Radiative Capture on Nuclear Isomers: Direct Measurement of the

We present the first direct measurement of an astrophysical reaction using a radioactive beam of isomeric nuclei. In particular, we have measured the strength of the key 447-keV resonance in the ^{26m}Al(p,γ)^{27}Si reaction to be 432_{-226}^{+146} meV and find that this resonance dominates the thermally averaged reaction rate for temperatures between 0.3 and 2.5 GK. This work represents a critical development in resolving one of the longest standing issues in nuclear astrophysics research, relating to the measurement of proton capture reactions on excited quantum levels, and offers unique insight into the destruction of isomeric ^{26}Al in astrophysical plasmas.

Direct Measurement of the Key E_{c.m.}=456 keV Resonance in the Astrophysical

We have performed a direct measurement of the ^{19}Ne(p,γ)^{20}Na reaction in inverse kinematics using a beam of radioactive ^{19}Ne. The key astrophysical resonance in the ^{19}Ne+p system has been definitely measured for the first time at E_{c.m.}=456_{-2}^{+5} keV with an associated strength of 17_{-5}^{+7} meV. The present results are in agreement with resonance strength upper limits set by previous direct measurements, as well as resonance energies inferred from precision (^{3}He, t) charge exchange reactions. However, both the energy and strength of the 456 keV resonance disagree with a recent indirect study of the ^{19}Ne(d, n)^{20}Na reaction. In particular, the new ^{19}Ne(p,γ)^{20}Na reaction rate is found to be factors of ∼8 and ∼5 lower than the most recent evaluation over the temperature range of oxygen-neon novae and astrophysical x-ray bursts, respectively. Nevertheless, we find that the ^{19}Ne(p,γ)^{20}Na reaction is likely to proceed fast enough to significantly reduce the flux of ^{19}F in nova ejecta and does not create a bottleneck in the breakout from the hot CNO cycles into the rp process.

Direct Measurement of the Astrophysical

We have performed the first direct measurement of the ^{38}K(p,γ)^{39}Ca reaction using a beam of radioactive ^{38}K. A proposed ℓ=0 resonance in the ^{38}K+p system has been identified at 679(2) keV with an associated strength of 120_{-30}^{+50} meV. Upper limits of 1.16 (3.5) and 8.6 (26) meV at the 68% (95%) confidence level were also established for two further expected ℓ=0 resonances at 386 and 515 keV, respectively. The present results have reduced uncertainties in the ^{38}K(p,γ)^{39}Ca reaction rate at temperatures of 0.4 GK by more than 2 orders of magnitude and indicate that Ar and Ca may be ejected in observable quantities by oxygen-neon novae. However, based on the newly evaluated rate, the ^{38}K(p,γ)^{39}Ca path is unlikely to be responsible for the production of Ar and Ca in significantly enhanced quantities relative to solar abundances.

Measurement of 23Na(α,p)26Mg at Energies Relevant to 26Al Production in Massive Stars.

26Al is an important radioisotope in astrophysics that provides evidence of ongoing nucleosynthesis in the Galaxy. The 23Na(α, p)26Mg reaction has been identified by a sensitivity study as being one of the most important reactions for the production of 26Al in the convective C/Ne burning shell of massive stars. Owing to large uncertainties in previous experimental data, model calculations are used for the reaction rate of 23Na(α, p)26Mg in this sensitivity study. Current experimental data suggest a reaction rate a factor of ∼40 higher than model calculations. However, a new measurement of this reaction cross section has been made in inverse kinematics in the energy range E(c.m.)=1.28-3.15 MeV at TRIUMF, and found to be in reasonable agreement with the model calculation. A new reaction rate is calculated and tight constraints on the uncertainty in the production of 26Al, due to this reaction, are determined.

Measurement of radiative proton capture on 18F and implications for oxygen-neon novae.

The rate of the 18F(p,γ)19Ne reaction affects the final abundance of the γ-ray observable radioisotope 18F, produced in novae. However, no successful measurement of this reaction exists and the rate used is calculated from incomplete information on the contributing resonances. Of the two resonances thought to play a significant role, one has a radiative width estimated from the assumed analogue state in the mirror nucleus, 19F. The second does not have an analogue state assignment at all, resulting in an arbitrary radiative width being assumed. Here, we report the first successful direct measurement of the 18F(p,γ)^19Ne reaction. The strength of the 665 keV resonance (Ex=7.076 MeV) is found to be over an order of magnitude weaker than currently assumed in nova models. Reaction rate calculations show that this resonance therefore plays no significant role in the destruction of ^{18}F at any astrophysical energy.

