Impurities in a 28Si-Enriched Single Crystal Produced for the Realization of the Redefined Kilogram.

The practical realization of the unit of mass is possible by manufacturing a perfect one-kilogram sphere from a 28Si-enriched single crystal. The mass of the sphere can be determined in terms of a fixed value of the Planck constant by counting the number of silicon atoms in the core of the single crystal. To reach the target 2.0 × 10-8 relative standard uncertainty, the mass of the surface layer and the mass deficit due to point defects such as impurities and vacancies must be investigated and corrected for. A sample of a 28Si-enriched single crystal produced to test the possibility of obtaining material at a scale useful to the dissemination of mass standards was measured by instrumental neutron activation analysis to check the purity with respect to a large number of possible contaminant elements. The results collected in a neutron activation experiment performed with the high thermal neutron flux available at the 20 MW OPAL research reactor are described. The data collected in this study showed that the produced material has a purity level never achieved with silicon used to manufacture previous one-kilogram spheres.

Measurement of the 30Si Mole Fraction in the New Avogadro Silicon Material by Neutron Activation and High-Resolution γ-Spectrometry.

The use of new silicon single crystals highly enriched in 28Si recently produced for the upcoming redetermination of the Avogadro constant requires knowledge of their molar masses. The isotopic composition data are collected independently in different laboratories but all using the virtual element technique with multicollector inductively coupled plasma mass spectrometers. In this framework, the comparison of the results with an independent measurement of the amount of at least one of the depleted isotopes is useful to limit hidden systematic errors. To this aim, the 30Si mole fraction of a sample of the new material was measured using a relative measurement protocol based on instrumental neutron activation analysis. The protocol is similar to that previously applied with the AVO28 silicon material used for the last determination of the Avogadro constant value with the exception that unknown and standard samples are not coirradiated. The x(30Si) = 5.701 × 10-7 mol mol-1 estimate is close to the expected one and is given with a standard uncertainty of 8.8 × 10-9 mol mol-1. This value, if adopted, gives a contribution to the relative standard uncertainty of the Avogadro constant of 6.3 × 10-10.

Trace metal content in inhalable particulate matter (PM2.5-10 and PM2.5) collected from historical mine waste deposits using a laboratory-based approach.

Mine wastes and tailings are considered hazardous to human health because of their potential to generate large quantities of highly toxic emissions of particulate matter (PM). Human exposure to As and other trace metals in PM may occur via inhalation of airborne particulates or through ingestion of contaminated dust. This study describes a laboratory-based method for extracting PM2.5-10 (coarse) and PM2.5 (fine) particles from As-rich mine waste samples collected from an historical gold mining region in regional, Victoria, Australia. We also report on the trace metal and metalloid content of the coarse and fine fraction, with an emphasis on As as an element of potential concern. Laser diffraction analysis showed that the proportions of coarse and fine particles in the bulk samples ranged between 3.4-26.6 and 0.6-7.6 %, respectively. Arsenic concentrations were greater in the fine fraction (1680-26,100 mg kg-1) compared with the coarse fraction (1210-22,000 mg kg-1), and Co, Fe, Mn, Ni, Sb and Zn were found to be present in the fine fraction at levels around twice those occurring in the coarse. These results are of particular concern given that fine particles can accumulate in the human respiratory system. Our study demonstrates that mine wastes may be an important source of metal-enriched PM for mining communities.

Purity of (28)Si-Enriched Silicon Material Used for the Determination of the Avogadro Constant.

At present, counting atoms in a one-kilogram sphere made of (28)Si-enriched silicon allows the determination of the Avogadro constant with the 2.0 × 10(-8) relative standard uncertainty required for the realization of the definition of the new kilogram. With the exception of carbon, oxygen, boron, nitrogen, and hydrogen, the claimed uncertainty is based on the postulation that the silicon material used to manufacture the sphere was above a particular level of purity. Two samples of the silicon were measured using instrumental neutron activation analysis to collect experimental data to test the purity assumption. The results obtained in two experiments carried out using different research reactor neutron sources are reported. The analysis confirmed that the silicon material was of sufficient purity by quantifying the ultratrace concentration of 12 elements and determining the detection limits of another 54 elements.

