Search

The application is described the synthetic function expansion (SFX) approach to large arrays of aperture-coupled antennas. The problem is formulated in terms of coupled magnetic-field continuity integral equations (MFCIE) and electric field integral equations (EFIE), and discretized via the method of moments (MoM). The SFX is a domain-decomposition technique; on each block of the broken-down structure, functions are generated with domain over the entire block. These ldquosynthetic functionsrdquo (SF) are obtained from the solution of the electromagnetic problem for the isolated block upon specification of appropriate sources on the block bounding box, and from a further singular value decomposition (SVD)-based procedure to select the relevant terms. The complete problem is solved using the SFs as basis functions for the MoM. This results in a strong reduction of the MoM matrix size. Applications are presented to configurations of open and cavity-backed radiators.

A study was conducted to investigate the antireflective properties of layers of GaP nanorods using wavelength- and angle-dependent transmission and reflection measurements. The broadband reduction of reflection was demonstrated by zero-order or direct transmission and specular reflection measurements. The nanorods were fabricated by chemical vapor deposition (CVD) using the VLS method. It was demonstrated that the enhanced transmission and reduced reflection of the layers was related to a graded refractive index in the nanorod layer. The enhanced direct transmission, along with the total transmission and reflection revealed that scattering and absorption were weak in these layers. It was observed that the antireflection behavior over a broad wavelength and angular range, along with low amount of light scattered improved the potential of the nanorod antireflection coatings for enhanced coupling in solar cells or for more efficient light extraction from light-emitting diodes (LEDs). U7 - Export Date: 2 August 2010 U7 - Source: Scopus

Background: The aim of the present study was to evaluate which of theclinico-angiographic parameters of acute ischemic extension and efficacy ofreperfusion in AMI treated with primary PCI are predictive of infarct size andone month left ventricular ejection fraction (LVEF).Patients and Method: Thirty-five patients with first AMI treated withprimary PCI underwent two rest 99mTc-sestamibi gated SPECT, 4-6 days and 30-40days after PCI. Clinical, electrocardiographic, angiographic and scintigraphicparameters for ischemic extent in acute phase, effective reperfusion,perfusional and kinetic outcome were collected.Results: There was a significant linear correlation among indices ofinitial ischemic extension and early perfusion defect and infarct size, whiletime to treatment (symptom onset to balloon) correlated with reperfusion indices(ST resolution, corrected TIMI frame count cTFC, myocardial perfusion grade MPG)and with late functional outcomes (smaller infarct size and better LVEF). A timeto treatment of

Auxiliary ICRF heating systems in tokamaks often involve large complex antennas, made up of several conducting straps hosted in distinct cavities that open towards the plasma. The same holds especially true in the LH regime, wherein the antennas are comprised of arrays of many phased waveguides. Upon observing that the various cavities or waveguides couple to each other only through the EM fields existing over the plasma-facing apertures, we self-consistently formulated the EM problem by a convenient set of multiple coupled integral equations. Subsequent application of the Method of Moments yields a highly sparse algebraic system; therefore formal inversion of the system matrix happens to be not so memory demanding, despite the number of unknowns may be quite large (typically 105 or so). The overall strategy has been implemented in an enhanced version of TOPICA (Torino Polytechnic Ion Cyclotron Antenna) and in a newly developed code named TOPLHA (Torino Polytechnic Lower Hybrid Antenna). Both are simulation and prediction tools for plasma facing antennas that incorporate commercial-grade 3D graphic interfaces along with an accurate description of the plasma. In this work we present the new proposed formulation along with examples of application to real life large LH antenna systems.

Slumped Glass Optics is a viable solution to build future X-ray telescopes. In our laboratories we use a direct hot slumping approach assisted by pressure, in which the glass optical surface is in contact with the mould, and a pressure is applied to enforce the replication of the mould shape on the glass optical surface. Several prototypes have been already produced and tested in X-rays, showing a continuous improvement in our technology. In this paper, we present the advances in our technology, in terms of slumped glass foils quality and expected performances upon an ideal integration. By using Eagle XG glass foils and Zerodur K20 for the slumping mould, we have fine tuned several process parameters: we present a critical analysis correlating the changes in the process to the improvements in different spatial frequency ranges encompassing the profile and roughness measurements. The use of a re-polished K20 mould, together with the optimized process parameters, lead to the latest result of glass foils with expected performance of less than 3 arcsec in single reflection at 1 keV X-ray energy. This work presents all the relevant steps forward in the hot slumping technology assisted by pressure, aimed at reaching angular resolutions of 5 arcsec for the whole mirror assembly.

