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We argue that the measurement of open charm gives a unique opportunity to test the validity of pQCD-based and statistical models of nucleus-nucleus collisions at high energies. We show that various approaches used to estimate D-meson multiplicity in central Pb+Pb collisions at 158 A GeV give predictions which differ by more than a factor of 100. Finally we demonstrate that decisive experimental results concerning the open charm yield in A+A collisions can be obtained using data of the NA49 experiment at the CERN SPS.
Charge fluctuations studied on event-by-event basis have been recently suggested to provide a signal of the equilibrium quark-gluon plasma produced in heavy-ion collisions at high energies. It is argued that the fluctuations generated at the early collision stage when the energy is released can fake the signal. PACS 25.75.-q, 12.38.Mh, 24.60.-k
Difficulties of the thermodynamical model approach to pion production in relativistic ion collisions
(1983)
Thermodynamical models with various forms of partial transparency of nuclear matter are considered. It is shown that the introduction of transparency, however, significantly improves agreement with pion data concerning multiplicities and transverse momenta leads to a serious discrepancy with average rapidities of pions. Qualitative arguments are given that difficulties of the thermodynamical approach can be overcome if one assumes hydrodynamical expansion in the first stage of nuclear interactions.
Data on the mean multiplicity of strange hadrons produced in minimum bias proton--proton and central nucleus--nucleus collisions at momenta between 2.8 and 400 GeV/c per nucleon have been compiled. The multiplicities for nucleon--nucleon interactions were constructed. The ratios of strange particle multiplicity to participant nucleon as well as to pion multiplicity are larger for central nucleus--nucleus collisions than for nucleon--nucleon interactions at all studied energies. The data at AGS energies suggest that the latter ratio saturates with increasing masses of the colliding nuclei. The strangeness to pion multiplicity ratio observed in nucleon--nucleon interactions increases with collision energy in the whole energy range studied. A qualitatively different behaviour is observed for central nucleus--nucleus collisions: the ratio rapidly increases when going from Dubna to AGS energies and changes little between AGS and SPS energies. This change in the behaviour can be related to the increase in the entropy production observed in central nucleus-nucleus collisions at the same energy range. The results are interpreted within a statistical approach. They are consistent with the hypothesis that the Quark Gluon Plasma is created at SPS energies, the critical collision energy being between AGS and SPS energies.
Maintenance of polymorphism in the orb weaving spider species Agalenatea redii (Araneae, Araneidae)
(2012)
The maintenance of polymorphism within populations may be the consequence of several elements of species life history such as use of space, activity rhythms, predation, parasitism and reproduction. The present study focuses on the latter aspect using an orb weaving spider, Agalenatea redii, which presents five different morphs of the opisthosoma pattern in the adult stage. Over the course of four years, from 2008 to 2011, adult spiders (males, females and pairs) were observed at different sites. In 2011, we also conducted a six-week survey of a single population, observing the number of spiders of each morph and the morph of paired spiders. We collected field data on the spatial and temporal distribution of spiders based on their sex and morph. Using a distance analysis, we compared the field distribution with a simulated one in which pairs were associated at random. The results showed that although there were changes over time and space in the proportions of females of the different morphs, as well as in the proportion of the pair associations, pairing according to morphs probably occurs at random.
COMP and TSP-4 interact specifically with the novel GXKGHR motif only found in fibrillar collagens
(2018)
COMP (cartilage oligomeric matrix protein) is a member of the thrombospondin family and forms homopentamers as well as mixed heterooligomers with its closely related family member TSP-4. COMP is long known to bind to collagens and to influence collagen fibril formation. Recent work indicates that already intracellular interaction with collagen is important for collagen secretion. However, the exact binding site of COMP on the collagen triple helix has not been described up to now. In this study we have identified a GXKGHR motif on the collagen II helix to bind to COMP, using a recombinantly expressed collagen II peptide library. This binding sequence is conserved throughout evolution and we demonstrate that TSP-4 binds to the same sequence. The identified binding motif overlaps with the recognition sites of many other collagen-binding partners (e.g. PEDF, Heparin) and also spans the lysine residues, which form collagen cross-links. COMP might thereby protect collagen helices from premature modification and cross-linking. Interestingly, this motif is only found in classical fibrillar collagens, although COMP is known to also bind other types. This might indicate that COMP has a unique interface for fibrillar collagens, thus making it an interesting target for the development of antifibrotic drugs.
