Phase and Charge reentrant phase transitions in two capacitively coupled Josephson arrays with ultra-small junction

We have studied the phase diagram of two capacitively coupled Josephson junction arrays with charging energy, $E_c$, and Josephson coupling energy, $E_J$. Our results are obtained using a path integral Quantum Monte Carlo algorithm. The parameter that quantifies the quantum fluctuations in the i-th array is defined by $\alpha_i\equiv \frac{E_{{c}_i}}{E_{J_i}}$. Depending on the value of $\alpha_i$, each independent array may be in the semiclassical or in the quantum regime: We find that thermal fluctuations are important when $\alpha \lesssim 1.5$ and the quantum fluctuations dominate when $2.0 \lesssim \alpha$. We have extensively studied the interplay between vortex and charge dominated individual array phases. The two arrays are coupled via the capacitance $C_{{\rm inter}}$ at each site of the lattices. We find a {\it reentrant transition} in $\Upsilon(T,\alpha)$, at low temperatures, when one of the arrays is in the semiclassical limit (i.e. $\alpha_{1}=0.5$) and the quantum array has $2.0 \leq\alpha_{2} \leq 2.5$, for the values considered for the interlayer capacitance. In addition, when $3.0 \leq \alpha_{2} < 4.0$, and for all the inter-layer couplings considered above, a {\it novel} reentrant phase transition occurs in the charge degrees of freedom, i.e. there is a reentrant insulating-conducting transition at low temperatures. We obtain the corresponding phase diagrams and found some features that resemble those seen in experiments with 2D JJA.Comment: 25 Latex pages including 8 encapsulated poscript figures. Accepted for publication in Phys. Rev B (Nov. 2004 Issue

Branchiosyllis salazari sp. n. (Polychaeta, Syllidae) del Caribe noroccidental y comentarios sobre el material tipo de B. exilis (Gravier, 1900)

Basándonos en el estudio de 195 ejemplares procedentes del Caribe Noroccidental, se describe una nueva especie de Branchiosyllis Ehlers, 1887. Branchiosyllis salazari sp. n. tiene tres pares de ojos (dos pares pequeños en el margen anterior del prostomio, el tercer par está en una línea transversal), sin branquias, sedas con artejo en forma de ganchos grandes ya en los setígeros medios, y proventrículo sin línea mediodorsal. El material tipo de B. exilis (Gravier, 1900), una especie aparentemente circuntropical, fue revisado para clarificar su presencia en el Mar Caribe. Sus características diagnósticas son: dos pares de ojos en una línea transversa, sin branquias, sedas con artejo en forma de gancho grande restringidas a los setígeros posteriores y proventrículo con una línea mediadorsal de células en forma de diamante. Se anexa una clave para las siete especies de Branchiosyllis en el Gran Caribe. Palabras clave: Branchiosyllis salazari sp. n., Taxonomía, Gran Caribe, Syllidae, Polychaeta.On the basis of 195 specimens from the Northwestern Caribbean Sea, a new species of Branchiosyllis Ehlers, 1887 is described. Branchiosyllis salazari n. sp. has three pairs of eyes (two small pairs above the anterior margin of the prostomium, the third pair in a transverse line), without branchia, setae with large hooked blades in median setigers, and proventricle without middorsal line. The type material of B. exilis (Gravier, 1900), an apparently circumtropical species, was revised to clarify its presence in the Caribbean Sea. Its diagnostic features are: two pairs of eyes in a transverse line, no branchia, setae with large hooked blades in posterior setigers only, and proventricle with a middorsal line of Diamond-shaped cells. A key for the seven species of Branchiosyllis in the Grand Caribbean is included. Key words: Branchiosyllis salazari n. sp., Taxonomy, Grand Caribbean, Syllidae, Polychaeta.Basándonos en el estudio de 195 ejemplares procedentes del Caribe Noroccidental, se describe una nueva especie de Branchiosyllis Ehlers, 1887. Branchiosyllis salazari sp. n. tiene tres pares de ojos (dos pares pequeños en el margen anterior del prostomio, el tercer par está en una línea transversal), sin branquias, sedas con artejo en forma de ganchos grandes ya en los setígeros medios, y proventrículo sin línea mediodorsal. El material tipo de B. exilis (Gravier, 1900), una especie aparentemente circuntropical, fue revisado para clarificar su presencia en el Mar Caribe. Sus características diagnósticas son: dos pares de ojos en una línea transversa, sin branquias, sedas con artejo en forma de gancho grande restringidas a los setígeros posteriores y proventrículo con una línea mediadorsal de células en forma de diamante. Se anexa una clave para las siete especies de Branchiosyllis en el Gran Caribe. Palabras clave: Branchiosyllis salazari sp. n., Taxonomía, Gran Caribe, Syllidae, Polychaeta

Studying polymer diffusiophoresis with non-equilibrium molecular dynamics.

