Obtaining efficient thermal engines from interacting Brownian particles under time-periodic drivings.

We introduce an alternative route for obtaining reliable cyclic engines, based on two interacting Brownian particles under time-periodic drivings which can be used as a work-to-work converter or a heat engine. Exact expressions for the thermodynamic fluxes, such as power and heat, are obtained using the framework of stochastic thermodynamic. We then use these exact expression to optimize the driving protocols with respect to output forces, their phase difference. For the work-to-work engine, they are solely expressed in terms of Onsager coefficients and their derivatives, whereas nonlinear effects start to play a role since the particles are at different temperatures. Our results suggest that stronger coupling generally leads to better performance, but careful design is needed to optimize the external forces.

Obtaining efficient collisional engines via velocity-dependent drivings.

Brownian particles interacting sequentially with distinct temperatures and driving forces at each stroke have been tackled as a reliable alternative for the construction of engine setups. However, they can behave very inefficiently depending on the driving used for the work source and/or when temperatures of each stage are very different from each other. Inspired by some models for molecular motors and recent experimental studies, a coupling between driving and velocities is introduced and detail investigated from stochastic thermodynamics. Exact expressions for thermodynamic quantities and distinct maximization routes have been obtained. The search of an optimal coupling provides a substantial increase of engine performance (mainly efficiency), even for large ΔT. A simple and general argument for the optimal coupling can be estimated, irrespective of the driving and other model details.

Influence of distinct kinds of temporal disorder in discontinuous phase transitions.

Based on mean-field theory (MFT) arguments, a general description for discontinuous phase transitions in the presence of temporal disorder is considered. Our analysis extends the recent findings [C. E. Fiore et al., Phys. Rev. E 98, 032129 (2018)2470-004510.1103/PhysRevE.98.032129] by considering discontinuous phase transitions beyond those with a single absorbing state. The theory is exemplified in one of the simplest (nonequilibrium) order-disorder (discontinuous) phase transitions with "up-down" Z_{2} symmetry: the inertial majority vote model for two kinds of temporal disorder. As for absorbing phase transitions, the temporal disorder does not suppress the occurrence of discontinuous phase transitions, but remarkable differences emerge when compared with the pure (disorderless) case. A comparison between the distinct kinds of temporal disorder is also performed beyond the MFT for random-regular complex topologies. Our work paves the way for the study of a generic discontinuous phase transition under the influence of an arbitrary kind of temporal disorder.

Current fluctuations in nonequilibrium discontinuous phase transitions.

Discontinuous phase transitions out of equilibrium can be characterized by the behavior of macroscopic stochastic currents. But while much is known about the average current, the situation is much less understood for higher statistics. In this paper, we address the consequences of the diverging metastability lifetime-a hallmark of discontinuous transitions-in the fluctuations of arbitrary thermodynamic currents, including the entropy production. In particular, we center our discussion on the conditional statistics, given which phase the system is in. We highlight the interplay between integration window and metastability lifetime, which is not manifested in the average current, but strongly influences the fluctuations. We introduce conditional currents and find, among other predictions, their connection to average and scaled variance through a finite-time version of large deviation theory and a minimal model. Our results are then further verified in two paradigmatic models of discontinuous transitions: Schlögl's model of chemical reactions, and a 12-state Potts model subject to two baths at different temperatures.

Entropy production and heat transport in harmonic chains under time-dependent periodic drivings.

Using stochastic thermodynamics, the properties of interacting linear chains subject to periodic drivings are investigated. The systems are described by Fokker-Planck-Kramers equation and exact solutions are obtained as functions of the modulation frequency and strength constants. Analysis will be carried out for short and long chains. In the former case, explicit expressions are derived for a chain of two particles, in which the entropy production is written down as a bilinear function of thermodynamic forces and fluxes, whose associated Onsager coefficients are evaluated for distinct kinds of periodic drivings. The limit of long chains is analyzed by means of a protocol in which the intermediate temperatures are self-consistently chosen and the entropy production is decomposed as a sum of two individual contributions, one coming from real baths (placed at extremities of lattice) and other from self-consistent baths. Whenever the former dominates for short chains, the latter contribution prevails for long ones. The thermal reservoirs lead to a heat flux according to Fourier's law.

