684 research outputs found
The Effect of Gravity on the Nervous System
Gravity affects the nervous system of living organisms. This book chapter reviews historical and recent findings on how changes in gravity affect cellular and subcellular parameters of human and animal cells as well as the timing and shaping of complex sensorimotor responses. With an emphasize on weightlessness, partial, and hypergravity conditions, the gravity dependencies of living organisms have been manifested on different levels of organization, ranging from changes in biophysical properties of single cells to the intact nervous system. An effort has been made to integrate the various findings into a consistent model for a better understanding of how the components of the nervous system interact as a response to acute and long-term gravitational variation. Especially with planned long-term manned missions to Mars and beyond, knowledge about the impact of increased and decreased gravity on the nervous system is essential for the physical and cognitive preparation to assure the success of space missions and human survival in space
Screening for hazardous alcohol use in the Emergency Department:Comparison of phosphatidylethanol with the Alcohol Use Disorders Identification Test and the Timeline Follow-back
Background: Up to 15% of all visits to the Emergency Department (ED) are alcohol related. Identification of problematic alcohol use is important in this setting because it allows for intervention and prevention efforts. This study investigated the correlation between the objective phosphatidylethanol (PEth) marker and the subjective Alcohol Use Disorders Identification Test (AUDIT) and Timeline Followback Questionnaire (TLFB) as screening methods for hazardous alcohol use in the general ED population. Methods: This prospective cohort study included 301 ED patients (57% male) who were seen in the ED and required to give a blood sample. The correlation between the values of PEth (PEth 16:0/18:1 and PEth 16:0/18:2) and the scores on the AUDIT and TLFB were analyzed using Spearman's rank correlation coefficient. Differences between risk categories of PEth and AUDIT were also examined. Results: The Spearman correlation coefficients between PEth 16:0/18:1|PEth 16:0/18:2 values and the AUDIT scores were moderate (PEth 16:0/18:1: 0.67, p < 0.001; PEth 16:0/18:2: 0.67, p < 0.001). Of the patients who scored ‘low risk drinking/abstinence’ according to the AUDIT questionnaire, respectively 1% and 4% had PEth 16:0/18:1|PEth 16:0/18:2 values indicating excessive alcohol use, and another 10% and 12% had PEth 16:0/18:1|PEth 16:0/18:2 values indicating moderate alcohol consumption. Of the 12 (PEth 16:0/18:1) and 25 (PEth 16:0/18:2) patients with high-risk values, respectively 25% and 40% scored in the lowest risk category on the AUDIT questionnaire. Spearman correlation coefficients between PEth 16:0/18:1|PEth 16:0/18:2 values and TLFB two-week scores were high (PEth 16:0/18:1: 0.74, p < 0.001; PEth 16:0/18:2: 0.82, p < 0.001). Conclusions: AUDIT scores were moderately correlated with PEth values in the general ED population. In almost all cases where there was not a good correlation, patients had high PEth values with low AUDIT scores. We conclude that PEth identifies patients with problematic alcohol use who are missed by the AUDIT questionnaire and therefore PEth could be used as an additional screening method for hazardous alcohol use in this population
Multiple Transitions to Chaos in a Damped Parametrically Forced Pendulum
We study bifurcations associated with stability of the lowest stationary
point (SP) of a damped parametrically forced pendulum by varying
(the natural frequency of the pendulum) and (the amplitude of the external
driving force). As is increased, the SP will restabilize after its
instability, destabilize again, and so {\it ad infinitum} for any given
. Its destabilizations (restabilizations) occur via alternating
supercritical (subcritical) period-doubling bifurcations (PDB's) and pitchfork
bifurcations, except the first destabilization at which a supercritical or
subcritical bifurcation takes place depending on the value of . For
each case of the supercritical destabilizations, an infinite sequence of PDB's
follows and leads to chaos. Consequently, an infinite series of period-doubling
transitions to chaos appears with increasing . The critical behaviors at the
transition points are also discussed.Comment: 20 pages + 7 figures (available upon request), RevTex 3.
