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The phase behavior and structural properties of hard anisotropic particles (prisms and dumbbells) are examined in one-dimensional channels using the Parsons–Lee (PL) theory, and the transfer-matrix and neighbor-distribution methods. The particles are allowed to move freely along the channel, while their orientations are constrained such that one particle can occupy only two or three different lengths along the channel. In this confinement setting, hard prisms behave as an additive mixture, while hard dumbbells behave as a non-additive one. We prove that all methods provide exact results for the phase properties of hard prisms, while only the neighbor-distribution and transfer-matrix methods are exact for hard dumbbells. This shows that non-additive effects are incorrectly included into the PL theory, which is a successful theory of the isotropic-nematic phase transition of rod-like particles in higher dimensions. In the one-dimensional channel, the orientational ordering develops continuously with increasing density, i.e., the system is isotropic only at zero density, while it becomes perfectly ordered at the close-packing density. We show that there is no orientational correlation in the hard prism system, while the hard dumbbells are orientationally correlated with diverging correlation length at close packing. On the other hand, positional correlations are present for all the systems, the associated correlation length diverging at close packing. [ABSTRACT FROM AUTHOR]

The structural properties of confined single-file hard-disk fluids are studied analytically by means of a mapping of the original system onto a one-dimensional mixture of non-additive hard rods, the mapping being exact in the polydisperse limit. Standard statistical-mechanical results are used as a starting point to derive thermodynamic and structural properties of the one-dimensional mixture, where the condition that all particles have the same chemical potential must be taken into account. Analytical results are then provided for the nth neighbor probability distribution function, the radial distribution function, and the structure factor, a very good agreement being observed upon comparison with simulation data from the literature. Moreover, we have analyzed the scaling form for the disappearance of defects in the zigzag configuration for high pressure and have obtained the translational correlation length and the structural crossover in the oscillation frequency for asymptotically large distances. [ABSTRACT FROM AUTHOR]

The exact transfer-matrix solution for the longitudinal equilibrium properties of the single-file hard-disk fluid is used to study the limiting low- and high-pressure behaviors analytically as functions of the pore width. In the low-pressure regime, the exact third and fourth virial coefficients are obtained, which involve single and double integrals, respectively. Moreover, we show that the standard irreducible diagrams do not provide a complete account of the virial coefficients in confined geometries. The asymptotic equation of state in the high-pressure limit is seen to present a simple pole at the close-packing linear density, as in the hard-rod fluid, but, in contrast to the latter case, the residue is 2. Since, for an arbitrary pressure, the exact transfer-matrix treatment requires the numerical solution of an eigenvalue integral equation, we propose here two simple approximations to the equation of state, with different complexity levels, and carry out an extensive assessment of their validity and practical convenience vs the exact solution and available computer simulations. [ABSTRACT FROM AUTHOR]

Granular gases demand models capable of capturing their distinct characteristics. The widely employed inelastic hard-sphere model (IHSM) introduces complexities that are compounded when incorporating realistic features like surface roughness and rotational degrees of freedom, resulting in the more intricate inelastic rough hard-sphere model (IRHSM). This paper focuses on the inelastic rough Maxwell model (IRMM), presenting a more tractable alternative to the IRHSM and enabling exact solutions. Building on the foundation of the inelastic Maxwell model (IMM) applied to granular gases, the IRMM extends the mathematical representation to encompass surface roughness and rotational degrees of freedom. The primary objective is to provide exact expressions for the Navier–Stokes–Fourier transport coefficients within the IRMM, including the shear and bulk viscosities, the thermal and diffusive heat conductivities, and the cooling-rate transport coefficient. In contrast to earlier approximations in the IRHSM, our study unveils inherent couplings, such as shear viscosity to spin viscosity and heat conductivities to counterparts associated with a torque-vorticity vector. These exact findings provide valuable insights into refining the Sonine approximation applied to the IRHSM, contributing to a deeper understanding of the transport properties in granular gases with realistic features. [ABSTRACT FROM AUTHOR]

This Perspective article provides an overview of some of our analytical approaches to the computation of the structural and thermodynamic properties of single-component and multicomponent hard-sphere fluids. For the structural properties, they yield a thermodynamically consistent formulation, thus improving and extending the known analytical results of the Percus–Yevick theory. Approximate expressions linking the equation of state of the single-component fluid to the one of the multicomponent mixtures are also discussed. [ABSTRACT FROM AUTHOR]

