Ghost images for optical systems with tilted object plane

Ghost images are formed by light that is partially reflected by optical surfaces. Ghost images may cause contrast reduction and may veil parts of the nominal image. Performing ghost image analysis during the design stage is important to ensure the success of the system. In a previous paper (Applied Optics, Vol. 50, Issue 15, pp. 2305-2315 (2011)), modeling ghost images was performed using a sequential ray tracing technique. Synthesizing ray paths into ghost and nominal paths and performing sequential ray tracing provides a powerful tool for describing ghost image formation in optical systems. We address the applicability of Scheimpflug principle for ghost image formation and we present a new criterion to identify problematic ghost images in the paraxial approximation. Numerical examples are considered and discussed

Measuring the refractive index of double-clad fibers using an interferometric technique

Multiple-beam Fizeau interferometry is an accurate, simple, and nondestructive technique in the field of fiber research. Inserting the fiber into the liquid silvered wedge causes the fringes to shift across the fiber region with respect to the fringes at the liquid region. Fringe shift is a function in the geometry of the different regions of the fiber and the refractive index profile of the fiber. In a previous paper (Applied Optics, Vol. 50, No. 31, (2011)) the theory for the interference pattern formation was developed. In this contribution, we extend the theory to include graded index double-clad fibers. In addition, we discuss the experimental aspects of the measuring system

Optische Systeme ohne Rotationssymmetrie: Bestimmung von Bildlage und Bildorientierung

Bei der Abbildung mit rotationssymmetrischen optischen Systemen lässt sich die Lage der Gauß‘schen Bildebene direkt über paraxiale Beziehungen ermitteln. Werden jedoch optische Systeme ohne Rotationssymmetrie betrachtet, muss ein anderer Ansatz gewählt werden. In diesem Beitrag diskutieren wir unterschiedliche Strategien zur Ermittlung der Lage und Orientierung der Bildebene in verallgemeinerten optischen Systemen ohne Rotationssymmetrie. Hierzu werden nach der Definition eines anstelle der optischen Achse nötigen Referenzstrahls sowohl numerische als auch analytische Ansätze untersucht. Der numerische Ansatz basiert auf einer vektoriellen Strahldurchrechnung für verschiedene Objektpunkte, wobei die gesuchten Größen über die Approximation der berechneten Bildpunkte mit einer Ebene bestimmt werden. Als mögliche Ausgangspunkte für eine analytische Bestimmung der Bildebenenlage und -orientierung dienen die astigmatische Strahldurchrechnung und die für schiefe Abbildungen verwendete Scheimpflugbedingung

Association Between Statin Use and Prevalence of Exercise-Related Injuries: A Cross-Sectional Survey of Amateur Runners in the Netherlands.

BACKGROUND: HMG-CoA reductase inhibitors (statins) are the first-choice therapy for primary prevention of cardiovascular disease. Some maintain that statins cause adverse musculoskeletal outcomes in highly active individuals, but few studies have examined the effects of statins on exercise-related injuries. OBJECTIVE: We sought to compare the prevalence of exercise-related injuries between runners who do or do not use statins. METHODS: Amateur runners (n = 4460) completed an extensive online questionnaire on their exercise patterns and health status. Participants replied to questions on the prevalence of exercise-related injuries in the previous year. Injuries were divided into general injuries, tendon- and ligament-related injuries, and muscle-related injuries. Participants were also queried about statin use: the type of statin, statin dose, and duration of treatment. Runners were divided into statin users, non-statin users with hypercholesterolemia, and controls for analysis. RESULTS: The crude odds ratios (ORs) for injuries, tendon- or ligament-related injuries, and muscle-related injuries in statin users compared with controls were 1.14 (95% confidence interval [CI] 0.79-1.66), 1.10 (95% CI 0.71-1.72), and 1.15 (95% CI 0.69-1.91), respectively. After adjustment for age, sex, body mass index (BMI), and metabolic equivalent of task (MET) h/week of exercise, the ORs were 1.11 (95% CI 0.76-1.62), 1.06 (95% CI 0.68-1.66), and 0.98 (95% CI 0.58-1.64), respectively. Similar effect measures were found when comparing non-statin users with hypercholesterolemia and controls. CONCLUSION: We did not find an association between statin use and the prevalence of exercise-related injuries or tendon-, ligament-, and muscle-related injuries. Runners receiving statins should continue normal physical activity without concern for increased risk of injuries

Continuously variable diffraction gratings using electroconvection in liquid crystals for beam steering applications

There is a great technological need for the development of devices capable of producing wide-angle and efficient, transmissive optical beam steering. In this article, variable pitch phase diffraction gratings using electroconvection in liquid crystals are considered for applications in electrically controllable beam-steerers. The devices contain thin layers of nematic liquid crystal mixtures of negative dielectric anisotropy, which are doped with different concentrations of an ionic species to determine the effect of conductivity on the beam-steering characteristics. The devices are seen to act as continuously variable diffraction gratings, where the pitch increases with the frequency of the applied electric field. The second order diffraction peak is found to be the most efficient, with absolute efficiency ranging from 5% to 15%, and continuous steering from 4° to 8° within 20 μm spaced devices. Devices with thinner layers of liquid crystal were also examined; these demonstrated wider angle steering but had substantial losses of efficiency due to lowering of optical contrast. Suggestions for possible methodologies for optimizing such devices are discussed

Lack of effect of dihydroergotamine on endothelial and smooth muscle cell proliferation and endothelial cell prostanoid production

The most important effect of dihydroergotamine is venoconstriction, but certain metabolic effects and changes in vessel prostanoid activity have also been suggested. In this study endothelial cell production of 6-keto PGF 1α and TxB 2 was quantitated in vitro. No evidence of altered prostanoid production was noted after incubation with dihydroergotamine (exposure ranging from 5×10 −3 to 5×10 −7 g/l). Similarly, no effect of dihydroergotamine on the growth rates of endothelial cells or smooth muscle cells in vitro was documented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42798/1/18_2005_Article_BF01941713.pd