Kinetic resolution of racemic {alpha}-olefins with ansa-zirconocene polymerization catalysts: Enantiomorphic site vs. chain end control

Copolymerization of racemic {alpha}-olefins with ethylene and propylene was carried out in the presence of enantiopure C1-symmetric ansa metallocene, {1,2-(SiMe2)2({eta}5-C5H-3,5-(CHMe2)2)({eta}5-C5H3)}ZrCl2 to probe the effect of the polymer chain end on enantioselection for the R- or S-{alpha}-olefin during the kinetic resolution by polymerization catalysis. Copolymerizations with ethylene revealed that the polymer chain end is an important factor in the enantioselection of the reaction and that for homopolymerization, chain end control generally works cooperatively with enantiomorphic site control. Results from propylene copolymerizations suggested that chain end control arising from a methyl group at the beta carbon along the main chain can drastically affect selectivity, but its importance as a stereo-directing element depends on the identity of the olefin

Postemergence Broadleaf Weed Control in Barley

Experiments were conducted from 1981-1983 to determine the efficacy and phytotoxicity of postemergence herbicides used to control broadleaf weeds in spring-planted barley. The following herbicides were evaluated: MCPA amine (0.37, 0.75, 1.5 lb/A, active ingredient), 2,4-D amine (0.25, 0.5, 1 lb/A), bromoxynil (0.21, 0.43, 0.86 lb/A), and metribuzin (0.11, 0.21, 0.43, 0.86 lb/A). In 1982 and 1983, three additional herbicides were included: dinoseb (0.25, 0.5, 1 Ib/A), dicamba (0.09, 0.18, 0.36 lb/A), and chlorsulfuron (0.04, 0.07, 0.14 lb/A). Weed control was determined through measurements of weed biomass in each herbicide and control plot. Phytotoxicity was measured by barley yield and test weight in all years, and additionally by germination of seed produced in 1982. None of the herbicides except dicamba in 1982 significantly reduced the yield or test weights of barley below that of the control. Common lambsquarters was the only weed present in 1981 and 1982. Bromoxynil and metribuzin provided both early-and late-season control MCPA, 2,4-D, and j dinoseb took longer to control common lambsquarters but provided adequate control by midseason. Dicamba did not control common lambsquarters as well as the other herbicides. In 1983, prostrate knotweed was also present at the study site. None of the herbicides significantly reduced the number of prostrate knotweed below that of the control Germination of 'Galt' barley was not \, affected by treating parent plants with any of the herbicides tested. The following barley varieties were screened for susceptibility to metribuzin injury in 1982: Galt, Lidal, Weal, Otal, Datal, Eero, Paavo, Otra, and Klondike. Only 'Klondike' was highly sensitive to metribuzin

Building a Bird: Musculoskeletal Modeling and Simulation of Wing-Assisted Incline Running during Avian Ontogeny

Flapping flight is the most power-demanding mode of locomotion, associated with a suite of anatomical specializations in extant adult birds. In contrast, many developing birds use their forelimbs to negotiate environments long before acquiring “flight adaptations,” recruiting their developing wings to continuously enhance leg performance and, in some cases, fly. How does anatomical development influence these locomotor behaviors? Isolating morphological contributions to wing performance is extremely challenging using purely empirical approaches. However, musculoskeletal modeling and simulation techniques can incorporate empirical data to explicitly examine the functional consequences of changing morphology by manipulating anatomical parameters individually and estimating their effects on locomotion. To assess how ontogenetic changes in anatomy affect locomotor capacity, we combined existing empirical data on muscle morphology, skeletal kinematics, and aerodynamic force production with advanced biomechanical modeling and simulation techniques to analyze the ontogeny of pectoral limb function in a precocial ground bird (Alectoris chukar). Simulations of wing-assisted incline running (WAIR) using these newly developed musculoskeletal models collectively suggest that immature birds have excess muscle capacity and are limited more by feather morphology, possibly because feathers grow more quickly and have a different style of growth than bones and muscles. These results provide critical information about the ontogeny and evolution of avian locomotion by (i) establishing how muscular and aerodynamic forces interface with the skeletal system to generate movement in morphing juvenile birds, and (ii) providing a benchmark to inform biomechanical modeling and simulation of other locomotor behaviors, both across extant species and among extinct theropod dinosaurs

Locating the pseudogap closing point in cuprate superconductors: absence of entrant or reentrant behavior

