Magnetic interactions in EuTe epitaxial layers and EuTe/PbTe superlattices

The magnetic properties of antiferromagnetic (AFM) EuTe epitaxial layers and short period EuTe/PbTe superlattices (SLs), grown by molecular beam epitaxy on (111) BaF$_2$ substrates, were studied by magnetization and neutron diffraction measurements. Considerable changes of the N\'eel temperature as a function of the EuTe layer thickness as well as of the strain state were found. A mean field model, taking into account the variation of the exchange constants with the strain-induced lattice distortions, and the nearest neighbor environment of a Eu atoms, was developed to explain the observed $T_{\text N}$ changes in wide range of samples. Pronounced interlayer magnetic correlations have been revealed by neutron diffraction in EuTe/PbTe SLs with PbTe spacer thickness up to 60 \AA. The observed diffraction spectra were analyzed, in a kinematical approximation, assuming partial interlayer correlations characterized by an appropriate correlation parameter. The formation of interlayer correlations between the AFM EuTe layers across the nonmagnetic PbTe spacer was explained within a framework of a tight-binding model. In this model, the interlayer coupling stems from the dependence of the total electronic energy of the EuTe/PbTe SL on the spin configurations in adjacent EuTe layers. The influence of the EuTe and PbTe layer thickness fluctuations, inherent in the epitaxial growth process, on magnetic properties and interlayer coupling is discussed.Comment: 17 pages, 19 figures, accepted to PR

Ferromagnetic GaMnAs/GaAs superlattices - MBE growth and magnetic properties

We have studied the magnetic properties of (GaMnAs)m/(GaAs)n superlattices with magnetic GaMnAs layers of thickness between 8 and 16 molecular layers (ML) (23-45 \AA), and with nonmagnetic GaAs spacers from 4 ML to 10 ML (11-28 \AA). While previous reports state that GaMnAs layers thinner than 50 \AA are paramagnetic in the whole Mn composition range achievable using MBE growth (up to 8% Mn), we have found that short period superlattices exhibit a paramagnetic-to-ferromagnetic phase transition with a transition temperature which depends on both the thickness of the magnetic GaMnAs layer and the nonmagnetic GaAs spacer. The neutron scattering experiments have shown that the magnetic layers in superlattices are ferromagnetically coupled for both thin (below 50 \AA) and thick (above 50 \AA) GaMnAs layers.Comment: Proceedings of 4th International Workshop on Molecular Beam Epitaxy and Vapour Phase Epitaxy Growth Physics and Technology, September 23 - 28 (2001), Warszawa, Poland, to appear in Thin Solid Films. 24 pages, 8 figure

How does gender influence the recognition of cardiovascular risk and adherence to self-care recommendations? : a study in polish primary care

Background: Studies have shown a correlation between gender and an ability to change lifestyle to reduce the risk of disease. However, the results of these studies are ambiguous, especially where a healthy lifestyle is concerned. Additionally, health behaviors are strongly modified by culture and the environment. Psychological factors also substantially affect engagement with disease-related lifestyle interventions. This study aimed to examine whether there are differences between men and women in the frequency of health care behavior for the purpose of reducing cardiovascular risk (CVR), as well as cognitive appraisal of this type of risk. We also aimed to identify the psychological predictors of engaging in recommended behavior for reducing the risk of cardiovascular disease after providing information about this risk in men and women. Methods: A total of 134 consecutive eligible patients in a family practice entered a longitudinal study. At initial consultation, the individual’s CVR and associated health burden was examined, and preventive measures were recommended by the physician. Self-care behavior, cognitive appraisal of risk, and coping styles were then assessed using psychological questionnaires. Six months after the initial data collection, the frequency of subjects’ self-care behavior was examined. Results: We found an increase in health care behavior after providing information regarding the rate of CVR in both sexes; this increase was greater for women than for men. Women followed self-care guidelines more often than men, particularly for preventive measures and dietary advice. Women were more inclined to recognize their CVR as a challenge. Coping style, cognitive appraisal, age, level of health behaviors at baseline and CVR values accounted for 48% of the variance in adherence to self-care guidelines in women and it was 52% in men. In women, total risk of CVD values were most important, while in men, cognitive appraisal of harm/loss was most important. Conclusions: Different predictors of acquisition of health behavior are encountered in men and women. Our results suggest that gender-adjusted motivation models influencing the recognition process need to be considered to optimize compliance in patients with CVR

