Non-equilibrium transitions in fully frustrated Josephson junction arrays

We study the effect of thermal fluctuations in a fully frustrated Josephson junction array driven by a current I larger than the apparent critical current I_c(T). We calculate numerically the behavior of the chiral order parameter of Z_2 symmetry and the transverse helicity modulus (related to the U(1) symmetry) as a function of temperature. We find that the Z_2 transition occurs at a temperature T_{Z_2}(I) which is lower than the temperature T_{U(1)}(I) for the U(1) transition. Both transitions could be observed experimentally from measurements of the longitudinal and transverse voltages.Comment: 4 pages, 4 figure

Mixed-valent regime of the two-channel Anderson impurity as a model for UBe_13

We investigate the mixed-valent regime of a two-configuration Anderson impurity model for uranium ions, with separate quadrupolar and magnetic doublets. With a new Monte Carlo approach and the non-crossing approximation we find: (i) A non-Fermi-liquid fixed point with two-channel Kondo model critical behavior; (ii) Distinct energy scales for screening the low-lying and excited doublets; (iii) A semi-quantitative explanation of magnetic-susceptibility data for U$_{1-x}$Th$_x$Be$_{13}$ assuming 60-70% quadrupolar doublet ground-state weight, supporting the quadrupolar-Kondo interpretation.Comment: 4 Pages, 3 eps figures; submitted to Phys. Rev. Let

Planetary Candidates Observed by Kepler. VII. The First Fully Uniform Catalog Based on The Entire 48 Month Dataset (Q1-Q17 DR24)

We present the seventh Kepler planet candidate catalog, which is the first to be based on the entire, uniformly processed, 48 month Kepler dataset. This is the first fully automated catalog, employing robotic vetting procedures to uniformly evaluate every periodic signal detected by the Q1-Q17 Data Release 24 (DR24) Kepler pipeline. While we prioritize uniform vetting over the absolute correctness of individual objects, we find that our robotic vetting is overall comparable to, and in most cases is superior to, the human vetting procedures employed by past catalogs. This catalog is the first to utilize artificial transit injection to evaluate the performance of our vetting procedures and quantify potential biases, which are essential for accurate computation of planetary occurrence rates. With respect to the cumulative Kepler Object of Interest (KOI) catalog, we designate 1,478 new KOIs, of which 402 are dispositioned as planet candidates (PCs). Also, 237 KOIs dispositioned as false positives (FPs) in previous Kepler catalogs have their disposition changed to PC and 118 PCs have their disposition changed to FP. This brings the total number of known KOIs to 8,826 and PCs to 4,696. We compare the Q1-Q17 DR24 KOI catalog to previous KOI catalogs, as well as ancillary Kepler catalogs, finding good agreement between them. We highlight new PCs that are both potentially rocky and potentially in the habitable zone of their host stars, many of which orbit solar-type stars. This work represents significant progress in accurately determining the fraction of Earth-size planets in the habitable zone of Sun-like stars. The full catalog is publicly available at the NASA Exoplanet Archive.Comment: Accepted to the Astrophysical Journal Supplement Series. 30 pages, 9 figures, 7 tables. We make the DR24 robovetter decision code publicly available at http://github.com/JeffLCoughlin/robovetter, with input and output examples provided using the same data as contained in the full paper's table

Multi-Messenger Astronomy with Extremely Large Telescopes

The field of time-domain astrophysics has entered the era of Multi-messenger Astronomy (MMA). One key science goal for the next decade (and beyond) will be to characterize gravitational wave (GW) and neutrino sources using the next generation of Extremely Large Telescopes (ELTs). These studies will have a broad impact across astrophysics, informing our knowledge of the production and enrichment history of the heaviest chemical elements, constrain the dense matter equation of state, provide independent constraints on cosmology, increase our understanding of particle acceleration in shocks and jets, and study the lives of black holes in the universe. Future GW detectors will greatly improve their sensitivity during the coming decade, as will near-infrared telescopes capable of independently finding kilonovae from neutron star mergers. However, the electromagnetic counterparts to high-frequency (LIGO/Virgo band) GW sources will be distant and faint and thus demand ELT capabilities for characterization. ELTs will be important and necessary contributors to an advanced and complete multi-messenger network.Comment: White paper submitted to the Astro2020 Decadal Surve

Planetary Candidates Observed by Kepler VI: Planet Sample from Q1-Q16 (47 Months)

\We present the sixth catalog of Kepler candidate planets based on nearly 4 years of high precision photometry. This catalog builds on the legacy of previous catalogs released by the Kepler project and includes 1493 new Kepler Objects of Interest (KOIs) of which 554 are planet candidates, and 131 of these candidates have best fit radii <1.5 R_earth. This brings the total number of KOIs and planet candidates to 7305 and 4173 respectively. We suspect that many of these new candidates at the low signal-to-noise limit may be false alarms created by instrumental noise, and discuss our efforts to identify such objects. We re-evaluate all previously published KOIs with orbital periods of >50 days to provide a consistently vetted sample that can be used to improve planet occurrence rate calculations. We discuss the performance of our planet detection algorithms, and the consistency of our vetting products. The full catalog is publicly available at the NASA Exoplanet Archive.Comment: 18 pages, to be published in the Astrophysical Journal Supplement Serie

