4,267 research outputs found
A 3D Printed Toolbox for Opto-Mechanical Components
Nowadays is very common to find headlines in the media where it is stated
that 3D printing is a technology called to change our lives in the near future.
For many authors, we are living in times of a third industrial revolution.
Howerver, we are currently in a stage of development where the use of 3D
printing is advantageous over other manufacturing technologies only in rare
scenarios. Fortunately, scientific research is one of them. Here we present the
development of a set of opto-mechanical components that can be built easily
using a 3D printer based on Fused Filament Fabrication (FFF) and parts that can
be found on any hardware store. The components of the set presented here are
highly customizable, low-cost, require a short time to be fabricated and offer
a performance that compares favorably with respect to low-end commercial
alternatives.Comment: 9 pages, 9 figure
Possible Disintegrating Short-Period Super-Mercury Orbiting KIC 12557548
We report here on the discovery of stellar occultations, observed with
Kepler, that recur periodically at 15.685 hour intervals, but which vary in
depth from a maximum of 1.3% to a minimum that can be less than 0.2%. The star
that is apparently being occulted is KIC 12557548, a K dwarf with T_eff = 4400
K and V = 16. Because the eclipse depths are highly variable, they cannot be
due solely to transits of a single planet with a fixed size. We discuss but
dismiss a scenario involving a binary giant planet whose mutual orbit plane
precesses, bringing one of the planets into and out of a grazing transit. We
also briefly consider an eclipsing binary, that either orbits KIC 12557548 in a
hierarchical triple configuration or is nearby on the sky, but we find such a
scenario inadequate to reproduce the observations. We come down in favor of an
explanation that involves macroscopic particles escaping the atmosphere of a
slowly disintegrating planet not much larger than Mercury. The particles could
take the form of micron-sized pyroxene or aluminum oxide dust grains. The
planetary surface is hot enough to sublimate and create a high-Z atmosphere;
this atmosphere may be loaded with dust via cloud condensation or explosive
volcanism. Atmospheric gas escapes the planet via a Parker-type thermal wind,
dragging dust grains with it. We infer a mass loss rate from the observations
of order 1 M_E/Gyr, with a dust-to-gas ratio possibly of order unity. For our
fiducial 0.1 M_E planet, the evaporation timescale may be ~0.2 Gyr. Smaller
mass planets are disfavored because they evaporate still more quickly, as are
larger mass planets because they have surface gravities too strong to sustain
outflows with the requisite mass-loss rates. The occultation profile evinces an
ingress-egress asymmetry that could reflect a comet-like dust tail trailing the
planet; we present simulations of such a tail.Comment: 14 pages, 7 figures; submitted to ApJ, January 10, 2012; accepted
March 21, 201
Effects of SKF-83566 and haloperidol on performance on progressive ratio schedules maintained by sucrose and corn oil reinforcement: quantitative analysis using a new model derived from the Mathematical Principles of Reinforcement (MPR)
RationaleMathematical models can assist the interpretation of the effects of interventions on schedule-controlled behaviour and help to differentiate between processes that may be confounded in traditional performance measures such as response rate and the breakpoint in progressive ratio (PR) schedules.ObjectiveThe effects of a D1-like dopamine receptor antagonist, 8-bromo-2,3,4,5-tetrahydro-3-methyl-5-phenyl-1H-3-benzazepin-7-ol hydrobromide (SKF-83566), and a D2-like receptor antagonist, haloperidol, on rats’ performance on PR schedules maintained by sucrose and corn oil reinforcers were assessed using a new model derived from Killeen’s (Behav Brain Sci 17:105–172, 1994) Mathematical Principles of Reinforcement.MethodSeparate groups of rats were trained under a PR schedule using sucrose or corn oil reinforcers. SKF-83566 (0.015 and 0.03 mg kg−1) and haloperidol (0.05 and 0.1 mg kg−1) were administered intraperitoneally (five administrations of each treatment). Running and overall response rates in successive ratios were analysed using the new model, and estimates of the model’s parameters were compared between treatments.ResultsHaloperidol reduced a (the parameter expressing incentive value) in the case of both reinforcers, but did not affect the parameters related to response time and post-reinforcement pausing. SKF-83566 reduced a and k (the parameter expressing sensitivity of post-reinforcement pausing to the prior inter-reinforcement interval) in the case of sucrose, but did not affect any of the parameters in the case of corn oil.ConclusionsThe results are consistent with the hypothesis that blockade of both D1-like and D2-like receptors reduces the incentive value of sucrose, whereas the incentive value of corn oil is more sensitive to blockade of D2-like than D1-like receptors
Modeling Kepler transit light curves as false positives: Rejection of blend scenarios for Kepler-9, and validation of Kepler-9d, a super-Earth-size planet in a multiple system
Light curves from the Kepler Mission contain valuable information on the
nature of the phenomena producing the transit-like signals. To assist in
exploring the possibility that they are due to an astrophysical false positive,
