Social stress is a negative emotional experience that can increase fear and anxiety. Dominance status can alter the way individuals react to and cope with stressful events. The underlying ...neurobiology of how social dominance produces stress resistance remains elusive, although experience-dependent changes in androgen receptor (AR) expression is thought to play an essential role. Using a Syrian hamster (Mesocricetus auratus) model, we investigated whether dominant individuals activate more AR-expressing neurons in the posterior dorsal and posterior ventral regions of the medial amygdala (MePD, MePV), and display less social anxiety-like behavior following social defeat stress compared to subordinate counterparts. We allowed male hamsters to form and maintain a dyadic dominance relationship for 12 days, exposed them to social defeat stress, and then tested their approach-avoidance behavior using a social avoidance test. During social defeat stress, dominant subjects showed a longer latency to submit and greater c-Fos expression in AR+ cells in the MePD/MePV compared to subordinates. We found that social defeat exposure reduced the amount of time animals spent interacting with a novel conspecific 24 h later, although there was no effect of dominance status. The amount of social vigilance shown by dominants during social avoidance testing was positively correlated with c-Fos expression in AR+ cells in the MePV. These findings indicate that dominant hamsters show greater neural activity in AR+ cells in the MePV during social defeat compared to their subordinate counterparts, and this pattern of neural activity correlates with their proactive coping response. Consistent with the central role of androgens in experience-dependent changes in aggression, activation of AR+ cells in the MePD/MePV contributes to experience-dependent changes in stress-related behavior.
•Social dominance increases stress-induced cFos expression in AR+ MePD/MePV neurons.•Proactive coping is associated with greater neural activity in AR+ MePV neurons.•Subordinates show reduced activity in MePD/MePV cells during avoidance testing.•c-Fos expression in AR+ MePV neurons predicts social vigilance.•AR+ cells in MePD/MePV modulate experience-dependent changes in stress behavior.
► We have developed a theoretical model of Titan’s atypical Schumann resonance. ► Characteristics of atmospheric-subsurface cavity are constrained by Huygens HASI–PWA data. ► Upper cavity boundaries ...involve thin ionized layers of aerosols up to 150km altitude. ► The inner boundary is likely a water–ammonia ocean buried 55–80km below the surface.
This study presents an approximate model for the atypical Schumann resonance in Titan’s atmosphere that accounts for the observations of electromagnetic waves and the measurements of atmospheric conductivity performed with the Huygens Atmospheric Structure and Permittivity, Wave and Altimetry (HASI–PWA) instrumentation during the descent of the Huygens Probe through Titan’s atmosphere in January 2005. After many years of thorough analyses of the collected data, several arguments enable us to claim that the Extremely Low Frequency (ELF) wave observed at around 36Hz displays all the characteristics of the second harmonic of a Schumann resonance. On Earth, this phenomenon is well known to be triggered by lightning activity. Given the lack of evidence of any thunderstorm activity on Titan, we proposed in early works a model based on an alternative powering mechanism involving the electric current sheets induced in Titan’s ionosphere by the Saturn’s magnetospheric plasma flow. The present study is a further step in improving the initial model and corroborating our preliminary assessments. We first develop an analytic theory of the guided modes that appear to be the most suitable for sustaining Schumann resonances in Titan’s atmosphere. We then introduce the characteristics of the Huygens electric field measurements in the equations, in order to constrain the physical parameters of the resonating cavity. The latter is assumed to be made of different structures distributed between an upper boundary, presumably made of a succession of thin ionized layers of stratospheric aerosols spread up to 150km and a lower quasi-perfect conductive surface hidden beneath the non-conductive ground. The inner reflecting boundary is proposed to be a buried water–ammonia ocean lying at a likely depth of 55–80km below a dielectric icy crust. Such estimate is found to comply with models suggesting that the internal heat could be transferred upwards by thermal conduction of the crust, while convective processes cannot be ruled out.
