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In this paper, we propose a novel cost model for Spark SQL. The cost model covers the class of Generalized Projection, Selection, Join (GPSJ) queries. The cost model keeps into account the network and IO costs as well as the most relevant CPU costs. The execution cost is computed starting from a physical plan produced by Spark. The set of operations adopted by Spark when executing a GPSJ query are analytically modeled based on the cluster and application parameters, together with a set of database statistics. Experimental results carried out on three benchmarks and on two clusters of different sizes and with different computation features show that our model can estimate the actual execution time with about the 20 percent of errors on the average. Such an accuracy is good enough to let the system choose the most effective plan even when the execution time differences are limited. The error can be reduced to 14 percent, if the analytic model is coupled with our straggler handling strategy.

The ability to drive a system with an external input is a fundamental aspect of light-matter interaction. The coherent perfect absorption (CPA) phenomenon extends to the general multibeam interference phenomenology the well known critical coupling concepts. This interferometric control of absorption can be employed to reach full delivery of optical energy to nanoscale systems such as plasmonic nanoparticles, and multi-port interference can be used to enhance the absorption of a nanoscale device when it is embedded in a strongly scattering system, with potential applications to nanoscale sensing. Here we review the two-port CPA in reference to photonic structures which can resonantly couple to the external fields. A revised two-port theory of CPA is illustrated, which relies on the Scattering Matrix formalism and is valid for all linear two-port systems with reciprocity. Through a semiclassical approach, treating two-port critical coupling conditions in a non-perturbative regime, it is demonstrated that the strong coupling regime and the critical coupling condition can indeed coexist; in this situation, termed strong critical coupling, all the incoming energy is converted into polaritons. Experimental results are presented, which clearly display the elliptical trace of absorption as function of input unbalance in a thin metallo-dielectric metamaterial, and verify polaritonic CPA in an intersubband-polariton photonic-crystal membrane resonator. Concluding remarks discuss the future perspectives of CPA with photonic structures., arXiv admin note: substantial text overlap with arXiv:1605.08906

Recent studies showed how the density of leaf vascular system can be involved in the performance of physiological parameters. Major veins are commonly elevated in the lower epidermis of the leaf, and this anatomical feature could play a subsidiary role in increasing heat dispersion in the surrounding environment and may help dissipate excess light energy in the leaves. The aim of this study is to analyse the role of the leaf vein network in the heat dissipation process in Vitis vinifera (L.). Major leaf veins were insulated with liquid paraffin and analysed using thermal imaging. A significantly higher temperature was found on the leaf tissues with insulated veins compared to untreated leaves. Further studies are required to assess the real contribution of the leaf vascular network in thermal dissipation.

In the present article we numerically investigated the magneto-optical behaviour of a sub-wavelength structure composed by a monolayer graphene and a metallic metasurface of optical resonators. Using this hybrid graphene-metal structure, a large increase of the non-reciprocal polarization rotation of graphene can be achieved over a broad range of terahertz frequencies. We demonstrate that the symmetry of the resonator geometry plays a key role for the performance of the system: in particular, increasing the symmetry of the resonator the non-reciprocal properties can be progressively enhanced. Moreover, the possibility to exploit the metallic metasurface as a voltage gate to vary the graphene Fermi energy allows the system working point to be tuned to the desired frequency range. Another peculiar result is the achievement of a structure able to operate both in transmission and reflection with almost the same performance, but in a different frequency range of operation. The described system is hence a sub-wavelength, tunable, multifunctional, effective non-reciprocal element in the terahertz region.

Resonators and the way they couple to external radiation rely on very different concepts if one considers devices belonging to the photonic and electronic worlds. The terahertz frequency range, however, provides intriguing possibilities for the development of hybrid technologies that merge ideas from both fields in novel functional designs. In this paper, we show that high-quality, subwavelength, whispering-gallery lasers can be combined to form a linear dipole antenna, which creates a very efficient, low-threshold laser emission in a collimated beam pattern. For this purpose, we employ a terahertz quantum-cascade active region patterned into two 19-μm-radius microdisks coupled by a suspended metallic bridge, which simultaneously acts as an inductive antenna and produces the dipole symmetry of the lasing mode. Continuous-wave vertical emission is demonstrated at approximately 3.5 THz in a very regular, low-divergence (±10°) beam, with a high slope efficiency of at least 160 mW A â '1 and a mere 6 mA of threshold current, which is ensured by the ultra-small resonator size (V RES/Î" 3 â ‰10 â '2). The extremely low power consumption and the superior beam brightness make this concept very promising for the development of miniaturized and portable THz sources to be used in the field for imaging and sensing applications as well as for exploring novel optomechanical intracavity effects.

