Continuous Function Characterizations of Stratifiable Spaces

The insertion of a continuous function between pairs of semicontinuous functions in a monotone manner is investigated. In particular, it is established that a topological space is stratifiable if and only if for every pair of semicontinuous functions......     

Measurement of the Bulk Modulus of a Liquid Using a Pump–Probe Laser Technique

We describe an undergraduate laboratory experiment that uses a time-resolved laser technique. Using pump-probe in a novel way, students determined the bulk modulus of a liquid. Employing the fourth harmonic from a pulsed Nd:YAG laser, an elastic wave is generated in an aqueous solution of N-acetyltryptophan, and the wave propagation is probed by a He-Ne laser. This experiment serves as a rare example of how a bulk property of a condensed phase can be measured using time-resolved optical measurements having relevance to undergraduate physical chemistry or material science laboratory.     

Integrated-circuit digital I?Requirements and features of a logic family; RTL, DTL, and HTL devices logic families

The purpose of this article is to categorize the needs and desired features that a logic or system designer should consider when selecting a family of digital integrated circuits. The various major digital IC families are evaluated and compared with these needs in view. The intended results are that the reader will gain facility in IC technology, terminology, and usage in various areas of application. Part II of this article will cover transistor-transistor logic (TTL) devices. Part III is devoted to emitter-coupled logic (ECL) and metal oxide semiconductor (MOS) devices.     

Certification of morphine-3-β-D-glucuronide in a human urine standard reference material

 The U.S. National Institute of Standards and Technology (NIST) has developed and certified a standard reference material, SRM 2382, for use in testing for bias in the determination of morphine present as a glucuronide in human urine. This SRM consists of three levels of morphine-3-β-D-glucuronide (M-3-G) in lyophilized urine. Two independent hydrolysis procedures, enzymatic and acidic, for quantitative release of morphine were investigated. The results of hydrolysis efficiency from these two procedures agreed well. These two hydrolysis procedures along with two analytical methods developed previously for measurement of free morphine [1] were used to certify M-3-G in SRM 2382. Enzymatic hydrolysis was used with the GC/MS method and acidic hydrolysis was used with LC/MS. The results from these two pairs of methods were in good agreement, and were statistically combined to yield certified values of 209±20, 437±21, and 853±39 ng/mL for morphine, as the free base. Round-robin studies on this material among ten military laboratories demonstrated the suitability of the SRM for its intended purpose. Received: 6 February 1996/Accepted: 29 April 1996     

On-resistance of V-v.m.o.s. power transistors

An expression for the on-resistance of a V-groove vertical-channel m.o.s. (V-v.m.o.s.) transistor is presented. The expression relates the on-resistance to the geometry and resistivity of the drain drift region and is useful in optimising the drift region parameters for minimum on-resistance and maximum drain-source breakdown.     

The effect of vibrational energy on the reaction of molecular hydrogen with atomic oxygen

An upper bound of 6 × 10¹⁰ cm³/moles on the rate constant for the reaction of atomic oxygen with vibrationally excited H₂ has been deduced from laboratory observations and from detailed computer calculations. From this result it can be shown that no more than 30% of the vibrational energy of H₂ is effective in overcoming the activation energy for the O + H₂ reaction.     

Fibre-supported optical generation and delivery of 60 GHz signals

A novel `frequency quadrupling' technique for the optical generation and delivery via fibre of modulated 60 GHz band millimetre-wave signals is described. The technique requires only microwave frequency capability for the optical modulator and drive electronics, and these are readily available commercially. The frequency quadrupling technique is demonstrated experimentally with a high spectral purity 60 GHz signal obtained using a 15 GHz source and optical modulator