Packaged AlGaAs waveguide modulator array at 830 nm wavelength

We report a fully packaged AlGaAs waveguide modulator array with four individually addressable elements operating at approximately 830 nm wavelength and a clock speed of 1 GHz. The modulators rely largely on the linear electro-optic effect for operation, and have been packaged with an E/D MESFET driver with complementary 3.5 V outputs, and a thick-film ceramic bias network. The device is compact, using multimode interference devices for on-chip splitters and combiners and has a 4 mm electrode length. Extinction ratios in excess of 10 dB have been demonstrated over a temperature range from room temperature to 143°C. The modulator array has been packaged with a remote high power (100 mW) diode laser using stable single mode input coupling, while the modulator output is packaged with a multimode fiber array of 52.5 μm core diameter     

How an investigator resolved the Vasa warship disaster

David Bristow, Q.C., of Toronto, provides a current practice lesson by detailing an old story of how a creative mediator diffused the effects of a national tragedy— the sinking of the Vasa in Stockholm's harbor in 1628     

Effects of SO2 on sulphur and nitrogen fractions and on free amino acids in perennial ryegrass

An investigation was made of the S and N fractions and of the free amino acids in the shoots of perennial ryegrass (Lolium perenne L.) cv S23 grown in soil with and without added sulphate and in filtered air containing 0 and 400 μg SO₂ m^?3. Exposure to SO₂ of potentially S-deficient plants alleviated the signs of deficiency; compared to deficient plants, the content of total and sulphate S was increased and the ratio N:S, as well as content of free amino acids, including asparagine and glutamine, was decreased. Similar exposure of plants grown with an adequate supply of S through the soil increased the content of sulphate but resulted in no significant alteration of the content of free amino acids.     

A numerical method for determining monotonicity and convergence rate in iterative learning control

In iterative learning control (ILC), a lifted system representation is often used for design and analysis to determine the convergence rate of the learning algorithm. Computation of the convergence rate in the lifted setting requires construction of large N×N matrices, where N is the number of data points in an iteration. The convergence rate computation is O(N²) and is typically limited to short iteration lengths because of computational memory constraints. As an alternative approach, the implicitly restarted Arnoldi/Lanczos method (IRLM) can be used to calculate the ILC convergence rate with calculations of O(N). In this article, we show that the convergence rate calculation using IRLM can be performed using dynamic simulations rather than matrices, thereby eliminating the need for large matrix construction. In addition to faster computation, IRLM enables the calculation of the ILC convergence rate for long iteration lengths. To illustrate generality, this method is presented for multi-input multi-output, linear time-varying discrete-time systems.     

Protective effect of clentiazem against epinephrine-induced cardiac injury in rats

We investigated the effects of clentiazem, a 1,5-benzothiazepine calcium antagonist, on epinephrine-induced cardiomyopathy in rats. With 2-week chronic epinephrine infusion, 16 of 30 rats died within 4 days, and severe ischemic lesions and fibrosis of the left ventricles were observed. In epinephrine-treated rats, left atrial and left ventricular papillary muscle contractile responses to isoproterenol were reduced, but responses to calcium were normal or enhanced compared to controls. Left ventricular alpha and beta adrenoceptor densities were also reduced compared to controls. Treatment with clentiazem prevented epinephrine-induced death (P < .05), and attenuated the ventricular ischemic lesions and fibrosis, in a dose-dependent manner. Left atrial and left ventricular papillary muscle contractile responses to isoproterenol were reduced compared to controls in groups treated with clentiazem alone, but combined with epinephrine, clentiazem restored left atrial responses and enhanced left ventricular papillary responses to isoproterenol. On the other hand clentiazem did not prevent epinephrine-induced down-regulation of alpha and beta adrenoceptors. Interestingly, clentiazem, infused alone, resulted in decreased adrenergic receptor densities in the left ventricle. Clentiazem also did not prevent the enhanced responses to calcium seen in the epinephrine-treated animals, although the high dose of clentiazem partially attenuated the maximal response to calcium compared to epinephrine-treated animals. In conclusion, clentiazem attenuated epinephrine-induced cardiac injury, possibly through its effect on the adrenergic pathway.     

Computer display of vowel quadrilateral with real-time representation of articulation

The classical characterisation of vowel sounds used by phoneticians is the vowel quadrilateral, which originally was assumed to be the locus of the tongue body between its four extreme vowel positions. A method of real-time computer analysis and display which represents the vowel quadrilateral is described. This has application in computer-based speech training aids, but may have wider use in speech research generally.     

The role of neuropeptide Y in the antiobesity action of the obese gene product

Recently Zhang et al. cloned a gene that is expressed only in adipose tissue of the mouse. The obese phenotype of the ob/ob mouse is linked to a mutation in the obese gene that results in expression of a truncated inactive protein. Human and rat homologues for this gene are known. Previous experiments predict such a hormone to have a hypothalamic target. Hypothalamic neuropeptide Y stimulates food intake, decreases thermogenesis, and increases plasma insulin and corticosterone levels making it a potential target. Here we express the obese protein in Escherichia coli and find that it suppresses food intake and decreases body weight dramatically when administered to normal and ob/ob mice but not db/db (diabetic) mice, which are thought to lack the appropriate receptor. High-affinity binding was detected in the rat hypothalamus. One mechanism by which this protein regulated food intake and metabolism was inhibition of neuropeptide-Y synthesis and release.