Characterization of an Inherited Neurologic Syndrome in Toyger Cats with Forebrain Commissural Malformations, Ventriculomegaly and Interhemispheric Cysts.

BackgroundIn children, frequent congenital malformations with concomitant agenesis of the corpus callosum are diagnosed by neuroimaging in association with other cerebral malformations, including interhemispheric cysts and ventriculomegaly. Similar studies providing full characterization of brain defects by in vivo magnetic resonance imaging (MRI), and correlations with the pertinent anatomic pathologic examinations are absent in veterinary medicine.Hypothesis/objectivesCongenital brain defects underlie the neurologic signs observed in Toyger cats selectively bred for a short ear phenotype.AnimalsUsing proper pedigree analysis and genetic evaluations, 20 related Oriental-derived crossbred Toyger cats were evaluated. Seven clinically healthy (carrier) cats and 13 clinically affected cats that had neurologic signs, short ear phenotype and concomitant complex brain anomalies were studied.MethodsComplete physical and neurologic examinations and MRI were performed in all clinically healthy and affected cats. Postmortem and histopathologic examinations were performed in 8 affected cats and 5 healthy cats.ResultsNeurologic and MRI investigations confirmed 13 clinically affected cats with structural brain abnormalities. Ventriculomegaly with frequent concomitant supratentorial interhemispheric, communicating ventricular type-1b cysts and multiple midline and callosal malformations were detected in all cats displaying neurologic signs. Genetic analysis confirmed autosomal recessive mode of inheritance with no chromosomal abnormalities.Conclusions and clinical importanceNeuroanatomic dissections and histopathology were helpful for evaluation of abnormalities in midline brain structures, and for the full characterization of cysts. However, MRI was more sensitive for detection of small cysts. In this feline model, MRI diagnosis had extremely good correlation with pathologic abnormalities noted in the subset of animals that were examined by both modalities

Computing the merger of black-hole binaries: the IBBH problem

Gravitational radiation arising from the inspiral and merger of binary black holes (BBH's) is a promising candidate for detection by kilometer-scale interferometric gravitational wave observatories. This paper discusses a serious obstacle to searches for such radiation and to the interpretation of any observed waves: the inability of current computational techniques to evolve a BBH through its last ~10 orbits of inspiral (~100 radians of gravitational-wave phase). A new set of numerical-relativity techniques is proposed for solving this ``Intermediate Binary Black Hole'' (IBBH) problem: (i) numerical evolutions performed in coordinates co-rotating with the BBH, in which the metric coefficients evolve on the long timescale of inspiral, and (ii) techniques for mathematically freezing out gravitational degrees of freedom that are not excited by the waves.Comment: 6 pages RevTe

A power filter for the detection of burst sources of gravitational radiation in interferometric detectors

We present a filter for detecting gravitational wave signals from burst sources. This filter requires only minimal advance knowledge of the expected signal: i.e. the signal's frequency band and time duration. It consists of a threshold on the total power in the data stream in the specified signal band during the specified time. This filter is optimal (in the Neyman-Pearson sense) for signal searches where only this minimal information is available.Comment: 3 pages, RevTeX, GWDAW '99 proceedings contribution, submitted to Int. J. Modern Phys.

Inferring the neutron star equation of state from binary inspiral waveforms

The properties of neutron star matter above nuclear density are not precisely known. Gravitational waves emitted from binary neutron stars during their late stages of inspiral and merger contain imprints of the neutron-star equation of state. Measuring departures from the point-particle limit of the late inspiral waveform allows one to measure properties of the equation of state via gravitational wave observations. This and a companion talk by J. S. Read reports a comparison of numerical waveforms from simulations of inspiraling neutron-star binaries, computed for equations of state with varying stiffness. We calculate the signal strength of the difference between waveforms for various commissioned and proposed interferometric gravitational wave detectors and show that observations at frequencies around 1 kHz will be able to measure a compactness parameter and constrain the possible neutron-star equations of state.Comment: Talk given at the 12th Marcel Grossman Meeting, Paris, France, 12-18 Jul 200

Conserved masses in GHS Einstein and string black holes

We analyze the relationship between quasilocal masses calculated for solutions of conformally related theories. We show that the ADM mass of a static, spherically symmetric solution is conformally invariant (up to a constant factor) only if the background action functional is conformally invariant. Thus, the requirement of conformal invariance places restrictions on the choice of reference spacetimes. We calculate the mass of the black hole solutions obtained by Garfinkle, Horowitz, and Strominger (GHS) for both the string and the Einstein metrics. In addition, the quasilocal thermodynamic quantities in the string metrics are computed and discussed.Comment: 16 pages REVTeX with packages amsfonts and amssym

Gravitational wave bursts from cosmic (super)strings: Quantitative analysis and constraints

We discuss data analysis techniques that can be used in the search for gravitational wave bursts from cosmic strings. When data from multiple interferometers are available, we describe consistency checks that can be used to greatly reduce the false alarm rates. We construct an expression for the rate of bursts for arbitrary cosmic string loop distributions and apply it to simple known solutions. The cosmology is solved exactly and includes the effects of a late-time acceleration. We find substantially lower burst rates than previous estimates suggest and explain the disagreement. Initial LIGO is unlikely to detect field theoretic cosmic strings with the usual loop sizes, though it may detect cosmic superstrings as well as cosmic strings and superstrings with non-standard loop sizes (which may be more realistic). In the absence of a detection, we show how to set upper limits based on the loudest event. Using Initial LIGO sensitivity curves, we show that these upper limits may result in interesting constraints on the parameter space of theories that lead to the production of cosmic strings.Comment: Replaced with version accepted for publication in PR

Moduli, Scalar Charges, and the First Law of Black Hole Thermodynamics

We show that under variation of moduli fields $\phi$ the first law of black hole thermodynamics becomes $dM = {\kappa dA\over 8\pi} + \Omega dJ + \psi dq + \chi dp - \Sigma d\phi$, where $\Sigma$ are the scalar charges. We also show that the ADM mass is extremized at fixed $A$, $J$, $(p,q)$ when the moduli fields take the fixed value $\phi_{\rm fix}(p,q)$ which depend only on electric and magnetic charges. It follows that the least mass of any black hole with fixed conserved electric and magnetic charges is given by the mass of the double-extreme black hole with these charges. Our work allows us to interpret the previously established result that for all extreme black holes the moduli fields at the horizon take a value $\phi= \phi_{\rm fix}(p,q)$ depending only on the electric and magnetic conserved charges: $\phi_{\rm fix}(p,q)$ is such that the scalar charges $\Sigma ( \phi_{\rm fix}, (p,q))=0$.Comment: 3 pages, no figures, more detailed versio