A Hundred Comets: The Visual-Wavelength Observations of the Survey of Ensemble Physical Properties of Cometary Nuclei (SEPPCoN)

We present new results from SEPPCoN, a Survey of Ensemble Physical Properties of Cometary Nuclei. This project is currently surveying 100 Jupiter-family comets (JFCs) to measure the mid-infrared thermal emission and visible reflected sunlight of the nuclei. The scientific goal is to determine the distributions of radius, geometric albedo, thermal inertia, axial ratio, and color among the JFC nuclei. In the past we have presented results from the completed mid-IR observations of our sample [1]; here we present preliminary results from ongoing, broadband visible-wavelength observations of nuclei obtained from a variety of ground-based facilities (Mauna Kea, Cerro Pachon, La Silla, La Palma, Apache Point, Table Mtn., and Palomar Mtn.), including contributions from the Near Earth Asteroid Telescope project (NEAT) archive. The nuclei were observed at high heliocentric distance (usually over 4 AU) and so many comets show either no or little contamination from dust coma. While several nuclei have been observed as snapshots, we have multiepoch photometry for many of our targets. With our datasets we are building a large database of photometry, and such a database is essential to the derivation of albedo and shape of a large number of nuclei, and to the understanding of biases in the survey. Support for this work was provided by NSF and the NASA Planetary Astronomy program. Reference: [1] Fernandez, Y.R., et al. 2007, BAAS 39, 827.

On the halogenation of N(1),N(2)-di-t-Boc-5-hydroxy-piperazic acid esters and the conformational preferences of their 5-halo-piperazic acid products. The importance of A1,3 rotameric-strain in determining N(2)-acyl piperazic acid ring conformation

In this Letter, an unambiguous synthetic strategy is reported for the preparation of enantiomerically purecis-5-halo-piperazic acid derivatives in single diastereoisomer form. Contrary to the recent report by Shin and co-workers (Chem. Lett. 2001, 1172), in which it is claimed that the Ph₃P and N-chlorosuccinimide (NCS)-mediated chlorination of (3R,5S)-trans-N(1),N(2)-di-t-Boc-5-hydroxy-piperazic acid derivative 1proceeds with retention of configuration at C(5) to give 2, we now show that this and related Ph₃P-mediated halogenations all occur with S_N2 inversion at the alcohol center, as is customary for such reactions. Specifically, we demonstrate that the (3R,5S)-trans-5-Cl-piperazic acid derivative 2 claimed by Shin and co-workers (Chem. Lett. 2001, 1172) is in actual fact the chlorinated (3S,5R)-enantiomer 6, which must have been prepared from the cis-(3S,5S)-alcohol 3, a molecule whose synthesis is not formally described in the Shin paper. We further show here that the cis-(3R,5R)-5-Cl-Piz 13 claimed by Shin and co-workers inChem. Lett. 2001, 1172, is also (3S,5R)-trans-5-Cl-Piz 6. Authentic 13 has now been synthesized by us, for the very first time, here. Since Lindsley and Kennedy have recently utilized the now invalid Shin and co-workers’ retentive Ph₃P/NCS chlorination procedure on 1 in their synthetic approach to piperazimycin A (Tetrahedron Lett. 2010, 51, 2493), it follows that their claimed 5-Cl-Piz-containing dipeptide 25 probably has the alternate structure 26, where the 5-Cl-Piz residue has a 3,5-cis-configuration. The aforementioned stereochemical misassignments appear to have come from a mix-up of starting materials by Shin and co-workers (Chem. Lett. 2001, 1172), and an under-appreciation of the various steric and conformational effects that operate in N(2)-acylated piperazic acid systems, most especially rotameric A^1,3-strain. The latter has now been unambiguously delineated and defined here under the banner of the A^1,3-rotamer effect.

