Probabilistic considerations on the effect of specimen size on the critical chloride content in reinforced concrete

A probabilistic model was used to predict the critical chloride content (C_crit) for reinforcement corrosion as a function of specimen size. The specimen size is likely to be a reason for the large scatter of C_crit values as well as for the high threshold levels often observed in laboratory setups. Regarding test methods, it is discussed that the common combination of small specimens and low numbers of parallel samples results in poor reproducibility. If experimental data is to be used for service life modelling, the geometrical dimensions of the specimens on which C_crit was measured have to be taken into account.     

Short communication: Staphylococcus aureus isolated from colostrum of dairy heifers represent a closely related group exhibiting highly homogeneous genomic and antimicrobial resistance features

In heifers, intramammary infections caused by Staphylococcus aureus affect milk production and udder health in the first and subsequent lactations, and can lead to premature culling. Not much is known about Staph. aureus isolated from heifers and it is also unclear whether or not these strains are readily transmitted between heifers and lactating herd mates. In this study, we compared phenotypic characteristics, spa types, and DNA microarray virulence and resistance gene profiles of Staph. aureus isolates obtained from colostrum samples of dairy heifers with isolates obtained from lactating cows. Our objective was to (1) characterize Staph. aureus strains associated with mastitis in heifers and (2) determine relatedness of Staph. aureus strains from heifers and lactating cows to provide data on transmission. We analyzed colostrum samples of 501 heifers and milk samples of 68 lactating cows within the same herd, isolating 48 and 9 Staph. aureus isolates, respectively. Staphylococcus aureus strains from heifers, lactating herd mates, and an unrelated collection of 78 strains from bovine mastitis milk of mature cows were compared. With 1 exception each, characterization of all strains from heifers and lactating cows in the same herd yielded highly similar phenotypic and genotypic results. The strains were Staphaurex latex agglutination test negative (Oxoid AG, Basel, Switzerland) and belonged to agr type II, CC705, and spa types tbl 2645 and t12926. They were susceptible to all antimicrobial agents tested. In contrast, the strains from mature cows in other herds were spread across different clonal complexes, spa types, and SplitsTree clusters (http://www.splitstree.org/), thus displaying a far higher degree of heterogeneity. We conclude that strains isolated from colostrum of heifers and mastitis milk of lactating cows in the same herd feature highly similar phenotypic and genomic characteristics, suggesting persistence of the organism during the first and potentially subsequent lactations or transmission between heifers and mature herd mates.     

Cascade ciphers: The importance of being first

The security of cascade ciphers, in which by definition the keys of the component ciphers are independent, is considered. It is shown by a counterexample that the intuitive result, formally stated and proved in the literature, that a cascade is at least as strong as the strongest component cipher, requires the uninterestingly restrictive assumption that the enemy cannot exploit information about the plaintext statistics. It is proved, for very general notions of breaking a cipher and of problem difficulty, that a cascade is at least as difficult to break as the first component cipher. A consequence of this result is that if the ciphers commute, then a cascade is at least as difficult to break as the most-difficult-to-break component cipher, i.e., the intuition that a cryptographic chain is at least as strong as its strongest link is then provably correct. It is noted that additive stream ciphers do commute, and this fact is used to suggest a strategy for designing secure practical ciphers. Other applications in cryptology are given of the arguments used to prove the cascade cipher result. The results of this paper were presented in part at the 1990 IEEE Symposium on Information Theory, January 14–19, 1990, San Diego, California.     

The Shared Proteome of the Apomictic Fern Dryopteris affinis ssp. affinis and Its Sexual Relative Dryopteris oreades

Ferns are a diverse evolutionary lineage, sister to the seed plants, which is of great ecological importance and has a high biotechnological potential. Fern gametophytes represent one of the simplest autotrophic, multicellular plant forms and show several experimental advantages, including a simple and space-efficient in vitro culture system. However, the molecular basis of fern growth and development has hardly been studied. Here, we report on a proteomic study that identified 417 proteins shared by gametophytes of the apogamous fern Dryopteris affinis ssp. affinis and its sexual relative Dryopteris oreades. Most proteins are predicted to localize to the cytoplasm, the chloroplast, or the nucleus, and are linked to enzymatic, binding, and structural activities. A subset of 145 proteins are involved in growth, reproduction, phytohormone signaling and biosynthesis, and gene expression, including homologs of SHEPHERD (SHD), HEAT SHOCK PROTEIN 90-5 (CR88), TRP4, BOBBER 1 (BOB1), FLAVONE 3’-O-METHYLTRANSFERASE 1 (OMT1), ZEAXANTHIN EPOXIDASE (ABA1), GLUTAMATE DESCARBOXYLASE 1 (GAD), and dsRNA-BINDING DOMAIN-LIKE SUPERFAMILY PROTEIN (HLY1). Nearly 25% of the annotated proteins are associated with responses to biotic and abiotic stimuli. As for biotic stress, the proteins PROTEIN SGT1 HOMOLOG B (SGT1B), SUPPRESSOR OF SA INSENSITIVE2 (SSI2), PHOSPHOLIPASE D ALPHA 1 (PLDALPHA1), SERINE/THREONINE-PROTEIN KINASE SRK2E (OST1), ACYL CARRIER PROTEIN 4 (ACP4), and NONHOST RESISTANCE TO P. S. PHASEOLICOLA1 (GLPK) are worth mentioning. Regarding abiotic stimuli, we found proteins associated with oxidative stress: SUPEROXIDE DISMUTASE[CU-ZN] 1 (CSD1), and GLUTATHIONE S-TRANSFERASE U19 (GSTU19), light intensity SERINE HYDROXYMETHYLTRANSFERASE 1 (SHM1) and UBIQUITIN-CONJUGATING ENZYME E2 35 (UBC35), salt and heavy metal stress included MITOCHONDRIAL PHOSPHATE CARRIER PROTEIN 3 (PHT3;1), as well as drought and thermotolerance: LEA7, DEAD-BOX ATP-DEPENDENT RNA HELICASE 38 (LOS4), and abundant heat-shock proteins and other chaperones. In addition, we identified interactomes using the STRING platform, revealing protein–protein associations obtained from co-expression, co-occurrence, text mining, homology, databases, and experimental datasets. By focusing on ferns, this proteomic study increases our knowledge on plant development and evolution, and may inspire future applications in crop species.     

