Showing papers by "University of Luxembourg published in 2010"

The MicroRNA Spectrum in 12 Body Fluids

Abstract: BACKGROUND: MicroRNAs (miRNAs) are small, noncoding RNAs that play an important role in regulating various biological processes through their interaction with cellular messenger RNAs. Extracellular miRNAs in serum, plasma, saliva, and urine have recently been shown to be associated with various pathological conditions including cancer. METHODS: With the goal of assessing the distribution of miRNAs and demonstrating the potential use of miRNAs as biomarkers, we examined the presence of miRNAs in 12 human body fluids and urine samples from women in different stages of pregnancy or patients with different urothelial cancers. Using quantitativePCR,weconductedaglobalsurveyofthemiRNA distribution in these fluids. RESULTS: miRNAs were present in all fluids tested and showed distinct compositions in different fluid types. Several of the highly abundant miRNAs in these fluids werecommonamongmultiplefluidtypes,andsomeof the miRNAs were enriched in specific fluids. We also observeddistinctmiRNApatternsintheurinesamples obtained from individuals with different physiopathological conditions. CONCLUSIONS: MicroRNAs are ubiquitous in all the body fluid types tested. Fluid type–specific miRNAs may have functional roles associated with the surrounding tissues. In addition, the changes in miRNA spectra observed in the urine samples from patients with different urothelial conditions demonstrates the potential for using concentrations of specific miRNAs in body fluids as biomarkers for detecting and monitoring various physiopathological conditions. © 2010 American Association for Clinical Chemistry

Good Education in an Age of Measurement: Ethics, Politics, Democracy

Abstract: The widespread use of the measurement of educational outcomes in order to compare the performance of education within and across countries seems to express a real concern for the quality of education. This book argues that the focus on the measurement of educational outcomes has actually displaced questions about educational purpose. Biesta explores why the question as to what constitutes good education has become so much more difficult to ask and shows why this has been detrimental for the quality of education and for the level of democratic control over education. He provides concrete suggestions for engaging with the question of purpose in education in a new, more precise and more encompassing way, with explicit attention to the ethical, political and democratic dimensions of education.

Crowdfunding of Small Entrepreneurial Ventures

Abstract: An inherent problem that entrepreneurs face at the very beginning of their entrepreneurial initiative is to attract outside capital, given the lack of collateral and sufficient cash flows and the presence of significant information asymmetry with investors. Recently, some entrepreneurs have started to rely on the Internet to directly seek financial help from the general public (the “crowd”) instead of approaching financial investors such as business angels, banks or venture capital funds. This technique, called “crowdfunding”, has made possible to seek capital for project-specific investments as well as for starting up new ventures. In this book chapter (forthcoming in the Handbook of Entrepreneurial Finance at Oxford University Press), we discuss crowdfunding as an alternative way of financing projects, with a focus on small, entrepreneurial ventures. We provide a description of crowdfunding and discusses existing research on the topic, putting crowdfunding into perspective of entrepreneurial finance and thereby describing factors affecting entrepreneurial preferences for crowdfunding as source of finance. We elaborate different business models used to raise money from the crowd, in particular with respect to the structure of the crowdfunding process. Building on this discussion, we present and discuss extensively a case study, namely Media No Mad (a French startup). Finally we conclude with recommendations for entrepreneurs seeking to make use of crowdfunding and with suggestions for researchers about yet unexplored avenues of research.

GreenCloud: A Packet-Level Simulator of Energy-Aware Cloud Computing Data Centers

Abstract: Cloud computing data centers are becoming increasingly popular for the provisioning of computing resources. The cost and operating expenses of data centers have skyrocketed with the increase in computing capacity. Several governmental, industrial, and academic surveys indicate that the energy utilized by computing and communication units within a data center contributes to a considerable slice of the data center operational costs. In this paper, we present a simulation environment for energy-aware cloud computing data centers. Along with the workload distribution, the simulator is designed to capture details of the energy consumed by data center components (servers, switches, and links) as well as packet-level communication patterns in realistic setups. The simulation results obtained for two-tier, three- tier, and three-tier high-speed data center architectures demonstrate the effectiveness of the simulator in utilizing power management schema, such as voltage scaling, frequency scaling, and dynamic shutdown that are applied to the computing and networking components.

