Information in feedback ratchets.

Feedback control uses the state information of the system to actuate on it. The information used implies an effective entropy reduction of the controlled system, potentially increasing its performance. How to compute this entropy reduction has been formally shown for a general system and has been explicitly computed for spatially discrete systems. Here, we address a relevant example of how to compute the entropy reduction by information in a spatially continuous feedback-controlled system. Specifically, we consider a feedback flashing ratchet, which constitutes a paradigmatic example for the role of information and feedback in the dynamics and thermodynamics of transport induced by the rectification of Brownian motion. A Brownian particle moves in a periodic potential that is switched on and off by a controller. The controller measures the position of the particle at regular intervals and performs the switching depending on the result of the measurement. This system reaches a long-time dynamical regime with a nonzero mean particle velocity, even for a symmetric potential. Here, we calculate the efficiency at maximum power in this long-time regime, computing all the required contributions. We show how the entropy reduction can be evaluated from the entropy of the non-Markovian sequence of control actions, and we also discuss the required sampling effort for its accurate computation. Moreover, the output power developed by the particle against an external force is investigated, which-for some values of the system parameters-is shown to become larger than the input power provided by the switching of the potential. The apparent efficiency of the ratchet thus becomes higher than one, if the entropy reduction contribution is not considered. This result highlights the relevance of including the entropy reduction by information in the thermodynamic balance of feedback-controlled devices, specifically when writing the second principle. The inclusion of the entropy reduction by information leads to a well-behaved efficiency over all the range of parameters investigated.

Barriers and applied activity, quality of life and self-efficacy in prostate cancer survivors 1 year after completing radiotherapy.

PURPOSE: The aims of the study were to assess self-reported physical activity (PA) levels, barriers to PA, quality of life and self-efficacy to manage chronic disease of prostate cancer survivor 1 year after radiotherapy treatment. METHODS: A cross-sectional case-control study was performed. Prostate cancer survivor patients treated with radiotherapy were recruited from the Radiation Oncology Service of the "Complejo Hospitalario Universitario" (Granada) and compared with age-matched healthy men. Outcomes included were perception of benefits for physical activity and potential barriers (Exercise Benefits/Barriers Scale), physical activity levels assessed by the International Physical Activity Questionnaire (IPAQ), quality of life (EuroQol five-dimension three-levels) and self-efficacy (Self-Efficacy to Manage Chronic Disease). RESULTS: A total of 120 patients were included in our study. Significant differences were found between groups with worse results for the prostate cancer patient group in the variable perception of the benefit of physical activity, potential barriers, and physical activity. Regarding quality of life and self-efficacy, significant differences were also observed between groups with a greater score in the control group. CONCLUSION: In conclusion, the results of this study reveal that self-reported PA levels, as measured using the IPAQ, were low in prostate cancer survivors after treatment. Results also showed worse perception of benefits for PA and potential barriers by the cancer survivors. Similarly, the quality of life and self-efficacy to manage chronic disease of prostate cancer survivors was lower.

Buckling in a rotationally invariant spin-elastic model.

Scanning tunneling microscopy experiments have revealed a spontaneous rippled-to-buckled transition in heated graphene sheets, in absence of any mechanical load. Several models relying on a simplified picture of the interaction between elastic and internal, electronic, degrees of freedom have been proposed to understand this phenomenon. Nevertheless, these models are not fully consistent with the classical theory of elasticity, since they do not preserve rotational invariance. Herein, we develop and analyze an alternative classical spin-elastic model that preserves rotational invariance while giving a qualitative account of the rippled-to-buckled transition. By integrating over the internal degrees of freedom, an effective free energy for the elastic modes is derived, which only depends on the curvature. Minimization of this free energy gives rise to the emergence of different mechanical phases, whose thermodynamic stability is thoroughly analyzed, both analytically and numerically. All phases are characterized by a spatially homogeneous curvature, which plays the role of the order parameter for the rippled-to-buckled transition, in both the one- and two-dimensional cases. In the latter, our focus is put on the honeycomb lattice, which is representative of actual graphene.

