Fringe Science: Defringing CCD Images with Neon Lamp Flat Fields

Fringing in CCD images is troublesome from the aspect of photometric quality and image flatness in the final reduced product. Additionally, defringing during calibration requires the inefficient use of time during the night to collect and produce a "supersky" fringe frame. The fringe pattern observed in a CCD image for a given near-IR filter is dominated by small thickness variations across the detector with a second order effect caused by the wavelength extent of the emission lines within the bandpass which produce the interference pattern. We show that essentially any set of emission lines which generally match the wavelength coverage of the night sky emission lines within a bandpass will produce an identical fringe pattern. We present an easy, inexpensive, and efficient method which uses a neon lamp as a flat field source and produces high S/N fringe frames to use for defringing an image during the calibration process.Comment: accepted to PAS

Dynamic programming and direct interaction for the optimum design of skeletal towers

A computer technique is proposed for automatically designing tower structures. Dynamic programming was used to find the optimum geometric configuration of the structural members, while the member sizes were proportioned by direct iteration. Tower structures are particularly suited to this method of automatic design since the rapidity of the analysis and design depends primarily upon substructuring. Substructuring of towers was comparatively simple because interaction between adjacent substructures is simulated with reasonable accuracy. Typical examples are presented to illustrate the method

A Computer Simulation Model of Waterhyacinth and Weevil Interactions

A personal computer simulation model termed INSECT has been developed to evaluate biological control of waterhyacinth (Eichhornia crassipes (Mart.) Solms.) by two species of weevil (Neochetina eichhorniae Warner, and N. bruchi Hustache). The model results were compared with the data from three different locations. For each data set, the simulated plant biomass, adult and larva populations were plotted aqainst the 95% confidence intervals of the actual field observations. In many cases, the simulation results were within the 95% confidence intervals, and especially during the growing season, they indicated trends similar to those seen in the field data. However, there were discrepancies in both the magnitude and the trend for early and the late periods of the year. These initial results suggest that development of a model to simulate the impact of a biocontrol agent on waterhyacinth populations is a feasible approach to better understand the interactions within this control system

A model for the screen printing of Newtonian fluids

A preliminary investigation into aspects of the off-contact screen-printing process is presented. A mathematical model for the printing of a thin film of Newtonian fluid is proposed, in which the screen is modelled as a permeable membrane, and the entire region above and below the screen is flooded. By drawing upon widely used industrial circuit printing practices, the distinguished limit of greatest interest to this industry is identified. Numerical and asymptotic solutions of this distinguished limit are presented that reproduce many of the features observed in industrial screen-printing

Is there Evidence for a Hubble bubble? The Nature of Type Ia Supernova Colors and Dust in External Galaxies

We examine recent evidence from the luminosity-redshift relation of Type Ia Supernovae (SNe Ia) for the $\sim 3 \sigma$ detection of a ``Hubble bubble'' -- a departure of the local value of the Hubble constant from its globally averaged value \citep{Jha:07}. By comparing the MLCS2k2 fits used in that study to the results from other light-curve fitters applied to the same data, we demonstrate that this is related to the interpretation of SN color excesses (after correction for a light-curve shape-color relation) and the presence of a color gradient across the local sample. If the slope of the linear relation ($\beta$) between SN color excess and luminosity is fit empirically, then the bubble disappears. If, on the other hand, the color excess arises purely from Milky Way-like dust, then SN data clearly favors a Hubble bubble. We demonstrate that SN data give $\beta \simeq 2$, instead of the $\beta \simeq 4$ one would expect from purely Milky-Way-like dust. This suggests that either SN intrinsic colors are more complicated than can be described with a single light-curve shape parameter, or that dust around SN is unusual. Disentangling these possibilities is both a challenge and an opportunity for large-survey SN Ia cosmology.Comment: Further information and data at http://qold.astro.utoronto.ca/conley/bubble/ Accepted for publication in ApJ

Cold acclimation of Concord grapevines III. Relationship between cold hardiness, tissue water content, and shoot maturation

Cold acclimation of Concord grapevines in Michigan begins as early as late August in tissues at the base of current season's growth.Increases in cold hardiness are closely related to decreases in tissue water content as stems achieve vegetative maturity.Greatest differences in hardiness and water content are found in tissues which vary the most in extent of maturation on both primary shoots and summer laterals.Increases in cold resistance are not related to water saturation deficit (WSD) of shoots

The influence of rootstock on the cold-hardiness of Seyval grapevines 1. Primary and secondary effects on growth, canopy development, yield, fruit quality and cold hardiness

