993 research outputs found

    Lunar drill footplate and casing

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    To prevent hole collapse during lunar drilling operations, a casing has been devised of a graphite reinforced polyimide composite which will be able to withstand the lunar environment. Additionally, this casing will be inserted into the ground in segments two meters long which will penetrate the regolith simultaneously with the auger. The vertical action of the mobile platform will provide a downward force to the casing string through a special adaptor, giving the casing the needed impetus to sink the anticipated depth of ten meters. Casing segments will be connected with a simple snap arrangement. Excess casing will be cut off by a cylindrical cutting tool which will also transport the excess casing away from the hole. A footplate will be incorporated to grasp the auger rod string during rod segment additions or removals. The footplate grasping mechanism will consist of a set of vice-like arms, one end of each bearing threaded to a common power screw. The power screw will be threaded such that one end's thread pitch opposes that of the other end. The weight of the auger and rod string will be transmitted through the arms to the power screw and absorbed by a set of three ball bearing assemblies. The power screw will be driven by a one-half horsepower brushless motor actuated by radio control. The footplate will rest on four short legs and be anchored with pins that are an integral part of each leg

    Pubertal lipid levels are significantly lower in youth with type 1 diabetes who experienced partial clinical remission

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    Importance: The physiologic changes in lipids during puberty in type 1 diabetes (T1D) is unclear as subjects in previous studies were not stratified by partial clinical remission (PCR) status. Aim: To determine the effect of PCR on lipid changes during puberty in youth with T1D. Subjects and Methods: A retrospective cross-sectional study of 194 subjects consisting of 71 controls of age 12.9±1.3y and 123 subjects with T1D stratified into remitters (n=44, age 13.0±0.8y) and non-remitters (n=79, age 11.2±0.6y). PCR was defined as insulin-dose adjusted HbA1c of ≤9. Pubertal status was determined by Tanner staging. Results: Among the pubertal cohort, low-density lipoprotein cholesterol concentration was significantly higher in the non-remitters compared to the remitters, 91.1±25.6mg/dL vs 77.2±25.8mg/dL, p=0.018; and the normal-weight controls, 91.1±25.6mg/dL vs 70.4±22.9 mg/dL, p=0.009; but was similar between the overweight/obese controls and non-remitters, 89.7±28.9mg/dL vs 91.1± 25.6mg/dL, p=0.81, and similarly between the normal-weight controls and remitters, 70.4±22.9mg/dL vs 77.2±25.8mg/dL, p=0.39. Total cholesterol was also significantly higher in the non-remitters compared to the remitters, 167.8±30.5 mg/dL vs 149.8±32.1mg/dL, p=0.012; and normal-weight controls, 167.8±30.5mg/dL vs 143.2±30.1mg/dL, p=0.011; but similar between the non-remitters and overweight/obese controls, p=0.098; and remitters and normal-weight controls, p=0.51. Non-HDL cholesterol was equally significantly higher in non-remitters compared to remitters, 111.3±30.1mg/dL vs 95.9±29.1mg/dL, p=0.028; and normal-weight controls, 111.3±30.1mg/dL vs 86.2± 32.2mg/dL, p=0.028; but similar between non-remitters and overweight/obese controls, p=0.48; and remitters versus normal-weight controls, p=0.39. Conclusions: Puberty-related reductions in LDL, TC, and non-HDL occur in remitters and normal-weight controls, but not in non-remitters and overweight/obese controls

    The Microbiome in Pediatric Cystic Fibrosis Patients: The Role of Shared Environment Suggests a Window of Intervention

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    Cystic fibrosis (CF) is caused by mutations in the CFTR gene that predispose the airway to infection. Chronic infection by pathogens such as Pseudomonas aeruginosa leads to inflammation that gradually degrades lung function, resulting in morbidity and early mortality. In a previous study of CF monozygotic twins, we demonstrate that genetic modifiers significantly affect the establishment of persistent P. aeruginosa colonization in CF. Recognizing that bacteria other than P. aeruginosa contribute to the CF microbiome and associated pathology, we used deep sequencing of sputum from pediatric monozygotic twins and nontwin siblings with CF to characterize pediatric bacterial communities and the role that genetics plays in their evolution. We found that the microbial communities in sputum from pediatric patients living together were much more alike than those from pediatric individuals living apart, regardless of whether samples were taken from monozygous twins or from nontwin CF siblings living together, which we used as a proxy for dizygous twins. In contrast, adult communities were comparatively monolithic and much less diverse than the microbiome of pediatric patients

