70 mJ nonlinear compression and scaling route for an Yb amplifier using large-core hollow fibers.

In this Letter, we investigate the energy-scaling rules of hollow-core fiber (HCF)-based nonlinear pulse propagation and compression merged with high-energy Yb-laser technology, in a regime where the effects such as plasma disturbance, optical damages, and setup size become important limiting parameters. As a demonstration, 70 mJ 230 fs pulses from a high-energy Yb laser amplifier were compressed down to 40 mJ 25 fs by using a 2.8-m-long stretched HCF with a core diameter of 1 mm, resulting in a record peak power of 1.3 TW. This work presents a critical advance of a high-energy pulse (hundreds of mJ level) nonlinear interactions platform based on high energy sub-ps Yb technology with considerable applications, including driving intense THz, X-ray pulses, Wakefield acceleration, parametric wave mixing and ultraviolet generation, and tunable long-wavelength generation via enhanced Raman scattering.

Observation and Control of Laser-Enabled Auger Decay.

Single-photon laser-enabled Auger decay (spLEAD) is predicted theoretically [B. Cooper and V. Averbukh, Phys. Rev. Lett. 111, 083004 (2013)PRLTAO0031-900710.1103/PhysRevLett.111.083004] and here we report its first experimental observation in neon. Using coherent, bichromatic free-electron laser pulses, we detect the process and coherently control the angular distribution of the emitted electrons by varying the phase difference between the two laser fields. Since spLEAD is highly sensitive to electron correlation, this is a promising method for probing both correlation and ultrafast hole migration in more complex systems.

Time-Resolved Measurement of Interatomic Coulombic Decay Induced by Two-Photon Double Excitation of Ne_{2}.

The hitherto unexplored two-photon doubly excited states [Ne^{*}(2p^{-1}3s)]_{2} were experimentally identified using the seeded, fully coherent, intense extreme ultraviolet free-electron laser FERMI. These states undergo ultrafast interatomic Coulombic decay (ICD), which predominantly produces singly ionized dimers. In order to obtain the rate of ICD, the resulting yield of Ne_{2}^{+} ions was recorded as a function of delay between the extreme ultraviolet pump and UV probe laser pulses. The extracted lifetimes of the long-lived doubly excited states, 390(-130/+450) fs, and of the short-lived ones, less than 150 fs, are in good agreement with ab initio quantum mechanical calculations.

Slow Interatomic Coulombic Decay of Multiply Excited Neon Clusters.

Ne clusters (∼5000 atoms) were resonantly excited (2p→3s) by intense free electron laser (FEL) radiation at FERMI. Such multiply excited clusters can decay nonradiatively via energy exchange between at least two neighboring excited atoms. Benefiting from the precise tunability and narrow bandwidth of seeded FEL radiation, specific sites of the Ne clusters were probed. We found that the relaxation of cluster surface atoms proceeds via a sequence of interatomic or intermolecular Coulombic decay (ICD) processes while ICD of bulk atoms is additionally affected by the surrounding excited medium via inelastic electron scattering. For both cases, cluster excitations relax to atomic states prior to ICD, showing that this kind of ICD is rather slow (picosecond range). Controlling the average number of excitations per cluster via the FEL intensity allows a coarse tuning of the ICD rate.

Long-term prospective study of osteoporotic patients treated with percutaneous vertebroplasty after fragility fractures.

SUMMARY: This paper presents a prospective study on factors that could influence fracture risk after percutaneous vertebroplasty (PVP) in 115 osteoporotic patients. The mean follow-up was 39 months. The incidence of new fractures after PVP was 27.8%. Low body mass index (BMI), bone mineral density (BMD), and vitamin D are factors associated with increased risk of new fractures. INTRODUCTION: The purpose of this study was to evaluate factors that could increase the occurrence of new vertebral fractures (VFx) after PVP. METHODS: In our prospective study, we included patients of both sexes with osteoporosis (OP) and at least one painful VFx. We performed a baseline biochemical evaluation (including vitamin D plasma levels) and collected demographic, BMD, and clinical data. One hundred fifteen patients were treated with PVP and assigned to oral bisphosphonates plus Ca and vitamin D. The patients returned to control visits after 1, 3, and 6 months and every 6 months thereafter. X-rays film of the dorsolumbar spine was repeated every 12 months, or in case of pain that would suggest VFx occurrence. RESULTS: The mean follow-up was 39 ± 16 months (range, 15-79). Thirty-two patients (27.8%) had new fragility VFx, all symptomatic. All the fractured patients agreed to undergo a new PVP. We compared the patients who had new VFx to those who had not, and we found significantly lower BMI, total hip, and femoral neck T-scores in the group with new VFx. Furthermore, baseline plasma levels of 25(OH) vitamin D (25(OH)D) were significantly lower in this group. Upon analyzing plasma levels of 25(OH)D 12 months after PVP, we found that a significant difference still persisted: 22 ± 12 (group with new VFx) vs. 41 ± 22 ng/ml (group with no VFx; p < 0.01). CONCLUSION: We found that in patients with OP treated with PVP, the incidence of new VFx was 27.8% after 39 months; low BMI, BMD, and vitamin D are factors associated with increased risk of new VFx in patients treated with PVP.

