Further observations on tissue heating patterns using an invasive ground probe with radiofrequency hyperthermia system

Critical modifications have been made in the grounded elements of a previously reported hybrid radiofrequency heating system with inductive, capacitive, and grounded elements designed for deep focal heating. These modifications facilitate introduction of the ground probe, the single invasive element of the system, into animals and humans. The modified grounded elements also enable monitoring and optimization of ground point current, thereby improving control of heating rate, and greatly increase the volume of tissue that can be heated using a single invasive grounding element, embedded in a lossy dielectric field in the near field of the radiofrequency hyperthermia system.     

Process control of laser conduction welding by thermal imaging measurement with a color camera

Conduction welding offers an alternative to keyhole welding. Compared with keyhole welding, it is an intrinsically stable process because vaporization phenomena are minimal. However, as with keyhole welding, an on-line process-monitoring system is advantageous for quality assurance to maintain the required penetration depth, which in conduction welding is more sensitive to changes in heat sinking. The maximum penetration is obtained when the surface temperature is just below the boiling point, and so we normally wish to maintain the temperature at this level. We describe a two-color optical system that we have developed for real-time temperature profile measurement of the conduction weld pool. The key feature of the system is the use of a complementary metal-oxide semiconductor standard color camera leading to a simplified low-cost optical setup. We present and discuss the real-time temperature measurement and control performance of the system when a defocused beam from a high power Nd:YAG laser is used on 5 mm thick stainless steel workpieces.     

A predictive approach to nutrient criteria

Violation of a water quality standard triggers the need for a total maximum daily load (TMDL); this should result in actions that improve water quality, but sometimes at significant cost. If the standard is well-conceived, a designated-use statement characterizes societal values, and a criterion provides a measurable surrogate for designated use. This latter provision means that scientists measure the criterion and view violations of the criterion as equivalent to noncompliance with the designated use. However, if a criterion is not a good indicator of designated use, it is apt to result in misallocation of the limited resources for water quality improvement through the TMDL process. This concern provides the basis for our assessment of the national nutrient criteria strategy recently proposed by the U.S. EPA. We acquired data sets for four case studies (Lake Washington, Neuse River Estuary, San Francisco Bay, and Lake Mendota) and then used expert elicitation to quantify designated-use attainment for each case. Applying structural equation modeling, we identified good water quality criteria as the best predictors of the designated use elicited response variable. Further, we used the model to relate the level (concentration) of each criterion to the probability of compliance with the designated use; this provides decision-makers with an estimate of risk associated with the criterion level, facilitating the selection of appropriate water quality criteria.     

Solid-State Photolysis of Azobis-3-Phenyl-3-Pentane. Crystal-Lattice Control of the Stereochemistry of Radical Disproportionation

The 3-phenyl-3-pentyl radicals from photolysis of azobis-3-phenyl-3-pentane (APP) in solution give 3,4-diethyl-3,4-diphenylhexane and a photolabile product assumed to arise by para coupling. Photolysis of APP as a crystalline solid at ?78° gives the disproportionation products 3-phenylpentane (PPH) and 3-phenyl-2-pentene (PP) as a 3:1 mixture of the E and Z isomers. This stereoisomeric ratio is surprising in terms of the solid-state molecular conformations, for which a topochemical scheme predicts predominance of the Z isomer. Isotopic distributions in PPH, Z-PP and E-PP from photolysis of solid APP which was 82% deuterated in its methylene groups shows: (1) that Z-PP is formed under strong lattice control; (2) that E-PP is formed in a process with greater, but not complete, molecular freedom; and (3) that there is often a dynamic competition for hydrogen-atom donation between the two radicals involved in disproportionation.     

Approximate describing function for double-valued nonlinearities

An approximate method for determining the describing function of a smooth double-valued nonlinearity is derived; the formula requires the values of the nonlinear function at only three input levels for symmetric nonlinear devices. The result is exact for third-order polynomials and should be sufficiently accurate for most practical problems.     

The kinetics of the gaseous extraction of gallium from mica

The gaseous reduction of gallium in white mica has been studied using natural gas as the reducing gas. From a study at three temperatures, the initial extraction was observed to be linear with time and independent of particle size. The results suggest that delamination of the mica lattice is important. The measured activation energy for the loss of gallium from the white mica is 184 × 21 kJ mol^?1.     

Housing conditions alter GABAA receptor of alcohol-preferring and -nonpreferring rats

The effects of housing conditions on some functional properties of the GABAA benzodiazepine (BZD) receptor in the cerebral cortex were examined in the selectively bred alcohol-preferring (P) and -nonpreferring (NP) lines of rats. Compared to rats housed in pairs (P with P and NP with NP), P and NP rats housed individually had 44% (p < 0.005) and 32% (p < 0.01) lower values, respectively, for GABA-stimulated 36Cl- influx into cortical microsacs. The maximal effect (Vmax) of flunitrazepam (FNZ) to enhance GABA-stimulated 36Cl- uptake was 44% higher in individually housed P rats than pair-housed P rats (p < 0.05) and 51% higher than individually housed NP rats (p < 0.05). There was no difference between single and pair-housed NP rats for Vmax values of FNZ enhancement of GABA-stimulated 36Cl- influx. The results show housing conditions can alter some of the functional properties of the GABAA/BZD receptor in the P and NP lines of rats. The differential effect of housing conditions on FNZ enhancement of 36Cl- influx, observed between the lines, may be a result of higher levels of anxiety being produced by brief isolation in the P rat.     

Improved in situ spring constant calibration for colloidal probe atomic force microscopy

In colloidal probe atomic force microscopy (AFM) surface forces cannot be measured without an accurate determination of the cantilever spring constant. The effective spring constant k depends upon the cantilever geometry and therefore should be measured in situ; additionally, k may be coupled to other measurement parameters. For example, colloidal probe AFM is frequently used to measure the slip length b at solid/liquid boundaries by comparing the measured hydrodynamic force with Vinogradova slip theory (V-theory). However, in this measurement k and b are coupled, hence, b cannot be accurately determined without knowing k to high precision. In this paper, a new in situ spring constant calibration method based upon the residuals, namely, the difference between experimental force-distance data and V-theory is presented and contrasted with two other popular spring constant determination methods. In this residuals calibration method, V-theory is fitted to the experimental force-distance data for a range of systematically varied spring constants where the only adjustable parameter in V-theory is the slip length b. The optimal spring constant k is that value where the residuals are symmetrically displaced about zero for all colloidal probe separations. This residual spring constant calibration method is demonstrated by studying three different liquids (n-decanol, n-hexadecane, and n-octane) and two different silane coated colloidal probe-silicon wafer systems (n-hexadecyltrichlorosilane and n-dodecyltrichlorosilane).