Melatonin the "light of night" in human biology and adolescent idiopathic scoliosis

Melatonin "the light of night" is secreted from the pineal gland principally at night. The hormone is involved in sleep regulation, as well as in a number of other cyclical bodily activities and circadian rhythm in humans. Melatonin is exclusively involved in signalling the 'time of day' and 'time of year' (hence considered to help both clock and calendar functions) to all tissues and is thus considered to be the body's chronological pacemaker or 'Zeitgeber'. The last decades melatonin has been used as a therapeutic chemical in a large spectrum of diseases, mainly in sleep disturbances and tumours and may play a role in the biologic regulation of mood, affective disorders, cardiovascular system, reproduction and aging. There are few papers regarding melatonin and its role in adolescent idiopathic scoliosis (AIS). Melatonin may play a role in the pathogenesis of scoliosis (neuroendocrine hypothesis) but at present, the data available cannot clearly support this hypothesis. Uncertainties and doubts still surround the role of melatonin in human physiology and pathophysiology and future research is needed

An Investigation Of The Effect Of Swirl Vane Angle On Fuel Concentration And Velocity Fields In Gas Turbine Mixers

The flow fields of two different Siemens-Westinghouse gas turbine mixers were studied experimentally in an effort to better understand fuel-air mixing in confined swirling flows found in industrial applications. The mixers consist of an annular flow region and mixing is achieved using swirl vanes, the pressure side of which is used to inject the fuel. The difference between the two mixers studied is the degree of swirl imparted on the flow by the swirl vanes (45° vs. 55°). Velocity (both axial and azimuthal) and fuel concentration profiles were obtained for non-reacting, atmospheric pressure flows at several axial and radial locations downstream of the swirl vanes by the use of LDV and infrared laser light absorption techniques, respectively. The fuel used in this work was a methane/air mixture, which was injected at a momentum flux ratio comparable to that under operational conditions. Results show that flow uniformity, as evidenced by velocity and fuel concentration profiles, is reached further downstream of the swirl vanes for the 45° mixer than for the 55° mixer. This indicates a lesser mixing performance in the 45° mixer. The axial and azimuthal RMS velocities were consistently higher for the 55° degree mixer and this was a likely contributor to its superior mixing performance. High velocity and fuel concentration gradients are common for both mixers and present in the near-field region close to the swirl vanes. The data obtained indicates that the flow behavior in the region near the swirl vanes strongly influences the mixing of the fuel and air. Frequency analysis of the fuel concentration data shows that some turbulent structures prevail throughout the mixing region in both mixers, revealing that some large scale flow features emanating from the swirl vanes are not dissipated even in the high degree of swirl hardware. Lastly, unmixedness levels in both mixers tested are calculated and compared with a discussion on how they might impact NO, emission levels. Copyright © 2005 by ASME

Enabling Much Higher Power Densities In Aerospace Power Electronics With High Temperature Evaporative Spray Cooling

A power electronics module was equipped with an evaporative spray cooling nozzle assembly that served to remove waste heat from the silicon devices. The spray cooling nozzle assembly took the place of the standard heat sink, which uses single phase convection. The purpose of this work was to test the ability of spray cooling to enable higher power density in power electronics with high temperature coolant, and to be an effective and lightweight system level solution to the thermal management needs of aerospace vehicles. The spray cooling work done here was with 95 °C water, and this data is compared to 100 °C water/propylene glycol spray cooling data from a previous paper so as to compare the spray cooling performance of a single component liquid to that of a binary liquid such as WPG. The module used during this work was a COTS module manufactured by Semikron, Inc., with a maximum DC power input of 180 kW (450 VDC and 400 A). With single phase convective cooling, the coolant must be kept at 25 °C in order to prevent the insulated gate bipolar transistor (IGBT) die temperatures from exceeding acceptable limits at full power. If the coolant temperature is higher (100 °C, for example) the module power rating is reduced by a factor of 4 to 45 kW. Due to the high heat transfer coefficient of the evaporative spray cooling nozzles, the module was run at full load while maintaining satisfactory die temperatures even with the coolant at high temperature. The temperatures of the IGBT dies were measured by electrically insulated type T thermocouples that were placed on the die surfaces by Semikron during the manufacturing process. It was found that water spray cooling yielded IGBT device temperatures about 10 °C lower than WPG did, and both offer a substantial improvement over single phase convective cooling. The ability to cool power electronics with high temperature coolant means that a large ΔT is available for heat rejection to ambient conditions, which translates into a small and lightweight condenser. This higher coolant temperature also means it is possible to reject heat to warm ambient air. Also, the use of lower coolant flow rates enables the use of a smaller and lighter liquid pump. These factors, combined with the higher power density achieved, mean that evaporative spray cooling has significant potential to yield a lightweight thermal management system for aerospace applications. Copyright © 2008 SAE International

