Plants for predators - a participatory experiment

Encouraging natural enemies by growing attractant plants is a highly effective method of pest control in organic systems. However, it is important to establish which plants are most effective at attracting benefi cial insects. Experiments were carried out by 179 HDRA members, who grew four plant species (Coriander, Corn Marigold, Fennel and Phacelia) in their gardens and allotments. Over the course of the growing season, assessments were made on the growth and flowering of the plants and the presence of four key groups of beneficial insect (ladybirds, hoverflies, lacewings and parasitic wasps). Phacelia established quickly and its long flowering period meant it attracted insects throughout the summer. However, Phacelia was only the most attractive plant at the end of the season and insects preferred the other trial plants when they were in flower. Results highlight the importance of growing a range of flowering plants to provide resources for beneficials throughout their activity period

Molecular line survey of Sagittarius B2(M) from 330 to 355 GHz and comparison with Sagittarius B2(N)

We have surveyed molecular line emission from Sgr B2 over the range from 330 to 355 GHz at the position designated Sgr B2(M). This position is prominent in millimeter continuum maps of the region and is associated with a compact H II region, a hot NH_3 core, and sources of H_2O and OH maser emission. We have also obtained observations contrasting the submillimeter molecular emission from Sgr B2(M) and Sgr B2(N), an additional center of activity thought to be a dense protostellar core. The picture of the interstellar chemistry of these regions which we derive is substantially different from that determined from previous observations at lower frequencies and with lower spatial resolution. In particular, molecules such as SO_2 and CH_3OH dominate the submillimeter spectrum to a much greater extent than they do the low-frequency observations. Much of this difference is due to the higher spatial resolution of the submillimeter observations, which makes them much more sensitive to emission from compact, dense cores. The millimeter data were most effective at sampling material in the surrounding lower density regions. The chemistry of the core sources in Sgr B2 appears similar to that of other dense cores, such as the core of the Orion molecular cloud. The spectral differences between Sgr B2(M) and Sgr B2(N) primarily relate to differences in excitation and column density. For most molecular species the northern source (N) has a column density significantly higher than that found in the middle source (M), often by a factor of about 5. The principal exceptions are the species SO and SO_2 which seem to be substantially more abundant in the middle source. Generally excitation seems to be higher in the northern source, suggesting a somewhat higher density core, although there are some departures indicating that the excitation situation is more complicated. High optical depths in many of the submillimeter transitions systematically bias the interpretation of both column densities and excitation. Many of the millimeter lines may also have high optical depths, particularly those lines arising from the compact core sources

On the Interpretation of the broad-band millimeter-wave flux from Orion

Spectral observations of the core of Orion A at wavelengths around 1.3 mm show a high density of strong, broad emission lines. The combined flux in lines with peak antenna temperatures stronger than 0.2 K accounts for approximately 40 percent of the broad-band millimeter-wave flux from the region. Thus the broad-band flux from Orion A is in large part due to sources other than dust emission

Molecular abundances in OMC-1: The chemical composition of interstellar molecular clouds and the influence of massive star formation

We present here an investigation of the chemical composition of the various regions in the core of the Orion molecular cloud (OMC-1) based on results from the Caltech Owens Valley Radio Observatory (OVRO) millimeter-wave spectral line survey (Sutton et al.; Blake et al.). This survey covered a 55 GHz interval in the 1.3 mm (230 GHz) atmospheric window and contained emission from over 800 resolved spectral features. Of the 29 identified species 14 have a sufficient number of detected transitions to be investigated with an LTE "rotation diagram" technique, in which large numbers of lines are used to estimate both the rotational excitation and the overall abundance. The rotational temperatures and column densities resulting from these fits have then been used to model the emission from those remaining species which either have too few lines or which are too weak to be so analyzed. When different kinematic sources of emission are blended to produce a single feature, Gaussian fits have been used to derive the individual contributions to the total line profile. The uniformly calibrated data in the unique and extensive Caltech spectral line survey lead to accurate estimates of the chemical and physical parameters of the Orion molecular cloud, and place significant constraints on models of interstellar chemistry. A global analysis of the observed abundances shows that the markedly different chemical compositions of the kinematically and spatially distinct Orion subsources may be interpreted in the framework of an evolving, initially quiescent, gas-phase chemistry influenced by the process of massive star formation. The chemical composition of the extended Orion cloud complex is similar to that found in a number of other objects, but the central regions of OMC-1 have had their chemistry selectively altered by the radiation and high-velocity outflow from the young stars embedded deep within the interior of the molecular cloud. Specifically, the extended ridge clouds are inferred to have a low (subsolar) gas-phase oxygen content from the prevalence of reactive carbon-rich species like CN, CCH, and C_3H_2 also found in more truly quiescent objects such as TMC-1. The similar abundances of these and other simple species in clouds like OMC-1, Sgr B2, and TMC-1 lend support to gas-phase ion-molecule models of interstellar chemistry, but grain processes may also play a significant role in maintaining the overall chemical balance in such regions through selective depletion mechanisms and grain mantle processing. In contrast, the chemical compositions of the more turbulent plateau and hot core components of OMC-1 are dominated by high-temperature, shock-induced gas and grain surface neutral-neutral reaction processes. The high silicon/sulfur oxide and water content of the plateau gas is best modeled by fast shock disruption of smaller grain cores to release the more refractory elements followed by a predominantly neutral chemistry in the cooling postshock regions, while a more passive release of grain mantle products driven toward kinetic equilibrium most naturally explains the prominence of fully hydrogenated N-containing species like HCN, NH_3 , CH_3CN, and C_2H_5CN in the hot core. The clumpy nature of the outflow is illustrated by the high-velocity emission observed from easily decomposed molecules such as H_2CO. Areas immediately adjacent to the shocked core in which the cooler, ion-rich gas of the surrounding molecular cloud is mixed with water/oxygen rich gas from the plateau source are proposed to give rise to the enhanced abundances of complex internal rotors such as CH_30H, HCOOCH_3 , and CH_30CH_3 whose line widths are similar to carbon-rich species such as CN and CCH found in the extended ridge, but whose rotational temperatures are somewhat higher and whose spatial extents are much more compact

