Shock-Wave Heating Model for Chondrule Formation: Prevention of Isotopic Fractionation

Chondrules are considered to have much information on dust particles and processes in the solar nebula. It is naturally expected that protoplanetary disks observed in present star forming regions have similar dust particles and processes, so study of chondrule formation may provide us great information on the formation of the planetary systems. Evaporation during chondrule melting may have resulted in depletion of volatile elements in chondrules. However, no evidence for a large degree of heavy-isotope enrichment has been reported in chondrules. In order to meet this observed constraint, the rapid heating rate at temperatures below the silicate solidus is required to suppress the isotopic fractionation. We have developed a new shock-wave heating model taking into account the radiative transfer of the dust thermal continuum emission and the line emission of gas molecules and calculated the thermal history of chondrules. We have found that optically-thin shock waves for the thermal continuum emission from dust particles can meet the rapid heating constraint, because the dust thermal emission does not keep the dust particles high temperature for a long time in the pre-shock region and dust particles are abruptly heated by the gas drag heating in the post-shock region. We have also derived the upper limit of optical depth of the pre-shock region using the radiative diffusion approximation, above which the rapid heating constraint is not satisfied. It is about 1 - 10.Comment: 58 pages, including 5 tables and 15 figures, accepted for publication in The Astrophysical Journa

The ionization structure of the Orion nebula: Infrared line observations and models

Observations of the (O III) 52 and 88 micron lines and the (N III) 57 micron line have been made at 6 positions and the (Ne III) 36 micron line at 4 positions in the Orion Nebula to probe its ionization structure. The measurements, made with a -40" diameter beam, were spaced every 45" in a line south from and including the Trapezium. The wavelength of the (Ne III) line was measured to be 36.013 + or - 0.004 micron. Electron densities and abundance ratios of N(++)/O(++) have been calculated and compared to other radio and optical observations. Detailed one component and two component (bar plus halo) spherical models were calculated for exciting stars with effective temperatures of 37 to 40,000K and log g = 4.0 and 4.5. Both the new infrared observations and the visible line measurements of oxygen and nitrogen require T sub eff approx less than 37,000K. However, the double ionized neon requires a model with T sub eff more than or equal to 39,000K, which is more consistent with that inferred from the radio flux or spectral type. These differences in T sub eff are not due to effects of dust on the stellar radiation field, but are probably due to inaccuracies in the assumed stellar spectrum. The observed N(++)/O(++) ratio is almost twice the N(+)/O(+) ratio. The best fit models give N/H = 8.4 x 10 to the -5 power, O/H = 4.0 x 10 to the -4 power, and Ne/H = 1.3 x 10 to the -4 power. Thus neon and nitrogen are approximately solar, but oxygen is half solar in abundance. From the infrared O(++) lines it is concluded that the ionization bar results from an increase in column depth rather than from a local density enhancement

Heat sterilizable and impact resistant Ni-Cd battery development Quarterly report, 1 Apr. - 30 Jun. 1969

Electrochemistry, battery engineering, and impact tests of heat sterilizable nickel cadmium cell

What lies beyond social capital? the role of social psychology in building community resilience to climate change

Climate change is increasing the prevalence and impact of extreme events, which may have severe psychosocial after-effects for the people and communities who are affected. To mitigate their impact, governments advocate developing community resilience. Most approaches to community resilience employ the concept of social capital, suggesting that communities with more dense pre-existing networks of trust and reciprocity are more likely to prepare for, respond to, and recover more effectively from disasters. Notwithstanding its benefits, we argue that social capital cannot account for microprocesses of disaster behaviour such as groups that emerge in absence of any pre-existing ties and provide social support. We propose a new conceptualisation of aspects of community resilience based on the social identity approach in social psychology and grounded upon the principles of collective psychosocial resilience – the way that shared identification allows groups to emerge, coordinate, express solidarity and provide social support. We argue that our approach overcomes the limitations of social capital, because it can explain the processes of group behaviour in disasters, acknowledges people’s propensity to organise collectively, promotes bottom-up approaches to community resilience, recognises emergent communities, and suggests evidence-based recommendations for policy and practice. Finally, we propose an agenda for future research

