Multilayer Complex Network Descriptors for Color-Texture Characterization

A new method based on complex networks is proposed for color-texture analysis. The proposal consists on modeling the image as a multilayer complex network where each color channel is a layer, and each pixel (in each color channel) is represented as a network vertex. The network dynamic evolution is accessed using a set of modeling parameters (radii and thresholds), and new characterization techniques are introduced to capt information regarding within and between color channel spatial interaction. An automatic and adaptive approach for threshold selection is also proposed. We conduct classification experiments on 5 well-known datasets: Vistex, Usptex, Outex13, CURet and MBT. Results among various literature methods are compared, including deep convolutional neural networks with pre-trained architectures. The proposed method presented the highest overall performance over the 5 datasets, with 97.7 of mean accuracy against 97.0 achieved by the ResNet convolutional neural network with 50 layers.Comment: 20 pages, 7 figures and 4 table

Transport on weighted Networks: when correlations are independent of degree

Most real-world networks are weighted graphs with the weight of the edges reflecting the relative importance of the connections. In this work, we study non degree dependent correlations between edge weights, generalizing thus the correlations beyond the degree dependent case. We propose a simple method to introduce weight-weight correlations in topologically uncorrelated graphs. This allows us to test different measures to discriminate between the different correlation types and to quantify their intensity. We also discuss here the effect of weight correlations on the transport properties of the networks, showing that positive correlations dramatically improve transport. Finally, we give two examples of real-world networks (social and transport graphs) in which weight-weight correlations are present.Comment: 8 pages, 8 figure

Happiness is assortative in online social networks

Social networks tend to disproportionally favor connections between individuals with either similar or dissimilar characteristics. This propensity, referred to as assortative mixing or homophily, is expressed as the correlation between attribute values of nearest neighbour vertices in a graph. Recent results indicate that beyond demographic features such as age, sex and race, even psychological states such as "loneliness" can be assortative in a social network. In spite of the increasing societal importance of online social networks it is unknown whether assortative mixing of psychological states takes place in situations where social ties are mediated solely by online networking services in the absence of physical contact. Here, we show that general happiness or Subjective Well-Being (SWB) of Twitter users, as measured from a 6 month record of their individual tweets, is indeed assortative across the Twitter social network. To our knowledge this is the first result that shows assortative mixing in online networks at the level of SWB. Our results imply that online social networks may be equally subject to the social mechanisms that cause assortative mixing in real social networks and that such assortative mixing takes place at the level of SWB. Given the increasing prevalence of online social networks, their propensity to connect users with similar levels of SWB may be an important instrument in better understanding how both positive and negative sentiments spread through online social ties. Future research may focus on how event-specific mood states can propagate and influence user behavior in "real life".Comment: 17 pages, 9 figure

Improving hospital operations management to reduce ineffective medical appointments

The main objective of this study is to meet management aspirations by promoting waste reduction and consequently improving patients` experience in a Portuguese public hospital. These aspirations include increasing hospital service quality in a continuous and efficient way. This management mindset uncovered divergences between medical appointment and magnetic resonance imaging (MRI) exam scheduling that were generating waste for both the hospital and patients. The main aspects considered in this study were the patients’ medical expectations, the quality, and cost of service provided. One-year retroactive encrypted data from medical appointments and MRI requisitions were provided for the algorithm development. Outcomes obtained from the algorithm revealed a high percentage of medical appointments occurring without the respective MRI exam results. These outcomes exposed waste existence that was hitherto unknown by the administration. Thus, the main algorithm function is to analyze future data to previously alert ineffective medical appointments. This progress contributes to reducing wasted medical and patient time. In summary, the main contribution of this article is to allow hospital managers to cross-check data from different sectors to identify divergences in future medical consultations that require exams or results of clinical analysis.This work was supported by the Fundacao para a Ciencia e a Tecnologia [POCI-01-0145-FEDER-030299]; Fundacao para a Ciencia e a Tecnologia [UIDB/00319/2020]

Selective isomerization of α-pinene oxide to campholenic aldehyde by ionic liquid-supported indenyl-molybdenum(II)-bipyridine complexes

