1,285 research outputs found
Femtosecond laser triggering of a sub-100 picosecond jitter high-voltage spark gap
Includes bibliographical references (page 3250).We have demonstrated sub-100 ps jitter operation of a pressurized high-voltage air spark gap triggered by a femtosecond Ti:Sapphire laser. Time delay statistical fluctuations with a standard deviation as low as +-σ=0.037 ns were obtained
Sending femtosecond pulses in circles: highly non-paraxial accelerating beams
We use caustic beam shaping on 100 fs pulses to experimentally generate
non-paraxial accelerating beams along a 60 degree circular arc, moving
laterally by 14 \mum over a 28 \mum propagation length. This is the highest
degree of transverse acceleration reported to our knowledge. Using diffraction
integral theory and numerical beam propagation simulations, we show that
circular acceleration trajectories represent a unique class of non-paraxial
diffraction-free beam profile which also preserves the femtosecond temporal
structure in the vicinity of the caustic
First record of Calma gobioophaga Calado and Urgorri, 2002 (Gastropoda: Nudibranchia) in the Mediterranean Sea
Specimens of the nudibranch genus Calma were observed under stones at two Croatian localities while feeding on gobiid eggs. Some ambiguous morphological features compared with the original descriptions of the known species of the genus, C. glaucoides and C. gobioophaga, hampered an easy identification. Genetic data (COI and 16S sequences) confirmed the distinction between the two species of the genus Calma, and allowed to unambiguously identify the Croatian specimens as Calma gobioophaga. This is the first record of this species for the Mediterranean and extends remarkably its distribution range. Finally, the eggs fed by the Croatian specimens have been taxonomically identified by using the 12S rDNA marker as Gobius cobitis
First record of Calma gobioophaga Calado and Urgorri, 2002 (Gastropoda: Nudibranchia)in the Mediterranean sea
Specimens of the nudibranch genus Calma were observed under boulders at two Croatian localities while feeding on gobiid eggs. Some ambiguous morphological features compared with the original descriptions of the known species of the genus, C. glaucoides and C. gobioophaga hampered easy identification. Genetic data (COI and 16S sequences) confirmed the distinction between the two species of the genus Calma, and allowed unambiguous identification of the Croatian specimens as Calma gobioophaga. This is the first record of this species for the Mediterranean and extends its distribution range remarkably. Finally, the eggs consumed by the Croatian C. gobioophaga specimens have been taxonomically identified by using the 12S rDNA marker as Gobius cobitis
First record of Calma gobioophaga Calado and Urgorri, 2002 (Gastropoda: Nudibranchia) in the Mediterranean Sea
Specimens of the nudibranch genus Calma were observed under stones at two Croatian localities while feeding on gobiid eggs. Some ambiguous morphological features compared with the original descriptions of the known species of the genus, C. glaucoides and C. gobioophaga, hampered an easy identification. Genetic data (COI and 16S sequences) confirmed the distinction between the two species of the genus Calma, and allowed to unambiguously identify the Croatian specimens as Calma gobioophaga. This is the first record of this species for the Mediterranean and extends remarkably its distribution range. Finally, the eggs fed by the Croatian specimens have been taxonomically identified by using the 12S rDNA marker as Gobius cobitis
Arbitrary non-paraxial accelerating periodic beams and spherical shaping of light
We report the observation of arbitrary accelerating beams designed using a
non-paraxial description of optical caustics. We use a spatial light
modulator-based setup and techniques of Fourier optics to generate circular and
Weber beams subtending over 95 degrees of arc. Applying a complementary binary
mask also allows the generation of periodic accelerating beams taking the forms
of snake-like trajectories, and the application of a rotation to the caustic
allows the first experimental synthesis of optical accelerating beams upon the
surface of a sphere in three dimensions.Comment: 4 pages, 4 figures articl
Realistic On-the-fly Outcomes of Planetary Collisions: Machine Learning Applied to Simulations of Giant Impacts
Planet formation simulations are capable of directly integrating the evolution of hundreds to thousands of planetary embryos and planetesimals as they accrete pairwise to become planets. In principle, these investigations allow us to better understand the final configuration and geochemistry of the terrestrial planets, and also to place our solar system in the context of other exosolar systems. While these simulations classically prescribe collisions to result in perfect mergers, recent computational advances have begun to allow for more complex outcomes to be implemented. Here we apply machine learning to a large but sparse database of giant impact studies, which allows us to streamline the simulations into a classifier of collision outcomes and a regressor of accretion efficiency. The classifier maps a four-dimensional (4D) parameter space (target mass, projectile-to-target mass ratio, impact velocity, impact angle) into the four major collision types: