Unbiased Offline Evaluation of Contextual-bandit-based News Article Recommendation Algorithms

Contextual bandit algorithms have become popular for online recommendation systems such as Digg, Yahoo! Buzz, and news recommendation in general. \emph{Offline} evaluation of the effectiveness of new algorithms in these applications is critical for protecting online user experiences but very challenging due to their "partial-label" nature. Common practice is to create a simulator which simulates the online environment for the problem at hand and then run an algorithm against this simulator. However, creating simulator itself is often difficult and modeling bias is usually unavoidably introduced. In this paper, we introduce a \emph{replay} methodology for contextual bandit algorithm evaluation. Different from simulator-based approaches, our method is completely data-driven and very easy to adapt to different applications. More importantly, our method can provide provably unbiased evaluations. Our empirical results on a large-scale news article recommendation dataset collected from Yahoo! Front Page conform well with our theoretical results. Furthermore, comparisons between our offline replay and online bucket evaluation of several contextual bandit algorithms show accuracy and effectiveness of our offline evaluation method.Comment: 10 pages, 7 figures, revised from the published version at the WSDM 2011 conferenc

Time-Explicit Simulation of Wave Interaction in Optical Waveguide Crossings at Large Angles

The time-explicit finite-difference time-domain method is used to simulate wave interaction in optical waveguide crossings at large angles. The wave propagation at the intersecting structure is simulated by time stepping the discretized form of the Maxwell’s time dependent curl equations. The power distribution characteristics of the intersections are obtained by extracting the guided-mode amplitudes from these simulated total field data. A physical picture of power flow in the intersection is also obtained from the total field solution; this provides insights into the switching behavior and the origin of the radiations

Analysis and Evaluation of Victorian Reform in General Damages for Personal Injury under the Tort of Negligence

This article examines the current legislative structures in Victoria for compensating non-economic losses for personal injuries under the tort of negligence. It first provides a background on the tort of negligence in general and damages for non-economic losses in particular. It then outlines the changes that have swept through Victoria and in the rest of Australia for comparative purposes. This article offers a critique of the rationale and justification for those changes, analyses the implications of the changes at both Victorian and Commonwealth levels across the public, professional and product liability areas, and concludes with a discussion of the overall effect of the Victorian reforms

Near-ionization-threshold emission in atomic gases driven by intense sub-cycle pulses

We study theoretically the dipole radiation of a hydrogen atom driven by an intense sub-cycle pulse. The time-dependent Schr\"odinger equation for the system is solved by ab initio calculation to obtain the dipole response. Remarkably, a narrowband emission lasting longer than the driving pulse appears at a frequency just above the ionization threshold. An additional calculation using the strong field approximation also recovers this emission, which suggests that it corresponds to the oscillation of nearly-bound electrons that behave similarly to Rydberg electrons. The predicted phenomenon is unique to ultrashort driving pulses but not specific to any particular atomic structure.Comment: 8 pages, 2 figure

Translation inhibition by rocaglates is independent of eIF4E phosphorylation status

Rocaglates are natural products that inhibit protein synthesis in eukaryotes and exhibit antineoplastic activity. In vitro biochemical assays, affinity chromatography experiments coupled with mass spectrometry analysis, and in vivo genetic screens have identified eukaryotic initiation factor (eIF) 4A as a direct molecular target of rocaglates. eIF4A is the RNA helicase subunit of eIF4F, a complex that mediates cap-dependent ribosome recruitment to mRNA templates. The eIF4F complex has been implicated in tumor initiation and maintenance through elevated levels or increased phosphorylation status of its cap-binding subunit, eIF4E, thus furthering the interest toward developing rocaglates as antineoplastic agents. Recent experiments have indicated that rocaglates also interact with prohibitins 1 and 2, proteins implicated in c-Raf-MEK-ERK signaling. Because increased ERK signaling stimulates eIF4E phosphorylation status, rocaglates are also expected to inhibit eIF4E phosphorylation status, a point that has not been thoroughly investigated. It is currently unknown whether the effects on translation observed with rocaglates are solely through eIF4A inhibition or also a feature of blocking eIF4E phosphorylation. Here, we show that rocaglates inhibit translation through an eIF4E phosphorylation-independent mechanism.P50 GM067041 - NIGMS NIH HHS; R01 GM073855 - NIGMS NIH HHS; GM-067041 - NIGMS NIH HHS; MOP-106530 - Canadian Institutes of Health Researc

System identification and structural control on the JPL Phase B testbed

The primary objective of NASA's CSI program at JPL is to develop and demonstrate the CSI technology required to achieve high precision structural stability on large complex optical class spacecraft. The focus mission for this work is an orbiting interferometer telescope. Toward the realization of such a mission, a series of evolutionary testbed structures are being constructed. The JPL's CSI Phase B testbed is the second structure constructed in this series which is designed to study the pathlength control problem of the optical train of a stellar interferometer telescope mounted on a large flexible structure. A detailed description of this testbed can be found. This paper describes our efforts in the first phase of active structural control experiments of Phase B testbed using the active control approach where a single piezoelectric active member is used as an actuation device and the measurements include both colocated and noncolocated sensors. Our goal for this experiment is to demonstrate the feasibility of active structural control using both colocated and noncolocated measurements by means of successive control design and loop closing. More specifically, the colocated control loop was designed and closed first to provide good damping improvement over the frequency range of interest. The noncolocated controller was then designed with respect to a partially controlled structure to further improve the performance. Based on our approach, experimental closed-loop results have demonstrated significant performance improvement with excellent stability margins

Synthesis of nitrogen-containing molecules by zinc-catalyzed [4+2] cycloaddition and photoredox-catalyzed C-H functionalization

2017 Spring.Includes bibliographical references.This work first describes an enantioselective Zn-catalyzed [4+2] cycloaddition of 1-azadienes and nitro-alkenes for the synthesis of medicinally valuable piperidines. The detrimental coordination of 1-azadienes to the Zn catalysts undermines the stereochemical control of the reaction. Fortunately, a novel bisoxazoline ligand limits this undesired coordination and delivers high stereoselectivity. Mechanistic studies suggest the reaction proceeds via a stepwise mechanism in which aza-Michael addition is followed by cyclization. This proposed mechanism also explains the successful cycloaddition between two electron-deficient reaction partners. Secondly, amide-directed carbon-carbon bond formation at unactivated sp3 C-H bonds has been achieved using photoredox catalysis. The reaction features a hydrogen atom abstraction from the C-H bond to a nitrogen radical generated from the amidyl N-H bond, leading to formation of a carbon-centered radical. Trapping of the resulting alkyl radical with an electrophilic alkene gives the desired C-C bond formation. Experimental evidence supports the generation of the nitrogen radical through a stepwise deprotonation/oxidation event in a closed catalytic cycle. The potential to incorporate other functionalities in the C-H bonds, as well as g functionalization of carbonyl compounds, is disclosed