Friendships, Rivalries, and Trysts: Characterizing Relations between Ideas in Texts

Understanding how ideas relate to each other is a fundamental question in many domains, ranging from intellectual history to public communication. Because ideas are naturally embedded in texts, we propose the first framework to systematically characterize the relations between ideas based on their occurrence in a corpus of documents, independent of how these ideas are represented. Combining two statistics --- cooccurrence within documents and prevalence correlation over time --- our approach reveals a number of different ways in which ideas can cooperate and compete. For instance, two ideas can closely track each other's prevalence over time, and yet rarely cooccur, almost like a "cold war" scenario. We observe that pairwise cooccurrence and prevalence correlation exhibit different distributions. We further demonstrate that our approach is able to uncover intriguing relations between ideas through in-depth case studies on news articles and research papers.Comment: 11 pages, 9 figures, to appear in Proceedings of ACL 2017, code and data available at https://chenhaot.com/pages/idea-relations.html (fixed a typo

Greenstone belts: Their boundaries, surrounding rock terrains and interrelationships

Greenstone belts are an important part of the fragmented record of crustal evolution, representing samples of the magmatic activity that formed much of the Earth's crust. Most belts developed rapidly, in less than 100 Ma, leaving large gaps in the geological record. Surrounding terrains provide information on the context of greenstone belts. The effects of tectonic setting, structural geometry and evolution, associated plutonic activity and sedimentation are discussed

Dynamics of leg muscle function in tammar wallabies (M. eugenii) during level versus incline hopping

The goal of our study was to examine whether the in vivo force-length behavior, work and elastic energy savings of distal muscle-tendon units in the legs of tammar wallabies (Macropus eugenii) change during level versus incline hopping. To address this question, we obtained measurements of muscle activation (via electromyography), fascicle strain (via sonomicrometry) and muscle-tendon force (via tendon buckles) from the lateral gastrocnemius (LG) and plantaris (PL) muscles of tammar wallabies trained to hop on a level and an inclined (10°, 17.4% grade) treadmill at two speeds (3.3 m s^(-1) and 4.2 m s^(-1)). Similar patterns of muscle activation, force and fascicle strain were observed under both level and incline conditions. This also corresponded to similar patterns of limb timing and movement (duty factor, limb contact time and hopping frequency). During both level and incline hopping, the LG and PL exhibited patterns of fascicle stretch and shortening that yielded low levels of net fascicle strain [LG: level, -1.0±4.6% (mean ± s.e.m.) vs incline, 0.6±4.5%; PL: level, 0.1±1.0% vs incline, 0.4±1.6%] and muscle work (LG: level, -8.4±8.4 J kg^(-1) muscle vs incline, -6.8±7.5 J kg^(-1) muscle; PL: level, -2.0±0.6 J kg^(-1) muscle vs incline, -1.4±0.7 J kg^(-1) muscle). Consequently, neither muscle significantly altered its contractile dynamics to do more work during incline hopping. Whereas electromyographic (EMG) phase, duration and intensity did not differ for the LG, the PL exhibited shorter but more intense periods of activation, together with reduced EMG phase (P<0.01), during incline versus level hopping. Our results indicate that design for spring-like tendon energy savings and economical muscle force generation is key for these two distal muscle-tendon units of the tammar wallaby, and the need to accommodate changes in work associated with level versus incline locomotion is achieved by more proximal muscles of the limb

Very Like a Whale

The author talks about his visit to Herman Melville\u27s house and the experiences he had while there

Words Having Three Rare Letters

For several years, logologists have been wrestling with the problem of finding an English word containing the four rarest letters JQXZ. In this article, we consider a closely related problem. There are 3,276 different ways that three letters can be chosen from the alphabet with repetition allowed (i.e., each letter is replaced after drawing, so that it can be drawn more than once). For each possible combination of letters, can one discover a word which uses them

Palindromic Letter-Sequences

There are about 7800 different trigrams which occur in words listed in boldface in Webster\u27s Second Edition, making it feasible to compile a dictionary of types. Approximately 80 per cent of these trigrams (those appearing in Webster\u27s Collegiate) were published in the August 1969, November 1969 and November 1970 Word Ways; since that time, Philip Cohen of Aliquippa, Pennsylvania has discovered examples for most of the remaining Websterian trigrams, as well as others in Webster\u27s Third. However, a type of dictionary for tetragrams or longer letter-sequences is a far more laborious undertaking, requiring the assistance of a high-speed digital computer; for example, it is likely that more than half a million different seven-letter sequences exist. Consequently, one must focus attention on long letter-sequences having interesting properties

A Survey of Letter-Frequencies

If one asks the man in the street (or even the average reader of Word Ways) for a listing of letters by frequency of occurrence, he is likely to come up with the linotyper\u27s nonsense-phrase ETAOIN SHRDLU. More serious students of letter-frequencies, such as solvers of monoalphabetic substitution ciphers, are likely to point out in addition that the frequencies of certain letters are so nearly alike (for example, A and O, or N and R) that the ordering depends upon the sample of letters tabulated. Although most people will readily understand that the listing is based on a sample of letters from some larger population, few will include a careful specification of this sample and population as part of their answer. It is the purpose of this article to show how important such a specification can be; we exhibit a number of startlingly different letter-orderings corresponding to different populations