Recent advancements in thin glass materials allowed the development and the mass production of very thin glass foils, like e.g. the Willow glass (thickness of 0.1-0.2 mm) produced by Corning or AF32 produced by Schott (thickness down to 0.055 mm). The thickness, strength and flexibility of these glass foils allow bending them up to very small radius of curvature without breaks. This feature, together with the very low micro-roughness, makes this kind of materials ideal candidates for pursuing a cold replication approach for cost-effective and fast making of grazing incidence astronomical optics. Starting from the very thin flat glass sheets, the process under development foresees to bond them onto the supporting structure while they are wrapped around reference mandrels. The assembly concept, based on the use of Wolter-I counter-form moulds, is also based on the use of reinforcing ribs that connect pairs of consecutive foils in the final assembly. The ribs do not only play the role of mechanical connectors, they keep the shape and increase the structural stiffness. Indeed, the ribs constrain the foil profile to the correct shape during the bonding, damping the low-frequency residuals with respect to the Wolter I configuration. This approach is particularly interesting because of their low weight and cost. They could e.g be used for the production of high throughput optics as those needed for the Chines XTP mission, in which the requirements on the angular resolution are not too tight. In fact, a Half Energy Width in the range of 20-60 arcsec is compatible with the expected residual error due to the spring back of the glass sheets. In this paper we provide an overview of the project, the expected performances and present the first preliminary results.

to assess in-hospital and long-term results of the novo unprotected left main (UPLM) percutaneous coronary intervention (PCI) in patients with acute coronary syndrome (ACS) or stable coronary artery disease (CAD), in an unselected population admitted to a single high- volume cathlab without on-site cardiac surgery.from 2008 to 2011, among 317 PCI performed in patients with the novo UPLM stenosis, 49 patients presented ST-elevation myocardial infarction (STEMI), 152 non ST-elevation MI/unstable angina (NSTEMI/UA), 116 stable CAD.in-hospital mortality was 20% in STEMI, 5.3% in NSTEMI/UA and 1.7% in stable CAD patients (p0.001). Two-year total mortality was 24.5%, 25.6% and 6% in the 3 groups, and cardiac death was 20%, 13.8% and 3.4% (p=0.002). Left main target lesion revascularization (TLR) was similar in the 3 groups, as the clinically- driven TLR (10% vs 11% vs 7.7% , p= 0.642), with neither definite nor probable stent thrombosis. Multivariate analysis showed the following independent predictors of 2-year mortality: bare-metal stent use (OR 4.53, p0.001), Syntax score32 (OR 3.53, p=0.012), ACS as the indication (OR 3.24, p=0.012), peripheral artery disease (OR 2.20, p=0.042), and age75 years (OR 2.09, p=0.05).our experience showed acceptable results of UPLM PCI in STEMI patients, where short-term prognosis was related to hemodynamic conditions, good results in NSTEMI/UA patients where mortality increased in the follow-up due to comorbidities, and very good results in patients with stable CAD.

The Slumped Glass Optics technology, developed at INAF/OAB since a few years, is becoming a competitive solution for the realization of the future X-ray telescopes with a very large collecting area, as e.g. the proposed Athena, with more than 2 m2 effective area at 1 keV and with a high angular resolution (5'' HEW). The developed technique is based on modular elements, named X-ray Optical Units (XOUs), made of several layers of thin foils of glass, previously formed by direct hot slumping in cylindrical configuration, and then stacked in a Wolter-I configuration, through interfacing ribs. The achievable global angular resolution of the optics relies on the surface shape accuracy of the slumped foils, on the smoothness of the mirror surfaces and on the correct integration and co-alignment of the mirror segments achieved with a dedicated Integration Machine (IMA). In this paper we provide an update of the project development, reporting on the last results achieved. In particular, we will present the results obtained with full illumination X-ray tests for the last developed prototypes.

This paper presents a new domain decomposition scheme for the analysis of structures in the Method of Moments context. The method is flexible in the sense that it allows the decomposition of complex structures according to the user needs, admitting tearing apart the structure into closed, open or closed-open portions (e.g. subdomains) without any limitation. Moreover, the use of Discontinuous Galerkin to enforce transmission conditions among the subdomains, permits both conformal/Non-conformal discretizations, decreasing in great manner the mesher burden, as for each subdomain can be discretized independently.

Background: In patients with primary hyperparathyroidism (pHPT) the therapeutical choice is surgery. In patients with high surgical and anesthetic risks, ultrasound-guided laser ablation (LTA) of parathyroid adenoma has been reported to reduce parathyroid hormone (PTH) hypersecretion without relevant side effects. No data are available from patients followed for >6 months. We report our 3-year follow-up experience with LTA in 3 patients affected by pHPT due to a parathyroid tumor. Methods: LTA was performed under color-Doppler ultrasound guidance with a continuous pulse at 2 W (total treatment duration: 300 s in each session; total energy: 1,200 J in two sessions). Results: In the first patient who refused to undergo the second LTA session, calcium, PTH levels and parathyroid lesion volume showed a slight reduction, returning to baseline values in a month. In the second patient, no modification of parathyroid lesion was obtained even if calcium levels temporarily normalized. In the third patient, LTA led to normalization of calcium and PTH levels and to a 99% reduction of parathyroid volume. Conclusion: After LTA procedures the long-term disease remission of pHPT is achievable in a minority of patients. Data from larger samples are needed to verify the usefulness of this procedure.

