7,392 research outputs found
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
Household fish preparation hygiene and cholera transmission in Monrovia, Liberia.
BACKGROUND: In the 1980s Vibrio cholerae was found to be an autochthonous resident of aquatic environments. As result, ingestion of undercooked, contaminated fish has been associated with cholera transmission. An alternative mechanism of transmission associated with fish was hypothesised by SchĂĽrmann et al. in 2002. He described a cholera case that was more likely to have been infected by contamination on the patient's hands rather than by ingestion of contaminated fish. METHODOLOGY: With fish being the main diet in Liberia, we decided to examine fish samples and preparation techniques in Monrovia. Excreta of 15 fish, caught in the estuarine waters of Monrovia, were analysed for V. cholerae. In addition, fish preparation methods were observed in 30 households. RESULTS: Two fish samples were found positive. Observations revealed that hygiene measures during the gutting process of fish were limited; although hands were usually rinsed, in all cases soap was not used. Furthermore, contaminated water was frequently reused during food preparation. CONCLUSIONS: Since the cooking process of fish (and thus elimination of bacteria) in Monrovia usually consists of both frying and boiling, it seems plausible that in this context, the hypothesis by SchĂĽrmann et al. could be applicable. Further research is necessary to confirm this association, which could be a starting point for more context-specific health education campaigns addressing food preparation hygiene as risk factor for cholera
Fluctuation-response relations for nonequilibrium diffusions with memory
Strong interaction with other particles or feedback from the medium on a
Brownian particle entail memory effects in the effective dynamics. We discuss
the extension of the fluctuation-dissipation theorem to nonequilibrium Langevin
systems with memory. An important application is to the extension of the
Sutherland-Einstein relation between diffusion and mobility. Nonequilibrium
corrections include the time-correlation between the dynamical activity and the
velocity of the particle, which in turn leads to information about the
correlations between the driving force and the particle's displacement
On the validity of entropy production principles for linear electrical circuits
We discuss the validity of close-to-equilibrium entropy production principles
in the context of linear electrical circuits. Both the minimum and the maximum
entropy production principle are understood within dynamical fluctuation
theory. The starting point are Langevin equations obtained by combining
Kirchoff's laws with a Johnson-Nyquist noise at each dissipative element in the
circuit. The main observation is that the fluctuation functional for time
averages, that can be read off from the path-space action, is in first order
around equilibrium given by an entropy production rate. That allows to
understand beyond the schemes of irreversible thermodynamics (1) the validity
of the least dissipation, the minimum entropy production, and the maximum
entropy production principles close to equilibrium; (2) the role of the
observables' parity under time-reversal and, in particular, the origin of
Landauer's counterexample (1975) from the fact that the fluctuating observable
there is odd under time-reversal; (3) the critical remark of Jaynes (1980)
concerning the apparent inappropriateness of entropy production principles in
temperature-inhomogeneous circuits.Comment: 19 pages, 1 fi
Depression and sickness behavior are Janus-faced responses to shared inflammatory pathways
It is of considerable translational importance whether depression is a form or a consequence of sickness behavior. Sickness behavior is a behavioral complex induced by infections and immune trauma and mediated by pro-inflammatory cytokines. It is an adaptive response that enhances recovery by conserving energy to combat acute inflammation. There are considerable phenomenological similarities between sickness behavior and depression, for example, behavioral inhibition, anorexia and weight loss, and melancholic (anhedonia), physio-somatic (fatigue, hyperalgesia, malaise), anxiety and neurocognitive symptoms. In clinical depression, however, a transition occurs to sensitization of immuno-inflammatory pathways, progressive damage by oxidative and nitrosative stress to lipids, proteins, and DNA, and autoimmune responses directed against self-epitopes. The latter mechanisms are the substrate of a neuroprogressive process, whereby multiple depressive episodes cause neural tissue damage and consequent functional and cognitive sequelae. Thus, shared immuno-inflammatory pathways underpin the physiology of sickness behavior and the pathophysiology of clinical depression explaining their partially overlapping phenomenology. Inflammation may provoke a Janus-faced response with a good, acute side, generating protective inflammation through sickness behavior and a bad, chronic side, for example, clinical depression, a lifelong disorder with positive feedback loops between (neuro)inflammation and (neuro)degenerative processes following less well defined triggers
Can Europium Atoms form Luminescent Centres in Diamond: A combined Theoretical-Experimental Study
The incorporation of Eu into the diamond lattice is investigated in a
combined theoretical-experimental study. The large size of the Eu ion induces a
strain on the host lattice, which is minimal for the Eu-vacancy complex. The
oxidation state of Eu is calculated to be 3+ for all defect models considered.
In contrast, the total charge of the defect-complexes is shown to be negative
-1.5 to -2.3 electron. Hybrid-functional electronic-band-structures show the
luminescence of the Eu defect to be strongly dependent on the local defect
geometry. The 4-coordinated Eu substitutional dopant is the most promising
candidate to present the typical Eu3+ luminescence, while the 6-coordinated
Eu-vacancy complex is expected not to present any luminescent behaviour.
Preliminary experimental results on the treatment of diamond films with
Eu-containing precursor indicate the possible incorporation of Eu into diamond
films treated by drop-casting. Changes in the PL spectrum, with the main
luminescent peak shifting from approximately 614 nm to 611 nm after the growth
plasma exposure, and the appearance of a shoulder peak at 625 nm indicate the
potential incorporation. Drop-casting treatment with an electronegative polymer
material was shown not to be necessary to observe the Eu signature following
the plasma exposure, and increased the background luminescence.Comment: 12 pages, 7 figures, 5 table
Comparison of five different methods to assess the concentration of boar semen
Both for research and practical purposes, accurate and repeatable methods are required to assess the concentration of boar semen samples. Since the method which is used may influence the results considerably, the aim of the present study was to compare 5 frequently used techniques to determine boar semen concentration. Fifty ejaculates were collected from 37 different boars at an artificial insemination centre. Subsequently, each ejaculate was analyzed for sperm concentration by means of 2 different types of colorimeters (Colorimeter 1: Model 252, Sherwood Scientific Ltd, Cambridge, UK; Colorimeter 2: Ciba-Corning, Schippers, Bladel, The Netherlands), the Burker counting chamber (golden standard), and the Hamilton Thorne Analyzer (Ceros 42.1) using 2 types of Leja chambers (the 'former' and the 'recently developed'). Each ejaculate was assessed 5 times with each of the 5 methods, and the repeatability, expressed by coefficient of variation (CV), was determined for each method. The different methods were compared using Pearson's correlations and limits of agreement. The colorimeters yielded the lowest CV's (both 3.7%), while the former Leja chamber resulted in the highest CV (12.4%). Moreover, significant (P0.71) were found between the results obtained by the different methods. The limits of agreement plots showed that none of the methods consistently over- or underestimated the sperm concentrations when compared to the Burker chamber, although there was a tendency toward higher over- or underestimation in highly concentrated sperm samples. Based on our results, there were no major differences in the assessment of sperm concentration between the evaluated methods. The choice of method used in a laboratory could therefore be based on factors such as cost, number of samples to be assessed and practical use, without thereby negatively affecting the validity of the results thus obtained
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