A simple model for straggling evaluation

Some straggling models had largely been abandoned in favor of Monte Carlo simulations of straggling which are accurate but time consuming, limiting their application in practice. The difficulty of simple analytic models is the failure to give accurate values past 85% of the particle range. A simple model is derived herein based on a second order approximation upon which rapid analysis tools are developed for improved understanding of material charged particle transmission properties.     

The thermoelastic problem for a half-plane with an internal line crack

The problem considered is that of determining the thermoelastic stresses in the vicinity of an internal line crack in a half-plane. By using transform techniques it is reduced to that of solving a singular integral equation. Formulae are derived for the stress intensity factors and the energy of crack formation. Two particular cases are considered in detail and numerical results given.     

Grain growth in samples of aluminum containing alumina particles

A study of the two-dimensional and three-dimensional grain size distributions before and after grain growth treatments has been made in samples having a range of oxide contents. In order to collect statistically useful amounts of data, an automatic image analyzer was used and the resulting data were subjected to a series of statistical tests which evaluate the difference between related distributions. Normal grain growth was observed in samples of the lowest oxide content; as the oxide level was increased, a significant narrowing of the grain size distribution was observed. In the latter samples the maximum or limiting grain size measured after prolonged heat treatment is approximately one half that predicted by Zener and is in broad agreement with the values calculated from the models due to Hillert and Gladman. Anomalous grain growth has been observed in samples where normal grain growth is restricted and where the initial grain size distribution is very wide.     

自发演化下的传统小城镇多样性公共空间营造——威尔士考布里奇的历史经验

公共空间的场所营造是每个城镇更新会遇到的典型问题。本文以威尔士传统小城镇考布里奇为例,以考布里奇老镇区中的街道、院落、花园三种典型公共空间为研究对象,从平面形态、界面组织、场所利用、营造机理等方面,分析公共空间的多样性特征与实现方式,并进一步总结考布里奇城镇更新在转化地域历史环境特征、发挥普通民众影响作用、建立灵活弹性管理机制方面的经验,形成对中国传统小城镇更新的启示。     

Cigarette smoking and hearing loss: the epidemiology of hearing loss study

CONTEXT: Clinical studies have suggested that cigarette smoking may be associated with hearing loss, a common condition affecting older adults. OBJECTIVE: To evaluate the association between smoking and hearing loss. DESIGN: Population-based, cross-sectional study. SETTING: Community of Beaver Dam, Wis. PARTICIPANTS: Adults aged 48 to 92 years. Of 4541 eligible subjects, 3753 (83%) participated in the hearing study. MAIN OUTCOME MEASURES: The examination included otoscopy, screening tympanometry, and pure-tone air-conduction and bone-conduction audiometry. Smoking history was ascertained by self-report. Hearing loss was defined as a pure-tone average (0.5, 1, 2, and 4 kHz) greater than 25-dB hearing level in the worse ear. RESULTS: After adjusting for other factors, current smokers were 1.69 times as likely to have a hearing loss as nonsmokers (95% confidence interval, 1.31-2.17). This relationship remained for those without a history of occupational noise exposure and in analyses excluding those with non-age-related hearing loss. There was weak evidence of a dose-response effect. Nonsmoking participants who lived with a smoker were more likely to have a hearing loss than those who were not exposed to a household member who smoked (odds ratio, 1.94; 95% confidence interval, 1.01-3.74). CONCLUSIONS: These data suggest that environmental exposures may play a role in age-related hearing loss. If longitudinal studies confirm these findings, modification of smoking habits may prevent or delay age-related declines in hearing sensitivity.     

A comparison of impulsive and instrumental subgroups of batterers

The physiological interactions between the dentate gyrus (DG) and CA3 were studied in urethane-anesthetized rats by using field potential recording and current source density (CSD) analysis. Stimulation of CA3b resulted in a short-latency (<2.5-ms onset latency) antidromic population spike in both the DG and CA3c. An excitation (current sink) at the middle molecular layer (MML) was observed at 3-ms latency, possibly mediated by the backfiring of perforant path fibers that projected to both DG and CA3. CA3 stimulation also resulted in a sink at the dendritic layers of CA3c, which was likely mediated by excitatory CA3 recurrent collaterals. It was inferred that the DG was excited at the inner molecular layer (IML) after stimulation near the CA3b/CA3c border. This IML excitation (sink) probably resulted from orthodromic CA3 or hilar projections to the IML and not from mossy fiber backfiring. The IML and the CA3c dendritic sinks were blocked by an intracerebroventricular injection of a non-N-methyl-D-aspartate receptor antagonist, 6-cyano-7-nitroquinoxaline-2, 3-dione, but not by a gamma-aminobutyric acid type A (GABA(A)) receptor antagonist, bicuculline. CA3b stimulation evoked population spike bursts (3-7-ms latency) in both DG and CA3c when GABA(A) inhibition was suppressed by bicuculline, thus confirming that the excitatory afferents project from CA3b to DG and CA3c. A CA3 conditioning stimulus pulse given 30-200 ms before a perforant-path test pulse increased the amplitude of the perforant-path-evoked DG population spike (as compared with the test response without conditioning). After a moderate-intensity stimulation of CA3, a late (<20-ms latency) excitation of the MML of the DG was found. The late DG excitation was blocked by procaine injection at the medial perforant path, suggesting its origin from the medial entorhinal cortex. In conclusion, rich interactions between CA3 and other hippocampal structures were studied quantitatively by CSD analysis in vivo. We infer that CA3 provides an early excitatory feedback path to DG through recurrent collaterals or hilar interneurons and a late feedback through the medial entorhinal cortex.     

