13,592 research outputs found
Boosting as a Product of Experts
In this paper, we derive a novel probabilistic model of boosting as a Product
of Experts. We re-derive the boosting algorithm as a greedy incremental model
selection procedure which ensures that addition of new experts to the ensemble
does not decrease the likelihood of the data. These learning rules lead to a
generic boosting algorithm - POE- Boost which turns out to be similar to the
AdaBoost algorithm under certain assumptions on the expert probabilities. The
paper then extends the POEBoost algorithm to POEBoost.CS which handles
hypothesis that produce probabilistic predictions. This new algorithm is shown
to have better generalization performance compared to other state of the art
algorithms
On Axionic Field Ranges, Loopholes and the Weak Gravity Conjecture
In this short note we clarify some aspects of the impact that the Weak
Gravity Conjecture has on models of (generalized) natural inflation. We address
in particular certain technical and conceptual concerns recently raised
regarding the stringent constraints and conclusions found in our previous work
(arXiv:1503.04783). We also point out the difficulties faced by attempts to
evade these constraints. These new considerations improve the understanding of
the quantum gravity constraints we found and further support the conclusion
that it remains challenging for axions to drive natural inflation.Comment: 14 page
Advances in breast cancer treatment and prevention: preclinical studies on aromatase inhibitors and new selective estrogen receptor modulators (SERMs).
Intensive basic and clinical research over the past 20 years has yielded crucial molecular understanding into how estrogen and the estrogen receptor act to regulate breast cancer and has led to the development of more effective, less toxic, and safer hormonal therapy agents for breast cancer management and prevention. Selective potent aromatase inhibitors are now challenging the hitherto gold standard of hormonal therapy, the selective estrogen-receptor modulator tamoxifen. Furthermore, new selective estrogen-receptor modulators such as arzoxifene, currently under clinical development, offer the possibility of selecting one with a more ideal pharmacological profile for treatment and prevention of breast cancer. Two recent studies in preclinical model systems that evaluate mechanisms of action of these new drugs and suggestions about their optimal clinical use are discussed
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A student-led comparison of techniques for augmenting the field experience
We report a study in which 30 university geography students compared five techniques to enhance the experience of visiting outdoor locations. The techniques were: a pre-prepared acetate overlay of the visual scene; a custom-designed visitor guide running on a PDA; the mScape location-based software running on a GPS-enabled mobile phone; Google Earth on a tablet PC; and a head-mounted virtual reality display. The students were given the assignment as part of their assessed coursework for a field trip to the UK Lake District, where they had to evaluate the techniques and propose improvements or future designs to enable tourists or students on field trips to gain an enhanced understanding of their surroundings. The paper describes these techniques, reports the process and results of the student assignment, and concludes with a discussion of some broader issues emerging from the project
Fencing in the Swampland: Quantum Gravity Constraints on Large Field Inflation
In this note we show that models of natural inflation based on closed string
axions are incompatible with the weak gravity conjecture (WGC). Specifically,
we use T-duality in order to map the bounds on the charge-to-mass ratio of
particles imposed by the WGC, to constraints on the ratio between instanton
actions and axion decay constants. We use this connection to prove that if the
WGC holds, even when multiple axions are present and mix with each other, one
cannot have large axion decay constants while remaining in a regime of
perturbative control. We also discuss the extension of the WGC to discrete
symmetries and its possible impact on models with axion monodromy, and the
distinction between the strong and mild versions of the WGC. Finally, we offer
some speculations regarding the import of these results to the general theory
of inflation.Comment: 25 page
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Augmenting the field experience: a student-led comparison of techniques and technologies
In this study we report on our experiences of creating and running a student fieldtrip exercise which allowed students to compare a range of approaches to the design of technologies for augmenting landscape scenes. The main study site is around Keswick in the English Lake District, Cumbria, UK, an attractive upland environment popular with tourists and walkers. The aim of the exercise for the students was to assess the effectiveness of various forms of geographic information in augmenting real landscape scenes, as mediated through a range of techniques and technologies. These techniques were: computer-generated acetate overlays showing annotated wireframe views from certain key points; a custom-designed application running on a PDA; a mediascape running on the mScape software on a GPS-enabled mobile phone; Google Earth on a tablet PC; and a head-mounted in-field Virtual Reality system. Each group of students had all five techniques available to them, and were tasked with comparing them in the context of creating a visitor guide to the area centred on the field centre. Here we summarise their findings and reflect upon some of the broader research questions emerging from the project
Dielectrowetting Driven Spreading of Droplets
The wetting of solid surfaces can be modified by altering the surface free energy balance between the solid, liquid, and vapor phases. Here we show that liquid dielectrophoresis induced by nonuniform electric fields can be used to enhance and control the wetting of dielectric liquids. In the limit of thick droplets, we show theoretically that the cosine of the contact angle follows a simple voltage squared relationship analogous to that found for electrowetting on dielectric. Experimental observations confirm this predicted dielectrowetting behavior and show that the induced wetting is reversible. Our findings provide a noncontact electrical actuation process for meniscus and droplet control
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