A novel cryptoprocessor architecture for chained Merkle signature scheme

One-time signature schemes rely on hash functions and are, therefore, assumed to be resistant to attacks by quantum computers. These approaches inherently raise a key management problem, as the key pair can be used only for one message. That means, for one-time signature schemes to work, the sender must deliver the verification key together with the message and the signature. Upon reception, the receiver has to verify the authenticity of the verification key before verifying the signature itself. Hash-tree based solutions tackle this problem by basing the authenticity of a large number of verification keys on the authenticity of a root key. This approach, however, causes computation, communication, and storage overhead. Due to hardware acceleration, this paper proposes, for the first time, a processor architecture which boosts the performance of a one-time signature scheme without degrading memory usage and communication properties. This architecture realizes the chained Merkle signature scheme on the basis of Winternitz one-time signature scheme. All operations, i.e., key generation, signing, and verification are implemented on an FPGA platform, which acts as a coprocessor. Timing measurements on the prototype show a performance boost of at least one order of magnitude compared to an identical software solution.     

Science and technology in the region: The output of regional science and technology, its strengths and its leading institutions

Summary We operationalize scientific output in a region by means of the number of articles (as in the SciSearch database) per year and technology output by means of the number of patent applications (as in the database of the European Patent Office) per priority year. All informetric analyses were done using the DIALOG online-system. The main research questions are the following: Which scientific and technological fields or topics are most influent within a region and which institutions or companies are mainly publishing articles or holding patents? Do the distributions of regional science and technology fields and of publishing institutions follow the well-known informetric function? Are there - as it is expected - only few fields and few institutions which dominate the region? Is there a connection between the economic power of a region and the regional publication and patent output? Examples studied in detail are seven German regions: Aachen, Düsseldorf, Hamburg, Köln (Cologne), Leipzig - Halle - Dessau, München (Munich), and Stuttgart. Three different indicators were used, science and technology attraction of a region (number of scientific articles and patents), science and technology intensity (articles and patents per 1,000 inhabitants), and science and technology density (articles and patents per 1 billion EURO gross value added). Top region concerning both attraction and intensity is Munich, concerning density it is Aachen.     

Morphology and mechanical properties of poly(propylene)/polystyrene blends compatibilized with polystyrene-block-poly(ethylene-co-propylene)

Compatibilizing effects of diblock copolymer polystyrene-block-poly(ethylene-co-propylene) (SEP) on the morphology and mechanical properties of immiscible blends of poly(propylene) (PP) and polystyrene (PS) were investigated. Notched impact strength, yield stress, elongation at yield and Young's modulus were determined as a function of different weight ratios of PP and PS and different amounts of added SEP as well. Scanning electron microscopy revealed a two-phase morphology of PP/PS blends, which exhibit poor mechanical properties. Even 2,5 wt.-% of SEP added to PP/PS blends can improve the notched impact strength and elongation at yield compared to non-compatibilized PP/PS blends. 10 wt.-% of SEP compatibilizer converted the brittle PP/PS blend to quite impactresistant polymeric material. Mechanical properties were improved because of the morphological changes and increased interfacial adhesion as a result of SEP localization between PP and PS phases. An analysis of yield stress data in terms of theoretical models showed that yield stress values of binary PP/PS blends can be predicted with Nielsen's model.     

Photobleaching Reveals Heterogeneous Stoichiometry for Equinatoxin II Oligomers

Equinatoxin II (EqtII), a sea anemone cytolysin, is known to oligomerize to form pores that spontaneously insert into membranes. Crystallographic and cryo‐EM studies of structurally similar cytolysins offer contradictory evidence for pore stoichiometry. Here we used single‐molecule photobleaching of fluorescently labeled EqtII to determine the stoichiometry of EqtII oligomers in supported lipid bilayers. A frequency analysis of photobleaching steps revealed a log‐normal distribution of stoichiometries with a mean of 3.4±2.3 standard deviations. Comparison of our experimental data with simulations of fixed stoichiometries supports our observation of a heterogeneous distribution of EqtII oligomerization. These data are consistent with a model of EqtII stoichiometry where pores are on average tetrameric, but with large variation in the number of subunits in individual pores.     

