DECIPHERING THE QUARK-GLUON STRUCTURE OF THE PHOTON IN E-GAMMA COLLISIONS

We investigate the capability of an egamma collider to unravel the hadronic content of the photon. The experimental problem for probing the gluonic structure of the photon is that small-x triggers overwhelmingly select soft photons rather than soft gluons in hard photons. We show that the problem can be finessed in experiments where laser back-scattering is used to prepare a source of very hard photons. We illustrate their power for studying the parton distributions of the photon and, specifically, for separating the quark and gluon components in events where dijets, jet-gamma pairs, and heavy quark pairs are produced.

Aircraft accident in Brazil: Boeing vs. Legacy?

Air accidents represent a small proportion of the flights registered worldwide. Airplane collisions in the air are rare. In September of 2006, a Boeing 737-800 collided in midair with a Legacy Jet. It was the largest accident registered in the history of Brazilian aviation until that time. The present study explores aspects of press coverage of the accident. Data and information reported in the media about the accident from September 2006 to August 2007 were collected and discussed. Media coverage called attention to two unusual aspects: politicisation of the discussion, culminating in the opening of congressional inquiries, and equally the concomitance of police investigations interfering in the work of agencies responsible for the official accident investigation. Emphasis on assigning guilt and establishing penalties may close the windows of opportunity an accident had opened for discussions on the improvement of air safety. In Brazil, political imperatives and organizational pressures have interfered and the possibilities of organizational learning from the accident have been drastically curtailed.

Ação do Profident sobre os tecidos gengivais. 2. Efeitos da ação do jato de bicarbonato de sódio sobre os tecidos gengivais, sob variação do ângulo de incidência. Análise histológica.

The effect of sodium bicarbonate jet (Profident System) on the gingival tissue was tested with comparison of application from 2 different angles: the angulation recommended by the manufacturer and ponted to the occlusal surface. The results showed a definite influence of the angulation on tissue trauma, with lesser degrees of injury when the modified angulation was applied.

Deciphering the quark-gluon structure of the photon in ey collisions

We investigate the capability of an ey collider to unravel the hadronic content of the photon. The experimental problem for probing the gluonic structure of the photon is that small-x triggers overwhelmingly select soft photons rather than soft gluons in hard photons. We show that the problem can be finessed in experiments where laser back-scattering is used to prepare a source of very hard photons. We illustrate their power for studying the parton distributions of the photon and, specifically, for separating the quark and gluon components in events where dijets, jet-y pairs, and heavy quark pairs are produced.

Signal and backgrounds for the single production of scalar and vector leptoquarks at the CERN LHC

We perform a detailed analysis of the potentiality of the CERN Large Hadron Collider to study the single production of leptoquarks via pp→e±q→ leptoquark →e± q, with e± generated by the splitting of photons radiated by the protons. Working with the most general SU(2)L⊗U( 1 )Y invariant effective Lagrangian for scalar and vector leptoquarks, we analyze in detail the leptoquark signals and backgrounds that lead to a final state containing an e± and a hard jet with approximately balanced transverse momenta. Our results indicate that the LHC will be able to discover leptoquarks with masses up to 2-3 TeV, depending on their type, for Yukawa couplings of the order of the electromagnetic one.

Single top quark at future hadron colliders: Complete signal and background study

We perform a detailed theoretical study including decays and jet fragmentation of all the important modes of single top quark production and all the basic background processes at the upgraded Fermilab Tevatron and CERN LHC colliders. Special attention is paid to the complete tree level calculation of the QCD fake background which was not considered in previous studies. An analysis of the various kinematical distributions for the signal and backgrounds allow us to work out a set of cuts for an efficient background suppression and extraction of the signal. It is shown that the signal to background ratio after optimized cuts could reach about 0.4 at the Tevatron and 1 at the LHC. The remaining after cuts signal rate at the LHC for the lepton+jets signature is expected to be about 6.1 pb and will be enough to study single top quark physics even during LHC operation at a low luminosity. ©1999 The American Physical Society.

Off-diagonal helicity density matrix elements for vector mesons produced in polarized e+e- processes

Final-state qq̄ interactions give origin to nonzero values of the off-diagonal element ρ1,-1 of the helicity density matrix of vector mesons produced in e+e- annihilations, as has been confirmed by recent OPAL data on φ, D*, and K*. New predictions are given for ρ1,-1 of several mesons produced at large XE and small pT - i.e., collinear with the parent jet - in the annihilation of polarized e+ and e-; the results depend strongly on the elementary dynamics and allow further nontrivial tests of the standard model.

Hunting a light U(1)B gauge boson coupled to baryon number in collider experiments

We analyze several signals at HERA and the Tevatron of a light U(1)B gauge boson (γB) coupling to baryon number. We show that the study of the production of bb pairs at the (upgraded) Tevatron can exclude γB with masses (mB) in the range 40 ≲ mB ≲ 300 GeV for γB couplings (αB) greater than 2 × 10-2 (3 × 10-3). We also show that the HERA experiments cannot improve the present bounds on γB. Moreover, we demonstrate that the production at HERA and the Tevatron of di-jet events with large rapidity gaps between the jets cannot be explained by the existence of a light γB. © 1999 Published by Elsevier Science B.V. All rights reserved.

Sand-water slurry erosion of API 5L X65 pipe steel as quenched from intercritical temperature

The objective of this study was to analyze the erosion of API 5L X65 pipe steel whose microstructure consisted of ferrite and martensite obtained by quenching from intercritical temperature (770 °C). Jet impingement tests with sand-water slurry were used. The changes in mechanical properties, caused by heat treatment carried out, did not induce changes in either the mechanism or erosion resistance. The erosion rate increased with angle of attack until 30° and later decreased until 90°. The microtexture of the eroded surfaces, at angles of attack of 30° and 90°, were similar for both conditions and were composed of craters and platelets at several stages of evolution. The erosion mechanism was by extrusion with the forming and forging of platelets.

