Kinetics and thermodynamics of first-order Markov chain copolymerization

We report a theoretical study of stochastic processes modeling the growth of first-order Markov copolymers, as well as the reversed reaction of depolymerization. These processes are ruled by kinetic equations describing both the attachment and detachment of monomers. Exact solutions are obtained for these kinetic equations in the steady regimes of multicomponent copolymerization and depolymerization. Thermodynamic equilibrium is identified as the state at which the growth velocity is vanishing on average and where detailed balance is satisfied. Away from equilibrium, the analytical expression of the thermodynamic entropy production is deduced in terms of the Shannon disorder per monomer in the copolymer sequence. The Mayo-Lewis equation is recovered in the fully irreversible growth regime. The theory also applies to Bernoullian chains in the case where the attachment and detachment rates only depend on the reacting monomer

Thermodynamic time asymmetry in nonequilibrium fluctuations

We here present the complete analysis of experiments on driven Brownian motion and electric noise in a $RC$ circuit, showing that thermodynamic entropy production can be related to the breaking of time-reversal symmetry in the statistical description of these nonequilibrium systems. The symmetry breaking can be expressed in terms of dynamical entropies per unit time, one for the forward process and the other for the time-reversed process. These entropies per unit time characterize dynamical randomness, i.e., temporal disorder, in time series of the nonequilibrium fluctuations. Their difference gives the well-known thermodynamic entropy production, which thus finds its origin in the time asymmetry of dynamical randomness, alias temporal disorder, in systems driven out of equilibrium.Comment: to be published in : Journal of Statistical Mechanics: theory and experimen

A fluctuation theorem for currents and non-linear response coefficients

We use a recently proved fluctuation theorem for the currents to develop the response theory of nonequilibrium phenomena. In this framework, expressions for the response coefficients of the currents at arbitrary orders in the thermodynamic forces or affinities are obtained in terms of the fluctuations of the cumulative currents and remarkable relations are obtained which are the consequences of microreversibility beyond Onsager reciprocity relations

Tarlov Cyst: A diagnostic of exclusion.

Tarlov cysts were first described in 1938 as an incidental finding at autopsy. The cysts are usually diagnosed on MRI, which reveals the lesion arising from the sacral nerve root near the dorsal root ganglion. Symptomatic sacral perineural cysts are uncommon and it is recommended to consider Tarlov cyst as a diagnostic of exclusion. We report a case of a patient with voluminous bilateral L5 and S1 Tarlov cyst, and right hip osteonecrosis to increase the awareness in the orthopaedic community. A 57-year-old female, in good health, with chronic low back pain since 20 years, presented suddenly right buttock pain, right inguinal fold pain and low back pain for two months, with inability to walk and to sit down. X-ray of the lumbo-sacral spine revealed asymmetric discopathy L5-S1 and L3-L4. X-ray of the right hip did not reveal anything. We asked for an MRI of the spine and it revealed a voluminous fluid-filled cystic lesion, arising from the first sacral nerve root on both side and measuring 3,3cm in diameter. The MRI also show a part of the hip and incidentally we discovered an osteonecrosis Ficat 3 of the right femoral head. The patient was taken for a total hip arthroplasty, by anterior approach. Patient appreciated relief of pain immediately after the surgery. The current case show that even if we find a voluminous cyst we always have to eliminate other diagnosis (especially the frequent like osteonecrosis of the femoral head) and mostly in the case of unclear neurological perturbation

Fluctuation theorem for currents in open quantum systems

A quantum-mechanical framework is set up to describe the full counting statistics of particles flowing between reservoirs in an open system under time-dependent driving. A symmetry relation is obtained which is the consequence of microreversibility for the probability of the nonequilibrium work and the transfer of particles and energy between the reservoirs. In some appropriate long-time limit, the symmetry relation leads to a steady-state quantum fluctuation theorem for the currents between the reservoirs. On this basis, relationships are deduced which extend the Onsager-Casimir reciprocity relations to the nonlinear response coefficients.Comment: 19 page

Fonctionnement hydrologique d'un interfluve sédimentaire de la plaine côtière ancienne de Guyane Française

