Die phytochemische Reduktion der Ketone. Biochemische Darstellung optisch-aktiver sekundärer Alkohole

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Spatially explicit stock assessment uncovers sequential depletion of northern shrimp stock components in the North Sea

Space is a critical component of fisheries management. Despite this, very few of the world's fish and shellfish stocks are currently assessed using methods that are spatially structured. In the Northeast Atlantic, northern shrimp in the North Sea and Skagerrak, is currently assessed using a spatially structured assessment model. This metapopulation model includes two spatial units (the Norwegian Deep and the Skagerrak), however, in the recent past, the fishery on northern shrimp in the North Sea also occurred in a third neighbouring fishing area, the Fladen Ground. Here, we have reconstructed the dynamics of northern shrimp in the Fladen Ground using historic landings, a standardized commercial index of abundance and fragmented survey data and integrated this third spatial unit into the assessment model of the stock. In doing so, we find evidence of sequential spatial depletion, whereby high rates of fishing mortality have successively eroded stock components in a west to east pattern of overexploitation and produced cryptic collapses. This finding is the first documented case of sequential spatial depletion in the Northeast Atlantic, a phenomenon that could be common and largely overlooked by stock assessment methods that are inherently non-spatial

Nonthermal Emission from the Arches Cluster (G0.121+0.017) and the Origin of γ\gamma-ray Emission from 3EG J1746-2851

High resolution VLA observations of the Arches cluster near the Galactic center show evidence of continuum emission at $\lambda$3.6, 6, 20 and 90cm. The continuum emission at $\lambda$90cm is particularly striking because thermal sources generally become optically thick at longer wavelengths and fall off in brightness whereas non-thermal sources increase in brightness. It is argued that the radio emission from this unique source has compact and diffuse components produced by thermal and nonthermal processes, respectively. Compact sources within the cluster arise from stellar winds of mass-losing stars (Lang, Goss & Rodriguez 2001a) whereas diffuse emission is likely to be due to colliding wind shocks of the cluster flow generating relativistic particles due to diffuse shock acceleration. We also discuss the possibility that $\gamma$-ray emission from 3EG J1746--2851, located within 3.3$'$ of the Arches cluster, results from the inverse Compton scattering of the radiation field of the cluster.Comment: 15 pages, four figures, ApJL (in press

Using skin temperature and activity profiles to assign chronotype in birds

Chronotypes describe consistent differences between individuals in biological time-keeping. They have been linked both with underlying variation in the circadian system and fitness. Quantification of chronotypes is usually by time of onset, midpoint, or offset of a rhythmic behaviour or physiological process. However, diel activity patterns respond flexibly to many short-term environmental influences, which can make chronotypes hard to identify. In contrast, rhythmic patterns in physiological processes, such as body temperature, may provide more robust insights into the circadian basis of chronotypes. These can be telemetrically recorded from skin-mounted, temperature-sensitive transmitters, offering minimally invasive opportunities for working on free-ranging animals in the wild. Currently, computational methods for deriving chronotype from skin temperature require further development, as time series are often noisy and incomplete. Here, we investigate such methods using simultaneous radio telemetry recordings of activity and skin temperature in a wild songbird model (Great Tit Parus major) temporarily kept in outdoor aviaries. Our aims were to first develop standardised selection criteria to filter noisy time series of skin temperature and activity, to second assign chronotype based on the filtered recordings, and to third compare chronotype as assigned based on each of the two rhythms. After the selection of rhythmic data using periodicity and autocorrelation parameters, chronotype estimates (onset and offset) were extracted using four different changepoint approaches for skin temperature and one approach for activity records. The estimates based on skin temperature varied between different approaches but were correlated to each other (onset: correlation coefficient r = 0.099–0.841, offset: r = 0.131–0.906). In contrast, chronotype estimates from skin temperature were more weakly correlated to those from activity (onset: r = −0.131–0.612, offset: r = −0.040– −0.681). Overall, chronotype estimates were less variable and timed later in the day for activity than for skin temperature. The distinctions between physiological and behavioural chronotypes in this study might reflect differences in underlying mechanisms and in responsiveness to external and internal cues. Thus, studying each of these rhythms has specific strengths, while parallel studies of both could inform broadly on natural variation in biological time-keeping, and may allow assessment of how biological rhythms relate to changes in the environment

