66 research outputs found
Quantitative Methods For Guiding Epilepsy Surgery From Intracranial Eeg
Despite advances in intracranial EEG (iEEG) technique, technology and neuroimaging, patients today are no more likely to achieve seizure freedom after epilepsy surgery than they were 20 years ago. These poor outcomes are in part due to the difficulty and subjectivity associated with interpreting iEEG recordings, and have led to widespread interest in developing quantitative methods to localize the epileptogenic zone. Approaches to computational iEEG analysis vary widely, spanning studies of both seizures and interictal periods, and encompassing a range of techniques including electrographic signal analysis and graph theory. However, many current methods often fail to generalize to new data and are sensitive to differences in pathology and electrode placement. Indeed, none have completed prospective clinical trials. In this dissertation, I develop and validate tools for guiding epilepsy surgery through the quantitative analysis of intracranial EEG. Specifically, I leverage methods from graph theory for mapping network synchronizability to predict surgical outcome from ictal recordings, and also investigate the effects of sampling bias on network models. Finally, I construct a normative intracranial EEG atlas as a framework for objectively identifying patterns of abnormal neural activity and connectivity. Overall, the methods and results of this dissertation support the implementation of quantitative iEEG analysis in epilepsy surgical evaluation
Light Dark Matter Detection Prospects at Neutrino Experiments
We consider the prospects for the detection of relatively light dark matter
through direct annihilation to neutrinos. We specifically focus on the
detection possibilities of water Cherenkov and liquid scintillator neutrino
detection devices. We find in particular that liquid scintillator detectors may
potentially provide excellent detection prospects for dark matter in the 4-10
GeV mass range. These experiments can provide excellent corroborative checks of
the DAMA/LIBRA annual modulation signal, but may yield results for low mass
dark matter in any case. We identify important tests of the ratio of electron
to muon neutrino events (and neutrino versus anti-neutrino events), which
discriminate against background atmospheric neutrinos. In addition, the
fraction of events which arise from muon neutrinos or anti-neutrinos (
and ) can potentially yield information about the branching
fractions of hypothetical dark matter annihilations into different neutrino
flavors. These results apply to neutrinos from secondary and tertiary decays as
well, but will suffer from decreased detectability.Comment: 13 pages, 2 figures, pdflatex, references, one figure and comments on
electron neutrino bounds and on spin-dependent scattering limits added.
Figures updated
Next-to-Minimal Supersymmetric Model Higgs Scenarios for Partially Universal GUT Scale Boundary Conditions
We examine the extent to which it is possible to realize the NMSSM "ideal
Higgs" models espoused in several papers by Gunion et al in the context of
partially universal GUT scale boundary conditions. To this end we use the
powerful methodology of nested sampling. We pay particular attention to whether
ideal-Higgs-like points not only pass LEP constraints but are also acceptable
in terms of the numerous constraints now available, including those from the
Tevatron and -factory data, and the relic density .
In general for this particular methodology and range of parameters chosen, very
few points corresponding to said previous studies were found, and those that
were found were at best away from the preferred relic density value.
Instead, there exist a class of points, which combine a mostly singlet-like
Higgs with a mostly singlino-like neutralino coannihilating with the lightest
stau, that are able to effectively pass all implemented constraints in the
region . It seems that the spin-independent direct detection cross
section acts as a key discriminator between ideal Higgs points and the hard to
detect singlino-like points.Comment: 22 pages, 15 figure
Dark Matter Detection With Electron Neutrinos in Liquid Scintillation Detectors
We consider the prospects for liquid scintillation experiments (with a focus
on KamLAND) to detect the flux of electron neutrinos arising from dark matter
annihilation in the core of the sun. We show that, with data already taken,
KamLAND can provide the greatest sensitivity to the dark matter-proton
spin-dependent scattering cross-section for dark matter lighter than 20 GeV. It
is also possible to probe the dark matter-nucleon spin-independent scattering
cross-section for isospin-violating dark matter lighter than 10 GeV. KamLAND
can thus potentially confirm the dark matter interpretation of the DAMA and
CoGeNT signals, utilizing data already taken.Comment: 5 pages, 4 figures, PDFLaTeX; v2: references added, figures updated,
more detailed comparison of liquid scintillation and water Cerenkov detectors
(journal version
The Higgs Sector and CoGeNT/DAMA-Like Dark Matter in Supersymmetric Models
Recent data from CoGeNT and DAMA are roughly consistent with a very light
dark matter particle with m\sim 4-10\gev and spin-independent cross section
of order \sigma_{SI} \sim (1-3)\times 10^{-4}\pb. An important question is
whether these observations are compatible with supersymmetric models obeying
without violating existing collider constraints and
precision measurements. In this talk, I review the fact the the Minimal
Supersymmetric Model allows insufficient flexibility to achieve such
compatibility, basically because of the highly constrained nature of the MSSM
Higgs sector in relation to LEP limits on Higgs bosons. I then outline the
manner in which the more flexible Higgs sectors of the Next-to-Minimal
Supersymmetric Model and an Extended Next-to-Minimal Supersymmetric Model allow
large and at low LSP mass without violating
LEP, Tevatron, BaBar and other experimental limits. The relationship of the
required Higgs sectors to the NMSSM "ideal-Higgs" scenarios is discussed.Comment: 11 pages, 3 figures. To appear in Proceedings of PASCOS 2010. The
paper is a compilation of talks given at: PASCOS 2010, ORSAY Workshop on
"Higgs Hunting", and SLAC Workshop on "Topologies for Early LHC Searches
Nuclear and nucleon transitions of the H di-baryon
We consider 3 types of processes pertinent to the phenomenology of an H
di-baryon: conversion of two 's in a doubly-strange hypernucleus to an
H, decay of the H to two baryons, and -- if the H is light enough -- conversion
of two nucleons in a nucleus to an H. We compute the spatial wavefunction
overlap using the Isgur-Karl and Bethe-Goldstone wavefunctions, and treat the
weak interactions phenomenologically. The observation of decays from
doubly-strange hypernuclei puts a constraint on the H wavefunction which is
plausibly satisfied. In this case the H is very long-lived as we calculate. An
absolutely stable H is not excluded at present. SuperK can provide valuable
limits
Astroparticle Aspects of Supersymmetry
After recalling the motivations for expecting supersymmetry to appear at
energies below 1 TeV, the reasons why the lightest supersymmetric particle is
an ideal candidate for cold dark matter are reviewed from a historical
perspective. Recent calculations of the relic density including coannihilations
and rapid annihilations through direct-channel Higgs boson poles are presented.
