An EAP-EHash authentication method adapted to resource constrained terminals

In the era of mobile and wireless networks, the growing complexity of end devices and the accentuated tendency towards miniaturization of them raise new security challenges. Authentication is a crucial concern in resource constrained environments, and despite the great number of existing EAP methods, as explained in the article, we are still in need for EAP methods tightly adapted to wireless environments and satisfying heterogeneity of terminals and their limitations of resources. After a first comparative analysis of existing EAP methods, this article presents a new EAP-EHash method (EHash for encrypted hash) that is adapted to the highly vulnerable wireless environment by supporting mutual authentication and session key derivation and offering simplicity, rapidity, and easy-to-deploy features. This EAP-EHash was formally proven to satisfy the claimed security properties, thanks to the AVISPA tool. Implementation of it on an 802.11 testbed platform gave realistic authentication delays averaging 26 ms and thus proved that EAP-EHash is competitive to EAP-MD5 that is known to be the simplest of the EAP methods. Features of EAP-EHash include short execution delays and low bandwidth consumption, and as such, it appears attractive for wireless.     

Celtic steel – an evaluation of depot finds

In the course of archaeological excavations on the Gründberg in Linz/Austria, several depots containing a total of 45 steel objects were discovered. These depots had been set up around 100 before Christ (BC). 25 objects were used to take samples for metallographic and microanalytical investigations. In the exercise of his trade, the Celtic smith could resort to different steel grades: non‐alloyed, carbon alloyed, phosphorus alloyed. The technique applied was that of fire‐forging single pieces of steel ‐ which had previously been widened by hammering – to give flat bars showing a multi‐layer structure. For workpieces with special requirements with regard both to hardness and to toughness, a number of carefully selected flat bars with differing contents of alloying metals were bonded by forge welding, which produced a compound material. Hardening by cold working as well as by torquing was already known to these Celtic craftsmen. To obtain tools with a hard edge and a tough core, cementation was used.     

On the verification of membrane systems with dynamic structure

We study computational properties of Gheorge Păun’s P-systems extended with rules that model in an abstract way creation, dissolution, fusion and cloning of membranes. We investigate decision problems like reachability of a configuration, boundedness (finiteness of the state space), and coverability (verification of safety properties). Our analysis is aimed at understanding the expressive power of rules that dynamically modify the structure of a membrane.     

ChunkStream: Interactive streaming of structured data

We present ChunkStream, a system for efficient streaming and interactive editing of online video. Rather than using a specialized protocol and stream format, ChunkStream makes use of a generic mechanism employing chunks. Chunks are fixed-size arrays that contain a mixture of scalar data and references to other chunks. Chunks allow programmers to expose large, but fine-grained, data structures over the network.ChunkStream represents video clips using simple data types like linked lists and search trees, allowing a client to retrieve and work with only the portions of the clips that it needs. ChunkStream supports resource-adaptive playback and “live” streaming of real-time video as well as fast, frame-accurate seeking; bandwidth-efficient high-speed playback; and compilation of editing decisions from a set of clips. Benchmarks indicate that ChunkStream uses less bandwidth than HTTP Live Streaming while providing better support for editing primitives.     

DNA replication of human papillomavirus type 31 is modulated by elements of the upstream regulatory region that lie 5' of the minimal origin

The viral replication factors E1 and E2 of papillomaviruses are necessary and sufficient to replicate plasmids containing the minimal origin of DNA replication in transient assays. Under physiological conditions, the upstream regulatory region (URR) governs expression of the early viral genes. To determine the effect of URR elements on E1 and E2 expression specifically, and on the regulation of DNA replication during the various phases of the viral life cycle, we carried out a systematic replication study with entire genomes of human papillomavirus type 31 (HPV31), a high-risk oncogenic type. We constructed a series of URR deletions, spacer replacements, and point mutations to analyze the role of the keratinocyte enhancer (KE) element, the auxiliary enhancer (AE) domain, and the L1-proximal end of the URR (5'-URR domain) in DNA replication during establishment, maintenance, and vegetative viral DNA amplification. Using transient and stable replication assays, we demonstrate that the KE and AE are necessary for efficient E1 and E2 gene expression and that the KE can also directly modulate viral replication. KE-mediated activation of replication is dependent on the position and orientation of the element. Mutation of either one of the four Ap1 sites, the single Sp1 site, or the binding site for the uncharacterized footprint factor 1 reduced replication efficiency through decreased expression of E1 and E2. Furthermore, the 5'-URR domain and the Oct1 DNA binding site are dispensable for viral replication, since such HPV31 mutants are able to replicate efficiently in a transient assay, maintain a stable copy number over several cell generations, and amplify viral DNA under vegetative conditions. Interestingly, deletion of the 5'-URR domain leads to increased transient and stable replication levels. These findings suggest that elements in the HPV31 URR outside the minimal origin modulate viral replication through both direct and indirect mechanisms.     

