Specific smartphone uses and how they relate to anxiety and depression in university students: a cross-cultural perspective

ABSTRACT

People around the world spend hours of their daily lives using smartphones; therefore, it is important to conduct cross-cultural research on the effects of smartphone use on health and well-being as culture influences values, motivations and communication patterns. The purpose of this study was to explore 5 popular uses of the smartphone – messaging, browsing the Internet, posting social content, reading social content, and playing games – how they relate to anxiety and depression scores, and how they vary depending on the country of the participants: Spain, the United States, and Colombia. In all three countries the ranking of most popular uses was the same: (1) Messaging, (2) Reading social content, and (3) Browsing the Internet. In the USA, game playing contributed to anxiety scores whereas reading social content was a protective factor; regarding depression scores, text messaging was a contributing factor. In Spain, browsing the Internet contributed to anxiety scores; regarding depression scores, messaging was a contributing factor and posting social content was a protective factor. In Colombia, no specific use influenced anxiety scores; regarding depression scores, only game playing was a protective factor. Our results showed that in all the countries, problematic smartphone use contributed to anxiety scores.     

Zebra mussels and Eurasian watermilfoil reporting patterns in Minnesota

Recognizing common reporting patterns of aquatic invasive Zebra mussels (Dreissena polymorpha, ZM) and Eurasian watermilfoil (Myriophyllum spicatum, EWM) helps to better understand invasions. We hypothesize that confirmed invasions may be confounded by human population density, leading to overrepresentation of invasions in highly populated areas and underrepresentation in less populated areas. Here we recognize dispersal patterns of confirmed ZM and EWM invasions in Minnesota, USA, using spatial clustering and directionality tests, while adjusting for human density. By 2015, 125 (0.68%) and 304 (1.65%) of 18,411 Minnesota waterbodies were reported to have ZM and EWM, respectively. A multivariate multinomial model of the scan test was used to identify clustering of invasions. The resulting 23 clusters included 13 with either or both ZM and EWM, and most clusters (11/13) occurred in areas with >10 people per square kilometer. Whereas, among the 10 clusters without invasion, nine were from less populated areas. The standard deviation ellipse and the spatiotemporal directionality tests indicated a northwestern trend of invasions, which is in the same direction as the I-94 interstate highway connecting urban centers. Results suggested that confirmed ZM and EWM invasions are potentially confounded by human densities, which is explained by varying human impact on either or both dispersal and reporting of invasions. Considering this impact of human density, we suggest that a combination of passive and targeted surveillance, where the magnitude of efforts are stratified by the human densities, may provide insight into the true invasion status and its progression in the Great Lakes region.     

Continuous fractionation of chilean anchovy oil with furfural

Useful data for liquid-liquid extraction were obtained by countercurrent fractionation of Chilean anchovy oil in an extraction column. Furfural was used as the extracting solvent while the oil was dissolved in petroleum naphtha. The data obtained by varying the velocity of agitation, the feed rate, the furfural oil ratio and the naphtha oil ratio are adequate for the design and operation of an extraction system.     

Solubilization of phospholipid bilayer caused by surfactants

The interaction of surfactants with liposomes eventually leads to the rupture of such structures and the solubilization of the phospholipid components. In this paper, solubilization is regarded as a decrease in light scattering of liposome suspensions. To this end, in accordance with the nomenclature, adopted by Lichtenberg, three parameters were considered as corresponding to the effective surfactant/lipid molar ratios (Re) at which light scattering starts to decrease, Re_sat; reaches 50% of the original value, Re₅₀; and shows no further decrease, Re_sol. These parameters corresponded to the Re at which the surfactant (i) saturated the liposomes, (ii) resulted in a 50% solubilization of vesicles and (iii) led to a total solubilization of liposomes. The surfactants tested were the nonionic surfactant octylphenol ethoxylated with 10 units of ethylene oxide or Triton X-100 (OP-10EO), two anionic surfactants, sodium dodecyl sulfate and sodium dodecyl ether sulfate, and an amphoteric surfactant dodecyl betaine (D-Bet). Unilamellar liposomes formed by egg phosphatidylcholine containing increasing amounts of phosphatidic acid were used. The Re parameters were the lowest for D-Bet, followed by OP-10EO, whereas the anionic surfactants always showed the highest values regardless of the electrical charge of the lipid bilayers. These parameters seem also to be inversely related to the critical micelle concentration (CMC) of the surfactant, except for OP-10EO. Moreover, the CMC values of the surfactant/lipid systems at 0.5 mM lipid concentration corresponded in all cases to the surfactant concentration at which liposomes were saturated by surfactants. As a consequence, this ratio can be regarded as an interesting parameter associated with the mixed micelle formation in liposome solubilization.     

