ALBERT

Description: Reaction of styrene oxide with sodium cyanoborohydride and a catalytic amount of Hf-NU-1000 yields the anti-Markovnikov product, 2-phenylethanol, with over 98% regioselectivity. On the other hand, propylene oxide is ring opened in a Markovnikov fashion to form 2-propanol with 95% regioselectivity. Both styrene oxide and propylene oxide failed to react with sodium cyanoborohydride without the addition of Hf-NU-1000 indicative of the crucial role of Hf-NU-1000 as a catalyst in this reaction. To the best of our knowledge, this is the first report of the use of a metal-organic framework material as a catalyst for ring-opening of epoxides with hydrides.

Description: Observations made near the Celtic Sea shelf edge are used to investigate the interaction between wind generated near-inertial oscillations and the semi-diurnal internal tide. Linear, baroclinic energy fluxes within the near-inertial ( f ) and semi-diurnal (M 2 ) wave bands are calculated from measurements of velocity and density structure at two moorings located 40 km from the internal tidal generation zone. Over the two week deployment period the semi-diurnal tide drove 28-48 W m -1 of energy directly on-shelf. Little spring-neap variability could be detected. Horizontal near-inertial energy fluxes were an order of magnitude weaker, but non-linear interaction between the vertical shear of inertial oscillations and the vertical velocity associated with the semi-diurnal internal tide led to a 25-43% increase in positive on-shelf energy flux. The phase relationship between f and M 2 determines whether this non-linear interaction enhances or dampens the linear tidal component of the flux, and introduces a 2-day counter clockwise beating to the energy transport. Two very clear contrasting regimes of (a) tidally and (b) inertially driven shear and energy flux are captured in the observations.

Description: Geodynamic models of mantle convection predict that Mexico and western North America share a history of dynamic support. We calculate admittance between gravity and topography, which indicates that the elastic thickness of the plate in Mexico is 11 km and in western North America it is 12 km. Admittance at wavelengths 〉 500 km in these regions suggests that topography is partly supported by sub-crustal processes. These results corroborate estimates of residual topography from isostatic calculations and suggest that the amount of North American topography supported by the mantle may exceed 1 km. The Cenozoic history of magmatism, sedimentary flux, thermochronometric denudation estimates and uplifted marine terraces imply that North American lithosphere was uplifted and eroded during the last 30 Ma. We jointly invert 533 Mexican and North American longitudinal river profiles to reconstruct a continent-scale rock uplift rate history. Uplift rate is permitted to vary in space and time. Erosional parameters are calibrated using incision rate data in southwest Mexico and the Colorado Plateau. Calculated rock uplift rates were 0.15–0.2 mm/yr between 25–10 Ma. Central Mexico experienced the highest uplift rates. Central and southern Mexico continued to uplift at 0.1 mm/yr until recent times. This uplift history is corroborated by independent constraints. We predict clastic flux to the Gulf of Mexico and compare it to independent estimates. We tentatively suggest that the loop between uplift, erosion and deposition can be closed here. Mexico's staged uplift history suggests that its dynamic support has changed during the last 30 Ma. This article is protected by copyright. All rights reserved.

Description: The potential for climate change mitigation by bioenergy crops and terrestrial carbon sinks has been the object of intensive research in the past decade. There has been much debate about whether energy crops used to offset fossil fuel use, or carbon sequestration in forests, would provide the best climate mitigation benefit. Most current food cropland is unlikely to be used for bioenergy, but in many regions of the world, a proportion of cropland is being abandoned, particularly marginal croplands, and some of this land is now being used for bioenergy. In this paper we assess the consequences of land use change on cropland. We first identify areas where cropland is so productive that it may never be converted, and assess the potential of the remaining cropland to mitigate climate change by identifying which alternative land use provides the best climate benefit: C 4 grass bioenergy crops, coppiced woody energy crops, or allowing forest regrowth to create a carbon sink. We do not present this as a scenario of land use change – we simply assess the best option in any given global location should a land use change occur. To do this we use global biomass potential studies based on food-crop productivity, forest inventory data, and Dynamic Global Vegetation Models to provide, for the first time, a global comparison of the climate change implications of either deploying bioenergy crops or allowing forest regeneration on current crop land, over a period of 20 years starting in the nominal year of 2000 AD. Globally, the extent of cropland on which conversion to energy crops or forest would result in a net carbon loss, and therefore likely always to remain as cropland, was estimated to be about 420.1 Mha, or 35.6% of the total cropland in Africa, 40.3% in Asia and Russia Federation, 30.8% in Europe-25, 48.4% in North America, 13.7% in South America, and 58.5% in Oceania. Fast growing C 4 Grasses such as Miscanthus and switch-grass cultivars are the bioenergy feedstock with the highest climate mitigation potential. Fast growing C 4 grasses such as Miscanthus and switch-grass cultivars provide the best climate mitigation option on ≈ 485 Mha of cropland worldwide with ~ 42% of this land characterized by a terrain slope equal or above 20%. If that land use change did occur, it would displace ≈ 58.1 Pg fossil fuel C equivalent (C eq oil). Woody energy crops such as poplar, willow, and Eucalyptus species would be the best option on only 2.4% (≈ 26.3 Mha) of current cropland, and if this land use change occurred it would displace ≈ 0.9 Pg C eq oil. Allowing cropland to revert to forest would be the best climate mitigation option on ≈ 17% of current cropland (≈ 184.5 Mha) and if this land use change occurred it would sequester ≈ 5.8 Pg C in biomass in the 20-year-old forest, and ≈ 2.7 Pg C in soil. This article is protected by copyright. All rights reserved.

Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Stephenson, Brian -- New York, N.Y. -- Science. 2014 May 2;344(6183):470. doi: 10.1126/science.344.6183.470-a.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Director, Advanced Photon Source, Associate Laboratory Director for Photon Sciences, Argonne National Laboratory, Argonne, IL 60439, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24786062" target="_blank"〉PubMed〈/a〉

Description: We ran finite-difference earthquake simulations for great subduction zone earthquakes in Cascadia to model the effects of source and path heterogeneity for the purpose of improving strong-motion predictions. We developed a rupture model for large subduction zone earthquakes based on a k –2 slip spectrum and scale-dependent rise times by representing the slip distribution as the sum of normal modes of a vibrating membrane. Finite source and path effects were important in determining the distribution of strong motions through the locations of the hypocenter, subevents, and crustal structures like sedimentary basins. Some regions in Cascadia appear to be at greater risk than others during an event due to the geometry of the Cascadia fault zone relative to the coast and populated regions. The southern Oregon coast appears to have increased risk because it is closer to the locked zone of the Cascadia fault than other coastal areas and is also in the path of directivity amplification from any rupture propagating north to south in that part of the subduction zone, and the basins in the Puget Sound area are efficiently amplified by both north and south propagating ruptures off the coast of western Washington. We find that the median spectral accelerations at 5 s period from the simulations are similar to that of the Zhao et al. (2006) ground-motion prediction equation, although our simulations predict higher amplitudes near the region of greatest slip and in the sedimentary basins, such as the Seattle basin.

Description: Ecology, Ahead of Print. Predation pressure can alter the morphology, physiology, life history and behavior of prey; this in turn can change how surviving prey interact with parasites. These trait-mediated indirect effects may change in direction or intensity during growth or, in sexually dimorphic species, between the sexes. The Trinidadian guppy Poecilia reticulata presents a unique opportunity to examine these interactions; its behavioral ecology has been intensively studied in wild populations with well-characterized predator faunas. Predation pressure is known to have driven the evolution of many guppy traits; for example, in high-predation sites, females (but not males) tend to shoal, and this anti-predator behavior facilitates parasite transmission. To test for evidence of predator-driven differences in infection in natural populations, we collected 4715 guppies from 62 sites across Trinidad between 2003 and 2009 and screened them for ectosymbionts including Gyrodactylus. A novel model-averaging analysis revealed that females were more likely to be infected with Gyrodactylus parasites than males, but only in populations with both high predation pressure and high infection incidence. We propose that the difference in shoaling tendency between the sexes could explain the observed difference in infection incidence between males and females in high-predation sites. The infection rate of juveniles did not vary with predation regime, probably because juveniles face constant predation pressure from conspecific adults and therefore tend to shoal both in high- and low-predation sites. This represents the first evidence for age- and sex-specific trait-mediated indirect effects of predators on the probability of infection in their prey.

Description: Non-polar orientations of III-nitride semiconductors have attracted significant interest due to their potential application in optoelectronic devices with enhanced efficiency. Using in situ surface x-ray scattering during metal-organic vapor phase epitaxy (MOVPE) of GaN on non-polar (m-plane) and polar (c-plane) orientations of single crystal substrates, we have observed the homoepitaxial growth modes as a function of temperature and growth rate. On the m-plane surface, we observe all three growth modes (step-flow, layer-by-layer, and three-dimensional) as conditions are varied. In contrast, the +c-plane surface exhibits a direct crossover between step-flow and 3D growth, with no layer-by-layer regime. The apparent activation energy of 2.8 ± 0.2 eV observed for the growth rate at the layer-by-layer to step-flow boundary on the m-plane surface is consistent with those observed for MOVPE growth of other III-V compounds, indicating a large critical nucleus size for islands.

Description: ABSTRACT A workshop was held at the University of the West Indies, Jamaica, in May 2012 to build capacity in climate data rescue and to enhance knowledge about climate change in the Caribbean region. Scientists brought their daily observational surface temperature and precipitation data from weather stations for an assessment of quality and homogeneity and for the calculation of climate indices helpful for studying climate change in their region. This study presents the trends in daily and extreme temperature and precipitation indices in the Caribbean region for records spanning the 1961–2010 and 1986–2010 intervals. Overall, the results show a warming of the surface air temperature at land stations. In general, the indices based on minimum temperature show stronger warming trends than indices calculated from maximum temperature. The frequency of warm days, warm nights and extreme high temperatures has increased while fewer cool days, cool nights and extreme low temperatures were found for both periods. Changes in precipitation indices are less consistent and the trends are generally weak. Small positive trends were found in annual total precipitation, daily intensity, maximum number of consecutive dry days and heavy rainfall events particularly during the period 1986–2010. Correlations between indices and the Atlantic multidecadal oscillation (AMO) index suggest that temperature variability and, to a lesser extent, precipitation extremes are related to the AMO signal of the North Atlantic surface sea temperatures: stronger associations are found in August and September for the temperature indices and in June and October for some of the precipitation indices.