3,235 research outputs found
Mapping Analysis in Ontology-based Data Access: Algorithms and Complexity (Extended Abstract)
Maximum population transfer in a periodically driven two-level system
We study the dynamics of a two-level quantum system under the influence of
sinusoidal driving in the intermediate frequency regime. Analyzing the Floquet
quasienergy spectrum, we find combinations of the field parameters for which
population transfer is optimal and takes place through a series of well defined
steps of fixed duration. We also show how the corresponding evolution operator
can be approximated at all times by a very simple analytical expression. We
propose this model as being specially suitable for treating periodic driving at
avoided crossings found in complex multi-level systems, and thus show a
relevant application of our results to designing a control protocol in a
realistic molecular modelComment: 7 pages, 6 figure
Characterizing dynamics with covariant Lyapunov vectors
A general method to determine covariant Lyapunov vectors in both discrete-
and continuous-time dynamical systems is introduced. This allows to address
fundamental questions such as the degree of hyperbolicity, which can be
quantified in terms of the transversality of these intrinsic vectors. For
spatially extended systems, the covariant Lyapunov vectors have localization
properties and spatial Fourier spectra qualitatively different from those
composing the orthonormalized basis obtained in the standard procedure used to
calculate the Lyapunov exponents.Comment: 4 pages, 3 figures, submitted to Physical Review letter
Effects of chronic social stress on oligodendrocyte proliferation-maturation and myelin status in prefrontal cortex and amygdala in adult mice
Stress-related neuropsychiatric disorders present with excessive processing of aversive stimuli. Whilst underlying pathophysiology remains poorly understood, within- and between-regional changes in oligodendrocyte (OL)-myelination status in anterior cingulate cortex and amygdala (ACC-AMY network) could be important. In adult mice, a 15-day chronic social stress (CSS) protocol leads to increased aversion responsiveness, accompanied by increased resting-state functional connectivity between, and reduced oligodendrocyte- and myelin-related transcript expression within, medial prefrontal cortex and amygdala (mPFC-AMY network), the analog of the human ACC-AMY network. In the current study, young-adult male C57BL/6 mice underwent CSS or control handling (CON). To assess OL proliferation-maturation, mice received 5-ethynyl-2'-deoxyuridine via drinking water across CSS/CON and brains were collected on day 16 or 31. In mPFC, CSS decreased the density of proliferative OL precursor cells (OPCs) at days 16 and 31. CSS increased mPFC myelin basic protein (MBP) integrated density at day 31, as well as increasing myelin thickness as determined using transmission electron microscopy, at day 16. In AMY, CSS increased the densities of total CC1+ OLs (day 31) and CC1+/ASPA+ OLs (days 16 and 31), whilst decreasing the density of proliferative OPCs at days 16 and 31. CSS was without effect on AMY MBP content and myelin thickness, at days 16 and 31. Therefore, CSS impacts on the OL lineage in mPFC and AMY and to an extent that, in mPFC at least, leads to increased myelination. This increased myelination could contribute to the excessive aversion learning and memory that occur in CSS mice and, indeed, human stress-related neuropsychiatric disorders
Pathophysiology in cortico-amygdala circuits and excessive aversion processing: the role of oligodendrocytes and myelination
Stress-related psychiatric illnesses, such as major depressive disorder, anxiety and post-traumatic stress disorder, present with alterations in emotional processing, including excessive processing of negative/aversive stimuli and events. The bidirectional human/primate brain circuit comprising anterior cingulate cortex and amygdala is of fundamental importance in processing emotional stimuli, and in rodents the medial prefrontal cortex-amygdala circuit is to some extent analogous in structure and function. Here, we assess the comparative evidence for: (i) Anterior cingulate/medial prefrontal cortexamygdala bidirectional neural circuits as major contributors to aversive stimulus processing; (ii) Structural and functional changes in anterior cingulate cortexamygdala circuit associated with excessive aversion processing in stress-related neuropsychiatric disorders, and in medial prefrontal cortexamygdala circuit in rodent models of chronic stress-induced increased aversion reactivity; and (iii) Altered status of oligodendrocytes and their oligodendrocyte lineage cells and myelination in anterior cingulate/medial prefrontal cortexamygdala circuits in stress-related neuropsychiatric disorders and stress models. The comparative evidence from humans and rodents is that their respective anterior cingulate/medial prefrontal cortexamygdala circuits are integral to adaptive aversion processing. However, at the sub-regional level, the anterior cingulate/medial prefrontal cortex structure-function analogy is incomplete, and differences as well as similarities need to be taken into account. Structure-function imaging studies demonstrate that these neural circuits are altered in both human stress-related neuropsychiatric disorders and rodent models of stress-induced increased aversion processing. In both cases, the changes include altered white matter integrity, albeit the current evidence indicates that this is decreased in humans and increased in rodent models. At the cellular-molecular level, in both humans and rodents, the current evidence is that stress disorders do present with changes in oligodendrocyte lineage, oligodendrocytes and/or myelin in these neural circuits, but these changes are often discordant between and even within species. Nonetheless, by integrating the current comparative evidence, this review provides a timely insight into this field and should function to inform future studies-human, monkey and rodent-to ascertain whether or not the oligodendrocyte lineage and myelination are causally involved in the pathophysiology of stress-related neuropsychiatric disorders
Editorial: ADAM10 in Cancer Immunology and Autoimmunity: More Than a Simple Biochemical Scissor
Space and Time pattern of mid-velocity IMF emission in peripheral heavy-ion collisions at Fermi energies
The emission pattern in the V_perp - V_par plane of Intermediate Mass
Fragments with Z=3-7 (IMF) has been studied in the collision 116Sn + 93Nb at
29.5 AMeV as a function of the Total Kinetic Energy Loss of the reaction. This
pattern shows that for peripheral reactions most of IMF's are emitted at
mid-velocity. Coulomb trajectory calculations demonstrate that these IMF's are
produced in the early stages of the reaction and shed light on geometrical
details of these emissions, suggesting that the IMF's originate both from the
neck and the surface of the interacting nuclei.Comment: 4 pages, 3 figures, RevTex 3.1, submitted to Phys. Rev. Letter
Energy and angular momentum sharing in dissipative collisions
Primary and secondary masses of heavy reaction products have been deduced
from kinematics and E-ToF measurements, respectively, for the direct and
reverse collisions of 93Nb and 116Sn at 25 AMeV. Light charged particles have
also been measured in coincidence with the heavy fragments.
Direct experimental evidence of the correlation of energy-sharing with net
mass transfer has been found using the information from both the heavy
fragments and the light charged particles.
The ratio of Hydrogen and Helium multiplicities points to a further
correlation of angular momentum sharing with net mass transfer.Comment: 21 pages, 20 figures. Submitted to European Physics Journal
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