7,139 research outputs found

    The Effects of Prices and Policies on the Demand for Marijuana: Evidence from the National Household Surveys on Drug Abuse

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    Recent studies have shown that efforts to curb alcohol use by increasing the price of alcohol and limiting youth's access have succeeded, but they may have had the unintended consequencce of increasing marijuana use. This possibility is troubling in light of a recent government report that shows that marijuana use among teens more than doubled between 1990 and 1997. What impact will the proposed large increase in cigarette prices have on the demand for other substances such as marijuana? To better understand how the demand for marijuana responds to changes in the policies and prices that affect its use, we explore the National Household Survy on Drug Abuse (NHSDA). Overall, we find that marijuana, alcohol, and tobacco are complements, sot that increasing the price of any one will decrease the demand for marijuana. The results of this paper will help guide the creation of comprehensive policies that curb the use of marijuana in two ways: first, they quantify the effects of policies aimed at curbing the use of each substance, allowing policymakers to evaluate alternative policy options; and second, they clarify the dynamics and interactions between alcohol, tobacco, and marijuana use in response to government policies.

    Diagnosis, management, and future developments of fibromuscular dysplasia

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    Fibromuscular dysplasia (FMD) is a nonatherosclerotic noninflammatory vascular disease that primarily affects women from age 20 to 60, but may also occur in infants and children, men, and the elderly. It most commonly affects the renal and carotid arteries but has been observed in almost every artery in the body. FMD has been considered rare and thus is often underdiagnosed and poorly understood by many health care providers. There are, however, data to suggest that FMD is much more common than previously thought, perhaps affecting as many as 4% of adult women. When it affects the renal arteries, the most common presentation is hypertension. When it affects the carotid or vertebral arteries, the patient may present with transient ischemic attack or stroke, or dissection. An increasing number of patients are asymptomatic and are only discovered incidentally when imaging is performed for some other reason or by the detection of an asymptomatic bruit. FMD should be considered in the differential diagnosis of a young person with a cervical bruit; a “swishing” sound in the ear(s); transient ischemic attack, stroke, or dissection of an artery; or in individuals aged ≤35 years with onset hypertension. Treatment consists of antiplatelet therapy for asymptomatic individuals and percutaneous balloon angioplasty for patients with indications for intervention. Patients with aneurysms should be treated with a covered stent or open surgical repair. Little new information has been published about FMD in the last 40 years. The recently instituted International Registry for Fibromuscular Dysplasia will remedy that situation and provide observational data on a large numbers of patients with FMD

    The Brugada syndrome mutation A39V does not affect surface expression of neuronal rat Cav1.2 channels

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    <p>Abstract</p> <p>Background</p> <p>A loss of function of the L-type calcium channel, Cav1.2, results in a cardiac specific disease known as Brugada syndrome. Although many Brugada syndrome channelopathies reduce channel function, one point mutation in the N-terminus of Cav1.2 (A39V) has been shown to elicit disease a phenotype because of a loss of surface trafficking of the channel. This lack of cell membrane expression could not be rescued by the trafficking chaperone Cavβ.</p> <p>Findings</p> <p>We report that despite the striking loss of trafficking described previously in the cardiac Cav1.2 channel, the A39V mutation while in the background of the brain isoform traffics and functions normally. We detected no differences in biophysical properties between wild type Cav1.2 and A39V-Cav1.2 in the presence of either a cardiac (Cavβ2b), or a neuronal beta subunit (Cavβ1b). In addition, the A39V-Cav1.2 mutant showed a normal Cavβ2b mediated increase in surface expression in tsA-201 cells.</p> <p>Conclusions</p> <p>The Brugada syndrome mutation A39V when introduced into rat brain Cav1.2 does not trigger the loss-of-trafficking phenotype seen in a previous study on the human heart isoform of the channel.</p

    Universal Chemomechanical Design Rules for Solid-Ion Conductors to Prevent Dendrite Formation in Lithium Metal Batteries

