Experimental demonstration of Aharonov-Casher interference in a Josephson junction circuit

A neutral quantum particle with magnetic moment encircling a static electric charge acquires a quantum mechanical phase (Aharonov-Casher effect). In superconducting electronics the neutral particle becomes a fluxon that moves around superconducting islands connected by Josephson junctions. The full understanding of this effect in systems of many junctions is crucial for the design of novel quantum circuits. Here we present measurements and quantitative analysis of fluxon interference patterns in a six Josephson junction chain. In this multi-junction circuit the fluxon can encircle any combination of charges on five superconducting islands, resulting in a complex pattern. We compare the experimental results with predictions of a simplified model that treats fluxons as independent excitations and with the results of the full diagonalization of the quantum problem. Our results demonstrate the accuracy of the fluxon interference description and the quantum coherence of these arrays

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).  

Fabrication of stable and reproducible sub-micron tunnel junctions

We have performed a detailed study of the time stability and reproducibility of sub-micron $Al/AlO_{x}/Al$ tunnel junctions, fabricated using standard double angle shadow evaporations. We have found that by aggressively cleaning the substrate before the evaporations, thus preventing any contamination of the junction, we obtained perfectly stable oxide barriers. We also present measurements on large ensembles of junctions which prove the reproducibility of the fabrication process. The measured tunnel resistance variance in large ensembles of identically fabricated junctions is in the range of only a few percents. Finally, we have studied the effect of different thermal treatments on the junction barrier. This is especially important for multiple step fabrication processes which imply annealing the junction.Comment: 4 pages, 3 figure

Non-invasive assessment of murine PD-L1 levels in syngeneic tumor models by nuclear imaging with nanobody tracers

Blockade of the inhibitory PD-1/PD-L1 immune checkpoint axis is a promising cancer treatment. Nonetheless, a significant number of patients and malignancies do not respond to this therapy. To develop a screen for response to PD-1/PD-L1 inhibition, it is critical to develop a non-invasive tool to accurately assess dynamic immune checkpoint expression. Here we evaluated non-invasive SPECT/CT imaging of PD-L1 expression, in murine tumor models with varying PD-L1 expression, using high affinity PD-L1-specific nanobodies (Nbs). We generated and characterized 37 Nbs recognizing mouse PD-L1. Among those, four Nbs C3, C7, E2 and E4 were selected and evaluated for preclinical imaging of PD-L1 in syngeneic mice. We performed SPECT/CT imaging in wild type versus PD-L1 knock-out mice, using Technetium-99m (99mTc) labeled Nbs. Nb C3 and E2 showed specific antigen binding and beneficial biodistribution. Through the use of CRISPR/Cas9 PD-L1 knock-out TC-1 lung epithelial cell lines, we demonstrate that SPECT/CT imaging using Nb C3 and E2 identifies PD-L1 expressing tumors, but not PD-L1 non-expressing tumors, thereby confirming the diagnostic potential of the selected Nbs. In conclusion, these data show that Nbs C3 and E2 can be used to non-invasively image PD-L1 levels in the tumor, with the strength of the signal correlating with PD-L1 levels. These findings warrant further research into the use of Nbs as a tool to image inhibitory signals in the tumor environment

Edible insects unlikely to contribute to transmission of coronavirus SARS-CoV-2

In the context of food safety, edible insects are evaluated for biological hazards such as microbial pathogens according to regulations currently in place. When the European Food Safety Authority evaluated the hazards of edible insects as a potential source of pathogenic viruses for humans and livestock, the novel zoonotic coronavirus SARS-CoV-2 had not yet emerged but other pathogenic coronaviruses such as SARS (SARS-CoV) and MERS (MERS-CoV) were known. As a result of the COVID-19 pandemic, animal sources of protein for human consumption are being evaluated for the risks of being a transmission vector of coronaviruses, like SARS-CoV-2. Insects lack a receptor that can bind SARS-CoV-2, thus preventing the virus from replicating in insects, unlike some vertebrate livestock species and companion animals. Despite extensive monitoring, coronaviruses have never been recorded in insect microbiomes. Contamination of insects produced for food or feed may occur during the production process, resulting from rearing substrate or from insect farmers. However, the currently permitted rearing substrates do not include animal products and the farming process is highly automated, thus limiting interactions between farmers and insects. If contamination would still occur, the fact that the insects in production are not hosts to SARS-CoV-2 precludes virus replication and the further processing of the insects will destroy the contamination. We conclude that the hazard of edible insects being a transmission vector of SARS-CoV-2 is extremely low.</p