The Flash Crash: An Examination of Shareholder Wealth and Market Quality

We investigate stock returns, market quality, and options market activity around the flash crash of May 6, 2010. Abnormal returns are negative on the day of and the day after the flash crash for stocks that had trades that executed during the crash subsequently cancelled by either Nasdaq or NYSE Arca. Consistent with studies that suggest that other sources of liquidity withdrew from the markets during the flash crash, we find that the fraction of trades executed by the NYSE increases during this volatile period. Market quality deteriorates following the flash crash as bid-ask spreads increase and quote depths decrease. Evidence from the options markets indicates that investor uncertainty increased around the time of the crash and remained elevated for several days

Extensional rheology and elastic instabilities of a wormlike micellar solution in a microfluidic cross-slot device

Wormlike micellar surfactant solutions are encountered in a wide variety of important applications, including enhanced oil recovery and ink-jet printing, in which the fluids are subjected to high extensional strain rates. In this contribution we present an experimental investigation of the flow of a model wormlike micellar solution (cetyl pyridinium chloride and sodium salicylate in deionised water) in a well-defined stagnation point extensional flow field generated within a microfluidic cross-slot device. We use micro-particle image velocimetry (m-PIV) and full-field birefringence microscopy coupled with macroscopic measurements of the bulk pressure drop to make a quantitative characterization of the fluid’s rheological response over a wide range of deformation rates. The flow field in the micromachined cross-slot is first characterized for viscous flow of a Newtonian fluid, and m-PIV measurements show the flow field remains symmetric and stable up to moderately high Reynolds number, Re z 20, and nominal strain rate, _3nom z 635 s1. By contrast, in the viscoelastic micellar solution the flow field remains symmetric only for low values of the strain rate such that _3nom # lM1, where lM ¼ 2.5 s is the Maxwell relaxation time of the fluid. In this stable flow regime the fluid displays a localized and elongated birefringent strand extending along the outflow streamline from the stagnation point, and estimates of the apparent extensional viscosity can be obtained using the stressoptical rule and from the total pressure drop measured across the cross-slot channel. For moderate deformation rates (_3nom $ lM1) the flow remains steady, but becomes increasingly asymmetric with increasing flow rate, eventually achieving a steady state of complete anti-symmetry characterized by a dividing streamline and birefringent strand connecting diagonally opposite corners of the cross-slot. Eventually, as the nominal imposed deformation rate is increased further, the asymmetric divided flow becomes time dependent. These purely elastic instabilities are reminiscent of those observed in crossslot flows of polymer solutions, but seem to be strongly influenced by the effects of shear localization of the micellar fluid within the microchannels and around the re-entrant corners of the cross-slot

Improvement of the design and generation of highly specific plant knockdown lines using primary synthetic microRNAs (pri-smiRNAs)

Niemeier S, Alves jun. L, Merkle T. Improvement of the design and generation of highly specific plant knockdown lines using primary synthetic microRNAs (pri-smiRNAs). BMC Research Notes. 2010;3(1): 59.Background: microRNAs (miRNAs) are endogenous small non-coding RNAs that post-transcriptionally regulate gene expression. In plants, they typically show high complementarity to a single sequence motif within their target mRNAs and act by catalyzing specific mRNA cleavage and degradation. miRNAs are processed from much longer primary transcripts via precursor miRNAs containing fold-back structures. Leaving these secondary structures intact, miRNAs can be re-designed experimentally to target mRNAs of choice. Results: We designed primary synthetic miRNAs (pri-smiRNAs) on the basis of the primary transcript of the Arabidopsis MIR159A gene by replacing the original miR159a and the corresponding miR159a* with novel sequences, keeping the overall secondary structure as predicted by the program RNAfold. We used the program RNAhybrid to optimize smiRNA design and to screen the complete Arabidopsis transcriptome for potential off-targets. To improve the molecular cloning of the pri-smiRNA we inserted restriction sites in the original MIR159A primary transcript to easily accommodate the smiRNA/smiRNA* DNA fragment. As a proof-of-concept, we targeted the single gene encoding chalcone synthase (CHS) in Arabidopsis. We demonstrate smiRNA(CHS) expression and CHS mRNA cleavage in different transgenic lines. Phenotypic changes in these lines were observed for seed color and flavonol derivatives, and quantified with respect to anthocyanin content. We also tested the effect of mismatches and excess G:U base pairs on knockdown efficiency. Conclusions: RNAhybrid-assisted design of smiRNAs and generation of pri-smiRNAs using a novel vector containing restriction sites greatly improves specificity and speed of the generation of stable knockdown lines for functional analyses in plants

Test-retest reliability of lung diffusing capacity for nitric oxide during light to moderate intensity cycling exercise