Anterior thalmic lesions stop immediate early gene activation in selective laminae of the retrosplenial cortex: evidence of covert pathology in rats

Lesions involving the anterior thalamic nuclei stopped immediate early gene (IEG) activity in specific regions of the rat retrosplenial cortex, even though there were no apparent cytoarchitectonic changes. Discrete anterior thalamic lesions were made either by excitotoxin (Experiment 1) or radiofrequency (Experiment 2) and, following recovery, the rats foraged in a radial-arm maze in a novel room. Measurements made 6-12 weeks postsurgery showed that, in comparison with surgical controls, the thalamic lesions produced the same, selective patterns of Fos changes irrespective of method. Granular (caudal granular cortex and rostral granular cortex), but not dysgranular (dysgranular cortex), retrosplenial cortex showed a striking loss of Fos-positive cells. While a loss of between 79 and 89% of Fos-positive cells was found in the superficial laminae, the deeper layers appeared normal. In Experiments 3 and 4, rats 9-10 months postsurgery were placed in an activity box for 30 min. Anterior thalamic lesions (Experiment 3) led to a pronounced IEG decrease of both Fos and zif268 throughout the retrosplenial cortex that now included the dysgranular area. These IEG losses were found even though the same regions appeared normal using standard histological techniques. Lesions of the postrhinal cortex (Experiment 4) did not bring about a loss of retrosplenial IEG activity even though this region is also reciprocally connected with the retrosplenial cortex. This selective effect of anterior thalamic damage upon retrosplenial activity may both amplify the disruptive effects of anterior thalamic lesions and help to explain the posterior cingulate hypoactivity found in Alzheimer's disease.

rbcL sequences indicate a single evolutionary origin of multinucleate cells in the red algal tribe Callithamnieae.

In the Ceramiaceae, one of the largest families of the red algae, there are from 1 to 4000 nuclei in each vegetative cell, but each tribe is homogeneous with respect to the uninucleate/multinucleate character state, except for the Callithamnieae. The goals of this study were to analyze rbcL gene sequences to clarify the evolution of taxa within the tribe Callithamnieae and to evaluate the potential evolutionary significance of the development of multinucleate cells in certain taxa. The genus Aglaothamnion, segregated from Callithamnion because it is uninucleate, was paraphyletic in all analyses. Callithamnion (including Aristothamnion) was monophyletic although not robustly so, apparently due to variations between taxa in rate of sequence evolution. Morphological synapomorphies were identified at different depths in the tree, supporting the molecular phylogenetic analysis. The uninucleate character state is ancestral in this tribe. The evolution of multinucleate cells has occurred once in the Callithamnieae. Multiple nuclei in each cell may combine the benefits of small C values (rapid cell cycle) with large cells (permitting morphological elaboration) while maintaining a constant ratio of nuclear volume: cytoplasmic volume.

Predisposition to arrhythmia and autonomic dysfunction in Nhlh1-deficient mice.

Nhlh1 is a basic helix-loop-helix transcription factor whose expression is restricted to the nervous system and which may play a role in neuronal differentiation. To directly study Nhlh1 function, we generated null mice. Homozygous mutant mice were predisposed to premature, adult-onset, unexpected death. Electrocardiograms revealed decreased total heart rate variability, stress-induced arrhythmia, and impaired baroreceptor sensitivity. This predisposition to arrhythmia is a likely cause of the observed death in the mutant mice. Heterozygosity for the closely related transcription factor Nhlh2 increased the severity of the Nhlh1-null phenotype. No signs of primary cardiac structural or conduction abnormalities could be detected upon necropsy of the null mice. The pattern of altered heart rhythm observed in basal and experimental conditions (stress and pharmacologically induced) suggests that a deficient parasympathetic tone may contribute to the arrhythmia in the Nhlh1-null mouse. The expression of Nhlh1 in the developing brain stem and in the vagal nuclei in the wild-type mouse further supports this hypothesis. The Nhlh1 mutant mouse may thus provide a model to investigate the contribution of the autonomic nervous system to arrhythmogenesis.

