PHOTOPERIOD EFFECTS ON 2N POLLEN PRODUCTION, RESPONSE TO ANTHER CULTURE, AND NET PHOTOSYNTHESIS OF A DIPLANDROUS CLONE OF SOLANUM PHUREJA

Flow-cytometric analysis of pollen samples obtained from Solanum phureja, clone PP5, grown under 10, 14, and 18 hour photoperiods at the Southeastern Plant Environment Laboratories of North Carolina State University yielded two populations of pollen based on size parameters. These populations corresponded to pollen separation based on propidium iodide staining of DNA. Anther culture response from plants grown under 14 and 18 hour photo periods for 8, I 0, 12, and 14 weeks was greatest from 8 week old plants grown under a 14 hour photoperiod. Net photosynthesis was significantly higher for plants grown under a 10 hour photoperiod than for plants grown under either a 14, or 18 hour photoperiod. A significant positive correlation was found between net photosynthesis and tuber yield. Results suggest that vegetative growth is increased under short photoperiods, floral development is favored under long photoperiods, and androgenesis is greatest from young plants grown under an intermediate photoperiod

Variability for Critical Photoperiod for Tuberization and Tuber Yield Among Monoploid, Anther-derived Genotypes of Solanum phureja

Monoploid genotypes (2n = x = 12), derived by anther culture of a diplandrous (2n pollen-producing) clone of Solanum phureja Juz. & Buk., a South American diploid potato species, were examined for their use in germplasm development. Nine monoploid genotypes and the anther-donor genotype were grown in three chambers (10-, 14-, and 18-hr daylengths) to examine the effect of photoperiod on tuber yield and to determine the variability for critical photoperiod for tuberization. Significant differences were found among the monoploid genotypes for tuber weight and tuber number. Longer photoperiod treatments decreased and delayed tuberization. Axillary tuber formation from single-node cuttings was used to estimate the onset of tuber induction and demonstrated variability among monoploid genotypes for critical photoperiod for tuberization

PHOTOPERIOD EFFECTS ON 2N POLLEN PRODUCTION, RESPONSE TO ANTHER CULTURE, AND NET PHOTOSYNTHESIS OF A DIPLANDROUS CLONE OF SOLANUM PHUREJA

Flow-cytometric analysis of pollen samples obtained from Solanum phureja, clone PP5, grown under 10, 14, and 18 hour photoperiods at the Southeastern Plant Environment Laboratories of North Carolina State University yielded two populations of pollen based on size parameters. These populations corresponded to pollen separation based on propidium iodide staining of DNA. Anther culture response from plants grown under 14 and 18 hour photo periods for 8, I 0, 12, and 14 weeks was greatest from 8 week old plants grown under a 14 hour photoperiod. Net photosynthesis was significantly higher for plants grown under a 10 hour photoperiod than for plants grown under either a 14, or 18 hour photoperiod. A significant positive correlation was found between net photosynthesis and tuber yield. Results suggest that vegetative growth is increased under short photoperiods, floral development is favored under long photoperiods, and androgenesis is greatest from young plants grown under an intermediate photoperiod

Impaired interferon-γ responses, increased interleukin-17 expression, and a tumor necrosis factor–α transcriptional program in invasive aspergillosis

This article is available open access through the publisher’s website. Copyright @ 2009 Oxford University Press.Background - Invasive aspergillosis (IA) is the most common cause of death associated with fungal infection in the developed world. Historically, susceptibility to IA has been associated with prolonged neutropenia; however, IA has now become a major problem in patients on calcineurin inhibitors and allogenic hematopoetic stem cell transplant patients following engraftment. These observations suggest complex cellular mechanisms govern immunity to IA. Methods - To characterize the key early events that govern outcome from infection with Aspergillus fumigatus we performed a comparative immunochip microarray analysis of the pulmonary transcriptional response to IA between cyclophosphamide-treated mice and immunocompetent mice at 24 h after infection. Results - We demonstrate that death due to infection is associated with a failure to generate an incremental interferon-γ response, increased levels of interleukin-5 and interleukin-17a transcript, coordinated expression of a network of tumor necrosis factor–α-related genes, and increased levels of tumor necrosis factor–α. In contrast, clearance of infection is associated with increased expression of a number genes encoding proteins involved in innate pathogen clearance, as well as apoptosis and control of inflammation. Conclusion - This first organ-level immune response transcriptional analysis for IA has enabled us to gain new insights into the mechanisms that govern fungal immunity in the lung.The BBSRC, CGD Research Trust, and the MRC

The complex network of global cargo ship movements

Transportation networks play a crucial role in human mobility, the exchange of goods, and the spread of invasive species. With 90% of world trade carried by sea, the global network of merchant ships provides one of the most important modes of transportation. Here we use information about the itineraries of 16,363 cargo ships during the year 2007 to construct a network of links between ports. We show that the network has several features which set it apart from other transportation networks. In particular, most ships can be classified in three categories: bulk dry carriers, container ships and oil tankers. These three categories do not only differ in the ships' physical characteristics, but also in their mobility patterns and networks. Container ships follow regularly repeating paths whereas bulk dry carriers and oil tankers move less predictably between ports. The network of all ship movements possesses a heavy-tailed distribution for the connectivity of ports and for the loads transported on the links with systematic differences between ship types. The data analyzed in this paper improve current assumptions based on gravity models of ship movements, an important step towards understanding patterns of global trade and bioinvasion.Comment: 7 figures Accepted for publication by Journal of the Royal Society Interface (2010) For supplementary information, see http://www.icbm.de/~blasius/publications.htm

