Energy transfer in N-component nanosystems enhanced by pulse-driven vibronic many-body entanglement.

The processing of energy by transfer and redistribution, plays a key role in the evolution of dynamical systems. At the ultrasmall and ultrafast scale of nanosystems, quantum coherence could in principle also play a role and has been reported in many pulse-driven nanosystems (e.g. quantum dots and even the microscopic Light-Harvesting Complex II (LHC-II) aggregate). Typical theoretical analyses cannot easily be scaled to describe these general N-component nanosystems; they do not treat the pulse dynamically; and they approximate memory effects. Here our aim is to shed light on what new physics might arise beyond these approximations. We adopt a purposely minimal model such that the time-dependence of the pulse is included explicitly in the Hamiltonian. This simple model generates complex dynamics: specifically, pulses of intermediate duration generate highly entangled vibronic (i.e. electronic-vibrational) states that spread multiple excitons - and hence energy - maximally within the system. Subsequent pulses can then act on such entangled states to efficiently channel subsequent energy capture. The underlying pulse-generated vibronic entanglement increases in strength and robustness as N increases.

Light-harvesting mechanism of bacteria exploits a critical interplay between the dynamics of transport and trapping.

Light-harvesting bacteria Rhodospirillum photometricum were recently found to adopt strikingly different architectures depending on illumination conditions. We present analytic and numerical calculations which explain this observation by quantifying a dynamical interplay between excitation transfer kinetics and reaction center cycling. High light-intensity membranes exploit dissipation as a photoprotective mechanism, thereby safeguarding a steady supply of chemical energy, while low light-intensity membranes efficiently process unused illumination intensity by channeling it to open reaction centers. More generally, our analysis elucidates and quantifies the trade-offs in natural network design for solar energy conversion.

Absence of circadian rhythm in the disposition of melatonin in the cow.

Five adult pasture-bred Prim Holstein cows were used to document the time invariance of melatonin disposition in the cow. Melatonin was administered by an intravenous route as a bolus (5 micrograms/kg of body weight) at either 1430 or 2230. Data were analysed according to a three-compartment open model with melatonin elimination from the central compartment. The mean (+/- SD) kinetic parameters describing melatonin disposition, during day and night, respectively, were plasma clearances: 0.0267 +/- 0.0084 l/kg per min and 0.0229 +/- 0.0031 l/kg per min; steady state volume of distribution: 0.826 +/- 0.229 l/kg and 0.780 +/- 0.193 l/kg; terminal half lives: 58.9 +/- 23.7 min and 64.1 +/- 33.7 min; mean residence times: 32.0 +/- 8.8 min and 33.9 +/- 6.2 min. No statistical difference was found between diurnal and nocturnal values for these parameters. These results support the concept of time invariance for melatonin kinetics in cattle and validate the use of diurnal experiments for the study of melatonin kinetics.

Circadian profile and production rate of melatonin in the cow.

Five adult pasture-bred French Friesian cows were used to qualify the circadian profile and characterized pulsatility of plasma melatonin, and to estimate melatonin secretion rate, around the summer solstice. Plasma concentrations of melatonin were low (5 pg/ml) during the photophase, began to rise at sunset (light intensity less than 20 lx) and reached a maximum (about 90 pg/ml) in the middle of the scotophase. The mean amplitude of peaks was 48.67 +/- 23.01 pg/ml, their mean duration was 32.30 +/- 21.50 min and the frequency was 1.5 +/- 0.3 peak/hr during the secretory period (537 +/- 42.3 min). The plasma clearance (ClB) was 0.0247 +/- 0.0013 1/kg per min, the steady state volume of distribution (Vss) was 1.404 +/- 0.225 1/kg, the elimination half life (t1/2 beta) was 66.66 +/- 11.30 min, the mean residence time was 51.37 +/- 9.92 min and the mean production rate was 399.9 +/- 57.37 ng/kg per 24 hr. These results support the concept of linearity for melatonin kinetics in cattle and the plasma clearance value suggest a first-pass hepatic effect.

[A serological study of the contagious equine metritis: comparison between indirect immunofluorescence, slow agglutination and complement fixation techniques (author's transl)]. / Sérologie de la métrite contagieuse de la jument: comparaison des réactions d'immunofluorescence indirecte, de séroagglutination lente et de fixation du complément.

Serological response of pony mares to contagious equine metritis is studied comparing three techniques: slow agglutination, complement fixation and indirect immunofluorescence. Sera were taken from pony mares vaccinated with a heat inactivated suspension of Haemophilus equigenitalis, from experimentally-infected pony mares and from healthy horses. All three reactions detected antibodies in vaccinated and infected animals. The highest titers are observed with vaccinated mares. Titers are low in infected animals. Antibodies detected by indirect immunofluorescence appeared sooner and persisted longer in diseased animals than agglutinating or complement fixing antibodies. Only indirect immunofluorescence revealed a new contamination of two mares following coitus with a stallion excreting H. equigenitalis. Indirect immunofluorescence must be recommended in diagnosis of contagious equine metritis and in detection of chronic carriers.

[Bacteriological studies of Haemophilus equigenitalis Taylor 1978, the causative organism of contagious equine metritis 1977 (author's transl)]. / Etude bactériologique de Haemophilus equigenitalis Taylor 1978, agent de la métrite contagieuse de la jument.

The cultural, biochemical, antigenic and antibiotic susceptibility characteristics of 17 strains of Haemophilus equigenitalis, the causative organism of contagious equine metritis (CEM), were studied. Biochemical characteristics were investigated using both conventional method and the API ZYM system of enzyme detection. The biochemical profile of the H. equigenitalis strains was unique and differed from the other bacterial species studied under the same experimental conditions (H. influenzae and H. parainfluenzae, B. abortus and B. melitensis, P. multocida, A. calcoaceticus). The required X and V factors were never demonstrated and therefore the placement of H. equigenitalis in the genus Haemophilus is discutable. This species presented an, antigenic homogeneity and exhibited no cross-reaction with the other strains tested in this study. Antibiotic susceptibility was studied by diffusion test and MIC determination. The strains were susceptible to all antibiotics with the exception of clindamycin, lincomycin and streptomycin; where the streptomycin resistance was inconstant.

[Clinical and epidemiological aspects of bovine brucellosis in tropical Africa]. / Aspects cliniques et épidémiologiques de la brucellose bovine en Afrique tropicale

Bovine brucellosis, in the tropical regions of Africa, is very different, both clinically and epidermiologically, from that observed in temperate zones. From the clinical point of view, abortion is rare and extra-genital lesions (hygromas and abscesses) are frequent. From the epidemiological point of view, the rate of infection is low and the disease has very little tendency to spread. The reason for these differences may be explained by climatic conditions (temperature, insolation, humidity) as well as by breeding conditions (principally nomadic or transhumant breeding). Where climatic and breeding conditions resemble those of intensive breeding in temperate zones the clinical and epidemiological aspects tend towards similarity with the usual form of bovine brucellosis.