Chirality of pollutants—effects on metabolism and fate

In most cases, enantiomers of chiral compounds behave differently in biochemical processes. Therefore, the effects and the environmental fate of the enantiomers of chiral pollutants need to be investigated separately. In this review, the different fates of the enantiomers of chiral phenoxyalkanoic acid herbicides, acetamides, organochlorines, and linear alkylbenzenesulfonates are discussed. The focus lies on biological degradation, which may be enantioselective, in contrast to non-biotic conversions. The data show that it is difficult to predict which enantiomer may be enriched and that accumulation of an enantiomer is dependent on the environmental system, the species, and the organ. Racemization and enantiomerization processes occur and make interpretation of the data even more complex. Enantioselective degradation implies that the enzymes involved in the conversion of such compounds are able to differentiate between the enantiomers. "Enzyme pairs” have evolved which exhibit almost identical overall folding. Only subtle differences in their active site determine their enantioselectivities. At the other extreme, there are examples of non-homologous "enzyme pairs” that have developed through convergent evolution to enantioselectively turn over the enantiomers of a chiral compound. For a better understanding of enantioselective reactions, more detailed studies of enzymes involved in enantioselective degradation need to be performe

Bacterial β-peptidyl aminopeptidases: on the hydrolytic degradation of β-peptides

The special chemical and biological features of β-peptides have been investigated intensively during recent years. Many studies emphasize the restricted biodegradability and the high metabolic stability of this class of compounds. β-Peptidyl aminopeptidases form the first family of enzymes that hydrolyze a variety of short β-peptides and β-amino-acid-containing peptides. All representatives of this family were isolated from Gram-negative bacteria. The substrate specificities of the peptidases vary greatly, but the enzymes have common structural properties, and a similar reaction mechanism can be expected. This review gives an overview on the β-peptidyl aminopeptidases with emphasis on their biochemical and structural properties. Their possible physiological function is discussed. Functionally and structurally related enzymes are compared to the β-peptidyl aminopeptidase

Ectrin Ear Tags for Horn Fly Control on Range Beef Cattle

Ectrin ear tags are insecticide-impregnated with the active ingredient fenvalerate (8%). They are approved for use on lactating dairy cattle, beef cattle and calves. Each time an animal turns on tosses its head, a layer of Ectrin is rubbed or falls off onto the animal. As one insecticide layter is rubbed off, another forms. This action continues for the life of the tag. Advantages to this type of horn fly control are tagging is quick and easy using the All-Flex specially designed pliers, dampness or rain has little effect on efficacy, and the fly control reservoir is carried and used by each treated animal. A random sample of 10 animals from each herd was counted using binoculars and looking out of a pickup window. Results are presented as an average number of horn flies/side of these 10 animals. An equal number of untreated or control animals was counted from a herd near the treated herd at nearly the same time. Problems of last tags or infected ears due to the tags were minimal

Surface Deformation Induced by Present-Day Ice Melting in Svalbard

The vertical movement of the Earth\u27s surface is the result of a number of internal processes in the solid Earth, tidal forces and mass redistribution in the atmosphere, oceans, terrestrial hydrosphere and cryosphere. Close to ice sheets and glaciers, the changes in the ice loads can induce large vertical motions at intraseasonal to secular timescales. The Global Positioning System (GPS) and Very Long Baseline Interferometry (VLBI) antennas in Ny-Ålesund, Svalbard that started observations in 1991 and 1995, respectively, observe vertical uplift rates on the order of mm yr−1, which are considerably larger than those predicted by postglacial rebound (PGR) models (order 2 mm yr−1). The observations also indicate increased uplift rates starting some time in 2000. A local GPS campaign network that has been reoccupied annually since 1998, reveals a tilting away from the neighbouring glaciers. The Svalbard glaciers have been undergoing melting and retreat during the last century, with increased melting since about 2000. We compared the observed vertical motion to the motion predicted by loading models using a detailed ice model with annual time resolution as forcing. The model predictions correlate well with the observations both with respect to the interannual variations and the spatial pattern of long-term trends. The regression coefficients for predicted and observed interannual variations in height is , whereas the regression coefficient for the predicted and observed spatial pattern turns out to be . Estimates of the predicted secular trend in height due to PGR and present-day melting are on the order of mm yr−1 and thus smaller than the observed secular trend in height. This discrepancy between predictions and observations is likely caused by the sum of errors in the secular rates determined from observations (due to technique-dependent large-scale offsets) and incomplete or erroneous models (unaccounted tectonic vertical motion, errors in the ice load history, scale errors in the viscoelastic PGR models and the elastic models for present-day melting)

