The use of permeation tube device and the development of empirical formula for accurate permeation rate

A series of laboratory experiments were conducted to assess the accuracy of permeation tube (PT) devices using a calibration gas generator system to measure permeation rate (PR) of volatile organic compounds (VOCs). Calibration gas standards of benzene, toluene, and m-xylene (BTX) were produced from PTs at varying flow rates (FR) of 20-1200 mL min(-1) and constant temperature (30°C). Results indicate that changes in flow rate greatly affected the permeation rate of each VOC at this temperature. This paper presents experimental approaches to accurately measure actual permeation rate (APR) and the derivation of empirical equations for predicted permeation rate (PPR). If the magnitude of bias is defined as the difference between PPR and the manufacturer's permeation rate (MPR), the bias was typically 19-40% for toluene (T) and 31-54% for m-xylene (X). Benzene (B) exhibited the least bias of 1.4-18.8%, nevertheless our PPR values for benzene were more reliable at lower flow rates (0.75-1.20%). This study highlights the importance of flow rate and associated pressure changes as a key to accurate permeation rate estimation from permeation tube devices.     

Three-dimensional localization of sperm whales using a single hydrophone

A three-dimensional localization method for tracking sperm whales with as few as one sensor is demonstrated. Based on ray-trace acoustic propagation modeling, the technique exploits multipath arrival information from recorded sperm whale clicks and can account for waveguide propagation physics like interaction with range-dependent bathymetry and ray refraction. It also does not require ray identification (i.e., direct, surface reflected) while utilizing individual ray arrival information, simplifying automation efforts. The algorithm compares the arrival pattern from a sperm whale click to range-, depth-, and azimuth-dependent modeled arrival patterns in order to estimate whale location. With sufficient knowledge of azimuthally dependent bathymetry, a three-dimensional track of whale motion can be obtained using data from a single hydrophone. Tracking is demonstrated using data from acoustic recorders attached to fishing anchor lines off southeast Alaska as part of efforts to study sperm whale depredation of fishing operations. Several tracks of whale activity using real data from one or two hydrophones have been created, and three are provided to demonstrate the method, including one simultaneous visual and acoustic localization of a sperm whale actively clicking while surfaced. The tracks also suggest that whales' foraging is shallower in the presence of a longline haul than without.     

Thermal boundary layer effects on the acoustical impedance of enclosures and consequences for acoustical sensing devices

Expressions are derived for the acoustical impedance of a rectangular enclosure and of a finite annular cylindrical enclosure. The derivation is valid throughout the frequency range in which all dimensions of the enclosure are much less than the wavelength. The results are valid throughout the range from adiabatic to isothermal conditions in the enclosure. The effect is equivalent to placing an additional, frequency-dependent complex impedance in parallel with the adiabatic compliance. As the thermal boundary layer grows to fill the cavity, the reactive part of the impedance varies smoothly from the adiabatic value to the isothermal value. In some microphones, this change in cavity stiffness is sufficient to modify the sensitivity. The resistive part of the additional cavity impedance varies as the inverse square root of frequency at high frequencies where the boundary layer has not grown to fill the enclosure. The thermal modification gives rise to a thermal noise whose spectral density varies asymptotically as l/f(3/2) above the isothermal transition frequency.     

Enhancement of superconducting transition temperature due to the strong antiferromagnetic spin fluctuations in the noncentrosymmetric heavy-fermion superconductor CeIrSi3: A 29Si NMR study under pressure

We report a (29)Si NMR study on the pressure-induced superconductivity (SC) in an antiferromagnetic (AFM) heavy-fermion compound CeIrSi(3) without inversion symmetry. In the SC state at P = 2.7-2.8 GPa, the temperature (T) dependence of the nuclear-spin lattice relaxation rate 1/T(1) below T(c) exhibits a T(3) behavior without any coherence peak just below T(c), revealing the presence of line nodes in the SC gap. In the normal state, 1/T(1) follows a square root T-like behavior, suggesting that the SC emerges under the non-Fermi-liquid state dominated by AFM spin fluctuations enhanced around a quantum critical point. The reason why the maximum T(c) in CeIrSi(3) is relatively high among the Ce-based heavy-fermion superconductors may be the existence of the strong AFM spin fluctuations. We discuss the comparison with the other Ce-based heavy-fermion superconductors.     

Adsorption of some metals on anion-exchange resins from potassium thiocyanate solutions

The adsorption of a number of metals on Dowcx-I from potassium thiocyanate solutions has been studied. Distribution coefficients were measured as a function of thiocyanate concentration for zinc, cobalt, cadmium, scandium, and silver. Some separations of metals employing thiocyanate as the complexing agent are reported.     

The thermal decomposition of transition-metal complexes containing heterocyclic ligands: I. Benzothiazole complexes

Enthalpies of the decomposition reactions MX₂L₂(c)→MX₂(c) + 2L (g), where M is Mn, Co, Ni, Cu, or Cd, X is Cl and/or Br, and L is benzothiazole or 2-methyl-benzothiazole have been measured by use of a differential scanning calorimeter. Specific heats and enthalpies of sublimation of some of the complexes have been obtained.     

The Acoustic Characteristics of Professional Opera Singers Performing in Chorus Versus Solo Mode

In this study, members of a professional opera chorus were recorded using close microphones, while singing in both choral and solo modes. The analysis included computation of long-term average spectra (LTAS) for the two song sections performed and calculation of singing power ratio (SPR) and energy ratio (ER), which provide an indication of the relative energy in the singer's formant region. Vibrato rate and extent were determined from two matched vowels, and SPR and ER were calculated for these vowels. Subjects sung with equal or more power in the singer's formant region in choral versus solo mode in the context of the piece as a whole and in individual vowels. There was no difference in vibrato rate and extent between the two modes. Singing in choral mode, therefore, required the ability to use a similar vocal timbre to that required for solo opera singing.     

Barriers to access: results from focus groups to identify genetic service needs in the community

OBJECTIVE: In efforts to prepare for implications of genomic advances, a needs assessment was undertaken from 2000 to 2002 by the Michigan Department of Community Health to develop a comprehensive state plan for genetic services. This paper reports on the access barriers to genetic services identified from focus groups conducted with members of the community and genetic service providers. METHODS: Included in this study were the following five target groups: a sickle cell anemia parent support group, a Native American student group, parents of children with birth defects or other special health care needs, adults with genetic conditions, and genetic service providers from the statewide genetic counselors' association. Discussions of all groups were audio taped, transcribed and analyzed using content analysis. RESULTS: Individual barriers to access identified included lack of awareness of personal risk, lack of knowledge of genetic services and resources, and lack of trust/fear of discrimination. Institutional barriers to access identified included provider lack of knowledge and awareness of genetic services, lack of workforce, coordination of care, cost and insurance, and location from services. CONCLUSIONS: Barriers to access cut across overlapping dimensions and overcoming these barriers will require solutions that target multiple dimensions in order to be effective.