Using Bad Learners to find Good Configurations

Finding the optimally performing configuration of a software system for a given setting is often challenging. Recent approaches address this challenge by learning performance models based on a sample set of configurations. However, building an accurate performance model can be very expensive (and is often infeasible in practice). The central insight of this paper is that exact performance values (e.g. the response time of a software system) are not required to rank configurations and to identify the optimal one. As shown by our experiments, models that are cheap to learn but inaccurate (with respect to the difference between actual and predicted performance) can still be used rank configurations and hence find the optimal configuration. This novel \emph{rank-based approach} allows us to significantly reduce the cost (in terms of number of measurements of sample configuration) as well as the time required to build models. We evaluate our approach with 21 scenarios based on 9 software systems and demonstrate that our approach is beneficial in 16 scenarios; for the remaining 5 scenarios, an accurate model can be built by using very few samples anyway, without the need for a rank-based approach.Comment: 11 pages, 11 figure

Can Deterministic Mechanical Size Effects Contribute to Fracture and Microdamage Accumulation in Trabecular Bone?

Failure of bone under monotonic and cyclic loading is related to the bone mineral density, the quality of the bone matrix, and the evolution of microcracks. The theory of linear elastic fracture mechanics has commonly been applied to describe fracture in bone. Evidence is presented that bone failure can be described through a non-linear theory of fracture. Thereby, deterministic size effects are introduced. Concepts of a non-linear theory are applied to discern how the interaction among bone matrix constituents (collagen and mineral), microcrack characteristics, and trabecular architecture can create distinctively differences in the fracture resistance at the bone tissue level. The non-linear model is applied to interpret pre-clinical data concerning the effects of anti-osteoporotic agents on bone properties. The results show that bisphosphonate (BP) treatments that suppress bone remodeling will change trabecular bone in ways such that the size of the failure process zone relative to the trabecular thickness is reduced. Selective estrogen receptor modulators (SERMs) that suppress bone remodeling will change trabecular bone in ways such that the size of the failure process zone relative to the trabecular thickness is increased. The consequences of these changes are reflected in bone mechanical response and predictions are consistent with experimental observations in the animal model which show that BP treatment is associated with more brittle fracture and microcracks without altering the average length of the cracks, whereas SERM treatments lead to a more ductile fracture and mainly increase crack length with a smaller increase in microcrack density. The model suggests that BPs may be more effective in cases in which bone mass is very low, whereas SERMS may be more effective when milder osteoporotic symptoms are present

An Efficient Network Model for Determining the Effective Thermal Conductivity of Particulate Thermal Interface Materials

Particulate composites are commonly used in Microelectronics applications. One example of such materials is Thermal Interface Materials (TIMs) that are used to reduce the contact resistance between the chip and the heat sink. The existing analytical descriptions of thermal transport in particulate systems do not accurately account for the effect of inter-particle interactions, especially in the intermediate volume fractions of 30-80%. Another crucial drawback in the existing analytical as well as the network models is the inability to model size distributions (typically bimodal) of the filler material particles that are obtained as a result of the material manufacturing process. While full-field simulations (using, for instance, the finite element method) are possible for such systems, they are computationally expensive. In the present paper, we develop an efficient network model that captures the physics of inter-particle interactions and allows for random size distributions. Twenty random microstructural arrangements each of Alumina as well as Silver particles in Silicone and Epoxy matrices were generated using an algorithm implemented using a java language code. The microstructures were evaluated through both full-field simulations as well as the network model. The full-field simulations were carried out using a novel meshless analysis technique developed in the author’s (GS) research [26]. In all cases, it is shown that the random network models are accurate to within 5% of the full field simulations. The random network model simulations were efficient since they required two orders of magnitude smaller computation time to complete in comparison to the full field simulation

Determination of sulfur and nitrogen compounds during the processing of dry fermented sausages and their relation to amino acid generation

© 2015 Elsevier Ltd. All rights reserved. The identification of odor-active sulfur and nitrogen compounds formed during the processing of dry fermented sausages was the objective of this study. In order to elucidate their possible origin, free amino acids (FAAs) were also determined. The volatile compounds present in the dry sausages were extracted using solvent assisted flavor evaporation (SAFE) and monitored by one and two-dimensional gas chromatography with different detectors: mass spectrometry (MS), nitrogen phosphorous (NPD), flame photometric (FPD) detectors, as well as gas chromatography-olfactometry. A total of seventeen sulfur and nitrogen compounds were identified and quantified. Among them, 2-acetyl-1-pyrroline was the most potent odor active compound, followed by methional, ethylpyrazine and 2,3-dihydrothiophene characterized by toasted, cooked potato, and nutty notes. The degradation of FAAs, generated during processing, was related to the production of aroma compounds, such as methionine forming methional and benzothiazole while ornithine was the precursor compound for 2-acetyl-1-pyrroline and glycine for ethylpyrazine.Financial support from AGL 2012-38884-C02-01 from MINECO (Spain), PROMETEO 2012-001 (GVA) and FEDER funds are fully acknowledged. The predoctoral scholarship and financial support from MINECO (BES-2010-030850 and EEBB-EEBB-I-13-05949) for the stay of S. Corral at Institute of Analytical Chemistry and Food Chemistry (Graz, Austria) is also acknowledged.Peer Reviewe

