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Search Results: 1 - 10 of 230841 matches for " Richard L Nelson "
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A survey of individual preference for colorectal cancer screening technique
Richard L Nelson, Alan Schwartz
BMC Cancer , 2004, DOI: 10.1186/1471-2407-4-76
Abstract: A cross-sectional survey was performed of healthy ambulatory adults in a pediatrics primary care office and neighboring church. Overall preference was ranked for each of four colorectal cancer screening modalities: Faecal Occult Blood, Fiberoptic Sigmoidoscopy, Barium Enema and Colonoscopy. Four additional domains of preference also were ranked: suspected discomfort, embarrassment, inconvenience and danger of each exam.80 surveys were analyzed, 57 of which were received from participants who had experienced none of the screening tests. Fecal Occult Blood Testing is significantly preferred over each other screening modality in overall preference and every domain of preference, among all subjects and those who had experienced none of the tests.Efforts to increase public participation in colorectal cancer screening may be more effective if undertaken in the context of public perceptions of screening choices.Screening for colorectal cancer lessens the risk of dying from that disease [1]. Knowledge of this fact has not solved all the problems related to screening. The optimal modality of screening is still the subject of debate [1-3]. More problematic is the very low participation of the general public in recommended screening [4]. In contrast to breast cancer screening, in which the Healthy People 2000 Goal of the U.S. National Institutes of Health was surpassed, at 64% participation by women over 40 years of age, only 20% of Americans over age 50 had fecal occult blood testing within the past year (This is the best estimate of actual screening, rather than diagnostic endeavors for symptoms for which endoscopy or radiologic imaging might be done.), and 34% had a sigmoidoscopy within the past 5 years [5,6] Even if screening is appropriately performed, it is far from certain that a positive screen will be followed by appropriate diagnostic testing, as has been shown in follow-up surveys of fecal occult blood testing [7].Most publication concerning colorectal cancer screen
Assessment of the usefulness of a diagnostic test: A survey of patient preference for diagnostic techniques in the evaluation of intestinal inflammation
Richard L Nelson, Alan Schwartz, Dan Pavel
BMC Medical Research Methodology , 2001, DOI: 10.1186/1471-2288-1-5
Abstract: Significant differences were seen in overall preference for white cell scan over barium enema and colonoscopy (p < 0.01) in both survey groups. Perceived discomfort and embarrassment demonstrated similar rankings.This patient preference combined with the reported accuracy of white cell scanning further establishes the usefulness of this means of IBD diagnosis.The radio labeled white cell scan has been shown to be an accurate means of detecting intestinal inflammation [1]. Our initial report of the use of Indium111 radiolabeled white cell scanning in the diagnosis of inflammatory bowel disease described a sensitivity and specificity of 97% and 100% respectively in 49 scans in 39 patients in all of whom confirmatory studies were done. Since that time, 1130 scans have been performed at our institution. Clinical follow-up of these patients has revealed only three cases of confirmed false negative scans. No cases of false positive scans have been encountered. This accuracy, it should be stressed, is not in the grading of disease activity, but in the dichotomous determination of disease presence and its anatomic location. The lack of confirmatory testing of all subsequent patients certainly results in the overestimation of accuracy [2], but not greatly so, since all patients have been available for clinical follow-up and diagnostic errors would become apparent with the passage of time. Even if it is a ten fold overestimate, the white cell scan still compares well with other diagnostic modalities. In 1993 Indium111 became unavailable in Chicago and we switched to the use of Technetium99. We found that the higher radiation dose of Technetium injected (20 mCI versus 0.5 mCI Indium) resulted in clearer images with less motion artifact, yet its shorter half life resulted in the total radiation dose to the patient being similar to Indium111. First images are available within 5 hours from the patient's arrival using Technetium, compared with 30 hours for Indium, making this appl
On the formation of planetary systems via oligarchic growth in thermally evolving viscous discs
Gavin A. L. Coleman,Richard P. Nelson
Physics , 2014, DOI: 10.1093/mnras/stu1715
Abstract: We present N-body simulations of planetary system formation in thermally-evolving, viscous disc models. The simulations incorporate type I migration (including corotation torques and their saturation), gap formation, type II migration, gas accretion onto planetary cores, and gas disc dispersal through photoevaporation. The aim is to examine whether or not the oligarchic growth scenario, when combined with self-consistent disc models and up-to-date prescriptions for disc-driven migration, can produce planetary systems similar to those that have been observed. The results correlate with the initial disc mass. Low mass discs form close-packed systems of terrestrial-mass planets and super-Earths. Higher mass discs form multiple generations of planets, with masses in the range 10 < mp < 45M_Earth. These planets generally type I migrate into the inner disc, because of corotation torque saturation, where they open gaps and type II migrate into the central star. Occasionally, a final generation of low-to-intermediate mass planets forms and survives due to gas disc dispersal. No surviving gas giants were formed in our simulations. Analysis shows that these planets can only survive migration if a core forms and experiences runaway gas accretion at orbital radii r > 10 au prior to the onset of type II migration. We conclude that planet growth above masses mp > 10M_Earth during the gas disc life time leads to corotation torque saturation and rapid inward migration, preventing the formation and survival of gas giants. This result is in contrast to the success in forming gas giant planets displayed by some population synthesis models. This discrepancy arises, in part, because the type II migration prescription adopted in the population synthesis models causes too large a reduction in the migration speed when in the planet dominated regime.
