155 research outputs found
Nonlinear dynamics of beta induced Alfv\'en eigenmode driven by energetic particles
Nonlinear saturation of beta induced Alfv\'en eigenmode, driven by slowing
down energetic particles via transit resonance, is investigated by the
nonlinear hybrid magnetohyrodynamic gyro-kinetic code (XHMGC). Saturation is
characterized by frequency chirping and symmetry breaking between co- and
counter-passing particles, which can be understood as the the evidence of
resonance-detuning. The scaling of the saturation amplitude with the growth
rate is also demonstrated to be consistent with radial resonance detuning due
to the radial non-uniformity and mode structure
Morphometry of the larger foraminifer Heterostegina explaining environmental dependence, evolution and paleogeographic diversification
The cosmopolitan, symbiont-bearing, larger benthic foraminifer (LBF)
Heterostegina sensu lato prefers oligotrophic environments in tropical and warm-temperate
seas. Harboring diatoms enables this species to be found across a wide illumination gradient
from intertidal pools, where H. depressa protects against strongest illumination by occupying
cryptic habitat, down to the base of the euphotic zone. Sheltered cryptic habitat, such as in
holes of boulders, allows this species to live in highly energetic zones down to the fairweather
wave base. Dependence on light for photosynthesis of its endosymbionts is managed
by increasing surface/volume ratios of the test correlated with decreasing light, resulting in
test flattening. Hydrodynamics also influences reproductive strategies. In high energy
environments, asexual reproduction by schizogony dominates, while sexual reproduction
(gametogony) is the dominant mode under low energy conditions. Thus, there is a shift in
proportions between schizonts with smaller proloculi and gamonts with larger proluculi along
the hydrodynamic gradient. Because there is a negative correlation between proloculus size
and the number of chambers undivided by septula (operculinid chambers), the latter character
shows negative dependence along the hydrodynamic gradient. Both proloculus size and
number of operculinid chambers have been used as metric characters not only in the evolution
of Heterostegina lineages starting in the middle Eocene, but also in many other nummulitds
(e.g., Nummulites, Spiroclypeus, Cycloclypeus), totally neglecting the environmental
dependence. Additionally, proloculus size can differ between biogeographically different
populations (e.g., Okinawa and Hawaii) taken under similar hydrodynamic conditions. Using
growth-independent and growth-invariant characters to describe the internal test morphology
can enhance interpretation of evolutionary tendencies as distinct from environmental and
paleogeographic diversification
Complementary Control of Sensory Adaptation by Two Types of Cortical Interneurons
Reliably detecting unexpected sounds is important for environmental awareness and survival. By selectively reducing responses to frequently, but not rarely, occurring sounds, auditory cortical neurons are thought to enhance the brain\u27s ability to detect unexpected events through stimulus-specific adaptation (SSA). The majority of neurons in the primary auditory cortex exhibit SSA, yet little is known about the underlying cortical circuits. We found that two types of cortical interneurons differentially amplify SSA in putative excitatory neurons. Parvalbumin-positive interneurons (PVs) amplify SSA by providing non-specific inhibition: optogenetic suppression of PVs led to an equal increase in responses to frequent and rare tones. In contrast, somatostatin-positive interneurons (SOMs) selectively reduce excitatory responses to frequent tones: suppression of SOMs led to an increase in responses to frequent, but not to rare tones. A mutually coupled excitatory-inhibitory network model accounts for distinct mechanisms by which cortical inhibitory neurons enhance the brain\u27s sensitivity to unexpected sounds
Morphometric analysis of Eocene nummulitids in western and central Cuba: taxonomy, biostratigraphy and evolutionary trends