Le fonctionnement hydrologique de la plaine côtière ancienne de Guyane française constitue une des contraintes majeures à sa mise en valeur agricole, du fait de l'existence de périodes d'excès d'eau prolongées.L'objectif de cet article est d'analyser, sur un interfluve caractéristique de la plaine côtière ancienne, la forme et la dynamique de la nappe et ses sources d'alimentation en relation avec la variabilité des propriétés physiques des sols.Sur le plan expérimental, le travail est conduit à partir d'un suivi hydrologique in situ des fluctuations de la nappe observées sur 21 stations et d'une caractérisation de la variabilité spatiale de la conductivité hydraulique des sols par la méthode du trou de tarière à charge variable. Sur le plan de la modélisation, l'identification de la répartition spatiale de la recharge sur l'interfluve est déterminée par une modélisation inverse. Les suivis montrent d'une part la rapidité de réponse de la nappe aux pluies et d'autre part des temps de présence de la nappe en surface variables selon les sols. La modélisation conforte l'hypothèse d'isolement hydraulique de l'interfluve. La dynamique de la nappe est directement reliée aux entrées pluviométriques et dans une moindre mesure aux sols. La variabilité spatiale de la recharge est par ailleurs sous la dépendance de la topographie et de l'hétérogénéité spatiale de la conductivité hydraulique. Enfin, une estimation du ruissellement de surface souligne son importance sur l'interfluve.Les résultats obtenus montrent que l'engorgement des sols de la plaine côtière est sous la dépendance directe des processus hydrologiques observés à l'échelle de chaque interfluve. La prédiction des zones à excès d'eau marqué et des zones où la recharge est homogène peut être envisagée à partir de la connaissance de la topographie et de la distribution des sols. Sur le plan agronomique et pour les sols à forte contrainte hydrique, la mise en place de systèmes de drainage permettant leur mise en valeur agricole est à considérer.The hydrological behaviour of the old coastal plain in French Guyana causes intense soil waterlogging, which is a major constraint to the agricultural development of this area. The old coastal plain presents a succession of similar old offshore bars (Fig. 1). To elucidate the factors affecting groundwater fluctuations in the plain, the hydrological behaviour of one typical bar was studied. This paper presents the results of the survey of the bar and of the identification of groundwater recharge by inverse modelling. It also investigates the relationships between the spatial variability of recharge rates, the topography, and the soil distribution over the bar to provide means for extrapolation to the whole plain.A bar, covering 0.16 km2, was chosen for the present study (Fig. 2). The maximum relief of the bar is 5 m and its general elevation lies between 2 and 7 m above sea level. The bar is drained by two convergent thalwegs. An important lateral and vertical soil differentiation was observed over a depth of approximately 1 m. Four main soil types (FAO/UNESCO classification) were identified at specific positions on the bar: podzols on the top, ferralsols on the upper slope, alluvial gleysols on the thalwegs and planosolic soils on the mid slope and between ferralsols and podzols. Ferralsols exhibit a progressive increase of clay content with increasing depth. The other soil types present sandy horizons with an irregular textural discontinuity (TD) located at a depth of 70 to 100 cm. Underneath the textural discontinuity lies a sandy clay marine alluvium, which is heterogeneous, ferrallitized and hydromorphic, with lenses of sand and clay. An impervious clay layer (NI) occurs at the base of the bar at an average height of 2 m above sea level. The climate is equatorial and has two marked seasons, wet and dry. Rain is mostly confined to the period November-July, but with a maximum from May to July. Mean annual rainfall is 2700 mm.A network of 21 piezometers was set up at the various topographic and pedological situations (Fig. 3). Six sampling sites were also equipped with tensiometers and access tubes for neutron probes. Groundwater monitoring lasted for three years from 1983 to 1986. The variability of soil hydraulic conductivity over the bar was measured by the auger hole method at the intersections of a 50 m square grid and at 25 m away from a few such intersections. A geostatistical analysis was performed and kriged maps of hydraulic conductivity were produced (Figs. 4 and 5). The comparison between the kriged maps and the soil map indicates that ferralsols exhibit higher conductivities than the other soils.Groundwater monitoring showed three main points. First, a fast response of groundwater fluctuations to rainfall was observed on the bar, which suggests that the hydrology of the bar is little influenced by contributions from neighbouring bars or from the Precambrian basement situated upgradient. Second, time length of soil saturation varied markedly over the bar and was related to the soil types (Fig. 7). Lastly, the observed spatial variability of the hydraulic conductivities and the evolution of water table levels indicate the possibility of a variable distribution of recharge over the bar.The deterministic flow model used for this study, WATASI (WAter TAble SImulation, Wolsack, 1982) is based on a Darcy-Dupuit hydraulic schematization. It is an integrated finite element and multilayer groundwater model with square cells of variable size. Here, three layers were considered: one representing the topsoil, from surface to the textural discontinuity, the second representing the sandy clayey alluvium, lying over the impervious layer, and the third representing the thalwegs surrounding the interfluve (Fig. 10). All layers were divided into cells whose length was either 25 m or 50 m. For the purpose of recharge identification, according to the results of the survey, the cells were grouped in six zones of homogeneous slope and soil type, with each zone assumed to exhibit constant recharge. Calibration of the parameters of the model and identification of recharge over the six zones were conducted over three periods, one exhibiting steady state flow and the two others transient flow, by minimizing the difference between the measured and simulated hydraulic heads. The results obtained by the simulation approach are:- No assumption of lateral inflow is necessary to simulate properly the evolution of hydraulic heads (Figs. 11 and 13); thus groundwater recharge only originates from the seepage of rainfall through the soil cover of the bar. - The spatial variability of recharge appears to follow firstly the slope distribution, and secondly the soil distribution: zones of high recharge correspond to zones of limited waterlogging and vice versa (Figs. 12 and 14). - The estimated rates of recharge are small in comparison to rainfall, and soil water budget calculations demonstrate the existence of large runoff rates. It can be concluded that the waterlogging of soils on the old coastal plain is mainly caused by the hydrological processes at the scale of each bar. Thus, for improving the agricultural suitability of the soils on the plain, local drainage of the waterlogged soils should be sufficient. To predict over the plain which zones should be drained, information on topography and soil distribution can be used as there are good correlations between the variability of these parameters and the variability in groundwater recharge and water table depths

