225 research outputs found
Entropy and efficiency of a molecular motor model
In this paper we investigate the use of path-integral formalism and the
concepts of entropy and traffic in the context of molecular motors. We show
that together with time-reversal symmetry breaking arguments one can find
bounds on efficiencies of such motors. To clarify this techinque we use it on
one specific model to find both the thermodynamic and the Stokes efficiencies,
although the arguments themselves are more general and can be used on a wide
class of models. We also show that by considering the molecular motor as a
ratchet, one can find additional bounds on the thermodynamic efficiency
Fluctuations and response of nonequilibrium states
A generalized fluctuation-response relation is found for thermal systems
driven out of equilibrium. Its derivation is independent of many details of the
dynamics, which is only required to be first-order. The result gives a
correction to the equilibrium fluctuation-dissipation theorem, in terms of the
correlation between observable and excess in dynamical activity caused by the
perturbation. Previous approaches to this problem are recovered and extended in
a unifying scheme
Practical guidance for applying the ADNEX model from the IOTA group to discriminate between different subtypes of adnexal tumors.
All gynecologists are faced with ovarian tumors on a regular basis, and the accurate preoperative diagnosis of these masses is important because appropriate management depends on the type of tumor. Recently, the International Ovarian Tumor Analysis (IOTA) consortium published the Assessment of Different NEoplasias in the adneXa (ADNEX) model, the first risk model that differentiates between benign and four types of malignant ovarian tumors: borderline, stage I cancer, stage II-IV cancer, and secondary metastatic cancer. This approach is novel compared to existing tools that only differentiate between benign and malignant tumors, and therefore questions may arise on how ADNEX can be used in clinical practice. In the present paper, we first provide an in-depth discussion about the predictors used in ADNEX and the ability for risk prediction with different tumor histologies. Furthermore, we formulate suggestions about the selection and interpretation of risk cut-offs for patient stratification and choice of appropriate clinical management. This is illustrated with a few example patients. We cannot propose a generally applicable algorithm with fixed cut-offs, because (as with any risk model) this depends on the specific clinical setting in which the model will be used. Nevertheless, this paper provides a guidance on how the ADNEX model may be adopted into clinical practice
Soils, Science and Community ActioN (SoilSCAN): a citizen science tool to empower community-led land management change in East Africa
Pastoralist communities worldwide face complex challenges regarding food and feed productivity. Primary production systems are under stress, nutritional choices are changing and the relationship between development and agriculture is undergoing profound transformation. Under increasing pressure from climate and land use change, East African agro-pastoral systems are approaching a tipping point in terms of land degradation. There is an urgent need for evidence-led sustainable land management interventions to reverse degradation of natural resources that support food and water security. A key barrier, however, is a lack of high spatial resolution soil health data wherein collecting such information for each individual community is beyond their means. In this context, we tested whether bridging such data gaps could be achieved through a coordinated programme at the boundary between participation and citizen science. Key outputs included a community-led trial of a hand-held soil scanner, which highlighted a range of positive benefits and practical challenges in using this technology in this context, with identification of some potential solutions; and a targeted soil organic matter and nutrient status dataset in a small catchment-based community setting. The results show that if the practical challenges can be resolved, use of portable soil scanner technology has the potential to fill key knowledge gaps and thereby improve resilience to the threat of land degradation through locally responsive farmer and community decision-making
Dynamical fluctuations for semi-Markov processes
We develop an Onsager-Machlup-type theory for nonequilibrium semi-Markov
processes. Our main result is an exact large time asymptotics for the joint
probability of the occupation times and the currents in the system,
establishing some generic large deviation structures. We discuss in detail how
the nonequilibrium driving and the non-exponential waiting time distribution
influence the occupation-current statistics. The violation of the Markov
condition is reflected in the emergence of a new type of nonlocality in the
fluctuations. Explicit solutions are obtained for some examples of driven
random walks on the ring.Comment: Minor changes, accepted for publication in Journal of Physics
A meaningful expansion around detailed balance
We consider Markovian dynamics modeling open mesoscopic systems which are
driven away from detailed balance by a nonconservative force. A systematic
expansion is obtained of the stationary distribution around an equilibrium
reference, in orders of the nonequilibrium forcing. The first order around
equilibrium has been known since the work of McLennan (1959), and involves the
transient irreversible entropy flux. The expansion generalizes the McLennan
formula to higher orders, complementing the entropy flux with the dynamical
activity. The latter is more kinetic than thermodynamic and is a possible
realization of Landauer's insight (1975) that, for nonequilibrium, the relative
occupation of states also depends on the noise along possible escape routes. In
that way nonlinear response around equilibrium can be meaningfully discussed in
terms of two main quantities only, the entropy flux and the dynamical activity.
