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.     

Faith is not enough: A response to the Baltes-Schaie claim that intelligence does not wane.

Faith has been defined as unfounded belief in the occurrence of the improbable. This seems to describe well the adherence of P. B. Baltes and K. W. Schaie (see PA, Vol 52:5053; also Schaie—Vol 53:7133) to a claim that little or no important age-related intellectual decline occurs. In replying to criticisms of their arguments that such decline is myth, the present paper argues that Baltes and Schaie (1976) have (a) obscured the basic points at issue by raising diversionary questions about plasticity and "dialectical posture"; (b) advanced the untenable argument that the search for lawful explanation of complex phenomena is futile; (c) fallaciously argued that criticisms are suspect unless they are based on a "theory-free" inductive interpretation of findings; (d) ignored results indicating decline and positive bias in the very data cited to support their argument for the myth of intellectual decline; (e) failed to explain what is systematic about the significance of the omnibus F test for cohort "effects," beyond what can parsimoniously be accounted for in terms of the confounded age variable; (f) not responded to reasoning suggesting that between-cohort differences in education, if these account for important intellectual variation, should be reflected in a manner contrary to what is actually observed; and (g) asserted that no statistically reliable age decrement occurs in a set of data for which analyses demonstrate statistically significant linear decline. (18 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

How to obtain and use X-Ray projection microscopy in the SEM

The primary electron beam of an SEM is used to generate a point source of x-rays, permitting x-ray microscopy within the SEM. The practical device described fits into the sample chamber of an SEM. Exact and reproducible adjustabilities of the sample support and the film holder allow two x-ray micrographs, e.g. stereo-micrographs, to be taken in one run without repressurization of the specimen chamber. By comparing x-ray and SEM micrographs of the same sample in the identical position it is possible to get additional information concerning surface morphology and inner structure of a specimen.     

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.