1,878 research outputs found
Floquet theory for temporal correlations and spectra in time-periodic open quantum systems: Application to squeezed parametric oscillation beyond the rotating-wave approximation
Open quantum systems can display periodic dynamics at the classical level
either due to external periodic modulations or to self-pulsing phenomena
typically following a Hopf bifurcation. In both cases, the quantum fluctuations
around classical solutions do not reach a quantum-statistical stationary state,
which prevents adopting the simple and reliable methods used for stationary
quantum systems. Here we put forward a general and efficient method to compute
two-time correlations and corresponding spectral densities of time-periodic
open quantum systems within the usual linearized (Gaussian) approximation for
their dynamics. Using Floquet theory we show how the quantum Langevin equations
for the fluctuations can be efficiently integrated by partitioning the time
domain into one-period duration intervals, and relating the properties of each
period to the first one. Spectral densities, like squeezing spectra, are
computed similarly, now in a two-dimensional temporal domain that is treated as
a chessboard with one-period x one-period cells. This technique avoids
cumulative numerical errors as well as efficiently saves computational time. As
an illustration of the method, we analyze the quantum fluctuations of a damped
parametrically-driven oscillator (degenerate parametric oscillator) below
threshold and far away from rotating-wave approximation conditions, which is a
relevant scenario for modern low-frequency quantum oscillators. Our method
reveals that the squeezing properties of such devices are quite robust against
the amplitude of the modulation or the low quality of the oscillator, although
optimal squeezing can appear for parameters that are far from the ones
predicted within the rotating-wave approximation.Comment: Comments and constructive criticism are welcom
Enhancement of the immunoregulatory potency of mesenchymal stromal cells by treatment with immunosuppressive drugs
Background aims Multipotent mesenchymal stromal cells (MSCs) are distinguished by their ability to differentiate into a number of stromal derivatives of interest for regenerative medicine, but they also have immunoregulatory properties that are being tested in a number of clinical settings. Methods We show that brief incubations with rapamycin, everolimus, FK506 or cyclosporine A increase the immunosuppressive potency of MSCs and other cell types. Results The treated MSCs are up to 5-fold more potent at inhibiting the induced proliferation of T lymphocytes in vitro. We show that this effect probably is due to adsorption of the drug by the MSCs during pre-treatment, with subsequent diffusion into co-cultures at concentrations sufficient to inhibit T-cell proliferation. MSCs contain measurable amounts of rapamycin after a 15-min exposure, and the potentiating effect is blocked by a neutralizing antibody to the drug. With the use of a pre-clinical model of acute graft-versus-host disease, we demonstrate that a low dose of rapamycin-treated but not untreated umbilical cord–derived MSCs significantly inhibit the onset of disease. Conclusions The use of treated MSCs may achieve clinical end points not reached with untreated MSCs and allow for infusion of fewer cells to reduce costs and minimize potential side effects
Editorial: Judgment and decision making under uncertainty. Descriptive, normative, and prescriptive perspectives
