803 research outputs found
The giant effect of magnetic ordering on a sound velocity in a sigma-Fe55Cr45 alloy
We studied atomic dynamics of sigma-Fe(100-x)Cr(x) (x=45 and 49.5) alloys
using nuclear inelastic scattering of synchrotron radiation. For the
sigma-Fe55Cr45 alloy, the derived reduced iron-partial density of phonon states
reveal a huge difference in the low-energy region between magnetic and
paramagnetic states. The latter implies a ca.36% increase of the sound velocity
in the magnetic phase, which testifies to a magnetically-induced hardening of
the lattice.Comment: 8 pages, 3 figures, 17 reference
Pressure-induced changes of the vibrational modes of spin-crossover complexes studied by nuclear resonance scattering of synchrotron radiation
Nuclear inelastic scattering (NIS) spectra were recorded for the
spin-crossover complexes STP and ETP (STP =
[Fe(1,1,1-trisf[N-(2-pyridylmethyl)-N-methylamino]methylg- ethane)](ClO4)2 and
ETP =
[Fe(1,1,1-trisf[N-(2-pyridylmethyl)-N-methylamino]methylg-butane)](ClO4)2) at
30 K and at room temperature and also at ambient pressure and applied pressure
(up to 2.6 GPa). Spin transition from the high-spin (HS) to the low-spin (LS)
state was observed by lowering temperature and also by applying pressure at
room temperature and has been assigned to the hardening of iron-bond stretching
modes due to the smaller volume in the LS isomer
Double-spiral magnetic structure of the Fe/Cr multilayer revealed by nuclear resonance scattering
We have studied the magnetization depth profiles in a [57Fe(dFe)/Cr(dCr)]x30
multilayer with ultrathin Fe layers and nominal thickness of the chromium
spacers dCr 2.0 nm using nuclear resonance scattering of synchrotron radiation.
The presence of a broad pure-magnetic half-order (1/2) Bragg reflection has
been detected at zero external field. The joint fit of the reflectivity curves
and Mossbauer spectra of reflectivity measured near the critical angle and at
the "magnetic" peak reveals that the magnetic structure of the multilayer is
formed by two spirals, one in the odd and another one in the even iron layers,
with the opposite signs of rotation. The double-spiral structure starts from
the surface with the almost antiferromagnetic alignment of the adjacent Fe
layers. The rotation of the two spirals leads to nearly ferromagnetic alignment
of the two magnetic subsystems at some depth, where the sudden turn of the
magnetic vectors by ~180 deg (spin-flop) appears, and both spirals start to
rotate in opposite directions. The observation of this unusual double-spiral
magnetic structure suggests that the unique properties of giant
magneto-resistance devices can be further tailored using ultrathin magnetic
layers.Comment: 9 pages, 3 figure
Tracking the connection between disorder and energy landscape in glasses using geologically hyperaged amber
Fossil amber offers the unique opportunity of investigating an amorphous
material which has been exploring its energy landscape for more than 110 Myears
of natural aging. By applying different x-ray scattering methods to amber
before and after annealing the sample to erase its thermal history, we identify
a link between the potential energy landscape and the structural and
vibrational properties of glasses. We find that hyperaging induces a depletion
of the vibrational density of states in the THz region, also ruling the sound
dispersion and attenuation properties of the corresponding acoustic waves.
Critically, this is accompanied by a densification with structural implications
different in nature from that caused by hydrostatic compression. Our results,
rationalized within the framework of fluctuating elasticity theory, reveal how
upon approaching the bottom of the potential energy landscape (9% decrease in
the fictive temperature ) the elastic matrix becomes increasingly less
disordered (6%) and longer-range correlated (22%).Comment: 9 pages, 10 figure
Density of Phonon States in Superconducting FeSe as a Function of Temperature and Pressure
The temperature and pressure dependence of the partial density of phonon
states of iron atoms in superconducting Fe1.01Se was studied by 57Fe nuclear
inelastic scattering (NIS). The high energy resolution allows for a detailed
observation of spectral properties. A sharpening of the optical phonon modes
and shift of all spectral features towards higher energies by ~4% with
decreasing temperature from 296 K to 10 K was found. However, no detectable
change at the tetragonal - orthorhombic phase transition around 100 K was
observed. Application of a pressure of 6.7 GPa, connected with an increase of
the superconducting temperature from 8 K to 34 K, results in an increase of the
optical phonon mode energies at 296 K by ~12%, and an even more pronounced
increase for the lowest-lying transversal acoustic mode. Despite these strong
pressure-induced modifications of the phonon-DOS we conclude that the
pronounced increase of Tc in Fe1.01Se with pressure cannot be described in the
framework of classical electron-phonon coupling. This result suggests the
importance of spin fluctuations to the observed superconductivity
Magnetic Phase Separation and Magnetic Moment Alignment in Ordered Alloys FE 65
The structure and the magnetic state of ordered Fe65Al35-xMx (Mx = Ga, B; x = 0; 5 at.%) alloys are investigated using X-ray diffraction, Mössbauer spectroscopy, and magnetic measurements. The behavior of the magnetic characteristics and Mössbauer spectra of the binary alloy Fe65Al35 and the ternary alloy with gallium addition Fe65Al30Ga5 is explained in terms of the phase separation into two magnetic phases: a ferromagnetic one and a spin density wave. It is shown that the addition of boron to the initial binary alloy Fe65Al35 results in the ferromagnetic behavior of the ternary alloy
EPIDEMIOLOGY OF AGE-RELATED ANDROGEN DEFICIENCY IN PATIENTS WITH BENIGN PROSTATIC HYPERPLASIA
Every fourth patient at the age of 50 years, every third patient at the age of 60 years, every second man at the age of 70 years and almost everyone (90%) older than 80 years have Benign prostatic hyperplasia (BPH). Lower urinary tract symptoms developing against the background of BPH are often connected both with manifestations of the hyperplasia of a prostate, and with the age androgenic deficiency (AAD). Aim: To determine the frequency of emergence of age androgenic deficiency of patients with Benign prostatic hyperplasia (BPH). Materials and Methods: 180 patients with clinical signs of Benign prostatic hyperplasia have been examined. All patients were conducted with standard clinical examination: survey, measurement of International prostate symptom score (IPSS), assessment of quality of life (QOL). The research of the androgenic status of patients included clinical assessment of deficiency of androgens with the use of the standard international questionnaire: “The questionnaire of Aging Males’ Symptoms” (AMS) and hormonal blood test with determination of level of the general testosterone, follicle-stimulating and luteinizing hormones. Results: There were 118 patients with the low level of the general testosterone (Tgen) (67,7%) of all people. An average level of Tgen was 8,74 ± 0,9 nmol/l. In group of patients with low testosterone the GPA (grade point average) on a scale of AMS was 47,3 ± 9,1. Patients with BPH and AAD frequently have the accompanying pathology which is generally presented in such diseases as arterial hypertension, a metabolic syndrome, coronary heart disease, diabetes of the II type, anurolithic disease. Conclusions: Monitoring of the Tgen level is necessary for patients with BPH. Considering the high risk of a combination of BPH with the deficiency of testosterone it is necessary to include in the standard scheme of inspection the hormonal blood test with determination of the Tgen level
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