Distance measurement by delayed optical feedback in a ring laser

We numerically study the behavior of a semiconductor ring laser subject to bidirectional delayed optical feedback, when the isolated laser is in the quasi-unidirectional regime. The optical feedback, provided by two external refectors located in front of the ring output waveguides, can modify the laser regime produced by the cross-saturation between the clockwise and the counter-clockwise mode. Thus, the system exhibits new diferent regimes, most of which are asymmetric and bidirectional, with alternating dominant mode. Two of these regimes are of special interest in view of applications, because the laser switching period, between the clockwise and the counter-clockwise mode, is linearly related to the time of fight from the laser to one or both refectors. In these operating conditions, the laser is thus suitable to implement a telemeter. A convenient electrical output signal is obtained by a photodiode located behind one (partially refecting) fxed mirror, or by measuring the voltage drop across the laser junction. Simulations are performed by mathematical models based on rate-equations, assuming typical literature parameters for a 1 mW ring laser

Overcoming laser diode nonlinearity issues in multi-channel radio-over-fiber systems

The authors demonstrate how external light injection into a directly modulated laser diode may be used to enhance the performance of a multi-channel radio-over-fiber system operating at a frequency of 6 GHz. Performance improvements of up to 2 dB were achieved by linearisation of the lasers-modulation response. To verify the experimental work a simulation of the complete system was carried out using Matlab. Good correlation was observed between experimental and simulated results

A real world experience with fingolimod in active RRMS patients naïve to second-line agents: a 2 years, intention-to-treat, observational, single center study

Fingolimod is approved by EMA as a second-line treatment for relapsing-remitting multiple sclerosis (RRMS). Experience with fingolimod in real life is still limited. Aim of our study was to report data on fingolimod effectiveness in a real life cohort of Italian active RRMS patients, naive to second-line agents, followed for 2 years. Fingolimod was a part of the patients' regular treatment and is produced by Novartis. We included all consecutive RRMS patients starting fingolimod at our center according to EMA criteria before January 1st 2013. Exclusion criteria were a previous treatment with natalizumab or an immunosuppressant therapy in the previous 12 months. All patients were clinically evaluated quarterly, and performed brain MRI yearly. Definition of "no evidence of disease activity" (NEDA-3): no relapses, no brain MRI activity and no 6-months confirmed worsening in EDSS score. We included 38 RRMS patients, 35 switched from first-line injectable therapies. Six patients were also previously treated with immunosuppressants (5 mitoxantrone, 1 cyclophosphamide). At 24th month 34 patients continued fingolimod treatment. Main adverse events were infections (18 %), liver-enzymes elevation (8 %), and leukopenia (8 %). After 12 and 24 months 79 and 63 % of patients were relapses-free. Fingolimod significantly reduced ARR compared to the previous year (0.3 ± 0.6 vs 1.2 ± 0.5; p < 0.001). After 12 and 24 months 63 and 37 % of patients had NEDA-3. Previous use of immunosuppressants and an ARR ≥1 in the 2 years predicted disease activity. Fingolimod significantly reduce disease activity in active RRMS patients, with no severe/unexpected safety issues. Patients previously treated with immunosuppressants and with a higher ARR at baseline may respond less to fingolimod treatment

123I-Interleukin-2 scintigraphy for the in vivo assessment of intestinal mononuclear cell infiltration in Chron's disease

Activated mononuclear cells expressing interleukin-2 (IL2) receptors (IL2-Rs) heavily infiltrate the Crohn’s disease (CD) gut wall. A new technique for the in vivo detection of tissue infiltrating IL2-R positive (IL2R1ve) cells was developed based on 123I-IL2 scintigraphy. The aim of this study was to investigate whether 123I-IL2 accumulates in the CD gut wall in different phases of the disease and to evaluate the specificity of 123I-IL2 binding to activated IL2R1ve cells infiltrating the gut wall. Methods: Fifteen patients with ileal CD (10 active and 5 inactive) and 10 healthy volunteers were studied by 123I-IL2 scintigraphy. Six patients with active CD were studied before and after 12 wk of steroid treatment. After scintigraphy, patients were followed up for 29–54 mo. Ex vivo autoradiography was performed to determine specificity of 125IIL2 binding to IL2R1ve cells. For bowel scintigraphy, 123I-IL2 (75 MBq) was injected intravenously and g camera images were acquired after 1 h. Bowel radioactivity was quantified in 64 regions of interest (ROIs). Results: Autoradiography showed specific binding of 125I-IL2 to IL2R1ve mononuclear cells infiltrating the CD gut wall. Intestinal 123I-IL2 uptake assessed by the number of positive ROIs was higher in patients with active or inactive CD than in healthy volunteers (P , 0.0001 andP 5 0.03, respectively) and positively correlated with the CD activity index (P 5 0.01). 123I-IL2 intestinal uptake significantly decreased in patients with CD in steroid-induced remission (P 5 0.03). A significant correlation was observed between the number of positive ROIs and time to disease relapse. Conclusion: 123I-IL2 accumulates in the diseased CD gut wall by specific binding to IL2R1ve cells, infiltrating the involved tissues. 123I-IL2 scintigraphy may be an objective tool for the in vivo assessment of intestinal activated mononuclear cell infiltration