Hegemonic masculinity is defined as the ability of human beings to use masculinized characteristics and traits as a method of control and domination of those who feel vulnerable. In this research, we developed and validated an instrument that measured the perception of gay men in Puerto Rico in the face of the problem of hegemonic masculinity. As a correlative strategy we used a gender violence perceived scale in order to identify whether the perception of hegemonic masculinity responds to or is compared with the perception of gender-based violence within the gay community. The sample was composed of 271 Puerto Rican participants over the age of 21 and self-identified as gay. The hegemonic masculinity scale gets a factorial structure of two factors with sound psychometric properties. As well, our findings suggest that the selected sample recognizes that the intragender violence exists and rejects masculinized hegemonic behaviors. [ABSTRACT FROM AUTHOR]

The most widely used model for granular gases is perhaps the inelastic hard-sphere model (IHSM), where the grains are assumed to be perfectly smooth spheres colliding with a constant coefficient of normal restitution. A much more tractable model is the inelastic Maxwell model (IMM), in which the velocity-dependent collision rate is replaced by an effective mean-field constant. This simplification has been taken advantage of by many researchers to find a number of exact results within the IMM. On the other hand, both the IHSM and IMM neglect the impact of roughness—generally present in real grains—on the dynamic properties of a granular gas. This is remedied by the inelastic rough hard-sphere model (IRHSM), where, apart from the coefficient of normal restitution, a constant coefficient of tangential restitution is introduced. In parallel to the simplification carried out when going from the IHSM to the IMM, we propose in this paper an inelastic rough Maxwell model (IRMM) as a simplification of the IRHSM. The tractability of the proposed model is illustrated by the exact evaluation of the collisional moments of first and second degree, and the most relevant ones of third and fourth degree. The results are applied to the evaluation of the rotational-to-translational temperature ratio and the velocity cumulants in the homogeneous cooling state. [ABSTRACT FROM AUTHOR]

We study a dilute granular gas immersed in a thermal bath made of smaller particles with masses not much smaller than the granular ones in this work. Granular particles are assumed to have inelastic and hard interactions, losing energy in collisions as accounted by a constant coefficient of normal restitution. The interaction with the thermal bath is modeled by a nonlinear drag force plus a white-noise stochastic force. The kinetic theory for this system is described by an Enskog–Fokker–Planck equation for the one-particle velocity distribution function. To get explicit results of the temperature aging and steady states, Maxwellian and first Sonine approximations are developed. The latter takes into account the coupling of the excess kurtosis with the temperature. Theoretical predictions are compared with direct simulation Monte Carlo and event-driven molecular dynamics simulations. While good results for the granular temperature are obtained from the Maxwellian approximation, a much better agreement, especially as inelasticity and drag nonlinearity increase, is found when using the first Sonine approximation. The latter approximation is, additionally, crucial to account for memory effects such as Mpemba and Kovacs-like ones. [ABSTRACT FROM AUTHOR]

A detailed comparison between the Boublík–Mansoori–Carnahan–Starling–Leland (BMCSL) equation of state of hard-sphere mixtures is made with Molecular Dynamics (MD) simulations of the same compositions. The Labík and Smith simulation technique [S. Labík and W. R. Smith, Mol. Simul. 12, 23–31 (1994)] was used to implement the Widom particle insertion method to calculate the excess chemical potential, β μ 0 ex , of a test particle of variable diameter, σ0, immersed in a hard-sphere fluid mixture with different compositions and values of the packing fraction, η. Use is made of the fact that the only polynomial representation of β μ 0 ex which is consistent with the limits σ0 → 0 and σ0 → ∞ has to be of the cubic form, i.e., c 0 ( η ) + c ¯ 1 ( η ) σ 0 / M 1 + c ¯ 2 ( η ) ( σ 0 / M 1 ) 2 + c ¯ 3 ( η ) ( σ 0 / M 1 ) 3 , where M1 is the first moment of the distribution. The first two coefficients, c0(η) and c ¯ 1 ( η ) , are known analytically, while c ¯ 2 ( η ) and c ¯ 3 ( η ) were obtained by fitting the MD data to this expression. This in turn provides a method to determine the excess free energy per particle, βaex, in terms of c ¯ 2 , c ¯ 3 , and the compressibility factor, Z. Very good agreement between the BMCSL formulas and the MD data is found for β μ 0 ex , Z, and βaex for binary mixtures and continuous particle size distributions with the top-hat analytic form. However, the BMCSL theory typically slightly underestimates the simulation values, especially for Z, differences which the Boublík–Carnahan–Starling–Kolafa formulas and an interpolation between two Percus–Yevick routes capture well in different ranges of the system parameter space. [ABSTRACT FROM AUTHOR]

