Stimulated Brillouin scattering effects and suppression techniques in high power fiber amplifiers

This dissertation develops a model for numerical analysis of stimulated Brillouin scattering (SBS) effects and the development of suppression techniques for the realization of increased output power levels for high power ytterbium-doped dual clad fiber amplifiers. The overall objective of this effort is to develop and validate a predictive model to assist in the determination of the most effective techniques for increasing SBS thresholds within ytterbium-doped fiber amplifiers in order to realize increased power output. The goal is to demonstrate an increase in SBS threshold that would increase the output power potential in ytterbium-doped fiber amplifiers by at least an order of magnitude. The approach determines the effect of changing the acoustic properties of fiber cores on the Brillouin frequencies and the effects of various signal modulation schemes on active ytterbium-doped fiber amplifiers. In addition, temperature effects and temperature differentials within the fibers are predicted and measured, both with passive and active fibers. Brillouin center frequency responses of various germanium dopant concentrations within the cores, as well as the effects of fiber segment combinations are measured in the lab. The effects of various phase modulation schemes of the signal are predicted and measured for passive fibers. Results from these measurements are used to validate and adjust the model accordingly. Finally, the manufacturability of relevant characteristics required to achieve such SBS suppression is evaluated, identifying constraints and limitations for utilization of low cost fabrication techniques. The final model, validated and adjusted with empirical results, supports the suppression of SBS in standard ytterbium-doped fiber amplifiers by over a decade

Resin hemoperfusion in dogs intoxicated with ethchlorvynol (Placidyl®)

Resin hemoperfusion in dogs intoxicated with ethchlorvynol (Placidyl®). Kinetic parameters were studied to determine the effectiveness of hemoperfusion in removing ethchlorvynol from the plasma and red blood cells (RBC) of intoxicated dogs. Perfusion columns contained polystyrene/divinyl benzene resin (XAD-4 Amberlite(®)). Column clearances of ethchlorvynol averaged 96.5 ± 0.4% of the plasma flow rate (mean ±SEM, 9 dogs). Plasma ethchlorvynol t1/2's during preperfusion periods averaged 94.1hr. During hemoperfusion, t1/2's averaged 3.8hr, or 90.3hr shorter than at the endogenous rate of detoxication. There was no significant difference between preperfusion and postperfusion half lives. An estimate based on plasma column clearance suggests that 1.5 ± 0.1g ethchlorvynol, or 19.0 ± 2.8% of the dose, was removed by hemoperfusion. The amount eluted from the resin was 2.9 ± 0.3g (37.2 ± 5.8% of the dose), or about twice the amount apparent from plasma clearance alone. Further, the volume of distribution of ethchlorvynol was 2.3 ± 0.2 liters/kg, suggesting significant distribution to intracellular and extravascular compartments. The results show that resin hemoperfusion removes a large fraction of ethchlorvynol from intoxicated dogs, and greatly adds to endogenous mechanisms for elimination. Ethchlorvynol was removed from RBC directly, and ultimately from extravascular sites as well.Hémoperfusion sur résine chez des chiens intoxiqués par l'éthchlorvynol (Placidyl®). Afin de déterminer l'efficacité de l'hémoperfusion dans la soustraction d'éthchlorvynol du plasma et des hématies de chiens intoxiqués, les paramètres cinétiques ont été mesurés. Les colonnes de perfusion contenaient une résine polystyrène/divinyl benzène (XAD-4 Amberlite®). La clearance de l'éthchlorvynol par les colonnes était en moyenne de 96,5 ± 0,4% du débit plasmatique (moyenne ±SEM, 9 chiens). La plasmatique de l'éthchlorvynol t½'s pendant la période préalable à la perfusion était de 94,1 heures. Pendant l'hémoperfusion, t½'s était en moyenne de 3,8 heures, soit 90,3 heures de moins qu'au cours de la détoxication spontanée. Il n'a pas été observé de différence entre les demi vies avant et après perfusion. Une estimation fondée sur la clearance des colonnes suggère que 1,5 ± 0,1g d'éthchlorvynol, soit 19,0 ± 2,8% de la dose a été soustrait par l'hémoperfusion. La quantité éluée de la résine a été de 2,9 ± 0,3g (37,2 ± 5,8% de la dose), soit le double de la quantité évaluée à partir de la clearance du plasma. De plus, le volume de distribution de l'éthchlorvynol était de 2,3 ± 0,2 litres/kg, ce qui suggère une distribution importante dans les compartiments intracellulaire et extravasculaire. Les résultats montrent que l'hémoperfusion sur résine soustrait une fraction importante de l'éthchlorvynol chez des chiens intoxiqués et ajoute une élimination importante aux mécanismes endogènes. L'ethchlorvynol a été soustrait des hématies directement et finalement des sites extravasculaires aussi

NIA Long Life Family Study: Objectives, design, and heritability of cross-sectional and longitudinal phenotypes

