22,271 research outputs found
Electronic Structure Calculations of Magnetic Exchange Interactions in Europium Monochalcogenides
Using a combination of local spin density and Hubbard 1 approximations we
study the mechansim of exchange interacion in EuX (X=O, S, Se and Te). We
reproduce known experimental results about bulk modulus, critical pressure for
structural phase transition, magnetic ordering temperature, spin--wave
dispersions as well as momentum-- and tempearuture--dependent band shift. Our
numerical results show pressure induced competition between the hybirization
enhanced exchange interaction and Kondo--like coupling in EuO. Possible ways to
enhance T_{c} are discussed
Fluctuation of Conductance Peak Spacings in Large Semiconductor Quantum Dots
Fluctuation of Coulomb blockade peak spacings in large two-dimensional
semiconductor quantum dots are studied within a model based on the
electrostatics of several electron islands among which there are random
inductive and capacitive couplings. Each island can accommodate electrons on
quantum orbitals whose energies depend also on an external magnetic field. In
contrast with a single island quantum dot, where the spacing distribution is
close to Gaussian, here the distribution has a peak at small spacing value. The
fluctuations are mainly due to charging effects. The model can explain the
occasional occurrence of couples or even triples of closely spaced Coulomb
blockade peaks, as well as the qualitative behavior of peak positions with the
applied magnetic field.Comment: 13 pages, 4 figures, accepted for publication in PR
Tripartite thermal correlations in an inhomogeneous spin-star system
We exploit the tripartite negativity to study the thermal correlations in a
tripartite system, that is the three outer spins interacting with the central
one in a spin-star system. We analyze the dependence of such correlations on
the homogeneity of the interactions, starting from the case where central-outer
spin interactions are identical and then focusing on the case where the three
coupling constants are different. We single out some important differences
between the negativity and the concurrence.Comment: 8 pages, 9 figure
Tracing the trophic fate of aquafeed macronutrients with carbon isotope ratios of Amino Acids
To meet future seafood demands, ingredients derived from algae and other novel and sustainable sources are increasingly being tested and used as replacers to traditional aquafeed ingredients. Algal ingredients in particular are being promoted for their sustainability and their additional functional attributes in farmed aquatic animals. Test on algal supplemented aquafeeds typically focus on a suite of immunological and physiological indicators along with fish growth performance or muscle quality. However, to optimize the replacement of fish meal with algal derived ingredients, it is crucial to understand the metabolic fate in the algal macronutrients (carbohydrates, fats, and proteins), and their nutritional interactions with other ingredients after ingestion. Here, we assess the potential of using the emerging technology- stable carbon isotope (δ13C) analysis of single amino acids (AAs) as a nutritional biomarker in aquaculture. Applications of δ13CAA-based approaches in feeding trials show promise in closing the knowledge gap in terms of understanding how fish and other aquaculture taxa assimilate and metabolize algal derived macronutrients. Source diagnostic δ13C fingerprints among the essential AAs can trace the protein origins to broad phylogenetic groups such as red macroalgae, brown macroalgae, bacteria, and terrestrial plants. Among the non-essential AAs, δ13C patterns have the potential to inform about metabolic routing and utilization of dietary lipids and carbohydrates. Despite the potential of δ13CAA as a nutritional biomarker, the few applications to date in fish feeding trials warrant further development and implementation of δ13CAA-based approaches to improve understanding of protein origins and macronutrient metabolic routing.Introduction Amino acid abbreviations Analitical considerations Digestive physiology and isotope effects Inferring diet and nutrition from amino acid 13C values - Essential Amino Acids - Non-essential Amino Acids Tracing aquafeed macronutrients with 13CAA Outlook and perpectives Materials and methods - Statistical Method
Damage-free single-mode transmission of deep-UV light in hollow-core PCF
Transmission of UV light with high beam quality and pointing stability is
desirable for many experiments in atomic, molecular and optical physics. In
particular, laser cooling and coherent manipulation of trapped ions with
transitions in the UV require stable, single-mode light delivery. Transmitting
even ~2 mW CW light at 280 nm through silica solid-core fibers has previously
been found to cause transmission degradation after just a few hours due to
optical damage. We show that photonic crystal fiber of the kagom\'e type can be
used for effectively single-mode transmission with acceptable loss and bending
sensitivity. No transmission degradation was observed even after >100 hours of
operation with 15 mW CW input power. In addition it is shown that
implementation of the fiber in a trapped ion experiment significantly increases
the coherence times of the internal state transfer due to an increase in beam
pointing stability
Online optimization of visual stimuli for reducing fatigue in SSVEP-based BCIs
INTRODUCTION: Visual fatigue induced by flickering stimuli has always been a problem to steady state visual evoked potential (SSVEP)-based brain-computer interfaces (BCIs). Some previous studies revealed that different stimulation properties such as frequencies, duty cycles and colors have impact on user’s fatigue and performance. Importantly, the stimulation inducing less fatigue usually causes a reduction of system performance [1], and thus to design an optimal visual stimulator for SSVEP-based BCIs, there is a tradeoff between the user’s fatigue and performance. Unfortunately, so far most of the visual fatigue evaluation methods relied on subjective ...published_or_final_versio
Symmetries of SU(2) Skyrmion in Hamiltonian and Lagrangian approaches
We apply the Batalin-Fradkin-Tyutin (BFT) method to the SU(2) Skyrmion to
study the full symmetry structure of the model at the first class Hamiltonian
level. On the other hand, we also analyze the symmetry structure of the action
having the WZ term, which corresponds to this Hamiltonian, in the framework of
the Lagrangian approach. Furthermore, following the BFV formalism we derive the
BRST invariant gauge fixed Lagrangian from the above extended action.Comment: 14 pages, final revised version, to appear in Mod. Phys. Lett.
Fatigue evaluation through EEG analysis using multi-scale entropy in SSVEP-based BCIs
INTRODUCTION: Fatigue is a big challenge when moving a steady state visual evoked potential (SSVEP) based brain-computer interfaces (BCIs) from laboratory into real-life applications [1], as it not only harms the system performance, but also causes users’ discomfort. Towards eventually fatigue reduction, an accurate and objective evaluation of fatigue level is the first and also a crucial step. On the other hand, multi-scale entropy (MSE) can ...published_or_final_versio
Cytotoxicity and Antioxidant Activity of Zingiber Officinale and 6-Gingerol on HepG2 Cells
The present study was designed to compare the effects of ethanolic extract of ginger (Zingiber officinale) and its phenolic component [6]-Gingerol on viability, antiproliferation and apoptotic levels of human hepatoma cell lines (HepG2) and its antioxidant activity. HepG2 cells were cultured in Eagles minimum essential medium (EMEM) and the percentage of cell cytotoxicity was evaluated by tetrazolium salt (MTS) assay. Antiproliferation and apoptotic levels were measured by 5Bromo-2deoxyuridine (BrdU) colorimetry. Antioxidant capacity was studied by 1.1-diphenyl-2-picryl-hydrazyl radical (DPPH) using spectrophotometry. We found that cytotoxicity and antiproliferative effect of ginger extract and [6]-Gingerol could be associated with induction of apoptosis. The ginger ethanol extract and [6]-Gingerol also showed remarkable antioxidant activities in comparison with ascorbic acid and N-acetyl-L-cysteine
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