2,324 research outputs found
Prognostic factors in primary and iterative surgery of colorectal liver metastases
No full textThe aim of this study was to evaluate the results of surgery of colorectal liver metastases and assess prognostic factors influencing the outcome. A total of 135 hepatic resections performed in 107 patients was reviewed. The following prognostic factors were analyzed: primary tumor localization, Dukes stage, number and presence of metastases in one or two lobes, synchronous or metachronous occurrence, type of resection, use and modality of chemotherapy. The perioperative morbidity rate was 6.5% and mortality was 1.9%. Overall survival was 41.2% and disease-free survival 31.5% at 5 years. Survival at 5 years was better for patients with metachronous than for those with synchronous lesions (60.9% vs 28.1%; p<0.05). There were no significant differences in terms of long-term survival between patients with synchronous metastases that were excised simultaneously or with a delay of 3-6 months (p=n.s.). Site of the primary tumor, Dukes stage, number of metastases and type of resection did not influence survival. A favorable survival trend was observed in those patients who underwent both neoadjuvant and adjuvant chemotherapy. The overall survival rate at 5 years was 45.3% for patients undergoing a second hepatic resection and 50% for those with a third or a fourth hepatic resection. Liver resection remains the "gold standard" for the treatment of patients with colorectal liver metastases, with metachronous type having a better outcome than synchronous. Simultaneous or delayed surgery for synchronous metastases does not influence prognosis. Iterative resection is very encouraging and justifies an aggressive surgical approach. © E.S.I.F.T. srl
Comparison of Wirsung-jejunal duct-to-mucosa and dunking technique for pancreatojejunostomy after pancreatoduodenectomy
No full textBACKGROUND: Pancreato-enteric reconstruction after pancreatoduodenectomy (PD) is still a source of debate because of the high incidence of complications. Among the various types of pancreato-jejunostomies we don't know yet which is the best in terms of anastomotic failure and related complications rates. Wirsung-jejunal duct-to-mucosa anastomosis (WJ) and "dunking" pancreato-jejunal anastomosis (DPJ) are the two most used ones worldwide but conflicting results are reported. To determine which is the safer anastomosis and to define when an anastomosis should be preferred, we retrospectively reviewed two groups of patients who underwent WJ or DPJ. METHODS: Twenty-three patients underwent PD with WJ (n = 17) with dilated (WJD) (n = 9) or not-dilated Wirsung's duct (WJND) (n = 8) or with a DPJ (n = 6) over a 3-year period at a single institution. RESULTS: The complications rate was high in all groups of patients (33.3% in WJD, 37.5% in WJND and 66.7% in DPJ). A pancreatic fistula developed in one patient in each group (11.1% in WJD, 12.5% in WJND and 16.7% in DPJ). All these patients were managed conservatively. Anastomotic disruption took place in the WJ patients especially in the WJND group (n = 2) compared to the WJD (n = 1) (25% vs. 11.1%) or DPJ groups (0%): these three patients required a re-operation. Overall, the anastomotic defects were higher in patients who underwent WJND (37.5%), compared to WJD (22.2%) and to DPJ (16.7%). However, no statistical differences were found among the groups. Delayed gastric emptying (DGE) and total parenteral nutrition (TPN) along with anastomotic defects were responsible for a prolonged hospital stay. CONCLUSIONS: Our results were not able to demonstrate any statistical difference between the two different techniques in preventing anastomotic failure. WJ can represent a valid choice in case of a dilated duct and a firm, fibrotic enlarged gland that could not be properly invaginated in a small jejunal loop. DGE may occur in those patients who experienced an anastomotic failure and required a TPN regimen with a prolonged hospital stay
Accessing Excited State Molecular Vibrations by Femtosecond Stimulated Raman Spectroscopy
No full textExcited state vibrations are crucial for determining the photophysical and photochemical properties of molecular compounds. Stimulated Raman scattering can coherently stimulate and probe molecular vibrations with optical pulses, but it is generally restricted to ground state properties. Working under resonance conditions enables cross-section enhancement and selective excitation to a targeted electronic level but is hampered by an increased signal complexity due to the presence of overlapping spectral contributions. Here, we show how detailed information about ground and excited state vibrations can be disentangled by exploiting the relative time delay between Raman and probe pulses to control the excited state population, combined with a diagrammatic formalism to dissect the pathways concurring with the signal generation. The proposed method is then exploited to elucidate the vibrational properties of the ground and excited electronic states in the paradigmatic case of cresyl violet. We anticipate that the presented approach holds the potential for selective mapping of the reaction coordinates pertaining to transient electronic stages implied in photoactive compounds
Broadband impulsive stimulated Raman scattering based on a chirped detection
