Resonant tunneling controlled by laser and constant electric fields

We develop the concept of scattering matrix and we use it to perform stable numerical calculations of resonant tunneling of electrons through a multiple potential barrier in a semiconductor heterostructure. Electrons move in two external nonperturbative electric fields: constant and oscillating in time. We apply our algorithm for different strengths and spatial configurations of the fields.Comment: 10 pages, 11 figure

Population and labour force projections for 27 European countries, 2002-052: impact of international migration on population ageing: Projections de population et de population active pour 27 pays européens 2002-052: impact de la migration internationale sur le vieillissement de la population

Population and labour force projections are made for 27 selected European countries for 2002-052, focussing on the impact of international migration on population and labour force dynamics. Starting from single scenarios for fertility, mortality and economic activity, three sets of assumptions are explored regarding migration flows, taking into account probable policy developments in Europe following the enlargement of the EU. In addition to age structures, various support ratio indicators are analysed. The results indicate that plausible immigration cannot offset the negative effects of population and labour force ageing

Resonant Tunneling Controlled by Laser and Constant Electric Fields

We develop the concept of scattering matrix and we use it to perform stable numerical calculations of resonant tunneling of electrons through a multiple potential barrier in a semiconductor heterostructure. Electrons move in two external nonperturbative electric fields: constant and oscillating in time. We apply our algorithm for different strengths and spatial configurations of the fields

Photoemission and high-order harmonic generation from solid surfaces in intense laser fields

Faisal F, Kaminski JZ, Saczuk E. Photoemission and high-order harmonic generation from solid surfaces in intense laser fields. PHYSICAL REVIEW A. 2005;72(2): 023412.We give a Floquet analysis of photoemission of electrons and high-order harmonic generation from a solid surface interacting with intense laser fields. A general theoretical algorithm, within a three-dimensional quasi-free-electron model, is presented. It takes account of the effective masses of the electron both within and outside the solid, as well as treating both reflected and refracted laser fields. The steady-state photocurrent is obtained from the diagonal photon components of the expectation value of the time-dependent current operator outside the surface, while the off-diagonal terms of the expectation value of the current operator from both inside and outside the surface provide the probability of coherent emission of high-order harmonic radiation. It is found, among other things, that electrons can be emitted from the surface requiring no net absorption of photons or even accompanied by emission of extra photons. The origin of the effect lies in the difference in the ponderomotive energy inside and outside the surface that can arise from the small ratio of the effective mass of the electron inside the solid (e.g., GaAs) and the mass of the free electron. Another result of qualitative significance is the formation of a plateau, well known in the atomic case, in both the kinetic energy distribution of the photocurrent and the spectrum of the high-order harmonic radiation. They are shown to arise in the present case from the evanescent part of the electron wave function at the surface

Photoemission from solid surfaces in intense laser fields

Faisal F, Kaminmski JZ, Saczuk E. Photoemission from solid surfaces in intense laser fields. LASER PHYSICS. 2006;16(2):284-288.We present a Floquet analysis of photoemission of electrons from a solid surface due to its interaction with a laser beam. The method we use is based on a three-dimensional quasifree electron model. The model takes account of the changes in the effective mass of the electron inside and outside the solid and in the reflected and refracted beams due to the presence of the surface. It is shown that the photoemission of electrons from the solid surface may take place not only with no absorption of photons but also along with the emission of extra photons

Household living conditions. The labour market

Household living conditions. The labour marke

Assessment of selected risk factors of cardiovascular diseases among a population with various nutritional status, based on the example of students of the Faculty of Physical Education and Sports at the University of Physical Education in Biala Podlaska

