866 research outputs found
Magnetic linear dichroism in x-ray emission spectroscopy: Yb in Yb3 Fe5 O12
A magnetic linear dichroism MLD effect of up to 5% has been observed in the 2p 1/2 4d x-ray emission
spectrum of Yb in Yb 3 Fe 5 O 12 . The spectral shape is well reproduced with an atomic multiplet calculation of
the 4d to 2p decay. It is shown that the details of the spectral shapes are determined by the 4d4 f exchange
interaction. While the integrated intensity of the MLD effect is zero, the magnitude of the effect is a direct
measure of the 4 f magnetic moment of Yb. The technique is applicable to all rare-earth and transition-metal
systems (probing the 3d magnetic moment). With respect to x-ray-absorption magnetic circular dichroism it
possesses the advantage that (i) hard x rays are involved and (ii) no circular polarization is needed. Therefore
all complications related to electron detection, soft x-ray experiments, and circular polarization disappear.
Potential applications include the study of ~buried! magnetic systems in situ, at high pressures, varying (high)
magnetic fields, and varying temperatures
Theoretical analysis of the magnetic circular dichroism in the 2p3d and 2p4d x-ray emission of Gd
The 2p3d and 2p4d x-ray emission spectral shapes have been calculated using a theoretical description of spin-polarized 2p photoemission and atomic multiplet calculations of the 2p3d and 2p4d radiative decay.
Emphasis is given to the use of circular-polarized x rays for the excitation process. Good agreement with experiment is found and all visible experimental structures can be explained. It is shown that because of weak multiplet effects in the intermediate state, it is possible to use the incoherent, two-step model. The angle
between the emitted x rays and the magnetization is able to affect the magnetic circular dichroism (MCD) spectral shape observed, while the angle between the incident x ray and the magnetization only affects the intensity of the MCD
Condensate fluctuations of a trapped, ideal Bose gas
For a non-self-interacting Bose gas with a fixed, large number of particles
confined to a trap, as the ground state occupation becomes macroscopic, the
condensate number fluctuations remain micrscopic. However, this is the only
significant aspect in which the grand canonical description differs from
canonical or microcanonical in the thermodynamic limit. General arguments and
estimates including some vanishingly small quantities are compared to explicit,
fixed-number calculations for 10^2 to 10^6 particles.Comment: 16 pages (REVTeX) plus 4 figures (ps), revision includes brief
comparison of repulsive-interaction vs. fixed-N fluctuation damping. To be
published in Phys. Rev.
Validation of Ultrahigh Dependability for Software-Based Systems
Modern society depends on computers for a number of critical tasks in which failure can have very high costs. As a consequence, high levels of dependability (reliability, safety, etc.) are required from such computers, including their software. Whenever a quantitative approach to risk is adopted, these requirements must be stated in quantitative terms, and a rigorous demonstration of their being attained is necessary. For software used in the most critical roles, such demonstrations are not usually supplied. The fact is that the dependability requirements often lie near the limit of the current state of the art, or beyond, in terms not only of the ability to satisfy them, but also, and more often, of the ability to demonstrate that they are satisfied in the individual operational products (validation). We discuss reasons why such demonstrations cannot usually be provided with the means available: reliability growth models, testing with stable reliability, structural dependability modelling, as well as more informal arguments based on good engineering practice. We state some rigorous arguments about the limits of what can be validated with each of such means. Combining evidence from these different sources would seem to raise the levels that can be validated; yet this improvement is not such as to solve the problem. It appears that engineering practice must take into account the fact that no solution exists, at present, for the validation of ultra-high dependability in systems relying on complex software
The Effect of Protein Supplementation versus Carbohydrate Supplementation on Muscle Damage Markers and Soreness Following a 15-km Road Race:A Double-Blind Randomized Controlled Trial
We assessed whether a protein supplementation protocol could attenuate running-induced muscle soreness and other muscle damage markers compared to iso-caloric placebo supplementation. A double-blind randomized controlled trial was performed among 323 recreational runners (age 44 ± 11 years, 56% men) participating in a 15-km road race. Participants received milk protein or carbohydrate supplementation, for three consecutive days post-race. Habitual protein intake was assessed using 24 h recalls. Race characteristics were determined and muscle soreness was assessed with the Brief Pain Inventory at baseline and 1–3 days post-race. In a subgroup (n = 149) muscle soreness was measured with a strain gauge algometer and creatine kinase (CK) and lactate dehydrogenase (LDH) concentrations were measured. At baseline, no group-differences were observed for habitual protein intake (protein group: 79.9 ± 26.5 g/d versus placebo group: 82.0 ± 26.8 g/d, p = 0.49) and muscle soreness (protein: 0.45 ± 1.08 versus placebo: 0.44 ± 1.14, p = 0.96). Subjects completed the race with a running speed of 12 ± 2 km/h. With the Intention-to-Treat analysis no between-group differences were observed in reported muscle soreness. With the per-protocol analysis, however, the protein group reported higher muscle soreness 24 h post-race compared to the placebo group (2.96 ± 2.27 versus 2.46 ± 2.38, p = 0.039) and a lower pressure muscle pain threshold in the protein group compared to the placebo group (71.8 ± 30.0 N versus 83.9 ± 27.9 N, p = 0.019). No differences were found in concentrations of CK and LDH post-race between groups. Post-exercise protein supplementation is not more preferable than carbohydrate supplementation to reduce muscle soreness or other damage markers in recreational athletes with mostly a sufficient baseline protein intake running a 15-km road race. View Full-Tex
The putative proteinase maturation protein A of Streptococcus pneumoniae is a conserved surface protein with potential to elicit protective immune responses
Surface-exposed proteins often play an important role in the interaction
between pathogenic bacteria and their host. We isolated a pool of
hydrophobic, surface-associated proteins of Streptococcus pneumoniae. The
opsonophagocytic activity of hyperimmune serum raised against this protein
fraction was high and species specific. Moreover, the opsonophagocytic
activity was independent of the capsular type and chromosomal genotype of
the pneumococcus. Since the opsonophagocytic activity is presumed to
correlate with in vivo protection, these data indicate that the protein
fraction has the potential to elicit species-specific immune protection
with cross-protection against various pneumococcal strains. Individual
proteins in the extract were purified by two-dimensional gel
electrophoresis. Antibodies raised against three distinct proteins
contributed to the opsonophagocytic activity of the serum. The proteins
were identified by mass spectrometry and N-terminal amino acid sequencing.
Two proteins were the previously characterized pneumococcal surface
protein A and oligopeptide-binding lipoprotein AmiA. The third protein was
the recently identified putative proteinase maturation protein A (PpmA),
which showed homology to members of the family of peptidyl-prolyl
cis/trans isomerases. Immunoelectron microscopy demonstrated that PpmA was
associated with the pneumococcal surface. In addition, PpmA was shown to
elicit species-specific opsonophagocytic antibodies that were
cross-reactive with various pneumococcal strains. This antibody
cross-reactivity was in line with the limited sequence variation of ppmA.
The importance of PpmA in pneumococcal pathogenesis was demonstrated in a
mouse pneumonia model. Pneumococcal ppmA-deficient mutants showed reduced
virulence. The properties of PpmA reported here indicate its potential for
inclusion in multicomponent protein vaccines
Het vóórkomen van suïcidaal gedrag en suïcidepogingen bij de psychiatrische crisisdienst
Multivariate analysis of psychological dat
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