Ram pressure stripping of the multiphase ISM in the Virgo cluster spiral galaxy NGC 4438

Ram pressure stripping of the multiphase ISM is studied in the perturbed Virgo cluster spiral galaxy NGC 4438. This galaxy underwent a tidal interaction ~100 Myr ago and is now strongly affected by ram pressure stripping. Deep VLA radio continuum observations at 6 and 20 cm are presented. We detect prominent extraplanar emission to the west of the galactic center, which extends twice as far as the other tracers of extraplanar material. The spectral index of the extraplanar emission does not steepen with increasing distance from the galaxy. This implies in situ re-acceleration of relativistic electrons. The comparison with multiwavelength observations shows that the magnetic field and the warm ionized interstellar medium traced by Halpha emission are closely linked. The kinematics of the northern extraplanar Halpha emission, which is ascribed to star formation, follow those of the extraplanar CO emission. In the western and southern extraplanar regions, the Halpha measured velocities are greater than those of the CO lines. We suggest that the ionized gas of this region is excited by ram pressure. The spatial and velocity offsets are consistent with a scenario where the diffuse ionized gas is more efficiently pushed by ram pressure stripping than the neutral gas. We suggest that the recently found radio-deficient regions compared to 24 mum emission are due to this difference in stripping efficiency.Comment: 8 pages, 6 figures, A&A, accepted for publicatio

Pre-peak ram pressure stripping in the Virgo cluster spiral galaxy NGC 4501

VIVA HI observations of the Virgo spiral galaxy NGC 4501 are presented. The HI disk is sharply truncated to the southwest, well within the stellar disk. A region of low surface-density gas, which is more extended than the main HI disk, is discovered northeast of the galaxy center. These data are compared to existing 6cm polarized radio continuum emission, Halpha, and optical broad band images. We observe a coincidence between the western HI and polarized emission edges, on the one hand, and a faint Halpha emission ridge, on the other. The polarized emission maxima are located within the gaps between the spiral arms and the faint Halpha ridge. Based on the comparison of these observations with a sample of dynamical simulations with different values for maximum ram pressure and different inclination angles between the disk and the orbital plane,we conclude that ram pressure stripping can account for the main observed characteristics. NGC 4501 is stripped nearly edge-on, is heading southwest, and is ~200-300 Myr before peak ram pressure, i.e. its closest approach to M87. The southwestern ridge of enhanced gas surface density and enhanced polarized radio-continuum emission is due to ram pressure compression. It is argued that the faint western Halpha emission ridge is induced by nearly edge-on ram pressure stripping. NGC 4501 represents an especially clear example of early stage ram pressure stripping of a large cluster-spiral galaxy.Comment: 22 pages, 25 figures, accepted for publication in A&

The influence of the cluster environment on the large-scale radio continuum emission of 8 Virgo cluster spirals

The influence of the environment on the polarized and total power radio continuum emission of cluster spiral galaxies is investigated. We present deep scaled array VLA 20 and 6 cm observations including polarization of 8 Virgo spiral galaxies. These data are combined with existing optical, HI, and Halpha data. Ram pressure compression leads to sharp edges of the total power distribution at one side of the galactic disk. These edges coincide with HI edges. In edge-on galaxies the extraplanar radio emission can extend further than the HI emission. In the same galaxies asymmetric gradients in the degree of polarization give additional information on the ram pressure wind direction. The local total power emission is not sensitive to the effects of ram pressure. The radio continuum spectrum might flatten in the compressed region only for very strong ram pressure. This implies that neither the local star formation rate nor the turbulent small-scale magnetic field are significantly affected by ram pressure. Ram pressure compression occurs mainly on large scales (>=1 kpc) and is primarily detectable in polarized radio continuum emission.Comment: 16 pages, 10 figures, accepted for publication in A&

Dislocation-mediated growth of bacterial cell walls

Recent experiments have illuminated a remarkable growth mechanism of rod-shaped bacteria: proteins associated with cell wall extension move at constant velocity in circles oriented approximately along the cell circumference (Garner et al., Science (2011), Dominguez-Escobar et al. Science (2011), van Teeffelen et al. PNAS (2011). We view these as dislocations in the partially ordered peptidoglycan structure, activated by glycan strand extension machinery, and study theoretically the dynamics of these interacting defects on the surface of a cylinder. Generation and motion of these interacting defects lead to surprising effects arising from the cylindrical geometry, with important implications for growth. We also discuss how long range elastic interactions and turgor pressure affect the dynamics of the fraction of actively moving dislocations in the bacterial cell wall.Comment: to appear in PNA

Genebank ‐ in vitro propagation of potato and sweetpotato. CIP‐SOP056 V 3.0

This procedure describes the in vitro multiplication of potato and sweetpotato germplasm for international and national germplasm distribution, as well as, in vitro conservation, phytosanitary, and cryopreservation activities

Phase Separation in Binary Fluid Mixtures with Continuously Ramped Temperature

We consider the demixing of a binary fluid mixture, under gravity, which is steadily driven into a two phase region by slowly ramping the temperature. We assume, as a first approximation, that the system remains spatially isothermal, and examine the interplay of two competing nonlinearities. One of these arises because the supersaturation is greatest far from the meniscus, creating inversion of the density which can lead to fluid motion; although isothermal, this is somewhat like the Benard problem (a single-phase fluid heated from below). The other is the intrinsic diffusive instability which results either in nucleation or in spinodal decomposition at large supersaturations. Experimental results on a simple binary mixture show interesting oscillations in heat capacity and optical properties for a wide range of ramp parameters. We argue that these oscillations arise under conditions where both nonlinearities are important

Public Discourses and Politics on Migration: A Precarious Situation and Dismal Outlook?

