Physics of the granular state

Granular materials display a variety of behaviors that are in many ways different from those of other substances. They cannot be easily classified as either solids or liquids. This has prompted the generation of analogies between the physics found in a simple sandpile and that found in complicated microscopic systems, such as flux motion in superconductors or spin glasses. Recently, the unusual behavior of granular systems has led to a number of new theories and to a new era of experimentation on granular systems.     

Channelrhodopsin-1: a light-gated proton channel in green algae

Phototaxis and photophobic responses of green algae are mediated by rhodopsins with microbial-type chromophores. We report a complementary DNA sequence in the green alga Chlamydomonas reinhardtii that encodes a microbial opsin-related protein, which we term Channelopsin-1. The hydrophobic core region of the protein shows homology to the light-activated proton pump bacteriorhodopsin. Expression of Channelopsin-1, or only the hydrophobic core, in Xenopus laevis oocytes in the presence of all-trans retinal produces a light-gated conductance that shows characteristics of a channel selectively permeable for protons. We suggest that Channelrhodopsins are involved in phototaxis of green algae.     

Photorefractive materials for nonvolatile volume holographic data storage

Optically gated recording and nonvolatile readout in a digital volume holographic data storage system that uses a pair of mutually incoherent light sources during recording and only one for readout were demonstrated recently. This approach used stoichiometric lithium niobate, which after post-growth processing gave rise to an at least two orders of magnitude improvement in sensitivity over the best materials reported previously. It is also shown that by adding certain dopants (iron and manganese) to near-stoichiometric lithium niobate, the dark storage time and gating efficiency can be increased compared with previous work. The underlying physical mechanisms of gated recording and the effectiveness of the gating process responsible for this manifold improved performance are discussed, and bipolarons and small polarons are identified as the responsible photorefractive species.     

Guadiamar Toxic Flood: Factors that Govern Heavy Metal Distribution in Soils

The remaining soil contamination after the removal of thesludge and the affected topsoil was studied in the northernpart of the Guadiamar river valley affected by the Aznalcóllartoxic spill. The easily soluble (NH₄NO₃-extraction)and the oxidisable fraction (H₂O₂/HNO₃-extraction)were analysed in samples of two calcareous and two non-calcareoussoils. Correlations between soil properties and heavy metal concentrations were tested with special respect to depth distribution. The spatial distributions of the easily soluble and the oxidisable fraction were highly skewed in both examineddepths (0–20 and 20–40 cm). Easily soluble heavymetal concentrations of a high percentage of samples exceededthresholds that have been given in the German soil protectionlaw particularly in the non-calcareous soils. Within the soillayers of the non-calcareous soils, the pH seems to control theeasily soluble concentrations. However no relation between thepH and depth distribution of heavy metals within the profilescould be found. Physical properties, which determine partlypenetration depth of the sludge and soil mixing caused by theremoval may be the more important factors. Accordingly, highheavy metal concentrations are to be expected even in thesubsoils of clayey sites. As heavy metal concentrations in theoxidisable fraction are still high, further oxidationaccompanied by pH lowering has to be expected. Thus, thestudied soils show a significant risk potential of availableheavy metals even after the removal of the sludge.     

The spread of Corynebacterium pseudotuberculosis infection to unvaccinated and vaccinated sheep

SUMMARY The decrease in the prevalence of Corynebacterium pseudotuberculosis after two generations of vaccination against the disease it causes, was used to estimate the rate of control of caseous lymphadenitis (CLA). Three groups of 150 sheep, of which 50 in each group were artificially infected with C pseudotuberculosis and 100 in each group were uninfected sheep, were run separately for 40 months and shorn 5 times to promote the spread of CLA. One lot of 50 infected sheep and 2 lots of 100 uninfected sheep were vaccinated against CLA. The rate of spread of CLA was recorded. Sheep vaccinated against CLA and naturally exposed to infection had a 74% lower infection rate than unvaccinated sheep. Sheep vaccinated against CLA and exposed to only vaccinated infected sheep had a 97% lower infection rate. Unvaccinated sheep had a 76% infection rate, with 77% of the transmission occurring at the 4th and 5th shearings, without any discharging CLA abscesses being observed. This study supports the view that in Australian wool producing flocks, CLA spreads mainly from sheep with discharging lung abscesses to sheep with shearing cuts. Vaccinated sheep infected with CLA have 96% fewer lung abscesses compared with unvaccinated infected sheep and are therefore less likely to spread this disease to other sheep .     

Stress Response of Veterinary Students to Gynaecological Examination of Horse Mares – Effects of Simulator‐Based and Animal‐Based Training

Invasive procedures in animals are challenging for veterinary students who may perceive a gynaecological examination of mares as stressful. Simulator‐based training may reduce stress. In this study, students received equine gynaecology training 4 times either on horses (group H; n = 14) or a teaching simulator (group SIM; n = 13). One day and 14 days thereafter, their diagnostic skills were tested on horses (skills tests 1 and 2). During the skills tests, the students’ stress response was analysed by heart rate, heart rate variability (HRV) parameters SDRR (standard deviation of beat‐to‐beat [RR] interval) and RMSSD (root‐mean‐square of successive RR differences), and salivary cortisol. In addition, students answered a questionnaire on their perceived stress. Sympathetic activation with increased heart rate (p < 0.001) occurred in both skills tests. In test 1, this increase was more pronounced in SIM than in H students (time × group p < 0.01). HRV decreased in students of both groups (p < 0.001). In skills test 1, this decrease was more pronounced for SIM than for H students (between groups and time × group p < 0.01 for SDRR and p < 0.05 for RMSSD). High cortisol concentrations before the skills tests may indicate an anticipatory stress response. Subjective stress perception of students was higher in skills test 1 vs 2 (p < 0.01). In skills test 2, H students felt more stressed than SIM students (p < 0.01). Self‐assessment thus differed from physiological stress parameters. In conclusion, gynaecological examination of mares evoked a moderate stress response in veterinary students, which was more evident after simulator‐based than animal‐based training.