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Rack and pinion drive systems are widely used in machine tools with long travel distances because the stiffness is independent of the travelled distance, in contrast to other drive systems such as ballscrews. Although the inherent backlash problem of gear systems has been solved by means of utilizing two pinions independently preloaded, the time-varying mesh stiffness causes periodic position differences between the motor encoder and table position, which is known as transmission error, and may lead to vibrations and dynamic load. Few experimental works have analyzed such transmission error, but there are no theoretical approaches in the scientific literature. Therefore, this work aims to first extend previous analytical and approximate equations for mesh stiffness of gearing to rack and pinion systems and validate them with finite element methods. Finally, the effect of geometry variations, such as pressure angle and tooth thickness tolerance, on transmission error is discussed.

The study examined the effects of national culture, self-construals, and power distance on face concerns and facework behaviors during conflicts with parents and siblings. A total of 449 participants of 4 national cultures completed a questionnaire in their respective languages: Germany, Japan, Mexico, and the United States. The questionnaire measured 3 face concerns and 11 facework behaviors in recalled conflicts with either a sibling or a parent. The major findings of the study are as follows: (a) self-construals had strong effects on face concerns and facework with independence positively associated with self-face and dominating facework and interdependence positively associated with other- and mutual-face and integrating and avoiding facework behaviors; (b) power distance had small, positive effects on self-face, other-face, avoiding facework, and dominating facework; (c) national culture had small to medium effects with individualistic, small power distance cultures having more self-face and mutual-face and using more dominating and integrating facework and less avoiding facework; (d) Germans have more self-face and used defending more than U.S. Americans; (e) Japanese used more expression than Mexicans; and (f) individuals in conflict with parents were more likely to use respect and expression and less likely to use aggression, pretend, and third party than individuals in conflict with siblings. [ABSTRACT FROM AUTHOR]

A comparison among different approaches of the meshing stiffness of spur gears has been carried out. The influence of each one on the load sharing, and subsequently on the determinant tooth-root and contact stresses, has also been studied. Equations for the evolution of the meshing stiffness along the path of contact according to all these formulations are also provided.

Profile modifications are commonly used to avoid shocks between meshing gear teeth produced by the delay of the driven gear, and the subsequent sooner start of contact, due to the teeth deflections. A suitable tip relief at the driven tooth shifts the start of contact to the proper location at the theoretical inner point of contact. The shape of the relief governs the loading curve of the tooth pair, while the length of relief determines the intervals in which this actual loading curve differs from the theoretical one of unmodified teeth. As at least one tooth pair should be in contact at the unmodified involute profile interval, the length of modification should be smaller than the length of the intervals of two pair tooth contact; otherwise, a shock at the end of contact of the previous pair is unavoidable. However this problem does not occur for high contact ratio spur gears, in which at least two couples of teeth are in contact at any moment. In this work, a study on the load sharing and the quasi-static transmission error for high contact ratio spur gears with long profile modification has been performed, and a model for the tooth contact has been developed.

Abstract: Toxoplasmosis is one of the most frequent protozoonosis in the human being. The objective of this study was to determine toxoplasmosis seroprevalence in an infantile population from the Mara Municipality, State of Zulia. 119 serum samples from both sexes (53 male and 66 female) with ages between 4-13 years were studied. The toxoplasmic antibodies were determined by the indirect hemaglutination technique. Statistical analysis was done using the Chi square test and Spearman’s correlation. General prevalence of the infection was 15.9%. The positive serum frequency was greater in the 10-13-year age range (8/25) with 32.0%. It was observed that the number of positive cases increased in relation to the age group. No statistically significant differences related to gender were observed; nevertheless, a greater positive tendency was observed for females in the 10-13-year group. The geometric average was 9.479. The range of positive titles was from 1:64 to 1:2.097.512; the lowest title was 1:64 with 5.26% (1/19) and the highest was 1:2.097.512 with 5.26% (1/19). Results indicate that this disease is frequent in this infantile population. Resumen: La Toxoplasmosis es una de las protozoonosis más frecuentes del ser humano. El objetivo de este estudio fue determinar la seroprevalencia de la toxoplasmosis en una población infantil del Municipio Mara, estado Zulia. Se estudiaron 119 muestras de sueros de ambos sexos (53 masculinos y 66 femeninos) con edades comprendidas entre 4-13 años. Los anticuerpos toxoplásmicos se determinaron por de la técnica de hemaglutinación indirecta. El análisis estadístico se realizó a través de la prueba de Chi cuadrado y la correlación de Spearman. La prevalencia general de infección fue de 15,9%. La frecuencia de sueros positivos fue mayor en el rango de edad de 10-13 años (8/25) con un 32,0%. Se observó que el número de casos positivos aumentó con relación al grupo de edad. No se observaron diferencias estadísticamente significativas con relación al sexo, sin embargo, se apreció una mayor tendencia de positividad para el sexo femenino en el grupo de 10-13 años. La media geométrica fue de 9.479. El rango de títulos positivos fue de 1:64 a 1:2.097.512, el título más bajo fue de 1:64 con 5,26% (1/19) y el más alto 1:2.097.512 con 5,26% (1/19). Los resultados obtenidos indican que esta enfermedad es frecuente en esta población infantil.

Aunque no seamos del todo conscientes, el ser humano ha cambiado el medioambiente de manera radical en los últimos cincuenta años, al punto de poner enpeligro la existencia de la vida sobre la tierra; y esto también ha pasado a ser motivode preocupación ética. (Osorio M C., 2000). Situación que nos conduce a vincular lapreocupación por el tema del medio ambiente y de la Ética sobre el medio ambiente,con el auge de la ciencia y la tecnología, especialmente desde la Segunda GuerraMundial, ya que ha sido sobre todo el desarrollo científico-tecnológico llevado a cabopor la mano del hombre en los últimos años, el que nos ha permitido sobreutilizar lanaturaleza para desencadenar situaciones que han puesto en peligro la continuidad dela vida (...)

Abstract Aims Illicit cocaine consumption in Spain is one of the highest in Europe. Our objective was to study the incidence of undisclosed cocaine consumption in patients attending in two Spanish Emergency Departments for chest pain. Methods We analysed urine samples from consenting consecutive patients attending ED for chest pain to determine the presence of cocaine, and other drugs, by semiquantative tests with fluorescence polarization immunoassay (FPIA). Results Of 140 cases, 15.7 presented positive test for drugs, and cocaine was present in 6.4%. All cocaine-positive patients were younger (p < 0.001); none was admitted to Hospital (p = 0.08). No significant differences in ED stay or need for hospitalization were found between cocaine-positive and negative patients. Conclusion This finding in chest pain patients who consented to urine analysis suggests that the true incidence of cocaine use leading to such ED visits may be higher.