Exploratory topic modeling with distributional semantics

As we continue to collect and store textual data in a multitude of domains, we are regularly confronted with material whose largely unknown thematic structure we want to uncover. With unsupervised, exploratory analysis, no prior knowledge about the content is required and highly open-ended tasks can be supported. In the past few years, probabilistic topic modeling has emerged as a popular approach to this problem. Nevertheless, the representation of the latent topics as aggregations of semi-coherent terms limits their interpretability and level of detail. This paper presents an alternative approach to topic modeling that maps topics as a network for exploration, based on distributional semantics using learned word vectors. From the granular level of terms and their semantic similarity relations global topic structures emerge as clustered regions and gradients of concepts. Moreover, the paper discusses the visual interactive representation of the topic map, which plays an important role in supporting its exploration.Comment: Conference: The Fourteenth International Symposium on Intelligent Data Analysis (IDA 2015

Investigation of a direction sensitive sapphire detector stack at the 5 GeV electron beam at DESY-II

Extremely radiation hard sensors are needed in particle physics experiments to instrument the region near the beam pipe. Examples are beam halo and beam loss monitors at the Large Hadron Collider, FLASH or XFEL. Currently artificial diamond sensors are widely used. In this paper single crystal sapphire sensors are considered as a promising alternative. Industrially grown sapphire wafers are available in large sizes, are of low cost and, like diamond sensors, can be operated without cooling. Here we present results of an irradiation study done with sapphire sensors in a high intensity low energy electron beam. Then, a multichannel direction-sensitive sapphire detector stack is described. It comprises 8 sapphire plates of 1 cm^2 size and 525 micro m thickness, metallized on both sides, and apposed to form a stack. Each second metal layer is supplied with a bias voltage, and the layers in between are connected to charge-sensitive preamplifiers. The performance of the detector was studied in a 5 GeV electron beam. The charge collection efficiency measured as a function of the bias voltage rises with the voltage, reaching about 10 % at 950 V. The signal size obtained from electrons crossing the stack at this voltage is about 22000 e, where e is the unit charge. The signal size is measured as a function of the hit position, showing variations of up to 20 % in the direction perpendicular to the beam and to the electric field. The measurement of the signal size as a function of the coordinate parallel to the electric field confirms the prediction that mainly electrons contribute to the signal. Also evidence for the presence of a polarisation field was observed.Comment: 13 pages, 7 figures, 3 table

‘Fixing’ the climate crisis: capital, states, and carbon offsetting in India

The paper analyzes dynamics of accumulation and displacement in the Clean Development Mechanism (CDM). It combines the theoretical work of David Harvey and James O’Connor with a case study of the Gujarat Fluorochemicals Limited HFC-23 destruction project in Gujarat, India. The framework is used to connect the factors driving opportunities for capital accumulation in the CDM market with the causes of social and ecological dislocation at the local project level. We argue that the CDM is a spatial fix to the ecological crisis of climate change which secures conditions of production for fossil fuel industries and promotes new sites of accumulation for other companies. The political–economic ‘fix’ is dependent on ‘fixing’ a global sociospatial divide between developed and developing countries down to ‘fixed’ projects at the local level. This spatial fix facilitates a displacement of the costs of responding to the climate crisis from North to South. </jats:p

Identification problems of muon and electron events in the Super-Kamiokande detector

In the measurement of atmospheric nu_e and nu_mu fluxes, the calculations of the Super Kamiokande group for the distinction between muon-like and electronlike events observed in the water Cerenkov detector have initially assumed a misidentification probability of less than 1 % and later 2 % for the sub-GeV range. In the multi-GeV range, they compared only the observed behaviors of ring patterns of muon and electron events, and claimed a 3 % mis-identification. However, the expressions and the calculation method do not include the fluctuation properties due to the stochastic nature of the processes which determine the expected number of photoelectrons (p.e.) produced by muons and electrons. Our full Monte Carlo (MC) simulations including the fluctuations of photoelectron production show that the total mis-identification rate for electrons and muons should be larger than or equal to 20 % for sub-GeV region. Even in the multi-GeV region we expect a mis-identification rate of several % based on our MC simulations taking into account the ring patterns. The mis-identified events are mostly of muonic origin.Comment: 17 pages, 12 figure

Multi-Modal Homing in Sea Turtles: Modeling Dual Use of Geomagnetic and Chemical Cues in Island-Finding

