Stochastic efficiency of thermodiffusion: an extended local equilibrium approach

The recently established connection between stochastic thermodynamics and fluctuating hydrodynamics is applied to a study of efficiencies in the coupled transport of heat and matter on a small scale. A stochastic model for a mesoscopic cell connected to two macroscopic reservoirs of heat and particles is developed, based on fluctuating hydrodynamics. Within this approach, the fluctuating separation and thermodynamic efficiencies are defined. The conditions required to observe bimodal distributions of these efficiencies are determined, and the evolution of these distributions is investigated in the large-size and in the long-time limits. The results obtained are not restricted to thermodiffusion and can be generalized to systems where efficiency is defined as a ratio of stochastic state variables or dissipation rates.Comment: Figure 11 is corrected when compared to the published versio

Active-passive mixtures with bulk loading: a minimal active engine in one dimension

We study a one-dimensional mixture of active (run-and-tumble) particles and passive (Brownian) particles, with single-file constraint, in a sawtooth potential. The active particles experience a ratchet effect: this generates a current, which can push passive particles against an applied load. The resulting system operates as an active engine. Using numerical simulations, we analyse the efficiency of this engine, and we discuss how it can be optimised. Efficient operation occurs when the active particles self-organise into teams, which can push the passive ones against large loads by leveraging collective behaviour. We discuss how the particle arrangement, conserved under the single-file constraint, affects the engine efficiency. We also show that relaxing this constraint still allows the engine to operate effectively.Comment: 21 pages, 17 figure

Données récentes relatives aux perturbations de la fonction ovarienne chez les bovins

peer reviewedThe hormonal pattern was studied in 54 animals: 34 heifers with seasonal anoestrus, 13 cows with post-partum anoestrus, 5 cows with nymphomania and 2 cows superovulated. Seasonal and post partum anoestrus are characterized by basal levels of progesterone, FSH and LH, while oestradiol level is more variable and higher in post partum anoestrus due to the proper activity of the ovary. Nymphomania is a hyperfolliculinemic syndrome; cystic puncture leads to a fall in oestradiol and a surge in FSH and LH but of inequal intensity. The level of the latter hormone is often too low to induce luteinization; cystic degeneration of the ovary is associated with LH deficiency. In superovulated cows, hormonal pattern is like in normal cyclic cows but more pronounced.Etude de la stérilité hormonale chez les bovin

Post partum anoestrus survey

peer reviewedThe authors give a survey of the actual knowledge about the fundamental endocrinology of the ovarian cycle in the bovine. In an experiment using 5 dry cows, 20 cows milked twice daily, and 5 freely suckled cows, a comparative study was made about the post partum ovarian activity by checking heat, by rectal palpation, and by analysis of daily blood and milk samples for ovarian steroids and gonadotropins. For the 3 groups of cows, the first postpartum ovulation was noted at respectively 23, 45, 115 days after parturition. Originally it was thought that a hypersecretion of prolactin was responsible, but no effect could be observed after administration of the prolactin-inhibitor bromocryptine. More recent experimental studies have shown that milking and especially suckling acts as a stess factor, provoking an increased secretion and release of corticosteroids and a decreased blood level of LH, largely responsible for the prolonged post-partum anoestrus period. The logical treatment is weaning, but this technique is often economically difficult to apply in beef cattle. The most indicated alternative treatment to speed up the first postpartum oestrus is the use of the vaginal coil (PRID) containing 2-3 g of progesterone and carrying a capsule with 10 mg of oestradiolbenzoate. The latter stimulates the resorption of progesterone. The coil was removed after 12 days and 500 IU of PMSG were injected. In anoestrous beef cattle, an ovulatory oestrus was induced with a conception rate of 45%

Recent knowledge in animal gynecology

Etude de la stérilité hormonale chez les bovin

Prostaglandins and sex cycle in domestic animals

In some domestic animal species, cow, ewe, sow, mare, luteal regression and therefore oestral regulation, depends on the action of a luteolytic of uterine origin. This luteolysine should be but a prostaglandin F2 alpha or an analogue. Progesterone is the regulator of the cycle; plasma level is low (basic level) at day of oestrus (0,5ng/ml) then increases gradually to reach a peak value of 6 to 9 ng/ml at days 6 to 16 of the cycle. Beta-oestradiol level fluctuates including a main peak before ovulation (9 pg/ml) and three accessory peaks at days 4-5, 8, 12-14 of the cycle; however the peak of the 8th day is inconstant. FSH and LH levels are constant during dioestrus, peak level values are observed at the beginning of oestrus, they are practically superposed and of a 6 to 9 hours duration. Administration of prostaglandins during luteal phase produces hormonal changes similar to those observed during the normal cycle. Because of its luteolytic action and its effect on uterine fibre, prostaglandin F2 alpha offers a special interest for stock farming and veterinary medicine. So a full expression can be given to AI and a more extended application of egg transfer can be foreseen. It constitutes an effective therapy in the case of corpus luteum persistence and a way to induce parturition.Chez un certain nombre d’espèces animales domestiques, vache, brebis, truie, jument, la régression lutéale, et donc la régulation oestrale, est liée à l’action d’un facteur lutéolytique d’origine utérine; cette lutéolysine ne serait autre qu’une prostaglandine F2 alpha ou un analogue. La progestérone constitue l’élément régulateur du cycle ; le taux plasmatique est à son niveau basal le jour de l’oestrus (0,5 ng/ml) puis il s’élève progressivement pour atteindre 6 à 9 ng/ml entre les jours 6 et 16 du cycle. Le beta oestradiol se caractérise par une courbe de fluctuation comprenant un pic principal pré-ovulatoire (9 pg/ml) et trois pics accessoires se situant respectivement aux jours 4-5, 8, 12-14 du cycle ; le pic du 8e jour est cependant inconstant. Les teneurs en FSH et LH sont pratiquement constantes au cours de la période dioestrale ; les pics de ces deux hormones se situent en début d’oestrus, ils sont pratiquement superposés et d’une durée de 6 à 9 heures. L’administration de prostaglandine en phase lutéale entraîne des modifications plasmatiques hormonales identiques et superposables quant à leur nature, leur intensité, leur apparition chronologique à celles observées lors du cycle normal. Du fait de son action lutéolytique d’une part, et de ses effets sur la fibre utérine d’autre part, la prostaglandine F2 alpha présente un intérêt particulier en matière d’élevage et de médecine vétérinaire. Elle permet de donner à l’IA sa pleine expression et laisse entrevoir une application plus étendue de la transplantation ovulaire. Elle présente une thérapeutique efficace des états liés à la persistance du corps jaune et un moyen de déclenchement de la parturition.Etude de la stérilité hormonale chez les bovin

Active–passive mixtures with bulk loading: a minimal active engine in one dimension

Abstract We study a one-dimensional mixture of active (run-and-tumble) particles and passive (Brownian) particles, with single-file constraint, in a sawtooth potential. The active particles experience a ratchet effect and this generates a current, which can push passive particles against an applied load. The resulting system operates as an active engine. Using numerical simulations, we analyse the efficiency of this engine and we discuss how it can be optimised. Efficient operation occurs when the active particles self-organise into teams, which can push the passive ones against large loads by leveraging collective behaviour. We discuss how the particle arrangement, conserved under the single-file constraint, affects the engine efficiency. We also show that relaxing this constraint still allows the engine to operate effectively.</jats:p