The Septin-Binding Protein Anillin is Over-Expressed in Diverse Human Tumours

Anillin is an actin-binding protein that can bind septins and is a component of the cytokinetic ring. We assessed the anillin expression in 7,579 human tissue samples and cell lines by DNA micro-array analysis. Anillin is expressed ubiquitously but with variable levels of expression, being highest in the central nervous system. The median level of anillin mRNA expression was higher in tumors than normal tissues (median fold increase 2.58; 95% confidence intervals, 2.19-5.68, P < 0.0001) except in the central nervous system where anillin in RNA levels were lower in tumors. We developed a sensitive reverse transcription-PCR strategy to show that anillin mRNA is expressed in cell lines and in cDNA panels derived from fetal and adult tissues, thus validating the microarray data. We compared anillin with Ki67 in RNA expression and found a significant linear relationship between anillin and Ki67 mRNA expression (Spearmann r similar to 0.6, P < 0.0001). Anillin mRNA expression was analyzed during tumor progression in breast, ovarian, kidney, colorectal, hepatic, lung, endometrial, and pancreatic tumors and in all tissues there was progressive, increase in anillin mRNA expression from normal to benign to malignant to metastatic disease. Finally, we used anti-anillin sera and found nuclear anillin immuncireactivity to be widespread in normal tissues, often not correlating with proliferative compartments. These data provide insight into the existence of non proliferation-associated activities of anillin and roles in interphase nuclei. Thus, anillin is overexpressed in diverse common human tumors, but not simply as a consequence of being a proliferation marker. Anillin may have potential as a novel biomarker.

Endogenous expression and localization of myostatin and its relation to MHC distribution in C2C12 skeletal muscle cells

Myostatin is a negative regulator of skeletal muscle growth. We have previously reported that recombinant myostatin protein inhibits DNA and protein synthesis in C2C12 cells. Our objective was to assess if C2C12 cells express myostatin, determine its sub-cellular localization and the developmental stage of C2C12 cells in which myostatin mRNA and protein are expressed. To study the endogenous expression of myostatin, C2C12 myoblasts were allowed to progress to myotubes, and changes in the levels of endogenous myostatin mRNA expression were determined by RT-PCR. The myostatin protein and the two major myosin heavy chain (MHC) isoforms (MHC-I and -II) were determined by Western blot. Confirmation of the relative MHC expression patterns was obtained by a modified polyacrylamide gel electropheretic (PAGE) procedure. Imunofluorescence staining was employed to localize the site of myostatin expression and the relative distribution of the MHC isoforms. Co-expression of these proteins was studied using a dual staining approach. Expression of myostatin mRNA was found in myotubes but not in myoblasts. Myostatin protein was seen in most but not all, of the nuclei of polynucleated fibers expressing MHC-II, and myostatin was detected in the cytoplasm of myotube. The localization of myostatin protein in myotube nuclei was confirmed by Western blot of isolated nuclear and cytoplasmic fractions. Incubation of C2C12 myotubes with graded doses of dexamethasone dose-dependently increased the intensity of nuclear myostatin immunostaining and also resulted in the appearance of cytoplasmic expression. In conclusion, myostatin was expressed mostly in C2C12 myotubes nuclei expressing MHC-II. Its predominant

Observations of the interstellar medium in the Magellanic Bridge.

