142 research outputs found
Electrophysiological Brain-Cardiac Coupling in Train Drivers during Monotonous Driving
Electrophysiological research has previously investigated monotony and the cardiac health of drivers independently; however, few studies have explored the association between the two. As such the present study aimed to examine the impact of monotonous train driving (indicated by electroencephalogram (EEG) activity) on an individual's cardiac health as measured by heart rate variability (HRV). Sixty-three train drivers participated in the present study, and were required to complete a monotonous train driver simulator task. During this task, a 32 lead EEG and a three-lead electrocardiogram were recorded from each participant. In the present analysis, the low (LF) and high frequency (HF) HRV parameters were associated with delta (p < 0.05), beta (p = 0.03) and gamma (p < 0.001) frequency EEG variables. Further, total HRV was associated with gamma activity, while sympathovagal balance (i.e., LF:HF ratio) was best associated fronto-temporal delta activity (p = 0.02). HRV and EEG parameters appear to be coupled, with the parameters of the delta and gamma EEG frequency bands potentially being the most important to this coupling. These relationships provide insight into the impact of a monotonous task on the cardiac health of train drivers, and may also be indicative of strategies employed to combat fatigue or engage with the driving task
Molecular Symmetry Properties of Conical Intersections and Nonadiabatic Coupling Terms: Theory and Quantum Chemical Demonstration for Cyclopenta-2,4-dienimine (C5H4NH)
This paper discovers molecular symmetry (MS) properties of conical intersections (CIs) and the related
nonadiabatic coupling terms (NACTs) in molecules which allow large amplitude motions such as torsion, in
the frame of the relevant molecular symmetry group, focusing on groups with one-dimensional (1-d) irreducible
representations (IREPs). If one employs corresponding MS-adapted nuclear coordinates, the NACTs can be
classified according to those IREPs. The assignment is supported by theorems which relate the IREPs of
different NACTs to each other, and by properties of the NACTs related to the CIs. For example, planar
contour integrals of the NACTs evaluated along loops around the individual CIs are equal to +Ï or -Ï,
depending on the IREP-adapted signs of the NACTs. The + or - signs for the contour integrals may also be
used to define the âchargesâ and IREPs of the CIs. We derive various general molecular symmetry properties
of the related NACTs and CIs. These provide useful applications; e.g., the discovery of an individual CI
allows one to generate, by means of all molecular symmetry operations, the complete set of CIs at different
symmetry-related locations. Also, we show that the seams of CIs with different IREPs may have different
topologies in a specific plane of MS-adapted coordinates. Moreover, the IREPs impose symmetrical nodes of
the NACTs, and this may support their calculations by quantum chemical ab initio methods, even far away
from the CIs. The general approach is demonstrated by application to an example. Specifically, we investigate
the CIs and NACTs of cyclopenta-2,4-dienimine (C5H4NH) which has C2V(M) molecular symmetry with 1-d
IREPs. The results are confirmed by quantum chemical calculations, starting from the location of a CI based
on the Longuet-Higgins phase change theorem, until a proof of self-consistency, i.e., the related symmetryadapted
NACTs fulfill quantization rules which have been derived in [Baer, M. Beyond Born-Oppenheimer:
Electronic non-Adiabatic Coupling Terms and Conical Intersections; Wiley & Sons Inc.: Hoboken, NJ, 2006].We thank Prof. Lluis Blancafort, Prof.
Dietrich Haase, Prof. Yehuda Haas, PD Dr. Dirk Andrae, Mr.
Thomas Grohmann, and Ms. Shireen Alfalah for advice and
stimulating discussions, and Mr. Dominik Sattler for preparing
Figures 1 and 2. This study was supported by the Deutsche
Forschungsgemeinschaft in the framework of Project No. MA
515/22-2, and by Fonds der Chemischen Industrie
Electric-Field-Induced Mott Insulating States in Organic Field-Effect Transistors
We consider the possibility that the electrons injected into organic
field-effect transistors are strongly correlated. A single layer of acenes can
be modelled by a Hubbard Hamiltonian similar to that used for the
kappa-(BEDT-TTF)(2)X family of organic superconductors. The injected electrons
do not necessarily undergo a transition to a Mott insulator state as they would
in bulk crystals when the system is half-filled. We calculate the fillings
needed for obtaining insulating states in the framework of the slave-boson
theory and in the limit of large Hubbard repulsion, U. We also suggest that
these Mott states are unstable above some critical interlayer coupling or
long-range Coulomb interaction.Comment: 9 pages, 7 figure
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Deportation Stigma and Re-migration
Many, if not most, of those who are forcibly expelled from the country to which they have migrated will not settle in the country to which they have been returned but will leave again. A recent article examined some of the reasons why this should be so. It was argued that in addition to the factors that had caused the original migration, such as fear of persecution, continuing conflict, insecurity, poverty and lack of opportunity, deportation creates at least three additional reasons that make re-migration the most likely outcome. These were debt, family commitments and the shame of failure and or âcontaminationâ leading to stigmatisation. In this article, we explore the stigma of failure and of contamination attached to those deported, and the ways in which they respond to and manage this stigmatisation, including by re-migrating. We use Goffman's concept of stigma and the refinement offered by to further nuance understanding of the impact of deportation
Locating Electronic Degeneracies of Polyatomic Molecules: A General Method for Nonsymmetric Molecules
A general method for finding all electronic degeneracies lying on the ground-state potential surface of a molecular system is proposed. The method is based on the idea that the spin pairing of the valence electrons is the major factor determining the topology of the potential surface. The number of different spin-pairing arrangements (anchors) that can be constructed from the constituent atoms determines the number of critical points (minima, transition states) on the ground-state surface. It is shown that whereas the interaction between two states leads in general to an avoided crossing of potential surfaces the interactions in a three-state system (consisting of three anchors) lead in general to a 2-fold degeneracy (conical intersection) and in a four-state system to a 3-fold degeneracy. It is further shown that in a 3D world the highest degree of nonaccidental electronic degeneracy is 3. Since the number of anchors in a polyatomic system can be large, in general numerous 3-fold degeneracies exist in the system, independent of nuclear symmetry. The whole topology of the potential surface can be constructed around the degeneracies since minima and transition states are directly accessible from them via a monotonic declining route. A practical procedure for establishing the approximate structures of the 3-fold degenerate "points" and also those of the more familiar 2-fold degeneracies (conical intersections) is proposed
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