2,531 research outputs found
Iterative Linearized Density Matrix Propagation for Modeling Coherent Energy Transfer in Photosynthetic Light Harvesting
We present results of calculations [1] that employ a new mixed quantum classical iterative density matrix propagation approach (ILDM , or so called IsâLandmap) [2] to explore the survival of coherence in different photo synthetic models. Our model studies confirm the long lived quantum coherence , while conventional theoretical tools (such as Redfield equation) fail to describe these phenomenon [3,4]. Our ILDM method is a numerical exactly propagation scheme and can be served as a bench mark calculation tools[2]. Result get from ILDM and from other recent methods have been compared and show agreement with each other[4,5]. Long lived coherence plateau has been attribute to the shift of harmonic potential due to the system bath interaction, and the harvesting efficiency is a balance between the coherence and dissipation[1]. We use this approach to investigate the excitation energy transfer dynamics in various light harvesting complex include FennaâMatthewsâOlsen light harvesting complex[1] and Cryptophyte Phycocyanin 645 [6].
[1] P.Huo and D.F.Coker ,J. Chem. Phys. 133, 184108 (2010) . [2] E.R. Dunkel, S. Bonella, and D.F. Coker, J. Chem. Phys. 129, 114106 (2008). [3] A. Ishizaki and G.R. Fleming, J. Chem. Phys. 130, 234111 (2009). [4] A. Ishizaki and G.R. Fleming, Proc. Natl. Acad. Sci. 106, 17255 (2009). [5] G. Tao and W.H. Miller, J. Phys. Chem. Lett. 1, 891 (2010). [6] P.Huo and D.F.Coker in preparationNational Science Foundation (CHE-0911635
Psychometric properties of the 21-item Depression Anxiety Stress Scale (DASS-21)
Depression, anxiety and stress are recognised as global public health problems especially in developing countries. Early detection of these disorders is essential to provide psychological interventions for individuals experiencing these negative emotional conditions. This study determined the Nigerian psychometric properties for the 21-item version of the depression, anxiety and stress scale among a sample of medical students. Two hundred and forty medical students from the Lagos State University College of Medicine, Lagos, Nigeria completed the depression anxiety and stress scale, state trait anxiety inventory and self-rating depression scale. The reliability, discriminative, concurrent and convergent properties were determined. The reliability of DASS-21 showed that it has excellent Cronbachâs alpha values of 0.81, 0.89 and 0.78 for the subscales of depressive, anxiety and stress respectively. It was found to have excellent internal consistency, discriminative, concurrent and convergent validities. The depression and anxiety subscales of DASS-21 had good correlations with self-rating depression scale and state trait anxiety inventory. The DASS-21 was found to have commendable psychometric properties. It is reliable, valid and easy to administer. Its utility by clinicians will enhance the diagnoses of depression, anxiety and stress among university students.Keywords: DASS-21, depression, anxiety, Stress, psychometric properties, Lagos, Nigeri
Determinants of Bankruptcy among US Households in the 2013 Survey of Consumer Finances
This study investigates behaviors and decisions made by US households and ho
Baseline design of the filters for the LAD detector on board LOFT
The Large Observatory for X-ray Timing (LOFT) was one of the M3 missions
selected for the phase A study in the ESA's Cosmic Vision program. LOFT is
designed to perform high-time-resolution X-ray observations of black holes and
neutron stars. The main instrument on the LOFT payload is the Large Area
Detector (LAD), a collimated experiment with a nominal effective area of ~10 m
2 @ 8 keV, and a spectral resolution of ~240 eV in the energy band 2-30 keV.
These performances are achieved covering a large collecting area with more than
2000 large-area Silicon Drift Detectors (SDDs) each one coupled to a collimator
based on lead-glass micro-channel plates. In order to reduce the thermal load
onto the detectors, which are open to Sky, and to protect them from out of band
radiation, optical-thermal filter will be mounted in front of the SDDs.
Different options have been considered for the LAD filters for best compromise
between high quantum efficiency and high mechanical robustness. We present the
baseline design of the optical-thermal filters, show the nominal performances,
and present preliminary test results performed during the phase A study.Comment: Proc. SPIE 9144, Space Telescopes and Instrumentation 2014:
Ultraviolet to Gamma Ray, 91446
Quantum initial condition sampling for linearized density matrix dynamics: Vibrational pure dephasing of iodine in krypton matrices
This paper reviews the linearized path integral approach for computing time
dependent properties of systems that can be approximated using a mixed
quantum-classical description. This approach is applied to studying vibrational
pure dephasing of ground state molecular iodine in a rare gas matrix. The
Feynman-Kleinert optimized harmonic approximation for the full system density
operator is used to sample initial conditions for the bath degrees of freedom.
This extremely efficient approach is compared with alternative initial
condition sampling techniques at low temperatures where classical initial
condition sampling yields dephasing rates that are nearly an order of magnitude
too slow compared with quantum initial condition sampling and experimental
results.Comment: 20 pages and 8 figure
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