Driving rapidly while remaining in control: classical shortcuts from Hamiltonian to stochastic dynamics.

Stochastic thermodynamics lays down a broad framework to revisit the venerable concepts of heat, work and entropy production for individual stochastic trajectories of mesoscopic systems. Remarkably, this approach, relying on stochastic equations of motion, introduces time into the description of thermodynamic processes-which opens the way to fine control them. As a result, the field of finite-time thermodynamics of mesoscopic systems has blossomed. In this article, after introducing a few concepts of control for isolated mechanical systems evolving according to deterministic equations of motion, we review the different strategies that have been developed to realize finite-time state-to-state transformations in both over and underdamped regimes, by the proper design of time-dependent control parameters/driving. The systems under study are stochastic, epitomized by a Brownian object immersed in a fluid; they are thus strongly coupled to their environment playing the role of a reservoir. Interestingly, a few of those methods (inverse engineering, counterdiabatic driving, fast-forward) are directly inspired by their counterpart in quantum control. The review also analyzes the control through reservoir engineering. Besides the reachability of a given target state from a known initial state, the question of the optimal path is discussed. Optimality is here defined with respect to a cost function, a subject intimately related to the field of information thermodynamics and the question of speed limit. Another natural extension discussed deals with the connection between arbitrary states or non-equilibrium steady states. This field of control in stochastic thermodynamics enjoys a wealth of applications, ranging from optimal mesoscopic heat engines to population control in biological systems.

Thermal versus entropic Mpemba effect in molecular gases with nonlinear drag.

Loosely speaking, the Mpemba effect appears when hotter systems cool sooner or, in a more abstract way, when systems further from equilibrium relax faster. In this paper, we investigate the Mpemba effect in a molecular gas with nonlinear drag, both analytically (by employing the tools of kinetic theory) and numerically (direct simulation Monte Carlo of the kinetic equation and event-driven molecular dynamics). The analysis is carried out via two alternative routes, recently considered in the literature: first, the kinetic or thermal route, in which the Mpemba effect is characterized by the crossing of the evolution curves of the kinetic temperature (average kinetic energy), and, second, the stochastic thermodynamics or entropic route, in which the Mpemba effect is characterized by the crossing of the distance to equilibrium in probability space. In general, a nonmutual correspondence between the thermal and entropic Mpemba effects is found, i.e., there may appear the thermal effect without its entropic counterpart or vice versa. Furthermore, a nontrivial overshoot with respect to equilibrium of the thermal relaxation makes it necessary to revise the usual definition of the thermal Mpemba effect, which is shown to be better described in terms of the relaxation of the local equilibrium distribution. Our theoretical framework, which involves an extended Sonine approximation in which not only the excess kurtosis but also the sixth cumulant is retained, gives an excellent account of the behavior observed in simulations.

Radiotherapy-Related Fatigue Associated Impairments in Lung Cancer Survivors during COVID-19 Voluntary Isolation.

The main objective of this study was to investigate the impairments presented after COVID-19 voluntary isolation by lung cancer survivors that experienced radiotherapy-related fatigue. In this observational study, data were collected after COVID-19 voluntary isolation. Patients were divided into two groups according to their fatigue severity reported with the Fatigue Severity Scale. Health status was assessed by the EuroQol-5D, anxiety and depression by the Hospital Anxiety and Depression Scale, and disability by the World Health Organization Disability Assessment Schedule 2.0. A total of 120 patients were included in the study. Patients with severe fatigue obtained higher impairment results compared to patients without severe fatigue, with significant differences in all the variables (p < 0.05). Lung cancer survivors who experienced severe radiotherapy-related fatigue presented higher impairments after COVID-19 voluntary isolation than lung cancer patients who did not experience severe radiotherapy-related fatigue, and showed high levels of anxiety, depression and disability, and a poor self-perceived health status.

