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E Bartsch

Publications and source records attributed to E Bartsch.

18 recordsLinked to original sources
PubMed2005

Spatial scale-dependent tracer diffusion in bulk polycarbonate studied by holographic relaxation.

The diffusion of a photochromic dye tracer in polycarbonate was studied by a holographic relaxation technique (forced Rayleigh scattering) at temperatures close to the glass transition temperature. By varying the holographic grating period the results could be interpreted via the spatial scale dependence of apparent diffusion coefficients within a two-state diffusion model. This indicates inhomogeneities on the scale of a few micrometers in the polymer glass.

Journal Article↗
PubMed2003

The effect of free polymer on the interactions and the glass transition dynamics of microgel colloids.

By studying the phase behaviour and the short range order of polystyrene microgel colloids in a good solvent we demonstrated that these particles can be considered as hard spheres or nearly hard spheres if the internal cross link density is made sufficiently high. A binary mixture of 1:50 crosslinked (1 crosslink per 50 monomers) particles with a size ratio R(small)/R(large) = 0.83 and a number ratio N(small)/N(large) = 2.7 was characterized with respect to the short range order and glass transition dynamics. We found that this mixture can be mapped onto a one-component hard sphere system with an effective polydispersity of 11%, even though for the particle interactions an inverse power potential u(r) alpha r(-35) was established. The only significant difference observed was a shift of the glass transition to a higher volume fraction of 0.595. Thus, the binary mixture was used as a non-crystallizing reference system to study the effect of free polymer on interactions and glass transition dynamics. Addition of linear polystyrene with a size ratio delta = R(g,polymer)/R(colloid) = 0.054 induced short-ranged depletion attractions between microgel particles. In the case of a glassy sample already a rather small amount of polymer leads to melting of the glass and a re-entrant glass transition is observed at high polymer content. From the difference of the line shapes of the density autocorrelation functions on approaching the different transition lines. measured over the full dynamic range, a change of the freezing mechanism from a packing-driven glass transition at low polymer content to a bonding-driven glass transition at high polymer content was deduced.

Journal Article↗
PubMed2002

Re-entrant glass transition in a colloid-polymer mixture with depletion attractions.

Performing light scattering experiments we show that introducing short-ranged attraction to a colloid suspension of nearly hard spheres by addition of a free polymer produces new glass-transition phenomena. We observe a dramatic acceleration of the density fluctuations amounting to the melting of a colloidal glass. Upon increasing the strength of the attractions the system freezes into another nonergodic state sharing some qualitative features with gel states occurring at lower colloid packing fractions. This re-entrant glass transition is in qualitative agreement with recent theoretical predictions.

Journal Article↗
PubMed1998

[Frequency specificity of acoustic evoked potentials of early and intermediate latency with high-pass noise masking].

In contrast to auditory brainstem potentials (ABR), a more apically defined generation of middle latency evoked potentials (MLR) can be assumed due to the longer integration time present. To date, the effect of stimulus frequency spectra on MLR has not been completely known. By using masking with high-pass filtered white noise in 12 normal-hearing adults, we measured the dependence of amplitude and latency of ABR and MLR on filter frequency. No differences were found between the masking effects for ABR and MLR evoked by tone bursts of 0.5 and 2 kHz. The high-pass masking of click stimuli showed a greater influence on the amplitude and latency of the ABR than on MLR. These different qualities have to be considered clinically when evaluating the methods and results of hearing testing with acoustic evoked potentials. Our findings show that MLR evoked by tone bursts should be used for the frequency selective diagnosis of hearing thresholds, especially in low-frequency ranges.

Acoustic Stimulation↗
PubMed1993

Psychophysical frequency modulation thresholds in a FM-bat, Tadarida brasiliensis.

