443 research outputs found
Theoretical study of electronic transport through a small quantum dot with a magnetic impurity
We model a small quantum dot with a magnetic impurity by the Anderson
Hamiltonian with a supplementary exchange interaction term. The transport
calculations are performed by means of the Green functions within the equation
of motion scheme, in which two decoupling procedures are proposed, for high and
low temperatures, respectively. The paper focuses on the charge fluctuations
for such a system, aspect not addressed before, as well as on the Kondo
resonance. We show a specific role of the excited state, which can be observed
in transport and in spin-spin correlations. Our studies show on a new many-body
feature of the phase shift of transmitted electrons, which is manifested in a
specific dip. In the Kondo regime, our calculations complement existing
theoretical results. The system shows three Kondo peaks in the density of
states: one at the Fermi energy and two side peaks, at a distance corresponding
to the singlet-triplet level spacing. The existence of the central peak is
conditioned by a degenerate state (the triplet) below the Fermi energy.Comment: 12 pages, 4 figure
Coulomb oscillations of the Fano-Kondo effect and zero bias anomalies in the double dot meso-transistor
We investigate theoretically the transport properties of the side-coupled
double quantum dots in connection with the experimental study of Sasaki {\it et
al.} Phys.Rev.Lett.{\bf 103}, 266806 (2009). The novelty of the set-up consists
in connecting the Kondo dot directly to the leads, while the side dot provides
an interference path which affects the Kondo correlations. We analyze the
oscillations of the source-drain current due to the periodical Coulomb blockade
of the many-level side-dot at the variation of the gate potential applied on
it. The Fano profile of these oscillations may be controlled by the
temperature, gate potential and interdot coupling. The non-equilibrium
conductance of the double dot system exhibits zero bias anomaly which, besides
the usual enhancement, may show also a suppression (a dip-like aspect) which
occurs around the Fano {\it zero}. In the same region, the weak temperature
dependence of the conductance indicates the suppression of the Kondo effect.
Scaling properties of the non-equilibrium conductance in the Fano-Kondo regime
are discussed. Since the SIAM Kondo temperature is no longer the proper scaling
parameter, we look for an alternative specific to the double-dot. The extended
Anderson model, Keldysh formalism and equation of motion technique are used.Comment: 19 pages, 8 figure
Educating on professional habits: attitudes of medical students towards diverse strategies for promoting influenza vaccination and factors associated with the intention to get vaccinated
BACKGROUND: Influenza vaccination coverage in medical students is usually low. Unlike health care workers, there is little information on the attitudes to and predictors of vaccination among medical students, and their attitudes towards institutional strategies for improving rates are unknown. METHODS: This cross-sectional study evaluated the effect of three influenza vaccination promotional strategies (Web page, video and tri-fold brochure) on medical students’ intention to get vaccinated and associated factors. A total of 538 medical students were asked to answer an anonymous questionnaire assessing the intention to get vaccinated after exposure to any of the promotional strategies. Sociodemographic data collected included: sex, age, university year, influenza risk group and cohabiting with member of a risk group. RESULTS: Four hundred twenty-one students answered the questionnaire, of whom 312 (74.1%) were female, 113 (26.8%) had done clinical rotations, and 111 (26.6%) reported intention to get the flu shot. Logistic regression showed the web group had a greater intention to get vaccinated than the reference group (OR: 2.42 95% CI: 1.16-5.03). Having done clinical rotations (OR: 2.55 95% CI: 1.36-4.38) and having received the shot in previous flu seasons (OR: 13.69 95% CI: 7.86-23.96) were independently associated with the intention to get vaccinated. CONCLUSION: Given that previous vaccination is a factor associated with the intention to get vaccinated, education on vaccination of health care workers should begin while they are students, thereby potentiating the habit. In addition, the intention to get vaccinated was greater during the clinical phase of the university career, suggesting this is a good time to introduce promotion strategies. Online promotional campaigns, such as a thematic Web to promote vaccination of health workers, could improve the intention to get vaccinated
Factors associated with risk behavior in travelers to tropical and subtropical regions
BACKGROUND: Recent decades have seen a rise in population
movements and, therefore, the spread of tropical diseases and
changes in the epidemiology of global disease patterns. Only 50%
of travelers to tropical areas receive pre-travel advice and
most of them present risk behaviors for acquiring infections.
