1,240 research outputs found

    Hanging drop crystal growth apparatus

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    This invention relates generally to control systems for controlling crystal growth, and more particularly to such a system which uses a beam of light refracted by the fluid in which crystals are growing to detect concentration of solutes in the liquid. In a hanging drop apparatus, a laser beam is directed onto drop which refracts the laser light into primary and secondary bows, respectively, which in turn fall upon linear diode detector arrays. As concentration of solutes in drop increases due to solvent removal, these bows move farther apart on the arrays, with the relative separation being detected by arrays and used by a computer to adjust solvent vapor transport from the drop. A forward scattering detector is used to detect crystal nucleation in drop, and a humidity detector is used, in one embodiment, to detect relative humidity in the enclosure wherein drop is suspended. The novelty of this invention lies in utilizing angular variance of light refracted from drop to infer, by a computer algorithm, concentration of solutes therein. Additional novelty is believed to lie in using a forward scattering detector to detect nucleating crystallites in drop

    Dark-Energy Dynamics Required to Solve the Cosmic Coincidence

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    Dynamic dark energy (DDE) models are often designed to solve the cosmic coincidence (why, just now, is the dark energy density ρde\rho_{de}, the same order of magnitude as the matter density ρm\rho_m?) by guaranteeing ρdeρm\rho_{de} \sim \rho_m for significant fractions of the age of the universe. This typically entails ad-hoc tracking or oscillatory behaviour in the model. However, such behaviour is neither sufficient nor necessary to solve the coincidence problem. What must be shown is that a significant fraction of observers see ρdeρm\rho_{de} \sim \rho_m. Precisely when, and for how long, must a DDE model have ρdeρm\rho_{de} \sim \rho_{m} in order to solve the coincidence? We explore the coincidence problem in dynamic dark energy models using the temporal distribution of terrestrial-planet-bound observers. We find that any dark energy model fitting current observational constraints on ρde\rho_{de} and the equation of state parameters w0w_0 and waw_a, does have ρdeρm\rho_{de} \sim \rho_m for a large fraction of observers in the universe. This demotivates DDE models specifically designed to solve the coincidence using long or repeated periods of ρdeρm\rho_{de} \sim \rho_m.Comment: 16 pages, 8 figures, Submitted to Phys. Rev.

    The Association of Maternal Obesity and Race with Pregnancy Weight Gain and Small for Gestational Age Infant Birth: The Effect of Prenatal Care

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    Objective: To examine the association of maternal obesity, race/ethnicity, and prenatal care on high gestational weight gain (GWG) and small for gestational age (SGA) infant birth. Methods: This was a retrospective cohort study of births included in the PRAMS Phase 8 dataset (2016-2017). The study population was 53,893 non-diabetic women with a singleton in-hospital birth between 37 and 42 weeks gestational age. Results: Only obese non-Hispanic white and Hispanic women showed a consistent decrease in adjusted odds of high GWG as prenatal care visit category increased. Only non-Hispanic white women showed a lower increase in adjusted odds of an SGA infant birth with more compared to intermediate prenatal care. Conclusions: The effectiveness of prenatal care in reducing high GWG varies by race for women with a BMI outside a healthy range. More prenatal care did not reduce SGA infant births amongst overweight or obese women. Policy implications: Interventions to improve prenatal care delivery for overweight or obese women should consider race

    Cost-Effective Use of Silver Dressings for the Treatment of Hard-to-Heal Chronic Venous Leg Ulcers

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    Aim To estimate the cost-effectiveness of silver dressings using a health economic model based on time-to-wound-healing in hard-to-heal chronic venous leg ulcers (VLUs). Background Chronic venous ulceration affects 1–3% of the adult population and typically has a protracted course of healing, resulting in considerable costs to the healthcare system. The pathogenesis of VLUs includes excessive and prolonged inflammation which is often related to critical colonisation and early infection. The use of silver dressings to control this bioburden and improve wound healing rates remains controversial. Methods A decision tree was constructed to evaluate the cost-effectiveness of treatment with silver compared with non-silver dressings for four weeks in a primary care setting. The outcomes: ‘Healed ulcer’, ‘Healing ulcer’ or ‘No improvement’ were developed, reflecting the relative reduction in ulcer area from baseline to four weeks of treatment. A data set from a recent meta-analysis, based on four RCTs, was applied to the model. Results Treatment with silver dressings for an initial four weeks was found to give a total cost saving (£141.57) compared with treatment with non-silver dressings. In addition, patients treated with silver dressings had a faster wound closure compared with those who had been treated with non-silver dressings. Conclusion The use of silver dressings improves healing time and can lead to overall cost savings. These results can be used to guide healthcare decision makers in evaluating the economic aspects of treatment with silver dressings in hard-to-heal chronic VLUs

    Measuring β\beta in BD+DKsB \to D^{*+}D^{*-}K_s Decays

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    We consider the possibility of measuring both sin(2β)\sin (2 \beta) and cos(2β)\cos (2 \beta) in the KM unitarity triangle using the process B0D+DKsB^0 \to D^{*+}D^{*-}K_s. This decay mode has a higher branching fraction (O(1%)) than the mode B0D+DB^0 \to D^{*+}D^{*-}. We use the factorization assumption and heavy hadron chiral perturbation theory to estimate the branching fraction and polarization. The time dependent rate for B0(t)D+DKsB^0(t) \to D^{*+} D^{*-} K_s can be used to measure sin(2β)\sin (2 \beta) and cos(2β)\cos(2 \beta) . Furthermore, examination of the D+KsD^{*+} K_s mass spectrum may be the best way to experimentally find the broad 1+1^+ p-wave DsD_s meson.Comment: Revtex, 28 pages, 7 figures, title changed, introduction expanded, added references, details of calculations moved to the appendi

    Effects of washer efficiency on characteristics of effluents from D(EPO)D bleaching of a softwood kraft pulp

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    "December 1997.""Submitted to TAPPI/CPPA-TS International Environmental Conference, Vancouver, British Columbia, Canada, April 5-8, 1998.

