Construction of Statistical Models

Bariatric surgery is an effective treatment for weight loss, but the patient's ability to reach a sustained weight loss depends upon several technical and individual factors. Creating an easy model that adapts bariatric surgery's weight loss goals for each patient is very important for pre-surgery and follow-up evaluations.

Single nucleotide polymorphisms (SNP) may be genotyped for use in case-control designs to test for association between a SNP marker and a disease using a 2 x 3 chi-squared test of independence. Genotyping is often based on underlying continuous measurements, ...

Proteases are shown to have greener mode of application in leather processing for dehairing of goat skins and cow hides. Production of protease by submerged fermentation with potent activity is reported using a new isolate P. aeruginosa MTCC 10501. The production parameters were optimized by statistical methods such as Plackett-Burman and response surface methodology. The optimized production medium contained (g/L); tryptone, 2.5; yeast extract, 3.0; skim milk 30.0; dextrose 1.0; inoculum concentration 4%: initial pH 6.0; incubation temperature 30 degrees C and optimum production at 48 h with protease activity of 7.6 U/mL. The protease had the following characteristics: pH optima, 9.0; temperature optima 50 degrees C; pH stability between 5.0-10.0 and temperature stability between 10-40 degrees C. The protease was observed to have high potential for dehairing of goat skins in the pre- tanning process comparable to that of the chemical process as evidenced by histology. The method of...

It is not widely appreciated that many subtleties are involved in the accurate measurement of intensity-correlated photons; even for the original experiments of Hanbury Brown and Twiss (HBT). Using a monolithic 4x4 array of single-photon avalanche diodes (SPADs), together with an off-chip algorithm for processing streaming data, we investigate the difficulties of measuring second-order photon correlations g2 in a wide variety of light fields that exhibit dramatically different correlation statistics: a multimode He-Ne laser, an incoherent intensity-modulated lamp-light source and a thermal light source. Our off-chip algorithm treats multiple photon-arrivals at pixel-array pairs, in any observation interval, with photon fluxes limited by detector saturation, in such a way that a correctly normalized g2 function is guaranteed. The impact of detector background correlations between SPAD pixels and afterpulsing effects on second-order coherence measurements is discussed. These results d...

A rapid, simple, and selective method was developed for the determination of etodolac. The method depends on complexation of etodolac with copper (II) acetate and iron (III) chloride followed by extraction of complexes with dichloromethane and then measuring the extracted ...

Genes that control circadian rhythms in organisms have been recognized, but have been difficult to detect because circadian behavior comprises periodically dynamic traits and is sensitive to environmental changes. We present a statistical model for mapping and characterizing specific genes or quantitative trait loci (QTL) that affect variations in rhythmic responses. This model integrates a system of differential equations into the framework for functional mapping, allowing hypotheses about the interplay between genetic actions and periodic rhythms to be tested. A simulation approach based on sustained circadian oscillations of the clock proteins and their mRNAs has been designed to test the statistical properties of the model. The model has significant implications for probing the molecular genetic mechanism of rhythmic oscillations through the detection of the clock QTL throughout the genome.

In this paper, we develop a simple diagnostic test for the random-effects distribution in mixed models. The test is based on the gradient function, a graphical tool proposed by Verbeke and Molenberghs to check the impact of assumptions about the random-effects distribution in mixed models on inferences. Inference is conducted through the bootstrap. The proposed test is easy to implement and applicable in a general class of mixed models. The operating characteristics of the test are evaluated in a simulation study, and the method is further illustrated using two real data analyses.

Credit scoring can be defined as a technique that helps credit providers decide whether to grant credit to consumers or customers.  Its increasing importance can be seen from the growing popularity and application of credit scoring in consumer credit.  There are advantages not only to construct effective credit scoring models to help improve the bottom-line of credit providers, but also to combine models to yield a better performing combined model.  This paper has two objectives.  First, it illustrates the use of data mining techniques to construct credit scoring models.  Second, it illustrates the combination of credit scoring models to give a superior final model.  The paper also highlights the prerequisites and limitations of the data mining approach.