The selfmixer properties of a laser compound cavity are investigated and experimentally exploited to couple the mechanical fluctuations of a silicon nitride membrane to the laser photons and electronical states, producing an active optomechanical system.

In this work we show how a continuous wave, low threshold and well collimated terahertz laser source can be obtained by coupling two sub-wavelength whispering galleries quantum cascade optical resonators with a suspended metallic bridge.

In this paper we investigate the effect of a static magnetic field and of optical pumping on the transmittance of a hybrid graphene-split ring resonator metasurface. A significant modulation of the transmitted spectra is obtained, both by optical pumping, and by a combination of optical pumping and magnetostatic biasing. The transmittance modulation features spectral fingerprints that are characteristic of a non-Trivial interplay between the bare graphene response and the split ring resonance.

Summary: Extracting chemical features like Atom–Atom Mapping (AAM), Bond Changes (BCs) and Reaction Centres from biochemical reactions helps us understand the chemical composition of enzymatic reactions. Reaction Decoder is a robust command line tool, which performs this task with high accuracy. It supports standard chemical input/output exchange formats i.e. RXN/SMILES, computes AAM, highlights BCs and creates images of the mapped reaction. This aids in the analysis of metabolic pathways and the ability to perform comparative studies of chemical reactions based on these features. Availability and implementation: This software is implemented in Java, supported on Windows, Linux and Mac OSX, and freely available at https://github.com/asad/ReactionDecoder Contact: asad@ebi.ac.uk or s9asad@gmail.com

In order to extend the Coherent Perfect Absorption (CPA) phenomenology to broadband operation, the interferometric control of absorption is investigated in two-port systems without port permutation symmetry. Starting from the two-port theory of CPA treated within the Scattering Matrix formalism, we demonstrate that for all linear two-port systems with reciprocity the absorption is represented by an ellipse as function of the relative phase and intensity of the two input beams, and it is uniquely determined by the device single-beam reflectance and transmittance, and by the dephasing of the output beams. The basic properties of the phenomenon in systems without port permutation symmetry show that CPA conditions can still be found in such asymmetric devices, while the asymmetry can be beneficial for broadband operation. As experimental proof, we performed transmission measurements on a metal-semiconductor metamaterial, employing a Mach-Zehnder interferometer. The experimental results clearly evidence the elliptical feature of absorption and trace a route towards broadband operation. In order to extend the Coherent Perfect Absorption (CPA) phenomenology to broadband operation, the interferometric control of absorption is investigated in two-port systems without port permutation symmetry. Starting from the two-port theory of CPA treated within the Scattering Matrix formalism, we demonstrate that for all linear two-port systems with reciprocity the absorption is represented by an ellipse as function of the relative phase and intensity of the two input beams, and it is uniquely determined by the device single-beam reflectance and transmittance, and by the dephasing of the output beams. The basic properties of the phenomenon in systems without port permutation symmetry show that CPA conditions can still be found in such asymmetric devices, while the asymmetry can be beneficial for broadband operation. As experimental proof, we performed transmission measurements on a metal-semiconductor metamaterial, employing a Mach-Zehnder interferometer. The experimental results clearly evidence the elliptical feature of absorption and trace a route towards broadband operation. (C) 2015 Optical Society of America

By placing a material in close vicinity of a resonant optical element, its intrinsic optical response can be tuned, possibly to a wide extent. Here, we show that a graphene monolayer, spaced a few tenths of nanometers from a split ring resonator metasurface, exhibits a magneto-optical response which is strongly influenced by the presence of the metasurface itself. This hybrid system holds promises in view of thin optical modulators, polarization rotators, and nonreciprocal devices, in the technologically relevant terahertz spectral range. Moreover, it could be chosen as the playground for investigating the cavity electrodynamics of Dirac fermions in the quantum regime. By placing a material in close vicinity of a resonant optical element, its intrinsic optical response can be tuned, possibly to a wide extent. Here, we show that a graphene monolayer, spaced a few tenths of nanometers from a split ring resonator metasurface, exhibits a magneto-optical response which is strongly influenced by the presence of the metasurface itself. This hybrid system holds promises in view of thin optical modulators, polarization rotators, and nonreciprocal devices, in the technologically relevant terahertz spectral range. Moreover, it could be chosen as the playground for investigating the cavity electrodynamics of Dirac fermions in the quantum regime. (C) 2015 AIP Publishing LLC.