Campholenic aldehyde (CPA), an important flavor and fragrance intermediate, can be obtained by the Lewis acid-catalyzed isomerization of α-pinene oxide (PinOx), although achieving high yields (>90%) is a difficult challenge due to the high reactivity of the epoxide. In the present work, indenyl-molybdenum(II)-bipyridine complexes [IndMo(bipyR)(CO)2](BF4) (bipyR = 2,2′-bipyridine (R = H) or 4,4′-disubstituted-2,2′-bipyridine) have been combined with various ionic liquid solvents to develop an efficient process for the selective conversion of PinOx to CPA under mild (35 °C) conditions. Excellent CPA yields (95%) were repeatedly obtained within 1 min reaction time for the easily recyclable catalytic system comprising [IndMo(4,4′-dinonyl-2,2′-bipyridine)(CO)2](BF4) and choline bis(trifluoromethylsulfonyl)imide.publishe

Human dynamics revealed through Web analytics

When the World Wide Web was first conceived as a way to facilitate the sharing of scientific information at the CERN (European Center for Nuclear Research) few could have imagined the role it would come to play in the following decades. Since then, the increasing ubiquity of Internet access and the frequency with which people interact with it raise the possibility of using the Web to better observe, understand, and monitor several aspects of human social behavior. Web sites with large numbers of frequently returning users are ideal for this task. If these sites belong to companies or universities, their usage patterns can furnish information about the working habits of entire populations. In this work, we analyze the properly anonymized logs detailing the access history to Emory University's Web site. Emory is a medium size university located in Atlanta, Georgia. We find interesting structure in the activity patterns of the domain and study in a systematic way the main forces behind the dynamics of the traffic. In particular, we show that both linear preferential linking and priority based queuing are essential ingredients to understand the way users navigate the Web.Comment: 7 pages, 8 figure

Random walks and search in time-varying networks

The random walk process underlies the description of a large number of real world phenomena. Here we provide the study of random walk processes in time varying networks in the regime of time-scale mixing; i.e. when the network connectivity pattern and the random walk process dynamics are unfolding on the same time scale. We consider a model for time varying networks created from the activity potential of the nodes, and derive solutions of the asymptotic behavior of random walks and the mean first passage time in undirected and directed networks. Our findings show striking differences with respect to the well known results obtained in quenched and annealed networks, emphasizing the effects of dynamical connectivity patterns in the definition of proper strategies for search, retrieval and diffusion processes in time-varying network

Propyl­ammonium 4,4,4-trifluoro-1-(naphthalen-2-yl)butane-1,3-dionate

The title salt, C3H10N+·C14H8F3O2 −, constitutes the first organic crystal containing a residue of 4,4,4-trifluoro-1-(naphthalen-2-yl)butane-1,3-dione. The terminal –CF3 group is disordered over two locations [occupancy ratio = 0.830 (7):0.170 (7)]. Bond delocalization involving the two carbonyl groups and the α-carbon was observed. The crystal packing is mediated by several supra­molecular inter­actions, namely charged-assisted N—H⋯O hydrogen bonds, C—H⋯F and C—F⋯F short contacts and C—H⋯π inter­actions

High-yield synthesis and catalytic response of chainlike hybrid materials of the [(MoO3)m(2,2′-bipyridine)n] family

The one-dimensional organic–inorganic hybrid material [MoO3(2,2'-bipy)] (1) (2,2'-bipy = 2,2'-bipyridine) has been used as a starting material to prepare the bipy-deficient phases [Mo2O6(2,2'-bipy)] (2) and [Mo3O9(2,2'-bipy)2] (3) in excellent yields. The hybrid 2 was obtained by a solid-state thermal treatment of 1 (300 ºC, 10 min) while 3 was obtained by a hydrothermal treatment of 1 (160 ºC, 6 d). A study was performed to compare the catalytic properties of 1–3 in the epoxidation of cis-cyclooctene at 55 ºC with tert-butylhydroperoxide (TBHP) or aqueous H2O2 as oxidant. In all cases Cy was converted to cyclooctene oxide (CyO) with 100% selectivity, and Cy conversions increased in the order 1 < 3 < 2, which parallels an increase in the Mo/2,20-bipy molar ratio of the hybrid (1 < 1.5 < 2). With compound 2, CyO yields at 24 h were 96% for TBHP (cosolvent a,a,a-trifluorotoluene) and 53% for H2O2 (cosolvent CH3CN). The catalytic reactions occurred in homogeneous phase with active species formed in situ from 1–3. All three hybrids react with aqueous H2O2 to give the catalytically active oxodiperoxo complex [MoO(O2)2(2,2'-bipy)]. The 2 : 1 hybrid 2 was further examined for the epoxidation of other cyclic and linear non-functionalised olefins with TBHP, namely cyclododecene, 1-octene and trans-2-octene, and the biomass-derived olefins DL-limonene, a-pinene and methyl oleate.publishe