How much time does a measurement take?

We consider the problem of measurement using the Lindblad equation, which allows the introduction of time in the interaction between the measured system and the measurement apparatus. We use analytic results, valid for weak system-environment coupling, obtained for a two-level system in contact with a measurer (Markovian interaction) and a thermal bath (non-Markovian interaction), where the measured observable may or may not commute with the system-environment interaction. Analysing the behavior of the coherence, which tends to a value asymptotically close to zero, we obtain an expression for the time of measurement which depends only on the system-measurer coupling, and which does not depend on whether the observable commutes with the system-bath interaction. The behavior of the coherences in the case of strong system-environment coupling, found numerically, indicates that an increase in this coupling decreases the measurement time, thus allowing our expression to be considered the upper limit for the duration of the process.Comment: REVISED VERSION: 17 pages, 2 figure

Welfare of horses from Mexico and the United States of America transported for slaughter in Mexico: Fitness profiles for transport and pre-slaughter logistics

Every year thousands of horses from Mexico and the United States of America (USA) are transported to slaughter in Mexico, but little is known about their welfare or pre-slaughter logistics. In this study, we recorded the origin, sex, age and condition of horses (121 journeys, 2648 animals) upon arrival to an abattoir in northern Mexico, including transport details. Horse welfare was measured indirectly via individual scores for body condition, coat quality, lameness, ocular and nasal discharge, as well as reactivity to a chute restraint test, all performed shortly after unloading. The average journey duration was 9.69 (±7.6) hours for horses from Mexico and 16.77 (±4.51) hours for horses from the USA (77 % of all journeys). The prevalence of ocular discharge, nasal discharge, skin wounds, lameness and diarrhoea, were 23 %, 12 %, 11 %, 9 %, 1 % (respectively) of all the horses observed, with no significant differences between Mexican and American horses (P = 0.05). During the chute test the American horses were calmer than the Mexican ones (P < 0.001), who were more restless and aggressive (P = 0.001). Likewise, vocalizations in their three variants during the restraint, neigh/whinny (P = 0.018), nicker (P < 0.001), and snort (P = 0.018), were more common in horses from Mexico. In order to help characterize fitness for transport, a two-step cluster analysis was applied using the welfare indicators, suggesting the existence of four clusters (C) evaluated on arrival at the abattoir (from good to very poor fitness): good (profile C4, n = 769, 29.1 %), average (profile C1, n = 799 horses, 30.2 %), poor (profile C3, n = 586, 22.1 %) and very poor (profile C2, n = 494, 18.6 %). In fact, the C4 best welfare group had 0% lame, 0% nasal discharge, 16.4 % ocular discharge, 7.9 % skin wounds. Instead, the C2 poorest welfare group had 45.8 % lame, 61.1 % nasal discharge, 42.8 % ocular discharge, and 19.9 % skin wounds. Results show potential for using nasal discharge, lameness and ocular discharge as key indicators of horse fitness and welfare on abattoir. The study provides detailed scientific data to help establish strategies regarding optimal days of recovery post-transport and fattening for homogenization of weights between animals of different origins, logistic planning, and optimization of logistic resources to minimize the biological cost of long-distance transport

Bosonization in Higher Dimensions

Using the recently discovered connection between bosonization and duality transformations (hep-th/9401105 and hep-th/9403173), we give an explicit path-integral representation for the bosonization of a massive fermion coupled to a U(1) gauge potential (such as electromagnetism) in d space (D=d+1 spacetime) dimensions. The bosonic theory is described by a rank d-1 antisymmetric Kalb-Ramond-type gauge potential. We construct the bosonized lagrangian explicitly in the limit of large fermion mass. We find that the resulting action is local for d=2 (and given by a Chern-Simons action), but nonlocal for d larger than 3. By coupling to a statistical Chern-Simons field for d=2, we obtain a bosonized formulation of anyons. The bosonic theory may be further dualized to a theory involving purely scalars, for any d, and we show this to be governed by a higher-derivative lagrangian for which the scalar decouples from the U(1) gauge potential.Comment: (We had omitted some references and had misspelled `aficionados') plain TeX, 11 pages, McGill-94/33, NEIP-94-006, OSLO-TP 10-9

Temporal Progression of Fatty Acids in Preterm and Term Human Milk of Mothers from Switzerland.

