Liquid desiccant dehumidification and regeneration process to meet cooling and freshwater needs of desert greenhouses

Agriculture accounts for ~70% of freshwater usage worldwide. Seawater desalination alone cannot meet the growing needs for irrigation and food production, particularly in hot, desert environments. Greenhouse cultivation of high-value crops uses just a fraction of freshwater per unit of food produced when compared with open field cultivation. However, desert greenhouse producers face three main challenges: freshwater supply, plant nutrient supply, and cooling of the greenhouse. The common practice of evaporative cooling for greenhouses consumes large amounts of fresh water. In Saudi Arabia, the most common greenhouse cooling schemes are fresh water-based evaporative cooling, often using fossil groundwater or energy-intensive desalinated water, and traditional refrigeration-based direct expansion cooling, largely powered by the burning of fossil fuels. The coastal deserts have ambient conditions that are seasonally too humid to support adequate evaporative cooling, necessitating additional energy consumption in the dehumidification process of refrigeration-based cooling. This project evaluates the use of a combined-system liquid desiccant dehumidifier and membrane distillation unit that can meet the dual needs of cooling and freshwater supply for a greenhouse in a hot and humid environment.

Radially rotating miniature heat pipes for turbine blade cooling applications

Aerospace turboengines present a demanding challenge to many heat transfer scientists and engineers. Designers in this field are seeking the best design to transform the chemical energy of the fuel into the useful work of propulsive thrust at maximum efficiency. To this aim, aerospace turboengines must operate at very high temperatures and pressures with very little heat losses. These requirements are often in conflict with the ability to protect the turboengine blades from this hostile thermal environment. Heat pipe technology provides a potential cooling means for the structure exposed to high heat fluxes. Therefore, the objective of this dissertation is to develop a new radially rotating miniature heat pipe, which would combine the traditional air-cooling technology with the heat pipe for more effective turboengine blade cooling. ^ In this dissertation, radially rotating miniature heat pipes are analyzed and studied by employing appropriate flow and heat transfer modeling as well as experimental tests. The analytical solutions for the flows of condensate film and vapor, film thickness, and vapor temperature distribution along the heat pipe length are derived. The diffuse effects of non-condensable gases on the temperature distribution along the heat pipe length are also studied, and the analytical solutions for the temperature distributions with the diffuse effects of non-condensable gases are obtained. Extensive experimental tests on radially rotating miniature heat pipes with different influential parameters are undertaken, and various effects of these parameters on the operation of the heat pipe performance are researched. These analytical solutions are in good agreement with the experimental data. ^ The theoretical and experimental studies have proven that the radially rotating miniature heat pipe has a very large heat transfer capability and a very high effective thermal conductance that is 60–100 times higher than the thermal conductivity of copper. At the same time, the heat pipe has a simple structure and low manufacturing cost, and can withstand strong vibrations and work in a high-temperature environment. Therefore, the combination of the traditional air-cooling technology with the radially rotating miniature heat pipe is a feasible and effective cooling means for high-temperature turbine blades. ^

Measurement of carotenoid levels in human serum and a catalog of the lutein conformation populations from semi-empirical calculations

Lutein is a principal constituent of the human macular pigment. This study is composed of two projects. The first studies the conformational geometries of lutein and its potential adaptability in biological systems. The second is a study of the response of human subjects to lutein supplements. Using semi-empirical parametric method 3 (PM3) and density functional theory with the B3LYP/6-31G* basis set, the relative energies of s- cis conformers of lutein were determined. All 512 s-cis conformers were calculated with PM3. A smaller, representative group was also studied using density functional theory. PM3 results were correlated systematically to B3LYP values and this enables the results to be calibrated. The relative energies of the conformers range from 1-30 kcal/mole, and many are dynamically accessible at normal temperatures. Four commercial formulations containing lutein were studied. The serum and macular pigment (MP) responses of human subjects to these lutein supplements with doses of 9 or 20 mg/day were measured, relative to a placebo, over a six month period. In each instance, lutein levels in serum increased and correlated with MP increases. The results demonstrate that responses are significantly dependent upon formulation and that components other than lutein have an important influence serum response.

Effects of a Cooling Vest on Core and Skin Temperature Following a Heat Stress Trial in Healthy Males

The purpose of this study was to examine the effects of a cooling vest on core body temperature following active dehydration and hyperthermia induced by exercising in a hot, humid environment. Based on our study, we recommend the ClimaTech HeatShieldTM only when athletes present with mild symptoms of heat exhaustion.