Entropy production as a tool for characterizing nonequilibrium phase transitions.

Nonequilibrium phase transitions can be typified in a similar way to equilibrium systems, for instance, by the use of the order parameter. However, this characterization hides the irreversible character of the dynamics as well as its influence on the phase transition properties. Entropy production has been revealed to be an important concept for filling this gap since it vanishes identically for equilibrium systems and is positive for the nonequilibrium case. Based on distinct and general arguments, the characterization of phase transitions in terms of the entropy production is presented. Analysis for discontinuous and continuous phase transitions has been undertaken by taking regular and complex topologies within the framework of mean-field theory (MFT) and beyond the MFT. A general description of entropy production portraits for Z_{2} ("up-down") symmetry systems under the MFT is presented. Our main result is that a given phase transition, whether continuous or discontinuous has a specific entropy production hallmark. Our predictions are exemplified by an icon system, perhaps the simplest nonequilibrium model presenting an order-disorder phase transition and spontaneous symmetry breaking: the majority vote model. Our work paves the way to a systematic description and classification of nonequilibrium phase transitions through a key indicator of system irreversibility.

Quenched disorder in the contact process on bipartite sublattices.

We study the effects of distinct types of quenched disorder in the contact process with a competitive dynamics on bipartite sublattices. In the model, the particle creation depends on its first and second neighbors and the extinction increases according to the local density. The clean (without disorder) model exhibits three phases: inactive (absorbing), active symmetric, and active asymmetric, where the latter exhibits distinct sublattice densities. These phases are separated by continuous transitions; the phase diagram is reentrant. By performing mean-field analysis and Monte Carlo simulations we show that symmetric disorder destroys the sublattice ordering and therefore the active asymmetric phase is not present. On the other hand, for asymmetric disorder (each sublattice presenting a distinct dilution rate) the phase transition occurs between the absorbing and the active asymmetric phases. The universality class of this transition is governed by the less-disordered sublattice. Finally, our results suggest that random-field disorder destroys the phase transition if it breaks the symmetry between two active states.

Partial inertia induces additional phase transition in the majority vote model.

Explosive (i.e., discontinuous) transitions have aroused great interest by manifesting in distinct systems, such as synchronization in coupled oscillators, percolation regime, absorbing phase transitions, and more recently, the majority-vote model with inertia. In the latter, the model rules are slightly modified by the inclusion of a term depending on the local spin (an inertial term). In such a case, Chen et al. [Phys Rev. E 95, 042304 (2017)2470-004510.1103/PhysRevE.95.042304] have found that relevant inertia changes the nature of the phase transition in complex networks, from continuous to discontinuous. Here we give a further step by embedding inertia only in vertices with degree larger than a threshold value 〈k〉k^{*}, 〈k〉 being the mean system degree and k^{*} the fraction restriction. Our results, from mean-field analysis and extensive numerical simulations, reveal that an explosive transition is presented in both homogeneous and heterogeneous structures for small and intermediate k^{*}'s. Otherwise, a large restriction can sustain a discontinuous transition only in the heterogeneous case. This shares some similarities with recent results for the Kuramoto model [Phys. Rev. E 91, 022818 (2015)PLEEE81539-375510.1103/PhysRevE.91.022818]. Surprisingly, intermediate restriction and large inertia are responsible for the emergence of an extra phase, in which the system is partially synchronized and the classification of phase transition depends on the inertia and the lattice topology. In this case, the system exhibits two phase transitions.

Temporal disorder does not forbid discontinuous absorbing phase transitions in low-dimensional systems.

