89,091 research outputs found

    Global well-posedness for the Schroedinger equation coupled to a nonlinear oscillator

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    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

    The Reality of the Employees Performance in the Palestinian Cellular Telecommunications Company (Jawwal)

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    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 ฮฑโ‰ค 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

    Efficient electron spin manipulation in a quantum well by an in-plane electric field

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    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

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    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

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    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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