Notes: A self-consistent three-dimensional numerical analysis using the newly developed BPHI-3D code was performed for the Debye/magnetic tokamak-type oblique incidence magnetic field sheath, with near-surface ionization and transport of thermally emitted surface material. The analysis uses Monte Carlo, kinetic treatment for deuterium–tritium and impurity ions/neutrals, Boltzmann/guiding-center electrons, and particle-in-cell time-independent Poisson solver. For typical predicted fusion edge plasma conditions for a liquid lithium divertor most evaporated lithium atoms—from a ∼1 cm2 overheated spot–are ionized in the ∼1 mm-wide magnetic sheath. These ions are strongly redeposited due to the sheath electric field. While this redeposition minimizes core plasma contamination, it increases the peak heat flux to the surface. A runaway situation is then possible due to superheating/evaporation positive feedback. Carbon may behave likewise as seen in code results obtained for a TORE SUPRA [Aymar et al., Plasma Physics and Controlled Nuclear Fusion Research (IAEA, Vienna, 1989)] carbon limiter. A semianalytic formula for sheath parameters as a function of emitted surface material flux is developed and verified with the code. © 2000 American Institute of Physics.

Notes: We discuss new opportunities that present themselves with the advent of very high magnetic field resistive magnets with appreciable central bore access. A detailed description of the parameters of the magnetic force environment for the case of diamagnetic materials in a water-cooled Bitter-type resistive magnet is provided for the reader who may have an interest in low-gravity experiments. We discuss emerging research activities involving novel uses of magnetic forces in high field resistive magnets at the National High Magnetic Field Laboratory. Particular attention is given to the area of diamagnetic materials that allow a low or "zero" gravity state, i.e., magnetic levitation. These include studies involving plant growth, protein crystallization, and dynamics of single particles and granular materials. In the latter case, unique aspects of the magnetic force environment allow low gravity experiments on particulates that cannot be performed on the Space Shuttle due to the lack of a weak confining potential in space. © 2000 American Institute of Physics.

Notes: We present a reliable method to account for the magnetoresistance of resistance sensors which are used as thermometers in many low temperature (T≤20 K) experiments carried out in high magnetic fields (to 31 T). To apply the method, a set of isothermal magnetoresistance data, and a zero magnetic field temperature calibration are first necessary. A simple algorithm, which uses this data set, can then be applied to compute the temperature from the measured resistance at any field. The method is particularly useful for temperature dependent measurements at fixed field, or where, in cases where the temperature may change unpredictably during a change in magnetic field. We apply this method to the treatment of data in two separate experiments with the two different thermometers, RuO2 (below 1 K) and Cernox (above 1 K) sensors, respectively. © 1999 American Institute of Physics.

Notes: Previous studies show that oral antihistamines affect the Weal and flare response to intradermal injections of the inflammatory mediators platelet-activating factor (PAF) and bradykinin (BK). The aim of this study was to compare the effects of terfenadine (an H2-antagonist) and cimetidine (an H2-antagonist) on weal and Hare responses to PAF and BK in healthy non-atopic human volunteers. The effects of doxepin on PAF responses were investigated, as there is evidence that doxepin may have direct anti-PAF ejects in addition to its known antihisiaminic actions.

Notes: A method to measure the resistance of fragile single crystals under high uniaxial stress is reported. To compensate for its natural brittleness, the crystal is embedded in epoxy, whose shape is optimized to sustain the stress. This method was used to study the magnetoresistance of (BEDT-TTF)2KHg(SCN)4 at low temperatures and high magnetic fields and the superconducting transition temperature of (BEDT-TTF)2Cu(NCS)2 under uniaxial stress perpendicular to the planes of BEDT-TTF molecules. The results obtained indicate a high degree of homogeneity of the stress in the crystal and comparison with previous hydrostatic pressure measurements reveal the true uniaxial nature of the stress applied. © 1995 American Institute of Physics.

