Implementation and validation of a CubeSat laser transmitter

The paper presents implementation and validation results for a CubeSat-scale laser transmitter. The master oscillator power amplifier (MOPA) design produces a 1550 nm, 200mW average power optical signal through the use of a directly modulated laser diode and a commercial fiber amplifier. The prototype design produces high-fidelity M-ary pulse position modulated (PPM) waveforms (M=8 to 128), targeting data rates > 10 Mbit/s while meeting a constraining 8W power allocation. We also present the implementation of an avalanche photodiode (APD) receiver with measured transmitter-to-receiver performance within 3 dB of theory. Via loopback, the compact receiver design can provide built-in self-test and calibration capabilities, and supports incremental on-orbit testing of the design

The Preliminary Evaluation of Liquid Lubricants for Space Applications by Vacuum Tribometry

Four different vacuum tribometers for the evaluation of liquid lubricants for space applications are described. These range from simple ball-on-flat sliders with maximum in-situ control and surface characterization to an instrument bearing apparatus having no in-situ characterization. Thus, the former provides an abundance of surface chemical information but is not particularly simulative of most triboelements. On the other hand, the instrument bearing apparatus is completely simulative, but only allows post-mortem surface chemical information. Two other devices, a four-ball apparatus and a ball-on-plate tribometer, provide varying degrees of surface chemical information and tribo-simulation. Examples of data from each device are presented

Bonding in Functionalized Aziridines: Nitrogen-15 and Carbon-13 Studies

Two isomeric pairs of cis- and trans-1-cyclohexyl-2-phenyl-3-benzoylaziridines have been synthesized: (1) with a nitrogen-15 labelled nitrogen, and (2) with carbon-13 labelled ring carbons. The carbon-13 to X (where X=nitrogen-15, carbon-13 or hydrogen-I) spin-spin coupling constants were measured and interpreted in terms of stereoelectronic effects. X-ray crystallographic data (earlier determined for cisand trans-1-cyclohexyl-2-phenyl-3-(p-toluyl)aziridines)1 appear in good agreement with the NMR data. Bonding is discussed for the three-ring itself (NMR studies) and for its substituents (X-ray studies). It is concluded that stereochemical interaction of the Van der Waals type is an important determinant of aziridine bond length. Three-ring to carbonyl hyperconjugation is correlated with stereoelectronic interactions in the trans isomer

Bonding in Functionalized Aziridines: Nitrogen-15 and Carbon-13 Studies

Two isomeric pairs of cis- and trans-1-cyclohexyl-2-phenyl-3-benzoylaziridines have been synthesized: (1) with a nitrogen-15 labelled nitrogen, and (2) with carbon-13 labelled ring carbons. The carbon-13 to X (where X=nitrogen-15, carbon-13 or hydrogen-I) spin-spin coupling constants were measured and interpreted in terms of stereoelectronic effects. X-ray crystallographic data (earlier determined for cisand trans-1-cyclohexyl-2-phenyl-3-(p-toluyl)aziridines)1 appear in good agreement with the NMR data. Bonding is discussed for the three-ring itself (NMR studies) and for its substituents (X-ray studies). It is concluded that stereochemical interaction of the Van der Waals type is an important determinant of aziridine bond length. Three-ring to carbonyl hyperconjugation is correlated with stereoelectronic interactions in the trans isomer

Implementing EM and Viterbi algorithms for Hidden Markov Model in linear memory

<p>Abstract</p> <p>Background</p> <p>The Baum-Welch learning procedure for Hidden Markov Models (HMMs) provides a powerful tool for tailoring HMM topologies to data for use in knowledge discovery and clustering. A linear memory procedure recently proposed by <it>Miklós, I. and Meyer, I.M. </it>describes a memory sparse version of the Baum-Welch algorithm with modifications to the original probabilistic table topologies to make memory use independent of sequence length (and linearly dependent on state number). The original description of the technique has some errors that we amend. We then compare the corrected implementation on a variety of data sets with conventional and checkpointing implementations.</p> <p>Results</p> <p>We provide a correct recurrence relation for the emission parameter estimate and extend it to parameter estimates of the Normal distribution. To accelerate estimation of the prior state probabilities, and decrease memory use, we reverse the originally proposed forward sweep. We describe different scaling strategies necessary in all real implementations of the algorithm to prevent underflow. In this paper we also describe our approach to a linear memory implementation of the Viterbi decoding algorithm (with linearity in the sequence length, while memory use is approximately independent of state number). We demonstrate the use of the linear memory implementation on an extended Duration Hidden Markov Model (DHMM) and on an HMM with a spike detection topology. Comparing the various implementations of the Baum-Welch procedure we find that the checkpointing algorithm produces the best overall tradeoff between memory use and speed. In cases where sequence length is very large (for Baum-Welch), or state number is very large (for Viterbi), the linear memory methods outlined may offer some utility.</p> <p>Conclusion</p> <p>Our performance-optimized Java implementations of Baum-Welch algorithm are available at <url>http://logos.cs.uno.edu/~achurban</url>. The described method and implementations will aid sequence alignment, gene structure prediction, HMM profile training, nanopore ionic flow blockades analysis and many other domains that require efficient HMM training with EM.</p

‘Preparing Ourselves to Become an International Organization’: Thailand Tobacco Monopoly’s Regional and Global Strategies

