The Distribution of Natural Enemies of the Corn Leaf Aphid (Homoptera: Aphdidae) on Field Corn

(excerpt) The corn leaf aphid (CLA), Rhopalosiphum maidis (Fitch), is found on field corn in the midwest Cnited States each year. Except for infrequent and scattered outbreaks, CLA populations remain at low levels. Injury to corn occurs during tasseling (Snelling et aL 1941) and is caused by CLAs which are the progeny of colonizers that arrived 2-3 weeks earlier when the corn was in the whorl stage (Bryson 1934, Falter 1963)

Virtual Assisted Self Interviewing (VASI): An Expansion of Survey Data Collection Methods to the Virtual Worlds by Means of VDCI

Changes in communication technology have allowed for the expansion of data collection modes in survey research. The proliferation of the computer has allowed the creation of web and computer assisted auto-interview data collection modes. Virtual worlds are a new application of computer technology that once again expands the data collection modes by VASI (Virtual Assisted Self Interviewing). The Virtual Data Collection Interface (VDCI) developed at Indiana University in collaboration with the German Socio-Economic Panel Study (SOEP) allows survey researchers access to the population of virtual worlds in fully immersive Heads-up Display (HUD)-based survey instruments. This expansion needs careful consideration for its applicability to the researcher's question but offers a high level of data integrity and expanded survey availability and automation. Current open questions of the VASI method are an optimal sampling frame and sampling procedures within e. g. a virtual world like Second Life (SL). Further multi-modal studies are proposed to aid in evaluating the VDCI and placing it in context of other data collection modes.Interviewing mode, PAPI, CAPI, CASI, VASI, VDCI, second life

Virtual Assisted Self Interviewing (VASI): An Expansion of Survey Data Collection Methods to the Virtual Worlds by Means of VDCI

Changes in communication technology have allowed for the expansion of data collection modes in survey research. The proliferation of the computer has allowed the creation of web and computer assisted auto-interview data collection modes. Virtual worlds are a new application of computer technology that once again expands the data collection modes by VASI (Virtual Assisted Self Interviewing). The Virtual Data Collection Interface (VDCI) developed at Indiana University in collaboration with the German Socio-Economic Panel Study (SOEP) allows survey researchers access to the population of virtual worlds in fully immersive Heads-up Display (HUD)-based survey instruments. This expansion needs careful consideration for its applicability to the researcher’s question but offers a high level of data integrity and expanded survey availability and automation. Current open questions of the VASI method are an optimal sampling frame and sampling procedures within e. g. a virtual world like Second Life (SL). Further multimodal studies are proposed to aid in evaluating the VDCI and placing it in context of other data collection modes.Interviewing Mode, PAPI, CAPI, CASI, VASI, VDCI, Second Life

Surveying The Virtual World. A Large Scale Survey in Second Life Using the Virtual Data Collection Interface (VDCI)

Technology has always introduced changes in the way researchers administer surveys. A new technology known as virtual worlds has now emerged that promises to change data collection once again. Virtual worlds are persistent, online, computer-rendered spaces populated by hundreds, thousands, or even millions of people at a time. Previously, this population has only been surveyed in ways that required respondents to exit the virtual world before giving their answers. No survey method has existed whereby they could be surveyed while remaining present in the virtual space. Needless to say, this is less than ideal for any survey about the respondent’s attitudes, perceptions, and behavior within the virtual world itself. This study introduces a method for solving this problem and a tool that allows surveys entirely within a virtual environment. The method is introduced as Virtual Assisted Self Interview (VASI), and the tool for implementing it, the Virtual Data Collection Interface (VDCI). The tool was created and deployed in the virtual world Second Life (SL), where users were asked questions about demographics and quality of life. The valid response numbers for the survey (N=2094) make it the largest in-virtualworld data collection seen so far. This paper discusses the VDCI and describes several different sampling methods, as well as results that provide unique, new insights into virtual world populations. It is found, for example, that the demographic make-up of SL is unlike that of other virtual worlds. Moreover, the SL population is unlike that of other worlds in its approach to gender-switching. The limitations and new hazards of virtual world survey research are also discussed, especially survey "hacking" by individuals hoping to exploit the survey for financial gain. Despite the challenges, the results generally suggest that the VDCI is a valuable new research tool for obtaining representative data on virtual world population.VASI, VDCI, Second Life, Survey Plan, Fieldwork

The Exchange Gate in Solid State Spin Quantum Computation: The Applicability of the Heisenberg Model

Solid state quantum computing proposals rely on adiabatic operations of the exchange gate among localized spins in nanostructures. We study corrections to the Heisenberg interaction between lateral semiconductor quantum dots in an external magnetic field. Using exact diagonalization we obtain the regime of validity of the adiabatic approximation. We also find qualitative corrections to the Heisenberg model at high magnetic fields and in looped arrays of spins. Looped geometries of localized spins generate flux dependent, multi-spin terms which go beyond the basic Heisenberg model.Comment: 13 pages, 8 figure

