8,972 research outputs found

    Wide-range optical spin orientation in Ge from near-infrared to visible light

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    Ge-based spin-photodiodes have been employed to investigate the spectral dependence of optical spin orientation in germanium, in the range 400-1550 nm. We found the expected maximum in the spin polarization of photocarriers for excitation at the direct gap in Γ (1550 nm) and a second sizable peak due to photogeneration in the L valleys (530 nm). Data suggest distinct spin depolarization mechanisms for excitation at Γ and L, with shorter spin relaxation times whether the X point is involved. These devices can be used as integrated photon-helicity detectors over a wide spectral range

    Evaluating space measures in P systems

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    P systems with active membranes are a variant of P systems where membranes can be created by division of existing membranes, thus creating an exponential amount of resources in a polynomial number of steps. Time and space complexity classes for active membrane systems have been introduced, to characterize classes of problems that can be solved by different membrane systems making use of different resources. In particular, space complexity classes introduced initially considered a hypothetical real implementation by means of biochemical materials, assuming that every single object or membrane requires some constant physical space (corresponding to unary notation). A different approach considered implementation of P systems in silico, allowing to store the multiplicity of each object in each membrane using binary numbers. In both cases, the elements contributing to the definition of the space required by a system (namely, the total number of membranes, the total number of objects, the types of different membranes, and the types of different objects) was considered as a whole. In this paper, we consider a different definition for space complexity classes in the framework of P systems, where each of the previous elements is considered independently. We review the principal results related to the solution of different computationally hard problems presented in the literature, highlighting the requirement of every single resource in each solution. A discussion concerning possible alternative solutions requiring different resources is presented

    Robot-assisted laparoscopic pyeloplasty (RALP) in children with horseshoe kidneys: results of a multicentric study

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    This multicentric study aimed to report our experience with robot-assisted laparoscopic pyeloplasty (RALP) in children with horseshoe kidney (HSK). METHODS: The records of 14 patients (11 boys and 3 girls with an average age of 9 years), who underwent RALP for repair of pelvi-ureteric junction obstruction (PUJO) in HSK in five international pediatric urology units over a 5-year period, were retrospectively reviewed. A dismembered pyeloplasty with no division of isthmus was performed in all the cases. RESULTS: The average operative time including docking was 143.5 min (range 100-205). No conversions to laparoscopy or open surgery or intra-operative complications occurred. Patients were discharged on postoperative day 2 following catheter and drain removal. The JJ stent was removed at mean 33 days postoperatively. Overall success rate was 92.8%. As for postoperative complications, we recorded a urinary tract infection (UTI) and stent-related irritative symptoms, managed with medical therapy, in two patients (II Clavien) and an anastomotic stricture in one patient needing surgical revision with no further recurrence (IIIb Clavien). At follow-up, all the patients (one after redo-surgery) reported complete resolution of symptoms, improvement of hydronephrosis on ultrasound and no residual obstruction on diuretic renogram. CONCLUSIONS: Our experience suggested that RALP in HSK is safe, feasible and with good medium-term outcomes in expert hands. An accurate pre-operative planning associated with a standardized technique is key points to achieve good surgical and functional outcomes in these challenging cases. The da Vinci robot technology offers the advantages of MIS procedures and overcomes the technical challenges of laparoscopic approach

    Versatile control of 9^9Be+^+ ions using a spectrally tailored UV frequency comb

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    We demonstrate quantum control of 9^9Be+^+ ions directly implemented by an optical frequency comb. Based on numerical simulations of the relevant processes in 9^9Be+^+ for different magnetic field regimes, we demonstrate a wide applicability when controlling the comb's spectral properties. We introduce a novel technique for the selective and efficient generation of a spectrally tailored narrow-bandwidth optical frequency comb near 313 nm. We experimentally demonstrate internal state control and internal-motional state coupling of 9^9Be+^+ ions implemented by stimulated-Raman manipulation using a spectrally optimized optical frequency comb. Our pulsed laser approach is a key enabling step for the implementation of quantum logic and quantum information experiments in Penning traps.Comment: Includes supplementary materia

