543 research outputs found

    The Separate or Concurrent Effects of Methylphenidate and Alcohol on Acquisition and Retention of the Morris Water Maze in Adolescent Rats

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    Alcohol’s (A) capacity to impair learning and memory has been well documented in the Morris Water Maze (MWM) but few studies have examined methylphenidate’s (MPH) impact on MWM performance (Haidun et al., 2010; Zeise et al., 2007). Even fewer studies have evaluated concurrent administration of these two drugs in adolescent rats (see Markwiese, et al., 1998). This project used a rat model of adolescent drug use to examine individual effects of MPH and A, as well as polypharmacy interactions between MPH and A, on MWM spatial acquisition and retention. Thirty-two adolescent (P30) male Long-Evans hooded rats were used. Subjects were assigned to one of 4 conditions based on drug administered prior to 6 consecutive acquisition sessions. Animals received 2 i.p. injections prior to each session. The methylphenidate group (MPH+S) received 2 mg/kg MPH and 1 ml/kg saline solution (S), the alcohol group (A+S) received 2 g/kg ethanol and S, the methylphenidate and alcohol group (MPH+A) received both MPH and A, and the saline control group (S+S) received S injections. MPH was administered 50 mins prior to each session and A administered 20 mins prior to each session. Each session consisted of 4 trials and rats swam from one of four start locations (N,E,S,W) to a submerged platform in the NE quadrant. Trial duration was 60 seconds and rats remained on the platform for 10 secs. Performances were video recorded, and latency and swim accuracy scored. Whishaw Corridors established a direct swim path from start location to platform and an error was recorded when swim paths exited the corridor. On day 7, the submerged platform was removed and a single, 60 sec retention test was conducted with no drug administered prior to test. Amount of time spent swimming in the NE quadrant was analyzed to assess retention. Acquisition: Both dependent measures, latency and swim accuracy, yielded similar outcomes. Factorial ANOVAs and post hoc tests showed improvement across training sessions for all groups. Importantly, the MPH+A group was impaired relative to all other conditions, and the S+S group performed better than the A group. No significant differences were observed between S+S and MPH+S groups. Retention: A one-way ANOVA of swim time in the NE quadrant revealed longer swim times for the S+S group compared to the A+S group, and longer swim times for the MPH+S group compared to the A+S group. No other significant differences were observed. While all groups improved performance during acquisition, methylphenidate + alcohol compromised spatial learning, and alcohol alone impaired learning relative to controls. Interestingly, measures of retention indicated only alcohol diminished spatial memory in adolescent rats

    ISO LWS Spectra of T Tauri and Herbig AeBe stars

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    We present an analysis of ISO-LWS spectra of eight T Tauri and Herbig AeBe young stellar objects. Some of the objects are in the embedded phase of star-formation, whereas others have cleared their environs but are still surrounded by a circumstellar disk. Fine-structure lines of [OI] and [CII] are most likely excited by far-ultraviolet photons in the circumstellar environment rather than high-velocity outflows, based on comparisons of observed line strengths with predictions of photon-dominated and shock chemistry models. A subset of our stars and their ISO spectra are adequately explained by models constructed by Chiang & Goldreich (1997) and Chiang et al. (2001) of isolated, passively heated, flared circumstellar disks. For these sources, the bulk of the LWS flux at wavelengths longward of 55 µm arises from the disk interior which is heated diffusively by reprocessed radiation from the disk surface. At 45 µm, water ice emission bands appear in spectra of two of the coolest stars, and are thought to arise from icy grains irradiated by central starlight in optically thin disk surface layers

