Embracing the future: embedding digital repositories in the University of London

Digital repositories can help Higher Education Institutions (HEIs) to develop coherent and coordinated approaches to capture, identify, store and retrieve intellectual assets such as datasets, course material and research papers. With the advances of technology, an increasing number of Higher Education Institutions are implementing digital repositories. The leadership of these institutions, however, has been concerned about the awareness of and commitment to repositories, and their sustainability in the future. This study informs a consortium of thirteen London institutions with an assessment of current awareness and attitudes of stakeholders regarding digital repositories in three case study institutions. The report identifies drivers for, and barriers to, the embedding of digital repositories in institutional strategy. The findings therefore should be of use to decision-makers involved in the development of digital repositories. Our approach was entirely based on consultations with specific groups of stakeholders in three institutions through interviews with specific individuals. The research in this report was prepared for the SHERPA-LEAP Consortium and conducted by RAND Europe

Spin effects in strong-field laser-electron interactions

The electron spin degree of freedom can play a significant role in relativistic scattering processes involving intense laser fields. In this contribution we discuss the influence of the electron spin on (i) Kapitza-Dirac scattering in an x-ray laser field of high intensity, (ii) photo-induced electron-positron pair production in a strong laser wave and (iii) multiphoton electron-positron pair production on an atomic nucleus. We show that in all cases under consideration the electron spin can have a characteristic impact on the process properties and their total probabilities. To this end, spin-resolved calculations based on the Dirac equation in the presence of an intense laser field are performed. The predictions from Dirac theory are also compared with the corresponding results from the Klein-Gordon equation.Comment: 9 pages, 6 figure

The interplay between exposure and preference for unpalatable foods by lambs

Herbivores satiate on single foods ingested too frequently or in excess. We hypothesized that exposure to the same unpalatable food too frequently or in excess causes satiety, which in turn would reduce subsequent use and preference for this food when alternatives become available. In each of three experiments, twenty-four lambs were randomly assigned to three treatment groups (8 lambs/group), where they received high (Ad libitum), intermediate (100–200 g/d) or low exposure (20–40 g/d) to three unpalatable foods: The invasive weed medusahead (Experiment 1), an alfalfa:quebracho tannin ration (70:30; QT) (Experiment 2), or wheat straw (Experiment 3). After exposure, all groups in Experiments 1 and 3 received a simultaneous offer of the unpalatable food and a novel food that changed across four consecutive preference tests: Grape pomace (Test 1), barley straw (Test 2), tall fescue hay (Test 3), and beet pulp (Test 4). Lambs in Experiment 2 received a simultaneous offer of each of these novel foods and the same novel food containing 30% quebracho tannins. During exposure, lambs in Experiment 1 showed a low and cyclic pattern of medusahead intake, and the group with intermediate level of medusahead exposure showed greater intake values than the Ad libitum group, followed by the group with the lowest level of exposure (P intermediate > low level of exposure (P < 0.05). During preference tests, lambs with the least level of exposure to the unpalatable foods tended to consume more medusahead (35% to 37%; P = 0.11) or wheat straw (15 to 30%; P = 0.10) than lambs that received greater levels of exposure. In contrast, differential exposure to QT did not influence subsequent preference for tannin-containing foods (P = 0.33), but animals with the greatest level of exposure to QT consumed 24% more alternatives (i.e., non-tannin containing foods) than lambs that had received the lowest level of QT exposure (P < 0.05). Intake of alternative novel foods during preference tests increased with increments in nutritional quality from grape pomace and barley straw to tall fescue hay and beet pulp (P < 0.05), suggesting that lambs discriminated the nutritional value of the novel foods. In conclusion, repeated exposure to unpalatable foods has the potential to further reduce their utilization when alternatives –even when novel– become available. This effect appeared to be influenced by the chemical characteristics of the unpalatable food and it has implications for the coexistence of plant species in grazed communities

Spectrum of the Relativistic Particles in Various Potentials

We extend the notion of Dirac oscillator in two dimensions, to construct a set of potentials. These potentials becomes exactly and quasi-exactly solvable potentials of non-relativistic quantum mechanics when they are transformed into a Schr\"{o}dinger-like equation. For the exactly solvable potentials, eigenvalues are calculated and eigenfunctions are given by confluent hypergeometric functions. It is shown that, our formulation also leads to the study of those potentials in the framework of the supersymmetric quantum mechanics

Tropical–North Pacific Climate Linkages over the Past Four Centuries

Analyses of instrumental data demonstrate robust linkages between decadal-scale North Pacific and tropical Indo-Pacific climatic variability. These linkages encompass common regime shifts, including the noteworthy 1976 transition in Pacific climate. However, information on Pacific decadal variability and the tropical high-latitude climate connection is limited prior to the twentieth century. Herein tree-ring analysis is employed to extend the understanding of North Pacific climatic variability and related tropical linkages over the past four centuries. To this end, a tree-ring reconstruction of the December-May North Pacific index (NPI)-an index of the atmospheric circulation related to the Aleutian low pressure cell-is presented (1600-1983). The NPI reconstruction shows evidence for the three regime shifts seen in the instrumental NPI data, and for seven events in prior centuries. It correlates significantly with both instrumental tropical climate indices and a coral-based reconstruction of an optimal tropical Indo-Pacific climate index, supporting evidence for a tropical-North Pacific link extending as far west as the western Indian Ocean. The coral-based reconstruction (1781-1993) shows the twentieth-century regime shifts evident in the instrumental NPI and instrumental tropical Indo-Pacific climate index, and three previous shifts. Changes in the strength of correlation between the reconstructions over time, and the different identified shifts in both series prior to the twentieth century, suggest a varying tropical influence on North Pacific climate, with greater influence in the twentieth century. One likely mechanism is the low-frequency variability of the El Nino-Southern Oscillation (ENSO) and its varying impact on Indo-Pacific climate.</p