Crystalline organization and toughening: example of polyamide-12

Improving the impact resistance of plastics is a key to many applications. Today, dispersing rubber and inorganic particles into semicrystalline polymers is widely used to increase their impact strength without greatly altering other interesting properties such as elastic modulus or chemical resistance. Yet, the underlying mechanisms controlling such toughening are controversial. Hitherto it has been often suggested that a critical distance between particles which controls the brittle-to-tough transition is an intrinsic property of the polymer. On the contrary, we demonstrate here that differences in crystalline organization of the matrix can induce dramatic changes in toughening efficiency. A thermal treatment and microscopic observations strongly suggest that crystalline orientation, size of crystalline grains and molecular organization at grain boundaries play a determinant role in the toughening mechanisms. These observations may have important implications for designing and manufacturing tough plastic materials.     

Effect of an oxygen plasma treatment on the specific surface of platinum electrodeposits for fuel cells

Fuel cells involve electrochemical reactions often catalysed by platinum whose surface has to be maximized. In this paper, platinum nano-particles are deposited onto graphite by a potentiostatic reduction of a dilute 1.0 mM solution of hexachloroplatinate acid. Some samples are pre-treated by highly dissociated oxygen plasma and exhibit an increase of their specific surface compared to the untreated ones. The gain factor on specific surface reaches 3.6 and even 4.4 when the plasma treatment is coupled with the impregnation technique. Surface functionalization made by the plasma treatment lead to denser deposits thanks to an organized nucleation and growth of platinum nuclei. XPS analyses suggest the existence of C–O bonds in the platinum clusters. Although the testing conditions were not optimized, we have measured the performances of a microfuel cell made with the optimized catalyst. The Scharifker and Hills electrocrystallisation model was used to fit the current transients. Untreated samples transients were correctly fitted by the model whereas plasma treated samples transients did not have the requested shape for this model. Hence, nucleation mechanism was determined and confirmed by observation on untreated samples only. The calculated value of the diffusion coefficient of the Pt(IV) anion PtCl₆²⁻ determined by the Cottrell theory was close to the literature, i.e. 2.6 ± 0.6 × 10⁻⁶ cm² s⁻¹.     

Phonoreception in some Coleoptera infesting stored products

Mechanoreceptors that could be phonoreceptive were located and studied in Sitophilus oryzae (L.), with preliminary tests also on Sitophilus granarius (L.). Tribolium confusum (Herbst), Attagenus piceus (Olivier), and Trogoderma inclusum LeC. Various behavioral responses of tethered (mounted) beetles were used as indices of reception of air-borne and solid-borne sounds of known frequencies and pound pressure levels. The probable receptors for air-borne sounds in S. oryzae are the well developed Johnston's organs in the second antennal segments, and tactile hairs on the bodies. Both are primarily sensitive to air movements or contact, and sounds are active only at relatively high intensities or in the near-field. The probable receptors for solid-borne sounds (vibrations) are chordotonal organs of the legs, which have relatively high sensitivity, and possibly the muscle receptor organs of the body wall. These four potential phonoreceptors are described and figured. The low sensitivity to air-borne sounds and high sensitivity to solid-borne sounds is probably related to the specialized habits of these insects.     

Probabilistic algorithms for computing resolvent representations of regular differential ideals

In a previous article (Cluzeau and Hubert in Appl Algebra Eng Commun Comput 13(5):395–425, 2003), we proved the existence of resolvent representations for regular differential ideals. The present paper provides practical algorithms for computing such representations. We propose two different approaches. The first one uses differential characteristic decompositions whereas the second one proceeds by prolongation and algebraic elimination. Both constructions depend on the choice of a tuple over the differential base field and their success relies on the chosen tuple to be separating. The probabilistic aspect of the algorithms comes from this choice. To control it, we exhibit a family of tuples for which we can bound the probability that one of its element is separating.