Bone mineral density and the subsequent risk of cancer in the NHANES I follow-up cohort
Richard L Nelson, Mary Turyk, Jane Kim, Victoria Persky
BMC Cancer , 2002, DOI: 10.1186/1471-2407-2-22
Abstract: Participants were members of the NHEFS cohort who had BMD measurement in 1974–1975. Age, race, and BMI adjusted rate ratios and 95% confidence intervals were calculated for incidence of cancers of the corpus uterus, breast, colorectum, prostate, and of osteoporosis and hip fracture related to baseline BMD.Data were available for 6046 individuals. One hundred cases of breast cancer, 94 prostate cancers, 115 colorectal cancers, 29 uterine cancers, 110 cases of hip fracture and 103 cases of osteoporosis were reported between 1974 and 1993. Hip fracture and osteoporosis were both significantly inversely associated with BMD. Uterine cancer was positively associated (p = 0.005, test for linear trend) and colorectal cancer negatively associated (p = 0.03) with BMD. No association was found between elevated BMD and incidence of breast cancer (p = 0.74) or prostate cancer (p = 0.37) in the overall cohort, although a weak association was seen between BMD and subsequent breast cancer incidence when BMD was measured in post-menopausal women (p = 0.04).The findings related to cancers of the uterus and colorectum as well as the weak association of BMD with breast cancer strengthen the use of BMD as a marker of estrogen exposure and cancer risk.Three recent reports, from the Study of Osteoporotic Fractures [1], Framingham [2], and the Fracture Intervention Trial [3] demonstrated a positive association between bone mineral density measurements (BMD) in women and subsequent onset of breast cancer. All of these reports were regarded as significant because estrogen has been thought to increase breast cancer risk [4] and BMD may be a more accurate measure of long term estrogen exposure than recall of hormone supplementation, measurements of endogenous estrogen, parity, or obesity [5,6].In the light of strong associations previously noted between estrogens and corpus uteri cancer, BMD should predict the occurrence of endometrial cancer [4], though this has not yet been directly assessed
Methicillin-Resistant Staphylococcus aureus Infection and Hospitalization in High-Risk Patients in the Year following Detection
Susan S. Huang, Virginia L. Hinrichsen, Rupak Datta, Laura Spurchise, Irina Miroshnik, Kimberly Nelson, Richard Platt
PLOS ONE , 2011, DOI: 10.1371/journal.pone.0024340
Abstract: Background Many studies have evaluated methicillin-resistant Staphylococcus aureus (MRSA) infections during single hospitalizations and subsequent readmissions to the same institution. None have assessed the comprehensive burden of MRSA infection in the period after hospital discharge while accounting for healthcare utilization across institutions. Methodology/Principal Findings We conducted a retrospective cohort study of adult patients insured by Harvard Pilgrim Health Care who were newly-detected to harbor MRSA between January 1991 and December 2003 at a tertiary care medical center. We evaluated all MRSA-attributable infections associated with hospitalization in the year following new detection, regardless of hospital location. Data were collected on comorbidities, healthcare utilization, mortality and MRSA outcomes. Of 591 newly-detected MRSA carriers, 23% were colonized and 77% were infected upon detection. In the year following detection, 196 (33%) patients developed 317 discrete and unrelated MRSA infections. The most common infections were pneumonia (34%), soft tissue (27%), and primary bloodstream (18%) infections. Infections occurred a median of 56 days post-detection. Of all infections, 26% involved bacteremia, and 17% caused MRSA-attributable death. During the admission where MRSA was newly-detected, 14% (82/576) developed subsequent infection. Of those surviving to discharge, 24% (114/482) developed post-discharge infections in the year following detection. Half (99/185, 54%) of post-discharge infections caused readmission, and most (104/185, 55%) occurred over 90 days post-discharge. Conclusions/Significance In high-risk tertiary care patients, newly-detected MRSA carriage confers large risks of infection and substantial attributable mortality in the year following acquisition. Most infections occur post-discharge, and 18% of infections associated with readmission occurred in hospitals other than the one where MRSA was newly-detected. Despite gains in reducing MRSA infections during hospitalization, the risk of MRSA infection among critically and chronically ill carriers persists after discharge and warrants targeted prevention strategies.