Trends in rainfall and economic growth in Africa: A neglected cause of the African growth tragedy

Abstract: We examine the role of rainfall trends in poor growth performance of sub-Saharan African nations relative to other developing countries, using a new cross-country panel climatic data set in an empirical economic growth framework. Our results show that rainfall has been a significant determinant of poor economic growth for African nations but not for other countries. Depending on the benchmark measure of potential rainfall, we estimate that the direct impact under the scenario of no decline in rainfall would have resulted in a reduction of between around 15% and 40% of today's gap in African GDP per capita relative to the rest of the developing world.

Complexity of the microRNA repertoire revealed by next-generation sequencing

Abstract: MicroRNAs (miRNAs) have been implicated to play key roles in normal physiological functions, and altered expression of specific miRNAs has been associated with a number of diseases. It is of great interest to understand their roles and a prerequisite for such study is the ability to comprehensively and accurately assess the levels of the entire repertoire of miRNAs in a given sample. It has been shown that some miRNAs frequently have sequence variations termed isomirs. To better understand the extent of miRNA sequence heterogeneity and its potential implications for miRNA function and measurement, we conducted a comprehensive survey of miRNA sequence variations from human and mouse samples using next generation sequencing platforms. Our results suggest that the process of generating this isomir spectrum might not be random and that heterogeneity at the ends of miRNA affects the consistency and accuracy of miRNA level measurement. In addition, we have constructed a database from our sequencing data that catalogs the entire repertoire of miRNA sequences (http://galas.systemsbiology.net/cgi-bin/isomir/find.pl). This enables users to determine the most abundant sequence and the degree of heterogeneity for each individual miRNA species. This information will be useful both to better understand the functions of isomirs and to improve probe or primer design for miRNA detection and measurement.

Holistic perception of individual faces in the right middle fusiform gyrus as evidenced by the composite face illusion

Abstract: The perception of a facial feature (e.g., the eyes) is influenced by the position and identity of other features (e.g., the mouth) supporting an integrated, or holistic, representation of individual faces in the human brain. Here we used an event-related adaptation paradigm in functional magnetic resonance imaging (fMRI) to clarify the regions representing faces holistically across the whole brain. In each trial, observers performed the same/different task on top halves (aligned or misaligned) of two faces presented sequentially. For each face pair, the identity of top and bottom parts could be both identical, both different, or different only for the bottom half. The latter manipulation resulted in a composite face illusion, i.e., the erroneous perception of identical top parts as being different, only for aligned faces. Release from adaptation in this condition was found in two sub-areas of the right middle fusiform gyrus responding preferentially to faces, including the "fusiform face area" ("FFA"). There were no significant effects in homologous regions of the left hemisphere or in the inferior occipital cortex. Altogether, these observations indicate that face-sensitive populations of neurons in the right middle fusiform gyrus are optimally tuned to represent individual exemplars of faces holistically.

DENS: Data Center Energy-Efficient Network-Aware Scheduling

Abstract: In modern data centers, energy consumption accounts for a considerably large slice of operational expenses. The state of the art in data center energy optimization is focusing only on job distribution between computing servers based on workload or thermal profiles. This paper underlines the role of communication fabric in data center energy consumption and presents a scheduling approach that combines energy efficiency and network awareness, termed DENS. The DENS methodology balances the energy consumption of a data center, individual job performance, and traffic demands. The proposed approach optimizes the tradeoff between job consolidation (to minimize the amount of computing servers) and distribution of traffic patterns (to avoid hotspots in the data center network).

