Semiclassical Dynamics of Electrons in Magnetic Bloch Bands: a Hamiltonian Approach

y formally diagonalizing with accuracy $\hbar$ the Hamiltonian of electrons in a crystal subject to electromagnetic perturbations, we resolve the debate on the Hamiltonian nature of semiclassical equations of motion with Berry-phase corrections, and therefore confirm the validity of the Liouville theorem. We show that both the position and momentum operators acquire a Berry-phase dependence, leading to a non-canonical Hamiltonian dynamics. The equations of motion turn out to be identical to the ones previously derived in the context of electron wave-packets dynamics.Comment: 4 page

From Feynman Proof of Maxwell Equations to Noncommutative Quantum Mechanics

In 1990, Dyson published a proof due to Feynman of the Maxwell equations assuming only the commutation relations between position and velocity. With this minimal assumption, Feynman never supposed the existence of Hamiltonian or Lagrangian formalism. In the present communication, we review the study of a relativistic particle using ``Feynman brackets.'' We show that Poincar\'e's magnetic angular momentum and Dirac magnetic monopole are the consequences of the structure of the Lorentz Lie algebra defined by the Feynman's brackets. Then, we extend these ideas to the dual momentum space by considering noncommutative quantum mechanics. In this context, we show that the noncommutativity of the coordinates is responsible for a new effect called the spin Hall effect. We also show its relation with the Berry phase notion. As a practical application, we found an unusual spin-orbit contribution of a nonrelativistic particle that could be experimentally tested. Another practical application is the Berry phase effect on the propagation of light in inhomogeneous media.Comment: Presented at the 3rd Feynman Festival (Collage Park, Maryland, U.S.A., August 2006

Orientation and distribution of recent gullies in the southern hemisphere of Mars: observations from HRSC/MEX and MOC/MGS data

Abstract not available

Intramammary infections in lactating Jersey cows: Prevalence of microbial organisms and association with milk somatic cell count and persistence of infection.

There is limited data available regarding pathogens causing intramammary infections (IMI) in Jersey cows. The objectives of this study were to characterize the prevalence of IMI caused by different microorganisms in lactating Jersey cattle and evaluate the associations among microbes and somatic cell count (SCC) and persistence of IMI. This prospective, observational, longitudinal study included lactating Jersey cows (n = 753) from 4 farms within a 250-mile radius of Columbia, Missouri. Quarter foremilk samples were aseptically collected monthly for 3 consecutive months. Microorganisms were identified using aerobic milk culture and MALDI-TOF mass spectrometry. A commercial laboratory measured SCC using flow cytometry. Milk culture results were used to classify single microorganism infections as persistent (same microorganism species identified at first sampling and one other sampling) or non-persistent infection. Mixed models were built to evaluate the associations between IMI status and lnSCC as well as persistence and lnSCC. Overall, staphylococci were the most commonly isolated microorganisms among the 7,370 quarter-level milk samples collected. Median prevalence (using all 3 samplings) of specific microbes varied among farms; however, Staphylococcus chromogenes was a common species found at all farms. The most common microbial species that persisted were Staph. chromogenes, Staphylococcus aureus, Staphylococcus simulans, and Streptococcus uberis. Streptococcus dysgalactiae and Staph. aureus were the IMI associated with the most inflammation based on lnSCC. The small number of herds included in this study with the large variation in herd type limits the generalizability of the data. However, results of this study seem to be similar to those of previous studies in other breeds, suggesting management factors are more important than breed-specific differences when evaluating causes of IMI and associated subclinical mastitis

Reading between Eye Saccades

Background: Skilled adult readers, in contrast to beginners, show no or little increase in reading latencies as a function of the number of letters in words up to seven letters. The information extraction strategy underlying such efficiency in word identification is still largely unknown, and methods that allow tracking of the letter information extraction through time between eye saccades are needed to fully address this question. Methodology/Principal Findings: The present study examined the use of letter information during reading, by means of the Bubbles technique. Ten participants each read 5,000 five-letter French words sampled in space-time within a 200 ms window. On the temporal dimension, our results show that two moments are especially important during the information extraction process. On the spatial dimension, we found a bias for the upper half of words. We also show for the first time that letter positions four, one, and three are particularly important for the identification of five-letter words. Conclusions/Significance: Our findings are consistent with either a partially parallel reading strategy or an optimal serial reading strategy. We show using computer simulations that this serial reading strategy predicts an absence of a wordlength effect for words from four- to seven letters in length. We believe that the Bubbles technique will play an importan

Stiffness modelling of parallelogram-based parallel manipulators

International audienceThe paper presents a methodology to enhance the stiffness analysis of parallel manipulators with parallelogram-based linkage. It directly takes into account the influence of the external loading and allows computing both the non-linear ``load-deflection" relation and relevant rank-deficient stiffness matrix. An equivalent bar-type pseudo-rigid model is also proposed to describe the parallelogram stiffness by means of five mutually coupled virtual springs. The contributions of this paper are highlighted with a parallelogram-type linkage used in a manipulator from the Orthoglide family

Monitoring photo-oxidative and salinity-induced bacterial stress in the Canadian Arctic using specific lipid tracers