Developing independent investigators for clinical research relevant for Africa
Yukari C Manabe, Elly Katabira, Richard L Brough, Alex G Coutinho, Nelson Sewankambo, Concepta Merry
Health Research Policy and Systems , 2011, DOI: 10.1186/1478-4505-9-44
Abstract: Research capacity building has been highlighted as an important strategy to improving health, alleviating poverty, and achieving the Millennium Development Goals in developing countries [1]. It has been defined as, "an approach to the development of sustainable skills, organizational structure, resources and commitment to health improvement... to multiply health gains many times over"[2]. Definitions of research capacity building often make reference to individual and institutional development as part of the process of research capacity building. Sustainable capacity building in clinical research, defined as research with human subjects or samples from human subjects, will require the development of a supportive environment conducive to individual development [3,4]. The increasing number of medical research grants with funded capacity building components has highlighted the need for increasing clarity regarding graduate research training in Africa. Defining the goals and the existing gaps in expertise to achieve these goals should be a priority. Institutions in Africa should seize the existing funding opportunities to create harmonized programs with clear, uniform expectations, accountability, and mentoring to ensure the success of individual trainees across programs. Finally, systems to increase resources and opportunities for students should be created at all levels to fill the pipeline with the quality, depth and number of trainees who can research medical questions relevant to sub-Saharan Africa (SSA) and sustainably mentor the next generation. Herein, we examine the training at the Infectious Diseases Institute (IDI) as a model for in-country training based on systems capacity building and attention to the academic environment.Within academic institutions in sub-Saharan Africa, a PhD is often needed to be promoted within the academic ranks. Opportunities for medical graduates to get a PhD have been limited and require protected time and financial resources. In
Cholesterol Side-Chain Cleavage Gene Expression in Theca Cells: Augmented Transcriptional Regulation and mRNA Stability in Polycystic Ovary Syndrome
Jessica K. Wickenheisser, Jessica M. Biegler, Velen L. Nelson-DeGrave, Richard S. Legro, Jerome F. Strauss, Jan M. McAllister
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0048963
Abstract: Hyperandrogenism is characteristic of women with polycystic ovary syndrome (PCOS). Ovarian theca cells isolated from PCOS follicles and maintained in long-term culture produce elevated levels of progestins and androgens compared to normal theca cells. Augmented steroid production in PCOS theca cells is associated with changes in the expression of genes for several steroidogenic enzymes, including CYP11A1, which encodes cytochrome P450 cholesterol side-chain cleavage. Here, we further examined CYP11A1 gene expression, at both the transcriptional and post-transcriptional level in normal and PCOS theca cells propagated in long-term culture utilizing quantitative RT-PCR, functional promoter analyses, and mRNA degradation studies. The minimal element(s) that conferred increased basal and cAMP-dependent CYP11A1 promoter function were determined. CYP11A1 mRNA half-life in normal and PCOS theca cells was compared. Results of these cumulative studies showed that basal and forskolin stimulated steady state CYP11A1 mRNA abundance and CYP11A1 promoter activity were increased in PCOS theca cells. Deletion analysis of the CYP11A1 promoter demonstrated that augmented promoter function in PCOS theca cells results from increased basal regulation conferred by a minimal sequence between ?160 and ?90 bp of the transcriptional start site. The transcription factor, nuclear factor 1C2, was observed to regulate basal activity of this minimal CYP11A1 element. Examination of mRNA stability in normal and PCOS theca cells demonstrated that CYP11A1 mRNA half-life increased >2-fold, from approximately 9.22+/?1.62 h in normal cells, to 22.38+/?0.92 h in PCOS cells. Forskolin treatment did not prolong CYP11A1 mRNA stability in either normal or PCOS theca cells. The 5′-UTR of CYP11A1 mRNA confers increased basal mRNA stability in PCOS cells. In conclusion, these studies show that elevated steady state CYP11A1 mRNA abundance in PCOS cells results from increased transactivation of the CYP11A1 promoter and increased CYP11A1 mRNA stability.
