Analysis of Faraday effect in multimode tellurite glass optical fiber for magneto-optical sensing and monitoring applications

The design and fabrication of a tellurite glass multimode optical fiber for magneto-optical applications are presented and discussed. The analysis of the polarization shows that an optical beam, linearly polarized at the fiber input, changes to elliptically polarized with an ellipticity of 1∶4.5 after propagating down the fiber. However, the elliptical distribution remains unchanged with or without an applied magnetic field, demonstrating that no circular dichroism occurs within the fiber. The Verdet constant of the tellurite glass in the fiber is measured to be 28±0.5 rad·(T·m)-1, diverging by less than 3% from the Verdet constant found on the same glass composition in bulk form. These results demonstrate the feasibility to develop reliable tellurite glass fibers by the preform drawing method for magneto-optical applications.     

Mechanical–thermal noise in micromachined gyros

In this paper we investigate the effect of mechanical–thermal fluctuations on a vibrating-mass surface-micromachined gyroscope. It is found that this noise source represents a practical sensitivity limit in such devices and is likely to restrict their performances to the automotive grade.     

Deep venous thrombosis in a patient with superficial thrombophlebitis. Apropos of 2 cases]

Many schools refer children who have sustained an injury, directly to the local Accident & Emergency (A&E) department. This prospective study monitored these referrals for one school term (08.01.96-31.03.96). During this time 200 children under the age of 14 years presented from school to the A&E department of the Royal Aberdeen Childrens Hospital (RACH). The majority presented with trivial or mild injuries and 45% of parents felt that attending A&E was inappropriate. Half the accidents happened to unsupervised children. Rural children and children of working parents were less likely to attend A&E. In Grampian Region school referrals to A&E generate a significant workload for the A&E department with resultant cost implications. It would appear that a large number of these attendances are medically unnecessary and result from a desire by the school to avoid any complaint or litigation.     

Measurements on a micromachined silicon gyroscope by feedbackinterferometry

Feedback interferometry is a useful tool to characterize micromachined devices. We consider a silicon vibrating gyroscope, in which the angular rotation is transduced into the vibration amplitude of a small suspended mass. Measurements of the mass displacement at submicrometer resolution are reported on a 400×400 μm sensor, using an 800-nm 20-mW laser diode. The resonance curves of the device have been determined for different values of pressure and other parameters, which allows us to tune the resonance frequency and maximize the Q factor. Hysteresis and other nonlinear phenomena on specific samples also have been detected. The proposed method provides a direct inspection tool and represents a practical alternative to the standard electrical measurements     

Spot optical measurements on micromachined mirrors for photonic switching

This paper describes and compares three optical methods for performing spot measurements on micromachined mirrors, designed for photonic switching in fiberoptic networks. For static characterization, two spot-position detection systems, one based on a vidicon camera and the other based on a bidimensional silicon position sensitive detector (PSD), are illustrated, tested, and compared. Moreover, the dynamic behavior has been monitored with the PSD-based detection arrangement and with a semiconductor laser feedback interferometer. Advantages and drawbacks of these methods are highlighted. Testing is reported on torsional, silicon micromachined mirrors, with a single degree of freedom. High dc voltage for static measurements, and sinusoidal or white-noise or step excitation for dynamic characterization, have been used for mirror driving.     

Investigation of the miscibility of polycarbonate–poly(ethyleneterephthalate) blends: Solid-state 1H-NMR T1 relaxation time measurements,transmission electron microscopy,and structure–properties relationship

Solid-State ¹H-NMR measurements of T₁ relaxation times performed on polycarbonate-poly(ethyleneterephthalate) (PC–PET) blends point out the presence of two separate domains with apparent dimensions of about 80 nm. The variation of PET domain relaxation time with the increase of PC content is explained in terms of an interface in which parts of the PC molecules are finely dispersed into the PET matrix. Relaxation parameters and compositions match very well an equation that quantitatively describes a three-phase model formed by two domains separated by an interface of mixed components. Micrographs obtained by transmission electron microscopy (TEM) clearly reveal the presence of two separate domains with a phase inversion at 40/60 wt% composition. PET domains, although larger than expected from NMR analysis, are characterized by a dispersion of small PC particles that are considered responsible for the observed diffusion of magnetization from PET to PC domains. The partial miscibility seems to be physical in nature rather than due to transesterification processes between the components, as stem from ¹H-NMR spectra in solution of PET and PC–PET blends. T₁ relaxation times measured in the same way on totally immiscible PC–PA-6 blends, support, by contrast, the NMR interpretation of PC–PET results. The mechanical properties of PC–PET blends exhibit ductile behavior throughout the entire range of composition. This indicates that PC and PET are mechanically compatible. This is also in agreement with the isothermal crystallization data for PET at various compositions of PC–PET. These results are in agreement with the existence of a partial miscibility between PET and PC. © 1994 John Wiley & Sons, Inc.     

Tumour kinetics, response to chemotherapy and survival in primary ovarian cancer

The analysis of thymidine labelling index (TLI) in relation to clinico-pathological variables and survival was carried out in 111 ovarian cancer patients. The significance of TLI in predicting response to aggressive first line chemotherapy regimens was examined. The overall median TLI value of 1.8% was used as a cut-off to discriminate slowly from highly proliferating cancers. 94 patients entered into two consecutive randomised trials, and were treated with six courses of cisplatin-based chemotherapy with or without doxorubicin. A significantly higher objective response of 60% was reported in the subset of patients with TLI > 1.8% as compared to 35% in patients with TLI < or = 1.8% (P = 0.03). In addition, patients achieving complete response had tumours with median TLI of 3.8% as compared to 2.4% for partial responders, 1.5% for patients with stable disease and 1.7% for those with progressive disease. A significant increase in tumour kinetics was observed in advanced cancers (P = 0.001), more undifferentiated tumours (P = 0.02) and postsurgical residual disease greater than 2 cm (P = 0.04). In univariate analysis, TLI failed to influence significantly clinical outcome: 26 versus 32 months median survival time for patients with high and low tumour TLI, respectively. In the Cox's regression model, the only independent prognostic variables were performance status and amount of residual disease after primary surgery (P = 0.000).     

Resistance to peroxide degradation of Hyflon Ion membranes

Perfluorosulfonic acid (PFSA) membranes have been used for 40 years as solid electrolytes in low temperature fuel cells and are considered from the scientific community superior to other polymeric products due to their good combination between chemical resistance and proton conductivity. In recent years, development of the class of PFSA membranes known as ‘short side chain’ membranes has been restarted from Solvay Solexis (Hyflon^® Ion).