250 research outputs found
The elusive excited states of bithiophene : a CASPT2 detective story
A systematic multi-reference perturbation theory
investigation of the excitation energies and oscillator
strengths for the lowest excited states of 2,20
-bithiophene
unequivocally shows that its optical spectrum is produced by
two 1
Bu states separated from each other by approximately
1 eV. This picture is confirmed by additional calculations
with alternative quantum chemical methods. Our findings
are in strong contrast with the previous CASPT2 results of
Rubio et al. [J Chem Phys 102:3580 (1995) and Chem Phys
Chem 4:1308 (2003)], who predicted that the two lowest 1
Bu
states are quasi-degenerate. The methodological reasons
responsible for the previous seemingly erroneous assignment of the optical spectrum of bithiophene are identified
and explained in terms of unusually large coupling between
the 1
Bu states introduced by dynamical correlation effects. A
general discussion of applicable computational techniques is
offered aiming at avoiding similar problems for other
molecular systems
Inverse Modeling for MEG/EEG data
We provide an overview of the state-of-the-art for mathematical methods that
are used to reconstruct brain activity from neurophysiological data. After a
brief introduction on the mathematics of the forward problem, we discuss
standard and recently proposed regularization methods, as well as Monte Carlo
techniques for Bayesian inference. We classify the inverse methods based on the
underlying source model, and discuss advantages and disadvantages. Finally we
describe an application to the pre-surgical evaluation of epileptic patients.Comment: 15 pages, 1 figur
Fast Evaluation of Interlace Polynomials on Graphs of Bounded Treewidth
We consider the multivariate interlace polynomial introduced by Courcelle
(2008), which generalizes several interlace polynomials defined by Arratia,
Bollobas, and Sorkin (2004) and by Aigner and van der Holst (2004). We present
an algorithm to evaluate the multivariate interlace polynomial of a graph with
n vertices given a tree decomposition of the graph of width k. The best
previously known result (Courcelle 2008) employs a general logical framework
and leads to an algorithm with running time f(k)*n, where f(k) is doubly
exponential in k. Analyzing the GF(2)-rank of adjacency matrices in the context
of tree decompositions, we give a faster and more direct algorithm. Our
algorithm uses 2^{3k^2+O(k)}*n arithmetic operations and can be efficiently
implemented in parallel.Comment: v4: Minor error in Lemma 5.5 fixed, Section 6.6 added, minor
improvements. 44 pages, 14 figure
The role of BMI in allostatic load and risk of cancer death
INTRODUCTION: Obesity and proinflammatory conditions are associated with increased risks of cancer. The associations of baseline allostatic load with cancer mortality and whether this association is modified by body mass index (BMI) were examined.
METHODS: A retrospective analysis was performed in March-September 2022 using National Health and Nutrition Examination Survey years 1988 through 2010 linked with the National Death Index through December 31, 2019. Fine and Gray Cox proportional hazard models were stratified by BMI status to estimate subdistribution hazard ratios of cancer death between high and low allostatic load status (adjusted for age, sociodemographics, and health factors).
RESULTS: In fully adjusted models, high allostatic load was associated with a 23% increased risk of cancer death (adjusted subdistribution hazard ratio=1.23; 95% CI=1.06, 1.43) among all participants, a 3% increased risk of cancer death (adjusted subdistribution hazard ratio=1.03; 95% CI=0.78, 1.34) among underweight/healthy weight adults, a 31% increased risk of cancer death (adjusted subdistribution hazard ratio=1.31; 95% CI=1.02, 1.67) among overweight adults, and a 39% increased risk of death (adjusted subdistribution hazard ratio=1.39; 95% CI=1.04, 1.88) among obese adults, when compared to those with low allostatic load.