The interest in the description of the properties of fluids of restricted dimensionality is growing for theoretical and practical reasons. In this work, we have firstly developed an analytical expression for the Helmholtz free energy of the two-dimensional square-well fluid in the Barker–Henderson framework. This equation of state is based on an approximate analytical radial distribution function for d-dimensional hard-sphere fluids (1 ≤ d ≤ 3) and is validated against existing and new simulation results. The so-obtained equation of state is implemented in a discrete perturbation theory able to account for general potential shapes. The prototypical Lennard-Jones and Yukawa fluids are tested in its two-dimensional version against available and new simulation data with semiquantitative agreement. [ABSTRACT FROM AUTHOR]

The Labík and Smith Monte Carlo simulation technique to implement the Widom particle insertion method is applied using Molecular Dynamics (MD) instead to calculate numerically the insertion probability, P0(η, σ0), of tracer hard-sphere (HS) particles of different diameters, σ0, in a host HS fluid of diameter σ and packing fraction, η, up to 0.5. It is shown analytically that the only polynomial representation of - ln P0(η, σ0) consistent with the limits σ0 → 0 and σ0 → ∞ has necessarily a cubic form, c0(η)+c1(η)σ0=σ +c2(η)(σ0=σ)² +c3(η)(σ0=σ)³. Our MD data for - ln P0(η, σ0) are fitted to such a cubic polynomial and the functions c0(η) and c1(η) are found to be statistically indistinguishable from their exact solution forms. Similarly, c2(η) and c3(η) agree very well with the Boublík-Mansoori- Carnahan-Starling-Leland and Boublík-Carnahan-Starling-Kolafa formulas. The cubic polynomial is extrapolated (high density) or interpolated (low density) to obtain the chemical potential of the host fluid, or σ0 → σ, as βαex = c0 + c1 + c2 + c3. Excellent agreement between the Carnahan-Starling and Carnahan-Starling-Kolafa theories with our MD data is evident. [ABSTRACT FROM AUTHOR]

The Newcomb–Benford law, also known as the first-digit law, gives the probability distribution associated with the first digit of a dataset so that, for example, the first significant digit has a probability of 30.1% of being 1 and 4.58% of being 9. This law can be extended to the second and next significant digits. This article presents an introduction to the discovery of the law and its derivation from the scale invariance property as well as some applications and examples. Additionally, a simple model of a Markov process inspired by scale invariance is proposed. Within this model, it is proved that the probability distribution irreversibly converges to the Newcomb–Benford law, in analogy to the irreversible evolution toward equilibrium of physical systems in thermodynamics and statistical mechanics. [ABSTRACT FROM AUTHOR]

The relevance of neglecting three- and four-body interactions in the coarse-grained version of the Asakura-Oosawa model is examined. A mapping between the first few virial coefficients of the binary nonadditive hard-sphere mixture representative of this model and those arising from the coarsegrained (pairwise) depletion potential approximation allows for a quantitative evaluation of the effect of such interactions. This turns out to be especially important for large size ratios and large reservoir polymer packing fractions. [ABSTRACT FROM AUTHOR]