Agreement between face-to-face and tele-assessment of upper limb disability in lung cancer survivors during COVID-19 era.

INTRODUCTION: Upper limb disability can limit the quality of life of lung cancer survivors. The COVID-19 era has required a finding of alternatives to attend the monitoring of presented disturbances with the minor risk of spread. Tele-assessment offers new possibilities for clinical assessment demonstrating good reliability compared to traditional face-to-face assessment in a variety of patients. No previous study has applied this type of assessment in lung cancer survivors. For this reason, the aim of this study was to evaluate the level of agreement between upper limb disability assessment using tele-assessment and the face-to-face method in lung cancer survivors. METHODS: A reliability study was conducted with 20 lung cancer survivors recruited from the Oncological Radiotherapy Service of the "Hospital PTS" (Granada). Patients attended a session for clinical face-to-face and real-time online tele-assessment. The main outcome measurements of the study included upper limb function (shirt task) and musculoskeletal disturbances (active range of movement and trigger points), and these outcomes were recorded by two independent researchers. RESULTS: The outcome measures showed good agreement between both assessments. The active range of movement presented heterogeneous results, being excellent reliability (ρ > 0.75) in extension, internal rotation, homolateral adduction, and contralateral abduction, good (0.4 < ρ < 0.75) for flexion, homolateral abduction, contralateral adduction and contralateral external rotation, and poor (ρ < 0.4) for homolateral external rotation. The measure evaluating upper limb function and trigger points show the highest interrater reliability with confidence interval lower limits ≥0.99. DISCUSSION: The tele-assessment of upper limb function and musculoskeletal disorders of lung cancer survivors present a good interrater reliability compared to face-to-face assessment. It could be useful for monitoring the disability presented by cancer survivors whose access is difficult by the residential situation, physical limitations or the risk of COVID-19 spread.

Optimal Control of Uniformly Heated Granular Fluids in Linear Response.

We present a detailed analytical investigation of the optimal control of uniformly heated granular gases in the linear regime. The intensity of the stochastic driving is therefore assumed to be bounded between two values that are close, which limits the possible values of the granular temperature to a correspondingly small interval. Specifically, we are interested in minimising the connection time between the non-equilibrium steady states (NESSs) for two different values of the granular temperature by controlling the time dependence of the driving intensity. The closeness of the initial and target NESSs make it possible to linearise the evolution equations and rigorously-from a mathematical point of view-prove that the optimal controls are of bang-bang type, with only one switching in the first Sonine approximation. We also look into the dependence of the optimal connection time on the bounds of the driving intensity. Moreover, the limits of validity of the linear regime are investigated.

Taming the Time Evolution in Overdamped Systems: Shortcuts Elaborated from Fast-Forward and Time-Reversed Protocols.

Using a reverse-engineering approach on the time-distorted solution in a reference potential, we work out the external driving potential to be applied to a Brownian system in order to slow or accelerate the dynamics, or even to invert the arrow of time. By welding a direct and time-reversed evolution toward a well chosen common intermediate state, we analytically derive a smooth protocol to connect two arbitrary states in an arbitrarily short amount of time. Not only does the reverse-engineering approach proposed in this Letter contain the current-rather limited-catalog of explicit protocols, but it also provides a systematic strategy to build the connection between arbitrary states with a physically admissible driving. Optimization and further generalizations are also discussed.

Linear response in the uniformly heated granular gas.

We analyze the linear response properties of the uniformly heated granular gas. The intensity of the stochastic driving fixes the value of the granular temperature in the nonequilibrium steady state reached by the system. Here, we investigate two specific situations. First, we look into the "direct" relaxation of the system after a single (small) jump of the driving intensity. This study is carried out by two different methods. Not only do we linearize the evolution equations around the steady state, but we also derive generalized out-of-equilibrium fluctuation-dissipation relations for the relevant response functions. Second, we investigate the behavior of the system in a more complex experiment, specifically a Kovacs-like protocol with two jumps in the driving. The emergence of an anomalous Kovacs response is explained in terms of the properties of the direct relaxation function: it is the second mode changing sign at the critical value of the inelasticity that demarcates anomalous from normal behavior. The analytical results are compared with numerical simulations of the kinetic equation, and a good agreement is found.

