Detection of single-threading properties in combinator notations

The detection of a property called single-threading in functional programs or denotational language definitions can be exploited to produce a more efficient implementation of the program or language, by allowing a program variable or semantic domain to be implemented by a global data structure. Earlier work by David A. Schmidt has given sufficient criteria for the detection of the single-threading property in [lambda]-calculus expressions. We extend that work by giving criteria for single-threading detection in combinator notations;Two sets of single-threading criteria are given: one for a particular combinator language, TML, and the other for a generalized combinator notation. In both cases, proofs are given which demonstrate the soundness of the criteria. We also discuss some reasons for the differences in the two sets of criteria;In order to evaluate the usefulness of single-threading detection and the associated globalization transformation in practice, a testbed implementation of the TML criteria is being programmed, using the PSI/DAOS compiler-generation system developed at Aalborg University. Some preliminary results from this work are discussed

Q is for WHAT, WHEN, WHERE?:The ‘q’ spellings for OE hw-

AbstractThere is a wide array of spellings attested in Middle English for initial OEhw- in words such aswhen, where, what, who, which. Those beginning with ‘q’, found mostly in the North (including Scotland) and Northeast Midlands, have long been the subject of scholarly debate. The consensus is that they represented an articulation stronger than [hw], usually assumed to be [xw]. Just a handful of scholars have suggested that the articulation could have been [kw], but there is so far little detailed argument for this position. We propose thatat least a subsetof reflexes of OEhw- words cameat least variablyto be pronounced with initial [kw]. We suggest that this strengthened pronunciation existed alongside [xw], and lenited [hw] and [w], as well as simple [h] with the [w] deleted. We link (as some other scholars have) the history of these spellings with that of northern lenition of original initial [kw] to [xw]/[hw]/[w]. We approach the problem from a strongly variationist perspective, presenting (in accompanying appendices) detailed information on the ‘q’ spellings accessible from LAEME and eLALME. We review all the data, from the earliest attested forms through to modern dialect surveys, including place-name evidence, and we assess previous arguments on the topic.</jats:p

A simple angle-resolved thermal molecular beam reactor: applied to CO oxidation on Pt{110}

We developed a simple form of thermal molecular beam catalytic reactor system which is capable of measuring sticking probabilities and reaction probabilities, together with angle-resolved scattering of molecules and products during catalytic reactions at the surface. This includes very fast determination of the angle dependence of the reaction product flux at steady-state. It was employed to determine the oxidation of CO on Pt{110}-(1 × 2), including individual molecular sticking and scattering. The initial sticking probability of oxygen on Pt{110} shows a small variation between 140 and 750 K surface temperature, from 0.45 to 0.28. The saturation uptake drops from 1.5 ± 0.2 ML at 140 K to 0.6 ML at 300 K and to 0.23 ± 0.02 ML at 750 K. The initial sticking probability of CO at 300 K is 0.80 and decreases to 0.62 at 470 K. Beyond that temperature, it descends steeply down to near zero at 570 K, due to the high desorption rate of CO at that temperature. Kisliuk precursor mobility parameters K were calculated from shape of the sticking curves. For 300 K, a value of 0.11 ± 0.01 was found, which increases to 0.76 ± 0.01 at 470 K, indicating a change from considerable mobility in the precursor state, to more limited mobility before desorption at high temperature. In temperature-programmed CO-O2 reaction experiments, CO2 production was observed to initiate in the temperature region 460–510 K. Using isothermal angle-resolved experiments, the CO2 flux was determined in the [11¯0] plane at temperatures of 470–620 K. Two sharp scattering lobes at positions of ±16° off the surface normal were found, with a high cosine power angle dependence, which were attributed to desorption from the {111}-like microfacets of the 1 × 2 reconstructed surface, with products evolving over a high barrier

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xxi, 419 p.; 23 cm