Common radiological measures of osteoarthritis (OA) relate poorly to symptoms as experienced by patients. We created a statistical model of shape and density to see if Dual Energy X-ray (DXA) images of the hip contain symptom-related information that is not captured by common radiological measures. DXA images of the hip were made in a prospective study of patients that met the American College of Rheumatology (ACR) criteria for hip OA. From the DXA scans, we constructed a statistical model of the appearance (shape combined with density) of the proximal femur of left and right side. The model yields a number of independent descriptors of the appearance (modes) which we related to various measures of radiological and clinical OA. These outcome measures were defined using Joint Space Width (JSW), Kellgren and Lawrence (K-L) scores, Visual Analogue Scale (VAS) and Western Ontario MacMaster Universities (WOMAC) pain scores and a self-reported global assessment score. Various modes showed...

The interplay of psychotic and affective symptoms is a crucial challenge in understanding the pathogenesis of psychosis. In this study, we analyzed the interplay between two subclinical psychosis symptoms dimensions, and one depression symptoms dimension, using longitudinal data from Zurich. The Zurich study started in 1979 with a representative sample of 591 participants who were aged 20/21. Follow-up interviews were

Despite progress in improving health outcomes in Afghanistan by contracting public health services through non-governmental organizations (NGOs), inequity in access persists between the poor and non-poor. This study examined the distributive effect of different contracting types on primary health services provision between the poor and non-poor in rural Afghanistan. Contracts to NGOs were made to deliver a common set of primary care services in each province, with the funding agencies determining contract terms. The contracting approaches could be classified into three contracting out types (CO-1, CO-2 and CO-3) and a contracting-in (CI) approach based on the contract terms, design and implementation. Exit interviews of patients attending randomly sampled primary health facilities were collected through systematic sampling across 28 provinces at two time points. The outcome, the odds that a client attending a health facility is poor, was modelled using logistic regression with a rob...

The Boston brace has been shown to efficiently prevent scoliosis curve progression. However, it rarely achieves complete 3-D correction; its adjustment being often empirical and its biomechanical modes of action still remaining poorly understood. This study investigates the in-brace spinal shape (correction) in relationship with the patient's out-of-brace deformation, and the adjustment parameters of the brace, namely the strap tensions and the equivalent forces calculated at the patient-brace interface. Many of the observed relationships illustrate the fact that the in-brace spinal shape is strongly related to the characteristics of the patient's out-of-brace deformation. The pattern of pressure distribution as described by the equivalent forces computed in the thoracic, lumbar, pelvic and sternal regions has important effect on the in-brace Cobb angles, lumbar lordosis, frontal and sagittal imbalances and the apical axial rotations. The complex role of the strap tension on...

The prevalence of schistosomiasis remains a key public health issue in China. Jiangling County in Hubei Province is a typical lake and marshland endemic area. The pattern analysis of schistosomiasis prevalence in Jiangling County is of significant importance for promoting schistosomiasis surveillance and control in the similar endemic areas. The dataset was constructed based on the annual schistosomiasis surveillance as well the socio-economic data in Jiangling County covering the years from 2009 to 2013. A village clustering method modified from the K-mean algorithm was used to identify different types of endemic villages. For these identified village clusters, a matrix-based predictive model was developed by means of exploring the one-step backward temporal correlation inference algorithm aiming to estimate the predicative correlations of schistosomiasis prevalence among different years. Field sampling of faeces from domestic animals, as an indicator of potential schistosomiasis p...

An extension of dosemeter issue period brings significant economic and logistic benefits. Therefore, it is desirable to have an extended period as long as possible without significant loss of the quality of dose measurements. There are many studies devoted to the investigation of fading or reduction of the dose accumulated in dosemeters with time. However, this is one of many critical factors that need's to be taken into account when extending the dosemeter issue period. Background radiation is also a critical factor that needs to be appropriately accounted. In this report, a new approach has been suggested for evaluating the effect of background radiation on the lower limit of detection (LLD) of occupational radiation dose. This approach is based on the data collected from control dosemeters that are routinely used for subtraction of background radiation from occupational dose measurements. The results show that for LiF:Mg,Cu,P thermoluminescence dosemeters, variations in background radiation have a higher impact on the LLD than dose fading and the absolute value of background radiation. Although there is no significant dose fading in LiF:Mg,Cu,P for a dosemeter issue period up to 1 y, variations in background radiation during this period of time can significantly increase photon LLDs (up to 700 microSv) for workers operating in an environment of variable radiation background.