Solar-insolation-induced changes in the coma morphology of comet 67P/Churyumov-Gerasimenko. Optical monitoring with the Nordic Optical Telescope

Context. 67P/Churyumov-Gerasimenko (67P/C-G) is a short-period Jupiter family comet with an orbital period of 6.55 years. Being the target comet of ESA’s Rosetta mission, 67P/C-G has become one of the most intensively studied minor bodies of the Solar System. The Rosetta Orbiter and the Philae Lander have brought us unique information about the structure and activity of the comet nucleus, as well as its activity along the orbit, composition of gas, and dust particles emitted into the coma. However, as Rosetta stayed in very close proximity to the cometary nucleus (less than 500 km with a few short excursions reaching up to 1500 km), it could not see the global picture of a coma at the scales reachable by telescopic observations (103 - 105 km). Aims. In this work we aim to connect in-situ observations made by Rosetta with the morphological evolution of the coma structures monitored by the ground-based observations. In particular, we concentrate on causal relationships between the coma morphology and evolution observed with the Nordic Optical Telescope (NOT) in the Canary Islands, and the seasonal changes of the insolation and the activity of the comet observed by the Rosetta instruments. Methods. Comet 67P/C-G was monitored with the NOT in imaging mode in two colors. Imaging optical observations were performed roughly on a weekly basis, which provides good coverage of short- and long-term variability. With the three dimensional modeling of the coma produced by active regions on the Southern Hemisphere, we aim to qualify the observed morphology by connecting it to the activity observed by Rosetta. Results. During our monitoring program, we detected major changes in the coma morphology of comet 67P/C-G. These were longterm and long-lasting changes. They do not represent any sudden outburst or short transient event, but are connected to seasonal changes of the surface insolation and the emergence of new active regions on the irregular shaped comet nucleus. We have also found significant deviations in morphological changes from the prediction models based on previous apparitions of 67P/C-G, like the time delay of the morphology changes and the reduced activity in the Northern Hemisphere. According to our modeling of coma structures and geometry of observations, the changes are clearly connected with the activity in the Southern Hemisphere observed by the Rosetta spacecraft

Empirical approach for the residual flexural tensile strength of steel fiber-reinforced concrete based on notched three-point bending tests

When designing steel fiber-reinforced concrete, for example, according to Model Code 2010, the residual flexural strength values must be specified as fundamental properties. It is often difficult to establish the relationship between residual flexural strength values and the required dosage of steel fibers depending on the type of steel fibers and the concrete quality. For an estimation of the presumably necessary dosage of steel fibers, various empirical approaches exist for the approximate determination of the residual flexural strength values, which, however, are based on different tests and have been almost exclusively been derived on the basis of few or “own” test results of the respective institute. For this reason, the validity of the respective approximation approach is often limited. Using the bending beam database “Steel Fibre Reinforced Concrete”, selected approaches were systematically analyzed and an improved approach for determining the residual flexural strength values of steel fiber-reinforced concrete was developed

Human Capital in Corporate Venture Capital Units and Its Relation to Parent Firms’ Innovative Performance

Incumbent firms utilize corporate venture capital (CVC) as a vehicle to enhance their innovative performance. Still, little is known about the central individual in this context: the CVC unit head, who acts as a knowledge broker between portfolio ventures and the parent organization. We combine human capital theory with the attention-based view to investigate the effects of various facets of CVC unit heads' experience on parent firms' innovative inputs in the form of explorative and exploitative patenting and innovative outputs, specifically market and technological breakthrough innovation. Drawing on a dataset of U.S.-listed firms with CVC units, our findings contribute to the CVC literature in three ways. First, we introduce CVC unit heads' career experiences as new individual-level antecedents of parent firms' innovative performance. Second, we enhance the understanding of the CVC-core paradox, which is the tension between exploration and exploitation in the parent firm. Finally, by employing a combination of patents and new product introductions as metrics for innovative performance, we bridge the gap between learning and innovation in extant CVC research, demonstrating that the effects of CVC unit heads include customer-facing outcomes.</p

Taming Bromine Azide for Use in Organic Solvents─Radical Bromoazidations and Alcohol Oxidations

The formation of bromine azide from the bisazidobromate(I) anion or alternatively from Zhdankin’s reagent, using a phosphonium bromide salt as a common starting point, is reported. After homolytic cleavage in the presence of alkenes or alcohols either 1,2-functionalization or alternatively the selective oxidation of secondary alcohols in the presence of primary alcohols occur. The scopes and limitations of the use of BrN3 are covered

Soil suction response of granular railway formation materials under cyclic loading

