2,077 research outputs found
Which lifestyle interventions effectively lower LDL cholesterol?
Counseling, weight loss, exercise, and drinking alcohol all effectively lower low- density lipoprotein cholesterol (LDL-C). Specifically, one to 2 daily drinks of alcohol lowers L DL-C, if consumed regularly for more than 4 weeks (strength of recommendation [SOR]: A, based on consistent results of multiple randomized controlled trials [RCTs])
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Geologic and Hydrologic Controls on Coalbed Methane: Sand Wash Basin, Colorado and Wyoming - April 1993
Large coal resources occur in the Upper Cretaceous Williams Fork Formation and lower Tertiary Fort Union Formation in the eastern part of the Sand Wash Basin. These coals are mainly subbituminous to high-volatile B bituminous and have average gas contents of less than 100 to 200 ft3/ton (<3.12 to 6.24 m3/t). Coalbed methane resources total xx Tcf (x.xx Tm3) and are xx.xx Tcf (xxx Bm3) at drilling depths of less than 6,000 ft (<1,830 m). More than 85 percent of them are in the Williams Fork. The basin's cumulative gas/water ratio is approximately 15 ft3/bbl (2.7 m3/m3). To date, low gas content and high water production have limited coalbed methane activity in the basin. Steep structural dip and coal distribution have restricted exploration to the eastern margins of the basin. Prospective Williams Fork and Fort Union coals, respectively, lie basinward in association with the Cedar Mountain fault system and westward along Cherokee Arch into the Powder Wash field area. High productivity requires that permeability, ground-water flow direction, coal distribution and rank, gas content, and structural grain be synergistically combined. That synergism explains prolific and marginal production in the San Juan and Sand Wash Basins, respectively. On the basis of a comparison between the basins, a basin-scale coalbed methane productivity model is proposed whose essential elements are: ground-water flow through thick coals of high rank, perpendicular to no-flow boundaries and conventional trapping along them.Bureau of Economic Geolog
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Geologic and Hydrologic Controls on Coalbed Methane: Sand Wash Basin, Colorado and Wyoming
Geologic and hydrologic analysis of the Upper Cretaceous Mesaverde Group shows that the major controls on the production of coalbed methane are: structural configuration, coal occurrence, gas content, hydrodynamics, and water production. Steep structural dip (500 ft/mi) and coal occurrence limit economic exploration to the eastern and southeastern margins of the basin. Coal resources occur mainly in the lower Williams Fork Formation (upper Mesaverde) in the eastern part of the basin. Most coal beds are high-volatile C to B bituminous rank and have gas contents of less than 200 scf/ton. Moreover, Williams Fork coals do not extend westward to the area of highest thermal maturity. Thus, they could not serve as conduits for long-distance migration of gas. Regionally, groundwater flows westward from an eastern recharge area across an area of low thermal maturity up the coal-rank gradient. Consequently, only a relatively small volume of gas may be available to be swept basinward for conventional trapping. The most prospective areas lie basinward, northwest of Craig, Colorado, on the upflow, downward side of a major fault zone. Gas contents in some coal beds on the downthrown side of the fault exceed 400 scf/ton. The Mesaverde is a thick, regionally interconnected aquifer system of high transmissivity, yielding large volumes of water. Paradoxically, coalbed permeabilities of 10's to 1,000's of md may be too high for economic gas production. To date, high water production and low gas content at the basin margins have limited coalbed activity in the Sand Wash Basin. Major Tertiary coal resources occur in the lower part of the Paleocene Fort Union Formation.Bureau of Economic Geolog
Genomic and proteomic profiling of responses to toxic metals in human lung cells.
Examining global effects of toxic metals on gene expression can be useful for elucidating patterns of biological response, discovering underlying mechanisms of toxicity, and identifying candidate metal-specific genetic markers of exposure and response. Using a 1,200 gene nylon array, we examined changes in gene expression following low-dose, acute exposures of cadmium, chromium, arsenic, nickel, or mitomycin C (MMC) in BEAS-2B human bronchial epithelial cells. Total RNA was isolated from cells exposed to 3 M Cd(II) (as cadmium chloride), 10 M Cr(VI) (as sodium dichromate), 3 g/cm2 Ni(II) (as nickel subsulfide), 5 M or 50 M As(III) (as sodium arsenite), or 1 M MMC for 4 hr. Expression changes were verified at the protein level for several genes. Only a small subset of genes was differentially expressed in response to each agent: Cd, Cr, Ni, As (5 M), As (50 M), and MMC each differentially altered the expression of 25, 44, 31, 110, 65, and 16 individual genes, respectively. Few genes were commonly expressed among the various treatments. Only one gene was altered in response to all four metals (hsp90), and no gene overlapped among all five treatments. We also compared low-dose (5 M, noncytotoxic) and high-dose (50 M, cytotoxic) arsenic treatments, which surprisingly, affected expression of almost completely nonoverlapping subsets of genes, suggesting a threshold switch from a survival-based biological response at low doses to a death response at high doses
Assessing motor deficits in compressive neuropathy using quantitative electromyography
