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A detailed analysis ofKs0 production in |<2.5 the average transverse momentum is found to be 0.53±0.07 GeV/c at 200 GeV and 0.62±0.08 GeV/c at 900 GeV, which is an increase with respect to data at c.m. energies below 60 GeV. TheKs0 production cross sections in inelastic collisions are 29±4 mb at 200 GeV and 63±6 mb at 900 GeV, showing an increase compared to lower energy data. The central kaon density is found to increase as a logarithmic function of energy. At 900 GeV, where statistics are sufficient to allow one to draw conclusions, the average transverse momentum is higher in events with large charged multiplicity than in events with low multiplicity.

We present data on two-particle pseudorapidity and multiplicity correlations of charged particles for non single-diffractive at c.m. energies of 200, 546 and 900 GeV. Pseudorapidity correlations interpreted in terms of a cluster model, which has been motivated by this and other experiments, require on average about two charged particles per cluster. The decay width of the clusters in pseudorapidity is approximately independent of multiplicity and of c.m. energy. The investigations of correlations in terms of pseudorapidity gaps confirm the picture of cluster production. The strength of forward-backward multiplicity correlations increases linearly with ins and depends strongly on position and size of the pseudorapidity gap separating the forward and backward interval. All our correlation studies can be understood in terms of a cluster model in which clusters contain on average about two charged particles, i.e. are of similar magnitude to earlier estimates from the ISR.

The equilibrium constants for the gas phase reactions: Cl−(HCl)n = Cl−(HCl)n−1 + HCl, (n, n−1) were measured at different temperatures with a pulsed electron beam high pressure mass spectrometer. This allowed determination of ΔGn,n−10, ΔHn,n−10, and ΔSn,n−10for reactions with n = 1 to n = 4. The enthalpy change for the reaction: (ClHCl)− = Cl− + HCl was ΔH1.00 = 23.7 kcal/mol. This value is much higher than the literature value of 14.2 kcal/mol based on Born cycles. The stabilities of the Cl−(HCl)nclusters are compared with those of OH−(H2O)nand Cl−(H2O)nmeasured earlier. It is found that the (ClHCl)−is nearly as stable as the (HOHOH)−species but that the stabilities of the higher Cl−(HCl)nclusters decreases much more rapidly than that of OH−(H2O)n. The initial strong interaction in (ClHCl) is assumed to be due to the high polarizability of Cl. For large nthis effect becomes unimportant. Cl−HOH is much more weakly bound than (ClHCl)−, however, at high nthe Cl−(H2O)ninteractions become more favorable.

Based on the minimal peptide sequence (Phe-Leu-Leu-Arg) that has been found to exhibit biological activity in a gastric smooth muscle contractile assay for thrombin receptor-activating peptides, the cyclic peptide analogues cyclo(Phe-Leu-Leu-Arg-Acp) (1), cyclo(Phe-Leu-Leu-Arg-εLys) (2), and cyclo(Phe-Leu-Leu-Arg-Gly) (3) have been synthesized by the solid-phase method using benzotriazol-1-yloxytris(dimethylamino)phosphonium hexafluoroborate or 2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate as cyclization reagents. The contractile activities of compounds 1−3 have been compared with that of the linear thrombin receptor-activating peptide (TRAP) Ser-Phe-Leu-Leu-Arg-NH2 (compound 4) using a gastric smooth muscle strip assay. Compound 2, wherein the ε-amino group of lysine was coupled to the α-carboxyl of arginine, exhibited a contractile activity comparable to that of the linear TRAP, compound 4. However compound 1, wherein the aminocaproic linker group yielded a ring size the same as for compound 2 but without a primary amino group, exhibited a contractile activity 600−1000-fold lower than compounds 2 and 4. Compound 3, which exhibited partial agonist activity, was about 100-fold less potent than either compound 2 or 4. NMR spectroscopy of compound 2 revealed a proximity of the Phe and Arg side chains, leading to a molecular model generated by distance geometry and molecular dynamics, wherein the Phe and Arg residues are shown in proximity on the same side of the peptide ring. We conclude that the Phe and Arg side chains along with the primary amino group form an active recognition motif that is augmented by the presence of a primary amino group in the cyclic peptide. We suggest that a comparable cyclic conformation may be responsible for the interaction of linear TRAPs with the thrombin receptor.

