The spectral function of a rho meson that is at rest in dense hadronic matter and couples strongly to the pion is studied in the vector dominance model by including the effect of the delta hole polarization on the pion. With the free rho-meson mass in the Lagrangian, we find that both the rho-meson peak and width increase with increasing nuclear density, and that a low-mass peak appears at invariant mass around three times the pion mass. Including the decreasing densitydependent hadron masses in the Lagrangian as suggested by the scaling law of Brown and Rho, we find instead that the rho peak moves to smaller invariant masses with diminishing strength when the nuclear density increases. The low-mass peak also shifts down with increasing density and becomes more pronounced. The relevance of the rho-meson property in dense matter to dilepton production in heavy-ion collisions is discussed.PACS number(s): 25.75+r, 14.40.Cs, 12.40.Vv In heavy-ion collisions the nuclear matter can be compressed to many times the normal nuclear matter density [1]. The study of the property of hadrons in dense matter has recently attracted a lot of attention [2]. We have previously studied dilepton production from the pion-pion annihilation in heavy-ion collisions to see whether one can learn about the pion dispersion relation in a dense medium [3 -5]. In particular, we have considered dileptons of invariant mass around twice the pion mass. Gale and Kapusta [6] were the first to show that the dilepton yield around this invariant mass would be enhanced if the softening of the pion spectrum in the nuclear matter is included. This is due to the large momentum range available for the two pions when the pion dispersion relation develops at high densities a minimum at energy less than the pion mass. We have obtained a similar result when the pion self-energy in the nuclear matter is calculated in the delta-hole model [3,4]. But for dileptons with zero three-momentum the enhancement is canceled by the delta-hole polarization correction to the zero vertex as shown by Korpa and Pratt [7], and one obtains instead a suppression of the dilepton yield for invariant mass around twice the pion mass. This cancellation is, however, reduced for dileptons with finite momenta, so there is still some enhancement of the dilepton yield around this invariant mass [5]. The experimental data [8,9] from the Bevalac on the dilepton invariant mass spectra from heavy-ion collisions have already shown clearly the contribution from the pion-pion annihilation [10, 11). But for dileptons with invariant masses below about 500 MeV, it is dominated by the eta Dalitz 'On leave from KFKI, Budapest, Hungary. decay and also has an appreciable bremsstrahlung contribution [12]. This makes the enhancement of dileptons with invariant masses around 280 MeV difBcult if not impossible to be observed.Since the electromagnetic form factor of a pion is dominated by the rho meson, the dilepton invariant mass spectrum should also reveal information about the property of the rho meson i...

The effect of the kaon loop correction to the property of a phi meson in dense matter is studied in the vector dominance model. Using the density-dependent kaon effective mass determined from the linear chiral perturbation theory, we find that with increasing baryon density the phi meson mass is reduced slightly while its width is broadened drastically.

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Hybrid photocatalysts of graphitic carbon nitride (g-C 3 N 4) and reduced graphene oxide (rGO) composites were prepared in one-pot via a thermal condensation of melamine with different amounts of graphene oxide (GO). As metal-free hybrids, the prepared photocatalysts presented enhanced performances in photooxidation of both methylene blue and phenol in water solutions under various light irradiations. The level of rGO significantly affected MB photodegradation efficiencies. The introduced graphene can improve the MB adsorption and optical absorption in visible light region, therefore enables the hybrids to efficiently degrade MB under visible light with wavelengths longer than 430 nm. The metal-free photocatalysts were also able to degrade phenol effectively and the effects of catalyst loading and initial phenol concentration were investigated. This study provided an efficient and environmentally benign photocatalyst for degradation of organic pollutants in water, with complete prevention of secondary contamination from metal-leaching.

To improve proton conduction properties of conventional sulfonated poly(ether ether ketone) (SPEEK), poly(2,5-benzimidazole)-grafted graphene oxide (ABPBI-GO) was prepared to fabricate nanocomposite membranes, which then were further doped with phosphoric acid (PA). The ABPBI-GO was synthesized through the reaction of 3,4-diaminobenzoic acid with the carboxyl acid groups present on the GO surface. The simultaneous incorporation of ABPBI-GO and PA into SPEEK did not only improve the physicochemical performance of the membranes in terms of thermal stability, water uptake, dimensional stability, proton conductivity, and methanol permeation resistance but also relieve PA leaching from the membranes though acid-base interactions. The resulting composite membranes exhibited enhanced proton conductivities in extended humidity ranges thanks to the hygroscopic character of PA and the increased water uptake. Moreover, the unique self-ionization, self-dehydration, and nonvolatile properties of PA improved the high-temperature proton conductivities (σ) of PA-doped membranes. The PA-doped SPEEK/ABPBI-GO-3.0 delivered a σ of 7.5 mS cm at 140 °C/0% RH. This value was fourfold higher than that of pristine SPEEK membranes. The PA-doped SPEEK/ABPBI-GO-3.0 based fuel cell membranes delivered power densities of 831.06 and 72.25 mW cm at 80 °C/95% RH and 120 °C/0% RH, respectively. By contrast, the PA-doped SPEEK membrane generated only 655.63 and 44.58 mW cm under the same testing conditions.