An SDN-based Approach For Defending Against Reflective DDoS Attacks

Distributed Reflective Denial of Service (DRDoS) attacks are an immanent threat to Internet services. The potential scale of such attacks became apparent in March 2018 when a memcached-based attack peaked at 1.7 Tbps. Novel services built upon UDP increase the need for automated mitigation mechanisms that react to attacks without prior knowledge of the actual application protocols used. With the flexibility that software-defined networks offer, we developed a new approach for defending against DRDoS attacks; it not only protects against arbitrary DRDoS attacks but is also transparent for the attack target and can be used without assistance of the target host operator. The approach provides a robust mitigation system which is protocol-agnostic and effective in the defense against DRDoS attacks

Rapid growth in agricultural trade: effects on global area efficiency and the role of management

Cropland is crucial for supplying humans with biomass products, above all, food. Globalization has led to soaring volumes of international trade, resulting in strongly increasing distances between the locations where land use takes place and where the products are consumed. Based on a dataset that allows tracing the flows of almost 450 crop and livestock products and consistently allocating them to cropland areas in over 200 nations, we analyze this rapidly growing spatial disconnect between production and consumption for the period from 1986 to 2009. At the global level, land for export production grew rapidly (by about 100 Mha), while land supplying crops for direct domestic use remained virtually unchanged. We show that international trade on average flows from high-yield to low-yield regions: compared to a hypothetical no-trade counterfactual that assumes equal consumption and yield levels, trade lowered global cropland demand by almost 90 Mha in 2008 (3-year mean). An analysis using yield gap data (which quantify the distance of prevailing yields to those attainable through the best currently available production techniques) revealed that differences in land management and in natural endowments contribute almost equally to the yield differences between exporting and importing nations. A comparison of the effect of yield differences between exporting and importing regions with the potential of closing yield gaps suggests that increasing yields holds greater potentials for reducing future cropland demand than increasing and adjusting trade volumes based on differences in current land productivity.Peer Reviewe

Flow Velocity Characterization in an Experimental Flume

Only seventeen percent of the United States’ energy generation in 2017 came from renewable sources, and hydroelectric power makes up a about forty percent of this. Hydroelectric power has large potential for growth, as new technologies develop. In particular, low-head dams and weirs across the country provide potential sources to harness more energy. Unfortunately, a lot of existing weirs have large economic and environmental impacts, and there has been little work done to improve the infrastructure and design of weirs themselves. In order to best analyze the effects of dams and weirs in a laboratory environment, experimental flumes can be used to simulate open channel flow of rivers and streams. The purpose of this research is to provide an understanding and process to characterize flow velocities in an experimental flume. Reviews of literature were used to guide purchasing decisions on equipment viable to suit the needs of the laboratory. Methods have included obtaining a slotted weir design and characterizing flow through and around the weir with yarn. In addition to this, a pitot tube and Hach FH950 electromagnetic sensor have been used to compare flow velocities in the open channel flume. Each measurement device was tested at varying flow velocities by altering the cross-sectional area of the flow and keeping the flow rate constant. To this point, flow characterized through the weir has behaved as expected, with increased flow velocity through the slot of the weir. The results of experiments characterizing flow in an open channel can be adapted to measure velocities through a modular slotted weir design to guide future weir construction projects to be used in conjunction with turbines to produce hydroelectric power. Therefore, it is important to develop a functioning measurement system and process in order to aid in future research, investigations, and educational projects involving experimental flumes.No embargoAcademic Major: Mechanical Engineerin

Enhanced gene silencing by the application of multiple specific small interfering RNAs

AbstractSmall interfering RNA duplexes (siRNA) induce gene silencing in various eukaryotic cells, although usually in an incomplete manner. Using chemically synthesized siRNAs targeting the HIV-1 co-receptor CXCR4 or the apoptosis-inducing Fas-ligand (FasL), co-transfection of cells with two or more siRNA duplexes targeting different sites on the same mRNA resulted in an enhanced gene silencing compared with each single siRNA. This was shown in the down-regulation of protein and mRNA expression, and functionally in the inhibition of CXCR4-mediated HIV infection and of FasL-mediated cell apoptosis. Transfection efficiency determined for the FasL-specific siRNAs was dose-dependent and varied among the siRNAs tested, but was not the main reason for the enhanced gene silencing

Differential proportionality - a normalization-free approach to differential gene expression

