Global MHD simulations of Saturns's magnetosphere at the time of Cassini approach

We present the results of a 3D global magnetohydrodynamic simulation of the magnetosphere of Saturn for the period of Cassini's initial approach and entry into the magnetosphere. We compare calculated bow shock and magnetopause locations with the Cassini measurements. In order to match the measured locations we use a substantial mass source due to the icy satellites (\sim1 x 10^{28} s^{-1} of water product ions). We find that the location of bow shock and magnetopause crossings are consistent with previous spacecraft measurements, although Cassini encountered the surfaces further from Saturn than the previously determined average location. In addition, we find that the shape of the model bow shock and magnetopause have smaller flaring angles than previous models and are asymmetric dawn-to-dusk. Finally, we find that tilt of Saturn's dipole and rotation axes results in asymmetries in the bow shock and magnetopause and in the magnetotail being hinged near Titan's orbit (\sim20 R _S)

High-Angular Resolution Electron Backscatter Diffraction as a New Tool for Mapping Lattice Distortion in Geological Minerals

Analysis of distortions of the crystal lattice within individual mineral grains is central to the investigation of microscale processes that control and record tectonic events. These distortions are generally combinations of lattice rotations and elastic strains, but a lack of suitable observational techniques has prevented these components being mapped simultaneously and routinely in earth science laboratories. However, the technique of high-angular resolution electron backscatter diffraction (HR-EBSD) provides the opportunity to simultaneously map lattice rotation and elastic strain gradients with exceptional precision, on the order of 0.01° for rotations and 10−4 in strain, using a scanning electron microscope. Importantly, these rotations and lattice strains relate to densities of geometrically necessary dislocations and residual stresses. Recent works have begun to apply and adapt HR-EBSD to geological minerals, highlighting the potential of the technique to provide new insights into the microphysics of rock deformation. Therefore, the purpose of this review is to provide a summary of the technique, to identify caveats and targets for further development, and to suggest areas where it offers potential for major advances. In particular, HR-EBSD is well suited to characterizing the roles of different dislocation types during crystal plastic deformation and to mapping heterogeneous internal stress fields associated with specific deformation mechanisms/microstructures or changes in temperature, confining pressure, or macroscopic deviatoric stress. These capabilities make HR-EBSD a particularly powerful new technique for analyzing the microstructures of deformed geological materials.D. Wallis, L. N. Hansen, and A. J. Wilkinson acknowledge support from the Natural Environment Research Council grant NE/M0009661. T. B. Britton acknowledges support for his research fellowship from the Royal Academy of Engineering

Ultraviolet photodissociation action spectroscopy of the N-pyridinium cation

© 2015 AIP Publishing LLC. The S1←S0 electronic transition of the N-pyridinium ion (C5H5NH+) is investigated using ultraviolet photodissociation (PD) spectroscopy of the bare ion and also the N2-tagged complex. Gas-phase N-pyridinium ions photodissociate by the loss of molecular hydrogen (H2) in the photon energy range 37 000-45 000 cm-1 with structurally diagnostic ion-molecule reactions identifying the 2-pyridinylium ion as the exclusive co-product. The photodissociation action spectra reveal vibronic details that, with the aid of electronic structure calculations, support the proposal that dissociation occurs through an intramolecular rearrangement on the ground electronic state following internal conversion. Quantum chemical calculations are used to analyze the measured spectra. Most of the vibronic features are attributed to progressions of totally symmetric ring deformation modes and out-of-plane modes active in the isomerization of the planar excited state towards the non-planar excited state global minimum

Determining Principal Component Cardinality through the Principle of Minimum Description Length