Tubular and sector heat pipes with interconnected branches for gas turbine and/or compressor cooling

Designing turbines for either aerospace or power production is a daunting task for any heat transfer scientist or engineer. Turbine designers are continuously pursuing better ways to convert the stored chemical energy in the fuel into useful work with maximum efficiency. Based on thermodynamic principles, one way to improve thermal efficiency is to increase the turbine inlet pressure and temperature. Generally, the inlet temperature may exceed the capabilities of standard materials for safe and long-life operation of the turbine. Next generation propulsion systems, whether for new supersonic transport or for improving existing aviation transport, will require more aggressive cooling system for many hot-gas-path components of the turbine. Heat pipe technology offers a possible cooling technique for the structures exposed to the high heat fluxes. Hence, the objective of this dissertation is to develop new radially rotating heat pipe systems that integrate multiple rotating miniature heat pipes with a common reservoir for a more effective and practical solution to turbine or compressor cooling. In this dissertation, two radially rotating miniature heat pipes and two sector heat pipes are analyzed and studied by utilizing suitable fluid flow and heat transfer modeling along with experimental tests. Analytical solutions for the film thickness and the lengthwise vapor temperature distribution for a single heat pipe are derived. Experimental tests on single radially rotating miniature heat pipes and sector heat pipes are undertaken with different important parameters and the manner in which these parameters affect heat pipe operation. Analytical and experimental studies have proven that the radially rotating miniature heat pipes have an incredibly high effective thermal conductance and an enormous heat transfer capability. Concurrently, the heat pipe has an uncomplicated structure and relatively low manufacturing costs. The heat pipe can also resist strong vibrations and is well suited for a high temperature environment. Hence, the heat pipes with a common reservoir make incorporation of heat pipes into turbo-machinery much more feasible and cost effective.

Laser cooling of a metastable argon atomic beam

A production of low velocity and monoenergetic atomic beams would increase the resolution in spectroscopic studies and many other experiments in atomic physics. Laser Cooling uses the radiation pressure to decelerate and cool atoms. The effusing from a glow discharge metastable argon atomic beam is affected by a counterpropagating laser light tuned to the cycling transition in argon. The Zeeman shift caused by a spatially varying magnetic field compensates for the changing Doppler shift that takes the atoms out of resonance as they decelerated. Deceleration and velocity bunching of atoms to a final velocity that depends on the detuning of the laser relative to a frequency of the transition have been observed. Time-of-Flight (TOF) spectroscopy is used to examine the velocity distribution of the cooled atomic beam. These TOF studies of the laser cooled atomic beam demonstrate the utility of laser deceleration for atomic-beam "velocity selection".

Effects of engine cooling water temperature on performance and emission characteristics of a CI engine operated with biofuel blend

The temperature of the coolant is known to have significant influence on engine performance and emissions. Whereas existing literature describes the effects of coolant temperature in engines using fossil derived fuels, very few studies have investigated these effects when biofuel is used. In this study, Jatropha oil was blended separately with ethanol and butanol. It was found that the 80% jatropha oil + 20% butanol blend was the most suitable alternative, as its properties were closest to that of fossil diesel. The coolant temperature was varied between 50°C and 95°C. The combustion process enhanced for both diesel and biofuel blend, when the coolant temperature was increased. The carbon dioxide emissions for both diesel and biofuel blend were observed to increase with temperature. The carbon monoxide, oxygen and lambda values were observed to decrease with temperature. When the engine was operated using diesel, nitrogen oxides emissions correlated in an opposite manner to smoke opacity; however, nitrogen oxides emissions and smoke opacity correlated in an identical manner for biofuel blend. Brake specific fuel consumption was observed to decrease as the temperature was increased and was higher on average when the biofuel was used. The study concludes that both biofuel blend and fossil diesel produced identical correlations between coolant temperature and engine performance. The trends of nitrogen oxides and smoke emissions with cooling temperatures were not identical to fossil diesel when biofuel blend was used in the engine.

Vanadate conformation variations in vanadium pentoxide nanostructures

We report the comparative structural-vibrational study of nanostructures of nanourchins, nanotubes, and nanorods of vanadium oxide. The tube walls comprise layers of vanadium oxide with the organic surfactant intercalated between atomic layers. Both Raman scattering and infrared spectroscopies showed that the structure of nanourchins, nanotubes, and nanorods of vanadium oxide nanocomposite are strongly dependent on the valency of the vanadium, its associated interactions with the organic surfactant template, and on the packing mechanism and arrangement of the surfactant between vanadate layers. Accurate assignment of the vibrational modes to the V-O coordinations has allowed their comparative classification and relation to atomic layer structure. Although all structures are formed from the same precursor, differences in vanadate conformations due to the hydrothermal treatment and surfactant type result in variable degrees of crystalline order in the final nanostructure. The nanotube-containing nanourchins contain vanadate layers in the nanotubes that are in a distorted γ- V5+ conformation, whereas the the nanorods, by comparison, show evidence for V5+ and V4+ species-containing ordered VOx lamina.

