Fuels treatment and wildfire effects on runoff from Sierra Nevada mixed-conifer forests

We applied an eco-hydrologic model (Regional Hydro-Ecologic Simulation System [RHESSys]), constrained with spatially distributed field measurements, to assess the impacts of forest-fuel treatments and wildfire on hydrologic fluxes in two Sierra Nevada firesheds. Strategically placed fuels treatments were implemented during 2011–2012 in the upper American River in the central Sierra Nevada (43 km2) and in the upper Fresno River in the southern Sierra Nevada (24 km2). This study used the measured vegetation changes from mechanical treatments and modelled vegetation change from wildfire to determine impacts on the water balance. The well-constrained headwater model was transferred to larger catchments based on geologic and hydrologic similarities. Fuels treatments covered 18% of the American and 29% of the Lewis catchment. Averaged over the entire catchment, treatments in the wetter central Sierra Nevada resulted in a relatively light vegetation decrease (8%), leading to a 12% runoff increase, averaged over wet and dry years. Wildfire with and without forest treatments reduced vegetation by 38% and 50% and increased runoff by 55% and 67%, respectively. Treatments in the drier southern Sierra Nevada also reduced the spatially averaged vegetation by 8%, but the runoff response was limited to an increase of less than 3% compared with no treatment. Wildfire following treatments reduced vegetation by 40%, increasing runoff by 13%. Changes to catchment-scale water-balance simulations were more sensitive to canopy cover than to leaf area index, indicating that the pattern as well as amount of vegetation treatment is important to hydrologic response

Nanoscale Morphological and Chemical Changes of High Voltage Lithium–Manganese Rich NMC Composite Cathodes with Cycling

Understanding the evolution of chemical composition and morphology of battery materials during electrochemical cycling is fundamental to extending battery cycle life and ensuring safety. This is particularly true for the much debated high energy density (high voltage) lithium–manganese rich cathode material of composition Li1 + xM1 – xO2 (M = Mn, Co, Ni). In this study we combine full-field transmission X-ray microscopy (TXM) with X-ray absorption near edge structure (XANES) to spatially resolve changes in chemical phase, oxidation state, and morphology within a high voltage cathode having nominal composition Li1.2Mn0.525Ni0.175Co0.1O2. Nanoscale microscopy with chemical/elemental sensitivity provides direct quantitative visualization of the cathode, and insights into failure. Single-pixel (∼30 nm) TXM XANES revealed changes in Mn chemistry with cycling, possibly to a spinel conformation and likely including some Mn(II), starting at the particle surface and proceeding inward. Morphological analysis of the particles revealed, with high resolution and statistical sampling, that the majority of particles adopted nonspherical shapes after 200 cycles. Multiple-energy tomography showed a more homogeneous association of transition metals in the pristine particle, which segregate significantly with cycling. Depletion of transition metals at the cathode surface occurs after just one cycle, likely driven by electrochemical reactions at the surface

Towards dialogue: audio feedback on politics essays

This paper evaluates the use of audio feedback on assignments through the case study of a politics course, highlighting a number of pedagogical benefits. In particular, and using student testimonies, it argues that audio feedback provides a more personal feel to feedback; criticism, it appears, is easier to accept in the spoken word – as one student suggests, you know the marker is ‘not being harsh’ and is ‘just trying to help you really’. In addition, the paper notes the chief practical benefit of audio feedback: it reduces the overall time spent by lecturers in providing comments. While this paper is positive in favour of audio feedback throughout, it also discusses some potential challenges including anonymous marking – which affects the relationship between marker and student – and the fact that one size does not fit all, with different students preferring different types of feedback. The paper also attempts to provide practical tips to professionals wishing to use this method of feedback

Audio versus written feedback: exploring learners’ preference and the impact of feedback format on students’ academic performance

Very little is known about the impact of the different types of feedback on students’ academic performance. This paper explores students’ preference in the use of audio and written feedback and how each type of feedback received by students impact on their academic performance in subsequent assignments. The study involved 68 students who were divided into two groups that received either audio or written feedback in their first assignment which was then recalled and applied into the second assignment. An analysis of results obtained in the second assignment was conducted and comparisons made between students in the audio and written feedback group. Students were also surveyed using an online questionnaire to ascertain their perceptions about the type of feedback they had received. The study established that the type of feedback received did not impact on students’ grades in the subsequent assignment. In addition, while students were broadly positive about audio feedback, they indicated a strong preference for written feedback in future assignments. The study recommends, among other things, further investigation into the link between students’ learning styles and their preferences for different types of feedback

