Discovering Valuable Items from Massive Data

Suppose there is a large collection of items, each with an associated cost and an inherent utility that is revealed only once we commit to selecting it. Given a budget on the cumulative cost of the selected items, how can we pick a subset of maximal value? This task generalizes several important problems such as multi-arm bandits, active search and the knapsack problem. We present an algorithm, GP-Select, which utilizes prior knowledge about similarity be- tween items, expressed as a kernel function. GP-Select uses Gaussian process prediction to balance exploration (estimating the unknown value of items) and exploitation (selecting items of high value). We extend GP-Select to be able to discover sets that simultaneously have high utility and are diverse. Our preference for diversity can be specified as an arbitrary monotone submodular function that quantifies the diminishing returns obtained when selecting similar items. Furthermore, we exploit the structure of the model updates to achieve an order of magnitude (up to 40X) speedup in our experiments without resorting to approximations. We provide strong guarantees on the performance of GP-Select and apply it to three real-world case studies of industrial relevance: (1) Refreshing a repository of prices in a Global Distribution System for the travel industry, (2) Identifying diverse, binding-affine peptides in a vaccine de- sign task and (3) Maximizing clicks in a web-scale recommender system by recommending items to users

Soil moisture, stressed vegetation and the spatial structure of soil erosion in a high latitude rangeland

Funding: Research was supported by a NERC PhD studentship (ref: NE/L002558/) to Polly Thompson and a World-Leading Scholarship, funded by St Leonard’s Postgraduate College, University of St Andrews, to Georg Kodl.Soil erosion has been a persistent problem in high-latitude regions and may worsen as climate change unfolds and encourages increased anthropogenic exploitation. We propose that soil moisture is likely to shape future erosion trends, as moisture stress reduces the capacity of vegetation cover to retard erosive processes. However, the spatial variability of soil moisture in high-latitude soils—and the ways in which this variability drives the spatial distribution of erosion features—is poorly understood. We addressed this knowledge gap with a study of andosol erosion in southern Iceland. Our study used a combination of high-resolution (10 m from eroded terrain. We found lower moisture availability close to existing erosion features: mean volumetric soil moisture content varied from 17% (proximal to erosion patch) to 36% (distal to erosion patch). We also found that variability in soil moisture decreased with distance from eroded areas: the coefficient of variation (CV) in soil moisture varied from 0.33 (proximal to erosion patch) to 0.13 (distal to erosion). Our findings indicate that the margins of erosion patches have a stressful soil environment due to exposure to the atmosphere. The vegetation in these locations grows less vigorously, and the exposed soil becomes more vulnerable to erosion, leading to erosion patch expansion and coalescence. If these conditions hold more generally, they may represent a feedback mechanism that facilitates the lateral propagation of soil erosion in high-latitude regions.Publisher PDFPeer reviewe

CD25 expression distinguishes functionally distinct alloreactive CD4+ CD134+ (OX40+) T-cell subsets in acute graft-versus-host disease

AbstractCD134 (OX40) is expressed on activated CD4+ donor T cells in allogeneic stem cell transplant recipients with acute graft-versus-host disease. The data presented here reveal that differential expression of CD25 by CD4+ CD134+ T cells allows separation of these activated cells into 2 phenotypically and functionally distinct alloreactive T-cell subsets. These subsets exhibit distinct tissue associations, with CD4+ CD134+ CD25− T cells preferentially found in lymphoid tissues and CD4+ CD134+ CD25+ T cells located in lymphoid tissues and inflamed extralymphoid tissues. The CD25− T-cell subset exhibited potent proliferative responses to both concanavalin A and allogeneic host leukocytes. By contrast, the CD25+ T-cell subset proliferated minimally in response to either treatment and inhibited alloantigen-induced proliferation of the CD25− subset. Proliferative unresponsiveness associated with the CD25+ T-cell subset did not extend to cytokine secretion. When stimulated with alloantigen, both CD4+ CD134+ T-cell subsets responded by secreting interferon-γ and interleukin (IL)-10, and neither T-cell subset produced detectable levels of IL-2 or IL-4. Three-day treatment of the CD25+ T-cell subset with IL-2 restored the proliferative responsiveness of these cells to host alloantigens, suggesting that the proliferative unresponsiveness associated with this T-cell subset reflected a requirement for IL-2. The preferential tissue associations and distinct functional properties associated with these separable alloreactive CD4+ CD134+ T-cell subsets suggest that they participate differentially in clinical graft-versus-host disease

How does tephra deposit thickness change over time? A calibration exercise based on the 1980 Mount St Helens tephra deposit

Tephra layers are frequently used to reconstruct past volcanic activity. Inferences made from tephra layers rely on the assumption that the preserved tephra layer is representative of the initial deposit. However, a great deal can happen to tephra after it is deposited; thus, tephra layer taphonomy is a crucial but poorly understood process. The overall goal of this research was to gain greater insight into the taphonomy of terrestrial tephra layers. We approached this by a) conducting a new survey of the tephra layer from the recent, well-studied eruption of Mount St Helens on May 18th, 1980 (MSH1980); b) modelling the tephra layer thickness using an objective mathematical technique and c) comparing our results with an equivalent model based on measurements taken immediately after the eruption. In this way, we aimed to quantify any losses and transformations that have occurred. During our study, we collected measurements of tephra layer thickness from 86 locations ranging from 600 km from the vent. Geochemical analysis was used to verify the identity of tephra of uncertain origin. Our results indicated that the extant tephra layer at undisturbed sites was representative of the original deposit: overall, preservation in these locations (in terms of thickness, stratigraphy and geochemistry) had been remarkably good. However, isopach maps generated from our measurements diverged from isopachs derived from the original survey data. Furthermore, our estimate of the quantity of tephra produced during eruption greatly exceeded previous estimates of the fallout volume. In this case, inaccuracies in the modelled fallout arose from issues of sampling strategy, rather than taphonomy. Our results demonstrate the sensitivity of volcanological reconstructions to measurement location, and the great importance of reliably measured low/zero values in reconstructing tephra deposits