Analiza wydajności harwestera Highlander przy maszynowym pozyskiwaniu drewna

The paper presents the work performance analysis of timber harvesting with the use of Highlander harvester produced by KONRAD Forsttechnik GmbH. The analysis was performed based on the timing of the working day. We also assessed the organization of the machine operation in the research area and its functional capability. The study was conducted in Miçdzylesie Forest Department, Nowu Wieś Forestry in fresh mixed mountain forest, where the machine acquired spruce. Timing was perfonned based on the registration of the machine operation on a video camera and the measurements of collected assortment. Based on the results of measurements it was found that organization of the machine operation was not the best. A one-shift work system and short duration of a shift caused that the effective working time occupied only 67.9% of the shift time (about 4 hours). This resulted in reduction of the operating perfonnance on a working day which was only 12,7 m3·h-1, while an effective high-efficiency was 18.7 m3·h-1.W artykule przedstawiono analizę wydajności harwestera Highlander firmy Konrad Forsttechnic GmbH, przy maszynowym pozyskiwaniu drewna. Analizę wykonano w oparciu o chronometraż dnia roboczego, co posłużyło również do oceny organizacji pracy oraz funkcjonalności badanego harwestera. Badania przeprowadzono na terenie Nadleśnictwa Międzylesie, Leśnictwo Nowa Wieś na typie siedliskowym lasu las mieszany górski świeży (LMGśw), gdzie harwester pozyskiwał drewno świerkowe. Chronometraż wykonano w oparciu o rejestrację czasu eksploatacji harwestera przy pomocy kamery wideo oraz pomiarów pozyskanego sortymentu. Na podstawie uzyskanych wyników stwierdzono, że organizacja pracy maszyny nie była najlepsza. Jednozmianowy system pracy oraz krótki czas trwania zmiany spowodował, że efektywny czas pracy wynosił tylko 67,9% czasu zmiany tj. ok 4 h. Pomimo wysokiej wydajności efektywnej harwestera, która wyniosła 18,7 m3·h-1, to uzyskana przez niego wydajność eksploatacyjna była niska i wyniosła 12,7 m3·h-1

Hardware Accelerated Simulation of Crest Factor Reduction Block for Mobile Telecommunications

This paper reports results of the hardware accelerated simulations of the crest factor reduction (CFR) block which is a common element of the radio signal processing path in base stations for mobile telecommunications. Presented approach increases productivity of radio system architects by shortening the time of model architecture evaluation. This enables unprecedented scale of CFR parameter optimization which requires thousands of simulation runs. We use FPGA device and Xilinx System Generator for DSP technology in order to model CFR block in MATLAB/Simulink environment, implement the accelerator and use it for mixed hardware-software simulation. Reported approach reduces simulation time by 70%, provides straight forward use of fixed-point arithmetic and lowers power consumption by 73% at the cost of constant and relatively low overhead on model development

Effect of Sewage Sludge Applied to Sandy Soils on the Sorption Complex Properties

Properties of soil sorption complex are thought to be one of the most important elements which affect its fertility and properties of plants. Extended sorption complex is the element which immobilizes and absorbs a variety of soil contaminants. Characteristics of sorption complex are affected by e.g. organic matter, humic relationships which occur during decomposition of organic matter, clay materials, pH, hydrolytic acidity. Soil reaction is regarded to be one of the most important indicators of soil fertility. Soil reaction largely determines its physical, chemical and biological properties. Foundation acidity affects the structure firmness and the related water and air conditions. One of the methods of disposal of sewage sludge, which is based on its fertilizing properties, is its use in nature, e.g. in farming (if all the permissible standards are met). However, the sludge used for soil fertilization might also contain heavy metals which cause soil contamination and are accumulated in plants. The effect of application of organic fertilizers on soil reaction and other properties of sorption complex are also essential. The authors of the present study aimed at analysis of the effect of use of sewage sludge and selected organic fertilizers on changes in sorption properties in the fertilized soils. Sewage sludge was (for comparison purposes) was introduced to sandy soil. One of organic additions was also composted pine bark. The experiment was carried out under conditions of pot experiment. The following doses of organic fertilizers were used: 0, 10, 50, 100 and 200 Mg/ha (maximal reclamation dose according to current recommendations at the time of experiment) which were calculated per pot with 10 kg of sandy soil. After 1, 2 and 3 years from fertilization, changes in active and hydrolytic acidity were analysed in the fertilized foundations. The contents of organic matter, total of alkali in sorption complex S, soil sorption capacity T in fertilized soils was also determined. In summary of the obtained results, one can conclude that the use of organic fertilizers, either manure or sewage sludge, considerably affects properties of sorption complex in fertilized soil. Organic fertilization improved soil properties. The total of exchangeable alkali and sorption complex capacity also increased. However, it was only manure used during the experiment that contributed to a reduction in the acidity of the fertilized soils in each case. It was found that the use of sewage sludge has significant effect on long-term phenomena of soil acidification. These mechanisms are confirmed by the obtained values of hydrolytic acidity

Studies of Interlayer Magnetic Coupling in All-Semiconductor Superlattices by Means of Neutron Scattering Techniques

An overview of neutron scattering studies of ferromagnetic and antiferromagnetic all-semiconductor superlattices is presented. Diffraction experiments on MnTe/CdTe, MnTe/ZnTe and EuTe/PbTe superlattices show pronounced correlations between the MnTe and EuTe layers across the non-magnetic spacers, even though these layers are antiferromagnetic and the systems are nearly-insulating. Current theory status of these systems is discussed. Diffractometry and reflectometry data from EuS/PbS superlattices reveal pronounced antiferromagnetic coupling between the ferromagnetic EuS block. First polarized neutron reflectometry data from superlattices prepared of a novel ferromagnetic"spintronics" material, Ga(Mn)As, are also presented