The insectivorous bat Myotis chiloensis is endemic of South America. Even though potentially pathogenic bacterial species of Mycoplasma have been reported from this species, there are no further studies regarding the bacterial communities they harbor. This may provide important insights for the better understanding of its ecology, diet and implications in cross-species pathogens transmission. Here we report a first survey on bacterial communities of M. chiloensis based on metagenomic analysis of fecal samples. We found that taxonomic profile is dominated by Proteobacteria (23.7 to 57.7%) and Firmicutes (11.8 to 61.6%), which main families are represented by Burkholderiaceae- Enterobacteriaceae and Veillonellaceae-Bacillaceae, respectively. Phyla Bacteroidetes, Actinobacteria, Cyanobacteria, Planctomycetes and Acidobacteria were also present with abundance above 1% of the total reads. Variations among individuals could be observed at genus level and no significant differences were found between sex groups regarding taxonomic profiles and diversity. Potentially pathogenic species were also detected in all the samples, including Staphylococcus aureus and Clostridium perfringens. Our results highlight the significance M. chiloensis as a reservoir of pathogenic bacteria and its microbiota as an interesting ecological model due to its wide distribution. Further metagenomic studies are necessary for a better understanding of M. chiloensis diet and its host-symbiont relationships. [ABSTRACT FROM AUTHOR]

The mutual entropic depletion force felt by two solute "big" hard spheres immersed in a binary mixture solvent of nonadditive "small" hard spheres is calculated as a function of the surface-to-surface distance by means of canonical Monte Carlo simulations and through a recently proposed rational-function approximation [R. Fantoni and A. Santos, Phys. Rev. E 84, 041201 (2011)]. Four representative scenarios are investigated: symmetric solute particles and the limit where one of the two solute spheres becomes a planar hard wall, in both cases with symmetric and asymmetric solvents. In all cases, the influence on the depletion force due to the nonadditivity in the solvent is determined in the mixed state. Comparison between results from the theoretical approximation and from the simulation shows a good agreement for surface-to-surface distances greater than the smallest solvent diameter. [ABSTRACT FROM AUTHOR]

The fourth virial coefficient of additive hard-sphere mixtures, as predicted by the Percus-Yevick (PY) and hypernetted-chain (HNC) theories, is derived via the compressibility, virial, and chemicalpotential routes, the outcomes being compared with exact results. Except in the case of the HNC compressibility route, the other five expressions exhibit a common structure involving the first three moments of the size distribution. In both theories, the chemical-potential route is slightly better than the virial one and the best behavior is generally presented by the compressibility route. Moreover, the PY results with any of the three routes are more accurate than any of the HNC results. [ABSTRACT FROM AUTHOR]

We look into the Mpemba effect—the initially hotter sample cools sooner—in a molecular gas with nonlinear viscous drag. Specifically, the gas particles interact among them via elastic collisions and with a background fluid at equilibrium. Thus, within the framework of kinetic theory, our gas is described by an Enskog–Fokker–Planck equation. The analysis is carried out using the first Sonine approximation, in which the evolution of temperature is coupled to that of excess kurtosis. This coupling leads to the emergence of the Mpemba effect, which is observed at an early stage of relaxation and when the initial temperatures of the two samples are close enough. This allows for the development of a simple theory, linearizing the temperature evolution around a reference temperature, namely, the initial temperature closer to the asymptotic equilibrium value. The linear theory provides a semiquantitative description of the effect, including expressions for crossover time and maximum temperature difference. We also discuss the limitations of our linearized theory. [ABSTRACT FROM AUTHOR]

The extreme weather conditions in the Antarctic have exerted selective pressures favoring differential features in bacteria to survive this untapped environment (i.e., antibiotic molecules). Notably, higher chances of antibiotic discovery from extremophiles have been proposed recently. Although new organic and environmentally friendly sources for helping in the control of plant pathogenic fungi are necessary, the information about anti-phytopathogenic applications of extremophile microorganisms from untapped environments is limited. In this study, we determined the antifungal effect of actinobacterial strains isolated from Antarctic soils and sediments. Co-culture inhibition assays and Minimum Inhibitory Concentration (MIC) determination revealed that all Antarctic strains (x28) can inhibit the growth of at least one phytopathogenic fungi including Fusarium oxysporum, Rhizoctonia solani, Botrytis sp. and Phytophthora infestans. Additionally, new novel antagonistic relationships are reported. Our work establishes a precedent on Antarctic actinobacteria strains with the capacity to produce antifungal compounds, and its potential for developing new fungicides or biocontrol agents solving current agriculture problems. [ABSTRACT FROM AUTHOR]

