Method of crystallization

A method is described for refining or growing bulk single crystals in an environment substantially free of gravity. The base material is suspended, positioned, and shaped as a containerless melt by wetting forces. Because no crucible is required, high temperature refractory materials can be processed

Allometry of Workers of the Fire Ant, Solenopsis invicta

The relationship between worker body size and the shape of their body parts was explored in the polymorphic ant, Solenopsis invicta. The data consisted of 20 measurements of body parts as well as sums of some of these measurements. Size-free shape variables were created by taking the ratios of relevant measures. After log-transformation, these ratios were regressed against the logarithm of total body length, or against the log of the size of the parent part. Slopes of zero indicated that shape did not change with size, and non-zero slopes signaled a size-related change of shape. Across the range of worker sizes, the head length retained a constant proportion to body length, but relative headwidth increased such that head shape changed from a barrel-profile to a somewhat heart-shaped profile. Antennae became relatively smaller, with the club contributing more to this decline than the other parts. The alinotum became relatively shorter and higher (more humped), and the gaster increased in both relative width and length, and therefore in volume. All three pairs of legs were isometric to body length. The component parts of the legs, with one exception, were isometric to their own total leg length. The body of S. invicta Abbreviation: / HL: head length BL: body length HW1: width across the eyes HW2: width above the eyes HW3: width below the eye

Relationship between X-ray and ultraviolet emission in 3C 273

In 3C 273, ultraviolet flux and X-ray flux measured by BATSE are not well correlated, contrarily to predictions of several models, unless the X-ray flux lags the UV emission by 1.75 yr. The absence of observed correlation at small lag cannot be due to spectral variability. A Comptonizing corona model is however compatible with all UV and X-ray observations covering the BATSE period.Comment: LaTeX, 4 pages, 6 figures. espcrc2.sty style file included. Poster contribution to the symposium "The Active X-ray Sky: Results from BepppoSAX and Rossi-XTE", Rome, October 199

Genetic Optimization Using Derivatives: The rgenoud Package for R

genoud is an R function that combines evolutionary algorithm methods with a derivative-based (quasi-Newton) method to solve difficult optimization problems. genoud may also be used for optimization problems for which derivatives do not exist. genoud solves problems that are nonlinear or perhaps even discontinuous in the parameters of the function to be optimized. When the function to be optimized (for example, a log-likelihood) is nonlinear in the model's parameters, the function will generally not be globally concave and may have irregularities such as saddlepoints or discontinuities. Optimization methods that rely on derivatives of the objective function may be unable to find any optimum at all. Multiple local optima may exist, so that there is no guarantee that a derivative-based method will converge to the global optimum. On the other hand, algorithms that do not use derivative information (such as pure genetic algorithms) are for many problems needlessly poor at local hill climbing. Most statistical problems are regular in a neighborhood of the solution. Therefore, for some portion of the search space, derivative information is useful. The function supports parallel processing on multiple CPUs on a single machine or a cluster of computers.

Fuel economy and exhaust emissions characteristics of diesel vehicles: Test results of a prototype Fiat 131 NA 2.4 liter automobile

The vehicle was tested on a chassis dynamometer over selected drive cycles and steady-state conditions. Two fuels were used, a U.S. no. 2 diesel and a European diesel fuel. The vehicle was tested with retarded timing and with and without an oxidation catalyst. Particulate emission rates were calculated from dilution tunnel measurements and large volume particulate samples were collected for biological and chemical analysis. It was determined that while the catalyst was generally effective in reducing hydrocarbon and carbon monoxide levels, it was also a factor in increasing particulate emissions. Increased particulate emission rates were particularly evident when the vehicle was operated on the European fuel which has a high sulfur content

Length-length and weight-length relationships of seven deep-water fishes in the Gulf of Mexico

Regression coefficients for equations of the form Y = a + bX were estimated for total length (TL) and whole weight (W) as a function of standard length (SL) and fork length (FL) and vice versa for seven deep-water fishes. All lengths were measured in millimeters and all weights in grams. There was a significant correlation between weight and length and the types of length measurements for all species. However, the amount of variation explained by each regression varied among species. Weight-length regressions were less precise than length-length regression, as they generally are, because weights of small fish measured at sea are more inaccurate than those of large fish.Marine Scienc

The Integral Burst Alert System (IBAS)

We describe the INTEGRAL Burst Alert System (IBAS): the automatic software for the rapid distribution of the coordinates of the Gamma-Ray Bursts detected by INTEGRAL. IBAS is implemented as a ground based system, working on the near-real time telemetry stream. During the first six months of operations, six GRB have been detected in the field of view of the INTEGRAL instruments and localized by IBAS. Positions with an accuracy of a few arcminutes are currently distributed by IBAS to the community for follow-up observations within a few tens of seconds of the event.Comment: 7 pages, latex, 5 figures, Accepted for publication on A&A Special Issue on First Science with INTEGRA

Compton processes in the bright AGN MCG+8-11-11

We present preliminary results on the hard X-ray emission properties of the Seyfert 1.5 galaxy MCG+8-11-11 as observed by INTEGRAL and SWIFT. All the INTEGRAL IBIS/ISGRI data available up to October 2009 have been analyzed together with two SWIFT/XRT snapshot observations performed in August and October 2009, quasi-simultaneously to INTEGRAL pointed observations of MCG+8-11-11. No correlation is observed between the hard X-ray flux and the spectral slope, while the position of the high-energy cut-off is found to have varied during the INTEGRAL observations. This points to a change in the temperature of the Comptonising medium from a minimum value of kT = 30-50 keV to values larger than 100-150 keV. There is no significant detection of Compton reflection, with a 3 sigma upper limit of R < 0.2, and no line has been detected at 112 keV, as previously claimed from HEAT observations (112 keV flux F < 2.4e-4 ph/cm^2/s). The variability behaviour of MCG+8-11-11 is found to be similar to that shown by IC 4329A, with different temperatures of the electron plasma for similar flux levels of the source, while other bright Seyfert galaxies present different variability patterns at hard X-rays, with spectral changes correlated to flux variations (e.g. NGC 4151).Comment: 6 pages, 4 figures. Accepted for publication on PoS (contribution PoS(INTEGRAL 2010)077), proceedings of the 8th INTEGRAL Workshop "The Restless Gamma-ray Universe" (September 2010, Dublin, Ireland