We report the fast switching capabilities of a two-dimensional Al0.3Ga0.7As photonic crystal slab around 1.5 μm. The slab is supported by an AlOx low-index thick layer that plays the role of an efficient heat sink. By pumping at 0.8 μm in the absorption of the Al0.3Ga0.7As quantum wells, the optical response is modified in the transparency region: a 200% change in the reflectivity is obtained with a total response time of 8ps.

Recent experimental and theoretical work on two-dimensional (2D) and waveguide-embedded photonic crystals is reviewed. The investigated systems are 2D macroporous silicon and photonic crystal slabs based on silicon-on-insulator as well as GaAs/AlGaAs. In all these structures, reflectance at varying angles of incidence allows to determine the dispersion of photonic modes above the light line. For macroporous silicon, reflectance from the side yields a complementary measurement of the photonic gaps. In the GaAs-based system, second-harmonic generation in reflection shows a resonant enhancement when the pump beam is frequency- and momentum-matched to a photonic mode in the slab. A theory of photonic states in waveguide-embedded photonic crystals leads to a determination of mode dispersion and diffraction losses for leaky photonic modes.

The present work has been developed within the frame of the EFDA task “HCD-08-03-01: LH4IT, EU contribution to the ITER LHCD Development Plan” The use of rectangular oversized waveguides in the Main Transmission Lines (MTLs) of the Lower Hybrid Current Drive (LHCD) system of ITER, requires to investigate the problem of bends. The high number of involved waveguides (from 24 to 48) must be also taken into account. Thus, it has to consider not only the best choice in terms of curved framework, but also the proper allocation of all the waveguides. In this context, the principal specifications that characterize the design of the bends are: a) to minimize the reflection of the fundamental TE10 mode; b) to maximize the transmission of the fundamental TE10 mode; c) to minimize the coupling between the TE10 mode and other spurious modes that propagate at 5 GHz. This paper presents an overview about the bend options, and it compares the performances of several frameworks analyzed by using the Finite Element Method (FEM) commercial software, HFSS®. First of all, simple circular trajectory curves with different angulations, are considered. Then, the so called Mitre Bends alternatives are deeply analyzed. These curves are studied by several authors in the mono-modal configuration, with different techniques but the propagation in an oversized environment is a topic not much attended in literature. The only design parameter of the simple circular trajectory bend is the bending radius, so that the design is not flexible; the Mitre Bend structure is at least more flexible than the previous one and it is of great interest to study this type of bend to check the possible advantages. Finally an innovative modified Mitre Bend solution based on a cascade of trapezoidal elements is proposed.

A 20 MW Lower Hybrid Current Drive system using an antenna based on the Passive Active Multijunction (PAM) concept is envisaged on ITER for steady state operation, including the current ramp-up phase. In the frame of an EFDA task, a conceptual design of such a system has been performed. This paper gives an insight of the mechanical analysis, modeling and design carried out on two elements of the antenna: the front face, and the RF windows which constitute the first tritium barrier. The front face of the antenna will have to withstand high heat and fast neutrons fluxes directly from the plasma. It will be actively cooled and present a beryllium coating upon ITER requirement. The main issues were to ensure a reasonable margin versus a maximum temperature fixed by safety concerns (650 °C for plasma facing beryllium), and to understand and assess resistance of the assembly while in operation. Analyses were conducted on some variants of this PAM. Manufacturing scenarios considering ITER requirements and involving various techniques (brazing, high isostatic pressure bonding, explosion bonding) were explored, and simulations over subsequent residual stresses were conducted. Analyses showed that surface temperatures do not exceed 500°C, and stresses should not affect the integrity of the antenna mouth. The RF window is a critical component since it also has a safety function. We planed to design a water cooled 5 GHz CW RF “pillbox” window capable of sustaining 500 kW of transmitted power. An RF optimization conducted on this concept allowed to combine good RF properties and low dielectric losses. It resulted in a maximum thermal stress in the ceramic of 31 MPa, well below the static fatigue limit of 50 MPa. The residual stresses resulting from the brazing methods involved in the manufacturing of this multi-material assembly (copper, copper alloys and ceramic) were also analyzed. Both studies allow us to move forward and focus on critical issues, such as manufacturing processes (beryllium, bonding techniques…) and R&D associated programs including test of mock-ups.