This study examined test-retest reliability of single-breath lung diffusing capacity for nitric oxide (DLNO) and carbon monoxide (DLCO) during exercise. Sixteen healthy subjects (age 20-67 years) performed DLNO-DLCO tests during light and moderate intensity cycling exercise at 50% and 80% of individual anaerobic threshold (IAT). Primary endpoint was DLNO at 80% IAT. Precision of DLNO, DLCO, and alveolar volume was quantified by within-subject standard deviation (SDws, measurement error) and intraclass correlation coefficients (ICC). Reproducibility was determined by SDws* 2.77. Overall, reliability was excellent for all outcomes. SDws and reproducibility for DLNO at 80% IAT were 4.6 and 12.7 mL.min-1.mmHg-1, and the ICC was 0.99 (95% confidence interval 0.98-0.99). Median breathlessness at 80% IAT was 4 (interquartile range 3-6) on a 0-10 scale. Our data suggest excellent reliability of single-breath DLNO during moderate intensity exercise, but perceived levels of breathlessness may limit its usefulness, especially at exercise intensities beyond IAT. Keywords: Diffusing capacity for nitric oxide; Exercise; Reliability; Reproducibility; Single breat

Reservoir leakage along concentric faults in the Southern North Sea: implications for the deployment of CCS and EOR techniques

High-quality 3D seismic and borehole data in the Broad Fourteens Basin, Southern North Sea, is used to investigate newly recognised concentric faults formed in salt-withdrawal basins flanking reactivated salt structures. Throw-depth and throw-distance plots were used to understand the growth histories of individual faults. As a result, three families of concentric faults are identified: a) intra-seal faults within a salt-withdrawal basin, b) faults connecting the seal and the reservoir on the crest of an inverted anticline, c) raft-bounding faults propagating into reservoir units. They have moved obliquely and show normal throws, even though they formed during a period of regional compression. Faults in the salt-withdrawal basin and on the inverted anticline are highly segmented, increasing the chances of compartmentalisation or localised fluid flow through fault linkages. Slip tendency analysis was carried out on the distinct fault families to compare the likelihood of slip along a fault at different pore fluid pressures and within different lithologies. Our results show that sections of the faults are optimally oriented with regards to maximum horizontal stresses (σHmax), increasing the slip tendency. The identified faults cut through a variety of lithologies, allowing different values of pore fluid pressures to build up before faults reactivate. Within the Vlieland Sandstones, pore fluid pressures of 30 MPa are not sufficient to reactivate pre-existing faults, whereas in the deeper Posidonia Shales faults might reactivate at pore fluid pressures of 25 MPa. Fluid flow features preferentially occur near fault segments close to failure. Heterogeneity in slip tendency along concentric faults, and high degrees of fault segmentation, present serious hazards when injecting CO2 into the subsurface. This study stresses the importance of high-quality 3D seismic data and the need to evaluate individual fault systems when investigating potential reservoirs for carbon capture and storage and enhanced oil recovery

The Age Dependent Luminosities of the Red Giant Branch Bump, Asymptotic Giant Branch Bump, and Horizontal Branch Red Clump

Color-magnitude diagrams of globular clusters often exhibit a prominent horizontal branch (HB) and may also show features such as the red giant branch (RGB) bump and the asymptotic giant branch (AGB) bump. Stellar evolution theory predicts that the luminosities of these features will depend on the metallicity and age of the cluster. We calculate theoretical lines of 2 to 12 Gyr constant age RGB-bumps and AGB-bumps in the V(HB-Bump)--[Fe/H] diagram, which shows the brightness difference between the bump and the HB as a function of metallicity. In order to test the predictions, we identify giant branch bumps in new Hubble Space Telescope color-magnitude diagrams for 8 SMC clusters. First, we conclude that the SMC cluster bumps are RGB-bumps. The data for clusters younger than ~6 Gyr are in fair agreement the relative age dependent luminosities of the HB and RGB-bump. The V(HB-Bump)--[Fe/H] data for clusters older then ~6 Gyr demonstrate a less satisfactory agreement with our calculations. We conclude that ~6 Gyr is a lower bound to the age of clusters for which the Galactic globular cluster, age independent V(HB-Bump)--[Fe/H] calibration is valid. Application of the V(HB-bump)--[Fe/H] diagram to stellar population studies is discussed.Comment: Accepted for publication in the Astrophysical Journal, 30 pages, Latex aaspp4.sty, including 7 postscript figure

