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Search Results: 1 - 10 of 461720 matches for " A. Hoser "
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Neutron Back- and Front-Face Bragg Diffraction on a Thin Si Single Crystal Excited by Ultrasound  [PDF]
E. Raitman, V. Gavrilov, D. Mjasischev, Ju. Ekmanis, A. Hoser, T. Hoffmann
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.61006
Abstract: In this research project, we measured and analyzed the spatial distribution of neutron beam Bragg diffracted from the front- and back-faces of thin Si single crystal undergoing on ultrasound excitation. For the perfect crystal, it is shown that when the acoustic wave amplitude is increased, the front-face peak position remains unchanged and its value grows linearly. The values of ultrasound wave amplitude were determined. The back-face peak becomes asymmetric and tends to disappear. New types of Pendellosung fringes in the center of the diffraction profiles were observed at the first time. It is supposed that in the perfect crystal this effect may be due to the appearance of the new “sonic” extinction length, depending on the amplitude of the ultrasonic wave. Thus, it leads to the new interference interactions between neutron wave and ultrasonic phonons. It is established that within the framework of the dynamical theory of the neutron scattering, some asymptotic models valid for the case of Laue geometry as well as Kato’s quasi-classical approximation can be applied in the case of Bragg geometry also. Good agreement between experimental data and the theory has been obtained.
Expression of Fas receptor on peripheral blood lymphocytes from patients with non-small cell lung cancer.
Grazyna Hoser,Danuta Wasilewska,Joanna Domaga?a-Kulawik
Folia Histochemica et Cytobiologica , 2005, DOI: 10.5603/4632
Abstract: In recent years many data indicate that lymphocytes from cancer patients undergo increased apoptosis. The objective of this study was to evaluate the expression of Fas receptor on lymphocytes obtained from patients with lung cancer. Eighteen patients with non-small cell lung cancer and 18 healthy volunteers were investigated. Expression of Fas (CD95) on CD4+ and CD8+ blood lymphocytes was evaluated by flow cytometry. The proportion of blood Fas+ lymphocytes was significantly higher in lung cancer patients when compared with healthy individuals and in smokers when compared with nonsmokers.
Proximity effect of vanadium on spin-density-wave magnetism in Cr films
E. Kravtsov,R. Brucas,B. Hjorvarsson,A. Hoser,A. Nefedov,F. Radu,A. Remhof,S. Wilkins
Physics , 2004, DOI: 10.1103/PhysRevB.70.054425
Abstract: The spin-density wave (SDW) state in thin chromium films is well known to be strongly affected by proximity effects from neighboring layers. To date the main attention has been given to effects arising from exchange interactions at interfaces. In the present work we report on combined neutron and synchrotron scattering studies of proximity effects in Cr/V films where the boundary condition is due to the hybridization of Cr with paramagnetic V at the interface. We find that the V/Cr interface has a strong and long-range effect on the polarization, period, and the N\'{e}el temperature of the SDW in rather thick Cr films. This unusually strong effect is unexpected and not predicted by theory.
Magnetic field induced Ising axis conversion in Tb0.5Dy0.5Cu2 single crystals
Loewenhaupt, M.;Doerr, M.;Rotter, M.;Reif, T.;Schneidewind, A.;Hoser, A.;
Brazilian Journal of Physics , 2000, DOI: 10.1590/S0103-97332000000400022
Abstract: we study the ising axis conversion in a mixed tb0.5dy0.5cu2 single crystal. interest is focused on how changes in the exchange interactions due to rare earth substitutions influence the existence of magnetic phases and the critical field values for the ising axis conversion. from magnetisation measurements we determined the (h - t ) phase diagram for magnetic fields parallel to the easy a-axis and the temperature dependence of the critical field for the ising axis conversion. both properties for the mixed crystal follow a simple composition scaling behavior. but in contrast to previous studies on the pure compounds tbcu2 and dycu2 the changes of magnetic and structural properties at the conversion cannot be recovered completely by thermal treatment. only a small part (10 % of the sample volume) goes back to the virgin state after warming the sample to 500 k. this behavior is of great interest for further neutron or x-ray diffraction studies of the ising axis conversion allowing to study the converted phase under routinely used experimental conditions.