Editorial: Phosphoinositides and their phosphatases: Linking electrical and chemical signals in biological processes

The voltage-sensing phosphatase (VSP) has changed the way we think about both cellular electrical activity and PIPs (phosphatidylinositol phosphates). Originally discovered in 1999 (Chen et al., 1999), these proteins were not recognized as electrically-controlled enzymes until 2005 (Murata et al., 2005). They constitute the first, and so far the only, example of an enzyme linking electrical signals at the plasma membrane to the catalysis of PIPs (Murata et al., 2005), a ubiquitous family of intracellular signaling molecules (Di Paolo and De Camilli, 2006; Balla, 2013). Before the discovery of VSP, there were no known direct links between the two. Textbook examples would represent this connection with arrows, alluding to indirect or “yet-to-be-defined” signaling pathways. Now we know that VSP serves as a direct connection between the electrical nature of the cell and PIPs, lipid second messengers that are critical for cell survival. However, many questions remain unanswered regarding VSP and its electrical regulation of cellular processes. With the discovery of VSP, the membrane potential must now be considered when studying PIP regulators. PIPs are involved in almost all aspects of cell physiology from survival, proliferation, and migration to pre-programed cell death (Di Paolo and De Camilli, 2006; Logothetis et al., 2010; Koch and Holt, 2012; Balla, 2013). For example, PIP concentrations are actively polarized in migrating cells with phosphatidylinositol-3,4,5-trisphosphate (PI(3,4,5)P3) on the leading edge and phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2) on the lagging edge (Leslie et al., 2008). These gradients in the concentration of PIPs are necessary for activation of Rac and Rho leading to cell motion. PIPs are also crucial for cell growth: PI(3,4,5)P3 activates the mTor cascade leading to increased protein, membrane, and nucleic acid production (Dibble and Manning,2013). Many human diseases have been associated with altered homeostasis of PIPs, including cancer, developmental disorders, and Alzheimer\u27s disease (Simpson and Parsons, 2001; McCrea and De Camilli, 2009; Hakim et al., 2012). Though the physiological relevance of VSP is not yet defined, it is still crucial to human health to understand how PIPs are regulated and that now includes VSP. All cells have an asymmetric composition of ions across their plasma membrane, which, combined with selective permeabilities for these ions, results in a difference in the electrical potential across their plasma membrane. This difference, called the membrane potential, constitutes a form of cell signaling and a source of energy, both driving many biological processes. This electrical potential difference powers neuronal excitability as well as more general processes like proliferation, migration, and development (Levin, 2007; Sundelacruz et al., 2009; Yao et al., 2011). Regulation by the membrane potential has long been the sole purview of ion channels and transporters and that has influenced what questions are asked regarding the changing potential. With our new knowledge of VSP, the changing membrane potential can directly signal the cell by modulating mTor and cell growth pathways, leading to abnormal growth or the M-current in sympathetic ganglion, leading to hyperexcitability. The articles in this Special Topic highlight several features of VSP including its unique activation, its similarities to other enzymes and its use as a versatile tool to study other proteins. In the review article by Hobiger and Friedrich (2015, p. 20), the authors compare the structural similarities and differences between the broader family of protein tyrosine phosphatases and one of its newest members, VSP. They suggest a catalytic mechanism based on this comparison. Castle et al. (2015, p. 63) investigate the activation mechanism of VSP by probing the C2 domain, the C-terminal domain of VSP that has been largely unrecognized before the recent crystal structures showed a direct contribution of the C2 residue Y522 into the active site. The work by Mavrantoni et al. (2015, p. 68) explores the techniques that are used to test VSP and address some of their limitations including the need for expensive electrophysiology equipment as well as the limitations of using channels as functional reporters. They take their methods and apply them to a chimera between the Ciona intestinalis VSP and human PTEN and show how the chimera allows for the investigation of PTEN using standard techniques but with the advantage of regulated activation, voltage. Beyond the molecular mechanism underlying VSP activity, Mori et al. (2015, p. 22) review the use of VSP as a relatively simple tool for manipulating PI(4,5)P2 concentrations in cells. They have used VSP to study the PI(4,5)P2 regulation of transient receptor potential canonical channels involved in receptor-operated calcium currents. Along the same lines, Rjasanow et al. (2015, p. 127) use VSP as a tool that gives them precise control over the PI(4,5)P2 concentrations in the membrane. These authors compared the relative PIP affinities between several ion channels. They also point out an important limitation that the channels must already have a known specificity for a particular PIP because VSP does not destroy PIPs in contrast to phospholipase C; instead, it generates multiple PIPs. All together, these articles underscore the features of VSP and expand our understanding of its function and utility. Though VSP remains relatively unknown to many, this nascent field has shown fast initial growth. The unique nature of these enzymes has inspired many to investigate their properties as well as take advantage of them. Many questions remain unanswered regarding VSP such as how the voltage sensor couples to the enzyme and whether the phosphatase domain is brought to the membrane for activation or whether a conformational change within the active site determines activation. We look forward to the studies that will address these and the many other questions that persist in this exciting field