The aim of this study was to describe the clinical and
epidemiological characteristics of travelers and identify
factors associated with risk behaviors. METHODS: We made a
retrospective, descriptive and analytical study of 772 travelers
consulting a tropical medicine clinic in Barcelona in 2010. Data
on demographic and clinical variables, travel characteristics
and risk behaviors were collected. RESULTS: Among all travelers
studied, 65.8% (466/708) received pre-travel advice and 30.7%
(209/680) took malaria prophylaxis. At least one risk behavior
was reported by 82.6% (587/711) of travelers. People travelling
for 1-6 months had a 3-fold higher likelihood of experiencing
risk behaviors than people travelling for <1 month (95% CI
1.54-5.81, p=0.001), and those travelling for >6 months had a
13-fold higher likelihood (95% CI 3.11-56.14, p<0.001)
compared with the same group. Increasing age was associated with
presenting less risk behaviors. CONCLUSIONS: Younger travelers
and those making longer trips have a higher number of risk
behaviors. Strategies emphasizing advice on risk behavior should
focus on these groups
Immunogenicity and immunization costs of adjuvanted versus non-adjuvanted hepatitis B vaccine in chronic kidney disease patients
Hepatitis B virus (HBV) vaccination is recommended for all
susceptible chronic pre-hemodialysis and hemodialysis patients.
This study assessed the immunogenicity of HBV vaccines
(adjuvanted and non-adjuvanted) in chronic kidney disease
patients vaccinated at the Hospital Clinic of Barcelona (Spain)
between January 2007 and July 2012. In addition, the costs for
the health system were evaluated according to the proportion of
vaccine responders after receiving either vaccine. Patients
receiving three doses of hepatitis B adjuvanted vaccine were
three times more likely to seroconvert than patients immunized
with non-adjuvanted vaccines, OR 3.56 (95% CI 1.84-6.85). This
resulted in fewer patients requiring a second course of HBV
vaccination and fewer outpatient visits, saving more than
euro9,500 per 100 patients. The higher immunogenicity of the
adjuvanted HBV vaccine would counterbalance the lower costs
associated with the non-adjuvanted vaccine
Towards a runtime verification framework for the Ada Programming Language
Runtime verification is an emerging discipline that investigates methods and tools to enable the verification of program properties during the execution of the application. The goal is to complement static analysis approaches, in particular when static verification leads to the explosion of states. Non-functional properties, such as the ones present in real-time systems are an ideal target for this kind of verification methodology, as are usually out of the range of the power and expressiveness of classic static analyses. In this paper, we present a framework that allows real-time programs written in Ada to be augmented with runtime verification capabilities. Our framework provides the infrastructures which is needed to instrument the code with runtime monitors. These monitors are responsible for observing the system and reaching verdicts about whether its behavior is compliant with its non-functional properties. We also sketch a contract language to extend the one currently provided by Ada, with the long term goal of having an elegant way in which runtime monitors can be automatically synthesized and instrumented into the target systems. The usefulness of the proposed approach is demonstrated by showing its use for an application scenario.This work was partially supported by Portuguese National Funds through FCT (Portuguese Founda- tion for Science and Technology) and by ERDF (European Regional Develop- ment Fund) through COMPETE (Operational Programme ’Thematic Factors of Competitiveness’), within projects FCOMP-01-0124-FEDER-037281 (CISTER), FCOMP-01-0124-FEDER-015006 (VIPCORE) and FCOMP-01-0124-FEDER- 020486 (AVIACC); and by FCT and EU ARTEMIS JU, within project ARTEMIS/0003/2012, JU grant nr. 333053 (CONCERTO)
Survival and residence times in disordered chains with bias
We present a unified framework for first-passage time and residence time of
random walks in finite one-dimensional disordered biased systems. The
derivation is based on exact expansion of the backward master equation in
cumulants. The dependence on initial condition, system size, and bias strength
is explicitly studied for models with weak and strong disorder. Application to
thermally activated processes is also developed.Comment: 13 pages with 2 figures, RevTeX4; v2:minor grammatical changes, typos
correcte
Carotenoides en agroalimentación y salud
Los carotenoides son compuestos especiales; si bien es común referirse a ellos como
pigmentos, lo cierto es que son compuestos de gran versatilidad e importancia en la
naturaleza. Más específicamente, son de gran interés en agroalimentación y salud.
Así, por ejemplo, son pigmentos naturales y por lo tanto tienen un importante papel en
la elección de alimentos por parte de los consumidores. Asimismo, algunos de ellos
son precursores de la vitamina A. Sin embargo, que cada vez exista más interés en los
carotenoides en este contexto se debe en gran parte a muchos estudios de distinta
naturaleza que indican que pueden proporcionar beneficios para la salud. Su interés
en alimentación funcional es por lo tanto indudable.
En este libro se refleja la experiencia en carotenoides de un gran número de
profesionales de la región iberoamericana. En conjunto, se ofrece una visión general
de la investigación sobre estos compuestos en agroalimentación y salud. Los autores
son miembros de la red IBERCAROT (http://carotenoides.us.es), que tiene entre sus
objetivos conformar una red estable y funcional de profesionales que aúnen esfuerzos
en pos de identificar nuevas fuentes de carotenoides de interés nutricional, mejorar su
producción y aumentar el valor de los productos que los contengan
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