Stratospheric constituent distributions from balloon-based limb thermal emission measurements

This research task deals with an analysis of infrared thermal emission observations of the Earth's atmosphere for determination of trace constituent distributions. Infrared limb thermal emission spectra in the 700-2000 cm(exp -1) region were obtained with a liquid nitrogen cooled Michelson interferometer-spectrometer (SIRIS) on a balloon flight launched from Palestine, Texas, at nighttime on September 15-16, 1986. An important objective of this work is to obtain simultaneously measured vertical mixing ratio profiles of O3, H2O, N2O, NO2, N2O5, HNO3 and ClONO2 and compare with measurements made with a variety of techniques by other groups as well as with photochemical model calculations. A portion of the observed spectra obtained by SIRIS from the balloon flight on September 15-16, 1986, has been analyzed with a focus on calculation of the total nighttime odd nitrogen budget from the simultaneously measured profiles of important members of the NO(sub x) family. The measurements permit first direct determination of the nighttime total odd nitrogen concentrations NO(sub y) and the partitioning of the important elements of the NO(sub x) family

Managing knowledge in project-based organizations: A cultural perspective

fi=vertaisarvioitu|en=peerReviewed

Extreme events and event size fluctuations in biased random walks on networks

Random walk on discrete lattice models is important to understand various types of transport processes. The extreme events, defined as exceedences of the flux of walkers above a prescribed threshold, have been studied recently in the context of complex networks. This was motivated by the occurrence of rare events such as traffic jams, floods, and power black-outs which take place on networks. In this work, we study extreme events in a generalized random walk model in which the walk is preferentially biased by the network topology. The walkers preferentially choose to hop toward the hubs or small degree nodes. In this setting, we show that extremely large fluctuations in event-sizes are possible on small degree nodes when the walkers are biased toward the hubs. In particular, we obtain the distribution of event-sizes on the network. Further, the probability for the occurrence of extreme events on any node in the network depends on its 'generalized strength', a measure of the ability of a node to attract walkers. The 'generalized strength' is a function of the degree of the node and that of its nearest neighbors. We obtain analytical and simulation results for the probability of occurrence of extreme events on the nodes of a network using a generalized random walk model. The result reveals that the nodes with a larger value of 'generalized strength', on average, display lower probability for the occurrence of extreme events compared to the nodes with lower values of 'generalized strength'

Dichromacy: Color Vision Impairment and Consanguinity in Heterogenous Population of Pakistan

Background and Objectives: Dichromacy, an X-linked recessive disorder is identified worldwide, more in males than females. In European Caucasians, its incidence is 8% in males and 0.5% in females. In India, it is 8.73% in males and 1.69% in females, and in Iran, it is 8.18% in males and 0.43% in females. Population based epidemiological data about dichromacy in different ethnic groups in Pakistan is not available. The aim of this study was to find out the population prevalence of inherited red-green dichromacy in a heterogenous population of the district of Chiniot, Punjab, Pakistan, and to determine the impact of consanguinity and ethnicity. Methods: In this cross-sectional study, boys and girls of the higher secondary schools were examined in the three tehsils of district Chiniot. Pseudoisochromatic Ishihara Test has been employed for detection of dichromacy in the study population. The sample size was calculated statistically as 260, which was expanded to 705 and divided by population density of the three tehsils. Results: Screening of 359 males and 346 females revealed 19 (5.29%) dichromat males and only 2 (0.58%) females. The study population belonged to 23 castes / isonym groups. The consanguinity found in the district of Chiniot is 84.82% and in the dichromat families, it is 85.71%, of which 52.37% are first cousin. Interpretation & Conclusion: The study has shown that the incidence of dichromacy could be reduced through genetic counselin

Conceptualizing trust in global context with focus on international projects and operations

fi=vertaisarvioimaton|en=nonPeerReviewed

Levels of mercury and arsenic contamination in popular fish and shrimp brands consumed in Saudi Arabia

ABSTRACT. Fish and shrimp are public sources of healthy protein for a large fragment of the Saudi population. Therefore, the present work was conducted to assess the level of possible arsenic (As) and mercury (Hg)          con­tamination of these sea foods. Eight species of fish and two species of shrimp were collected from the local mar­kets of Eastern Province, Saudi Arabia. Mercury and arsenic concentration of samples was determined by hydride generation atomic absorption spectrometry (HG-AAS). Highest average concentration of total Hg was found in Siganus canaliculatus (0.54 ± 0.06 µg/g) while the lowest level was detected in Lethrinus miniatus (0.24 ± 0.07 µg/g). For shrimp species, the levels varied from 0.13 to 0.91 µg/g for mercury and 0.19 to 0.53 µg/g for arsenic. The rank order of shrimp species based upon mercury level was Penaeus semisulcatus > Penaeus indicus; whereas based upon arsenic level it was almost similar. Mean levels of both Hg and As in all the species studied are lower than the limits set by international health agencies; 0.550 µg/g for mercury and 6.0 µg/g for arsenic.               KEY WORDS: Arabian Gulf, Fish, Shrimp, Arsenic, Mercury Bull. Chem. Soc. Ethiop. 2019, 33(3), 573-578.      DOI: https://dx.doi.org/10.4314/bcse.v33i3.1

Ultrabroadband Nonlinear Optics in Nanophotonic Periodically Poled Lithium Niobate Waveguides

Quasi-phasematched interactions in waveguides with quadratic nonlinearities enable highly efficient nonlinear frequency conversion. In this article, we demonstrate the first generation of devices that combine the dispersion-engineering available in nanophotonic waveguides with quasi-phasematched nonlinear interactions available in periodically poled lithium niobate (PPLN). This combination enables quasi-static interactions of femtosecond pulses, reducing the pulse energy requirements by several orders of magnitude, from picojoules to femtojoules. We experimentally demonstrate two effects associated with second harmonic generation. First, we observe efficient quasi-phasematched second harmonic generation with <100 fJ of pulse energy. Second, in the limit of strong phase-mismatch, we observe spectral broadening of both harmonics with as little as 2-pJ of pulse energy. These results lay a foundation for a new class of nonlinear devices, in which co-engineering of dispersion with quasi-phasematching enables efficient nonlinear optics at the femtojoule level