Flame liftoff height dependence on geometrically modified bluffbodies in a vitiated flow

In this study, the improvement of liftoff height of bluffbody-stabilized, partially premixed methane flames and the change of flow field in the recirculation zone of bluffbodies, of variously modified base geometries, are investigated in a high temperature (~1,315 K) vitiated flow. The basic geometry of the bluffbody consists of a two-dimensional rectangular body with a rounded nose with fuel jets being discharged from the body at several locations upstream of the base. Flame liftoff height measurements are characterized by CH chemiluminescence, while the three-dimensional flow field is determined using stereo particle image velocimetry (PIV). The lowest liftoff height is observed when the geometric modifications from the original rectangular bluffbody base are carried out such that the base has three-dimensional local cavities together with two-dimensionally modified geometries. PIV measurements show that the improvement of liftoff height is primarily attributed to an intense recirculation induced by multi-dimensional vortex structures in the presence of the two- and three-dimensionally modified base.     

Density functional theory studies on the reagent Ph3PBr2

We report density functional theory geometry optimizations at the B3LYP/6-311G(d,p) level of theory for the title reagent. Four stationary points on the molecular potential energy surface were located and characterized. Three of these stationary points are energy minima, one a saddle point. The minima correspond to the conventional Ph3PBr2 (three-fold Br-P-Br axis with twisted phenyl rings), the ion-pair [Ph3PBr]+Br- and a four-coordinated Ph3PBr2 spoke structure that can best be described as charge transfer on account of the substantial charge transfer from the Ph3P fragment to Br2 (as determined by a standard Mulliken population analysis and other considerations). The particular saddle point found corresponds to a three-fold Br-P-Br structure with coplanar phenyl rings. Single point B3LYP/6-311+g(3d,2p) calculations were done at the stationary point geometries in order to investigate possible deficiencies in the basis set. Solvent effects for the three solvents water, dichloroethane and cyclohexane were modelled using the self consistent reaction field Onsager method at the single point B3LYP/6-311+g(3d,2p) level of theory. In the gas phase, the charge transfer complex is the most stable of the four; in solution it is the least stable.     

Global prevention of all folic acid-preventable spina bifida and anencephaly by 2010

Folic acid-preventable spina bifida and anencephaly are pandemic, affecting 225,000 children a year. These birth defects are as preventable as polio. As we near the eradication of polio, it is time to make the commitment to global prevention of all folic acid-preventable spina bifida and anencephaly (FA-P SBA) by 2010. Folic acid fortification of centrally processed foods, such as wheat and corn flour, could immediately prevent all of these birth defects for much of the world's population. These fortification programs will also help adults by increasing serum folate concentration, eradicating folate deficiency anemia, providing human genome stability and reducing homocysteine serum concentration, which will probably prevent heart attacks and strokes, and may prevent colon cancer and Alzheimer's disease. Where there is no centrally processed and distributed food to fortify, intense efforts must be made to increase consumption of synthetic folic acid through vitamin supplements. Geneticists can play a major role in preventing FA-P SBA by helping to create the political will in each country to implement fortification and supplement programs to eliminate disease caused by the current pandemic of folate deficiency.     

Vibration Analysis by Phase Shifting Digital Holography

Phase-shifting digital holography has been used for the study of vibrating objects. The time-averaged complex amplitude of Fresnel diffracted field due to a vibrating object was obtained by using a three-step phase-shifting algorithm. Taking the inverse Fresnel transform of the complex amplitude resulted in an image of the object superimposed with Bessel fringes. The Bessel fringes are contour map of the vibration amplitude. By sinusoidally modulating the phase of the reference beam at the vibration frequency, the brightest fringe could be shifted to points of interest, thus extending the measurable range of vibration amplitude.     

Rotational spectrum and bending potential of LiOH: A semirigid bender analysis

Some 29 microwave transitions in the millimeter region have been measured in the high-temperature vapor of LiOH, ranging up toJ=5, including lines from the isotopomers⁷Li¹⁶OH,⁷Li¹⁶OD in both ground and excited bending states, and⁷Li¹⁸OH in the vibrational ground state only. An analysis of these transitions, together with nine previously known radio-frequency transitions, based on the semirigid bender model of vibration-rotation interaction has been used to investigate the form of the bending potential and to measure the semirigidity parameters that show the variation in the bond lengths that accompany the large-amplitude bending motion. The molecule was found to be linear in its equilibrium configuration, with an essentially harmonic bending potential. The experimentally derived quadratic semirigidity parameter for the Li-O bond was found to agree to within less than 5% with that from an ab initio calculation at the MP3/6-311G^** level.     

The structure of H2CSe from microwave spectroscopy

The microwave spectra of six isotopic species of selenoformaldehyde, H₂¹³C^78,80Se, D₂C^78,80Se, and DHC^78,80Se have been assigned. The resultant rotational constants, together with those of previous work yield the following substitution structure: r(C=Se) = 175.31 pm, HCH = 117.93°, and r(C---H) = 109.04 pm. This structure is compared with the equilibrium structure derived from ab initio calculations. The fundamental vibrational frequencies and centrifugal distortion constants of H₂C⁸⁰Se have been calculated.     

Prediction of clad angle in laser cladding by powder using response surface methodology and scatter search

Currently, laser cladding is an important process that allows the deposition of thick protective coatings on substrates. The article presents an experimental investigation of the influence of processing parameters on clad angle in laser cladding by powder (LCP). The clad angle is determined from the mathematical expression relating to the clad height and clad width. The cladding angle model was developed in terms of laser power, scanning speed, and powder mass flow rate by means of response surface methodology. A first-order equation covering a narrow range of the variables and a second-order equation covering a wide range of the variables are presented. An optimization technique, Scatter Search, is used to determine optimal processing parameters. The adequacy of the predictive model was tested by analysis of variance and found to be adequate.