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In this article, we discuss the notions of experts and expertise in resource discovery in the context of collaborative tagging systems. We propose that the level of expertise of a user with respect to a particular topic is mainly determined by two factors. First, an expert should possess a high-quality collection of resources, while the quality of a Web resource in turn depends on the expertise of the users who have assigned tags to it, forming a mutual reinforcement relationship. Second, an expert should be one who tends to identify interesting or useful resources before other users discover them, thus bringing these resources to the attention of the community of users. We propose a graph-based algorithm, SPEAR (spamming-resistant expertise analysis and ranking), which implements the above ideas for ranking users in a folksonomy. Our experiments show that our assumptions on expertise in resource discovery, and SPEAR as an implementation of these ideas, allow us to promote experts and demote spammers at the same time, with performance significantly better than the original hypertext-induced topic search algorithm and simple statistical measures currently used in most collaborative tagging systems.
The formation of secondary Ln(III) solid phases (e.g., Nd-2(CO3)(3) and Sm-2(CO3)(3)) was studied as a function of the humic acid concentration in 0.1 mol/L NaClO4 aqueous solution in the neutral pH range (5-6.5). The solid phases under investigation were prepared by alkaline precipitation under 100% CO2 atmosphere and characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD), time-resolved laser fluorescence spectroscopy (TRLFS), diffuse reflectance ultraviolet-visible (DR-UV-Vis), Raman spectroscopy, and solubility measurements. The spectroscopic data obtained indicated that Nd-2(CO3)(3) and Sm-2(CO3)(3) were stable and remained the solubility limiting solid phases even in the presence of increased humic acid concentration (0.5 g/L) in solution. Upon base addition in the Ln(III)-HA system, decomplexation of the previously formed Ln(III)-humate complexes and precipitation of two distinct phases occurred, the inorganic (Ln(2)(CO3)(3)) and the organic phase (HA), which was adsorbed on the particle surface of the former. Nevertheless, humic acid affected the particle size of the solid phases. Increasing humic acid concentration resulted in decreasing crystallite size of the Nd-2(CO3)(3) and increasing crystallite size of the Sm-2(CO3)(3) solid phase, and affected inversely the solubility of the solid phases. However, this impact on the solid phase properties was expected to be of minor relevance regarding the chemical behavior and migration of trivalent lanthanides and actinides in the geosphere.
Mate choice copying was mostly described as a strategy employed by females to assess the quality of potential mates, but also males can copy other males' mate choice. An open question in this context is whether and how copying males evaluate sperm competition risk, as mating with a female that has already copulated with another male obviously sets the stage for intense sperm competition (i.e., in species with internal fertilization). Using the livebearing Atlantic molly (Poecilia mexicana) as a model, we asked (a) whether males of that species indeed copy other males' choices, and if they do so, (b) whether copying males strategically adjust their behavior to sperm competition risk. We used an approach where focal males could first choose to associate with a large or a small stimulus female. Mate choice tests were then repeated after an "observation phase" during which either no model male was present (treatment 1, control) or the previously non-preferred female could be seen associating (treatment 2) or physically interacting (treatment 3) with a model male. We found that, after the observation phase, males spent considerably more time with the previously non-preferred female in treatment (2), i.e., they copied the model male's choice. This effect was much weaker during treatment (3) where sexual interactions between the model male and the formerly non-preferred female were allowed. Males, therefore, seem to adjust their copying behavior strategically to the perceived risk of sperm competition.
The mechanism of action of 2-hydroxyoleic acid (2OHOA), a potent antitumor compound, has not yet been fully elucidated. Here, we show that human cancer cells have markedly lower levels of sphingomyelin (SM) than nontumor (MRC-5) cells. In this context, 2OHOA treatment strongly augments SM mass (4.6-fold), restoring the levels found in MRC-5 cells, while a loss of phosphatidylethanolamine and phosphatidylcholine is observed (57 and 30%, respectively). The increased SM mass was due to a rapid and highly specific activation of SM synthases (SMS). This effect appeared to be specific against cancer cells as it did not affect nontumor MRC-5 cells. Therefore, low SM levels are associated with the tumorigenic transformation that produces cancer cells. SM accumulation occurred at the plasma membrane and caused an increase in membrane global order and lipid raft packing in model membranes. These modifications would account for the observed alteration by 2OHOA in the localization of proteins involved in cell apoptosis (Fas receptor) or differentiation (Ras). Importantly, SMS inhibition by D609 diminished 2OHOA effect on cell cycle. Therefore, we propose that the regulation of SMS activity in tumor cells is a critical upstream event in 2OHOA antitumor mechanism, which also explains its specificity for cancer cells, its potency, and the lack of undesired side effects. Finally, the specific activation of SMS explains the ability of this compound to trigger cell cycle arrest, cell differentiation, and autophagy or apoptosis in cancer cells.
