Scaling of an Optically Pumped Mid-Infrared Rubidium Laser

An optically pumped mid-infrared rubidium (Rb) pulsed laser has been demonstrated in a heat pipe along the 62P3/2 - 62S1/2 transition at 2.730 µm and the 62P1/2 - 62S1/2 transition at 2.790 µm. The bleached limit, slope efficiency, and maximum laser output energy of the mid-IR Rb laser have been shown to scale linearly with increasing Rb density, contrary to prior laser demonstrations. A maximum output energy of 5 nJ per pulse had previously been observed before a rollover occurred in the scaling of output energy with Rb concentration. In this experiment, the maximum laser output energy observed was 100 nJ, with linear scaling to a Rb concentration of 7 x 1015 cm-3. A maximum slope efficiency of 1.7 x 104 was observed. Evidence that only a small percentage (2%) of the available pump photons were absorbed at a concentration of 2 x 1015 cm-3 and a pump energy of 10 µJ. This indicated that there were ~20,000 pump photons per Rb atom at a pump energy of 10 mJ, and that the effective laser efficiency was 0.65% or higher. The hyperfine structure and absorption spectral profile of the 52S1/2 - 62P1/2 and 52S1/2 - 62P3/2 (blue) pump transitions were studied using a continuous wave (cw) pump source

Materials chemistry under high pressures - Some recent aspects

Among the thermodynamic parameters governing the preparation of novel materials, temperature (T) and pressure (p) play an important role. In Materials Chemistry, the synthesis of materials needs energy in order to enhance the diffusion of atoms to the equilibrium positions required by the specific structure and to induce the formation of chemical bonds..

The Parsec‐Scale Accretion Disk in NGC 3393

We present a Very Long Baseline Interferometry image of the water maser emission in the nuclear region of NGC 3393. The maser emission has a linear distribution oriented at a position angle of ~–34°, perpendicular to both the kiloparsec-scale radio jet and the axis of the narrow-line region. The position-velocity diagram displays a red-blue asymmetry about the systemic velocity and the estimated dynamical center, and is thus consistent with rotation. Assuming Keplerian rotation in an edge-on disk, we obtain an enclosed mass of ($3.1 ± 0.2) × 10^7 M☉$ within 0.36 ± 0.02 pc (1.48 ± 0.06 mas), which corresponds to a mean mass density of $\sim10^{8.2} M☉ pc^{−3}$. We also report the measurement with the Green Bank Telescope of a velocity drift, a manifestation of centripetal acceleration within the disk, of $5 ± 1 km s^{−1} yr^{−1}$ in the $\sim3880 km s^{−1}$ maser feature, which is most likely located along the line of sight to the dynamical center of the system. From the acceleration of this feature, we estimate a disk radius of 0.17 ± 0.02 pc, which is smaller than the inner disk radius (0.36 ± 0.02 pc) of emission that occurs along the midline (i.e., the line of nodes). The emission along the line of sight to the dynamical center evidently occurs much closer to the center than the emission from the disk midline, contrary to the situation in the archetypal maser systems NGC 4258 and NGC 1068. The outer radius of the disk as traced by the masers along the midline is about 1.5 pc.Astronom

Proper Motion of Water Masers Associated with IRAS 21391+5802: Bipolar Outflow and an AU-Scale Dusty Circumstellar Shell

We present VLBA observations of water maser emission associated with the star-forming region IRAS 21391+5802, which is embedded in a bright rimmed cometary globule in IC1396. The angular resolution of the maps is about 0.8 mas, corresponding to a spatial resolution of about 0.6 AU, at an estimated distance of 750 pc. Proper motions are derived for 10 maser features identified consistently over three epochs, which were separated by intervals of about one month. The masers appear in four groups, which are aligned linearly on the sky, roughly along a northeast-southwest direction, with a total separation of about 520 AU (about 0.7 arcseconds). The 3-D velocities of the masers have a maximum value of about 42 km/s (about 9 AU/yr). The average error on the derived proper motions is about 4 km/s. The overall pattern of proper motions is indicative of a bipolar outflow. Proper motions of the masers in a central cluster, with a projected extent of about 20 AU, show systematic deviations from a radial outflow. However, we find no evidence of Keplerian rotation, as has been claimed elsewhere. A nearly circular loop of masers lies near the middle of the cluster. The radius of this loop is 1 AU and the line-of-sight velocities of the masers in the loop are within 2 km/s of the systemic velocity of the region. These masers presumably exist at the radial distance where significant dust condensation occurs in the outflow emanating from the star.Comment: 15 pages, 4 figures. Accepted for publication in the Astrophysical Journal. Version 2.12.00: Astrometric coordinates of maser revise