Finite-time adiabatic processes: Derivation and speed limit.

Obtaining adiabatic processes that connect equilibrium states in a given time represents a challenge for mesoscopic systems. In this paper, we explicitly show how to build these finite-time adiabatic processes for an overdamped Brownian particle in an arbitrary potential, a system that is relevant at both the conceptual and the practical level. This is achieved by jointly engineering the time evolutions of the binding potential and the fluid temperature. Moreover, we prove that the second principle imposes a speed limit for such adiabatic transformations: there appears a minimum time to connect the initial and final states. This minimum time can be explicitly calculated for a general compression or decompression situation.

Derivation of a Langevin equation in a system with multiple scales: The case of negative temperatures.

We consider the problem of building a continuous stochastic model, i.e., a Langevin or Fokker-Planck equation, through a well-controlled coarse-graining procedure. Such a method usually involves the elimination of the fast degrees of freedom of the "bath" to which the particle is coupled. Specifically, we look into the general case where the bath may be at negative temperatures, as found, for instance, in models and experiments with bounded effective kinetic energy. Here, we generalize previous studies by considering the case in which the coarse graining leads to (i) a renormalization of the potential felt by the particle, and (ii) spatially dependent viscosity and diffusivity. In addition, a particular relevant example is provided, where the bath is a spin system and a sort of phase transition takes place when going from positive to negative temperatures. A Chapman-Enskog-like expansion allows us to rigorously derive the Fokker-Planck equation from the microscopic dynamics. Our theoretical predictions show excellent agreement with numerical simulations.

Large Mpemba-like effect in a gas of inelastic rough hard spheres.

We report the emergence of a giant Mpemba effect in the uniformly heated gas of inelastic rough hard spheres: The initially hotter sample may cool sooner than the colder one, even when the initial temperatures differ by more than one order of magnitude. In order to understand this behavior, it suffices to consider the simplest Maxwellian approximation for the velocity distribution in a kinetic approach. The largeness of the effect stems from the fact that the rotational and translational temperatures, which obey two coupled evolution equations, are comparable. Our theoretical predictions agree very well with molecular dynamics and direct simulation Monte Carlo data.

Hydrodynamics of granular particles on a line.

We investigate a lattice model representing a granular gas in a thin channel. We deduce the hydrodynamic description for the model from the microscopic dynamics in the large-system limit, including the lowest finite-size corrections. The main prediction from hydrodynamics, when finite-size corrections are neglected, is the existence of a steady "uniform longitudinal flow" (ULF), with the granular temperature and the velocity gradient both uniform and directly related. Extensive numerical simulations of the system show that such a state can be observed in the bulk of a finite-size system by attaching two thermostats with the same temperature at its boundaries. The relation between the ULF state and the shocks appearing in the late stage of a cooling gas of inelastic hard rods is discussed.

Relevance of the Speed and Direction of Pulling in Simple Modular Proteins.

A theoretical framework capable of predicting the first unit that unfolds in pulled modular proteins has been recently introduced, for "fast enough" pulling velocities. Within this picture, we investigate the unfolding pathway in a chain of identical units and predict that the module closest to the pulled end opens first. Steered molecular dynamics of a simple construct, specifically a chain composed of two coiled-coil motives, shows that this is indeed the case. Notwithstanding, the unfolding behavior strongly depends on the terminus (C or N) from which this homopolyprotein is pulled. Therefore, anisotropic features are revealed and seem to play an important role for the observed unfolding pathway.

