Integrated quantitative PIXE analysis and EDX spectroscopy using a laser-driven particle source.

Among the existing elemental characterization techniques, particle-induced x-ray emission (PIXE) and energy-dispersive x-ray (EDX) spectroscopy are two of the most widely used in different scientific and technological fields. Here, we present the first quantitative laser-driven PIXE and laser-driven EDX experimental investigation performed at the Centro de Láseres Pulsados in Salamanca. Thanks to their potential for compactness and portability, laser-driven particle sources are very appealing for materials science applications, especially for materials analysis techniques. We demonstrate the possibility to exploit the x-ray signal produced by the co-irradiation with both electrons and protons to identify the elements in the sample. We show that, using the proton beam only, we can successfully obtain quantitative information about the sample structure through laser-driven PIXE analysis. These results pave the way toward the development of a compact and multifunctional apparatus for the elemental analysis of materials based on a laser-driven particle source.

Effects of Talinum paniculatum (Jacq.) Gaertn. leaf extract on general toxicity and pubertal development of rats.

Talinum paniculatum (Jacq.) Gaertn. (Talinaceae), popularly known as "major gomes," is a Brazilian Cerrado plant used in traditional medicine and as a food source. Recent studies have demonstrated its diuretic effects. However, no studies have been performed on its effects on the reproductive system. Therefore, we aimed to investigate the effects of the ethanol-soluble fraction of T. paniculatum leaves (ESTP) on general toxicity and on the pubertal development of male and female Wistar rats. For this purpose, the uterotrophic and the pubertal assays were performed. In the uterotrophic test, female immature rats were treated for three consecutive days with 30, 100, or 300 mg/kg of ESTP. Uterus without luminal fluid was weighed and the relative weight calculated. For the pubertal assay, male and female immature rats were submitted to 30-day treatment with 30 or 300 mg/kg of ESTP. Clinical signs of toxicity, biochemical, and histopathological parameters were evaluated. ESTP treatment did not promote estrogenic effects in female rats. In the pubertal test, no daily signs of toxicity or weight loss were observed. Moreover, ESTP did not affect the onset of vaginal opening and preputial separation and did not cause significant changes in biochemical parameters as well as in organ weight and histopathological analyses of animals.

Superintense Laser-driven Ion Beam Analysis.

Ion beam analysis techniques are among the most powerful tools for advanced materials characterization. Despite their growing relevance in a widening number of fields, most ion beam analysis facilities still rely on the oldest accelerator technologies, with severe limitations in terms of portability and flexibility. In this work we thoroughly address the potential of superintense laser-driven proton sources for this application. We develop a complete analytical and numerical framework suitable to describe laser-driven ion beam analysis, exemplifying the approach for Proton Induced X-ray/Gamma-ray emission, a technique of widespread interest. This allows us to propose a realistic design for a compact, versatile ion beam analysis facility based on this novel concept. These results can pave the way for ground-breaking developments in the field of hadron-based advanced materials characterization.

Electron heating in subpicosecond laser interaction with overdense and near-critical plasmas.

In this work we investigate electron heating induced by intense laser interaction with micrometric flat solid foils in the context of laser-driven ion acceleration. We propose a simple law to predict the electron temperature in a wider range of laser parameters with respect to commonly used existing models. An extensive two-dimensional (2D) and 3D numerical campaign shows that electron heating is due to the combined actions of j×B and Brunel effect. Electron temperature can be well described with a simple function of pulse intensity and angle of incidence, with parameters dependent on pulse polarization. We then combine our model for the electron temperature with an existing model for laser-ion acceleration, using recent experimental results as a benchmark. We also discuss an exploratory attempt to model electron temperature for multilayered foam-attached targets, which have been proven recently to be an attractive target concept for laser-driven ion acceleration.

Pulsed laser deposition of two-dimensional ZnO nanocrystals on Au(111): growth, surface structure and electronic properties.