Polarization shaping of high-order harmonics in laser-aligned molecules.

The present work reports on the generation of short-pulse coherent extreme ultraviolet radiation of controlled polarization. The proposed strategy is based on high-order harmonics generated in pre-aligned molecules. Field-free molecular alignment produced by a short linearly-polarized infrared laser pulse is used to break the isotropy of a gas medium. Driving the aligned molecules by a circularly-polarized infrared pulse allows to transfer the anisotropy of the medium to the polarization of the generated harmonic light. The ellipticity of the latter is controlled by adjusting the angular distribution of the molecules at the time they interact with the driving pulse. Extreme ultraviolet radiation produced with high degree of ellipticity (close to circular) is demonstrated.

Gadolinium-enhanced nerve roots in lumbar disk herniation.

PURPOSE: To analyze contrast-enhanced features of intrathecal nerve roots in lumbar disk herniation in patients who have not had surgery and to evaluate the possible correlation with herniated disk, peridiscal enhancement, and symptomatology. METHODS: Twenty patients with a syndrome of lumbar herniated disk without surgery were studied with pre- and postcontrast MR imaging. RESULTS: In six patients (30%), ipsilateral intradural roots affected with large disk herniations showed consistent enhancement along their whole length, from the site of compression to the root-medullary junction. This enhancement persisted on delayed scanning. "Selective" enhancement differed from the minimal enhancement seen in normal intrathecal roots in 11 (55%) patients. Enhancement around herniated disks was a common finding (92% of patients) and did not correlate with selective or normal root enhancement (P > .05). No symptom differences were found among patients with and without selective enhancement. CONCLUSION: Selective intrathecal root enhancement seems to be the direct visualization of the radiculopathy resulting from disk herniation. It is probably a transient event more likely to be noted in the acute phase. Although there is no evidence of immediate clinical utility of this finding, gadolinium-enhanced MR gives insights into the basic pathophysiologic alterations involved in degenerative disk disease.

Leptomeningeal carcinomatosis presenting as progressive multineuritis: clinical, pathologic, and MRI study.

Two patients developed a persistent illness characterized clinically and electrophysiologically by asymmetric involvement of spinal roots, of cranial and peripheral nerves. In the first case the disease was not discovered clinically but only after autopsy. The primary neoplasm remained undetected at autopsy. There was profound infiltration of the leptomeninges by tumor cells with features of metastatic adenocarcinoma. In the second patient onset of neurological symptoms occurred 16 years after surgery for breast cancer, which may be reasonably considered the primary malignancy-CSF cytology was positive only in the second patient in whom Gd-DTPA MRI supported the diagnosis. Our cases demonstrate that diagnosis in leptomeningeal carcinomatosis may be a challenging clinical problem.

[Transitory ischemic attacks, migraine and progestogen drugs. Etiopathogenetic correlations]. / Attacchi ischemici transitori, emicrania e progestinici. Correlazioni etiopatogenetiche.

Two cases of transitory ischaemic attacks, which occurred during progestogen therapy, are reported. Clinical history and symptoms of both patients suggested migraine disorder. Therefore, the hypothesis is made that also progestogen-only preparations, likewise oestrogen-progestogen oral contraceptives, may cause neurological troubles by vasomotor mechanisms.

A compact collinear polarization gating scheme for many cycle laser pulses.

We demonstrate the generation of a broadband coherent continuum extreme-ultraviolet (XUV) radiation produced by the interaction of gases with a many-cycle infrared (IR) laser field, utilizing a compact collinear many cycle-polarization gating (CMC-PG) device. The spectral width of the XUV radiation can support isolated pulses of 200 asec duration. The CMC-PG device forms a high energy content ultra-short temporal gate in a many-cycle laser pulse, within which the XUV emission is taking place. The gate width has been measured and is in agreement with the theoretical calculations. The simplicity, the compactness, the long term stability, and the high IR energy output within the gate, make the CMC-PG device an ideal tool for generating energetic isolated attosecond pulses and measure the carrier-envelope phase of a high-power many-cycle laser field.

Phase Contrast MR as Non-Invasive Tool in the Diagnosis of Benign Intracranial Hypertension.

Idiopathic intracranial hypertension (IIH) is characterized by an increased intracranial pressure in the absence of expansive lesions or cerebrospinal fluid (CSF) circulation obstructions. Its physiopathology is still not fully understood. The diagnosis is currently established on clinical grounds (Dandy criteria) along with an invasive measurement of CSF dynamic parameters through the infusion test. This study compares the invasive pressure measurements with the biomechanical CSF parameters derived from a phase-contrast MR protocol to evaluate the accuracy and reliability of the phase-contrast MR protocol.

MRI of intracranial meningiomas: correlations with histology and physical consistency.

Magnetic resonance imaging (MRI) appearances of 43 intracranial meningiomas were reviewed and correlated with their histology and consistency at surgery and on pathological examination. There was a statistically significant prevalence of hard tumours within the fibroblastic subtypes. No statistically significant correlation between signal intensity and histology or consistency was found. A meningioma hyperintense on T2-weighted images is, however, unlikely to be fibroblastic or hard.