Optimal sequential fingerprinting: Wald vs. Tardos

We study sequential collusion-resistant fingerprinting, where the fingerprinting code is generated in advance but accusations may be made between rounds, and show that in this setting both the dynamic Tardos scheme and schemes building upon Wald's sequential probability ratio test (SPRT) are asymptotically optimal. We further compare these two approaches to sequential fingerprinting, highlighting differences between the two schemes. Based on these differences, we argue that Wald's scheme should in general be preferred over the dynamic Tardos scheme, even though both schemes have their merits. As a side result, we derive an optimal sequential group testing method for the classical model, which can easily be generalized to different group testing models.Comment: 12 pages, 10 figure

Division of the Dowry on the Death of the Daughter: An Instance in the Negotiation of Laws and Jewish Customs in Early Modern Tuscany

Tuscan notarial acts permit the exploration of the often elusive relationship of Jewish practice, Jewish law and the corresponding laws of the state. One issue in early modern Italian Jewish marriage negotiations was the eventual disposition of the dowry of a childless wife who predeceased her husband. Jewish law on the succession of the childless woman was complicated by traditional or regional customs and communal ordinances. Moreover, in sixteenth-century Tuscany there was no official code, court or arbiter of Jewish law. Nonetheless, Christian notaries who wrote pre-nuptial stipulations or pacts for Jews worked with the assumption that Jews were allowed to live according to their own law. This essay argues that individual Jews used to advantage the state's assumption that they could follow Jewish law (despite the absence of any universally-acknowledged or applicable law on this specific subject) by employing notaries to write contracts in disregard of both local statutes and well-known Jewish customs. In the second part of this essay I locate the stipulations in the Jewish marriage system and suggest that the process of negotiation over the fate of the dowry was integrally related to the system's emphasis – in contrast to that of contemporary Christians – on universal marriage and procreation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43003/1/10835_2004_Article_394391.pd

Caracterização e avaliação da pastagem do rebanho de agricultores familiares do nordeste paraense.

No Nordeste Paraense alguns agricultores familiares têm implantado pequenas áreas de pastagens e manejado pequenos rebanhos com o objetivo de aplicar eventuais ganhos obtidos com os cultivos, criando uma poupança a ser utilizada nas necessidades futuras da família ou da propriedade. Há indícios de problemas nas pastagens e no rebanho que limitam tanto a produção e a sustentabilidade da pecuária, como comprometem os cultivos agrícolas que realmente sustentam a propriedade. Este estudo tratou de identificar as principais limitações e propor alternativas de manejo que sejam econômica e ecologicamente mais sustentáveis. Na primeira fase do estudo, numa amostra ao acaso de 38 propriedades, descreveu-se o manejo da pastagem e do rebanho, e na segunda, numa amostra menor, de doze propriedades e por um período de 29 meses, avaliou-se o potencial desses dois componentes. As propriedades estudadas desenvolvem uma pecuária de baixa produtividade. Devido à baixa fertilidade do solo e o deficiente manejo, as pastagens não suprem os alimentos necessários ao rebanho, tanto em quantidade como em qualidade. Também foram identificadas deficiências no manejo do rebanho, próprias de sistemas extensivos. Contudo, as limitações podem ser solucionadas com práticas amplamente conhecidas de manejo da pastagem (como formação, manutenção e manejo) e do rebanho (reprodução, manejo de bezerros e sanidade em geral). Novos modelos de exploração também foram sugeridos

Interleukin-18: A Mediator of Inflammation and Angiogenesis in Rheumatoid Arthritis

Interleukin-18 (IL-18) is a highly regulated inflammatory cytokine that is elevated in synovial tissues and synovial fluids of patients with rheumatoid arthritis (RA) compared with patients with osteoarthritis (OA) and patients with other arthropathies. Within the RA joint, IL-18 can contribute to the inflammatory process by inducing leukocyte extravasation through upregulation of endothelial cell adhesion molecules, the release of chemokines from RA synovial fibroblasts, and directly as a monocytes, lymphocyte, and neutrophil chemoattractant. IL-18 can also help maintain and develop the inflammatory pannus by inducing endothelial cell migration and angiogenesis. IL-18 does this directly by binding and activating endothelial cells and indirectly by inducing RA synovial fibroblasts to produce angiogenic chemokines and vascular endothelial growth factor. IL-18 is present in RA synovial fluid in high levels, where it functions as an angiogenic mediator and leukocyte chemoattractant. IL-18 mediates all these inflammatory processes by binding to its receptor, IL-18 receptor, and initiating the activation of different signaling cascades leading to changes in target cells gene expression and behavior. IL-18 has been identified as a potential therapeutic target in the treatment of RA.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90485/1/jir-2E2011-2E0050.pd

The response of the smallholder farm to the introduction of cattle in eastern amazon: the case of the Bragantina region.

Editado por Reinhard Lieberei, Helmut Bianchi, Vera Boehm, Christoph Reisdorff