The experimental constraints from LEP and elsewhere on supersymmetric dark
matter are reviewed, and the prospects for its indirect or direct detection are
mentioned. The potential implications of a Higgs boson weighing about 115 GeV
and the recent measurement of the anomalous magnetic moment of the muon are
summarized.Comment: 12 pages, 10 eps figures, invited plenary talk at conference on 30
Years Of Supersymmetry, Oct. 2000, Minneapolis, Minnesot
Impact of COVID-19-Related Lockdown on Psychosocial, Cognitive, and Functional Well-Being in Adults With Down Syndrome
People with Down Syndrome (DS) have a high prevalence of physical and psychiatric comorbidities and experience early-onset dementia. With the outbreak of CoVID-19 pandemic, strict social isolation measures have been necessary to prevent the spreading of the disease. Effects of this lockdown period on behavior, mood and cognition in people with DS have not been assessed so far. In the present clinical study, we investigated the impact of CoVID-19-related lockdown on psychosocial, cognitive and functional well-being in a sample population of 46 adults with DS. The interRAI Intellectual Disability standardized assessment instrument, which includes measures of social withdrawal, functional impairment, aggressive behavior and depressive symptoms, was used to perform a three time-point evaluation (two pre-lockdown and one post-lockdown) in 37 subjects of the study sample, and a two time point evaluation (one pre- and one post-lockdown) in 9 subjects. Two mixed linear regression models - one before and one after the lockdown - have been fitted for each scale in order to investigate the change in the time-dependent variation of the scores. In the pre-lockdown period, significant worsening over time (i.e., per year) was found for the Depression Rating Scale score (beta = 0.55; 95% CI 0.34; 0.76). In the post-lockdown period, a significant worsening in social withdrawal (beta = 3.05, 95% CI 0.39; 5.70), instrumental activities of daily living (beta = 1.13, 95% CI 0.08; 2.18) and depression rating (beta = 1.65, 95% CI 0.33; 2.97) scales scores was observed, as was a significant improvement in aggressive behavior (beta = -1.40, 95% CI -2.69; -0.10). Despite the undoubtful importance of the lockdown in order to reduce the spreading of the CoVID-19 pandemic, the related social isolation measures suggest an exacerbation of depressive symptoms and a worsening in functional status in a sample of adults with DS. At the opposite, aggressive behavior was reduced after the lockdown period. This finding could be related to the increase of negative and depressive symptoms in the study population. Studies with longer follow-up period are needed to assess persistence of these effects
Constraints from Accelerator Experiments on the Elastic Scattering of CMSSM Dark Matter
We explore the allowed ranges of cross sections for the elastic scattering of
neutralinos \chi on nucleons in the constrained minimal supersymmetric
extension of the Standard Model (CMSSM), in which scalar and gaugino masses are
each assumed to be universal at some input grand unification scale. We extend
previous calculations to larger \tan \beta and investigate the limits imposed
by the recent LEP lower limit on the mass of the Higgs boson and by b \to s
\gamma, and those suggested by g_\mu - 2. The Higgs limit and b \to s \gamma
provide upper limits on the cross section, particularly at small and large \tan
\beta, respectively, and the value of g_\mu - 2 suggests a lower limit on the
cross section for \mu > 0. The spin-independent nucleon cross section is
restricted to the range 6 \times 10^{-8} pb > \sigma_{SI} > 2 \times 10^{-10}
pb for \mu > 0, and the spin-dependent nucleon cross section to the range
10^{-5} pb > \sigma_{SD} > 2 \times 10^{-7} pb. Lower values are allowed if \mu
<0.Comment: 15 pages, latex, 18 eps figure
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