Megalospheric specimens of Nummulitidae from eight localities in western and central Cuba were morphometrically investigated using test characters described by 11 growth-independent and growth-invariant attributes that provide a complete geometric reconstruction of nummulitid equatorial morphology. The species Nummulites striatoreticulatus, Palaeonummulites trinitatensis, Operculinoides floridensis and O. soldadensis were classified by an agglomerative cluster analysis. Discriminant analysis yielded significant morphological separators between the species such as the backbend angle, marginal radius increase, perimeter ratio and first chamber length. The transition of tightness to laxity of the spiral was an important morphological separator at the generic level, representing a clear general trend coupled with the change in palaeodepth. Based on further discriminant analysis, an increase in proloculus size was detected in Nummulites striatoreticulatus from the middle Eocene to early late Eocene, supporting this important evolutionary pattern in many lineages of Nummulites. Operculinid forms showed an opposite and more weakly pronounced time-dependent trend in the size decrease of the proloculus. In the Cuban localities, Nummulites striatoreticulatus occurs from the Lutetian to Priabonian, while Palaeonummulites trinitatensis is restricted to the Bartonian to Priabonian. The moderately to loosely coiled operculinid taxa O. floridensis and O. soldadensis have longer stratigraphical ranges from the middle Eocene to probably the early Oligocene. Operculinoides floridensis and O. soldadensis show a broader variability in marginal radius increase, and thus probably occupied wider niches than N. striatoreticulatus. The latter seems to be restricted to the shelf edge and to the shallowest parts of the upper slope. A possible phylogenetic connection between Heterostegina and Operculinoides is suggested by the closest equatorial morphology of Heterostegina sp. indet. to tightly coiled forms of Operculinoides floridensis. Discriminant analysis documents the strongest similarities in perimeter ratio, backbend angle, initial marginal radius and proloculus mean diameter
Healthy Eating, Physical Activity, and Sleep Hygiene (HEPAS) as the Winning Triad for Sustaining Physical and Mental Health in Patients at Risk for or with Neuropsychiatric Disorders: Considerations for Clinical Practice
Neuropsychiatric disorders stem from gene-environment interaction and their development can be, at least in some cases, prevented by the adoption of healthy and protective lifestyles. Once full blown, neuropsychiatric disorders are prevalent conditions that patients live with a great burden of disability. Indeed, the determinants that increase the affliction of neuropsychiatric disorders are various, with unhealthy lifestyles providing a significant contribution in the interplay between genetic, epigenetic, and environmental factors that ultimately represent the pathophysiological basis of these impairing conditions. On one hand, the adoption of Healthy Eating education, Physical Activity programs, and Sleep hygiene promotion (HEPAS) has the potential to become one of the most suitable interventions to reduce the risk to develop neuropsychiatric disorders, while, on the other hand, its integration with pharmacological and psychological therapies seems to be essential in the overall management of neuropsychiatric disorders in order to reduce the disability and improve the quality of life of affected patients. We present an overview of the current evidence in relation to HEPAS components in the prevention and management of neuropsychiatric disorders and provide suggestions for clinical practice
The absolute age of the globular cluster M15 using near-infrared adaptive optics images from PISCES/LBT
We present deep near-infrared (NIR) J, Ks photometry of the old, metal-poor
Galactic globular cluster M\,15 obtained with images collected with the LUCI1
and PISCES cameras available at the Large Binocular Telescope (LBT). We show
how the use of First Light Adaptive Optics system coupled with the (FLAO)
PISCES camera allows us to improve the limiting magnitude by ~2 mag in Ks. By
analyzing archival HST data, we demonstrate that the quality of the LBT/PISCES
color magnitude diagram is fully comparable with analogous space-based data.
The smaller field of view is balanced by the shorter exposure time required to
reach a similar photometric limit. We investigated the absolute age of M\,15 by
means of two methods: i) by determining the age from the position of the main
sequence turn-off; and ii) by the magnitude difference between the MSTO and the
well-defined knee detected along the faint portion of the MS. We derive
consistent values of the absolute age of M15, that is 12.9+-2.6 Gyr and
13.3+-1.1 Gyr, respectively.Comment: 13 pages, 8 figures, ApJ accepte
Islands of relationality and resilience: the shifting stakes of the Anthropocene
In recent decades island studies scholars have done much to disrupt static notions of the island form, increasingly foregrounding how islands form part of complex networks of relations, assemblages and flows. In this paper, we shift the terms of debate more explicitly to relationality in the Anthropocene. We consider the implications and challenges that a wider set of debates, particularly surrounding island âresilienceâ, concerning the Anthropocene in the social sciences and humanities pose for island studies
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