Background: Although noise is one of the leading work-related health risk factors for teachers, many nursery schools lack sufficient noise reduction measures. Methods: This intervention study evaluated the noise exposure of nursery school teachers when dropping DUPLO toy bricks into storage cases. Sound analyses of the impact included assessment of the maximum sound pressure level (LAFmax) as well as frequency analyses with 1/3 octave band filter. For the purpose of standardization, a customized gadget was developed. Recordings were performed in 11 cases of different materials and designs to assess the impact on sound level reduction. Thereby, the acoustic effects of three damping materials (foam rubber, carpet, and PU-foam) were investigated. Results: The lowest LAFmax was measured in cases consisting of “metal grid” (90.71 dB) or of a woven willow “basket” (91.61 dB), whereas a case of “aluminium” (103.34 dB) generated the highest impact LAFmax. The frequency analyses determined especially low LAFmax in the frequency bands between 80 and 2500 Hz in cases designs “metal grid” and “basket”. The insertion of PU-foam achieved the most significant attenuation of LAFmax (−13.88 dB) and, in the frequency analyses, the best sound damping. Conclusion: The dropping of DUPLO bricks in cases contributes to the high noise level in nursery schools, but measured LAFmax show no evidence for the danger of acute hearing loss. However, continuous exposure may lead to functional impairment of the hair cells and trigger stress reactions. We recommend noise reduction by utilizing cases of woven “basket” with an insert of PU-foam.
In the culture of the Pero, Longuda and Tula People in the south-eastern part of Bauchi State, north-eastern Nigeria, terraces are found as traditional means to improve the environmental condition and to secure the survival of the people. To classify those terraces according to their form and function, the techniques and customs of their building and the traditional structures of their development they have to be compared in the context of their own culture. The paper gives a few examples showing that the importance of terraces for the historic and religious concepts of the Pero, Longuda and Tula People is expressed through a tight network of oral traditions, social and religious customs and structures of belief and explanation, which, once they were woven together, eventually build what a malam from Tula called a glue of inheritance, identity, integrity, continuity and security.
Water-filtered infrared-A radiation (wIRA) is not implicated in cellular degeneration of human skin
(2007)
Background: Excessive exposure to solar ultraviolet radiation is involved in the complex biologic process of cutaneous aging. Wavelengths in the ultraviolet-A and -B range (UV-A and UV-B) have been shown to be responsible for the induction of proteases, e. g. the collagenase matrix metalloproteinase 1 (MMP-1), which are related to cell aging. As devices emitting longer wavelengths are widely used in therapeutic and cosmetic interventions and as the induction of MMP-1 by water-filtered infrared-A (wIRA) had been discussed, it was of interest to assess effects of wIRA on the cellular and molecular level known to be possibly involved in cutaneous degeneration.
Objectives: Investigation of the biological implications of widely used water-filtered infrared-A (wIRA) radiators for clinical use on human skin fibroblasts assessed by MMP-1 gene expression (MMP-1 messenger ribonucleic acid (mRNA) expression).
Methods: Human skin fibroblasts were irradiated with approximately 88% wIRA (780-1400 nm) and 12% red light (RL, 665-780 nm) with 380 mW/cm² wIRA(+RL) (333 mW/cm² wIRA) on the one hand and for comparison with UV-A (330-400 nm, mainly UV-A1) and a small amount of blue light (BL, 400-450 nm) with 28 mW/cm² UV-A(+BL) on the other hand. Survival curves were established by colony forming ability after single exposures between 15 minutes and 8 hours to wIRA(+RL) (340-10880 J/cm² wIRA(+RL), 300-9600 J/cm² wIRA) or 15-45 minutes to UV-A(+BL) (25-75 J/cm² UV-A(+BL)). Both conventional Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) and quantitative real-time RT-PCR techniques were used to determine the induction of MMP-1 mRNA at two physiologic temperatures for skin fibroblasts (30°C and 37°C) in single exposure regimens (15-60 minutes wIRA(+RL), 340-1360 J/cm² wIRA(+RL), 300-1200 J/cm² wIRA; 30 minutes UV-A(+BL), 50 J/cm² UV-A(+BL)) and in addition at 30°C in a repeated exposure protocol (up to 10 times 15 minutes wIRA(+RL) with 340 J/cm² wIRA(+RL), 300 J/cm² wIRA at each time).
Results: Single exposure of cultured human dermal fibroblasts to UV-A(+BL) radiation yielded a very high increase in MMP-1 mRNA expression (11 ±1 fold expression for RT-PCR and 76 ±2 fold expression for real-time RT-PCR both at 30°C, 75 ±1 fold expression for real-time RT-PCR at 37°C) and a dose-dependent decrease in cell survival. In contrast, wIRA(+RL) did not produce cell death and did not induce a systematic increase in MMP-1 mRNA expression (less than twofold expression, within the laboratory range of fluctuation) detectable with the sensitive methods applied. Additionally, repeated exposure of human skin fibroblasts to wIRA(+RL) did not induce MMP-1 mRNA expression systematically (less than twofold expression by up to 10 consecutive wIRA(+RL) exposures and analysis with real-time RT-PCR).
Conclusions: wIRA(+RL) even at the investigated disproportionally high irradiances does not induce cell death or a systematic increase of MMP-1 mRNA expression, both of which can be easily induced by UV-A radiation. Furthermore, these results support previous findings of in vivo investigations on collagenase induction by UV-A but not wIRA and show that infrared-A with appropriate irradiances does not seem to be involved in MMP-1 mediated photoaging of the skin. As suggested by previously published studies wIRA could even be implicated in a protective manner.