Optimization of Cooling Protocols for Hearts Destined for Transplantation

Design and analysis of conceptually different cooling systems for the human heart preservation are numerically investigated. A heart cooling container with required connections was designed for a normal size human heart. A three-dimensional, high resolution human heart geometric model obtained from CT-angio data was used for simulations. Nine different cooling designs are introduced in this research. The first cooling design (Case 1) used a cooling gelatin only outside of the heart. In the second cooling design (Case 2), the internal parts of the heart were cooled via pumping a cooling liquid inside both the heart’s pulmonary and systemic circulation systems. An unsteady conjugate heat transfer analysis is performed to simulate the temperature field variations within the heart during the cooling process. Case 3 simulated the currently used cooling method in which the coolant is stagnant. Case 4 was a combination of Case 1 and Case 2. A linear thermoelasticity analysis was performed to assess the stresses applied on the heart during the cooling process. In Cases 5 through 9, the coolant solution was used for both internal and external cooling. For external circulation in Case 5 and Case 6, two inlets and two outlets were designed on the walls of the cooling container. Case 5 used laminar flows for coolant circulations inside and outside of the heart. Effects of turbulent flow on cooling of the heart were studied in Case 6. In Case 7, an additional inlet was designed on the cooling container wall to create a jet impinging the hot region of the heart’s wall. Unsteady periodic inlet velocities were applied in Case 8 and Case 9. The average temperature of the heart in Case 5 was +5.0oC after 1500 s of cooling. Multi-objective constrained optimization was performed for Case 5. Inlet velocities for two internal and one external coolant circulations were the three design variables for optimization. Minimizing the average temperature of the heart, wall shear stress and total volumetric flow rates were the three objectives. The only constraint was to keep von Mises stress below the ultimate tensile stress of the heart’s tissue.

DES14X3taz: A Type I Superluminous Supernova Showing a Luminous, Rapidly Cooling Initial Pre-peak Bump

We present DES14X3taz, a new hydrogen-poor superluminous supernova (SLSN-I) discovered by the Dark Energy Survey (DES) supernova program, with additional photometric data provided by the Survey Using DECam for Superluminous Supernovae. Spectra obtained using Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy on the Gran Telescopio CANARIAS show DES14X3taz is an SLSN-I at z = 0.608. Multi-color photometry reveals a double-peaked light curve: a blue and relatively bright initial peak that fades rapidly prior to the slower rise of the main light curve. Our multi-color photometry allows us, for the first time, to show that the initial peak cools from 22,000 to 8000 K over 15 rest-frame days, and is faster and brighter than any published core-collapse supernova, reaching 30% of the bolometric luminosity of the main peak. No physical 56Ni-powered model can fit this initial peak. We show that a shock-cooling model followed by a magnetar driving the second phase of the light curve can adequately explain the entire light curve of DES14X3taz. Models involving the shock-cooling of extended circumstellar material at a distance of 400  are preferred over the cooling of shock-heated surface layers of a stellar envelope. We compare DES14X3taz to the few double-peaked SLSN-I events in the literature. Although the rise times and characteristics of these initial peaks differ, there exists the tantalizing possibility that they can be explained by one physical interpretation.

Internal cooling in rotational molding-A review

Rotational molding suffers from a relatively long cycle time, which hampers more widespread growth of the process. During each cycle, both the polymer and mold must be heated from room temperature to above polymer melting temperature and subsequently cooled to room temperature. The cooling time in this process is relatively long due to the poor thermal conductivity of plastics. Although rapid external cooling is possible, internal cooling rates are the major limitation. This causes the process to be uneconomical for large production runs of small parts. Various researchers have strived to minimize cycle times by applying various internal cooling procedures. This article presents a review of these methods, including computer simulations and practical investigations published to date. The effects of cooling rate on the morphology, shrinkage, warpage, and impact properties of rotationally molded polyolefins are also highlighted. In general, rapid and symmetrical cooling across the mold results in smaller spherulite size, increased mechanical properties and less potential warpage or distortion in moldings. POLYM. ENG. SCI., 2011. ©2011 Society of Plastics Engineers.

