Theory and simulation of short-range models of globular protein solutions

We report theoretical and simulation studies of phase coexistence in model globular protein solutions, based on short-range, central, pair potential representations of the interaction among macro-particles. After reviewing our previous investigations of hard-core Yukawa and generalised Lennard-Jones potentials, we report more recent results obtained within a DLVO-like description of lysozyme solutions in water and added salt. We show that a one-parameter fit of this model based on Static Light Scattering and Self-Interaction Chromatography data in the dilute protein regime, yields demixing and crystallization curves in good agreement with experimental protein-rich/protein-poor and solubility envelopes. The dependence of cloud and solubility points temperature of the model on the ionic strength is also investigated. Our findings highlight the minimal assumptions on the properties of the microscopic interaction sufficient for a satisfactory reproduction of the phase diagram topology of globular protein solutions.Comment: 17 pages, 8 figures, Proc. of Conference "Structural Arrest Transitions in Colloidal Systems with Short-Range Attractions", Messina (ITALY) 17-20 December 200

Novel Approaches towards Highly Selective Self-Powered Gas Sensors

The prevailing design approaches of semiconductor gas sensors struggle to overcome most of their current limitations such as poor selectivity, and high power consumption. Herein, a new sensing concept based on devices that are capable of detecting gases without the need of any external power sources required to activate interaction of gases with sensor or to generate the sensor read out signal. Based on the integration of complementary functionalities (namely; powering and sensing) in a singular nanostructure, self-sustained gas sensors will be demonstrated. Moreover, a rational methodology to design organic surface functionalization that provide high selectivity towards single gas species will also be discussed. Specifically, theoretical results, confirmed experimentally, indicate that precisely tuning of the sterical and electronic structure of sensor material/organic interfaces can lead to unprecedented selectivity values, comparable to those typical of bioselective processes. Finally, an integrated gas sensor that combine both the self-powering and selective detection strategies in one single device will also be presented. © 2015 Published by Elsevier Ltd.Peer ReviewedPostprint (published version

Learning to Recharge: UAV Coverage Path Planning through Deep Reinforcement Learning

Coverage path planning (CPP) is a critical problem in robotics, where the goal is to find an efficient path that covers every point in an area of interest. This work addresses the power-constrained CPP problem with recharge for battery-limited unmanned aerial vehicles (UAVs). In this problem, a notable challenge emerges from integrating recharge journeys into the overall coverage strategy, highlighting the intricate task of making strategic, long-term decisions. We propose a novel proximal policy optimization (PPO)-based deep reinforcement learning (DRL) approach with map-based observations, utilizing action masking and discount factor scheduling to optimize coverage trajectories over the entire mission horizon. We further provide the agent with a position history to handle emergent state loops caused by the recharge capability. Our approach outperforms a baseline heuristic, generalizes to different target zones and maps, with limited generalization to unseen maps. We offer valuable insights into DRL algorithm design for long-horizon problems and provide a publicly available software framework for the CPP problem.Comment: This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

Theoretical description of phase coexistence in model C60

We have investigated the phase diagram of the Girifalco model of C60 fullerene in the framework provided by the MHNC and the SCOZA liquid state theories, and by a Perturbation Theory (PT), for the free energy of the solid phase. We present an extended assessment of such theories as set against a recent Monte Carlo study of the same model [D. Costa et al, J. Chem. Phys. 118:304 (2003)]. We have compared the theoretical predictions with the corresponding simulation results for several thermodynamic properties. Then we have determined the phase diagram of the model, by using either the SCOZA, or the MHNC, or the PT predictions for one of the coexisting phases, and the simulation data for the other phase, in order to separately ascertain the accuracy of each theory. It turns out that the overall appearance of the phase portrait is reproduced fairly well by all theories, with remarkable accuracy as for the melting line and the solid-vapor equilibrium. The MHNC and SCOZA results for the liquid-vapor coexistence, as well as for the corresponding critical points, are quite accurate. All results are discussed in terms of the basic assumptions underlying each theory. We have selected the MHNC for the fluid and the first-order PT for the solid phase, as the most accurate tools to investigate the phase behavior of the model in terms of purely theoretical approaches. The overall results appear as a robust benchmark for further theoretical investigations on higher order C(n>60) fullerenes, as well as on other fullerene-related materials, whose description can be based on a modelization similar to that adopted in this work.Comment: RevTeX4, 15 pages, 7 figures; submitted to Phys. Rev.