The expansion makes mathematical sense as shown in the simplest cases from
exponential ergodicity.Comment: 19 page
Neutron transmission and capture of 241Am
A set of neutron transmission and capture experiments based on the Time Of Flight (TOF) technique, were performed in order to determine the 241Am capture cross section in the energy range from 0.01 eV to 1 keV. The GELINA facility of the Institute for Reference Materials and Measurements (IRMM) served as the neutron source. A pair of C6D6 liquid scintillators was used to register the prompt gamma rays emerging from the americium sample, while a Li-glass detector was used in the transmission setup. Results from the capture and transmission data acquired are consistent with each other, but appear to be inconsistent with the evaluated data files. Resonance parameters have been derived for the data up to the energy of 100 eV.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard
Monotone return to steady nonequilibrium
We propose and analyze a new candidate Lyapunov function for relaxation
towards general nonequilibrium steady states. The proposed functional is
obtained from the large time asymptotics of time-symmetric fluctuations. For
driven Markov jump or diffusion processes it measures an excess in dynamical
activity rates. We present numerical evidence and we report on a rigorous
argument for its monotonous time-dependence close to the steady nonequilibrium
or in general after a long enough time. This is in contrast with the behavior
of approximate Lyapunov functions based on entropy production that when driven
far from equilibrium often keep exhibiting temporal oscillations even close to
stationarity.Comment: Accepted for publication in Phys. Rev. Let
Nonequilibrium Linear Response for Markov Dynamics, II: Inertial Dynamics
We continue our study of the linear response of a nonequilibrium system. This
Part II concentrates on models of open and driven inertial dynamics but the
structure and the interpretation of the result remain unchanged: the response
can be expressed as a sum of two temporal correlations in the unperturbed
system, one entropic, the other frenetic. The decomposition arises from the
(anti)symmetry under time-reversal on the level of the nonequilibrium action.
The response formula involves a statistical averaging over explicitly known
observables but, in contrast with the equilibrium situation, they depend on the
model dynamics in terms of an excess in dynamical activity. As an example, the
Einstein relation between mobility and diffusion constant is modified by a
correlation term between the position and the momentum of the particle
ENDF-6 compatible evaluation of neutron induced reaction cross sections for 106,108,110,111,112,113,114,116Cd
An ENDF-6 compatible evaluation for neutron induced reactions in the resonance region has been completed for 106,108,110,111,112,113,114,116Cd. The parameters are the result of an analysis of experimental data available in the literature together with a parameter adjustment on transmission and capture data obtained at the time-of-flight facility GELINA. Complete evaluated data files in ENDF-6 format have been produced by joining the evaluations in the resonance region with corresponding files from the JEFF-3.1.2 nuclear data library (or with the JEFF-Beta-CAD proposed evaluation in case of 113Cd). These files were produced for use in the JEFF32T2 library. For neutron induced reactions in the unresolved resonance region the JENDL-4.0 evaluation for 111Cd and 113Cd was adopted. The evaluated files have been processed with the latest updates of NJOY.99 to test their format and application consistency as well as to produce a continuous-energy data library in ACE format for use in Monte Carlo codes. The ACE files have been utilized to study the effect of the evaluated resonance parameters on results of integral experiments. The evaluated files will be implemented in the next release of the JEFF-3 library which is maintained by the Nuclear Energy Agency of the OECD.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard
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