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Université de Fribourg

Uncovering missing links with cold ends

Zhu, Yu-Xiao ; Lü, Linyuan ; Zhang, Qian-Ming ; Zhou, Tao

In: Physica A: Statistical Mechanics and its Applications, 2012, vol. 139, no. 22, p. 5769–5778

To evaluate the performance of prediction of missing links, the known data are randomly divided into two parts, the training set and the probe set. We argue that this straightforward and standard method may lead to terrible bias, since in real biological and information networks, missing links are more likely to be links connecting low-degree nodes. We therefore study how to uncover missing links...

Université de Fribourg

Recommender systems

Lü, Linyuan ; Medo, Matúš ; Yeung, Chi Ho ; Zhang, Yi-Cheng ; Zhang, Zi-Ke ; Zhou, Tao

In: Physics Reports, 2012, vol. 519, no. 1, p. 1–49

The ongoing rapid expansion of the Internet greatly increases the necessity of effective recommender systems for filtering the abundant information. Extensive research for recommender systems is conducted by a broad range of communities including social and computer scientists, physicists, and interdisciplinary researchers. Despite substantial theoretical and practical achievements, unification...

Université de Fribourg

ER-localized auxin transporter PIN8 regulates auxin homeostasis and male gametophyte development in Arabidopsis

Ding, Zhaojun ; Wang, Bangjun ; Moreno, Ignacio ; Dupláková, Nikoleta ; Simon, Sibu ; Carraro, Nicola ; Reemmer, Jesica ; Pěnčík, Aleš ; Chen, Xu ; Tejos, Ricardo ; Skůpa, Petr ; Pollmann, Stephan ; Mravec, Jozef ; Petrášek, Jan ; Zažímalová, Eva ; Honys, David ; Rolčík, Jakub ; Murphy, Angus ; Orellana, Ariel ; Geisler, Markus ; Friml, Jiří

In: Nature Communications, 2012, p. -

Auxin is a key coordinative signal required for many aspects of plant development and its levels are controlled by auxin metabolism and intercellular auxin transport. Here we find that a member of PIN auxin transporter family, PIN8 is expressed in male gametophyte of Arabidopsis thaliana and has a crucial role in pollen development and functionality. Ectopic expression in sporophytic tissues...

Université de Fribourg

Testing spatial noncommutativity via magnetic hyperfine structure induced by fractional angular momentum of Rydberg system

Zhang, Jian-Zu ; Liu, Hong-Ping ; Cao, Wei ; Gao, Ke-Lin

In: EPL - Europhysics Letters, 2012, vol. 98, no. 4, p. 40002

An approach to solve the critical problem of testing quantum effects of spatial noncommutativity is proposed. Magnetic hyperfine structures in a Rydberg system induced by fractional angular momentum originated from spatial noncommutativity are discussed. The orders of the corresponding magnetic hyperfine splitting of the spectrum ~10−7–10− 8 eV lie within the limits of accuracy of current...

Université de Fribourg

How altruism works: An evolutionary model of supply networks

Ge, Zehui ; Zhang, Zi-Ke ; Lü, Linyuan ; Zhou, Tao ; Xi, Ning

In: Physica A: Statistical Mechanics and its Applications, 2012, vol. 391, no. 3, p. 647–655

Recently, supply networks have attracted increasing attention from the scientific community. However, it lacks serious consideration of social preference in Supply Chain Management. In this paper, we develop an evolutionary decision-making model to characterize the effects of suppliers’ altruism in supply networks, and find that the performances of both suppliers and supply chains are improved...

Université de Fribourg

A novel putative auxin carrier family regulates intracellular auxin homeostasis in plants

Barbez, Elke ; Kubeš, Martin ; Rolčík, Jakub ; Béziat, Chloé ; Pěnčík, Aleš ; Wang, Bangjun ; Rosquete, Michel Ruiz ; Zhu, Jinsheng ; Dobrev, Petre I. ; Lee, Yuree ; Zažímalovà, Eva ; Petrášek, Jan ; Geisler, Markus ; Friml, Jiří ; Kleine-Vehn, Jürgen

In: Nature, 2012, p. -

The phytohormone auxin acts as a prominent signal, providing, by its local accumulation or depletion in selected cells, a spatial and temporal reference for changes in the developmental program. The distribution of auxin depends on both auxin metabolism (biosynthesis, conjugation and degradation) and cellular auxin transport. We identified in silico a novel putative auxin transport facilitator...

Université de Fribourg

Tag-aware recommender systems : a state-of-the-art survey

Zhang, Zi-Ke ; Zhou, Tao ; Zhang, Yi-Cheng

In: Journal of Computer Science and Technology, 2011, vol. 26, no. 5, p. 767-777

In the past decade, Social Tagging Systems have attracted increasing attention from both physical and computer science communities. Besides the underlying structure and dynamics of tagging systems, many efforts have been addressed to unify tagging information to reveal user behaviors and preferences, extract the latent semantic relations among items, make recommendations, and so on....

Université de Fribourg

Onset of cooperation between layered networks

Gu, Chang-Gui ; Zou, Sheng-Rong ; Xu, Xiu-Lian ; Qu, Yan-Qing ; Jiang, Yu-Mei ; He, Da Ren ; Liu, Hong-Kun ; Zhou, Tao

In: Physical Review E - Statistical, Nonlinear, and Soft Matter Physics, 2011, vol. 84, no. 2, p. 026101

Functionalities of a variety of complex systems involve cooperations among multiple components; for example, a transportation system provides convenient transfers among airlines, railways, roads, and shipping lines. A layered model with interacting networks can facilitate the description and analysis of such systems. In this paper we propose a model of traffic dynamics and reveal a transition at...

Université de Fribourg

Developing Cultural Differences in Face Processing

Kelly, David J. ; Liu, Shaoying ; Rodger, Helen ; Miellet, Sebastien ; Ge, Liezhong ; Caldara, Roberto

In: Developmental Science, 2011, vol. 14, no. 5, p. 1176-1184

Perception and eye movements are affected by culture. Adults from Eastern societies (e.g. China) display a disposition to process information holistically, whereas individuals from Western societies (e.g. Britain) process information analytically. Recently, this pattern of cultural differences has been extended to face processing. Adults from Eastern cultures fixate centrally towards the nose...

Université de Fribourg

Opinion spreading with mobility on scale-free networks

Guo, Qiang ; Liu, Jian-Guo ; Wang, Bing-Hong ; Zhou, Tao ; Chen, Xing-Wen ; Yao, Yu-Hua

In: Chinese Physics Letters, 2008, vol. 25, no. 2, p. 773-775

A continuum opinion dynamic model is presented based on two rules. The first one considers the mobilities of the individuals, the second one supposes that the individuals update their opinions independently. The results of the model indicate that the bounded confidence ∈c, separating consensus and incoherent states, of a scale-free network is much smaller than the one of a...