Catch bond drives stator mechanosensitivity in the bacterial flagellar motor

The bacterial flagellar motor (BFM) is the rotary motor that rotates each bacterial flagellum, powering the swimming and swarming of many motile bacteria. The torque is provided by stator units, ion motive force-powered ion channels known to assemble and disassemble dynamically in the BFM. This turnover is mechanosensitive, with the number of engaged units dependent on the viscous load experienced by the motor through the flagellum. However, the molecular mechanism driving BFM mechanosensitivity is unknown. Here, we directly measure the kinetics of arrival and departure of the stator units in individual motors via analysis of high-resolution recordings of motor speed, while dynamically varying the load on the motor via external magnetic torque. The kinetic rates obtained, robust with respect to the details of the applied adsorption model, indicate that the lifetime of an assembled stator unit increases when a higher force is applied to its anchoring point in the cell wall. This provides strong evidence that a catch bond (a bond strengthened instead of weakened by force) drives mechanosensitivity of the flagellar motor complex. These results add the BFM to a short, but growing, list of systems demonstrating catch bonds, suggesting that this "molecular strategy" is a widespread mechanism to sense and respond to mechanical stress. We propose that force-enhanced stator adhesion allows the cell to adapt to a heterogeneous environmental viscosity and may ultimately play a role in surface-sensing during swarming and biofilm formation

Magnetic Dipole Sum Rules for Odd-Mass Nuclei

Sum rules for the total- and scissors-mode M1 strength in odd-A nuclei are derived within the single-j interacting boson-fermion model. We discuss the physical content and geometric interpretation of these sum rules and apply them to ^{167}Er and ^{161}Dy. We find consistency with the former measurements but not with the latter.Comment: 13 pages, Revtex, 1 figure, Phys. Rev. Lett. in pres

Can Food Stamps Do More to Improve Food Choices? An Economic Perspective

Food stamp recipients, like other Americans, struggle with nutrition problems associated with choice of foods, as well as amounts. This series of Economic Information Bulletins compiles evidence to help answer the question of whether the Food Stamp Program can do more to improve the food choices of participants. It examines the role of affordability and price of healthful foods in influencing food choices and the likely success of any policy targeted at changing food choices through food stamp bonuses or restrictions. It also examines other approaches to changing food choices, including nutrition education and potential strategies drawn from behavioral economics literature. Meaningful improvements in the diets of food stamp recipients will likely depend on a combination of many tactics. Measuring the effect of any policy change on food choices and health outcomes remains a challenge.Food Stamp Program, food consumption, food prices, food expenditures, nutrition education, behavioral economics, food choices, diet, health, fruits and vegetables, Food Assistance and Nutrition Research Program, FANRP, ERS, USDA, Agricultural and Food Policy, Consumer/Household Economics, Food Consumption/Nutrition/Food Safety, Institutional and Behavioral Economics,

The magnetic environment in the central region of nearby galaxies

The central regions of galaxies harbor some of the most extreme physical phenomena, including dense stellar clusters, non-circular motions of molecular clouds and strong and pervasive magnetic field structures. In particular, radio observations have shown that the central few hundred parsecs of our Galaxy has a striking magnetic field configuration. It is not yet clear whether these magnetic structures are unique to our Milky Way or a common feature of all similar galaxies. Therefore, we report on (a) a new radio polarimetric survey of the central 200 pc of the Galaxy to better characterize the magnetic field structure and (b) a search for large-scale and organized magnetized structure in the nuclear regions of nearby galaxies using data from the Very Large Array (VLA) archive. The high angular resolution of the VLA allows us to study the central 1 kpc of the nearest galaxies to search for magnetized nuclear features similar to what is detected in our own Galactic center. Such magnetic features play a important role in the nuclear regions of galaxies in terms of gas transport and the physical conditions of the interstellar medium in this unusual region of galaxies.Comment: 8 pages; Proceedings for "The Universe under the Microscope" (AHAR 2008), held in Bad Honnef (Germany) in April 2008, to be published in Journal of Physics: Conference Series by Institute of Physics Publishing, R. Schoedel, A. Eckart, S. Pfalzner, and E. Ros (eds.