Sea turtles are capable of navigating across large expanses of ocean to arrive at remote islands for nesting, but how they do so has remained enigmatic. An interesting example involves green turtles (Chelonia mydas) that nest on Ascension Island, a tiny land mass located approximately 2000 km from the turtles’ foraging grounds along the coast of Brazil. Sensory cues that turtles are known to detect, and which might hypothetically be used to help locate Ascension Island, include the geomagnetic field, airborne odorants, and waterborne odorants. One possibility is that turtles use magnetic cues to arrive in the vicinity of the island, then use chemical cues to pinpoint its location. As a first step toward investigating this hypothesis, we used oceanic, atmospheric, and geomagnetic models to assess whether magnetic and chemical cues might plausibly be used by turtles to locate Ascension Island. Results suggest that waterborne and airborne odorants alone are insufficient to guide turtles from Brazil to Ascension, but might permit localization of the island once turtles arrive in its vicinity. By contrast, magnetic cues might lead turtles into the vicinity of the island, but would not typically permit its localization because the field shifts gradually over time. Simulations reveal, however, that the sequential use of magnetic and chemical cues can potentially provide a robust navigational strategy for locating Ascension Island. Specifically, one strategy that appears viable is following a magnetic isoline into the vicinity of Ascension Island until an odor plume emanating from the island is encountered, after which turtles might either: (1) initiate a search strategy; or (2) follow the plume to its island source. These findings are consistent with the hypothesis that sea turtles, and perhaps other marine animals, use a multi-modal navigational strategy for locating remote islands

Tiny Publics and Social Worlds—Toward a Sociology of the Local. Gary Alan Fine in Conversation With Reiner Keller

Gary Alan FINE gehört weltweit zu den prominentesten Persönlichkeiten der zeitgenössischen soziologischen Ethnografie. In diesem Gespräch spricht er über Einflüsse in seiner akademischen Laufbahn und prägende intellektuelle Entscheidungen. Er gilt als "serieller Ethnograf", der in zahlreichen Feldkontexten gearbeitet hat und dabei einerseits Kleingruppen und eine von Menschen bevölkerte Ethnografie favorisiert, sich andererseits mit Gerüchten, Klatsch und moralischen Geschichten beschäftigt, die in kleinen und größeren Publiken erzählt werden. FINE beschreibt sein theoretisches Kerninteresse als die Untersuchung des Wechselspiels von Struktur, Interaktion und Kultur. In seinem Werk analysiert er die vielfältigen ortsgebundenen Arten und Weisen, in denen Gesellschaft von Menschen in formellen und informellen sozialen Settings verwirklicht wird, angefangen bei Baseballteams über Restaurantküchen oder die Wetterberichterstattung bis hin zum Schachspielen –um nur einige wenige Gegenstände seiner Forschungen zu nennen. Wesentlich beeinflusst durch symbolisch-interaktionistisches Denken und im Rekurs auf weitere wichtige Perspektiven auf soziale Welten plädiert er für eine selbstbewusste Haltung der ethnografischen Forschung und des ethnografischen Schreibens sowie für die Bedeutung der Konzeptarbeit in einer theorie-informierten empirischen Soziologie dessen, was Menschen zusammen tun.Gary Alan FINE is among the most prominent figures in contemporary sociological ethnography worldwide. In this conversation, he talks about influences in his academic career and key intellectual choices. Considered to be a "serial ethnographer" who has worked in multiple settings, his work focuses on small groups and peopled ethnography, as well as on rumors, gossip, and moral story telling in tiny and larger publics. FINE describes his core theoretical interest as residing in the interplay of structure, interaction, and culture and discusses the multiple local ways society is realized by people in formal and informal social settings: ranging from baseball teams, restaurant kitchens, weather reporting to chess players—to name but a few research sites. Influenced by symbolic interactionist thinking and other important approaches to social worlds, he argues for a confident voice of ethnographic research and writing as well as the importance of conceptual work in a theory-informed empirical sociology of what people do together

Resolving Non-Determinism in Choreographies

Resolving non-deterministic choices of choreographies is a crucial task. We introduce a novel notion of realisability for choreographies –called whole-spectrum implementation– that rules out deterministic implementations of roles that, no matter which context they are placed in, will never follow one of the branches of a non-deterministic choice. We show that, under some conditions, it is decidable whether an implementation is whole-spectrum. As a case study, we analyse the POP protocol under the lens of whole-spectrum implementation