    Hormone and Adpokine Alterations across Eleven Weeks of Training in Division I Collegiate Throwers: an Exploratory Study

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    Conceptually, it is important to understand the underlying physiological mechanisms of any training program model. This understanding aids the coach/sport scientist in making better choices in manipulating variables in formulating the training model. These underlying mechanisms can be associated with training variable manipulation and fatigue management aspects as well as the overall health of the athlete. Hormone and cytokine concentrations can be linked to alterations resulting from the manipulation of training variables and to subsequent alterations in performance (Haff et al., 2008; Ishigaki et al., 2005; Jurimae et al., 2010; Stone et al., 2007). For example, alterations in the testosterone: cortisol ratio (T:C) has been associated with alterations in training volume as well as physiological aspects such as lean body mass (LBM), fat content and strength/power performance (Haff et al., 2008; Häkkinen, 1989; Stone et al., 2007). Although cytokine production is part of the adaptive process, markedly increased/excessive cytokine production has been related poor fatigue management and over training (Angeli et al., 2004; Jurimae et al., 2010; Smith, 2000). The present study followed NCAA division 1 (D-1) collegiate throwers over a period of an 11 week fall semester preparation-phase block form of periodized training. Volume and intensity alterations and their effects on physiological variables (e.g. neuromuscular, hormonal, cytokine) are a key component in understanding the effects of a training process. Alterations in these physiological variables were tracked over time in Division-1 collegiate throwers

    Sediment-Water Interactions Affecting Dissolved-Mercury Distributions in Camp Far West Reservoir, California

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    Field and laboratory studies were conducted in April and November 2002 to provide the first direct measurements of the benthic flux of dissolved (0.2-micrometer filtered) mercury species (total and methylated forms) between the bottom sediment and water column at three sampling locations within Camp Far West Reservoir, California: one near the Bear River inlet to the reservoir, a second at a mid-reservoir site of comparable depth to the inlet site, and the third at the deepest position in the reservoir near the dam (herein referred to as the inlet, midreservoir and near-dam sites, respectively; Background, Fig. 1). Because of interest in the effects of historic hydraulic mining and ore processing in the Sierra Nevada foothills just upstream of the reservoir, dissolved-mercury species and predominant ligands that often control the mercury speciation (represented by dissolved organic carbon, and sulfides) were the solutes of primary interest. Benthic flux, sometimes referred to as internal recycling, represents the transport of dissolved chemical species between the water column and the underlying sediment. Because of the affinity of mercury to adsorb onto particle surfaces and to form insoluble precipitates (particularly with sulfides), the mass transport of mercury in mining-affected watersheds is typically particle dominated. As these enriched particles accumulate at depositional sites such as reservoirs, benthic processes facilitate the repartitioning, transformation, and transport of mercury in dissolved, biologically reactive forms (dissolved methylmercury being the most bioavailable for trophic transfer). These are the forms of mercury examined in this study. In contrast to typical scientific manuscripts, this report is formatted in a pyramid-like structure to serve the needs of diverse groups who may be interested in reviewing or acquiring information at various levels of technical detail (Appendix 1). The report enables quick transitions between the initial summary information (figuratively at the top of the pyramid) and the later details of methods or results (figuratively towards the base of the pyramid) using hyperlinks to supporting figures and tables, and an electronically linked Table of Contents. During two sampling events, two replicate sediment cores (Coring methods; Fig. 2) from each of three reservoir locations (Fig. 1) were used in incubation experiments to provide flux estimates and benthic biological characterizations. Incubation of these cores provided “snapshots” of solute flux across the sediment-water interface in the reservoir, under benthic, environmental conditions representative of the time and place of collection. Ancillary data, including nutrient and ligand fluxes, were gathered to provide a water-quality framework from which to compare the results for mercury

    The optical counterpart to gamma-ray burst GRB970228 observed using the Hubble Space Telescope

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    Although more than 2,000 astronomical gamma-ray bursts (GRBs) have been detected, and numerous models proposed to explain their occurrence, they have remained enigmatic owing to the lack of an obvious counterpart at other wavelengths. The recent ground-based detection of a transient source in the vicinity of GRB 970228 may therefore have provided a breakthrough. The optical counterpart appears to be embedded in an extended source which, if a galaxy as has been suggested, would lend weight to those models that place GRBs at cosmological distances. Here we report the observations using the Hubble Space Telescope of the transient counterpart and extended source 26 and 39 days after the initial gamma-ray outburst. We find that the counterpart has faded since the initial detection (and continues to fade), but the extended source exhibits no significant change in brightness between the two dates of observations reported here. The size and apparent constancy between the two epochs of HST observations imply that it is extragalactic, but its faintness makes a definitive statement about its nature difficult. Nevertheless, the decay profile of the transient source is consistent with a popular impulsive-fireball model, which assumes a merger between two neutron stars in a distant galaxy.Comment: 11 pages + 2 figures. To appear in Nature (29 May 1997 issue
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