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Monotone Branch-and-Bound Search for Restricted Combinatorial Auctions
Faced with an intractable optimization problem, a common approach to computational mechanism design seeks a polynomial time approximation algorithm with an approximation guarantee. Rather than adopt this worst-case viewpoint, we introduce a new paradigm that seeks to obtain good performance on typical instances through a modification to the branch-and-bound search paradigm. Incentive compatibility in single-dimensional domains requires that an outcome improves monotonically for an agent as the agent's reported value increases. We obtain a monotone search algorithm by coupling an explicit sensitivity analysis on the decisions made during search with a correction to the outcome to ensure monotonicity. Extensive computational experiments on single-minded combinatorial auctions show better welfare performance than that available from existing approximation algorithms.Engineering and Applied Science
Carbon and Strontium Abundances of Metal-Poor Stars
We present carbon and strontium abundances for 100 metal-poor stars measured
from R7000 spectra obtained with the Echellette Spectrograph and Imager
at the Keck Observatory. Using spectral synthesis of the G-band region, we have
derived carbon abundances for stars ranging from [Fe/H] to
[Fe/H]. The formal errors are dex in [C/Fe]. The strontium
abundance in these stars was measured using spectral synthesis of the resonance
line at 4215 {\AA}. Using these two abundance measurments along with the barium
abundances from our previous study of these stars, we show it is possible to
identify neutron-capture-rich stars with our spectra. We find, as in other
studies, a large scatter in [C/Fe] below [Fe/H]. Of the stars with
[Fe/H], 94% can be classified as carbon-rich metal-poor stars. The Sr
and Ba abundances show that three of the carbon-rich stars are
neutron-capture-rich, while two have normal Ba and Sr. This fraction of carbon
enhanced stars is consistent with other studies that include this metallicity
range.Comment: ApJ, Accepte
An Evaluation of Journaling File Systems
Many statisticians would agree that, had it not been for systems, the synthesis of virtual machines might never have occurred. In fact, few systems engineers would disagree with the improvement of the location-identity split. We motivate an algorithm for the synthesis of compilers, which we call Nap
Generalized Random Utility Models with Multiple Types
We propose a model for demand estimation in multi-agent, differentiated product settings and present an estimation algorithm that uses reversible jump MCMC techniques to classify agents' types. Our model extends the popular setup in Berry, Levinsohn and Pakes (1995) to allow for the data-driven classification of agents' types using agent-level data. We focus on applications involving data on agents' ranking over alternatives, and present theoretical conditions that establish the identifiability of the model and uni-modality of the likelihood/posterior. Results on both real and simulated data provide support for the scalability of our approach.EconomicsEngineering and Applied SciencesMathematic
Super-Reflection in Fluid Discs: Corotation Amplifier, Corotation Resonance, Rossby Waves, and Overstable Modes
In differentially rotating discs with no self-gravity, density waves cannot
propagate around the corotation, where the wave pattern rotation speed equals
the fluid rotation rate. Waves incident upon the corotation barrier may be
super-reflected (commonly referred to as corotation amplifier), but the
reflection can be strongly affected by wave absorptions at the corotation
resonance/singularity. The sign of the absorption is related to the Rossby wave
zone very near the corotation radius. We derive the explicit expressions for
the complex reflection and transmission coefficients, taking into account wave
absorption at the corotation resonance. We show that for generic discs, this
absorption plays a much more important role than wave transmission across the
corotation barrier. Depending on the sign of the gradient of the specific
vorticity of the disc the corotation resonance can either enhance or diminish
the super-reflectivity, and this can be understood in terms of the location of
the Rossby wave zone relative to the corotation radius. Our results provide the
explicit conditions (in terms of disc thickness, rotation profile and specific
vorticity gradient) for which super-reflection can be achieved. Global
overstable disc modes may be possible for discs with super-reflection at the
corotation barrier.Comment: 16 pages, 5 figures, MNRAS in pres
Payment Rules through Discriminant-Based Classifiers
In mechanism design it is typical to impose incentive compatibility and then
derive an optimal mechanism subject to this constraint. By replacing the
incentive compatibility requirement with the goal of minimizing expected ex
post regret, we are able to adapt statistical machine learning techniques to
the design of payment rules. This computational approach to mechanism design is
applicable to domains with multi-dimensional types and situations where
computational efficiency is a concern. Specifically, given an outcome rule and
access to a type distribution, we train a support vector machine with a special
discriminant function structure such that it implicitly establishes a payment
rule with desirable incentive properties. We discuss applications to a
multi-minded combinatorial auction with a greedy winner-determination algorithm
and to an assignment problem with egalitarian outcome rule. Experimental
results demonstrate both that the construction produces payment rules with low
ex post regret, and that penalizing classification errors is effective in
preventing failures of ex post individual rationality
Alternative functions for the multifarious inflammasome
The inflammasome has been mainly studied in innate immune cells in which it senses microbes and cellular damage, and induces secretion of pro-inflammatory cytokines. This process induces an inflammatory response that is critical for the resolution of infections and repair of tissue damage following injury. Recent studies indicate that inflammasome complex formation also participates in many other cellular and physiological processes beyond modulation of inflammation, such as autophagy, metabolism, eicosanoids production, and phagosome maturation
Novel and Known Protein Tyrosine Kinases and Their Abnormal Expression in Human Melanoma
We have used the polymerase chain reaction and Northern blotting to identify protein tyrosine kinases that may play an an important role in the process of melanoma initiation and progression. Degenerate primers from the conserved catalytic domain of tyrosine kinase genes were used to amplify and clone partial cDNA sequences from a human melanoma cell line (DX3-LT5.1) and normal human melanocytes. When the melanoma reaction products were sequenced, 13 distinct clones were found, of which one is novel to date and has provisionally been named MEK (for melanocytic kinase). Of the remaining 12 known kinases, only two, ERB-B2 and IGFI-1-R, have previously been reported in pigment cells. Reaction products from melanocytes included only eight of these 13 sequences. To test for quantitative differences in tyrosine kinase expression between normal and malignant cells, a panel of eight melanoma lines and normal melanocytes was analyzed by Northern blotting. Two tyrosine kinases (JTK-14/TIE and TYRO-9) were detected in some melanomas but were not found in normal melanocytes, whereas others, including MEK, appeared to be overexpressed in some malignant lines. A minority of kinases showed either no change or a reduction in the level of mRNA. Expression of tyrosine kinases varied independently, and individual lines contained various combinations of these enzymes. Our findings are consistent with an increased overall expression of these putative growth factor receptors during melanoma development
Nuclear Effects on Heavy Boson Production at RHIC and LHC
We predict W and Z transverse momentum distributions from proton-proton and
nuclear collisions at RHIC and LHC. A resummation formalism with power
corrections to the renormalization group equations is used. The dependence of
the resummed QCD results on the non-perturbative input is very weak for the
systems considered. Shadowing effects are discussed and found to be unimportant
at RHIC, but important for LHC. We study the enhancement of power corrections
due to multiple scattering in nuclear collisions and numerically illustrate the
weak effects of the dependence on the nuclear mass.Comment: 21 pages, 11 figure
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