Size-dependent characterisation of historical gold mine wastes to examine human pathways of exposure to arsenic and other potentially toxic elements.

Abandoned historical gold mining wastes often exist as geographically extensive, unremediated, and poorly contained deposits that contain elevated levels of As and other potentially toxic elements (PTEs). One of the key variables governing human exposure to PTEs in mine waste is particle size. By applying a size-resolved approach to mine waste characterisation, this study reports on the proportions of mine waste relevant to human exposure and mobility, as well as their corresponding PTE concentrations, in four distinct historical mine wastes from the gold province in Central Victoria, Australia. To the best of our knowledge, such a detailed investigation and comparison of historical mining wastes has not been conducted in this mining-affected region. Mass distribution analysis revealed notable proportions of waste material in the readily ingestible size fraction (≤250 µm; 36.1-75.6 %) and the dust size fraction (≤100 µm; 5.9-45.6 %), suggesting a high potential for human exposure and dust mobilisation. Common to all mine waste types were statistically significant inverse trends between particle size and levels of As and Zn. Enrichment of As in the finest investigated size fraction (≤53 µm) is of particular concern as these particles are highly susceptible to long-distance atmospheric transport. Human populations that reside in the prevailing wind direction from a mine waste deposit may be at risk of As exposure via inhalation and/or ingestion pathways. Enrichment of PTEs in the finer size fractions indicates that human health risk assessments based on bulk contaminant concentrations may underestimate potential exposure intensities.

Elemental characterization of single-wall carbon nanotube certified reference material by neutron and prompt γ activation analysis.

Instrumental neutron activation analysis with both relative and k0 standardization was used in four experienced laboratories to determine element mass fractions in single-wall carbon nanotube certified reference material (CRM) SWCNT-1. Results obtained were evaluated using the National Institute of Standards and Technology (NIST) "Type B On Bias" approach and yielded consensus values in agreement with National Research Council Canada (NRCC) certified values for Fe, Co, Ni, and Mo and provided mass fraction values for 13 additional elements, namely, Na, Mg, Al, K, Ca, Ti, V, Cr, Mn, Br, La, W, and Au. In addition, prompt γ neutron activation analysis was employed to determine mass fractions of H, B, Co, Ni, and Mo. Results of this work provide a basis for the establishment of reference values of element mass fractions in CRM SWCNT-1, thus expanding its usability for more accurate characterization and benchmarking of similar nanotechnology materials.

Copper removal using bio-inspired polydopamine coated natural zeolites.

Herein, for the first time, natural clinoptilolite-rich zeolite powders modified with a bio-inspired adhesive, polydopamine (PDA), have been systematically studied as an adsorbent for copper cations (Cu(II)) from aqueous solution. Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) revealed successful grafting of PDA onto the zeolite surface. The effects of pH (2-5.5), PDA treatment time (3-24h), contact time (0 to 24h) and initial Cu(II) ion concentrations (1 to 500mgdm(-3)) on the adsorption of Cu(II) ions were studied using atomic absorption spectroscopy (AAS) and neutron activation analysis (NAA). The adsorption behavior was fitted to a Langmuir isotherm and shown to follow a pseudo-second-order reaction model. The maximum adsorption capacities of Cu(II) were shown to be 14.93mgg(-1) for pristine natural zeolite and 28.58mgg(-1) for PDA treated zeolite powders. This impressive 91.4% increase in Cu(II) ion adsorption capacity is attributed to the chelating ability of the PDA on the zeolite surface. Furthermore studies of recyclability using NAA showed that over 50% of the adsorbed copper could be removed in mild concentrations (0.01M or 0.1M) of either acid or base.

Achieving better in-hospital and after-hospital care of patients with acute cardiac disease.

