18,381 research outputs found

    2,3-Dimethoxy-10-oxostrychnidinium 2-(2,4,6-trinitroanilino)benzoate monohydrate: a 1:1 proton-transfer salt of brucine with o-picraminobenzoic acid

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    In the structure of the 1:1 proton-transfer compound of brucine with 2-(2,4,6-trinitroanilino)benzoic acid C23H27N2O4+ . C13H7N4O8- . H~2~O, the brucinium cations form the classic undulating ribbon substructures through overlapping head-to-tail interactions while the anions and the three related partial water molecules of solvation (having occupancies of 0.73, 0.17 and 0.10) occupy the interstitial regions of the structure. The cations are linked to the anions directly through N-H...O(carboxyl) hydrogen bonds and indirectly by the three water molecules which form similar conjoint cyclic bridging units [graph set R2/4(8)] through O-H...O(carbonyl) and O(carboxyl) hydrogen bonds, giving a two-dimensional layered structure. Within the anion, intramolecular N-H...O(carboxyl) and N H...O(nitro) hydrogen bonds result in the benzoate and picrate rings being rotated slightly out of coplanarity inter-ring dihedral angle 32.50(14)\%]. This work provides another example of the molecular selectivity of brucine in forming stable crystal structures and also represents the first reported structure of any form of the guest compound 2-(2,4,6-trinitroanilino)benzoic acid

    Evaluating unsupervised methods to size and classify suspended particles using digital in-line holography

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    Substantial information can be gained from digital in-line holography of marine particles, eliminating depth-of-field and focusing errors associated with standard lens-based imagingmethods.However, for the technique to reach its full potential in oceanographic research, fully unsupervised (automated) methods are required for focusing, segmentation, sizing, and classification of particles. These computational challenges are the subject of this paper, in which the authors draw upon data collected using a variety of holographic systems developed at Plymouth University, United Kingdom, from a significant range of particle types, sizes, and shapes. A new method for noise reduction in reconstructed planes is found to be successful in aiding particle segmentation and sizing. The performance of an automated routine for deriving particle characteristics (and subsequent size distributions) is evaluated against equivalent size metrics obtained by a trained operative measuring grain axes on screen. The unsupervised method is found to be reliable, despite some errors resulting from oversegmentation of particles. A simple unsupervised particle classification system is developed and is capable of successfully differentiating sand grains, bubbles, and diatoms from within the surfzone. Avoiding miscounting bubbles and biological particles as sand grains enables more accurate estimates of sand concentrations and is especially important in deployments of particle monitoring instrumentation in aerated water. Perhaps the greatest potential for further development in the computational aspects of particle holography is in the area of unsupervised particle classification. The simple method proposed here provides a foundation upon which further development could lead to reliable identification of more complex particle populations, such as those containing phytoplankton, zooplankton, flocculated cohesive sediments, and oil droplets

    Design of a Direct-Detection Wind and Aerosol Lidar for Mars Orbit

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    The present knowledge of the Mars atmosphere is greatly limited by a lack of global measurements of winds and aerosols. Hence, measurements of height-resolved wind and aerosol profiles are a priority for new Mars orbiting missions. We have designed a direct-detection lidar (MARLI) to provide global measurements of dust, winds and water ice profiles from Mars orbit. From a 400-km polar orbit, the instrument is designed to provide wind and backscatter measurements with a vertical resolution of 2 km and with resolution of 2 in latitude along track. The instrument uses a single-frequency, seeded Nd:YAG laser that emits 4 mJ pulses at 1064 nm at a 250 Hz pulse rate. The receiver utilizes a 50-cm diameter telescope and a double edge Fabry-Prot etalon as a frequency discriminator to measure the Doppler shift of the aerosol-backscatter profiles. The receiver also includes a polarization-sensitive channel to detect the cross-polarized backscatter profiles from water ice. The receiver uses a sensitive 4 4 pixel HgCdTe avalanche photodiode array as a detector for all signals. Here we describe the measurement concept, instrument design, and calculate its performance for several cases of Mars atmospheric conditions. The calculations show that under a range of atmospheric conditions MARLI is capable of measuring wind speed profiles with random error of 24 m/s within the first three scale heights, enabling vertically resolved mapping of transport processes in this important region of the atmosphere