A very preliminary design of the Lower Hybrid Current Drive system for ITER was developed in the early years of the 2000's. Many parameters of the system were defined on the base of knowledge and technology of those times. Experimental results obtained in the last few years, like the successful tests of a PAM launcher on FTU and on Tore Supra have definitely indicated this concept as a possible candidate for the LHCD launcher for ITER. The successful development of a prototype klystron at 5GHz with a target RF power of 500kW CW has indicated this power as an upper limit for the present high vacuum electron tubes technology at this frequency. From the physics point of view the ITER operational scenarios have been well defined, while the last experiments have pointed out the effectiveness of the LHCD waves at high plasma density. All these results imposed a revision of the existing design of the LHCD system. The RF power limited to a maximum of 500kW per klystron has determined a new modularity of the whole system and of the PAM launcher. In addition a relatively shorter distance between klystrons and ITER machine suggested the possibility of using rectangular oversized waveguides, excited in the fundamental TE01 mode, for the realization of the Main Transmission Lines (MTLs). Therefore all the main microwave components of the system have been revised on these basis and different and more suitable solutions have been investigated. In particular this paper compares the performances of the two different MTLs, based respectively on circular and rectangular waveguides, describes the main components of the proposed rectangular MTL and analyzes their main microwave characteristics. Companion papers in this Conference cover all the other aspects of the updated design of the LHCD system for ITER. The present revision has been carried out in the frame of the EFDA task “HCD-08-03-01: EU Contribution to the ITER LHCD Development Plan (LH4IT)”.

Thin glass foils are considered good candidates to build a segmented X -ray telescope with effective area as large as 2 m 2 and angular resolution better than 5 arcsec . In order to produce thin glass mirror segments, we developed a direct hot slumping technique assisted by pressure, in which the shape of a mould is replicated onto the optical surface of the glass. In this paper we present the result obtained with AF32 ( by Schott) and EAGLE XG (by Corning) glass types. The selected mould material is Zerodur K20, as it does not require any anti -sticking layer and has a good matching , in terms of Coefficient of Thermal Expansion, with both glass types. Our group already pro duced a few prototypes, reaching angular resolution near 20 arcsec . In this work , relevant steps forward aimed at attaining a 5 arcsec angular r esolution are described, along with the tuning of f ew key parameters in the slumping process. The results obtain ed on a newly procured cylindrical Zerodur K20 mould are presented. Keywords: hot slumping, thin glass mirrors, Zerodur K20, X-ray astronomy, astronomical telescopes

At INAF-Astronomical Observatory of Brera a study is under way to explore the problems related to the ion beam figuring of full scale Zerodur hexagonal mirrors of M1 for the European Extremely Large Telescope (E-ELT), having size of 1.4 m corner to corner. During this study it is initially foreseen the figuring of a scaled down version mirror of the same material having size of 1 m corner to corner to assess the relevant figuring problems and issues. This specific mirror has a radius of curvature of 3 m, which allows for easy interferometric measurement. A mechanical support was designed to minimize its deformations due to the gravity. The Ion Beam Figuring Facility used for this study has been recently completed in the Brera Observatory and has a figuring area of 140 cm x 170 cm. It employs a Kaufman ion source having 50 mm grids mounted on three axis. This system has been designed and developed to be autonomous and self-monitoring during the figuring process. The software and the mathematical tools used to compute the dwell time solution have been developed at INAF-OAB as well. Aim of this study is the estimation and optimization of the time requested to correct the surface adopting strategies to mitigate the well-known thermal problems related to the Zerodur material. In this paper, the results obtained figuring the 1 m corner-to-corner test segment are reported.

Future X-ray telescopes with very large collecting area, like the proposed Athena with more than 2 m2 effective area at 1 keV, need to be realized as assemblies of a large number of X-ray optical units, named X-ray Optical Units (XOUs). The Brera Astronomical Observatory (INAF-OAB) is developing a new technology to manufacture these modular elements, compatible with an angular resolution of 5 arcsec HEW (Half-Energy-Width). This technique consists in stacking in a Wolter-I configuration several layers of thin foils of glass, previously formed by direct hot slumping. The achievable global angular resolution of the optics relies on the required surface shape accuracy of slumped foils, on the smoothness of the mirror surfaces and on the correct integration and co-alignment of the mirror segments operated trough a dedicated Integration Machine (IMA). In this paper we provide an overview of the project development, reporting on the very promising results achieved so far, including in-focus full illumination X-ray tests of the prototype (Proof of Concept, POC#2, integrated at the beginning of 2013) for which an HEW of 22.1’’ has been measured at Panter/MPE. Moreover we report on the on-going activities, with a new integrated prototype (PoC#3). X-ray test in pencil beam revealed that at least a segment between two external ribs is characterized by an HEW well below 10’’. Lastly, the overall process up-grade to go from 20 m to 12m focal length (to be compatible with Athena+ configuration) is presented.

Percutaneous mechanical thrombectomy (PMT) for treatment of clinically significant pulmonary embolism (PE) has been shown to be technically feasible and effective, aiming at thrombus resolution without increase in major bleeding. Despite its success, use of PMT in clinical practise has not become widespread, because it is challenging. Among several devices proposed, AngioJet rheolytic thrombectomy (ART) appears as the most effective and easy-to-use. We present the case of a 69-year-old woman who developed acute intermediate-risk PE, with right ventricular dysfunction and major myocardial necrosis, who was successfully treated by ART. The peculiarities of the case, toghether with the principles, tecnique and tips and tricks of ART, its effectiveness and potential complications are discussed.

