24,311 research outputs found
Use of depot medroxyprogesterone acetate and fracture risk
Depot medroxyprogesterone acetate (DMPA), which has a high rate of use among teenagers in Europe and the United States, has been associated with impaired bone mineral acquisition during adolescence and accelerated bone loss in later life. Studies on the association between DMPA use and fracture risk are limited.; We aimed at evaluating the relationship between use of hormonal contraceptives, specifically DMPA, and fracture risk.; We conducted a case-control analysis using the United Kingdom-based General Practice Research Database.; Participants were females aged 20-44 yr with an incident fracture diagnosis between 1995 and 2008.; Odds ratios (OR) with 95% confidence intervals (CI) of incident fracture in relation to exposure to DMPA or combined oral contraceptives were assessed. Adjustments were made for smoking, body mass index, and additional potential confounders.; We identified 17,527 incident fracture cases and 70,130 control patients (DMPA exposure: 11 and 8%, respectively). Compared with nonuse, current use of one to two, three to nine, or 10 or more DMPA prescriptions yielded adjusted OR for fractures of 1.18 (95% CI = 0.93-1.49), 1.36 (95% CI = 1.15-1.60), and 1.54 (95% CI = 1.33-1.78), respectively. Fracture risk was highest after longer treatment duration (<2-3 yr), and there was no difference in patients below and above the age of 30 yr. For users of combined estrogen-containing oral contraceptives, the OR were around 1.; This population-based study suggests that use of DMPA is associated with a slightly increased risk of fractures
Comparison of different methods for estimating snowcover in forested, mountainous basins using LANDSAT (ERTS) images
Snow-covered areas on LANDSAT (ERTS) images of the Santiam River basin, Oregon, and other basins in Washington were measured using several operators and methods. Seven methods were used: (1) Snowline tracing followed by measurement with planimeter, (2) mean snowline altitudes determined from many locations, (3) estimates in 2.5 x 2.5 km boxes of snow-covered area with reference to snow-free images, (4) single radiance-threshold level for entire basin, (5) radiance-threshold setting locally edited by reference to altitude contours and other images, (6) two-band color-sensitive extraction locally edited as in (5), and (7) digital (spectral) pattern recognition techniques. The seven methods are compared in regard to speed of measurement, precision, the ability to recognize snow in deep shadow or in trees, relative cost, and whether useful supplemental data are produced
Gas Bubbles Emerging from a Submerged Granular Bed
This fluid dynamics video was submitted to the Gallery of Fluid Motion for
the 2009 APS Division of Fluid Dynamics Meeting in Minneapolis, Minnesota. In
this video we show some results from a simple experiment where air was injected
by a single nozzle at known constant flow rates in the bottom of a granular bed
submerged in water. The injected air propagates through the granular bed in one
of two modes. Mode 1 emergence involves small discrete bubbles taking tortuous
paths through the interstitial space of the bed. Multiple small bubbles can be
emitted from the bed in an array of locations at the same time during Mode 1
emergence. Mode 2 emergence involves large discrete bubbles locally fluidizing
the granular bed and exiting the bed approximately above the injection site.
Bead diameter, bead density, and air flow rate were varied to investigate the
change in bubble release behavior at the top of the granular bed.
This system is a useful model for methane seeps in lakes. Methane bubbles are
released from the decomposition of organic matter in the lake bed. The initial
size of the bubble determines how much of the gas is absorbed into the lake and
how much of the gas reaches the surface and is released into the atmosphere.
The size and behavior of the emerging bubbles may also affect the amount of
vertical mixing occurring in the lake, as well as the mixing from the lake bed
into the benthic layer.Comment: 2009 APS DFD Gallery of Fluid Motion Submissio
Developing Schwann cells acquire the ability to survive without axons by establishing an autocrine circuit involving IGF, NT-3 and PDGF-BB
Gate tunability of stray-field-induced electron spin precession in a GaAs/InGaAs quantum well below an interdigitated magnetized Fe grating
Time-resolved Faraday rotation is used to measure the coherent electron spin
precession in a GaAs/InGaAs quantum well below an interdigitated magnetized Fe
grating. We show that the electron spin precession frequency can be modified by
applying a gate voltage of opposite polarity to neighboring bars. A tunability
of the precession frequency of 0.5 GHz/V has been observed. Modulating the gate
potential with a gigahertz frequency allows the electron spin precession to be
controlled on a nanosecond timescale
CO-induced, reversible insertion of a terminal imido ligand into an η1η2-isocyanide bridge in the dimolybdenum complex Cp(CO)2Mo(μ-CNPh)Mo(NPh)Cp (Cp = η5-C5H5)
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