CONCLUSIONS: The risk of cancer death is highest among those with high allostatic load and obese BMI, but this effect was attenuated among those with high allostatic load and underweight/healthy or overweight BMI
Microglia actively remove NR1 autoantibody-bound NMDA receptors and associated post-synaptic proteins in neuron microglia co-cultures
Autoantibodies against the NR1 subunit of NMDA receptors (NMDARs) have been shown to promote crosslinking and internalization of bound receptors in NMDAR encephalitis (NMDARE). This internalization-mediated loss of NMDARs is thought to be the major mechanism leading to pathogenic outcomes in patients. However, the role of bound autoantibody in engaging the resident immune cells, microglia, remains poorly understood. Here, using a patient-derived monoclonal NR1 autoantibody (hNR1-mAb) and a co-culture system of microglia and neurons, we could show that hNR1-mAb bound to hippocampal neurons led to microglia-mediated removal of hNR1-mAb bound NMDARs. These complexes were found to accumulate inside endo-lysosomal compartments of microglia. Utilizing another patient isolated monoclonal autoantibody, against the α1-subunit of GABA(A) receptors (α1-GABA(A)-mAb), such removal of receptors was found to be specific to the antibody-bound receptor targets. Interestingly, along with receptor removal, we also observed a reduction in synapse number, more specifically in the numbers of post-synaptic proteins like PSD95 and Homer 1, when microglia were present in the culture. Importantly, mutations in the Fc region of hNR1-mAb, blocking its Fcγ receptor (FcγR) and complement binding, attenuated hNR1-mAb driven loss of NMDARs and synapses, indicating that microglia engagement by bound hNR1-mAb is critical for receptor and synapse loss. Our data argues for an active involvement of microglia in removal of NMDARs and other receptors in individuals with autoimmune encephalitis, thereby contributing to the etiology of these diseases
Comparative study of nonlinear properties of EEG signals of a normal person and an epileptic patient
Background: Investigation of the functioning of the brain in living systems
has been a major effort amongst scientists and medical practitioners. Amongst
the various disorder of the brain, epilepsy has drawn the most attention
because this disorder can affect the quality of life of a person. In this paper
we have reinvestigated the EEGs for normal and epileptic patients using
surrogate analysis, probability distribution function and Hurst exponent.
Results: Using random shuffled surrogate analysis, we have obtained some of
the nonlinear features that was obtained by Andrzejak \textit{et al.} [Phys Rev
E 2001, 64:061907], for the epileptic patients during seizure. Probability
distribution function shows that the activity of an epileptic brain is
nongaussian in nature. Hurst exponent has been shown to be useful to
characterize a normal and an epileptic brain and it shows that the epileptic
brain is long term anticorrelated whereas, the normal brain is more or less
stochastic. Among all the techniques, used here, Hurst exponent is found very
useful for characterization different cases.
Conclusions: In this article, differences in characteristics for normal
subjects with eyes open and closed, epileptic subjects during seizure and
seizure free intervals have been shown mainly using Hurst exponent. The H shows
that the brain activity of a normal man is uncorrelated in nature whereas,
epileptic brain activity shows long range anticorrelation.Comment: Keywords:EEG, epilepsy, Correlation dimension, Surrogate analysis,
Hurst exponent. 9 page
Circadian Control of Dendrite Morphology in the Visual System of Drosophila melanogaster
In the first optic neuropil (lamina) of the fly's visual system, monopolar cells L1 and L2 and glia show circadian rhythms in morphological plasticity. They change their size and shape during the day and night. The most pronounced changes have been detected in circadian size of the L2 axons. Looking for a functional significance of the circadian plasticity observed in axons, we examined the morphological plasticity of the L2 dendrites. They extend from axons and harbor postsynaptic sites of tetrad synaptic contacts from the photoreceptor terminals.The plasticity of L2 dendrites was evaluated by measuring an outline of the L2 dendritic trees. These were from confocal images of cross sections of L2 cells labeled with GFP. They were in wild-type and clock mutant flies held under different light conditions and sacrified at different time points. We found that the L2 dendrites are longest at the beginning of the day in both males and females. This rhythm observed under a day/night regime (LD) was maintained in constant darkness (DD) but not in continuous light (LL). This rhythm was not present in the arrhythmic per(01) mutant in LD or in DD. In the clock photoreceptor cry(b) mutant the rhythm was maintained but its pattern was different than that observed in wild-type flies.The results obtained showed that the L2 dendrites exhibit circadian structural plasticity. Their morphology is controlled by the per gene-dependent circadian clock. The L2 dendrites are longest at the beginning of the day when the daytime tetrad presynaptic sites are most numerous and L2 axons are swollen. The presence of the rhythm, but with a different pattern in cry(b) mutants in LD and DD indicates a new role of cry in the visual system. The new role is in maintaining the circadian pattern of changes of the L2 dendrite length and shape
Resource Re-allocation for Data Inter-dependent Continuous Tasks in Grids
Many researchers focus on resource intensive tasks which have to be run continuously over long periods. A Grid may offer resources for these tasks, but they are contested by multiple client agents. Hence, a Grid might be unwilling to allocate its resources for long terms, leading to tasks’ interruptions. This issue becomes more substantial when tasks are data inter-dependent, where one interrupted task may cause an interruption of a bundle of other tasks. In this paper, we discuss a new resource re-allocation strategy for a client, in which resources are re-allocated between the client tasks in order to avoid prolonged interruptions. Those re-allocations are decided by a client agent, but they should be agreed with a Grid and can be performed only by a Grid. Our strategy has been tested within different Grid environments and noticeably improves client utilities in almost all cases
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