541 research outputs found
Demonstration of efficient nonreciprocity in a microwave optomechanical circuit
The ability to engineer nonreciprocal interactions is an essential tool in
modern communication technology as well as a powerful resource for building
quantum networks. Aside from large reverse isolation, a nonreciprocal device
suitable for applications must also have high efficiency (low insertion loss)
and low output noise. Recent theoretical and experimental studies have shown
that nonreciprocal behavior can be achieved in optomechanical systems, but
performance in these last two attributes has been limited. Here we demonstrate
an efficient, frequency-converting microwave isolator based on the
optomechanical interactions between electromagnetic fields and a mechanically
compliant vacuum gap capacitor. We achieve simultaneous reverse isolation of
more than 20 dB and insertion loss less than 1.5 dB over a bandwidth of 5 kHz.
We characterize the nonreciprocal noise performance of the device, observing
that the residual thermal noise from the mechanical environments is routed
solely to the input of the isolator. Our measurements show quantitative
agreement with a general coupled-mode theory. Unlike conventional isolators and
circulators, these compact nonreciprocal devices do not require a static
magnetic field, and they allow for dynamic control of the direction of
isolation. With these advantages, similar devices could enable programmable,
high-efficiency connections between disparate nodes of quantum networks, even
efficiently bridging the microwave and optical domains.Comment: 9 pages, 6 figure
Buitenzorg Ayrshire Farm Breeding Diagram
A diagram of a family tree of the Ayrshire cows on Ralph LeCocq\u27s farm, with photos and descriptions.https://nwcommons.nwciowa.edu/lecocqfarm/1000/thumbnail.jp
On discretization in time in simulations of particulate flows
We propose a time discretization scheme for a class of ordinary differential
equations arising in simulations of fluid/particle flows. The scheme is
intended to work robustly in the lubrication regime when the distance between
two particles immersed in the fluid or between a particle and the wall tends to
zero. The idea consists in introducing a small threshold for the particle-wall
distance below which the real trajectory of the particle is replaced by an
approximated one where the distance is kept equal to the threshold value. The
error of this approximation is estimated both theoretically and by numerical
experiments. Our time marching scheme can be easily incorporated into a full
simulation method where the velocity of the fluid is obtained by a numerical
solution to Stokes or Navier-Stokes equations. We also provide a derivation of
the asymptotic expansion for the lubrication force (used in our numerical
experiments) acting on a disk immersed in a Newtonian fluid and approaching the
wall. The method of this derivation is new and can be easily adapted to other
cases
Haematological and pathological findings of pigs experimentally inoculated with a Chilean isolate of porcine reproductive and respiratory syndrome virus
The aims of this study were to characterize the haematological and bone marrow changes, gross and microscopic lesions of pigs
experimentally inoculated with the Chilean isolate of porcine reproductive and respiratory syndrome virus. Twelve 3-week-old pigs
were divided in 4 groups of 3, one of which corresponded to the negative control group sacrificed at 0 days post-inoculation (dpi),
and the 3 remaining groups corresponded to the inoculated pigs sacrificed at 7, 14 and 21 dpi. For each sampling period blood was
collected for complete haemograme and at the necropsy time gross lesions were registered and samples for both bone marrow smears
and histopathology were taken. The results of this study revealed haematological alterations characterized by a significant reduction
(P<0.05) in the haematocrit and a significant increase (P<0.05) in the total leukocyte count associated with an increase in the
monocytes and baciliforms. The bone marrow did not show significant variations in the ratio of myeloid to erythroid cells (P>0.05).
At the same time, the gross lesions were mild and mainly characterized by the presence of conjunctivitis, periocular edema and a
slight increase in the size of the lymph nodes. Microscopic lesions were characterized by the presence of interstitial pneumonia,
depletion and necrosis in lymphoid organs, rhinitis, hepatitis, myocarditis and non-purulent encephalitis. These findings suggest that
the Chilean isolate of the vPRRS to a strain with a low virulenc
Clay fine fissuring monitoring using miniature geo-electrical resistivity arrays
Abstract This article describes a miniaturised electrical imaging (resistivity tomography) technique to map the cracking pattern of a clay model. The clay used was taken from a scaled flood embankment built to study the fine fissuring due to desiccation and breaching process in flooding conditions. The potential of using a miniature array of electrodes to follow the evolution of the vertical cracks and number them during the drying process was explored. The imaging technique generated two-dimensional contoured plots of the resistivity distribution within the model before and at different stages of the desiccation process. The change in resistivity associated with the widening of the cracks were monitored as a function of time. Experiments were also carried out using a selected conductive gel to slow down the transport process into the cracks to improve the scanning capabilities of the equipment. The main vertical clay fissuring network was obtained after inversion of the experimental resistivity measurements and validated by direct observations
Enfermedades producidas por priones en los Animales
Las encefalopatías espongiformes transmisibles (EETs) o enfermedades producidas por priones, son un grupo de enfermedades neurodegenerativas, de progresión lenta y fatales. Afectan tanto a los humanos como a los animales. Dentro de este grupo se encuentra la Encefalopatía Espongiforme Bovina (EEB), que se diagnosticó en Gran Bretaña y que posteriormente ha afectado a otros países. Esta patología ha causado gran impacto por el daño que ha provocado en la salud animal, en la economía y por su relevancia en la salud pública de estos países, al ser una enfermedad zoonótica. El agente etiológico de todas las EETs, se denomina "prión", que corresponde a la forma alterada (PrPSc) de una proteína constitutiva de la membrana celular (PrPC). La forma patológica es infectiva, capaz de producir la enfermedad, extremadamente resistente al calor y a otros métodos tradicionales de esterilización, que son efectivos contra otros patógenos. Entre las características comunes de estas patologías, se incluyen su curso con un largo periodo de incubación, el que puede durar hasta 3 años, posterior a la exposición. Los signos clínicos aparecen después de este período, los animales afectados presentan signos neurológicos progresivos y cambios morfológicos degenerativos del sistema nervioso central, que terminan con la muerte del individuo. Las principales EETs en los animales, que se describen en este trabajo son: el scrapie de ovinos y caprinos, la Encefalopatía Espongiforme Bovina (EEB), la Encefalopatía Transmisible del Visón (ETV), la Enfermedad del Desgaste Crónico (EDC) en ciervos y alces y la Encefalopatía Espongiforme Felina (EEF).
Strong tunable coupling between a superconducting charge and phase qubit
We have realized a tunable coupling over a large frequency range between an
asymmetric Cooper pair transistor (charge qubit) and a dc SQUID (phase qubit).
Our circuit enables the independent manipulation of the quantum states of each
qubit as well as their entanglement. The measurements of the charge qubit's
quantum states is performed by resonant read-out via the measurement of the
quantum states of the SQUID. The measured coupling strength is in agreement
with an analytic theory including a capacitive and a tunable Josephson coupling
between the two qubits.Comment: 5 page
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