Aplicación de la termodifractometría de neutrones al estudio de procesos de cristalización en mullitas sol-gel
Villar, M. P.,Gago-Duport, L.,Hoser, A.,García, R.
Boletín de la Sociedad Espa?ola de Cerámica y Vidrio , 2000,
Abstract: Neutron thermodiffractometry experiments are carried out with linear increase of temperature as function of time. At each constant time range a pattern is obtained, corresponding to an average of the temperatures in this interval, so an in-situ study of several processes such as crystallization from amorphous powders and phase transitions is possible. Mullite is a wellknown material, however some controversial concerning aspects of its formation still remains. This is the case of the knowledge about the full phases sequence during mullite crystallization, even more if some transition metal is present in the system. In the present paper we use this techique to analyse, in real time, the Cr-doped mullite formation from an amorphous gel heated in the temperature range of 200-1400oC. Los experimentos de termodifractometría de neutrones, o difracción de neutrones a alta temperatura, se realizan variando linealmente la temperatura de la muestra con el tiempo. Así, a intervalos de tiempo constantes se obtiene un difractograma que corresponde a un promedio del intervalo de temperaturas variado. Ello permite el seguimiento in-situ de procesos tales como cristalización de amorfos y transiciones de fases en diversos materiales. A pesar de que la mullita es una cerámica ampliamente conocida desde hace a os, aún existen aspectos de su formación que no han sido caracterizados de manera bien definida y sobre los que no existe un consenso claro. Uno de ellos es el de la determinación de la secuencia de fases que culminan en su cristalización, sobre todo tratándose de materiales dopados con metales de transición, escasamente estudiados en la literatura. Además, la aplicación de la termodifractometría de neutrones a estos materiales permite eliminar ambigüedades inherentes al empleo de radiación X. Por todo ello, en la presente comunicación, se hace uso de esta técnica para analizar, en tiempo real, el proceso de formación de mullita dopada con Cr a partir de la cristalización de un gel amorfo sometido a tratamiento térmico en un intervalo de temperaturas comprendido entre 200 y 1400oC.
Columnar magnetic structure coupled with orthorhombic distortion in the antiferromagnetic iron arsenide SrFe$_2$As$_2$
K. Kaneko,A. Hoser,N. Caroca-Canales,A. Jesche,C. Krellner,O. Stockert,C. Geibel
Physics , 2008, DOI: 10.1103/PhysRevB.78.212502
Abstract: Neutron powder diffraction experiments were carried out on polycrystalline SrFe$_2$As$_2$ in order to determine the magnetic structure and its relationship with the crystallographic one. Below $T_0$=205 K, magnetic reflections appear simultaneously with the onset of the orthorhombic distortion. From a detailed Rietveld analysis, the magnetic propagation vector of SrFe$_2$As$_2$ is determined to be {\textit{\textbf{q}}}=(1 0 1); the coupling of Fe moments is antiferromagnetic along the longer $a$ direction within the Fe-As layer, and the interlayer coupling is antiferromagnetic as well. The size of the Fe magnetic moment is deduced to be 1.01(3) ${\mu}_{\rm B}$ with an orientation parallel to the a-axis. The temperature dependence of the magnetic moment shows excellent agreement with not only that of the muon precession frequency but also with that of the structural distortion, revealing the strong coupling of the columnar magnetic order and the structural distortion in SrFe$_2$As$_2$.
