Deckschichtbildung und Korrosionsverhalten des hochsiliciumlegierten austenitischen Sonderstahls X 2 CrNiSi 18 15 in Salpetersäuren

The Formation of Surface Films and the Corrosion Resistance of the Silicon Containing Austenitic Steel X 2 CrNiSi 18 15 in Nitric Acids The oxide layers consist of two parts: the lower one is mainly Croxide, the upper one is SiO₂. ESCA and AAS measurements were made in order to study the formation of the surface layer on the austenitic steel X2 CrNiSi 18 15 in nitric acids. A film, which is chromium oxide, is formed first. On top of this film a second film consisting of SiO₂ grows. The elements nickel and manganese are not found in the formation of the oxide films. Immediately below the oxide layer the steel is enrichened with chromium and depleted of iron. In order to find the in some cases very small corrosion rates (5 · 10^?5 mm · a^?1) in a reproducible manner, the amounts of iron, chromium and nickel which had been dissolved were measured by means of the AAS method as a function of time. For stationary samples apparent activation energies of 65.2 kJ/Mol (azeotropic nitric acid) and 37.5 kJ/Mol (highly concentrated nitric acid), respectively, were found. These data confirm the assumption that the corrosion rate is determined by reactions at the phase boundaries. No appreciable influence of the flow velocity on the corrosion rate was detected.     

Good news for commuters: better and faster rapid transit

Rail signal systems have traditionally been employed to prevent collision of trains while permitting them to adhere to a schedule that is adequate for moving passengers and/or freight. In today's rapid-transit systems, however, the corollary objectives of a signal system?namely, controlling the speed of trains, increasing the capacity of the line, and minimizing schedule disruptions caused by transient disturbances in train operations?are critical to providing satisfactory service to passengers.     

Engineering thermal stability in RNA phage capsids via disulphide bonds

The RNA bacteriophages, a group that includes phages Qbeta and MS2, have a number of potential bionanotechnological applications, including cell specific drug delivery and as substrates for the formation of novel materials. Despite extensive sequence identity between their coat protein subunits, and an almost identical three-dimensional fold, Qbeta and MS2 capsids have dramatically different thermal stabilities. The increased stability of Qbeta has been correlated with the inter-subunit disulphide bonds present in that capsid and not present in MS2. We have tested this hypothesis directly using mass spectrometry. Analysis of the dissociated coat protein subunits suggests that inter-molecular disulphides are formed at the capsid five-fold but may not be at the three-fold axes. This conclusion has been tested by engineering disulphide cross-links into either the five-fold or three-fold positions of the recombinant MS2 capsid. Five-fold cross-linking results in a mutant with stability properties similar to those of Qbeta. Three-fold cross-linking results in a mutant unable to assemble T = 3 shells, implying that five-fold structures are on pathway to capsid assembly in these phages. The results demonstrate how it is possible to redesign the physical properties of phage shells and may be of general relevance to future applications of viruses and virus-like particles.     

Dämpfungsuntersuchungen an aufgestickten Eisen-Molybdän- und Eisen-Vanadin-Legierungen

Dämpfungsmessungen an aufgestickten Reineisenlegierungen mit Molybdän- und Vanadingehalten zwischen 0,7 und 4%. Einfluß des Stickstoffgehaltes, der Wärmebehandlung und des Verformungsgrades auf die Ausbildung der verschiedenen Dämpfungshöchstwerte. Erörterung der Ergebnisse.     

Time Diversity with Adaptive Error Detection to Combat Rayleigh Fading in Digital Mobile Radio

A new diversity technique is proposed to combat Rayleigh fading in digital mobile radio systems transmitting speech signals. The speech signals are μ-law PCM encoded (mu = 255, 8 kHz sampling, 8 bits/code word, 64 kbit/s data rate), and alternate data words are used to form two streams called "odd" and "even." The even stream is delayed by τ seconds and the streams are interleaved prior to radio transmission using two-level PSK modulation. At the receiver the odd data stream is delayed by τ and interleaved with the even stream. Consequently, if an error burst occurs, the effect of the reshuffling of the data stream is, in general, to place words with bit errors in juxtaposition to those correctly received. After μ-law PCM decoding of the words, a statistical error detection strategy is evoked to identify the erroneous samples. These samples are replaced by adjacent sample interpolation to give the recovered speech sequence. No recourse to channel protection coding is made. In our experiments a Rayleigh fading envelope was generated from a hardware simulator and stored in a computer, along with four sentences of speech. The system was then simulated and the recovered speech perceived. The objective performance measures were segmental SNR for the audio signal, and BER. Different error detection strategies were examined and restrictions on τ investigated. For a mobile speed of 30 mph, SNR values of 32, 21, and 16 dB were obtained for BER values of 0.1, 1, and 2 percent, corresponding to SNR gains over an uncorrected system of 3, 9, and 11 dB, respectively.     

Human abilities revealed through auditory tests.

Used established findings from studies of visual, musical, and speech perception abilities to guide the construction of auditory ability tests. 44 measures based on these tests were obtained from a sample of 241 adult males (mean age 25.64 yrs). Correlation and factorial analyses were used to indicate structural interrelationships and relationships with education, musical experience, general intelligence, and age. The results indicate separate capacities for Auditory Verbal Comprehension, Auditory Immediate Memory, Temporal Tracking, Auditory Cognition of Relationships, Discrimination Among Sound Patterns, Speech Perception Under Distraction/Distortion, and Maintaining and Judging Rhythm. (61 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hydrothermal durability of Ca-polyester complexed polymer concrete

Polymer concretes (PC) consisting of an unsaturated polyester (UP)-styrene (St) copolymer binder and a silica-type aggregate possess very poor hydrothermal durability because of the hydrolytic instability of the carboxylic ester existing in the main chains of the UP. It was found that the addition of beta dicalcium silicate (β-C₂S) as a filler in the PC helps to prevent the severe physical degradation of UP-PC which occurs when the hydrolysis reactions take place. This is due to the formation of ionic bonding between the strongly nucleophilic reagent Ca²⁺ ions released from β-C₂S in an aqueous medium and the carboxylate anions (?COO^?) of esters. UP-PC specimens containing Ca²⁺ ion complexed bridge structures of ionic bonding in their main chains display significant improvement in hydrothermal stability at elevated temperatures. In addition, the interaction mechanism of UP with β-C₂S occurring during exposure in an autoclave is also discussed from the results of infrared absorption analysis.     

On the scientific basis of ability testing.

Presents an overview of the development of a science of human abilities and discusses some of the criticisms of the derivative technology of mental testing. The criticisms concern the general misunderstanding of the premises and methodologies of mental-ability research, the magnification of disputes about technical issues that have little practical import, and the premature conversion of theoretical understandings of intelligence into the meaning and interpretation of IQ scores. A plea is entered for support of an objective science of mental abilities by the public and by the psychological profession at large. (54 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The speed of sound in non-equilibrium gas-liquid flow: Predicting the onset of choked flow in the vents of a sodium-water heat exchanger

In the event of a water leak into the sodium in a sodium-water heat exchanger the products of the reaction must be vented from the system. In order to predict the possible behaviour of the two-phase reaction products as they are expelled through the venting system an analysis has been performed to determine the speed of sound and the factors affecting the onset of choking in a gas—liquid bubble flow. In particular the influence of velocity and temperature non-equilibrium between the phases is examined.