<p>Abstract</p> <p>Background</p> <p>Studying the changes that occur in motor unit potential trains (MUPTs) may provide insight into the extent of motor unit loss and neural re-organization resulting from nerve compression injury. The purpose of this study was to determine the feasibility of using decomposition-based quantitative electromyography (DQEMG) to study the pathophysiological changes associated with compression neuropathy.</p> <p>Methods</p> <p>The model used to examine compression neuropathy was carpal tunnel syndrome (CTS) due to its high prevalence and ease of diagnosis. Surface and concentric needle electromyography data were acquired simultaneously from the abductor pollicis brevis muscle in six individuals with severe CTS, eight individuals with mild CTS and nine healthy control subjects. DQEMG was used to detect intramuscular MUPTs during constant-intensity contractions and to estimate parameters associated with the surface- and needle-detected motor unit potentials (SMUPs and MUPs, respectively). MUP morphology and stability, SMUP morphology and motor unit number estimates (MUNEs) were compared among the groups using Kruskal-Wallis tests.</p> <p>Results</p> <p>The severe CTS group had larger amplitude and longer duration MUPs and smaller MUNEs than the mild CTS and control groups, suggesting that the individuals with severe CTS had motor unit loss with subsequent collateral reinnervation, and that DQEMG using a constant-intensity protocol was sensitive to these changes. SMUP morphology and MUP complexity and stability did not significantly differ among the groups.</p> <p>Conclusions</p> <p>These results provide evidence that MUP amplitude parameters and MUNEs obtained using DQEMG, may be a valuable tool to investigate pathophysiological changes in muscles affected by compressive motor neuropathy to augment information obtained from nerve conduction studies. Although there were trends in many of these measures, in this study, MUP complexity and stability and SMUP parameters were, of limited value.</p
Coherent electronic transfer in quantum dot systems using adiabatic passage
We describe a scheme for using an all-electrical, rapid, adiabatic population
transfer between two spatially separated dots in a triple-quantum dot system.
The electron spends no time in the middle dot and does not change its energy
during the transfer process. Although a coherent population transfer method,
this scheme may well prove useful in incoherent electronic computation (for
example quantum-dot cellular automata) where it may provide a coherent
advantage to an otherwise incoherent device. It can also be thought of as a
limiting case of type II quantum computing, where sufficient coherence exists
for a single gate operation, but not for the preservation of superpositions
after the operation. We extend our analysis to the case of many intervening
dots and address the issue of transporting quantum information through a
multi-dot system.Comment: Replaced with (approximately) the published versio
Effects of Aging on Genioglossus Motor Units in Humans
The genioglossus is a major upper airway dilator muscle thought to be important in obstructive sleep apnea pathogenesis. Aging is a risk factor for obstructive sleep apnea although the mechanisms are unclear and the effects of aging on motor unit remodeled in the genioglossus remains unknown. To assess possible changes associated with aging we compared quantitative parameters related to motor unit potential morphology derived from EMG signals in a sample of older (n = 11; >55 years) versus younger (n = 29; <55 years) adults. All data were recorded during quiet breathing with the subjects awake. Diagnostic sleep studies (Apnea Hypopnea Index) confirmed the presence or absence of obstructive sleep apnea. Genioglossus EMG signals were analyzed offline by automated software (DQEMG), which estimated a MUP template from each extracted motor unit potential train (MUPT) for both the selective concentric needle and concentric needle macro (CNMACRO) recorded EMG signals. 2074 MUPTs from 40 subjects (mean±95% CI; older AHI 19.6±9.9 events/hr versus younger AHI 30.1±6.1 events/hr) were extracted. MUPs detected in older adults were 32% longer in duration (14.7±0.5 ms versus 11.1±0.2 ms; P = 0.05), with similar amplitudes (395.2±25.1 µV versus 394.6±13.7 µV). Amplitudes of CNMACRO MUPs detected in older adults were larger by 22% (62.7±6.5 µV versus 51.3±3.0 µV; P<0.05), with areas 24% larger (160.6±18.6 µV.ms versus 130.0±7.4 µV.ms; P<0.05) than those detected in younger adults. These results confirm that remodeled motor units are present in the genioglossus muscle of individuals above 55 years, which may have implications for OSA pathogenesis and aging related upper airway collapsibility
Resolving Gas Dynamics in the Circumnuclear Region of a Disk Galaxy in a Cosmological Simulation
Using a hydrodynamic adaptive mesh refinement code, we simulate the growth
and evolution of a galaxy, which could potentially host a supermassive black
hole, within a cosmological volume. Reaching a dynamical range in excess of 10
million, the simulation follows the evolution of the gas structure from
super-galactic scales all the way down to the outer edge of the accretion disk.
Here, we focus on global instabilities in the self-gravitating, cold,
turbulence-supported, molecular gas disk at the center of the model galaxy,
which provide a natural mechanism for angular momentum transport down to sub-pc
scales. The gas density profile follows a power-law scaling as r^-8/3,
consistent with an analytic description of turbulence in a quasi-stationary
circumnuclear disk. We analyze the properties of the disk which contribute to
the instabilities, and investigate the significance of instability for the
galaxy's evolution and the growth of a supermassive black hole at the center.Comment: 16 pages (includes appendix), submitted to ApJ. Figures here are at
low resolution; for higher resolution version, download
http://casa.colorado.edu/~levinerd/ms.pd
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