Evaporative Spray Cooling Of Power Electronics Using High Temperature Coolant

A pressure atomized evaporative spray cooling nozzle array was used to thermally manage the power electronics of a 3 phase inverter module. The module tested was a COTS module manufactured by Semikron, Inc., and has a maximum DC power input of 180 kW (450 VDC and 400 A) with 25°C coolant. However, the standard heat sink that the module uses is a single phase liquid heat sink and when 100°C coolant is used (as in automotive applications), the maximum module power is de-rated to 45 kW so that the IGBT chips will not overheat. The module tested here incorporated a custom heat sink that allowed for the use of spray cooling nozzles, which were designed and developed by RTI. The spray liquid was a 50/50 mixture of water and propylene glycol (WPG) at a temperature of 100°C. The sprays impinged directly onto the bottom surface of the DBC boards to which the power electronics were mounted. This arrangement, combined with the high heat transfer coefficient of evaporative spray cooling, greatly reduced the thermal resistance of the power electronics material stack up, but did so without directly wetting the electronics. The results of this work were that the unique evaporative spray cooling nozzle design and patented electronics interface design allowed the module to be run to full power while keeping the IGBT junction temperatures acceptable, despite the high coolant temperature. The junction temperatures of the IGBT\u27s were measured by electrically insulated type T thermocouples placed on top of the devices, and the thermocouple readings at the full load were within several degrees of one another. Consistent and uniform junction temperatures are an important factor in long term device reliability. For the standard heat sink, which uses single phase liquid cooling, the pressure drop and flow rate required for maximum heat removal would be 17 psi and 5.3 GPM. For the pressure atomizer spray nozzles, the module would require a pressure drop and flow rate of 40 psi and only 2.7 GPM. ©2008 IEEE

AN INVESTIGATION OF THE EFFECT OF SWIRL VANE ANGLE ON FUEL CONCENTRATION AND VELOCITY FIELDS IN GAS TURBINE MIXERS

ABSTRACT The flow fields of two different Siemens-Westinghouse gas turbine mixers were studied experimentally in an effort to better understand fuel-air mixing in confined swirling flows found in industrial applications. The mixers consist of an annular flow region and mixing is achieved using swirl vanes, the pressure side of which is used to inject the fuel. The difference between the two mixers studied is the degree of swirl imparted on the flow by the swirl vanes (45 o vs. 55 o ). Velocity (both axial and azimuthal) and fuel concentration profiles were obtained for non-reacting, atmospheric pressure flows at several axial and radial locations downstream of the swirl vanes by the use of LDV and infrared laser light absorption techniques, respectively. The fuel used in this work was a methane/air mixture, which was injected at a momentum flux ratio comparable to that under operational conditions. Results show that flow uniformity, as evidenced by velocity and fuel concentration profiles, is reached further downstream of the swirl vanes for the 45 o mixer than for the 55 o mixer. This indicates a lesser mixing performance in the 45 o mixer. The axial and azimuthal RMS velocities were consistently higher for the 55 o degree mixer and this was a likely contributor to its superior mixing performance. High velocity and fuel concentration gradients are common for both mixers and present in the near-field region close to the swirl vanes. The data obtained indicates that the flow behavior in the region near the swirl vanes strongly influences the mixing of the fuel and air. Frequency analysis of the fuel concentration data shows that some turbulent structures prevail throughout the mixing region in both mixers, revealing that some large scale flow features emanating from the swirl vanes are not dissipated even in the high degree of swirl hardware. Lastly, unmixedness levels in both mixers tested are calculated and compared with a discussion on how they might impact NO x emission levels

Nonthermal activation of transient receptor potential vanilloid-1 channels in abdominal viscera tonically inhibits autonomic cold-defense effectors

An involvement of the transient receptor potential vanilloid (TRPV) 1 channel in the regulation of body temperature (T b) has not been established decisively. To provide decisive evidence for such an involvement and determine its mechanisms were the aims of the present study. We synthesized a new TRPV1 antagonist, AMG0347 [(E)-N-(7-hydroxy-5,6,7,8-tetrahydronaphthalen-1- yl)-3-(2-(piperidin-1-yl)-6-(trifluoromethyl)pyridin-3-yl)acrylamide], and characterized it in vitro. We then found that this drug is the most potent TRPV1 antagonist known to increase T b of rats and mice and showed (by using knock-out mice) that the entire hyperthermic effect of AMG0347 is TRPV1 dependent. AMG0347-induced hyperthermia was brought about by one or both of the two major autonomic cold-defense effector mechanisms (tail-skin vasoconstriction and/or thermogenesis), but it did not involve warmth-seeking behavior. The magnitude of the hyperthermic response depended on neither T b nor tail-skin temperature at the time of AMG0347 administration, thus indicating that AMG0347-induced hyperthermia results from blockade of tonic TRPV1 activation by nonthermal factors. AMG0347 was no more effective in causing hyperthermia when administered into the brain (intracerebroventricularly) or spinal cord (intrathecally) than when given systemically (intravenously), which indicates a peripheral site of action. We then established that localized intra-abdominal desensitization of TRPV1 channels with intraperitoneal resiniferatoxin blocks the T b response to systemic AMG0347; the extent of desensitization was determined by using a comprehensive battery of functional tests. We conclude that tonic activation of TRPV1 channels in the abdominal viscera by yet unidentified nonthermal factors inhibits skin vasoconstriction and thermogenesis, thus having a suppressive effect on T b. Copyright © 2007 Society for Neuroscience

Magnetic Properties of Gold Nanoparticles: A Room-Temperature Quantum Effect:

Persistent currents: The magnetism of Au nanoparticles might result from persistent currents. Limited portions of a given sample may even support self‐sustained currents, thus exhibiting remnant magnetization and hysteresis. Observing such a quantum effect at room temperature with user‐friendly samples opens unforeseen possibilities