Recent papers have shown that spatial (quenched) disorder can suppress discontinuous absorbing phase transitions. Conversely, the scenario for temporal disorder is still unknown. To shed some light in this direction, we investigate its effect in three different two-dimensional models which are known to exhibit discontinuous absorbing phase transitions. The temporal disorder is introduced by allowing the control parameter to be time dependent p→p(t), either varying as a uniform distribution with mean p[over ¯] and variance σ or as a bimodal distribution, fluctuating between a value p and a value p_{l}≪p. In contrast to spatial disorder, our numerical results strongly suggest that such uncorrelated temporal disorder does not forbid the existence of a discontinuous absorbing phase transition. We find that all cases are characterized by behaviors similar to their pure (without disorder) counterparts, including bistability around the coexistence point and common finite-size scaling behavior with the inverse of the system volume, as recently proposed [M. M. de Oliveira et al., Phys. Rev. E 92, 062126 (2015)PLEEE81539-375510.1103/PhysRevE.92.062126]. We also observe that temporal disorder does not induce temporal Griffiths phases around discontinuous phase transitions, at least not for d=2.

Comparing the influence of distinct kinds of temporal disorder in a low-dimensional absorbing transition model.

Recently it was stated that temporal disorder constitutes a relevant perturbation in absorbing phase transitions for all dimensions. However, its effect on systems other than the standard contact process (CP), its competition with other ingredients (e.g., particle diffusion), and other kinds of disorder (besides the standard types) are unknown. In order to shed some light on the above-mentioned points, we investigate a variant of the usual CP, namely, the triplet annihilation model, in which the competition between triplet annihilation and single particle diffusion leads to an unusual phase diagram behavior, with reentrant shape and endless activity for sufficiently large diffusion rates. Two kinds of time-dependent disorder have been considered. In the former, it is introduced in the creation-annihilation parameters (as commonly considered in recent studies), whereas in the latter, the diffusion rate D is allowed to be time dependent. In all cases, the disorder follows a uniform distribution with fixed mean and width σ. Two values of σ have been considered in order to exemplify the regime of "weaker" and "stronger" temporal disorder strengths. Our results show that in the former approach, the disorder suppresses the reentrant phase diagram with a critical behavior deviating from the directed percolation (DP) universality class in the regime of low diffusion rates, while they strongly suggest that the DP class is recovered for larger hopping rates. An opposite scenario is found in the latter disorder approach, with a substantial increase of reentrant shape and the maximum diffusion, in which the reentrant shape also displays a critical behavior consistent with the DP universality class (in similarity with the pure model). In order to compare with very recent claims, the results from taking a bimodal distribution and critical behavior in the limit of strong disorder are presented. Also, the results derived from the mean-field theory are performed, presenting partial agreement with numerical results. Lastly, a comparison with the diffusive disordered CP is undertaken.

The utility of lumbar spine trabecular bone score and femoral neck bone mineral density for identifying asymptomatic vertebral fractures in well-compensated type 2 diabetic patients.

UNLABELLED: The objective of the study was to evaluate the usefulness of trabecular bone score (TBS) and bone mineral density (BMD) for identifying vertebral fractures (VFx) in well-compensated type 2 diabetic (T2D) patients. TBS and femoral neck BMD below certain cutoffs may be useful for identifying VFx in well-compensated T2D patients. INTRODUCTION: In T2D, the prevalence of VFx is increased, especially in poorly compensated and complicated diabetic patients. The possibility of predicting the fracture risk in T2D patients by measuring BMD and TBS, an indirect parameter of bone quality, is under debate. Therefore, the objective was to evaluate the usefulness of TBS and BMD for identifying VFx in well-compensated T2D patients. METHODS: Ninety-nine T2D postmenopausal women in good metabolic control (glycosylated haemoglobin 6.8 ± 0.7 %) and 107 control subjects without T2D were evaluated. In all subjects, we evaluated the following: the BMD at the lumbar spine (LS) and the femoral neck (FN); the TBS by dual X-ray absorptiometry; and VFx by radiography. In T2D subjects, the presence of diabetic retinopathy, neuropathy, and nephropathy was evaluated. RESULTS: T2D subjects had increased VFx prevalence (34.3 %) as compared to controls (18.7 %) (p = 0.01). T2D subjects presented higher BMD (LS -0.8 ± 1.44, FN -1.06 ± 1.08), as compared to controls (LS -1.39 ± 1.28, p = 0.002; FN -1.45 ± 0.91, p = 0.006, respectively). TBS was not different between diabetics and controls. In fractured T2D patients, LS-BMD, FN-BMD, and TBS were reduced (-1.2 ± 1.44; -1.44 ± 1.04; 1.072 ± 0.15) and the prevalence of retinopathy (15.4 %) was increased than in nonfractured T2D subjects (-0.59 ± 1.4, p = 0.035; -0.87 ± 1.05, p = 0.005; 1.159 ± 0.15, p = 0.006; 1.8 %, p = 0.04, respectively). The combination of TBS ≤1.130 and FN-BMD less than -1.0 had the best diagnostic accuracy for detecting T2D fractured patients (SP 73.8 %, SN 63.6 %, NPV 78.9 %, PPV 56.8 %). CONCLUSIONS: TBS and FN-BMD below certain cutoffs may be useful for identifying VFx in well-compensated T2D patients.