Glass Polymorphism in TIP4P/2005 Water: A Description Based on the Potential Energy Landscape Formalism

The potential energy landscape (PEL) formalism is a statistical mechanical approach to describe supercooled liquids and glasses. Here we use the PEL formalism to study the pressure-induced transformations between low-density amorphous ice (LDA) and high-density amorphous ice (HDA) using computer simulations of the TIP4P/2005 molecular model of water. We find that the properties of the PEL sampled by the system during the LDA-HDA transformation exhibit anomalous behavior. In particular, at conditions where the change in density during the LDA-HDA transformation is approximately discontinuous, reminiscent of a first-order phase transition, we find that (i) the inherent structure (IS) energy, $e_\text{IS}(V)$, is a concave function of the volume, and (ii) the IS pressure, $P_\text{IS}(V)$, exhibits a van der Waals-like loop. In addition, the curvature of the PEL at the IS is anomalous, a non-monotonic function of $V$. In agreement with previous studies, our work suggests that conditions (i) and (ii) are necessary (but not sufficient) signatures of the PEL for the LDA-HDA transformation to be reminiscent of a first-order phase transition. We also find that one can identify two different regions of the PEL, one associated to LDA and another to HDA. Our computer simulations are performed using a wide range of compression/decompression and cooling rates. In particular, our slowest cooling rate (0.01 K/ns) is within the experimental rates employed in hyperquenching experiments to produce LDA. Interestingly, the LDA-HDA transformation pressure that we obtain at $T=80$ K and at different rates extrapolates remarkably well to the corresponding experimental pressure.Comment: Manuscript and Supplementary Materia

The representation of abstract task rules in the human prefrontal cortex

We have previously reported sustained activation in the ventral prefrontal cortex while participants prepared to perform 1 of 2 tasks as instructed. But there are studies that have reported activation reflecting task rules elsewhere in prefrontal cortex, and this is true in particular when it was left to the participants to decide which rule to obey. The aim of the present experiment was to use functional magnetic resonance imaging (fMRI) to find whether there was activation in common, irrespective of the way that the task rules were established. On each trial, we presented a word after a variable delay, and participants had to decide either whether the word was abstract or concrete or whether it had 2 syllables. The participants either decided before the delay which task they would perform or were instructed by written cues. Comparing the self-generated with the instructed trials, there was early task set activation during the delay in the middle frontal gyrus. On the other hand, a conjunction analysis revealed sustained activation in the ventral prefrontal and polar cortex for both conditions. We argue that the ventral prefrontal cortex is specialized for handling conditional rules regardless of how the task rules were established

Two-Stream Instability of Counter-Rotating Galaxies

The present study of the two-stream instability in stellar disks with counter-rotating components of stars and/or gas is stimulated by recently discovered counter-rotating spiral and S0 galaxies. Strong linear two-stream instability of tightly-wrapped spiral waves is found for one and two-armed waves with the pattern angular speed of the unstable waves always intermediate between the angular speed of the co-rotating matter ($+\Omega$) and that of the counter-rotating matter ($-\Omega$). The instability arises from the interaction of positive and negative energy modes in the co- and counter-rotating components. The unstable waves are in general convective - they move in radius and radial wavenumber space - with the result that amplification of the advected wave is more important than the local growth rate. For a galaxy of co-rotating stars and counter-rotating stars of mass-fraction $\xi_* < {1\over 2}$, or of counter-rotating gas of mass-fraction $\xi_g < {1\over 2}$, the largest amplification is usually for the one-armed leading waves (with respect to the co-rotating stars). For the case of both counter-rotating stars and gas, the largest amplifications are for $\xi_*+\xi_g \approx {1\over 2}$, also for one-armed leading waves. The two-armed trailing waves usually have smaller amplifications. The growth rates and amplifications all decrease as the velocity spreads of the stars and/or gas increase. It is suggested that the spiral waves can provide an effective viscosity for the gas causing its accretion.Comment: 14 pages, submitted to ApJ. One table and 17 figures can be obtained by sending address to R. Lovelace at [email protected]

A Catalog of Very Isolated Galaxies from the SDSS Data Release 1

We present a new catalog of isolated galaxies obtained through an automated systematic search. These 2980 isolated galaxies were found in approximately 2099 sq deg of sky in the Sloan Digital Sky Survey Data Release 1 (SDSS DR1) photometry. The selection algorithm, implementing a variation on the criteria developed by Karachentseva in 1973, proved to be very efficient and fast. This catalog will be useful for studies of the general galaxy characteristics. Here we report on our results.Comment: 67 pages, which includes 14 figures. Accepted for publication by A

Global periodicity conditions for maps and recurrences via Normal Forms

We face the problem of characterizing the periodic cases in parametric families of (real or complex) rational diffeomorphisms having a fixed point. Our approach relies on the Normal Form Theory, to obtain necessary conditions for the existence of a formal linearization of the map, and on the introduction of a suitable rational parametrization of the parameters of the family. Using these tools we can find a finite set of values p for which the map can be p-periodic, reducing the problem of finding the parameters for which the periodic cases appear to simple computations. We apply our results to several two and three dimensional classes of polynomial or rational maps. In particular we find the global periodic cases for several Lyness type recurrences.Comment: 25 page