869 research outputs found

    Abnormalities in the Ozark Hellbender, (Cryptobranchus alleganiensis bishopi) in Arkansas: A Comparison Between Two Rivers with a Historical Perspective

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    We documented abnormalities of Ozark hellbender (Cryptobranchus alleganiensis bishopi) populations in the Eleven Point River (Randolph County, Arkansas) and the Spring River (Fulton County, Arkansas) as part of ongoing monitoring efforts in this species. We found abnormalities in 90% (9 of 10) and 40% (36 of 97) of hellbenders in the Spring River and Eleven Point River, respectively, during the 2003-2004 field seasons. Most abnormalities found in Eleven Point hellbenders were generally less invasive and seemed to be more intrinsic to the species\u27 natural history (i.e., vicissitudes of living), whereas those found in Spring River hellbenders were gross morphological aberrations. We compared the type and rate of observed abnormalities with those found in museum vouchers collected from the Spring River between 1970 and 1975. Abnormalities were found in 12.5% of the museum specimens from our Spring River localities. This rate is much higher than previously reported for hellbenders. The increase in the abnormality rate appears to be concurrent with the documented population decline observed in the Spring River. Our study illustrates an increasing trend of hellbenders exhibiting unusual morphological problems (e.g., epidermal papillomas, extreme abrasions/lacerations, fungal infections, etc.) and also stresses the need for inclusion of abnormalities observed in field data. The causes of hellbender abnormalities remain speculative; however, plausible explanations may be related to intraspecific interactions, anthropogenic interactions with the microhabitat, viral infections, non-point/point source pollution, and the preponderance of older individuals. These findings emphasize the need for a proactive conservation effort within this species

    Candidate genes mediating magnetoreception in rainbow trout ( Oncorhynchus mykiss )

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    Diverse animals use Earth's magnetic field in orientation and navigation, but little is known about the molecular mechanisms that underlie magnetoreception. Recent studies have focused on two possibilities: (i) magnetite-based receptors; and (ii) biochemical reactions involving radical pairs. We used RNA sequencing to examine gene expression in the brain of rainbow trout ( Oncorhynchus mykiss ) after exposure to a magnetic pulse known to disrupt magnetic orientation behaviour. We identified 181 differentially expressed genes, including increased expression of six copies of the frim gene, which encodes a subunit of the universal iron-binding and trafficking protein ferritin. Functions linked to the oxidative effects of free iron (e.g. oxidoreductase activity, transition metal ion binding, mitochondrial oxidative phosphorylation) were also affected. These results are consistent with the hypothesis that a magnetic pulse alters or damages magnetite-based receptors and/or other iron-containing structures, which are subsequently repaired or replaced through processes involving ferritin. Additionally, some genes that function in the development and repair of photoreceptive structures (e.g. crggm3 , purp , prl , gcip , crabp1 and pax6 ) were also differentially expressed, raising the possibility that a magnetic pulse might affect structures and processes unrelated to magnetite-based magnetoreceptors

    Synthesis and Structural Investigation of an \u27Oxazinoquinolinespirohexadienone\u27 That Only Exists as Its Long-Wavelength Ring-Opened Quinonimine Isomer

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    The spirocyclic oxazinoquinolinespirohexadienone (OSHD) photochromes are computationally predicted to be an attractive target as electron deficient analogues of the perimidinespirohexadienone (PSHD) photochromes, for eventual application as photochromic photooxidants. We have found the literature method for their preparation unsuitable and present an alternative synthesis. Unfortunately the product of this synthesis is the long wavelength (LW) ring-opened quinonimine isomer of the OSHD. We have found this isomer does not close to the spirocyclic short wavelength isomer (SW) upon prolonged standing in the dark, unlike other PSHD photochromes. The structure of this long wavelength isomer was found by NMR and X-ray crystallography to be exclusively the quinolinone (keto) tautomer, though experimental cyclic voltammetry supported by our computational methodology indicates that the quinolinol (enol) tautomer (not detected by other means) may be accessible through a fast equilibrium lying far toward the keto tautomer. Computations also support the relative stability order of keto LW over enol LW over SW

    Fully automated segmentation of the cervical cord from T1-weighted MRI using PropSeg: Application to multiple sclerosis.

