Inelastic neutron scattering studies of the quantum frustrated magnet clinoatacamite, γ\gamma-Cu2(OD)3Cl, a proposed valence bond solid (VBS)

The frustrated magnet clinoatacamite, $\gamma$-Cu$_2$(OH)$_3$Cl, is attracting a lot of interest after suggestions that at low temperature it forms an exotic quantum state termed a Valence Bond Solid (VBS) made from dimerised Cu$^{2+}$ ($S=1/2$) spins.\cite{Lee_clinoatacamite} Key to the arguments surrounding this proposal were suggestions that the kagom\'e planes in the magnetic pyrochlore lattice of clinoatacamite are only weakly coupled, causing the system to behave as a quasi-2-dimensional magnet. This was reasoned from the near 95$^\circ$ angles made at the bridging oxygens that mediate exchange between the Cu ions that link the kagom\'e planes. Recent work pointed out that this exchange model is inappropriate for $\gamma$-Cu$_2$(OH)$_3$Cl, where the oxygen is present as a $\mu_3$-OH.\cite{Wills_JPC} Further, it used symmetry calculations and neutron powder diffraction to show that the low temperature magnetic structure ($T<6$ K) was canted and involved significant spin ordering on all the Cu$^{2+}$ spins, which is incompatible with the interpretation of simultaneous VBS and N\'eel ordering. Correspondingly, clinoatacamite is best considered a distorted pyrochlore magnet. In this report we show detailed inelastic neutron scattering spectra and revisit the responses of this frustrated quantum magnet.Comment: Proceedings of The International Conference on Highly Frustrated Magnetism 2008 (HFM2008

Tunnel and thermal c-axis transport in BSCCO in the normal and pseudogap state

We consider the problem of c-axis transport in double-layered cuprates, in particular with reference to Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$ compounds. We exploit the effect of the two barriers on the thermal and tunnel transport. The resulting model is able to describe accurately the normal state c-axis resistivity in Bi$_{2}$Sr$_{2}$CaCu$_{2}$O$_{8+\delta}$, from the underdoped side up to the strongly overdoped. We extend the model, without introducing additional parameters, in order to allow for the decrease of the barrier when an external voltage bias is applied. The extended model is found to describe properly the c-axis resistivity for small voltage bias above the pseudogap temperature $T^{*}$, the c-axis resistivity for large voltage bias even below $T_c$, and the differential $dI/dV$ curves taken in mesa structures.Comment: 12 pages, 6 figures. Submitted to Superconductor Science and Technolog

Electron spin-orbit splitting in InGaAs/InP quantum well studied by means of the weak antilocalization and spin-zero effects in tilted magnetic fields

The coupling between Zeeman spin splitting and Rashba spin-orbit terms has been studied experimentally in a gated InGaAs/InP quantum well structure by means of simultaneous measurements of the weak antilocalization (WAL) effect and beating in the SdH oscillations. The strength of the Zeeman splitting was regulated by tilting the magnetic field with the spin-zeros in the SdH oscillations, which are not always present, being enhanced by the tilt. In tilted fields the spin-orbit and Zeeman splittings are not additive, and a simple expression is given for the energy levels. The Rashba parameter and the electron g-factor were extracted from the position of the spin zeros in tilted fields. A good agreement is obtained for the spin-orbit coupling strength from the spin-zeros and weak antilocalization measurements.Comment: Accepted for publication in Semiconductors Science and Technolog

Extraction of Visual Information to Predict Crowdfunding Success

Researchers have increasingly turned to crowdfunding platforms to gain insights into entrepreneurial activity and dynamics. While previous studies have explored various factors influencing crowdfunding success, such as technology, communication, and marketing strategies, the role of visual elements that can be automatically extracted from images has received less attention. This is surprising, considering that crowdfunding platforms emphasize the importance of attention-grabbing and high-resolution images, and previous research has shown that image characteristics can significantly impact product evaluations. Indeed, a comprehensive review of empirical articles (n = 202) that utilized Kickstarter data, focusing on the incorporation of visual information in their analyses. Our findings reveal that only 29.70% controlled for the number of images, and less than 12% considered any image details. In this manuscript, we review the literature on image processing and its relevance to the business domain, highlighting two types of visual variables: visual counts (number of pictures and number of videos) and image details. Building upon previous work that discussed the role of color, composition and figure-ground relationships, we introduce visual scene elements that have not yet been explored in crowdfunding, including the number of faces, the number of concepts depicted, and the ease of identifying those concepts. To demonstrate the predictive value of visual counts and image details, we analyze Kickstarter data. Our results highlight that visual count features are two of the top three predictors of success. Our results also show that simple image detail features such as color matter a lot, and our proposed measures of visual scene elements can also be useful. We supplement our article with R and Python codes that help authors extract image details (https://osf.io/ujnzp/).Comment: 32 pages, 5 figure

