Freeze-out conditions in ultrarelativistic heavy-ion collisions

We present recent results on single particle transverse momentum distributions of pions, kaons and protons, measured in CERN Experiment NA44, of 200 AGeV/c S+S and 158 AGeV/c Pb+Pb central collisions. By comparing these data with thermal and transport models, freeze-out parameters like the temperatureT _fo and the chemical potentials (μ _q ,μ _s ) are extracted and discussed.     

Dispersion relations for elastic n-d scattering in the Amado model

The formulation of rigorous, dispersion relations for on-shell three-body amplitudes in a separable model is reported. The results of approximate $\text{N}\text{D}$ calculations of s-wave n-d elastic scattering are compared with exact, numerical solutions of the Faddeev equations.     

The role of pion exchange in high-energy hadron collisions

The contribution of pion exchange processes to the total cross section and to the construction of the pomeron is estimated in the dual unitary approach to high-energy collisions and is found to be small.     

The Logistic Diffusion of Information through Randomly Overlapped Cliques

The logistic model expects: If an item is told and heard in a set of people and periods under conditions of steady, pairing off, with equal opportunity, then Δ_t = kp _t q _t , i.e. increments in knowers are proportional to joint probabilities.Unequal opportunities result (among many causes) from “clique effects” where people communicate more within their daily circles of contacts (in homes, work, transit, eating and in leisure or other activities) than between such cliques.We hypothesized that if cliques are randomly overlapped in membership, then as clique size increases from 2 to all N persons, the diffusion-retarding effect of clique barriers will tend to vanish. “Larger cliques accelerate diffusion.”Previous experiments confirmed this hypothesis up to 4-man cliques and contradicted it thereafter, as larger cliques exceeded logistic expectations, and did so systematically. This was due to a constraint of “seeking out non-knowers” which was eliminated in the present experiments.With three replications from a population of playing cards, simulating increasing sizes of cliques, the curves rose steadily towards the logistic as upper limit just as hypothesized. The parameter r_ic measuring agreement of observed with expected increments rose from zero for the 2-man cliques up to r_ic = 0·98 for the N-man clique-of-the-whole.From this and other experiments, we infer that logistic diffusion of items is likely to be approximated in so far as populations are homogeneous with very diversely overlapped cliques which are larger than pairs. As cliques enlarge, the diffusion curve approaches the simplest logistic model. At cliques of four persons, acceleration from “seeking non-knowers” offset deceleration from clique barriers.     

Synthesis of a novel cyclic sulfone dihydropyridine: An investigation of the isomerization reaction converting an exocyclic double bond isomer into a 1,4-dihydropyridine

An eight membered cyclic sulfone 1,4-dihydropyridine, RWJ 22726, 1 , with remarkable cardiovascular activity was prepared by isomerization of an exocyclic double bond isomer using various reaction conditions. Under acidic and thermal isomerization conditions, an equilibrium mixture of products in an optimum ratio of 1:3.5 in favor of the desired 1,4-dihydropyridine was obtained. Equilibration using basic reaction conditions could not be effected. Complete conversion to the 1,4-dihydropyridine during the isomerization reaction was ultimately achieved by selective precipitation of the hydrochloride salt of the desired isomer.     

<Emphasis Type="Italic">N</Emphasis>-arachidonoyl glycine,an abundant endogenous lipid,potently drives directed cellular migration through GPR18, the putative abnormal cannabidiol receptor

Background  

Microglia provide continuous immune surveillance of the CNS and upon activation rapidly change phenotype to express receptors that respond to chemoattractants during CNS damage or infection. These activated microglia undergo directed migration towards affected tissue. Importantly, the molecular species of chemoattractant encountered determines if microglia respond with pro- or anti-inflammatory behaviour, yet the signaling molecules that trigger migration remain poorly understood. The endogenous cannabinoid system regulates microglial migration via CB₂ receptors and an as yet unidentified GPCR termed the 'abnormal cannabidiol' (Abn-CBD) receptor. Abn-CBD is a synthetic isomer of the phytocannabinoid cannabidiol (CBD) and is inactive at CB₁ or CB₂ receptors, but functions as a selective agonist at this G_i/o-coupled GPCR. N-arachidonoyl glycine (NAGly) is an endogenous metabolite of the endocannabinoid anandamide and acts as an efficacious agonist at GPR18. Here, we investigate the relationship between NAGly, Abn-CBD, the unidentified 'Abn-CBD' receptor, GPR18, and BV-2 microglial migration.     

Iodine(III)-mediated ethoxychlorination of enamides with iron(III) chloride

The combination of (diacetoxyiodo)benzene and iron(III) chloride in ethanol allows the efficient regioselective ethoxychlorination of a broad range of enamides. Mechanistic studies tend to rule out the involvement of free radical species and point towards the implication of a mixed [chloro(ethoxy)iodo]benzene intermediate.     

Thermoelectrically pumped light-emitting diodes operating above unity efficiency

A heated semiconductor light-emitting diode at low forward bias voltage V相似文献