The electronic structure of chalcopyrites—bands, point defects and grain boundaries

Abstract: We summarize the progress made recently in understanding the electronic structure of chalcopyrites. New insights into the dispersion of valence and conduction band allow conclusions on the effective masses of charge carriers and their orientation dependence, which influences the transport in solar cell absorbers of different orientation. Native point defects are responsible for the doping and thus the band bending in solar cells. Results of optoelectronic defect spectroscopy are reviewed. Native defects are also the source for a number of metastabilities, which strongly affect the efficiency of solar cells. Recent theoretical findings relate these effects to the Se vacancy and the InCu antisite defect. Experimentally determined activation energies support these models. Absorbers in chalcopyrite solar cells are polycrystalline, which is only possible because of the benign character of the grain boundaries. This can be related to an unusual electronic structure of the GB. Copyright © 2010 John Wiley & Sons, Ltd.

Automated and Scalable T-wise Test Case Generation Strategies for Software Product Lines

Abstract: Software Product Lines (SPL) are difficult to validate due to combinatorics induced by variability across their features. This leads to combinatorial explosion of the number of derivable products. Exhaustive testing in such a large space of products is infeasible. One possible option is to test SPLs by generating test cases that cover all possible T feature interactions (T-wise). T-wise dramatically reduces the number of test products while ensuring reasonable SPL coverage. However, automatic generation of test cases satisfying T-wise using SAT solvers raises two issues. The encoding of SPL models and T-wise criteria into a set of formulas acceptable by the solver and their satisfaction which fails when processed ``all-at-once''. We propose a scalable toolset using Alloy to automatically generate test cases satisfying T-wise from SPL models. We define strategies to split T-wise combinations into solvable subsets. We design and compute metrics to evaluate strategies on Aspect OPTIMA, a concrete transactional SPL.

Foundations of attack-defense trees

Abstract: We introduce and give formal definitions of attack-defense trees. We argue that these trees are a simple, yet powerful tool to analyze complex security and privacy problems. Our formalization is generic in the sense that it supports different semantical approaches. We present several semantics for attack-defense trees along with usage scenarios, and we show how to evaluate attributes.

Signatures of MicroRNAs and Selected MicroRNA Target Genes in Human Melanoma

Abstract: Small noncoding microRNAs (miRNA) regulate the expression of target mRNAs by repressing their translation or orchestrating their sequence-specific degradation. In this study, we investigated miRNA and miRNA target gene expression patterns in melanoma to identify candidate biomarkers for early and progressive disease. Because data presently available on miRNA expression in melanoma are inconsistent thus far, we applied several different miRNA detection and profiling techniques on a panel of 10 cell lines and 20 patient samples representing nevi and primary or metastatic melanoma. Expression of selected miRNAs was inconsistent when comparing cell line-derived and patient-derived data. Moreover, as expected, some discrepancies were also detected when miRNA microarray data were correlated with qPCR-measured expression levels. Nevertheless, we identified miRNA-200c to be consistently downregulated in melanocytes, melanoma cell lines, and patient samples, whereas miRNA-205 and miRNA-23b were markedly reduced only in patient samples. In contrast, miR-146a and miR-155 were upregulated in all analyzed patients but none of the cell lines. Whole-genome microarrays were performed for analysis of selected melanoma cell lines to identify potential transcriptionally regulated miRNA target genes. Using Ingenuity pathway analysis, we identified a deregulated gene network centered around microphthalmia-associated transcription factor, a transcription factor known to play a key role in melanoma development. Our findings define miRNAs and miRNA target genes that offer candidate biomarkers in human melanoma.

Precursor-mediated Crystallization Process in Suspensions of Hard Spheres

Abstract: We report on a large scale computer simulation study of crystal nucleation in hard spheres. Through a combined analysis of real- and reciprocal-space data, a picture of a two-step crystallization process is supported: First, dense, amorphous clusters form which then act as precursors for the nucleation of well-ordered crystallites. This kind of crystallization process has been previously observed in systems that interact via potentials that have an attractive as well as a repulsive part, most prominently in protein solutions. In this context the effect has been attributed to the presence of metastable fluid-fluid demixing. Our simulations, however, show that a purely repulsive system (that has no metastable fluid-fluid coexistence) crystallizes via the same mechanism.

