Understanding the Role of Personal, Psychosocial and Occupational Factors and their Interactions on Low Back Pain Severity in Workers

Low back pain (LBP) is the most prevalent work-related musculoskeletal disorder. Occupational risk factors have been studied for current ergonomic prevention strategies; however, other underlying mechanisms may exist since not all workers performing the same task develop the same severity. Previous research has identified personal and psychosocial risk factors that also contribute to LBP. Research quantifying the interactive effects of the various personal, psychosocial and occupational factors is limited, along with research on the effect of risk factor combinations on LBP severity. The objectives of this study were to: 1) study the various factors that are known to be involved in low back pain and analyze interactions, and 2) develop a model to predict low back pain and validate it. In order to address these objectives, 2 studies were conducted. The first study investigated the effects of various personal, genetic, occupational and psychosocial factors on two subjective LBP severity ratings: Oswestry Disability Index (ODI) and a Visual Analog Scale (VAS), and three physician-based ratings: MRI severity, canal stenosis and nerve impingement. Personal and psychosocial factors, in addition to occupational factors, were found to significantly affect the severity ratings. The second study involved building predictive models of LBP severity for each risk factor category as well as a combined risk factor model. Results showed that the combined risk factor models considering interaction effects both within and across risk factor categories were significantly better in predicting severity ratings than the individual models. However, validation conducted using 5 random samples showed inconsistent accuracies. Results obtained may help to develop a more reliable way to predict and, hence, prevent chronic LBP

Least squares approximations of measures via geometric condition numbers

For a probability measure on a real separable Hilbert space, we are interested in "volume-based" approximations of the d-dimensional least squares error of it, i.e., least squares error with respect to a best fit d-dimensional affine subspace. Such approximations are given by averaging real-valued multivariate functions which are typically scalings of squared (d+1)-volumes of (d+1)-simplices. Specifically, we show that such averages are comparable to the square of the d-dimensional least squares error of that measure, where the comparison depends on a simple quantitative geometric property of it. This result is a higher dimensional generalization of the elementary fact that the double integral of the squared distances between points is proportional to the variance of measure. We relate our work to two recent algorithms, one for clustering affine subspaces and the other for Monte-Carlo SVD based on volume sampling

Understanding the Role of Personal, Psychosocial and Occupational Factors and their Interactions on Low Back Pain Severity in Workers

Low back pain (LBP) is the most prevalent work-related musculoskeletal disorder. Occupational risk factors have been studied for current ergonomic prevention strategies; however, other underlying mechanisms may exist since not all workers performing the same task develop the same severity. Previous research has identified personal and psychosocial risk factors that also contribute to LBP. Research quantifying the interactive effects of the various personal, psychosocial and occupational factors is limited, along with research on the effect of risk factor combinations on LBP severity. The objectives of this study were to: 1) study the various factors that are known to be involved in low back pain and analyze interactions, and 2) develop a model to predict low back pain and validate it. In order to address these objectives, 2 studies were conducted. The first study investigated the effects of various personal, genetic, occupational and psychosocial factors on two subjective LBP severity ratings: Oswestry Disability Index (ODI) and a Visual Analog Scale (VAS), and three physician-based ratings: MRI severity, canal stenosis and nerve impingement. Personal and psychosocial factors, in addition to occupational factors, were found to significantly affect the severity ratings. The second study involved building predictive models of LBP severity for each risk factor category as well as a combined risk factor model. Results showed that the combined risk factor models considering interaction effects both within and across risk factor categories were significantly better in predicting severity ratings than the individual models. However, validation conducted using 5 random samples showed inconsistent accuracies. Results obtained may help to develop a more reliable way to predict and, hence, prevent chronic LBP

Serum uric acid as a prognostic indicator in acute ischemic stroke

Background: Association between serum uric acid (SUA) and the outcome of acute ischemic stroke is debated and needs to be evaluated. The present study was conducted to study the serum uric acid concentration as an indicator of   outcome among acute ischaemic stroke and to determine the role of serum uric acid as a risk factor for acute ischemic stroke.Methods: An observational study where 50 patients who presented within 48 hours of onset of stroke admitted to medical wards of government general Hospital Guntur were selected for the study.Results: Out of 50 patients included for the study, 6 belonged to the age group of 30-40 years. Majority were male (66%) and 44.5% of the males and 76.5% of females showed raised serum uric acid levels. 25 out of 50 patients were diabetic (i.e. 50%) Among them 16 had serum uric acid >6 mg% (ie.64%), 56% of the patients were hypertensive and among them 71% were found to have uric acid levels greater than 6mgs%, 38 out of 50 patients had bad outcome, with elevated uric acid levels found 30 among them. In the present study, BMI and outcome of Stroke were significantly associated with Serum Uric acid levels.Conclusions: Serum uric acid levels can be used as a prognostic indicator as a marker for increased risk of stroke. Elevated serum urate concentration may stratify risk of death after acute stroke