Emergent social identities in a flood: implications for community psychosocial resilience

Although the mobilization of pre‐existing networks is crucial in psychosocial resilience in disasters, shared identities can also emerge in the absence of such previous bonds, due to survivors sharing a sense of common fate. Common fate seems to operate in sudden‐impact disasters (e.g., bombings), but to our knowledge, no research has explored social identity processes in “rising‐tide” incidents. We interviewed an opportunity sample of 17 residents of York, United Kingdom, who were involved in the 2015–2016 floods. Using thematic and discourse analysis, we investigated residents' experiences of the floods and the strategic function that invocations of community identities perform. We show how shared community identities emerged (e.g., because of shared problems, shared goals, perceptions of vulnerability, and collapse of previous group boundaries) and show how they acted as a basis of social support (both given and expected). The findings serve to further develop the social identity model of collective psychosocial resilience in rising‐tide disasters. Implications for policy and practice are discussed

\u3csup\u3e12\u3c/sup\u3eC/\u3csup\u3e13\u3c/sup\u3eC Ratio in Planetary Nebulae from the \u3cem\u3eIUE\u3c/em\u3e Archives

We investigated the abundance ratio of 12C/13C in planetary nebulae by examining emission lines arising from C III 2s2p3Po2,1,0 → 2s21S0. Spectra were retrieved from the International Ultraviolet Explorer archives, and multiple spectra of the same object were co-added to achieve improved signal-to-noise ratio. The 13C hyperfine structure line at 1909.6 Å was detected in NGC 2440. The 12C/13C ratio was found to be ~4.4+/-1.2. In all other objects, we provide an upper limit for the flux of the 1910 Å line. For 23 of these sources, a lower limit for the 12C/13C ratio was established. The impact on our current understanding of stellar evolution is discussed. The resulting high-signal-to-noise ratio C III spectrum helps constrain the atomic physics of the line formation process. Some objects have the measured 1907/1909 Å flux ratio outside the low-electron density theoretical limit for 12C. A mixture of 13C with 12C helps to close the gap somewhat. Nevertheless, some observed 1907/1909 Å flux ratios still appear too high to conform to the currently predicted limits. It is shown that this limit, as well as the 1910/1909 Å flux ratio, are predominantly influenced by using the standard partitioning among the collision strengths for the multiplet 1S0-3PoJ according to the statistical weights. A detailed calculation for the fine-structure collision strengths between these individual levels would be valuable

Bar imprints on the inner gas kinematics of M33

We present measurements of the stellar and gaseous velocities in the central 5' of the Local Group spiral M33. The data were obtained with the ARC 3.5m telescope. Blue and red spectra with resolutions from 2 to 4\AA covering the principal gaseous emission and stellar absorption lines were obtained along the major and minor axes and six other position angles. The observed radial velocities of the ionized gas along the photometric major axis of M33 remain flat at ~22 km s^{-1} all the way into the center, while the stellar velocities show a gradual rise from zero to 22 km s^{-1} over that same region. The central star cluster is at or very close to the dynamical center, with a velocity that is in accordance with M33's systemic velocity to within our uncertainties. Velocities on the minor axis are non-zero out to about 1' from the center in both the stars and gas. Together with the major axis velocities, they point at significant deviations from circular rotation. The most likely explanation for the bulk of the velocity patterns are streaming motions along a weak inner bar with a PA close to that of the minor axis, as suggested by previously published IR photometric images. The presence of bar imprints in M33 implies that all major Local Group galaxies are barred. The non-circular motions over the inner 200 pc make it difficult to constrain the shape of M33's inner dark matter halo profile. If the non-circular motions we find in this nearby Sc galaxy are present in other more distant late-type galaxies, they might be difficult to recognize.Comment: 20 pages, 12 figures, ApJ in pres

Global monopole, dark matter and scalar tensor theory

In this article, we discuss the space-time of a global monopole field as a candidate for galactic dark matter in the context of scalar tensor theory.Comment: 8 pages, Accepted in Mod. Phys. Lett.

