The Influence of Geometry Variation and Heat Sink Angle on its Thermal Performance

Light-emitting diodes (LEDs) are becoming substantially more popular than traditional lighting methods. LED lights are high power density devices that need thermal management systems to extend their useful life. This paper presents an experimental study on radial aluminum heat sink fabricated by metal additive manufacturing process operating under natural convection conditions. New design considerations such as adapting the middle fin, fin height gradient towards the centre of the heat sink, along with fin perforations and a spiral cut out of the central pillar have been used to improve the thermal performance of the heat sink. For different fin numbers, the effect of the orientation on the natural heat transfer was studied. The performance of three different geometries with 6, 8 and 10 long fins (6LF, 8LF and 10LF) were evaluated under three different heat flux conditions (471.57W/m2, 943.14W/m2 and 1257.52W/m2) for 10 different orientation angles from 0 to 90. It was found that the orientation has a weaker effect on high-density heat sinks than on low ones due to the hindered convective fluid flow by the overlapping of thermal boundary layers. The Rayleigh number was showed to have a significant effect on heat transfer and this effect was the most prominent for the 6LF heat sink. The overall Nusselt number correlations to predict the heat transfer as a function of the Rayleigh number for the 6LF, 8LF and 10LF heat sinks are 0.2748Ra^0.3425, 0.3868Ra^0.2747 and 0.3317Ra^0.2708, respectively

Validation of full-scale and small-scale transmission line test results on dynamic loads with numerical modeling

This research presents the numerical validation of two different failure test data. These are: (1) suspension insulator failure test and (2) conductor failure test. The first failure scenario deals with the study of the effect of dynamic load on adjacent towers due to a broken suspension insulator; while the second scenario deals with the effect of dynamic load on a tower when the adjacent tower has failed due to conductor rupture. The published data were gathered from full scale as well as scale model tests for model validations. A finite element model of the line was developed using three different element types. Incremental nonlinear dynamic analysis was carried out in the time domain using a commercially available software package. -- Using full-scale test data from broken insulator at the suspension point, a numerical model was developed. Upon validation of the numerical model with the test results, a sensitivity study was carried out for various insulator lengths, ice thicknesses and initial tensions to determine the effects of these parameters on the impact loads on the tower cross arm. Results of the study show that the impact loads are less sensitive to the change in insulator length and initial tension but they do vary significantly when the ice loads are increased. The magnitude of the effect of incremental ice thickness has not been quantified in any previous study. A coordination of strength study showed that a suspension insulator failure can increase the conductor tension considerably thus initiating conductor rupture and therefore, a possible cascade failure in the longitudinal direction. -- Using the scale model test data for broken conductor, a numerical model was developed where a number of towers were allowed to fail (one at a time) in a preferred sequence and the peak forces predicted on the surviving tower. This predicted peak force was compared to the experimental results and a reasonable correlation was established. Results show clearly that by allowing a few structures to fail, the longitudinal peak load on the surviving tower can be reduced significantly. This information can then be used in the design of the anti-cascading tower for proper cascade failure containment. -- The study results show clearly that the analysis of dynamic load assessment on transmission system is possible and is cost effective using commercially available finite element software

A preliminary report on the contact-independent antagonism of Pseudogymnoascus destructans by Rhodococcus rhodochrous strain DAP96253.

BackgroundThe recently-identified causative agent of White-Nose Syndrome (WNS), Pseudogymnoascus destructans, has been responsible for the mortality of an estimated 5.5 million North American bats since its emergence in 2006. A primary focus of the National Response Plan, established by multiple state, federal and tribal agencies in 2011, was the identification of biological control options for WNS. In an effort to identify potential biological control options for WNS, multiply induced cells of Rhodococcus rhodochrous strain DAP96253 was screened for anti-P. destructans activity.ResultsConidia and mycelial plugs of P. destructans were exposed to induced R. rhodochrous in a closed air-space at 15°C, 7°C and 4°C and were evaluated for contact-independent inhibition of conidia germination and mycelial extension with positive results. Additionally, in situ application methods for induced R. rhodochrous, such as fixed-cell catalyst and fermentation cell-paste in non-growth conditions, were screened with positive results. R. rhodochrous was assayed for ex vivo activity via exposure to bat tissue explants inoculated with P. destructans conidia. Induced R. rhodochrous completely inhibited growth from conidia at 15°C and had a strong fungistatic effect at 4°C. Induced R. rhodochrous inhibited P. destructans growth from conidia when cultured in a shared air-space with bat tissue explants inoculated with P. destructans conidia.ConclusionThe identification of inducible biological agents with contact-independent anti- P. destructans activity is a major milestone in the development of viable biological control options for in situ application and provides the first example of contact-independent antagonism of this devastating wildlife pathogen

