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

Development of a knowledge based expert system on casting defects

Knowledge based expert systems are computer programs which use a collection of facts, rules of thumb to suggest solutions to specific problems. Foundry related practices are rich in thumb rules and knowledge bases which can be implemented in such programs to help the foundrymen. One such very important use of expert systems can be in the diagnosis of casting defects. This paper outlines the proc-edure adopted to design an expert system, to identify the casting defect by appearance and at the same time also suggest the remedial solution for the casting defect ident-ified. The knowledge-base of this expert system (named NCDA, NIFFT Casting Defect Analysis) is rule based. A large number of rules have been built that constitute the decis-ion making sequence for each area of defect, which when consulted by the user gives a probable or certain solution depending upon the parameters supplied by him/her. The system has been built using the expert system shell VP-EXPERT. A friendly environment has been created for the user that tries to sumulate actual human interaction. The knowledge base is open to further additions or modifi-cations

Crack Growth Studies in a welded Ni-base superalloy

It is well known that the introduction of sustained tensile loads during high-temperature fatigue (dwell-fatigue) significantly increases the crack propagation rates in many superalloys. One such superalloy is the Ni-Fe based Alloy 718, which is a high-strength corrosion resistant alloy used in gas turbines and jet engines. As the problem is typically more pronounced in fine-grained materials, the main body of existing literature is devoted to the characterization of sheets or forgings of Alloy 718. However, as welded components are being used in increasingly demanding applications, there is a need to understand the behavior. The present study is focused on the interaction of the propagating crack with the complex microstructure in Alloy 718 weld metal during cyclic and dwell-fatigue loading at 550 °C and 650 °C

Room temperature plasticity in sub-micrometer thermally grown oxide scales

Thermally grown oxides (TGOs) are generally considered to be brittle, capable of sustaining very limited plastic deformation before fracture. As they are prone to exhibit different forms of defects, the fracture toughness, typically measured to be some 1–2 MPa m1/2 [1], is typically reached well before sufficiently high stresses to induce plasticity can be applied [2]. This is particularly true at room temperature, where possible low-stress thermally activated creep mechanisms are suppressed. However, the occurrence of plasticity in e.g. Al2O3 single crystals at room temperature can occur for samples in the micrometer range [3]. Most measurements of the deformation of TGOs have been made on relatively thick scales, (\u3e1 micrometer), which are limited by the fracture originating from inherent defects. Furthermore, the studies have been limited in resolution and sensitivity, as the scales were adherent to the substrates and tested as a composite. Recently, micro-mechanical testing has been introduced as a method to evaluate mechanical behavior of TGOs on a ferritic/martensitic steel [4], where micro-cantilever bending was used to test specimen extracted from different layers in a 5–10 micrometers thick oxide. Still, the cantilever cross-section was typically several micrometers, and the very similar fracture stresses for notched and un-notched cantilevers seems to indicate that the deformation is still limited by inherent defects. Please click Additional Files below to see the full abstract

Microscale fracture of chromia scales

High temperature materials such as superalloys rely on the formation of a protective surface oxide scale for prevention of corrosion. Such materials undergo periods of varying thermal and mechanical loads during operation, which can lead to cracking of the surface oxide. This exposes the material to corrosion, and can also act as stress concentrations, which affects the life of the underlying material. It is therefore necessary to consider the mechanical integrity of these scales while estimating material life. Several models have been developed in which fracture mechanics is utilized to estimate failure. But there is a lack of data such as fracture strains and elastic modulus for oxide scales. Conventional mechanical testing methods such as tensile and bending tests have been modified to obtain mechanical data, but it mainly applies to thick oxide scales (several µm thick). These methods are also limited with respect to isolating substrate and residual stress effects. For advanced materials, where the oxide formation kinetics are low, new methods are required in order to assess the mechanical properties. Please click Additional Files below to see the full abstract

Imaging ultrafast dynamical diffraction wavefronts in strained Si with coherent X-rays

Dynamical diffraction effects in single crystals produce highly monochromatic parallel X-ray beams with a mutual separation of a few micrometer and a time-delay of a few fs -the so-called echoes. This ultrafast diffraction effect is used at X-ray Free Electron Lasers in self-seeding schemes to improve beam monochromaticity. Here, we present a coherent X-ray imaging measurement of echoes from Si crystals and demonstrate that a small surface strain can be used to tune their temporal delay. These results represent a first step towards the ambitious goal of strain-tailoring new X-ray optics

Systemic and Local Corticosteroid Use Is Associated with Reduced Executive Cognition, and Mood and Anxiety Disorders

