A probe for measuring ultrasonic pressures

In the study of acoustics, the term ultrasonics is defined as those wave motions that have frequencies greater than about 20,000 cycles per second. The characteristics of a sound wave at any point in a medium can be regarded as completely defined when the amplitude, frequency, and phase of its Fourier components are known. Sound measurements at their best are difficult. In the last few years sensitive linear microphones and electronic amplifiers have become available. Still, there are two difficulties of prime importance with their use in a sound field. First, there is the precise, absolute calibration of the equipment over a wide range of sound frequencies and intensities. In addition, any detection device whose dimensions are comparable to the wave length of the sound introduces a disturbing effect upon the field of sound itself. Also, there is always the possibility of reflected sound being picked up by the detector. Intensity or pressure measurement of audible sound and ultrasonic sound contains many experimental errors and great care is necessary in order to secure an accurate determination. All known measuring devices are limited in that their indications are dependent on the dimensions relative to the wave length of the incident sound. Any type of detector is dependent among other influences on the following factors: (a) wave length of the incident sound, (b) the law of pressure volume variation assumed in the neighborhood of the obstacle, (c) the scattering and diffraction of sound energy from the obstacle. Most pressure or intensity measuring devices such as radiometers or Rayleigh discs, are inconvenient and laborious to use. Yet, in some types of research work in physics, chemical engineering, and other phases of the physical and biological sciences, it is desirable to measure ultrasonic pressure at various points in liquids. Relative intensity measurements as well as absolute intensity measurements are needed. It is the purpose of this investigation to design, construct, and calibrate an ultrasonic probe for measuring ultrasonic pressures. With this probe, measurements of the sound pressures in the ultrasonic field can be obtained and the ultrasonic field can be mapped --Introduction, pages 1-2

An Avoidance Principle with an Application to the Asymptotic Behaviour of Graded Local Cohomology

We present an Avoidance Principle for certain graded rings. As an application we fill a gap in the proof of a result by Brodmann, Rohrer and Sazeedeh about the antipolynomiality of the Hilbert-Samuel multiplicity of the graded components of the local cohomology modules of a finitely generated module over a Noetherian homogeneous ring with two-dimensional local base ring.Comment: 6 pages; to appear in Journal of Pure and Applied Algebra; corrected typo

Rural residence is not a risk factor for frequent mental distress: a behavioral risk factor surveillance survey

BACKGROUND: Residents of rural areas may be at increased risk of mental health problems. If so, public health programs aimed at preventing poor mental health may have to be customized for delivery to rural areas. The purpose of this study was to examine the relationship between residing in a rural area and frequent mental distress, which is one indicator of poor mental health. METHODS: The Behavioral Risk Factor Surveillance System (BRFSS) survey for the state of Texas was the source of information about obesity, demographic characteristics, and frequent mental distress (FMD). FMD was defined as poor self-rated mental health during at least half of the days in the last month. Adjusted odds for FMD were computed for rural and suburban respondents relative to urban respondents. RESULTS: FMD was found to be independently associated with lower education, being younger, being non-Hispanic, being unmarried, and being female. FMD also was associated with being obese or underweight and suburban residence (relative to metro-central city). FMD was not more common among rural respondents than in the metro-central city. CONCLUSION: Rural respondents were not at greater risk of frequent mental distress than urban respondents in this sample. Programs seeking to improve community mental health should target persons with less education and extremes in body weight, along with women and single persons, regardless of whether they live in rural or urban areas

Advances and controversies in frontotemporal dementia: diagnosis, biomarkers, and therapeutic considerations

Frontotemporal dementia comprises a group of clinical syndromes that are characterised by progressive changes in behaviour, executive function, or language. The term frontotemporal lobar degeneration encompasses the neurodegenerative diseases that give rise to these clinical syndromes and involve proteinopathies associated with frontotemporal network dysfunction. Improvements in clinical, genetic, and molecular characterisation have provided new insights into frontotemporal dementia and frontotemporal lobar degeneration, with a much broader range of signs and symptoms at presentation than has been previously considered. Accurate and early diagnosis of frontotemporal dementia is now a possibility due to development of neuropsychological measures with a special focus on social cognition. Advances in plasma and CSF biomarkers, and innovations in structural and functional imaging, will prove useful for future clinical trials in people with frontotemporal dementia

Characterisation of the photolytic HONO-source in the atmosphere simulation chamber SAPHIR

HONO formation has been proposed as an important OH radical source in simulation chambers for more than two decades. Besides the heterogeneous HONO formation by the dark reaction of NO₂ and adsorbed water, a photolytic source has been proposed to explain the elevated reactivity in simulation chamber experiments. However, the mechanism of the photolytic process is not well understood so far. As expected, production of HONO and NO_x was also observed inside the new atmospheric simulation chamber SAPHIR under solar irradiation. This photolytic HONO and NO_x formation was studied with a sensitive HONO instrument under reproducible controlled conditions at atmospheric concentrations of other trace gases. It is shown that the photolytic HONO source in the SAPHIR chamber is not caused by NO₂ reactions and that it is the only direct NO_y source under illuminated conditions. In addition, the photolysis of nitrate which was recently postulated for the observed photolytic HONO formation on snow, ground, and glass surfaces, can be excluded in the chamber. A photolytic HONO source at the surface of the chamber is proposed which is strongly dependent on humidity, on light intensity, and on temperature. An empirical function describes these dependencies and reproduces the observed HONO formation rates to within 10%. It is shown that the photolysis of HONO represents the dominant radical source in the SAPHIR chamber for typical tropospheric O₃/H₂O concentrations. For these conditions, the HONO concentrations inside SAPHIR are similar to recent observations in ambient air

Intercomparison of Hantzsch and fiber-laser-induced-fluorescence formaldehyde measurements

Two gas-phase formaldehyde (HCHO) measurement techniques, a modified commercial wet-chemical instrument based on Hantzsch fluorimetry and a custom-built instrument based on fiber laser-induced fluorescence (FILIF), were deployed at the atmospheric simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction Chamber) to compare the instruments' performances under a range of conditions. Thermolysis of para-HCHO and ozonolysis of 1-butene were used as HCHO sources, allowing for calculations of theoretical HCHO mixing ratios. Calculated HCHO mixing ratios are compared to measurements, and the two measurements are also compared. Experiments were repeated under dry and humid conditions (RH 60%) to investigate the possibility of a water artifact in the FILIF measurements. The ozonolysis of 1-butene also allowed for the investigation of an ozone artifact seen in some Hantzsch measurements in previous intercomparisons. Results show that under all conditions the two techniques are well correlated (R2 ≥ 0.997), and linear regression statistics show measurements agree with within stated uncertainty (15% FILIF + 5% Hantzsch). No water or ozone artifacts are identified. While a slight curvature is observed in some Hantzsch vs. FILIF regressions, the potential for variable instrument sensitivity cannot be attributed to a single instrument at this time. Measurements at low concentrations highlight the need for a secondary method for testing the purity of air used in instrument zeroing and the need for further FILIF White cell outgassing experiments