Agricultural Chemicals. Book I--Insecticides. W.T. Thomson. Thomson Publications (P.O. Box 989, Davis, California 95616), 1967. 366 p. $10.00.

Excerpt: This book contains a wealth of information which would be extremely useful to people dealing with various aspects of insecticide usage ranging from laboratory investigations to field applications

On the Collapsar Model of Long Gamma-Ray Bursts: Constraints from Cosmic Metallicity Evolution

We explore the consequences of new observational and theoretical evidence that long gamma-ray bursts prefer low metallicity environments. Using recently derived mass-metallicity correlations and the mass function from SDSS studies, and adopting an average cosmic metallicity evolution from \citet{kewley2005} and \citet{savaglio2005} we derive expressions for the the relative number of massive stars formed below a given fraction of solar metallicity, $\epsilon$, as function of redshift. We demonstrate that about 1/10th of all stars form with $\epsilon < 0.1$. Therefore, a picture where the majority of GRBs form with $\epsilon < 0.1$ is not inconsistent with an empirical global SN/GRB ratio of 1/1000. It implies that (1) GRB's peak at a significantly higher redshift than supernovae; (2) massive star evolution at low metallicity may be qualitatively different and; (3) the larger the low-metallicity bias of GRBs the less likely binary evolution channels can be significant GRB producers.Comment: 12 pages, 2 figures; accepted as ApJ Lette

Prominence and flare fine structure from cross-field thermal conduction

Thermal conduction across a magnetic field is strongly suppressed compared with conduction along the field. However, if a flare is heated by a highly filamented beam directed along the field, then the array of heated cells in a cross-section of the flare will result in both small spatial scales (with consequently large temperature gradients) and a large surface area for the heated volume, providing a geometrical enhancement of the total cross-field energy flux. To investigate the importance of this filamentary geometry, we present a simple model of a single heated filament surrounded by an optically thin radiating shell, obtain an analytical expression for the stable equilibrium temperature profile within the shell, and use this to impose limits on the size of filament for which this model is appropriate. We find that this mechanism by itself is capable of transporting a power of the same order as a large flare, with a moderate range of filament sizes. The length scales are substantially smaller than can be resolved at present, although they should be regarded as underestimates.Comment: 7 pages, LaTeX, 4 figures. Source, figures and PS at http://www.astro.gla.ac.uk/preprints/95-05.html . To appear in A&

Maize Germplasm Conservation in Southern California's Urban Gardens: Introduced Diversity Beyond ex situ and in situ Management.

Contemporary germplasm conservation studies largely focus on ex situ and in situ management of diversity within centers of genetic diversity. Transnational migrants who transport and introduce landraces to new locations may catalyze a third type of conservation that combines both approaches. Resulting populations may support reduced diversity as a result of evolutionary forces such as genetic drift, selection, and gene flow, yet they may also be more diverse as a result of multiple introductions, selective breeding and cross pollination among multiple introduced varietals. In this study, we measured the amount and structure of maize molecular genetic diversity in samples collected from home gardens and community gardens maintained by immigrant farmers in Southern California. We used the same markers to measure the genetic diversity and structure of commercially available maize varieties and compared our data to previously reported genetic diversity statistics of Mesoamerican landraces. Our results reveal that transnational dispersal creates an opportunity for the maintenance of maize genetic diversity beyond its recognized centers of diversity

Temperature Effects on Development in \u3ci\u3eAphelinus Albipodus\u3c/i\u3e (Hymenoptera: Aphelinidae) From Two Geographic Regions

Aphelinus albipodus Hayat & Fatima was imported to the United States for classical biological control of the Russian wheat aphid, Diuraphis noxia (Mordvilko). Temperature effects on development of A. albipodus from two geographic regions (hereafter referred to as strains) were measured using the Russian wheat aphid as host. Temperature thresholds for egg to mummy, mummy to adult, and egg to adult development were 8.9,10.9, and 9.7°C for A. albipodus collected near Pingluo, China, and were and 8.5, 10.3, and 9.6°C for A. albipodus collected near Urumqi, China. The time required to develop from egg to adult did not differ among strains. However, when total immature development was partitioned into egg to mummy and mummy to adult, the time required for development through these two periods differed among strains. The Urumqi strain developed faster than the Pingluo strain from egg to mummy, while the Pingluo strain developed faster from mummy to adult. Degree-day requirements for egg to mummy development were 135 and 104 for the Pingluo and Urumqi strains, respectively. Corresponding requirements for mummy to adult development were 70 and 101 degree-days. The ability to vary immature development rate in response to climate or other factors could have adaptive significance because it would permit the parasitoid to exploit environments over a broad geographic range