Bridge windshield design to avoid aeroelastic phenomena

Since in 1940 the Tacoma Narrows Bridge was destroyed by the wind, aeroelastic instabilities have been recognized as one of the most challenging aspects of bridge design. They can produce long-term fatigue failure through vortex induced vibrations, or sudden collapse through self-excited flutter. These vibrations may also cause discomfort for the users and temporary closure of the bridge. Wind tunnel studies are a very helpful tool to understand these phenomena. By means of them, the critical wind speed at which vortex induced vibration and flutter appear can be precisely determined and the design of the bridge can be reconsidered in the early steps of the process. In this paper, an optimum design of the bridge section is sought. One of the most relevant parameters that influence the stability of a certain deck is the porosity of the barriers. Section model tests have been carried out to find whether an optimum value of the porosity of the barrier exists. This value or range of values must present neither vortex induced vibration nor flutter.

Caring and being cared -for: Perceptions of adolescent males at -risk for school failure

This qualitative study used grounded theory methods and purposeful sampling to explore perceptions on caring and being cared-for. Twenty-four adolescent male participants, identified as at-risk for school failure, completed a two phase interview process exploring these phenomena within three relationships; the relationship with the friend, with the most caring person they knew and with the teacher they felt cared for them. ^ Each participant was asked a predetermined set of open questions in an initial semi-structured interview. In addition each participant was encouraged to explore his own reflections on caring. A second interview allowed for member checking and for the participant to continue sharing his meaning of caring and being cared-for. ^ Line by line analysis with open, axial and selective coding was applied to interview transcripts along with a constant comparative method. Results indicated that the core category integrating all other categories was attachment bonding. Participants' stories manifested characteristics of proximity seeking, secure base, safe haven and distress upon involuntary separation from an attachment figure. ^ Strategies facilitating attachment bonding were influenced by the power positions of the relational players. Participants responded positively to the one-caring when they felt cared-for. Results further indicated that participants did not need to feel a sense of belonging in order to feel cared-for. Teacher behaviors indicating openness for authentic connections with students were specific to teacher's friendliness and professional competence. Teachers who nurtured feelings of being cared-for were uncommon in the participants' educational experience. ^ The number of adolescent males leaving high school prematurely is both a personal problem and a social problem. Despite a “mask” of indifference often exhibited by adolescent males at-risk for school failure, teachers might consider the social/emotional needs of these students when implementing the curriculum. In addition, policy makers might consider the social/emotional needs of this vulnerable population when developing programs meant to foster psychological well-being and connectedness for adolescent males at-risk for school failure. ^

NOTCH1 Gain of Function in Germ Cells Causes Failure of Spermatogenesis in Male Mice

NOTCH1 is a member of the NOTCH receptor family, a group of single-pass trans-membrane receptors. NOTCH signaling is highly conserved in evolution and mediates communication between adjacent cells. NOTCH receptors have been implicated in cell fate determination, as well as maintenance and differentiation of stem cells. In the mammalian testis expression of NOTCH1 in somatic and germ cells has been demonstrated, however its role in spermatogenesis was not clear. To study the significance of NOTCH1 in germ cells, we applied a cre/loxP approach in mice to induce NOTCH1 gain- or loss-of function specifically in male germ cells. Using a Stra8-icretransgene we produced mice with conditional activation of the NOTCH1 intracellular domain (NICD) in germ cells. Spermatogenesis in these mutants was progressively affected with age, resulting in decreased testis weight and sperm count. Analysis of downstream target genes of NOTCH1 signaling showed an increased expression of Hes5, with a reduction of the spermatogonial differentiation marker, Neurog3 expression in the mutant testis. Apoptosis was significantly increased in mouse germ cells with the corresponding elevation of pro-apoptotic Trp53 and Trp63genes' expression. We also showed that the conditional germ cell-specific ablation of Notch1 had no effect on spermatogenesis or male fertility. Our data suggest the importance of NOTCH signaling regulation in male germ cells for their survival and differentiation.

The Dyad School Success/Failure in the Academic Development of the Working Class Women from Mendoza

The notion of academic performance renders account of the results achieved by the students during their school education.  Internally, there are two opposed phenomena:  school success and school failure.  Sociology of education has contributed to the discussion of both notions revealing their social nature closely related to the institutional and socio-cultural contexts in which education is developed.  This paper is the result of a research project conducted for our doctoral thesis.  Its purpose is to contribute to enlighten the scopes of this discussion, by analyzing the school development of a group of working class women from Mendoza. We were interested, in the first place, in knowing the reasons why they quit school when they were young girls or adolescents.  Subsequently, we have approached the opportunities they had to access the system again during their adulthood, the obstacles they had to face and the resources to be able to complete the medium level.