We longitudinally compared fatty acids (FA) from human milk (HM) of mothers delivering term and preterm infants. HM was collected for 4 months postpartum at 12 time points for preterm and for 2 months postpartum at 8 time points for term group. Samples were collected from the first feed of the morning, and single breast was fully expressed. FA were analyzed by gas chromatography coupled with flame ionization detector. Oleic, palmitic and linoleic acids were the most abundant FA across lactation and in both groups. Preterm colostrum contained significantly (p &lt; 0.05) higher 8:0, 10:0, 12:0, sum medium chain fatty acids (MCFA), 18:3 n-3 FA compared to term counterparts. Preterm mature milk contained significantly higher 12:0, 14:0, 18:2 n-6, sum saturated fatty acids (SFA), and sum MCFA. We did not observe any significant differences between the preterm and term groups for docosahexaenoic acid, arachidonic acid and eicosapentaenoic acid at any stage of lactation. Overall, preterm milk was higher for SFA with a major contribution from MCFA and higher in 18:2 n-6. These observational differences needs to be studied further for their implications on preterm developmental outcomes and on fortification strategies of either mothers' own milk or donor human milk

Longitudinal Analysis of Macronutrient Composition in Preterm and Term Human Milk: A Prospective Cohort Study.

Mother's own milk is the optimal source of nutrients and provides numerous health advantages for mothers and infants. As they have supplementary nutritional needs, very preterm infants may require fortification of human milk (HM). Addressing HM composition and variations is essential to optimize HM fortification strategies for these vulnerable infants. To analyze and compare macronutrient composition in HM of mothers lactating very preterm (PT) (28 0/7 to 32 6/7 weeks of gestational age, GA) and term (T) infants (37 0/7 to 41 6/7 weeks of GA) over time, both at similar postnatal and postmenstrual ages, and to investigate other potential factors of variations. Milk samples from 27 mothers of the PT infants and 34 mothers of the T infants were collected longitudinally at 12 points in time during four months for the PT HM and eight points in time during two months for the T HM. Macronutrient composition (proteins, fat, and lactose) and energy were measured using a mid-infrared milk analyzer, corrected by bicinchoninic acid (BCA) assay for total protein content. Analysis of 500 HM samples revealed large inter- and intra-subject variations in both groups. Proteins decreased from birth to four months in the PT and the T HM without significant differences at any postnatal time point, while it was lower around term equivalent age in PT HM. Lactose content remained stable and comparable over time. The PT HM contained significantly more fat and tended to be more caloric in the first two weeks of lactation, while the T HM revealed higher fat and higher energy content later during lactation (three to eight weeks). In both groups, male gender was associated with more fat and energy content. The gender association was stronger in the PT group, and it remained significant after adjustments. Longitudinal measurements of macronutrients compositions of the PT and the T HM showed only small differences at similar postnatal stages in our population. However, numerous differences exist at similar postmenstrual ages. Male gender seems to be associated with a higher content in fat, especially in the PT HM. This study provides original information on macronutrient composition and variations of HM, which is important to consider for the optimization of nutrition and growth of PT infants

Finite-Temperature Transport in Finite-Size Hubbard Rings in the Strong-Coupling Limit

We study the current, the curvature of levels, and the finite temperature charge stiffness, D(T,L), in the strongly correlated limit, U>>t, for Hubbard rings of L sites, with U the on-site Coulomb repulsion and t the hopping integral. Our study is done for finite-size systems and any band filling. Up to order t we derive our results following two independent approaches, namely, using the solution provided by the Bethe ansatz and the solution provided by an algebraic method, where the electronic operators are represented in a slave-fermion picture. We find that, in the U=\infty case, the finite-temperature charge stiffness is finite for electronic densities, n, smaller than one. These results are essencially those of spinless fermions in a lattice of size L, apart from small corrections coming from a statistical flux, due to the spin degrees of freedom. Up to order t, the Mott-Hubbard gap is \Delta_{MH}=U-4t, and we find that D(T) is finite for n<1, but is zero at half-filling. This result comes from the effective flux felt by the holon excitations, which, due to the presence of doubly occupied sites, is renormalized to \Phi^{eff}=\phi(N_h-N_d)/(N_d+N_h), and which is zero at half-filling, with N_d and N_h being the number of doubly occupied and empty lattice sites, respectively. Further, for half-filling, the current transported by any eigenstate of the system is zero and, therefore, D(T) is also zero.Comment: 15 pages and 6 figures; accepted for PR