The accumulation of charges on cloud particles by the charge transfer of ions and attachment of electrons in the atmosphere of Venus is investigated in the present work. Three cloud layers between 45 ...and 70 km exist in the atmosphere of Venus. Ions and electrons are produced by the interaction of galactic cosmic rays with the neutral molecules. Ion to particle and electron to particle attachment coefficients are calculated. The charge balance equations include ion‐ion recombination, ion‐electron recombination, electron attachment to neutrals, electron detachment from negative ions, and attachment of electron and charge transfer from ions to particles. It is found that the ion concentrations are reduced by a maximum of a factor of 5 by charging of the particles, while the earlier studies showed a maximum reduction of about an order of magnitude due to the differences in the surface area of the particles. A similar result is observed in the calculation of electrical conductivity. Both monodisperse and polydisperse distribution of particles are considered. The conductivity was reduced by a factor of 3 when using the monodisperse distribution of particles, while the maximum reduction observed was a factor of 2 when using the polydisperse distribution. This result implies that the monodisperse particle distribution overestimates the effect of particles on the atmospheric conductivity. The ratio of negative to positive charges is found to be very large in the middle and upper cloud layers. The low abundance of the aerosols and high conductivity of the atmosphere appear to rule out lightning activity in the 40 to 70 km altitude region.
At the Brookhaven National Laboratory (BNL) Relativistic Heavy Ion Collider (RHIC) the Beam-Beam Counter (BBC) array for the Solenodial Tracker at RHIC (STAR) is a very versatile tool for polarized ...proton beam diagnostics. The BBC setup provides an excellent minimum bias trigger; and for hits on the inner annuli of six hexagonal scintillator tiles the BBC coincidence trigger with a suitable algorithm has a quite large single spin analyzing power ~8X10-3 for 100 GeV polarized proton -100 GeV polarized proton collisions. The STAR BBC is a very effective local polarimeter at these energies. For 100 GeV 'p-vector '-100 GeV 'p-vector ' running in 2006 the BBC measured single spin asymmetries to a statistical accuracy of better than 2% for a data run of 20-30 minutes; and these measurements were quite robust. For fills with a duration of at least six hours these STAR BBC asymmetry measurements were used to study the time dependence of the polarization for 100 GeV proton beams in the RHIC rings. The decrease of the polarization is quite small, < 0.01PB per hour.
Historic DNA data have the potential to identify phenotypic information otherwise invisible in the historical, archaeological and palaeontological record. In order to determine whether a single ...nucleotide polymorphism typing protocol based on single based extension (SNaPshot™) could produce reliable phenotypic data from historic samples, we genotyped three coat colour markers for a sample of historic Thoroughbred horses for which both phenotypic and correct genotypic information were known from pedigree information in the General Stud Book. Experimental results were consistent with the pedigrees in all cases. Thus we demonstrate that historic DNA techniques can produce reliable phenotypic information from museum specimens.
