Stable Operation of a Free-Electron Laser Driven by a Plasma Accelerator.

The breakthrough provided by plasma-based accelerators enabled unprecedented accelerating fields by boosting electron beams to gigaelectronvolt energies within a few centimeters [1-4]. This, in turn, allows the realization of ultracompact light sources based on free-electron lasers (FELs) [5], as demonstrated by two pioneering experiments that reported the observation of self-amplified spontaneous emission (SASE) driven by plasma-accelerated beams [6,7]. However, the lack of stability and reproducibility due to the intrinsic nature of the SASE process (whose amplification starts from the shot noise of the electron beam) may hinder their effective implementation for user purposes.

BriXS, a new X-ray inverse Compton source for medical applications.

MariX is a research infrastructure conceived for multi-disciplinary studies, based on a cutting-edge system of combined electron accelerators at the forefront of the world-wide scenario of X-ray sources. The generation of X-rays over a large photon energy range will be enabled by two unique X-ray sources: a Free Electron Laser and an inverse Compton source, called BriXS (Bright compact X-ray Source). The X-ray beam provided by BriXS is expected to have an average energy tunable in the range 20-180 keV and intensities between 10 and 10 photon/s within a relative bandwidth ΔE/E=1-10%.

Inverse Compton radiation: a novel x-ray source for K-edge subtraction angiography?

Coronary angiography is clinically used worldwide to diagnose diseases of coronary arteries. Despite its effectiveness, this technique is quite invasive and it is associated with significant risks due to the arterial catheterisation needed to inject the contrast agent. A valid alternative is using the K-edge subtraction (KES) method, which is based on the subtraction of two images acquired at energies bracketing the K-edge of the contrast element.

Compton Scattered X-Gamma Rays with Orbital Momentum.

We study the possibility of producing x-gamma rays with orbital angular momentum by means of the inverse Compton backscattering between a high brightness electron beam and a twisted laser pulse. We use the classical electrodynamics retarded fields for evaluating the orbital angular momentum of the radiation and connecting it to that of the primary laser pulse. We then propose the dimensioning of a linearly polarized x-ray source with orbital angular momentum, starting from the parameters of operating Thomson setups.

Two-Color Radiation Generated in a Seeded Free-Electron Laser with Two Electron Beams.

We present the experimental evidence of the generation of coherent and statistically stable two-color free-electron laser radiation obtained by seeding an electron beam double peaked in energy with a laser pulse single spiked in frequency. The radiation presents two neat spectral lines, with time delay, frequency separation, and relative intensity that can be accurately controlled. The analysis of the emitted radiation shows a temporal coherence and a shot-to-shot regularity in frequency significantly enhanced with respect to the self-amplified spontaneous emission.

Mapping the transverse coherence of the self amplified spontaneous emission of a free-electron laser with the heterodyne speckle method.

The two-dimensional single shot transverse coherence of the Self-Amplified Spontaneous Emission of the SPARC_LAB Free-Electron Laser was measured through the statistical analysis of a speckle field produced by heterodyning the radiation beam with a huge number of reference waves, scattered by a suspension of particles. In this paper we report the measurements and the evaluation of the transverse coherence along the SPARC_LAB undulator modules. The measure method was demonstrated to be precise and robust, it does not require any a priori assumptions and can be implemented over a wide range of wavelengths, from the optical radiation to the x-rays.

Two color free-electron laser and frequency beating.

We review the theory of two color high gain free-electron laser emission, derive the integral equation characterizing the evolution of the optical intensities, and provide a description of the relevant dynamics. The characteristic feature of this regime is the existence of a mutual bunching, whose origin and role are discussed.

Observation of time-domain modulation of free-electron-laser pulses by multipeaked electron-energy spectrum.

We present the experimental demonstration of a new scheme for the generation of ultrashort pulse trains based on free-electron-laser (FEL) emission from a multipeaked electron energy distribution. Two electron beamlets with energy difference larger than the FEL parameter ρ have been generated by illuminating the cathode with two ps-spaced laser pulses, followed by a rotation of the longitudinal phase space by velocity bunching in the linac. The resulting self-amplified spontaneous emission FEL radiation, measured through frequency-resolved optical gating diagnostics, reveals a double-peaked spectrum and a temporally modulated pulse structure.

Superradiant cascade in a seeded free-electron laser.

