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1.  Comparison of Pressurized Liquid Extraction and Matrix Solid Phase Dispersion for the Measurement of Semi-Volatile Organic Compound Accumulation in Tadpoles 
Analytical methods capable of trace measurement of semi-volatile organic compounds (SOCs) are necessary to assess the exposure of tadpoles to contaminants as a result of long-range and regional atmospheric transport and deposition. The following study compares the results of two analytical methods, one using pressurized liquid extraction (PLE) and the other using matrix solid phase dispersion (MSPD), for the trace measurement of over 70 SOCs, including current-use pesticides, in tadpole tissue. The MSPD method resulted in improved SOC recoveries and precision compared to the PLE method. The MSPD method also required less time, consumed less solvent, and resulted in the measurement of a greater number of SOCs than the PLE method.
PMCID: PMC4153355  PMID: 19432502
tadpoles; semi-volatile organic compounds; pesticides; pressurized liquid extraction; matrix phase solid dispersion
2.  Spatial Patterns of Atmospherically Deposited Organic Contaminants at High-Elevation in the Southern Sierra Nevada Mountains, California, USA 
Atmospherically deposited contaminants in the Sierra Nevada mountains of California, USA have been implicated as adversely affecting amphibians and fish, yet little is known about the distributions of contaminants within the mountains, particularly at high elevation. We tested the hypothesis that contaminant concentrations in a high-elevation portion of the Sierra Nevada decrease with distance from the adjacent San Joaquin Valley. We sampled air, sediment, and tadpoles twice at 28 water bodies in 14 dispersed areas in Sequoia and Kings Canyon National Parks (2785 – 3375 m elevation; 43 – 82 km from Valley edge). We detected up to 15 chemicals frequently in sediment and tadpoles, including current- and historic-use pesticides, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons. Only β-endosulfan was found frequently in air. Concentrations of all chemicals detected were very low, averaging in the parts-per-billion range or less in sediment and tadpoles, and on the order of 10 pg/m3 for β-endosulfan in air. Principal components analysis indicated that chemical compositions were generally similar among sites, suggesting that chemical transport patterns were likewise similar among sites. In contrast, transport processes did not appear to strongly influence concentration differences among sites because variation in concentrations among nearby sites was high relative to sites far from each other. Moreover, a general relationship for concentrations as a function of distance from the valley was not evident across chemical, medium, and time. Nevertheless, concentrations for some chemical/medium/time combinations showed significant negative relationships with metrics for distance from the Valley. However, the magnitude of these distance effects among high-elevation sites was small relative to differences found in other studies between the valley edge and the nearest high-elevation sites.
PMCID: PMC3104601  PMID: 20821540
Amphibian; Polycyclic aromatic hydrocarbon; Polychlorinated biphenyl; Pesticide; Tadpole
3.  Attitudes towards screening for lung cancer among smokers and their non‐smoking counterparts 
Thorax  2006;62(2):126-130.
There has been resurgence of interest in lung cancer screening using low‐dose computed tomography. The implications of directing a screening programme at smokers has been little explored.
A nationwide telephone survey was conducted. Demographics, certain clinical characteristics and attitudes about screening for lung cancer were ascertained. Responses of current, former and never smokers were compared.
2001 people from the US were interviewed. Smokers were significantly (p<0.05) more likely than never smokers to be male, non‐white, less educated, and to report poor health status or having had cancer, and less likely to be able to identify a usual source of healthcare. Compared with never smokers, current smokers were less likely to believe that early detection would result in a good chance of survival (p<0.05). Smokers were less likely to be willing to consider computed tomography screening for lung cancer (71.2% (current smokers) v 87.6% (never smokers) odds ratio (OR) 0.48; 95% confidence interval (CI) 0.32 to 0.71). More never smokers as opposed to current smokers believed that the risk of disease (88% v 56%) and the accuracy of the test (92% v 71%) were important determinants in deciding whether to be screened (p<0.05). Only half of the current smokers would opt for surgery for a screen‐diagnosed cancer.
The findings suggest that there may be substantial obstacles to the successful implementation of a mass‐screening programme for lung cancer that will target cigarette smokers.
PMCID: PMC2111262  PMID: 17101739
4.  Umbrella test 
BMJ : British Medical Journal  2007;334(7584):58.
