Sodium-mediated magnesiation of thiophene and tetrahydrothiophene : structural contrasts with furan and tetrahydrofuran

Sulfur-containing heterocycles are currently attracting agreat deal of interest in several diverse fields. For instance, substituted tetrahydrothiophenes have received considerable attention due to their extremely wide-ranging chemical and biological applications.These include their use as potent a-glucosidase inhibitors, as an inhibitor of copper amine oxidases and as selective A3 agonists and antagonists. In addition, they have been utilised in chemical transformations, such as catalytic asymmetric epoxidation, catalytic intramolecular cyclopropanation, and asymmetric metal catalysis hydrogenation. From a nanochemical perspective,the adsorption chemistries and physical propertiesof various thiophenes and tetrahydrothiophenes on gold surfaces have recently come to the fore.[7] Polythiophenes are also key compounds in modern materials research, currently utilised in, for example, the fabrication of semi-conducting, fluorescent, and electronic and optoelectronic materials.[8]In this work, metallation (exchange of a hydrogen atom with a metal atom) of the parent heterocycles, tetrahydrothiophene (THT) and thiophene is considered. Metallation is one of the most fundamental reactions in modern day synthesis and is a key tool in the preparation of functionalised aromaticand heterocyclic compounds. It is usually achieved bythe utilisation of commercially accessible organolithiums (or lithium amides); however, these reactions do have theirdrawbacks, including the intolerance of certain functionalgroups, the need for cryoscopic temperatures and the inadvertent reactivity with polar reaction solvents

Probabilistically Accurate Program Transformations

18th International Symposium, SAS 2011, Venice, Italy, September 14-16, 2011. ProceedingsThe standard approach to program transformation involves the use of discrete logical reasoning to prove that the transformation does not change the observable semantics of the program. We propose a new approach that, in contrast, uses probabilistic reasoning to justify the application of transformations that may change, within probabilistic accuracy bounds, the result that the program produces. Our new approach produces probabilistic guarantees of the form ℙ(|D| ≥ B) ≤ ε, ε ∈ (0, 1), where D is the difference between the results that the transformed and original programs produce, B is an acceptability bound on the absolute value of D, and ε is the maximum acceptable probability of observing large |D|. We show how to use our approach to justify the application of loop perforation (which transforms loops to execute fewer iterations) to a set of computational patterns.National Science Foundation (U.S.) (Grant CCF-0811397)National Science Foundation (U.S.) (Grant CCF-0905244)National Science Foundation (U.S.) (Grant CCF-1036241)National Science Foundation (U.S.) (Grant IIS-0835652)United States. Dept. of Energy (Grant DE-SC0005288

2W/nm Peak-power All-Fiber Supercontinuum Source and its Application to the Characterization of Periodically Poled Nonlinear Crystals

We demonstrate a uniform high spectral brightness and peak power density all-fiber supercontinuum source. The source consists of a nanosecond Ytterbium fiber laser and an optimal length PCF producing a continuum with a peak power density of 2 W/nm and less than 5 dB of spectral variation between 590 to 1500 nm. The Watt level per nm peak power density enables the use of such sources for the characterization of nonlinear materials. Application of the source is demonstrated with the characterization of several periodically poled crystals.Comment: 8 pages 4 figures v2 includes revisions to the description of the continuum formatio

Reducing erosion from surface irrigation by furrow spacing and plant position

Erosion is a serious problem in many furrow-irrigated fields. Erosion abatement can be costly or inconvenient. Plant placement, row spacing, and choice of trafficked or non-trafficked furrow have not been thoroughly exploited for furrow erosion control. It was hypothesized that reducing furrow spacing and plant distance to the furrow would reduce erosion for equal amounts of water applied. A study in 1986 and 1987 observed the effect of narrow rows or twin rows with plants in close proximity to the furrow on infiltration, sediment loss, and yields in three crops grown under conventional tillage on a Portneuf silt loam (coarse-silty, mixed, mesic Durixerollic Calciorthids) with 1% slope. Yields of twin-row dry bean (Phaseolus vulgaris L.) significantly increased in both years (P < 0.05), whereas yield of sugarbeet or corn (Beta vulgaris L., or Zea Mays L.) were not affected significantly by any planting pattern. Sediment loss, runoff, and the ratio of sediment loss to infiltration were greatly reduced by twin-row configurations, and somewhat reduced, although less consistently, by narrow single-row configurations. The results point the way to a low-cost, low-maintenance method of reducing furrow erosion

Erosion and infiltration of furrow irrigated potato fields as affected by zone subsoiling

Soil compaction is a problem in many potato fields of the Pacific Northwest. It was hypothesized that zone subsoiling could increase infiltration, potato (Solanum tuberosum L, cv Russet Burbank) yield, or quality and decrease bed bulk density, runoff, and sediment loss of furrow irrigated fields, while maintaining trafficability and irrigability of furrows. A two year field study was established in Fall 1988 near Kimberly, Idaho, on a Portneuf silt loam soil (coarse-silty, mixed mesic Durixerollic Calciorthids). In the Fall of each year plots were in wheat stubble (1988) or bean stover (1989) the previous season, and were either disked (10-12 cm), chiselled (25-30cm), or moldboard plowed (20-25cm) in the Fall. Fall tillage plots were split in Spring, half of each plot receiving in-row zone subsoiling after planting. The overall effect of zone subsoiling on infiltration in 1989 was small as a result of variation of its effect in the different fall tillage treatments. In 1990 zone subsoiling increased infiltration an average of 10% in all fall tillage treatments. Sediment loss by treatments were generally related to runoff, decreasing with zone subsoiling. Zone subsoiling was generally more effective at reducing erosion than at increasing infiltration as indicated by 2-3 fold decreases in the ratio of sediment loss to water infiltrated with zone subsoiling. The relative effectiveness of zone subsoiling at increasing infiltration and reducing sediment loss was greater in 1990 when the study was conducted on a field with a greater slope than in 1989 and at higher water application rates than in 1989. Yield of #1 tubers was increased 3.8 t ha-l and quality was improved by zone subsoiling in 1989. Overall yield was not significantly increased (P = 0.05), but showed a favorable trend. Yield data were not available for 1990 at this writing, but early season growth analysis indicate a positive response to subsoiling. Zone subsoiling would require extra attention on the part of the irrigator early in the season to insure uniform irrigation but offers the potential to conserve both soil and water while raising quality and possibly yield in Russet Burbank potatoes