We report a numerical study of the diffusiophoresis of short polymers using non-equilibrium molecular dynamics simulations. More precisely, we consider polymer chains in a fluid containing a solute that has a concentration gradient and examine the variation of the induced diffusiophoretic velocity of the polymer chains as the interaction between the monomer and the solute is varied. We find that there is a non-monotonic relation between the diffusiophoretic mobility and the strength of the monomer-solute interaction. In addition, we find a weak dependence of the mobility on the length of the polymer chain, which shows clear difference from the diffusiophoresis of a solid particle. Interestingly, the hydrodynamic flow through the polymer is much less screened than for pressure driven flows.European Union Grant No. 674979 Horizon 2020 program through 766972-FET-OPEN- NANOPHLOW

General Non-equilibrium Theory of Colloid Dynamics

A non-equilibrium extension of Onsager's canonical theory of thermal fluctuations is employed to derive a self-consistent theory for the description of the statistical properties of the instantaneous local concentration profile n(r,t) of a colloidal liquid in terms of the coupled time evolution equations of its mean value n(r,t) and of the covariance {\sigma}(r,r';t) \equiv of its fluctuations {\delta}n(r, t) = n(r, t) - n(r, t). These two coarse-grained equations involve a local mobility function b(r, t) which, in its turn, is written in terms of the memory function of the two-time correlation function C(r, r' ; t, t') \equiv <{\delta}n(r, t){\delta}n(r',t')>. For given effective interactions between colloidal particles and applied external fields, the resulting self-consistent theory is aimed at describing the evolution of a strongly correlated colloidal liquid from an initial state with arbitrary mean and covariance n^0(r) and {\sigma}^0(r,r') towards its equilibrium state characterized by the equilibrium local concentration profile n^(eq)(r) and equilibrium covariance {\sigma}^(eq)(r,r'). This theory also provides a general theoretical framework to describe irreversible processes associated with dynamic arrest transitions, such as aging, and the effects of spatial heterogeneities

In situ surface coverage analysis of RuO₂-catalysed HCl oxidation reveals the entropic origin of compensation in heterogeneous catalysis

In heterogeneous catalysis, rates with Arrhenius-like temperature dependence are ubiquitous. Compensation phenomena, which arise from the linear correlation between the apparent activation energy and the logarithm of the apparent pre-exponential factor, are also common. Here, we study the origin of compensation and find a similar dependence on the rate-limiting surface coverage term for each Arrhenius parameter. This result is derived from an experimental determination of the surface coverage of oxygen and chlorine species using temporal analysis of products and prompt gamma activation analysis during HCl oxidation to Cl2 on a RuO2 catalyst. It is also substantiated by theory. We find that compensation phenomena appear when the effect on the apparent activation energy caused by changes in surface coverage is balanced out by the entropic configuration contributions of the surface. This result sets a new paradigm in understanding the interplay of compensation effects with the kinetics of heterogeneously catalysed processes

Rare-gas solids under pressure: A path-integral Monte Carlo simulation

Rare-gas solids (Ne, Ar, Kr, and Xe) under hydrostatic pressure up to 30 kbar have been studied by path-integral Monte Carlo simulations in the isothermal-isobaric ensemble. Results of these simulations have been compared with available experimental data and with those obtained from a quasiharmonic approximation (QHA). This comparison allows us to quantify the overall anharmonicity of the lattice vibrations and its influence on several structural and thermodynamic properties of rare-gas solids. The vibrational energy increases with pressure, but this increase is slower than that of the elastic energy, which dominates at high pressures. In the PIMC simulations, the vibrational kinetic energy is found to be larger than the corresponding potential energy, and the relative difference between both energies decreases as the applied pressure is raised. The accuracy of the QHA increases for rising pressure.Comment: 9 pages, 6 figure

Low X-Ray Luminosity Galaxy Clusters: Main goals, sample selection, photometric and spectroscopic observations

We present the study of nineteen low X-ray luminosity galaxy clusters (L$_X \sim$ 0.5--45 $\times$ $10^{43}$ erg s$^{-1}$), selected from the ROSAT Position Sensitive Proportional Counters (PSPC) Pointed Observations (Vikhlinin et al. 1998) and the revised version of Mullis et al. (2003) in the redshift range of 0.16 to 0.7. This is the introductory paper of a series presenting the sample selection, photometric and spectroscopic observations and data reduction. Photometric data in different passbands were taken for eight galaxy clusters at Las Campanas Observatory; three clusters at Cerro Tololo Interamerican Observatory; and eight clusters at the Gemini Observatory. Spectroscopic data were collected for only four galaxy clusters using Gemini telescopes. With the photometry, the galaxies were defined based on the star-galaxy separation taking into account photometric parameters. For each galaxy cluster, the catalogues contain the PSF and aperture magnitudes of galaxies within the 90\% completeness limit. They are used together with structural parameters to study the galaxy morphology and to estimate photometric redshifts. With the spectroscopy, the derived galaxy velocity dispersion of our clusters ranged from 507 km~s$^{-1}$ for [VMF98]022 to 775 km~s$^{-1}$ for [VMF98]097 with signs of substructure. Cluster membership has been extensively discussed taking into account spectroscopic and photometric redshift estimates. In this sense, members are the galaxies within a projected radius of 0.75 Mpc from the X-ray mission peak and with cluster centric velocities smaller than the cluster velocity dispersion or 6000 km~s$^{-1}$, respectively. These results will be used in forthcoming papers to study, among the main topics, the red cluster sequence, blue cloud and green populations; the galaxy luminosity function and cluster dynamics.Comment: 13 pages, 6 tables, 9 figures. Uses emulateapj. Accepted for publication in The Astronomical Journal. Some formatting errors fixe