Probing the Magnetic Field at Sub-Parsec Radii in the Accretion Disk of NGC 4258

We present an analysis of polarimetric observations at 22 GHz of the water vapor masers in NGC 4258 obtained with the VLA and the GBT. We do not detect any circular polarization in the spectrum indicative of Zeeman-induced splitting of the maser lines of water, a non-paramagnetic molecule. We have improved the 1-sigma upper limit estimate on the toroidal component of the magnetic field in the circumnuclear disk of NGC 4258 at a radius of 0.2 pc from 300 mG to 90 mG. We have developed a new method for the analysis of spectra with blended features and derive a 1-sigma upper limit of 30 mG on the radial component of the magnetic field at a radius of 0.14 pc. Assuming thermal and magnetic pressure balance, we estimate an upper limit on the mass accretion rate of ~10^(-3.7) M_sun/yr for a total magnetic field of less than 130 mG. We discuss the ramifications of our results on current maser models proposed to explain the observed maser emission structure and the consequences for current accretion theories. We find from our magnetic field limits that the thin-disk model and the jet-disk model are better candidates for accounting for the extremely low-luminosity nature of NGC 4258, than models that include advection-dominated accretion flows.Comment: 20 pages, including 10 figures and 2 tables. Accepted for publication in the Astrophysical Journa

Interpreting Ambiguous Social Cues in Unpredictable Contexts

Unpredictable environments can be anxiety-provoking and elicit exaggerated emotional responses to aversive stimuli. Even neutral stimuli, when presented in an unpredictable fashion, prime anxiety-like behavior and elicit heightened amygdala activity. The amygdala plays a key role in initiating responses to biologically relevant information, such as facial expressions of emotion. While some expressions clearly signal negative (anger) or positive (happy) events, other expressions (e.g. surprise) are more ambiguous in that they can predict either valence, depending on the context. Here, we sought to determine whether unpredictable presentations of ambiguous facial expressions would bias participants to interpret them more negatively. We used functional magnetic resonance imaging and facial electromyography (EMG) to characterize responses to predictable vs unpredictable presentations of surprised faces. We observed moderate but sustained increases in amygdala reactivity to predictable presentations of surprised faces, and relatively increased amygdala responses to unpredictable faces that then habituated, similar to previously observed responses to clearly negative (e.g. fearful) faces. We also observed decreased corrugator EMG responses to predictable surprised face presentations, similar to happy faces, and increased responses to unpredictable surprised face presentations, similar to angry faces. Taken together, these data suggest that unpredictability biases people to interpret ambiguous social cues negatively

Colorado Native Plant Society Newsletter, Vol. 4 No. 2, March-April 1980

The Colorado Native Plant Society Newsletter will be published on a bimonthly basis. The contents will consist primarily of a calendar of events, notes of interest, editorials, listings of new members and conservation news. Until there is a Society journal, the Newsletter will include short articles also. The deadline for the Newsletter is one month prior to its release.https://epublications.regis.edu/aquilegia/1018/thumbnail.jp

Neutral Evolution as Diffusion in phenotype space: reproduction with mutation but without selection

The process of `Evolutionary Diffusion', i.e. reproduction with local mutation but without selection in a biological population, resembles standard Diffusion in many ways. However, Evolutionary Diffusion allows the formation of local peaks with a characteristic width that undergo drift, even in the infinite population limit. We analytically calculate the mean peak width and the effective random walk step size, and obtain the distribution of the peak width which has a power law tail. We find that independent local mutations act as a diffusion of interacting particles with increased stepsize.Comment: 4 pages, 2 figures. Paper now representative of published articl

Support received after bereavement by suicide and other sudden deaths:a cross-sectional UK study of 3,432 young bereaved adults

OBJECTIVE: To test the hypothesis that people bereaved by suicide are less likely to receive formal or informal support than people bereaved by other causes of sudden death. DESIGN: National cross-sectional study. SETTING: Adults working or studying at any UK higher education institution (HEI) in 2010. PARTICIPANTS: A total of 3432 eligible respondents aged 18-40 years bereaved by the sudden death of a close friend or relative, sampled from approximately 659 572 bereaved and non-bereaved staff and students at 37 of 164 UK HEIs invited to participate. EXPOSURES: Bereavement by suicide (n=614; 18%), by sudden unnatural causes (n=712; 21%) and by sudden natural causes (n=2106; 61%). MAIN OUTCOME MEASURES: Receipt of formal and informal support postbereavement; timing of valued support. RESULTS: 21% (725/3432) of our sample of bereaved adults reported receiving no formal or informal bereavement support, with no evidence for group differences. People bereaved by suicide were less likely to have received informal support than those bereaved by sudden natural causes (adjusted OR (AOR)=0.79; 95% CI 0.64 to 0.98) or unnatural causes (AOR=0.74; 95% CI 0.58 to 0.96) but did not differ from either comparison group on receipt of formal support. People bereaved by suicide were less likely to have received immediate support (AOR=0.73; 95% CI 0.59 to 0.90) and more likely to report delayed receipt of support (AOR=1.33; 95% CI 1.08 to 1.64) than people bereaved by sudden natural causes. Associations were not modified by gender, or age bereaved, but became non-significant when adjusting for stigma. CONCLUSIONS: People bereaved by suicide are less likely to receive informal support than people bereaved by other causes of sudden death and are more likely to perceive delays in accessing any support. This is concerning given their higher risk of suicide attempt and the recommendations within suicide prevention strategies regarding their need for support. STUDY REGISTRATION: http://www.ucl.ac.uk/psychiatry/bereavementstudy/