Library Search UX report summer 2016

During Summer 2016, Imperial College London's Library Information Systems team ran a round of user experience research into the information-seeking behaviour of undergraduate and postgraduate students with a specific focus on the use of the library catalogue and discovery interface. The purpose of the work was to understand user behaviours and preferences to target development of practical improvements to the Library Search interface

The Simple Economics of Extortion: Evidence from Trucking in Aceh

This paper tests whether the behavior of corrupt officials is consistent with standard industrial organization theory. We designed a study in which surveyors accompanied truck drivers on 304 trips along their regular routes in two Indonesian provinces, during which we directly observed over 6,000 illegal payments to traffic police, military officers, and attendants at weigh stations. Using plausibly exogenous changes in the number of police and military checkpoints, we show that market structure affects the level of illegal payments, finding evidence consistent with double-marginalization and hold-up along a chain of vertical monopolies. Furthermore, we document that the illegal nature of these payments does not prevent corrupt officials from extracting additional revenue using complex pricing schemes, including third-degree price discrimination and a menu of two-part tariffs. Our findings illustrate the importance of considering the market structure for bribes when designing anti-corruption policy.

Conodont biostratigraphy of the Crawford Group, Southern Uplands, Scotland

Extensive new conodont collections from the Crawford Group, the oldest succession in the Southern Uplands of Scotland, support the previously documented biostratigraphical ages for the included formations. The Raven Gill Formation is lower Whitlandian, Arenig (comparable in age to the Dounans Limestone in the Highland Border Complex) and the Kirkton Formation is latest Llandeilian-Aurelucian, Llanvirn to Caradoc in age. It is concluded that there is a significant stratigraphical gap within the Crawford Group. The restricted and probably fault-bounded nature of the Raven Gill outcrops suggests that these may represent olistoliths within a mélange of Llandeilian-Aurelucian age. The chert-bearing succession of the Northern Belt of the Southern Uplands thus represents the juxtaposed sedimentary records of two entirely separate basins – the oldest pre-dates the Grampian assembly of the Laurentian margin, and the younger, the Northern Belt Basin sensu stricto, entirely post-dates this event

Giant circular dichroism of a molecule in a region of strong plasmon resonances between two neighboring gold nanocrystals

We report on giant circular dichroism (CD) of a molecule inserted into a plasmonic hot spot. Naturally occurring molecules and biomolecules have typically CD signals in the UV range, whereas plasmonic nanocrystals exhibit strong plasmon resonances in the visible spectral interval. Therefore, excitations of chiral molecules and plasmon resonances are typically off-resonant. Nevertheless, we demonstrate theoretically that it is possible to create strongly-enhanced molecular CD utilizing the plasmons. This task is doubly challenging since it requires both creation and enhancement of the molecular CD in the visible region. We demonstrate this effect within the model which incorporates a chiral molecule and a plasmonic dimer. The associated mechanism of plasmonic CD comes from the Coulomb interaction which is greatly amplified in a plasmonic hot spot.Comment: Manuscript: 4+pages, 4 figures; Supplemental_Material: 10 pages, 7 figure

The equatorial Pacific High-Productivity Belt: Elements for a Synthesis of Deep Sea Drilling Project Leg 85 Resultspaleoceanography

Leg 85 of the Deep Sea Drilling Project operated in the eastern central Pacific in the region of the equatorial highproductivity belt. We recovered uppermost Eocene to Quaternary reference sections amenable to fine-scale stratigraphic and paleoceanographic research, using primarily the hydraulic piston corer. Four sites (572 to 575) were drilled along an east-west (about 114 to 133°W) and north-south (about 0.5 to 6°N) transect across the equatorial belt. At Site 572 an apparently complete lower middle Miocene to Quaternary sequence was recovered: the sediment sections are dominantly siliceous-calcareous oozes and chalks, and sediment accumulation rates were high (30 to 60 m/ m.y.). Sediments at Sites 573 to 575 are similar and dominated by siliceous and calcareous oozes and chalks. Sediment accumulation rates at Site 573 were generally between 10 and 35 m/m.y. The upper Eocene to Quaternary sequence is punctuated by seven hiatuses. At Site 574 a nearly complete upper Eocene to Quaternary sequence was retrieved, including a continuous Eocene to Oligocene transition. At Site 575 a lower Miocene to Quaternary section was cored. The lower to middle Miocene section is characterized by high, constant carbonate contents and sediment accumulation rates of about 20 m/m.y.; the top of the recovered section contains two hiatuses and has accumulated at rates of less than 10 m/m.y. Except for thin, basal metalliferous layers, compositional changes in Leg 85 sediments result from shifts in the relative abundances of the biogenic siliceous or calcareous components. Leg 85 sites subsided and migrated at about 0.3 cm/yr., from about 3000 m in the eastern Pacific, south of the equator, to deeper (4000 to 4600 m), more western locations at or north of the equator. The sedimentary sequences recorded regional changes in productivity (biogenic sedimentation), dissolution, and erosion associated with the equatorial belt, as well as global paleoceanographic events. The most striking regional trend is an east-west decreasing gradient in deposition of biogenic silica, prevailing from middle Miocene to Recent, which mirrors present-day surface-water productivity. A less pronounced middle Miocene to Recent latitudinal trend in deposition appears to be the result of enhanced carbonate solution to the north. The effects of deposition in the equatorial high-productivity belt have not changed since the early Miocene. Below the middle/upper Miocene boundary, the sediments have a relatively constant high carbonate content, whereas above, carbonate percentages are highly variable. The changeover level is generally marked by a hiatus and significant changes in physical, chemical, and magnetic properties of the sediments. Results of Leg 85 contributed to advances in the four elements needed for an eventual paleoceanographic synthesis: (1) a high-resolution, multidisciplinary, and integrated datum-plane scheme and time scale, with an overall resolution of 0.13 to 0.38 m.y., was established; (2) a system of correctable acoustic reflectors was delineated over vast distances, and these reflectors were calibrated against age and physical and chemical properties at Sites 574; (3) a fine-scale geochemical (stable isotope and CaCO3) and micropaleontological climatic reconstruction was developed (discontinuously) from Oligocene to Pleistocene; and (4) broadly correctable hiatuses (NH, PH), defined by previous work, were recognized at Sites 573 to 575. The interval from 8 to 9 Ma serves to outline how integration of the foregoing elements could lead to a future synthesis. In the central basin of the equatorial Pacific, the interval from 8 to 9 Ma is marked by a hiatus (NH5) in siliceous clays. A correlative hiatus occurs in carbonate oozes of the equatorial region and in the northeastern Pacific rim, and may be correlated with the Purple equatorial Pacific reflector. The interval is characterized globally by a regression, by strong carbonate dissolution, and by isotopic and micropaleontological evidence of marked cooling. Further study of these paleoceanographic phenomena in a variety of depositional environments will lead to an understanding of their relationships and functioning