Ge-rich graded-index Si_1-xGex waveguides with broadband tight mode confinement and flat anomalous dispersion for nonlinear mid-infrared photonics

This work explores the use of Ge-rich graded-index Si1-xGex rib waveguides as building blocks to develop integrated nonlinear optical devices for broadband operation in the mid-IR. The vertical Ge gradient concentration in the waveguide core renders unique properties to the guided optical mode, providing tight mode confinement over a broadband mid-IR wavelength range from λ = 3 µm to 8 µm. Additionally, the gradual vertical confinement pulls the optical mode upwards in the waveguide core, overlapping with the Ge-rich area where the nonlinear refractive index is larger. Moreover, the Ge-rich graded-index Si1-xGex waveguides allow efficient tailoring of the chromatic dispersion curves, achieving flat anomalous dispersion for the quasi-TM optical mode with D ≤ 14 ps/nm/km over a ~1.4 octave span while retaining an optimum third-order nonlinear parameter, γeff. These results confirm the potential of Ge-rich graded-index Si1-xGex waveguides as an attractive platform to develop mid-IR nonlinear approaches requiring broadband dispersion engineering

Bacterial growth inhibitory activity for nanostructured copper minerals obtained from the Marañon region: comparison with commercial copper

En el presente trabajo se reporta la actividad inhibitoria del crecimiento bacteriano por nanopartículas de cobre cementado y de cobre comercial. Se utilizaron las cepas de Staphylococcus aureus ATCC 6538 (Gram positiva) y Escherichia coli ATCC 35218 (Gram negativa) para determinar el efecto inhibitorio mediante la concentración mínima inhibitoria de las nanopartículas diluidas en caldo de cultivo nutritivo y distribuidas en placas de ELISA. Las muestras de cobre cementado (obtenidas por procesos hidrometalúrgicos) y de cobre comercial fueron nanoestructuradas empleando un equipo de molienda mecánica. Los resultados indican que las nanopartículas de cobre comercial (a 2.5 horas de molienda) muestran acción inhibitoria del crecimiento de la cepa S. aureus y no así en la cepa E. coli. Asimismo, se determinó que la concentración mínima inhibitoria de la muestra de cobre comercial fue de 20 μg/mL frente a S. aureus. El cobre cementado (en su forma sólida y nanoestructurada) no mostró efecto inhibitorio del crecimiento en ninguna de las dos cepas estudiadas.In this paper, we report on the bacterial growth inhibitory activity of nanoparticles of cemented and commercial copper. Strains of Staphylococcus aureus ATCC 6538 (Gram positive) and Escherichia coli ATCC 35218 (Gram negative) were used to determine the inhibitory effect by the minimal inhibitory concentration of the nanoparticles diluted in nutrient culture broth and distributed in ELISA plates. The copper cements (obtained from hydrometallurgical processes) and the commercial one were nanostructured employing a mechanical milling equipment. The results indicate that commercial copper nanoparticles (after 2.5 hours of milling) show growth inhibitory action of S. aureus strain. However, in the case of E. coli strains no inhibitory action has been observed. It was also determined that the minimal inhibitory concentration of the commercial copper is 20 μg/mL against S. aureus. On the other hand, copper cements (in solid and nanostructured form) do not show inhibitory effects

Adaptive fractional PID control of biped robots with time-delayed feedback

This paper presents the application of Fractional Order Time- Delay adaptive neural networks to the trajectory tracking for chaos synchronization between Fractional Order delayed plant, reference and Fractional Order Time-Delay adaptive neural networks. The proposed new control scheme is applied via simulations to control of a 4-DOF Biped Robot [1]. The main methodologies, on which the approach is based, are Fractional Order PID the Fractional Order Lyapunov-Krasovskii functions methodology. The structure of the biped robot is designed with two degrees of freedom per leg, corresponding to the knee and hip joints. Since torso and ankle are not considered, it is obtained a 4-DOF system, and each leg, we try to force this biped robot to track a reference signal given by undamped Duffing equation. The tracking error is globally asymptotically stabilized by two control laws derived based on a Lyapunov-Krasovski functional

The Need for Laboratory Measurements and Ab Initio Studies to Aid Understanding of Exoplanetary Atmospheres

We are now on a clear trajectory for improvements in exoplanet observations that will revolutionize our ability to characterize their atmospheric structure, composition, and circulation, from gas giants to rocky planets. However, exoplanet atmospheric models capable of interpreting the upcoming observations are often limited by insufficiencies in the laboratory and theoretical data that serve as critical inputs to atmospheric physical and chemical tools. Here we provide an up-to-date and condensed description of areas where laboratory and/or ab initio investigations could fill critical gaps in our ability to model exoplanet atmospheric opacities, clouds, and chemistry, building off a larger 2016 white paper, and endorsed by the NAS Exoplanet Science Strategy report. Now is the ideal time for progress in these areas, but this progress requires better access to, understanding of, and training in the production of spectroscopic data as well as a better insight into chemical reaction kinetics both thermal and radiation-induced at a broad range of temperatures. Given that most published efforts have emphasized relatively Earth-like conditions, we can expect significant and enlightening discoveries as emphasis moves to the exotic atmospheres of exoplanets.Comment: Submitted as an Astro2020 Science White Pape