Predictability of conversation partners

Recent developments in sensing technologies have enabled us to examine the nature of human social behavior in greater detail. By applying an information theoretic method to the spatiotemporal data of cell-phone locations, [C. Song et al. Science 327, 1018 (2010)] found that human mobility patterns are remarkably predictable. Inspired by their work, we address a similar predictability question in a different kind of human social activity: conversation events. The predictability in the sequence of one's conversation partners is defined as the degree to which one's next conversation partner can be predicted given the current partner. We quantify this predictability by using the mutual information. We examine the predictability of conversation events for each individual using the longitudinal data of face-to-face interactions collected from two company offices in Japan. Each subject wears a name tag equipped with an infrared sensor node, and conversation events are marked when signals are exchanged between sensor nodes in close proximity. We find that the conversation events are predictable to some extent; knowing the current partner decreases the uncertainty about the next partner by 28.4% on average. Much of the predictability is explained by long-tailed distributions of interevent intervals. However, a predictability also exists in the data, apart from the contribution of their long-tailed nature. In addition, an individual's predictability is correlated with the position in the static social network derived from the data. Individuals confined in a community - in the sense of an abundance of surrounding triangles - tend to have low predictability, and those bridging different communities tend to have high predictability.Comment: 38 pages, 19 figure

Derivatives of flat functions

We remark that there is no smooth function $f(x)$ on $[0, 1]$ which is flat at $0$ such that the derivative $f^{(n)}$ of any order $n\geq 0$ is positive on $(0,1]$. Moreover, the number of zeros of the $n$-th derivative $f^{(n)}$ grows to the infinity and the zeros accumulate to $0$ when $n \to \infty$.Comment: 5 page

A small remark on flat functions

We remark that there is no smooth flat function f (x) on [0,∞) such that for a fixed interval (0, α) (α > 0) on which the derivative of any higher order is positive

Development of a TDEM Data Acquisition System Based on a SQUID Magnetometer for Mineral Exploration

Summary We report on the research and development of a TDEM data acquisition system (SQUITEM) by JOGMEC using a highly sensitive high-temperature superconductor (HTS) SQUID vector magnetometer cooled by liquid nitrogen, which is suitable for mineral exploration. JOGMEC has achieved stable long-term operation of all three channels during field tests. SQUITEM meets high requirements for slew rate (6.8mT/s), dynamic range (100dB) and bandwidth (DC -100kHz). It offers deeper penetration of depth than the induction coil system because it can record the step response that decreases with time slower than the impulse response of the induction coil system. SQUITEM also performs horizontal gradient observations that can provide much better resolution of shallow conductive targets than conventional EM field component observations. We have obtained good reproducibility of SQUID data and correlation between the output signals of the reference induction coils and the derivatives of the SQUID signals in TDEM field tests

First detection of triterpenyl acetates in soils: sources and potential as new palaeoenvironmental biomarkers

International audienceUnderstanding past reactions of ecosystems under natural and anthropic constraints is of crucial importance to anticipate the consequences of the current global changes. Unraveling natural and anthropic impacts on environments requires the reconstruction of ancient land-uses. As a part of a larger project aiming at developing new molecular biomarkers in soils that could be specific of their overlying vegetation, we have analyzed the neutral lipid content of soils developed under distinct types of plants. Soils were sampled around Lake Aydat, in Central France, of which the catchment is covered with pastures/meadows, forests and moors. The ketone/ester lipid fraction from soils under pastures or meadows contains a series of 14 pentacyclic triterpenyl acetates with a large structural diversity (Fig. 1). This discovery motivated an extensive phytochemical literature survey (240 references) that showed restricted potential sources of triterpenyl acetates. -amyrin, taraxeryl, glutinyl, -amyrin, and multiflorenyl, acetates are found in very distinct taxa and are thus poorly informative. Conversely, lupeyl, bauerenyl, isobauerenyl, taraxasteryl and -taraxasteryl acetates appear more specific since they are majoritary reported in Asteraceae. Pichierenyl, isopichierenyl and gammacerenyl acetates seem to be the more specific ones since they are produced by a single known species, Picris hieracioides L. (hawkweed oxtongue, Asteraceae)

Etiler'de Locanda

Taha Toros Arşivi, Dosya No: 112-Lokantalarİstanbul Kalkınma Ajansı (TR10/14/YEN/0033) İstanbul Development Agency (TR10/14/YEN/0033