Experimental Study on Acoustic Emission of Weakly Cemented Sandstone considering Bedding Angle

Uniaxial compression experiments and acoustic emission (AE) tests were conducted on weakly consolidated sandstone samples with bedding angle of 0°, 45°, and 90° collected from Xiaojihan coal mine in Shaanxi Province, China; the acoustic emission (AE) characteristics of bedding sandstone were investigated, including the influencing mechanism of bedding angle on characteristics, spatial distribution, and b value changes of AE activity. According to the research, AE ringing counting rate and energy rate are the highest and energy release is intense during the loading process when the bedding angle is 0°, and these values decrease and the energy release is gentle with rising of the angle. Based on spatial distribution, the number of AE events was the largest and cluster phenomenon occurs between the bedding plane when the bedding inclination was 0°, which decreased and sprouted along the plane of bedding plane at 45° and which was smaller and evenly distributed in the space at 90°. With the increase of bedding angle, the proportion of large-scale microcracks decreases and the variation range of microcracks narrows down. Therefore, under the same uniaxial compression conditions, the b value increases by the increase of bedding angle. The research results offer reliable reference to carry out monitoring work on acoustic emission and microseism of mine with layer rock (rock mass).

Wilfred Harris' Early Description of Cluster Headache

Wilfred Harris was a London neurologist with a significant interest in the treatment of neuralgia. Harris' descriptions of what he called migrainous neuralgia were the first recorded of cluster headache in the English medical literature. He was probably one of the first to describe the cluster phenomenon itself and the effectiveness of ergotamine in treating acute attacks of cluster headache. His seminal contributions to the clinical and therapeutic spectrum of cluster headache are reviewed.

Evidence from a Nine-Year Birth Cohort Study in Japan of Transmission Pathways of Helicobacter pyloriInfection

We examined the longitudinal changes of Helicobacter pylori infection within 46 families with children and 48 couples without children living in Japan. The study cohort was monitored from 1986 to 1994. H. pylori status was assessed by the presence of anti-H. pylori immunoglobulin G antibodies. At study entry, H. pylori prevalence in children with positive mothers was 23% versus 5% in children with negative mothers (odds ratio = 5.3; 95% confidence interval = 0.6 to 42.8). Seroconversion (rate of 1.5%/year) was evident only among children living with positive mothers and did not differ among adults living with or without children. These data strongly support the cluster phenomenon of H. pylori infection among families, the key role of the infected mothers in the transmission within families, and the importance of adult-child transmission and not vice versa.

Clustered Microsatellite Mutations in the Pipefish Syngnathus typhle

Clustered mutations are copies of a mutant allele that enter a population's gene pool together due to replication from a premeiotic germline mutation and distribution to multiple successful gametes of an individual. Although the phenomenon has been studied in Drosophila and noted in a few other species, the topic has received scant attention despite claims of being of major importance to population genetics theory. Here we capitalize upon the reproductive biology of male-pregnant pipefishes to document the occurrence of clustered microsatellite mutations and to estimate their rates and patterns from family data. Among a total of 3195 embryos genetically screened from 110 families, 40% of the 35 detected de novo mutant alleles resided in documented mutational clusters. Most of the microsatellite mutations appeared to involve small-integer changes in repeat copy number, and they arose in approximately equal frequency in paternal and maternal germlines. These findings extend observations on clustered mutations to another organismal group and motivate a broader critique of the mutation cluster phenomenon. They also carry implications for the evolution of microsatellites with respect to mutational models and homoplasy among alleles.