4,096 research outputs found

    Regional climate-model performance in Greenland firn derived from in situ observations

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    Recent record-warm summers in Greenland (Khan et al. 2015) have started affecting the higher regions of the ice sheet (i.e. the accumulation area), where increased melt has altered the properties of firn (i.e. multi-year snow). At high altitudes, meltwater percolates in the porous snow and firn, where it refreezes. The result is mass conservation, as the refrozen meltwater is essentially stored (Harper et al. 2012). However, in some regions increased meltwater refreezing in shallow firn has created thick ice layers. These ice layers act as a lid, and can inhibit meltwater percolation to greater depths, causing it to run off instead (Machguth et al. 2016). Meltwater at the surface also results in more absorbed sunlight, and hence increased melt in the accumulation area (Charalampidis et al. 2015). These relatively poorly understood processes are important for ice-sheet mass-budget projections

    Climate Change Adaptation Policy in Ghana: Priorities for the Agriculture Sector

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    This report is intended to complement the 2011 CCAFS publication “State of Climate Change Adaptation and Mitigation Efforts for Agriculture in Ghana” (Domozoro 2011). It provides relevant updates regarding the policies, projects, or initiatives introduced therein, and an assessment of the evolving political scenario. Specifically, this document presents an objective look at 17 key policy documents within three thematic areas: (1) governance, (2) agriculture, and (3) climate change institutions in Ghana. Several key projects are also included in this analysis given their relevance and status within Ghana’s agricultural adaptation regime. A discussion of the institutional arrangements in each of the thematic areas is provided first, along with a short description of each of the 17 policies and projects. Then, in the following analysis section, objectives and priorities for each of the policies are outlined, together with their evolution over time, intending to identify the temporal shifts in agricultural climate change policy direction in the country. Policy interplay between and within these thematic areas is also addressed. Power and influence dynamics between actors in Ghana’s climate change adaptation regime are discussed in the following section and the results of a Multilevel Stakeholder Influence Mapping (MSIM) exercise are provided. Finally, a discussion of key challenges and recommendations are provided, as identified through semi-structured interviews with actors across the country’s adaptation regime

    User Identification Using Games

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    There is a significant shift towards a digital identity and yet the most common means of user authentication, username and password pairs, is an imperfect system. In this paper we present the notion of using videogames, specifically Tetris, to supplement traditional authentication methods and provide an additional layer of identity validation. Two experiments were undertaken that required participants to play a modified version of Tetris; the first experiment with a randomly ordered set of pieces and the second with the pieces appearing in a fixed order. The results showed that even simple games like Tetris demonstrate significant complexity in the available game states and that while some users displayed repeatable strategic behaviour, others were effectively random in their behaviours exhibiting no discernible strategy or repeatable behaviour. However, some pieces and gameboard scenarios encouraged users to exhibit behaviours that are more unique than others

    Concomitant Carcinoma in situ in Cystectomy Specimens Is Not Associated with Clinical Outcomes after Surgery

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    Objective: The aim of this study was to externally validate the prognostic value of concomitant urothelial carcinoma in situ (CIS) in radical cystectomy (RC) specimens using a large international cohort of bladder cancer patients. Methods: The records of 3,973 patients treated with RC and bilateral lymphadenectomy for urothelial carcinoma of the bladder (UCB) at nine centers worldwide were reviewed. Surgical specimens were evaluated by a genitourinary pathologist at each center. Uni- and multivariable Cox regression models addressed time to recurrence and cancer-specific mortality after RC. Results: 1,741 (43.8%) patients had concomitant CIS in their RC specimens. Concomitant CIS was more common in organ-confined UCB and was associated with lymphovascular invasion (p < 0.001). Concomitant CIS was not associated with either disease recurrence or cancer-specific death regardless of pathologic stage. The presence of concomitant CIS did not improve the predictive accuracy of standard predictors for either disease recurrence or cancer-specific death in any of the subgroups. Conclusions: We could not confirm the prognostic value of concomitant CIS in RC specimens. This, together with the discrepancy between pathologists in determining the presence of concomitant CIS at the morphologic level, limits the clinical utility of concomitant CIS in RC specimens for clinical decision-making. Copyright (C) 2011 S. Karger AG, Base

