Masculinity in Adolescent Males’ Early Romantic and Sexual Heterosexual Relationships

There is a need to understand better the complex interrelationship between the adoption of masculinity during adolescence and the development of early romantic and sexual relationships. The purpose of this study was to describe features of adolescent masculinity and how it is expressed in the contexts of early to middle adolescent males’ romantic and sexual relationships. Thirty-three 14- to 16-year-old males were recruited from an adolescent clinic serving a community with high sexually transmitted infection rates and were asked open-ended questions about their relationships—how they developed, progressed, and ended. Participants described a high degree of relationally oriented beliefs and behaviors related to romantic and sexual relationships, such as a desire for intimacy and trust. The males also described a more limited degree of conventionally masculine beliefs and behaviors. These beliefs and behaviors often coexisted or overlapped. Implications for the clinical care of similar groups of adolescents are described

Erosion of materials used in heart valves prosthesis

Se estudia la erosión de materiales utilizados en la construcción de prótesis de válvulas cardíacas, Acero inoxidable 316 y Poli-metacrilato de metilo (PMMA) a niveles de desgaste bajos, esperados en estos dispositivos. Como material erosivo se utilizó SiC 220 mesh (65 μm de diámetro), en dos composiciones diferentes: 0,1 y 1 % en peso, suspendidas en una solución de glucosa al 50%P/P, (viscosidad de 0,01540 kg/(m.s)). Se usó un flujo de 2200 cm3/min y dos tamaños de boquillas de: 2,3 y 6,4 mm de diámetro, en dos ángulos de incidencia diferentes,60º y 90º. Los ensayos se realizaron por un período de 11 horas. Se partió de probetas de PMMA y Acero inoxidable 316 pulidas a espejo. Las escaras de desgaste se observaron al microscopio óptico. El tipo de fallas observadas en las probetas luego de los ensayos fueron: Puntos o cráteres (pequeños y grandes), Rayas largas, Rayas cortas y Rayas en forma de comas. En PMMA el desgaste se incrementó al aumentar la cantidad de partículas erosivas, tanto en los ensayos a 60º como a 90º. En cambio, no se observaron cambios en el nivel de con el ángulo de incidencia. En el acero inoxidable 316 se observó un incremento en el nivel de desgaste al reducir el ángulo de incidencia, de 90º a 60º.Erosion of poly-methil-metacrilate (PMMA) and 316 stainless steel, materials used in the fabrication of prosthetic heart valves, were studied. Particles of SiC, 65 μm in diameter (200 mesh), are used as erosive materials carried on a glucose solution as a carrier fluid. Two compositions of particles were used: 0.1 and 1 %wt. A flow rate of 2200 cm3 /min and two different outlet holes were used, the sample was located at 3 cm approximately of the outlet hole. The tests were performed for 11 hours. The initial surface of the PMMA and the stainless steel were polished up to a mirror like surface. The erosion scars were observed by optical microscopy. The types of failures found were: points or craters (smalls or larges), large scratches, short scratches and comma-like scratches. On the PMMA the wear increase when the amount of particles increase; however, no difference was observed when the incidence angle was changed. On the 316 stainless steel there the wear increased when the incidence angle change from 90º to 60 º.Fil: Rosenberger, Mario Roberto. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico Nordeste. Instituto de Materiales de Misiones; ArgentinaFil: Guerrero, L. A.. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico Nordeste. Instituto de Materiales de Misiones; ArgentinaFil: Vera, Maria Laura. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico Nordeste. Instituto de Materiales de Misiones; ArgentinaFil: Schvezov, Carlos Enrique. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico Nordeste. Instituto de Materiales de Misiones; Argentin

Condoms and developmental contexts in younger adolescent boys

BACKGROUND: Condom use is a key part of sexually transmitted infection (STI) prevention for young men. Yet little is known about how younger adolescent boys initially learn about and use condoms. We examined sources of information, attitudes towards, acquisition, practice and early use of condoms among 14-16-year-old boys. METHODS: Thirty 14-16-year-old boys were recruited from a teen clinic serving a community with high STI rates and were asked open-ended questions about condoms, such as, "Where did you learn about condoms?" and "In what situations would you/would you not, use condoms." Interviews were audio recorded, transcribed and coded. Qualitative analysis focused upon key concepts and shared social cognitions related to condom use. RESULTS: Both sexually inexperienced and experienced participants perceived that sex feels or would feel less pleasurable with condoms. For almost all participants, families were the primary source of both information about condoms and of condoms themselves. This information focused on pregnancy prevention, with STIs secondary. Participants' views of condoms fell into three developmental groups: not interested in condoms and equating their use with interest in sex; exploring condoms out of either curiosity or in preparation for sex; and experienced with condom use. Exploring included behaviours such as checking condoms out and trying them on. CONCLUSIONS: Our findings of existing negative perceptions of condoms, the importance of families in learning about condoms and the developmental need to test and try on condoms before use have implications for adolescent STI prevention programmes

Intrinsic Dynamical Instability in Optical Bistability with Two-Level Atoms

Self-pulsing instability is reported in an experiment in which two-level atoms couple to a single mode of a traveling-wave resonator to produce optical bistability. The threshold for the onset of oscillation together with the characteristics of the dynamical state are described. The self-pulsing instability observed is the analog in an absorbing system of the single-mode laser instability

Optical bistability in the mixed absorptive-dispersive regime with two-state atoms

Quantitative comparisons between experiment and theory for the steady-state characteristics in optical bistability with two-state atoms are reported. Nonresonant conditions for both the cavity and the atomic medium are investigated in two different cavity geometries (ring and standing wave). The experiment fulfills to a very good degree the conditions that have been widely employed in theoretical models that consider a collection of two-state atoms interacting with a single mode of the electromagnetic field in a cavity

Observation of absorptive bistability with two-level atoms in a ring cavity

Observations of steady-state hysteresis in absorptive bistability are reported for well-collimated atomic beams of sodium within a traveling-wave interferometer. The atomic medium approximates a system of homogeneously broadened "two-level" atoms, and effects due to standing waves are eliminated. The experiment thus represents the first demonstration of optical bistability under conditions that have been widely employed in theoretical models. Absolute measurements of switching intensities versus atomic cooperativity C are reported, and a preliminary comparison with Gaussian-beam theory is made