Two-dimensional (2D) ZnO structures have been deposited on the Au(111) surface by means of the pulsed laser deposition technique. In situ scanning tunneling microscopy and scanning tunneling spectroscopy measurements have been performed to characterize morphological, structural and electronic properties of 2D ZnO at the nanoscale. Starting from a sub-monolayer coverage, we investigated the growth of ZnO, identifying different atomic layers (up to the fifth). At low coverage, we observed single- and bi-layer nanocrystals, characterized by a surface moiré pattern that is associated to a graphene-like ZnO structure. By increasing the coverage, we revealed a morphological change starting from the fourth layer, which was attributed to a transition toward a bulk-like structure. Investigation of the electronic properties revealed the semiconducting character of 2D ZnO. We observed a dependence of the density of states (DOS) and, in particular, of the conduction band (CB) on the ZnO thickness, with a decreasing of the CB onset energy for increasing thickness. The CB DOS of 2D ZnO shows a step-like behaviour which may be interpreted as due to a 2D quantum confinement effect in ZnO atomic layers.

Electron Acceleration by Relativistic Surface Plasmons in Laser-Grating Interaction.

The generation of energetic electron bunches by the interaction of a short, ultraintense (I>10(19) W/cm(2)) laser pulse with "grating" targets has been investigated in a regime of ultrahigh pulse-to-prepulse contrast (10(12)). For incidence angles close to the resonant condition for surface plasmon excitation, a strong electron emission was observed within a narrow cone along the target surface, with energy spectra peaking at 5-8 MeV and total charge of ∼100 pC. Both the energy and the number of emitted electrons were strongly enhanced with respect to simple flat targets. The experimental data are closely reproduced by three-dimensional particle-in-cell simulations, which provide evidence for the generation of relativistic surface plasmons and for their role in driving the acceleration process. Besides the possible applications of the scheme as a compact, ultrashort source of MeV electrons, these results are a step forward in the development of high-field plasmonics.

Tungsten oxide nanowires grown on amorphous-like tungsten films.

Tungsten oxide nanowires have been synthesized by vacuum annealing in the range 500-710 °C from amorphous-like tungsten films, deposited on a Si(100) substrate by pulsed laser deposition (PLD) in the presence of a He background pressure. The oxygen required for the nanowires formation is already adsorbed in the W matrix before annealing, its amount depending on deposition parameters. Nanowire crystalline phase and stoichiometry depend on annealing temperature, ranging from W18O49-Magneli phase to monoclinic WO3. Sufficiently long annealing induces the formation of micrometer-long nanowires, up to 3.6 µm with an aspect ratio up to 90. Oxide nanowire growth appears to be triggered by the crystallization of the underlying amorphous W film, promoting their synthesis at low temperatures.

Note: Fabrication and characterization of molybdenum tips for scanning tunneling microscopy and spectroscopy.

We present a method for the preparation of bulk molybdenum tips for Scanning Tunneling Microscopy and Spectroscopy and we assess their potential in performing high resolution imaging and local spectroscopy by measurements on different single crystal surfaces in UHV, namely, Au(111), Si(111)-7 × 7, and titanium oxide 2D ordered nanostructures supported on Au(111). The fabrication method is versatile and can be extended to other metals, e.g., cobalt.

Evidence of resonant surface-wave excitation in the relativistic regime through measurements of proton acceleration from grating targets.

The interaction of laser pulses with thin grating targets, having a periodic groove at the irradiated surface, is experimentally investigated. Ultrahigh contrast (~10(12)) pulses allow us to demonstrate an enhanced laser-target coupling for the first time in the relativistic regime of ultrahigh intensity >10(19) W/cm(2). A maximum increase by a factor of 2.5 of the cutoff energy of protons produced by target normal sheath acceleration is observed with respect to plane targets, around the incidence angle expected for the resonant excitation of surface waves. A significant enhancement is also observed for small angles of incidence, out of resonance.

Laser ion acceleration using a solid target coupled with a low-density layer.

We investigate by particle-in-cell simulations in two and three dimensions the laser-plasma interaction and the proton acceleration in multilayer targets where a low-density ("near-critical") layer of a few-micron thickness is added on the illuminated side of a thin, high-density layer. This target design can be obtained by depositing a "foam" layer on a thin metallic foil. The presence of the near-critical plasma strongly increases both the conversion efficiency and the energy of electrons and leads to enhanced acceleration of protons from a rear side layer via the target normal sheath acceleration mechanism. The electrons of the foam are strongly accelerated in the forward direction and propagate on the rear side of the target, building up a high electric field with a relatively flat longitudinal profile. In these conditions the maximum proton energy is up to three times higher than in the case of the bare solid target.