merger, graze-and-merge, hit-and-run, and disruption. The definition of the four regimes and their boundary is fully data-driven. The results do not suffer from any model assumption in the fitting. The classifier maps the structure of the parameter space and it provides insights into the outcome regimes. The regressor is a neural network that is trained to closely mimic the functional relationship between the 4D space of collision parameters, and a real-variable outcome, the mass of the largest remnant. This work is a prototype of a more complete surrogate model, that will be based on extended sets of simulations (big data), that will quickly and reliably predict specific collision outcomes for use in realistic N-body dynamical studies of planetary formation.NASA Planetary Science Division; University of ArizonaThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]
Bacteriophage Therapy: Clinical Trials and Regulatory Hurdles
Increasing reports of antimicrobial resistance and limited new antibiotic discoveries and development have fuelled innovation in other research fields and led to a revitalization of bacteriophage (phage) studies in the Western world. Phage therapy mainly utilizes obligately lytic phages to kill their respective bacterial hosts, while leaving human cells intact and reducing the broader impact on commensal bacteria that often results from antibiotic use. Phage therapy is rapidly evolving and has resulted in cases of life-saving therapeutic use and multiple clinical trials. However, one of the biggest challenges this antibiotic alternative faces relates to regulations and policy surrounding clinical use and implementation beyond compassionate cases. This review discusses the multi-drug resistant Gram-negative pathogens of highest critical priority and summarizes the current state-of-the-art in phage therapy targeting these organisms. It also examines phage therapy in humans in general and the approaches different countries have taken to introduce it into clinical practice and policy. We aim to highlight the rapidly advancing field of phage therapy and the challenges that lie ahead as the world shifts away from complete reliance on antibiotics
Algoritmo de visión estereo en tiempo real implementado en GPGPU
En el este trabajo se presenta una implementación en tiempo real de un sistema de visión artificial en tres dimensiones sobre GPGPU.
Se logra optimizar el procesamiento de visión estéreo mediante el algoritmo de Suma de Diferencias Absolutas (SAD), seleccionado en virtud de su costo computacional moderado. Se aplican sobre la imagen resultante sendos kernels de sustracción de fondo y suavizado, con el objeto de minimizar los errores de procesamiento intrínsecos de SAD, obteniéndose en forma experimental los parámetros óptimos para cada kernel. Se aplica esta cadena de procesamiento sobre una plataforma basada en GPGPU, y sobre un equipo basado en CPU convencional de arquitectura x86.
Se comparan los resultados con el mismo procesamiento ejecutado en una CPU convencional y se demuestra una mejora 13x en el tiempo de ejecución, y por consecuencia, la factibilidad de aplicar el método para procesamiento de video en tiempo real utilizando GPGPUs como plataforma de ejecución, hecho que permite proyectar futuros trabajos en aplicaciones industriales de tiempo real que se valgan de la visión 3D para verificación de ensamble de productos sobre líneas de montaje.Sociedad Argentina de Informática e Investigación Operativa (SADIO
The Effect of Inefficient Accretion on Planetary Differentiation
Pairwise collisions between terrestrial embryos are the dominant means of
accretion during the last stage of planet formation. Hence, their realistic
treatment in N-body studies is critical to accurately model the formation of
terrestrial planets and to develop interpretations of telescopic and spacecraft
observations. In this work, we compare the effects of two collision
prescriptions on the core-mantle differentiation of terrestrial planets: a
model in which collisions are always completely accretionary (``perfect
merging'') and a more realistic model based on neural networks that has been
trained on hydrodynamical simulations of giant impacts. The latter model is
able to predict the loss of mass due to imperfect accretion and the evolution
of non-accreted projectiles in hit-and-run collisions. We find that the results
of the neural-network model feature a wider range of final core mass fractions
and metal-silicate equilibration pressures, temperatures, and oxygen fugacities
than the assumption of perfect merging. When used to model collisions in N-body
studies of terrestrial planet formation, the two models provide similar answers
for planets more massive than 0.1 Earth's masses. For less massive final
bodies, however, the inefficient-accretion model predicts a higher degree of
compositional diversity. This phenomenon is not reflected in planet formation
models of the solar system that use perfect merging to determine collisional
outcomes. Our findings confirm the role of giant impacts as important drivers
of planetary diversity and encourage a realistic implementation of inefficient
accretion in future accretion studies.Comment: 21 pages, 2 tables, 7 figures. Published open access on PSJ:
https://iopscience.iop.org/article/10.3847/PSJ/abf0a
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