Direct signals for large extra dimensions in the production of fermion pairs at linear colliders

We analyze the potential of the next generation of e+e- linear colliders to search for large extra dimensions via the production of fermion pairs in association with Kaluza-Klein gravitons (G), i.e., e+e- →ff̃G. This process leads to a final state exhibiting a significant amount of missing energy in addition to acoplanar lepton or jet pairs. We study in detail this reaction using the full tree level contributions due to the graviton emission and the standard model backgrounds. After choosing the cuts to enhance the signal, we show that a linear collider with a center-of-mass energy of 500 GeV will be able to probe quantum gravity scales from 0.96 (0.86) up to 4.1 (3.3) TeV at a 2 (5)σ level, depending on the number of extra dimensions. ©2001 The American Physical Society.

Effect of air-powder system on titanium surface on fibroblast adhesion and morphology.

PURPOSE: To evaluate the number and morphology of fibroblasts grown on machined titanium healing abutments treated with an airpowder system. MATERIALS AND METHODS: Twenty-six abutments were assigned to two experimental groups: control (no treatment) and treated (exposed to the Prophy-Jet for 30 seconds). The specimens were incubated for 24 hours with fibroblastic cells in multiwell plates, followed by routine laboratory processing for scanning electron microscope analysis. The specimens were photographed at x 350, and the cell number was counted on an area of approximately 200 um2. RESULTS: No significant differences were found on morphology between the groups (P > 0.05); however, the control group presented a significantly greater amount of cells (71.44 +/- 31.93, mean +/- SD) in comparison with treated group (35.31 +/- 28.14), as indicated by a nonpaired t test (P = 0.001). CONCLUSION: The use of an air-abrasive prophylaxis system on the surface of titanium healing abutments reduced the cells proliferation but did not influence cell morphology.

Flow injection amperometric determination of persulfate in cosmetic products using a Prussian Blue film-modified electrode

A flow-injection system with a glassy carbon disk electrode modified with Prussian Blue film is proposed for the determination of persulfate in commercial samples of hair bleaching boosters by amperometry. The detection was obtained by chronoamperometric technique and the sample is injected into the electrochemical cell in a wall jet configuration. Potassium chloride at concentration of 0.1 mol L-1 acted as sample carrier at a flow rate of 4.0 mL min-1 and supporting-electrolyte. For 0.025 V (vs. Ag/AgCl) applied voltage, the proposed system handles ca. 160 samples per hour (1.0 10-4 - 1.0 10-3 mol L-1 of persulfate), consuming about 200 μL sample and 11 mg KCl per determination. Typical linear correlations between electrocatalytic current and persulfate concentration was ca. 0.9998. The detection limit is 9.0 10-5 mol L-1 and the calculated amperometric sensibility 3.6 103 μA L mol -1. Relative standard deviation (n =12) of a 1.0 10-4 mol L-1 sample is about 2.2%. The method was applied to persulfate determination in commercial hair-bleaching samples and results are in agreement with those obtained by titrimetry at 95% confidence level and good recoveries (95 - 112%) of spiked samples were found. © 2003 by MDPI.

CH and C2 radicals characterization in natural gas turbulent diffusion flames

This paper reports the construction of an axisymmetric nonpremixed piloted jet burner, with well-defined initial and boundary conditions, known as the Delft burner, to assess turbulence-chemistry interaction in non-premixed turbulent flames. Detailed experimental information is described, involving hot-wire anemometry, thin-wire thermocouples and chemiluminescence visualization measurements. Radial profile of the axial mean velocity indicates excellent agreement between flow patterns developed within Delft installation and the one described herein. Chemiluminescence emissions from CH and C2 free-radicals were acquired with a CCD camera. Tomography reconstruction analysis was utilised to compare radical emissions and temperature spatial distributions. There was a strong dependence between temperature and CH/C 2 emissions. This is an indication that these radicals can be used in flame front studies.

Search for squarks and gluinos in events with jets and missing transverse energy in p(p)over-bar collisions at root s-=1.96 TeV

The results of a search for squarks and gluinos using data from p over(p, ̄) collisions recorded at a center-of-mass energy of 1.96 TeV by the DØ detector at the Fermilab Tevatron Collider are reported. The topologies analyzed consist of acoplanar-jet and multijet events with large missing transverse energy. No evidence for the production of squarks or gluinos was found in a data sample of 310 pb-1. Lower limits of 325 and 241 GeV were derived at the 95% C.L. on the squark and gluino masses, respectively, within the framework of minimal supergravity with tan β = 3, A0 = 0, and μ < 0. © 2006 Elsevier B.V. All rights reserved.

Global analysis of aerodynamics deflectors efficiency in the grinding process

The conventional, grinding methods in some cases are not very efficient because the arising of thermal damages in the pieces is very common. Optimization methods of cutting fluid application in the grinding zone are essential to prevent thermal problems from interaction of the wheel grains with the workpiece. surface. The optimization can happen through the correct selection of the cut parameters and development of devices that eliminate air layer effects generated around the grinding wheel. This article will collaborate with the development of an experimentation methodology which allows evaluating, comparatively, the performance of the deflectors in the cutting region to minimize the air layer effect of the high speed of the grinding wheel. The air layers make the cutting fluid jet to dissipate in the machine. An optimized nozzle was used in order to compare the results with the conventional method (without baffles or deflectors) of cutting fluid application. The results showed the high eficciency of the deflectors or baffles in the finish results. Copyright © 2006 by ABCM.