Current descriptions of the pseudogap in underdoped cuprates envision a doping-dependent transition line $T^*(p)$ which descends monotonically towards zero just beyond optimal doping. There is much debate as to the location of the terminal point $p^*$ where $T^*(p)$ vanishes, whether or not there is a phase transition at $T^*$ and exactly how $T^*(p)$ behaves below $T_c$ within the superconducting dome. One perspective sees $T^*(p)$ cutting the dome and continuing to descend monotonically to zero at $p_{crit} \approx 0.19$ holes/Cu $-$ referred to here as `entrant behavior'. Another perspective derived from photoemission studies is that $T^*(p)$ intersects the dome near $p_{crit} \approx 0.23$ holes/Cu then turns back below $T_c$, falling to zero again around $p_{crit} \approx 0.19$ $-$ referred to here as `reentrant behavior'. By examining thermodynamic data for Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ we show that neither entrant nor reentrant behavior is experimentally supported. Rather, $p_{crit} \approx 0.19$ sharply delimits the pseudogap regime and for $p < 0.19$ the pseudogap is always present, independent of temperature. Similar results are found for Y$_{0.8}$Ca$_{0.2}$Ba$_2$Cu$_3$O$_{7-\delta}$. For both materials $T^*(p)$ is not a temperature but a crossover scale, $\approx E^*(p)/2k_B$, reflecting instead the underlying pseudogap energy $E^*(p)$ which vanishes as $p \rightarrow 0.19$.Comment: 20 Pages, 9 Figures, in press Phys. Rev.

Systematic Regional Planning for Multiple Objective Natural Resource Management. A Case Study in the South Australian River Murray Corridor.

The aim of this study is to assess the feasibility of different policy options for encouraging the large scale NRM actions required for achieving stated regional resource condition targets for NRM. To achieve this, the concept of systematic regional planning is developed to identify geographic priorities for NRM actions that most cost effectively meet multiple-objective regional targets based on established biophysical and economic principles.Water;Australia;Rivers;Biodiversity;Natural Resource Management;Revegetation

Medical Implications of Space Radiation Exposure Due to Low Altitude Polar Orbits

Space radiation research has progressed rapidly in recent years, but there remain large uncertainties in predicting and extrapolating biological responses to humans. Exposure to cosmic radiation and Solar Particle Events may pose a critical health risk to future spaceflight crews and can have a serious impact to all biomedical aspects of space exploration. The relatively minimal shielding of the cancelled 1960's Manned Orbiting Laboratory program's space vehicle and the high inclination polar orbits would have left the crew susceptible to high exposures of cosmic radiation and high dose-rate SPEs that are mostly unpredictable in frequency and intensity. In this study, we have modeled the nominal and off-nominal radiation environment that a MOL-like spacecraft vehicle would be exposed to during a 30-day mission using high performance, multi-core computers. Projected doses from a historically large SPE (e.g. the August 1972 solar event) have been analyzed in the context of the MOL orbit profile, providing an opportunity to study its impact to crew health and subsequent contingencies.It is reasonable to presume that future commercial, government, and military spaceflight missions in low-Earth orbit will have vehicles with similar shielding and orbital profiles. Studying the impact of cosmic radiation to the mission's operational integrity and the health of MOL crewmembers provides an excellent surrogate and case-study for future commercial and military spaceflight missions.Comment: 6 pages, 4 figures, 2 table

Exploring the Cost Effectiveness of Land Conservation Auctions and Payment Policies

Until recently public efforts to encourage conservation on private land in many countries has primarily been through uniform payment policies. Auctions are increasingly used as a payment mechanism to acquire public benefits such as conservation actions that provide environmental improvements on private land (e.g. the US Conservation Reserve Program (CRP). The economic rationale for use of auctions is that they create decentralised incentives to offer bids at close to the true landholder opportunity costs, even when the implementing agency holds little information about these opportunity costs. This paper assesses the cost of a case study auction relative to four payment policies that use varying levels of information strategically to reduce rent payment and to prioritise funding based on environmental value. The results suggest that the estimated cost savings achievable with the discriminant price auction for conservation contracts depends on the policy to which the auction outcomes are compared. Auction cost savings are likely to be greatest when compared to policy alternatives involving little effort to discriminate amongst offers based on differences in landholder opportunity costs. A further key finding is that, for this case study, most of the savings resulting from the discriminant price auction could be attributed to the use of the environmental benefits index in project ranking and selection.Land Economics/Use,