227 research outputs found
Forces and atomic relaxations in the pSIC approach with ultrasoft pseudopotentials
We present the scheme that allows for efficient calculations of forces in the
framework of pseudopotential self-interaction corrected (pSIC) formulation of
the density functional theory. The scheme works with norm conserving and also
with ultrasoft pseudopotentials and has been implemented in the plane-wave
basis code {\sc quantum espresso}. We have performed tests of the internal
consistency of the derived expressions for forces considering ZnO and CeO
crystals. Further, we have performed calculations of equilibrium geometry for
LaTiO, YTiO, and LaMnO perovskites and also for Re and Mn pairs in
silicon. Comparison with standard DFT and DFT+U approaches shows that in the
cases where spurious self-interaction matters, the pSIC approach predicts
different geometry, very often closer to the experimental data.Comment: 11 pages, 2 figure
Growth Kinetics of Vitamin C Crystals in a Batch L(+)-Ascorbic Acid â Methanol â Ethanol â Water System: Size Independent Growth Model Approach
The experimental data concerning growth kinetics of vitamin C (L(+)-ascorbic acid, LAA) crystals in a seeded and cooling batch mass crystallization process realized in a fourâcompound: L(+)-ascorbic acidâmethanolâethanolâwater system are reported. Influences of initial composition of solution and its linear cooling rate on âaverage, effectiveâ values of crystal linear growth rate were examined. Small divergences between LAA crystal size distributions (CSDs) data from granulometric analysis and Coulter counter were interpreted theoretically and discussed. Linear growth rates of crystals in a batch crystallizer were acquired with a proposed by NĂ˝vlt indirect method, based on the analysis of population density n(L) data in a MSMPR (mixed suspension mixed product removal) crystallizer. Sizeâindependent growth (SIG) kinetics was assumed. It can be concluded, that the largest and the most uniform particles of purified, crystalline vitamin C correspond to higher initial concentration of L(+)-ascorbic acid in a solution and lower cooling rate applied
Effect of electron correlations in Pd, Ni, and Co monowires
We investigated the effect of mean-field electron correlations on the band
electronic structure of Co, Ni, and Pd ultra-thin monatomic nanowires, at the
breaking point, by means of density-functional calculations in the
self-interaction corrected LDA approach (LDA+SIC) and alternatively by the
LDA+ scheme. We find that adding static electron correlations increases the
magnetic moment in Pd monowires, but has negligible effect on the magnetic
moment in Co and Ni. Furthermore, the number of -dominated conductance
channels decreases somewhat compared to the LDA value, but the number of
-dominated channels is unaffected, and remains equal to one per spin.Comment: to appear in PR
Serum levels of IL-6 type cytokines and soluble IL-6 receptors in active B-cell chronic lymphocytic leukemia and in cladribine induced remission.