    Impact of written emotional disclosure of trauma on laboratory induced pain

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    This study was undertaken to determine whether written emotional disclosure of trauma impacted capsaicin induced pain immediately after writing and at a one-month follow-up, and the extent to which a lifetime history of trauma alters pain under neutral conditions. Three experiments were conducted to answer these questions. In Experiment 1 participants were randomly assigned to write about either a neutral or a trauma topic, and they concurrently completed the capsaicin test. In Experiment 2, the capsaicin test was administered to trauma history and no trauma history participants and pain ratings and secondary hyperalgesia were recorded under neutral conditions. In Experiment 3, participants wrote for three days and completed the radiant heat test before writing on day 1 and after writing on day 3. They also completed the capsaicin test on either day 4 or at a one-month follow-up (day 30). Taken together, these studies had several important results. First, radiant heat withdrawal latencies, ratings of pain intensity and unpleasantness, and area of secondary hyperalgesia were all significantly increased when participants had a history of traumatic experiences. This is evidence that trauma history is sufficient to alter pain regulatory mechanisms, and this may be attributable to the chronic negative affective state induced by trauma history and sensitization of shared circuits involved in both pain and emotion. Furthermore, our findings suggest that written emotional disclosure may lead to long-term changes in pain modulatory pathways that regulate central sensitization, without altering systems that regulate spontaneous pain

    The impact of written emotional disclosure on laboratory induced pain

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    Previous research has demonstrated the impact of negative emotional states on pain modulation. The direction of this modulation has been shown to correspond to the arousal level and the valence of the emotional state, whether naturally occurring or induced in the laboratory. Other research has consistently linked written emotion disclosure of trauma to better long-term health outcomes among several populations. As most of these studies have focused on long-term health outcome effects of disclosure, little research has been done on the immediate effects of the paradigm on affective or physiological states. This study investigated the short-term effects of written disclosure of trauma on laboratory-induced pain, affective state, and other physiological measures of stress and arousal. Other goals of the study included investigating preexisting differences in pain sensitivity between participants corresponding to lifetime experience of trauma, and determining the degree to which baseline pain testing alters pain sensitivity after emotion induction by creating a conditioned, contextual fear. This is the first study to apply the written emotional disclosure paradigm to laboratory-induced pain

    Interferometric Studies of the extreme binary, ϵ\epsilon Aurigae: Pre-eclipse Observations

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    We report new and archival K-band interferometric uniform disk diameters obtained with the Palomar Testbed Interferometer for the eclipsing binary star ϵ\epsilon Aurigae, in advance of the start of its eclipse in 2009. The observations were inteded to test whether low amplitude variations in the system are connected with the F supergiant star (primary), or with the intersystem material connecting the star with the enormous dark disk (secondary) inferred to cause the eclipses. Cepheid-like radial pulsations of the F star are not detected, nor do we find evidence for proposed 6% per decade shrinkage of the F star. The measured 2.27 +/- 0.11 milli-arcsecond K band diameter is consistent with a 300 times solar radius F supergiant star at the Hipparcos distance of 625 pc. These results provide an improved context for observations during the 2009-2011 eclipse.Comment: Accepted for Ap.J. Letters, Oct. 200

    Spectral Energy Distributions of T Tauri and Herbig Ae Disks: Grain Mineralogy, Parameter Dependences, and Comparison with ISO LWS Observations

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    We improve upon the radiative, hydrostatic equilibrium models of passive circumstellar disks constructed by Chiang & Goldreich (1997). New features include (1) account for a range of particle sizes, (2) employment of laboratory-based optical constants of representative grain materials, and (3) numerical solution of the equations of radiative and hydrostatic equilibrium within the original 2-layer (disk surface + disk interior) approximation. We explore how the spectral energy distribution (SED) of a face-on disk depends on grain size distributions, disk geometries and surface densities, and stellar photospheric temperatures. Observed SEDs of 3 Herbig Ae and 2 T Tauri stars, including spectra from the Long Wavelength Spectrometer (LWS) aboard the Infrared Space Observatory (ISO), are fitted with our models. Silicate emission bands from optically thin, superheated disk surface layers appear in nearly all systems. Water ice emission bands appear in LWS spectra of 2 of the coolest stars. Infrared excesses in several sources are consistent with vertical settling of photospheric grains. While this work furnishes further evidence that passive reprocessing of starlight by flared disks adequately explains the origin of infrared-to-millimeter wavelength excesses of young stars, we emphasize how the SED alone does not provide sufficient information to constrain particle sizes and disk masses uniquely.Comment: Accepted to ApJ, 35 pages inc. 14 figures, AAS preprin