Low prevalence of hearing aid use among older adults with hearing loss: the Epidemiology of Hearing Loss Study

OBJECTIVES: To measure the prevalence of hearing aid use among older adults with hearing loss and to identify factors associated with those currently using hearing aids. DESIGN: Population-based cohort study. SETTING: The south-central Wisconsin community of Beaver Dam. PARTICIPANTS: A total of 1629 adults, aged 48 to 92 years, who have hearing loss and are participating in the Epidemiology of Hearing Loss Study and the Beaver Dam Eye Study. MEASUREMENTS: A hearing-related risk factor and medical history questionnaire, the Hearing Handicap Inventory for the Elderly (screening version), screening tympanometry, pure-tone air- and bone-conduction audiometry, and word recognition tests were administered by trained examiners using standard protocols. RESULTS: The prevalence of current hearing aid use among those with a hearing loss (pure-tone average > 25 decibels hearing level over 500, 1000, 2000, and 4000 Hertz, worse ear) was 14.6%. The prevalence was 55% in a subset of the most severely affected participants. In univariate analyses, current hearing aid use was associated with age, severity of loss, word recognition scores, self-reported hearing loss, self-perceived hearing handicap, and history of noise exposure. Factors associated with current hearing aid use in multivariate logistic regression models were age, severity of loss, education, word recognition scores, Hearing Handicap Inventory for the Elderly (screening version) score, and self-report of a hearing loss. CONCLUSIONS: Few older adults with hearing loss are currently utilizing hearing aids. Improved screening and intervention programs to identify older adults who would benefit from amplification are needed to improve hearing-related quality of life for this large segment of the population.     

Optimizing gaze control in three dimensions

Horizontal and vertical movements of the human eye bring new objects to the center of the visual field, but torsional movements rotate the visual world about its center. Ocular torsion stays near zero during head-fixed gaze shifts, and eye movements to visual targets are thought to be driven by purely horizontal and vertical commands. Here, analysis of eye-head gaze shifts revealed that gaze commands were three-dimensional, with a separate neural control system for torsion. Active torsion optimized gaze control as no two-dimensional system could have, stabilizing the retinal image as quickly as possible when it would otherwise have spun around the fixation point.     

Ruminal micro‐organisms do not adapt to increase utilization of poly‐phenol oxidase protected red clover protein and glycerol‐based lipid

BACKGROUND: The enzyme polyphenol oxidase (PPO) reduces the extent of proteolysis and lipolysis within red clover fed to ruminants with subsequent increases in the efficiency of N utilization and the level of beneficial polyunsaturated fatty acids in their products (meat and milk). It has also been reported that red clover feeding alters the rumen microbial population compared to grass feeding. This study investigated whether the observed shifts in the microbial population of the rumen when ruminants are fed red clover silage (RC) as opposed to grass silage (G) represented an adaptation by the micro‐organisms to increase the utilization of PPO‐protected protein and glycerol‐based lipid. RESULTS: The experiment consisted of two periods where ruminally fistulated dairy cows were offered either RC or G for 2 weeks, followed by collection of rumen fluid, which was then used in in vitro incubations to investigate lipolysis and proteolysis over time in plant material derived from red clover plants with either wild type PPO expression (PPO+) or PPO expression reduced to undetectable levels by gene silencing (PPO?). Proteolysis and lipolysis (P < 0.05) were lower after 24 h of incubation in the PPO+ treatment than the PPO? treatment irrespective of rumen fluid. Biohydrogenation of C18 polyunsaturated fatty acids was also lower on the PPO+ treatment than the PPO? treatment, with no effect of rumen fluid. CONCLUSION: These results suggest that microbial changes to red clover feeding did not result in an increased ability of the micro‐organisms in the present study to utilize either PPO‐protected protein or glycerol‐based lipid. Copyright © 2008 Society of Chemical Industry     

Aging and high-frequency hearing sensitivity

As part of a large population-based study of hearing and aging, ultra high-frequency (9-20 kHz) threshold measures are reported for 3396 participants grouped by age (48-59 years, n = 1233; 60-69 years, n = 1031; 70-79 years, n = 851; 80-92 years, n = 281). Ultra high-frequency (UHF) thresholds were higher for older age groups. The percentage of unmeasurable responses also was significantly higher for older age groups and for higher frequencies in the UHF range. The observed age effects remained significant after adjusting for gender. In general, UHF thresholds were significantly higher for men compared to those for women at lower UHF frequencies (9-14 kHz), but were not significantly different by gender for the highest UHF frequencies (16, 18, and 20 kHz). After accounting for hearing loss at traditional audiometric frequencies (250-8000 Hz), the age effect still remained; even for comparable degrees of sensorineural hearing loss, participants in older age groups evidenced higher UHF thresholds.