We have investigated the serum concentrations of interleukin-6 (IL-6) and two IL-6 family cytokines-oncostatin M (OSM) and leukemia inhibitory factor (LIF)-in 63 patients with B-cell chronic lymphocytic leukemia (B-CLL) and 17 healthy controls using the enzyme-linked immunosorbent assay (ELISA) method. Simultaneously, we measured the serum levels of the soluble forms of two subunits of the IL-6 receptor complex-ligand binding glycoprotein 80 (sIL-6R) and glycoprotein 130 (sgp130). The cytokines and receptors were evaluated in 25 untreated patients and 38 patients treated with cladribine (2-CdA), as well as in 17 healthy controls. We have correlated the serum levels of these proteins with Rai's clinical stage of the disease, the response to 2-CdA treatment and some hematological parameters. We have also evaluated the correlation of the IL-6 serum level with the concentration of OSM and IL-6 soluble receptors. IL-6 was measurable in 62/63 (98.4%), OSM in 20/25 (80%) of untreated and 14/38 (37.8%) of the treated patients. sIL-6R and sgp130 were detectable in all 63 patients and LIF in none of the CLL patients. IL-6 serum level in untreated patients was not significantly different as compared to its concentration in the control group (P>0.05). However, in the patients treated with 2-CdA the IL-6 level was significantly lower (P<0.02), and the lowest concentration was found in the patients with complete remission (CR; median 1.4pg/ml; P<0.02). The concentration of sIL-6R was significantly higher in untreated (median 61.8 ng/ml) and treated (median 50.1 ng/ml) CLL patients when compared to normal persons (median 41.2 ng/ml; P=0.04; P<0.001, respectively). There was no difference between the sIL-6R levels in the patients with CR and the healthy controls. In non-responders sIL-6R concentration was the highest and similar to its level in the untreated patients. OSM level was higher in the untreated patients (median 1.8pg/ml) than in the normal controls (median 0.0pg/ml; P<0.001) and in the CR patients (median 0.0pg/ml; P<0.03). The serum concentration of sgp130 was similar in the untreated (median 480 pg/ml) and treated (median 470 pg/ml) patients, as well as in the healthy persons (median 420 pg/ml; P>0.05). We have found significant positive correlation between the levels of sIL-6R and the lymphocytes count in CLL patients (p=0.423; P<0.001). In addition, sIL-6R and OSM serum concentrations correlated also with CLL Rai stage. In conclusion, the serum level of IL-6, OSM and sIL-6R, but not LIF and sgp130, are useful indicators of CLL activity
Different origin of the ferromagnetic order in (Ga,Mn)As and (Ga,Mn)N
The mechanism for the ferromagnetic order of (Ga,Mn)As and (Ga,Mn)N is
extensively studied over a vast range of Mn concentrations. We calculate the
electronic structures of these materials using density functional theory in
both the local spin density approximation and the LDA+U scheme, that we have
now implemented in the code SIESTA.
For (Ga,Mn)As, the LDA+U approach leads to a hole mediated picture of the
ferromagnetism, with an exchange constant =~ -2.8 eV. This is smaller
than that obtained with LSDA, which overestimates the exchange coupling between
Mn ions and the As holes.
In contrast, the ferromagnetism in wurtzite (Ga,Mn)N is caused by the
double-exchange mechanism, since a hole of strong character is found at the
Fermi level in both the LSDA and the LDA+U approaches. In this case the
coupling between the Mn ions decays rapidly with the Mn-Mn separation. This
suggests a two phases picture of the ferromagnetic order in (Ga,Mn)N, with a
robust ferromagnetic phase at large Mn concentration coexisting with a diluted
weak ferromagnetic phase.Comment: 12 pages, 11 figure
J1420--0545: The radio galaxy larger than 3C236
We report the discovery of the largest giant radio galaxy, J1420-0545: a FR
type II radio source with an angular size of 17.4' identified with an optical
galaxy at z=0.3067. Thus, the projected linear size of the radio structure is
4.69 Mpc (if we assume that H_{0}=71 km\s\Mpc, Omega_{m}=0.27, and
Omega_{\Lambda}=0.73). This makes it larger than 3C236, which is the largest
double radio source known to date. New radio observations with the 100 m
Effelsberg telescope and the Giant Metrewave Radio Telescope, as well as
optical identification with a host galaxy and its optical spectroscopy with the
William Herschel Telescope are reported. The spectrum of J1420-0545 is typical
of elliptical galaxies in which continuum emission with the characteristic
4000A discontinuity and the H and K absorption lines are dominated by evolved
stars. The dynamical age of the source, its jets' power, the energy density,
and the equipartition magnetic field are calculated and compared with the
corresponding parameters of other giant and normal-sized radio galaxies from a
comparison sample. The source is characterized by the exceptionally low density
of the surrounding IGM and an unexpectedly high expansion speed of the source
along the jet axis. All of these may suggest a large inhomogeneity of the IGM.Comment: 20 pages, 5 figures, 3 table
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