Coulomb effects on the transport properties of quantum dots in strong magnetic field

We investigate the transport properties of quantum dots placed in strong magnetic field using a quantum-mechanical ' approach based on the 2D tight-binding Hamiltonian with direct Coulomb interaction and the Landauer-B\"{u}ttiker (LB) formalism. The electronic transmittance and the Hall resistance show Coulomb oscillations and also prove multiple addition processes. We identify this feature as the 'bunching' of electrons observed in recent experiments and give an elementary explanation in terms of spectral characteristics of the dot. The spatial distribution of the added electrons may distinguish between edge and bulk states and it has specific features for bunched electrons. The dependence of the charging energy on the number of electrons is discussed for strong and vanishing magnetic field. The crossover from the tunneling to quantum Hall regime is analyzed in terms of dot-lead coupling.Comment: 17 pages,8 figures,Revtex,submitted to Physical Review

Magnetization and Level Statistics at Quantum Hall Liquid-Insulator Transition in the Lattice Model

Statistics of level spacing and magnetization are studied for the phase diagram of the integer quantum Hall effect in a 2D finite lattice model with Anderson disorder.Comment: 4 pages, 6 figure

Resonant and coherent transport through Aharonov-Bohm interferometers with coupled quantum dots

A detailed description of the tunneling processes within Aharonov-Bohm (AB) rings containing two-dimensional quantum dots is presented. We show that the electronic propagation through the interferometer is controlled by the spectral properties of the embedded dots and by their coupling with the ring. The transmittance of the interferometer is computed by the Landauer-B\"uttiker formula. Numerical results are presented for an AB interferometer containing two coupled dots. The charging diagrams for a double-dot interferometer and the Aharonov Bohm oscillations are obtained, in agreement with the recent experimental results of Holleitner {\it et al}. [Phys. Rev. Lett. {\bf 87}, 256802 (2001)] We identify conditions in which the system shows Fano line shapes. The direction of the asymetric tail depends on the capacitive coupling and on the magnetic field. We discuss our results in connection with the experiments of Kobayashi {\it et al} [Phys. Rev. Lett. {\bf 88}, 256806 (2002)] in the case of a single dot.Comment: 30 pages, 12 figure

Curvas de crecimiento y de consumo de alimento durante la fase de transición de los lechones ibérico x duroc en explotaciones semiextensivas de la Sierra Norte de Cádiz

En 1997 en el término municipal de Olvera (Cádiz) se cebaron 4.400 cerdos, aproximadamente la cuarta parte de los lechones producidos en dicho término. Ello indica que la actividad básica. en las explotaciones porcinas de la zona es la producción de lechones y no el cebo. Según Sanchez Vargas (1998, comunicación personal) en este término municipal existen 50 explotaciones porcinas extensivas, de las que una realiza el ciclo completo, cuatro son cebaderos y las 44 restantes son únicamente productoras de lechones. En el presente estudio realizado en la Sierra Norte de Cádiz, se ha planteado el cálculo de la función de producción de los lechones en la fase de transición, desde el destete, que tiene lugar normalmente a los 40 días de edad, hasta los 23 kg de peso vivo. Los principales objetivos han sido obtener por un lado ajustes de regresión entre el peso y la edad de los lechones y por otra parte el peso y el consumo de alimento por los mismos. Asimismo a partir de las ecuaciones de regresión se ha obtenido el índice de conversió

Factors influencing completion of multi-dose vaccine schedules in adolescents: a systematic review.

BACKGROUND: Completion of multiple dose vaccine schedules is crucial to ensure a protective immune response, and maximise vaccine cost-effectiveness. While barriers and facilitators to vaccine uptake have recently been reviewed, there is no comprehensive review of factors influencing subsequent adherence or completion, which is key to achieving vaccine effectiveness. This study identifies and summarises the literature on factors affecting completion of multi-dose vaccine schedules by adolescents. METHODS: Ten online databases and four websites were searched (February 2014). Studies with analysis of factors predicting completion of multi-dose vaccines were included. Study participants within 9-19 years of age were included in the review. The defined outcome was completion of the vaccine series within 1 year among those who received the first dose. RESULTS: Overall, 6159 abstracts were screened, and 502 full texts were reviewed. Sixty one studies were eligible for this review. All except two were set in high-income countries. Included studies evaluated human papillomavirus vaccine, hepatitis A, hepatitis B, and varicella vaccines. Reported vaccine completion rates, among those who initiated vaccination, ranged from 27% to over 90%. Minority racial or ethnic groups and inadequate health insurance coverage were risk factors for low completion, irrespective of initiation rates. Parental healthcare seeking behaviour was positively associated with completion. Vaccine delivery in schools was associated with higher completion than delivery in the community or health facilities. Gender, prior healthcare use and socio-economic status rarely remained significant risks or protective factors in multivariate analysis. CONCLUSIONS: Almost all studies investigating factors affecting completion have been carried out in developed countries and investigate a limited range of variables. Increased understanding of barriers to completion in adolescents will be invaluable to future new vaccine introductions and the further development of an adolescent health platform. PROSPERO reg# CRD42014006765