Bright X-ray radiation from plasma bubbles in an evolving laser wakefield accelerator

We show that the properties of the electron beam and bright x-rays produced by a laser wakefield accelerator can be predicted if the distance over which the laser self-focuses and compresses prior to self-injection is taken into account. A model based on oscillations of the beam inside a plasma bubble shows that performance is optimised when the plasma length is matched to the laser depletion length. With a 200~TW laser pulse this results in an x-ray beam with median photon energy of \unit[20]{keV}, $> 6\times 10^{8}$ photons above \unit[1]{keV} per shot and a peak brightness of \unit[3 \times 10^{22}]{photons~s^{-1}mrad^{-2}mm^{-2} (0.1\% BW)^{-1}}.Comment: 5 pages, 4 figure

Effect of Three Initial Implant Programs with a Common Terminal Revalor®- 200 on Feedlot Performance and Carcass Traits of Weaned Steers

A commercial feedlot study utilizing 1,350 calf- fed steers (initial BW = 623 lb; ±23 lb) compared three initial implant strategies: Revalor®- IS (day 1), Revalor®- IS (day 1) and Revalor®- 200 (day 67), or Revalor®- XS (day 1). Each initial implant strategy was followed by a terminal Revalor®- 200 implant (day 133) to determine effects on performance and carcass traits. No differences in final body weight, intake, gain, or feed conversion were observed on either a live, or carcass adjusted basis. Th ere were also no differences in hot carcass weight, USDA quality grade, or USDA yield grade. Results from this study suggest initial implant strategy has minimal impact on feedlot and carcass performance when following with a terminal Revalor®- 200 implant

Effect of increasing initial implant dosage on feedlot performance and carcass characteristics of long-fed steer and heifer calves1,2

Three experiments evaluated initial implant strategies for finishing cattle. In Exp. 1, heifers (n = 1,405; initial BW = 282 kg) were given (1) Revalor-IH followed by Revalor-200 (REV-IH/200), (2) Revalor-H followed by Revalor-200 (REV-H/200), or (3) Revalor-200 followed by Revalor-200 (REV-200/200). Intake, ADG, and G:F were not affected (P ≥ 0.14) by implant strategies, nor were HCW and LM area (P ≥ 0.16). Percent USDA Choice was greater (P \u3c 0.01) for Rev-IH/200 compared with Rev-H/200 and Rev-200/200. Experiment 2 used steers (n = 1,858; initial BW = 250 kg) given (1) Revalor-IS reimplanted with Revalor-200 (Rev-IS/200), (2) Revalor-XS followed by Revalor-IS (Rev-XS/IS), (3) Revalor-XS followed by Revalor-S (Rev-XS/S), or (4) Revalor-XS followed by Revalor-200 (Rev-XS/200). Implanting strategies did not affect (P ≥ 0.32) DMI or G:F. Carcass traits were not different (P ≥ 0.18) among treatments, except steers implanted with Rev-XS/200 had greater (P \u3c 0.01) LM area. In Exp. 3, steers (n = 1,408; initial BW = 305 kg) were given (1) Rev-IS/200, (2) Rev-200/200, or (3) Rev-XS/200. Gain and G:F did not differ (P ≥ 0.36) among the 3 implant strategies, nor did HCW or marbling score (P ≥ 0.15). Steers given Rev-XS/200 had greater (P \u3c 0.01) LM area and decreased (P ≤ 0.05) 12th-rib fat and YG compared with Rev-200/200 and Rev-IS/200. Using Rev-200/200 and Rev-XS/200 increased (P = 0.03) USDA Select compared with Rev-IS/200. Using greater-initial-dose implant strategies may not affect ADG or G:F but appears to increase leanness

Cryogenic aspects of the experience in operating the U-25 superconducting MHD magnet in conjunction with the MHD generator

In order to facilitate the rapid development of MHD technology for the generation of electrical energy, the U.S. and U.S.S.R. are jointly conducting research within the framework of the Program of Scientific and Technical Cooperation. The Institute for High Temperature (IVTAN) of the U.S.S.R. has designed and fabricated a special MHD facility which uses as its base much of the equipment of the existing U-25 Facility. The new MHD fow train consisting of a combustor, magnet, channel, and diffuser is named U-25B. The U.S. has provided a superconducting magnet system for the U-25B MHD Facility. As a result of these joint efforts, a unique and broad range of experimental test conditions similar to those that will exist in operation of commercial MHD generators has been created. The United States Superconducting Magnet System (U.S. SCMS) was designed, fabricated, and delivered to the U-25B Facility by the Argonne National Laboratory (ANL) under the sponsorship of the U.S. Department of Energy. The following description focuses on the cryogenic-related aspects of the magnet system commissioning and operation in the U.S.S.R

Design and operating experience of the cryogenic system of the U. S. SCMS as incorporated into the bypass loop of the U-25 MHD generator facility

The design features and accumulated operating experience, from a cryogenics point of view, of the United States Superconducting Magnet System (U.S. SCMS) are presented. The principal cryogenic system design parameters are enumerated. Details of the cryogenic aspects of magnetic system commissioning, standby mode, and operation with MHD generators are discussed. Included are system operation, problems encountered and corrective actions taken, and measured operating parameters which include liquid helium boiloff, cryostat pressure and level versus time, etc. The aspects of the transition between operation in the laboratory and in an MHD plant are elaborated