136 research outputs found
Hole-burning experiments within solvable glassy models
We reproduce the results of non-resonant spectral hole-burning experiments
with fully-connected (equivalently infinite-dimensional) glassy models that are
generalizations of the mode-coupling approach to nonequilibrium situations. We
show that an ac-field modifies the integrated linear response and the
correlation function in a way that depends on the amplitude and frequency of
the pumping field. We study the effect of the waiting and recovery-times and
the number of oscillations applied. This calculation will help descriminating
which results can and which cannot be attributed to dynamic heterogeneities in
real systems.Comment: 4 pages, 8 figures, RevTe
Observation of Fluctuation-Dissipation-Theorem Violations in a Structural Glass
The fluctuation-dissipation theorem (FDT), connecting dielectric
susceptibility and polarization noise was studied in glycerol below its glass
transition temperature Tg. Weak FDT violations were observed after a quench
from just above to just below Tg, for frequencies above the alpha peak.
Violations persisted up to 10^5 times the thermal equilibration time of the
configurational degrees of freedom under study, but comparable to the average
relaxation time of the material. These results suggest that excess energy flows
from slower to faster relaxing modes.Comment: Improved discussion; final version to appear in Phys. Rev. Lett. 4
pages, 5 PS figures, RevTe
Nanometer Scale Dielectric Fluctuations at the Glass Transition
Using non-contact scanning probe microscopy (SPM) techniques, dielectric
properties were studied on 50 nanometer length scales in poly-vinyl-acetate
(PVAc) films in the vicinity of the glass transition. Low frequency (1/f) noise
observed in the measurements, was shown to arise from thermal fluctuations of
the electric polarization. Anomalous variations observed in the noise spectrum
provide direct evidence for cooperative nano-regions with heterogeneous
kinetics. The cooperative length scale was determined. Heterogeneity was
long-lived only well below the glass transition for faster than average
processes.Comment: 4 pages, 4 embedded PS figures, RevTeX - To appear in Phys. Rev. Let
Marine macroalgae as food for earthworms: Growth and selection experiments across ecotypes
Historically, subsistence farmers around the Atlantic coast of NW Europe utilised marine algae as a fertiliser in agroecosystems, a practice that continued in small areas and is now considered to have real potential for re-establishing sustainable food production systems on marginal soils. Earthworms form a significant component of soil fauna and their ecosystem services are well documented. Therefore, palatability of marine organic amendments to faunal detritivores of terrestrial systems is of interest. This work aimed to assess the potential for growth of Aporrectodea caliginosa, Lumbricus rubellus and Aporrectodea longa fed with two common macroalgae (seaweeds), Laminaria digitata and Fucus serratus. In addition, choice chambers were constructed to permit earthworm selection of these macroalgae with more conventional organic materials, horse manure (HM) and birch leaves (BL). Over a period of two months, earthworm species showed significantly greater mass gain with conventional food (p<0.05). Laminaria outperformed Fucus, which in turn was superior to soil alone. Similarly, when given a choice, a significant preference (p<0.001) was shown for the more nitrogen-rich HM and BL over the seaweeds. No removal was recorded for A. caliginosa when offered seaweeds only. By contrast, L. rubellus and A. longa showed significant preferences (p<0.001) for Laminaria over Fucus and fresh material over degraded. These results underline an interest to profit from natural resources (seaweeds) to maintain or improve soil biological quality in marginal coastal areas
UVA/UVA1 phototherapy and PUVA photochemotherapy in connective tissue diseases and related disorders: a research based review
BACKGROUND: Broad-band UVA, long-wave UVA1 and PUVA treatment have been described as an alternative/adjunct therapeutic option in a number of inflammatory and malignant skin diseases. Nevertheless, controlled studies investigating the efficacy of UVA irradiation in connective tissue diseases and related disorders are rare. METHODS: Searching the PubMed database the current article systematically reviews established and innovative therapeutic approaches of broad-band UVA irradiation, UVA1 phototherapy and PUVA photochemotherapy in a variety of different connective tissue disorders. RESULTS: Potential pathways include immunomodulation of inflammation, induction of collagenases and initiation of apoptosis. Even though holding the risk of carcinogenesis, photoaging or UV-induced exacerbation, UVA phototherapy seems to exhibit a tolerable risk/benefit ratio at least in systemic sclerosis, localized scleroderma, extragenital lichen sclerosus et atrophicus, sclerodermoid graft-versus-host disease, lupus erythematosus and a number of sclerotic rarities. CONCLUSIONS: Based on the data retrieved from the literature, therapeutic UVA exposure seems to be effective in connective tissue diseases and related disorders. However, more controlled investigations are needed in order to establish a clear-cut catalogue of indications
Frequency of employer changes and their financial return: gender differences amongst German university graduates
Gender differences in the frequency of employer changes and their financial return were examined in a sample of Bavarian university graduates. The search and matching theories were used to develop hypotheses which were then tested against each other. The results show that in the first few years after graduation women change employer more frequently than men. In large part this can be explained by gender differences in labor market structures, in particular the fact that a woman's first job is less likely to be in a large company, in an executive position or on a permanent contract and women tend to be less satisfied with their first job. After controlling for variance in these factors the coefficient changes sign, indicating that under similar circumstances men change employer more often. Furthermore, both men and women benefit financially from changing employer. The absolute return is higher for men, but as men tend to have a higher starting salary there is no gender difference in the relative return and hence no effect on the gender gap. The results are also discussed in the light of the specifics of the structure of the German labor market.Diese Studie nutzt eine Stichprobe bayerischer Hochschulabsolventen, um Geschlechtsunterschiede sowohl in der HĂ€ufigkeit als auch in den finanziellen ErtrĂ€gen von Arbeitgeberwechseln zu untersuchen. Die Such- und Matchingtheorien werden genutzt, um Hypothesen zu entwickeln, die anschlieĂend gegeneinander getestet werden. Die Ergebnisse zeigen, dass Frauen ihren Arbeitgeber in den ersten Jahren nach dem Abschluss hĂ€ufiger wechseln als MĂ€nner. Das kann zu einem groĂen Teil durch unterschiedliche Arbeitsmarktstrukturen erklĂ€rt werden, vor allem durch die Tatsache, dass Frauen in ihrer ersten BeschĂ€ftigung seltener in GroĂbetrieben, in FĂŒhrungspositionen und mit unbefristeten VertrĂ€gen arbeiten und weniger zufrieden mit ihrer Arbeit sind. Sobald auf all diese Faktoren kontrolliert wird, Ă€ndert der Koeffizient sein Vorzeichen, d. h. unter gleichen UmstĂ€nden wechseln MĂ€nner den Arbeitgeber hĂ€ufiger. Weiterhin profitieren sowohl MĂ€nner als auch Frauen finanziell von Arbeitgeberwechseln. MĂ€nner erhalten höhere absolute ErtrĂ€ge, aber aufgrund ihrer höheren Einstiegseinkommen existiert bei den relativen ErtrĂ€gen kein Unterschied zwischen MĂ€nnern und Frauen und somit auch kein Einfluss auf die Gender Pay Gap. Die Ergebnisse werden vor dem Hintergrund der Besonderheiten des deutsche
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