scholarly journals 72. Some problems of meteor astronomy: Introductory Lecture

1957 ◽  
Vol 4 ◽  
pp. 375-389
Author(s):  
F. L. Whipple

We are now in an era of remarkable progress in the study of meteors. The electronic techniques developed at Jodrell Bank by Lovell, Clegg and others, and now by Davies, have culminated in giving us the power to observe the equivalent of 8th or 9th magnitude meteors for velocities, radiants and orbits. And certainly the limit has not yet been reached. The Harvard Super-Schmidt meteor cameras represent nearly the limit of current photographic-optical techniques; they approach close to the visual limit for very slow meteors, and with great precision, to 0·1 % in velocity and radiant.

1967 ◽  
Vol 31 ◽  
pp. 177-179
Author(s):  
W. W. Shane

In the course of several 21-cm observing programmes being carried out by the Leiden Observatory with the 25-meter telescope at Dwingeloo, a fairly complete, though inhomogeneous, survey of the regionl11= 0° to 66° at low galactic latitudes is becoming available. The essential data on this survey are presented in Table 1. Oort (1967) has given a preliminary report on the first and third investigations. The third is discussed briefly by Kerr in his introductory lecture on the galactic centre region (Paper 42). Burton (1966) has published provisional results of the fifth investigation, and I have discussed the sixth in Paper 19. All of the observations listed in the table have been completed, but we plan to extend investigation 3 to a much finer grid of positions.


1994 ◽  
Vol 4 (12) ◽  
pp. 2149-2159 ◽  
Author(s):  
John Philip ◽  
Jean-Ren� Lalanne ◽  
Jean-Paul Marcerou ◽  
Gilles Sigaud
Keyword(s):  

1973 ◽  
Vol 2 (1) ◽  
pp. 84-88 ◽  
Author(s):  
N. C. Stoskopf ◽  
G. M. Jenkinson
Keyword(s):  

2002 ◽  
Vol 8 (2-3) ◽  
pp. 209-233 ◽  
Author(s):  
OLIVIER FERRET ◽  
BRIGITTE GRAU

Topic analysis is important for many applications dealing with texts, such as text summarization or information extraction. However, it can be done with great precision only if it relies on structured knowledge, which is difficult to produce on a large scale. In this paper, we propose using bootstrapping to solve this problem: a first topic analysis based on a weakly structured source of knowledge, a collocation network, is used for learning explicit topic representations that then support a more precise and reliable topic analysis.


2020 ◽  
Vol 54 (1) ◽  
pp. 1-12
Author(s):  
Martin Potthast ◽  
Matthias Hagen ◽  
Benno Stein

No Web technology has undergone such an impressive evolution as Web search engines did and still do. Starting with the promise of "Bringing order to the Web" 1 by compiling information sources matching a query, retrieval technology has been evolving to a kind of "oracle machinery", being able to recommend a single source, and even to provide direct answers extracted from that source. Notwithstanding the remarkable progress made and the apparent user preferences for direct answers, this paradigm shift comes at a price which is higher than one might expect at first sight, affecting both users and search engine developers in their own way. We call this tradeoff "the dilemma of the direct answer"; it deserves an analysis which has to go beyond system-oriented aspects but scrutinize the way our society deals with both their information needs and means to information access. The paper in hand contributes to this analysis by putting the evolution of retrieval technology and the expectations at it in the context of information retrieval history. Moreover, we discuss the trade offs in information behavior and information system design that users and developers may face in the future.


2021 ◽  
Vol 22 (15) ◽  
pp. 8139
Author(s):  
Tomoko Tadokoro ◽  
Asahiro Morishita ◽  
Tsutomu Masaki

Remarkable progress has been made in the treatment and control of hepatitis B and C viral infections. However, fundamental treatments for diseases in which liver fibrosis is a key factor, such as cirrhosis, alcoholic/nonalcoholic steatohepatitis, autoimmune hepatitis, primary biliary cholangitis, and primary sclerosing cholangitis, are still under development and remain an unmet medical need. To solve this problem, it is essential to elucidate the pathogenesis of liver fibrosis in detail from a molecular and cellular perspective and to develop targeted therapeutic agents based on this information. Recently, microRNAs (miRNAs), functional RNAs of 22 nucleotides, have been shown to be involved in the pathogenesis of liver fibrosis. In addition, extracellular vesicles called “exosomes” have been attracting attention, and research is being conducted to establish noninvasive and extremely sensitive biomarkers using miRNAs in exosomes. In this review, we summarize miRNAs directly involved in liver fibrosis, miRNAs associated with diseases leading to liver fibrosis, and miRNAs related to complications of cirrhosis. We will also discuss the efficacy of each miRNA as a biomarker of liver fibrosis and pathology, and its potential application as a therapeutic agent.


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