The absorption properties of a resonator can be tuned by varying the phase between incoming coherent light beams. Such control is now shown under strong coupling conditions, allowing all incoming energy to be converted into polaritons. The ability to drive a system with an external input is a fundamental aspect of light–matter interaction. The key concept in many photonic applications is the ‘critical coupling’ condition1,2: at criticality, all the energy fed to the system is dissipated within the system itself. Although this idea was crucial to enhance the efficiency of many devices, it was never considered in the context of systems operating in a non-perturbative regime. In this so-called strong-coupling regime, the matter and light degrees of freedom are mixed into dressed states, leading to new eigenstates called polaritons3,4,5,6,7,8,9,10. Here we demonstrate that the strong-coupling regime and the critical coupling condition can coexist; in such a strong critical coupling situation, all the incoming energy is converted into polaritons. A general semiclassical theory reveals that such a situation corresponds to a special curve in the phase diagram of the coupled light–matter oscillators. In the case of a system with two radiating ports, the phenomenology shown is that of coherent perfect absorption (CPA; refs 11, 12), which is then naturally understood in the framework of critical coupling. Most importantly, we experimentally verify polaritonic CPA in a semiconductor-based intersubband-polariton photonic crystal resonator. This result opens new avenues in polariton physics, making it possible to control the pumping efficiency of a system independent of the energy exchange rate between the electromagnetic field and the material transition.

Though most approaches to protein comparison are based on their structure, several studies produced evidence of a strict correlation between the surface characteristics of proteins and the way they interact. Surface-based techniques for protein comparison typically require applying clustering algorithms to the punctual 3D description of the surface in order to produce a compact surface representation, capable of effectively condensing its description. In this paper, we propose a formalization of the requirements for surface clustering in the biochemical context and present two different clustering techniques that meet them, based, respectively, on region-growing and on an original template matching algorithm. We discuss the validity of these techniques with the support of tests performed on a set of about one hundred protein models generated by punctual mutations of four structurally characterized proteins. Finally, an analysis is made of how different factors impact on the effectiveness of clustering in capturing surface similarities.

Surface-based techniques for protein comparison and classification typically require a compact surface representation, capable of effectively condensing its description. In this paper we propose an original template-matching algorithm for multi-feature surface clustering in the biochemical context. The effectiveness of our clustering algorithm in capturing surface similarities is then discussed within a larger framework for protein classification based on surface comparison, with the support of tests performed on a dataset including 25 proteins.

We demonstrate the use of a compound optical cavity as linear displacement detector, by measuring the thermal motion of a silicon nitride suspended membrane acting as the external mirror of a near-infrared Littrow laser diode. Fluctuations in the laser optical power induced by the membrane vibrations are collected by a photodiode integrated within the laser, and then measured with a spectrum analyzer. The dynamics of the membrane driven by a piezoelectric actuator is investigated as a function of air pressure and actuator displacement in a homodyne configuration. The high Q-factor (~3.4 · 104 at 8.3 · 10−3 mbar) of the fundamental mechanical mode at ~73 kHz guarantees a detection sensitivity high enough for direct measurement of thermal motion at room temperature (~87 pm RMS). The compound cavity system here introduced can be employed as a table-top, cost-effective linear displacement detector for cavity optomechanics. Furthermore, thanks to the strong optical nonlinearities of the laser compound cavity, these systems open new perspectives in the study of non-Markovian quantum properties at the mesoscale.

The huge amount of data made available by the technologies for sequencing the human genome calls for sophisticated and automated analysis techniques. In this direction, the GOLAM framework has been developed within the scope of the GenData 2020 Project to enable multi-resolution analysis and mining of matches between genomic regions. In this paper we show how the GOLAM framework can be used for OLAP analysis of the mappings between regions and samples resulting from queries expressed in GMQL against repositories of genomic data. In particular we show the multidimensional schema that represents mappings and we briefly address the main research challenge implied by GOLAM, i.e., on-demand ETL.