we describe a procedure (BLENDER) to model the photometry in terms of a "blend"
rather than a planet orbiting a star. A blend may consist of a background or
foreground eclipsing binary (or star-planet pair) whose eclipses are attenuated
by the light of the candidate and possibly other stars within the photometric
aperture. We apply BLENDER to the case of Kepler-9, a target harboring two
previously confirmed Saturn-size planets (Kepler-9b and Kepler-9c) showing
transit timing variations, and an additional shallower signal with a 1.59-day
period suggesting the presence of a super-Earth-size planet. Using BLENDER
together with constraints from other follow-up observations we are able to rule
out all blends for the two deeper signals, and provide independent validation
of their planetary nature. For the shallower signal we rule out a large
fraction of the false positives that might mimic the transits. The false alarm
rate for remaining blends depends in part (and inversely) on the unknown
frequency of small-size planets. Based on several realistic estimates of this
frequency we conclude with very high confidence that this small signal is due
to a super-Earth-size planet (Kepler-9d) in a multiple system, rather than a
false positive. The radius is determined to be 1.64 (+0.19/-0.14) R(Earth), and
current spectroscopic observations are as yet insufficient to establish its
mass.Comment: 20 pages in emulateapj format, including 8 tables and 16 figures. To
appear in ApJ, 1 January 2010. Accepted versio
Activation of Ventral Tegmental Area 5-HT2C Receptors Reduces Incentive Motivation
FUNDING AND DISCLOSURE The research was funded by Wellcome Trust (WT098012) to LKH; and National Institute of Health (DK056731) and the Marilyn H. Vincent Foundation to MGM. The University of Michigan Transgenic Core facility is partially supported by the NIH-funded University of Michigan Center for Gastrointestinal Research (DK034933). The remaining authors declare no conflict of interest. ACKNOWLEDGMENTS We thank Dr Celine Cansell, Ms Raffaella Chianese and the staff of the Medical Research Facility for technical assistance. We thank Dr Vladimir Orduña for the scientific advice and technical assistance.Peer reviewedPublisher PD
Persistent right aortic arch in peruvian hairless dog - a case report
Un canino de la raza Perro sin Pelo del Perú, de dos meses de edad, fue atendido con historia de regurgitación por un mes y pérdida progresiva de su condición corporal desde el destete. Al examen clínico presentó un estado de alerta y baja condición corporal. El paciente recibió tratamiento de sostén y se le realizó estudios imagenológicos, radiografía cervical, torácica y esofagografía, evidenciando una dilatación de esófago craneal al corazón. Se realizó la eutanasia a solicitud del propietario. En el examen anatomopatológico, se evidenció la persistencia del cuarto arco aórtico derecho y un ligamento arterioso que unía la arteria pulmonar a la aorta anómala formando un anillo vascular que produjo el desarrollo de cambios anatomopatológicos secundarios comunes a esta alteración en esófago y tráquea. Este caso constituye el primer reporte de un defecto congénito cardiovascular en el Perro sin Pelo del Perú.A Peruvian Hairless puppy dog, two months old, presented a history of regurgitation for a month and progressive loss of body condition since weaning. Clinical examination showed an alert status and poor body condition. The patient received supportive treatment and imagenologic studies were taken: cervical and thoracic radiography, and esophagography, indicating a dilated oesophagus cranial to the heart. Euthanasia was performed at the request of the owner. The animal was subjected to pathological examination, showing the persistence of the fourth right aortic arch and ligament arteriosum that joined the pulmonary artery to the anomalous aorta forming a vascular ring, which resulted in the development of pathological changes, secondary to this alteration in the esophagus and trachea. This case represents the first report of a congenital cardiovascular defect in the Peruvian Hairless Dog
Kepler-21b: A 1.6REarth Planet Transiting the Bright Oscillating F Subgiant Star HD 179070
We present Kepler observations of the bright (V=8.3), oscillating star HD
179070. The observations show transit-like events which reveal that the star is
orbited every 2.8 days by a small, 1.6 R_Earth object. Seismic studies of HD
179070 using short cadence Kepler observations show that HD 179070 has a
frequencypower spectrum consistent with solar-like oscillations that are
acoustic p-modes. Asteroseismic analysis provides robust values for the mass
and radius of HD 179070, 1.34{\pm}0.06 M{\circ} and 1.86{\pm}0.04 R{\circ}
respectively, as well as yielding an age of 2.84{\pm}0.34 Gyr for this F5
subgiant. Together with ground-based follow-up observations, analysis of the
Kepler light curves and image data, and blend scenario models, we
conservatively show at the >99.7% confidence level (3{\sigma}) that the transit
event is caused by a 1.64{\pm}0.04 R_Earth exoplanet in a 2.785755{\pm}0.000032
day orbit. The exoplanet is only 0.04 AU away from the star and our
spectroscopic observations provide an upper limit to its mass of ~10 M_Earth
(2-{\sigma}). HD 179070 is the brightest exoplanet host star yet discovered by
Kepler.Comment: Accepted to Ap
Lorcaserin improves glycemic control via a melanocortin neurocircuit.
