Attosecond pulses are central to the investigation of valence- and core-electron dynamics on their natural timescales
. The reproducible generation and characterization of attosecond waveforms has ...been demonstrated so far only through the process of high-order harmonic generation
. Several methods for shaping attosecond waveforms have been proposed, including the use of metallic filters
, multilayer mirrors
and manipulation of the driving field
. However, none of these approaches allows the flexible manipulation of the temporal characteristics of the attosecond waveforms, and they suffer from the low conversion efficiency of the high-order harmonic generation process. Free-electron lasers, by contrast, deliver femtosecond, extreme-ultraviolet and X-ray pulses with energies ranging from tens of microjoules to a few millijoules
. Recent experiments have shown that they can generate subfemtosecond spikes, but with temporal characteristics that change shot-to-shot
. Here we report reproducible generation of high-energy (microjoule level) attosecond waveforms using a seeded free-electron laser
. We demonstrate amplitude and phase manipulation of the harmonic components of an attosecond pulse train in combination with an approach for its temporal reconstruction. The results presented here open the way to performing attosecond time-resolved experiments with free-electron lasers.
Quantum mechanically, photoionization can be fully described by the complex photoionization amplitudes that describe the transition between the ground state and the continuum state. Knowledge of the ...value of the phase of these amplitudes has been a central interest in photoionization studies and newly developing attosecond science, since the phase can reveal important information about phenomena such as electron correlation. We present a new attosecond-precision interferometric method of angle-resolved measurement for the phase of the photoionization amplitudes, using two phase-locked extreme ultraviolet pulses of frequencyωand2ω, from a free-electron laser. Phase differencesΔη˜between one- and two-photon ionization channels, averaged over multiple wave packets, are extracted for neon2pelectrons as a function of the emission angle at photoelectron energies 7.9, 10.2, and 16.6 eV.Δη˜is nearly constant for emission parallel to the electric vector but increases at 10.2 eV for emission perpendicular to the electric vector. We model our observations with both perturbation and ab initio theory and find excellent agreement. In the existing method for attosecond measurement, reconstruction of attosecond beating by interference of two-photon transitions (RABBITT), a phase difference between two-photon pathways involving absorption and emission of an infrared photon is extracted. Our method can be used for extraction of a phase difference between single-photon and two-photon pathways and provides a new tool for attosecond science, which is complementary to RABBITT.
Intense, mutually coherent beams of multiharmonic extreme ultraviolet light can now be created using seeded free-electron lasers, and the phase difference between harmonics can be tuned with ...attosecond accuracy. However, the absolute value of the phase is generally not determined. We present a method for determining precisely the absolute phase relationship of a fundamental wavelength and its second harmonic, as well as the amplitude ratio. Only a few easily calculated theoretical parameters are required in addition to the experimental data.
Single-photon laser enabled Auger decay (spLEAD) is an electronic de-excitation process which was recently predicted and observed in Ne. We have investigated it using bichromatic phase-locked free ...electron laser radiation and extensive angle-resolved photoelectron measurements, supported by a detailed theoretical model. We first used separately the fundamental wavelength resonant with the Ne+ 2s-2p transition, 46.17 nm, and its second harmonic, 23.08 nm, then their phase-locked bichromatic combination. In the latter case the phase difference between the two wavelengths was scanned, and interference effects were observed, confirming that the spLEAD process was occurring. The detailed theoretical model we developed qualitatively predicts all observations: branching ratios between the final Auger states, their amplitudes of oscillation as a function of phase, the phase lag between the oscillations of different final states, and partial cancellation of the oscillations under certain conditions.
Free-electron lasers (FELs) can produce radiation in the short wavelength range extending from the extreme ultraviolet (XUV) to the X-rays with a few to a few tens of femtoseconds pulse duration. ...These facilities have enabled significant breakthroughs in the field of atomic, molecular, and optical physics, implementing different schemes based on two-color photoionization mechanisms. In this article, we present the generation of attosecond pulse trains (APTs) at the seeded FEL FERMI using the beating of multiple phase-locked harmonics. We demonstrate the complex attosecond waveform shaping of the generated APTs, exploiting the ability to manipulate independently the amplitudes and the phases of the harmonics. The described generalized attosecond waveform synthesis technique with an arbitrary number of phase-locked harmonics will allow the generation of sub-100 as pulses with programmable electric fields.
