The Random Walk of High Frequency Trading

This paper builds a model of high-frequency equity returns by separately modeling the dynamics of trade-time returns and trade arrivals. Our main contributions are threefold. First, we characterize the distributional behavior of high-frequency asset returns both in ordinary clock time and in trade time. We show that when controlling for pre-scheduled market news events, trade-time returns of the highly liquid near-month E-mini S&P 500 futures contract are well characterized by a Gaussian distribution at very fine time scales. Second, we develop a structured and parsimonious model of clock-time returns by subordinating a trade-time Gaussian distribution with a trade arrival process that is associated with a modified Markov-Switching Multifractal Duration (MSMD) model. This model provides an excellent characterization of high-frequency inter-trade durations. Over-dispersion in this distribution of inter-trade durations leads to leptokurtosis and volatility clustering in clock-time returns, even when trade-time returns are Gaussian. Finally, we use our model to extrapolate the empirical relationship between trade rate and volatility in an effort to understand conditions of market failure. Our model suggests that the 1,200 km physical separation of financial markets in Chicago and New York/New Jersey provides a natural ceiling on systemic volatility and may contribute to market stability during periods of extremely heavy trading

Kinematics of fault-propagation folding: Analysis of velocity fields in numerical modeling simulations

Fault-propagation folding occurs when a shallow fold is created by an underlying propagating thrust fault. These structures are common features of fold and thrust belts and hold key economic relevance as groundwater or hydrocarbon reservoirs. Reconstructing a fault-propagation fold is commonly done by means of the trishear model of the forelimb, a theoretical approach that assumes simplistic rheological rock properties. Here we present a series of numerical models that elucidate the kinematics of fault-propagation folding within an anisotropic sedimentary cover using complex visco-elasto-plastic rheologies. We explore the influence of different parameters like cohesion, angle of internal friction, and viscosity during folding and compare the velocity field with results from the purely kinematic trishear model. In the trishear paradigm, fault-propagation folding features a triangular shear zone ahead of the fault tip whose width is defined by the apical angle that in practice serves as a freely tunable fitting parameter. In agreement with this framework, a triangular zone of concentrated strain forms in all numerical models. We use our models to relate the apical angle to the rheological properties of the modeled sedimentary layers. In purely visco-plastic models, the geometry of the forelimb obtained can be approximated using a trishear kinematic model with high apical angles ranging between 60° and 70°. However, additionally accounting for elastic deformation produces a significant change in the geometry of the beds that require lower apical angles (25°) for trishear kinematics. We conclude that all analyzed numerical models can be represented by applying the theoretical trishear model, whereby folds involving salt layers require high apical angle values while more competent sedimentary rocks need lower values.Fil: Plotek, Berenice Lia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Heckenbach, Esther. Universitat Potsdam; AlemaniaFil: Brune, Sascha. German Research Centre for Geosciences; AlemaniaFil: Cristallini, Ernesto Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Likerman, Jeremias. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; Argentin

Salmonella in pigs and pork and their antimicrobial resistance - 10 years of surveillance in Germany

Salmonella from pigs and pork have been submitted to the National Reference Laboratory for the Analysis and Testing of Zoonoses (Salmonella) (NRL Salm) for a number of years. This study retrospectively analyses the data of Salmonella and their antimicrobial resistance generated between 2000 and 2009. A total of 4163 isolates from pigs and 1839 isolates from pork submitted to the NRL Salm were serotyped and tested for antimicrobial resistance using the broth microdilution method. Minimum inhibitory concentrations (MIC) were evaluated using epidemiological cut-off values as provided by EUCAST (www.eucast.org) at the time of interpretation (2010). The majority of isolates from pigs and pork belonged to three serovars: S. Typhimurium (66 and 52%), monophasic variant of S. Typhimurium (1,4,[5],12:i:-) (11 and 10%) and S. Derby (7 and 10%). In both origins the number of S. Typhimurium decreased by roughly 50% while monophasic variant of S. Typhimurium increased from zero to 32 and 26%, respectively. The proportion of S. Derby varied between 5 and 12% in both origins

End-results of plastic operations on the kidney pelvis for hydronephrosis

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32613/1/0000755.pd

Antibiotics for the common cold: expectations of Germany’s general population

Physicians mention patients’ expectations as a reason for prescribing antibiotics for common (viral) upper respiratory tract infections despite clinical evidence against their use and the physicians’ better judgement. We aimed to assess the prevalence of such expectations and factors of influence (knowledge and attitudes) in Germany’s general population. In November 2008, 1,778 persons registered with a large market research company were invited to complete an online questionnaire on expectations concerning prescription of antibiotics and on knowledge and attitudes regarding the effectiveness and use of antibiotics for upper respiratory tract infections. A total of 1,076 persons aged 15–78 years participated (response: 61%), of whom 91.8% reported using antibiotics ‘only if absolutely necessary’. Prescription of antibiotics was expected by 113 (10.5%) of the 1,076 respondents for the common cold and by 997 (92.7%) for pneumonia. In a logistic regression analysis, predictors for expecting a prescription for antibiotics for the common cold included the following opinions: ‘common cold or flu can effectively be treated with antibiotics’ (prevalence: 37.6%; odds ratio (OR): 9.6; 95% confidence interval (CI): 3.8 to 24.3) and ‘antibiotics should be taken when having a sore throat to prevent more serious illness’ (prevalence 8.6%; OR: 7.6; 95% CI: 3.9 to 14.5). Among those expecting a prescription (n=113), 80 (71%) reported that they would trust their physician when he or she deems a prescription unnecessary; a further eight (7%) would be unsatisfied, but would accept the decision. Our results suggest that only a minority expects antibiotics for the treatment of cold symptoms. Physicians should be educated that their decisions not to prescribe antibiotics for the common cold, even when against patients’ expectations, are apparently accepted by the majority