Un système pédologique aval en Guyane française : organisation et fonctionnement hydrodynamique

Cet article présente l'étude de la différentiation pédologique à l'aval des versants des barres prélittorales (Guyane française). L'analyse de l'organisation morphologique, à différentes échelles, montre l'existence d'un système de transformation où les horizons sableux de bas versant sont développés aux dépens d'horizons plus argileux. L'étude par tensiométrie et humidimBetrie neutronique du fonctionnement hydrodynamique montre que ce système de transformation est lié à une dynamique perticulière de l'ea

Single electron transistor strongly coupled to vibrations: Counting Statistics and Fluctuation Theorem

Using a simple quantum master equation approach, we calculate the Full Counting Statistics of a single electron transistor strongly coupled to vibrations. The Full Counting Statistics contains both the statistics of integrated particle and energy currents associated to the transferred electrons and phonons. A universal as well as an effective fluctuation theorem are derived for the general case where the various reservoir temperatures and chemical potentials are different. The first relates to the entropy production generated in the junction while the second reveals internal information of the system. The model recovers Franck-Condon blockade and potential applications to non-invasive molecular spectroscopy are discussed.Comment: extended discussion, to appear in NJ

Dermatillomania: Strategies for developing protective biomaterials/cloth

Dermatillomania or skin picking disorder (SPD) is a chronic, recurrent, and treatment resistant neuropsychiatric disorder with an underestimated prevalence that has a concerning negative impact on an individual’s health and quality of life. The current treatment strategies focus on behavioral and pharmacological therapies that are not very effective. Thus, the primary objective of this review is to provide an introduction to SPD and discuss its current treatment strategies as well as to propose biomaterial-based physical barrier strategies as a supporting or alternative treatment. To this end, searches were conducted within the PubMed database and Google Scholar, and the results obtained were organized and presented as per the following categories: prevalence, etiology, conse-quences, diagnostic criteria, and treatment strategies. Furthermore, special attention was provided to alternative treatment strategies and biomaterial-based physical treatment strategies. A total of six products with the potential to be applied as physical barrier strategies in supporting SPD treatment were shortlisted and discussed. The results indicated that SPD is a complex, underestimated, and underemphasized neuropsychiatric disorder that needs heightened attention, especially with regard to its treatment and care. Moreover, the high synergistic potential of biomaterials and nanosystems in this area remains to be explored. Certain strategies that are already being utilized for wound healing can also be further exploited, particularly as far as the prevention of infections is concerned

Gallavotti-Cohen-Type symmetry related to cycle decompositions for Markov chains and biochemical applications

We slightly extend the fluctuation theorem obtained in \cite{LS} for sums of generators, considering continuous-time Markov chains on a finite state space whose underlying graph has multiple edges and no loop. This extended frame is suited when analyzing chemical systems. As simple corollary we derive in a different method the fluctuation theorem of D. Andrieux and P. Gaspard for the fluxes along the chords associated to a fundamental set of oriented cycles \cite{AG2}. We associate to each random trajectory an oriented cycle on the graph and we decompose it in terms of a basis of oriented cycles. We prove a fluctuation theorem for the coefficients in this decomposition. The resulting fluctuation theorem involves the cycle affinities, which in many real systems correspond to the macroscopic forces. In addition, the above decomposition is useful when analyzing the large deviations of additive functionals of the Markov chain. As example of application, in a very general context we derive a fluctuation relation for the mechanical and chemical currents of a molecular motor moving along a periodic filament.Comment: 23 pages, 5 figures. Correction