Network-Independent Partner Selection and the Evolution of Innovation Networks

Abstract: Empirical research on strategic alliances has focused on the idea that partners are selected on the basis of social capital considerations. In this paper we emphasize instead the role of complementary knowledge stocks and knowledge dynamics, which have received surprisingly limited attention relative to social capital as forces behind the formation and dynamics of innovation networks. To marshal evidence in this regard, we design a simple model of partner selection in which firms ally for the purpose of learning and innovating, and in doing so create an industry network. We abstract completely from network-based structural and strategic motives for partner selection and focus instead on the idea that firms' knowledge bases must “fit” for joint learning and innovation to be possible, and thus for an alliance to be feasible. The striking result is that, despite containing no social capital considerations, this simple model replicates the firm conduct, network structure, and contingent effects of network position on performance observed and discussed in the empirical literature.

Curcumin―The Paradigm of a Multi-Target Natural Compound with Applications in Cancer Prevention and Treatment

Abstract: As cancer is a multifactor disease, it may require treatment with compounds able to target multiple intracellular components. We summarize here how curcumin is able to modulate many components of intracellular signaling pathways implicated in inflammation, cell proliferation and invasion and to induce genetic modulations eventually leading to tumor cell death. Clinical applications of this natural compound were initially limited by its low solubility and bioavailability in both plasma and tissues but combination with adjuvant and delivery vehicles was reported to largely improve bio-availability of curcumin. Moreover, curcumin was reported to act in synergism with several natural compounds or synthetic agents commonly used in chemotherapy. Based on this, curcumin could thus be considered as a good candidate for cancer prevention and treatment when used alone or in combination with other conventional treatments.

Harbor seal vibrissa morphology suppresses vortex-induced vibrations.

Abstract: SUMMARY Harbor seals ( Phoca vitulina ) often live in dark and turbid waters, where their mystacial vibrissae, or whiskers, play an important role in orientation. Besides detecting and discriminating objects by direct touch, harbor seals use their whiskers to analyze water movements, for example those generated by prey fish or by conspecifics. Even the weak water movements left behind by objects that have passed by earlier can be sensed and followed accurately (hydrodynamic trail following). While scanning the water for these hydrodynamic signals at a swimming speed in the order of meters per second, the seal keeps its long and flexible whiskers in an abducted position, largely perpendicular to the swimming direction. Remarkably, the whiskers of harbor seals possess a specialized undulated surface structure, the function of which was, up to now, unknown. Here, we show that this structure effectively changes the vortex street behind the whiskers and reduces the vibrations that would otherwise be induced by the shedding of vortices from the whiskers (vortex-induced vibrations). Using force measurements, flow measurements and numerical simulations, we find that the dynamic forces on harbor seal whiskers are, by at least an order of magnitude, lower than those on sea lion ( Zalophus californianus ) whiskers, which do not share the undulated structure. The results are discussed in the light of pinniped sensory biology and potential biomimetic applications.

Key recovery attacks of practical complexity on AES-256 variants with up to 10 rounds

Abstract: AES is the best known and most widely used block cipher. Its three versions (AES-128, AES-192, and AES-256) differ in their key sizes (128 bits, 192 bits and 256 bits) and in their number of rounds (10, 12, and 14, respectively). While for AES-128, there are no known attacks faster than exhaustive search, AES-192 and AES-256 were recently shown to be breakable by attacks which require 2176 and 299.5 time, respectively. While these complexities are much faster than exhaustive search, they are completely non-practical, and do not seem to pose any real threat to the security of AES-based systems. In this paper we aim to increase our understanding of AES security, and we concentrate on attacks with practical complexity, i.e., attacks that can be experimentally verified. We show attacks on reduced-round variants of AES-256 with up to 10 rounds with complexity which is feasible. One of our attacks uses only two related keys and 239 time to recover the complete 256-bit key of a 9-round version of AES-256 (the best previous attack on this variant required 4 related keys and 2120 time). Another attack can break a 10-round version of AES-256 in 245 time, but it uses a stronger type of related subkey attack (the best previous attack on this variant required 64 related keys and 2172 time). While the full AES-256 cannot be directly broken by these attacks, the fact that 10 rounds can be broken with such a low complexity raises serious concerns about the remaining safety margin offered by AES-256.

