Fluid Flow Thermometry Using Thermographic Phosphors

Phosphor thermometry is a non-intrusive thermometry technique that allows for spatially and temporally resolved surface temperature measurements. The thermographic method has been employed in a number of applications that include combustion, sprays, and gas flows. In the current work, we investigate the implementation of thermographic phosphors in liquid flows, which is of interest in a wide range of applications in heat transfer, fluid mechanics, and thermal systems. Zinc oxide doped with Zinc (ZnO:Zn) was the phosphor employed for experimentation due to its high emission intensity and insolubility. In order to explore this application, the phosphor powder was uniformly dispersed in water using a magnetic stirring rod. The phosphor was excited by the third harmonic 355 nm output of a Nd:YAG laser, and the luminescence was examined using a fiber-coupled spectrometer. Analysis of the spectral data showed a significant redshift as the temperature approached boiling point. Further characterization of effects of temperature and experimental parameters such as ZnO:Zn concentration on the luminescence signal was performed

Canonical Analysis of the Jackiw-Teitelboim Model in the Temporal Gauge. I. The Classical Theory

As a preparation for its quantization in the loop formalism, the 2-dimensional gravitation model of Jackiw and Teitelboim is analysed in the classical canonical formalism. The dynamics is of pure constraints as it is well-known. A partial gauge fixing of the temporal type being performed, the resulting second class constraints are sorted out and the corresponding Dirac bracket algebra is worked out. Dirac observables of this classical theory are then calculated.Comment: 15 pages, Latex. Misprint correction

Libration-induced Orbit Period Variations Following the DART Impact

The Double Asteroid Redirection Test (DART) mission will be the first test of a kinetic impactor as a means of planetary defense. In late 2022, DART will collide with Dimorphos, the secondary in the Didymos binary asteroid system. The impact will cause a momentum transfer from the spacecraft to the binary asteroid, changing the orbit period of Dimorphos and forcing it to librate in its orbit. Owing to the coupled dynamics in binary asteroid systems, the orbit and libration state of Dimorphos are intertwined. Thus, as the secondary librates, it also experiences fluctuations in its orbit period. These variations in the orbit period are dependent on the magnitude of the impact perturbation, as well as the system’s state at impact and the moments of inertia of the secondary. In general, any binary asteroid system whose secondary is librating will have a nonconstant orbit period on account of the secondary’s fluctuating spin rate. The orbit period variations are typically driven by two modes: a long period and a short period, each with significant amplitudes on the order of tens of seconds to several minutes. The fluctuating orbit period offers both a challenge and an opportunity in the context of the DART mission. Orbit period oscillations will make determining the post-impact orbit period more difficult but can also provide information about the system’s libration state and the DART impact

Momentum transfer from the DART mission kinetic impact on asteroid Dimorphos

The NASA Double Asteroid Redirection Test (DART) mission performed a kinetic impact on asteroid Dimorphos, the satellite of the binary asteroid (65803) Didymos, at 23:14 UTC on 26 September 2022 as a planetary defence test1. DART was the first hypervelocity impact experiment on an asteroid at size and velocity scales relevant to planetary defence, intended to validate kinetic impact as a means of asteroid deflection. Here we report a determination of the momentum transferred to an asteroid by kinetic impact. On the basis of the change in the binary orbit period2, we find an instantaneous reduction in Dimorphos’s along-track orbital velocity component of 2.70 ± 0.10 mm s−1, indicating enhanced momentum transfer due to recoil from ejecta streams produced by the impact3,4. For a Dimorphos bulk density range of 1,500 to 3,300 kg m−3, we find that the expected value of the momentum enhancement factor, β, ranges between 2.2 and 4.9, depending on the mass of Dimorphos. If Dimorphos and Didymos are assumed to have equal densities of 2,400 kg m−3, β=3.61+0.19−0.25(1σ). These β values indicate that substantially more momentum was transferred to Dimorphos from the escaping impact ejecta than was incident with DART. Therefore, the DART kinetic impact was highly effective in deflecting the asteroid Dimorphos

New insights into the classification and nomenclature of cortical GABAergic interneurons.

A systematic classification and accepted nomenclature of neuron types is much needed but is currently lacking. This article describes a possible taxonomical solution for classifying GABAergic interneurons of the cerebral cortex based on a novel, web-based interactive system that allows experts to classify neurons with pre-determined criteria. Using Bayesian analysis and clustering algorithms on the resulting data, we investigated the suitability of several anatomical terms and neuron names for cortical GABAergic interneurons. Moreover, we show that supervised classification models could automatically categorize interneurons in agreement with experts' assignments. These results demonstrate a practical and objective approach to the naming, characterization and classification of neurons based on community consensus

Ionized Gas in the Smith Cloud

We present WHAM observations of Halpha, [N II], and [S II] in the Smith Cloud. A map of Halpha emission from the cloud shows ionized gas coincident with the brightest H I emission, but nearly-as-bright Halpha in some regions with faint H I. The ionized mass of the cloud is at least as large as the neutral mass, > 10^6 M_sun. Ionized gas in the core of the Smith Cloud has an electron temperature 6000 K < T < 16000 K. The observed ratio [N II] / Halpha = 0.39 \pm 0.09 shows that the cloud has a non-primordial nitrogen abundance, 0.1 - 1 times solar.Comment: 4 pages, 2 figures. To appear in the proceedings of "The Role of Disk-Halo Interaction in Galaxy Evolution: Outflow vs Infall?", EAS Publication Serie

EPR analysis of multiple forms of [4Fe–4S] 3+ clusters in HiPIPs

The electron paramagnetic resonance (EPR) spectrum from the [4Fe–4S] 3+ cluster in several high-potential iron–sulfur proteins (HiPIPs) is complex: it is not the pattern of a single, isolated S =1/2 system. Multifrequency EPR from 9 to 130 GHz reveals that the apparent peak positions ( g values) are frequency-independent: the spectrum is dominated by the Zeeman interaction plus g -strain broadening. The spectra taken at frequencies above the X-band are increasingly sensitive to rapid-passage effects; therefore, the X-band data, which are slightly additionally broadened by dipolar interaction, were used for quantitative spectral analysis. For a single geometrical [4Fe–4S] 3+ structure the (Fe–Fe) 5+ mixed-valence dimer can be assigned in six different ways to a pair of iron ions, and this defines six valence isomers. Systematic multicomponent g -strain simulation shows that the [4Fe–4S] 3+ paramagnets in seven HiPIPs from different bacteria each consist of three to four discernible species, and these are assigned to valence isomers of the clusters. This interpretation builds on previous EPR analyzes of [4Fe–4S] 3+ model compounds, and it constitutes a high-resolution extension of the current literature model, proposed from paramagnetic NMR studies.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47867/1/775_2005_Article_656.pd

Bridging Alone: Religious Conservatism, Marital Homogamy, and Voluntary Association Membership

This study characterizes social insularity of religiously conservative American married couples by examining patterns of voluntary associationmembership. Constructing a dataset of 3938 marital dyads from the second wave of the National Survey of Families and Households, the author investigates whether conservative religious homogamy encourages membership in religious voluntary groups and discourages membership in secular voluntary groups. Results indicate that couples’ shared affiliation with conservative denominations, paired with beliefs in biblical authority and inerrancy, increases the likelihood of religious group membership for husbands and wives and reduces the likelihood of secular group membership for wives, but not for husbands. The social insularity of conservative religious groups appears to be reinforced by homogamy—particularly by wives who share faith with husbands