A quantum algorithm for ray casting using an orthographic camera

Quantum computing has the potential to provide solutions to many problems which are challenging or out of reach of classical computers. There are several problems in rendering which are amenable to being solved in quantum computers, but these have yet to be demonstrated in practice. This work takes a first step in applying quantum computing to one of the most fundamental operations in rendering: ray casting. This technique computes visibility between two points in a 3D model of the world which is described by a collection of geometric primitives. The algorithm returns, for a given ray, which primitive it intersects closest to its origin. Without a spatial acceleration structure, the classical complexity for this operation is O(N). In this paper, we propose an implementation of Grover's Algorithm (a quantum search algorithm) for ray casting. This provides a quadratic speed up allowing for visibility evaluation for unstructured primitives in O(√N). However, due to technological limitations associated with current quantum computers, in this work the geometrical setup is limited to rectangles and parallel rays (orthographic projection).This work was partially financed by National Funds through the Portuguese funding agency, FCT – Fundação para a Ciência e a Tecnologia – within project: UID/EEA/50014/2019. This work was partially funded by SmartEGOV/NORTE-01-0145-FEDER-000037, supported by Norte Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement, through the European Regional Development Fund (EFDR)

Paralog-Specific Primers for the Amplification of Nuclear Loci in Tetraploid Barbels (Barbus: Cypriniformes)

Thirty paralog-specific primers were developed, following an intron-primed exon-crossing strategy, for S7 and growth hormone genes in Barbus (subgenera Barbus and Luciobarbus). We found that paralog-specific amplification requires the use of only one paralog-specific primer, allowing their simultaneous use with universal exon-primed intron-crossing primers of broad taxonomic applicability. This hybrid annealing strategy guarantees both specificity and generality of amplification reactions and represents a step forward in the amplification of duplicated nuclear loci in polyploid organisms and members of multigene families. Assays of several representative taxa identified high levels of segregating single nucleotide polymorphisms (SNPs) and nucleotide diversity within each of these subgenera. Additionally, several insertions-deletions (indels) that are diagnostic across species are found in intronic regions. Therefore, these primers provide a reliable source of valuable nuclear SNP and indel data for population and species level studies of barbels, such as applied conservation and basic evolutionary studie

Chitin-Glucan Complex Hydrogels: Optimization of Gel Formation and Demonstration of Drug Loading and Release Ability

Chitin-glucan complex (CGC) hydrogels were fabricated through a freeze–thaw procedure for biopolymer dissolution in NaOH 5 mol/L, followed by a dialysis step to promote gelation. Compared to a previously reported methodology that included four freeze–thaw cycles, reducing the number of cycles to one had no significant impact on the hydrogels’ formation, as well as reducing the total freezing time from 48 to 18 h. The optimized CGC hydrogels exhibited a high and nearly spontaneous swelling ratio (2528 +- 68%) and a water retention capacity of 55 +- 3%, after 2 h incubation in water, at 37 ºC. Upon loading with caffeine as a model drug, an enhancement of the mechanical and rheological properties of the hydrogels was achieved. In particular, the compressive modulus was improved from 23.0 +-0.89 to 120.0 +- 61.64 kPa and the storage modulus increased from 149.9 +- 9.8 to 315.0 +- 76.7 kPa. Although the release profile of caffeine was similar in PBS and NaCl 0.9% solutions, the release rate was influenced by the solutions’ pH and ionic strength, being faster in the NaCl solution. These results highlight the potential of CGC based hydrogels as promising structures to be used as drug delivery devices in biomedical applicationsinfo:eu-repo/semantics/publishedVersio

Fluorine variations in the globular cluster NGC 6656 (M22): implications for internal enrichment timescales

Observed chemical (anti)correlations in proton-capture elements among globular cluster stars are presently recognized as the signature of self-enrichment from now extinct, previous generations of stars. This defines the multiple population scenario. Since fluorine is also affected by proton captures, determining its abundance in globular clusters provides new and complementary clues regarding the nature of these previous generations, and supplies strong observational constraints to the chemical enrichment timescales. In this paper we present our results on near-infrared CRIRES spectroscopic observations of six cool giant stars in NGC 6656 (M22): the main objective is to derive the F content and its internal variation in this peculiar cluster, which exhibits significant changes in both light and heavy element abundances. We detected F variations across our sample beyond the measurement uncertainties and found that the F abundances are positively correlated with O and anticorrelated with Na, as expected according to the multiple population framework. Furthermore, our observations reveal an increase in the F content between the two different sub-groups, s-process rich and s-process poor, hosted within M22. The comparison with theoretical models suggests that asymptotic giant stars with masses between 4 and 5 Msun are responsible for the observed chemical pattern, confirming evidence from previous works: the difference in age between the two sub-components in M22 must be not larger than a few hundreds Myr.Comment: Accepted for publication in The Astrophysical Journal, 10 pages, 10 figure