A high-resolution pointing system for fast scanning platforms: The EBEX example

The E and B experiment (EBEX) is a balloon-borne telescope designed to measure the polarization of the cosmic microwave background with 8' resolution employing a gondola scanning with speeds of order degree per second. In January 2013, EBEX completed 11 days of observations in a flight over Antarctica covering $\sim$ 6000 square degrees of the sky. The payload is equipped with two redundant star cameras and two sets of three orthogonal gyroscopes to reconstruct the telescope attitude. The EBEX science goals require the pointing to be reconstructed to approximately 10" in the map domain, and in-flight attitude control requires the real time pointing to be accurate to $\sim$ 0.5$^{\circ}$ . The high velocity scan strategy of EBEX coupled to its float altitude only permits the star cameras to take images at scan turnarounds, every $\sim$ 40 seconds, and thus requires the development of a pointing system with low noise gyroscopes and carefully controlled systematic errors. Here we report on the design of the pointing system and on a simulation pipeline developed to understand and minimize the effects of systematic errors. The performance of the system is evaluated using the 2012/2013 flight data, and we show that we achieve a pointing error with RMS=25" on 40 seconds azimuth throws, corresponding to an error of $\sim$ 4.6" in the map domain.Comment: 14 pages, Proceedings of the 2015 IEEE Aerospace Conferenc

Transcranial Electrical Stimulation targeting limbic cortex increases the duration of human deep sleep

Background: Researchers have proposed that impaired sleep may be a causal link in the progression from Mild Cognitive Impairment (MCI) to Alzheimer's Disease (AD). Several recent findings suggest that enhancing deep sleep (N3) may improve neurological health in persons with MCI, and buffer the risk for AD. Specifically, Transcranial Electrical Stimulation (TES) of frontal brain areas, the inferred source of the Slow Oscillations (SOs) of N3 sleep, can extend N3 sleep duration and improve declarative memory for recently learned information. Recent work in our laboratory using dense array Electroencephalography (dEEG) localized the sources of SOs to anterior limbic sites – suggesting that targeting these sites with TES may be more effective for enhancing N3. Methods: For the present study, we recruited 13 healthy adults (M = 42 years) to participate in three all-night sleep EEG recordings where they received low level (0.5 mA) TES designed to target anterior limbic areas and a sham stimulation (placebo). We used a convolutional neural network, trained and tested on professionally scored EEG sleep staging, to predict sleep stages for each recording. Results: When compared to the sham session, limbic-targeted TES significantly increased the duration of N3 sleep. TES also significantly increased spectral power in the 0.5–1 Hz frequency band (relative to pre-TES epochs) in left temporoparietal and left occipital scalp regions compared to sham. Conclusion: These results suggest that even low-level TES, when specifically targeting anterior limbic sites, can increase deep (N3) sleep and thereby contribute to healthy sleep quality.Fil: Hathaway, Evan. Brain Electrophysiology Laboratory Company; Estados UnidosFil: Morgan, Kyle. Brain Electrophysiology Laboratory Company; Estados UnidosFil: Carson, Megan. Brain Electrophysiology Laboratory Company; Estados UnidosFil: Shusterman, Roma. Brain Electrophysiology Laboratory Company; Estados UnidosFil: Fernandez Corazza, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales. Universidad Nacional de La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales; ArgentinaFil: Luu, Phan. University of Oregon; Estados UnidosFil: Tucker, Don M.. University of Oregon; Estados Unido

Focal limbic sources create the large slow oscillations of the EEG in human deep sleep

