Formation of laser plasma channels in a stationary gas

The formation of plasma channels with nonuniformity of about +- 3.5% has been demonstrated. The channels had a density of 1.2x10^19 cm-3 with a radius of 15 um and with length >= 2.5 mm. The channels were formed by 0.3 J, 100 ps laser pulses in a nonflowing gas, contained in a cylindrical chamber. The laser beam passed through the chamber along its axis via pinholes in the chamber walls. A plasma channel with an electron density on the order of 10^18 - 10^19 cm-3 was formed in pure He, N2, Ar, and Xe. A uniform channel forms at proper time delays and in optimal pressure ranges, which depend on the sort of gas. The influence of the interaction of the laser beam with the gas leaking out of the chamber through the pinholes was found insignificant. However, the formation of an ablative plasma on the walls of the pinholes by the wings of the radial profile of the laser beam plays an important role in the plasma channel formation and its uniformity. A low current glow discharge initiated in the chamber slightly improves the uniformity of the plasma channel, while a high current arc discharge leads to the formation of overdense plasma near the front pinhole and further refraction of the laser beam. The obtained results show the feasibility of creating uniform plasma channels in non-flowing gas targets.Comment: 15 pages, 7 figures, submitted to Physics of Plasma

Fretting-Fatigue Analysis of Shot-Peened Al 7075-T651 Test Specimens

Shot peening is a mechanical treatment that induces several changes in the material: surface roughness, increased hardness close to the surface, and, the most important, compressive residual stresses. This paper analyzes the effect of this treatment on alloy Al 7075-T651 in the case of fretting fatigue with cylindrical contact through the results of 114 fretting fatigue tests. There are three independent loads applied in this type of test: a constant normal load N, pressing the contact pad against the specimen; a cyclic bulk stress σ in the specimen; and a cyclic tangential load Q through the contact. Four specimens at each of 23 different combinations of these three parameters were tested—two specimens without any treatment and two treated with shot peening. The fatigue lives, contact surface, fracture surface, and residual stresses and hardness were studied. Improvement in fatigue life ranged from 3 to 22, depending on fatigue life. The relaxation of residual-stress distribution related to the number of applied cycles was also measured. Finally, another group of specimens treated with shot peening was polished and tested, obtaining similar lives as in the tests with specimens that were shot-peened but not polished.Junta de Andalucía P12-TEP-263

Career Development and Professional Attrition of Novice ESL Teachers of Adults

Research and development in language teacher education and, more recently, teacher accreditation has had enormous impact on the professional lives of ESL teachers in Canada. There has been less interest, however, in examining the career development and employment experiences of accredited ESL teachers as they transition from TESL programs to ESL classrooms. In this article, we report on a study examining this issue for ESL teachers of adults in Ontario, in which 147 ESL teachers responded to a survey and a select group participated in follow-up interviews. The data were collected for a broader study investigating the link between teacher education and teaching efficacy of novice ESL teachers. Quantitative analysis of the survey data revealed the professional backgrounds and career development of recently accredited ESL teachers in Ontario. Qualitative data analysis revealed concerns with employment in the first years of practice. The findings suggested a high risk of attrition for novice ESL teachers and highlighted the impact of current teacher education programs and the professional landscape of ESL teaching on their career development. We discuss the implications of these findings for TESL institutions, accreditation bodies, and ESL teachers

The Evaluation of Partnership Method in the Business in Indonesia

This research aims to analyze how to build a business connection using partnership based on coordination method using PT.Nipsea& Chemicals as the example. PT.Nipsea& Chemicals use a very effective partnership method that we will explain in the later part of this paper, it needs to be conducted because of the crowded competition of businesses nowadays. In order to analyze the method, data will be collected by survey and observation. Then data will be analyzed and compared to the product development method using descriptive quantitative research. We aims to take the positive aspects and get rid of the negative aspects from both of the methods and create a better method that willmake more profits, and assuring a stable relationship with the customers

Mucho bardo y pocas nueces. Una nueva visita a la “trampa” shakesperiana

Reseña de la obra teatral marplatense "Mucho bardo y pocas nueces", que se presentó en la temporada 2023 en la sala Roberto J. Payró del complejo Auditorium, bajo la dirección de Leo Rizzi