The Thailand Tobacco Monopoly (TTM) controlled the country\u27s tobacco industry from its formation in the 1940s, until the government dropped restrictions on imported cigarettes in the late 1980s in response to pressure from the United States. The TTM has since competed with transnational tobacco companies (TTCs) in a semi-monopoly market in which TTCs have steadily increased their market share. Coupled with a decline in national smoking prevalence, the result of Thailand\u27s stringent tobacco control agenda, the TTM now accounts for a diminishing share of a contracting market. In response, the monopoly has looked to regional trade liberalisation, and proximity to markets with some of the world\u27s highest smoking rates to expand its operations. Expansion strategies have gone largely unrealised however, and the TTM effectively remains a domestic operation. Using TTM publications, market and trade reports, industry publications, tobacco industry documents and other resources, this paper analyses TTM expansion strategies, and the limited extent to which they have been achieved. This inability to expand its operations has left the monopoly potentially vulnerable to global strategies of its transnational competitors. This article is part of the special issue \u27The Emergence of Asian Tobacco Companies: Implications for Global Health Governance\u27

Probenecid Blocks Human P2X7 Receptor-Induced Dye Uptake via a Pannexin-1 Independent Mechanism

P2X7 is a ligand-gated ion channel which is activated by ATP and displays secondary permeability characteristics. The mechanism of development of the secondary permeability pathway is currently unclear, although a role for the hemichannel protein pannexin-1 has been suggested. In this study we investigated the role of pannexin-1 in P2X7-induced dye uptake and ATP-induced IL-1β secretion from human monocytes. We found no pharmacological evidence for involvement of pannexin-1 in P2X7-mediated dye uptake in transfected HEK-293 cells with no inhibition seen for carbenoxolone and the pannexin-1 mimetic inhibitory peptide, 10Panx1. However, we found that probenecid inhibited P2X7-induced cationic and anionic dye uptake in stably transfected human P2X7 HEK-293 cells. An IC50 value of 203 μM was calculated for blockade of ATP-induced responses at human P2X7. Probenecid also reduced dye uptake and IL-1β secretion from human CD14+ monocytes whereas carbenoxolone and 10Panx1 showed no inhibitory effect. Patch clamp and calcium indicator experiments revealed that probenecid directly blocks the human P2X7 receptor

A Copine family member, Cpne8, is a candidate quantitative trait gene for prion disease incubation time in mouse

Prion disease incubation time in mice is determined by many factors including genetic background. The prion gene itself plays a major role in incubation time; however, other genes are also known to be important. Whilst quantitative trait loci (QTL) studies have identified multiple loci across the genome, these regions are often large, and with the exception of Hectd2 on Mmu19, no quantitative trait genes or nucleotides for prion disease incubation time have been demonstrated. In this study, we use the Northport heterogeneous stock of mice to reduce the size of a previously identified QTL on Mmu15 from approximately 25 to 1.2 cM. We further characterised the genes in this region and identify Cpne8, a member of the copine family, as the most promising candidate gene. We also show that Cpne8 mRNA is upregulated at the terminal stage of disease, supporting a role in prion disease. Applying these techniques to other loci will facilitate the identification of key pathways in prion disease pathogenesis

Climatic and geographic predictors of life history variation in Eastern Massasauga (Sistrurus catenatus): A range-wide synthesis

Elucidating how life history traits vary geographically is important to understanding variation in population dynamics. Because many aspects of ectotherm life history are climate-dependent, geographic variation in climate is expected to have a large impact on population dynamics through effects on annual survival, body size, growth rate, age at first reproduction, size-fecundity relationship, and reproductive frequency. The Eastern Massasauga (Sistrurus catenatus) is a small, imperiled North American rattlesnake with a distribution centered on the Great Lakes region, where lake effects strongly influence local conditions. To address Eastern Massasauga life history data gaps, we compiled data from 47 study sites representing 38 counties across the range. We used multimodel inference and general linear models with geographic coordinates and annual climate normals as explanatory variables to clarify patterns of variation in life history traits. We found strong evidence for geographic variation in six of nine life history variables. Adult female snout-vent length and neonate mass increased with increasing mean annual precipitation. Litter size decreased with increasing mean temperature, and the size-fecundity relationship and growth prior to first hibernation both increased with increasing latitude. The proportion of gravid females also increased with increasing latitude, but this relationship may be the result of geographically varying detection bias. Our results provide insights into ectotherm life history variation and fill critical data gaps, which will inform Eastern Massasauga conservation efforts by improving biological realism for models of population viability and climate change

Molecular and cellular mechanisms underlying the evolution of form and function in the amniote jaw.

The amniote jaw complex is a remarkable amalgamation of derivatives from distinct embryonic cell lineages. During development, the cells in these lineages experience concerted movements, migrations, and signaling interactions that take them from their initial origins to their final destinations and imbue their derivatives with aspects of form including their axial orientation, anatomical identity, size, and shape. Perturbations along the way can produce defects and disease, but also generate the variation necessary for jaw evolution and adaptation. We focus on molecular and cellular mechanisms that regulate form in the amniote jaw complex, and that enable structural and functional integration. Special emphasis is placed on the role of cranial neural crest mesenchyme (NCM) during the species-specific patterning of bone, cartilage, tendon, muscle, and other jaw tissues. We also address the effects of biomechanical forces during jaw development and discuss ways in which certain molecular and cellular responses add adaptive and evolutionary plasticity to jaw morphology. Overall, we highlight how variation in molecular and cellular programs can promote the phenomenal diversity and functional morphology achieved during amniote jaw evolution or lead to the range of jaw defects and disease that affect the human condition