Why Choose LTAs? An Empirical Study of Ohio Manufacturers’ Contractual Choices Through a Bargaining Lens

This Article contributes to recent scholarship regarding Long Term Agreements (“LTAs”) by providing empirical evidence that suppliers are more likely to undertake the costs of an LTA if the transaction requires significant capital expenditures or the potential for large sunk costs. Through a survey of a random group of sixty-three Ohio manufacturers, the Article explores why manufacturers with a full range of contractual and non-contractual solutions might choose one set of arrangements over others.1 It then seeks to link its findings to a broader theory of how parties bargain to solve durable problems under conditions of uncertainty, sunk costs, and opportunism, while minimizing costs. Although only a small portion (seventeen percent) of our sample size indicated that they used LTAs in the majority of their transactions, this group indicated they were more likely to produce customizable goods and have significant capital expenditures. Such a finding is consistent with a model of bargaining in which parties in a transaction seek to achieve their overall goals of wealth maximization while minimizing costs under conditions that include bounded rationality, sunk costs, and opportunism. If a product is customized for a particular buyer, and the supplier invests sunk costs toward customization, that investment makes it difficult and costly to exit the relationship or resell to others. Where such vulnerabilities exist, the need for protection may justify the costs of LTAs. The non-adoption of LTAs by some suppliers demonstrates that the new organizational form of networked firms, governed by an LTA and straddling markets and hierarchies, has not captured all of manufacturing and reflects a diversity of arrangement. The nonadoption of LTAs may be one way suppliers respond to the stresses and frictions of the new architecture of supplier relations. Those stresses show that the new organizational paradigm is not static and suffers from the same hazards as an exchange relation. The willingness of suppliers to adopt an LTA when facing large sunk costs shows the continuing importance of sunk costs in institutional decision making and offers an additional reason beyond the need to collaborate under conditions of uncertainty to explain why parties adopt LTAs. The other type of risks — opportunism and vulnerability from investing large resources — may be best handled by entering into an LTA because it offers security, including implicit protections needed for the supplier to invest. The switching costs that lock parties into a mutual dependency and protect parties who have invested comes gradually, but without the LTA, the supplier would be reluctant to undertake the initial investment. The importance of sunk costs may also explain the choice of buyers to operate under an LTA. Since many of the benefits of LTAs, including information sharing, could be achieved by buyers hierarchically and imposed on suppliers, the explanation for adopting LTAs may lie with the need to collaborate under conditions of uncertainty and the benefits in terms of added value derived from “managerial contracting” practices, but with the need to protect large investments through the security offered by an LTA. Thus, there are two functions of LTAs: (1) how-to provisions to guide and improve production; and (2) provisions offering security of a continuing commitment either through express provisions or implicit protections. This Article suggests that although information-sharing protocols serve to “institutionalize learning,” help parties when there is an “inability” to know how to solve a production problem, and offer more information to informally enforce new types of behavior that are non-compliant, these benefits might occur by means other than an LTA. For example, a quality manual may impose a quality assessment be done by the buyer at the supplier’s plant. Alternate means of obtaining the information outside of an LTA raise the question of why LTAs are adopted

Neutron Halo Isomers in Stable Nuclei and their Possible Application for the Production of Low Energy, Pulsed, Polarized Neutron Beams of High Intensity and High Brilliance

We propose to search for neutron halo isomers populated via $\gamma$-capture in stable nuclei with mass numbers of about A=140-180 or A=40-60, where the $4s_{1/2}$ or $3s_{1/2}$ neutron shell model state reaches zero binding energy. These halo nuclei can be produced for the first time with new $\gamma$-beams of high intensity and small band width ($\le$ 0.1%) achievable via Compton back-scattering off brilliant electron beams thus offering a promising perspective to selectively populate these isomers with small separation energies of 1 eV to a few keV. Similar to single-neutron halo states for very light, extremely neutron-rich, radioactive nuclei \cite{hansen95,tanihata96,aumann00}, the low neutron separation energy and short-range nuclear force allows the neutron to tunnel far out into free space much beyond the nuclear core radius. This results in prolonged half lives of the isomers for the $\gamma$-decay back to the ground state in the 100 ps-$\mu$s range. Similar to the treatment of photodisintegration of the deuteron, the neutron release from the neutron halo isomer via a second, low-energy, intense photon beam has a known much larger cross section with a typical energy threshold behavior. In the second step, the neutrons can be released as a low-energy, pulsed, polarized neutron beam of high intensity and high brilliance, possibly being much superior to presently existing beams from reactors or spallation neutron sources.Comment: accepted for publication in Applied Physics