Local randomness in pseudorandom sequences

The concept of provable cryptographic security for pseudorandom number generators that was introduced by Schnorr is investigated and extended. The cryptanalyst is assumed to have infinite computational resources and hence the security of the generators does not rely on any unproved hypothesis about the difficulty of solving a certain problem, but rather relies on the assumption that the number of bits of the generated sequence the enemy can access is limited. The concept of perfect local randomness of a sequence generator is introduced and investigated using some results from coding theory. The theoretical and practical cryptographic implications of this concept are discussed. Possible extensions of the concept of local randomness as well as some applications are proposed.A preliminary version of this paper was presented at Crypto '89, Santa Barbara, and will appear in the proceedings.     

On the oracle complexity of factoring integers

The problem of factoring integers in polynomial time with the help of an infinitely powerful oracle who answers arbitrary questions with yes or no is considered. The goal is to minimize the number of oracle questions. LetN be a given compositen-bit integer to be factored, wheren = log₂ N. The trivial method of asking for the bits of the smallest prime factor ofN requiresn/2 questions in the worst case. A non-trivial algorithm of Rivest and Shamir requires onlyn/3 questions for the special case whereN is the product of twon/2-bit primes. In this paper, a polynomial-time oracle factoring algorithm for general integers is presented which, for any >0, asks at most n oracle questions for sufficiently largeN, thus solving an open problem posed by Rivest and Shamir. Based on a plausible conjecture related to Lenstra's conjecture on the running time of the elliptic curve factoring algorithm, it is shown that the algorithm fails with probability at mostN ^–/2 for all sufficiently largeN.     

Minimal Complete Primitives for Secure Multi-Party Computation

The study of minimal cryptographic primitives needed to implement secure computation among two or more players is a fundamental question in cryptography. The issue of complete primitives for the case of two players has been thoroughly studied. However, in the multi-party setting, when there are n > 2 players and t of them are corrupted, the question of what are the simplest complete primitives remained open for t n/3. (A primitive is called complete if any computation can be carried out by the players having access only to the primitive and local computation.) In this paper we consider this question, and introduce complete primitives of minimal cardinality for secure multi-party computation. The cardinality issue (number of players accessing the primitive) is essential in settings where primitives are implemented by some other means, and the simpler the primitive the easier it is to realize. We show that our primitives are complete and of minimal cardinality possible for most cases.     

Patient's and therapist's views of early alliance building in dynamic psychotherapy: Patterns and relation to outcome.

Patients and therapists have somewhat divergent perspectives of alliance. Usually in psychotherapy research, the focus is on the patient's view of alliance, predicting parts of outcome. This study questions this hypothesis by applying the shape-of-change procedure to patient's and therapist's view of alliance-building processes in dynamic psychotherapy. The results of this naturalistic study indicate that none of the 3 patient patterns is related to outcome at the end of psychotherapy, but a specific therapist's pattern--out of 2--is linked to positive symptom change. These results are discussed in the context of present research on therapeutic alliance, especially in terms of level and process, its measurement, and potential in predicting outcome in dynamic psychotherapy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Diffusion potentials in porous mortar in a moisture state below saturation

Diffusion potentials (membrane potentials) were measured in mortar in a moisture state below saturation for the first time. In contrast to conventional diffusion cell setups, the experimental approach was based on embedded ion selective electrodes. A numerical model with coupled Nernst-Planck equations for the most abundant species in the pore solution allowed simulating ion transport processes and the correspondingly arising diffusion potentials. It was found that Portland cement mortar with a water/cement ratio of 0.6 does not exhibit any significant permselective behaviour - even not in an unsaturated state determined by self-desiccation. Apparently, the stable radius of water-filled capillaries is still large enough to allow ionic transport through those fractions of pore solution that are unaffected by double layer effects. In addition, the relative importance of liquid junction potentials at the reference electrode/sample interface and internal diffusion or membrane potentials are discussed with respect to application of direct potentiometry to cement based materials.