Decreased bone cortical density at the forearm in subjects with subclinical peripheral arterial disease.

UNLABELLED: The association between peripheral arterial disease (PAD) and low bone mass is controversial. In our study, peripheral quantitative computed tomography shows a reduction of cortical but not trabecular, bone mineral density (BMD) at the forearm, in patients with subclinical PAD. INTRODUCTION: Some controversy exists regarding the association between peripheral arterial disease (PAD) and low bone mass. Previous studies have evaluated bone mineral density (BMD) in patients with subclinical PAD, with mixed results. Inconsistency of data may depend on the fact that most studies measured areal bone mineral density (aBMD) by Dual-energy-x ray absorptiometry (DXA). Because DXA cannot distinguish between cortical and trabecular compartments, we reasoned that a study aimed to establish whether these compartments were differentially affected by PAD status could give more information on the nature of this association. METHODS: In this cross-sectional study, we used peripheral quantitative computed tomography (pQCT) to examine volumetric cortical and trabecular mineral density at the radius (vBMD) in a cohort of subjects with subclinical PAD as defined by ABI ≤0.90 and compared them with healthy subjects with no evidence of PAD. RESULTS: Patients with subclinical PAD had significantly reduced cortical density (1101.0 ± 45.4 vs 1156.2 ± 51.3 mg/cm(3), p < 0.001) and cortical area (75.0 ± 20.9 vs 99.9 ± 18.2 mm(2), p < 0.001) than healthy subjects. Trabecular density (178.1 ± 47.9 vs 165.8 ± 29.6 mg/cm(3)) was not significantly different in the two groups. CONCLUSION: Subclinical PAD induces a selective bone loss at the radius compartment, not identified by standard DXA, which seems to occur primarily at the cortical level.

Generic finite size scaling for discontinuous nonequilibrium phase transitions into absorbing states.

Based on quasistationary distribution ideas, a general finite size scaling theory is proposed for discontinuous nonequilibrium phase transitions into absorbing states. Analogously to the equilibrium case, we show that quantities such as response functions, cumulants, and equal area probability distributions all scale with the volume, thus allowing proper estimates for the thermodynamic limit. To illustrate these results, five very distinct lattice models displaying nonequilibrium transitions-to single and infinitely many absorbing states-are investigated. The innate difficulties in analyzing absorbing phase transitions are circumvented through quasistationary simulation methods. Our findings (allied to numerical studies in the literature) strongly point to a unifying discontinuous phase transition scaling behavior for equilibrium and this important class of nonequilibrium systems.

Relationships between osteoprotegerin, receptor activator of the nuclear factor kB ligand serum levels and carotid intima-media thickness in patients with type 2 diabetes mellitus.

