Detection of Axial Cracks in Pipes Using Focused Guided Waves

The implementation of synthetic guided wave focusing to locate axially aligned defects in pipes has been investigated. Results from both finite element computer models and experiments on real pipes are presented and the data show good agreement. Focusing is necessary to improve the reflection coefficient from axially aligned defects, as the signals are very weak. The Common Source Method (CSM) of synthetic focusing has been applied which makes it possible to apply focusing via post processing to previously collected data. The dependence of reflection coefficient on crack length was measured for both through thickness and part depth axially aligned defects, at a range of frequencies, using the torsional guided wave family. The results show that the reflection coefficient is approximately doubled when focusing is employed, compared to the sensitivity for unfocused fundamental torsional waves. However the sensitivity is still very low, so in practise this approach could only be used to find severe defects.     

Electron-microscopic examination of the transition zone of aluminum-tantalum bimetallic joints (explosion welding)

A study of the structure of an aluminum-tantalum joint and a comparison of this structure with the structures of iron-silver and copper-tantalum joints have revealed the following processes of the interpenetration of the materials that occur during explosion welding: the formation of protrusions, the injection of particles of one material into the other, and the formation of zones of local melting. Regardless of the mutual solubility of the metals being welded, two types of fragmentation occur, i.e., (1) a granulating fragmentation (GF), which includes the formation, explosion-governed (EG) dispersion, and partial consolidation of particles, and (2) the fragmentation that is usually observed during severe plastic deformation. It is important that this traditional fragmentation is not accompanied by the formation and EG dispersion of particles. This feature allows one to easily distinguish these types of fragmentation (traditional and GF fragmentation).     

Histone Tail Sequences Balance Their Role in Genetic Regulation and the Need To Protect DNA against Destruction in Nucleosome Core Particles Containing Abasic Sites

Abasic sites (AP) are produced 10 000 times per day in a single cell. Strand cleavage at AP is accelerated ≈100-fold within a nucleosome core particle (NCP) compared to free DNA. The lysine-rich N-terminal tails of histone proteins catalyze single-strand breaks through a mechanism used by base-excision-repair enzymes, despite the general dearth of glutamic acid, aspartic acid, and histidine—the amino acids that are typically responsible for deprotonation of Schiff base intermediates. Incorporating glutamic acid, aspartic acid, or histidine proximal to lysine residues in histone N-terminal tails increases AP reactivity as much as sixfold. The rate acceleration is due to more facile DNA cleavage of Schiff-base intermediates. These observations raise the possibility that histone proteins could have evolved to minimize the presence of histidine, glutamic acid, and aspartic acid in their lysine-rich N-terminal tails to guard against enhancing the toxic effects of DNA damage.     

Selection Criteria for Water Disinfection Techniques in Agricultural Practices

This paper comprises a selection tool for water disinfection methods for fresh produce pre- and postharvest practices. A variety of water disinfection technologies is available on the market and no single technology is the best choice for all applications. It can be difficult for end users to choose the technology that is best fit for a specific application. Therefore, the different technologies were characterized in order to identify criteria that influence the suitability of a technology for pre- or postharvest applications. Introduced criteria were divided into three principal components: (i) criteria related to the technology and which relate to the disinfection efficiency, (ii) attention points for the management and proper operation, and (iii) necessities in order to sustain the operation with respect to the environment. The selection criteria may help the end user of the water disinfection technology to obtain a systematic insight into all relevant aspects to be considered for preliminary decision making on which technologies should be put to feasibility testing for water disinfection in pre- and postharvest practices of the fresh produce chain.     

Is it possible for dislocations to self-lock after high-pressure torsion?

The evolution of the dislocation structure of the intermetallic compound Ni₃Ge upon high-pressure torsion has been investigated. It has been determined that, under certain conditions, subsequent heating without loading leads to the self-locking of dislocations, while in other cases, this does not take place. The role played by the lattice distortions that arise under torsion is emphasized.     

Social network architecture and the maintenance of deleterious cultural traits

How have changes in communications technology affected the way that misinformation spreads through a population and persists? To what extent do differences in the architecture of social networks affect the spread of misinformation, relative to the rates and rules by which individuals transmit or eliminate different pieces of information (cultural traits)? Here, we use analytical models and individual-based simulations to study how a ‘cultural load’ of misinformation can be maintained in a population under a balance between social transmission and selective elimination of cultural traits with low intrinsic value. While considerable research has explored how network architecture affects percolation processes, we find that the relative rates at which individuals transmit or eliminate traits can have much more profound impacts on the cultural load than differences in network architecture. In particular, the cultural load is insensitive to correlations between an individual''s network degree and rate of elimination when these quantities vary among individuals. Taken together, these results suggest that changes in communications technology may have influenced cultural evolution more strongly through changes in the amount of information flow, rather than the details of who is connected to whom.