PMCID: PMC1767282  PMID: 17218677
5.  The instant axis of rotation influences facet forces at L5/S1 during flexion/extension and lateral bending 
European Spine Journal  2005;15(3):299-307.
Because the disc and facets work together to constrain spinal kinematics, changes in the instant axis of rotation associated with disc degeneration or disc replacement may adversely influence risk for facet overloading and arthritis. The relationships between L5/S1 segmental kinematics and facet forces are not well defined, since previous studies have separated investigations of spinal motion and facet force. The goal of this cadaveric biomechanical study was to report and correlate a measure of intervertebral kinematics (the centrode, or the path of the instant axis of rotation) and the facet forces at the L5/S1 motion segment while under a physiologic combination of compression and anterior shear loading. Twelve fresh-frozen human cadaveric L5/S1 joints (age range 50–64 years) were tested biomechanically under semi-constrained conditions by applying compression plus shear forces in several postures: neutral, and 3° and 6° of flexion, extension and lateral bending. The experimental boundary conditions imposed compression and shear representative of in vivo conditions during upright stance. The 3-D instantaneous axis of rotation (IAR) was calculated between two consecutive postures. The facet joint force was simultaneously measured using thin-film sensors placed between both facet surfaces. Variations of IAR location and facet force during motion were analyzed. During flexion and extension, the IAR was oriented laterally. The IAR intersection with the mid-sagittal plane moved cephalad relative to S1 endplate during flexion (P=0.010), and posterior during extension (P=0.001). The facet force did not correlate with posture (P=0.844). However, changes in the facet force between postures did correlate with IAR position: higher IAR’s during flexion correlated with lower facet forces and vice versa (P=0.04). During lateral bending, the IAR was oblique relative to the main plane of motion and translated parallel to S1 endplate, toward the side of the bending. Overall, the facet force was increased on the ipsilateral side of bending (P=0.002). The IAR positions demonstrate that the L5 vertebral body primarily rotates forward during flexion (IAR close to vertebral body center) and rotates/translates backward during extension (IAR at or below the L5/S1 intervertebral disc). In lateral bending, the IAR obliquity demonstrated coupling with axial torsion due to resistance of the ipsilateral facet.
PMCID: PMC3489304  PMID: 16175392
Human; Lumbosacral joint; Spine biomechanics; Instantaneous axis of rotation; Facet force
6.  Clinical applications of bone graft substitutes in spine surgery: consideration of mineralized and demineralized preparations and growth factor supplementation 
European Spine Journal  2001;10(Suppl 2):S169-S177.
Bone graft substitutes may be broadly classified as mineralized and demineralized preparations. This article reviews the basic science and biology underlying each preparation. A review of the clinical and experimental applications of each preparation follows. The text concludes with a review of growth factors as biological supplements.
PMCID: PMC3611549  PMID: 11716015
Allograft Demineralized bone matrix Ceramics Growth factors Spinal fusion
7.  A Method to Report Utilization for Quality Initiatives in Medical Facilities 
The Ochsner Journal  2001;3(4):200-206.
Objective: We undertook this project to outline a methodology for quantifying aggregate health care utilization of medical “technologies” that could be rank ordered by volume. The identification of specific high-volume technologies could guide future efforts for quality initiatives such as program planning, preventive services implementation, quality improvement activities, and innovative and cost-effective technology development. Design: This study utilized a retrospective cross-sectional study design. Methods: We generated combined ranks for the top 200 high-volume procedures from three data sources that incorporated in- and outpatient procedures. Data were collected using primarily ICD-9 and CPT-4 codes; all codes were translated into CPT-4 codes and collapsed into categories using truncated three-digit CPT-4 codes. Frequencies for each collapsed code were determined with each dataset; procedures were reranked based on the mean rank of the three sources. Main Outcome Measures: We itemized the individual procedure codes making up each of the top 20 categories and reported the unique codes making up at least 80% of the procedure code category. Results: The top five procedure categories identified in this study were patient visits (inpatient and outpatient), chest x-rays, mammograms, ophthalmological services, and electrocardiograms. Conclusion: The methodology described provides a new way to combine and concisely report on utilization of procedures that is relevant to data obtained from different sources. This methodology may be of potential benefit to health care administrators, technology developers, and other planners as they contemplate ways to identify quality and technology development initiatives that can have a broad impact on populations served by health care organizations.
PMCID: PMC3116746  PMID: 21765738

Results 1-10 (10)