We present ultraviolet and optical spectra of DI 1388, a young star in the Magellanic Bridge, a region of gas between the Small and Large Magellanic Clouds. The data have signal-to-noise ratios of 20-45 and a spectral resolution of 6.5 km s-1. Interstellar absorption by the Magellanic Bridge at vLSR~200 km s-1 is visible in the lines of C I, C II, C II*, C IV, N I, O I, Al II, Si II, Si III, Si IV, S II, Ca II, Fe II, and Ni II. The relative gas-phase abundances of C II, N I, O I, Al II, Si II, Fe II, and Ni II with respect to S II are similar to those found in Galactic halo clouds, despite a significantly lower metallicity in the Magellanic Bridge. The higher ionization species in the cloud have a column density ratio N(C+3)/N(Si+3)~1.9, similar to that inferred for collisionally ionized Galactic cloud interfaces at temperatures ~105 K. We identify substructure in the stronger interstellar lines, with a broad component (FWHM~20 km s-1) at ~179 km s-1 and a sharp component (FWHM~11 km s-1) at 198 km s-1. The abundance analysis for these clouds indicates that the feature at 198 km s-1 consists of a low electron density, mainly neutral gas that may be associated with an interface responsible for the highly ionized gas. The 179 km s-1 cloud consists of warmer, lower density gas that is partially ionized.

High-resolution spectroscopic observations of B-type stars from the Edinburgh-Cape Survey - III. Completion of a magnitude range limited survey

High spectral resolution (R similar to 40 000) and signal-to- noise ratio observations of five high Galactic latitude early- type stars taken from the Edinburgh-Cape (EC) Faint Blue Object Survey are presented. These were required to complete a magnitude range-limited survey of young B-type objects with 11 <V <15. Of the five stars, four were rejected on the grounds that they are either subluminous (subdwarf or horizontal branch), were part of a binary system or possessed colours later than the (U - B) = -0.5 cut-off employed. The remaining star in the data set, EC 19596-5356, is found to exhibit normal young B-type stellar properties. A kinematic analysis reveals that an origin in the Galactic disc appears likely for all the stars in the sample. Some statistics are drawn about the number density of young stars in the Galactic halo.

CCD photometry of distant comets. III - Ensemble properties of Jupiter-family comets

We describe the results of a ground-based observational "snapshot" study of Jupiter-family comets in the heliocentric range 2.29 AU less than or equal to R-h less than or equal to 5.72 AU. Results are presented based on observations from the 1m JKT on the island of La Palma. A total of 25 comets were targeted with 15 being positively detected. Broad-band VRI photometry was performed to determine dimensions, colour indices, and dust production rates in terms of the "A frho" formalism. The results for selected comets are compared with previous investigations. Ensemble properties of the Jupiter- family population have been investigated by combining the results presented here with those of Lowry et al. (1999), and Lowry & Fitzsimmons (2001). We find that the cumulative size distribution of the Jupiter-family comets can be described by a power law of the form; Sigma(> r) proportional to r(-1.6+/- 0.1). This size distribution is considerably shallower than that found for the observed Edgeworth-Kuiper belt objects, which may reflect either an intrinsic difference at small km- sizes in the belt, or the various processes affecting the nuclei of comets as their orbits evolve from the Edgeworth- Kuiper belt to the inner Solar system. Also, there would appear to be no correlation between nuclear absolute magnitude and perihelion distance. Finally, for the sample of active comets, there is a distinct correlation between absolute R band magnitude and perihelion distance, which can be explained by either a discovery bias towards brighter comets or in terms of "rubble" mantle formation.

The extreme-ultraviolet structure and properties of a newly emerged active region