We report measurements demonstrating the concept of the free-electron laser (FEL) superradiant cascade. Radiation (λ(rad) = 200 nm) at the second harmonic of a short, intense seed laser pulse (λ(seed) = 400 nm) was generated by the cascaded FEL scheme at the transition between the modulator and radiator undulator sections. The superradiance of the ultrashort pulse is confirmed by detailed measurements of the resulting spectral structure, the intensity level of the produced harmonics, and the trend of the energy growth along the undulator.

SOCS1 gene transfer accelerates the transition to heart failure through the inhibition of the gp130/JAK/STAT pathway.

Aims: The suppressors of cytokine signalling (SOCS) are identified inhibitors of cytokine and growth factor signalling that act via the Janus kinase (JAK) signal transducers and activators of transcription (STAT) pathways. Aberrant JAK/STAT signalling promotes progression from hypertrophy to heart failure. Little information is available concerning the role of SOCS in the transition from hypertrophy to heart failure.

High-order-harmonic generation and superradiance in a seeded free-electron laser.

Higher order harmonic generation in a free-electron laser amplifier operating in the superradiant regime [R. H. Dicke, Phys.

High-gain harmonic-generation free-electron laser seeded by harmonics generated in gas.

The injection of a seed in a free-electron laser (FEL) amplifier reduces the saturation length and improves the longitudinal coherence. A cascaded FEL, operating in the high-gain harmonic-generation regime, allows us to extend the beneficial effects of the seed to shorter wavelengths. We report on the first operation of a high-gain harmonic-generation free-electron laser, seeded with harmonics generated in gas.

Complementary therapeutic effects of dual delivery of insulin-like growth factor-1 and vascular endothelial growth factor by gelatin microspheres in experimental heart failure.

Aims: Strategies to prevent adverse left ventricular (LV) remodelling after myocardial infarction have included several traditional approaches and novel cell-based or gene therapies. Delivery of growth factors in post-infarction heart failure has emerged as a valuable alternative strategy. Our aim was to investigate the effects of sequential release of vascular endothelial growth factor (VEGF) and insulin-like growth factor-1 (IGF-1) from biodegradable gelatin microspheres in experimental heart failure.

Self-amplified spontaneous emission free-electron laser with an energy-chirped electron beam and undulator tapering.

We report the first experimental implementation of a method based on simultaneous use of an energy chirp in the electron beam and a tapered undulator, for the generation of ultrashort pulses in a self-amplified spontaneous emission mode free-electron laser (SASE FEL). The experiment, performed at the SPARC FEL test facility, demonstrates the possibility of compensating the nominally detrimental effect of the chirp by a proper taper of the undulator gaps. An increase of more than 1 order of magnitude in the pulse energy is observed in comparison to the untapered case, accompanied by FEL spectra where the typical SASE spiking is suppressed.

Generation of very high-frequency waves by up-conversion in a plasma-loaded free-electron laser.

A free-electron laser loaded with a plasma is able to resonate at two different frequencies. The two waves are copropagating, one with positive slippage while the other has negative slippage. We deduce the nonlinear partial differential equations describing the interaction between the two waves in the slowly-varying-envelope approximation.

A case report of vascular catheter-associated bacteremia caused by mycobacterium tuberculosis in a non-immunosuppressed patient.

Mycobacterium tuberculosis was isolated from a central venous catheter in a non-immunosuppressed patient with systemic tuberculosis. This case report represents a very uncommon form of isolation of Mycobacterium tuberculosis. A total improvement was obtained after treatment.

Chronic secretory otitis media: negative bacteriology.

There is disagreement on the role of bacteria in the genesis and maintenance of chronic secretory otitis media (CSOM). Extensive studies from other countries report up to 40% of middle ear cultures with bacterial growth. For the present study, material was collected from 94 ears of children with both clinical and tympanometric diagnoses of CSOM.

Endogenous endophthalmitis due to Listeria monocytogenes.

The authors report a case of Listeria monocytogenes endophthalmitis in a patient who had undergone cardiac revascularization surgery and was receiving systemic corticosteroids. The organism was isolated both in the aqueous humor and in blood culture. The infection was successfully treated with intravenous crystalline penicillin, but the patient developed a bullous keratopathy and secondary glaucoma, resulting in poor visual acuity (counting fingers at 0.