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    Spinal cord (SC) atrophy, i.e. a reduction in the SC cross-sectional area (CSA) over time, can be measured by means of image segmentation using magnetic resonance imaging (MRI). However, segmentation methods have been limited by factors relating to reproducibility or sensitivity to change. The purpose of this study was to evaluate a fully automated SC segmentation method (PropSeg), and compare this to a semi-automated active surface (AS) method, in healthy controls (HC) and people with multiple sclerosis (MS). MRI data from 120 people were retrospectively analysed; 26 HC, 21 with clinically isolated syndrome, 26 relapsing remitting MS, 26 primary and 21 secondary progressive MS. MRI data from 40 people returning after one year were also analysed. CSA measurements were obtained within the cervical SC. Reproducibility of the measurements was assessed using the intraclass correlation coefficient (ICC). A comparison between mean CSA changes obtained with the two methods over time was performed using multivariate structural equation regression models. Associations between CSA measures and clinical scores were investigated using linear regression models. Compared to the AS method, the reproducibility of CSA measurements obtained with PropSeg was high, both in patients and in HC, with ICC > 0.98 in all cases. There was no significant difference between PropSeg and AS in terms of detecting change over time. Furthermore, PropSeg provided measures that correlated with physical disability, similar to the AS method. PropSeg is a time-efficient and reliable segmentation method, which requires no manual intervention, and may facilitate large multi-centre neuroprotective trials in progressive MS

    Disk-Jet Connection in the Radio Galaxy 3C 120

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    We present the results of extensive multi-frequency monitoring of the radio galaxy 3C 120 between 2002 and 2007 at X-ray, optical, and radio wave bands, as well as imaging with the Very Long Baseline Array (VLBA). Over the 5 yr of observation, significant dips in the X-ray light curve are followed by ejections of bright superluminal knots in the VLBA images. Consistent with this, the X-ray flux and 37 GHz flux are anti-correlated with X-ray leading the radio variations. This implies that, in this radio galaxy, the radiative state of accretion disk plus corona system, where the X-rays are produced, has a direct effect on the events in the jet, where the radio emission originates. The X-ray power spectral density of 3C 120 shows a break, with steeper slope at shorter timescale and the break timescale is commensurate with the mass of the central black hole based on observations of Seyfert galaxies and black hole X-ray binaries. These findings provide support for the paradigm that black hole X-ray binaries and active galactic nuclei are fundamentally similar systems, with characteristic time and size scales linearly proportional to the mass of the central black hole. The X-ray and optical variations are strongly correlated in 3C 120, which implies that the optical emission in this object arises from the same general region as the X-rays, i.e., in the accretion disk-corona system. We numerically model multi-wavelength light curves of 3C 120 from such a system with the optical-UV emission produced in the disk and the X-rays generated by scattering of thermal photons by hot electrons in the corona. From the comparison of the temporal properties of the model light curves to that of the observed variability, we constrain the physical size of the corona and the distances of the emitting regions from the central BH.Comment: Accepted for publication in the Astrophysical Journal. 28 pages, 21 figures, 2 table

    The Touch of Iconoclasm

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    This article reflects on some depicted, intentional acts of iconoclasm undertaken by Isis in Northern Iraq, and viewed as online videos. It attempts to consider what makes these moving images compelling to audiences who share an orientation to the protection and preservation of ancient artefacts. In doing so it prompts a reflection on their circulation as part of stories that get told about cultural heritage, and particularly the simple civilizational oppositions that get set up between ‘Western’ and ‘Islamic’ culture. Centring on the significance of the sensation of touch to practices of cultural inscription, it suggests that the Northern Iraq videos animate forms of synaesthesic material engagement that are denied by the modernist technologies of museum culture
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