Echolocating bats hunting flying insects discriminate complex temporal patterns of acoustic stimuli. For bats using frequency modulated sonar calls (FM bats), there are no behavioral data on the perception of sinusoidally frequency modulated (SFM) stimuli. Discrimination performance for SFM stimuli of varying modulation depth was measured in 4 Tadarida brasiliensis in a two-alternative, forced choice procedure. A center frequency of 40 kHz was modulated with rates between 10 and 2000 Hz. It was found that discrimination performance improved from a mean threshold modulation depth of 3.05 kHz at a modulation rate of 2000 Hz to 1.58 kHz at a modulation rate of 10 Hz. Psychoacoustical modulation depth thresholds of T. brasiliensis are thus distinctly larger than those observed in bat species emitting constant frequency (CF) components followed by an FM-sweep, in active echolocation experiments. The modulation thresholds of T. brasiliensis are discussed in connection with the ability of bats to discriminate insect wingbeats. A comparison between non-echolocating mammals and the FM bat T. brasiliensis shows that the ability to echolocate is not reflected in the modulation thresholds.

Acoustic Stimulation↗
PubMed1979

Phenol oxidase activity and pigment synthesis in conidiospores of Penicillium cyclopium.

Phenol oxidase (PO) of Penicillium cyclopium belongs to the laccases (E.C. 1.14.18.1). By PAA-gel electrophoresis three forms of the enzyme were detected. Most of the PO in emerged sporulating cultures accumulates in the cell wall of the conidiospores. However, a high percentage is not bound to the wall constituents and can be easily removed with aqueous solutions. This soluble fraction was 570-fold enriched by (NH4)2SO4-precipitation, followed by chromatography on sephadex G 200 and on hydroxylapatite-cellulose, The necessity of PO for conidiospore pigmentation was shown by means of suspended spores whose rates of pigment accumulation resemble those of conidia maturing in situ. Pigmentation is stopped if PO is inhibited by diethyldithiocarbamate. This corresponds to the fact that in strains with heavily pigmented conidiospores PO activity is much higher than in strains with weakly pigmented or unpigmented spores. Also the time course of PO accumulation in the latter strains is different from that of the former. Furthermore, in mutant res-eth 1 which has unpigmented conidiospores, PO isoenzyme no. 3 could not be detected.

Catechol Oxidase↗
PubMed1976

[The effects of the weather on hemophilic hemarthrosis (author's transl)].

Hemophilic hemarthroses occur more frequently in spring and autumn. In the present study, possible weather situations are investigated which are characterized by a particular action on the increasing of hemorrhagic tendency. In 574 hemarthroses in 45 patients, the regional weather events were set in relation to the hemarthroses by means of a computer program. The following weather constellations significantly increase the tendency to bleed: Regional west weather conditions combined with longer lasting ascending procedures. The weather dynamics are dominated by the warm face of weak frontal zones with formation of a warm front. The biotropic weather elements demonstrated are also shown to be biotropic in other disease processes.

Germany, West↗
PubMedDate not supplied

Herpes simplex and mood: a prospective study.

The effect of mood, the common cold, amount of sleep, and sunshine on recurring herpes simplex virus (HSV) infection was investigated using daily self-reports over a 3-month period from 23 female and 15 male patients with genital herpes and 26 female and two male patients with oral herpes. Results showed recurring genital HSV infection to be preceded by reduced and decreasing overall emotional well being over a period of 10 days, with a temporary improvement in the middle of the period. This pattern was significantly represented by rated nervousness and rated alertness. Females showed more marked trends for reported mood than did the males, which could not be attributed to the menstrual cycle. Conversely, males showed a more marked, strongly significant fourth-order trend for reported amount of sleep, with nadirs on the 8th and the 3rd day before the recurrence. Neither exposure to sunshine nor the common cold showed any relation to recurrence of genital HSV infection. The common cold appeared as the major precipitating factor in oral herpes. Except for a significant fourth-order trend for rated alertness, no relationship between mood and subsequent onset was found. This negative finding was interpreted as a masking effect of the common cold. Two alternative physiological theories, the ganglion trigger theory and the skin trigger theory, were discussed in relation to present findings. It was suggested that various possible mediators between mood states and recurring herpes should be investigated using the present approach, with structured diaries as complement to the rating scales.

Adult↗