Of current interest: World's largest horn planned as part of space communications ground station

1961 ◽  
Vol 80 (6) ◽  
pp. 467-467
2016 ◽  
Author(s):  
W. T. Roberts ◽  
D. Antsos ◽  
A. Croonquist ◽  
S. Piazzolla ◽  
L. C. Roberts ◽  
...  

Author(s):  
A.R. Pelton ◽  
A.F. Marshall ◽  
Y.S. Lee

Amorphous materials are of current interest due to their desirable mechanical, electrical and magnetic properties. Furthermore, crystallizing amorphous alloys provides an avenue for discerning sequential and competitive phases thus allowing access to otherwise inaccessible crystalline structures. Previous studies have shown the benefits of using AEM to determine crystal structures and compositions of partially crystallized alloys. The present paper will discuss the AEM characterization of crystallized Cu-Ti and Ni-Ti amorphous films.Cu60Ti40: The amorphous alloy Cu60Ti40, when continuously heated, forms a simple intermediate, macrocrystalline phase which then transforms to the ordered, equilibrium Cu3Ti2 phase. However, contrary to what one would expect from kinetic considerations, isothermal annealing below the isochronal crystallization temperature results in direct nucleation and growth of Cu3Ti2 from the amorphous matrix.


Author(s):  
D. R. Clarke ◽  
G. Thomas

Grain boundaries have long held a special significance to ceramicists. In part, this has been because it has been impossible until now to actually observe the boundaries themselves. Just as important, however, is the fact that the grain boundaries and their environs have a determing influence on both the mechanisms by which powder compaction occurs during fabrication, and on the overall mechanical properties of the material. One area where the grain boundary plays a particularly important role is in the high temperature strength of hot-pressed ceramics. This is a subject of current interest as extensive efforts are being made to develop ceramics, such as silicon nitride alloys, for high temperature structural applications. In this presentation we describe how the techniques of lattice fringe imaging have made it possible to study the grain boundaries in a number of refractory ceramics, and illustrate some of the findings.


Author(s):  
J. R. Sellar ◽  
J. M. Cowley

Current interest in high voltage electron microscopy, especially in the scanning mode, has prompted the development of a method for determining the contrast and resolution of images of specimens in controlled-atmosphere stages or open to the air, hydrated biological specimens being a good example. Such a method would be of use in the prediction of microscope performance and in the subsequent optimization of environmental cell design for given circumstances of accelerating voltage, cell gas pressure and constitution, and desired resolution.Fig. 1 depicts the alfresco cell of a focussed scanning transmission microscope with a layer of gas L (and possibly a thin window W) between the objective O and specimen T. Using the principle of reciprocity, it may be considered optically equivalent to a conventional transmission electron microscope, if the beams were reversed. The layer of gas or solid material after the specimen in the STEM or before the specimen in TEM has no great effect on resolution or contrast and so is ignored here.


Author(s):  
Arthur V. Jones

In comparison with the developers of other forms of instrumentation, scanning electron microscope manufacturers are among the most conservative of people. New concepts usually must wait many years before being exploited commercially. The field emission gun, developed by Albert Crewe and his coworkers in 1968 is only now becoming widely available in commercial instruments, while the innovative lens designs of Mulvey are still waiting to be commercially exploited. The associated electronics is still in general based on operating procedures which have changed little since the original microscopes of Oatley and his co-workers.The current interest in low-voltage scanning electron microscopy will, if sub-nanometer resolution is to be obtained in a useable instrument, lead to fundamental changes in the design of the electron optics. Perhaps this is an opportune time to consider other fundamental changes in scanning electron microscopy instrumentation.


2018 ◽  
Vol 68 (2) ◽  
pp. 498-516
Author(s):  
Neil O'Sullivan

Of the hundreds of Greek common nouns and adjectives preserved in our MSS of Cicero, about three dozen are found written in the Latin alphabet as well as in the Greek. So we find, alongside συμπάθεια, also sympathia, and ἱστορικός as well as historicus. This sort of variation has been termed alphabet-switching; it has received little attention in connection with Cicero, even though it is relevant to subjects of current interest such as his bilingualism and the role of code-switching and loanwords in his works. Rather than addressing these issues directly, this discussion sets out information about the way in which the words are written in our surviving MSS of Cicero and takes further some recent work on the presentation of Greek words in Latin texts. It argues that, for the most part, coherent patterns and explanations can be found in the alphabetic choices exhibited by them, or at least by the earliest of them when there is conflict in the paradosis, and that this coherence is evidence for a generally reliable transmission of Cicero's original choices. While a lack of coherence might indicate unreliable transmission, or even an indifference on Cicero's part, a consistent pattern can only really be explained as an accurate record of coherent alphabet choice made by Cicero when writing Greek words.


2018 ◽  
Vol 1 (2) ◽  
pp. 75-79
Author(s):  
Abdulghani Alsamarai

Introduction   The International Journal of Medical Sciences [IJMS], ISSN 2522-7386, is a peer-reviewed, 3 issues published annually. Authors are invited to submit for publication articles with a wide spectrum of coverage reporting original work, in the fields of medicine, nursery, dentistry, and pharmacy sciences. Review articles are usually by invitation only. However, Review articles of current interest and high standard will be considered. Prospective work should not be back dated. There are also sections for Case Reports, Brief Communication, correspondence and medical news items. Authors should read the editorial policy and publication ethics before submitting their manuscripts. Authors should also use the appropriate reporting guidelines in preparing their manuscripts


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