Sports-related correlates of disordered eating a comparison between aesthetic and ballgame sports
(2011)
Prevalence rates for disordered eating vary between different types of sports (Sundgot-Borgen & Torstveit, 2004). In this study, athletes of sports with a high risk and low risk for disordered eating were compared regarding potential sports-related risk factors for disordered eating. One hundred and seventy-one aesthetic and ballgame sports athletes participated in this study (mean age 14.1 +/- 1.8 years). Aesthetic sports athletes reported more disordered eating behaviors, sports-related body dissatisfaction, a greater desire to be leaner to improve sports performance and greater social pressure from the sports environment than did ballgame sports athletes. Emotional distress resulting from missed exercise sessions and the desire to be leaner to improve sports performance predicted disordered eating in both sport types. The results suggest that the kinds of risk factors for disordered eating are equal among sport types, but some potential risk factors are more prevalent in aesthetic sports.
Objectives: Eating disorders are more prevalent in aesthetic sports such as figure skating or gymnastics. While many descriptive studies on their prevalence already exist, more and more studies are now examining the reasons for the specific risk of these athletes. The purpose of this study was to focus on sport-specific variables in aesthetic sports and to examine their relation to disordered eating.
Design: Cross-sectional.
Method: 96 Elite athletes from aesthetic sports (61 girls, 35 boys) were compared to a control group of 96 sex-matched non-athletes. The mean age of participants was M = 14.0 years (SD = 2.2). The questionnaire package included disordered eating, general body dissatisfaction, sports-related body dissatisfaction, desire to be leaner to improve sports performance and social pressure to be lean from sports environment.
Results: Athletes from aesthetic sports displayed more eating disorder symptoms but did not differ from the control group with respect to general body dissatisfaction. For athletes in aesthetic sports, the desire to be leaner to improve sports performance was a significant predictor for disordered eating, and mediated the relationship between social pressure from the sports environment and disordered eating.
Conclusions: The results suggest that sports-related parameters are relevant for understanding eating disorder symptomatology in aesthetic sports. Athletes from aesthetic sports seem to be more at risk if they perceive the possibility to enhance sports performance through weight-regulation, which appears to be triggered by social pressure to be lean from sports environment.
P>Despite ample research, understanding plant spread and predicting their ability to track projected climate changes remain a formidable challenge to be confronted. We modelled the spread of North American wind-dispersed trees in current and future (c. 2060) conditions, accounting for variation in 10 key dispersal, demographic and environmental factors affecting population spread. Predicted spread rates vary substantially among 12 study species, primarily due to inter-specific variation in maturation age, fecundity and seed terminal velocity. Future spread is predicted to be faster if atmospheric CO2 enrichment would increase fecundity and advance maturation, irrespective of the projected changes in mean surface windspeed. Yet, for only a few species, predicted wind-driven spread will match future climate changes, conditioned on seed abscission occurring only in strong winds and environmental conditions favouring high survival of the farthest-dispersed seeds. Because such conditions are unlikely, North American wind-dispersed trees are expected to lag behind the projected climate range shift.
Squatting as a housing strategy and as a tool of urban social movements accompanies the development of capitalist cities worldwide. We argue that the dynamics of squatter movements are directly connected to strategies of urban renewal in that movement conjunctures occur when urban regimes are in crisis. An analysis of the history of Berlin squatter movements, their political context and their effects on urban policies since the 1970s, clearly shows how massive mobilizations at the beginning of the 1980s and in the early 1990s developed in a context of transition in regimes of urban renewal. The crisis of Fordist city planning at the end of the 1970s provoked a movement of 'rehab squatting' (Instandbesetzung), which contributed to the institutionalization of 'cautious urban renewal'(behutsame Stadterneuerung) in an important way. The second rupture in Berlin's urban renewal became apparent in 1989 and 1990, when the necessity of restoring whole inner-city districts constituted a new, budget-straining challenge for urban policymaking. Whilst in the 1980s the squatter movement became a central condition for and a political factor of the transition to 'cautious urban renewal', in the 1990s large-scale squatting - mainly in the eastern parts of the city - is better understood as an alien element in times of neoliberal urban restructuring.
In the present paper, the influence of the surfactant concentration and the degree of charge of a polymer on foam film properties of oppositely charged polyelectrolyte/surfactant mixtures has been investigated. To verify the assumption that the position of the isoelectric point (IEP) does not change the character of the foam film stabilities, the position of the IEP of the polyelectrolyte/surfactant mixtures has been shifted in two different ways. Within the first series of experiments, the foam. film properties were studied using a fixed surfactant concentration of 3 x 10(-5) M in the mixture. Due to the low surfactant concentration, this is a rather dilute system. In the second approach, a copolymer of nonionic and ionic monomer units was Used to lower the charge density of the polymer. This gave rise to additional interactions between the polyelectrolyte and the surfactant, which makes the description of the foam film behavior more complex. In both systems, the same characteristics of the foam film stabilities were found: The foam film stability is reduced toward the IEP of the system, followed by a destabilization around the IEP., At polyelectrolyte concentrations above the IEP, foam films are very stable. However, the concentration range where unstable films were formed was rather broad, and the mechanisms leading to the destabilization had different origins. The results were compared with former findings on PAMPS/C(14)TAB mixtures with an IEP of 10(-4)M.(1)
Dielectric measurements have been carried out on all-organic metal-insulator-semiconductor structures with the ferroelectric polymer poly(vinylidenefluoride-trifluoroethylene) as the gate insulator. It is shown that the polarization states remain stable after poling with accumulation and depletion voltage. However, negative charge trapped at the semiconductor-insulator interface during the depletion cycle masks the negative shift in flatband voltage expected during the sweep to accumulation voltages.