Background Internal carotid artery occlusion (ICAO) is defined as “untouchable” by all specialists; no treatment is indicated because intervention risks (carotid endarterectomy (CEA) or endovascular ...treatment) are usually much more than benefits.1,2 We report the case of a patient admitted to our hospital with an atherothrombotic ischemic stroke due to symptomatic acute ICAO, who developed a recurrent stroke with hemispheric hypoperfusion and was treated in the emergency department with ICAO revascularization after 60 days of occlusion finding. Case Description D.G., a 62-year-old man, came to our attention for a transient episode of left weakness and hypoesthesia. The electrocardiogram revealed a new diagnosis of atrial fibrillation. CT angiography showed right ICAO; computed tomography and magnetic resonance imaging studies with perfusion imaging revealed a severe hemispheric hypoperfusion. Full anticoagulation therapy was started, and antihypertensive therapy was reduced to help collateral circulation. Some weeks later, the patient was readmitted to the stroke unit for 2 episodes of left-hand weakness. Cerebral angiography confirmed right ICAO from the proximal tract to the siphon. After some days, the patient suffered a femoral hemorrhagic lesion, with active bleeding, and was treated with surgical intervention. On the following day, the patient presented with left hemiplegia with hemianesthesia (National Institutes of Health Stroke Scale score = 14). The patient was treated in the emergency department with a complex endovascular treatment with complete recanalization of ICAO by positioning 3 stents through the intravenous infusion of abciximab. After intensive rehabilitation, at the 3- and 6-month follow-up evaluations, the patient regained autonomy. Conclusion In literature, treatment of chronic ICAO is not indicated. Endovascular recanalization may be beneficial to patients with chronic cerebral hypoperfusion due to ICAO, when all conservative medical therapies have failed.
The essay deals with some related topics in the history of the architectural complex that constitutes the Ducal Palace of Mantua. In the mid-16th century Giovan Battista Bertani, “prefetto delle ...fabbriche”, started for Guglielmo Gonzaga, on pre-existences, the arrangement of the Corte Nuova Apartment, contiguous to that of Troy built by Giulio Romano in the thirties of the 16th century. Well known for its decorative and pictorial furnishings (the panels by Lorenzo Costa, the stuccos by Pirro Ligorio, and the Fasti Gonzagheschi – today in Monaco – by Tintoretto for the halls of the Marquis and Dukes), today the apartment appears bare and unadorned on the outside. A painting by Francesco Borgani (San Francesco in prayer, around 1618) allows to return the original aspect of the façade towards the lake, characterized by architectures (an order of giant pilasters, a pediment) made in trompe-l’oeil, a device widely used in the Ducal Palace of Mantua. At the end of 1580 Bernardino Facciotto undertook a “riforma del Prato di Castello”, first of all by building a corridor above the portico of the courtyard of honor. The corridor, passing over the moat of the Castle of San Giorgio, served as a link between the Corte Vecchia apartment (started in 1578) and the Corte Nuova one. In 1587 Facciotto arranged, in frieze at Corte Nuova, the “Baluardo della Palata”, of which only traces survive today, but well known through pictorial and cartographic sources; the bulwark constituted the mooring for the boats. In 1591 Jacopo Tintoretto obtained the position of “Capitano della Palata”, perhaps an expedient to honor an old debt contracted by the Gonzaga with the painter at the time of the realization of the Fasti (1578-1579).
Abstract Purpose The purpose of this study was to prospectively evaluate results and complications of percutaneous vertebroplasty (PV) performed in 6 different Italian Centres belonging to the ...European VErtebroplasty RESearch Team (E.VE.RES.T) in a large series of patients. Materials and methods Follow-up was obtained in 4547 patients (3211 females and 1336 males; mean age 70.2 years) that underwent PV for a total of 13.437 treated vertebrae. Procedures were performed by using fluoroscopic guidance or combined CT-fluoroscopic guidance. All patients underwent PV in local anaesthesia except for second cervical vertebrae treated with a trans-oral approach that required general anaesthesia. Results 4004 out of 4547 (88.0%) patients reported significant pain relief (difference > or = 2 point in pain evaluated with an 11-point visual analogue scale; p < 0.0001) within 48 h: an average of 7.7 ± 0.4 dropped to 1.8 ± 0.6 in the osteoporotic patients; 8.3 ± 0.4 to 2.4 ± 0.4 in metastases; 8.3 ± 0.4 to 1.7 ± 1.0 in myeloma; 6.2 ± 3.5 to 0.3 ± 0.2 in angioma and 7.4 ± 0.4 to 1.4 ± 0.9 in trauma. 430 osteoporotic patients (13%) were retreated for a subsequent fracture; in 302/430 patients (70.2%), the new fracture occurred in the contiguous vertebra. No major neurologic complications were reported and the most frequent minor complication was venous leakage (20.5%). Conclusions This large series of patients confirms that percutaneous vertebroplasty is an effective and safe procedure in the treatment of vertebral fractures. Best results are obtained in the treatment of myeloma and trauma.
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