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A retained microcatheter is a rare complication of endovascular treatment of cerebral aneurysms. We describe such a case that was complicated by delayed microcatheter fracture within the internal carotid artery and subsequent thrombo-embolism resulting in transient ischaemic attacks. We also describe endovascular management of this complication through the use of several carotid stents.

Spontaneous and laser emission from In1-xGaxP1-zAszdouble heterojunction diodes near the direct-indirect crossover (EΓ= EX, x≡ xc, z≡ zc) are studied at 77°K as a function of hydrostatic pressure up to 6 kbar. The pressure coefficients of the spontaneous emission peaks and of the laser modes are ∼- 10.5 × 10-6eV/bar which is characteristics of the Γ band edge in III–V semiconductors. Laser threshold current is found to rise rapidly as pressure is applied owing to the decreasing Γ-Xseparation and the resultant carrier transfer to the Xminima. Experimental lower limits for the direct-indirect crossover at three points in the In1-xGaxP1-zAszquaternary system are determined. These three points and the established crossover in GaAs1-yPy(yc≈ 0.46, 77°K) give for the quaternary crossover (77°K) xc− 0.52zc= 0.72. and the value xc≈ 0.72 for the limiting case of In1-xGaxP. Band edge bowing effects along the direct-indirect crossover in the In1-xGaxP1-zAszsystem are discussed. The highest energy laser (77°K) for this quaternary system is estimated from pressure measurements to be ∼ 2.155 eV (5752 Å).

Gerald Edelman's Neural Darwinism advances an hypothesis that the brain develops epigenetically in the individual according to principles of natural selection operating over populations of neuronal groups. The central idea is that the organism does not adapt to a pre-categorized world, but generates categories (for instance for visual recognition) that have survival value. Hence, it is argued, brain process-development can not be modeled by instructionist - program-driven sequential processes - methods. AI must therefore fail in principle in attempting to explain cognitive processes.The alternative is the parallel, distributed processing model, which must be subject to evolutional change and devoid of precategorization or based on assumptions of a 'pre-labelled' world.In the present paper I argue that computational models are not limited to sequential programs, but that embodied algorithms as are realized in hardware and probably in neural circuits do afford adequate models. Thus there is no principled reason for adoption of nondigital models, although Edelman is right about conventional AI, which uses free sequential algorithms.I conclude by remarking that semantical and intentional properties of the mind/brain can not be modeled by the type of parallel connectionist system Edelman advocates, but requires computational (recursive) models.

Nitric oxide is formed in the brain primarily by neurons containing neuronal nitric oxide synthase (nNOS), though some neurons may express endothelial NOS (eNOS), and inducible NOS (iNOS) only occurs in neurons following toxic stimuli4,5,12 Mice with targeted disruption of nNOS (nNOS−) display distended stomachs with hypertrophied pyloric sphincters reflecting loss of nNOS in myenteric plexus neurons.7 nNOS− animals resist brain damage following middle cerebral artery occlusion8 consistent with evidence that excess release of nitric oxide mediates neurotoxicity in ischemic stroke.3

We report the generation of high-speed optical pulses in gain-switched short-cavity InGaAsP injection lasers by high-frequency direct modulation. Short pulses (25 ps) with high on/off ratio were obtained at 11.2 GHz from a short-cavity double-channel planar buried-heterostructure (DCPBH) InGaAsP semiconductor laser biased at three times the threshold current. This is the first report of direct modulation above 10 GHz for InGaAsP lasers.

High-temperature operation of InGaAsP double-channel buried-heterostructure (DCBH) lasers emitting at 1.55 μm is reported. The 1.55 μm InGaAsP DCBH lasers have threshold currents as low as 18 mA at 20°C. The threshold current temperature sensitivity between 10°C and 75°C is characterised by a T0 value of 55–66 K. Electro-optical derivative measurements show that the 1.55 μm InGaAsP DCBH laser does not have substantial above-threshold leakage current for junction temperatures as high as 75°C. Finally, these devices were operated at temperatures as high as 110°C, the highest CW operating temperature obtained to date for a 1.55 μm InGaAsP laser.

High-speed operation of cleaved coupled cavity (C3) lasers made from double-channel planar buried-heterostructure (DCPBH) lasers operating at 1.5 μm wavelength is reported. Error-free (error rate<10−11/s) operation through a spectrometer at a data rate of 2 Gbit/s and with large on-off and mode rejection ratios is demonstrated. Small-signal bandwidth measurements indicate possible operation of these lasers up to about 4 Gbit/s.

Short-cavity (50–100 μm) index-guided lasers made by recleaving conventional 1.3 μm BH devices have been found to provide improved single-frequency output under both CW and modulated conditions.

A value of 1.8 for the astigmatism factor K in narrow stripe InGaAsP/InP lasers is obtained by direct measurement of the beam parameters. Previously, values from 10 to 30 were found for AlGaAs/GaAs lasers of similar geometry.

Measurements are reported of the electrical characteristics and temperature dependence of threshold current of InGaAsP-InP d.h. lasers (λ = 1.3 μm). Analysis of the I dV/dI characteristics of these devices indicates that drift leakage of carriers from the active region is not responsible for the high temperature sensitivity of threshold in this material system.

Measured small-signal frequency-response characteristics of directly modulated long-cavity and short-cavity InGaAsP double-channel buried-heterostructure (DCBH) lasers are reported. Relaxation oscillation resonance frequencies as high as 9.4 GHz at a bias current of twice threshold have been obtained with short-cavity devices.