AIM: The aim of this paper was to investigate the association of circulating osteoprotegerin (OPG) and receptor activator of the nuclear factor kB ligand (RANKL) levels with carotid intima-media thickness (CIMT) in type 2 diabetes mellitus (T2DM). METHODS: We performed a cross-sectional community-based study including 40 T2DM postmenopausal women and 40 healthy controls. CIMT was measured by B-mode ultrasound. Serum OPG and RANKL were measured by solid-phase enzyme-linked immunosorbent assay (ELISA). RESULTS: Serum OPG levels were higher in T2DM than in controls (median 2.9 vs 2.0 pmol/liter; P<0.001), significantly associated with CIMT in T2DM (P<0.001). RANKL levels were lower in T2DM than in controls (median 0.45 vs 0.60 pmol/liter; P<0.0001), however no association was found with CIMT. Serum OPG levels were associated with cross-sectional measure of CIMT in T2DM. CONCLUSION: The data would support the role of an increased OPG/RANKL ratio as a possible marker of progression of vascular dysfunction in diabetes.

Fluorescent epibiotic microbial community on the carapace of a Bahamian ostracod.

Ostracods collected from shallow coral reefs in the Bahamas were found to exhibit blue light-stimulated orange fluorescence at night. Fluorescent spectra revealed the presence of orange fluorescence with a maximum emission at ~595 nm on the carapace of these ostracods, while scanning electron microscopy revealed a morphologically diverse microbial community covering the entire carapace of these ostracods. Pyrosequencing and cyanobacterial-specific 16S rRNA sequencing reveals that this epibiont community is highly diverse and highly variable between individual ostracods. Many species of Cyanobacteria in the orders Oscillatoriales and Chroococcales, as well as other Proteobacteria and diatom chloroplast sequences, were identified using the cyanobacterial-specific primers. While no fluorescent proteins or phycoerythrin were detected in these ostracods, it is possible that the observed orange fluorescence is the result of carotenoid fluorescence from Cyanobacteria. The microbial consortium forms an epibiotic biofilm on the carapace of these ostracods whose functions are unknown.

Side effects of cocaine abuse: multiorgan toxicity and pathological consequences.

Cocaine is a powerful stimulant of the sympathetic nervous system by inhibiting catecholamine reuptake, stimulating central sympathetic outflow, and increasing the sensitivity of adrenergic nerve endings to norepinephrine (NE). It is known, from numerous studies, that cocaine causes irreversible structural changes on the brain, heart, lung and other organs such as liver and kidney and there are many mechanisms involved in the genesis of these damages. Some effects are determined by the overstimulation of the adrenergic system. Most of the direct toxic effects are mediated by oxidative stress and by mitochondrial dysfunction produced during the metabolism of noradrenaline or during the metabolism of norcocaina, as in cocaine-induced hepathotoxicity. Cocaine is responsible for the coronary arteries vasoconstriction, atherosclerotic phenomena and thrombus formation. In this way, cocaine favors the myocardial infarction. While the arrhythmogenic effect of cocaine is mediated by the action on potassium channel (blocking), calcium channels (enhances the function) and inhibiting the flow of sodium during depolarization. Moreover chronic cocaine use is associated with myocarditis, ventricular hypertrophy, dilated cardiomyopathy and heart failure. A variety of respiratory problems temporally associated with crack inhalation have been reported. Cocaine may cause changes in the respiratory tract as a result of its pharmacologic effects exerted either locally or systemically, its method of administration (smoking, sniffing, injecting), or its alteration of central nervous system neuroregulation of pulmonary function. Renal failure resulting from cocaine abuse has been also well documented. A lot of studies demonstrated a high incidence of congenital cardiovascular and brain malformations in offspring born to mothers with a history of cocaine abuse.

Energetic ion loss detector on the Alcator C-Mod tokamak.

