Evidence for a Nuclear Electric Quadrupole Moment for Sb^(123)

Measurements of the hyperfine structure of the line λ5895 of Sb II by the use of a Fabry-Perot interferometer have shown that there are deviations from the interval rule in the case of the isotope with mass number 123. The hyperfine structure intervals of the ^3D_1 level of Sb^(121) (I=5/2) are found to be 0.6801 and 0.4832 cm^(−1). The corresponding intervals in Sb^(123) (I=7/2) are 0.4814 and 0.3603 cm^(−1). The error in these measurements is of the order of 0.001 cm. The observed ratio of the two separations gives 1.407 and 1.336 for the light and heavy isotope, respectively, whereas the corresponding ratios on the basis of the interval rule are 1.400 and 1.286. The deviation in the case of the light isotope is within the experimental error. The deviation for the heavy isotope, however, is a real effect which cannot be accounted for on the basis of perturbing effects of neighboring levels and must therefore be ascribed to the presence of an electric quadrupole moment of the nucleus of Sb^(123)

Nuclear Physics. A. Stationary States of Nuclei

[No abstract

The use of 2-Chlorophenoxyacetyl Chloride in the Preparation of Mixed Diacyl Derivatives of Ortho Aminophenols

Raiford and coworkers (1) have proved by a long series of experiments that when two acyl radicals, R-Ć=O and R\u27-Ć =O, are introduced into an ortho aminophenol only one mixed diacyl derivative can generally be obtained, regardless of the order of introduction of the radicals; and in this product the heavier and more acidic of these groups is usually found attached to nitrogen. To meet this requirement the migration of acyl from nitrogen to oxygen must occur in one of these reactions. If the acyls are R-Ć=O and R-0-Ć=O the latter is most frequently found on nitrogen

Projecting the continental accumulation of alien species through to 2050

Biological invasions have steadily increased over recent centuries. However, we still lack a clear expectation about future trends in alien species numbers. In particular, we do not know whether alien species will continue to accumulate in regional floras and faunas, or whether the pace of accumulation will decrease due to the depletion of native source pools. Here, we apply a new model to simulate future numbers of alien species based on estimated sizes of source pools and dynamics of historical invasions, assuming a continuation of processes in the future as observed in the past (a business‐as‐usual scenario). We first validated performance of different model versions by conducting a back‐casting approach, therefore fitting the model to alien species numbers until 1950 and validating predictions on trends from 1950 to 2005. In a second step, we selected the best performing model that provided the most robust predictions to project trajectories of alien species numbers until 2050. Altogether, this resulted in 3,790 stochastic simulation runs for 38 taxon–continent combinations. We provide the first quantitative projections of future trajectories of alien species numbers for seven major taxonomic groups in eight continents, accounting for variation in sampling intensity and uncertainty in projections. Overall, established alien species numbers per continent were predicted to increase from 2005 to 2050 by 36%. Particularly, strong increases were projected for Europe in absolute (+2,543 ± 237 alien species) and relative terms, followed by Temperate Asia (+1,597 ± 197), Northern America (1,484 ± 74) and Southern America (1,391 ± 258). Among individual taxonomic groups, especially strong increases were projected for invertebrates globally. Declining (but still positive) rates were projected only for Australasia. Our projections provide a first baseline for the assessment of future developments of biological invasions, which will help to inform policies to contain the spread of alien species

γ-H2AX foci as in vivo effect biomarker in children emphasize the importance to minimize x-ray doses in paediatric CT imaging

Objectives: Investigation of DNA damage induced by CT x-rays in paediatric patients versus patient dose in a multicentre setting. Methods: From 51 paediatric patients (median age, 3.8 years) who underwent an abdomen or chest CT examination in one of the five participating radiology departments, blood samples were taken before and shortly after the examination. DNA damage was estimated by scoring gamma-H2AX foci in peripheral blood T lymphocytes. Patient-specific organ and tissue doses were calculated with a validated Monte Carlo program. Individual lifetime attributable risks (LAR) for cancer incidence and mortality were estimated according to the BEIR VII risk models. Results: Despite the low CT doses, a median increase of 0.13 gamma-H2AX foci/cell was observed. Plotting the induced gamma-H2AX foci versus blood dose indicated a low-dose hypersensitivity, supported also by an in vitro dose-response study. Differences in dose levels between radiology centres were reflected in differences in DNA damage. LAR of cancer mortality for the paediatric chest CT and abdomen CT cohort was 0.08 and 0.13% respectively. Conclusion: CT x-rays induce DNA damage in paediatric patients even at low doses and the level of DNA damage is reduced by application of more effective CT dose reduction techniques and paediatric protocols

