4,003 research outputs found
Pion Interactions in the X(3872)
We consider pion interactions in an effective field theory of the narrow
resonance X(3872), assuming it is a weakly bound molecule of the charm mesons
D^{0} \bar D^{*0} and D^{*0} \bar D^{0}. Since the hyperfine splitting of the
D^{0} and D^{*0} is only 7 MeV greater than the neutral pion mass, pions can be
produced near threshold and are non-relativistic. We show that pion exchange
can be treated in perturbation theory and calculate the next-to-leading-order
correction to the partial decay width \Gamma[X \to D^0 \bar D^{0} \pi^0].Comment: 26 pages, 11 figures, revtex4, to appear in Phys. Rev.
Combined SIMS-SPM Instrument For High Sensitivity And High Resolution Elemental 3D Analysis
Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 - August 2, 201
The [4+2]âCycloaddition of αâNitrosoalkenes with Thiochalcones as a Prototype of Periselective HeteroâDielsâAlder ReactionsâExperimental and Computational Studies
The [4+2]âcycloadditions of αânitrosoalkenes with thiochalcones occur with high selectivity at the thioketone moiety of the dienophile providing styrylâsubstituted 4Hâ1,5,2âoxathiazines in moderate to good yields. Of the eight conceivable heteroâDielsâAlder adducts only this isomer was observed, thus a prototype of a highly periselective and regioselective cycloaddition has been identified. Analysis of crude product mixtures revealed that the αânitrosoalkene also adds competitively to the thioketone moiety of the thiochalcone dimer affording bisâheterocyclic [4+2]âcycloadducts. The experiments are supported by highâlevel DFT calculations that were also extended to related heteroâDielsâAlder reactions of other nitroso compounds and thioketones. These calculations reveal that the title cycloadditions are kinetically controlled processes confirming the role of thioketones as superdienophiles. The computational study was also applied to the experimentally studied thiochalcone dimerization, and showed that the 1,2âdithiin and 2Hâthiopyran isomers are in equilibrium with the monomer. Again, the DFT calculations indicate kinetic control of this process
Minimal Position-Velocity Uncertainty Wave Packets in Relativistic and Non-relativistic Quantum Mechanics
We consider wave packets of free particles with a general energy-momentum
dispersion relation . The spreading of the wave packet is determined by
the velocity v = \p_p E. The position-velocity uncertainty relation is saturated by minimal uncertainty wave
packets . In addition to the
standard minimal Gaussian wave packets corresponding to the non-relativistic
dispersion relation , analytic calculations are presented for
the spreading of wave packets with minimal position-velocity uncertainty
product for the lattice dispersion relation as well
as for the relativistic dispersion relation . The
boost properties of moving relativistic wave packets as well as the propagation
of wave packets in an expanding Universe are also discussed
Are 3D virtual environments better than 2D interfaces in serious games performance? An explorative study for the assessment of executive functions
This is an Accepted Manuscript of an article published by Taylor & Francis in Applied Neuropsychology: Adult on 05/09/2019, available online: http://www.tandfonline.com/10.1080/23279095.2019.1607735[EN] Executive functions refer to higher-order cognitive processes that supervise and guide goaldirected and adaptive behaviors in response to everyday situations. The traditional measures
used to assess executive functions include paper-and-pencil tests and/or computerized tests
that have been found to have a moderate level of ecological validity in predicting
real-world performance. Serious games (SG) represent a novel methodological approach,
allowing investigating subjectsÂż performance in real-simulated situations. Serious games are
computer games whose primary purposes include investigating human behaviors and
changes. Furthermore, SG can also vary according to the technology used and the interaction. Indeed, a SG can be rendered via a nonimmersive screen-based (2D) or via an
immersive virtual reality game (3D). Starting from these premises, we compared a narrativecontextualized SG in 2D and 3D, correlating them with traditional tests. Findings showed