Notes: Stand density reductions have been proposed as a method by which old-growth ponderosa pine (Pinus ponderosa) forests of North America can be converted back to pre-1900 conditions, thereby reducing the danger of catastrophic forest fires and insect attacks while increasing the productivity of the remaining old-growth individuals. However, the duration of productivity response of individual trees and the physiological mechanisms underlying such a response remain speculative issues, particularly in old trees. Tree-ring measurements of carbon isotope ratios (δ13C) and basal area increment (BAI) were used to assess the response of intrinsic water-use efficiency (the ratio of photosynthesis, A to stomatal conductance, g) and growth of individual〉 250-year-old-ponderosa pine trees to stand density reductions. It was hypothesized that reductions in stand density would increase soil moisture availability, thus decreasing canopy A/g and increasing carbon isotope discrimination (Δ). Cellulose-δ13C of annual tree rings, soil water availability (estimated from pre-dawn leaf water potential), photosynthetic capacity, stem basal growth and xylem anatomy were measured in individual trees within three pairs of thinned and un-thinned stands. The thinned stands were treated 7 to 15 years prior to measurement. The values of δ13C and BAI were assessed for 20 consecutive years overlapping the date of thinning in a single intensively studied stand, and was measured for 3 years on either side of the date of thinning for the two other stands to assess the generality of the response.After thinning, Δ increased by 0.89‰ (± 0.15‰). The trees in the un-thinned stands showed no change in Δ (0.00‰ ± 0.04‰). In the intensively studied trees, significant differences were expressed in the first growing season after the thinning took place but it took 6 years before the full 0.89‰ difference was observed. BAI doubled or tripled after disturbance, depending on the stand, and the increased BAI lasted up to 15 years after thinning. In the intensively studied trees, the BAI response did not begin until 3 years after the Δ response, peaked 1 year after the Δ peak, and then BAI and Δ oscillated in unison. The lag between BAI and Δ was not due to slow changes in anatomical properties of the sapwood, because tracheid dimensions and sapwood-specific conductivity remained unchanged after disturbance. The Δ response of thinned trees indicated that A/g decreased after thinning. Photosynthetic capacity, as indexed by foliar nitrogen ([N]) and by the relationship between photosynthesis and internal CO2 (A–Ci curves), was unchanged by thinning, confirming our suspicion that the decline in A/g was due to a relatively greater increase in g in comparison with A. Model estimates agreed with this conclusion, predicting that g increased by nearly 25% after thinning relative to a 15% increase in A. Pre-dawn leaf water potential averaged 0.11 MPa (± 0.03 MPa) less negative for the thinned compared with the un-thinned trees in all stands, and was strongly correlated with Δ post-thinning (R2 = 0.91). There was a strong relationship between BAI and modelled A, suggesting that changes in water availability and g have a significant effect on carbon assimilation and growth of these old trees. These results confirm that stand density reductions result in increased growth of individual trees via increased stomatal conductance. Furthermore, they show that a physiological response to stand density reductions can last for up to 15 years in old ponderosa pines if stand leaf area is not fully re-established.

Notes: The carbon isotope composition of C4 grasses has the potential to be used as an indicator of changes in the isotopic composition and concentration of atmospheric CO2, especially for climate reconstruction. The usefulness of C4 grasses for this purpose hinges on the assumption that their photosynthetic discrimination against 13C remains constant in a wide range of environmental conditions. We tested this assumption by examining the effects of light and water stress on the carbon isotope composition of C4 grasses using different biochemical subtypes (NADP-ME, NAD-ME, PCK) in glasshouse experiments. We grew 14 different C4 grass species in four treatments: sun-watered, sun-drought, shade-watered and shade-drought. Carbon isotope discrimination (Δ) rarely remained constant. In general, Δ values were lowest in sun-watered grasses, greater for sun-drought plants and even higher for plants of the shade-watered treatment. The highest Δ values were generally found in the most stressed grasses, the shade-drought plants. Grasses of the NADP-ME subtype were the least influenced by a change in environmental variables, followed by PCK and NAD-ME subtypes. Water availability affected the carbon isotope discrimination less than light limitation in PCK and NAD-ME subtypes, but similarly in NADP-ME subtypes.In another experiment, we studied the effect of increasing light levels (150 to 1500 μmol photons m−2 s−1) on the Δ values of 18 well-watered C4 grass species. Carbon isotope discrimination remained constant until photon flux density (PFD) was less than 700 μmol photons m−2 s−1. Below this light level, Δ values increased with decreasing irradiance for all biochemical subtypes. The change in A was less pronounced in NADP-ME and PCK than in NAD-ME grasses. Grasses grown in the field and in the glasshouse showed a similar pattern. Thus, caution should be exercised when using C4 plants under varying environmental conditions to monitor the concentration or carbon isotopic composition of atmospheric CO2 in field/glasshouse studies or climate reconstruction.