Publisher policy: author can archive post-print on open access repository after an embargo period of 18 months.Publisher's version/PDF cannot be used. Must link to publisher version with DOI. Author's post-print must be released with a Creative Commons Attribution Non-Commercial No Derivatives License

Cracking the code of oscillatory activity

Neural oscillations are ubiquitous measurements of cognitive processes and dynamic routing and gating of information. The fundamental and so far unresolved problem for neuroscience remains to understand how oscillatory activity in the brain codes information for human cognition. In a biologically relevant cognitive task, we instructed six human observers to categorize facial expressions of emotion while we measured the observers' EEG. We combined state-of-the-art stimulus control with statistical information theory analysis to quantify how the three parameters of oscillations (i.e., power, phase, and frequency) code the visual information relevant for behavior in a cognitive task. We make three points: First, we demonstrate that phase codes considerably more information (2.4 times) relating to the cognitive task than power. Second, we show that the conjunction of power and phase coding reflects detailed visual features relevant for behavioral response-that is, features of facial expressions predicted by behavior. Third, we demonstrate, in analogy to communication technology, that oscillatory frequencies in the brain multiplex the coding of visual features, increasing coding capacity. Together, our findings about the fundamental coding properties of neural oscillations will redirect the research agenda in neuroscience by establishing the differential role of frequency, phase, and amplitude in coding behaviorally relevant information in the brai

Effects of plant extracts and essential oils as feed supplements on quality and microbial traits of rabbit meat

[EN] The effects of dietary supplementation of onion, cranberry,  strawberry and essentials oils on meat quality were analysed. Five groups of 48 Grimaud female weaned rabbits received the supplemented or the control ration; the experimental unit was a cage of 6 rabbits. Each experimental diet contained 10 ppm of added active ingredients.  Rabbits were fed with the experimental diets for 4 wk before determining slaughter and carcass traits and determining the pH at 1 and 24 h post mortem (pHu) of the Longissimus dorsi (LD) and the Biceps femoris (BF) muscle, left and right, respectively. Cooking loss, drip loss and L*, a* and b* color parameters were obtained of the right LD and for ground meat and antioxidant status (TBARS, DNPH, Folin Ciocalteu). Only the pHu of the LD muscle for the strawberry supplemented group was significantly lower when compared to the control group (P=0.04). However, we note that for the pH of the LD, the average was less than 6 for the meat of animals who received a diet enriched in polyphenols, compared to the control group. Plant extract supplementation did not influence meat quality traits, growth performance or oxidative stability. But under aerobic and anaerobic conditions, our results indicate that diet supplementation with extracts rich in polyphenols, especially with essential oils, had a small bot sporadic positive effect in reducing bacterial microflora compared to the control group (P<0.05). In conclusion, plant extracts and essential oils can be used in a rabbit diet without adverse effects on performance and meat quality traits. This effect could be optimized by investigating higher doses.Kone, AP.; Cinq-Mars, D.; Desjardins, Y.; Guay, F.; Gosselin, A.; Saucier, L. (2016). Effects of plant extracts and essential oils as feed supplements on quality and microbial traits of rabbit meat. 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Foodborne illnesses and nutritional status: a statement from an american society for nutritional sciences working group. J. Nutr., 130: 2613-2617.Magdelaine P. 2003. Économie et avenir des filières avicoles et cunicoles. INRA Prod. Anim., 16: 349-356.Peiretti, P. G., & Meineri, G. (2008). Effects on growth performance, carcass characteristics, and the fat and meat fatty acid profile of rabbits fed diets with chia (Salvia hispanica L.) seed supplements. Meat Science, 80(4), 1116-1121. doi:10.1016/j.meatsci.2008.05.003Pla M. 1999. Carcass and meat quality of growing rabbits under high ambient temperature using high fat diets. In: Testik A., Baselga M. (ed). 2nd International Conference on rabbit production in hot climates. Ciheam-Iamz Adana (Turquía). Cahiers Options Méditerranéennes, 41: 93-98.Rasmussen A.J., Andersson M. 1996. New method for determination of drip loss in pork muscles. In Proc.: 42nd International Congress of Meat Science and Technology,1-6 September, 1996. Lillehammer, Norway. 286-287.Rotolo, L., Gai, F., Nicola, S., Zoccarato, I., Brugiapaglia, A., & Gasco, L. (2013). Dietary Supplementation of Oregano and Sage Dried Leaves on Performances and Meat Quality of Rabbits. Journal of Integrative Agriculture, 12(11), 1937-1945. doi:10.1016/s2095-3119(13)60631-0Salvini S., Parpinel M., Gnagnarella P., Maisonneuve P., Turrini A. 1998. Banca dati di composizione degli alimenti per studi epidemiologici in Italia. Ed. Istituto Superiore di Oncologia, Genova, Italy.SAS. 2002. SAS/STAT User's Guide (Release 9.1). SAS Institute, Inc., Cary NC, USA.Subramanian K.N., Padmanaban G., Sarma P.S. 1965. Folin-Ciocalteu reagent for the estimation of siderochromes. Anal. Biochem., 12: 106-112. doi:10.1016/0003-2697(65)90147-Thomas M.K., Majowicz S.E, Pollari F., Sockett P.N. 2008. Burden of acute gastrointestinal illness in Canada, 1999-2007: Interim summary of NSAGI activities. Canada Communicable Disease Report, 34: 8-13