AbstractGene expression data, such as those generated by next generation sequencing technologies (RNA-seq), are of an inherently relative nature: the total number of sequenced reads has no biological meaning. This issue is most often addressed with various normalization techniques which all face the same problem: once information about the total mRNA content of the origin cells is lost, it cannot be recovered by mere technical means. Additional knowledge, in the form of an unchanged reference, is necessary; however, this reference can usually only be estimated. Here we propose a novel method where sample normalization is unnecessary, but important insights can be obtained nevertheless. Instead of trying to recover absolute abundances, our method is entirely based on ratios, so normalization factors cancel by default. Although the differential expression of individual genes cannot be recovered this way, the ratios themselves can be differentially expressed (even when their constituents are not). Yet, most current analyses are blind to these cases, while our approach reveals them directly. Specifically, we show how the differential expression of gene ratios can be formalized by decomposing log-ratio variance (LRV) and deriving intuitive statistics from it. Although small LRVs have been used to detect proportional genes in gene expression data before, we focus here on the change in proportionality factors between groups of samples (e.g. tissue-specific proportionality). For this, we propose a statistic that is equivalent to the squared t-statistic of one-way ANOVA, but for gene ratios. In doing so, we show how precision weights can be incorporated to account for the peculiarities of count data, and, moreover, how a moderated statistic can be derived in the same way as the one following from a hierarchical model for individual genes. We also discuss approaches to deal with zero counts, deriving an expression of our statistic that is able to incorporate them. In providing a detailed analysis of the connections between the differential expression of genes and the differential proportionality of pairs, we facilitate a clear interpretation of new concepts. The proposed framework is applied to a data set from GTEx consisting of 98 samples from the cerebellum and cortex, with selected examples shown. A computationally efficient implementation of the approach in R has been released as an addendum to the propr package.1</jats:p

Association of Symptomatic Human Infection with Toxoplasma gondii with Imbalance of Monocytes and Antigen-Specific T Cell Subsets

During recent symptomatic toxoplasmosis, alterations in quantity and function of mononuclear cellsin peripheral blood were observed. Flow cytofluorometric analysis and differential leukocyte counts revealed increasedabsolute numbers of T8 + cells, Leu 7 + (natural killer/killer) cells, and monocytes. T4+ cells and HLA-DR+ cells were not significantly changed. T4/T8 cell ratios were reversed in symptomatic toxoplasmosis (0.7 ± 0.3) and normal in chronic infection (1.7 ± 0.5). Toxoplasma antigen induced higher numbers of T8 + and TQ1 + cells in four T cell lines from two individuals with symptomatic infection than in five T cell lines from three individuals with asymptomatic infection. Eight cloned T cell lines produced γ interferon in an antigen-specific fashion and in higher amounts when they originated from an asymptomatic subject than from a symptomatic subject. These results indicate that marked alterations in properties of immunoregulatory cells are characteristic of recent symptomatic toxoplasmosis. The transient immune dysfunction may be a major part of the observed disease and/or a feature of successful parasitis

Magnetic excitations and amplitude fluctuations in insulating cuprates

We present results from light scattering experiments on three insulating antiferromagnetic cuprates, YBa$_2$Cu$_3$O$_{6.05}$, Bi$_2$Sr$_2$YCu$_2$O$_{8+\delta}$, and La$_2$CuO$_4$ as a function of polarization and excitation energy {using samples of the latest generation. From the raw data we derive symmetry-resolved spectra.} The spectral shape in $B_{1g}$ symmetry is found to be nearly universal and independent of the excitation energy. The spectra agree quantitatively with predictions by field theory [\onlinecite{Weidinger:2015}] facilitating the precise extraction of the Heisenberg coupling $J$. {In addition, the asymmetric line shape on the high-energy side is found to be related to amplitude fluctuations of the magnetization. In La$_2$CuO$_4$ alone minor contributions from resonance effects may be identified.} The spectra in the other symmetries are not universal. The variations may be traced back to weak resonance effects and extrinsic contributions. For all three compounds we find support for the existence of chiral excitations appearing as a continuum in $A_{2g}$ symmetry having an onset slightly below $3J$. In La$_2$CuO$_4$ an additional isolated excitation appears on top of the $A_{2g}$ continuum.Comment: 8 pages, 7 figure

Aitchison's Compositional Data Analysis 40 Years On: A Reappraisal

The development of John Aitchison's approach to compositional data analysis is followed since his paper read to the Royal Statistical Society in 1982. Aitchison's logratio approach, which was proposed to solve the problematic aspects of working with data with a fixed sum constraint, is summarized and reappraised. It is maintained that the principles on which this approach was originally built, the main one being subcompositional coherence, are not required to be satisfied exactly -- quasi-coherence is sufficient, that is near enough to being coherent for all practical purposes. This opens up the field to using simpler data transformations, such as power transformations, that permit zero values in the data. The additional principle of exact isometry, which was subsequently introduced and not in Aitchison's original conception, imposed the use of isometric logratio transformations, but these are complicated and problematic to interpret, involving ratios of geometric means. If this principle is regarded as important in certain analytical contexts, for example unsupervised learning, it can be relaxed by showing that regular pairwise logratios, as well as the alternative quasi-coherent transformations, can also be quasi-isometric, meaning they are close enough to exact isometry for all practical purposes. It is concluded that the isometric and related logratio transformations such as pivot logratios are not a prerequisite for good practice, although many authors insist on their obligatory use. This conclusion is fully supported here by case studies in geochemistry and in genomics, where the good performance is demonstrated of pairwise logratios, as originally proposed by Aitchison, or Box-Cox power transforms of the original compositions where no zero replacements are necessary.Comment: 26 pages, 18 figures, plus Supplementary Material. This is a complete revision of the first version of this paper, placing the geochemical example upfront and adding a large section on CoDA of wide matrice