different condition correlations with the traditional tasks and the comparison between the
two systems have revealed that 3D is able to generate lower reaction times, higher correct
answers, and lower perseverative responses in attentional abilities, inhibition control, and
cognitive shifting than 2D condition. The present study yielded evidence on the use of
more ecological tools to identify the functional cognitive status in real-simulated contexts
along with traditional evaluation.This work was supported by the Spanish Ministry of
Economy, Industry, and Competitiveness funded project Advanced Therapeutically Tools for Mental Health (DPI2016-77396-R).Chicchi-Giglioli, IA.; Juan-Ripoll, CD.; Parra Vargas, E.; Alcañiz Raya, ML. (2019). Are 3D virtual environments better than 2D interfaces in serious games performance? An explorative study for the assessment of executive functions. Applied Neuropsychology. Adult (Online). 1-10. https://doi.org/10.1080/23279095.2019.1607735S110Baddeley, A. (1981). The cognitive psychology of everyday life*. British Journal of Psychology, 72(2), 257-269. doi:10.1111/j.2044-8295.1981.tb02184.xChaytor, N., & Schmitter-Edgecombe, M. (2003). The Ecological Validity of Neuropsychological Tests: A Review of the Literature on Everyday Cognitive Skills. Neuropsychology Review, 13(4), 181-197. doi:10.1023/b:nerv.0000009483.91468.fbCHAYTOR, N., SCHMITTEREDGECOMBE, M., & BURR, R. (2006). Improving the ecological validity of executive functioning assessment. Archives of Clinical Neuropsychology, 21(3), 217-227. doi:10.1016/j.acn.2005.12.002Chelune, G. J. & Moehle, K. A. (1986). Neuropsychological assessment and everyday functioning. In D.Wedding, A.M. Horton, Jr. & J.S. Webster (Eds.), The neuropsychology handbook: Behavioral and clinical perspectives (pp. 489-525). New York, NY, US: Springer Publishing Co.Chevignard, M., Pillon, B., Pradat-Diehl, P., Taillefer, C., Rousseau, S., Le Bras, C., & Dubois, B. (2000). An Ecological Approach to Planning Dysfunction: Script Execution. Cortex, 36(5), 649-669. doi:10.1016/s0010-9452(08)70543-4Connolly, T. M., Boyle, E. A., MacArthur, E., Hainey, T., & Boyle, J. M. (2012). A systematic literature review of empirical evidence on computer games and serious games. Computers & Education, 59(2), 661-686. doi:10.1016/j.compedu.2012.03.004DĂaz-Orueta, U., Garcia-LĂłpez, C., Crespo-EguĂlaz, N., SĂĄnchez-Carpintero, R., Climent, G., & Narbona, J. (2013). AULA virtual reality test as an attention measure: Convergent validity with Connersâ Continuous Performance Test. Child Neuropsychology, 20(3), 328-342. doi:10.1080/09297049.2013.792332Elkind, J. S., Rubin, E., Rosenthal, S., Skoff, B., & Prather, P. (2001). A Simulated Reality Scenario Compared with the Computerized Wisconsin Card Sorting Test: An Analysis of Preliminary Results. CyberPsychology & Behavior, 4(4), 489-496. doi:10.1089/109493101750527042Fillmore, M. T., Rush, C. R., & Hays, L. (2006). Acute effects of cocaine in two models of inhibitory control: implications of non-linear dose effects. Addiction, 101(9), 1323-1332. doi:10.1111/j.1360-0443.2006.01522.xFleming, T. M., Bavin, L., Stasiak, K., Hermansson-Webb, E., Merry, S. N., Cheek, C., ⊠Hetrick, S. (2017). Serious Games and Gamification for Mental Health: Current Status and Promising Directions. Frontiers in Psychiatry, 7. doi:10.3389/fpsyt.2016.00215Folstein, M. F., Folstein, S. E., & McHugh, P. R. (1975). «Mini-mental state». Journal of Psychiatric Research, 12(3), 189-198. doi:10.1016/0022-3956(75)90026-6Fleming, T. M., Cheek, C., Merry, S. N., Thabrew, H., Bridgman, H., Stasiak, K., Shepherd, M., Perry, Y. Hetrick, S. (2014). Serious games for the treatment or prevention of depression: A systematic review.Chicchi Giglioli, I. A., de Juan Ripoll, C., Parra, E., & Alcañiz Raya, M. (2018). EXPANSE: A novel narrative serious game for the behavioral assessment of cognitive abilities. PLOS ONE, 13(11), e0206925. doi:10.1371/journal.pone.0206925Grant, D. A., & Berg, E. (1948). A behavioral analysis of degree of reinforcement and ease of shifting to new responses in a Weigl-type card-sorting problem. Journal of Experimental Psychology, 38(4), 404-411. doi:10.1037/h0059831Henry, M., Joyal, C. C., & Nolin, P. (2012). Development and initial assessment of a new paradigm for assessing