Learning Multiple Defaults for Machine Learning Algorithms

The performance of modern machine learning methods highly depends on their hyperparameter configurations. One simple way of selecting a configuration is to use default settings, often proposed along with the publication and implementation of a new algorithm. Those default values are usually chosen in an ad-hoc manner to work good enough on a wide variety of datasets. To address this problem, different automatic hyperparameter configuration algorithms have been proposed, which select an optimal configuration per dataset. This principled approach usually improves performance, but adds additional algorithmic complexity and computational costs to the training procedure. As an alternative to this, we propose learning a set of complementary default values from a large database of prior empirical results. Selecting an appropriate configuration on a new dataset then requires only a simple, efficient and embarrassingly parallel search over this set. We demonstrate the effectiveness and efficiency of the approach we propose in comparison to random search and Bayesian Optimization

Integrated Java Bytecode Verification

AbstractExisting Java verifiers perform an iterative data-flow analysis to discover the unambiguous type of values stored on the stack or in registers. Our novel verification algorithm uses abstract interpretation to obtain definition/use information for each register and stack location in the program, which in turn is used to transform the program into Static Single Assignment form. In SSA, verification is reduced to simple type compatibility checking between the definition type of each SSA variable and the type of each of its uses. Inter-adjacent transitions of a value through stack and registers are no longer verified explicitly. This integrated approach is more efficient than traditional bytecode verification but still as safe as strict verification, as overall program correctness can be induced once the data flow from each definition to all associated uses is known to be type-safe

Untyped Memory in the Java Virtual Machine

We have implemented a virtual execution environment that executes legacy binary code on top of the type-safe Java Virtual Machine by recompiling native code instructions to type-safe bytecode. As it is essentially impossible to infer static typing into untyped machine code, our system emulates untyped memory on top of Java’s type system. While this approach allows to execute native code on any off-the-shelf JVM, the resulting runtime performance is poor. We propose a set of virtual machine extensions that add type-unsafe memory objects to JVM. We contend that these JVM extensions do not relax Java’s type system as the same functionality can be achieved in pure Java, albeit much less efficiently

Permeation of Low-Z Atoms through Carbon Sheets: Density Functional Theory Study on Energy Barriers and Deformation Effects

Energetic and geometric aspects of the permeation of low-Z atoms through graphene sheets are investigated. Energy barriers and deformations are calculated via density functional theory for the permeation of H, He, Li and Be atoms at several surface sites and at a hollow site for atoms B, C, O and Ne atoms. Graphene is modeled by large planar polycyclic aromatic hydrocarbons and the convergence of both energy barriers and deformation curves with increasing size of these hydrocarbons is investigated. Effective energy curves are summarized for the atoms under consideration in three different interaction regimes realized different geometrical constraints. In addition to the bare graphene model, the interaction between low-Z atoms and 100% hydrogenated coronene as a model for graphane is also investigated. The adiabatic barriers range from about 5 eV (1 eV = 1.602 x 10-19 J) for H to about 20 eV for Ne. Facilitation of the permeation by temporary chemical bonding is observed for O and C and for B and Be when interacting with hydrogenated coronene. The results are in good agreement with existing experimental and theoretical work and reflect the essential physics of the dynamics of H bombardment of graphite (0001) surfaces. Implications for modeling chemical sputtering of graphite in a mixed-material scenario as it will be the case in the next step fusion experiment ITER and potential building are discussed.Comment: 21 pages, 14 figures, 3 table

Identifying the origins of local atmospheric deposition in the steel industry basin of Luxembourg using the chemical and isotopic composition of the lichen Xanthoria parietina

Trace metal atmospheric contamination was assessed in one of the oldest European industrial sites of steel production situated in the southern part of the Grand-Duchy of Luxembourg. Using elemental ratios as well as Pb, Sr, and Nd isotopic compositions as tracers, we found preliminary results concerning the trace metal enrichment and the chemical/isotopic signatures of the most important emission sources using the lichen Xanthoria parietina sampled at 15 sites along a SW-NE transect. The concentrations of these elements decreased with increasing distance from the historical and actual steel-work areas. The combination of the different tracers (major elements, Rare Earth Element ratios, Pb, Sr and Nd isotopes) enabled us to distinguish between three principal sources: the historical steel production (old tailings corresponding to blast-furnace residues), the present steel production (industrial sites with arc electric furnace units) and the regional background (baseline) components. Other anthropogenic sources including a waste incinerator and major roads had only weak impacts on lichen chemistry and isotopic ratios. The correlation between the Sr and Nd isotope ratios indicated that the Sr–Nd isotope systems represented useful tools to trace atmospheric emissions of factories using scrap metal for steel production

Magnetic resonance imaging basedcomputer-guideddental implant surgery-A clinical pilot study

Background: Computer-guided implant surgery is currently based on radiographic techniques exposing patients to ionizing radiation. Purpose: To assess, whether computer-assisted 3D implant planning with template-guided placement of dental implants based on magnetic resonance imaging (MRI) is feasible. Materials and methods: 3-Tesla MRI was performed in 12 subjects as a basis for prosthetically driven virtual planning and subsequent guided implant surgery. To evaluate the transferability of the virtually planned implant position, deviations between virtually planned and resulting implant position were studied. Matching of occlusal surfaces was assessed by comparing surface scans with MRI-derived images. In addition, the overall image quality and the ability of depicting anatomically important structures were rated. Results: MRI-based guided implant surgery with subsequent prosthetic treatment was successfully performed in nine patients. Mean deviations between virtually planned and resulting implant position (error at entry point 0.8 +/- 0.3 mm, error at apex 1.2 +/- 0.6 mm, angular deviation 4.9 +/- 3.6 degrees), mean deviation of occlusal surfaces between surface scans and MRI-based tooth reconstructions (mean 0.254 +/- 0.026 mm) as well as visualization of important anatomical structures were acceptable for clinical application. Conclusion Magnetic resonance imaging (MRI) based computer-assisted implant surgery is a feasible and accurate procedure that avoids exposure to ionizing radiation

Caring for a loved one with a malignant fungating wound

Purpose: Caring for a loved one with a malignant fungating wound is very challenging and causes extreme physical and psychological distress. The aim of this study was to explore the experiences of carers who care for a loved one with a fungating breast wound. Method: To explore the lived experiences of carers, a methodological framework using Heideggerian hermeneutic phenomenology and semi-structured interviews was used. Seven carers were interviewed from January until November 2009. Results: Having to deal with a situation of a loved one with a visible cancer was hard for all the carers. The visibility of the cancer was one of the most shocking aspects to deal with from the perspective of the patient and the carer. The presence of the visible wound and a cancer at an advanced stage contributed to a change in the relationship and extreme suffering for both the patient and the carer. Despite many problems such as wound odour and copious discharge from the wound, which was difficult to control, carers did their best to help their loved one with the wound. Gradually, the wound became the centre of the patient and carer's life, and a great deal of time was spent trying to control the wound symptoms. All carers managed the wound on their own without help and advice from health care practitioners. For all of them, it was a major burden and they felt isolated. Conclusion: This study contributes to an understanding that the care of women and their carers needs strategies that are integrated in palliative wound care that takes a holistic and empathic approach that responds to patients' and carers' psychosocial and emotional needs and a practical need for information to help carers assist in managing the wound-related symptom