321 research outputs found
Quantum interferometry with three-dimensional geometry
Quantum interferometry uses quantum resources to improve phase estimation
with respect to classical methods. Here we propose and theoretically
investigate a new quantum interferometric scheme based on three-dimensional
waveguide devices. These can be implemented by femtosecond laser waveguide
writing, recently adopted for quantum applications. In particular, multiarm
interferometers include "tritter" and "quarter" as basic elements,
corresponding to the generalization of a beam splitter to a 3- and 4-port
splitter, respectively. By injecting Fock states in the input ports of such
interferometers, fringe patterns characterized by nonclassical visibilities are
expected. This enables outperforming the quantum Fisher information obtained
with classical fields in phase estimation. We also discuss the possibility of
achieving the simultaneous estimation of more than one optical phase. This
approach is expected to open new perspectives to quantum enhanced sensing and
metrology performed in integrated photonic.Comment: 7 pages (+4 Supplementary Information), 5 figure
Quantum enhanced positioning and clock synchronization
A wide variety of positioning and ranging procedures are based on repeatedly
sending electromagnetic pulses through space and measuring their time of
arrival. This paper shows that quantum entanglement and squeezing can be
employed to overcome the classical power/bandwidth limits on these procedures,
enhancing their accuracy. Frequency entangled pulses could be used to construct
quantum positioning systems (QPS), to perform clock synchronization, or to do
ranging (quantum radar): all of these techniques exhibit a similar enhancement
compared with analogous protocols that use classical light. Quantum
entanglement and squeezing have been exploited in the context of
interferometry, frequency measurements, lithography, and algorithms. Here, the
problem of positioning a party (say Alice) with respect to a fixed array of
reference points will be analyzed.Comment: 4 pages, 2 figures. Accepted for publication by Natur
Quantum-inspired interferometry with chirped laser pulses
We introduce and implement an interferometric technique based on chirped
femtosecond laser pulses and nonlinear optics. The interference manifests as a
high-visibility (> 85%) phase-insensitive dip in the intensity of an optical
beam when the two interferometer arms are equal to within the coherence length
of the light. This signature is unique in classical interferometry, but is a
direct analogue to Hong-Ou-Mandel quantum interference. Our technique exhibits
all the metrological advantages of the quantum interferometer, but with signals
at least 10^7 times greater. In particular we demonstrate enhanced resolution,
robustness against loss, and automatic dispersion cancellation. Our
interferometer offers significant advantages over previous technologies, both
quantum and classical, in precision time delay measurements and biomedical
imaging.Comment: 6 pages, 4 figure
Single to Double Hump Transition in the Equilibrium Distribution Function of Relativistic Particles
We unveil a transition from single peaked to bimodal velocity distribution in
a relativistic fluid under increasing temperature, in contrast with a
non-relativistic gas, where only a monotonic broadening of the bell-shaped
distribution is observed. Such transition results from the interplay between
the raise in thermal energy and the constraint of maximum velocity imposed by
the speed of light. We study the Bose-Einstein, the Fermi-Dirac, and the
Maxwell-J\"uttner distributions, all exhibiting the same qualitative behavior.
We characterize the nature of the transition in the framework of critical
phenomena and show that it is either continuous or discontinuous, depending on
the group velocity. We analyze the transition in one, two, and three
dimensions, with special emphasis on two-dimensions, for which a possible
experiment in graphene, based on the measurement of the Johnson-Nyquist noise,
is proposed.Comment: 5 pages, 5 figure
Graphene for spintronics: giant Rashba splitting due to hybridization with Au
Graphene in spintronics has so far primarily meant spin current leads of high
performance because the intrinsic spin-orbit coupling of its pi-electrons is
very weak. If a large spin-orbit coupling could be created by a proximity
effect, the material could also form active elements of a spintronic device
such as the Das-Datta spin field-effect transistor, however, metal interfaces
often compromise the band dispersion of massless Dirac fermions. Our
measurements show that Au intercalation at the graphene-Ni interface creates a
giant spin-orbit splitting (~100 meV) in the graphene Dirac cone up to the
Fermi energy. Photoelectron spectroscopy reveals hybridization with Au-5d
states as the source for the giant spin-orbit splitting. An ab initio model of
the system shows a Rashba-split dispersion with the analytically predicted
gapless band topology around the Dirac point of graphene and indicates that a
sharp graphene-Au interface at equilibrium distance will account for only ~10
meV spin-orbit splitting. The ab initio calculations suggest an enhancement due
to Au atoms that get closer to the graphene and do not violate the sublattice
symmetry.Comment: 16 pages (3 figures) + supplementary information 16 pages (14
figures
Nonlinear atom interferometer surpasses classical precision limit
Interference is fundamental to wave dynamics and quantum mechanics. The
quantum wave properties of particles are exploited in metrology using atom
interferometers, allowing for high-precision inertia measurements [1, 2].