The rotational emission-line spectrum of Orion A between 247 and 263 GHz

Results are presented from a molecular line survey of the core of the Orion molecular cloud between 247 and 263 GHz. The spectrum contains a total of 243 resolvable lines from 23 different chemical species. When combined with the earlier survey of Orion from 215 to 247 GHz by Sutton et al. (1985), the complete data set includes over 780 emission features from 29 distinct molecules. Of the 23 molecules detected in this survey, only NO, CCH, and HCO^+ were not identified in the lower frequency data. As a result of the supporting laboratory spectroscopy performed to supplement existing millimeter-wave spectral line catalogs, only 33 of the more than 780 lines remain unidentified, of which 16 occur in the upper frequency band. A significant chance remains that a number of these unidentified lines are due to transitions between states of either isotopically substituted or highly excited abundant and complex molecules such as CH_3OH, CH_3OCH_3, and HCOOCH_3, whose rotational spectra are poorly known at present. The very small percentage and weak strength of the unidentified lines implies that the dominant chemical constituents visible at millimeter wavelengths have been identified in the Orion molecular cloud

Heterodyne detection of CO2 emission lines and wind velocities in the atmosphere of Venus

Strong 10 micrometer line emission from (c-12)(o-16)2 in the upper atmosphere of Venus was detected by heterodyne techniques. Observations of the absolute Doppler shift of the emission features indicate mean zonal wind velocities less than 10 m/sec in the upper atmosphere near the equator. No evidence was found of the 100 m/sec wind velocity implied by the apparent 4-day rotation period of ultraviolet cloud features

Excitation of methyl cyanide in the hot core of Orion

The excitation of CH_3CN in the hot core of Orion is examined using high-sensitivity observational data at 1.3 mm. Observed line fluxes are analyzed by means of multilevel statistical equilibrium (SE) calculations which incorporate current theoretical values of the collisional excitation rates. The analysis is applied to both optically thin models of the hot core region and models with significant optical depths. Trapping is found to play a critical role in the excitation of CH_3CN. An optically thin analysis yields a kinetic temperature of 275 K and a cloud density of 2 x 10^6 cm^(-3). Unequal column densities are deduced in this case for the two symmetry species: N_A = 1.4 x 10^(14) cm^(-2) and N_E = 2.0 x 10^(14) cm^(-2). The deduced cloud density and temperature are lowered to 1.5 x 10^6 cm^(-3) and 240 K. The model with trapping is favored because of the agreement with measured sizes of the hot core source and the more plausible N_A/N_E ratio. Analysis of radiative excitation in the hot core indicates it is unlikely to significantly affect the ground vibrational state populations of CH_3CN. It most likely is significant for excitation of the V_8 band

Heterodyne detection of CO2 emission lines and wind velocities in the atmosphere of Venus

Strong 10 micrometer line emission from (C-12)(O-16)2 in the upper atmosphere of Venus was detected by heterodyne techniques. Observations of the absolute Doppler shift of the emission features indicate mean zonal wind velocities less than 10 m/sec in the upper atmosphere near the equator. No evidence was found of the 100 m/sec wind velocity implied by the apparent 4-day rotation period of ultraviolet cloud features

Synthesizing Program Input Grammars

We present an algorithm for synthesizing a context-free grammar encoding the language of valid program inputs from a set of input examples and blackbox access to the program. Our algorithm addresses shortcomings of existing grammar inference algorithms, which both severely overgeneralize and are prohibitively slow. Our implementation, GLADE, leverages the grammar synthesized by our algorithm to fuzz test programs with structured inputs. We show that GLADE substantially increases the incremental coverage on valid inputs compared to two baseline fuzzers