Mean Net Charge Research Articles

Event-by-event fluctuations at SPS

Results on event-by-event fluctuations of the mean transverse momentum and net charge in Pb-Au collisions, measured by the CERES Collaboration at CERN-SPS, are presented. We discuss the centrality and beam energy dependence and compare our data to cascade calculations.

Event-by-event fluctuations at 40, 80 and 158 A GeV/c in Pb + Au collisions

Event-by-event fluctuations of mean pT and net charge in 40, 80 and 158 A GeV/c Pb+Au collisions are presented. The observed dynamical mean pT fluctuations in central events of about 1% are very similar to results from RHIC. The centrality dependence of mean pT fluctuations at 158 A GeV/c shows a peculiar non-monotonic pattern with respect to the extrapolation from the fluctuations measured in p+p collisions. Dynamical net charge fluctuations smaller than the charge conservation limit are observed. After correction for charge conservation, the measured fluctuation signal in central events is comparable to RHIC results.

Monte Carlo Simulations of Primitive Model (PM) Electrolytes in Non-Euclidean Geometries

Monte Carlo canonical ensemble (NVT) simulations of unrestricted primitive model electrolytes (PM) on the 3D “surface” of a 4D hypersphere are reported here. The effects of concentration, ionic charge and/or ionic radii on the mean internal energy (⟨U⟩), individual and mean ionic activities (⟨γ +⟩, ⟨γ -⟩ or ⟨γ ±⟩) and the mean net charge density distributions were studied. Our results showed that either higher charge, higher concentration or smaller ionic radii favoured ion–ion aggregation. The individual ionic activity coefficients of ions with different radii and/or charge differed significantly at higher concentrations. We also compared mean ionic activity coefficients for aqueous KCl and NaBr from simulations with reported experimental values in the literature and the agreement within 0.7–10%, depending upon concentration were found.

Measures of charge fluctuations in nuclear collisions

The properties of two measures of charge fluctuations D and Delta Phi_q are discussed within several toy models of nuclear collisions. In particular their dependence on mean particle multiplicity, multiplicity fluctuations and net electric charge are studied. It is shown that the measure Delta Phi_q is less sensitive to these trivial biasing effects than the originally proposed measure D. Furthermore the influence of resonance decay kinematics is analysed and it is shown that it is likely to shadow a possible reduction of fluctuations due to QGP creation.

Mean net charge of hadron jets

The behaviour of the mean net charge for the simplen-quark distribution function of hadron jets is discussed. The behaviour of the mean net charge of proton jet treated as quark-diquark system and threequark system is shown.

Mean ionic charge on two components of technetium pyrophosphate prepared using stannous chloride

Ionic charge, complexation equilibria, and acid-base equilibria can be measured at tracer concentrations by ion-exchange chromatography. To characterize better the principal components found in [ 99 m Tc]pyrophosphate preparations used for diagnostic bone and heart scanning, these were studied in two ion-exchange chromatographic systems: (A) DEAE-cellulose in pyrophosphate form at pH 6.0–7.5, and (B) DEAE-cellulose in perchlorate form at pH 3.7–4.8. The chromatographic retention times were measured as a function of pH and electrolyte concentration, and compared with those of trisoxalachromium (III) complex, which was chosen as reference ion because of its similarity in charge and retention to the Tc-pyrophosphate complexes. The pyrophosphate complexes were even more sensitive to electrolyte concentration than was the triply negative reference ion: the calculated mean net charge in the mobile phase for the two principal Tc-pyrophosphate species were −4.5 ±0.5 and −4.9 ± 0.5 at pH 4.3, and −11.2 ± 1.3 and −10.1 ± 1.0 at pH 7.0. It can be concluded that the two principal radioactive components in clinical Tc-pyrophosphate preparations both bear a high, pH-dependent negative charge.

The Net Surface Charge of Mammalian Spermatozoa as Determined by Isoelectric Focusing. Changes Following Sperm Maturation, Ejaculation, Incubation in the Female Tract, and after Enzyme Treatment

The mean net surface charge of living mammalian spermatozoa from various regions of the male reproductive tract has been investigated by whole cell isoelectric focusing techniques. In all cases, spermatozoa released from the caput epididymidis had a significantly higher mean isoelectric point than those from the cauda region. The net charge of spermatozoa from the rat and hamster was further modified by seminal vesicular fluid but not by prostatic secretion.Whereas the isoelectric point of caudal spermatozoa from rodents increased significantly after exposure to neuraminidase or trypsin, that of spermatozoa from the caput region was altered to a lesser extent. By contrast, neuraminidase failed to influence the surface charge of ejaculated human and rabbit spermatozoa, as did the incubation of spermatozoa in the female tract or with capacitating media. Finally, a preliminary study showed that spermatozoa from some apparently infertile men have an isoelectric point consistently higher than those from fertile men.

5-125I-iododeoxyuridine as prototype for radionuclide therapy with Auger emitters.

MANY of the physical and biological requirements for treating cancer with internally emitting radionuclides are met by 5-125I-iododeoxyuridine (125IUdR). The decay of 123I is associated with a highly localised deposition of energy1. Cascades of very low energy and thus densely ionising Auger electrons are released. In addition, a charge transfer reaction takes place leaving the resultant tellurium nucleus with a transient mean net charge of +9 (ref. 2). These unique physical characteristics can be used for cell destruction by labelling DNA with 125IUdR, a thymidine analogue. The marked radiotoxicity of 125I incorporated into DNA as 125IUdR has been demonstrated by lethality, mutations and DNA strand breaks in bacteria and bacteriophage3–7, by lethality and chromosome aberrations in mammalian cells cultured in vitro8–10, and by diminished survival of prelabelled tumour cells assayed in vivo11. The intranuclear location is of major importance: 125I located extracellularly9 or bound to cell membranes is much less toxic (unpublished work of R. L. Warters and K. G. Hofer). These findings suggested that 125IUdR might have significant anti-neoplastic activity. We tested this hypothesis in a murine ascites tumour model12,13. In a pilot study using therapeutic doses of 125IUdR, the agent substantially augmented the median and absolute survival of treated animals. The critical factors affecting treatment of a 1-d-old ascites tumour model with 125IUdR are detailed here.

The solubility of fibrinogen in dilute salt solutions

Highly purified human fibrinogen was dialyzed versus eleven different sodium salts at ionic strengths of 0.005–0.3 and pH values of 4.5–8.0. After equilibration and centrifugation of the protein solutions, fibrinogen solubilities were determined spectrophotometrically and were analyzed as functions of pH, ionic strength, and specific anion. Bell-shaped curves are obtained when fibrinogen solubility is plotted as a function of pH. The solubility exhibits a minimum at a given pH and rises at acid and alkaline values. As the ionic strength is increased, the solubility curves shift toward more acid pH values. At constant pH values between 6 and 7, fibrinogen solubility increases with an increase in ionic strength. At constant pH values below pH 6, a decrease in solubility occurs as the ionic strength is increased. The isoionic pH of a saturated aqueous fibrinogen solution has been determined to be 6.25, meaning that fibrinogen in pure water behaves as a weak acid with a mean net charge of −0.9. At pH values acid to 6.25, the anions solubilize fibrinogen in the following order of increasing efficacy: thiocyanate, perchlorate, sulfate, citrate, bromide, nitrate, phosphate, chloride, acetate, fluoride, and formate. This order is reversed at pH values alkaline to 6.25. Anion binding parameters calculated from the solubility data indicate that those anions which most effectively solubilize fibrinogen at alkaline pH and precipitate it at acid pH have the highest apparent binding affinities for the protein. Anions with less pronounced solubility effects have lower binding affinities.