We present an EFIE fast solver that is stable down to very low frequencies, for very dense meshes and multi-scale problems. The proposed approach uses a split-potentials formulation in association to a hierarchic pre-conditioner for the underlying low-rank fast factorization. Potential splitting prevents the numerical cancellation problem that undermines the effectiveness of the low-rank factorization, negatively impacting on the necessary factorization tolerance. The fast method presented in this work can be directly implemented into existing codes.

This paper reports the results of a 17-year-long follow-up covering 17 members of a family affected by multiple endocrine neoplasia (MEN) type 2A, first diagnosed in 1980. This family is enrolled in our screening program. The thyroid, parathyroid and adrenal glands of the family members were investigated using the most sophisticated and sensitive techniques which have become available during this period, and their DNA was genetically tested for detecting RET mutations. Thanks to the combination of these two approaches it was possible to confirm the diagnosis in the members concerned from the genetic point of view, and to achieve an early diagnosis in the young members of the last generation before the clinical onset of the disease. The detection of a RET mutation also prompted a prophylactic thyroidectomy in a four year-old boy, in a pre-tumoral stage of the disease. Lastly, evidence is provided that genetic analysis of the DNA of the chorionic villi can be carried out as a prenatal test during routine amniocentesis.

Spontaneous coronary artery dissection is a rare cause of acute ischemic coronary events and sudden cardiac death. It usually occurs in young women not experiencing traditional risk factors for coronary artery disease during pregnancy or postpartum period. The pathophysiology of spontaneous arterial dissection remains uncertain and the management may be challenging. Herein, we report a case of a 41-year woman with no apparent cardiovascular risk factors, who underwent a successfull in vitro fertilization and embryo transfer with a subsequent at term cesarean section of a twin pregnancy. Six days after delivery, she presented with anterior ST-segment elevation myocardial infarction. Coronary angiography revealed dissection of all three coronary arteries with involvement of left main stem, which was successfully treated with percutaneous coronary intervention and drug-eluting stents implantation. The peculiarities of the case, toghether with the treatment strategy and the clinical and angiographic six-month follow-up are discussed.

Detection of high-energy neutrinos from distant astrophysical sources will open a new window on the Universe. The detection principle exploits the measurement of Cherenkov light emitted by charged particles resulting from neutrino interactions in the matter containing the telescope. A novel multi-PMT digital optical module (DOM) was developed to contain 31 3-inch photomultiplier tubes (PMTs). In order to maximize the detector sensitivity, each PMT will be surrounded by an expansion cone which collects photons that would otherwise miss the photocathode. Results for various angles of incidence with respect to the PMT surface indicate an increase in collection efficiency by 30% on average for angles up to 45° with respect to the perpendicular. Ray-tracing calculations could reproduce the measurements, allowing to estimate an increase in the overall photocathode sensitivity, integrated over all angles of incidence, by 27% (for a single PMT). Prototype DOMs, being built by the KM3NeT consortium, will be equipped with these expansion cones.© 2013 IOP Publishing Ltd and Sissa Medialab srl.

A recent analysis of the Fermi Large Area Telescope data provided evidence for a high-intensity emission of high-energy gamma rays with a E-2 spectrum from two large areas, spanning 50° above and below the Galactic centre (the "Fermi bubbles"). A hadronic mechanism was proposed for this gamma-ray emission making the Fermi bubbles promising source candidates of high-energy neutrino emission. In this work Monte Carlo simulations regarding the detectability of high-energy neutrinos from the Fermi bubbles with the future multi-km3 neutrino telescope KM3NeT in the Mediterranean Sea are presented. Under the hypothesis that the gamma-ray emission is completely due to hadronic processes, the results indicate that neutrinos from the bubbles could be discovered in about one year of operation, for a neutrino spectrum with a cutoff at 100 TeV and a detector with about 6 km3 of instrumented volume. The effect of a possible lower cutoff is also considered. © 2012 Elsevier B.V. All rights reserved.

Second-harmonic (SH) radiation generated in reflection is measured from the surface of a two-dimensional triangular photonic crystal in a GaN layer. A very large SH enhancement is observed when the incident radiation is resonant with a leaky photonic mode. The potential of second-harmonic generation as a tool for photonic band mapping is also envisaged. The extended transparency window of III-nitride wide band gap semiconductors coupled with large nonlinearities is an appealing feature pointing toward light control and manipulation in photonic structures.

An efficient approach for the full-wave analysis of printed structures is presented. It is based on the use of vector multiresolution (MR) functions in conjunction with the impedance matrix compression (IMC) technique, which leads to a reduced set of iteratively selected basis functions. The multilevel structure of the functions makes the matrix compression possible and also allows its further sparsification, with the subsequent reduction of the computational time and the matrix memory occupancy. Numerical results confirm the efficiency of the technique.