The conformational properties of the pentapeptide Ser-Phe-Leu-Leu-Arg (P5), a human thrombin receptor-derived sequence forming part of a tethered ligand which activates the thrombin receptor, and its more active amide derivative Ser-Phe-Leu-Leu-Arg-NH2(P5-NH2), have been studied by proton NMR spectroscopy in dimethylsulfoxide. Measurements of nuclear Overhauser effects, performed using two-dimensional rotating frame nuclear Overhauser (ROESY) and one-dimensional nuclear Overhauser enhancement (NOE) spectroscopy, revealed that P5 exists mainly in an extended conformation. However, proton–proton 1D-NOEs between Phe CαH and Ser CαH, Leu3CαH and Leu3NH, and Leu4CαH and Leu4NH, as well as between the Ser and Arg sidechains, also implicated a minor conformer for P5 having a curved backbone and a near-cyclic structure. In contrast to P5, measurements of NOEs and ROEs for P5-NH2revealed a more stabilized cyclic structure which may account for its higher biological potency. Thus strong interresidue sequential NH (i)–NH (i+ 1) interactions, as well as C-terminal carboxamide to N-terminal side-chain interactions, i.e., Arg CONH2to Phe ring and Arg CONH2to Ser , observed at lower levels of the ROESY spectrum, supported a curved backbone structure for SFLLR-NH2. Since the higher potaency P5-NH2analogue adopts predominantly a cyclic structure, a cyclic bioactive conformation for thrombin receptor agonist peptides is suggested.

A preliminary design of a compact first-level calorimeter trigger, implemented as a farm of local bit-serial systolic arrays, is presented. The bit-serial data representation allows higher processing rates and more compact designs than are possible when using parallel data. More functionality can be incorporated into the Application Specific Integrated Circuits (ASICs) that serve as the main processing elements. The trigger processor seeks local energy clusters, evaluates isolation criteria within the electromagnetic calorimeter and leakage into the hadron calorimeter in order to detect electrons. It uses cluster finding algorithms to identify jets and missing transverse energy to estimate neutrino energies. The processor output serves as decision support for the central first-level trigger and delivers region-of-interest positions to the second-level trigger. In its present form the trigger processor design relies on optical fibers to deliver the input data from the front-end modules and multi-chip modules (MCMs) to harbor the processing ASICs. The fact that the main part of the trigger processor can fit into one or two large crates suggests that the design is not limited by size nor is it strictly limited by cost but can be expanded to accommodate extended algorithms if these are found necessary. Extensive physics simulations will explore these possibilities.<>

By measuring the A−(H2O)n−1 + H2O = A−(H2O)nequilibria in the gas phase and their temperature dependence, the equilibrium constants and ΔHn, n–1and ΔSn, n–1for some of the hydrates of NO2−, NO3−, CN−, and OH−were determined. Available thermochemical data are used for the evaluation of the total heats of hydration of the above ions. The total heats of hydration were then compared with the ΔH1,0. Relative to the total hydration energies the ΔH1,0of the above ions were found larger than the ΔH1,0of the halide ions.An approximate linear correlation was found to exist between ΔH1,0of negative ions and the heterolytic bond dissociation energy D(A−–H+). With this relationship independent estimates for the electron affinities of NO2and NO3could be obtained.The ΔHn, n–1of OH−were found in essential agreement with earlier measurements from this laboratory and in disagreements with recent measurements (Friedman) which gave much higher values.

Determination of the temperature dependence of the equilibrium constants Kn,n−1for the reactions A −Bn = A −Bn−1 + B where A−equals Cl−and O2−and B is HOH, CH3OH, or CH3CN leads to the corresponding ΔH0n−1, ΔG0n−1,n, and ΔS0n−1,nvalues. The experimental technique is based on mass spectrometric detection of ions escaping from a high pressure ion source. At n = 1, Cl−is solvated most strongly by methanol, then CH3CN and HOH. At higher na cross over is observed with water becoming the best solvent. These results are in agreement with the positive transfer enthalpies and free energies for Cl−from the liquid solvents HOH → CH3OH and HOH → CH3CN reported in the literature.O2−is solvated more strongly than Cl−appearing thus as an ion of "size" intermediate between Cl−and F−Again CH3OH gives the highest interaction for n = 1, however for n > 1 water gives stronger interactions.

Measurements of the proton transfer equilibria: A1− + A2H = A2−with a pulsed electron beam high pressure mass spectrometer were extended to α, β, γ chlorosubstituted aliphatic acids. The equilibrium constants were used to evaluate ΔG0for the proton transfer reactions. Assuming ΔG ≈ ΔHand using standard acids AH for which the difference between the bond dissociation energy D(A—H)and the electron affinity of A, EA(A) was known one could evaluate the corresponding difference for the newly measured acids and place them on an absolute acidity scale. The gas phase acidity was observed to increase in the order: acetic, propionic, butyric, γ-Cl butyric, β-Cl butyric, β-Cl propionic, α-Cl butyric, α-Cl propionic, α-Cl acetic. The gas phase acidities are compared with those observed in aqueous solution. The effects of the Cl substituent parallel those in solution but are much larger. The attenuation occurring in solution is attributed to weaker hydrogen bonding of the chloro stabilized acid anions to water molecules.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.