Corrosion Behaviour of Type 316L Stainless Steel in Hot Caustic Aqueous Environments

Metals and Materials International - The corrosion behaviour of type 316L stainless steel in aqueous 30–50 wt%. NaOH at temperatures up to 90 °C has been elucidated....     

Secure Distributed Key Generation for Discrete-Log Based Cryptosystems

A Distributed Key Generation (DKG) protocol is an essential component of threshold cryptosystems required to initialize the cryptosystem securely and generate its private and public keys. In the case of discrete-log-based (dlog-based) threshold signature schemes (ElGamal and its derivatives), the DKG protocol is further used in the distributed signature generation phase to generate one-time signature randomizers (r = g^k). In this paper we show that a widely used dlog-based DKG protocol suggested by Pedersen does not guarantee a uniformly random distribution of generated keys: we describe an efficient active attacker controlling a small number of parties which successfully biases the values of the generated keys away from uniform. We then present a new DKG protocol for the setting of dlog-based cryptosystems which we prove to satisfy the security requirements from DKG protocols and, in particular, it ensures a uniform distribution of the generated keys. The new protocol can be used as a secure replacement for the many applications of Pedersen's protocol. Motivated by the fact that the new DKG protocol incurs additional communication cost relative to Pedersen's original protocol, we investigate whether the latter can be used in specific applications which require relaxed security properties from the DKG protocol. We answer this question affirmatively by showing that Pedersen's protocol suffices for the secure implementation of certain threshold cryptosystems whose security can be reduced to the hardness of the discrete logarithm problem. In particular, we show Pedersen's DKG to be sufficient for the construction of a threshold Schnorr signature scheme. Finally, we observe an interesting trade-off between security (reductions), computation, and communication that arises when comparing Pedersen's DKG protocol with ours.     

Determination of copper in water by means of chalcocite copper ion-selective electrode

The possibility of determination of copper in natural waters was tested by direct potentiometry with chalcocite copper sensitive ion selective electrode. This can be carried out for the copper concentration down to 6 μg l⁻¹ when the standard additions procedure is used. The electrode characteristics was investigated and as a medium was proposed a TFB solution containing Tris, potassium fluoride and potassium nitrate. However at the extreme low concentrations of copper the water samples after addition of TFB should be heated to boiling. In these conditions the accuracy of determination for the average of five measurements is not worse than 25%, and precision is of the order of 20%.     

N2- and C8-substituted oligodeoxynucleotides with enhanced thrombin inhibitory activity in vitro and in vivo

2'-Deoxyguanosine (G) analogues carrying various hydrophobic substituents in the N2 and C8 positions were synthesized and introduced through solid-phase synthesis into 15-mer oligodeoxynucleotide, GGTTGGTGTGGTTGG, which forms a chairlike structure consisting of two G-tetrads and is a potent thrombin inhibitor. The effects of the substitutions at N2 and C8 of the G-tetrad-forming G residues on the thrombin inhibitory activity are relatively small, suggesting that these substitutions cause relatively small perturbations on the chairlike structure formed by the oligodeoxynucleotide. Introduction of a benzyl group into N2 of G6 and G11 and naphthylmethyl groups into N2 of G6 increased the thrombin inhibitory activity, whereas other substituents in these positions had almost no effect or decreased the activity. Particularly, the oligodeoxynucleotide carrying a 1-naphthylmethyl group in the N2 position of G6 showed an increase in activity by about 60% both in vitro and in vivo. Substitutions on the N2 position of other G residues had little effect or decreased the activity. Introduction of a relatively small group, such as methyl and propynyl, into the C8 positions of G1, G5, G10, and G14 increased the activity, presumably due to the stabilization of a chairlike structure, whereas introduction of a large substituent group, phenylethynyl, decreased the activity, probably due to the steric hindrance.     

A New Analyzer Based on Pellistor Sensor with Neural Network Data Postprocessing for Measurement of Hydrocarbons in Lower Explosive Limit Range

We present the results of a first stage of development work on a new type of analyzer for hydrogen and C₁–C₃ hydrocarbons concentration measurements in the lower explosive limit range, based on single pellistor sensor with artificial neural network data postprocessing.     

A new static field solver with open boundary conditions in the3D-CAD-system MAFIA

The numerical solution of Maxwell's equations involves calculation in a finite volume enclosing the structure of interest. Using simple Dirichlet or Neumann boundary conditions causes inaccuracies or requires excessively large meshes. For a static problem, which can be reduced to a scalar potential problem that can be described by Poisson's equation, it is shown that one can formulate more accurate boundary conditions. A multipole expansion of the well-known solutions of the Poisson equation can be used to yield better boundary values from the neighboring inner potentials. This modified formulation is used in solving electrostatic and magnetostatic problems with the recently developed solver of the 3-D CAD system MAFIA, which solves Maxwell's equations for a very broad range of applications