A field trial of a reusable, hollow, cast-in-situ pile

This paper describes the concept and field testing of a hollow, cast-in-situ, rotary bored pile foundation 1200 mm diameter and 30 m deep. The aim of the foundation is to allow large-diameter piles to be constructed using less concrete than in an equivalent conventional solid pile, and with a view to allowing reuse at a later date. Reuse is made possible because the hollow core of the pile allows access for inspection after demolition of an existing structure. The new piles may also allow modification to enhance load capacity by augering through the base and extending their length. In addition, the piles are better suited than conventional piles for use as ‘energy piles' to allow environmentally friendly heating and cooling. The geotechnical performance of the hollow test pile was comparable with that of a conventional solid pile constructed during the same trial. Details of construction are given, including lessons learned

Why Choose LTAs? An Empirical Study of Ohio Manufacturer’s Contractual Choices Through a Bargaining Lens

This paper contributes to recent scholarship regarding Long Term Agreements (LTAs) by providing empirical evidence that suppliers are more likely to undertake the costs of an LTA if the transaction requires significant capital expenditures or the potential for large sunk costs. Through a survey of a random group of 63 Ohio supplier/manufacturers, the paper explores why supplier/manufacturers with a full range of contractual and non-contractual solutions might choose one set of arrangements over others. It then seeks to link its findings to a broader theory of how parties bargain to solve durable problems under conditions of uncertainty, sunk costs and opportunism, while minimizing costs. Although only a small portion (17%) of our sample size indicated that they used LTAs in the majority of their transactions, this group indicated they were more likely to produce customizable goods and have significant capital expenditures. Such a finding is consistent with a model of bargaining in which parties in a transaction seek to achieve their overall goals of wealth maximization while minimizing costs under conditions that include bounded rationality, sunk costs and opportunism. If a product is customized for a particular buyer, and the supplier invests sunk costs toward customization, that investment makes it difficult and costly to exit the relationship or resale to others. Where such vulnerabilities exist, the need for protection may justify the costs of LTAs. The non-adoption of an LTA by some suppliers demonstrates that the new organizational form of networked firms governed by an LTA and straddling markets and hierarchies has not captured all of manufacturing, reflecting a diversity of arrangements. The non-adoption of the LTA may be one way suppliers respond to the stresses and frictions of the new architecture of supplier relations. Those stresses show that the new organizational paradigm is not static and it suffers from the same hazards as any exchange relation. The willingness of suppliers to adopt an LTA when facing large sunk costs shows the continuing importance of sunk costs in institutional decision making and offers an additional reason beyond the need to collaborate under conditions of uncertainty to explain why parties adopt LTAs. The other type of risks of opportunism and vulnerability from investing large resources may be best handled by entering an LTA because it offers security, including implicit protections needed for the supplier to invest. The switching costs that lock parties into to a mutual dependency and protect parties who have invested comes gradually but without the LTA, the supplier would be reluctant to undertake the initial investment

Anatomy of a Dansgaard-Oeschger warming transition: High-resolution analysis of the North Greenland Ice Core Project ice core

Large and abrupt temperature oscillations during the last glacial period, known as Dansgaard‐Oeschger (DO) events, are clearly observed in the Greenland ice core record. Here we present a new high‐resolution chemical (2 mm) and stable isotope (20 mm) record from the North Greenland Ice Core Project (NGRIP) ice core at the onset of one of the most prominent DO events of the last glacial, DO‐8, observed ∼38,000 years ago. The unique, subannual‐resolution NGRIP record provides a true sequence of change during a DO warming with detailed annual layer counting of very high depth resolution geochemical measurements used to determine the exact duration of the transition. The continental ions, indicative of long‐range atmospheric loading and dustiness from East Asia, are the first to change, followed by the snow accumulation, the moisture source conditions, and finally the atmospheric temperature in Greenland. The sequence of events shows that atmospheric and oceanic source and circulation changes preceded the DO warming by several years