4,267 research outputs found
Adult social isolation leads to anxiety and spatial memory impairment: Brain activity pattern of COx and c-Fos
Social isolation during adulthood is a frequent problem that leads to a large variety of adverse emotional and cognitive effects. However, most of the social isolation rodent procedures begin the separation early post-weaning. This work explores locomotor activity, anxiety-like behaviour, and spatial working memory after twelve weeks of adult social isolation. In order to study the functional contribution of selected brain areas following a working memory task, we assessed neuronal metabolic activity through quantitative cytochrome oxidase histochemistry and c-Fos immunohistochemistry. Behaviourally, we found that isolated animals (IS) showed anxiety-like behaviour and worse working memory than controls, whereas motor functions were preserved. Moreover, IS rats showed lower levels of learning-related c-Fos immunoreactivity, compared to controls, in the medial prefrontal cortex (mPFC), ventral tegmental area (VTA), and nucleus accumbens shell. In addition, the IS group showed lower neuronal metabolic activity in the mPFC, VTA, and CA1 subfield of the hippocampus. These results indicate that twelve weeks of social isolation in adult rats leads to different behavioural and brain alterations, and they highlight the importance of social support, not only in development, but also in adulthood
On The Low Frequency Quasi Periodic Oscillations of X-ray Sources
Based on the interpretation of the twin kilohertz Quasi Periodic Oscillations
(kHz QPOs) of X-ray spectra of Low Mass X-Ray Binaries
(LMXBs) to the Keplerian and the periastron precession frequencies at the
magnetosphere-disk of X-ray neutron star (NS) respectively, we ascribe the low
frequency Quasi Periodic Oscillations (LFQPO) and HBO (15-60 Hz QPO for Z
sources or Atoll sources) to the periastron precession at some outer disk
radius.
The obtained conclusions include: all QPO frequencies increase with
increasing the accretion rate. The obtained theoretical relations between HBO
(LFQPO) frequency and the kHz QPO frequency are similar to the measured
empirical formula. Further, the possible dynamical mechanism for QPO production
is discussed.Comment: 6 pages, 2 figures, accepted by APSS, 200
Experimental determination of the absorption strength in absorbing chaotic cavities
Due to the experimental necessity we present a formula to determine the
absorption strength by power losses inside a chaotic system (cavities, graphs,
acoustic resonators, etc) when the antenna coupling, always present in
experimental measurements, is taken into account. This is done by calculating
the average of the absorption coefficient as a function of the absorption
strength and the coupling of the antenna to the system, in the one channel
case.Comment: 6 pages, 3 figures, Submitted to Phys. Rev.
Association between olfactory dysfunction and mood disturbances with objective and subjective cognitive deficits in long-COVID
Background and purposeThe coronavirus disease 2019 (COVID-19) has been associated with olfactory dysfunction. The persistent symptoms of anosmia or hyposmia were associated in previous studies with the development of memory impairment and mood disturbances. We aimed to investigate the association between the chronicity of reported olfactory dysfunction and subjective and objective cognitive performance in long-COVID patients and to explore whether their emotional symptoms are related to their cognition.MethodsOne hundred twenty-eight long-COVID participants were recruited. Reported symptomatology, subjective memory complaints, anxiety and depression symptomatology, and trait-anxiety were assessed. Subjective memory complaints and mood disturbances were compared among groups of participants with olfactory dysfunction as an acute (AOD), persistent (POD), or nonexistent (NOD) symptom. Seventy-six of the volunteers also participated in a face-to-face session to assess their objective performance on tests of general cognitive function and verbal declarative memory. Objective cognitive performance and mood disturbances were compared among the AOD, POD, and NOD groups.ResultsThe subjective memory complaints and the anxiety and depression symptoms were similar among the groups, but the score in general cognitive function was lower in the participants with symptoms of acute olfactory dysfunction than in those with no olfactory symptoms at any time. Participants’ memory complaints were positively related to their emotional symptoms. The relationship between depressive symptomatology and memory complaints interacted with the olfactory dysfunction, as it only occurred in the participants without symptoms of olfactory dysfunction. Depressive symptomatology and acute olfactory symptoms were negatively associated with general cognitive function and delayed memory performance. The months elapsed from diagnosis to assessment also predicted delayed memory performance. Anxious symptomatology was negatively associated with the immediate ability to recall verbal information in participants who did not present olfactory dysfunction in the acute phase of the infection.ConclusionOlfactory dysfunction in the acute phase of the infection by COVID-19 is related to cognitive deficits in objective tests, and mood disturbances are associated with self-reported and objective memory. These findings may contribute to further understanding the neuropsychological and emotional aspects of long-COVID