Vapor-Pressure Lowering of Sulfur Dioxide Solutions of Potassium Thiocyanate from 15 to 25 C. (Abstract)

The vapor-pressure lowering of sulfur dioxide by potassium thiocyanate at 15°, 20° and 25° C. was measured by means of a differential mercury manometer connected to an all glass apparatus which employed no stopcocks. Readings were made to 0.001 cm. with a cathetometer. All concentrations were corrected for the amount of sulfur dioxide in the vapor phase. The molal lowering was approximately one-half the theoretical value at 0.005 molal and decreased with increasing concentration up to 1 molal, the highest concentration studied

Chandra observations of the HII complex G5.89-0.39 and TeV gamma-ray source HESSJ1800-240B

We present the results of our investigation, using a Chandra X-ray observation, into the stellar population of the massive star formation region G5.89-0.39, and its potential connection to the coincident TeV gamma-ray source HESSJ1800-240B. G5.89-0.39 comprises two separate HII regions G5.89-0.39A and G5.89-0.39B (an ultra-compact HII region). We identified 159 individual X-ray point sources in our observation using the source detection algorithm \texttt{wavdetect}. 35 X-ray sources are associated with the HII complex G5.89-0.39. The 35 X-ray sources represent an average unabsorbed luminosity (0.3-10\,keV) of $\sim10^{30.5}$\,erg/s, typical of B7-B5 type stars. The potential ionising source of G5.89-0.39B known as Feldt's star is possibly identified in our observation with an unabsorbed X-ray luminosity suggestive of a B7-B5 star. The stacked energy spectra of these sources is well-fitted with a single thermal plasma APEC model with kT$\sim$5\,keV, and column density N$_{\rm H}=2.6\times10^{22}$\,cm$^{-2}$ (A$_{\rm V}\sim 10$). The residual (source-subtracted) X-ray emission towards G5.89-0.39A and B is about 30\% and 25\% larger than their respective stacked source luminosities. Assuming this residual emission is from unresolved stellar sources, the total B-type-equivalent stellar content in G5.89-0.39A and B would be 75 stars, consistent with an earlier estimate of the total stellar mass of hot stars in G5.89-0.39. We have also looked at the variability of the 35 X-ray sources in G5.89-0.39. Ten of these sources are flagged as being variable. Further studies are needed to determine the exact causes of the variability, however the variability could point towards pre-main sequence stars. Such a stellar population could provide sufficient kinetic energy to account for a part of the GeV to TeV gamma-ray emission in the source HESSJ1800-240B.Comment: 34 pages, 9 figure

Vapor Density, Liquid Density and Surface Tension of Solutions of Potassium Thiocyanate in Liquid Sulfur Dioxide for 10° to 25° C

The vapor density, liquid density and differential capillary rise of pure liquid sulfur dioxide, and sulfur dioxide solutions of potassium thiocyanate were measured at 10, 15, 20, and 25°C in a sealed apparatus which allowed the measurement of all these quantities on the same solution. The apparatus consisted of two Pyrex capillaries sealed on to a Pyrex tube of 16.3 mm diameter in which a quartz bob was suspended from a calibrated quartz spring. By weighing the bob in the vapor, inverting, and weighing in the liquid, the densities could be determined to ± 0.02 mg/ml. All distances including the capillary heights were measured by a special microscope which could be read to ±0.00006 cm. Differential capillary rises could be duplicated to better than ± 0.0002 cm. From the surface tension and its rate of change with temperature the Fötvös constant, critical temperature, total surface energy and Paracor for sulfur dioxide were calculated. For the concentrations of potassium thiocyanate studied, a rise in the surface tension and liquid density was found at each temperature

The Formation of Gas Bubbles in Liquids

Gas bubbles which were formed by passing nitrogen through a glass capillary into liquids were studied by means of stroboscopic frequency measurements, rate of gas flow, and instantaneous ( approx. 10-5 sec. exposure) photographs. The size of the bubbles was determined both from the frequency and rate of gas flow and from measurements of the photographic images of the bubbles. The following pure liquids and solutions were used at room temperature: ethyl alcohol, n-propyl alcohol, aniline, acetone, benzene, chloroform, carbon tetrachloride, methyl alcohol, n-butyl alcohol, ether, and three aqueous solutions of ethyl alcohol. The pressures used were varied from the lowest pressure which would give a steady stream of bubbles (approx. 0.6 cm. of Hg) up to about 2.3 cm. of Hg. Capillary diameters were from 0.0137 to 0.0341 cm. The bubble frequency was practically constant (45-50 bubbles/sec.) for the pure liquids studied at all pressures and capillary diameters used. It follows therefore that the size of each bubble (cm3) is directly proportional to the rate of gas flow (cm3/sec.) and is independent of the properties of the liquid and the capillary diameter in the range of experimental conditions used. Higher pressures, larger capillary diameters, and lower surface tension give larger bubbles as a result of the increased rate of flow. In the case of 20.2, 70.0, and 40.7 per cent aqueous solutions of ethyl alcohol the bubble frequency was greater than with pure liquids and showed a much greater variation with pressure