The fourth virial coefficient of asymmetric nonadditive binary mixtures of hard disks is computed with a standard Monte Carlo method. Wide ranges of size ratio (0.05 <= q <= 0.95) and nonadditivity (-0.5 <= Δ <= 0.5) are covered. A comparison is made between the numerical results and those that follow from some theoretical developments. The possible use of these data in the derivation of new equations of state for these mixtures is illustrated by considering a rescaled virial expansion truncated to fourth order. The numerical results obtained using this equation of state are compared with Monte Carlo simulation data in the case of a size ratio q = 0.7 and two nonadditivities Δ = ±0.2. [ABSTRACT FROM AUTHOR]

A possible approximate route to obtain the equation of state of the monodisperse hard-sphere system in the metastable fluid region from the knowledge of the equation of state of a hard-sphere mixture at high densities is discussed. The proposal is illustrated by using recent Monte Carlo simulation data for the pressure of a binary mixture. It is further shown to exhibit high internal consistency. [ABSTRACT FROM AUTHOR]

The question of whether the known virial coefficients are enough to determine the packing fraction η∞ at which the fluid equation of state of a hard-sphere fluid diverges is addressed. It is found that the information derived from the direct Padé approximants to the compressibility factor constructed with the virial coefficients is inconclusive. An alternative approach is proposed which makes use of the same virial coefficients and of the equation of state in a form where the packing fraction is explicitly given as a function of the pressure. The results of this approach both for hard-disk and hard-sphere fluids, which can straightforwardly accommodate higher virial coefficients when available, lends support to the conjecture that η∞ is equal to the maximum packing fraction corresponding to an ordered crystalline structure. [ABSTRACT FROM AUTHOR]

Different theoretical approaches for the thermodynamic properties and the equation of state for multicomponent mixtures of nonadditive hard spheres in d dimensions are presented in a unified way. These include the theory by Hamad, our previous formulation, the original MIX1 theory, a recently proposed modified MIX1 theory, as well as a nonlinear extension of the MIX1 theory proposed in this paper. Explicit expressions for the compressibility factor, Helmholtz free energy, and second, third, and fourth virial coefficients are provided. A comparison is carried out with recent Monte Carlo data for the virial coefficients of asymmetric mixtures and with available simulation data for the compressibility factor, the critical consolute point, and the liquid-liquid coexistence curves. The merits and limitations of each theory are pointed out. [ABSTRACT FROM AUTHOR]

As is well known, approximate integral equations for liquids, such as the hypernetted chain (HNC) and Percus–Yevick (PY) theories, are in general thermodynamically inconsistent in the sense that the macroscopic properties obtained from the spatial correlation functions depend on the route followed. In particular, the values of the fourth virial coefficient B4 predicted by the HNC and PY approximations via the virial route differ from those obtained via the compressibility route. Despite this, it is shown in this paper that the value of B4 obtained from the virial route in the HNC theory is exactly three halves the value obtained from the compressibility route in the PY theory, irrespective of the interaction potential (whether isotropic or not), the number of components, and the dimensionality of the system. This simple relationship is confirmed in one-component systems by analytical results for the one-dimensional penetrable-square-well model and the three-dimensional penetrable-sphere model, as well as by numerical results for the one-dimensional Lennard-Jones model, the one-dimensional Gaussian core model, and the three-dimensional square-well model. [ABSTRACT FROM AUTHOR]

The Kirkwood–Buff integrals for two-component mixtures in one-dimensional systems are calculated directly. The results are applied to square-well particles and found to agree with those obtained by the inversion of the Kirkwood–Buff theory of solutions. [ABSTRACT FROM AUTHOR]

Using the first seven known virial coefficients and forcing it to possess two branch-point singularities, a new equation of state for the hard-sphere fluid is proposed. This equation of state predicts accurate values of the higher virial coefficients, a radius of convergence smaller than the close-packing value, and it is as accurate as the rescaled virial expansion and better than the Padé [3/3] equations of state. Consequences regarding the convergence properties of the virial series and the use of similar equations of state for hard-core fluids in d dimensions are also pointed out. [ABSTRACT FROM AUTHOR]