    Electron-Phonon Coupling in High-Temperature Cuprate Superconductors Determined from Electron Relaxation Rates

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    We determined electronic relaxation times via pump-probe optical spectroscopy using sub-15 fs pulses for the normal state of two different cuprate superconductors.We show that the primary relaxation process is the electron-phonon interaction and extract a measure of its strength, the second moment of the Eliashberg function\lambda=800\pm200 meV^{2} for La_{1.85}Sr_{0.15}CuO_{4} and \lambda=400\pm100 meV^{2} for YBa_{2}Cu_{3}O_{6.5}. These values suggest a possible fundamental role of the electron-phonon interaction in the superconducting pairing mechanism.Comment: As published in PR

    Existence of the Bogoliubov S(g) operator for the (:Ď•4:)2(:\phi^4:)_2 quantum field theory

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    We prove the existence of the Bogoliubov S(g) operator for the (:Ď•4:)2(:\phi^4:)_2 quantum field theory for coupling functions gg of compact support in space and time. The construction is nonperturbative and relies on a theorem of Kisy\'nski. It implies almost automatically the properties of unitarity and causality for disjoint supports in the time variable.Comment: LaTeX, 24 pages, minor modifications, typos correcte

    The PACE study: past-year prevalence of tension-type headache and its subtypes in Parma's adult general population.

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    The mean global prevalence of tension-type headache (TTH) in adult is 42 %. To date, there have been no Italian studies on TTH prevalence in the adult general population. Therefore, we conducted a cross-sectional study, called PACE, aimed at detecting the prevalence of primary headaches in the city of Parma's adult general population. 904 subjects representative of Parma's adult general population were interviewed face to face by a physician of our Headache Centre. Crude past-year prevalence for definite TTH was 19.4 % (95 % CI 16.8-21.9; 18.4 %, 95 % CI 14.6-22.3 in men, and 20.1 %, 95 % CI 16.6-23.6 in women), namely, 9.0 % (95 % CI 7.1-10.8) for infrequent TTH, 9.8 % (95 % CI 7.9-11.8) for frequent TTH, and 0.6 % (95 % CI 0.1-1) for chronic TTH. Crude prevalence for probable TTH was 2.3 % (95 % CI 1.3-3.3; 2 %, 95 % CI 0.6-3.4 in men, and 2.6 %, 95 % CI 1.2-3.9 in women). Our results indicate a TTH prevalence (19.4 %) at the lower limit of data ranges for Western countries, and prevalence rates for infrequent forms (9 %) do not appear different from those of frequent forms (9.8 %)

    Bioecologia e sugestões para o Manejo da traça-dos-cachos em uva de vinho no Submédio do Vale do São Francisco.

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    bitstream/item/31860/1/Circular-Tecnica-93.pd

    Performances of a portable Fourier transform hyperspectral imaging camera for rapid investigation of paintings

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    Abstract: Scientific investigation in the cultural heritage field is generally aimed at the characterization of the constituent materials and the conservation status of artworks. Since the 1990s, reflectance spectral imaging proved able to map pigments, reveal hidden details and evaluate the presence of restorations in paintings. Over the past two decades, hyperspectral imaging has further improved our understanding of paints and of its changes in time. In this work, we present an innovative hyperspectral camera, based on the Fourier transform approach, utilising an ultra-stable interferometer and we describe its advantages and drawbacks with respect to the commonly used line- and spectral-scanning methods. To mitigate the weaknesses of the Fourier transform hyperspectral imaging, we propose a strategy based on the virtual extension of the dynamic range of the camera and on the design of an illumination system with a balanced emission throughout the spectral range of interest. The hyperspectral camera was employed for the analysis of a painting from the “Album of Nasir al-din Shah”. By applying analysis routines based on supervised spectral unmixing, we demonstrate the effectiveness of our camera for pigment mapping. This work shows how the proposed hyperspectral imaging camera based on the Fourier transform is a promising technique for robust and compact in situ investigation of artistic objects in conditions compatible with museum and archaeological sites. Graphic abstract: [Figure not available: see fulltext.
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