Modified SPEEK membranes for direct ethanol fuel cell

Membranes with low ethanol crossover were prepared aiming their application for direct ethanol fuel cell (DEFC). They were based on (1) sulfonated poly(ether ether ketone) (SPEEK) coated with carbon molecular sieves (CMS) and (2) on SPEEK/PI homogeneous blends. The membranes were characterized concerning their water and ethanol solution uptake, water and ethanol permeability in pervaporation experiments and their performance in DEFC tests. The ethanol permeabilities for the CMS-coated (180 nm and 400 nm thick layers) SPEEK were 8.5 and 3.1 × 10⁻¹⁰ kg m s⁻¹ m⁻² and for the homogeneous SPEEK/PI blends membranes with 10, 20 and 30 wt.% of PI were 4.4, 1.0 and 0.4 × 10⁻¹⁰ kg m s⁻¹ m⁻² respectively, which is 2- to 50-fold lower than that for plain SPEEK (19 × 10⁻¹⁰ kg m s⁻¹ m⁻²). Particularly the SPEEK/PI membranes had substantially better performance than Nafion 117^® membranes in DEFC tests at 60 °C and 90 °C.     

Physicochemical properties of pre-treated cuttlebone powder and its potential as an alternative calcium source

This study was aimed to investigate the potential use of pre-treated cuttlebone powder (CBP) as an alternative calcium source by evaluating the physicochemical properties of CBP pre-treated with distilled water (CBP1), 1% acetic acid (CBP2), and 2% sodium hydroxide (NaOH) solutions (CBP3). Proximate analysis revealed ash as the major component of all samples. The presence of phenols, flavonoids, alkaloids, and glycosides were detected but tannins appeared to be absent in cuttlebones. Mineral analysis indicated that CBP was rich in calcium, which means the material may be considered as a potential calcium source for food products or calcium supplements. The bulk density of CBP2 was significantly lower (p < .05) than those of CBP1 and CBP3, and the water holding capacity (WHC) of CBP1 was significantly higher (p < .05) than those of CBP2 and CBP3. The high bulk density, water and oil holding capacities of CBP demonstrated its potential use as a functional food ingredient.     

Coupled Tamm waves guided by an isotropic and homogeneous dielectric layer in a rugate filter

The propagation of Tamm waves (also known as Bloch surface waves) guided by a layer of homogeneous dielectric material in a rugate filter was studied theoretically. A canonical boundary-value problem was set up and a dispersion equation was obtained. The solution of the dispersion equation indicated the existence of coupled modes of Tamm waves that were absent when the homogeneous dielectric material was taken to occupy a half space. The spatial profiles of the electric and magnetic fields of Tamm waves showed that Tamm waves propagate localized to either one or both interfaces. Multiple Tamm waves may lead to multi-analyte chemical sensors and multi-channel communication.     

Optical probe for absolute measurement of surface-acoustic-wave amplitude

A simple method is proposed for absolute measurement of s.a.w. mechanical deformation normal to the surface of propagation. Experimental results are given with an error smaller than 5%.     

Anterior and antero-lateral surgery of the lower cervical spine (25 years after H. Verbiest). 2: Indications, results, complications)

The present course on the anterior and antero-lateral surgical approach of the lower cervical spine was organized for the neurosurgery trainees by the French Speaking Neurosurgical Society, and was held during the winter meeting in December 1995. The aim of this course was to recall the basic technical principles of the microsurgical anterior cervical approach, and to discuss the main indications of this surgical treatment. Many theoretical points were strengthened by the author's personal experience and comments. In Part I, the technical bases of the different anterior or antero-lateral approaches were presented (1996, 42 : 105-122). In the present Part II, the main indications of the anterior surgical approach to the cervical disk or the vertebral body are detailed, and the requirement of a bone graft and/or an osteosynthesis are discussed with their consequences on the final results. Secondly, variants of the surgical technics in use in case of cervical spinal instability are commented. Then various approaches to the cervical spinal tumors and to the vertebral artery are detailed and commented. Lastly, general and specific complications of the anterior cervical approach are listed with their rate of occurrence, and their prevention and management are discussed.     

Glass reinforced GaAs beam lead Schottky diode with airbridge for millimetre wavelengths

We describe the fabrication and measurement of a glass reinforced beam lead Schottky diode with an airbridge for use at millimetre wavelengths. We report an extremely low single sideband (SSB) noise figure for these diodes of 7.9 dB at 94 GHz, including a 1.5 dH IF (30 MHz) contribution.     

Prism-coupled excitation of multiple Tamm waves

Abstract

A Tamm wave is guided by the interface of a homogeneous dielectric material and a periodically nonhomogeneous dielectric material, both isotropic. We found theoretically that multiple Tamm waves of different linear polarization states can be guided by such an interface incorporated in a prism-coupled configuration. The Tamm waves have different linear polarization states, phase speeds, and spatial profiles, but the same frequency. The narrow absorptance peaks associated with the excitation of Tamm waves in the prism-coupled configuration offer the application as chemical sensors with very high sensitivity.     

94 GHz microstrip monolithic GaAs mixer

A microstrip monolithic GaAs mixer has been designed and fabricated for operation in the millimetre-wave band. A 6.5 dB minimum conversion loss has be achieved in narrowband operation (fLO = 93.7GHz and fIF= 130MHz); this figure includes the effect of losses and mismatch in the circuit and test fixture.