When the Hotter Cools More Quickly: Mpemba Effect in Granular Fluids.

Under certain conditions, two samples of fluid at different initial temperatures present a counterintuitive behavior known as the Mpemba effect: it is the hotter system that cools sooner. Here, we show that the Mpemba effect is present in granular fluids, both in uniformly heated and in freely cooling systems. In both cases, the system remains homogeneous, and no phase transition is present. Analytical quantitative predictions are given for how differently the system must be initially prepared to observe the Mpemba effect, the theoretical predictions being confirmed by both molecular dynamics and Monte Carlo simulations. Possible implications of our analysis for other systems are also discussed.

The DNA load of six high-risk human papillomavirus types and its association with cervical lesions.

BACKGROUND: Analysing human papillomavirus (HPV) viral load is important in determining the risk of developing cervical cancer (CC); most knowledge to date regarding HPV viral load and cervical lesions has been related to HPV-16. This study evaluated the association between the viral load of the six most prevalent high-risk viral types in Colombia and cervical intraepithelial neoplasia (CIN) frequency. METHODS: 114 women without CIN and 59 women having CIN confirmed by colposcopy, all of them positive by conventional PCR for HPV infection in the initial screening, were included in the study. Samples were tested for six high-risk HPV types to determine viral copy number by real-time PCR. Crude and adjusted odds ratios (ORa) were estimated for evaluating the association between each viral type's DNA load and the risk of cervical lesions occurring. RESULTS: The highest viral loads were identified for HPV-33 in CIN patients and for HPV-31 in patients without lesions (9.33 HPV copies, 2.95 interquartile range (IQR); 9.41 HPV copies, 2.58 IQR). Lesions were more frequent in HPV-16 patients having a low viral load (3.53 ORa, 1.16-10.74 95%CI) compared to those having high HPV-16 load (2.62 ORa, 1.08-6.35 95%CI). High viral load in HPV-31 patients was associated with lower CIN frequency (0.34 ORa, 0.15-0.78 95%CI). CONCLUSIONS: An association between HPV DNA load and CIN frequency was seen to be type-specific and may have depended on the duration of infection. This analysis has provided information for understanding the effect of HPV DNA load on cervical lesion development.

Persistence, clearance and reinfection regarding six high risk human papillomavirus types in Colombian women: a follow-up study.

BACKGROUND: The design of new healthcare schemes which involve using molecular HPV screening means that both persistence and clearance data regarding the most prevalent types of HR-HPV occurring in cities in Colombia must be ascertained. METHODS: This study involved 219 HPV positive women in all of whom 6 types of HR-HPV had been molecularly identified and quantified; they were followed-up for 2 years. The Kaplan-Meier survival function was used for calculating the time taken for the clearance of each type of HPV. The role of a group of independent variables concerning the time taken until clearance was evaluated using a Cox proportional-hazards regression model or parametric (log-logistic) methods when necessary. Regarding viral load, the Wilcoxon rank-sum test was used for measuring the difference of medians for viral load for each type, according to the state of infection (cleared or persistent). The Kruskal-Wallis test was used for evaluating the change in the women's colposcopy findings at the start of follow-up and at the end of it (whether due to clearance or the end of the follow-up period). RESULTS: It was found that HPV-18 and HPV-31 types had the lowest probability of becoming cleared (1.76 and 2.75 per 100 patients/month rate, respectively). Women from Colombian cities other than Bogotá had a greater probability of being cleared if they had HPV-16 (HR 2.58: 1.51-4.4 95% CI) or HPV-58 (1.79 time ratio: 1.33-2.39 95% CI) infection. Regarding viral load, HPV-45-infected women having 1 × 106 to 9.99 × 109 viral copies had better clearance compared to those having greater viral loads (1.61 time ratio: 1.01-2.57 95% CI). Lower HPV-31 viral load values were associated with this type's persistence and changes in colposcopy findings for HPV-16 gave the worst prognosis in women having low absolute load values. CONCLUSIONS: HPV infection clearance in this study was related to factors such as infection type, viral load and the characteristics of the cities from which the women came. Low viral load values would indicate viral persistence and a worse prognosis regarding a change in colposcopy findings.

