Close-spaced fused fibre wavelength division multiplexers with very low polarisation sensitivity

The authors describe the fabrication of high performance narrowband fused fibre wavelength multiplexers. A twisting technique is employed to reduce the polarisation sensitivity. Unlike other polarisation quenching methods, twisting maintains the intrinsically good temperature stability of the device. The twisting mechanism has been studied theoretically using a model with a realistic coupler cross-section.<>     

Quantum chaotic transport in double barrier tunnel structures

The transition from regular to chaotic classical electron dynamics in a wide potential well with a high tilted magnetic field is investigated using Poincaré sections. The corresponding quantized energy level spectrum for the well is calculated as a function of the tilt angle π. For values of π where the system exhibits strong classical chaos, the distribution of nearest-neighbor level spacings obeys universal Wigner statistics. Regular long-range fluctuations in the density of levels are identified and related to distinct unstable closed classical orbits in accordance with the Gutzwiller trace formula. These orbits are found to produce regions of high probability density (scars) in the wavefunctions associated with subsets of almost equally-spaced energy levels. The energies of these scarred states can be located using a simple semiclassical quantization rule. This periodic scarring of individual wavefunctions is shown to have a pronounced influence on the tunneling characteristics of double barrier structures. Tunneling transitions into the scarred states dominate the current-voltage curves and generate a series of resonant peaks as observed in recent magnetotunneling experiments. Regimes in which resonant tunneling spectroscopy might provide experimental evidence for the existence of scarred states are identified.     

Readout circuit for CMOS active pixel image sensor

The design and simulation results of a new readout circuit for a CMOS active pixel image sensor are presented. This scheme removes the fixed pattern noise and reduces the signal degradation while offering an increase in readout speed, compared with the conventional approach     

Review of high level fault modeling approaches for mixed-signal systems

In the modern analogue design, Transistor Level Fault Simulation (TLFS) plays the important part since every fault in the whole circuit has to be simulated at that level. Unfortunately, it is a very CPU intensive task even though it maintains the high accuracy. Therefore, High Level Fault Modeling (HLFM) and High Level Fault Simulation (HLFS) are required in order to alleviate the efforts of simulation. In this paper, different HLFM approaches are reviewed at the device level during last two decades. We clarify their domains of application and evaluate their strengths and current limitations. We also analyze causes of faults and introduce various test approaches.     

Degradation of polymer electrolyte membranes

One of the predominant failure modes of polymer electrolyte membrane (PEM) fuel cells is the degradation of the PEM, especially when the fuel cell is used for transportation applications. Numerous studies have been carried out regarding this issue but many aspects of the degradation are not yet understood. This paper reviews the available literature regarding membrane degradation, and attempts to classify the degradation modes into three categories: mechanical, thermal and chemical/electrochemical. The factors that contribute to each mode are discussed, along with detailed mechanisms for some degradations. Some possible mitigation strategies are also explored.     

Partial replacement of chicken semen by turkey semen in artificial insemination of chickens

Chicken semen undiluted, diluted with a diluent containing fructose and/or mixed with turkey semen was used to inseminate Leghorn hens. In two of three experiments there was an improvement in fertility from insemination by mixed semen as compared to semen diluted to the same extent with the diluent.     

An improved technique for prolonged arterial catheterization in infants and children

Arterial catheterization for blood gas analysis and direct monitoring of blood pressure in infants and children can be attended by a variety of complications, which limit its use to short periods of time. An improved technique, consisting of elimination of stopcocks, the use of a continuous flushing system adapted for infants and children, and meticulous care of the system, was used in 57 children whose ages ranged from the neonatal period to 16 years. The mean duration of cannulation was 5.5 days (range, 1-31 days). All but one of the catheters were functional at the time of discontinuation. There were no thromboembolic phenomena, local or systemic infections or accidental bleeding. We feel that our approach to prolonged arterial cannulation can be an extremely valuable aid in the management of critically ill children.     

The effect of caffeine on the serum insulin level during intravenous glucose tolerance test in patients with chemical diabetes

A small but significant number of tritiated thymidine labelled cells were found, by autoradiography, in the glomeruli of rats with Masugi nephritis or chronic serum sickness nephritis. There were no labelled glomerular cells in sections of untreated animals. The findings favour the contention that in proliferative glomerulonephritis, glomerular hypercellularity is due to infiltration of monocytic cells into the tufts where they divide.     

Serial measurements of left ventricular ejection fraction by radionuclide angiography early and late after myocardial infarction

1-Acyl-2-succinyl glycero-3-phosphorylcholine (GPC) was synthesized and its properties described. Although 1-acyl-2-succinyl GPC is a good substrate for succinate dehydrogenase, experiments on the incorporation of [2,3-14C] succinate into mitochondrial lipids gave no evidence to indicate that it is an intermediate in the enzymic oxidation of succinate to fumerate, as has been suggested earlier.