We demonstrate the coupling of bright and dark Surface Lattice Resonances (SLRs), which are collective Fano resonances in 2D plasmonic crystals. As a result of this coupling, a frequency stop-gap in the dispersion relation of SLRs is observed. The different field symmetries of the low and high frequency SLR bands lead to pronounced differences in their coupling to free space radiation. Standing waves of very narrow spectral width compared to localized surface plasmon resonances are formed at the high frequency band edge, while subradiant damping onsets at the low frequency band edge leading the resonance into darkness. We introduce a coupled oscillator analog to the plasmonic crystal, which serves to elucidate the physics of the coupled plasmonic resonances and to estimate very high quality factors (Q>700) for SLRs, which are the highest known for any 2D plasmonic crystal., 13 pages (in preprint), 4 figures, 1 table

"In the frame of the EFDA task HCD-08-03-01, a 5 GHz Lower Hybrid system which should be able to deliver 20 MW CW on ITER and sustain the expected high heat fluxes has been reviewed. The design and overall dimensions of the key RF elements of the launcher and its subsystem has been updated from the 2001 design in collaboration with ITER organization. Modeling of the LH wave propagation and absorption into the plasma shows that the optimal parallel index must be chosen between 1.9 and 2.0 for the ITER steady-state scenario. The present study has been made with n|| = 2.0 but can be adapted for n|| = 1.9. Individual components have been studied separately giving confidence on the global RF design of the whole antenna. © 2011 Elsevier B.V. All Rights Reserved."

Domain-decomposition (DD) for Integral Equation can be achieved by aggregating standard basis functions into specialized basis functions on each sub-domain; this results in a strong compression of the MoM matrix, which allows an iteration-free (e.g., LU decomposition) solution also for electrically large problems. Fast matrix-vector product algorithms can be used in the matrix filling and compression process of the employed aggregate-functions approach: this hybrid approach has received considerable attention in recent literature. In order to quantitatively assess the performance, advantages and limitations of this class of methods, we start by proposing and demonstrating the use of the Adaptive Integral Method (AIM) fast factorization to accelerate the Synthetic Function eXpansion (SFX) DD approach. The method remains iteration free, with a significant boost in memory and time performances, with analytical predictions of complexity scalings confirmed by numerical results. Then, we address the complexity scaling of both stand-alone DD and its combined use with fast MoM; this is done analytically and discussed with respect to known literature accounts of various implementations of the DD paradigm, with nonobvious results that highlight needs and limitations, and yielding practical indications.

This work deals with the determination of the spatial phase distribution in a cesium fountain microwave cavity, taking into account functional requirements such as beam apertures and feeding holes, and the effect of imperfect metallic walls. >

Lattice surface modes in two-dimensional plasmonic crystals of metallic nanoantennas are sustained by the diffractive coupling between localized plasmon resonances. We have investigated experimentally the dispersion of these modes by combining variable-angle transmittance and reflectance spectroscopy. Transmittance spectra through plasmonic crystals reveal quality factors for these modes exceeding 150 in the near infrared, 30 times higher than the quality factor associated to localized plasmon resonances. We have derived the characteristic lengths of the lattice surface modes, distinguishing a regime in which the group velocity is reduced while the mode intensity is strongly confined near the nanoantennas and a regime in which the surface mode propagates over several unit cells of the plasmonic crystal.

TOPLHA (Torino Polytechnic Lower Hybrid Antenna) code is an innovative tool for the 3D/1D simulation of Lower Hybrid (LH) antennas, i.e. accounting for realistic 3D waveguides geometry and for accurate 1D plasma models, and without restrictions on waveguide shape, including curvature. This tool provides a detailed performances prediction of any LH launcher, by computing the antenna scattering parameters, the current distribution, electric field maps and power spectra for any user‐specified waveguide excitation. In addition, a fully parallelized and multi‐cavity version of TOPLHA permits the analysis of large and complex waveguide arrays in a reasonable simulation time. A detailed analysis of the performances of the proposed ITER LH antenna geometry has been carried out, underlining the strong dependence of the antenna input parameters with respect to plasma conditions. A preliminary optimization of the antenna dimensions has also been accomplished. Electric current distribution on conductors, electric field distribution at the interface with plasma, and power spectra have been calculated as well. The analysis shows the strong capabilities of the TOPLHA code as a predictive tool and its usefulness to LH launcher arrays detailed design.

We demonstrate that the emission of light by fluorescent molecules in the proximity of periodic arrays of nanoantennas or plasmonic crystals can be strongly modified when the arrays are covered by a dielectric film. The coupling between localized surface plasmon resonances and photonic states leads to surface modes which increase the density of optical states and improve light extraction. Excited dye molecules preferentially decay radiatively into these modes, exhibiting an enhanced and directional emission., Comment: 5 figures

High impedance surfaces or electromagnetic band gap (EBG) surfaces have proved themselves to be useful in wireless communications applications due to their unique characteristics such as no propagating surface wave support, no conduction of RF current for a given bandwidth, in‐phase electromagnetic reflection and non‐inverted image of the electric charge in front of them [1]. These characteristics make possible to design compact antennas achieving better performance in terms of radiation and input impedance. ICRF and LH antennas in plasma experiments can take advantage of using EBG surfaces. One of the main issues in ICRF plasma heating is the low power coupling of the plasma facing antenna. The adoption of EBG surfaces in the ICRF antenna structure and the advantages offered by a predictive designing tool as TOPICA [2] offer the possibility to improve significantly the coupled power to plasma. The adoption of EBG surfaces in the LH waveguides permits to reduce the major dimension of waveguides not affect...