Piloting the use of 2D barcode and patient safety-software in an Australian tertiary hospital setting.

OBJECTIVES: Errors in administration of blood products can lead to poor patient outcomes including fatal ABO incompatible transfusions. This pilot study sought to establish whether the use of two-dimensional (2D) barcode technology combined with patient identification software designed to assist in blood administration improves the bedside administration of transfusions in an Australian tertiary hospital. STUDY DESIGN AND METHODS: The study was conducted in a Haematology/Oncology Day Clinic of a major metropolitan hospital, to evaluate the use of 2D barcode technology and patient safety-software and hand-held PDAs to assist nursing staff in patient identification and blood administration. Comparative audits were conducted before and after the technology's implementation. RESULTS: The preimplementation transfusion practice audits demonstrated a poor understanding of the blood checking process, with focus on the product rather than patient identification. Following the implementation of 2D barcode technology and patient safety-software, there was significant improvement in administration practice. Positive, verbal patient identification improved from 57% (51/90) to 94% (75/80). Similarly, the cross-referencing of the patient's identification with the patient's wristband improved from 36% (32/90) to 94% (75/80), and the cross-referencing of patient ID on the compatibility tag to wristbands improved from 48% (43/90) to 99% (79/80). Importantly, the 2D barcode technology and patient safety-software saw 100% (80/80) of checks being conducted at the patient bedside, compared with 76% (68/90) in the preimplementation audits. CONCLUSION: This pilot study demonstrates that 2D barcode technology and patient safety-software significantly improves the bedside check of patient and blood product identification in an Australian setting.

A randomized trial of leukapheresis volumes, 7 L versus 10 L: an assessment of efficacy and patient tolerance.

High-dose chemotherapy followed by autologous PBSC transplantation (PBSCT) has become an accepted form of therapy for a number of malignant hematologic diseases. The optimal method for the collection of PBSC is yet to be defined. Large-volume leukapheresis may be able to collect adequate numbers of PBSC with the patient undergoing fewer procedures. We routinely process 7 L of blood per leukapheresis. Hence, we elected to assess whether a modest increase in the blood volume processed would, on average, decrease the number of leukaphereses each patient needed to undergo to collect > or =2 x 10(6) CD34+ cells/kg body weight. Sixty patients were randomized to undergo 7 L leukaphereses (n = 31 patients; 87 leukaphereses) or 10 L leukaphereses (n = 29 patients; 81 leukaphereses). The median number of leukaphereses required per patient to collect the target number of CD34+ cells was two (range one to five) for both groups (p = 0.83). The median number of nucleated cells collected per patient was greater for the 10 L group (8.2 x 10(8)/kg versus 5.3 x 10(8)/kg, p = 0.005), as was the median number of mononuclear cells (MNC) (4.7 x 10(8)/kg versus 3.6 x 10(8)/kg, p = 0.0001), whereas there was no statistical difference between the groups for the median number of CD34+ cells collected per patient (3.2 x 10(6)/kg versus 3.7 x 10(6)/kg, p = 0.98). Therefore, over the 18-month period of this trial, the use of a 10 L leukapheresis volume did not decrease the number of leukaphereses performed compared with a 7 L leukapheresis volume.

Minitron II system for precise control of the plant growth environment.

A transparent, cylindrical chamber system was developed to allow measurement of gas-exchange by small crop canopies in the undisturbed plant growth environment. The system is an elaboration of the Minitron system developed previously to compare growth of small plants in different environments within the same general growth area. The Minitron II system described herein accommodates hydroponic culture and separate control of atmospheric composition in individual chambers. Root and shoot environments are compartmented separately to accommodate atmospheres of different flow rate and/or gaseous composition. A series of 0-rings and tension-adjustable springs allow carbon dioxide in the flowing atmosphere to be analyzed without cross-contamination between chamber compartments or from external gas sources. Carbon dioxide has been maintained at set point +/- 9 g m-3 over a range of CO2 concentrations from 382 to 2725 g m-3 and with an atmosphere turnover rate of 136.7 cm3 s-1 by computer-assisted mass flow controllers. Each chamber has dimensions large enough (61 cm internal diameter, 0.151 m3 internal volume) to allow adequate replication of individual plants for statistical purposes (e.g., up to 36 equally-spaced plant holders). No significant variation in growth or photosynthetic rate of leaf lettuce occurred between chambers for a given set of environmental conditions. Gas-exchange rates in different chambers changed to a similar extent as CO2 concentration in the flowing atmosphere or chamber temperature were varied by the same amount. When coupled with appropriate control systems, Minitron II chambers can provide separate controlled environments for multiple small plants with adequate precision and at relatively low cost.

