30 research outputs found
Self Gravitating Fundamental Strings
We study the configuration of a typical highly excited string as one slowly
increases the string coupling. The dominant interactions are the long range
dilaton and gravitational attraction. In four spacetime dimensions, the string
slowly contracts from its initial (large) size until it approaches the string
scale where it forms a black hole. In higher dimensions, the string stays large
until the coupling reaches a critical value, and then it rapidly collapses to a
black hole. The implications for the recently proposed correspondence principle
are discussed.Comment: 20 pages, LaTe
The entropy of black holes: a primer
After recalling the definition of black holes, and reviewing their energetics
and their classical thermodynamics, one expounds the conjecture of Bekenstein,
attributing an entropy to black holes, and the calculation by Hawking of the
semi-classical radiation spectrum of a black hole, involving a thermal
(Planckian) factor. One then discusses the attempts to interpret the black-hole
entropy as the logarithm of the number of quantum micro-states of a macroscopic
black hole, with particular emphasis on results obtained within string theory.
After mentioning the (technically cleaner, but conceptually more intricate)
case of supersymmetric (BPS) black holes and the corresponding counting of the
degeneracy of Dirichlet-brane systems, one discusses in some detail the
``correspondence'' between massive string states and non-supersymmetric
Schwarzschild black holes.Comment: 51 pages, 4 figures, talk given at the "Poincare seminar" (Paris, 6
December 2003), to appear in Poincare Seminar 2003 (Birkhauser
Venous Sinus Thrombosis in Lemierre's Syndrome
Pseudotumor cerebri is characterized by increased intracranial pressure without a space-occupying lesion. Associated causes include cranial venous obstruction. We present a case of pseudotumor cerebri in Lemierre's syndrome. Lemierre's syndrome is an acute oropharyngeal infection with septic thrombophlebitis of the internal jugular vein. In our patient the thrombophlebitis extended intracranially to include the saggital, sigmoid, and straight sinuses
Temporal Arteroma
Loss of vision OSA 69-year old female with an 11-day history of progressive loss of vision OS. Previous history significant for mild chronic leukopenia.VA: 20/20 OD, NLP OS; Color plates 11/15 ODMRIAggregates of small cell immature atypical lymphocytes with clumped chromatin; Elevated ESRIV corticosteroidsAttache
Hydrocephalus Secondary to Isolated Spinal Cysticerosis
Hydrocephalus is a common complication of Neurocysticercosis and is usually due to obstruction by cisternal or ventricular cysts, or subarachnoid spaces by diffuse basilar meningitis. Spinal cysticercosis is an uncommon manifestation seen in 0.7 to 6% of cases. It is thought to be due to downward migration of larvae from the cerebral to the spinal subarachnoid spaces with possible ventriculoependymal infiltration or hematogenous dissemination. We report the unusual case of isolated spinal involvement leading to hydrocephalus
Nivolumab Plus Ipilimumab Induced Aseptic Meningitis And Bilateral Sixth Nerve Palsy In Metastatic Melanoma Treatment
"Nivolumab and Ipilimumab are recombinant human immunoglobulin monoclonal antibodies that prolong overall survival in metastatic melanoma. Reported adverse effects include orbital inflammation and hypophysitis. Aseptic meningitis is exceedingly rare with one case reported in Ipilimumab montherapy.
Bitemporal Superior Quadrantic Defects Associated with an Anomalous A1
Bitemporal superior quadrantic defects are thought to be secondary to lesions disrupting inferonasal retinal fibers as they decussate in the anterior chiasm. They can be seen with compressive lesions such as pituitary adenomas, meningiomas, or anterior cerebral artery aneurysms most commonly
Familial Isolated Foveal Hypoplasia Simulating Hereditary Congenital Nystagmus and Gaze Holding Failure
Usually associated with other ocular anomalies, isolated foveal hypoplasia is a rare developmental defect In addition to decreased vision, nystagmus is a prominent feature of the condition
Optic Neuropathy in Systemic Lupus Erythematosus: MRI Characteristics
Central nervous system involvement in systemic lupus erythematous (SLE) has been estimated to occur in 30% to 40% of patients. Though less common, optic nerve disease can be seen in 1% of those patients with SLE. Gadolinium enhanced Magnetic Resonance Imaging (MRI) has increased the sensitivity in evaluating CNS lesions. Two reports of the MRI characteristics of optic neuropathy in SLE were normal although Gadolinium contrast was not used