    Salinity Reduces the Forage Quality of Forage Kochia: A Halophytic Chenopodiaceae Shrub

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    Forage kochia (Bassia prostrata [L.] A.J. Scott) is a perennial, halophytic Chenopodiaceae shrub adapted to semiarid rangelands and steppes. It is noted for its ability to produce edible forage in saline environments, but the effect of salinity on its nutritive value has not been determined. Therefore, this study evaluated the dose-response of increasing salinity on the forage quality of forage kochia and Gardner’s saltbush (Atriplex gardneri [Moq.] D. Dietr., a chenopod forage shrub indigenous to the United States). Individual plants were evaluated in hydroponics for 28 days at 0, 150, 300, and 600 mM NaCl. Salt from accumulated ions, minerals, and forage nutritive value were determined using ground shoot samples. Analysis of forage nutritive value is problematic in plants with high salt concentrations, so neutral detergent fiber (NDF) and in vitro true digestibility (IVTD) were also predicted on an ash-corrected dry matter (DM) basis (NDFcorrected and IVTDcorrected). Forage kochia exhibited a dose-response for salt concentration, IVTDcorrected, and crude protein (CP) as salinity increased. Salt concentrations increased to 19% of DM at 600 mM NaCl, which may reduce voluntary intake by ruminants grazing forage kochia. Results indicated that uncorrected IVTD estimates were inflated as forage kochia IVTDcorrected decreased from 65% to 56% with the major change between 300 and 600 mM NaCl. Crude protein did not differ between two forage kochia cultivars but decreased from 26% to 15% between 0 and 600 mM NaCl, whereas Gardner’s saltbush CP decreased by only five percentage points as salinity increased. Nonetheless, despite the greater CP sensitivity to salinity level, forage kochia salt concentration was less and digestibility and metabolizable energy (ME) were greater than Gardner’s saltbush. Overall, salinity reduced the forage quality of forage kochia, though not as dramatically as for Gardner’s saltbush, thus supporting use of forage kochia to improve the forage base of saline rangelands

    Planet Formation Imager (PFI): Introduction and Technical Considerations

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    Complex non-linear and dynamic processes lie at the heart of the planet formation process. Through numerical simulation and basic observational constraints, the basics of planet formation are now coming into focus. High resolution imaging at a range of wavelengths will give us a glimpse into the past of our own solar system and enable a robust theoretical framework for predicting planetary system architectures around a range of stars surrounded by disks with a diversity of initial conditions. Only long-baseline interferometry can provide the needed angular resolution and wavelength coverage to reach these goals and from here we launch our planning efforts. The aim of the "Planet Formation Imager" (PFI) project is to develop the roadmap for the construction of a new near-/mid-infrared interferometric facility that will be optimized to unmask all the major stages of planet formation, from initial dust coagulation, gap formation, evolution of transition disks, mass accretion onto planetary embryos, and eventual disk dispersal. PFI will be able to detect the emission of the cooling, newly-formed planets themselves over the first 100 Myrs, opening up both spectral investigations and also providing a vibrant look into the early dynamical histories of planetary architectures. Here we introduce the Planet Formation Imager (PFI) Project (www.planetformationimager.org) and give initial thoughts on possible facility architectures and technical advances that will be needed to meet the challenging top-level science requirements.Comment: SPIE Astronomical Telescopes and Instrumentation conference, June 2014, Paper ID 9146-35, 10 pages, 2 Figure
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