The depletion force and depletion potential between two in principle unequal “big” hard spheres embedded in a multicomponent mixture of “small” hard spheres are computed using the rational function approximation method for the structural properties of hard-sphere mixtures [S. B. Yuste, A. Santos, and M. López de Haro, J. Chem. Phys. 108, 3683 (1998)]. The cases of equal solute particles and of one big particle and a hard planar wall in a background monodisperse hard-sphere fluid are explicitly analyzed. An improvement over the performance of the Percus–Yevick theory and good agreement with available simulation results are found. [ABSTRACT FROM AUTHOR]

Bounded potentials are good models to represent the effective two-body interaction in some colloidal systems, such as the dilute solutions of polymer chains in good solvents. The simplest bounded potential is that of penetrable spheres, which takes a positive finite value if the two spheres are overlapped, being 0 otherwise. Even in the one-dimensional case, the penetrable-rod model is far from trivial, since interactions are not restricted to nearest neighbors and so its exact solution is not known. In this paper the structural properties of one-dimensional penetrable rods are studied. We first derive the exact correlation functions of the penetrable-rod fluids to second order in density at any temperature, as well as in the high-temperature and zero-temperature limits at any density. It is seen that, in contrast to what is generally believed, the Percus-Yevick equation does not yield the exact cavity function in the hard-rod limit. Next, two simple analytic theories are constructed: a high-temperature approximation based on the exact asymptotic behavior in the limit T→∞ and a low-temperature approximation inspired by the exact result in the opposite limit T→0. Finally, we perform Monte Carlo simulations for a wide range of temperatures and densities to assess the validity of both theories. It is found that they complement each other quite well, exhibiting a good agreement with the simulation data within their respective domains of applicability and becoming practically equivalent on the borderline of those domains. A comparison with numerical solutions of the Percus-Yevick and the hypernetted-chain approximations is also carried out. Finally, a perspective on the extension of our two heuristic theories to the more realistic three-dimensional case is provided. [ABSTRACT FROM AUTHOR]

The contact values g(σ,σ′) of the radial distribution functions of a fluid of (additive) hard spheres with a given size distribution f(σ) are considered. A “universality” assumption is introduced, according to which, at a given packing fraction η,g(σ,σ′)=G(z(σ,σ′)), where G is a common function independent of the number of components (either finite or infinite) and z(σ,σ′)=[2σσ′/(σ+σ′)]μ2/μ3 is a dimensionless parameter, μn being the nth moment of the diameter distribution. A cubic form proposal for the z dependence of G is made and known exact consistency conditions for the point particle and equal size limits, as well as between two different routes to compute the pressure of the system in the presence of a hard wall, are used to express G(z) in terms of the radial distribution at contact of the one-component system. For polydisperse systems we compare the contact values of the wall-particle correlation function and the compressibility factor with those obtained from recent Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

We report molecular dynamics results for the contact values of the radial distribution functions of binary additive mixtures of hard disks. The simulation data are compared with theoretical predictions from expressions proposed by Jenkins and Mancini [J. Appl. Mech. 54, 27 (1987)] and Santos et al. [J. Chem. Phys. 117, 5785 (2002)]. Both theories agree quantitatively within a very small margin, which renders the former still a very useful and simple tool to work with. The latter (higher-order and self-consistent) theory provides a small qualitative correction for low densities and is superior especially in the high-density domain.© 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The exact statistical-mechanical solution for the equilibrium properties, both thermodynamic and structural, of one-dimensional fluids of particles interacting via the triangle-well and the ramp potentials is worked out. In contrast to previous studies, where the radial distribution function g(r) was obtained numerically from the structure factor by Fourier inversion, we provide a fully analytic representation of g(r) up to any desired distance. The solution is employed to perform an extensive study of the equation of state, the excess internal energy per particle, the residual multiparticle entropy, the structure factor, the radial distribution function, and the direct correlation function. In addition, scatter plots of the bridge function versus the indirect correlation function are used to gauge the reliability of the hypernetted-chain, Percus–Yevick, and Martynov–Sarkisov closures. Finally, the Fisher–Widom and Widom lines are obtained in the case of the triangle-well model. [ABSTRACT FROM AUTHOR]