The NIA Long Life Family Study (LLFS) is a longitudinal, multicenter, multinational, population-based multigenerational family study of the genetic and nongenetic determinants of exceptional longevity and healthy aging. The Visit 1 in-person evaluation (2006-2009) recruited 4 953 individuals from 539 two-generation families, selected from the upper 1% tail of the Family Longevity Selection Score (FLoSS, which quantifies the degree of familial clustering of longevity). Demographic, anthropometric, cognitive, activities of daily living, ankle-brachial index, blood pressure, physical performance, and pulmonary function, along with serum, plasma, lymphocytes, red cells, and DNA, were collected. A Genome Wide Association Scan (GWAS) (Ilumina Omni 2.5M chip) followed by imputation was conducted. Visit 2 (2014-2017) repeated all Visit 1 protocols and added carotid ultrasonography of atherosclerotic plaque and wall thickness, additional cognitive testing, and perceived fatigability. On average, LLFS families show healthier aging profiles than reference populations, such as the Framingham Heart Study, at all age/sex groups, for many critical healthy aging phenotypes. However, participants are not uniformly protected. There is considerable heterogeneity among the pedigrees, with some showing exceptional cognition, others showing exceptional grip strength, others exceptional pulmonary function, etc. with little overlap in these families. There is strong heritability for key healthy aging phenotypes, both cross-sectionally and longitudinally, suggesting that at least some of this protection may be genetic. Little of the variance in these heritable phenotypes is explained by the common genome (GWAS + Imputation), which may indicate that rare protective variants for specific phenotypes may be running in selected families

Simple tandem repeat (TTTA)(n )polymorphism in CYP19 (aromatase) gene and breast cancer risk in Nigerian women

BACKGROUND: Breast cancer is the most common cancer and the leading cause of cancer related deaths in women worldwide. The incidence of the disease is increasing globally and this increase is occurring at a faster rate in population groups that hirtherto enjoyed low incidence. This study was designed to evaluate the role of a simple tandem repeat polymorphism (STRP) in the aromatase (CYP19) gene in breast cancer susceptibility in Nigerian women, a population of indigenous sub-Saharan African ancestry. METHODS: A case-control study recruiting 250 women with breast cancer and 250 women without the disease from four University Teaching Hospitals in Southern Nigeria was carried out between September 2002 and April 2004. Participants were recruited from the surgical outpatient clinics and surgical wards of the Nigerian institutions. A polymerase chain reaction (PCR)-based assay was employed for genotyping and product sizes were detected with an ABI 3730 DNA Analyzer. RESULTS: Conditional logistic regression analysis revealed that harboring the putative high risk genotypes conferred a 29% increased risk of breast cancer when all women in the study were considered (Odds ratio [OR] = 1.29, 95% confidence interval [CI] 0.83–2.00), although this association was not statistically significant. Subgroup analysis based on menopausal status showed similar results among premenopausal women (OR = 1.35, 95% CI 0.76–2.41 and postmenopausal women (OR = 1.27, 95% CI 0.64–2.49). The data also demonstrated marked differences in the distribution of (TTTA)(n )repeats in Nigerian women compared with other populations. CONCLUSION: This study has shown that harboring 10 or more repeats of the microsatellite (TTTA)(n )repeats of the CYY19 gene is associated with a modest increased risk of breast cancer in Nigerian women

Leukocyte telomere length is unrelated to cognitive performance among non-demented and demented persons: An examination of long life family study participants

OBJECTIVE: Leukocyte telomere length (LTL) is a widely hypothesized biomarker of biological aging. Persons with shorter LTL may have a greater likelihood of developing dementia. We investigate whether LTL is associated with cognitive function, differently for individuals without cognitive impairment versus individuals with dementia or incipient dementia. METHOD: Enrolled subjects belong to the Long Life Family Study (LLFS), a multi-generational cohort study, where enrollment was predicated upon exceptional family longevity. Included subjects had valid cognitive and telomere data at baseline. Exclusion criteria were age ≤ 60 years, outlying LTL, and missing sociodemographic/clinical information. Analyses were performed using linear regression with generalized estimating equations, adjusting for sex, age, education, country, generation, and lymphocyte percentage. RESULTS: Older age and male gender were associated with shorter LTL, and LTL was significantly longer in family members than spouse controls (p \u3c 0.005). LTL was not associated with working or episodic memory, semantic processing, and information processing speed for 1613 cognitively unimpaired individuals as well as 597 individuals with dementia or incipient dementia (p \u3c 0.005), who scored significantly lower on all cognitive domains (p \u3c 0.005). CONCLUSIONS: Within this unique LLFS cohort, a group of families assembled on the basis of exceptional survival, LTL is unrelated to cognitive ability for individuals with and without cognitive impairment. LTL does not change in the context of degenerative disease for these individuals who are biologically younger than the general population

DARKNESS: A Microwave Kinetic Inductance Detector Integral Field Spectrograph for High-Contrast Astronomy

We present DARKNESS (the DARK-speckle Near-infrared Energy-resolving Superconducting Spectrophotometer), the first of several planned integral field spectrographs to use optical/near-infrared Microwave Kinetic Inductance Detectors (MKIDs) for high-contrast imaging. The photon counting and simultaneous low-resolution spectroscopy provided by MKIDs will enable real-time speckle control techniques and post-processing speckle suppression at framerates capable of resolving the atmospheric speckles that currently limit high-contrast imaging from the ground. DARKNESS is now operational behind the PALM-3000 extreme adaptive optics system and the Stellar Double Coronagraph at Palomar Observatory. Here we describe the motivation, design, and characterization of the instrument, early on-sky results, and future prospects.Comment: 17 pages, 17 figures. PASP Publishe