Bilayer 3He: a simple two-dimensional heavy-fermion system with quantum criticality

Two-dimensional helium-3 (3He) provides a simple model for the experimental investigation of the emergence of quantum complexity in a strongly correlated Fermi system. We have observed two-dimensional, two-band heavy-fermion behavior in bilayer films of 3He atoms when adsorbed on the surface of graphite preplated by a solid bilayer of 4He. Thermodynamic measurements on this system showed that the relevant control parameter is the total density of the 3He film. The 3He bilayer system can be driven toward a quantum critical point at which the effective mass appears to diverge, interband coupling vanishes, and a local-moment state appears. It opens a new testing ground for theories of quantum criticality in heavy-fermion materials.     

Patterning of the zebrafish retina by a wave of sonic hedgehog activity

The Drosophila retina is patterned by a morphogenetic wave driven by the Hedgehog signaling protein. Hedgehog, secreted by the first neurons, induces neuronal differentiation and hedgehog expression in nearby uncommitted cells, thereby propagating the wave. Evidence is presented here that the zebrafish Hedgehog homolog, Sonic Hedgehog, is also expressed in the first retinal neurons, and that Sonic Hedgehog drives a wave of neurogenesis across the retina, strikingly similar to the wave in Drosophila. The conservation of this patterning mechanism is unexpected, given the highly divergent structures of vertebrate and invertebrate eyes, and supports a common evolutionary origin of the animal visual system.     

Agroenvironmental determinants associated with the presence of antimicrobial-resistant Escherichia coli in beach waters in Quebec, Canada

Exposure to microorganisms resistant to antimicrobials may constitute a health risk to human populations. It is believed that one route of exposure occurs when people engage in recreational activities in water contaminated with these microorganisms. The main objective of this study was to explore population-level and environmental determinants specifically associated with the presence of antimicrobial resistant (AMR) generic Escherichia coli isolated from recreational waters sampled from beaches located in southern Quebec, Canada. Water samples originated from the Quebec provincial beach surveillance program for the summers of 2004 and 2005. This study focused on three classes of determinants, namely: agricultural, population-level and beach characteristics for a total of 19 specific factors. The study was designed as a retrospective observational analysis and factors were assessed using logistic regression methods. From the multivariable analysis, the data suggested that the percentage of land used for spreading liquid manure was a significant factor associated with the presence of AMR E. coli (OR=27.73). Conceptually, broad factors potentially influencing the presence of AMR bacteria in water must be assessed specifically in addition to factors associated with general microbial contamination. Presence of AMR E. coli in recreational waters from beaches in southern Quebec may represent a risk for people engaging in water activities and this study provides preliminary evidence that agricultural practices, specifically spreading liquid manure in agricultural lands nearby beaches, may be linked to the contamination of these waters by AMR E. coli.     

Thiamine (vitamin B1) seed treatment enhances germination and seedling growth of bean (Phaseolus vulgaris L.) exposed to soaking injury

Seed treatment with thiamine mononitrate significantly increased germination rate of bean (Phasenius vulgaris L.) seedlings germinated at high soil moisture levels and low night-temperature (5° C). Beneficial effects of thiamine applications on germination were also observed in soil-free germination tests when the seeds were submerged in water for 1–4 d at 18°C. Optimum response was achieved at thiamine concentrations of 3 mM, applied during the first 24 h of imbibition. As an early response to the thiamine treatment, vital staining with triphenyltetrazolium chloride revealed a lower proportion of damaged tissue of the embryonic axes. In later stages of seedling development, thiamine seed treatment resulted in a lower proportion of abnormal seedlings with malformations of the shoot apex and of the primary leaves. The beneficial effect of thiamine was more pronounced when the temperature during submergence was kept at 25° C compared to 5° C. There was no response to thiamine applications when the germinating seeds were exposed to low temperature treatments only. The thiamine effect could be mimicked by raising the osmotic potential of the incubation medium, indicating a relationship to soaking injuries. The results suggest that normal seedling development may be impaired by thiamine deficiency in the embryonic tissue induced by soaking injury, whereas low temperatures are not involved as a stress-factor.     

The occurrence of Campylobacter spp. and Salmonella spp. in gulls in northern Germany

Out of a total of 207 gulls--20 Black headed gulls, 185 Herring gulls and 2 Common gulls--128 (62%) and 23 (11%) birds, respectively, were infected with Campylobacter spp. (C.) and Salmonella spp. C. jejuni was predominant in gulls less than two years old (89%) and C. coli in older birds (75%). Furthermore, the infection rate with Campylobacters was depending on the habitats of the birds. The rate for C. jejuni and C. coli, respectively, was in gulls from regional garbage dumps 78% and 4%, from the coast 58% and 21%, and from islands 47% and 47% of the isolations in the corresponding area. Salmonellae were mainly isolated in the period from September to February from gulls less than one year old and from birds from the coast.     

Comparative studies of the acid-base status in venous, capillary and mixed blood from the ear of the dog

Ten experimental dogs were tested in twelve experimental arrangements, with a view to finding out the extent to which results of acid-base determination or blood gas analysis could be significantly affected by induced hyperaemia of the ear or by the choice of a site for blood collection, including puncture of an ear vein. No difference was secured. Hence, ear vein puncture may be used to collect so-called capillary blood. Reference is made to the author's own values for use as criteria.