    Endurance of SN 2005ip after a decade: X-rays, radio, and H-alpha like SN 1988Z require long-lived pre-supernova mass loss

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    SN2005ip was a TypeIIn event notable for its sustained strong interaction with circumstellar material (CSM), coronal emission lines, and IR excess, interpreted as shock interaction with the very dense and clumpy wind of an extreme red supergiant. We present a series of late-time spectra of SN2005ip and a first radio detection of this SN, plus late-time X-rays, all of which indicate that its CSM interaction is still strong a decade post-explosion. We also present and discuss new spectra of geriatric SNe with continued CSM interaction: SN1988Z, SN1993J, and SN1998S. From 3-10 yr post-explosion, SN2005ip's H-alpha luminosity and other observed characteristics were nearly identical to those of the radio-luminous SN1988Z, and much more luminous than SNe1993J and 1998S. At 10 yr after explosion, SN2005ip showed a drop in Hα\alpha luminosity, followed by a quick resurgence over several months. We interpret this variability as ejecta crashing into a dense shell located at around 0.05 pc from the star, which may be the same shell that caused the IR echo at earlier epochs. The extreme H-alpha luminosities in SN2005ip and SN1988Z are still dominated by the forward shock at 10 yr post-explosion, whereas SN1993J and SN1998S are dominated by the reverse shock at a similar age. Continuous strong CSM interaction in SNe~2005ip and 1988Z is indicative of enhanced mass loss for about 1e3 yr before core collapse, longer than Ne, O, or Si burning phases. Instead, the episodic mass loss must extend back through C burning and perhaps even part of He burning.Comment: 14 pages, 8 figs. accepted in MNRA

    Differential gene expression in multiple neurological, inflammatory and connective tissue pathways in a spontaneous model of human small vessel stroke

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    Aims: Cerebral small vessel disease (SVD) causes a fifth of all strokes plus diffuse brain damage leading to cognitive decline, physical disabilities and dementia. The aetiology and pathogenesis of SVD are unknown, but largely attributed to hypertension or microatheroma. Methods: We used the spontaneously hypertensive stroke-prone rat (SHRSP), the closest spontaneous experimental model of human SVD, and age-matched control rats kept under identical, non-salt-loaded conditions, to perform a blinded analysis of mRNA microarray, qRT-PCRand pathway analysis in two brain regions (frontal and midcoronal) commonly affected by SVD in the SHRSP at age five, 16 and 21 weeks. Results: We found gene expression abnormalities, with fold changes ranging from 2.5 to 59 for the 10 most differentially expressed genes, related to endothelial tight junctions (reduced), nitric oxide bioavailability (reduced), myelination (impaired), glial and microglial activity (increased), matrix proteins (impaired), vascular reactivity (impaired) and albumin (reduced), consistent with protein expression defects in the same rats. All were present at age 5 weeks thus pre-dating blood pressure elevation. ‘Neurological’ and ‘inflammatory’ pathways were more affected than ‘vascular’ functional pathways. Conclusions: This set of defects, although individually modest, when acting in combination could explain the SHRSP's susceptibility to microvascular and brain injury, compared with control rats. Similar combined, individually modest, but multiple neurovascular unit defects, could explain susceptibility to spontaneous human SVD

