Determination of Dark Matter Properties at High-Energy Colliders

If the cosmic dark matter consists of weakly-interacting massive particles, these particles should be produced in reactions at the next generation of high-energy accelerators. Measurements at these accelerators can then be used to determine the microscopic properties of the dark matter. From this, we can predict the cosmic density, the annihilation cross sections, and the cross sections relevant to direct detection. In this paper, we present studies in supersymmetry models with neutralino dark matter that give quantitative estimates of the accuracy that can be expected. We show that these are well matched to the requirements of anticipated astrophysical observations of dark matter. The capabilities of the proposed International Linear Collider (ILC) are expected to play a particularly important role in this study.Comment: 124 pages, 62 figures; corrections and new material in Section 2.6 (direct detection); misc. additional correction

The Quartic Higgs Coupling at Hadron Colliders

The quartic Higgs self-coupling is the final measurement in the Higgs potential needed to fully understand electroweak symmetry breaking. None of the present or future colliders are known to be able to determine this parameter. We study the chances of measuring the quartic self-coupling at hadron colliders in general and at the VLHC in particular. We find the prospects challenging.Comment: 5 pages, 4 figure

Presenting evidence-based health information for people with multiple sclerosis : the IN-DEEP project protocol

Background - Increasingly, evidence-based health information, in particular evidence from systematic reviews, is being made available to lay audiences, in addition to health professionals. Research efforts have focused on different formats for the lay presentation of health information. However, there is a paucity of data on how patients integrate evidence-based health information with other factors such as their preferences for information and experiences with information-seeking. The aim of this project is to explore how people with multiple sclerosis (MS) integrate health information with their needs, experiences, preferences and values and how these factors can be incorporated into an online resource of evidence-based health information provision for people with MS and their families.Methods - This project is an Australian-Italian collaboration between researchers, MS societies and people with MS. Using a four-stage mixed methods design, a model will be developed for presenting evidence-based health information on the Internet for people with MS and their families. This evidence-based health information will draw upon systematic reviews of MS interventions from The Cochrane Library. Each stage of the project will build on the last. After conducting focus groups with people with MS and their family members (Stage 1), we will develop a model for summarising and presenting Cochrane MS reviews that is integrated with supporting information to aid understanding and decision making. This will be reviewed and finalised with people with MS, family members, health professionals and MS Society staff (Stage 2), before being uploaded to the Internet and evaluated (Stages 3 and 4).Discussion - This project aims to produce accessible and meaningful evidence-based health information about MS for use in the varied decision making and management situations people encounter in everyday life. It is expected that the findings will be relevant to broader efforts to provide evidence-based health information for patients and the general public. The international collaboration also permits exploration of cultural differences that could inform international practice.<br /

Hypervelocity Stars: Predicting the Spectrum of Ejection Velocities

The disruption of binary stars by the tidal field of the black hole in the Galactic Center can produce the hypervelocity stars observed in the halo. We use numerical models to simulate the full spectrum of observable velocities of stars ejected into the halo by this binary disruption process. Our model includes a range of parameters for binaries with 3-4 M_Solar primaries, consideration of radial orbits of the ejected stars through an approximate mass distribution for the Galaxy, and the impact of stellar lifetimes. We calculate the spectrum of ejection velocities and reproduce previous results for the mean ejection velocity at the Galactic center. The model predicts that the full population of ejected stars includes both the hypervelocity stars with velocities large enough to escape from the Galaxy and a comparable number of ejected, but bound, stars of the same stellar type. The predicted median speeds of the population of ejected stars as a function of distance in the halo are consistent with current observations. Combining the model with the data also shows that interesting constraints on the properties of binaries in the Galactic Center and on the mass distribution in the Galaxy can be obtained even with modest samples of ejected stars.Comment: 26 pages, including 6 figures, accepted for publication in the Astrophysical Journa