The structure and properties of a newly emerged solar active region (NOAA Active Region 7985) are discussed using the Coronal Diagnostic Spectrometer (CDS) and the Extreme- Ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory. CDS obtained high-resolution EUV spectra in the 308-381 Angstrom and 513-633 Angstrom wavelength ranges, while EIT recorded full-disk EUV images in the He II (304 Angstrom), Fe IX/X (171 Angstrom), Fe xii (195 Angstrom), and Fe XV (284 Angstrom) bandpasses. Electron density measurements from Si rx, Si X, Fe xii, Fe XIII, and Fe xiv line ratios indicate that the region consists of a central high- density core with peak densities of the order of 1.2 x 10(10) cm(-3), which decrease monotonically to similar to5.0 X 10(8) cm(-3) at the active region boundary. The derived electron densities also vary systematically with temperature. Electron pressures as a function of both active region position and temperature were estimated using the derived electron densities and ion formation temperatures, and the constant pressure assumption was found to be an unrealistic simplification. Indeed, the active region is found to have a high-pressure core (1.3 x 10(16) cm(-3) K) that falls to 6.0 x 10(14) cm(-3) K just outside the region. CDS line ratios from different ionization stages of iron, specifically Fe xvi (335.4 Angstrom) and Fe xiv (334.4 Angstrom), were used to diagnose plasma temperatures within the active region. Using this method, peak temperatures of 2.1 x 10(6) K were identified. This is in good agreement with electron temperatures derived using EIT filter ratios and the two-temperature model of Zhang et al. The high- temperature emission is confined to the active region core, while emission from cooler (1-1.6) x 10(6) K lines originates in a system of loops visible in EIT 171 and 195 X images. Finally, the three-dimensional geometry of the active region is investigated using potential field extrapolations from a Kitt Peak magnetogram. The combination of EUV and magnetic field extrapolations extends the "core-halo" picture of active region structure to one in which the core is composed of a number of compact coronal loops that confine the hot, dense, high- pressure core plasma while the halo emission emerges from a system of cooler and more extended loops.

Model atmosphere and kinematical analyses of early-type stars from the Edinburgh-Cape Survey

We present high-resolution spectroscopic observations of 21 B- type stars, selected from the Edinburgh-Cape Blue Object Survey. Model atmosphere analyses confirm that 14 of these stars are young, main-sequence B-type objects with Population I chemical compositions. The remaining seven are found to be evolved objects, including subdwarfs, horizontal branch and post-AGB objects. A kinematical analysis shows that all 14 young main-sequence stars could have formed in the disc and subsequently been ejected into the halo. These results are combined with the analysis of a previous subsample of stars taken from the Survey. Of the complete sample, 31 have been found to be young, main-sequence objects, with formation in the disc, and subsequent ejection into the halo, again being found to be a plausible scenario.

Multiwavelength observations of the M15 intermediate-velocity cloud

We present Westerbork Synthesis Radio Telescope HI images, Lovell telescope multibeam H I wide-field mapping, William Herschel Telescope long-slit echelle Ca II observations, Wisconsin Halpha Mapper (WHAM) facility images, and IRAS ISSA 60- and 100-mum co-added images towards the intermediate- velocity cloud (IVC) at + 70 km s(-1), located in the general direction of the M15 globular cluster. When combined with previously published Arecibo data, the H I gas in the IVC is found to be clumpy, with a peak H I column density of similar to1.5 x 10(20) cm(-2), inferred volume density (assuming spherical symmetry) of similar to24 cm(-3)/D (kpc) and a maximum brightness temperature at a resolution of 81 x 14 arcsec(2) of 14 K. The major axis of this part of the IVC lies approximately parallel to the Galactic plane, as does the low- velocity H I gas and IRAS emission. The H I gas in the cloud is warm, with a minimum value of the full width at half-maximum velocity width of 5 km s(-1) corresponding to a kinetic temperature, in the absence of turbulence, of similar to540 K. From the H I data, there are indications of two-component velocity structure. Similarly, the Ca II spectra, of resolution 7 km s(-1), also show tentative evidence of velocity structure, perhaps indicative of cloudlets. Assuming that there are no unresolved narrow-velocity components, the mean values of log(10)[N(Ca II K) cm(2)] similar to 12.0 and Ca II/H I similar to2 5 x 10(-8) are typical of observations of high Galactic latitude clouds. This compares with a value of Ca II/H I>10(-6) for IVC absorption towards HD 203664, a halo star of distance 3 kpc, some 3.degrees1 from the main M15 IVC condensation. The main IVC condensation is detected by WHAM in Halpha with central local-standard-of-rest velocities of similar to60-70 km s(-1), and intensities uncorrected for Galactic extinction of up to 1.3 R, indicating that the gas is partially ionized. The FWHM values of the Halpha IVC component, at a resolution of 1degrees, exceed 30 km s(-1). This is some 10 km s(-1) larger than the corresponding H I value at a similar resolution, and indicates that the two components may not be mixed. However, the spatial and velocity coincidence of the Halpha and H I peaks in emission towards the main IVC component is qualitatively good. If the Halpha emission is caused solely by photoionization, the Lyman continuum flux towards the main IVC condensation is similar to2.7 x 10(6) photon cm(-2) s(-1). There is not a corresponding IVC Halpha detection towards the halo star HD 203664 at velocities exceeding similar to60 km s(- 1). Finally, both the 60- and 100-mum IRAS images show spatial coincidence, over a 0.675 x 0 625 deg(2) field, with both low- and intermediate-velocity H I gas (previously observed with the Arecibo telescope), indicating that the IVC may contain dust. Both the Halpha and tentative IRAS detections discriminate this IVC from high-velocity clouds, although the H I properties do not. When combined with the H I and optical results, these data point to a Galactic origin for at least parts of this IVC.