Insertar las instituciones en la teoría evolutiva del crecimiento
Richard R. Nelson
Análisis Económico , 2003,
En busca de una teoría útil de la innovación In search of a useful innovation theory
Nelson Richard,Winter Sidney
Cuadernos de Economía , 2000,
Abstract: Con este artículo clásico, los profesores Nelson Y Winter dieron inicio a la corriente evolutiva de estirpe schumpeteriana para el análisis de los procesos de innovación tecnológica. Su propuesta metodológica mostró la necesidad de abordar el cambio tecnológico con un enfoque menos formal -como el que aún predomina en la economía y de elaborar una teoría fundamentada empíricamente que explicara los procesos de innovación concretos y reales, como el que ilustra el ejemplo de la química de colorantes sintéticos. Este trabajo muestra que este enfoque permite integrar elementos de otras disciplinas, los cuales no se pueden reducir al postulado de la racionalidad optimizadora. Este texto es un documento fundamental en la historia del análisis del cambio técnico y la innovación tecnológica, y es un punto de referencia imprescindible para todo aquél que se interese en el tema. With this classic article, Professors Nelson and Winter launched the evolutionary approach, of Schumpeterian lineage, for the analysis of technological innovation processes. Their methodological proposal showed the need to tackle technological change with a less formal approach than that which is still dominant in economics, and to construct an empirically founded theory which would explain real, concrete innovation processes, such as the one they illustrate with the example of the chemistry of synthetic colorants. This paper showsthat this approach allows the integration of elements of other disciplines,which cannot be reduced to the postulate of optimizing rationality. This text is a fundamental document in the history of the analysis of technical change and technological innovation, andis an essential point of reference for all who are interested in thetopic.
Evolution of warped and twisted accretion discs in close binary systems
Moritz Fragner,Richard Nelson
Physics , 2009, DOI: 10.1051/0004-6361/200913088
Abstract: We aim to examine the detailed disc structure that arises in a misaligned binary system as a function of the disc aspect ratio h, viscosity parameter alpha, disc outer radius R, and binary inclination angle gamma_F. We also aim to examine the conditions that lead to an inclined disc being disrupted by strong differential precession. We use a grid-based hydrodynamic code to perform 3D simulations. This code has a relatively low numerical viscosity compared with the SPH schemes that have been used previously to study inclined discs. This allows the influence of viscosity on the disc evolution to be tightly controlled. We find that for thick discs (h=0.05) with low alpha, efficient warp communication in the discs allows them to precess as rigid bodies with very little warping or twisting. Such discs are observed to align with the binary orbit plane on the viscous evolution time. Thinner discs with higher viscosity, in which warp communication is less efficient, develop significant twists before achieving a state of rigid-body precession. Under the most extreme conditions we consider (h=0.01, alpha=0.005 and alpha=0.1), we find that discs can become broken or disrupted by strong differential precession. Discs that become highly twisted are observed to align with the binary orbit plane on timescales much shorter than the viscous timescale, possibly on the precession time. We find agreement with previous studies that show that thick discs with low viscosity experience mild warping and precess rigidly. We also find that as h is decreased substantially, discs may be disrupted by strong differential precession, but for disc thicknesses that are significantly less (h=0.01) than those found in previous studies (h=0.03).
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