Changing climatic conditions worldwide are causing a change in moisture conditions of railway formations and slopes, thereby either strengthening or weakening them. Current railway formation design methods do not take into account the changing moisture conditions over the predicted life of a railway formation. These changes in soil strength are due to the influence of soil suctions. The basic principles of unsaturated soil mechanics have been well established in the field of geotechnics, and this study joins an international body of work that seeks to apply unsaturated soil theory to the field of railway and pavement formation materials. This study comprised of box testing of subgrade and subballast formation materials at different moisture contents. These formation models were instrumented with tensiometers to monitor the effect of cyclic loading on soil suctions under typical heavy haul loading magnitudes (26 tonne/axle). The materials were tested under a number of different loading frequencies subjected to the same cyclic heavy haul load magnitude. The study investigated the suctions present in railway formation materials, as well as the application of suction instrumentation in railway conditions. Initial testing of the tensiometers showed evidence of interference caused by the stress imposed by the soil skeleton on the tensiometer housing. This prompted a development program that resulted in an improved tensiometer model that was isolated from the effects of external loading and could therefore successfully measure the suctions present in the formation material. Suctions were successfully measured in both the subgrade and subballast material under various moisture contents demonstrating the different suction magnitudes generated by the materials under expected formation conditions. The subballast material was found to generate suctions of between 1 and 15 kPa over a wide range of degrees of saturation (Sr: 0.32 – 0.96), while the subgrade material was found to generate a greater range of suctions between 1 and 95 kPa with a smaller variation in degree of saturation (Sr: 0.61 – 0.88). The deformability of both the subgrade and subballast materials were affected to different degrees as a function of the soil suctions. The subgrade material was found to be dependent on the moisture state and soil suctions to a greater degree than the subballast material. A deformation of 141 % of the failure criterion was observed at low suctions (1 – 5 kPa) in the subgrade material at loads similar to those experienced by South African heavy haul railway formations. In contrast, the deformation significantly reduced to 55 % of the failure criterion when the suctions increased by a relatively small amount ( 10 kPa). Further desaturation of the subgrade material resulted in higher suctions (40 – 95 kPa) strengthening the formation further to a final deformation of 47 % of the failure criterion. It was found that subballast deformation was significantly affected by the loading frequency and less by moisture state. Due to the low suctions present in the subballast material, the maximum deformation observed was 61 % of the failure criterion under effectively saturated conditions with suctions B1 kPa. Under the highest suctions present in the subballast material ( 14 kPa), the material only strengthened to the point where 47 % of the failure criterion was observed. The application of geotechnical testing methods to granular formation materials are also investigated and discussed, in terms of the effectiveness of tensiometers and filter paper methods in determining suction, as well as considerations when sampling granular soil for moisture content. The study therefore provides important information for laboratory testing of formation materials, the techniques required to successfully measure suctions in railway formations and the implications of cyclic loading on formations at various degrees of saturation.Dissertation (MEng)--University of Pretoria, 2018.Civil EngineeringMEngUnrestricte

Q&A: Epistasis

Molecular and Cellular Biolog

MixHMM: Inferring Copy Number Variation and Allelic Imbalance Using SNP Arrays and Tumor Samples Mixed with Stromal Cells

BACKGROUND: Genotyping platforms such as single nucleotide polymorphism (SNP) arrays are powerful tools to study genomic aberrations in cancer samples. Allele specific information from SNP arrays provides valuable information for interpreting copy number variation (CNV) and allelic imbalance including loss-of-heterozygosity (LOH) beyond that obtained from the total DNA signal available from array comparative genomic hybridization (aCGH) platforms. Several algorithms based on hidden Markov models (HMMs) have been designed to detect copy number changes and copy-neutral LOH making use of the allele information on SNP arrays. However heterogeneity in clinical samples, due to stromal contamination and somatic alterations, complicates analysis and interpretation of these data. METHODS: We have developed MixHMM, a novel hidden Markov model using hidden states based on chromosomal structural aberrations. MixHMM allows CNV detection for copy numbers up to 7 and allows more complete and accurate description of other forms of allelic imbalance, such as increased copy number LOH or imbalanced amplifications. MixHMM also incorporates a novel sample mixing model that allows detection of tumor CNV events in heterogeneous tumor samples, where cancer cells are mixed with a proportion of stromal cells. CONCLUSIONS: We validate MixHMM and demonstrate its advantages with simulated samples, clinical tumor samples and a dilution series of mixed samples. We have shown that the CNVs of cancer cells in a tumor sample contaminated with up to 80% of stromal cells can be detected accurately using Illumina BeadChip and MixHMM. AVAILABILITY: The MixHMM is available as a Python package provided with some other useful tools at http://genecube.med.yale.edu:8080/MixHMM

On-line Sensor Control for Milk Powder and Cheese Manufacture.

End of Project ReportThis project investigated the use of on-line sensors of rheological characteristics which can be measured during the manufacture of milk powder and cheese. The objective is to use on-line measurements to fine tune each process, so as to compensate for the variability of milk.Department of Agriculture, Food and the Marin