cognitive and motor inhibition: The bimodal virtual-reality Stroop. Journal of Neuroscience Methods, 210(2), 125-131. doi:10.1016/j.jneumeth.2012.07.025Hughes, C. (2013). Executive function: Development, individual differences, and clinical insights. In Neural Circuit Development and Function in the Brain, 429â445.Iriarte, Y., Diaz-Orueta, U., Cueto, E., Irazustabarrena, P., Banterla, F., & Climent, G. (2012). AULAâAdvanced Virtual Reality Tool for the Assessment of Attention. Journal of Attention Disorders, 20(6), 542-568. doi:10.1177/1087054712465335Lang, P. J. (2005). International affective picture system (IAPS): Affective ratings of pictures and instruction manual. Technical report.Li, J., Theng, Y.-L., & Foo, S. (2016). Effect of Exergames on Depression: A Systematic Review and Meta-Analysis. Cyberpsychology, Behavior, and Social Networking, 19(1), 34-42. doi:10.1089/cyber.2015.0366Lo Priore, C., Castelnuovo, G., Liccione, D., & Liccione, D. (2003). Experience with V-STORE: Considerations on Presence in Virtual Environments for Effective Neuropsychological Rehabilitation of Executive Functions. CyberPsychology & Behavior, 6(3), 281-287. doi:10.1089/109493103322011579Martin, M. M., & Rubin, R. B. (1995). A New Measure of Cognitive Flexibility. Psychological Reports, 76(2), 623-626. doi:10.2466/pr0.1995.76.2.623Matheis, R. J., Schultheis, M. T., Tiersky, L. A., DeLuca, J., Millis, S. R., & Rizzo, A. (2007). Is Learning and Memory Different in a Virtual Environment? The Clinical Neuropsychologist, 21(1), 146-161. doi:10.1080/13854040601100668Miller, M. A., & Fillmore, M. T. (2010). The effect of image complexity on attentional bias towards alcohol-related images in adult drinkers. Addiction, 105(5), 883-890. doi:10.1111/j.1360-0443.2009.02860.xParsey, C. M., & Schmitter-Edgecombe, M. (2013). Applications of Technology in Neuropsychological Assessment. The Clinical Neuropsychologist, 27(8), 1328-1361. doi:10.1080/13854046.2013.834971Parsons, T. D., Bowerly, T., Buckwalter, J. G., & Rizzo, A. A. (2007). A Controlled Clinical Comparison of Attention Performance in Children with ADHD in a Virtual Reality Classroom Compared to Standard Neuropsychological Methods. Child Neuropsychology, 13(4), 363-381. doi:10.1080/13825580600943473PUGNETTI, L., MENDOZZI, L., ATTREE, E. A., BARBIERI, E., BROOKS, B. M., CAZZULLO, C. L., ⊠Psychol, C. (1998). Probing Memory and Executive Functions with Virtual Reality: Past and Present Studies. CyberPsychology & Behavior, 1(2), 151-161. doi:10.1089/cpb.1998.1.151Pugnetti, L., Mendozzi, L., Motta, A., Cattaneo, A., Barbieri, E., & Brancotti, A. (1995). Evaluation and retraining of adultsâ cognitive impairments: Which role for virtual reality technology? Computers in Biology and Medicine, 25(2), 213-227. doi:10.1016/0010-4825(94)00040-wRand, D., Katz, N., & (Tamar) Weiss, P. L. (2007). Evaluation of virtual shopping in the VMall: Comparison of post-stroke participants to healthy control groups. Disability and Rehabilitation, 29(22), 1710-1719. doi:10.1080/09638280601107450Rand, D., Rukan, S. B.-A., (Tamar) Weiss, P. L., & Katz, N. (2009). Validation of the Virtual MET as an assessment tool for executive functions. Neuropsychological Rehabilitation, 19(4), 583-602. doi:10.1080/09602010802469074Reitan, R. M. (1958). Validity of the Trail Making Test as an Indicator of Organic Brain Damage. Perceptual and Motor Skills, 8(3), 271-276. doi:10.2466/pms.1958.8.3.271Renison, B., Ponsford, J., Testa, R., Richardson, B., & Brownfield, K. (2012). The Ecological and Construct Validity of a Newly Developed Measure of Executive Function: The Virtual Library Task. Journal of the International Neuropsychological Society, 18(03), 440-450. doi:10.1017/s1355617711001883Slater, M. (2009). Place illusion and plausibility can lead to realistic behaviour in immersive virtual environments. Philosophical Transactions of the Royal Society B: Biological Sciences, 364(1535), 3549-3557. doi:10.1098/rstb.2009.0138Stroop, J. R. (1935). Studies of interference in serial verbal reactions. Journal of Experimental Psychology, 18(6), 643-662. doi:10.1037/h0054651Stuss, D. T., & Alexander, M. P. (2000). Executive functions and the frontal lobes: a conceptual view. Psychological Research, 63(3-4), 289-298. doi:10.1007/s00426990000
