89,091 research outputs found
Global well-posedness for the Schroedinger equation coupled to a nonlinear oscillator
The Schroedinger equation with the nonlinearity concentrated at a single
point proves to be an interesting and important model for the analysis of
long-time behavior of solutions, such as the asymptotic stability of solitary
waves and properties of weak global attractors. In this note, we prove global
well-posedness of this system in the energy space H\sp 1.Comment: 11 page
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Challenges in the Development of Micro Gas Turbines for Concentrated Solar Power Systems
Parabolic solar dish systems have gained more interest recently as a reliable way for harnessing the solar power in form of electricity. Micro gas turbines can be usedas engines in such system to convert the heat available from the solar collector o electricity. In this paper the technical challenges related to using micro gas turbines for utilising concentrated solar power will be addressed based on the experience gained from the EU funded project OMSoP (Optimised Microturbine Solar Power system) which aims todevelop and demonstrate a micro gas turbine coupled to a parabolic dish for the power range of 5โ10 kW. The technical challenges related to the turbomachinery design, rotordynamics and dynamic stability, control system, power electronics and thermal storage will be briefly reviewed. Techno economic considerations of the system will also be discussed
The Reality of the Employees Performance in the Palestinian Cellular Telecommunications Company (Jawwal)
The aim of this study was to identify the reality of the performance of the employees in The Palestinian Cellular Telecommunications Company (Jawwal), and to find the differences between the views of the study sample on the variables of the study according to the variables (age, scientific qualification, field of work and years of service). To achieve the objectives of the study, a questionnaire was designed and developed to measure the variables of the study applied to the company's 70 employees. The Complete Census method was used and 60 samples were recovered for analysis with a recovery rate (85.7%). The SPSS statistical package was adopted. The study reached several results, the most important of which is that the degree of approval for the job performance of the employees working in The Palestinian Cellular Telecommunications Company (Jawwal) is 81.56%. The results showed that there were no statistically significant differences at the level of ฮฑโค 0.05 between the average of the respondents' opinions on the performance of the workers in the Palestinian Cellular Telecommunications Company (Jawwal) due to the following variables (age, scientific qualification, field of work, number of years of service). The most important recommendations were to increase the efficiency of the employees of the company using the equipment of their work, and the need to pay attention to the development of the skills of employees through specialized training programs to improve their performance. And focus on moral incentives because of their role in improving the performance of employees by spreading the spirit of cooperation between
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Comparison of different dietary sources of n-3 polyunsaturated fatty acids on immune response in broiler chickens
The study aims to research the effects of varied dietary sources of n-3 polyunsaturated fatty acids (PUFA) on the immune response in broiler chickens with stress on natural killer (NK) cell activity. Diets supplemented with one of the four sources of n-3 PUFA: linseed oil-, echium oil-, fish oil (FO) or algal biomass-enriched diets at levels of 18, 18, 50 and 15 g/kg fresh weight, were provided for one-d-old male Ross 308 broilers, totaling 340 in number, until they were slaughtered. The analyses included total lipid profile using gas chromatography (GC) for plasma, spleen, thymus, and blood. Additionally, NK cell activity and cell proliferation were investigated for thymocytes and splenocytes. The results indicated that the source of n-3 PUFA had a strong influence on fatty acid composition across all tissues. NK activity was highest in splenocytes and PBMCs from broilers fed linseed oil, followed by those fed algal biomass or echium oil, and lowest for those from broilers fed FO. The proliferative response of lymphocytes from algal biomass-fed chickens tended to be the highest, followed by those fed linseed oil in most cases. Lymphocytes from chickens fed fish oil showed the lowest proliferative response. These results could mean that a docosahexaenoic acid (DHA)-rich algal product might enrich chicken meat with n-3 PUFA without significant damaging effects on chicken immunity
Efficient electron spin manipulation in a quantum well by an in-plane electric field
Electron spins in a semiconductor quantum well couple to an electric field
{\it via} spin-orbit interaction. We show that the standard spin-orbit coupling
mechanisms can provide extraordinary efficient electron spin manipulation by an
in-plane ac electric field
Placental Morphology of Pregnant Iraqi Women with Rheumatic Heart Disease
Background: Placental morphology and cellular arrangement can be altered in maternal diseases. Rheumatic heart disease (RHD) is a chronic heart condition that can lead to death in pregnant women. The aim of this study is to determine the histological changes of the placenta in pregnant women suffering from RHD. Methods: Placentae were collected from 10 healthy pregnant women, and 31 pregnant women with heart conditions (26 with RHD and 5 with NRHD) who had been admitted to the Baghdad Teaching Hospital. Placental tissues were fixed in 10% formal-saline and were processed for light microscopy. Measurements including the placental weight and diameter of the chorionic villi capillaries were recorded. Results: The results indicate that there are many histological changes in pregnant women with RHD such as hyalinisation, fibrosis of the chorionic villi, proliferation of trophoblastic cells, and thickening of its membrane. Additionally, expectant mothers with RHD experience a reduction in capillary diameter and thickening of the capillary walls, and decreased size and weight of their placenta when compared with the control. Conclusions: Heart diseases, especially RHD, are associated with developmental damage of the placenta in pregnant women by injuring the endothelial cells of the placentas capillaries
Electron spin synchronization induced by optical nuclear magnetic resonance feedback
We predict a new physical mechanism explaining the electron spin precession
frequency focusing effect observed recently in singly charged quantum dots
exposed to a periodic train of resonant circularly polarized short optical
pulses [A. Greilich et al, Science 317, 1896 (2007), Ref. 1]. We show that
electron spin precession in an external magnetic field and a field of nuclei
creates a Knight field oscillating at the frequency of nuclear spin resonance.
This field drives the projection of the nuclear spin onto magnetic field to the
value that makes the electron spin precession frequency a multiple of the train
cyclic repetition frequency, which is the condition at which the Knight field
vanishes.Comment: 4+ pages, 3 figure
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