Background: Use of local corticosteroids, especially the inhaled types, has increasingly been associated with systemic uptake and consequent adverse effects. In this study, we assessed the associations between the use of different corticosteroid types with cognitive and neuropsychiatric adverse effects related to high glucocorticoid exposure. Methods: In 83,592 adults (mean age 44 years, 59% women) of the general population (Lifelines Cohort Study), we analyzed the relationship between corticosteroid use with executive cognitive functioning (Ruff Figural Fluency Test), and presence of mood and anxiety disorders (Mini-International Neuropsychiatric Interview survey). We performed additional exploration for effects of physical quality of life (QoL; RAND-36), and inflammation (high-sensitive C-reactive protein [CRP]). Results: Cognitive scores were lower among corticosteroid users, in particular of systemic and inhaled types, when compared to nonusers. Users of inhaled types showed lower cognitive scores irrespective of physical QoL, psychiatric disorders, and high-sensitive CRP. Overall corticosteroid use was also associated with higher likelihood for mood and anxiety disorders. Users of inhaled corticosteroids were more likely to have mood disorders (OR 1.40 [95% CI 1.19-1.65], p < 0.001) and anxiety disorders (OR 1.19 [95% CI 1.06-1.33], p = 0.002). These findings were independent of physical QoL. A higher likelihood for mood disorders was also found for systemic users whereas nasal and dermal corticosteroid users were more likely to have anxiety disorders. Conclusions: Commonly used local corticosteroids, in particular inhaled types, and systemic corticosteroids are associated with reduced executive cognitive functioning and a higher likelihood of mood and anxiety disorders in the general adult population

Long-term glucocorticoid exposure and incident cardiovascular diseases - the Lifelines cohort

CONTEXT: Long-term glucocorticoid levels in scalp hair (HairGCs), including cortisol and the inactive form cortisone, represent the cumulative systemic exposure to glucocorticoids over months. HairGCs have repeatedly shown associations with cardiometabolic and immune parameters, but longitudinal data are lacking.DESIGN: We investigated 6341 hair samples of participants from the Lifelines cohort study for cortisol and cortisone levels, and associated these to incident cardiovascular diseases (CVD) during 5-7 years of follow-up. We computed the odds ratio (OR) of HairGC levels for incident CVD via logistic regression, adjusting for classical cardiovascular risk factors, and performed a sensitivity analysis in subcohorts of participants &lt;60 years and &gt;= 60 years. Also, we associated HairGC levels to immune parameters (total leukocytes and subtypes).RESULTS: Hair cortisone levels (available in n = 4701) were independently associated with incident CVD (p &lt; 0.001), particularly in younger individuals (multivariate-adjusted OR 4.21, 95% confidence interval (CI) 1.91-9.07 per point increase in 10-log cortisone concentration (pg/mg), p &lt; 0.001). All immune parameters except eosinophils were associated with hair cortisone (all multivariate-adjusted p &lt; 0.05).CONCLUSIONS: In this large, prospective cohort study, we found that long-term cortisone levels, measured in scalp hair, represent a relevant and significant predictor for future cardiovascular diseases in younger individuals. These results highlight glucocorticoid action as possible treatment target for CVD prevention, where hair glucocorticoid measurements could help identify individuals that may benefit from such treatments.</p

Anti-cancer effects and mechanism of actions of aspirin analogues in the treatment of glioma cancer

INTRODUCTION: In the past 25 years only modest advancements in glioma treatment have been made, with patient prognosis and median survival time following diagnosis only increasing from 3 to 7 months. A substantial body of clinical and preclinical evidence has suggested a role for aspirin in the treatment of cancer with multiple mechanisms of action proposed including COX 2 inhibition, down regulation of EGFR expression, and NF-κB signaling affecting Bcl-2 expression. However, with serious side effects such as stroke and gastrointestinal bleeding, aspirin analogues with improved potency and side effect profiles are being developed. METHOD: Effects on cell viability following 24 hr incubation of four aspirin derivatives (PN508, 517, 526 and 529) were compared to cisplatin, aspirin and di-aspirin in four glioma cell lines (U87 MG, SVG P12, GOS – 3, and 1321N1), using the PrestoBlue assay, establishing IC50 and examining the time course of drug effects. RESULTS: All compounds were found to decrease cell viability in a concentration and time dependant manner. Significantly, the analogue PN517 (IC50 2mM) showed approximately a twofold increase in potency when compared to aspirin (3.7mM) and cisplatin (4.3mM) in U87 cells, with similar increased potency in SVG P12 cells. Other analogues demonstrated similar potency to aspirin and cisplatin. CONCLUSION: These results support the further development and characterization of novel NSAID derivatives for the treatment of glioma