Wprowadzenie. Nieprawidłowe żywienie, nadciśnienie tętnicze, nadmierna masa ciała oraz zaburzenia wskaźników biochemicznych krwi u młodych osób mogą mieć znaczący wpływ na rozwój chorób układ krążenia w wieku dorosłym. Wczesne wykrywanie i przeciwdziałanie występowaniu czynników ryzyka może radykalnie zmniejszyć zachorowalność w przyszłości. Cel pracy. Celem pracy było zbadanie, czy występują różnice w zwyczajowo spożywanej diecie, profilu lipidowym i ciśnieniu tętniczym krwi, oraz wykazanie, czy analizowane czynniki stanowią ryzyko zagrożenia rozwoju chorób układu krążenia u studentów Wydziału Wychowania Fizycznego i Sportu AWF w Białej Podlaskiej różniących się wskaźnikiem względnej masy ciała (BMI). Materiał i metody. Badaniami objęto 340 studentów. Wielkość cech somatycznych i żywieniowych oceniono ogólnie przyjętymi metodami. Wykonano standardowe pomiary ciśnienia tętniczego oraz oznaczono stężenie cholesterolu (TC) i triglicerydów (TG) w surowicy krwi. Analizie poddano parametry antropometryczne, biochemiczne, żywieniowe, oraz ciśnienie tętnicze krwi w grupach osób różniących się wskaźnikiem względnej masy ciała. Wyniki. Wykazano, że wraz ze wzrostem BMI nastąpił spadek spożycia energii, białka oraz tłuszczu, którego pobranie z diety było istotnie niższe (p≤0,05) u mężczyzn z nadwagą aniżeli z masą ciała w normie (80,1±36,3 kcal∙d-1 vs. 94,7±35,9 kcal∙d-1). Wzrost masy ciała nie powodował natomiast istotnych zmian odsetka osób, u których średnie wartości stężenia TC i TG w surowicy krwi przekraczały wartości graniczne (TC>190mg/dl i TG>150mg/dl), jednakże miał wpływ na istotne zwiększenie odsetka kobiet (G=6,04; p≤0,05) z ciśnieniem prawidłowym wysokim. Wnioski. Przeprowadzone badania przyczyniły się do pogłębienia wiedzy na temat zależności pomiędzy BMI a czynnikami ryzyka chorób układu krążenia. Wykazano, że masa ciała miała znaczący wpływ na zmiany niektórych czynników ryzyka chorób układu krążenia.Introduction. Inappropriate nutrition, arterial hypertension, excessive body weight and improper levels of biochemical blood indices among the young population may exert a considerable influence on the development of cardiovascular diseases in adulthood. Early detection and counteracting the occurrence of risk factors may radically decrease the morbidity rate in the future. Objective. The objective of the study was to discover whether there occur differences in diet, lipid profile and blood pressure, and to reveal whether the studied factors may lead to the development of cardiovascular diseases in students of the Faculty of Physical Education and Sport at the University of Physical Education in Biala Podlaska, who differed with respect to the body mass index (BMI). Material and methods. The study included 340 students. Somatic and nutritional characteristics were assessed with the use of commonly adopted methods. Standard measurements of blood pressure were made. Standard measurements of arterial blood pressure were performed, and levels of total cholesterol (TC) and triglycerides (TG) in blood serum determined. Anthropometric, biomechanical and nutritional parameters were analysed and blood pressure was measured in the groups of subjects that differed in BMI. Results. It was found that an increase in the BMI was accompanied by a decrease in energy, fat and protein intake. Fat intake was significantly lower (p≤0.05) in overweight males than in males who had a normal body weight (80.1±36.3 kcal•d-1 vs. 94.7±35.9 kcal•d-1). An increase in body weight, however, did not bring about any significant changes in the proportion of subjects whose mean values of TC and TG levels in blood serum exceeded threshold values (TC>190mg/dl and TG>150mg/dl), but this led to a significant increase in the percentage of women examined (G=6.04; p≤0.05) with prehypertension. Conclusions. The study contributed to the expansion of knowledge regarding relations between BMI and risk factors of cardiovascular diseases. It was confirmed that body weight had a significant effect on changes in some of the risk factors of cardiovascular diseases