Modeling active electrolocation in weakly electric fish

In this paper, we provide a mathematical model for the electrolocation in weakly electric fishes. We first investigate the forward complex conductivity problem and derive the approximate boundary conditions on the skin of the fish. Then we provide a dipole approximation for small targets away from the fish. Based on this approximation, we obtain a non-iterative location search algorithm using multi-frequency measurements. We present numerical experiments to illustrate the performance and the stability of the proposed multi-frequency location search algorithm. Finally, in the case of disk- and ellipse-shaped targets, we provide a method to reconstruct separately the conductivity, the permittivity, and the size of the targets from multi-frequency measurements.Comment: 37 pages, 11 figure

Species richness-environment relationships of European arthropods at two spatial grains : habitats and countries

We study how species richness of arthropods relates to theories concerning net primary productivity, ambient energy, water-energy dynamics and spatial environmental heterogeneity. We use two datasets of arthropod richness with similar spatial extents (Scandinavia to Mediterranean), but contrasting spatial grain (local habitat and country). Samples of ground-dwelling spiders, beetles, bugs and ants were collected from 32 paired habitats at 16 locations across Europe. Species richness of these taxonomic groups was also determined for 25 European countries based on the Fauna Europaea database. We tested effects of net primary productivity (NPP), annual mean temperature (T), annual rainfall (R) and potential evapotranspiration of the coldest month (PETmin) on species richness and turnover. Spatial environmental heterogeneity within countries was considered by including the ranges of NPP, T, R and PETmin. At the local habitat grain, relationships between species richness and environmental variables differed strongly between taxa and trophic groups. However, species turnover across locations was strongly correlated with differences in T. At the country grain, species richness was significantly correlated with environmental variables from all four theories. In particular, species richness within countries increased strongly with spatial heterogeneity in T. The importance of spatial heterogeneity in T for both species turnover across locations and for species richness within countries suggests that the temperature niche is an important determinant of arthropod diversity. We suggest that, unless climatic heterogeneity is constant across sampling units, coarse-grained studies should always account for environmental heterogeneity as a predictor of arthropod species richness, just as studies with variable area of sampling units routinely consider area

Real-Time Somatosensory Feedback for Neural Prosthesis Control: System Development and Experimental Validation

Recent advances in neural prosthetics have provided patients with the ability to use signals derived from motor areas of the cerebral cortex to directly control an external device under visually guided closed-loop control. To attain a more natural form of prosthesis control, it is desirable to develop systems capable of providing real-time somatosensory feedback as well as visual feedback, akin to how we naturally process sensory information to control our limbs. To this end, a sophisticated data acquisition, control and feedback system was developed for neural prosthetics and psychophysics research. The system deterministically collects and processes high volume neural ensemble activity, limb kinematics, and eye movements while generating visual stimuli in an immersive three-dimensional virtual reality (VR) environment. A vibrotactile feedback device was also developed and incorporated into the system. It delivers real-time limb kinematics feedback in the form of continuous, graded vibratory stimulation. A flexible and intuitive user interface allows the researcher to design experimental paradigms and adjust parameters on the fly during experiments. A psychophysical study was conducted using this system to evaluate the potential use of vibrotactile feedback as a sensory substitution method to provide somatosensory feedback for neural prosthesis control. The study also aimed to provide insight into the mechanisms of multimodal sensory processing and sensory-motor control. Able-bodied human subjects performed a trajectory-following reach task in the VR environment under different visual and vibrotactile feedback conditions. The study showed that vibrotactile feedback is capable of enhancing motor performance, implying that subjects were able to integrate and effectively use this new 'proprioceptive-like' sensory modality. Subjects were also able to partially maintain task performance using vibrotactile feedback in the absence of visual feedback. Improved motor learning and motor skill consolidation were also observed after training in the VR environment with vibrotactile feedback. These results suggest that vibrotactile feedback may be a viable method for delivering somatosensory feedback for applications such as neural prosthesis control, motor rehabilitation, and enhanced human-computer interaction