Role of serial ultrasound screening of venous thrombosis in oncologic children with central lines

Objective: Pediatric oncology patients are more likely to develop venous thromboembolic events related to central venous catheter (CVC). Study aim was to determine the incidence of catheter related thrombosis (CRT) in a cohort of pediatric oncology patients using vascular ultrasound (US). Methods: Consecutive children of a single cancer referral center, requiring medium to long term CVC implantation, were screened for CRT, using serial ultrasound exams. Measurements and main results: US examinations were taken 15, 30 and 90 days after CVC implantation. A total of 113 catheters were studied in 103 patients (median age 10.5 years old). Ultrasound screening was completed in 80.5% patients. Apart from three subjects, US investigations were well tolerated. Patients were followed for a median of 87 days. No symptomatic CRT was recorded throughout. Three cases of asymptomatic thrombosis were identified with early US screening; incidence of CRT events for 1000 catheter-days was 0.11. The presence of previous catheter-related infection and an history of one or more previous CVC placement were identified as risk factors. Conclusions: In our pediatric patients the incidence of CRT is low. Ultrasound monitoring is well tolerated and allows detecting asymptomatic CRT. Patients with previous CVC infection or insertion seem to have a higher risk of CRT (p =0.003 and p = 0.043 respectively). Keywords: Central venous catheters, Venous thrombosis, Vascular ultrasound, Vascular catheter infections, Childre

Random bit generation through polarization chaos in nonlinear optical fibers

Nowadays, cryptographic applications are becoming of paramount importance in order to guarantee ultimately secure communications. Performances of classical and quantum key distribution and encryption algorithms are strongly dependent on the used Random Number Generator (RNG). A good RNG must produce unpredictable, unreproducible and unbiased sequences of numbers. For this reason, many true random number generators relying on chaotic physical phenomena, such as chaotic oscillations of high-bandwidth lasers [1,2] or polarization chaos from a VCSEL diode [3], have been developed. In this work, we propose a RNG implementation based on a different physical mechanism than the ones previously used in literature: the polarization chaos induced in an optical fiber by the nonlinear interaction between a forward beam and its amplified backward replica. Basically, we operate the device called Omnipolarizer, originally used in our previous works as an all-optical polarization attractor or beam splitter [4], in an additional operating mode, namely the chaotic mode [5]

Coherent fiber-optic sensor for vibration localization

A novel distributed fiber-optic vibration sensor is proposed and experimentally demonstrated. The sensor relies on a dual Mach-Zehnder ring interferometric architecture associated to a new coherent detection scheme, borrowed from high bit rate coherent optical communications, which performs a completely passive management of polarization and phase variables of the received optical signal. The proposed solution thus makes feasible the actual in-field applicability of the cost-effectiveness and high sensitivity featured by interferometric sensors. Sensor performance in terms of vibration localization accuracy has been experimentally verified

Demonstration and performance investigation of hybrid OFDM systems for optical access network applications

We propose a hybrid solution to exploit the capabilities of the optical orthogonal frequency-division multiplexing (OFDM) for passive optical network applications implemented by the electronic generation of the OFDM signal at the transmitter and by the all-optical demultiplexing of the OFDM subcarriers at the remote node by means of a passive element, such as suitable arrayed waveguide grating, performing the fast Fourier transform (FFT) in the optical domain. Drastic simplicity at the optical network unit is achieved with neither coherent detection nor any high-speed electronics, allowing an effective exploitation of all the available transmission spectra. By means of simulations and preliminary experimentation, we demonstrate 4 x 10-Gb/s transmission over more than 40-km standard single-mode fiber, the main limitation to the number of subcarriers being the employed device's actual electronic bandwidth

Experimented phase noise limitations in directly-detected single side-band optical OFDM systems

We experimentally evaluate the impact of realistic phase noise on single side-band optical OFDM systems, directly detected after uncompensated propagation. Measures obtained with sources typical of short-medium reach applications are compared to a semi-analytical model

Monitoring Strategic Hydraulic Infrastructures by Brillouin Distributed Fiber Optic Sensors

We present a case study of a Structural Health Monitoring (SHM) hybrid system based on Brillouin Distributed Fiber Optic Sensors (D-FOS), Vibrating Wire (VW) extensometers and temperature probes for an existing historical water penstock bridge positioned in a mountain valley in Valle d’Aosta Region, Northwestern Italy. We assessed Brillouin D-FOS performances for this kind of infrastructure, characterized by a complex structural layout and located in a harsh environment. A comparison with the more traditional strain monitoring technology offered by VW strain gauges was performed. The D-FOS strain cable has been bonded to the concrete members using a polyurethane-base adhesive, ensuring a rigid strain transfer. The raw data from all sensors are interpolated on a unique general timestamp with hourly resolution. Strain data from D-FOS and VW strain gauges are then corrected from temperature effects and compared. Considering the inherent differences between the two monitoring technologies, results show a good overall matching between strain time series collected by D-FOS and VW sensors. Brillouin D-FOS proves to be a good solution in terms of performance and economic investment for SHM systems on complex infrastructures such as hydropower plants, which involve extensive geometry combined with the need for detailed and continuous strain monitoring