6,884 research outputs found
The Unique Type Ib Supernova 2005bf: A WN Star Explosion Model for Peculiar Light Curves and Spectra
Observations and modeling for the light curve (LC) and spectra of supernova
(SN) 2005bf are reported. This SN showed unique features: the LC had two
maxima, and declined rapidly after the second maximum, while the spectra showed
strengthening He lines whose velocity increased with time. The double-peaked LC
can be reproduced by a double-peaked Ni distribution, with most
Ni at low velocity and a small amount at high velocity. The rapid
post-maximum decline requires a large fraction of the -rays to escape
from the Ni-dominated region, possibly because of low-density ``holes''.
The presence of Balmer lines in the spectrum suggests that the He layer of the
progenitor was substantially intact. Increasing -ray deposition in the
He layer due to enhanced -ray escape from the Ni-dominated
region may explain both the delayed strengthening and the increasing velocity
of the He lines. The SN has massive ejecta (\sim6-7\Msun), normal kinetic
energy ( ergs), high peak bolometric luminosity
( erg s) for an epoch as late as 40 days,
and a large Ni mass (\sim0.32\Msun). These properties, and the
presence of a small amount of H suggest that the progenitor was initially
massive (M\sim 25-30 \Msun) and had lost most of its H envelope, and was
possibly a WN star. The double-peaked Ni distribution suggests that the
explosion may have formed jets that did not reach the He layer. The properties
of SN 2005bf resemble those of the explosion of Cassiopeia A.Comment: 10 pages, 4 figures. Figure of UBVr'i'JHKs light curves is revised.
Accepted for publication in the Astrophysical Journal (Letters) on 5 October
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The Optical/Near-Infrared Light Curves of SN 2002ap for the First 1.5 Years after Discovery
Late-time BVRIJHK photometry of the peculiar Type Ic SN 2002ap, taken between
2002 June 12 and 2003 August 29 with the MAGNUM telescope, is presented. The
light curve decline rate is derived in each band and the color evolution is
studied through comparison with nebular spectra and with SN 1998bw. Using the
photometry, the OIR bolometric light curve is built, extending from before
light maximum to day 580 after explosion. The light curve has a late-time shape
strikingly similar to that of the hypernova SN 1998bw. The decline rate changes
from 0.018 mag/day between day 130 and 230 to 0.014 mag/day between day 270 and
580. To reproduce the late-time light curve, a dense core must be added to the
1-D hypernova model that best fits the early-time observations, bringing the
ejecta mass from 2.5 Msun to 3 Msun without much change in the kinetic energy,
which is 4 times 10^51 ergs. This is similar to the case of other hypernovae
and suggests asymmetry. A large H-band bump developed in the spectral energy
distribution after about day 300, probably caused by strong [Si I] 1.646 micron
and 1.608 micron emissions. The near-infrared flux contribution increased
simultaneously from 50% at day 580. The near-infrared light curves
were compared with those of other Type Ib/c supernovae, among which SN 1983I
seems similar to SN 2002ap both in the near-infrared and in the optical.Comment: 24pages, 9 figures, ApJ in press (10 June 2006, v644 1 issue).
Acknowledgements update
Imaging diagnosis: magnetic resonance imaging of diffuse leptomeningeal oligodendrogliomatosis in a dog with "dural tail sign"
A case of diffuse leptomeningeal oligodendrogliomatosis affecting the brain and spinal cord of a dog is presented. A 7.5-year old, male neutered Staffordshire bull terrier presented for evaluation of a chronic history of tetraparesis and seizures, with a multifocal neuroanatomical localization was determined. Extra-axial intradural lesions with an atypical presentation of a dural tail sign were seen on MRI. Histologically, the lesions were consistent with leptomeningeal oligodendrogliomatosis. To the authors’ knowledge, a dural tail sign has not previously been reported as an MRI characteristic of diffuse leptomeningeal oligodendrogliomatosis in dogs
Post-Traumatic Syringomyelia: A Case Series
It is relatively common to occur in a Tertiary Care Neurosurgical setup to get a case of Syringomyelia proximal or distal to a space-occupying lesion (SOL) or site of spinal cord compression. In this case series, we are presenting two cases in which syringomyelia developed after traumatic spinal cord injury. On initial radiological investigations, the first case presented as an old D12 fracture with Post-traumatic syrinx formation but on complete workup for the extent of the syrinx, another lesion was found incidentally in the form of an intradural extramedullary SOL at the level of cervicomedullary junction. The SOL turned out histologically as WHO Grade I Meningioma. The second case presented as syrinx formation after gunshot (fire-arm) penetrating spinal cord injury to the D11-12 vertebrae. Treatment plans of both these patients are presented here in detail along with the literature review
The welfare of water buffaloes during the slaughter process: a review
