PotLLL: A Polynomial Time Version of LLL With Deep Insertions

Lattice reduction algorithms have numerous applications in number theory, algebra, as well as in cryptanalysis. The most famous algorithm for lattice reduction is the LLL algorithm. In polynomial time it computes a reduced basis with provable output quality. One early improvement of the LLL algorithm was LLL with deep insertions (DeepLLL). The output of this version of LLL has higher quality in practice but the running time seems to explode. Weaker variants of DeepLLL, where the insertions are restricted to blocks, behave nicely in practice concerning the running time. However no proof of polynomial running time is known. In this paper PotLLL, a new variant of DeepLLL with provably polynomial running time, is presented. We compare the practical behavior of the new algorithm to classical LLL, BKZ as well as blockwise variants of DeepLLL regarding both the output quality and running time.Comment: 17 pages, 8 figures; extended version of arXiv:1212.5100 [cs.CR

The Effect of Central Exit Examinations on Student Achievement: Quasi-experimental Evidence from TIMSS Germany

This paper makes use of the regional variation in schooling legislation within the German secondary education system to estimate the causal effect of central exit examinations on student performance. We propose a difference-in-differences framework that exploits the quasi-experimental nature of the German TIMSS middle-school sample. The estimates show that students in federal states with central exit examinations clearly outperform students in other federal states, but that only part of the difference can be attributed to central exit examinations. Our results suggest that central examinations increase student achievement by about one third school year equivalent.education, central examinations, difference-in-differences, quasi-experiment

Group Communication Patterns for High Performance Computing in Scala

We developed a Functional object-oriented Parallel framework (FooPar) for high-level high-performance computing in Scala. Central to this framework are Distributed Memory Parallel Data structures (DPDs), i.e., collections of data distributed in a shared nothing system together with parallel operations on these data. In this paper, we first present FooPar's architecture and the idea of DPDs and group communications. Then, we show how DPDs can be implemented elegantly and efficiently in Scala based on the Traversable/Builder pattern, unifying Functional and Object-Oriented Programming. We prove the correctness and safety of one communication algorithm and show how specification testing (via ScalaCheck) can be used to bridge the gap between proof and implementation. Furthermore, we show that the group communication operations of FooPar outperform those of the MPJ Express open source MPI-bindings for Java, both asymptotically and empirically. FooPar has already been shown to be capable of achieving close-to-optimal performance for dense matrix-matrix multiplication via JNI. In this article, we present results on a parallel implementation of the Floyd-Warshall algorithm in FooPar, achieving more than 94 % efficiency compared to the serial version on a cluster using 100 cores for matrices of dimension 38000 x 38000

The role of the actin regulators cyclase-associated proteins (CAP) in growth cone function and neuron differentiation

Wiring of the brain is established by axons, which elongate from a neuron and are guided through the brain to their target neurons. Growth cones are actin-rich structures located at the tips of axons and are responsible for sensing environmental cues as well as controlling directed axonal outgrowth. Motility and function of growth cones are mediated by underlying actin dynamics, which in turn are regulated by actin-binding proteins (ABPs). Among these proteins is the family of cyclase-associated proteins (CAPs), which comprises two members (CAP1, CAP2), which are both expressed in the brain. Despite recent progress in uncovering their molecular function in actin dynamics, their physiological role during brain development remains largely unknown. Therefore, we used knockout (KO) mouse models for both CAPs to investigate their function in brain development. We found both proteins expressed in the embryonic brain as well as in cultured neurons and being localized within growth cones. CAP1-KO brains displayed impaired fiber track formation, but had no alterations in neuron migration or precursor proliferation. In addition, CAP1-KO neurons were delayed in development and exhibited shorter and thicker neurites. This was accompanied by enlarged growth cones, which had fewer filopodia, reduced motility, impaired actin dynamics and consequently disturbed responses to guidance cues. Instead, the loss of CAP2 did not cause any changes in brain morphology or neuron differentiation. Alterations in differentiation and morphology in CAP1-KO neurons as well as growth cone size could be rescued by overexpression of either CAP1 or CAP2, suggesting functional redundancy of both proteins. Further analysis exploiting CAP1 mutants revealed that the helical fold domain and therefore the interaction with the actin regulator cofilin1 is important in mediating growth cone function. Establishing a neuron replating protocol to study early neuron differentiation and growth cone function upon knockout of either CAP1, cofilin1 or both ABPs allowed a more detailed analysis on the functional interaction of CAP1 and cofilin1 in the growth cone. This approach revealed that both proteins synergistically regulate F-actin dynamics within the growth cone and that they are functionally dependent on each other. Taken together, this study showed that CAP1 and CAP2 are redundant in regulating growth cone function in vitro, but that CAP1 is the dominant family member in neuron differentiation and brain development. Furthermore, this study provides a new protocol for studying protein function during early aspects of neuron differentiation and showed that CAP1 and cofilin1 functionally interact in the growth cone and regulate its dynamics, thereby providing new insights into the physiological role of CAP1-cofilin1 interaction

Raffinose in Chloroplasts is Synthesized in the Cytosol and Transported across the Chloroplast Envelope

In chloroplasts, several water-soluble carbohydrates have been suggested to act as stress protectants. The trisaccharide raffinose (α-1,6-galactosyl sucrose) is such a carbohydrate but has received little attention. We here demonstrate by compartmentation analysis of leaf mesophyll protoplasts that raffinose is clearly (to about 20%) present in chloroplasts of cold-treated common bugle (Ajuga reptans L.), spinach (Spinacia oleracea L.) and Arabidopsis [Arabidopsis thaliana (L.) Heynh.] plants. The two dedicated enzymes needed for raffinose synthesis, galactinol synthase and raffinose synthase, were found to be extra-chloroplastic (probably cytosolic) in location, suggesting that the chloroplast envelope contains a raffinose transporter. Uptake experiments with isolated Ajuga and Arabidopsis chloroplasts clearly demonstrated that raffinose is indeed transported across the chloroplast envelope by a raffinose transporter, probably actively. Raffinose uptake into Ajuga chloroplasts was a saturable process with apparent Km and vmax values of 27.8 mM and 3.3 μmol mg−1 Chl min−1, respectivel

Analysing Errors of Open Information Extraction Systems

We report results on benchmarking Open Information Extraction (OIE) systems using RelVis, a toolkit for benchmarking Open Information Extraction systems. Our comprehensive benchmark contains three data sets from the news domain and one data set from Wikipedia with overall 4522 labeled sentences and 11243 binary or n-ary OIE relations. In our analysis on these data sets we compared the performance of four popular OIE systems, ClausIE, OpenIE 4.2, Stanford OpenIE and PredPatt. In addition, we evaluated the impact of five common error classes on a subset of 749 n-ary tuples. From our deep analysis we unreveal important research directions for a next generation of OIE systems.Comment: Accepted at Building Linguistically Generalizable NLP Systems at EMNLP 201

Messung der akademischen Forschungsleistung in den Wirtschaftswissenschaften: Reputation vs. Zitierhäufigkeiten

This article discusses the provision of sophisticated architecture from the perspective of welfare economics. Given that rational real estate investors do not take into account the external effects of building design quality on the neighborhood, there is a risk of underinvestment into the external appearance of buildings in the market equilibrium. Whether public interventions as well as recent attempts to promote urban economic development by architectural landmark projects are justified, however, essentially depends on the existence of significant spillovers. On this background, we discuss evidence on architectural externalities available for Berlin, Germany and provide fist estimates of aggregated external benefit