6,705 research outputs found
Spins in few-electron quantum dots
This review describes the physics of spins in quantum dots containing one or
two electrons, from an experimentalist's viewpoint. Various methods for
extracting spin properties from experiment are presented, restricted
exclusively to electrical measurements. Furthermore, experimental techniques
are discussed that allow for: (1) the rotation of an electron spin into a
superposition of up and down, (2) the measurement of the quantum state of an
individual spin and (3) the control of the interaction between two neighbouring
spins by the Heisenberg exchange interaction. Finally, the physics of the
relevant relaxation and dephasing mechanisms is reviewed and experimental
results are compared with theories for spin-orbit and hyperfine interactions.
All these subjects are directly relevant for the fields of quantum information
processing and spintronics with single spins (i.e. single-spintronics).Comment: final version (52 pages, 49 figures), Rev. Mod. Phy
Neuromorphometric characterization with shape functionals
This work presents a procedure to extract morphological information from
neuronal cells based on the variation of shape functionals as the cell geometry
undergoes a dilation through a wide interval of spatial scales. The targeted
shapes are alpha and beta cat retinal ganglion cells, which are characterized
by different ranges of dendritic field diameter. Image functionals are expected
to act as descriptors of the shape, gathering relevant geometric and
topological features of the complex cell form. We present a comparative study
of classification performance of additive shape descriptors, namely, Minkowski
functionals, and the nonadditive multiscale fractal. We found that the proposed
measures perform efficiently the task of identifying the two main classes alpha
and beta based solely on scale invariant information, while also providing
intraclass morphological assessment
Quasiparticle Hall Transport of d-wave Superconductors in Vortex State
We present a theory of quasiparticle Hall transport in strongly type-II
superconductors within their vortex state. We establish the existence of
integer quantum spin Hall effect in clean unconventional
superconductors in the vortex state from a general analysis of the
Bogoliubov-de Gennes equation. The spin Hall conductivity is
shown to be quantized in units of . This result does not
rest on linearization of the BdG equations around Dirac nodes and therefore
includes inter-nodal physics in its entirety. In addition, this result holds
for a generic inversion-symmetric lattice of vortices as long as the magnetic
field satisfies . We then derive the
Wiedemann-Franz law for the spin and thermal Hall conductivity in the vortex
state. In the limit of , the thermal Hall conductivity satisfies
. The
transitions between different quantized values of as well as
relation to conventional superconductors are discussed.Comment: 18 pages REVTex, 3 figures, references adde
What are the living conditions and health status of those who don't report their migration status? a population-based study in Chile
BACKGROUND: Undocumented immigrants are likely to be missing from population databases, making it impossible to identify an accurate sampling frame in migration research. No population-based data has been collected in Chile regarding the living conditions and health status of undocumented immigrants. However, the CASEN survey (Caracterizacion Socio- Economica Nacional) asked about migration status in Chile for the first time in 2006 and provides an opportunity to set the base for future analysis of available migration data. We explored the living conditions and health of self-reported immigrants and respondents who preferred not to report their migration status in this survey. METHODS: Cross-sectional secondary analysis of CASEN survey in Chile in 2006. Outcomes: any disability, illness/accident, hospitalization/surgery, cancer/chronic condition (all binary variables); and the number of medical/emergency attentions received (count variables). Covariates: Demographics (age, sex, marital status, urban/rural, ethnicity), socioeconomic status (education level, employment status and household income), and material standard of living (overcrowding, sanitation, housing quality). Weighted regression models were estimated for each health outcome, crude and adjusted by sets of covariates, in STATA 10.0. RESULTS: About 1% of the total sample reported being immigrants and 0.7% preferred not to report their migration status (Migration Status - Missing Values; MS-MV). The MS-MV lived in more deprived conditions and reported a higher rate of health problems than immigrants. Some gender differences were observed by health status among immigrants and the MS-MV but they were not statistically significant. Regressions indicated that age, sex, SES and material factors consistently affected MS-MVs’ chance of presenting poor health and these patterns were different to those found among immigrants. Great heterogeneity in both the MS-MV and the immigrants, as indicated by wide confidence intervals, prevented the identification of other significantly associated covariates. CONCLUSION: This is the first study to look at the living conditions and health of those that preferred not to respond their migration status in Chile. Respondents that do not report their migration status are vulnerable to poor health and may represent undocumented immigrants. Surveys that fail to identify these people are likely to misrepresent the experiences of immigrants and further quantitative and qualitative research is urgently required
Ponzano-Regge model revisited I: Gauge fixing, observables and interacting spinning particles
We show how to properly gauge fix all the symmetries of the Ponzano-Regge
model for 3D quantum gravity. This amounts to do explicit finite computations
for transition amplitudes. We give the construction of the transition
amplitudes in the presence of interacting quantum spinning particles. We
introduce a notion of operators whose expectation value gives rise to either
gauge fixing, introduction of time, or insertion of particles, according to the
choice. We give the link between the spin foam quantization and the hamiltonian
quantization. We finally show the link between Ponzano-Regge model and the
quantization of Chern-Simons theory based on the double quantum group of SU(2)Comment: 48 pages, 15 figure
Zero modes in a system of Aharonov-Bohm fluxes
We study zero modes of two-dimensional Pauli operators with Aharonov--Bohm
fluxes in the case when the solenoids are arranged in periodic structures like
chains or lattices. We also consider perturbations to such periodic systems
which may be infinite and irregular but they are always supposed to be
sufficiently scarce
Casimir energy of massive MIT fermions in a Bohm-Aharonov background
We study the effect of a background flux string on the vacuum energy of
massive Dirac fermions in 2+1 dimensions confined to a finite spatial region
through MIT boundary conditions. We treat two admissible self-adjoint
extensions of the Hamiltonian and compare the results. In particular, for one
of these extensions, the Casimir energy turns out to be discontinuous at
integer values of the flux.Comment: 16 pages, 3 figure
Previsão do teor de proteína bruta e digestibilidade da silagem de mandioca por meio da espectroscopia NIR.
Resumo: O cultivo da mandioca é amplamente difundido na região nordeste, tendo grande importância na alimentação de pequenos rebanhos. Uma boa alternativa para a época de seca é a silagem da parte área da mandioca, que apresenta valores significativos de proteínas, vitaminas e minerais. Contudo o valor desses compostos podem apresentar variações advindas do processo de fermentação. Para garantir a presenças destes compostos na silagem é necessário que se faça a analise bromatológica, que pode ter alto custo e demandar grande quantidade de tempo, assim, não sendo viável ao produtor. Uma alternativa ao uso das analises tradicionais é o uso da espectroscopia de reflectância na região do infravermelho próximo (NIRS), por ser uma tecnologia de alta precisão e acurácia, que é econômica e sustentável. Objetivou-se com este trabalho avaliar modelos para previsão de proteína bruta (PB), digestibilidade in vitro da matéria seca (DIVMS).Edición de las Memorias de la 25a. Reunión de la Asociación Latinoamericana de Producción Animal (ALPA), 2016, Recife, Brasil
- …