Rôle de la conformation des glycoprotéines de l’enveloppe du VIH-1 dans la réponse cytotoxique cellulaire dépendante des anticorps et impact des protéines virales Nef et Vpu

Alors que d’énormes efforts sont mis de l’avant pour mettre en place des stratégies thérapeutiques contre l’infection au VIH-1, il est nécessaire de mieux cerner les déterminants viraux qui aideront à l’efficacité de celles-ci. En ce sens, une volumineuse littérature scientifique suggère que les anticorps contre le VIH-1 possédant une capacité à induire une réponse effectrice dépendante de leur portion Fc puissent jouer un rôle important dans la prévention de l’infection et dans la progression de la maladie. Cependant, peu d’information est disponible concernant les déterminants reconnus par ces anticorps et comment le virus s’en protège. Le but des travaux présentés dans cette thèse est donc d’élucider les mécanismes viraux contrôlant la reconnaissance des cellules infectées par ces anticorps capables d’induire une réponse effectrice. De par les corrélats de protection identifiés au cours de l’essai vaccinal RV144, les travaux présentés ici se concentrent sur la réponse cytotoxique dépendante des anticorps (ADCC), puisqu’il s’agit d’une réponse effectrice suggérée pour avoir joué un rôle dans la protection observée dans le RV144, seul essai vaccinal anti-VIH à avoir démontré un certain degré de protection. De plus, plusieurs anticorps capables d’induire cette réponse contre le VIH sont connus pour reconnaître les glycoprotéines de surface du virus (Env) dans une conformation dite ouverte, c’est-à-dire la conformation adoptée lors de la liaison d’Env avec son récepteur CD4 (épitopes CD4i). Nous avons mis au point deux techniques in vitro permettant d’étudier ces changements de conformation ainsi que leur impact sur la réponse ADCC. Les techniques mises au point, un ÉLISA sur base cellulaire pour mesurer les changements de conformation d’Env ainsi que la mesure de la réponse ADCC par cytométrie en flux, nous ont permis de démontrer comment le virus empêche l’exposition des épitopes d’Env CD4i. L’activité simultanée des protéines accessoires virales Nef et Vpu sur le retrait du récepteur CD4 de la surface des cellules infectées et l’inhibition du facteur de restriction Tétherine / BST-2 par Vpu contrôlent à la fois les niveaux d’Env et de CD4 à la surface cellulaire et donc modulent l’interaction Env-CD4 et ultimement la susceptibilité à la réponse ADCC contre les épitopes CD4i reconnus par des anticorps hautement prévalents lors de l’infection au VIH. Également, nous démontrons comment de petits composés mimant la liaison de CD4 sur Env sont capables de forcer l’exposition des épitopes CD4i, même en présence des protéines Nef et Vpu, et donc d’augmenter la susceptibilité des cellules infectées à la réponse ADCC. Une autre découverte présentée ici est la démonstration que la portion soluble d’Env produite par les cellules infectées peut interagir avec le récepteur CD4 des cellules non-infectées avoisinantes et induire leur reconnaissance et élimination par la réponse ADCC contre Env. Somme toute, la modulation de la réponse ADCC par l’interaction Env–CD4 représente un important pilier de la relation hôte – pathogène du VIH-1 de la perspective des réponses Fc-dépendantes. Les travaux présentés dans cette thèse ont le potentiel d’être utilisés dans l’élaboration de nouvelles stratégies antivirales tout en élargissant les connaissances fondamentales de cette interaction hôte – pathogène.

Effect of cooling rate on properties of plasma nitrided AISI 1010 steel

In this work, AISI 1010 steel samples were plasma nitrided into 20% N 2 100 Pa and 400 Pa for N 2 and H 2 , respectively), temperatures of 500 and 580 °C, during 2 h. Three different procedures for cooling were accomplished after nitriding. In the first procedure the cooling occurred naturally, that is, the sample was kept on substrate holder. In the second one the sample was pulled off and cooling in a cold surface. Finally, in the third cooling process the sample was pulled off the substrate holder down into special reservoir filled with oil held at ambient temperature. The properties of the AISI 1010 steel samples were characterized by optical and electron microscopy, X-ray diffraction, Mössbauer spectroscopy and microhardness tests. Thermal gradient inside the sample kept on substrate holder during cooling process was measured by three inserted thermocouples at different depths. When samples were cooled rapidly the transformation of ϵ-Fe 2 − 3 N to γ′-Fe 4 N was inhibited. Such effect is indicated by the high concentration of ϵ-Fe compound zone. To get solid state solution of nitrogen in the diffusion zone, instead of precipitates of nitride phases, the cooling rate should be higher than a critical value of about 0.95 °C/s. When this value is reached at any depth of the diffusion zone, two distinct diffusion zones will appear. Temperature gradients were measured inside the samples as a consequence of the plasma treatment. It's suggested the need for standardization of the term “treatment temperature” for plasma treatment because different nitrided layer properties could be reported for the same “treatment temperature”.

Ergosterol peroxide from Rhizoctonia repens: Composition, conformation, and origin

Ergosterol peroxide (ep), synthetic or from fungal extracts, is shown to be a mixture of isomers arising from α- and β-attack by O 2(1Δg) on ergosterol; the stereochemistry of the peroxide bridge is assigned.