Deuteron and triton production with high energy sulphur and lead beams

Proton and deuteron production has been observed in S+S and S+Pb collisions at 200 AGeV and in Pb+Pb reactions at 158 AGeV at the CERN SPS accelerator. For Pb+Pb triton production was also measured. The p and d spectra as well as the p and t spectra were observed in similar rapidity ranges and over similar ranges of transverse momenta per nucleon, making it possible to interpret the cross sections of the composite particles in terms of coalescence mechanisms. Volumes of homogeneity were extracted and compared to pion-pair HBT interferometry results. Special attention is given to the dependence on transverse mass, centrality and rapidity. Received: 23 July 2001 / Revised version: 16 November 2001 / Published online: 25 January 2002     

Space-time evolution of the hadronic source in peripheral to central Pb+Pb collisions

Two-particle correlations of negative pions as a function of charged particle multiplicity are studied in Pb+Pb collisions at GeV per nucleon using the NA44 experiment at the CERN Super Proton Synchrotron(SPS). We find that the source size parameters increase with the charged particle multiplicity. However the slope of the source size parameters plotted as a function of charged multiplicity is slightly larger at high multiplicity than at low multiplicity. The value of is independent of charged multiplicity. For Pb+Pb collisions, is larger than and for all multiplicity intervals, whereas these three radius parameters were approximately equal in S+Nucleus collisions. The ratios () and () for Pb+Pb data show almost no dependence on charged multiplicity. The duration of pion emission is constant at 3.81.1 fm/c as a function of the charged multiplicity in Pb+Pb collisions. Effective volume (V) is also calculated as V=, assuming a cylindrically shaped source. We found, within the limited statistics, the effective volume rapidly increases at high multiplicity. Received: 17 July 2000 / Revised version: 3 November 2000 / Published online: 8 December 2000     

Explanation of the Motionless Electromagnetic Generator with O(3) Electrodynamics

Recently, Bearden el al. developed a device which is known as a motionless electromagnetic generator (MEG) and which produces a coefficient of performance (COP) far in excess of unity. The device has been independently replicated by Naudin. In this communication, the fundamental operational principle of the MEG is explained using a version of higher symmetry electrodynamics known as O(3) electrodynamics, which is based on the empirical existence of two circular polarization states of electromagnetic radiation, and which has been developed extensively in the literature. The theoretical explanation of the MEG with O(3) electrodynamics is straightforward: Magnetic energy is taken directly ex vacua and used to replenish the permanent magnets of the MEG device, which therefore produces a source of energy that, in theory, can be replenished indefinitely from the vacuum. Such a result is incomprehensible in U(1) Maxwell-Heaviside electrodynamics.     

Rapidity dependence of antiproton-to-proton ratios in Au+Au collisions at square root of (sNN) = 130 GeV

Measurements, with the BRAHMS detector, of the antiproton-to-proton ratio at midrapidities and forward rapidities, are presented for Au+Au reactions at square root of [s(NN)] = 130 GeV, and for three different collision centralities. For collisions in the 0%-40% centrality range, we find N(&pmacr;)/N(p) = 0.64+/-0.04((stat))+/-0.06((syst)) at y approximately 0, 0.66+/-0.03+/-0.06 at y approximately 0.7, and 0.41+/-0.04+/-0.06 at y approximately 2. The ratios are found to be nearly independent of collision centrality and transverse momentum. The antiproton and proton rapidity densities vary differently with rapidity, and indicate a significant degree of collision transparency, although a net-baryon free midrapidity plateau (Bjorken limit) is not yet reached.     

Nuclear stopping in Au+Au collisions at square root of S(NN)=200 GeV

Transverse momentum spectra and rapidity densities, dN/dy, of protons, antiprotons, and net protons (p-p) from central (0%-5%) Au+Au collisions at square root of S(NN)=200 GeV were measured with the BRAHMS experiment within the rapidity range 0相似文献   

Aharonov-bohm effect as the basis of electromagnetic energy inherent in the vacuum

The Aharonov-Bohm effect shows that the vacuum is structured, and that there can exist a finite vector potentialA in the vacuum when the electric field strengthE and magnetic flux densityB are zero. It is shown on this basis that gauge theory produces energy inherent in the vacuum. The latter is considered as the internal space of the gauge theory, containing a field made up of components ofA, to which a local gauge transformation is applied to produce the electromagnetic field tensor, a vacuum charge/current density, and a topological charge g. Local gauge transformation is the result of special relativity and introduces spacetime curvature, which gives rise to an electromagnetic field whose source is a vacuum charge current density made up ofA and g. The field carries energy to a device which can in principle extract energy from the vacuum. The development is given forU(1) andO(3) invariant gauge theory applied to electrodynamics. Former Edward Davies Chemical Laboratories, University College of Wales, Aberystwyth SY32 1NE, Wales, United Kingdom.     

On Positivity and Roots in Operator Algebras

In earlier papers the second author and Charles Read have introduced and studied a new notion of positivity for operator algebras, with an eye to extending certain C*-algebraic results and theories to more general algebras. The present paper consists of complements to some facts in the just mentioned papers, concerning this notion of positivity. For example we prove a result on the numerical range of products of the roots of commuting operators with numerical range in a sector.     

A fast,fully validated GC-MS method using a simplified pretreatment for the quantification of short and branched chain fatty acids in human stool

The study of short (SCFAs) and branched chain fatty acids (BCFAs) in human stool related to gastrointestinal diseases, gut microbiota, metabolism, and diet has dramatically increased. As a result, a fast, reliable method with minimal pretreatment is needed for quantification of these metabolites (acetic, propionic, isobutyric, butyric, isovaleric, valeric, and caproic acid) in stool. Therefore, a GC-MS method meeting this criterion was developed. A bias sampling study showed no statistical difference (p > 0.05) in analyte means when comparing 100 mg subsamples of homogenized to non-homogenized samples (n = 6, p values 0.153–0.910). Stool samples were homogenized, diluted with 80:20 water:methanol (v/v), and adjusted to a pH of 1.5–2.5. Samples were vortexed, centrifuged, and directly injected into the GC-MS using pulsed splitless injection offering twofold-to-threefold signal enhancement over a 10:1 split injection. DB-FATWAX Ultra Inert Polyethylene Glycol (PEG) Column showed no peak tailing, reduced responses, or retention time shifts after 1,476 stool injections, while other columns failed before 361 injections. Intra- and inter-day accuracy for stool supernatant samples ranged from −10.21% to 8.88% and −13.25% to 9.91%, while intra- and inter-day precision ranged from 0.21% to 1.21% and 0.89% to 2.84% coefficient of variation (CV), respectively. This method demonstrates excellent linearity (0.9999–1.0000) and low limits of quantification (1.50–8.01 μM). Stool samples proved stable stored at −20°C up to 28 days, and recoveries ranged from 85.04% to 106.59%. Matrix effects in stool are non-significant determined by comparing standard and stool supernatant calibration curve slopes (p > 0.05).