Human papillomavirus detection in women with and without human immunodeficiency virus infection in Colombia.

BACKGROUND: HIV infection leads to a decreasing immune response, thereby facilitating the appearance of other infections, one of the most important ones being HPV. However, studies are needed for determining associations between immunodeficiency caused by HIV and/or the presence of HPV during the course of cervical lesions and their degree of malignancy. This study describes the cytological findings revealed by the Papanicolaou test, laboratory characteristics and HPV molecular profile in women with and without HIV infection. METHODS: A total of 216 HIV-positive and 1,159 HIV-negative women were invited to participate in the study; PCR was used for the molecular detection of HPV in cervical samples. Statistical analysis (such as percentages, Chi-square test and Fisher's exact test when applicable) determined human papillomavirus (HPV) infection frequency (single and multiple) and the distribution of six types of high-risk-HPV in women with and without HIV infection. Likewise, a logistic regression model was run to evaluate the relationship between HIV-HPV infection and different risk factors. RESULTS: An association was found between the frequency of HPV infection and infection involving 2 or more HPV types (also known as multiple HPV infection) in HIV-positive women (69.0% and 54.2%, respectively); such frequency was greater than that found in HIV-negative women (44.3% and 22.7%, respectively). Statistically significant differences were observed between both groups (p = 0.001) regarding HPV presence (both in infection and multiple HPV infection). HPV-16 was the most prevalent type in the population being studied (p = 0.001); other viral types had variable distribution in both groups (HIV-positive and HIV-negative). HPV detection was associated with <500 cell/mm(3) CD4-count (p = 0.004) and higher HIV-viral-load (p = 0.001). HPV-DNA detection, <200 cell/mm(3) CD4-count (p = 0.001), and higher HIV-viral-load (p = 0.001) were associated with abnormal cytological findings. CONCLUSIONS: The HIV-1 positive population in this study had high multiple HPV infection prevalence. The results for this population group also suggested a greater association between HPV-DNA presence and cytological findings. HPV detection, together with low CD4 count, could represent useful tools for identifying HIV-positive women at risk of developing cervical lesions.

Classical molecular tests using urine samples as a potential screening tool for human papillomavirus detection in human immunodeficiency virus-infected women.

Human papillomavirus (HPV) is the main risk factor associated with the development of cervical cancer (CC); however, there are other factors, such as immunosuppression caused by the human immunodeficiency virus (HIV), that favor progression of the illness. This study was thus aimed at evaluating the functionality of classical PCR-based molecular tests for the generic identification of HPV DNA (GP5+/GP6+, MY09/MY11, and pU1M/2R primers, individually or in combination) using cervical and urine samples from 194 HIV-positive women. Infected samples were tested with type-specific primers for six high-risk types (HPV-16, -18, -31, -33, -45, and -58) and two low-risk types (HPV-6 and -11). HPV infection prevalence rates were 70.1% for the cervical samples and 63.9% for the urine samples. HPV-16 was the most prevalent viral type in the cervical and urine samples, with higher rates of multiple infections than single infections detected in such samples. HPV DNA detection by PCR (mainly with the pU1M/2R primer set) in urine samples was positively associated with abnormal cytological findings (atypical squamous cells of undetermined significance/squamous intraepithelial lesions [ASCUS/SIL]). It was determined that the operative characteristics for detection of cytological abnormalities were similar for cervical and urine samples. This suggested using PCR for the detection of HPV DNA in urine samples as a potential screening strategy for CC prevention in future prevention and control programs along with currently implemented strategies for reducing the impact of the disease, i.e., urine samples are economical, are easy to collect, have wide acceptability among women, and have operative characteristics similar to those of cervical samples.