Primary (direct) and secondary (indirect) influences of rootstocks on vine cold hardiness were determined independently. Vine size (kg of cane prunings per vine) reflects the number of shoots produced per m of row and is closely associated with shoot crowding and internal canopy shading. This shading is a secondary rootstock influence.Own-rooted Seyval (Sey/own), Seyval grafted to Seyval (Sey/Sey), Kober 5 BB (Sey/5 BB), and Couderc 3309 (Sey/3309) were the rootstock treatments used. Vine size classes were large (1.82-2.27 kg), medium (1.14-1.59 kg) and small (0.45-0.91 kg) and were established within each rootstock group.Rootstock choice had no effect on vine growth and canopy development. Vine productivity was influenced slightly, primarily through differences in cluster weight. By contrast, vine size, regardless of rootstock chosen, had a great impact on both vine growth and yield.Direct rootstock effects on cold hardiness were assessed via measurement of cumulative injury to buds and expressed as shootless nodes. Cane cold hardiness was based on the within-vine distribution of canes with differing characteristics associated with hardiness (diameter, exposure to sunlight during growth and the development of 5 or more mature nodes).Both primary and secondary influences of rootstocks on cold hardiness were observed. Bud hardiness was best on scions grafted to Couderc 3309, and there was a significant graft union effect; Sey/own vines had more bud mortality than Sey/Sey vines. Vine size did not influence the percentage of shootless nodes when canes of comparable quality were evaluated. The within-vine distribution of cane quality was influenced, however, and large vines had a greater number of both poorly matured and canes with superior hardiness status. By contrast, rootstock did not influence the within-vine distribution of cane quality.Large vines are not inferior to small vines in the number of best quality canes produced and should be equally hardy if careful cane selection is practiced at pruning.Assessment of the within-vine distribution of canes with superior cold hardiness appears to be a useful method of determining secondary treatment effects on vine cold hardiness. This aspect of vine cold hardiness should receive greater attention by viti-culture researchers.Einßuß der Unterlage auf die Kälteresistenz der Rebsorte Seyval1. Primärer und sekundärer Einfluß auf Wuchsstärke, Dichte der Laubwand, Ertrag, Traubenqualität und FrosthärteDer Einfluß der Unterlage und der Wuchsleistung (kg Schnittholz je Rebe) auf die Kälteresistenz der Sorte Seyval wurden getrennt untersucht. In dem Unterlagenversuch wurden folgende Varianten geprüft: Wurzelechte Seyval-Reben (Sey/own). Seyval auf Seyval gepfropft (Sey/Sey), Kober 5 BB (Sey/5 BB), und Couderc 3309 (Sey/3309). Die Reben jeder Unterlagenvariante wurden in drei Wuchsklassen - stark, mittel und schwach eingeteilt. Die Wirkung der Unterlage auf die Kälteresistenz wurde in Form der gesamten Knospenschädigung (Prozent tote Knospen) erfaßt. Als weiteres Merkmal für die Frosthärte diente die Qualität der Triebe innerhalb einer Rebe: mittlerer Triebdurchmesser und gute Exposition zur Sonne während der Vegetationsperiode.Die verwendete Unterlage hatte keinen Einfluß auf das Wachstum der Reben und die Entwicklung der Laubwand. Der Traubenertrag wurde nur schwach, in erster Linie über das Traubengewicht, beeinflußt. Im Unterschied hierzu wirkte sich die Größe einer Rebe, unabhängig von der Unterlage, maßgeblich auf das Wachstum und den Ertrag aus.Die Frosthärte hängt sowohl von Primär- wie Sekundäreinflüssen der Unterlage ab. Von allen Kombinationen wiesen die Sey/3309-Reben den geringsten Prozentsatz toter Knospen auf. Die Wuchsgröße beeinflußte den Ausfall von Knospen nicht signifikant, wenn Triebe gleicher Qualität beurteilt wurden. Die Unterlage beeinflußte ebenfalls nicht die Qualität der Triebe innerhalb einer Rebe.Starkwüchsige Reben hatten sowohl eine größere Anzahl schlecht ausgereifter Triebe als auch mehr reife Triebe mit guter Frosthärte. Starke Reben scheinen nicht weniger kälteresistent zu sein als schwächer wachsende, sofern beim Rebschnitt eine sorgfältige Auswahl der Tragruten getroffen wird

Spitzer Space Telescope Observations of Circumbinary Dust Disks around Polars

We present Spitzer Space Telescope IRAC photometry of the magnetic cataclysmic variables EF Eri, MR Ser, VV Pup, V834 Cen, GG Leo and V347 Pav. When we combine our results with the 2MASS data, we find that at least five of the polars have flux densities in the mid-IR in excess of the emission expected from the stellar components alone. We are unable to model this mid-IR excess with cyclotron emission, but we can recreate the observed spectral energy distributions with the inclusion of a simple circumbinary dust disk model. Importantly, we find that the masses of our modelled disks are approximately 12 orders of magnitude lower than required to significantly affect CV evolution. The accretion disk-less polars are ideal places to search for these disks, since the luminous accretion disk in most CVs would drown out the faint IR signature of the cooler, dimmer circumbinary disks

Influence of shoot number and crop load on potted Chambourcin grapevines. 2. Whole-vine vs. single-leaf photosynthesis

Two-year-old potted Chambourcin grapevines were trained to one shoot with 0 or 1 cluster (1/0 and 1/1 respectively) or four shoots with 0 or 4 clusters (4/0 and 4/4 respectively) to determine the effects of canopy development rate, canopy morphology, and crop load on whole-vine photosynthesis. Significant differences in canopy development rate, canopy morphology and dry matter partitioning occurred among treatments but whole-vine net photosynthesis (Pn) and dry matter production were not affected. Photosynthetic compensation by leaves of severely pruned vines enabled them to produce quantities of dry matter similar to vines with greater leaf area. Vines bearing crop supported the development of berries by partitioning carbohydrate to fruit at the expense of vegetative tissues so overall vine dry weight was not different among cropped and non-cropped treatments. Whole-vine Pn determinations were linearly related to vine dry mass. By contrast, single leaf measurements used to estimate whole-vine Pn were not related to dry mass. If a similar relationship can be demonstrated in field vines, it may be possible to quantify the influence of biotic and abiotic stresses on vine biomass production and subsequent yields