Laboratory millimeter and submillimeter spectrum of HOC^+

The J = 1→2, 2→3, and 3→4 rotational transitions of the molecular ion HOC^+ have been measured in the laboratory at frequencies from 178 to 358 GHz. The data should permit astronomers to confirm the recent possible sighting of the J = 1→0 transition of HOC^+ in Sgr B2 at 89.5 GHz

The laboratory millimeter-wave spectrum of methyl formate in its ground torsional E state

Over 250 rotational transitions of the internal rotor methyl formate (HCOOCH_3) in its ground v_t = 0 degenerate (E) torsional substate have been measured in the millimeter-wave spectral region. These data and a number of E-state lines identified by several other workers have been analyzed using an extension of the classical principal-axis method in the high barrier limit. The resulting rotational constants allow accurate prediction of the v_t = 0 E substate methyl formate spectrum below 300 GHz between states with angular momentum J ≤ 30 and rotational energy E_(rot)≤ 350cm^(-1). The calculated transition frequencies for the E state, when combined with the results of the previous analysis of the ground-symmetric, nondegenerate state, account for over 200 of the emission lines observed toward Orion in a recent survey of the 215-265 GHz band

Steps towards a map of the nearby universe

We present a new analysis of the Sloan Digital Sky Survey data aimed at producing a detailed map of the nearby (z < 0.5) universe. Using neural networks trained on the available spectroscopic base of knowledge we derived distance estimates for about 30 million galaxies distributed over ca. 8,000 sq. deg. We also used unsupervised clustering tools developed in the framework of the VO-Tech project, to investigate the possibility to understand the nature of each object present in the field and, in particular, to produce a list of candidate AGNs and QSOs.Comment: 3 pages, 1 figure. To appear in Nucl Phys. B, in the proceedings of the NOW-2006 (Neutrino Oscillation Workshop - 2006), R. Fogli et al. ed

Effects of mixing on evolution of hydrocarbon ratios in the troposphere

Nonmethane hydrocarbon (NMHC) concentration ratios provide useful indicators of tropospheric oxidation and transport processes. However, the influences of both photochemical and mixing processes are inextricably linked in the evolution of these ratios. We present a model for investigating these influences by combining the transport treatment of the Lagrangian particle dispersion model FLEXPART with an ultrasimple (i.e., constant OH concentration) chemical treatment. Required model input includes NMHC emission ratios, but not ad hoc assumed background NMHC concentrations. The model results give NMHC relationships that can be directly compared, in a statistical manner, with measurements. The measured concentration ratios of the longest-lived alkanes show strong deviations from purely kinetic behavior, which the model nicely reproduces. In contrast, some measured aromatic ratio relationships show even stronger deviations that are not well reproduced by the model for reasons that are not understood. The model-measurement comparisons indicate that the interaction of mixing and photochemical processing prevent a simple interpretation of "photochemical age," but that the average age of any particular NMHC can be well defined and can be approximated by a properly chosen and interpreted NMHC ratio. In summary, the relationships of NMHC concentration ratios not only yield useful measures of photochemical processing in the troposphere, but also provide useful test of the treatment of mixing and chemical processing in chemical transport models. Copyright 2007 by the American Geophysical Union

The millimeter and submillimeter laboratory spectrum of methyl formate in its ground symmetric torsional state

Over 200 rotational lines of methyl formate in its ground (v-t = 0), symmetric (A) torsional state have been measured in the frequency range 140-550 GHz. Analysis of these and lower frequency transitions permits accurate prediction (≤0.1 MHz) of over 10,000 transitions at frequencies below 600 GHz with angular momentum J ≤ 50. The measured spectral lines have permitted identification of over 100 new methyl formate lines in Orion