    SN Hunt 248: a super-Eddington outburst from a massive cool hypergiant

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    We present photometric and spectroscopic observations of SN Hunt 248, a new supernova (SN) impostor in NGC 5806, which began a multi-stage outburst in 2014 May. The initial '2014a' discovery brightening exhibited an absolute magnitude of M~-12 and the spectral characteristics of a cool dense outflow, including P-Cygni lines of Fe II, H I, Na I, and strong line blanketing from metals. The source rapidly climbed and peaked near M~-15 mag after two additional weeks. During this bright '2014b' phase the spectrum became dominated by Balmer emission and a stronger blue continuum, similar to the SN impostor SN 1997bs. Archival images from the Hubble Space Telescope between 1997 and 2005 reveal a luminous (4e5 Lsun) variable precursor star. Its location on the Hertzsprung-Russell diagram is consistent with a massive (M_init~30 Msun) cool hypergiant having an extremely dense wind and an Eddington ratio just below unity. At the onset of the recent 2014a brightening, however, the object became super-Eddington. The subsequent boost in luminosity during the 2014b phase probably resulted from circumstellar interaction. SN Hunt 248 provides the first case of a cool hypergiant undergoing a giant eruption reminiscent of outbursts from luminous blue variable (LBV) stars. This lends support to the hypothesis that some cool hypergiants, such as Rho Cas, could be LBVs masquerading under a pseudo-photosphere created by their extremely dense winds. Moreover, SN Hunt 248 demonstrates that eruptions stemming from such stars can rival in peak luminosity the giant outbursts of much more massive systems like Eta Car.Comment: Accepted to MNRAS on 2014 Dec 1. Post-proof version. 14 pages, 9 figure

    Community experiences of organised crime in Scotland

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    The research explored community experiences of serious organised crime in Scotland (SOC). The report provides information on the nature and extent of the impact of SOC on everyday life in the community, as well as offering suggestions for policy development. The study sought to answer the following questions: 1)What are the relationships that exist between SOC and communities in Scotland? 2)What are the experiences and perceptions of residents, stakeholders and organisations of the scope and nature of SOC within their local area? and 3)How does SOC impact on community wellbeing, and to what extent can the harms associated with SOC be mitigated

    Vertical migration maintains phytoplankton position in a tidal channel with residual flow

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    A tidal channel can retain phytoplankton, despite a residual flow, if the phytoplankton migrate vertically with a daily rhythm. Tidal currents are slowed down by bed friction and so plankton experience faster flow when higher in the water column. The lateral movement of the plankton depends on the nature of the vertical migration, particularly the time spent near the surface and the phase of the tide. A model of this process accorded with observations of chlorophyll derived from in situ fluorescence at a mooring in a tidal channel. Peaks in chlorophyll at the end of the flood tide indicated the presence of a phytoplankton bloom downstream of the mooring. Peaks in chlorophyll at the ends of the morning flood tides were 3 to 4 times larger than at the ends of the evening floods, over several days. In contrast, well-mixed particulates were removed from the channel by the residual flow in just 2 d. Both the day-night asymmetry and the sustained presence of chlorophyll were explained by allowing for vertical migration of the phytoplankton and constraining the period during which they were near the surface. Tidal channels retaining phytoplankton that migrate vertically can be ecologically more diverse and yield higher commercial output of farmed bivalves. The natural timings of some phytoplankton blooms in tidal channels are controlled by the nature of the migration. Although a by-product of vertical migration, longer residence in the tidal channel affords the phytoplankton more nutrients than phytoplankton that advect offshore

    The vulnerability of public spaces: challenges for UK hospitals under the 'new' terrorist threat

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    This article considers the challenges for hospitals in the United Kingdom that arise from the threats of mass-casualty terrorism. Whilst much has been written about the role of health care as a rescuer in terrorist attacks and other mass-casualty crises, little has been written about health care as a victim within a mass-emergency setting. Yet, health care is a key component of any nation's contingency planning and an erosion of its capabilities would have a significant impact on the generation of a wider crisis following a mass-casualty event. This article seeks to highlight the nature of the challenges facing elements of UK health care, with a focus on hospitals both as essential contingency responders under the United Kingdom's civil contingencies legislation and as potential victims of terrorism. It seeks to explore the potential gaps that exist between the task demands facing hospitals and the vulnerabilities that exist within them
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