Judgment and Decision Making Under Uncertainty: Descriptive, Normative, and Prescriptive Perspectives was motivated by our interest in better understanding why people judge and decide as they do (descriptive perspective), how they ideally ought to judge and decide (normative perspective), and how their judgment and decision-making processes might be improved in practice (prescriptive perspective). We sought papers that addressed some aspect of judgment and decision making from one or more of these three theoretical perspectives. We further sought contributions that examined judgment and decision making under conditions of uncertainty, which we intentionally left loosely defined. Our focus on uncertainty reflects the fact that the vast majority of decisions people make in life are not made under conditions of complete certainty, and the uncertainties may be more or less well-defined. Indeed, different components of a single judgment or decision may have multiple uncertainties associated with it, some of which may be fuzzier than others. Following our call for papers, we received 32 submissions, 17 of which were accepted. The latter set comprises this book. There are 11 original research articles, 2 hypothesis and theory articles, 2 perspectives, and 1 book review and systematic review each
Estructura de tallas y composición sexual de Eurypodius Latreillii Guérin, 1828 (Brachyura) y Pagurus Comptus White, 1847 (Anomura) en el extremo sur de Chile
The decapod crustaceans Eurypodius latreillii (Brachyura) and Pagurus comptus (Paguridae) were the most frequently occurring species in Agassiz trawl (AGT) samples obtained during the Chilean - German - Italian Victor Hensen Expedition in the Straits of Magellan and south of the Beagle Channel. Sex composition and length structure aspects were studied using the material from 15 stations in the two areas, which comprised 773 specimens of E. latreillii and 647 P. comptus. The size frequency of both species was characterized by the presence of small individuals in shallow waters. The sex composition varied with depth, indicating a dominance of E. latreillii females in deep waters, whereas no such pattern was observed in P. comptus. These differences may be caused by epizoites of E. latreillii and the availability of vacant gastropod shells for P. comptus, in addition to geographical aspects and life-cycle patterns of these speciesLos crustáceos decápodos Eurypodius latreillii (Brachyura) y Pagurus comptus (Anomura), fueron las especies encontradas con mayor frecuencia en las muestras obtenidas durante la Expedición Chilena - Alemana - Italiana “Victor Hensen” (Octubre/Noviembre de 1994) en el Estrecho de Magallanes y al sur del Canal del Beagle, en el extremo sur de Chile. En estas localidades se obtuvieron las muestras mediante una red de tipo Agassiz. Los ejemplares fueron medidos, pesados y sexados, posteriormente se analizó la composición sexual y la estructura de tallas de estas especies. Se recolectaron un total de 773 individuos de E. latreillii y 647 individuos de P. comptus. Este material corresponde a los especímenes capturados en 15 estaciones. La estructura de tallas para ambas especies se caracterizó por la presencia de ejemplares de menor tamaño hacia zonas someras. La composición sexual presentó variaciones respecto de la profundidad, indicando una dominancia de hembras en aguas profundas para E. latreillii, pero este patrón no se observó en P. comptus. Los patrones observados dependerían de la presencia de epibiontes sobre el caparazón de E. latreillii y la disponibilidad de conchas vacías de gastrópodos para P. comptus, además de aspectos geográficos y de los ciclos de vida que presentarían ambas especies en la región
Condrosarcoma metatarsiano: aportación de un caso
Se presenta un caso de condrosarcoma de bajo grado de malignidad, de localización
y evolución inusual. Se revisa la literatura y los criterios disponibles en la actualidad
para el diagnóstico de estas lesiones controvertidas tanto histológica como clínicamente.We report a low grade chondrosarcoma with atypical behaviour and localitation.