The Minitron system for growth of small plants under controlled environment conditions.

The design and operation of a system is described in which small plants can be grown under controlled environment conditions. Important features of this "Minitron" system include precise control of temperature and CO2 concentration in a flowing atmosphere. Plants can be grown either hydroponically or in solid root support medium. For either culture method, nutrient solution or water is added from an external reservoir, altering neither atmospheric composition nor temperature equilibrium within a closed Minitron chamber.

Spectrometric analysis of the influence of metal substrates on the color of metal-ceramic restorations.

The development and use of ceramic alloys have created the potential for variation in the color of dental porcelain. In order to define the nature of the alterations, it is necessary to examine quantitatively the color of dental porcelain baked onto ceramic alloys. The purpose of this study was to examine spectrometrically where color differences occur in the fabrication process. One shade of Vita porcelain was baked onto coupons of three ceramic alloys (high gold, palladium-silver, base metal). Eight replications were made in each alloy at seven fabrication steps: prepared metal, oxide, first opaque, second opaque, first dentin, second dentin, and glaze. Spectrometric analyses were performed for each replication at each step. Data were tabulated every 10 nm over the recorded 380-750-nm range, for conversion to the CIE color measurement system. Tristimulus values X, Y, and Z and chromaticity coordinates x and y were calculated. Differences from spectrographic inspection were seen among the metal substrate series. The greatest variation appeared at the first dentin step between the palladium-silver and high-gold alloys and between the palladium-silver and base metal alloys. Mean tristimulus values were significantly different (p less than 0.0001) for all steps and alloys. The distribution of plotted values followed the same pattern of spectral changes throughout the seven fabrication steps. Analysis of these data shows that color differences of metal-ceramic coupons based on dissimilar metal substrates can be quantified, and that spectral reflectance values can be converted to CIE notation. As depicted spectrally, notable color differences appeared with the first dentin porcelain layer.

Degradative effects of conventional steam sterilization on biomaterial surfaces.

Prior to implantation trials in animals, the effect of steam sterilization on the surface properties of metallic and coated biomaterials was studied. Pure germanium plates and cast surgical Vitallium discs and subperiosteal implants were treated to present three standard types of biomaterials surfaces prior to steam sterilization, ranging from scrupulously clean, high-energy metals to uniformly low-energy organic layers. Both before and after sterilization, the sample surfaces were characterized by a variety of nondestructive physiochemical techniques. The results indicate that steam sterilization is likely to compromise the properties of otherwise carefully prepared biomedical implants by depositing hydrophobic organic and hygroscopic salt contaminants over the implant surfaces.

Organic surface film contamination of Vitallium implants.

Conventional finishing and polishing techniques used to prepare Vitallium subperiosteal dental implant castings were found to produce low energy surfaces as measured by critical surface tension. Standard metallographic preparation gave slightly higher values. Glow discharge cleaning of both types of polished surface gave much higher critical surface tension values. This suggests the presence of an organic film after surface polishing of the implant which may later affect tissue reaction, in particular attachment, as has been noticed in related animal studies.

Reply to "myelin membrane structure as revealed by x-ray diffraction" by David Harker.

The interpretation of the heavy metal-labeled data can either be accomplished with the analysis of the observed intensity differences (Akers and Parsons) or with the analysis of the observed structure amplitude changes (Harker). Both methods of analysis give essentially the same results: that two possible electron density distributions are valid, within experimental error, depending on whether there are one or two metal-labeling sites within the membrane. At present, the correct choice must rest on either the introduction of additional physical and chemical data on the position of the proteins and lipids or on an independent phasing technique such as the Hosemann-Bagchi Q-function.