Background: Initial observations with the human electroencephalogram (EEG) have interpreted slow oscillations (SOs) of the EEG during deep sleep (N3) as reflecting widespread surface-negative traveling waves that originate in frontal regions and propagate across the neocortex. However, mapping SOs with a high-density array shows the simultaneous appearance of posterior positive voltage fields in the EEG at the time of the frontal-negative fields, with the typical inversion point (apparent source) around the temporal lobe. Methods: Overnight 256-channel EEG recordings were gathered from 10 healthy young adults. Individual head conductivity models were created using each participant's own structural MRI. Source localization of SOs during N3 was then performed. Results: Electrical source localization models confirmed that these large waves were created by focal discharges within the ventral limbic cortex, including medial temporal and caudal orbitofrontal cortex. Conclusions: Although the functional neurophysiology of deep sleep involves interactions between limbic and neocortical networks, the large EEG deflections of deep sleep are not created by distributed traveling waves in lateral neocortex but instead by relatively focal limbic discharges.Fil: Morgan, Kyle K.. Brain Electrophysiology Laboratory Company; Estados UnidosFil: Hathaway, Evan. Brain Electrophysiology Laboratory Company; Estados UnidosFil: Carson, Megan. Brain Electrophysiology Laboratory Company; Estados UnidosFil: Fernandez Corazza, Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales. Universidad Nacional de La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales; ArgentinaFil: Shusterman, Roma. Brain Electrophysiology Laboratory Company; Estados UnidosFil: Luu, Phan. Brain Electrophysiology Laboratory Company; Estados Unidos. University of Oregon; Estados UnidosFil: Tucker, Don M.. University of Oregon; Estados Unidos. Brain Electrophysiology Laboratory Company; Estados Unido

Bremelanotide for Treatment of Female Hypoactive Sexual Desire

Hypoactive sexual desire disorder (HSDD) is a persistent deficiency or absence of sexual fantasies and desire resulting in significant distress or interpersonal difficulty. Women with this disorder may display a lack of motivation for sexual activity, reduced responsiveness to erotic cues, a loss of interest during sexual activity, and avoidance of situations that could lead to sexual activity. The pathophysiology of HSDD is thought to be centered around inhibitory and excitatory hormones, neurotransmitters, and specific brain anatomy. Due to the multifactorial nature of HSDD, treatment can be complex and must attempt to target the biological and psychosocial aspects of the disorder. Bremelanotide is a melanocortin receptor agonist and has been recently approved by the FDA to treat HSDD. Bremelanotide is administered intranasally or as a subcutaneous injection. The recommended dosage of bremelanotide is 1.75 mg injected subcutaneously in the abdomen or thigh at least 45 min before sexual activity. Studies showed improvements in desire, arousal, and orgasm scores when 1.75 mg of bremelanotide was administered before sexual activity compared to a placebo. Bremelanotide is a promising way to treat HSDD

Modeling and characterization of the SPIDER half-wave plate

Spider is a balloon-borne array of six telescopes that will observe the Cosmic Microwave Background. The 2624 antenna-coupled bolometers in the instrument will make a polarization map of the CMB with approximately one-half degree resolution at 145 GHz. Polarization modulation is achieved via a cryogenic sapphire half-wave plate (HWP) skyward of the primary optic. We have measured millimeter-wave transmission spectra of the sapphire at room and cryogenic temperatures. The spectra are consistent with our physical optics model, and the data gives excellent measurements of the indices of A-cut sapphire. We have also taken preliminary spectra of the integrated HWP, optical system, and detectors in the prototype Spider receiver. We calculate the variation in response of the HWP between observing the CMB and foreground spectra, and estimate that it should not limit the Spider constraints on inflation

Software systems for operation, control, and monitoring of the EBEX instrument

We present the hardware and software systems implementing autonomous operation, distributed real-time monitoring, and control for the EBEX instrument. EBEX is a NASA-funded balloon-borne microwave polarimeter designed for a 14 day Antarctic flight that circumnavigates the pole. To meet its science goals the EBEX instrument autonomously executes several tasks in parallel: it collects attitude data and maintains pointing control in order to adhere to an observing schedule; tunes and operates up to 1920 TES bolometers and 120 SQUID amplifiers controlled by as many as 30 embedded computers; coordinates and dispatches jobs across an onboard computer network to manage this detector readout system; logs over 3~GiB/hour of science and housekeeping data to an onboard disk storage array; responds to a variety of commands and exogenous events; and downlinks multiple heterogeneous data streams representing a selected subset of the total logged data. Most of the systems implementing these functions have been tested during a recent engineering flight of the payload, and have proven to meet the target requirements. The EBEX ground segment couples uplink and downlink hardware to a client-server software stack, enabling real-time monitoring and command responsibility to be distributed across the public internet or other standard computer networks. Using the emerging dirfile standard as a uniform intermediate data format, a variety of front end programs provide access to different components and views of the downlinked data products. This distributed architecture was demonstrated operating across multiple widely dispersed sites prior to and during the EBEX engineering flight.Comment: 11 pages, to appear in Proceedings of SPIE Astronomical Telescopes and Instrumentation 2010; adjusted metadata for arXiv submissio