Attosecond pulse shaping using a seeded free-electron laser.

Attosecond pulses are central to the investigation of valence- and core-electron dynamics on their natural timescales1-3. The reproducible generation and characterization of attosecond waveforms has been demonstrated so far only through the process of high-order harmonic generation4-7. Several methods for shaping attosecond waveforms have been proposed, including the use of metallic filters8,9, multilayer mirrors10 and manipulation of the driving field11. 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 millijoules12,13. Recent experiments have shown that they can generate subfemtosecond spikes, but with temporal characteristics that change shot-to-shot14-16. Here we report reproducible generation of high-energy (microjoule level) attosecond waveforms using a seeded free-electron laser17. 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.

Wave packet dynamics and control in excited states of molecular nitrogen.

Wave packet interferometry with vacuum ultraviolet light has been used to probe a complex region of the electronic spectrum of molecular nitrogen, N2. Wave packets of Rydberg and valence states were excited by using double pulses of vacuum ultraviolet (VUV), free-electron-laser (FEL) light. These wave packets were composed of contributions from multiple electronic states with a moderate principal quantum number (n ∼ 4-9) and a range of vibrational and rotational quantum numbers. The phase relationship of the two FEL pulses varied in time, but as demonstrated previously, a shot-by-shot analysis allows the spectra to be sorted according to the phase between the two pulses. The wave packets were probed by angle-resolved photoionization using an infrared pulse with a variable delay after the pair of excitation pulses. The photoelectron branching fractions and angular distributions display oscillations that depend on both the time delays and the relative phases of the VUV pulses. The combination of frequency, time delay, and phase selection provides significant control over the ionization process and ultimately improves the ability to analyze and assign complex molecular spectra.

Time-resolved photoelectron imaging of complex resonances in molecular nitrogen.

We have used the FERMI free-electron laser to perform time-resolved photoelectron imaging experiments on a complex group of resonances near 15.38 eV in the absorption spectrum of molecular nitrogen, N2, under jet-cooled conditions. The new data complement and extend the earlier work of Fushitani et al. [Opt. Express 27, 19702-19711 (2019)], who recorded time-resolved photoelectron spectra for this same group of resonances. Time-dependent oscillations are observed in both the photoelectron yields and the photoelectron angular distributions, providing insight into the interactions among the resonant intermediate states. In addition, for most states, we observe an exponential decay of the photoelectron yield that depends on the ionic final state. This observation can be rationalized by the different lifetimes for the intermediate states contributing to a particular ionization channel. Although there are nine resonances within the group, we show that by detecting individual photoelectron final states and their angular dependence, we can identify and differentiate quantum pathways within this complex system.

Complete Characterization of Phase and Amplitude of Bichromatic Extreme Ultraviolet Light.

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.

Electron spectroscopic study of nanoplasma formation triggered by intense soft x-ray pulses.

Using electron spectroscopy, we investigated the nanoplasma formation process generated in xenon clusters by intense soft x-ray free electron laser (FEL) pulses. We found clear FEL intensity dependence of electron spectra. Multistep ionization and subsequent ionization frustration features are evident for the low FEL-intensity region, and the thermal electron emission emerges at the high FEL intensity. The present FEL intensity dependence of the electron spectra is well addressed by the frustration parameter introduced by Arbeiter and Fennel [New J. Phys. 13, 053022 (2011)].

"Opening the Unopenable": Endovascular Treatment in a Patient with Three Months' Internal Carotid Artery Occlusion and Hemispheric Symptomatic Hypoperfusion.

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.

HHG at the Carbon K-Edge Directly Driven by SRS Red-Shifted Pulses from an Ytterbium Amplifier.

In this work, we introduce a simplified approach to efficiently extend the high harmonic generation (HHG) cutoff in gases without the need for laser frequency conversion via parametric processes. Instead, we employ postcompression and red-shifting of a Yb:CaF2 laser via stimulated Raman scattering (SRS) in a nitrogen-filled stretched hollow core fiber. This driving scheme circumvents the low-efficiency window of parametric amplifiers in the 1100-1300 nm range. We demonstrate this approach being suitable for upscaling the power of a driver with an optimal wavelength for HHG in the highly desirable XUV range between 200 and 300 eV, up to the carbon K-edge. Due to the combination of power scalability of a low quantum defect ytterbium-based laser system with the high conversion efficiency of the SRS technique, we expect a significant increase in the generated photon flux in comparison with established platforms for HHG in the water window. We also compare HHG driven by the SRS scheme with the conventional self-phase modulation (SPM) scheme.

Tympanoplasty: an up-to-date pictorial review.

The indications for tympanoplasty are mainly chronic ear pathologies, such as cholesteatoma, atelectasis and chronic tympanosclerotic otitis. Usually, modification of the mastoid and temporal tissues in general mostly involves bone work, which means bone removal by burs or appropriate bone curettes. It is for this reason that, in both the pre- and postoperative periods, the computed tomography (CT) scan is the primary radiological tool for studying the middle-ear, and temporal bone structures and pathologies. The aim of this review is to illustrate the most up-to-date postoperative results for tympanoplasty, including the emerging endoscopic techniques. The present work focuses on the five types of tympanoplasty that are likely to be encountered by the radiologist: radical surgery; open tympanoplasty; closed tympanoplasty; closed endoscopic tympanoplasty; and open endoscopic tympanoplasty. Understanding and interpreting temporal bone images in relation to the different types of surgery are important, especially at the postoperative stage, because of the high risk of recurrence of middle-ear pathologies, and a good working knowledge of surgical changes is fundamental for distinguishing iatrogenic bone demolition from complications and new pathological foci.

