1,927 research outputs found

    Experiments On Gravel-Sand Transitions: Behavior Of The Grain Size Gap Material

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    River bed sediments often lack fine gravel between 1 and 5 mm, a phenomenon referred to as the “grain size gap.” The gap corresponds to the rapid reduction in grain size associated with the gravel-sand transition (GST), where median bed material grain size reduces from ∼10 mm gravel to ∼1 mm sand. Fine gravel grain sizes are often present in hillslope sediment, so it is not clear why they are absent on riverbed surfaces. We present a phenomenological laboratory experiment examining changes in sediment dynamics across a GST to examine the behavior of grain size gap material when included in the bed and feed grain size distributions. Our observations indicate that where sand falls out of washload, forming persistent surficial deposits at the GST, grain size gap material experiences enhanced mobility. This is due to hydraulic smoothing by sand that occurs because of a geometric effect, where medium sand bridges interstitial pockets in fine gravel bed surfaces. Our experiments show that gap gravel flux is enhanced by sand deposition, making gravel beds mobile at the threshold of motion. We are unable to maintain an immobile grain size gap gravel bed when sand is fed which explains why gravel beds composed of 1–5 mm particles are so rare on Earth. We hypothesize that in natural systems, grain size gap particles are either buried in the diffuse extension of GSTs or transported into coastal and marine environments where they are more commonly observed

    Development of new physical activity and sedentary behavior change self-efficacy questionnaires using item response modeling

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    BACKGROUND: Theoretically, increased levels of physical activity self-efficacy (PASE) should lead to increased physical activity, but few studies have reported this effect among youth. This failure may be at least partially attributable to measurement limitations. In this study, Item Response Modeling (IRM) was used to develop new physical activity and sedentary behavior change self-efficacy scales. The validity of the new scales was compared with accelerometer assessments of physical activity and sedentary behavior. METHODS: New PASE and sedentary behavior change (TV viewing, computer video game use, and telephone use) self-efficacy items were developed. The scales were completed by 714, 6(th )grade students in seven US cities. A limited number of participants (83) also wore an accelerometer for five days and provided at least 3 full days of complete data. The new scales were analyzed using Classical Test Theory (CTT) and IRM; a reduced set of items was produced with IRM and correlated with accelerometer counts per minute and minutes of sedentary, light and moderate to vigorous activity per day after school. RESULTS: The PASE items discriminated between high and low levels of PASE. Full and reduced scales were weakly correlated (r = 0.18) with accelerometer counts per minute after school for boys, with comparable associations for girls. Weaker correlations were observed between PASE and minutes of moderate to vigorous activity (r = 0.09 – 0.11). The uni-dimensionality of the sedentary scales was established by both exploratory factor analysis and the fit of items to the underlying variable and reliability was assessed across the length of the underlying variable with some limitations. The reduced sedentary behavior scales had poor reliability. The full scales were moderately correlated with light intensity physical activity after school (r = 0.17 to 0.33) and sedentary behavior (r = -0.29 to -0.12) among the boys, but not for girls. CONCLUSION: New physical activity and sedentary behavior change self-efficacy scales have fewer items than classical test theory derived alternatives and have reasonable validity for boys, but more work is needed to develop comparable scales for girls. Fitting the items to a underlying variable could be useful in tailoring interventions to this scale

    HEALTHY Intervention: Fitness, Physical Activity, and Metabolic Syndrome Results

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    This study aimed to assess the effect of the HEALTHY intervention on the metabolic syndrome (Met-S), fitness, and physical activity levels of US middle-school students

    Student public commitment in a school-based diabetes prevention project: impact on physical health and health behavior

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    <p>Abstract</p> <p>Background</p> <p>As concern about youth obesity continues to mount, there is increasing consideration of widespread policy changes to support improved nutritional and enhanced physical activity offerings in schools. A critical element in the success of such programs may be to involve students as spokespeople for the program. Making such a public commitment to healthy lifestyle program targets (improved nutrition and enhanced physical activity) may potentiate healthy behavior changes among such students and provide a model for their peers. This paper examines whether student's "public commitment"--voluntary participation as a peer communicator or in student-generated media opportunities--in a school-based intervention to prevent diabetes and reduce obesity predicted improved study outcomes including reduced obesity and improved health behaviors.</p> <p>Methods</p> <p>Secondary analysis of data from a 3-year randomized controlled trial conducted in 42 middle schools examining the impact of a multi-component school-based program on body mass index (BMI) and student health behaviors. A total of 4603 students were assessed at the beginning of sixth grade and the end of eighth grade. Process evaluation data were collected throughout the course of the intervention. All analyses were adjusted for students' baseline values. For this paper, the students in the schools randomized to receive the intervention were further divided into two groups: those who participated in public commitment activities and those who did not. Students from comparable schools randomized to the assessment condition constituted the control group.</p> <p>Results</p> <p>We found a lower percentage of obesity (greater than or equal to the 95<sup>th </sup>percentile for BMI) at the end of the study among the group participating in public commitment activities compared to the control group (21.5% vs. 26.6%, p = 0.02). The difference in obesity rates at the end of the study was even greater among the subgroup of students who were overweight or obese at baseline; 44.6% for the "public commitment" group, versus 53.2% for the control group (p = 0.01). There was no difference in obesity rates between the group not participating in public commitment activities and the control group (26.4% vs. 26.6%).</p> <p>Conclusions</p> <p>Participating in public commitment activities during the HEALTHY study may have potentiated the changes promoted by the behavioral, nutrition, and physical activity intervention components.</p> <p>Trial Registration</p> <p>ClinicalTrials.gov number, <a href="http://www.clinicaltrials.gov/ct2/show/NCT00458029">NCT00458029</a></p

    The estrogen and c-Myc target gene HSPC111 is over-expressed in breast cancer and associated with poor patient outcome

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    Introduction: Estrogens play a pivotal role in the initiation and progression of breast cancer. The genes that mediate these processes are not fully defined, but potentially include the known mammary oncogene MYC. Characterization of estrogen-target genes may help to elucidate further the mechanisms of estrogen-induced mitogenesis and endocrine resistance.Methods: We used a transcript profiling approach to identify targets of estrogen and c-Myc in breast cancer cells. One previously uncharacterized gene, namely HBV pre-S2 trans-regulated protein 3 (HSPC111), was acutely upregulated after estrogen treatment or inducible expression of c-Myc, and was selected for further functional analysis using over-expression and knock-down strategies. HSPC111 expression was also analyzed in relation to MYC expression and outcome in primary breast carcinomas and published gene expression datasets.Results: Pretreatment of cells with c-Myc small interfering RNA abrogated estrogen induction of HSPC111, identifying HSPC111 as a potential c-Myc target gene. This was confirmed by the demonstration of two functional E-box motifs upstream of the transcription start site. HSPC111 mRNA and protein were over-expressed in breast cancer cell lines and primary breast carcinomas, and this was positively correlated with MYC mRNA levels. HSPC111 is present in a large, RNA-dependent nucleolar complex, suggesting a possible role in ribosomal biosynthesis. Neither over-expression or small interfering RNA knock-down of HSPC111 affected cell proliferation rates or sensitivity to estrogen/antiestrogen treatment. However, high expression of HSPC111 mRNA was associated with adverse patient outcome in published gene expression datasets.Conclusion: These data identify HSPC111 as an estrogen and c-Myc target gene that is over-expressed in breast cancer and is associated with an adverse patient outcome

    Differential cross section measurements for the production of a W boson in association with jets in proton–proton collisions at √s = 7 TeV

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    Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript −1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio
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