Tests of QCD: Summary of DIS 2000

This summary of the working group 2 of DIS 2000 encompasses experimental and theoretical results of jet physics, open and bound state heavy flavour production, prompt photon production, next-to-leading order QCD calculations and beyond, instantons, fragmentation, event shapes, and power corrections, primarily from deep-inelastic scattering and photoproduction at HERA, but also from the LEP and Tevatron colliders.Comment: 16 pages, LaTeX, including 8 PostScript figures. Talk given at the 8th International Workshop on Deep-Inelastic Scattering (DIS2000), 25th-30th April 2000, Liverpool, England, to appear in the proceeding

High Distance Bridge Surfaces

Given integers b, c, g, and n, we construct a manifold M containing a c-component link L so that there is a bridge surface Sigma for (M,L) of genus g that intersects L in 2b points and has distance at least n. More generally, given two possibly disconnected surfaces S and S', each with some even number (possibly zero) of marked points, and integers b, c, g, and n, we construct a compact, orientable manifold M with boundary S \cup S' such that M contains a c-component tangle T with a bridge surface Sigma of genus g that separates the boundary of M into S and S', |T \cap Sigma|=2b and T intersects S and S' exactly in their marked points, and Sigma has distance at least n.Comment: 17 pages, 13 figures; v2 clarifying revisions made based on referee's comment

Locally Estimating Core Numbers

Graphs are a powerful way to model interactions and relationships in data from a wide variety of application domains. In this setting, entities represented by vertices at the "center" of the graph are often more important than those associated with vertices on the "fringes". For example, central nodes tend to be more critical in the spread of information or disease and play an important role in clustering/community formation. Identifying such "core" vertices has recently received additional attention in the context of {\em network experiments}, which analyze the response when a random subset of vertices are exposed to a treatment (e.g. inoculation, free product samples, etc). Specifically, the likelihood of having many central vertices in any exposure subset can have a significant impact on the experiment. We focus on using $k$-cores and core numbers to measure the extent to which a vertex is central in a graph. Existing algorithms for computing the core number of a vertex require the entire graph as input, an unrealistic scenario in many real world applications. Moreover, in the context of network experiments, the subgraph induced by the treated vertices is only known in a probabilistic sense. We introduce a new method for estimating the core number based only on the properties of the graph within a region of radius $\delta$ around the vertex, and prove an asymptotic error bound of our estimator on random graphs. Further, we empirically validate the accuracy of our estimator for small values of $\delta$ on a representative corpus of real data sets. Finally, we evaluate the impact of improved local estimation on an open problem in network experimentation posed by Ugander et al.Comment: Main paper body is identical to previous version (ICDM version). Appendix with additional data sets and enlarged figures has been added to the en

The effects of Reynolds number, rotor incidence angle, and surface roughness on the heat transfer distribution in a large-scale turbine rotor passage

A combined experimental and computational program was conducted to examine the heat transfer distribution in a turbine rotor passage geometrically similiar to the Space Shuttle Main Engine (SSME) High Pressure Fuel Turbopump (HPFTP). Heat transfer was measured and computed for both the full-span suction and pressure surfaces of the rotor airfoil as well as for the hub endwall surface. The primary objective of the program was to provide a benchmark-quality data base for the assessment of rotor passage heat transfer computational procedures. The experimental portion of the study was conducted in a large-scale, ambient temperature, rotating turbine model. Heat transfer data were obtained using thermocouple and liquid-crystal techniques to measure temperature distributions on the thin, electrically-heated skin of the rotor passage model. Test data were obtained for various combinations of Reynolds number, rotor incidence angle and model surface roughness. The data are reported in the form of contour maps of Stanton number. These heat distribution maps revealed numerous local effects produced by the three-dimensional flows within the rotor passage. Of particular importance were regions of local enhancement produced on the airfoil suction surface by the main-passage and tip-leakage vortices and on the hub endwall by the leading-edge horseshoe vortex system. The computational portion consisted of the application of a well-posed parabolized Navier-Stokes analysis to the calculation of the three-dimensional viscous flow through ducts simulating the a gas turbine passage. These cases include a 90 deg turning duct, a gas turbine cascade simulating a stator passage, and a gas turbine rotor passage including Coriolis forces. The calculated results were evaluated using experimental data of the three-dimensional velocity fields, wall static pressures, and wall heat transfer on the suction surface of the turbine airfoil and on the end wall. Particular attention was paid to an accurate modeling of the passage vortex and to the development of the wall boundary layers including crossflow

Polyunsaturated aldehyde production by a temporally varying field assemblage of diatoms in the San Juan Island Archipelago: can diatom metabolites affect microzooplankton grazing?