Furthermore, the state-of-the-art time standard is based on an interferometric
technique known as Ramsey spectroscopy. However, the precision of an
interferometer is limited by classical statistics owing to the finite number of
atoms used to deduce the quantity of interest [3]. Here we show experimentally
that the classical precision limit can be surpassed using nonlinear atom
interferometry with a Bose-Einstein condensate. Controlled interactions between
the atoms lead to non-classical entangled states within the interferometer;
this represents an alternative approach to the use of non-classical input
states [4-8]. Extending quantum interferometry [9] to the regime of large atom
number, we find that phase sensitivity is enhanced by 15 per cent relative to
that in an ideal classical measurement. Our nonlinear atomic beam splitter
follows the "one-axis-twisting" scheme [10] and implements interaction control
using a narrow Feshbach resonance. We perform noise tomography of the quantum
state within the interferometer and detect coherent spin squeezing with a
squeezing factor of -8.2dB [11-15]. The results provide information on the
many-particle quantum state, and imply the entanglement of 170 atoms [16]
Interaction between gemcitabine and topotecan in human non-small-cell lung cancer cells: effects on cell survival, cell cycle and pharmacogenetic profile
The pyrimidine analogue gemcitabine is an established effective agent in the treatment of non-small-cell lung cancer (NSCLC). The present study investigates whether gemcitabine would be synergistic with the topoisomerase I inhibitor topotecan against the NSCLC A549 and Calu-6 cells. Cells were treated with gemcitabine and topotecan for 1 h and the type of drug interaction was assessed using the combination index (CI). Cell cycle alterations were analysed by flow cytometry, while apoptosis was examined by the occurrence of DNA internucleosomal fragmentation, nuclear condensation and caspase-3 activation. Moreover, the possible involvement of the PI3K-Akt signalling pathway was investigated by the measurement of Akt phosphorylation. Finally, quantitative, real-time PCR (QRT-PCR) was used to study modulation of the gemcitabine-activating enzyme deoxycytidine kinase (dCK) and the cellular target enzyme ribonucleotide reductase (RR). In results, it was found that simultaneous and sequential topotecan → gemcitabine treatments were synergistic, while the reverse sequence was antagonistic in both cell lines. DNA fragmentation, nuclear condensation and enhanced caspase-3 activity demonstrated that the drug combination markedly increased apoptosis in comparison with either single agent, while cell cycle analysis showed that topotecan increased cells in S phase. Furthermore, topotecan treatment significantly decreased the amount of the activated form of Akt, and enhanced the expression of dCK (+155.0 and +115.3% in A549 and Calu-6 cells, respectively), potentially facilitating gemcitabine activity. In conclusion, these results indicate that the combination of gemcitabine and topotecan displays schedule-dependent activity in vitro against NSCLC cells. The gemcitabine → topotecan sequence is antagonistic while drug synergism is obtained with the simultaneous and the sequential topotecan → gemcitabine combinations, which are associated with induction of decreased Akt phosphorylation and increased dCK expression
Confiabilidad de un instrumento para clasificar al recién nacido de acuerdo con la complejidad de la atención
Na maioria das maternidades, a classificação, a avaliação e a definição da unidade a encaminhar o recém-nascido (RN) após o nascimento são realizadas pelo médico. A\ud
avaliação ocorre na sala de parto considerando: peso ao nascer; idade gestacional;\ud
condutas que definem quadro clínico e doença. Este estudo observacional teve\ud
como objetivo avaliar a confiabilidade de um instrumento de classificação de RN. A pesquisa foi realizada no berçário de um hospital público, São Paulo. Nove enfermeiras\ud
aplicaram o instrumento a 63 RN, sendo duas simultaneamente em cada um dos\ud
cinco setores do berçário. Verificou-se que o nível de concordância Kappa entre as enfermeiras foi excelente para a maioria das áreas de cuidado (69,0%). Concluiu-se que houve consenso e concordância das enfermeiras quanto ao instrumento ser completo, de fácil entendimento e aplicável, porém despende muito tempo. As enfermeiras reconhecem a importância do instrumento para o dimensionamento dos profissionais, organização e planejamento do cuidado.In most maternity units, the physician classifies, evaluates, and determines which unit will receive the newborn (NB) after birth. Evaluation occurs in the delivery room, taking into consideration the following factors: birth weight, gestational age, and behaviors that define the clinical picture and disease. This observational study evaluates the reliability of an NB classification instrument. The study was conducted at the nursery of a public hospital in São Paulo. Nine nurses applied the instrument to 63 NB, with two of the nurses working simultaneously in each of the nursery’s fi ve sectors. The Kappa level of agreement among the nurses was found to be excellent for most care areas\ud