HI and optical spectroscopy towards the M15 intermediate- velocity cloud

We present single-dish Arecibo 21-cm H i observations, covering a 0 degrees 675x0 degrees 625 RA-Dec. grid, of the intermediate-velocity cloud (IVC) centred upon the M15 globular cluster. The velocity and positional structure of the IVC gas at V-LSR=70 km s(-1) are investigated; it is found to be clumpy and has a peak surface density N(H i)similar to 8x10(19) cm(- 2). Additionally, we have performed a long H i integration towards HD 203664, a Galactic halo star some 3 degrees1 from M15, in which optical IVC absorption has previously been detected. No H i with a velocity exceeding 60 km s(-1) was found to a brightness temperature limit of 0.05 K. However, additional pointings did detect IVC gas approximately mid-way between HD 203664 and M15. Finally, we present both Arecibo H i pointings and low-resolution spectra in the Ca ii H and K lines towards 15 field stars in the general field towards M15, in an attempt to obtain the distance to the IVC. Intermediate- velocity H i is detected towards seven sightlines. Stellar spectral types are derived for 12 of the sample. Assuming that these stars lie on the main sequence, their distances are estimated to lie in the range 150 less than or equal tod less than or equal to 1350 pc. No Ca ii absorption is observed, either because the IVC is further away than similar to 1350 pc or more likely because the gas along these sightlines is of too low a density to be detected by the current observations.

Boron abundances in B-type stars: A test of rotational depletion during main-sequence evolution

Boron abundances have been derived for seven main-sequence B- type stars from Hubble Space Telescope STIS spectra around the B III lambda2066 line. In two stars, boron appears to be undepleted with respect to the presumed initial abundance. In one star, boron is detectable but is clearly depleted. In the other four stars, boron is undetectable, implying depletions of 1-2 dex. Three of these four stars are nitrogen enriched, but the fourth shows no enrichment of nitrogen. Only rotationally induced mixing predicts that boron depletions are unaccompanied by nitrogen enrichments. The inferred rate of boron depletion from our observations is in good agreement with these predictions. Other boron-depleted nitrogen-normal stars are identified from the literature. In addition, several boron- depleted nitrogen-rich stars are identified, and while all fall on the boron-nitrogen trend predicted by rotationally induced mixing, a majority have nitrogen enrichments that are not uniquely explained by rotation. The spectra have also been used to determine iron group (Cr, Mn, Fe, and Ni) abundances. The seven B-type stars have near-solar iron group abundances, as expected for young stars in the solar neighborhood. We have also analyzed the halo B-type star PG 0832 + 676. We find [Fe/H] = -0.88 +/- 0.10, and the absence of the B III line gives the upper limit [B/H] <-2.5. These and other published abundances are used to infer the star's evolutionary status as a post-asymptotic giant branch star.