12^{12}C/13^{13}C ratio in planetary nebulae from the IUE archives

We investigated the abundance ratio of $^{12}$C/$^{13}$C in planetary nebulae by examining emission lines arising from \ion{C}{3} 2s2p ^3P_{2,1,0} \to 2s^2 ^1S_0. Spectra were retrieved from the International Ultraviolet Explorer archives, and multiple spectra of the same object were coadded to achieve improved signal-to-noise. The $^{13}$C hyperfine structure line at 1909.6 \AA was detected in NGC 2440. The $^{12}$C/$^{13}$C ratio was found to be $\sim4.4\pm$1.2. In all other objects, we provide an upper limit for the flux of the 1910 \AA line. For 23 of these sources, a lower limit for the $^{12}$C/$^{13}$C ratio was established. The impact on our current understanding of stellar evolution is discussed. The resulting high signal-to-noise \ion{C}{3} spectrum helps constrain the atomic physics of the line formation process. Some objects have the measured 1907/1909 flux ratio outside the low-electron density theoretical limit for $^{12}$C. A mixture of $^{13}$C with $^{12}$C helps to close the gap somewhat. Nevertheless, some observed 1907/1909 flux ratios still appear too high to conform to the presently predicted limits. It is shown that this limit, as well as the 1910/1909 flux ratio, are predominantly influenced by using the standard partitioning among the collision strengths for the multiplet $^1S_0$--$^3P_J$ according to the statistical weights. A detailed calculation for the fine structure collision strengths between these individual levels would be valuable.Comment: ApJ accepted: 19 pages, 3 Figures, 2 Table

Neuronal bursting: interactions of the persistent sodium and CAN currents

The pre-Botzinger complex (pBC) is a heterogeneous neuronal network within the mammalian brainstem and has been experimentally found to generate robust, synchronous bursts [1]. Significant modeling research has been conducted on characterizing the dynamics of individual neurons within the pBC. [2, 3] It is well known that the persistent sodium current (INaP) contributes to square-wave bursting seen in the pBC [4]. Recent experimental work within the pBC identified a signaling cascade that starts with presynaptic glutamate and ends with the release of intracellular calcium that activates a nonspecific cationic current (ICAN) [5]. A subsequent model demonstrated that ICAN may contribute to bursts within the pBC that exhibit depolarization block [6]. With these two mechanisms for generating bursts present within the pBC, an open question is how do they combine to generate the robust bursts seen in the network? The present work seeks to analyze the result of including both INaP and ICAN within the same model. We consider the effects of heterogeneity in the conductance gNaP of INaP and the conductance gCAN of ICAN; with this heterogeneity in mind, the model cell may be quiescent, tonically active, have only square-wave bursts, have only depolarization-block exhibiting bursts, or may show both types of bursting. Using the mathematical tools of bifurcation analysis and slow-fast decomposition, we illuminate the mechanisms underlying the transitions of a model cell between the types of dynamics listed above. Our results show that, in cases where gCAN is relatively high, increasing gNaP increases the range of gCAN where the resultant cell has depolarization-block exhibiting bursts. On the other hand, when gCAN is relatively low, increasing gNaP may cause the cell to transition from quiescence, to square wave bursting, to tonic activity, to square wave bursts with high duty cycles, and finally further increase of gNaP causes the cell to again be tonically active. The latter two transitions do not occur if ICAN is absent. The interactions of ICAN and INaP are relevant to many systems beyond the pBC. Individually, ICAN and INaP have been focused on as important to rhythmic burst generation in other systems such as the entorhinal cortex [7]; however, it is likely that both currents are present in these systems. Thus, a detailed account for the interaction of ICAN and INaP may help explain the rhythm generation encountered in other systems beyond the pBC