The main histologic features in the diagnosis of these controversial lesion are discussed
Deep recurrent networks predicting the gap evolution in adiabatic quantum computing
One of the main challenges in quantum physics is predicting efficiently the dynamics of observables in many-body problems out of equilibrium. A particular example occurs in adiabatic quantum computing, where finding the structure of the instantaneous gap of the Hamiltonian is crucial in order to optimize the speed of the computation. Inspired by this challenge, in this work we explore the potential of deep learning for discovering a mapping from the parameters that fully identify a problem Hamiltonian to the full evolution of the gap during an adiabatic sweep applying different network architectures. Through this example, we find that a limiting factor for the learnability of the dynamics is the size of the input, that is, how the number of parameters needed to identify the Hamiltonian scales with the system size. We demonstrate that a long short-term memory network succeeds in predicting the gap when the parameter space scales linearly with system size. Remarkably, we show that once this architecture is combined with a convolutional neural network to deal with the spatial structure of the model, the gap evolution can even be predicted for system sizes larger than the ones seen by the neural network during training. This provides a significant speedup in comparison with the existing exact and approximate algorithms in calculating the gap
Deep Learning of Quantum Many-Body Dynamics via Random Driving
Neural networks have emerged as a powerful way to approach many practical problems in quantumphysics. In this work, we illustrate the power of deep learning to predict the dynamics of a quantummany-body system, where the training is based purely on monitoring expectation values of observables under random driving. The trained recurrent network is able to produce accurate predictions for driving trajectories entirely different than those observed during training. As a proof of principle, here we train the network on numerical data generated from spin models, showing that it can learn the dynamics of observables of interest without needing information about the full quantum state.This allows our approach to be applied eventually to actual experimental data generated from aquantum many-body system that might be open, noisy, or disordered, without any need for a detailedunderstanding of the system. This scheme provides considerable speedup for rapid explorations andpulse optimization. Remarkably, we show the network is able to extrapolate the dynamics to times longer than those it has been trained on, as well as to the infinite-system-size limit
Producción de huevos en Eurypodius latreillii Guérin, 1828 (Decapoda: Majidae) en el Estrecho de Magallanes, sur de Chile
Egg production and reproductive investment were studied in the spider crab Eurypodius latreillii from the Straits of Magellan, southern Chile. A total of 66 ovigerous females were analyzed, ranging in size from 29.0 to 62.9 mm carapace length. E. latreillii produced up to 15886 embryos, and clutch size increased with maternal size. Initial egg size was large (0.162 mm3), and the embryo volume increase during the incubation period was 32 %. Brood mortality was substantial (83 %), and since egg volume increase could not compensate for the egg loss, average egg mass volume decreased considerably during embryogenesis. The average brood mass at laying accounted for 13 % of the maternal body mass (on a wet mass basis), and this value coincides with previous findings concerning energy allocation for egg production in other brachyuran crabs. In general, our data regarding E. latreillii correspond well with those from spider crab species inhabiting the northern hemisphere. The large egg size of E. latreillii compared with majids from other geographical regions may be an indication of a latitudinal gradient in the reproductive biology of majid crabs. Future studies with spider crabs from the southern hemisphere are desirable to substantiate this assumption.Se estudió la producción de huevos y la inversión reproductiva del cangrejo araña Eurypodius latreillii proveniente del Estrecho de Magallanes, sur de Chile. Se analizaron un total de 66 hembras ovígeras con un rango de tamaños entre 29,0 y 62,9 mm de longitud de caparazón. E. latreilli produjo hasta un máximo de 15886 embriones, y el número de huevos aumentó con el tamaño de la hembra. El tamaño inicial del huevo fue grande (0,162 mm3) y el aumento del volumen embrionario durante el período de incubación fue de 32 %. La mortalidad de huevos fue considerable (83 %), y como el aumento en el volumen de los huevos no pudo compensar la pérdida de huevos, el promedio del volumen de la masa de los huevos disminuyó de forma considerable durante la embriogénesis. La masa de huevos representó un 13 % de la masa corporal de la madre, y este valor coincide con observaciones previas sobre la asignación de energía para la producción de huevos en otros braquiuros. En general, nuestros datos sobre E. latreillii concuerdan con datos sobre especies del cangrejo araña del hemisferio norte. El tamaño grande de huevos de E. latreillii comparado con Majidae de otras regiones geográficas podría ser interpretado como una indicación de un gradiente latitudinal en la biología reproductiva de cangrejos májidos. Para corroborar esta interpretación se requerirían estudios futuros con cangrejos araña del hemisferio sur