Federal tax policies, congressional voting and natural resources

Can abundance of natural resources affect legislators' voting behaviour over federal tax policies? We construct a political economy model of a federalized economy with district heterogeneity in natural resource abundance. The model shows that representatives of natural resource-rich districts are more (less) willing to vote in favour of federal tax increases (decreases). This occurs because resource-rich districts are less responsive to federal tax changes due to the immobile nature of their natural resources. We test the model's predictions using data on roll-call votes in the US House of Representatives over the major federal tax bills initiated during the period of 1945–2003, in conjunction with the presence of active giant oil fields in US congressional districts. Our identification strategy rests on plausibly exogenous giant oil field discoveries and exploitation and narrative-based aggregate federal tax shocks that are exogenous to individual congressional districts and legislators. We find that: (i) resource-rich congressional districts are less responsive to changes in federal taxes and (ii) representatives of resource-rich congressional districts are more (less) supportive of federal tax increases (decreases), controlling for legislator, congressional district and state indicators. Our results indicate that resource richness is approximately half as dominant as the main determinant, namely party affiliation, in driving legislators' voting behaviour over federal tax policies

Microstructure of nanocrystalline diamond powders studied by powder diffractometry

High resolution x-ray diffraction peaks of diamond nanosize powders of nominal sizes ranging from 5 to 250 nm were analyzed and provided information on grain structure, average size of crystallites, and concentration of dislocations. Selected samples were heat treated at 1670 K at pressures 2.0 and 5.5 GPa or had surface modified by outgassing, heat treatment at vacuum conditions, and by controlled adsorption of gases. The apparent lattice parameter method was applied to characterize the structure of a shell-core model of nanosize particles. The multiple whole profile fitting provided information on crystallite sizes and density of dislocations. Population of dislocations increased with applied pressure, while strain and interplanar distances in the surface layers decreased. Adsorption of foreign gases on the grain surface modified the structure of the surface layers but did not affect dislocations near the center of the grains

Evaluation of a spring-powered captive bolt gun for killing kangaroo pouch young

Context: During commercial harvesting or non-commercial kangaroo culling programs, dependent young of shot females are required to be euthanased to prevent suffering and because they would be unlikely to survive. However, the current method for killing pouch young, namely a single, forceful blow to the base of the skull, is applied inconsistently by operators and perceived by the public to be inhumane. Aims: To determine whether an alternative method for killing pouch young, namely a spring-operated captive bolt gun, is effective at causing insensibility in kangaroo pouch young. Methods: Trials of spring-operated captive bolt guns were conducted first on the heads of 15 dead kangaroo young and then on 21 live pouch young during commercial harvesting. We assessed the effectiveness at causing insensibility in live animals and damage caused to specific brain areas. We also measured depth of bolt penetration and skull thickness. Performance characteristics (e.g. bolt velocity) of two types of spring-operated guns were also measured and compared with cartridge-powered devices. Key results: When tested on the heads of dead animals, the spring-operated captive bolt gun consistently produced a large entrance cavity and a well defined wound tract, which extended into the cerebrum, almost extending the full thickness of the brain, including the brainstem. When tested on live pouch young, the captive bolt gun caused immediate insensibility in only 13 of 21 animals. This 62% success rate is significantly below the 95% minimum acceptable threshold for captive bolt devices in domestic animal abattoirs. Failure to stun was related to bolt placement, but other factors such as bolt velocity, bolt diameter and skull properties such as thickness and hardness might have also contributed. Spring-operated captive bolt guns delivered 20 times less kinetic energy than did cartridge-powered devices. Conclusions: Spring-operated captive bolt guns cannot be recommended as an acceptable or humane method for stunning or killing kangaroo pouch young. Implications: Captive bolt guns have potential as a practical alternative to blunt head trauma for effective euthanasia and reducing animal (and observer) distress. However, operators must continue to use the existing prescribed killing methods until cartridge-powered captive bolt guns have been trialled as an alternative bolt propelling method. Additional keywords: animal welfare, blunt trauma, culling, euthanasia, humaneness, kangaroo harvesting

A-Z of postural care: how to have a good posture when sitting, standing, exercising and relaxing, a guide for teachers and parents and everyone

An A to Z of Postural Care was designed to help those who work with children with postural care needs. It has been written jointly by specialist teachers, therapists and parents of children with physical impairments. The information provided is informed by research that explored the views of teachers and teaching assistants about their experiences of looking after children with physical impairments in mainstream primary schools in Kent. This A to Z booklet aims to give basic information and may act as a starting point for discussions with the therapy team, the child’s family and others in the school. It should link to more general awareness raising within a school of the importance of good posture for learning. The A-Z can be used together with other POSTED training materials to provide the basis for a training programme for parents and teachers. When using/referring to this booklet please acknowledge authorship as appropriate. Details of the other POSTED training resources and publications can be found at CREATE http://create.canterbury.ac.uk/ Hutton, E. and Coxon, K. (2011) Posture for learning: meeting the postural care needs of children with physical disabilities in mainstream primary schools in England - a research into practice exploratory study. Disability and Rehabilitation. 33 (19–20), pp.1012–1924

Photometric Calibration of the Swift Ultraviolet/Optical Telescope

We present the photometric calibration of the Swift UltraViolet/Optical Telescope (UVOT) which includes: optimum photometric and background apertures, effective area curves, colour transformations, conversion factors for count rates to flux, and the photometric zero points (which are accurate to better than 4 per cent) for each of the seven UVOT broadband filters. The calibration was performed with observations of standard stars and standard star fields that represent a wide range of spectral star types. The calibration results include the position dependent uniformity, and instrument response over the 1600-8000A operational range. Because the UVOT is a photon counting instrument, we also discuss the effect of coincidence loss on the calibration results. We provide practical guidelines for using the calibration in UVOT data analysis. The results presented here supersede previous calibration results.Comment: Minor improvements after referees report. Accepted for publication in MNRA