(69.0%). It was concluded that there was a consensus and agreement among the\ud
nurses that the instrument was complete, easy to understand and applicable, but was\ud
very time consuming. The nurses recognize the instrument’s importance for the allocation of professionals, organization, and care planning.En la mayoría de las maternidades la clasificación, la evaluación y la definición de la unidad para referir el recién nacido (RN), son realizadas por el médico. La evaluación se realiza en la sala de parto, considerando: peso al nacer, edad gestacional y conductas que definen el cuadro clínico y la enfermedad. Este estudio observacional tuvo como objetivo evaluar la confiabilidad de un instrumento de clasificación del RN. Fue realizada en el servicio de neonatología de un hospital público en Sao Paulo. Nueve enfermeras\ud
aplicaron el instrumento a 63 RN, siendo aplicados dos de forma simultánea en los cinco sectores de la unidad neonatal. El nivel de concordancia Kappa fue excelente para la mayoría de las áreas de atención (69,0%). Se concluyó que hubo consenso y\ud
concordancia entre las enfermeras, quienes expresaron que el instrumento es completo, fácil de entender y de aplicar, pero se necesita mucho tempo. Las enfermeras reconocen la importancia de este instrumento para dimensionar el número de profesionales, la organización y la planificación de la atención
Photonic quantum technologies
The first quantum technology, which harnesses uniquely quantum mechanical
effects for its core operation, has arrived in the form of commercially
available quantum key distribution systems that achieve enhanced security by
encoding information in photons such that information gained by an eavesdropper
can be detected. Anticipated future quantum technologies include large-scale
secure networks, enhanced measurement and lithography, and quantum information
processors, promising exponentially greater computation power for particular
tasks. Photonics is destined for a central role in such technologies owing to
the need for high-speed transmission and the outstanding low-noise properties
of photons. These technologies may use single photons or quantum states of
bright laser beams, or both, and will undoubtably apply and drive
state-of-the-art developments in photonics
Honokiol Arrests Cell Cycle, Induces Apoptosis, and Potentiates the Cytotoxic Effect of Gemcitabine in Human Pancreatic Cancer Cells
Survival rates for patients with pancreatic cancer are extremely poor due to its asymptomatic progression to advanced and metastatic stage for which current therapies remain largely ineffective. Therefore, novel therapeutic agents and treatment approaches are desired to improve the clinical outcome. In this study, we determined the effects of honokiol, a biologically active constituent of oriental medicinal herb Magnolia officinalis/grandiflora, on two pancreatic cancer cell lines, MiaPaCa and Panc1, alone and in combination with the standard chemotherapeutic drug, gemcitabine. Honokiol exerted growth inhibitory effects on both the pancreatic cancer cell lines by causing cell cycle arrest at G1 phase and induction of apoptosis. At the molecular level, honokiol markedly decreased the expression of cyclins (D1 and E) and cyclin-dependent kinases (Cdk2 and Cdk4), and caused an increase in Cdk inhibitors, p21 and p27. Furthermore, honokiol treatment led to augmentation of Bax/Bcl-2 and Bax/Bcl-xL ratios to favor apoptosis in pancreatic cancer cells. These changes were accompanied by enhanced cytoplasmic accumulation of NF-κB with a concomitant decrease in nuclear fraction and reduced transcriptional activity of NF-κB responsive promoter. This was associated with decreased phosphorylation of inhibitor of kappa B alpha (IκB-α) causing its stabilization and thus increased cellular levels. Importantly, honokiol also potentiated the cytotoxic effects of gemcitabine, in part, by restricting the gemcitabine-induced nuclear accumulation of NF-κB in the treated pancreatic cancer cell lines. Altogether, these findings demonstrate, for the first time, the growth inhibitory effects of honokiol in pancreatic cancer and indicate its potential usefulness as a novel natural agent in prevention and therapy
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