In patients hospitalised with acute coronary syndromes (ACS) and congestive heart failure (CHF), evidence suggests opportunities for improving in-hospital and after-hospital care, patient self-care, and hospital-community integration. A multidisciplinary quality improvement program was designed and instigated in Brisbane in October 2000 involving 250 clinicians at three teaching hospitals, 1080 general practitioners (GPs) from five Divisions of General Practice, 1594 patients with ACS and 904 patients with CHF. Quality improvement interventions were implemented over 17 months after a 6-month baseline period and included: clinical decision support (clinical practice guidelines, reminders, checklists, clinical pathways); educational interventions (seminars, academic detailing); regular performance feedback; patient self-management strategies; and hospital-community integration (discharge referral summaries; community pharmacist liaison; patient prompts to attend GPs). Using a before-after study design to assess program impact, significantly more program patients compared with historical controls received: ACS: Angiotensin-converting enzyme (ACE) inhibitors and lipid-lowering agents at discharge, aspirin and beta-blockers at 3 months after discharge, inpatient cardiac counselling, and referral to outpatient cardiac rehabilitation. CHF: Assessment for reversible precipitants, use of prophylaxis for deep-venous thrombosis, beta-blockers at discharge, ACE inhibitors at 6 months after discharge, imaging of left ventricular function, and optimal management of blood pressure levels. Risk-adjusted mortality rates at 6 and 12 months decreased, respectively, from 9.8% to 7.4% (P = 0.06) and from 13.4% to 10.1% (P = 0.06) for patients with ACS and from 22.8% to 15.2% (P < 0.001) and from 32.8% to 22.4% (P = 0.005) for patients with CHF. Quality improvement programs that feature multifaceted interventions across the continuum of care can change clinical culture, optimise care and improve clinical outcomes.

A computerised prescribing decision support system to improve patient adherence with prescribing. A randomised controlled trial.

BACKGROUND: Medication adherence is often suboptimal and this leads to poorer health outcomes. PARTICIPANTS: 179 adult patients taking three or more, long term medications in one academic general practice in Brisbane, Queensland. DESIGN: Unblinded, factorial, randomised controlled trial of computer generated consumer product information, computer generated medication timetable, both, or usual care. MAIN OUTCOME MEASURES: We derived adherence to medication by measuring the relative prescription rate for six groups of medications extracted by the Health Insurance Commission. We also measured patients' knowledge of, and satisfaction with, medications, and general practitioners' attitudes to the decision support system. RESULTS: There was no effect on medication adherence. Although GPs were supportive of the system, neither patients' self reported knowledge of medications, nor satisfaction with care, was increased by the intervention. CONCLUSION: Simply providing patients with medication timetables and computer generated consumer product information does not improve drug adherence in primary care.

Computerised reminders and feedback in medication management: a systematic review of randomised controlled trials.

OBJECTIVE: To systematically review randomised controlled trials (RCTs) of computer-generated medication reminders or feedback directed to healthcare providers or patients. DATA SOURCES: Extensive computerised and manual literature searches identified 76 English-language reports of RCTs reported before 1 January 2002. Searches were conducted between June 1998 and April 2002. STUDY SELECTION: 26 papers making 29 comparisons (two papers reported on multiple interventions) of computer-supported medication management to a control group. DATA EXTRACTION: The quality of the RCTs was systematically assessed and scored independently by two reviewers. Rates of compliance with (potential) reminders for the control and intervention groups were extracted. DATA SYNTHESIS: Heterogeneity of studies prevented a meta-analysis. Where possible, rates were calculated using the intention-to-treat principle. The comparisons were grouped into five areas. Reminders to providers in outpatient settings: six of 12 comparisons demonstrated positive effects (relative rates [RRs: intervention rates/control rates], 1.0 to 42.0). Provider feedback in outpatient settings: five of seven comparisons showed improved clinician behaviour (RRs, 1.0 to 2.5). Combined reminders and feedback in outpatient settings: the single comparison found no improvement. Reminders to providers in inpatient settings: three of five comparisons showed improvements (RRs, 1.0 to 2.1). Patient-directed reminders: two of four comparisons showed improvements in patient compliance. CONCLUSION: Reminders are more effective than feedback in modifying physician behaviour related to medication management. Patient-directed reminders can improve medication adherence.