Presence of markers of activation pathways of macrophages in chronic periodontitis
Indexación: Web of Science; ScieloLa periodontitis crónica es una patología infecciosa, causada por un complejo de especies bacterianas, que afecta principalmente los tejidos de inserción de los dientes. La respuesta inmune-inflamatoria producida se caracteriza por la presencia de un infiltrado inflamatorio, en el cual los macrófagos representan entre 5 al 30%. Es sabido que los macrófagos se activan mediante dos vías: Clásica y Alterna, caracterizadas por la presencia de marcadores indirectos: IFN-γ e IL-6 para la vía clásica e IL-4 para la vía alterna, ampliamente abordados. Recientemente, se ha descrito a la subunidad A del factor XIII de la coagulación (FXIII-A) como un buen marcador de la vía alterna. El objetivo de este estudio consiste en determinar la presencia de IFN-γ, IL-6, FXIII-A e IL-4 como marcadores de las vías de activación de los macrófagos, en pacientes con periodontitis crónica. Para tal efecto, se realizó inmunohistoquímica y Western-Blot para los cuatro marcadores junto a CD-68, marcador de macrófagos, en 18 biopsias de tejido periodontal sano y 18 con periodontitis crónica. Se detectó la presencia de IFN-γ, IL-6, IL-4 y FXIII-A junto a CD68+, en todas las muestras de pacientes sanos y con periodontitis. Los resultados obtenidos sugieren que al estar presente IFN-γ, IL-6, IL-4 y FXIII-A, los macrófagos se activarían a través de ambas vías, lo cual, produciría una respuesta tanto proinflamatoria (Th1) como antinflamatoria (Th2). Son necesarios más estudios para determinar si existe una vía preferencial de activación.Periodontitis is a chronic infectious disease caused by a bacterial species complex, which affects mainly the insertion tissues of the teeth. The immune-inflammatory response produced is characterized by an inflammatory infiltrate in which macrophages represent between 5 to 30%. It is known and has been widely discussed that macrophages are activated in two ways: Classical and Alterna, characterized by the presence of indirect markers: IFN-γ and IL-6 for the classical pathway and IL-4 for the alternative pathway. Recently the subunit A of the clotting factor XIII (FXIII-A) has been described as a good marker of the alternative pathway. The objective of this study is to determine the presence of IFN-γ, IL-6, IL-4 and FXIII-A as markers of the macrophage activation pathways in patients with chronic periodontitis. To this end, we performed immunohistochemistry and Western blot for the four markers with CD68 macrophage marker, in 18 healthy periodontal tissue biopsies and 18 with chronic periodontitis. We detected the presence of IFN-γ, IL-6, IL-4 and FXIII-A with CD68 +, in all samples of healthy patients and periodontitis. The results suggest that when present, IFN-γ, IL-6, IL-4 and FXIII-A, activate macrophages through both routes, which would produce a proinflammatory response (Th1) as antiinflammatory (Th2). Further studies are necessary to determine whether there is a preferential pathway activation.http://www.scielo.cl/pdf/piro/v5n3/art06.pd
Symbiotic Stars in OGLE Data I. Large Magellanic Cloud Systems
Symbiotic stars are long-orbital-period interacting-binaries characterized by
extended emission over the whole electromagnetic range and by complex
photometric and spectroscopic variability. In this paper, the first of a
series, we present OGLE light curves of all the confirmed symbiotic stars in
the Large Magellanic Cloud, with one exception. By careful visual inspection
and combined time-series analysis techniques, we investigate for the first time
in a systematic way the photometric properties of these astrophysical objects,
trying in particular to distinguish the nature of the cool component (e.g.,
Semi-Regular Variable vs. OGLE Small-Amplitude Red Giant), to provide its
first-order pulsational ephemerides, and to link all this information with the
physical parameters of the binary system as a whole. Among the most interesting
results, there is the discovery of a 20-year-long steady fading of Sanduleak's
star, a peculiar symbiotic star known to produce the largest stellar jet ever
discovered. We discuss by means of direct examples the crucial need for
long-term multi-band observations to get a real understanding of symbiotic and
other interacting binary stars. We eventually introduce BOMBOLO, a multi-band
simultaneous imager for the SOAR 4m Telescope, whose design and construction we
are currently leading.Comment: 16 pages, 4 Tables, 12 Figures. Accepted for publication in MNRA
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