Realization of phase grating comb reflectors and their application to widely tunable DBR lasers

Widely tunable InP lasers often require comb reflectors as an integral part of their design. It is desirable to achieve comb reflectors with as "top-hat" like a response as possible. There are several ways to do this, but one simple and practical way is by utilizing a phase grating. Previously these have been discussed theoretically, but here we will describe the fabrication of such gratings and how they can find application as the reflectors in widely tunable InP lasers. The example devices which we will discuss show that phase-grating-based distributed Bragg reflector lasers can have tuning ranges of around 35 nm combined with excellent sidemode suppression ratio of better than 45 dB at the mode centers.     

Fabrication of films of hydrogen uranyl phosphate tetrahydrate and their use as solid electrolytes in electrochromic displays

We have found that the high proton conductivity of hydrogen uranyl phosphate tetrahydrate HUO₂PO₄·4H₂O (HUP) is sufficient to enable an HUP/H_xWO₃ electrochromic cell to function as fast as a cell with an acidic solution electrolyte. Switching times down to 0.3 s were found. The fabrication procedure to obtain the stable and uniform films of HUP required has been optimized, and dense sintered films up to 6 cm in diameter have been produced.     

The European videotex standard

The European PTTs have been working for several years to develop a standard for videotex that is compatible with Recommendations S-100 and F-300 from the CCITT, but which can use low-cost, character-based services. The paper describes the European standard developed by the CEPT. It discusses its structure, the character sets it provides and their associated ‘attributes’, control characters, page scrolling, colour tables and code-table switching. The relative advantages and disadvantages of alphamosaic and alphageometric systems are discussed, with examples of both. Finally, the relationship of the European standard to developments in other parts of the world are examined.     

Battery and other applications of a new proton conductor: Hydrogen uranyl phosphate tetrahydrate,HUO2PO4.4H2O

The recent discovery by Shilton and Howe that hydrogen uranyl phosphate tetrahydrate HUO₂PO₄.4H₂O (HUP) is a rapid proton conductor, with a     

Fluorometric measurement of aflatoxins

An accurate, precise and sensitive fluorometric method for quantifying purified aflatoxins in solution is proposed. After purification, aflatoxin samples are read in a fluorometer with a primary filter of 365 nm and a secondary filter of 435 nm for B₁ and B₂ and 465 nm for G₁ and G₂. The method is precise at as little as 0.0002 μg/ml B₁ and G₁ and 0.00006 μg/ml B₂ and G₂, and accurate at concentrations of 0.002 μg/ml B₁ and G₁ and 0.0006 μg/ml B₂ and G₂. University of Georgia College of Agriculture Experiment stations, Journal Series Paper No. 810, College Station, Athens, Georgia 30601.     

Dichloroacetate enhanced myocardial functional recovery post-ischemia : ATP and NADH recovery

This study was undertaken to determine the effect of dichloroacetate (DCA) on myocardial functional and metabolic recovery following global ischemia. Isolated rabbit hearts were subjected to 120 min of mildly hypothermic (34 degrees C), cardioplegic arrest with multidose, modified St. Thomas' cardioplegia. Hearts were reperfused with either physiologic salt solution (PSS) as controls, (CON, n = 10) or PSS containing DCA (DCA, n = 6) at a concentration of 1 mM. Functional and metabolic indices were determined at baseline and at 15, 30, and 45 min of reperfusion. In four DCA and four CON hearts, myocardial biopsies were taken at baseline, end-ischemia, 15 and 45 min for nucleotide levels. Functional recovery was significantly better in hearts reperfused with DCA as demonstrated by recovery of baseline developed pressure (DCA = 69 +/- 5%, CON = 45 +/- 9%) and dP/dt (DCA = 64% +/- 10% versus CON = 48% +/- 10%). Coronary blood flow was not different between groups either at baseline or during reperfusion, but myocardial oxygen consumption (MVO2) was increased in the DCA versus CON hearts (79% +/- 20% of baseline vs 50% +/- 18%). Recovery of myocardial adenylate energy status was improved in the DCA versus CON hearts (ATP recovered to 45% +/- 20% versus 8% +/- 6% of baseline). Coronary sinus lactate concentration was decreased in DCA perfused hearts at 45 min of reperfusion. Percent of baseline NADH values was similar at 15 min of reperfusion, but at 45 min, DCA hearts showed a decrease in NADH levels, while CON hearts showed an increase (DCA = 48%; CON = 121%). The enhanced myocardial function and improved metabolic status noted with DCA may result from increased oxidative phosphorylation due to altered pyruvate dehydrogenase (PDH) activity.     

The effects of thermal history and composition on the hot ductility of low carbon steels

The hot tensile test was used to investigate the effects of certain key variables on the hot ductility of low carbon steels. A transition from high to low ductility occurred at about 2200°F (1204°C) during continuous cooling of both wrought and cast specimens of low carbon steel after relatively brief exposure to temperatures above 2400°F (1316°C). The observed loss in ductility on cooling below 2200°F (1204°C): (a) increased with decreasing manganese-sulfur ratios, (b) was minimized by appropriate variations in thermal history. Metallographic and fractographic examination of the tensile specimens after thermal cycling indicated that this low ductility below 2200°F (1204°C) resulted from microcracking associated with (Mn, Fe)S precipitates found at the austenite grain boundaries. The results of this investigation help explain why different levels of hot ductility are observed in low carbon steels and what steps can be taken to improve this ductility.