    Site-Selective Excitation And Polarized Absorption Spectra Of Nd3+ In Sr-5(Po4)(3)F And Ca-5(Po4)(3)F

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    Polarized absorption and fluorescence spectra were analyzed to establish individual energy (Stark) levels of Nd3+ ions in host crystals of Sr-5(PO4)(3)F (SFAP) and Ca-5(PO4)(3)F (FAP). Site-selective excitation and fluorescence facilitated differentiation between Nd3+ ions in emitting sites-associated with 1.06 mu m stimulated emission, and nonemitting Nd3+ ions in other sites. Measurements were made on samples containing different concentrations of Nd3+ at 4 K and higher temperatures. Substitution of Nd3+ for Sr2+ or Ca2+ was accompanied by passive charge compensation during crystal growth. Crystal-field splitting calculations were performed according to site for Stark levels of Nd3+ ions identified spectroscopically. We obtained a final set of crystal-field parameters B-nm for Nd3+ ions in fluorescing sites with a rms, deviation of 7 cm(-1) (52 levels in Nd:SFAP) and 8 cm(-1) (59 levels in Nd:FAP). For one of the nonemitting sites in Nd:FAP we obtained a final set of B-nm parameters which gave a rms deviation of 6 cm(-1) between 46 experimental and calculated levels

    Continuous glucose monitoring reduces pubertal hyperglycemia of type 1 diabetes

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    Background: Physiologic hyperglycemia of puberty is a major contributor to poor glycemic control in youth with type 1 diabetes (T1D). This study\u27s aim was to determine the effectiveness of continuous glucose monitoring (CGM) to improve glycemic control in pubertal youth with T1D compared to a non-CGM cohort after controlling for age, sex, BMI, duration, and insulin delivery methodology. The hypothesis is that consistent CGM use in puberty improves compliance with diabetes management, leading to increased percentage (%) time in range (TIR70-180 mg/dL) of glycemia, and lowering of HbA1c. Methods A longitudinal, retrospective, case-controlled study of 105 subjects consisting of 51 T1D controls (60.8% male) age 11.5 +/- 3.8 y; and 54 T1D subjects (48.1% male) age 11.1 +/- 5.0 y with confirmed CGM use for 12 months. Pubertal status was determined by Tanner staging. Results were adjusted for baseline HbA1c and diabetes duration. Results HbA1c was similar between the controls and the CGM group at baseline: 8.2 +/- 1.1% vs 8.3 +/- 1.2%, p=0.48 respectively; but was significantly lower in the CGM group 12 months later, 8.2 +/- 1.1% vs. 8.7 +/- 1.4%, p=0.035. Longitudinal change in HbA1c was similar in the prepubertal cohort between the control- and CGM groups: -0.17 +/- 0.98% vs. 0.38 +/- 1.5%, p=0.17. In contrast, HbA1c increased with advancing age and pubertal status in the pubertal controls but not in the pubertal CGM group: 0.55 +/- 1.4 vs -0.22 +/- 1.1%, p=0.020. Percent TIR was inversely related to HbA1c in the CGM group, r=-0.6, p=0.0004, for both prepubertal and pubertal subjects. Conclusions CGM use significantly improved glycemic control in pubertal youth with T1D compared to non-CGM users

    Niche-breadth of freshwater macrophytes occurring in tropical southern African rivers predicts species global latitudinal range