Cyberbullying as an Act of Revenge

Abstract: Despite significant overlaps between victim status in traditional forms of bullying and cyberbullying, and qualitative results about self-reported reasons for cyberbullying, the role of revenge and retaliation as a motive to engage in acts of cyberbullying has not yet been examined systematically. As a first step, this study investigates whether and to what extent traditional victims, when they become cyberbullies, actually choose their former (traditional) perpetrators as targets of their own cyberbullying behavior. Furthermore, the impact of individual differences in relevant traits, such as vengefulness and justice sensitivity, on the choice of cybervictims is examined. Data from 473 students were collected via an online survey. Of these, 149 were identified as traditional victims/cyberbullies. Results show that traditionally bullied students indeed tend to choose their former perpetrators as cybervictims, and that individual differences play a role in the choice of their victims. Implications for further research, as well as for interventions and prevention programmes, are discussed.

Stein’s method and Normal approximation of Poisson functionals

Abstract: We combine Stein’s method with a version of Malliavin calculus on the Poisson space. As a result, we obtain explicit Berry–Esseen bounds in Central limit theorems (CLTs) involving multiple Wiener–Ito integrals with respect to a general Poisson measure. We provide several applications to CLTs related to Ornstein–Uhlenbeck Levy processes.

The structure of academic self-concepts revisited: The nested Marsh/Shavelson model

Abstract: The nested Marsh/Shavelson (NMS) model integrates structural characteristics of academic self-concepts that have proved empirically incompatible in previous studies. Specifically, it conceives of academic self-concepts to be subject specific, strongly separated across domains, and hierarchically organized, with general academic self-concept at the top of the hierarchy. In Part 1 of the present study, data from a representative sample of eighth graders (N = 4,847) from Luxembourg showed that the NMS model captures the structure of self-concepts in six core subjects. In Part 2, the NMS model was integrated into a longitudinal extended internal/external frame-of-reference model. The developmental dynamics between general and subject-specific achievement, as measured in Grade 6, and the corresponding academic self-concepts in Grade 8 were examined, with data from a subsample of students (N = 3,045). Given its theoretical and empirical bases, the NMS model has clear potential to guide future research on academic self-concepts.

The dark side of global integration: Increasing tail dependence

Abstract: We measure stock market coexceedances using the methodology of Cappiello, Gerard and Manganelli (2005, ECB Working Paper 501). This method enables us to measure comovement at each point of the return distribution. First, we construct annual coexceedance probabilities for both lower and upper tail return quantiles using daily data from 1974–2006. Next, we explain these probabilities in a panel gravity model framework. Results show that macroeconomic variables asymmetrically impact stock market comovement across the return distribution. Financial liberalization significantly increases left tail comovement, whereas trade integration significantly increases comovement across all quantiles. Decreasing exchange rate volatility results in increasing lower tail comovement. The introduction of the euro increases comovement across the entire return distribution, thereby significantly reducing the benefits of portfolio diversification within the euro area.

