Experimental Comparison of Cycle Modifications to a Multi-Stage Two-Evaporator Transcritical CO2 Refrigeration Cycle

With increasing awareness of the adverse effects of carbon emissions on the environment, researchers within the heating, ventilation, air conditioning, and refrigeration (HVAC&R) community have been pushing for lower global warming potential (GWP) and natural working fluids as well as systems that are more efficient than the higher-GWP systems they replace. One such working fluid is carbon dioxide (CO2). While CO2 has the advantages of being low-cost, non-flammable, and possessing a high volumetric heat capacity, it has a high critical pressure associated with a low critical temperature, thus often necessitating transcritical operation that requires significant compressor input power. As such, numerous cycle modifications have been proposed that enable the transcritical CO2 cycle to match, and in some cases surpass, the coefficient of performance (COP) of existing hydrofluorocarbon (HFC) cycles under the same operating conditions. This work provides an experimental comparison of four cycle architectures that utilize the same compressors and heat exchangers. This enables a meaningful comparison of these modifications, consisting of open economization with an evaporator bypass, as well as both electronic expansion valve (EXV) and ejector expansion strategies, along with a pump applied between the gas cooler outlet and the ejector motive nozzle inlet for control and increased recoverable pressure differential. Experimental parametric studies were conducted, and comparisons of architecture costs and benefits are presented. Design recommendations are provided along with future work

Investigation of Two-phase Refrigerant Behavior Upon Cycle Startup for Compressor Protection in Microgravity Applications

Vapor compression cycles (VCCs) are a promising technology for refrigeration needs on future space craft due to their generally high cooling COP. However, due to microgravity there lies a risk of liquid flooding the compressor during start-up. Thus, to better prepare VCCs for microgravity applications, it is significant to understand the dependence of two-phase refrigerant on gravity during start-up. In this work, liquid flooding is evaluated at the start-up of a VCC and a possibility for passive compressor protection is considered. The experimental setup has two configurations. In the first, two-phase phenomena can be observed in a transparent tube and different tube insertions can be tested for their effectiveness as a liquid flooding obstruction. In the second configuration, liquid flooding from a commercial evaporator can be evaluated for different charge levels. The results show a clear effect of tube insertions on liquid flooding in a straight tube and find the felt tube insertion to be most effective at impeding flow. The evaporator test results also present a strong correlation of liquid flooding parameters with the charge level and show only a small dependence on the orientation of the evaporator

Gamma Band Activity in the Reticular Activating System

This review considers recent evidence showing that cells in three regions of the reticular activating system (RAS) exhibit gamma band activity, and describes the mechanisms behind such manifestation. Specifically, we discuss how cells in the mesopontine pedunculopontine nucleus (PPN), intralaminar parafascicular nucleus (Pf), and pontine subcoeruleus nucleus dorsalis (SubCD) all fire in the beta/gamma band range when maximally activated, but no higher. The mechanisms behind this ceiling effect have been recently elucidated. We describe recent findings showing that every cell in the PPN have high-threshold, voltage-dependent P/Q-type calcium channels that are essential, while N-type calcium channels are permissive, to gamma band activity. Every cell in the Pf also showed that P/Q-type and N-type calcium channels are responsible for this activity. On the other hand, every SubCD cell exhibited sodium-dependent subthreshold oscillations. A novel mechanism for sleep–wake control based on well-known transmitter interactions, electrical coupling, and gamma band activity is described. The data presented here on inherent gamma band activity demonstrates the global nature of sleep–wake oscillation that is orchestrated by brainstem–thalamic mechanism, and questions the undue importance given to the hypothalamus for regulation of sleep–wakefulness. The discovery of gamma band activity in the RAS follows recent reports of such activity in other subcortical regions like the hippocampus and cerebellum. We hypothesize that, rather than participating in the temporal binding of sensory events as seen in the cortex, gamma band activity manifested in the RAS may help stabilize coherence related to arousal, providing a stable activation state during waking and paradoxical sleep. Most of our thoughts and actions are driven by pre-conscious processes. We speculate that continuous sensory input will induce gamma band activity in the RAS that could participate in the processes of pre-conscious awareness, and provide the essential stream of information for the formulation of many of our actions