Synthesis of Multiwall Carbon Nanotubes by Inductive Heating CCVD

The CCVD syntheses of MWCNTs from acetylene on Fe:Co:CaCO 3 and Fe:Co:CaO were performed using two different methods of heating: outer furnace and inductive heating. The comparative analysis of the MWCNTs obtained by the two methods show that the tubes grown in inductive heating have smaller diameters (5-25 nm), with fewer walls and aspect ratio of the order of hundreds. The ratio of outer to inner diameter (od/id) is ranging between 2 and 2.5. Inductively assisted CCVD is a very attractive method because of the major advantages that it presents, like low energetic consumption, thinner, well crystallized and more uniform tubes

Angle-dependence of quantum oscillations in YBa2Cu3O6.59 shows free spin behaviour of quasiparticles

Measurements of quantum oscillations in the cuprate superconductors afford a new opportunity to assess the extent to which the electronic properties of these materials yield to a description rooted in Fermi liquid theory. However, such an analysis is hampered by the small number of oscillatory periods observed. Here we employ a genetic algorithm to globally model the field, angular, and temperature dependence of the quantum oscillations observed in the resistivity of YBa2Cu3O6.59. This approach successfully fits an entire data set to a Fermi surface comprised of two small, quasi-2-dimensional cylinders. A key feature of the data is the first identification of the effect of Zeeman splitting, which separates spin-up and spin-down contributions, indicating that the quasiparticles in the cuprates behave as nearly free spins, constraining the source of the Fermi surface reconstruction to something other than a conventional spin density wave with moments parallel to the CuO2 planes.Comment: 8 pages, 4 figure

Study of the goat production system and the quality of milk produced in the Sierra Norte of Seville (Spain)

The objective of this study is to determine the situation of semi-extensive goat farms in the Sierra Norte of Seville (Spain) related to the bacteriological and hygienic quality of the raw milk. Twenty percent of the farms in the district were characterized, covering aspects related mainly to the milking and hygienic management. The bacteria and somatic cell content of raw milk coming directly from the udder and from churns (first at the end of the milking and second few hours after milking), were monitorized for a period of nine months in 14 farms. Besides all the farms hold general sanitary norms, most of them do not carry out the general dairy herd recommendations for milking routine. It is observed that most germ contamination in milk occurred in the hours after milking (from 46,000 up to 267,000 germ/ml), always below the maximum allowed. Somatic cells in all farms with more than 50 goats are above 1,500,000 somatic cells/ml."Etude du système de production caprine et de la qualité du lait produit dans la Sierra Norte de Séville (Espagne)". Le but de ce travail est de connaître la situation des exploitations caprines semiextensives dans la contrée de la Sierra Norte de Séville (Espagne), concernant la qualité hygiénique et sanitaire du lait. La caractérisation a été faite sur 20% des exploitations en tenant compte des aspects de la production les plus liés à la qualité du lait. On a contrôlé la teneur en bactéries et en cellules somatiques du lait dans 14 exploitations pendant neuf mois ; on a pris des échantillons directement du pis ainsi que du bidon à deux moments : tout de suite après la traite et quand ceci arrivait au magasin communautaire, avant de mélanger le lait. Malgré le fait que toutes les exploitations sont aux normes hygiéniques et sanitaires, la plupart ne tiennent pas tout à fait compte des conseils qu'on leur donne pour réaliser correctement la traite. La contamination principale a lieu après la traite (on passe de 46 000 jusqu'à 267 000 germes/ml), en étant toujours en dessous du maximum permis. On trouve la principale concentration de cellules somatiques par ml, plus de 1 500 000, dans les fermes qui ont plus de 50 chèvres