The High-Frequency QPOs in GRS 1915+105
We analyzed two 1996 observations of the Galactic Microquasar GRS 1915+105 taken with the Proportional Counter Array on board the Rossi X-ray Timing Explorer. We focus on the properties of the high-frequency QPO as a function of the `dip' oscillations, a factor of 1000 slower. In one observation, 1996 May 5th, we find that the energy spectrum of the QPO at ~65 Hz changes drastically between the high-intervals and the dips, hardening during the dips to the point that the QPO peak is no longer detected at low energies. In the second observation, 1996 May 14th, although it has similar overall characteristics, the 65 Hz QPO is not seen, but another broader QPO peak appears at 27 Hz, only during the dips. This peak is too weak to obtain reliable information about its spectrum. Our results indicate that the presence/absence of high-frequency features in this enigmatic source are intimately linked to the slower oscillations and variations that happen on longer time scales
The Landau problem and noncommutative quantum mechanics
The conditions under which noncommutative quantum mechanics and the Landau
problem are equivalent theories is explored. If the potential in noncommutative
quantum mechanics is chosen as with defined in the
text, then for the value (that
measures the noncommutative effects of the space), the Landau problem and
noncommutative quantum mechanics are equivalent theories in the lowest Landau
level. For other systems one can find differents values for
and, therefore, the possible bounds for should be searched in
a physical independent scenario. This last fact could explain the differents
bounds for found in the literature.Comment: This a rewritten and corrected version of our previous preprint
hep-th/010517
Dependence of the Frequency of the Kilohertz Quasi-Periodic Oscillations on X-ray Count Rate and Colors in 4U 1608-52
We present new results based on observations carried out with the Rossi X-ray
Timing Explorer during the decay of an outburst of the low-mass X-ray binary
(LMXB) and atoll source 4U 1608-52. Our results appear to resolve, at least in
4U 1608-52, one of the long-standing issues about the phenomenology of the
kilohertz quasi-periodic oscillations (kHz QPOs), namely, the lack of a unique
relation between the frequency of the kHz QPOs and the X-ray flux. We show that
despite its complex dependence on the X-ray flux, the frequency of the kHz QPOs
is monotonically related to the position of the source in the color-color
diagram. Our findings strengthen the idea that, as in the case of Z sources, in
the atoll sources the X-ray flux is not a good indicator of , and that
the observed changes in the frequency of the kHz QPOs in LMXBs are driven by
changes in . These results raise some concern about the recently
reported detection of the orbital frequency at the innermost stable orbit in 4U
1820-30.Comment: Accepted for publication in The Astrophysical Journal Letters. Uses
AAS LaTex v4.0 (5 pages plus 4 postscript figures
Kilohertz Quasi-Periodic Oscillation Peak Separation is not Constant in the Atoll Source 4U 1608-52
We present new Rossi X-ray Timing Explorer observations of the low-mass X-ray
binary 4U 1608-52 during the decay of its 1998 outburst. We detect by a direct
FFT method the existence of a second kilohertz quasi-periodic oscillation (kHz
QPO) in its power density spectrum, previously only seen by means of the
sensitivity-enhancing `shift and add' technique. This result confirms that 4U
1608-52 is a twin kHz QPO source. The frequency separation between these two
QPO decreased significantly, from 325.5 +/- 3.4 Hz to 225.3 +/- 12.0 Hz, as the
frequency of the lower kHz QPO increased from 470 Hz to 865 Hz, in
contradiction with a simple beat-frequency interpretation. This change in the
peak separation of the kHz QPOs is closely similar to that previously seen in
Sco X-1, but takes place at a ten times lower average luminosity. We discuss
this result within the framework of models that have been proposed for kHz QPO.
Beat frequency models where the peak separation is identified with the neutron
star spin rate, as well as the explanations previously proposed to account for
the similar behavior of the QPOs in Sco X-1, are strongly challenged by this
result.Comment: To appear in ApJL. AAS LaTex v4.0 (6 pages plus 3 postscript figures
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