No full textIn impulsive stimulated Raman scattering, vibrational oscillations, coherently stimulated by a femtosecond Raman pulse, are monitored in real time and read out as intensity modulations in the transmission of a temporally delayed probe pulse. Critically, in order to retrieve broadband Raman spectra, a fine sampling of the time delays between the Raman and probe pulses is required, making conventional ISRS ineffective for probing irreversible phenomena and/or weak scatterers typically demanding long acquisition times, with signal-to-noise ratios that crucially depend on the pulse fluences and overlap stabilities. To overcome such limitations, here we introduce the chirped-based impulsive stimulated raman scattering (CISRS) technique. Specifically, we show how introducing a chirp in the probe pulse can be exploited for recording the Raman information without the need to scan over the Raman-probe pulse delay. We then experimentally demonstrate with a few examples how to use the introduced scheme to measure Raman spectra
Stimulated Raman lineshapes in the large light–matter interaction limit
No full textStimulated Raman scattering (SRS) represents a powerful tool for accessing the vibrational properties of molecular compounds or solid state systems. From a spectroscopic perspective, SRS is able to capture Raman spectra free from incoherent background processes and typically ensures a signal enhancement of several orders of magnitude with respect to its spontaneous counterpart. Since its discovery in 1962, SRS has been applied to develop technological applications, such as Raman-based lasers, frequency shifters for pulsed sources and Raman amplifiers. For the full exploitation of their potential, however, it is crucial to have an accurate description of the SRS processes under the large gain regime. Here, by taking as an example the stimulated Raman spectrum of a model solvent, namely liquid cyclohexane, we discuss how the spectral profiles and the lineshapes of Raman excitations critically depend on the pump excitation regime. In particular, we show that in the large light–matter interaction limit the Raman gain undergoes an exponential increase (decrease) in the red (blue) side of the spectrum, with the Raman linewidths that appear sharpened (broadened)
Coherent anti-Stokes Raman spectroscopy of single and multi-layer graphene.
No full textSpontaneous Raman spectroscopy is a powerful characterization tool for graphene research. Its extension to the coherent regime, despite the large nonlinear third-order susceptibility of graphene, has so far proven challenging. Due to its gapless nature, several interfering electronic and phononic transitions concur to generate its optical response, preventing to retrieve spectral profiles analogous to those of spontaneous Raman. Here we report stimulated Raman spectroscopy of the G-phonon in single and multi-layer graphene, through coherent anti-Stokes Raman Scattering. The nonlinear signal is dominated by a vibrationally non-resonant background, obscuring the Raman lineshape. We demonstrate that the vibrationally resonant coherent anti-Stokes Raman Scattering peak can be measured by reducing the temporal overlap of the laser excitation pulses, suppressing the vibrationally non-resonant background. We model the spectra, taking into account the electronically resonant nature of both. We show how coherent anti-Stokes Raman Scattering can be used for graphene imaging with vibrational sensitivity
Frontier Detectors for Frontier Physics - Proceedings of the 7th Pisa Meeting on Advanced Detectors, La Biodola, Isola d'Elba, Italy, May 25-31, 1997
No full textFrontier detectors for frontier physics - Proceedings of the 8th Pisa Meeting on Advanced Detectors La Biodola, Isola d' Elba, Italy, May 21-27, 2000
No full textProceedings of the 9th Pisa Meeting on Advanced Detectors - La Biodola, - Isola d'Elba, Italy, May 25-31, 2003
No full textN-p-n bipolar-junction-transistor detector with integrated p-n-p biasing transistor – feasibility study, design, and first experimental results.
No full textWe propose a novel n-p-n BJT radiation detector on high-resistivity silicon with integrated p-n-p transistor providing the quiescent base current of the detector. The do operational limits of the proposed detector are analysed by means of numerical device simulations, pointing out that, by properly distancing the base of the p-n-p transistor from the emitter of the n-p-n detector, the latch-up of the parasitic thyristor embedded within the detector-plus-biasing-transistor structure takes place at relatively high current levels, where detector operation should anyway be avoided in order to prevent the associated current-gain loss. Numerical simulations provides insight about the bias dependence of charge-collection waveforms, indicating that minimization of the collecting time requires the detector quiescent current to be adjusted at the highest value still allowing high-injection effects to be avoided. A small-signal equivalent circuit of the proposed structure is also derived, allowing the impact of p-n-p biasing transistor and load resistance on the charge-collecting time constant to be evaluated. First experimental results show that fabricated structures are immune from the latch-up of the parasitic thyristor throughout their high-current-gain operating region and feature a minimum charge-collecting time constant of 35 mu s, as tested by pulsed laser illumination
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