An Efficient Bandit Algorithm for Realtime Multivariate Optimization

Optimization is commonly employed to determine the content of web pages, such as to maximize conversions on landing pages or click-through rates on search engine result pages. Often the layout of these pages can be decoupled into several separate decisions. For example, the composition of a landing page may involve deciding which image to show, which wording to use, what color background to display, etc. Such optimization is a combinatorial problem over an exponentially large decision space. Randomized experiments do not scale well to this setting, and therefore, in practice, one is typically limited to optimizing a single aspect of a web page at a time. This represents a missed opportunity in both the speed of experimentation and the exploitation of possible interactions between layout decisions. Here we focus on multivariate optimization of interactive web pages. We formulate an approach where the possible interactions between different components of the page are modeled explicitly. We apply bandit methodology to explore the layout space efficiently and use hill-climbing to select optimal content in realtime. Our algorithm also extends to contextualization and personalization of layout selection. Simulation results show the suitability of our approach to large decision spaces with strong interactions between content. We further apply our algorithm to optimize a message that promotes adoption of an Amazon service. After only a single week of online optimization, we saw a 21% conversion increase compared to the median layout. Our technique is currently being deployed to optimize content across several locations at Amazon.com.Comment: KDD'17 Audience Appreciation Awar

Influence of quantum confinement on the ferromagnetism of (Ga,Mn)As diluted magnetic semiconductor

We investigate the effect of quantum confinement on the ferromagnetism of diluted magnetic semiconductor Ga$_{1-x}$Mn$_x$As using a combination of tight-binding and density functional methods. We observe strong majority-spin Mn $d$-As $p$ hybridization, as well as half metallic behavior, down to sizes as small as 20 \AA in diameter. Below this critical size, the doped holes are self-trapped by the Mn-sites, signalling both valence and electronic transitions. Our results imply that magnetically doped III-V nanoparticles will provide a medium for manipulating the electronic structure of dilute magnetic semiconductors while conserving the ferromagnetic properties and even enhancing it in certain size regime.Comment: 4 pages, 3 figure

Seed Quality Testing for Novel Endophyte Technology

Fungal endophyte (Epichloë coenophiala (Morgan-Jones & W.Gams)) in Kentucky-31 tall fescue (Lolium arundinaceum (Schreb.) Darbyshire) produces ergot alkaloids that adversely affect livestock. Novel endophyte-infected tall fescue cultivars, with agronomic enhancing properties without livestock toxicity, are commercially available but producer perception and adoption of the technology has been apprehensive. Educational programs by the Alliance for Grassland Renewal were developed to promote use of the novel endophyte technology. Standards of endophyte quality in seed for existing and new novel technologies were established and used to educate producers and ancillary professionals in Alliance-sponsored schools. Surveys of the presentation on seed quality were highly favorable and considered “useful.” The number of seed lots tested for novel endophyte technology increased steadily once the Alliance-sponsored schools were implemented. Attempts to develop new technologies to provide alternatives to immunochemical testing for novel endophyte technologies are in progress

Commensurate Dy magnetic ordering associated with incommensurate lattice distortion in orthorhombic DyMnO3

Synchrotron x-ray diffraction and resonant magnetic scattering experiments on single crystal DyMnO3 have been carried out between 4 and 40 K. Below TN(Dy) = 5K, the Dy magnetic moments order in a commensurate structure with propagation vector 0.5 b*. Simultaneous with the Dy magnetic ordering, an incommensurate lattice modulation with propagation vector 0.905 b* evolves while the original Mn induced modulation is suppressed and shifts from 0.78 b* to 0.81 b*. This points to a strong interference of Mn and Dy induced structural distortions in DyMnO3 besides a magnetic coupling between the Mn and Dy magnetic moments.Comment: submitted to Phys. Rev. B Rapid Communication

Evaluation of high temperature structural adhesives for extended service, phase 4

The evaluation of three phenylquinoxaline polymers as high temperature structural adhesives is presented. These included an experimental crisskubjabke oiktner (X-PQ) and two experimental materials (PPQ-2501) and (PPQ-HC). Lap shear, crack extension, and climing drum peel specimens were fabricated from all three polymers, and tested after thermal, combined thermal/humidity, and stressed Skydrol exposure. All three polymers generally performed well as adhesives at initial test temperatures from 219K (-67 F) to 505K (450 F) and after humidity exposure. The 644K (700 F) cured test specimens exhibited superior Skydrol resistance and thermal stability at 505K (450 F) when compared to the 602K (625 F) cured test specimens