Fresh re-keying: security against side-channel and fault attacks for low-cost devices

Abstract: The market for RFID technology has grown rapidly over the past few years. Going along with the proliferation of RFID technology is an increasing demand for secure and privacy-preserving applications. In this context, RFID tags need to be protected against physical attacks such as Differential Power Analysis (DPA) and fault attacks. The main obstacles towards secure RFID are the extreme constraints of passive tags in terms of power consumption and silicon area, which makes the integration of countermeasures against physical attacks even more difficult than for other types of embedded systems. In this paper we propose a fresh re-keying scheme that is especially suited for challenge-response protocols such as used to authenticate tags. We evaluate the resistance of our scheme against fault and side-channel analysis, and introduce a simple architecture for VLSI implementation. In addition, we estimate the cost of our scheme in terms of area and execution time for various security/performance trade-offs. Our experimental results show that the proposed re-keying scheme provides better security (and does so at less cost) than state-of-the-art countermeasures.

Indirect Measures of Sexual Interest in Child Sex Offenders A Multimethod Approach

Abstract: Although there is strong meta-analytical evidence that deviant sexual interest in children is a major risk factor for recidivism in child sex offenders, the assessment of deviant sexual interest with self-report or phallometric measures is problematic. As an alternative approach for assessment, the Explicit and Implicit Sexual Interest Profile (EISIP) is introduced. It features direct self-report and indirect latency-based measures (Implicit Association Tests [IATs] and viewing time measures) of sexual interest in adults and children. The reliability and validity of the EISIP was investigated using a selected sample of child sex offenders (n = 38) and offender (n = 37) and nonoffender (n = 38) controls. Among the indirect measures, viewing time measures showed higher reliability and convergent and criterion validity than the IATs. However, the IATs independently accounted for criterion variance in multivariate analyses. The combined indirect measures showed good discriminative validity between child sex offenders and controls.

Rotational cryptanalysis of ARX

Abstract: In this paper we analyze the security of systems based on modular additions, rotations, and XORs (ARX systems). We provide both theoretical support for their security and practical cryptanalysis of real ARX primitives. We use a technique called rotational cryptanalysis, that is universal for the ARX systems and is quite efficient. We illustrate the method with the best known attack on reduced versions of the block cipher Threefish (the core of Skein). Additionally, we prove that ARX with constants are functionally complete, i.e. any function can be realized with these operations.

Proteogenomic basis for ecological divergence of closely related bacteria in natural acidophilic microbial communities

Abstract: Bacterial species concepts are controversial. More widely accepted is the need to understand how differences in gene content and sequence lead to ecological divergence. To address this relationship in ecosystem context, we investigated links between genotype and ecology of two genotypic groups of Leptospirillum group II bacteria in comprehensively characterized, natural acidophilic biofilm communities. These groups share 99.7% 16S rRNA gene sequence identity and 95% average amino acid identity between their orthologs. One genotypic group predominates during early colonization, and the other group typically proliferates in later successional stages, forming distinct patches tens to hundreds of micrometers in diameter. Among early colonizing populations, we observed dominance of five genotypes that differed from each other by the extent of recombination with the late colonizing type. Our analyses suggest that the specific recombinant variant within the early colonizing group is selected for by environmental parameters such as temperature, consistent with recombination as a mechanism for ecological fine tuning. Evolutionary signatures, and strain-resolved expression patterns measured via mass spectrometry–based proteomics, indicate increased cobalamin biosynthesis, (de)methylation, and glycine cleavage in the late colonizer. This may suggest environmental changes within the biofilm during development, accompanied by redirection of compatible solutes from osmoprotectants toward metabolism. Across 27 communities, comparative proteogenomic analyses show that differential regulation of shared genes and expression of a small subset of the ∼15% of genes unique to each genotype are involved in niche partitioning. In summary, the results show how subtle genetic variations can lead to distinct ecological strategies.

Coevaporation of Cu2ZnSnSe4 thin films

Abstract: Cu2ZnSnSe4 thin films grown by coevaporation are investigated in a wide temperature range and for different Se partial pressures during growth. At temperatures higher than 350 °C Sn is re-evaporating as SnSe from the surface whereas Zn is lost at temperatures higher than 430 °C. Moreover the Se partial pressure dramatically changes the Zn and Sn concentrations in the resulting film. Interrupted processes at 380 °C show that single-stage coevaporation intrinsically induces a secondary phase at the substrate/film interface.