High Magnetic Field Behaviour of the Triangular Lattice Antiferromagnet, CuFeO_2
O. A. Petrenko,G. Balakrishnan,M. R. Lees,D. McK Paul,A. Hoser
Physics , 2000, DOI: 10.1103/PhysRevB.62.8983
Abstract: The high magnetic field behaviour of the triangular lattice antiferromagnet CuFeO_2 is studied using single crystal neutron diffraction measurements in a field of up to 14.5 T and also by magnetisation measurements in a field of up to 12 T. At low temperature, two well-defined first order magnetic phase transitions are found in this range of applied magnetic field (H // c): at H_c1=7.6(3)/7.1(3) T and H_c2=13.2(1)/12.7(1) T when ramping the field up/down. In a field above H_c2 the magnetic Bragg peaks show unusual history dependence. In zero field T_N1=14.2(1) K separates a high temperature paramagnetic and an intermediate incommensurate structure, while T_N2=11.1(3) K divides an incommensurate phase from the low-temperature 4-sublattice ground state. The ordering temperature T_N1 is found to be almost field independent, while T_N2 decreases noticeably in applied field. The magnetic phase diagram is discussed in terms of the interactions between an applied magnetic field and the highly frustrated magnetic structure of CuFeO_2
Observation of Field-Induced Transverse Néel Ordering in the Spin Gap System TlCuCl$_3$
H. Tanaka,A. Oosawa,T. Kato,H. Uekusa,Y. Ohashi,K. Kakurai,A. Hoser
Physics , 2001, DOI: 10.1143/JPSJ.70.939
Abstract: Neutron elastic scattering experiments have been performed on the spin gap system TlCuCl$_3$ in magnetic fields parallel to the $b$-axis. The magnetic Bragg peaks which indicate the field-induced N\'{e}el ordering were observed for magnetic field higher than the gap field $H_{\rm g}\approx 5.5$ T at $Q=(h, 0, l)$ with odd $l$ in the $a^*-c^*$ plane. The spin structure in the ordered phase was determined. The temperature and field dependence of the Bragg peak intensities and the phase boundary obtained were discussed in connection with a recent theory which describes the field-induced N\'{e}el ordering as a Bose-Einstein condensation of magnons.
Neutron diffraction study of spin and charge ordering in SrFeO(3-delta)
M. Reehuis,C. Ulrich,A. Maljuk,Ch. Niedermayer,B. Ouladdiaf,A. Hoser,T. Hofmann,B. Keimer
Physics , 2012, DOI: 10.1103/PhysRevB.85.184109
Abstract: We report a comprehensive neutron diffraction study of the crystal structure and magnetic order in a series of single-crystal and powder samples of SrFeO$_{3-\delta}$ in the vacancy range $0 \leq \delta \leq 0.23$. The data provide detailed insights into the interplay between the oxygen vacancy order and the magnetic structure of this system. In particular, a crystallographic analysis of data on Sr8Fe8O23 revealed a structural transition between the high-temperature tetragonal and a low-temperature monoclinic phase with a critical temperature T = 75 K, which originates from charge ordering on the Fe sublattice and is associated with a metal-insulator transition. Our experiments also revealed a total of seven different magnetic structures of SrFeO$_{3-\delta}$ in this range of $\delta$, only two of which (namely an incommensurate helix state in SrFeO3 and a commensurate, collinear antiferromagnetic state in Sr4Fe4O11) had been identified previously. We present a detailed refinement of some of the magnetic ordering patterns and discuss the relationship between the magneto-transport properties of SrFeO$_{3-\delta}$ samples and their phase composition and magnetic microstructure.
Characterization of a new small cell lung cancer (SCLC) cell line STP54 derived from a metastatic bioptate of a combined type of SCLC with Non-SCLC component.
Tomasz Skirecki,Grazyna Hoser,Joanna Domaga?a-Kulawik,Jerzy Kawiak
Folia Histochemica et Cytobiologica , 2009, DOI: 10.5603/4370
Abstract: Small cell lung cancer constitutes 15-20% cases of lung cancers, currently the leading cause of death from malignant diseases. It also causes the demise of >90% of affected individuals in 5 years. We have established a new SCLC cell line STP54 derived from fine needle aspirate of metastatic supraclavicular lymph node of 54 -year-old women for model experiments. The primary tumor was diagnosed by histopathological examination as combined type of small cell lung cancer with a non-small cell component. We cultured the cancer cells in the RPMI 1640 medium. In the long-term culture only the small cell component survived. The cell line was established after 30 passages and then characterized by performing cell morphology, cell growth analysis, tumorigenicity in vitro and flow cytometry analysis of selected markers (like NCAM, cytokeratines, HLA-ABC, Fas, Bcl-2, p53, CXCR4, CD210). The cells were growing in floating aggregates and show features suggesting its invasiveness. We suggest that this new cell line may serve as a valuable tool for further studies on lung tumor biology, molecular pathogenesis and metastatic mechanism.
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