PCA (Principal Component Analysis) and its variants areubiquitous techniques for matrix dimension reduction and reduced-dimensionlatent-factor extraction. One significant challenge in using PCA, is thechoice of the number of principal components. The information-theoreticMDL (Minimum Description Length) principle gives objective compression-based criteria for model selection, but it is difficult to analytically applyits modern definition - NML (Normalized Maximum Likelihood) - to theproblem of PCA. This work shows a general reduction of NML prob-lems to lower-dimension problems. Applying this reduction, it boundsthe NML of PCA, by terms of the NML of linear regression, which areknown.Comment: LOD 201

The Effect of Heat Waves on Mental Health in a Temperate Australian City

Objective: The goal of this study was to identify mental, behavioral, and cognitive disorders that may be triggered or exacerbated during heat waves, predisposing individuals to heat-related morbidity and mortality. Design: Using health outcome data from Adelaide, South Australia, for 1993–2006, we estimated the effect of heat waves on hospital admissions and mortalities attributed to mental, behavioral, and cognitive disorders. We analyzed data using Poisson regression accounting for overdispersion and controlling for season and long-term trend, and we performed threshold analysis using hockey stick regression. Results: Above a threshold of 26.7°C, we observed a positive association between ambient temperature and hospital admissions for mental and behavioral disorders. Compared with non–heat-wave periods, hospital admissions increased by 7.3% during heat waves. Specific illnesses for which admissions increased included organic illnesses, including symptomatic mental disorders ; dementia ; mood (affective) disorders ; neurotic, stress related, and somatoform disorders ; disorders of psychological development ; and senility. Mortalities attributed to mental and behavioral disorders increased during heat waves in the 65- to 74-year age group and in persons with schizophrenia, schizotypal, and delusional disorders. Dementia deaths increased in those up to 65 years of age. Conclusion: Our results suggest that episodes of extreme heat pose a salient risk to the health and well-being of the mentally ill. Relevance to Clinical or Professional Practice: Improvements in the management and care of the mentally ill need to be addressed to avoid an increase in psychiatric morbidity and mortality as heat waves become more frequent.Alana Hansen, Peng Bi, Monika Nitschke, Philip Ryan, Dino Pisaniello and Graeme Tucke

Tutorial: Crystal orientations and EBSD - Or which way is up?

Electron backscatter diffraction (EBSD) is an automated technique that can measure the orientation of crystals in a sample very rapidly. There are many sophisticated software packages that present measured data. Unfortunately, due to crystal symmetry and differences in the set-up of microscope and EBSD software, there may be accuracy issues when linking the crystal orientation to a particular microstructural feature. In this paper we outline a series of conventions used to describe crystal orientations and coordinate systems. These conventions have been used to successfully demonstrate that a consistent frame of reference is used in the sample, unit cell, pole figure and diffraction pattern frames of reference. We establish a coordinate system rooted in measurement of the diffraction pattern and subsequently link this to all other coordinate systems. A fundamental outcome of this analysis is to note that the beamshift coordinate system needs to be precisely defined for consistent 3D microstructure analysis. This is supported through a series of case studies examining particular features of the microscope settings and/or unambiguous crystallographic features. These case studies can be generated easily in most laboratories and represent an opportunity to demonstrate confidence in use of recorded orientation data. Finally, we include a simple software tool, written in both MATLAB® and Python, which the reader can use to compare consistency with their own microscope set-up and which may act as a springboard for further offline analysis.The authors would like to thank a range of funders that underpin this collaborative work: T.B. Britton has a fellowship from the Royal Academy of Engineering. J. Jiang is funded by AVIC BIAM. T.B. Britton and A.J. Wilkinson have project funding from EPSRC through the HexMat programme grant (www.imperial.ac.uk/hexmat EP/K034332/1). DW, A.J. Wilkinson and L. Hanson have project funding from NERC through NE/M000966/1. A.J. Wilkinson and A. Vilalta-Clemente have project funding from EPSRC through EP/J016098/1