SUSY vertex algebras and supercurves

This article is a continuation of math.QA/0603633 Given a strongly conformal SUSY vertex algebra V and a supercurve X we construct a vector bundle V_X on X, the fiber of which, is isomorphic to V. Moreover, the state-field correspondence of V canonically gives rise to (local) sections of these vector bundles. We also define chiral algebras on any supercurve X, and show that the vector bundle V_X, corresponding to a SUSY vertex algebra, carries the structure of a chiral algebra.Comment: 50 page

High titers of transmissible spongiform encephalopathy infectivity associated with extremely low levels of PrP in vivo

Rona Barron - ORCID: 0000-0003-4512-9177 https://orcid.org/0000-0003-4512-9177Diagnosis of transmissible spongiform encephalopathy (TSE) disease in humans and ruminants relies on the detection in post-mortem brain tissue of the protease-resistant form of the host glycoprotein PrP. The presence of this abnormal isoform (PrPSc) in tissues is taken as indicative of the presence of TSE infectivity. Here we demonstrate conclusively that high titers of TSE infectivity can be present in brain tissue of animals that show clinical and vacuolar signs of TSE disease but contain low or undetectable levels of PrPSc. This work questions the correlation between PrPSc level and the titer of infectivity and shows that tissues containing little or no proteinase K-resistant PrP can be infectious and harbor high titers of TSE infectivity. Reliance on protease-resistant PrPSc as a sole measure of infectivity may therefore in some instances significantly underestimate biological properties of diagnostic samples, thereby undermining efforts to contain and eradicate TSEs.https://doi.org/10.1074/jbc.M704329200282pubpub4

A closer look at ARSA activity in a patient with metachromatic leukodystrophy.

Metachromatic leukodystrophy (MLD) is an autosomal recessive lysosomal storage disease mainly caused by a deficiency of arylsulfatase A activity. The typical clinical course of patients with the late infantile form includes a regression in motor skills with progression to dysphagia, seizures, hypotonia and death. We present a case of a 4-year-old female with rapidly progressive developmental regression with loss of motor milestones, spasticity and dysphagia. MRI showed volume loss and markedly abnormal deep white matter. Enzymatic testing in one laboratory showed arylsulfatase A activity in their normal range. However, extraction of urine showed a large increase in sulfatide excretion in a second laboratory. Measurement of arylsulfatase A in that laboratory showed a partial decrease in arylsulfatase A activity measured under typical conditions (about 37% of the normal mean). When the concentration of substrate in the assay was lowered to one quarter of that normally used, this individual had activity \u3c10% of controls. The patient was found to be homozygous for an unusual missense mutation in the arylsulfatase A gene confirming the diagnosis of MLD. This case illustrates the importance of careful biochemical and molecular testing for MLD if there is suspicion of this diagnosis

Relating Agulhas leakage to the Agulhas Current retroflection location

The relation between the Agulhas Current retroflection location and the magnitude of Agulhas leakage, the transport of water from the Indian to the Atlantic Ocean, is investigated in a high-resolution numerical ocean model. Sudden eastward retreats of the Agulhas Current retroflection loop are linearly related to the shedding of Agulhas rings, where larger retreats generate larger rings. Using numerical Lagrangian floats a 37 year time series of the magnitude of Agulhas leakage in the model is constructed. The time series exhibits large amounts of variability, both on weekly and annual time scales. A linear relation is found between the magnitude of Agulhas leakage and the location of the Agulhas Current retroflection, both binned to three month averages. In the relation, a more westward location of the Agulhas Current retroflection corresponds to an increased transport from the Indian Ocean to the Atlantic Ocean. When this relation is used in a linear regression and applied to almost 20 years of altimetry data, it yields a best estimate of the mean magnitude of Agulhas leakage of 13.2 Sv. The early retroflection of 2000, when Agulhas leakage was probably halved, can be identified using the regression