Adiabatic evolution of a coupled-qubit Hamiltonian

We present a general method for studying coupled qubits driven by adiabatically changing external parameters. Extended calculations are provided for a two-bit Hamiltonian whose eigenstates can be used as logical states for a quantum CNOT gate. From a numerical analysis of the stationary Schroedinger equation we find a set of parameters suitable for representing CNOT, while from a time-dependent study the conditions for adiabatic evolution are determined. Specializing to a concrete physical system involving SQUIDs, we determine reasonable parameters for experimental purposes. The dissipation for SQUIDs is discussed by fitting experimental data. The low dissipation obtained supports the idea that adiabatic operations could be performed on a time scale shorter than the decoherence time.Comment: 10 pages, 4 figures, to be pub.in Phys Rev

Human Milk Oligosaccharides in the Milk of Mothers Delivering Term versus Preterm Infants.

Human milk oligosaccharides (HMOs) are a major component of human milk, and play an important role in protecting the infant from infections. Preterm infants are particularly vulnerable, but have improved outcomes if fed with human milk. This study aimed to determine if the HMO composition of preterm milk differed from that of term milk at equivalent stage of lactation and equivalent postmenstrual age. In all, 22 HMOs were analyzed in 500 samples of milk from 25 mothers breastfeeding very preterm infants (&lt; 32 weeks of gestational age, &lt; 1500g of birthweight) and 28 mothers breastfeeding term infants. The concentrations of most HMOs were comparable at equivalent postpartum age. However, HMOs containing α-1,2-linked fucose were reduced in concentration in preterm milk during the first month of lactation. The concentrations of a number of sialylated oligosaccharides were also different in preterm milk, in particular 3'-sialyllactose concentrations were elevated. At equivalent postmenstrual age, the concentrations of a number of HMOs were significantly different in preterm compared to term milk. The largest differences manifest around 40 weeks of postmenstrual age, when the milk of term infants contains the highest concentrations of HMOs. The observed differences warrant further investigation in view of their potential clinical impact

Produtividade e vigor do maracujazeiro-amarelo plantado em covas e plantio direto sob manejo orgânico.

O objetivo deste trabalho foi avaliar o vigor e a produtividade do maracujazeiro-amarelo plantado em diferentes tamanhos de cova e plantio direto sob manejo orgânico. O experimento foi conduzido de 2005 a 2007, no Setor de Agricultura Ecológica da Universidade Federal do Acre, em delineamento de blocos casualizados, constituídos de cinco tratamentos, quatro repetições e quatro plantas por parcela. Foram avaliados cinco tipos de preparo do solo: T1 cova do tamanho do torrão (0,19 x 0,063m) com adubação em cobertura; T2 cova de 0,30 x 0,30 x 0,30m com adubação de plantio na cova; T3 cova de 0,30 x 0,30 x 0,30m com adubação de plantio em cobertura; T4 cova de 0,50 x 0,50 x 0,50m com adubação de plantio na cova; e T5 cova de 0,50 x 0,50 x 0,50m com adubação de plantio em cobertura. O tamanho da cova e o plantio direto não influenciaram o vigor da planta e a biomassa de raízes. O número de frutos por planta e a produtividade, na segunda e na somatória das duas safras, foram maiores com plantio direto e com covas cúbicas de 0,30m. Após dois anos de cultivo, a densidade do solo foi maior na camada de 0-5cm de profundidade num raio de 20cm da planta para o plantio em covas de 0,50m com adubação na cova e menor para o plantio direto, não havendo diferença entre os demais tratamentos. O plantio direto ou o plantio em covas pequenas com dimensões de 0,30 x 0,30 x 0,30m proporcionou maior produtividade de maracujá que o plantio em covas maiores, mesmo não influenciando o vigor das plantas e a massa seca de raízes