Cerebral malaria: Gamma-interferon redux

There are two theories that seek to explain the pathogenesis of cerebral malaria, the mechanical obstruction hypothesis and the immunopathology hypothesis. Evidence consistent with both ideas has accumulated from studies of the human disease and experimental models. Thus, some combination of these concepts seems necessary to explain the very complex pattern of changes seen in cerebral malaria. The interactions between malaria parasites, erythrocytes, the cerebral microvascular endothelium, brain parenchymal cells, platelets and microparticles need to be considered. One factor that seems able to knit together much of this complexity is the cytokine interferon-gamma (IFN-?). In this review we consider findings from the clinical disease, in vitro models and the murine counterpart of human cerebral malaria in order to evaluate the roles played by IFN-? in the pathogenesis of this often fatal and debilitating condition. © 2014 Hunt, Ball, Hansen, Khaw, Guo, Bakmiwewa, Mitchell, Combes and Grau

Lie detector

Novel, semicrystalline polyamides and copolyamides were synthesized from a new carbohydrate-based diamine, namely isoidide-2,5-dimethyleneamine (IIDMA). In combination with 1,6-hexamethylene diamine (1,6-HDA) as well as the biobased sebacic acid (SA) or brassylic acid (BrA), the desired copolyamides were obtained via melt polymerization of the nylon salts followed by a solid-state polycondensation (SSPC) process. Depending on the chemical compositions, the number average molecular weights (Mn) of the polyamides were in the range of 4000–49000 g/mol. With increasing IIDMA content in the synthesized copolyamides, their corresponding glass transition temperatures (Tg) increased from 50 °C to approximately 60–67 °C while the melting temperatures (Tm) decreased from 220 to 160 °C. The chemical structures of the polyamides were analyzed by NMR and FT-IR spectroscopy. Both differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) analyses revealed the semicrystalline character of these novel copolyamides. Variable-temperature (VT) 13C{1H} cross-polarization/magic-angle spinning (CP/MAS) NMR and FT-IR techniques were employed to study the crystal structures as well as the distribution of IIDMA moieties over the crystalline and amorphous phases of the copolyamides. The performed ab initio calculations reveal that the stability of the IIDMA moieties is due to a pronounced boat conformation of the bicyclic rings. The incorporation of methylene segments in between the isohexide group and the amide groups enables the hydrogen bonds formation and organization of the polymer chain fragments. Given the sufficiently high Tm values (200 °C) of the copolyamides containing less than 50% of IIDMA, these biobased semicrystalline copolyamides can be useful for engineering plastic applications

Explanation of the Colour Change in Alexandrites.

Alexandrites are remarkable and rare gemstones. They display an extraordinary colour change according to the ambient lighting, from emerald green in daylight to ruby red in incandescent light from tungsten lamps or candles. While this colour change has been correctly attributed to chromium impurities and their absorption band in the yellow region of the visible light spectrum, no adequate explanation of the mechanism has been given. Here, the alexandrite effect is fully explained by considering the von Kries model of the human colour constancy mechanism. This implies that our colour constancy mechanism is real (objective) and primarily attuned to correct for the colour temperature of black-body illuminants

Closing the sea surface mixed layer temperature budget from in situ observations alone: Operation Advection during BoBBLE

Sea surface temperature (SST) is a fundamental driver of tropical weather systems such as monsoon rainfall and tropical cyclones. However, understanding of the factors that control SST variability is lacking, especially during the monsoons when in situ observations are sparse. Here we use a ground-breaking observational approach to determine the controls on the SST variability in the southern Bay of Bengal. We achieve this through the first full closure of the ocean mixed layer energy budget derived entirely from in situ observations during the Bay of Bengal Boundary Layer Experiment (BoBBLE). Locally measured horizontal advection and entrainment contribute more significantly than expected to SST evolution and thus oceanic variability during the observation period. These processes are poorly resolved by state-of-the-art climate models, which may contribute to poor representation of monsoon rainfall variability. The novel techniques presented here provide a blueprint for future observational experiments to quantify the mixed layer heat budget on longer time scales and to evaluate these processes in models