This work demonstrates pulsed and continuous-wave (cw) operations of photonic band-edge lasers at telecom wavelength (1.55 μm). This InP-based two-dimensional photonic crystal (2DPC) laser is integrated over a silicon wafer, opening new perspectives towards practical silicon-based photonics.

Study of novel radiating geometries and availability of accurate analysis tools have had a contribution in the explosive growth of mobile communications by enabling highly functional and aesthetic devices bearing low cost radiating structures. A critical consideration in the design of antennas for mobile terminals is the impact of different operational scenarios on performance. The importance of characterizing those effects is clear; however, conducting such a study is difficult and time-consuming since each operational scenario must be modeled accurately and presents in principle a completely different (and usually much more complex) electromagnetic problem. Even more complicated is the consideration of such effects at design stage given its iterative nature.This work presents an approach to environment-aware optimization of compact antennas, in which the performance of candidate structures under a number of operational scenarios is evaluated at the design stages. The approach builds upon a previously published work (J.L. Araque Quijano, 2006), and to our knowledge constitutes a study not performed elsewhere. This work takes advantage of the genetic algorithm in conjunction with an efficient MoM implementation to attack the difficult problem of optimizing antenna shape in the quest of good performance for the various environments considered.

The aim of this study was to assess the safety of direct coronary stenting, its influence on costs, duration of the procedure, radiation exposure, clinical outcome and the incidence of periprocedural myocardial damage as assessed by enzyme release determination.We randomized 103 patients (109 lesions) to direct stent implant or stent implant following balloon predilatation. Patients with heavily calcified lesions, bifurcations, total occlusions, left main lesions and very tortuous vessels were excluded. Three samples of blood were drawn; before, 12 and 24 h after the procedure and total CK, CK MB mass and troponin I determination was carried out in a single centralized laboratory.Direct stenting was successful in 62/62 lesions (100%). No single loss or embolization of the stent occurred. All stents in the group with predilatation were effectively deployed. The immediate post procedure angiographic results were similar with both techniques. Contrast media consumption and procedural time were significantly lower in direct stenting (150+/-82 cc and 30+/-13 min) than in pre-dilated stenting (184+/-85 cc and 36+/-14 min) (P=0.04 and P=0.036 respectively) while fluoroscopy time was similar (9.1+/-12 vs 9.19+/-15 min, P=0.97). The incidence of enzyme release was similar in the groups with only three non Q MI all in the pre-dilated group (P=0.149). Any elevation of CK MB and troponin I occurred in 7% of direct stent vs 12% of pre-dilated group (P=0.66), isolated troponin I elevation in 21% of both groups. Major adverse cardiac events during hospitalization were 0 in direct and 3 in pre-dilated stenting (P=0.66), but there were no significant differences at follow-up at 1, 6 and 12 months between the 2 groups (target lesion revascularization at 12 months 11 vs 14% in the 2 groups respectively).Direct stenting is as safe as pre-dilated stenting in selected coronary lesions. Acute results and myocardial damage as assessed by enzyme release determination are similar, but procedural costs (as measured by resource consumption) and duration of the procedure are lower in direct stenting. Overall success rate and mid-term clinical outcome are similar with both techniques.

We present continuous-wave laser operation at room temperature at 1.55 μm by optically pumping a photonic crystal structure containing an InGaAs/InP quantum well active layer. The active layer is integrated onto a Silicon chip by means of Au/In bonding technology. This metallic layer provides the reduction of heating by thermal dissipation into the substrate, and increases the quality-factor by reducing the radiative losses.

We manufactured an optically active InP-on-insulator structure using spin-on-glass bonding. A ninefold improvement of photoluminescence was obtained by patterning a photonic crystal with graphite lattice into the InP layer.

In recent years electromagnetic (RF) plasma generation and acceleration concepts for plasma-based propulsion systems have received growing interest, inasmuch as they can yield continuous thrust as well as highly controllable and wide-ranging exhaust velocities. The acceleration units mostly adopt the Ion Cyclotron Resonance Frequency (ICRF)—a proven technology in fusion experiments for transferring large RF powers into magnetized plasmas, and also used by the VASIMR propulsion system. In this work we propose and demonstrate the use of TOPICA code to design and optimize the ICRF antenna of a typical acceleration stage. To this end, TOPICA was extended to cope with magnetized cylindrically-symmetric radially-inhomogeneous warm plasmas, which required coding a new module charged with solving Maxwell’s equations within the plasma to obtain the relevant Green’s function ~Y(m;kz) in the Fourier domain, i.e. the relation between the transverse magnetic and electric fields at the air-plasma interface. Then, calculating the antenna input impedance—and hence the loading—relies on an integral-equation formulation and subsequent finite-element weighted-residual solution scheme for the self-consistent evaluation of the current density distribution on the conducting bodies and at the air-plasma interface.