Induced four fold anisotropy and bias in compensated NiFe/FeMn double layers

A vector spin model is used to show how frustrations within a multisublattice antiferromagnet such as FeMn can lead to four-fold magnetic anisotropies acting on an exchange coupled ferromagnetic film. Possibilities for the existence of exchange bias are examined and shown to exist for the case of weak chemical disorder at the interface in an otherwise perfect structure. A sensitive dependence on interlayer exchange is found for anisotropies acting on the ferromagnet through the exchange coupling, and we show that a wide range of anisotropies can appear even for a perfect crystalline structure with an ideally flat interface.Comment: 7 pages, 7 figure

The ecology of sex explains patterns of helping in arthropod societies

Authors thank the Natural Sciences and Engineering Research Council of Canada (NGD), the Clarendon Fund (NGD) and the Natural Environment Research Council (LR, NE/K009516/1; AG, NE/K009524/1) for funding.Across arthropod societies, sib-rearing (e.g. nursing or nest defence) may be provided by females, by males or by both sexes. According to Hamilton's ‘haplodiploidy hypothesis’, this diversity reflects the relatedness consequences of diploid vs. haplodiploid inheritance. However, an alternative ‘preadaptation hypothesis’ instead emphasises an interplay of ecology and the co-option of ancestral, sexually dimorphic traits for sib-rearing. The preadaptation hypothesis has recently received empirical support, but remains to be formalised. Here, we mathematically model the coevolution of sex-specific helping and sex allocation, contrasting these hypotheses. We find that ploidy per se has little effect. Rather, the ecology of sex shapes patterns of helping: sex-specific preadaptation strongly influences who helps; a freely adjustable sex ratio magnifies sex biases and promotes helping; and sib-mating, promiscuity, and reproductive autonomy also modulate the sex and abundance of helpers. An empirical survey reveals that patterns of sex-specific helping in arthropod taxa are consistent with the preadaptation hypothesis.Publisher PDFPeer reviewe

Cow- and herd-level risk factors for lameness in partly housed pasture-based dairy cows

Lameness in dairy cows is a major animal welfare concern and has substantial economic impact through reduced production and fertility. Previous risk factor analyses have focused on housed systems, rather than those where cows were grazed for the majority of the year and housed only for the winter period. Therefore, the aim of this observational study was to identify a robust set of cow-level and herd-level risk factors for lameness in a pasture-based system, based on predictors from the housing and grazing periods. Ninety-nine farms were visited during the grazing period (April 2019–September 2019), and 85 farms were revisited during the housing period (October 2019–February 2020). At each visit, all lactating cows were scored for lameness (0 = good mobility, 1 = imperfect mobility, 2 = impaired mobility, 3 = severely impaired mobility), and potential herd-level risk factors were recorded through questionnaires and infrastructure measurements. Routine cow-level management data were also collected. Important risk factors for lameness were derived though triangulation of results from elastic net regression, and from logistic regression model selection using modified Bayesian information criterion. Both selection methods were implemented using bootstrapping. This novel approach has not previously been used in a cow-level or herd-level risk factor analysis in dairy cows, to the authors' knowledge. The binary outcome variable was lameness status, whereby cows with a lameness score of 0 or 1 were classed as non-lame and cows with a score of 2 or 3 were classed as lame. Cow-level risk factors for increased lameness prevalence were age and genetic predicted transmitting ability for lameness. Herd-level risk factors included farm and herd size, stones in paddock gateways, slats on cow tracks near the collecting yard, a sharper turn at the parlor exit, presence of digital dermatitis on the farm, and the farmers' perception of whether lameness was a problem on the farm. This large-scale study identified the most important associations between risk factors and lameness, based on the entire year (grazing and housing periods), providing a focus for future randomized clinical trials

Migratory monarchs that encounter resident monarchs show life‐history differences and higher rates of parasite infection

Environmental change induces some wildlife populations to shift from migratory to resident behaviours. Newly formed resident populations could influence the health and behaviour of remaining migrants. We investigated migrant–resident interactions among monarch butterflies and consequences for life history and parasitism. Eastern North American monarchs migrate annually to Mexico, but some now breed year‐round on exotic milkweed in the southern US and experience high infection prevalence of protozoan parasites. Using stable isotopes (δ2H, δ13C) and cardenolide profiles to estimate natal origins, we show that migrant and resident monarchs overlap during fall and spring migration. Migrants at sites with residents were 13 times more likely to have infections and three times more likely to be reproductive (outside normal breeding season) compared to other migrants. Exotic milkweed might either attract migrants that are already infected or reproductive, or alternatively, induce these states. Increased migrant–resident interactions could affect monarch parasitism, migratory success and long‐term conservation.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146381/1/ele13144_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146381/2/ele13144.pd