Vertebral augmentation: 7 years experience.

Percutaneous vertebroplasty and kyphoplasty are procedures used to treat pain associated with vertebral compression fractures. Controversies are still open regarding indications, efficacy and safety of the procedures, and regarding the potential benefits, advantages and shortcomings of PV versus KP.Aim of this article is to report 7 years' experience in vertebral augmentation of the E.VE.RES.T. (European VErtebroplasty RESearch Team) group. The main topics are the treatments of hemangioma and malignant lesions, technically challenging cases such as vertebra plana, multifragmented fractures, multilevel treatments, refracture of augmented vertebra, and treatment of cervical junction and sacrum.

Symptomatic anterior cerebral artery vasospasm after brainstem hemangioblastoma resection. A case report.

Diffuse cerebral vasospasm is a rare complication after brain tumour resection as opposed to that following an aneurysmal subarachnoid haemorrhage. Sellar tumours are among the most common pathologies and locations associated with this complication. Removal of posterior cranial fossa lesions is uncommonly associated with vasospasm, with only nine reported cases. We describe a case of diffuse symptomatic vasospasm mainly involving the right anterior cerebral artery, angiographically confirmed, after resection of a haemangioblastoma of the medulla in an adult patient with von Hippel-Lindau disease. The possible pathogenesis of this phenomenon is discussed.

Intra-arterial therapy as a rescue strategy after clinically failed intravenous thrombolysis may increase the likelihood of a good outcome in patients with severe ischaemic stroke. A retrospective two centre study.

The purpose of this study was to evaluate the efficacy and safety of intra-arterial therapy as a rescue strategy after clinically failed intravenous thrombolysis (IVT) in acute ischaemic stroke patients. We conducted a retrospective analysis of consecutive acute ischaemic stroke patients treated with rescue therapy. The results from this study group were compared with those obtained from a control group consisting of 260 consecutive patients treated with IVT alone. The study group consisted of 52 patients with a mean age of 63 years and a median NIHSS score at admission of 17. Recanalization was achieved in 92% with a symptomatic haemorrhage rate of 9.6%. Rescue patients admitted with a severe stroke (NIHSS score >12) had a significantly better outcome at 90 days compared to patients with the same score but treated with IVT alone. No difference was seen for patients with a lower score at admission. This study indicates that rescue therapy may increase the proportion of patients with independent outcome if presenting with a severe stroke (NIHSS score >12) without increasing the rate of symptomatic haemorrhage.

Percutaneous vertebroplasty: multi-centric results from EVEREST experience in large cohort of patients.

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.

Clinical results of an open prospective study of a bis-GMA composite in percutaneous vertebral augmentation.

In this open prospective trial, 53 patients with acute pain from osteoporotic vertebral fracture related to osteoporosis or malignancy underwent vertebral augmentation with a new bisphenol-a-glycidyl dimethacrylate (bis-GMA) resin (Cortoss, Orthovita, Malvern, Pa, USA). Treatment consisted of up to 8 ml of Cortoss injected into a given vertebra. The procedure encompassed single and multiple injections (including the contralateral hemivertebra, to a maximum of 3 vertebral levels). Follow-up was at 4 and 8 days and at 1, 3, and 6 months. The primary efficacy end point was patient-rated pain using a 100-point visual analog scale (VAS, with 100 as severest pain) on day 4 following treatment; secondary end points were analgesic use and quality-of-life and disability scores from the Oswestry Disability Index (ODI) and a short-form 12-item questionnaire (SF-12). The present report contains interim results collected up to the 1-month post-treatment time point. At baseline, the group's mean VAS score was 69, indicating moderate to severe pain; at day 4, 32 of 53 patients (60.4%) reported a 30% or greater reduction in baseline pain accompanied by a VAS pain score less than 50 (mean 38.1). Pain reduction was maintained at 1 month (mean VAS 31.3). The average ODI score at baseline was 55, suggesting significant disability among participants prior to Cortoss treatment. Following treatment, the ODI scores were significantly reduced from these baseline levels (day 8, 47.4; 1 month, 33.6). Further, SF-12 physical and mental component scores at 1 month after treatment increased from baseline by 26% and 11%, respectively; while analgesic use decreased concomitantly, primarily among patients with underlying osteoporosis. A total of 20 adverse events were deemed to be device-related. The most frequent clinically significant adverse events attributed to Cortoss were leakage of Cortoss from within the vertebral body at placement (12%), back pain (7%), and unspecified pain (7%). These results indicate that vertebral augmentation with Cortoss rapidly reduces pain, decreases disability, and improves physical functioning in patients with painful vertebral compression fractures.