Water production in comet 81P/Wild 2 as determined by Herschel/HIFI

The high spectral resolution and sensitivity of Herschel/HIFI allows for the detection of multiple rotational water lines and accurate determinations of water production rates in comets. In this Letter we present HIFI observations of the fundamental 1_(10)–1_(01) (557 GHz) ortho and 1_(11)–0_(00) (1113 GHz) para rotational transitions of water in comet 81P/Wild 2 acquired in February 2010. We mapped the extent of the water line emission with five point scans. Line profiles are computed using excitation models which include excitation by collisions with electrons and neutrals and solar infrared radiation. We derive a mean water production rate of 1.0 × 10^(28) molecules s^(−1) at a heliocentric distance of 1.61 AU about 20 days before perihelion, in agreement with production rates measured from the ground using observations of the 18-cm OH lines. Furthermore, we constrain the electron density profile and gas kinetic temperature, and estimate the coma expansion velocity by fitting the water line shapes

Spatially Resolved Spectroscopy of the E+A Galaxies in the z=0.32 Cluster AC114

We present spatially resolved intermediate resolution spectroscopy of a sample of twelve E+A galaxies in the z=0.32 rich galaxy cluster AC 114, obtained with the FLAMES multi-integral field unit system on the European Southern Observatory's VLT. Previous integrated spectroscopy of all these galaxies by Couch & Sharples (1987) had shown them to have strong Balmer line absorption and an absence of [OII 3727] emission -- the defining characteristics of the``E+A'' spectral signature, indicative of an abrupt halt to a recent episode of quite vigorous star formation. We have used our spectral data to determine the radial variation in the strength of Hdelta absorption in these galaxies and hence map out the distribution of this recently formed stellar population. Such information provides important clues as to what physical event might have been responsible for this quite dramatic change in star formation activity in these galaxies' recent past. We find a diversity of behaviour amongst these galaxies in terms of the radial variation in Hdelta absorption: Four galaxies show little Hdelta absorption across their entire extent; it would appear they were misidentified as E+A galaxies in the earlier integrated spectroscopic studies. The remainder show strong Hdelta absorption, with a gradient that is either negative (Hdelta equivalent width decreasing with radius), flat, or positive. By comparing with numerical simulations we suggest that the first of these different types of radial behaviour provides evidence for a merger/interaction origin, whereas the latter two types of behaviour are more consistent with the truncation of star formation in normal disk galaxies. It would seem therefore that more than one physical mechanism is responsible for E+A formation in the same environment.Comment: 15 pages, 10 figures, accepted MNRA

Spreading Dynamics of Polymer Nanodroplets

The spreading of polymer droplets is studied using molecular dynamics simulations. To study the dynamics of both the precursor foot and the bulk droplet, large drops of ~200,000 monomers are simulated using a bead-spring model for polymers of chain length 10, 20, and 40 monomers per chain. We compare spreading on flat and atomistic surfaces, chain length effects, and different applications of the Langevin and dissipative particle dynamics thermostats. We find diffusive behavior for the precursor foot and good agreement with the molecular kinetic model of droplet spreading using both flat and atomistic surfaces. Despite the large system size and long simulation time relative to previous simulations, we find no evidence of hydrodynamic behavior in the spreading droplet.Comment: Physical Review E 11 pages 10 figure

HID-1 controls formation of large dense core vesicles by influencing cargo sorting and trans-Golgi network acidification

Large dense core vesicles (LDCVs) mediate the regulated release of neuropeptides and peptide hormones. They form at the trans-Golgi network (TGN), where their soluble content aggregates to form a dense core, but the mechanisms controlling biogenesis are still not completely understood. Recent studies have implicated the peripheral membrane protein HID-1 in neuropeptide sorting and insulin secretion. Using CRISPR/Cas9, we generated HID-1 KO rat neuroendocrine cells, and we show that the absence of HID-1 results in specific defects in peptide hormone and monoamine storage and regulated secretion. Loss of HID-1 causes a reduction in the number of LDCVs and affects their morphology and biochemical properties, due to impaired cargo sorting and dense core formation. HID-1 KO cells also exhibit defects in TGN acidification together with mislocalization of the Golgi-enriched vacuolar H+-ATPase subunit isoform a2. We propose that HID-1 influences early steps in LDCV formation by controlling dense core formation at the TGN.</jats:p