93,647 research outputs found
Compilation of head and strong reduction
Functional language compilers implement only weak-head reduction. However, there are cases where head normal forms or full normal forms are needed. Here, we study how to use cps conversion for the compilation of head and strong reductions. We apply cps expressions to a special continuation so that their head or strong normal can be obtained by the usual weak-head reduction. We remain within the functional framework and no special abstract machine is needed. Used as a preliminary step our method allows a standard compiler to evaluate under l's
A peptidoglycan hydrolase motif within the mycobacteriophage TM4 tape measure protein promotes efficient infection of stationary phase cells
The predominant morphotype of mycobacteriophage virions has a DNA-containing capsid attached to a long flexible non-contractile tail, features characteristic of the Siphoviridae. Within these phage genomes the tape measure protein (tmp) gene can be readily identified due to the well-established relationship between the length of the gene and the length of the phage tail - because these phages typically have long tails, the tmp gene is usually the largest gene in the genome. Many of these mycobacteriophage Tmp's contain small motifs with sequence similarity to host proteins. One of these motifs (motif 1) corresponds to the Rpf proteins that have lysozyme activity and function to stimulate growth of dormant bacteria, while the others (motifs 2 and 3) are related to proteins of unknown function, although some of the related proteins of the host are predicted to be involved in cell wall catabolism. We show here that motif 3-containing proteins have peptidoglycan-hydrolysing activity and that while this activity is not required for phage viability, it facilitates efficient infection and DNA injection into stationary phase cells. Tmp's of mycobacteriophages may thus have acquired these motifs in order to avoid a selective disadvantage that results from changes in peptidoglycan in non-growing cells. © 2006 The Authors
Airborne geophysical survey of part of Anglesey, North Wales
An airborne magnetic, electromagnetic and radiometric survey was
carried out over part of Anglesey, North Wales. In this report
of the survey, an outline of the geology, with brief descriptions
of survey techniques, data reduction and presentation are given.
General descriptions are presented of four areas of distinct
magnetic character, with interpretations of the more prominent
anomalies such as those associated with the Carmel Head Thrust,
with Tertiary dykes and with various hornfels bodies.
Possible extensions of known ultrabasic bodies and areas where
other such potentially mineralised bodies may be concealed have
been shown, in particular near Llandyfrydog (SH 44 85)and near
the coast south of Valley (SH 31 76).
The electromagnetic survey data are not described in detail
because radio transmissions caused strong anomalies unrelated to
the geology and masked most of the real anomalies. Those
anomalies which remained were due largely to man-made objects.
Examination of the radiometric traces showed no indication of
uranium mineralisation or any other substantial concentration of
radioactive elements
Palgol: A High-Level DSL for Vertex-Centric Graph Processing with Remote Data Access
Pregel is a popular distributed computing model for dealing with large-scale
graphs. However, it can be tricky to implement graph algorithms correctly and
efficiently in Pregel's vertex-centric model, especially when the algorithm has
multiple computation stages, complicated data dependencies, or even
communication over dynamic internal data structures. Some domain-specific
languages (DSLs) have been proposed to provide more intuitive ways to implement
graph algorithms, but due to the lack of support for remote access --- reading
or writing attributes of other vertices through references --- they cannot
handle the above mentioned dynamic communication, causing a class of Pregel
algorithms with fast convergence impossible to implement.
To address this problem, we design and implement Palgol, a more declarative
and powerful DSL which supports remote access. In particular, programmers can
use a more declarative syntax called chain access to naturally specify dynamic
communication as if directly reading data on arbitrary remote vertices. By
analyzing the logic patterns of chain access, we provide a novel algorithm for
compiling Palgol programs to efficient Pregel code. We demonstrate the power of
Palgol by using it to implement several practical Pregel algorithms, and the
evaluation result shows that the efficiency of Palgol is comparable with that
of hand-written code.Comment: 12 pages, 10 figures, extended version of APLAS 2017 pape
Nonmotion factors which can affect ride quality
Data pertaining to nonmotion factors affecting ride quality of transport aircraft were obtained as part of NASA in-house and sponsored research studies carried out onboard commuter-airline and research aircraft. From these data, quantitative effects on passenger discomfort of seat width, seat legroom, change in cabin pressure, and cabin noise are presented. Visual cue effects are also discussed
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