Flexural capacity of eco-friendly reinforced concrete beams.

In the construction industry, concrete is the most utilized building material. It is produced from different natural resources such as sand and gravel, as well as cement. The production of concrete is causing harm to the environment, yet its use became a necessity. To solve this humongous environmental challenge, many researchers devoted a considerable effort to partially replacing concrete mix components with waste material derived from glass, plastics, aluminum, wood ash, construction and demolition wastes, or tires. In the current study, a novel effort was conducted to incorporate all the above-mentioned wastes in a concrete mix design and to assess its performance. Five recycled mix designs were explored and based on the concrete mechanical properties derived, an optimum mix was realized. The optimum mix incorporated the following waste percentages: 2% crumb rubber (CR) partially replacing sand, 20% powdered glass (PG) partially replacing sand, 50% recycled concrete aggregates (RCA) partially replacing coarse aggregates, and the addition of 0.5% plastic. The optimum recycled mix was utilized to cast a real-life-size reinforced concrete beam which was compared to a normal mix beam.

Approach to the vaso-occlusive crisis in adults with sickle cell disease.

The vaso-occlusive crisis, or sickle cell crisis, is a common painful complication of sickle cell disease in adolescents and adults. Acute episodes of severe pain (crises) are the primary reason that these patients seek medical care in hospital emergency departments. Frequently, however, the pain is incompletely treated. Despite advances in pain management, physicians are often reluctant to give patients adequate dosages of narcotic analgesics because of concerns about addiction, tolerance and side effects. It is important to recognize a pain crisis early, correct the inciting causes, control pain, maintain euvolemia and, when necessary, administer adequate hemoglobin to decrease the hemoglobin S level. The family physician and the hematologist must work together to treat acute pain episodes promptly and effectively, manage the long-term sequelae of chronic pain and prevent future vaso-occlusive crises.

Acute chest syndrome in sickle cell disease. Crucial considerations in adolescents and adults.

Rapid recognition of acute chest syndrome is essential in patients with sickle cell disease. The condition can be particularly severe in adolescents and adults and often leads to death. In this article, the authors review the challenges of evaluating the syndrome and outline current treatment and supportive care.

Phase retardometer: a proposed device for measuring phase retardance.

The realization of a standard device for measuring phase retardance has been retarded by the lack of a simple underlying physical concept that can be formulated in a simple mathematical expression to provide quick, direct, and accurate results. A proposed device that meets these requirements and simple formulas for retardance measurements are presented.

Comparison of vaginal and cesarean section delivery for fetuses in breech presentation.

OBJECTIVES: Our purpose was to evaluate the perinatal mortality and morbidity of deliveries with fetuses presenting by the breech comparing outcomes of two groups according to mode of delivery: vaginal and cesarean section. RESULTS: Of 756 fetuses studied, 271 were delivered vaginally and 485 by cesarean section. In infants weighing > or = 1500 grams, "further corrected" mortality and morbidity rates were low and similar for both delivery routes: one neonatal death (NNM) in each. Among very low birth weight (VLBW) infants (< 1500 grams) the "further corrected" mortality rate was higher in the vaginal group: 57.4%, and 18.0% in abdominal deliveries (odds ratio [OR] = 6.1, 95% CI: 3.1 to 12.1). Likewise, rate of depression at five minutes were higher in the vaginal group (p < 0.001). However, the average fetal weight among the vaginal deliveries VLBW (787 grams) was 250 grams less than in the cesarean section group (1040 grams). After adjustment for fetal weight, gestational age, and other prognostic variables the odds ratio for neonatal death was no longer statistically significant (adjusted OR = 2.1, 95% CI: 0.9 to 5.2, p = 0.105). Comparison of planned vaginal delivery with elective cesarean section yielded smaller differences (adjusted OR for neonatal death = 1.3, 95% CI: 0.6 to 2.9, p = 0.525). CONCLUSION: The poor perinatal outcomes of breech delivered infants are due primarily to VLBW, congenital malformations, and premature labor. Although abdominal delivery had a lower NNM rate than vaginal delivery, the difference was not significant after adjustment for confounding factors. The results confirm the findings of a previously analyzed similar series delivered at our institution between 1980 and 1987. They suggest that, with appropriate technique, abdominal delivery is not mandatory in breech presentation.

Phase retarders highly insensitive to the input angle.

In the few exceptional cases of total internal reflection phase retarders that are weakly sensitive to variations in the input angle of incidence i, the devices are of increasingly larger size; deviate or translate the emergent beam; are difficult to align in optical systems; or, in coated rhombs, have an impermanent stability of the retardance. Based on new compensating effects, novel devices of high retardance stability and advantageous characteristics are presented. One device is stable to within 0.09 degrees of 90 degrees for i ? 3 degrees . It is a two-reflection quarter-wave retarder that does not alter the path of the compact size light beam, is of compact size (one seventh the size occupied by the achromatic device AD-1 for equal aperture lengths), and can be easily aligned in optical systems or used as a rotating element. The path length of the beam inside the device is less than one third the corresponding length inside the achromatic device AD-1.

Theory of oblique-incidence phase retarders.

Phenomenological and mathematical analyses of oblique incidence in total-internal-reflection phase retarders and the procedure for constructing extremely achromatic quarter-wave retarders are presented. It is shown that the retardance can assume the same value twice at two definite spectral lines. As an example, a quarter-wave phase retarder is described that introduces a retardance of exactly 90 degrees at two He-Ne laser lines of 632.8 and 1150 nm with a maximum deviation of 0.007 degrees for other wavelengths between these two lines. This application is advantageous in conjunction with two-line and multiline lasers where the radiation is usually pumped in a state of circular polarization.

Optimization of a rhomb-type quarter-wave phase retarder.

Apreviously reported two-reflection, undeviating-beam total internal reflection (TIR) quarter-wave phase retarder is optimized. The specifications and characteristics of the device are sensitive to the refractive index n of the rhomb material. In particular, the size of the rhomb can be reduced by a factor of 11 for the same aperture size if a glass with n = 1.70 is used instead of one with n = 1.53. Optimal conditions are in the refractive-index interval n = 1.68-1.71. Coated rhombs of this type are mentioned.

Phase retarders with variable angles of total internal reflection.

Results for three λ/4 phase retarders are reported. One of them is achromatic to within ± 0.06° of 90° in the visible region. It is shown that, under certain conditions, oblique incidence on the entrance face of total internal reflection phase retarders can greatly improve the achromaticity.