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    The study tested the hypothesis that measurement, using multivariate Principal Components Analy-sis (PCA), of the niche-breadth of river macrophyte species in southern tropical Africa, may predicttheir larger-scale biogeographical range. Two measures of niche-breadth were calculated for 44 riverinemacrophyte species, from 20 families commonly occurring in Zambia, using an approach based on PCAordination with 16 bio-physico-chemical input variables. These included altitude, stream order, streamflow, pH, conductivity and soluble reactive phosphate concentration (SRP). In the absence of additionalchemical water quality data for Zambian rivers, invertebrate-based measures of general water qualitywere also used. These were benthic macroinvertebrate Average Score per Taxon (ASPT), and individualabundance of nine macroinvertebrate families with differing water quality tolerance, indicated by theirSensitivity Weightings within the Zambian Invertebrate Scoring System (ZISS). Macrophyte large-scalelatitudinal range was derived from world geopositional records held by online databases, and additionalrecords held by the authors. The two niche-breadth metrics divided the species into narrow-niche andintermediate/broad-niche categories, showing significant variation (from one or both of correlation andANOVA test outcomes) in altitude, stream flow, conductivity, SRP, pH and ASPT, but not stream order.Macrophyte alpha-diversity (as a measure of number of individual niches co-existing per habitat) showedno significant relationship with individual species niche-breadth. Narrow-niche species included a higherproportion of Afrotropical endemics than did species with broader niche size. There were significant pre-dictive relationships between macrophyte niche-breadth and latitudinal range of the target species atglobal and Afrotropical scales, but not for the Neotropics.Fil: Kennedy, Michael. University Of Aberdeen; Reino UnidoFil: Lang, Pauline. University of Glasgow; Reino UnidoFil: Tapia Grimaldo, Julissa. University of Glasgow; Reino UnidoFil: Varandas Martins, Sara. University of Glasgow; Reino UnidoFil: Bruce, Alannah. University of Glasgow; Reino UnidoFil: Moore, Isabel. University of Glasgow; Reino UnidoFil: Taubert, Rebeca. University of Glasgow; Reino UnidoFil: Macleod-Nolan, Chantal. University of Glasgow; Reino UnidoFil: McWaters, Stephanie. University of Glasgow; Reino UnidoFil: Briggs, John. University of Glasgow; Reino UnidoFil: Lowe, Steve. University of Glasgow; Reino UnidoFil: Saili, Kochelani. University Of Zambia;Fil: SICHINGABULA, Henry. University Of Zambia;Fil: Dallas, Helen. Nelson Mandela Metropolitan University, Sudafrica; SudáfricaFil: Morrison, Sean. University of Glasgow; Reino UnidoFil: Franceschini, Maria Celeste. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Willems, Frank. The Kasanka Trust; ZambiaFil: Bottino, Flavia. Universidad Federal de San Carlos; BrasilFil: MURPHY Kevin. University of Glasgow; Reino Unid

    Thermodynamic Description of the Relaxation of Two-Dimensional Euler Turbulence Using Tsallis Statistics

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    Euler turbulence has been experimentally observed to relax to a metaequilibrium state that does not maximize the Boltzmann entropy, but rather seems to minimize enstrophy. We show that a recent generalization of thermodynamics and statistics due to Tsallis is capable of explaining this phenomenon in a natural way. The maximization of the generalized entropy S1/2S_{1/2} for this system leads to precisely the same profiles predicted by the Restricted Minimum Enstrophy theory of Huang and Driscoll. This makes possible the construction of a comprehensive thermodynamic description of Euler turbulence.Comment: 15 pages, RevTe

    An optimization principle for deriving nonequilibrium statistical models of Hamiltonian dynamics

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    A general method for deriving closed reduced models of Hamiltonian dynamical systems is developed using techniques from optimization and statistical estimation. As in standard projection operator methods, a set of resolved variables is selected to capture the slow, macroscopic behavior of the system, and the family of quasi-equilibrium probability densities on phase space corresponding to these resolved variables is employed as a statistical model. The macroscopic dynamics of the mean resolved variables is determined by optimizing over paths of these probability densities. Specifically, a cost function is introduced that quantifies the lack-of-fit of such paths to the underlying microscopic dynamics; it is an ensemble-averaged, squared-norm of the residual that results from submitting a path of trial densities to the Liouville equation. The evolution of the macrostate is estimated by minimizing the time integral of the cost function. The value function for this optimization satisfies the associated Hamilton-Jacobi equation, and it determines the optimal relation between the statistical parameters and the irreversible fluxes of the resolved variables, thereby closing the reduced dynamics. The resulting equations for the macroscopic variables have the generic form of governing equations for nonequilibrium thermodynamics, and they furnish a rational extension of the classical equations of linear irreversible thermodynamics beyond the near-equilibrium regime. In particular, the value function is a thermodynamic potential that extends the classical dissipation function and supplies the nonlinear relation between thermodynamics forces and fluxes
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