Quantum Computing of Quantum Chaos in the Kicked Rotator Model
We investigate a quantum algorithm which simulates efficiently the quantum
kicked rotator model, a system which displays rich physical properties, and
enables to study problems of quantum chaos, atomic physics and localization of
electrons in solids. The effects of errors in gate operations are tested on
this algorithm in numerical simulations with up to 20 qubits. In this way
various physical quantities are investigated. Some of them, such as second
moment of probability distribution and tunneling transitions through invariant
curves are shown to be particularly sensitive to errors. However,
investigations of the fidelity and Wigner and Husimi distributions show that
these physical quantities are robust in presence of imperfections. This implies
that the algorithm can simulate the dynamics of quantum chaos in presence of a
moderate amount of noise.Comment: research at Quantware MIPS Center http://www.quantware.ups-tlse.fr,
revtex 11 pages, 13 figs, 2 figs and discussion adde
Cooling flow bulk motion corrections to the Sunyaev Zel'dovich effect
We study the influence of converging cooling flow bulk motions on the
Sunyaev-Zel'dovich (SZ) effect. To that purpose we derive a modified Kompaneets
equation which takes into account the contribution of the accelerated electron
media of the cooling flow inside the cluster frame. The additional term is
different from the usual kinematic SZ-effect, which depends linearly on the
velocity, whereas the contribution described here is quadratic in the
macroscopic electron fluid velocity, as measured in the cluster frame. For
clusters with a large cooling flow mass deposition rate and/or a small central
electron density, it turns out that this effect becomes relevant.Comment: accepted for publication in New Astronom
Dynamical localization simulated on a few qubits quantum computer
We show that a quantum computer operating with a small number of qubits can
simulate the dynamical localization of classical chaos in a system described by
the quantum sawtooth map model. The dynamics of the system is computed
efficiently up to a time , and then the localization length
can be obtained with accuracy by means of order computer runs,
followed by coarse grained projective measurements on the computational basis.
We also show that in the presence of static imperfections a reliable
computation of the localization length is possible without error correction up
to an imperfection threshold which drops polynomially with the number of
qubits.Comment: 8 pages, 8 figure
Sensitive detection of colorectal cancer in peripheral blood by septin 9 DNA methylation assay
BACKGROUND: Colorectal cancer (CRC) is the second leading cause of cancer deaths despite the fact that detection of this cancer in early stages results in over 90% survival rate. Currently less than 45% of at-risk individuals in the US are screened regularly, exposing a need for better screening tests. We performed two case-control studies to validate a blood-based test that identifies methylated DNA in plasma from all stages of CRC. METHODOLOGY/PRINCIPAL FINDINGS: Using a PCR assay for analysis of Septin 9 (SEPT9) hypermethylation in DNA extracted from plasma, clinical performance was optimized on 354 samples (252 CRC, 102 controls) and validated in a blinded, independent study of 309 samples (126 CRC, 183 controls). 168 polyps and 411 additional disease controls were also evaluated. Based on the training study SEPT9-based classification detected 120/252 CRCs (48%) and 7/102 controls (7%). In the test study 73/126 CRCs (58%) and 18/183 control samples (10%) were positive for SEPT9 validating the training set results. Inclusion of an additional measurement replicate increased the sensitivity of the assay in the testing set to 72% (90/125 CRCs detected) while maintaining 90% specificity (19/183 for controls). Positive rates for plasmas from the other cancers (11/96) and non-cancerous conditions (41/315) were low. The rate of polyp detection (>1 cm) was approximately 20%. CONCLUSIONS/SIGNIFICANCE: Analysis of SEPT9 DNA methylation in plasma represents a straightforward, minimally invasive method to detect all stages of CRC with potential to satisfy unmet needs for increased compliance in the screening population. Further clinical testing is warranted
Chaos in a double driven dissipative nonlinear oscillator
We propose an anharmonic oscillator driven by two periodic forces of
different frequencies as a new time-dependent model for investigating quantum
dissipative chaos. Our analysis is done in the frame of statistical ensemble of
quantum trajectories in quantum state diffusion approach. Quantum dynamical
manifestation of chaotic behavior, including the emergence of chaos, properties
of strange attractors, and quantum entanglement are studied by numerical
simulation of ensemble averaged Wigner function and von Neumann entropy.Comment: 9 pages, 18 figure
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