Ultrafast all-optical switching in GaAlAs integrated interferometer in 1.55 mu m spectral region

The first observation is reported of ultrafast all-optical switching in an integrated asymmetric Mach-Zehnder interferometer, using the nonresonant nonlinearity in Ga/sub 0.82/Al/sub 0.18/As below half the bandgap. A relative switching fraction of more than 80% has been achieved using 330 fs pulses at around 1.55 mu m from a coupled-cavity mode-locked colour centre laser.<>     

Time and frequency in fundamental metrology

The author shows that because time and frequency are the most accurately measured physical quantities, it is desirable to tie other physical quantities to time and frequency measurements. A review of the progress that has been made in this direction along with speculation on possibilities for the future are given. The role of time and frequency in a wide range of measurements is discussed, particularly those involving the International System of Units (SI) and fundamental physical constants     

Minimum mean-squared error decision-feedback equalization fordigital subscriber line transmission with possibly correlated line codes

The author presents a theory on MMSE (minimum mean-squared error) decision-feedback equalization which augments previously published results by allowing both a correlated symbol sequence and a fractionally spaced DFE (decision-feedback equalizer) forward filter. This theory facilitates calculating the potential DSL (digital subscriber line) transmission performance in cases of correlated line codes, especially for situations where one or both of the DFE filters are infinite in length. The situation of an infinite-length DFE is of interest because it provides information on the limit of MMSE equalization and can thus serve as a benchmark against which the performance of a finite-length DFE may be compared. The author also presents a few numerical examples of the performance of MMSE decision-feedback equalization in DSL transmission at ISDN (integrated services digital network) basic access rates with several well-known line codes     

Comparative toxicity of organotin compounds to rainbow trout (Oncorhynchus mykiss) yolk sac fry

The comparative toxicity of various organotin compounds was investigated in early life stages of the rainbow trout. Beginning with yolk sac fry, trout were continuously exposed for 110 days to tributyl- (TBTC), triphenyl- (TPhTC) or tricyclohexyltin chloride (TCHTC) at concentrations of 0.12-15 nM, to trimethyltin chloride (TMTC) at concentrations of 3-75 nM or to dibutyl- (DBTC) or diphenyltin chloride (DPhTC) at 160-4000 nM. The diorganotin compounds DBTC and DPhTC were about three orders of magnitude less toxic than the triorganotin homologs TBTC and TPhTC. Both for DBTC and DPhTC, a no-observable-effect concentration (NOEC) of 160 nM was established, corresponding to 40 and 60 ppb, respectively. Of the triorganotin compounds, TCHTC appeared to be the most toxic, inducing 100% mortality within 1 week at a concentration of 3 nM. Only a few trout survived exposure to 0.6 nM TCHTC for 110 days. TBTC and TPhTC caused acute mortality at a concentration of 15 nM. For both TBTC and TPhTC a NOEC of 0.12 nM was established, corresponding to water concentrations of 40 and 50 ppt, respectively. Histopathological examination revealed depletion of glycogen in liver cells of both di- and triorganotin exposed fish, except in the case of TMTC. No signs of toxicity were observed in fish exposed to up to 75 nM TMTC, the highest concentration tested. Atrophy of the thymus, the most prominent sign of toxicity of di- and tributyltin compounds in mammalian species, was not observed in early life stages of rainbow trout. Tail melanization was observed in the groups exposed to 3 nM TPhTC, 3 nM TBTC, 800 nM DBTC and 800 nM DPhTC. At the end of the exposure period, resistance to infection was examined by an intraperitoneal challenge with Aeromonas hydrophila, a secondary pathogenic bacterium to fish. Resistance of bacterial challenge was found to be decreased even at the lowest-effect concentration of both di- and triorganotin compounds.     

Addressing the special concerns of landfill closures: VLDPE and textured geomembranes

Landfill closures often require a somewhat different set of properties for synthetic liners than do landfill bottom liner installations. In particular, cap design usually presents the geotechnical engineer with greater concerns regarding long-term slope stability and accommodation of differential settlement. Friction between synthetic liners and materials contacting those liners, multiaxial elongation, and flexibility increase in importance. Since leachate does not contact the liners, chemical resistance becomes less important. Resistance to the components of landfill gas is, in most cases, all that is necessary.

As a result, synthetic liners with a textured surface to improve friction angles, and very low density polyethylene (VLDPE) geomembranes are becoming very attractive to geotechnical engineers. They provide considerable improvement in those areas which are important for cap installation. These materials, however, behave differently in standard index and performance testing of geomembranes, when compared with traditional polyethylene liners. These behaviors and differences are important for geotechnical engineers to understand. They are discussed in this paper.     

Role of Milk Fat Globule Membrane in Autoxidation of Milk Fat

The influence of the milk fat globule membrane (MFGM) on oxidation of milk fat under various conditions was monitored by fatty acid analysis and oxygen consumption at 50°C. The rate of copper-catalyzed oxidation of cream containing the membrane was faster than when the membrane was removed. In the dry state, the isolated MFGM, membrane lipids (ML) and the nonlipid membrane solids (NLMS) inhibited oxidation at 50°C and 95°C. In the presence of water, however, all membrane components enhanced oxidation at 50°C. The balance between the accelerating effects of membrane components and the inhibiting influence of other factors appeared to depend on processing conditions.     

Alternating minimization and Boltzmann machine learning

Training a Boltzmann machine with hidden units is appropriately treated in information geometry using the information divergence and the technique of alternating minimization. The resulting algorithm is shown to be closely related to gradient descent Boltzmann machine learning rules, and the close relationship of both to the EM algorithm is described. An iterative proportional fitting procedure for training machines without hidden units is described and incorporated into the alternating minimization algorithm.     

Two-level optimal output feedback stabilizer design

Design of two-level system stabilizers is considered using an optimal reduced-order model whose state variables are torque angles and speeds. The reduced-order model retains their physical meaning and is used to design a two-level linear feedback controller that takes into account the realities and constraints of the electrical power systems. The two-level control strategy is used, and a global control signal is generated from the output variables to minimize the effect of interaction. The effectiveness of this controller is evaluated, and an example, the multimachine system, is given to illustrate the advantages of the proposed method. The responses of the system with the two-level scheme and optimal reduced order scheme are included for comparative analyses