TOPICA (Torino Polytechnic Ion Cyclotron Antenna) code is an innovative tool for the 3D/1D simulation of Ion Cyclotron Radio Frequency (ICRF) antennas, i.e. accounting for realistic 3D antenna geometries and for accurate 1D plasma models. The tool calculates the antenna input parameters at the feeding ports given the exact port excitation. Moreover, it calculates the current distribution and electric field maps wherever specified. The recent upgraded parallelized version of TOPICA permits the analysis of large and complex antenna structures in a reasonable simulation time (less than one day). A detailed analysis of the performances of two ITER ICRF antenna geometries has been carried out, underlining the strong dependence and the asymmetries of the antenna input parameters due to plasma conditions. An optimization of the antenna dimensions has also been accomplished. Electric current distribution on conductors in the vacuum region and electric field distribution in the vacuum region and at the interface with plasma edge have been calculated as well. The analysis shows the strong capabilities of the parallelized TOPICA code as a predictive tool and its usefulness to ICRF antennas final design.

Matrices arising from field problems generally have very wide eigenvalue spectra, and therefore the use of a suitable preconditioner becomes necessary to reduce the total solution time, especially when the mesh is dense, as typical in antenna and circuit problems. In this paper, the preconditioning issue is addressed by having recourse to the multiresolution (MR) scheme that manages to generate "wavelet-like" hierarchical multiscale vector functions for any meshed geometry and well controls the method-of-moments (MoM) condition number, by the simple application of a diagonal preconditioner. The MR functions are expressed in terms of sub-domain functions, therefore their generation leads to the construction of a changing basis matrix T that is very sparse, and therefore it has a low memory occupation and its multiplication for any matrix in the RWG basis is low cost. For this reason, the computational cost required for the construction and the application of the MR preconditioner is very low and smaller than the one needed for the application of other preconditioners

This communication proposes the integration of the MAGMAS code with the multi-resolution (MR) approach described in F. Vipiana et al. (2005); the latter can be viewed, inter alia, as a powerful pre-conditioner. The MR scheme essentially consists in the generation and use of vector basis functions, applicable to the analysis of planar and/or 3D antennas, having properties similar to those of scalar wavelet. In particular the MR functions are spectrally localized and this allows the control of the condition number of the MoM matrix in the MR basis simply by application of a diagonal preconditioner. The MR approach leads to the construction of a basis transformation matrix, very sparse and frequency independent, whose rows express the MR functions as a linear combination of the RWG functions defined on the same mesh. For this reason the MR scheme could be quite easily integrated with other MoM-based codes that used the same sub-domain (RWG in the specific case of a triangular mesh) functions to represent the unknown current. The considerations offered in this contribution about the integration of the MR basis into an existing code make obvious reference to the MAGMAS code, but their validity extends to virtually all MoM codes.

Ultrafast optical bistability is demonstrated at 1550 nm in an InP-based two-dimensional photonic crystal distributed resonator. A low intensity threshold of 4 kW/cm2 is observed, with a contrast of 65% between the high and low reflectivity states.

Fast switching is demonstrated on a two dimensional Al/sub 0.3/Ga/sub 0.7/As photonic crystal slab around 1.5 /spl mu/m. An AlO/sub x/ slab ensures efficient heat sink. A 200% change in the reflectivity is obtained with a recovery time of 8 ps.

Two-dimensional photonic crystals etched into GaAs/AlGaAs waveguides have been investigated by means of second-harmonic generation (SHG) from the surface of the samples. 130-fs laser pulses from a tunable Ti:sapphire source at 800 nm and from an optical parametric oscillator in the range 1.4-1.6 micron have been chosen to excite SH signals in reflection and diffraction directions. Their observed behavior reflects the GaAs crystalline symmetry and the photonic crystal structure, respectively.

The second-harmonic field generated has been measured in reflection from the surface of one-dimensional and two-dimensional photonic crystals etched into a GaN layer. A very large second-harmonic enhancement is observed when simultaneously the incident beam at the fundamental frequency w excites a resonant Bloch mode and the second-harmonic field generated is coupled into a resonant Bloch mode at 2w. A smaller, but still substantially enhanced, second-harmonic generation level was also observed when the fundamental field was coupled into a resonant mode, while the second-harmonic field was not. By using calculated and experimental equifrequency surfaces, it is possible to identify the geometrical configurations that will allow quasi-phase matching to be satisfied - and observed experimentally in the available wavelength tuning range of the laser. The extended transparency window of III-nitride wide-bandgap semiconductors, coupled with large non linearities, is an appealing feature pointing towards the control and manipulation of light in photonic structures.