The aim of this paper is to make a descriptive analysis of Problematic Internet Use in college students, evaluating the possible association with health problems and addictive behaviors, as well as gender differences in user types. A total of 2,780 students participated in the study between 2011 and 2014, 29% of them being males (age 20.8 ± 5.1 years) and 71% females (age 20.3 ± 4.4 years). The prevalence of Problematic Internet Use (PIU) assessed by the Internet Addiction Test was 6.08%. Being under 21 years of age and studying for degrees in subjects other than the health sciences were associated factors with a higher frequency of this problem, no differences by gender or type of address were found. The results show a significant association with some health problems (migraines, back pain, excess weight or obesity, insufficient rest), psychological aspects (risk of eating disorders, risk of mental disorder, depression), family problems and discrimination; with no associations with substance use (alcohol, cannabis or tobacco) being found. Concerning the time of Internet use, weekly hours were significantly higher in women than in men, both the total time as for leisure. The analysis of the profile use in problematic users revealed that males are related to aspects of entertainment such as games or shopping online and females are related to aspects of socialization, such as chats and social networks. Uso problemático de internet en estudiantes universitarios: factores asociados y diferencias de géneroProblematic Internet Use in University Students: associated factors and differences of gender Tania Fernández-Villa*, Juan Alguacil Ojeda**,***, Ana Almaraz Gómez****, José María Cancela Carral*****, Miguel Delgado-Rodríguez**,******, Miguel García-Martín*******, Eladio Jiménez-Mejías*******, Javier Llorca**,********, Antonio José Molina*,*********, Rocío Ortíz Moncada**********, Luiz Félix Valero-Juan***********, Vicente Martín*,**,********* *Departamento de Ciencias Biomédicas. Área de Medicina Preventiva y Salud Pública. Universidad de León; **Centro de Investigación Biomédica en Red de Epidemiología y Salud Pública (CIBERESP); ***Centro de Investigación en Salud y Medio Ambiente (CYSMA). Universidad de Huelva; ****Departamento de Medicina Preventiva y Salud Pública, Universidad de Valladolid; *****Grupo de Investigación Healthy Fit. Facultad de Ciencias de la Educación y el Deporte. Universidad de Vigo; ******Área de Medicina Preventiva y Salud Pública. Universidad de Jaén; *******Departamento de Medicina Preventiva y Salud Pública. Universidad de Granada; ********Universidad de Cantabria -IDIVAL; *********Grupo de Investigación de Interacción Gen-Ambiente-Salud (GIIGAS). Universidad de León; **********Grupo de Investigación Alimentación y Nutrición, Área de Medicina Preventiva y Salud Pública. Universidad de Alicante.; ***********Área de Medicina Preventiva y Salud Pública. Universidad de Salamanca.

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We implement microfluidic technology to miniaturize a thermal cycling system for amplifying DNA fragments. By using a microfluidic thermal heat exchanger to cool a Peltier junction, we have demonstrated rapid heating and cooling of small volumes of solution. We use a miniature K-type thermocouple to provide a means for in situ sensing of the temperature inside the microrefrigeration system. By combining the thermocouple, two power supplies controlled by a relay system, and computer automation, we reproduce the function of a commercial polymerase chain reaction thermal cycler and demonstrate amplification of a DNA sample of about 1000 base pairs.

Chiral metamaterials are widely used to implement devices that transform the polarization of an incident electromagnetic wave, such as polarization rotators and linear to circular converters, but rarely used as circular polarization converters. This letter presents a chiral metamaterial that changes the handedness of a circularly polarized incident wave. This structure, which presents subwavelength thickness, provides polarization conversion with independence on both the front and back directions and the handedness of the incident wave. High polarization conversion efficiency is shown by both simulations and experiments.

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ABSTRACT:The application of the coupled-mode method (CMM) for calculating the propagation constants and the electromagnetic-field distribution in chirowaveguides is well known. In this paper, two different formulations of the method are revised and compared, and are then extended to partially filled parallel-plate waveguides.