Pairwise kSZ signal extraction efficacy and optical depth estimation

We determine the efficacy of the kinematic Sunyaev-Zel'dovich signal extraction pipeline, using pairwise kSZ measurements, in recovering unbiased estimates of the signal and inference of the associated optical depth. We consider the impact of cluster co-alignments along the line of sight, the modeling of baryonic clustering, and the presence of diffuse gas, as well as instrument beam convolution and noise. We demonstrate that two complementary approaches, aperture photometry, and a matched filter, can be used to recover an unbiased estimate of the cluster kSZ signal and the associated optical depth. Aperture photometry requires a correction factor accounting for the subtraction of signal in the annulus while the matched filter requires a tuning of the signal template profile. We show that both of these can be calibrated from simulated survey data. The optical depth estimates are also consistent with those inferred from stacked thermal SZ measurements. We apply the approaches to the publicly available Atacama Cosmology Telescope (ACT) data. The techniques developed here provide a promising method to leverage upcoming kSZ measurements, from ACT, Simons Observatory, CCAT, and CMB-S4 with spectroscopic galaxy surveys from DESI, Euclid, and Roman, to constrain cosmological properties of the dark energy, gravity, and neutrino masses

Strong interlayer coupling in van der Waals heterostructures built from single-layer chalcogenides

Semiconductor heterostructures are the fundamental platform for many important device applications such as lasers, light-emitting diodes, solar cells and high-electron-mobility transistors. Analogous to traditional heterostructures, layered transition metal dichalcogenide (TMDC) heterostructures can be designed and built by assembling individual single-layers into functional multilayer structures, but in principle with atomically sharp interfaces, no interdiffusion of atoms, digitally controlled layered components and no lattice parameter constraints. Nonetheless, the optoelectronic behavior of this new type of van der Waals (vdW) semiconductor heterostructure is unknown at the single-layer limit. Specifically, it is experimentally unknown whether the optical transitions will be spatially direct or indirect in such hetero-bilayers. Here, we investigate artificial semiconductor heterostructures built from single layer WSe2 and MoS2 building blocks. We observe a large Stokes-like shift of ~100 meV between the photoluminescence peak and the lowest absorption peak that is consistent with a type II band alignment with spatially direct absorption but spatially indirect emission. Notably, the photoluminescence intensity of this spatially indirect transition is strong, suggesting strong interlayer coupling of charge carriers. The coupling at the hetero-interface can be readily tuned by inserting hexagonal BN (h-BN) dielectric layers into the vdW gap. The generic nature of this interlayer coupling consequently provides a new degree of freedom in band engineering and is expected to yield a new family of semiconductor heterostructures having tunable optoelectronic properties with customized composite layers.Comment: http://www.pnas.org/content/early/2014/04/10/1405435111.abstrac

BAAD: a Biomass And Allometry Database for woody plants

Understanding how plants are constructed—i.e., how key size dimensions and the amount of mass invested in different tissues varies among individuals—is essential for modeling plant growth, carbon stocks, and energy fluxes in the terrestrial biosphere. Allocation patterns can differ through ontogeny, but also among coexisting species and among species adapted to different environments. While a variety of models dealing with biomass allocation exist, we lack a synthetic understanding of the underlying processes. This is partly due to the lack of suitable data sets for validating and parameterizing models. To that end, we present the Biomass And Allometry Database (BAAD) for woody plants. The BAAD contains 259 634 measurements collected in 176 different studies, from 21 084 individuals across 678 species. Most of these data come from existing publications. However, raw data were rarely made public at the time of publication. Thus, the BAAD contains data from different studies, transformed into standard units and variable names. The transformations were achieved using a common workflow for all raw data files. Other features that distinguish the BAAD are: (i) measurements were for individual plants rather than stand averages; (ii) individuals spanning a range of sizes were measured; (iii) plants from 0.01–100 m in height were included; and (iv) biomass was estimated directly, i.e., not indirectly via allometric equations (except in very large trees where biomass was estimated from detailed sub‐sampling). We included both wild and artificially grown plants. The data set contains the following size metrics: total leaf area; area of stem cross‐section including sapwood, heartwood, and bark; height of plant and crown base, crown area, and surface area; and the dry mass of leaf, stem, branches, sapwood, heartwood, bark, coarse roots, and fine root tissues. We also report other properties of individuals (age, leaf size, leaf mass per area, wood density, nitrogen content of leaves and wood), as well as information about the growing environment (location, light, experimental treatment, vegetation type) where available. It is our hope that making these data available will improve our ability to understand plant growth, ecosystem dynamics, and carbon cycling in the world\u27s vegetation