Emotions dominating normative frameworks is not new in the making of migration-related policies or in public discourses on migration. However, this matter has entered a different dimension in the age of populism and post-factualism reshuffling the parameters of this issue to a large extent. I will argue in this article that we can find a mixture of developments that consecutively reveals a state of public discourses that is highly precarious and that needs change and counteraction. Instead of retreating into welltrodden policy issues and overtly neglecting the potentiality for a constructive discourse that includes the deliberation on migration realties and migratory processes and its complexities, a vision is needed for new evidencebased, well-informed, yet not technocratic, forms of discourse and a future of reflexive knowledge production. Öffentliche Diskurse und Migrationspolitik: Eine prekäre Situation und ein düsterer Ausblick? Die Prägung politischer und öffentlicher Migrationsdiskurse durch Emotionen und Normativität ist nicht neu. Im Zeitalter von Populismus und Post- Faktizität hat diese Prägung jedoch Dimensionen angenommen, die die Parameter dieses Sachverhalts deutlich verschieben. Ich werde in diesem Beitrag verschiedene Entwicklungen diskutieren, die einen öffentlichen Diskurs kenntlich machen, der als hochgradig prekär bezeichnet werden kann und der Änderungen sowie Gegenmaßnahmen benötigt. Anstatt bekannte und veraltete Politiken zu rekurrieren und einen potenziell konstruktiven Diskurs zu vernachlässigen, braucht es Ideen und Visionen einer evidenzbasierten, jedoch nicht technokratischen, Form eines Migrationsdiskurses und einer zukünftigen reflexiven Wissensproduktion

GPS-Derived Precipitable Water Compared with the Air Force Weather Agency\u27s MM5 Model Output

Lightning poses a threat to aircraft in flight. To mitigate this threat, the U.S. Air Force requested a study of lightning distances. Three-Dimensional lightning data were examined for this study, spanning 1 March 1997 to 31 May 2001 and obtained from the Lightning Detection and Ranging System (LDAR) at the Kennedy Space Center, FL. The LDAR data points were first grouped into lightning flashes and branches using spatial and temporal criteria. Rawinsonde data were vertically interpolated to determine the temperature at the flash source point and each branch end point. The horizontal distance from flash sources to branch end was calculated. Percentiles of branch distance were examined as a function of altitude and temperature of the flash source and branch end points. The longest 99th percentile of branch distance (35 to 40 km) was found at 2 to 7 km altitude and between 10 and -20C. The altitude range of the longest branches remained similar by season, but the longest branches were found in the winter and spring months, with summer and autumn distances shorter by 5 to 10 km. Summer results showed longer branch distances to the south and the winter data showed a significant elongation to the north

Rare Parthenogenic Reproduction in a Common Reef Coral, Porites astreoides

Multiple stressors have caused a decline in coral populations. Broadcast spawning corals once dominated the Florida Reef Tract (FRT), but since their decline, smaller brooding corals, soft corals, and macroalgae are replacing them. Brooding corals are more resilient to current threats in part because they are reproductive throughout much of the year and their larvae are competent to settle after release. Despite the ubiquity of brooders on Florida reefs, much of their reproductive strategy remains unknown. This study aimed to examine paternity as a function of colony size and density in Porites astreoides, a common brooding coral in the FRT. Porites astreoides colonies were configured in arrays at three densities that were replicated three times. A focal colony was surrounded by six other colonies, separated from the focal colony at different distances (1m, 7m, and 15m) representing high, moderate, and low population densities, respectively. All arrays were placed in the field but were separated from the reef and naturally occurring P. astreoides colonies by at least 50 m. Four days before the new moon, colonies were transported to the laboratory for larval collection. Over a four day period, a total of 3,184 larvae were collected from 24 colonies, 13 of which released larvae over consecutive days. The resulting larvae were genotyped using seven microsatellite markers. All larvae had the exact genotypes of the colony from which the larvae were collected, i.e. maternal- egg donor. This suggested the larvae were parthenogenically produced and no sperm was used to fertilize the eggs. This is the first study to suggest that parthenogenesis is occurring in P. astreoides. In today\u27s oceans that have been depleted of corals, parthenogenesis may be an advantageous reproductive strategy used to boost populations. However, parthenogenesis reduces the genetic diversity which could hinder successful sexual reproduction in the future causing fragmented populations