On the Second Law of thermodynamics and the piston problem

The piston problem is investigated in the case where the length of the cylinder is infinite (on both sides) and the ratio $m/M$ is a very small parameter, where $m$ is the mass of one particle of the gaz and $M$ is the mass of the piston. Introducing initial conditions such that the stochastic motion of the piston remains in the average at the origin (no drift), it is shown that the time evolution of the fluids, analytically derived from Liouville equation, agrees with the Second Law of thermodynamics. We thus have a non equilibrium microscopical model whose evolution can be explicitly shown to obey the two laws of thermodynamics.Comment: 29 pages, 9 figures submitted to Journal of Statistical Physics (2003

Hypoxia response in Arabidopsis roots infected by Plasmodiophora brassicae supports the development of clubroot

BackgroundThe induction of alcohol fermentation in roots is a plant adaptive response to flooding stress and oxygen deprivation. Available transcriptomic data suggest that fermentation-related genes are also frequently induced in roots infected with gall forming pathogens, but the biological significance of this induction is unclear. In this study, we addressed the role of hypoxia responses in Arabidopsis roots during infection by the clubroot agent Plasmodiophora brassicae.ResultsThe hypoxia-related gene markers PYRUVATE DECARBOXYLASE 1 (PDC1), PYRUVATE DECARBOXYLASE 2 (PDC2) and ALCOHOL DEHYDROGENASE 1 (ADH1) were induced during secondary infection by two isolates of P. brassicae, eH and e2. PDC2 was highly induced as soon as 7 days post inoculation (dpi), i.e., before the development of gall symptoms, and GUS staining revealed that ADH1 induction was localised in infected cortical cells of root galls at 21 dpi. Clubroot symptoms were significantly milder in the pdc1 and pdc2 mutants compared with Col-0, but a null T-DNA insertional mutation of ADH1 did not affect clubroot susceptibility. The Arg/N-end rule pathway of ubiquitin-mediated proteolysis controls oxygen sensing in plants. Mutants of components of this pathway, ate1 ate2 and prt6, that both exhibit constitutive hypoxia responses, showed enhanced clubroot symptoms. In contrast, gall development was reduced in quintuple and sextuple mutants where the activity of all oxygen-sensing Group VII Ethylene Response Factor transcription factors (ERFVIIs) is absent (erfVII and prt6 erfVII).ConclusionsOur data demonstrate that the induction of PDC1 and PDC2 during the secondary infection of roots by P. brassicae contributes positively to clubroot development, and that this is controlled by oxygen-sensing through ERFVIIs. The absence of any major role of ADH1 in symptom development may also suggest that PDC activity could contribute to the formation of galls through the activation of a PDH bypass

Polarisation effects in semiconductor optical amplifiers

THESIS 8266Optical switches based on SOAs are critical elements for the implementation of alloptical gating. The various wavelength conversion schemes are limited by their polarisation sensitivity. The polarisation sensitivity of SOAs, due to different gain and refractive indices in the TE and TM modes is well known and the resulting non-linear polarisation rotation can also be used for optical switching. Manufacturers characterize their devices in the continuous wave (CW) regime. However low gain anisotropy does not mean preservation of the input signal state of polarisation and for switching applications both CW and pulsed sources are used. The object of this thesis is to experimentally investigate the origins of the polarisation effects and how they affect the performance of SOAs, both in the continuous wave and dynamic regimes

Examining Sen's capability approach to development as guiding theory for development policy

The purpose of this dissertation is to examine to what extent Sen's freedom-centred view of development, with its existing theoretical foundations, offers sufficient theoretical insights for guiding development policies towards the enhancement of human freedoms. The theoretical part of the dissertation focuses on the three foundational building stones of Sen's freedom-centred view of development. First, the capability approach sets the evaluation space of development in the capabilities that people have reason to choose and value, but by doing so, it is argued that Sen's capability approach contains tensions between human freedom and human well-being that can be loosened by thickening this evaluation space with a substantial view of human well-being. Second, the capability approach views individual agency as central in development, but because of the socio-historical dimension of human freedom and agency, it is argued that concepts of collective capabilities and of socio-historical agency are more central in promoting human freedoms. Third, promoting human freedoms cannot be dissociated from democratic policy-making. But because the link between the two is not necessary, it is argued that the capability approach's consequentialist evaluation of human well-being will have to be thickened by a procedural evaluation which assesses the exercise of political freedom through certain normative principles of decision-making. The empirical part of the thesis illustrates these theoretical arguments through the analysis of two case studies, Costa Rica and the Dominican Republic. The case studies particularly point to a country's socio-historical agency, or collective capability in promoting human well-being, through socio-historical narratives. These narratives assess a country's collective capability in promoting human freedoms by looking at the country's socio-historical reality, and how its members have appropriated that reality in the course of the country's history, opening up or closing down opportunities for realising policy decisions towards the removal of unfreedoms.</p

Modelling Mortality with Common Stochastic Long-Run Trends

Modelling mortality and longevity risk is critical to assessing risk for insurers issuing longevity risk products. It has challenged practitioners and academics alike because of first the existence of common stochastic trends and second the unpredictability of an eventual mortality improvement in some age groups. When considering cause-of-death mortality rates, both aforementioned trends are additionally affected by the cause of death. Longevity trends are usually forecasted using a Lee-Carter model with a single stochastic time series for period improvements, or using an age-based parametric model with univariate time series for the parameters. We assess a multivariate time series model for the parameters of the Heligman-Pollard function, through Vector Error Correction Models which include the common stochastic long-run trends. The model is applied to circulatory disease deaths in U.S. over a 50-year period and is shown to be an improvement over both the Lee-Carter model and the stochastic parameter ARIMA Heligman-Pollard model.

Modelling of the relationship between infliximab exposure, faecal calprotectin and endoscopic remission in patients with Crohn's disease

Aims: Evidence for the benefits of pharmacokinetic (PK) and pharmacodynamic (PD) monitoring of infliximab in patients with Crohn's disease (CD) remains scarce. We aimed to develop a population (pop)PK/PD model to characterise the infliximab dose–exposure–biomarker–response (faecal calprotectin [fCal] and endoscopic remission [ER]) relationship. Methods: Data were obtained from 116 patients with CD in a phase 4 dose-escalation study. Three sequential models were developed: a 2-compartment popPK model linking infliximab dose to exposure; an indirect response popPK/PD model describing the inhibitory effect of infliximab exposure on fCal; and a first-order Markov popPD model linking fCal to transitions between states of ER, no ER and dropout. Results: Infliximab clearance increased with increasing fCal, decreasing albumin, increasing CD activity index and presence of anti-drug antibodies. Baseline fCal increased with increasing C-reactive protein and decreasing platelet count. Lower fCal increased the probability of attaining ER and decreased the probability of losing ER. Probability of dropping out given an earlier state of absence of ER increased with time. Large interpatient PK and PD variability resulted in a flat dose–response curve. Predicted fraction of patients achieving ER was 45% [30–61] (median [interquartile range], n = 50 000) when on 5 mg/kg infliximab (~46% observed in data). Simulations with 10 mg/kg induction doses predicted an increase to 48% [32–63]. This minor benefit at the population level argues against systematic 10 mg/kg induction dosing in all patients. Conclusion: Model-informed infliximab dose optimisation towards a predefined fCal concentration (while accounting for PK and PD variability) may improve effectiveness of infliximab therapy