DRAINAGE BEHAVIOR OF AQUEOUS, POLYMERIC, AND OIL-BASED NITROGEN FOAMS: THEORETICAL AND EXPERIMENTAL INVESTIGATION

Foams can be formulated to have a wide range of densities and viscosities. This unique behavior makes foam suitable for underbalanced drilling where pressure exerted on formation is maintained below pore pressure and at the same time, favorable conditions for a good hole-cleaning can be established in the wellbore. Foams are also used as in fracturing, cementing, and, enhanced oil recovery applications. However, the disadvantage of foam is its inherent instability. The stability of aqueous foams in vertical conduits has been extensively investigated. However, in many industrial applications such as underbalanced drilling foam is used in inclined configurations. The stability of foams inclined conduits is not well understood. The effect of geometry is often ignored. In addition, polymer-based and non-aqueous foams with more complex flow and stability behavior are becoming more common. As a result, there is a strong need to investigate foams to better understand the effects of different operational factors (inclination, conduit geometry, base fluid type, and shearing) on their stability. Thus, the main goal of this study is to investigate each of these factors with respect to their impact on foam stability. To achieve this, foam stability experiments were conducted in concentric annulus and straight pipe sections. The pipe section is manufactured from a fully transparent PVC pipe, enabling visual inspection of foam structure and liquid drainage. The annulus is made of stainless steel casing and a rotating inner PTFE (polytetrafluoroethylene) rod. Three types of foams (aqueous, polymeric-based and oil-based foams) were used in the investigation. All tests were performed at 400 KPa and ambient temperature (22 ± 2oC). Foam quality was ranged from 40 - 80%, except for oil-based foam which was limited to 70% due to instability at high qualities. Foam rheology data was obtained from pipe viscometers before conducting stability tests. Two inclination angles (0o and 30o) were considered in this study. For tests conducted in the annulus, the rotation speed of the inner rod was varied (0, 4, and 7 rpm) to examine the impact of shearing on foam stability. Hydrostatic pressure data measured from the annular test section is converted into density profiles, which are used to determine the drained liquid volume as a function of time. In straight pipe sections, the volume of drained liquid was measured using a measuring tape. A digital camera with a microscope was used to capture images of foam in real-time to examine the process of foam decay (i.e. the degree of bubble coarsening and coalescence). Foam stability increased with quality. For a given quality, foam prepared with polymeric fluid was the most stable, while oil-based foam was the least. The wall effects can hinder bubble and drained liquid motion and consequently delay drainage. As a result, foam drained more slowly in the annulus than in pipe. Inclining the test sections resulted in much faster drainage, possibly due to the formation of a liquid layer between foam structure and container walls that flows down due to gravity, effectively avoiding the hydraulic flow resistance of foam structure. The effect of shearing on drainage was minimal for the level of shear rate applied. Channel-dominated model developed in this study is suitable for all foams considered (40-80%). Node-dominated model is not recommended for these wet foams as it tends to over predict liquid volume fractions at early time steps

Synergistic interactions of xanthan and guar gum polymers

Polymers such as xanthan and guar gum are widely used in the oilfield and food industry as viscosifiers. In hydraulic fracturing operation, guar gum polymer solution is used as fracturing fluid to create fracture in a target zone that contains hydrocarbon. Fracturing fluid viscosity helps transport propppant down the well and into the fracture. If the fluid is not viscous enough, the proppant is deposited at the mouth of the fracture and fracture closes. However, high concentration of polymer in the fluid leads to gel damage in the fracture and reduces its conductivity.Poor fracture conductivity could lead to expensive re-fracturing operation or abandonment. One way to avoid gel damage/polymer residue problem is to use surfactant or surfactant based fluid. These fluids form micelles that are similar to polymer structure and, thereby, increase the viscosity. This micelle structure breaks down when it comes in contact with hydrocarbon. However, surfactant based fluids arc expensive and can form emulsion. The trend in the oil industry is to reduce the polymer content in the fracturing fluid and to crosslink it. Crosslinking is nece sary so as to increase the viscosity of the low polymer concentration linear gel. Despite these measures, gel damage to fracture conductivity is a concern and affects productivity or a well.Blends of xanthan and guar gum are used in the food industry to prepare fluids that have superior viscosity then either parent polymer. This synergy between these polymers can be used to prepare new fracturing fluids that have desirable viscosity at low polymer concentration, thereby, solving the problem of proppant placement and fracture conductivity. In addition, prepared fluids would be cheaper than high concentration guar gum fluids as they require addition of less polymer.In this study, the effect of polymer concentration, ratio of xanthan to guar polymer, and temperature on the synergy of xanthan and guar gum polymers is investigated. Particle settling behavior in these complex fluids under static conditions has been studied as well. Results show that increase in polymer concentration increases the strength of synergistic interaction while increase in temperature decreases it. Based on the results a 40 lbm/ Mgal guar gum/xanthan fluid blend was identified as a suitable fracturing fluid. This blend showed better viscosities at low shear rates than both 40 and 60 lbm/Mgal guar gum fluids. In addition, it is less expensive than 60 lbm/Mgal guar gum fluid

A Multi-View Extension of the ICP algorithm

ABSTRACT Although the Iterative Closest Point (ICP) algorithm has been an extremely popular method for 3D points or surface registration, it can only be applied to two point sets at a time. By only registering two scans at a time, ICP fails to exploit the redundant information available in multiple scans that have overlapping regions. In this paper, we present a multi-view extension of the ICP algorithm by a method that simultaneously averages the redundant information available in the scans with overlapping regions. Variants of this method that carry out such simultaneous registration in a causal manner and that utilise the transitive property of point correspondences are also presented. The improved accuracy of this motion averaged approach in comparison with ICP and some multi-view methods is established through multiple tests. We also present results of our method applied to some well-known real datasets