Non-Markovian Dynamics and Entanglement of Two-level Atoms in a Common Field
We derive the stochastic equations and consider the non-Markovian dynamics of
a system of multiple two-level atoms in a common quantum field. We make only
the dipole approximation for the atoms and assume weak atom-field interactions.
From these assumptions we use a combination of non-secular open- and
closed-system perturbation theory, and we abstain from any additional
approximation schemes. These more accurate solutions are necessary to explore
several regimes: in particular, near-resonance dynamics and low-temperature
behavior. In detuned atomic systems, small variations in the system energy
levels engender timescales which, in general, cannot be safely ignored, as
would be the case in the rotating-wave approximation (RWA). More problematic
are the second-order solutions, which, as has been recently pointed out, cannot
be accurately calculated using any second-order perturbative master equation,
whether RWA, Born-Markov, Redfield, etc.. This latter problem, which applies to
all perturbative open-system master equations, has a profound effect upon
calculation of entanglement at low temperatures. We find that even at zero
temperature all initial states will undergo finite-time disentanglement
(sometimes termed "sudden death"), in contrast to previous work. We also use
our solution, without invoking RWA, to characterize the necessary conditions
for Dickie subradiance at finite temperature. We find that the subradiant
states fall into two categories at finite temperature: one that is temperature
independent and one that acquires temperature dependence. With the RWA there is
no temperature dependence in any case.Comment: 17 pages, 13 figures, v2 updated references, v3 clarified results and
corrected renormalization, v4 further clarified results and new Fig. 8-1
The equilibrium states of open quantum systems in the strong coupling regime
In this work we investigate the late-time stationary states of open quantum
systems coupled to a thermal reservoir in the strong coupling regime. In
general such systems do not necessarily relax to a Boltzmann distribution if
the coupling to the thermal reservoir is non-vanishing or equivalently if the
relaxation timescales are finite. Using a variety of non-equilibrium formalisms
valid for non-Markovian processes, we show that starting from a product state
of the closed system = system + environment, with the environment in its
thermal state, the open system which results from coarse graining the
environment will evolve towards an equilibrium state at late-times. This state
can be expressed as the reduced state of the closed system thermal state at the
temperature of the environment. For a linear (harmonic) system and environment,
which is exactly solvable, we are able to show in a rigorous way that all
multi-time correlations of the open system evolve towards those of the closed
system thermal state. Multi-time correlations are especially relevant in the
non-Markovian regime, since they cannot be generated by the dynamics of the
single-time correlations. For more general systems, which cannot be exactly
solved, we are able to provide a general proof that all single-time
correlations of the open system evolve to those of the closed system thermal
state, to first order in the relaxation rates. For the special case of a
zero-temperature reservoir, we are able to explicitly construct the reduced
closed system thermal state in terms of the environmental correlations.Comment: 20 pages, 2 figure
Recommended from our members
A letter of intent for a neutrino scattering experiment on the booster neutrino meanline: FINeSSE
