo were grouped according to their area type (regular or winter sport area) and monthly analyses of admission rates were performed. RESULTS: Of HSAo within the defined winter sport areas 70.8% show a seasonal, summer-winter peak hospital admission rate pattern and only 1 HSAo outside the defined winter sport areas shows such a pattern. Seasonal hospital admission rates in HSAo in winter sport areas can be up to 4 times higher in winter than the intermediate seasons, and they are almost entirely due to admissions of nonlocal residents. These nonlocal residents are in general -and especially in winter- younger than local residents, and nonlocal residents have a shorter length of stay in winter sport than in regular areas. The overall geographic distribution of nonlocal residents admitted for emergencies shows highest rates during the winter as well as the summer in the winter sport areas. CONCLUSION: Small area analysis using orthopedic hospital service areas is a reliable method for the evaluation of seasonality in hospital admission rates. In Switzerland, HSAo defined as winter sport areas show a clear seasonal fluctuation in admission rates of only nonlocal residents, whereas HSAo defined as regular, non-winter sport areas do not show such seasonality. We conclude that leisure sport, and especially ski/snowboard tourism demands great flexibility in hospital beds, staff and resource planning in these areas.

Source: BMC Health Serv Res, Vol. 6 (2006)
Small area variations in health related behaviours; do these depend on the behaviour itself, its measurement, or on personal characteristic s?: Health & place, Vol. 6, No. 4. (December 2000), pp. 261-274.In this paper we examine the patterning, by small areas, of four health related behaviours (smoking, alcohol consumption, diet, and exercise) in the West of Scotland, after controlling for a range of individual/hou sehold characteristic s, using multilevel models. Smoking and drinking were measured both as binary and as continuous variables, and diet and exercise were each measured in two ways: 'good' (health promoting) and 'bad' (health damaging). 'Area effects' (unattributed variation by post code sector) were found for 'bad' diet only. 'Good' and 'bad' diet, 'bad' exercise patterns and current smoking were associated with postcode sector deprivation. For 'bad' diet this effect was found only for individuals in more affluent households, and for 'good' exercise and current smoking the association with area deprivation differed between adolescents and adults. We conclude that the influence of area on health related behaviours varies according to the behaviour and the way it is measured, and that the influence of area deprivation and/or of area can vary by age and household deprivation.

Source: Health & place, Vol. 6, No. 4. (December 2000), pp. 261-274.

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