This paper reviews the scientific literature on water buffalo welfare in all stages of the live animal supply chain from the farm gate to slaughter (loading/unloading, markets, transportation, handling, lairage, stunning and slaughter) with the objective of identifying risk factors and potential mitigation strategies. Although in some countries legislation exists to protect the welfare of farm animals during transport and killing, the handling practices used to load and unload buffaloes and move them in livestock markets and abattoirs are often harsh. This is frequently due to inadequate equipment designed principally for cattle, and the fact that water buffaloes are considered more temperamental than cattle. Additionally, more reactive animals have increased stress responses to handling, which can lead to more negative human interventions with increased numbers of skin lesions and bruises to the carcasses. During transport, buffaloes may suffer periods of thermal stress due to overstocking, inadequate ventilation and because in many tropical climates trips are made during the hottest time of the day. The anatomical and physiological characteristics of water buffalo make them particularly susceptible to thermal stress in the absence of water for wallowing. Although water buffaloes belong to the same Bovidae family as domestic cattle, certain anatomical features of the head make effective stunning very problematic. Buffaloes have extensive sinuses and frontal bones, meaning that the penetrating captive bolt devices recommended for cattle may prove ineffective in reliably inducing unconsciousness. There is a need for further development of procedures, stunning positions and appropriate devices to improve the efficiency of buffalo stunning. Finally, in many parts of the world where buffalo are routinely slaughtered in basic conditions without prior stunning. Slaughter without stunning can result in pain and stress associated with delays in the time to loss of consciousness, pain from the cutting of the neck and potential distress associated with aspiration of blood into the respiratory tract. Specific legislation, guidelines and handler/stockman/operator training programmes should be developed to improve the welfare of buffaloes during all ante mortem stages of loading, unloading, handling, stunning and slaughter
A unifying hypothesis for hydrocephalus, Chiari malformation, syringomyelia, anencephaly and spina bifida
This work is a modified version of the Casey Holter Memorial prize essay presented to the Society for Research into Hydrocephalus and Spina Bifida, June 29th 2007, Heidelberg, Germany. It describes the origin and consequences of the Chiari malformation, and proposes that hydrocephalus is caused by inadequate central nervous system (CNS) venous drainage. A new hypothesis regarding the pathogenesis, anencephaly and spina bifida is described
The iron law of democratic socialism: British and Austrian influences on the young Karl Polanyi
This article has been made available through the Brunel Open Access Publishing Fund.A central thesis of Karl Polanyi's The great transformation concerns the tensions between capitalism and democracy: the former embodies the principle of inequality, while democracy represents that of equality. This paper explores the intellectual heritage of this thesis, in the ‘functional theory’ of G.D.H. Cole and Otto Bauer and in the writings of Eduard Bernstein. It scrutinizes Polanyi's relationship with Bernstein's ‘evolutionary socialism’ and charts his ‘double movement’ vis-à-vis Marxist philosophy: in the 1910s he reacted sharply against Marxism's deterministic excesses, but he then, in the 1920s, engaged in sympathetic dialogue with Austro-Marxist thinkers. The latter, like Bernstein, disavowed economic determinism and insisted upon the importance and autonomy of ethics. Yet they simultaneously predicted a law-like expansion of democracy from the political to the economic arena. Analysis of this contradiction provides the basis for a concluding discussion that reconsiders the deterministic threads in Polanyi's oeuvre. Whereas for some Polanyi scholars these attest to his residual attraction to Marxism, I argue that matters are more complex. While Polanyi did repudiate the more rigidly deterministic of currents in Marxist philosophy, those to which he was attracted, notably Bernstein's ‘revision’ and Austro-Marxism, incorporated a deterministic fatalism of their own, in respect of democratization. Herein lies a more convincing explanation of Polanyi's incomplete escape from a deterministic philosophy of history, as exemplified in his masterwork, The great transformation
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Karl Polanyi’s the great transformation: Perverse effects, protectionism and gemeinschaft
Drawing upon Karl Polanyi’s journalistic writings and unpublished lectures from the 1920s and 1930s, this article reconstructs the lineaments of his research programme that was to assume its finished form in The Great Transformation. It identifies and corrects a common misinterpretation of the thesis of that book, and argues that Polanyi’s basic theoretical framework is best conceived as Tönniesian: the ‘protective counter-movement’ of The Great Transformation is Gemeinschaft, understood dynamically, while the market society is Gesellschaft. It examines the two central mechanisms by which, in Polanyi’s understanding, Gesellschaft broke down in the mid-twentieth century: the ‘clash between democracy and capitalism,’ and a doctrine of ‘perverse effects’ whereby political intervention in markets impairs profitability and saps the vitality of the market system
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