65 resultados para Cold atoms


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Catecholamines are viewed as major stimulants of diet- and cold-induced thermogenesis and of fasting-induced lipolysis, through the β-adrenoceptors (β1/β2/β3). To test this hypothesis, we generated β1/β2/β3-adrenoceptor triple knockout (TKO) mice and compared them to wild type animals. TKO mice exhibited normophagic obesity and cold-intolerance. Their brown fat had impaired morphology and lacked responses to cold of uncoupling protein-1 expression. In contrast, TKO mice had higher circulating levels of free fatty acids and glycerol at basal and fasted states, suggesting enhanced lipolysis. Hence, β-adrenergic signalling is essential for the resistance to obesity and cold, but not for the lipolytic response to fasting.

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The main objective of a steel strip rolling process is to produce high quality steel at a desired thickness.  Thickness reduction is the result of the speed difference between the incoming and the outgoing steel strip and the application of the large normal forces via the backup and the work rolls.  Gauge control of a cold rolled steel strip is achieved using the gaugemeter principle that works adequately for the input gauge changes and the strip hardness changes.  However, the compensation of some factors is problematic, for example, eccentricity of the backup rolls.  This cyclic eccentricity effect causes a gauge deviation, but more importantly, a signal is passed to the gap position control so to increase the eccentricity deviation.  Consequently, the required high product tolerances are severely limited by the presence of the roll eccentricity effects.
In this paper a direct model reference adaptive control (MRAC) scheme with dynamically constructed neural controller was used.  The aim here is to find the simplest controller structure capable of achieving an optimal performance.  The stability of the adaptive neural control scheme (i.e. the requirement of persistency of excitation and bounded learning rates) is addressed by using as the inputs to the reference model the plant's state variables.  In such a case, excitation is due to actual plant signals (states) affected by plant disturbances and noise.  In addition, a reference model in the form of a filter with a desired transfer function using Modulus Optimum design was used to ensure variance in the desired dynamic characteristics of the system.  The gradually decreasing learning rate employed by the neural controller in this paper is aimed at eliminating controller instability resulting from over-aggressive control.  The moving target problem (i.e. the difficulty of global neural networks to perfrom several separate computational tasks in closed -loop control) is addressed by the localized architecture of the controller.  The above control scheme and learning algorithm offers a method for automatic discovery of an efficient controller.
The resulting neural controller produces an excellent disturbance rejection in both cases of eccentricity and hardness disturbances, reducing the gauge deviation due to eccentricity disturbance from 33.36% to 4.57% on average, and the gauge deviation due to hardness disturbance from 12.59% to 2.08%.

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The effect of fenitrothion exposure on birds was examined by measuring aerobic metabolism, blood hemoglobin content, plasma cholinesterases, and body weight for up to 21 d postdose. Peak metabolic rate was measured in a flight chamber in three-dose groups of house sparrows (Passer domesticus; 100 mg/kg = high, 60 mg/kg = medium, 30 mg/kg = low) and one-dose groups of zebra finches (Taeniopygia guttata; 3 mg/kg) and king quails (Coturnix chinensis; 26 mg/kg). Aerobic metabolism was measured during 1 h of exposure to subfreezing thermal conditions in low-dose house sparrows and king quails (26 mg/kg). Fenitrothion had no effect on metabolic rate during cold exposure or on blood hemoglobin at any time. By contrast, aerobic performance during exercise in sparrows was reduced by 58% (high), 18% (medium), and 20% (low), respectively, 2 d postdose. House sparrows (high) had the longest recovery period for peak metabolic rate (21 d) and plasma cholinesterase activity (14 d). House sparrows (high) and treated king quails had significantly lower myoglobin at 48 h postdose, whereas myoglobin was invariant in zebra finches and house sparrows (medium and low). Cholinesterase was maximally inhibited at 6 h postdose, and had recovered within 24 h, in house sparrows (low), king quails, and zebra finches. Exercise peak metabolic rate in zebra finches and king quails was reduced by 23% at 2 d and 3 d, respectively, despite these birds being asymptomatic in both behavior and plasma cholinesterase activities.

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South Asia has emerged in the post-Cold War era as a region where ongoing nuclear rivalry has the potential to result in a nuclear exchange between India and Pakistan. The United States, together with the global community, is devoting considerable effort to prevent the further development and deployment of nuclear weapons by India and Pakistan. This thesis analyses the underlying reasons for the ongoing nuclear rivalry between India and Pakistan, details post-Cold War initiatives to end the nuclear rivalry and examines the prospect of United States efforts to cap, reduce and eventually eliminate the nuclear arsenals of India and Pakistan. The thesis finds that historical factors form the basis of the continuing hostility and animosity between the two nations. The two nations have been bitter rivals since the time of partition in 1947 and the disputed territory of Kashmir continues to be the manifestation of deep seated antagonism and hostility. Pakistan's geography leaves it extremely vulnerable to conventional Indian attack and possession of nuclear weapons is seen as a means to redress the imbalance. Strong domestic support together with fervent nationalism and international prestige will continue to drive the nuclear programs of each nation. This thesis concludes that the nuclear rivalry between India and Pakistan is regional in nature and the end of the Cold War has done little to improve the prospects for nuclear disarmament in the region. United States led efforts have failed to persuade India or Pakistan to either accede to the Non-Proliferation Treaty (NPT) or dismantle their nuclear weapons. The thesis also notes that the United States has failed to take account of China as a significant regional power and it's impact on the nuclear programs of India and Pakistan. A fresh approach (to include China) with more emphasis on regional dialogue is suggested as a first step to ending the nuclear rivalry.

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The thesis seeks to assess the concept of power in relation to Bosnia's experience after the Cold War. It argues that power is best conceptualised as compromising two parts: 'agent power' which involves an ability of an actor to directly influence another and 'impersonal governance' which refers to the indirect effects of power.

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Cold drawing is a process that sizes and smooths the surface of steel before it is cold headed to produce bolts. The effect of the changes in the mechanical properties due to cold drawing on the surface strain and ductility during the upsetting process was analysed showing that the stress and strain state can be more readily altered by changes in the process conditions (friction and height-to-diameter ratio) to cause greater increase in the failure strains than can be achieved by pre-drawing.

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The thesis describes the development of a model of the cold forging process that accurately predicts the initiation of ductile fracture. The effect of the deformation history of the material during multiple forming operations is considered. Both two- and three-dimensional numerical models of the forging process were combined with a ductile fracture criterion to predict the material ductility and damage distribution in the workpiece.

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By arguing that international relations scholarship fails to explain adequately the end of the Cold War because it gives insufficient consideration to the role performed by Mikhail Gorbachev, the thesis makes a case for the systematic examination of the part played by individual political actors in international affairs.

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Investigates the significance and interactive effects of lubricant type, workpiece surface texture and deformation rate under bulk metal, deformation conditions. A novel test rig was developed in conjunction with statistical test techniques. The result of this work identified a cold forming lubrication system with potential economic and environmental advantages over traditional lubrication systems.