2,444 research outputs found
Formation of a carcinogenic aromatic amine from an azo dye by human skin bacteria in vitro
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Azo dyes represent the major class of dyestuffs. They are metabolised to the corresponding amines by liver enzymes and the intestinal microflora following incorporation by both experimental animals and humans. For safety evaluation of the dermal exposure of consumers to azo dyes from wearing coloured textiles, a possible cleavage of azo dyes by the skin microflora should be considered since, in contrast to many dyes, aromatic amines are easily absorbed by the skin. A method for measuring the ability of human skin flora to reduce azo dyes was established. In a standard experiment, 361011 cells of a culture of Staphylococcus aureus wereincubatedinsyntheticsweat (pH 6.8, final volume 20 mL) at 288C for 24 h with Direct Blue 14 (C.I. 23850, DB 14). The reaction products were extracted and analysed using HPLC. The reduction product o-tolidine (3,3'-dimethylbenzidine, OT) could indeed be detected showing that the strain used was able to metabolise DB 14 to the corresponding aromatic amine. In addition to OT, two further metabolites of DB 14 were detected. Using mass spectrometry they were identified as 3,3'-dimethyl-4-amino-4'-hydroxybiphenyl and 3,3'-di methyl-4-aminobiphenyl. The ability to cleave azo dyes seems to be widely distributed among human skin bacteria, as, under these in vitro conditions, bacteria isolated from healthy human skin and human skin bacteria from strain collections also exhibited azo reductase activity. Further studies are in progress in order to include additional azo dyes and coloured textiles. At the moment, the meaning of the results with regard to consumer health cannot be finally assessed
The Relationship Between Social Change Involvement and Education
Positive social change is part of Walden University’s mission. As such, the institution sponsored the Social Change Impact Report, which includes data from three online surveys that investigated participants’ experiences with social change because factors related to involvement in social action to improve the lives of individuals and communities are not fully known. Data were collected from the Social Change Impact Report to examine the relationship between the level of education an individual has achieved and how they rate the importance of and the involvement in positive social change activities. Results of chi square and analysis of variance indicated significant relationships between variables and an apparent upward trend in perceptions of and self-reported involvement in social change activities as level of education increases
Resonance Patterns in a Stadium-shaped Microcavity
We investigate resonance patterns in a stadium-shaped microcavity around
, where is the refractive index, the vacuum
wavenumber, and the radius of the circular part of the cavity. We find that
the patterns of high resonances can be classified, even though the
classical dynamics of the stadium system is chaotic. The patterns of the high
resonances are consistent with the ray dynamical consideration, and appears
as the stationary lasing modes with low pumping rate in the nonlinear dynamical
model. All resonance patterns are presented in a finite range of .Comment: 8 pages, 9 figure
Fractal Weyl law behavior in an open, chaotic Hamiltonian system
We numerically show fractal Weyl law behavior in an open Hamiltonian system
that is described by a smooth potential and which supports numerous
above-barrier resonances. This behavior holds even relatively far away from the
classical limit. The complex resonance wave functions are found to be localized
on the fractal classical repeller.Comment: 4 pages, 3 figures. to appear in Phys Rev
Factors governing macrozoobenthic assemblages in perennial springs in north-western Switzerland
Springs are important freshwater habitats that provide refuge for many rare species. In this study, the fauna and abiotic parameters of 20 perennial springs in north-western Switzerland were investigated. Correlation of abiotic and macrozoobenthos data showed that physicochemical parameters had little impact on macrozoobenthic composition, whereas specific substrate parameters strongly influenced the composition of the macrofauna. Surprisingly, nonmetric multidimensional scaling did not reveal a grouping of springs with similar substrate composition or macrozoobenthic assemblages. However, discharge was identified as the factor significantly determining substrate and the composition of macroinvertebrate assemblages. This justifies the hypothesis that, variation in discharge is the disturbance factor governing the macrofaunal composition temporally and spatially within and between patche
Attractive Casimir Forces in a Closed Geometry
We study the Casimir force acting on a conducting piston with arbitrary cross
section. We find the exact solution for a rectangular cross section and the
first three terms in the asymptotic expansion for small height to width ratio
when the cross section is arbitrary. Though weakened by the presence of the
walls, the Casimir force turns out to be always attractive. Claims of repulsive
Casimir forces for related configurations, like the cube, are invalidated by
cutoff dependence.Comment: An updated version to coincide with the one published December 2005
in PRL. 4 pages, 2 figure
Successful ageing in an area of deprivation: Part 1—A qualitative exploration of the role of life experiences in good health in old age
Objectives: To determine the life histories and current circumstances of healthy and unhealthy older people who share an ecology marked by relative deprivation and generally poor health.
Study design: In-depth interview study with a qualitative analysis.
Methods: Matched pairs of healthy and unhealthy ‘agers’ were interviewed face-to-face. Healthy ageing was assessed in terms of hospital morbidity and self-reported health. Study participants consisted of 22 pairs (44 individuals), aged 72–89 years, matched for sex, age and deprivation category, and currently resident in the West of Scotland. All study participants were survivors of the Paisley/Renfrew (MIDSPAN) survey, a longitudinal study commenced in 1972 with continuous recording of morbidity and mortality since.
Detailed life histories were obtained which focused on family, residence, employment, leisure and health. This information was supplemented by more focused data on ‘critical incidents’, financial situation and position in social hierarchies.
Results: Data provided rich insights into life histories and current circumstances but no differences were found between healthy and unhealthy agers.
Conclusions: It is important to understand what differentiates individuals who have lived in circumstances characterized by relative deprivation and poor health, yet have aged healthily. This study collected rich and detailed qualitative data. Yet, no important differences were detected between healthy and unhealthy agers. This is an important negative result as it suggests that the phenomenon of healthy ageing and the factors that promote healthy ageing over a lifetime are so complex that they will require even more detailed studies to disentangle
Weyl asymptotics: From closed to open systems
We present microwave experiments on the symmetry reduced 5-disk billiard
studying the transition from a closed to an open system. The measured microwave
reflection signal is analyzed by means of the harmonic inversion and the
counting function of the resulting resonances is studied. For the closed system
this counting function shows the Weyl asymptotic with a leading exponent equal
to 2. By opening the system successively this exponent decreases smoothly to an
non-integer value. For the open systems the extraction of resonances by the
harmonic inversion becomes more challenging and the arising difficulties are
discussed. The results can be interpreted as a first experimental indication
for the fractal Weyl conjecture for resonances.Comment: 9 pages, 7 figure
Sonoluminescence: Nature's Smallest BlackBody
The Spectrum of the light emitted by a sonoluminescing bubble is extremely
well fit by the spectrum of a blackbody. Furthermore the radius of emission can
be smaller than the wavelength of the light. Consequences, for theories of
sonoluminescence are discussed.Comment: 8 pages, 3 Figure
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