Coupled-mode analysis of light propagation in optically active crystals

A new mathematical formalism, based on a coupled-mode approach, is presented to describe light propagation in birefringent optically active crystals. An arbitrary light wave in the medium is represented as an expansion in terms of linearly polarized eigenmodes; explicit solutions of the equations for the coupled-wave amplitudes show how power is transferred between the principal components in the presence of optical activity. The (generally elliptically polarized) eigenmodes of the optically active crystal are also derived by a diagonalization of the coupled-mode equations. The analysis is extended to include electro-optic crystals, yielding a more general, complex coupling parameter. The predictions of the theory are in excellent agreement with spectral-transmission measurements in AgGaS2 near its isoindex point at 497 nm

Preliminary Results on the Structure and Functioning of a Taiga Watershed

Comprehensive research in ecosystem functioning may logically be undertaken in the conceptual and physical context of complete drainage basins (watersheds or catchments). The watershed forms a fundamental, cohesive landscape unit in terms of water movement following initial receipt of precipitation. Water itself is a fundamental agent in energy flux, nutrient transport, and in plant and animal life. The Caribou-Poker Creeks Research Watershed is an interagency endeavor aimed at understanding hydrologic and, ultimately, ecological functioning in the subarctic taiga, the discontinuous permafrost uplands of central Alaska. Initial work includes acquisition and analysis of data on soils, vegetation, local climate, hydrology, and stream quality. Information acquired in the research watershed is summarized here, and implications for future data acquisition and research are considered

Distributed Control of a Swarm of Autonomous Unmanned Aerial Vehicles

With the increasing use of Unmanned Aerial Vehicles (UAV)s military operations, there is a growing need to develop new methods of control and navigation for these vehicles. This investigation proposes the use of an adaptive swarming algorithm that utilizes local state information to influence the overall behavior of each individual agent in the swarm based upon the agent\u27s current position in the battlespace. In order to investigate the ability of this algorithm to control UAVs in a cooperative manner, a swarm architecture is developed that allows for on-line modification of basic rules. Adaptation is achieved by using a set of behavior coefficients that define the weight at which each of four basic rules is asserted in an individual based upon local state information. An Evolutionary Strategy (ES) is employed to create initial metrics of behavior coefficients. Using this technique, three distinct emergent swarm behaviors are evolved, and each behavior is investigated in terms of the ability of the adaptive swarming algorithm to achieve the desired emergent behavior by modifying the simple rules of each agent. Finally, each of the three behaviors is analyzed visually using a graphical representation of the simulation, and numerically, using a set of metrics developed for this investigation

Extrapolation before imputation reduces bias when imputing censored covariates

Modeling symptom progression to identify informative subjects for a new Huntington's disease clinical trial is problematic since time to diagnosis, a key covariate, can be heavily censored. Imputation is an appealing strategy where censored covariates are replaced with their conditional means, but existing methods saw over 200% bias under heavy censoring. Calculating these conditional means well requires estimating and then integrating over the survival function of the censored covariate from the censored value to infinity. To estimate the survival function flexibly, existing methods use the semiparametric Cox model with Breslow's estimator, leaving the integrand for the conditional means (the estimated survival function) undefined beyond the observed data. The integral is then estimated up to the largest observed covariate value, and this approximation can cut off the tail of the survival function and lead to severe bias, particularly under heavy censoring. We propose a hybrid approach that splices together the semiparametric survival estimator with a parametric extension, making it possible to approximate the integral up to infinity. In simulation studies, our proposed approach of extrapolation then imputation substantially reduces the bias seen with existing imputation methods, even when the parametric extension was misspecified. We further demonstrate how imputing with corrected conditional means helps to prioritize patients for future clinical trials.Comment: 16 pages main text (incl. 2 tables and 3 figures); Supplemental Materials, R code, and R package available on GitHub (linked in main text

Adherence to Themes in Rural Local Education Agency Reorganization Research: a Meta-analysis Review

As the United States education system has developed, local education agencies (LEAs) have found the role of serving as a tool to define collective identity within rural communities. The purpose of this study is to understand current perceptions community members might hold about LEA reorganization through the utilization of interdisciplinary lenses: educational policy and rural sociology. This study has critically evaluated completed perceptions survey research on rural LEA reorganization by quantitatively collecting trend data from a sample of seven case study dissertations published between 2000 and 2014. Within the sample, it was found that the researcher’s first null hypothesis concerning perceptions of social identity aligned with Howley, Johnson, & Petrie’s (2011) policy brief [the community’s perceptions of loss of democratic identity]. The researcher’s second and third research hypothesis concerning perceptions of economies of scale and opportunities available, however, fell in line with Smith’s (1938) research [reorganized LEAs provide greater efficiencies with highly qualified staff and that a broadened academic and extra-curricular education would provide competition in more activities, versus less opportunities]. Results were determined through the use of five independent coders to collectively verify themes. There is a shift in rural communities in the face of globalization, but this change should take place with the knowledge of research-based perceptions of rural identity to replace vanishing regional social structures and diversifying commodities markets.Ope