OBJECTIVE: The increasing prevalence of type 2 diabetes (T2D) and associated morbidity and mortality emphasizes the need for a more complete understanding of the mechanisms mediating glucose homeostasis to accelerate the identification of new medications. Recent reports indicate that the obesity medication lorcaserin, a 5-hydroxytryptamine (5-HT, serotonin) 2C receptor (5-HT2CR) agonist, improves glycemic control in association with weight loss in obese patients with T2D. Here we evaluate whether lorcaserin has an effect on glycemia without body weight loss and how this effect is achieved. METHODS: Murine models of common and genetic T2D were utilized to probe the direct effect of lorcaserin on glycemic control. RESULTS: Lorcaserin dose-dependently improves glycemic control in mouse models of T2D in the absence of reductions in food intake or body weight. Examining the mechanism of this effect, we reveal a necessary and sufficient neurochemical mediator of lorcaserin's glucoregulatory effects, brain pro-opiomelanocortin (POMC) peptides. To clarify further lorcaserin's therapeutic brain circuit, we examined the receptor target of POMC peptides. We demonstrate that lorcaserin requires functional melanocortin4 receptors on cholinergic preganglionic neurons (MC4RChAT) to exert its effects on glucose homeostasis. In contrast, MC4RChAT signaling did not impact lorcaserin's effects on feeding, indicating a divergence in the neurocircuitry underpinning lorcaserin's therapeutic glycemic and anorectic effects. Hyperinsulinemic-euglycemic clamp studies reveal that lorcaserin reduces hepatic glucose production, increases glucose disposal and improves insulin sensitivity. CONCLUSIONS: These data suggest that lorcaserin's action within the brain represents a mechanistically novel treatment for T2D: findings of significance to a prevalent global disease
Elevated Plasma Endothelin-1 and Pulmonary Arterial Pressure in Children Exposed to Air Pollution
BackgroundControlled exposures of animals and humans to particulate matter (PM) or ozone air pollution cause an increase in plasma levels of endothelin-1, a potent vasoconstrictor that regulates pulmonary arterial pressure.ObjectivesThe primary objective of this field study was to determine whether Mexico City children, who are chronically exposed to levels of PM and O3 that exceed the United States air quality standards, have elevated plasma endothelin-1 levels and pulmonary arterial pressures.MethodsWe conducted a study of 81 children, 7.9 ± 1.3 years of age, lifelong residents of either northeast (n = 19) or southwest (n = 40) Mexico City or Polotitlán (n = 22), a control city with PM and O3 levels below the U.S. air quality standards. Clinical histories, physical examinations, and complete blood counts were done. Plasma endothelin-1 concentrations were determined by immunoassay, and pulmonary arterial pressures were measured by Doppler echocardiography.ResultsMexico City children had higher plasma endothelin-1 concentrations compared with controls (p < 0.001). Mean pulmonary arterial pressure was elevated in children from both northeast (p < 0.001) and southwest (p < 0.05) Mexico City compared with controls. Endothelin-1 levels in Mexico City children were positively correlated with daily outdoor hours (p = 0.012), and 7-day cumulative levels of PM air pollution < 2.5 μm in aerodynamic diameter (PM2.5) before endothelin-1 measurement (p = 0.03).ConclusionsChronic exposure of children to PM2.5 is associated with increased levels of circulating endothelin-1 and elevated mean pulmonary arterial pressure
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