Exposure to volatile organic compounds (VOC) in public buses of Pamplona, Northern Spain

This study examines the exposure level of passengers and drivers to VOC in public buses in a medium-size metropolitan area (Northern Spain). In-vehicle monitoring was performed on different routes, on peak and non-peak hours, during January and February 2007. A total of 112 air samples were collected onto adsorbent tubes and analysed by thermal desorption (TD) and gas chromatography/mass selective detector (GC/MSD) technique. Statistical differences were found among route to route concentrations, with those routes with major prevalence in the commercial area of the city displaying higher values; differences between peak and non-peak hours were also observed. A decrease in VOC concentrations was also registered during the weekend. BTEX ratios were estimated and found to be related to traffic emissions and similar for all the surveyed routes. Correlations confirmed traffic as the main emission source for BTEX and trimethylbenzene, their concentrations being highly associated to changes in meteorological conditions.     

Quantification of unidirectional nonlinear associations between multidimensional signals

In this paper, we present a rigorous, general definition of the nonlinear association index, known as h2. Proving equivalence between different definitions we show that the index measures the best dynamic range of any nonlinear map between signals. We present also a construction for removing the influence of one signal from another, providing, thus, the basis of an independent component analysis. Our definition applies to arbitrary multidimensional vector-valued signals and depends on an aperture function. In this way, the bin-related classic definition of h2 can be generalized. We show that upon choosing suitable aperture functions the bin-related intuitive definition can be deduced. Special attention is dedicated to the direction of the association index that in general is taken in only one sense. We show that for linearly coupled signals high associations are always bidirectional. As a consequence, high asymmetric nonlinear associations are indicators of nonlinear relations, possibly critical, between the dynamic systems underlying the measured signals. We give a simple simulated example to illustrate this property. As a potential clinical application, we show that unidirectional associations between electroencephalogram (EEG) and electromyogram (EMG) recorded from patient with pharmacologically intractable epilepsy can be used to study the cortical involvement in the generation of motor seizures.     

Recycling of the Products Obtained in the Pyrolysis of Fibre-Glass Polyester SMC

An SMC (Sheeting Moulding Compound) of fibre-glass and orthophthalic polyester has been pyrolysed in a 3·5 dm³ autoclave for 30 min in a nitrogen atmosphere at 300, 400, 500, 600 and 700°C. Gas yields of 8–13 weight%, liquid yields of 9–16 weight% and solid residues of 72–82 weight% were obtained. The suitability of the pyrolysis process for recycling SMC is discussed. The characteristics, compositions and possible ways of reusing the liquid and gaseous fractions are presented. The solid pyrolysis residue has been recycled in another thermoset composite (Bulk Moulding Compound, BMC) and its mechanical properties have been compared with those of virgin BMC. The main conclusion is that pyrolysis can be an appropriate method for recycling thermoset polymeric composites such as SMC. The pyrolysis gas fraction can be sufficient to provide the energy requirements of the process plant. The pyrolysis liquids have high gross calorific values (36·8 MJ kg⁻¹) and are non-polluting liquid fuels; about 40 weight% of such liquids could be used as petrols, and the remaining 60% could be mixed with fuel oils. The solid pyrolysis residue can be recycled in BMC with no detrimental effect on the BMC mechanical properties. Concerning temperature, it has been concluded that 400–500°C are the most suitable temperatures for recycling SMC by pyrolysis. © 1997 SCI.     

Continuous Converting of Copper Matte to Blister Copper in a High-Intensity Molten-Layer Reactor

Continuous converting of copper matte or white metal into blister copper is carried out in a new, high-intensity falling film type of molten-layer reactor that operates with dry, high-grade matte or white metal ground to ?65 mesh and technical oxygen. The reactor operates at up to 1500°C to 1600°C producing a blister copper with 0.5–0.8% S, which can be refined in a conventional manner, and a slag containing less than 8% Cu. The reactor is designed to operate continuously producing an off-gas containing over 50% SO₂. The developed phenomenological model of the molten-layer reactor was found to predict with good agreement the results obtained in a one-tonne-per-day pilot reactor.     

A genetic algorithm for a bicriteria supplier selection problem

In this paper, we discuss the problem of selecting suppliers for an organisation, where a number of suppliers have made price offers for supply of items, but have limited capacity. Selecting the cheapest combination of suppliers is a straightforward matter, but purchasers often have a dual goal of lowering the number of suppliers they deal with. This second goal makes this issue a bicriteria problem – minimisation of cost and minimisation of the number of suppliers. We present a mixed integer programming (MIP) model for this scenario. Quality and delivery performance are modelled as constraints. Smaller instances of this model may be solved using an MIP solver, but large instances will require a heuristic. We present a multi-population genetic algorithm for generating Pareto-optimal solutions of the problem. The performance of this algorithm is compared against MIP solutions and Monte Carlo solutions.