Target normal sheath acceleration analytical modeling, comparative study and developments.

Ultra-intense laser interaction with solid targets appears to be an extremely promising technique to accelerate ions up to several MeV, producing beams that exhibit interesting properties for many foreseen applications. Nowadays, most of all the published experimental results can be theoretically explained in the framework of the target normal sheath acceleration (TNSA) mechanism proposed by Wilks et al. [Phys. Plasmas 8(2), 542 (2001)]. As an alternative to numerical simulation various analytical or semi-analytical TNSA models have been published in the latest years, each of them trying to provide predictions for some of the ion beam features, given the initial laser and target parameters. However, the problem of developing a reliable model for the TNSA process is still open, which is why the purpose of this work is to enlighten the present situation of TNSA modeling and experimental results, by means of a quantitative comparison between measurements and theoretical predictions of the maximum ion energy. Moreover, in the light of such an analysis, some indications for the future development of the model proposed by Passoni and Lontano [Phys. Plasmas 13(4), 042102 (2006)] are then presented.

Early detection of the graft failure after pediatric liver transplantation: a Bergamo experience.

BACKGROUND: Effective indicators of the early graft failure after pediatric liver transplantation are currently a crucial question. The aim of this study was to analyze retrospectively laboratory parameters that may help anticipate an early graft loss (GL). METHODS: The 131 pediatric liver transplantations, performed in our hospital from January 2002 to December 2005, were reviewed. Post-operative laboratory parameters, collected in the first 36 h of the Paediatric Intensive Care Unit (PICU) stay, were analyzed for children with both graft survival and GL. Receiver operating characteristics analysis was used to identify the optimal cut-off for the laboratory parameters. Multivariate logistic regression analysis was used to calculate the adjusted risk of GL for the prognostic parameters identified. RESULTS: The mean age at transplant was 1.1 years. The two groups were comparable for all recipient and donor variables considered. Children with GL showed significantly higher levels of ammonia and transaminase at the admission to the PICU and higher levels of prothrombin time, creatinine, lactate and a lower level of platelets at the 36 h of PICU. The laboratory parameters over the cut-off value by the multivariate logistic regression identified all early thromboses earlier than Doppler ultrasound. CONCLUSIONS: This study suggests that routine blood tests may help to anticipate an early loss of liver grafts in children after transplantation and may improve our diagnostic investigation in the case of thrombosis suspicion. Further validation by a prospective study is needed to carefully assess the sensitivity and specificity of the identified criteria.

Theory of light-ion acceleration driven by a strong charge separation.

A theoretical model of the quasistatic electric field, formed at the rear surface of a thin solid target irradiated by a ultraintense subpicosecond laser pulse, due to the appearance of a cloud of ultrarelativistic bound electrons, is developed. It allows one to correctly describe the spatial profile of the accelerating field and to predict the maximum energies and the energy spectra of the accelerated ions. The agreement of the theoretical expectations with the experimental data looks satisfactory in a wide range of conditions. Previsions of regimes achievable in the future are given.

Orthotopic liver transplantation for biliary atresia.

Biliary atresia (BA) represents the most frequent indication for liver transplantation (OLTX) in the pediatric population. The aim of this paper was to present a series collected over the last 7 years from October 1997 through July 2004, including 260 pediatric OLTX in 231 patients. BA was the indication in 137 patients. There were 69 boys and 68 girls of mean weight 10.68 kg and median age 0.9 years. As a primary transplant, 99 patients received a LLS graft; 27 a whole graft; four a I+IV-VIII segment, and two a I-IV segment. Mean follow up was 1047 days (range, 1-2496 day). Infections were diagnosed in 45 patients, vascular complications in 27 patients. Surgical complications that required reintervention occurred in 25 patients. In 41 cases biliary complications occurred, 11 requiring reintervention. 16 patients were retransplanted. In two cases another re-OLTx was performed. Currently 126 patients are alive, showing an actuarial 1 year survival of 92% and 5 year 91%, with actuarial graft survivals of 85% at 1 year and 82% at 3 and 5 years. Our results confirm the effectiveness of OLTx for the treatment of children with BA and a failed Kasai procedure. Split liver grafts represent an excellent organ supply for these patients, achieving optimal results with no mortality on the waiting list.