Highlights • Antarctic bacterial strain So13.3 produces a pigment with DSSC sensitizer activity. • Pigment from Antarctic bacteria can produce energy and is a type of melanin. • Pigment-producing microorganisms from Antarctic can be a source for DSSC use. Abstract The study of bacterial pigment for their application in DSSC is an in-development area of solar energy. However, studies on bacterial pigments for application in solar cells are scarce. We evaluated the use of a pigment obtained from the Antarctic So13.3 bacterial strain as a sensitizer in DSSC. Based on the sequence of the 16S gene, the So13.3 strain was identified as Streptomyces fildesensis. The bacterial pigment was characterized by UV–Vis and Fourier-Transform Infrared Spectroscopy (FTIR). Results indicate that the pigment has very similar characteristics to melanin. DSSC showed the best performance at a concentration of 6500 (μg/mL), obtaining a voltage of 493 [mV], a current density of 0.091 [mA/cm2], 0.026% efficiency and a 0.579 Filling Factor (FF). Considering that there are few studies on bacterial pigments applied in DSSC, we demonstrate the importance of focusing research on pigment-producing microorganism isolation and evaluating their potential use in DSSC. [ABSTRACT FROM AUTHOR]

The Antarctic continent is undergoing a rapid warming, affecting microbial communities throughout its ecosystems. This continent is a natural laboratory for studying the effect of climate change, however, assessing the microbial communities' responses to environmental changes is challenging from a methodological point of view. We suggest novel experimental designs, including multivariable assessments that apply multiomics methods in combination with continuous environmental data recording and new warming simulation systems. Moreover, we propose that climate change studies in Antarctica should consider three main objectives, including descriptive studies, short-term temporary adaptation studies, and long-term adaptive evolution studies. This will help us to understand and manage the effects of climate change on the Earth. [Display omitted] • Antarctic as natural laboratory for climate change studies. • Novel multiscale and multiomics designs for the assessment of climate change effects • Application of in situ warming simulation systems for climate change studies. [ABSTRACT FROM AUTHOR]

The linearized Debye–Hückel theory for liquid state is shown to provide thermodynamically consistent virial and energy routes for any potential and for any dimensionality. The importance of this result for bounded potentials is discussed. [ABSTRACT FROM AUTHOR]

As is well known, one-dimensional systems with interactions restricted to first nearest neighbors admit a full analytically exact statistical-mechanical solution. This is essentially due to the fact that the knowledge of the first nearest-neighbor probability distribution function, $$p_1(r)$$ , is enough to determine the structural and thermodynamic properties of the system. On the other hand, if the interaction between second nearest-neighbor particles is turned on, the analytically exact solution is lost. Not only the knowledge of $$p_1(r)$$ is not sufficient anymore, but even its determination becomes a complex many-body problem. In this work we systematically explore different approximate solutions for one-dimensional second nearest-neighbor fluid models. We apply those approximations to the square-well and the attractive two-step pair potentials and compare them with Monte Carlo simulations, finding an excellent agreement. [ABSTRACT FROM AUTHOR]

In a previous work, a simple approach to derive the jamming packing fraction of a hard-sphere mixture from the knowledge of the random close-packing fraction of the monocomponent system was proposed. Now, an extension of that approach is applied to provide an approximate formula for the densest packing fraction of a given hard-sphere mixture in terms of the fcc close-packing fraction of a monocomponent hard-sphere system and of a single parameter encapsulating the dependence on the size ratios and the number of spheres in the unit cell. Comparison with recent results for such densest packing fraction of binary and ternary systems is performed and reasonable agreement is obtained. • Simple approximation for the densest packing fraction of any given hard-sphere mixture. • Fair ordering of data for the densest packing fraction of binary and ternary systems. • Possibly useful to identify and look for geometric structures not reported yet. • Approach easily extended to deal with mixtures of d -dimensional hard spheres. [ABSTRACT FROM AUTHOR]

In recent years microorganisms as fungi, yeasts and especially bacteria have been used to produce nanoparticles biosynthesis. Several types of bacteria are described as nanoparticles producers, however, psychrophilic and psychrotolerant bacterias have not been studied widely, although its use in the production of nanoparticles could provide advantages related to the stability of nanoparticles, energy expenditure on its production, while being an environmentally friendly alternative. This article provides a brief overview of Antarctic bacterias, both psychrophilic and psychrotolerant that synthesis nanoparticles, possible mechanisms associated to this synthesis and future perspectives related to bacterial biosynthesis of nanoparticles. [ABSTRACT FROM AUTHOR]