Multi physics modelling for a hybrid rocket engine with liquefying fuel: a sensitivity analysis on combustion instability

Hybrid rocket engines represent a promising alternative to both solid rocket motors and liquid rocket engines. They have throttling and restart capabilities with performance similar to storable liquids, but are safer and are low-cost. However, some drawbacks, such as low regression rate and combustion instability, are limiting their effective application. Paraffin-based fuels are a solution envisaged to face the low regression rate issue, and the capability to describe and predict combustion instability in the presence of liquefying fuels becomes an enabling step towards the application of hybrid rockets in next-generation space launchers. In this work, a multi physics model for hybrid rocket engines is presented and discussed. The model is based on a network of submodels, in which the chamber gas dynamics is described by a quasi-1D Euler model for reacting flows while thermal diffusion in the grain is described by the 1D heat equation in the radial direction. The need to introduce strong modelling simplifications introduces a significant uncertainty in the predictive capability of the numerical simulation. For this reason, a sensitivity analysis is performed in order to identify the key parameters which have the largest influence on combustion instability. Results are presented on a test case which refers to a paraffin-based grain burnt with hydrogen peroxide

Experimental investigation of the impact of optical injection on vital parameters of a gain-switched pulse source

An analysis of optical injection on a gain-switched distributed feedback (DFB) laser and its impact on pulse parameters that influence the performance of the pulse source in high-speed optical communication systems is presented in this paper. A range of 10 GHz in detuning and 5 dB in injected power has been experimentally identified to attain pulses, from an optically injected gain-switched DFB laser, with durations below 10 ps and pedestal suppression higher than 35 dB. These pulse features are associated with a side mode suppression ratio of about 30 dB and a timing jitter of less than 1 ps. This demonstrates the feasibility of using optical injection in conjunction with appropriate pulse compression schemes for developing an optimized and cost-efficient pulse source, based on a gain-switched DFB laser, for high-speed photonic systems

Stability of the nonlinear dynamics of an optically injected VCSEL

Automated protocols have been developed to characterize time series data in terms of stability. These techniques are applied to the output power time series of an optically injected vertical cavity surface emitting laser (VCSEL) subject to varying injection strength and optical frequency detuning between master and slave lasers. Dynamic maps, generated from high resolution, computer controlled experiments, identify regions of dynamic instability in the parameter space. © 2012 Optical Society of America

Short-term variability of biomarkers of proteinase activity in patients with emphysema associated with type Z alpha-1-antitrypsin deficiency

BACKGROUND: The burden of proteinases from inflammatory cells in the lung of subjects with type Pi ZZ of alpha-1-antitrypsin deficiency is higher than in those without the deficiency. Cross-sectional studies have shown increased levels of biomarkers of extracellular matrix degradation in vivo. Longitudinal variability of these biomarkers is unknown but desirable for clinical studies with proteinase inhibitors. METHODS: We measured three different types of biomarkers, including desmosines, elastase-formed fibrinogen fragments and heparan sulfate epitope JM403, in plasma and urine for a period of 7 weeks in a group of 12 patients who participated in a placebo-controlled study to assess the safety of a single inhalation of hyaluronic acid. RESULTS: Effect of study medication on any of the biomarkers was not seen. Baseline desmosines in plasma and urine correlated with baseline CO diffusion capacity (R = 0.81, p = 0.01 and R = 0.65, p = 0.05). Mean coefficient of variation within patients (CVi) for plasma and urine desmosines was 18.7 to 13.5%, respectively. Change in urinary desmosine levels correlated significantly with change in plasma desmosine levels (R = 0.84, p < 0.01). Mean CVi for fibrinogen fragments in plasma was 20.5% and for JM403 in urine was 27.8%. No correlations were found between fibrinogen fragments or JM403 epitope and desmosines. CONCLUSION: We found acceptable variability in our study parameters, indicating the feasibility of their use in an evaluation of biochemical efficacy of alpha-1-antitrypsin augmentation therapy in Pi Z subjects