Stellar Kinematics in the Complicated Inner Spheroid of M31: Discovery of Substructure Along the Southeastern Minor Axis and its Relationship to the Giant Southern Stream

We present the discovery of a kinematically-cold stellar population along the SE minor axis of the Andromeda galaxy (M31) that is likely the forward continuation of M31's giant southern stream. This discovery was made in the course of an on-going spectroscopic survey of red giant branch (RGB) stars in M31 using the DEIMOS instrument on the Keck II 10-m telescope. Stellar kinematics are investigated in eight fields located 9-30 kpc from M31's center (in projection). A likelihood method based on photometric and spectroscopic diagnostics is used to isolate confirmed M31 RGB stars from foreground Milky Way dwarf stars: for the first time, this is done without using radial velocity as a selection criterion, allowing an unbiased study of M31's stellar kinematics. The radial velocity distribution of the 1013 M31 RGB stars shows evidence for the presence of two components. The broad (hot) component has a velocity dispersion of 129 km/s and presumably represents M31's virialized spheroid. A significant fraction (19%) of the population is in a narrow (cold) component centered near M31's systemic velocity with a velocity dispersion that decreases with increasing radial distance, from 55.5 km/s at R_proj=12 kpc to 10.6 km/s at R_proj=18 kpc. The spatial and velocity distribution of the cold component matches that of the "Southeast shelf" predicted by the Fardal et al. (2007) orbital model of the progenitor of the giant southern stream. The metallicity distribution of the cold component matches that of the giant southern stream, but is about 0.2 dex more metal rich on average than that of the hot spheroidal component. We discuss the implications of our discovery on the interpretation of the intermediate-age spheroid population found in this region in recent ultra-deep HST imaging studies.Comment: 23 pages, 16 figures, 2 tables, accepted for publication in the Astrophysical Journal. Changes from previous version: expanded discussion in sections 4.2 and 7.2, removal of section 7.1.4 and associated figure (discussion moved to section 7.1.2

Solar cell efficiency enhancement via light trapping in printable resonant dielectric nanosphere arrays

Resonant dielectric structures are a promising platform for addressing the key challenge of light trapping in thin-film solar cells. We experimentally and theoretically demonstrate efficiency enhancements in solar cells from dielectric nanosphere arrays. Two distinct amorphous silicon photovoltaic architectures were improved using this versatile light-trapping platform. In one structure, the colloidal monolayer couples light into the absorber in the near-field acting as a photonic crystal light-trapping element. In the other, it acts in the far-field as a graded index antireflection coating to further improve a cell which already included a state-of-the-art random light-trapping texture to achieve a conversion efficiency over 11%. For the near-field flat cell architecture, we directly fabricated the colloidal monolayer on the device through Langmuir–Blodgett deposition in a scalable process that does not degrade the active material. In addition, we present a novel transfer printing method, which utilizes chemical crosslinking of an optically thin adhesion layer to tether sphere arrays to the device surface. The minimally invasive processing conditions of this transfer method enable the application to a wide range of solar cells and other optoelectronic devices. False-color SEM image of an amorphous silicon solar cell with resonant spheres on top

Reflecting on loss in Papua New Guinea

This article takes up the conundrum of conducting anthropological fieldwork with people who claim that they have 'lost their culture,' as is the case with Suau people in the Massim region of Papua New Guinea. But rather than claiming culture loss as a process of dispossession, Suau claim it as a consequence of their own attempts to engage with colonial interests. Suau appear to have responded to missionization and their close proximity to the colonial-era capital by jettisoning many of the practices characteristic of Massim societies, now identified as 'kastom.' The rejection of kastom in order to facilitate their relations with Europeans during colonialism, followed by the mourning for kastom after independence, both invite consideration of a kind of reflexivity that requires action based on the presumed perspective of another