Dust-Impregnated Ear Tags for Horn Fly Control of Pasure Cattle

Fly control is a problem to all cattlemen during the summer months. The irritation of flies has been shown to cause decreased weight gains and loss in milk production. Cattlemen are continually looking for economical and effective means of controlling flies under various management systems. Among the more recently developed fly control possibilities has been an insecticide dust-impregnated ear tag. The idea was developed for control of ear ticks in Texas. The tags are white, about 2 by 2 1/2 inches in size and about the same weight as a standard, plastic tag commonly used for identifying cattle. They are applied with a standard Allflex pliers. Rabon (2-chloro-1-(2, 4, 5,-trichlorophenyl)) vinyl dimethyl phosphate (13.7 w/w) is impregnated in the plastic ear tag in such a way the tag continually dusts the animal as it moves its head. Marking paint on the tags lasted up to 5 months in these studies

First principles calculation of structural and magnetic properties for Fe monolayers and bilayers on W(110)

Structure optimizations were performed for 1 and 2 monolayers (ML) of Fe on a 5 ML W(110) substrate employing the all-electron full-potential linearized augmented plane-wave (FP-LAPW) method. The magnetic moments were also obtained for the converged and optimized structures. We find significant contractions ($\sim$ 10 %) for both the Fe-W and the neighboring Fe-Fe interlayer spacings compared to the corresponding bulk W-W and Fe-Fe interlayer spacings. Compared to the Fe bcc bulk moment of 2.2 $\mu_B$, the magnetic moment for the surface layer of Fe is enhanced (i) by 15% to 2.54 $\mu_B$ for 1 ML Fe/5 ML W(110), and (ii) by 29% to 2.84 $\mu_B$ for 2 ML Fe/5 ML W(110). The inner Fe layer for 2 ML Fe/5 ML W(110) has a bulk-like moment of 2.3 $\mu_B$. These results agree well with previous experimental data

Learning in Informal Networks: Contraceptive Choice and Other Technological Dynamics

This paper devises three formal models of 'learning in informal networks' to study the long term implications of word-of-mouth communications for the diffusion of contraceptive knowledge. The models differ in the information that is shared among network partners, and with respect to the sophistication of women's decision rules. The theoretical properties of these models are compared with empirical evidence based on the 1973 Korean survey on women's social networks and contraceptive choices. The analysis proposes a qualitative choice rule that models women's contraceptive decisions as an econometrician's problem to infer the differential quality of contraceptives from informal conversations

Structural health monitoring through dense instrumentation by community participants: the Community Seismic Network and Quake-Catcher Network

The Community Seismic Network and Quake-Catcher Network involve participants from communities at large to install low-cost accelerometers in houses and buildings for assessment of shaking intensity due to earthquakes. The seismometers are designed for two types of connec-tions: a USB-connected device which connects to the host’s computer, and a stand-alone sensor-plug-computer device that directly connects to the internet. The three-component sensors report both continuous data and amplitude anomalies in local acceleration to a Cloud computing service consisting of data centers geographically distributed across the continent, or to a distributed computing system. The continuous time series waveform data are being used to evaluate response parameters such as peak acceleration, peak velocity, and inter-story drift values. In addition, modal properties such as fundamental and higher mode frequencies and mode shapes are being computed from small and moderate earthquake data from the building. Building motion is computed for every floor of the building using only earthquake records from a single floor. Visualization models that map the instrumented buildings’ responses have been construct-ed using SketchUp and an associated plug-in to Matlab with recorded shaking data. This data visualization approach is different from other techniques because each building model is customized to show actual data recorded from that building on varying spatial scales, without the need for large-scale parallel computing facilities or complicated software that requires a steep learning curve

Monitoring Entanglement Evolution and Collective Quantum Dynamics

We generalize a recently developed scheme for monitoring coherent quantum dynamics with good time-resolution and low backaction [Reuther et al., Phys. Rev. Lett. 102, 033602 (2009)] to the case of more complex quantum dynamics of one or several qubits. The underlying idea is to measure with lock-in techniques the response of the quantum system to a high-frequency ac field. We demonstrate that this scheme also allows one to observe quantum dynamics with many frequency scales, such as that of a qubit undergoing Landau-Zener transitions. Moreover, we propose how to measure the entanglement between two qubits as well as the collective dynamics of qubit arrays.Comment: 11 pages, 5 figure