818 research outputs found
A possible flyby anomaly for Juno at Jupiter
[EN] In the last decades there have been an increasing interest in improving the accuracy of spacecraft navigation and trajectory data. In the course of this plan some anomalies have been found that cannot, in principle, be explained in the context of the most accurate orbital models including all known effects from classical dynamics and general relativity. Of particular interest for its puzzling nature, and the lack of any accepted explanation for the moment, is the flyby anomaly discovered in some spacecraft flybys of the Earth over the course of twenty years. This anomaly manifest itself as the impossibility of matching the pre and post-encounter Doppler tracking and ranging data within a single orbit but, on the contrary, a difference of a few mm/s in the asymptotic velocities is required to perform the fitting.
Nevertheless, no dedicated missions have been carried out to elucidate the origin of this phenomenon with the objective either of revising our understanding of gravity or to improve the accuracy of spacecraft Doppler tracking by revealing a conventional origin.
With the occasion of the Juno mission arrival at Jupiter and the close flybys of this planet, that are currently been performed, we have developed an orbital model suited to the time window close to the perijove. This model shows that an anomalous acceleration of a few mm/s(2) is also present in this case. The chance for overlooked conventional or possible unconventional explanations is discussed. (C) 2018 COSPAR. Published by Elsevier Ltd. All rights reserved.Acedo RodrĂguez, L.; Piqueras, P.; Moraño Fernández, JA. (2018). A possible flyby anomaly for Juno at Jupiter. Advances in Space Research. 61(10):2697-2706. https://doi.org/10.1016/j.asr.2018.02.037S26972706611
The State-of-the-Art of Phase II/III Clinical Trials for Targeted Pancreatic Cancer Therapies
Pancreatic cancer is a devastating disease with very poor prognosis. Currently, surgery followed by adjuvant chemotherapy represents the only curative option which, unfortunately, is only available for a small group of patients. The majority of pancreatic cancer cases are diagnosed at advanced or metastatic stage when surgical resection is not possible and treatment options are limited. Thus, novel and more effective therapeutic strategies are urgently needed. Molecular profiling together with targeted therapies against key hallmarks of pancreatic cancer appear as a promising approach that could overcome the limitations of conventional chemo- and radio-therapy. In this review, we focus on the latest personalised and multimodal targeted therapies currently undergoing phase II or III clinical trials. We discuss the most promising findings of agents targeting surface receptors, angiogenesis, DNA damage and cell cycle arrest, key signalling pathways, immunotherapies, and the tumour microenvironment
Comparison of Monolithic Optical Frequency Comb Generators Based on Passively Mode-Locked Lasers for Continuous Wave mm-Wave and Sub-THz Generation
In this paper, two different Passive Mode-Locked Laser Diodes (PMLLD) structures, a Fabry-Perot cavity and a ring cavity laser are characterized and evaluated as monolithic Optical Frequency Comb Generators (OFCG) for CW sub-THz generation. An extensive characterization of the devices under study is carried out based on an automated measurement system that systematically evaluates the dynamic characteristics of the devices, focusing on the figures of merit that define the optimum performance of a pulsed laser source when considered as an OFCG. Sub-THz signals generated with both devices at 60 GHz and 90 GHz are presented and analyzed in terms of electrical linewidth to compare such components for mm-Wave and sub-THz photonic generation. This work offers a systematic comparison of PMLLD devices for OFCG operation and provides reference information of the performance of two different device topologies that can be used for the implementation of photonic integrated sub-THz CW generation.We acknowledge COBRA Research Institute, Eindhoven University of Technology, the Netherlands for the fabrication of the ring lasers within the joint European platform for InP-based components and circuits, JePPIX.Publicad
A Study on the Dependence of Water Tree Permittivity with Time
During the growth of water trees in the insulation of a
cable the distribution of the electric field is modified
because of the local change of the dielectric properties
of the material. It results a local enhancement of the
electric field which could increase the risk of
breakdown. The key factor is the permittivity of the
water tree and the aim of the work is to determine its
possible values and, particularly, the law of its increase
with time during the of the trees. The paper
presents permittivity measurements in uniform field in MV and powe
Biliary Strictures and Cholangiocarcinoma - Untangling a Diagnostic Conundrum
Cholangiocarcinoma is an uncommon and highly aggressive biliary tract malignancy with few manifestations until late disease stages. Diagnosis is currently achieved through a combination of clinical, biochemical, radiological and histological techniques. A number of reported cancer biomarkers have the potential to be incorporated into diagnostic pathways, but all lack sufficient sensitivity and specificity limiting their possible use in screening and early diagnosis. The limitations of standard serum markers such as CA19-9, CA125 and CEA have driven researchers to identify multiple novel biomarkers, yet their clinical translation has been slow with a general requirement for further validation in larger patient cohorts. We review recent advances in the diagnostic pathway for suspected CCA as well as emerging diagnostic biomarkers for early detection, with a particular focus on non-invasive approaches
Observation of phase noise reduction in photonically synthesized sub-THz signals using a passively mode-locked laser diode and highly selective optical filtering
A Continuous Wave (CW) sub-THz photonic synthesis setup based on a single Passively Mode-Locked Laser Diode (PMLLD) acting as a monolithic Optical Frequency Comb Generator (OFCG) and highly selective optical filtering has been implemented to evaluate the phase noise performance of the generated sub-THz signals. The analysis of the synthesized sub-THz signals up to 120 GHz gives as a result an effective reduction of the electrical linewidth when compared to direct harmonic generation that begins at 50 GHz and becomes greater as the frequency increases. The phase noise reduction offered by the setup, along with its integration potential, cost and bandwidth, make it a promising candidate to the development of an integrated and high performance low phase noise local oscillator in the sub-THz range.Work supported by the Spanish Ministry of Science and Technology through the project TEC2009-14525-C02-02 and by the European Commission FP7 iPHOS Project. The work by A.R. Criado has been supported by the Spanish Ministry of Science and Technology under the FPI Program, Grant# BES2010-030290.Publicad
Average shape of fluctuations for subdiffusive walks
We study the average shape of fluctuations for subdiffusive processes, i.e.,
processes with uncorrelated increments but where the waiting time distribution
has a broad power-law tail. This shape is obtained analytically by means of a
fractional diffusion approach. We find that, in contrast with processes where
the waiting time between increments has finite variance, the fluctuation shape
is no longer a semicircle: it tends to adopt a table-like form as the
subdiffusive character of the process increases. The theoretical predictions
are compared with numerical simulation results.Comment: 4 pages, 6 figures. Accepted for publication Phys. Rev. E (Replaced
for the latest version, in press.) Section II rewritte
Velocity Tails for Inelastic Maxwell Models
We study the velocity distribution function for inelastic Maxwell models,
characterized by a Boltzmann equation with constant collision rate, independent
of the energy of the colliding particles. By means of a nonlinear analysis of
the Boltzmann equation, we find that the velocity distribution function decays
algebraically for large velocities, with exponents that are analytically
calculated.Comment: 4 pages, 2 figure
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