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    Dendrite formation during electrodeposition while charging lithium metal batteries compromises their safety. While high shear modulus solid-ion conductors (SICs) have been prioritized to resolve pressure-driven instabilities that lead to dendrite propagation and cell shorting, it is unclear whether these or alternatives are needed to guide uniform lithium electrodeposition, which is intrinsically density-driven. Here, we show that SICs can be designed within a universal chemomechanical paradigm to access either pressure-driven dendrite-blocking or density-driven dendrite-suppressing properties, but not both. This dichotomy reflects the competing influence of the SICs mechanical properties and partial molar volume of Li+ relative to those of the lithium anode on plating outcomes. Within this paradigm, we explore SICs in a previously unrecognized dendrite-suppressing regime that are concomitantly soft, as is typical of polymer electrolytes, but feature atypically low Li+ partial molar volume, more reminiscent of hard ceramics. Li plating mediated by these SICs is uniform, as revealed using synchrotron hard x-ray microtomography. As a result, cell cycle-life is extended, even when assembled with thin Li anodes and high-voltage NMC-622 cathodes, where 20 percent of the Li inventory is reversibly cycled

    Shock Radiation Tests for Saturn and Uranus Entry Probes

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    This paper describes a test series in the Electric Arc Shock Tube at NASA Ames Research Center with the objective of quantifying shock-layer radiative heating magnitudes for future probe entries into Saturn and Uranus atmospheres. Normal shock waves are measured in Hydrogen-Helium mixtures (89:11 by volume) at freestream pressures between 13-66 Pa (0.1-0.5 Torr) and velocities from 20-30 kms. No shock layer radiation is detected within measurement limits below 25 kms, a finding consistent with predictions for Uranus entries. Between 25-30 kms, radiance is quantified from the Vacuum Ultraviolet through Near Infrared, with focus on the Lyman-a and Balmer series lines of Hydrogen. Shock profiles are analyzed for electron number density and electronic state distribution. The shocks do not equilibrate over several cm, and in many cases the state distributions are non-Boltzmann. Radiation data are compared to simulations of Decadal Survey entries for Saturn and shown to be as much as 8x lower than predicted with the Boltzmann radiation model. Radiance is observed in front of the shock layer, the characteristics of which match the expected diffusion length

    Shock Radiation Tests for Saturn and Uranus Entry Probes

    Get PDF
    This paper describes a test series in the Electric Arc Shock Tube at NASA Ames Research Center with the objective of quantifying shock-layer radiative heating magnitudes for future probe entries into Saturn and Uranus atmospheres. Normal shock waves are measured in Hydrogen/Helium mixtures (89:11 by mole) at freestream pressures between 13-66 Pa (0.1-0.5 Torr) and velocities from 20-30 km/s. No shock layer radiation is detected below 25 km/s, a finding consistent with predictions for Uranus entries. Between 25-30 km/s, radiance is quantified from the Vacuum Ultraviolet through Near Infrared, with focus on the Lyman-alpha and Balmer series lines of Hydrogen. Shock profiles are analyzed for electron number density and electronic state distribution. The shocks do not equilibrate over several cm, and distributions are demonstrated to be non-Boltzmann. Radiation data are compared to simulations of Decadal survey entries for Saturn and shown to be significantly lower than predicted with the Boltzmann radiation model

    Gaussian approximations for stochastic systems with delay: chemical Langevin equation and application to a Brusselator system

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    We present a heuristic derivation of Gaussian approximations for stochastic chemical reaction systems with distributed delay. In particular we derive the corresponding chemical Langevin equation. Due to the non-Markovian character of the underlying dynamics these equations are integro-differential equations, and the noise in the Gaussian approximation is coloured. Following on from the chemical Langevin equation a further reduction leads to the linear-noise approximation. We apply the formalism to a delay variant of the celebrated Brusselator model, and show how it can be used to characterise noise-driven quasi-cycles, as well as noise-triggered spiking. We find surprisingly intricate dependence of the typical frequency of quasi-cycles on the delay period.Comment: 14 pages, 9 figure
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