Pedunculopontine nucleus gamma band activity-preconscious awareness, waking, and REM sleep

The pedunculopontine nucleus (PPN) is a major component of the reticular activating system (RAS) that regulates waking and REM sleep, states of high-frequency EEG activity. Recently,we described the presence of high threshold, voltage-dependent N- and P/Q-type calcium channels in RAS nuclei that subserve gamma band oscillations in the mesopontine PPN, intralaminar parafascicular nucleus (Pf), and pontine subcoeruleus nucleus dorsalis (SubCD). Cortical gamma band activity participates in sensory perception, problem solving, and memory. Rather than participating in the temporal binding of sensory events as in the cortex, gamma band activity in the RAS may participate in the processes of preconscious awareness, and provide the essential stream of information for the formulation of many of our actions.That is, the RAS may play an early permissive role in volition. Our latest results suggest that (1) the manifestation of gamma band activity during waking may employ a separate intracellular pathway compared to that during REM sleep, (2) neuronal calcium sensor (NCS-1) protein, which is over expressed in schizophrenia and bipolar disorder, modulates gamma band oscillations in the PPN in a concentration-dependent manner, (3) leptin, which undergoes resistance in obesity resulting in sleep dysregulation, decreases sodium currents in PPN neurons, accounting for its normal attenuation of waking, and (4) following our discovery of electrical coupling in the RAS, we Hypothesize that there are cell clusters within the PPN that may act in concert. These results provide novel information on the mechanisms controlling high-frequency activity related to waking and REM sleep by elements of the RAS.Fil: Urbano Suarez, Francisco Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Farmacológicas (i); ArgentinaFil: Donofrio, Stasia M.. University Of Arkansas For Medical Sciences; Estados UnidosFil: Luster, Brennon R.. University Of Arkansas For Medical Sciences; Estados UnidosFil: Beck, Paige B.. University Of Arkansas For Medical Sciences; Estados UnidosFil: Hyde, James Robert. University Of Arkansas For Medical Sciences; Estados UnidosFil: Bisagno, Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Farmacológicas (i); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Garcia Rill, Edgar. University Of Arkansas For Medical Sciences; Estados Unido

The <i>Castalia</i> mission to Main Belt Comet 133P/Elst-Pizarro

We describe Castalia, a proposed mission to rendezvous with a Main Belt Comet (MBC), 133P/Elst-Pizarro. MBCs are a recently discovered population of apparently icy bodies within the main asteroid belt between Mars and Jupiter, which may represent the remnants of the population which supplied the early Earth with water. Castalia will perform the first exploration of this population by characterising 133P in detail, solving the puzzle of the MBC’s activity, and making the first in situ measurements of water in the asteroid belt. In many ways a successor to ESA’s highly successful Rosetta mission, Castalia will allow direct comparison between very different classes of comet, including measuring critical isotope ratios, plasma and dust properties. It will also feature the first radar system to visit a minor body, mapping the ice in the interior. Castalia was proposed, in slightly different versions, to the ESA M4 and M5 calls within the Cosmic Vision programme. We describe the science motivation for the mission, the measurements required to achieve the scientific goals, and the proposed instrument payload and spacecraft to achieve these

Allosteric Modulators of Steroid Hormone Receptors : Structural Dynamics and Gene Regulation

Peer reviewedPublisher PD

The Gallery \u2714

This is a digital copy of the print book produced by the Gallery 2014 team. Contents: Preface p. 4, Core Studios p. 8, Graphic Design p. 20, Illustration p. 32, Painting p. 44, Photography p. 56, Printmaking p. 68, Ceramics p. 80, Metals & Jewelry p. 92, Sculpture p. 104, Credits p. 116, Artist Index p. 118. Files for individual sections may be viewed on the detailed metadata page by clicking on the book title.https://rdw.rowan.edu/the_gallery/1002/thumbnail.jp