The success of diatoms in a wide range of global habitats, together with common observations of the post-bloom sinking of diatom biomass, indicates that this taxon has evolved a mechanism to reduce the largest loss process for phytoplankton in the ocean, microzooplankton grazing. Recent research has shown that polyunsaturated aldehydes (PUAs), lipid oxidation products generated by various species of diatoms, can reduce copepod fecundity and egg hatching success. This leads to the question of whether PUAs adversely affect the major global consumers of phytoplankton, microzooplankton. In the late spring to early fall 2007, I used the seawater dilution technique to quantify phytoplankton growth and microzooplankton grazing; at the same time I determined diatom and microzooplankton abundances and biomasses at Rosario Point, Orcas Island, WA (N 48° 38.614, W 122°52.750). In addition, I measured production of PUAs by the phytoplankton community to assess whether these chemicals functioned as chemical grazing deterrents, to look for novel PUA-producing diatom genera, and to evaluate environmental factors that potentially influenced PUA production. Four hydrographic structural change (HSC) events in the water column were identified during the spring-summer sampling period that probably reflected flushing by outside water masses. These events altered environmental conditions with distinct planktonic communities (termed community states) emerging during post-event water column stabilization. The first two community states were characterized by low nutrient concentrations with chlorophyll a between 6.5 and 13.1μg L-1 and several instances of negative growth and grazing rates. This suggested the release of an unidentified chemical by the Pseudo-nitzschia spp. dominated first community state that additionally had moderately high PUA production levels of 771-1520 μg PUA g C-1. Harmful algal bloom species Heterosigma akashiwo dominated the mid-summer community state with chlorophyll a reaching 10.45 μg chl L-1 and microzooplankton grazing rates reduced to nearly zero. Lastly, the diatom dominated mid-to-late summer community state reached 15.84 μg chl L-1 with Thalassiosira spp, Chaetoceros spp., and Skeletonema sp. all present as major constituents of the community that produced high PUA levels (1280- 3410 μg PUA g C-1). Each of the genera found in this study contain species that have previously been identified as producing PUA. Low phosphate concentrations within each of the PUA-producing communities appeared to influence production, as well as the presence of low light levels in the first community state that possibly increased PUAprecursor molecule formation. Furthermore, changes to growth rates in the \u3e20-μm (diatom) community with nutrient addition often occurred during PUA production, however this response by sampled diatom communities did not preclude PUA production. Community grazing on the \u3e20-μm size fraction was observed to decrease when PUA production was high. During the spring state negative grazing along with low microzooplankton biomass made interpretation difficult. During the mid-to-late summer state grazing was reduced to -0.02 to 0.08 d-1 with a large biomass of 143 to 180 μg C L-1 of non-feeding microzooplankton that included known diatom-feeding dinoflagellates Protoperidinium sp., 40 to 59 μm Gyro/Gymnodinium, and \u3e60-μm Gyro/Gymnodinium. With this reduced grazing, diatoms grew from 23.2 to 244 μg C L-1. Since diatom grazing genera of microzooplankton did not feed during the initiation and maintenance of the August bloom, my data suggests that PUA played a role in bloom initiation and allowed the diatom community to avoid predation

An Analysis of the Migration Policies of the European Union and Their Effectiveness in Managing the Current Migration Crisis

The current migration of individuals into the European Union is creating an unparalleled and unprecedented crisis that has completely overwhelmed the EU Member States. Migrants entering the European Union have done so via dangerous and deadly sea and land routes, resulting in a devastating humanitarian crisis throughout Europe. As conflicts and instability around the world continue to evolve and escalate, larger flows of migrants continue to pour into the European Union causing the irregular migration of people across Europe’s borders. To counter this, European Union officials have attempted to create migration policies based on border management and security ideals. However, many authors, researchers, humanitarian groups, non-governmental organizations, and some policymakers have countered this approach and called upon the European Union to expand its policies to include more humanitarian measures. Up to this point, the Union remains thoroughly fragmented and indecisive in its response. With this research on the European Union migration policies, along with case studies of EU Member States such as Germany, Hungary, and Greece, the goal of this thesis is to advance new approaches to this difficult situation and to provide policy recommendations, program advice as well as suggestions for further analysis

Evolutionary quantitative genetics of nonlinear developmental systems

In quantitative genetics, the effects of developmental relationships among traits on microevolution are generally represented by the contribution of pleiotropy to additive genetic covariances. Pleiotropic additive genetic covariances arise only from the average effects of alleles on multiple traits, and therefore the evolutionary importance of nonlinearities in development is generally neglected in quantitative genetic views on evolution. However, nonlinearities in relationships among traits at the level of whole organisms are undeniably important to biology in general, and therefore critical to understanding evolution. I outline a system for characterizing key quantitative parameters in nonlinear developmental systems, which yields expressions for quantities such as trait means and phenotypic and genetic covariance matrices. I then develop a system for quantitative prediction of evolution in nonlinear developmental systems. I apply the system to generating a new hypothesis for why direct stabilizing selection is rarely observed. Other uses will include separation of purely correlative from direct and indirect causal effects in studying mechanisms of selection, generation of predictions of medium‐term evolutionary trajectories rather than immediate predictions of evolutionary change over single generation time‐steps, and the development of efficient and biologically motivated models for separating additive from epistatic genetic variances and covariances.PostprintPeer reviewe

The geophysical evolution of impact basins and volcanic structures on Mercury and the Moon

The geologic histories of most terrestrial bodies are dominated by two major processes: meteorite bombardment and volcanism. The forms that the resulting impact craters and volcanic structures take can tell us a great deal about the ways in which these processes occur and about the environment of the host body at the time of their formation. The surfaces of bodies like Mercury and the Moon are old, however, and most such features formed more than a billion years in the past. Impact craters and volcanic structures are thus generally not visible in their original states, but instead in a form which has evolved over geologic time. ^ In this work, I combine observations of planetary surfaces from spacecraft like MESSENGER and GRAIL with modern numerical modeling techniques in order to explore the various ways in which the long-term geophysical evolution of impact craters and volcanic structures can reveal information about the subsurface environment. I find that the pattern of fractures on the floors of the Rachmaninoff, Raditladi, and Mozart peak-ring impact basins on Mercury reveals the contours of the underlying terrain; that the present-day gravitational and topographic signatures over Orientale Basin emerged due to a combination of syn- and post-impact processes which can help to constrain both the parameters of the impact and the rheology of the lunar mantle; and that the tremendous sizes at which lunar lava tubes can be stable open up both new ways of interpreting GRAIL observations of the lunar gravity field and new possibilities for human exploration of the Moon