• A semi-analytical and nonperturbative approach (RFA) is applied to fluids of molecules interacting via step potentials. • Comparison with recent simulation data for structural and thermodynamic properties shows a good agreement. • The RFA and exact properties at low densities are explicitly derived. The structural and thermodynamic properties of fluids whose molecules interact via potentials with a hard-core plus a square well, a square shoulder, and a second square well, are considered. Those properties are derived by using a (semi-analytical) rational-function approximation method as a particular case of the more general formulation provided earlier involving potentials with a hard-core plus n piecewise constant sections. Comparison of the results with recent simulation data confirms the usefulness of the approach. [ABSTRACT FROM AUTHOR]

We study here the steady state attained in a granular gas of inelastic rough spheres that is subject to a spatially uniform random volume force. The stochastic force has the form of the so-called white noise and acts by adding impulse to the particle translational velocities. We work out an analytical solution of the corresponding velocity distribution function from a Sonine polynomial expansion that displays energy non-equipartition between the translational and rotational modes, translational and rotational kurtoses, and translational-rotational velocity correlations. By comparison with a numerical solution of the Boltzmann kinetic equation (by means of the direct simulation Monte Carlo method), we show that our analytical solution provides a good description that is quantitatively very accurate in certain ranges of inelasticity and roughness. We also find three important features that make the forced granular gas steady state very different from the homogeneous cooling state (attained by an unforced granular gas). First, the marginal velocity distributions are always close to a Maxwellian. Second, there is a continuous transition to the purely smooth limit (where the effects of particle rotations are ignored). And third, the angular translational-rotational velocity correlations show a preference for a quasiperpendicular mutual orientation (which is called "lifted-tennis-ball" behavior). [ABSTRACT FROM AUTHOR]

We study the role of multi-particle spatial correlations in the appearance of a liquid–vapour critical point. Our analysis is based on the exact infinite hierarchy of equations relating spatial integrals of (k+ 1)-particle correlations to thek-particle ones and their derivatives with respect to the density. Critical exponents corresponding to generalised compressibility equations resulting from the hierarchy are shown to grow linearly with the order of correlations. We prove that the critical behaviour requires taking into account correlation functions of arbitrary order. It is however only a necessary condition. Indeed, approximate closures of the hierarchy obtained by expressing higher order correlations in terms of lower order ones (Kirkwood's superposition approximation and its generalisations) turn out to be inconsistent with the critical behaviour. [ABSTRACT FROM PUBLISHER]

We use the Percus-Yevick approach in the chemical-potential route to evaluate the equation of state of hard hyperspheres in five dimensions. The evaluation requires the derivation of an analytical expression for the contact value of the pair distribution function between particles of the bulk fluid and a solute particle with arbitrary size. The equation of state is compared with those obtained from the conventional virial and compressibility thermodynamic routes and the associated virial coefficients are computed. The pressure calculated from all routes is exact up to third density order, but it deviates with respect to simulation data as density increases, the compressibility and the chemical-potential routes exhibiting smaller deviations than the virial route. Accurate linear interpolations between the compressibility route and either the chemical-potential route or the virial one are constructed. [ABSTRACT FROM AUTHOR]

The Boltzmann equation for inelastic and rough hard spheres is considered as a model of a dilute granular gas. In this model, the collisions are characterized by constant coefficients of normal and tangential restitution, and hence the translational and rotational degrees of freedom are coupled. A normal solution to the Boltzmann equation is obtained by means of the Chapman-Enskog method for states near the homogeneous cooling state. The analysis is carried out to first order in the spatial gradients of the number density, the flow velocity, and the granular temperature. The constitutive equations for the momentum and heat fluxes and for the cooling rate are derived, and the associated transport coefficients are expressed in terms of the solutions of linear integral equations. For practical purposes, a first Sonine approximation is used to obtain explicit expressions of the transport coefficients as nonlinear functions of both coefficients of restitution and the moment of inertia. Known results for purely smooth inelastic spheres and perfectly elastic and rough spheres are recovered in the appropriate limits. [ABSTRACT FROM AUTHOR]