The experiment described in this Letter of Intent provides a decisive measurement of {Delta}s, the spin of the nucleon carried by strange quarks. This is crucial as, after more than thirty years of study, the spin contribution of strange quarks to the nucleon is still not understood. The interpretation of {Delta}s measurements from inclusive Deep Inelastic Scattering (DIS) experiments using charged leptons suffers from two questionable techniques; an assumption of SU(3)-flavor symmetry, and an extrapolation into unmeasured kinematic regions, both of which provide ample room for uncertain theoretical errors in the results. The results of recent semi-inclusive DIS data from HERMES paint a somewhat different picture of the contribution of strange quarks to the nucleon spin than do the inclusive results, but since HERMES does not make use of either of the above-mentioned techniques, then the results are somewhat incomparable. What is required is a measurement directly probing the spin contribution of the strange quarks in the nucleon. Neutrino experiments provide a theoretically clean and robust method of determining {Delta}s by comparing the neutral current interaction, which is isoscalar plus isovector, to the charged current interaction, which is strictly isovector. A past experiment, E734, performed at Brookhaven National Laboratory, has pioneered this effort. Building on what they have learned, we present an experiment which achieves a measurement to {+-} 0.025 using neutrino scattering, and {+-} 0.04 using anti-neutrino scattering, significantly better than past measurements. The combination of the neutrino and anti-neutrino data, when combined with the results of the parity-violating electron-nucleon scattering data, will produce the most significant result for {Delta}s. This experiment can also measure neutrino cross sections in the energy range required for accelerator-based precision oscillation measurements. Accurate measurements of cross sections have been identified as a priority of the neutrino community, as determined through the APS Multidisciplinary Study on the Future of Neutrino Physics. From the APS report, the Neutrino Matrix makes its recommendations in context of several assumptions regarding the neutrino program, including: ''Determination of the neutrino reaction and production cross sections required for a precise understanding of neutrino oscillation physics and the neutrino astronomy of astrophysical and cosmological sources. Our broad and exacting program of neutrino physics is built upon precise knowledge of how neutrinos interact with matter''. The experiment described here will provide unique information on cross sections of {approx}1 GeV neutrinos, in precisely the range explored by present and future long baseline oscillation programs. Fermi National Accelerator Laboratory is the natural place to perform this experiment. The physics goals proposed here grow the existing program and are necessary ingredients for the next generation oscillation physics measurements in this same energy range. This is a small, cost-effective, and timely experiment which fits well with the growing neutrino program at Fermilab
The Rotating-Wave Approximation: Consistency and Applicability from an Open Quantum System Analysis
We provide an in-depth and thorough treatment of the validity of the
rotating-wave approximation (RWA) in an open quantum system. We find that when
it is introduced after tracing out the environment, all timescales of the open
system are correctly reproduced, but the details of the quantum state may not
be. The RWA made before the trace is more problematic: it results in incorrect
values for environmentally-induced shifts to system frequencies, and the
resulting theory has no Markovian limit. We point out that great care must be
taken when coupling two open systems together under the RWA. Though the RWA can
yield a master equation of Lindblad form similar to what one might get in the
Markovian limit with white noise, the master equation for the two coupled
systems is not a simple combination of the master equation for each system, as
is possible in the Markovian limit. Such a naive combination yields inaccurate
dynamics. To obtain the correct master equation for the composite system a
proper consideration of the non-Markovian dynamics is required.Comment: 17 pages, 0 figures
Optimal control strategies for tuberculosis treatment: a case study in Angola
We apply optimal control theory to a tuberculosis model given by a system of
ordinary differential equations. Optimal control strategies are proposed to
minimize the cost of interventions. Numerical simulations are given using data
from Angola.Comment: This is a preprint of a paper whose final and definite form will
appear in the international journal Numerical Algebra, Control and
Optimization (NACO). Paper accepted for publication 15-March-201
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