    Characterization of Shewanella oneidensis MtrC: a cell-surface decaheme cytochrome involved in respiratory electron transport to extracellular electron acceptors

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    MtrC is a decaheme c-type cytochrome associated with the outer cell membrane of Fe(III)-respiring species of the Shewanella genus. It is proposed to play a role in anaerobic respiration by mediating electron transfer to extracellular mineral oxides that can serve as terminal electron acceptors. The present work presents the first spectropotentiometric and voltammetric characterization of MtrC, using protein purified from Shewanella oneidensis MR-1. Potentiometric titrations, monitored by UV–vis absorption and electron paramagnetic resonance (EPR) spectroscopy, reveal that the hemes within MtrC titrate over a broad potential range spanning between approximately +100 and approximately -500 mV (vs. the standard hydrogen electrode). Across this potential window the UV–vis absorption spectra are characteristic of low-spin c-type hemes and the EPR spectra reveal broad, complex features that suggest the presence of magnetically spin-coupled low-spin c-hemes. Non-catalytic protein film voltammetry of MtrC demonstrates reversible electrochemistry over a potential window similar to that disclosed spectroscopically. The voltammetry also allows definition of kinetic properties of MtrC in direct electron exchange with a solid electrode surface and during reduction of a model Fe(III) substrate. Taken together, the data provide quantitative information on the potential domain in which MtrC can operate

    On the Mechanistic Origins of Toughness in Bone

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    One of the most intriguing protein materials found in nature is bone, a material composed of assemblies of tropocollagen molecules and tiny hydroxyapatite mineral crystals that form an extremely tough, yet lightweight, adaptive and multifunctional material. Bone has evolved to provide structural support to organisms, and therefore its mechanical properties are of great physiological relevance. In this article, we review the structure and properties of bone, focusing on mechanical deformation and fracture behavior from the perspective of the multidimensional hierarchical nature of its structure. In fact, bone derives its resistance to fracture with a multitude of deformation and toughening mechanisms at many size scales ranging from the nanoscale structure of its protein molecules to the macroscopic physiological scale.United States. Army Research Office (contract number W911NF-06-1-0291)National Science Foundation (U.S.) (CAREER award (contract number 0642545))Lawrence Berkeley National Laboratory (Laboratory Directed Research and Development Program)United States. Dept. of Energy (Office of Science, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, contract number DE-AC02-05CH11231

    Unrelated Helpers in a Primitively Eusocial Wasp: Is Helping Tailored Towards Direct Fitness?

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    The paper wasp Polistes dominulus is unique among the social insects in that nearly one-third of co-foundresses are completely unrelated to the dominant individual whose offspring they help to rear and yet reproductive skew is high. These unrelated subordinates stand to gain direct fitness through nest inheritance, raising the question of whether their behaviour is adaptively tailored towards maximizing inheritance prospects. Unusually, in this species, a wealth of theory and empirical data allows us to predict how unrelated subordinates should behave. Based on these predictions, here we compare helping in subordinates that are unrelated or related to the dominant wasp across an extensive range of field-based behavioural contexts. We find no differences in foraging effort, defense behaviour, aggression or inheritance rank between unrelated helpers and their related counterparts. Our study provides no evidence, across a number of behavioural scenarios, that the behaviour of unrelated subordinates is adaptively modified to promote direct fitness interests

    Boundary Conditions and Unitarity: the Maxwell-Chern-Simons System in AdS_3/CFT_2

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    We consider the holography of the Abelian Maxwell-Chern-Simons (MCS) system in Lorentzian three-dimensional asymptotically-AdS spacetimes, and discuss a broad class of boundary conditions consistent with conservation of the symplectic structure. As is well-known, the MCS theory contains a massive sector dual to a vector operator in the boundary theory, and a topological sector consisting of flat connections dual to U(1) chiral currents; the boundary conditions we examine include double-trace deformations in these two sectors, as well as a class of boundary conditions that mix the vector operators with the chiral currents. We carefully study the symplectic product of bulk modes and show that almost all such boundary conditions induce instabilities and/or ghost excitations, consistent with violations of unitarity bounds in the dual theory.Comment: 50+1 pages, 6 figures, PDFLaTeX; v2: added references, corrected typo
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