Young Scientists – Juniorprofessor Gregor D. Wehinger stellt sich vor

This article introduces assistant professor Gregor D. Wehinger of the Institute of Chemical and Electrochemical Process Engineering at Clausthal University of Technology. Besides recent research projects and teaching activities, he gives an overview about his commitment to the community. He reports on current research results in the field of CFD modeling of packed-bed reactors, redox-flow batteries, and multiphase systems. Furthermore, the use of virtual reality in teaching is presented.     

Synthesis and Antiangiogenic Properties of Tetrafluorophthalimido and Tetrafluorobenzamido Barbituric Acids

The development of novel thalidomide derivatives as immunomodulatory and anti‐angiogenic agents has revived over the last two decades. Herein we report the design and synthesis of three chemotypes of barbituric acids derived from the thalidomide structure: phthalimido‐, tetrafluorophthalimido‐, and tetrafluorobenzamidobarbituric acids. The latter were obtained by a new tandem reaction, including a ring opening and a decarboxylation of the fluorine‐activated phthalamic acid intermediates. Thirty compounds of the three chemotypes were evaluated for their anti‐angiogenic properties in an ex vivo assay by measuring the decrease in microvessel outgrowth in rat aortic ring explants. Tetrafluorination of the phthalimide moiety in tetrafluorophthalimidobarbituric acids was essential, as all of the nonfluorinated counterparts lost anti‐angiogenic activity. An opening of the five‐membered ring and the accompanying increased conformational freedom, in case of the corresponding tetrafluorobenzamidobarbituric acids, was well tolerated. Their activity was retained, although their molecular structures differ in torsional flexibility and possible hydrogen‐bond networking, as revealed by comparative X‐ray crystallographic analyses.     

Dynamic Methanation of CO2 – Effect of Concentration Forcing

Investigating the effect of concentration forcing of the CO₂ methanation is not only relevant for power‐to‐gas plants but also for the study of dynamic phenomena of this reaction. In this study a Ni/Al₂O₃ catalyst is investigated under concentration forcing at industrially relevant conditions. The dynamic experiments allow an evaluation in terms of the reaction rate and enable the study of the reaction mechanism. The experiments show that no methane is formed in the CO₂‐rich part of the cycle, whereas a fast hydrogenation of carbonaceous species to methane takes place upon switching to H₂.     

An empirical examination of application frameworks success based on technology acceptance model

Framework-based development is currently regarded as one of the most promising software development approaches when it comes to improvements in lead time, productivity and quality. However, many frameworks and projects based on frameworks still report failures, which indicate that there are problems related to both frameworks technology and frameworks usage. The objective of our research was to examine the major drivers that have an impact on a framework’s acceptance and a framework’s success. We used the technology acceptance model (TAM) and Seddon’s information systems success model as our underlying theory. Data collected from an online survey of 389 active framework users was used to test hypothesized models. Data analysis was performed via structural equation modeling. Our findings support the post-adoption version of TAM and the relationship between continuous use and the successful use of systems, where more use also means more net benefits. We found that the successful use of frameworks is mainly dependent on two factors: continuous framework usage intention and the perceived usefulness of the framework. Several practical and theoretical implications can be foreseen including advances in framework development guidelines and insight into the relationship between the acceptance and success of frameworks.     

Focus on Extracellular Vesicles: Development of Extracellular Vesicle-Based Therapeutic Systems

Many types of cells release phospholipid membrane vesicles thought to play key roles in cell-cell communication, antigen presentation, and the spread of infectious agents. Extracellular vesicles (EVs) carry various proteins, messenger RNAs (mRNAs), and microRNAs (miRNAs), like a “message in a bottle” to cells in remote locations. The encapsulated molecules are protected from multiple types of degradative enzymes in body fluids, making EVs ideal for delivering drugs. This review presents an overview of the potential roles of EVs as natural drugs and novel drug-delivery systems.     

Application of Two Independent Measurement Techniques for Determination of Ductile Crack Growth Initiation

Charpy impact testing of the high strength low-alloyed steel has been performed by simultaneously recording two independent signals. The magnetic emission (ME) and potential drop (PD) techniques were used to determine critical crack initiation properties on standard three-point pre-cracked bending specimens at room temperature. Both signals (ME and PD) were recorded by digital oscilloscope with a high sampling rate and compared, with the purpose of more precise identification of critical fracture mechanics parameters determining the onset of ductile crack growth. This revised version was published online in July 2006 with corrections to the Cover Date.