The Week Before Judgement

This dissertation study proposal is two-fold: (1) to present the basic principles, which underlie the methods of interpretation, and to demonstrate that these principles determine one’s eschatological position. This dissertation research will demonstrate that the grammatical-historical principles of hermeneutics are the only sensible methods to be used to comprehend the Scriptures, and (2) to research, investigate and analyze the events of the seven seals, the seven trumpets, and the seven vials of Revelation, as they relate to the seventieth week of Daniel’s prophecy comparing them with the teachings of Jesus in the Olivet discourse

The `Why' behind including `Y' in your imputation model

Missing data is a common challenge when analyzing epidemiological data, and imputation is often used to address this issue. Here, we investigate the scenario where a covariate used in an analysis has missingness and will be imputed. There are recommendations to include the outcome from the analysis model in the imputation model for missing covariates, but it is not necessarily clear if this recommmendation always holds and why this is sometimes true. We examine deterministic imputation (i.e., single imputation where the imputed values are treated as fixed) and stochastic imputation (i.e., single imputation with a random value or multiple imputation) methods and their implications for estimating the relationship between the imputed covariate and the outcome. We mathematically demonstrate that including the outcome variable in imputation models is not just a recommendation but a requirement to achieve unbiased results when using stochastic imputation methods. Moreover, we dispel common misconceptions about deterministic imputation models and demonstrate why the outcome should not be included in these models. This paper aims to bridge the gap between imputation in theory and in practice, providing mathematical derivations to explain common statistical recommendations. We offer a better understanding of the considerations involved in imputing missing covariates and emphasize when it is necessary to include the outcome variable in the imputation model

ASCORBATE-SENSING uORF CONTROLS GDP-L-GALACTOSE PHOSPHORYLASE (GGP) mRNA TRANSLATION

According to the scanning model of eukaryotic translation initiation, ribosomes bind near the 5’ cap of an mRNA and then initiate translation at the first start codon they encounter as they progress down the mRNA. Upstream open reading frames (uORFs) can regulate translation initiation at downstream start codons. Recently, a uORF in the GDP-L-galactose phosphorylase (GGP) mRNA was reported to mediate autoregulation of ascorbate, or Vitamin C, production. Ascorbate is an essential enzymatic cofactor and antioxidant in plants and animals. Ascorbate concentrations are tightly regulated in plants through post-transcriptional repression of GGP, the major enzyme controlling ascorbate biosynthesis. Key attributes of the noncanonical GGP uORF include: (1) initiation at either a near-cognate start codon or an AUG codon in poor context; (2) it encodes a 32-65 residue peptide containing conserved motifs; and (3) ribosome profiling indicates the presence of an elongation pause at the uORF C-terminus. These attributes suggest that the GGP uORF is a novel upstream Conserved Coding region (uCC), a new paradigm of translational control involving a uORF whose initiation at a weak start site is triggered by queuing of scanning ribosomes behind an elongating ribosome paused at a conserved amino acid motif within the uCC. We hypothesize that ascorbate promotes pausing of translation elongation in the uORF to enhance uORF translation and to repress translation of GGP. To assess ascorbate mediated GGP repression by the uORF, we examined reporter constructs in mammalian cell lines and in rabbit reticulocyte lysate in vitro translation systems. Alignment of 20 algae species’ GGP uORFs shows absolute conservation of five amino acid motifs. Consistent with the GGP uORF being a uCC, conservation of all five motifs and their spacing is essential for regulation of GGP mRNA translation by ascorbate in vivo and in vitro, and the elongation pause is specific to ascorbate. Ribosome profiling from Chlamydomonas reinhardtii and Solanum lycopersicum showed an elongation pause at the C-terminal glycine repeat. In support of the queuing model, reducing ribosome loading by inserting a cap-proximal stem-loop in the GGP mRNA abolished ascorbate specific regulation of GGP expression. Taken together, these data indicate that the GGP uORF is a uCC. We propose that ascorbate interacts with conserved residues of the uCC nascent peptide within the ribosome exit tunnel, causing an elongation pause that regulates GGP mRNA translation

Oil. Changing Geopolitics of Oil in Asia & the USA

One of the most important responsibilities the United States assumed following World War II was ensuring the stable flow of relatively inexpensive oil to the industrialized and industrializing countries of the world. A glance at a list of the top petroleum exporting countries shows that most of them are poor, have despotic governments, and experience frequent bouts of political instability and ideological extremism