Charge separation effects in solid targets and ion acceleration with a two-temperature electron distribution.

The electrostatic field at the solid-vacuum interface generated by two electron populations with different thermal energies, each following a Boltzmann distribution, is analytically derived from the Poisson equation and studied in terms of plasma parameters. In particular, the effect of the pressure of each of the two populations on the amplitude of the electric field and on its spatial extension is described. In order to evaluate the cold electron temperature, an analytical model for the Ohmic heating of the background electron population by laser generated fast electrons is developed and the consequences on ion detachment, ionization, and acceleration processes in laser-solid experiments are discussed. The efficiency of ion acceleration is shown to be controlled by the heating rate of the background electrons.

[Treatment of large tumors of the cerebellopontile angle using a combined transtentorial and translabyrinthine approach to the middle cranial fossa]. / Trattamento dei grossi tumori dell'angolo ponto-cerebellare attraverso la via combinata della fossa cranica media transtentoriale e translabirintica.

The Authors have reported on 7 patients with large tumors (larger than 4 cm) of the cerebello-pontine angle operated-on utilizing a subtemporal-transtentorial-translabyrinthine-trans-occipital approach. The technique, the results and complications of this approach to the cerebello-pontine angle are discussed. The advantages are the delineation of the cranial nerves and of the ventrolateral brainstem with its blood supply. This approach has been associated with a low morbidity and no operative mortality in 5 cases of acoustic nerve tumor and 2 meningiomas.

[Neuropsychologic and behavioral sequelae of cranial injuries: remarks on classification, diagnosis and correlation with injury variables]. / I postumi neuropsicologici e comportamentali dei traumi cranici: osservazioni sulla classificazione, sulla diagnostica e sulle correlazioni con le variabili del trauma.

The psychological and behavioural impairment following head injury has been investigated in order to throw light on and assess the related epidemiological aspects, methodological approaches, clinical manifestations, and the correlations between the sequelae and the variables of head trauma, i.e. degree of severity of trauma, age of patients, presence or absence of fractures and haematoma. This study was conducted on 117 head- injured patients and 43 matched "control" subjects. The findings point out the following: a) Even the medical staff is often largely misinformed about this type of sequelae. The methods used for assessment should therefore be further developed and a more systematic evaluation of the higher functions following head injury appears to be necessary. b) The syndromes observed are mostly of a composite and diffuse type. It is therefore difficult to classify them according to strict criteria; indeed, it appears that the only possible approach is to define large groups of head- injured patients based on clinical description, which are partly borne out and partly described ex novo in the present series. c) As regards the correlations between the variables of the injury and the resulting neuropsychological impairment, the age factor should be distinguished from the severity of injury. If it is true that the older patients, the greater the impairment, such a direct correlation no longer exists when severity of the injury is considered. Indeed, the latter does not appear to be a significant differential factor in determining the degree of impairment. Similarly, whether the injury is an "open" or "closed" one, or the presence of haematoma do not appear to be differential factors, either.

[Observations on an unusual case of motor preservation (author's transl)]. / Osservazioni su un insolito caso di perseverzione motoria.

The Authors describe an unusual motor preservation case, induced by right basal ganglia lesion and with not previously reported characteristics. Possible pathogenetic mechanisms are discussed.

[Trigeminal neuralgia: interpretation of the results of the Dandy method of rhizotomy]. / Nevralgia del trigemino: interpretazione dei risultati in 29 casi di rizotomia alla Dandy.

The patterns of sensory loss in 29 cases of Juxta pontine trigeminal rhizotomy are reported. The section of 70% of the portio major gave a similar impairment of tactile, thermal and pain sensibility in the facial area corresponding to the portio of the nerve section in all the patients. These findings do not support Jannetta and Rand's statement that partial to complete section of the porto major at the pons with complete preservation of the intermediate fibre does not affect the perception of light touch. The reported data suggest: 1--intermediate fibres are not mode specific fibres for light touch; 2--clear separation between thermoalgesic and tactile afferent rootlets does not exist in the trigeminal root; 3--saving the portio minor and the intermediate fibres ensures the preservation of perception of tactile, thermal and pain sensibility, thus avoiding postoperative painful anesthesia and keratitis.