The electrical conductivity and electrical charge on the aerosols in atmosphere of Titan are computed for altitudes between 0 and 400 km. Ionization of methane and nitrogen due to galactic cosmic ...rays (GCR) is important at night where these ions are converted to ion clusters such as CH
+
5CH
4, C
7H
+
7, C
4H
+
7, and H
4C
7N
+. The ubiquitous aerosols observed also play an important role in determining the charge distribution in the atmosphere. Because polycyclic aromatic hydrocarbons (PAHs) are expected in Titan's atmosphere and have been observed in the laboratory and found to be electrophilic, we consider the formation of negative ions. During the night, the very smallest molecular complexes accept free electrons to form negative ions. This results in a large reduction of the electron abundance both in the region between 150 and 350 km over that predicted when such aerosols are not considered. During the day time, ionization by photoemission from aerosols irradiated by solar ultraviolet (UV) radiation overwhelms the GCR-produced ionization. The presence of hydrocarbon and nitrile minor constituents substantially reduces the UV flux in the wavelength band from the cutoff of CH
4 at 155 to 200 nm. These aerosols have such a low ionization potential that the bulk of the solar radiation at longer wavelengths is energetic enough to produce a photoionization rate sufficient to create an ionosphere even without galactic cosmic ray (GCR) bombardment. At altitudes below 60 km, the electron and positive ion abundances are influenced by the three-body recombination of ions and electrons. The addition of this reaction significantly reduces the predicted electron abundance over that previously predicted. Our calculations for the dayside show that the peaks of the charge distributions move to larger values as the altitude increases. This variation is the result of the increased UV flux present at the highest altitudes. Clearly, the situation is quite different than that for the night where the peak of the distribution for a particular size is nearly constant with altitude when negative ions are not present. The presence of very small aerosol particles (embryos) may cause the peak of the distribution to decrease from about 8 negative charges to as little as one negative charge or even zero charge. This dependence on altitude will require models of the aerosol formation to change their algorithms to better represent the effect of charged aerosols as a function of altitude. In particular, the charge state will be much higher than previously predicted and it will not be constant with altitude during the day time. Charging of aerosol particles, whether on the dayside or nightside, has a major influence on both the electron abundance and electrical conductivity. The predicted conductivities are within the measurement range of the HASI PWA instrument over most but not all, of the altitude range sampled.
The electrical conductivity and electrical charge on cloud particles (composed of ammonia, ammonium hydrosulfide, and water) in the atmosphere of Jupiter are computed for pressures between 5.5 and ...0.1 bars. The source of ionization is galactic cosmic rays (GCR). The distribution of charge among the various reservoirs is a function of altitude and the total area of the aerosol particles. For pressures below 4 bars, the electrons are scavenged efficiently by the cloud particles, decreasing the electron‐ion recombination rate and resulting in increased positive ion abundance over that in the absence of the particles. For the upper regions of each cloud layer, the area of the aerosols and the large diffusion rate of the electrons cause most aerosol particles to be negatively charged. Near the bases of the cloud layers, the larger total area of the aerosols causes most of the charge, positive and negative, to reside on particles. Where clouds are present, the reduction of the electron conductivity ranges from a factor of 30 at 0.1 bar to 104 at 4 bars. At pressures near 1 bar and 4 bars, the positive ion conductivity increases by a factor of 10 over that expected for the clear atmosphere. A parametric study of negative ions shows that they are likely to be insignificant. For altitudes below the 0.3‐bar level the predicted positive and negative conductivities are well below the detection limit of the relaxation and mutual impedance instruments such as those employed on the Huygens entry probe.
The electrical conductivity and electrical charge on Titan's atmosphere are computed for altitudes between 0 and 400 km on the nightside for which the main source of ionization is galactic cosmic ...rays (GCR). Unlike the dayside, electrical charging of the aerosol particles at night is not only negative but also time‐dependent. Hence a time‐dependent model must be employed for computations of electron and ion densities as well as aerosol charging over the night hemisphere. After developing a method for computing the time‐dependent charge states of the aerosol particles, we found that that at altitudes above about 60 km (the effusion range) the charging of the aerosols at the antisolar point is quite close to that at steady state; however, at lower altitudes where (the slow) diffusion of the electrons and ions prevails, the electron density is larger (and the charging of the aerosol particles is smaller) than at steady state. Because polycyclic aromatic hydrocarbons (PAHs) are expected in Titan's atmosphere and have been observed in the laboratory and found to be electrophillic, we have included the formation of negative ions in the aerosol charging model. Such ions are of major importance at night between about 170 and 360 km where they capture most of the negative charge. As a result they greatly reduce the electron density and thus the electrical conductivity in that altitude range. The charge distributions at 50 km (diffusion range), 150 km (effusion range with few negative ions), and 250 km (effusion range) are presented.
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