A scintillator-based energetic ion loss detector has been successfully commissioned on the Alcator C-Mod tokamak. This probe is located just below the outer midplane, where it captures ions of energies up to 2 MeV resulting from ion cyclotron resonance heating. After passing through a collimating aperture, ions impact different regions of the scintillator according to their gyroradius (energy) and pitch angle. The probe geometry and installation location are determined based on modeling of expected lost ions. The resulting probe is compact and resembles a standard plasma facing tile. Four separate fiber optic cables view different regions of the scintillator to provide phase space resolution. Evolving loss levels are measured during ion cyclotron resonance heating, including variation dependent upon individual antennae.

[Lung diffusion capacity and quality of life 6 months after discharge from the ICU among survivors of acute respiratory distress syndrome due to influenza A H1N1]. / Capacidad de difusión pulmonar y calidad de vida a los 6 meses del alta de la unidad de cuidados intensivos en sobrevivientes a síndrome de distrés respiratorio agudo por influenza A H1N1.

OBJECTIVE: An evaluation is made of lung function and quality of life 6 months after discharge from the Intensive Care Unit (ICU) among survivors of acute respiratory distress syndrome (ARDS) due to pandemic 2009 influenza A H1N1, based on studies of lung function and the EQ-5D health questionnaire. DESIGN: Case series. SETTING: The ICU of Dr. Leónidas Lucero Acute Cases Municipal Hospital, Bahía Blanca, Argentina. PATIENTS: PATIENTS discharged from the ICU who had been admitted with ARDS in 2009 due to influenza A H1N1. RESULTS: Eleven patients were studied. Seven were positive for influenza H1N1 and four were negative. The mean age was 37±9.5 years, and 73% were males. Quality of life, as measured by the EQ-5D, showed changes in the 5 components in all patients, particularly in the pain/discomfort dimension 1.55±0.52; health status (EQ%health) was 70%±24. The indices adjusted for Argentina were Time Trade Off (TTO) 0.903±0.085 and Visual Analog Scale (VAS) 0.827±0.153. In all patients, spirometry and the study of pulmonary diffusion (DLCO) showed values of >80%. There was no correlation between lung diffusion and quality of life (%DLCO and EQ%health). A correlation was observed between quality of life and TTO (EQ%health and TTO), and between quality of life and the VAS score (EQ%health and VAS). CONCLUSION: Although the sample is small, our results suggest that patients with ARDS due to influenza A H1N1 evaluated 6 months after discharge from the ICU show no deterioration of lung function, and the impact on quality of life is moderate-in contrast to the situation found in patients with ARDS of other etiologies.

[Minimally invasive treatment of chronic subdural hematoma in adults. Results in 116 patients]. / Tratamiento mínimamente invasivo del hematoma subdural crónico del adulto. Resultados en 116 pacientes.

INTRODUCTION: Chronic subdural hematoma in adults (CSDH) has a global crude incidence of 14.1/100,000 per year in our institution captive population. There is no single treatment protocol. In our hospital we choose a minimal invasive technique (trans-marrow puncture) without general anaesthesia due to the age of the population. A descriptive study of patients with CSDH and treatment results, including a laterality analysis, is presented. MATERIAL AND METHODS: We retrospectively searched patients with (CSDH) between January 1998 and May 2009. The diagnosis was made by neuroimaging techniques in all patients. The preferred treatment was trans-marrow puncture; exceptionally some patients were treated by burr holes or craniotomy. RESULTS: We found 127 patients. Age, gender, midline displacement, hospitalisation days, and number of procedures, were not a predictive factor of mortality in the first month. A slight majority (55%) of CSDH were on the left side, with no statistically significant difference. There were 6 (4.7%) deaths during hospitalisation. In our series cumulative mortality at six months was 11.8%. Markwalder scale at admission was not a predictive factor of statistically significant mortality. An 80% of the patients received trans-marrow puncture as single procedure was performed on 80% of the patients. CONCLUSIONS: The results of our study suggest that trans-marrow puncture is an acceptable procedure, with low mortality, and less hospitalisation days and complications. Mortality, associated mechanisms, age, gender, midline displacement are no different than in others previous publications. We found a higher frequency of hematomas to the left, as in other series. Meta-analysis studied need to be performed to determine more accurately the frequency of this dominance.