Reinvestigation of the B

Conventional, high resolution molecular spectroscopy has been employed to record emission spectra of the first negative bands system in the 12C16O+ molecule. Twenty two bands form the $0-v'',1-v'', 2-v'', 3-v'', 4-v'', 5-v''$ progressions and 6-10 band were photographed in the $34000{-}46000$ cm-1 spectral region. The reduction of the spectrum for the individual bands has been performed via a nonlinear least-squares fit with the effective Hamiltonians of Brown et al. [J. Mol. Spectrosc. 74, 294 (1979)]. The final molecular constants for both the $B^{2}\Sigma^{+}$ ($v=0-6$) and $X^{2}\Sigma^{+}$ ($v=0-10$) states were obtained from global merge calculations of the present data of the $B\rightarrow X$ system and previously obtained in our laboratory data for $A \rightarrow X$ and $B \rightarrow A$ systems in the CO+ molecule. Merged molecular parameters have been used in order to the determine the equilibrium constants for both considered states. The $\gamma_{e}=2.194(14) \times 10 ^{-2}$ cm-1 and $\alpha_{\gamma e}=-1.021(64)\times 10^{-4}$ cm-1 constants for the $B^{2}\Sigma^{+}$ state were obtained for the first time. The RKR potentials have been calculated for both combining states, as well as Franck-Condon factor and r-centroids for the first negative system in the 12C16O+ molecule. Furthermore, we report the value of the electronic isotopic shift $\Delta\nu_{e} = -0.395$ cm -1 of the $B\rightarrow X$ system in 13C16O+, calculated on the basis the presents results and those obtained by us previously for the 13C16O+ molecule.

Analysis of the A 1

This paper presents an attempt of examining the irregularities appearing in a complicated A$\text{}^{1}$Π state of the CH$\text{}^{+}$ molecule with their reasons provided. By using the experimental data for the A$\text{}^{1}$Π-X$\text{}^{1}$Σ$\text{}^{+}$ bands system of the $\text{}^{12}$CH$\text{}^{+}$ ion radical, it was proved that the vibrational and rotational quanta of the upper state reveal the same unusual behaviour, i.e. very clear nonlinear dependence on vibrational quantum number (v'≥3) of the upper state. Therefore, upper vibrational levels (v'≥3) of the A$\text{}^{1}$Π state cannot be determined by means of the equilibrium constants calculated in the previous works. Due to so far unidentified A$\text{}^{1}$Π state perturbations, the reduction of the wave numbers to the rovibronic parameters was carried out by means of individual, band-by-band analysis method, using with this end in view the nonlinear least squares method introduced by Curl and Dane, and Watson. This method allowed one to make already calculated constants of the rovibronic structure of regular lower state X$\text{}^{1}$Σ$\text{}^{+}$ of A-X system independent of possible perturbations appearing in the upper state of A$\text{}^{1}$Π of this system. It also enabled one to calculate for the first time the real (perturbed) term values for the A$\text{}^{1}$Π (v' =0, 1, 2, and 3) state of the $\text{}^{12}$CH$\text{}^{+}$ ion molecule. These values suggest that rotational irregularities in the A$\text{}^{1}$Π state examined are negligibly small. In order to confirm the nonexistence of rotational perturbations in the A$\text{}^{1}$Π (v' =0, 1, 2, and 3) state, up to the observed J$\text{}_{m}$ax level, appropriate graphs of functions f$\text{}_{x}$(J) and g$\text{}_{x}$(J) introduced by Gerö and Kovács, where x = Q, PR, and overline{PR}, were drawn. Also, their course was analysed in detail

Emission Spectroscopy of AlH: the X¹Σ⁺, A¹Π and C¹Σ⁺ States Characteristics

The visible spectrum of AlH has been investigated at high resolution between 20000 and 21500 $cm^{-1}$ using a conventional spectroscopic technique. The AlH molecules were formed and excited in an aluminium hollow-cathode lamp with two anodes, filled with a mixture of Ne carried gas and a trace of $NH_3$. The emission from the discharge was observed with a plane grating spectrograph and recorded by a photomultiplier tube. The 0-0 and 1-1 bands of the C¹Σ⁺-A¹Π system and 0-2 band of the A¹Π-X¹Σ⁺ were identified at 21126, 21368 and 20276 $cm^{-1}$, respectively. In total 121 transition wave numbers belonging to three bands were precisely measured (with accuracy of ±0.003 cm^{-1}) and rotationally analysed. The new data were elaborated with the help of recent X¹Σ⁺ state parameters reported by White et al. and of the C¹Σ⁺, A¹Π states constants reported by Szajna and Zachwieja. As a result of this merged analysis the set of the molecular parameters and rotational terms values for the three lower lying states of the AlH molecule have been significantly improved