Infinite compressibility states in the Hierarchical Reference Theory of fluids. II. Numerical evidence

Continuing our investigation into the Hierarchical Reference Theory of fluids for thermodynamic states of infinite isothermal compressibility kappa[T] we now turn to the available numerical evidence to elucidate the character of the partial differential equation: Of the three scenarios identified previously, only the assumption of the equations turning stiff when building up the divergence of kappa[T] allows for a satisfactory interpretation of the data. In addition to the asymptotic regime where the arguments of part I (cond-mat/0308467) directly apply, a similar mechanism is identified that gives rise to transient stiffness at intermediate cutoff for low enough temperature. Heuristic arguments point to a connection between the form of the Fourier transform of the perturbational part of the interaction potential and the cutoff where finite difference approximations of the differential equation cease to be applicable, and they highlight the rather special standing of the hard-core Yukawa potential as regards the severity of the computational difficulties.Comment: J. Stat. Phys., in press. Minor changes to match published versio

Ab initio study of the vapour-liquid critical point of a symmetrical binary fluid mixture

A microscopic approach to the investigation of the behaviour of a symmetrical binary fluid mixture in the vicinity of the vapour-liquid critical point is proposed. It is shown that the problem can be reduced to the calculation of the partition function of a 3D Ising model in an external field. For a square-well symmetrical binary mixture we calculate the parameters of the critical point as functions of the microscopic parameter r measuring the relative strength of interactions between the particles of dissimilar and similar species. The calculations are performed at intermediate ($\lambda=1.5$) and moderately long ($\lambda=2.0$) intermolecular potential ranges. The obtained results agree well with the ones of computer simulations.Comment: 14 pages, Latex2e, 5 eps-figures included, submitted to J.Phys:Cond.Ma

Screening and Management of Coronary Artery Disease in Kidney Transplant Candidates

Cardiovascular disease (CVD) is a major cause of morbidity and mortality in patients with chronic kidney disease (CKD), especially in end-stage renal disease (ESRD) patients and during the first year after transplantation. For these reasons, and due to the shortage of organs available for transplant, it is of utmost importance to identify patients with a good life expectancy after transplant and minimize the transplant peri-operative risk. Various conditions, such as severe pulmonary diseases, recent myocardial infarction or stroke, and severe aorto-iliac atherosclerosis, need to be ruled out before adding a patient to the transplant waiting list. The effectiveness of systematic coronary artery disease (CAD) treatment before kidney transplant is still debated, and there is no universal screening protocol, not to mention that a nontailored screening could lead to unnecessary invasive procedures and delay or exclude some patients from transplantation. Despite the different clinical guidelines on CAD screening in kidney transplant candidates that exist, up to today, there is no worldwide universal protocol. This review summarizes the key points of cardiovascular risk assessment in renal transplant candidates and faces the role of noninvasive cardiovascular imaging tools and the impact of coronary revascularization versus best medical therapy before kidney transplant on a patient’s cardiovascular outcome

Hybrid sputtering/evaporation deposition of Cu(In,Ga)Se2 thin film solar cells

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Prediction of vascular events in subjects with subclinical atherosclerosis and the metabolic syndrome: the role of markers of inflammation.

AIM: The presence of the metabolic syndrome (MS) increases cardiovascular morbidity and mortality and we aimed to assess the outcome in subjects with the MS and subclinical atherosclerosis. METHODS: We followed-up for five years 339 Mediterranean subjects with asymptomatic carotid intima-media thickness >0.9 mm (men: 60%; age: 66±5 years), of whom 130 had the MS (men: 59%; age: 66±5 years), evaluating at baseline traditional cardiovascular risk factors (including male gender, older age, obesity, hypertension, diabetes, smoking, family history of cardiovascular diseases, dyslipidemia) and plasma levels of C-reactive protein and fibrinogen. RESULTS: Cardio- and cerebrovascular events were registered in the 29% of subjects with the MS and in the 20% of those without it and the presence of more criteria for the diagnosis of the MS was significantly associated with vascular morbidity and mortality. By multivariate analysis, including all baseline variables, independent predictive roles for the events were found for elevated markers of inflammation (OR 3.8), elevated fasting glucose (OR 2.1) and elevated triglycerides (OR 1.4). CONCLUSION: These findings confirm a worst vascular outcome in subjects with more criteria for the diagnosis of the MS and further suggest the need of future research to understand the combined role of inflammation and the MS in the progression from subclinical to clinical atherosclerosis

Implementation of the Hierarchical Reference Theory for simple one-component fluids

Combining renormalization group theoretical ideas with the integral equation approach to fluid structure and thermodynamics, the Hierarchical Reference Theory is known to be successful even in the vicinity of the critical point and for sub-critical temperatures. We here present a software package independent of earlier programs for the application of this theory to simple fluids composed of particles interacting via spherically symmetrical pair potentials, restricting ourselves to hard sphere reference systems. Using the hard-core Yukawa potential with z=1.8/sigma for illustration, we discuss our implementation and the results it yields, paying special attention to the core condition and emphasizing the decoupling assumption's role.Comment: RevTeX, 16 pages, 2 figures. Minor changes, published versio