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: 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.

Notes: The in viva integration strength and degree of bone apposition were compared for oral endosseous implants with different plasma-sprayed hydroxylapatite (HA) coatings. Pullout strength measurements and histological analysis were used to compare two different commercially available coatings from the same manufacturer. One coating does not receive a post-plasma-spray treatment and contains about 75% crystalline HA. The other coating is treated with the MP-l process, a pressurized hydrothermal post-plasma-spray process, which increases the coating composition to approximately 95% crystalline HA without changing the coating's adhesive or cohesive strength. Comparisons were made in dogs after healing times of 3 and 15 weeks in the mandible. No significant differences were found in either case between the two coatings. Two different methods were used to determine the degree of bone apposition at 15 weeks. Both methods confirmed that the MP-1 process does not affect the osseointegration rate of plasma-sprayed HA coatings. Qualitative histology data suggest that the treated coating is more stable than the control coating, especially in cases of direct soft tissue attachment to the implant. The present data suggest that extensive dissolution of calcium phosphate components into surrounding tissue is not a necessary precursor for direct 1 apposition of bone to HA-coated implants.

Notes: A novel pressurized hydrothermal post-plasma-spray process, referred to as MP-l, has been developed to convert the crystalline non-HA and amorphous components of plasma-sprayed hydroxylapatite coatings back into crystalline HA. No detrimental effects are observed on the strength of either the base metal or the coating. X-ray diffraction (XRD) and FTIR analysis, surface roughness, shear adhesion strength and calcium solubility testing were conducted on Calcitit® coated samples before and after treatment with this process. Other commercially available coatings were also studied using XRD and solubility testing. Quantitative XRD data show that the MP-1 treatment increases the average crystalline HA content of the Calcitite coating from 17% to 96%, while the amorphous content decreases from 21% to 4%. Other commercially available dental implant coatings ranged in crystalline HA content from 45% to 73%, with amorphous phase content ranging from 29% to 62%. FTIR spectra for treated coatings were significantly more well defined, and showed an increase in peak separation and intensity. Surface roughness and shear adhesion strength were not affected by the treatment. In vitro solubility testing revealed that for all coatings there is an initial introduction of calcium into solution over the first 2 h of testing; however, the amount of calcium dissolved was significantly lower for the MP-1 coating. Under a pH and temperature representative of normal physiologic conditions, the rate of calcium dissolution for the MP-1 coating was significantly lower than that of the other commercial HA coatings. In increasingly acidic conditions, the MP-1 coating was compared to the Calcitite coating and was found to have a significantly slower rate of calcium release. The MP-1 treatment enhances typical HA coatings by increasing the crystalline HA content at the expense of the plasma-spray-induced soluble phases without a reduction in the strength of the coating. The resulting coatings exhibit significantly decreased in vitro solubility over a wide range of pH. The results of this solubility testing suggest that the treated coating may show significantly enhanced in viva stability, even under the extreme conditions encountered during periods of infection or rigorous detoxification procedures. The significant differences between plasma-sprayed HA coatings reported here underscore the need for industry and academic researchers to raise the level of discourse and understanding of HA coatings. By offering consistent and accurate descriptions of coating compositions and methods of analysis, meaningful comparisons between different HA coatings can be made.

Notes: Abstract Fish (Notothenia gibberifrons) collected in pristine Antarctic sites were injected with Diesel Fuel Arctic (DFA). Gas chromatography/mass spectrometry (GC/MS) was used to identify and quantify polycyclic aromatic hydrocarbon (PAH) metabolites obtained from hydrolyzed fish bile. The concentrations of naphthols (NPH), phenanthrenols (PHN), dibenzothiophenols (DBT), and total PAH metabolites (∑PAH) vary with time. The response curve (production of PAH metabolites vs. time) resembled a Sigmoid curve, with an initial low response at 24 h followed by a rapid rise in production of PAH metabolites (55.74 μg/g) 120 h after exposure to DFA. PAH metabolites identified include NPH, PHN, and DBT and their alkylated derivatives, reflecting the composition of the DFA to which the fish were exposed. The GC/MS technique is highly sensitive, particularly in the detection of multi-ring PAH metabolites. The results suggest that analysis of PAH metabolites is a valuable tool for environmental monitoring and assessment of exposure to petroleum.

Notes: Abstract Variation in the photosynthetic function ofAbies amabilis foliage within a canopy was examined and related to three different processes that affect foliage function: foliage aging, sun-shade acclimation that occurred while foliage was expanding, and reacclimation after expansion was complete. Foliage produced in the sun had higher photosynthesis at light saturation (A max, μmol·m-2·s-1), dark respiration (μmol·m-2·s-1), nitrogen content (g·m-2), chlorophyll content (g·m-2), and chlorophylla:b ratio, and a lower chlorophyll to nitrogen ratio (chl:N), than foliage produced in the shade. As sun foliage becomes shaded, it becomes physiologically similar to shade foliage, even though it still retains a sun morphology. Shaded sun foliage exhibited lowerA max, dark respiration, nitrogen content, and chlorophylla:b ratio, and a higher chl:N ratio than sun foliage of the same age remaining in the open. However, shaded sun foliage had a higher chlorophyll content than sun foliage remaining in the open, even though true shade foliage had a lower chlorophyll content than sun foliage. This anomaly arises because as sun foliage becomes shaded, it retains a higher nitrogen content than shade foliage in a similar light environment, but the two forms have similar chl:N ratios. Within the canopy, most physiological indicators were more strongly correlated with the current light environment than with foliage age or leaf thickness, with the exception of chlorophyll content.A max decreased significantly with both decreasing current light environment of the foliage and increasing foliage age. The same trend with current light and age was found for the chlorophylla:b ratio. Foliage nitrogen content also decreased with a decrease in current light environment, but no distinct pattern was found with foliage age. Leaf thickness was also important for predicting leaf nitrogen content: thicker leaves had more nitrogen than thinner leaves regardless of light environment or age. The chl:N ratio had a strong negative correlation with the current light environment, and, as with nitrogen content, no distinct pattern was found with foliage age. Chlorophyll content of the foliage was not well correlated with any of the three predictor variables: current light environment, foliage age or leaf thickness. On the other hand, chlorophyll content was positively correlated with the amount of nitrogen in a leaf, and once nitrogen was considered, the current light environment was also highly significant in explaining the variation in chlorophyll content. It has been suggested that the redistribution of nitrogen both within and between leaves is a mechanism for photosynthetic acclimation to the current light environment. Within theseA. amabilis canopies, both leaf nitrogen and the chl:N ratio were strongly correlated with the current light environment, but only weakly with leaf age, supporting the idea that changing light is the driving force for the redistribution of nitrogen both within and between leaves. Thus, our results support previous theories on nitrogen distribution and partitioning. However,A max was significantly affected by both foliage age and the current light environment, indicating that changes in light alone are not enough to explain changes inA max with time.