Van der Waals-corrected density functional theory: benchmarking for hydrogen-nanotube and nanotube-nanotube interactions

Density functional theory (DFT) is a powerful approach to electronic structure calculations in extended systems, but suffers currently from inadequate incorporation of long-range dispersion, or Van der Waals (VdW) interactions. VdW-corrected DFT is tested for interactions involving molecular hydrogen, graphite, single-walled carbon nanotubes (SWCNTs), and SWCNT bundles. The energy correction, based on an empirical London dispersion term with a damping function at short range, allows a reasonable physisorption energy and equilibrium distance to be obtained for H-2 on a model graphite surface. The VdW-corrected DFT calculation for an (8, 8) nanotube bundle reproduces accurately the experimental lattice constant. For H-2 inside or outside an (8, 8) SWCNT, we find the binding energies are respectively higher and lower than that on a graphite surface, correctly predicting the well known curvature effect. We conclude that the VdW correction is a very effective method for implementing DFT calculations, allowing a reliable description of both short-range chemical bonding and long-range dispersive interactions. The method will find powerful applications in areas of SWCNT research where empirical potential functions either have not been developed, or do not capture the necessary range of both dispersion and bonding interactions.

Van der Waals interactions between two parallel infinitely long single-walled nanotubes

The potential energies of van der Waals (VDW) interactions between two parallel, infinitely long and perfect SWNTs with identical, and different sizes were studied based on the continuum Lennard-Jones model. The conclusion of Girifalco's work on (n, n) SWNTs that the potentials of SWNT-SWNT fell on a single curve, is also applicable to SWNTs with different sizes. We further obtained the corresponding constants of the well depth phi(0) and equilibrium VDW gap g(0) for SWNTs with a radius from 2 to 25 Angstrom. (C) 2005 Elsevier B.V. All rights reserved.

Simple approach to estimating the van der Waals interaction between carbon nanotubes

The van der Waals (vdW) interactions between carbon nanotubes (CNTs) were studied based on the continuum Lennard-Jones model. It was found that all the vdW potentials between two arbitrary CNTs fall on the same curve when plotted in terms of certain reduced parameters, the well depth, and the equilibrium vdW gap. Based on this observation, an approximate approach is developed to obtain the vdW potential between two CNTs without time-consuming computations. The vdW potential estimated by this approach is close to that obtained from complex integrations. Therefore, the developed approach can greatly simplify the calculation of vdW interactions between CNTs.

London-van der Waals adhesiveness of rough particles

Van der Waals forces often dominate interactions and adhesion between fine particles and, in turn, decisively influence the bulk behaviour of powders. However, so far there is no effective means to characterize the adhesive behaviour of such particles. A complication is that most powder particles have rough surfaces, and it is the asperities on the surfaces that touch, confounding the actual surface that is in contact. Conventional approaches using surface energy provide limited information regarding adhesion, and pull-off forces measured through atomic force microscope (AFM) are highly variable and difficult to interpret. In this paper we develop a model which combines the Rumpf-Rabinovich and the JKR-DMT theories to account simultaneously for the effects of surface roughness and deformation on adhesion. This is applied to a 'characteristic asperity' which may be easily obtained from AFM measurements. The concept of adhesiveness, a material property reflecting the influences of elastic deformability, surface roughness, and interfacial surface energy, is introduced as an efficient and quantitative measure of the adhering tendency of a powder. Furthermore, a novel concept of specific adhesiveness is proposed as a convenient tool for characterizing and benchmarking solid materials. This paper provides an example to illustrate the use of the proposed theories. (c) 2005 Elsevier B.V. All rights reserved.

General practice in Australia 2020: "robust and ready" or "rudderless and reeling"?

The future role and structure of Australian general practice remains uncertain, despite a decade of seemingly constant change following the release of the National Health Strategy papers. Some of the suggested change strategies (such as rural Practice Incentive Payments and practice accreditation) have been implemented; others (such as general practitioner involvement with area health authorities in delivering national goals and targets for communities) still await attention. An overarching vision for our health care system in 2020 and general practice's role within it are still to be clearly enunciated. Australia is at variance with other Western countries, such as the United Kingdom, Canada and New Zealand, which have spent significant time refocusing their health systems to deal with an ageing population with an increased burden of chronic disease. Health bureaucrats and governments need to invest strategically in operational primary care now. This will require the active commitment of general practice's national bodies to articulate and actively promote a shared vision for Australian general practice.

Multisite, quality-improvement collaboration to optimise cardiac care in Queensland public hospitals

Objective: To evaluate changes in quality of in-hospital care of patients with either acute coronary syndromes (ACS) or congestive heart failure (CHF) admitted to hospitals participating in a multisite quality improvement collaboration. Design: Before-and-after study of changes in quality indicators measured on representative patient samples between June 2001 and January 2003. Setting: Nine public hospitals in Queensland. Study populations: Consecutive or randomly selected patients admitted to study hospitals during the baseline period (June 2001 to January 2002; n = 807 for ACS, n = 357 for CHF) and post-intervention period (July 2002 to January 2003; n = 717 for ACS, n = 220 for CHF). Intervention: Provision of comparative baseline feedback at a facilitative workshop combined with hospital-specific quality-improvement interventions supported by on-site quality officers and a central program management group. Main outcome measure: Changes in process-of-care indicators between baseline and post-intervention periods. Results: Compared with baseline, more patients with ACS in the post-intervention period received therapeutic heparin regimens (84% v 72%; P < 0.001), angiotensin-converting enzyme inhibitors (64% v 56%; P = 0.02), lipid-lowering agents (72% v 62%; P < 0.001), early use of coronary angiography (52% v 39%; P < 0.001), in-hospital cardiac counselling (65% v 43%; P < 0.001), and referral to cardiac rehabilitation (15% v 5%; P < 0.001). The numbers of patients with CHF receiving β-blockers also increased (52% v 34%; P < 0.001), with fewer patients receiving deleterious agents (13% v 23%; P = 0.04). Same-cause 30-day readmission rate decreased from 7.2% to 2.4% (P = 0.02) in patients with CHF. Conclusion: Quality-improvement interventions conducted as multisite collaborations may improve in-hospital care of acute cardiac conditions within relatively short time frames.

Metformin and serious adverse effects

Metformin, a biguanide derivative, has been used in the treatment of type 2 diabetes for nearly 50 years. It acts as an insulin-sensitising agent, lowering fasting plasma insulin concentrations by inducing greater peripheral uptake of glucose, as well as decreasing hepatic glucose output. In 1998, the United Kingdom Prospective Diabetes Study reported that, in overweight patients with type 2 diabetes, treatment with metformin compared with diet alone resulted in statistically significant absolute risk reductions (ARRs) in all-cause mortality (ARR, 7%), diabetes-related deaths (ARR, 5%), any diabetes-related endpoint (ARR, 10%), and macrovascular disease (myocardial infarction, sudden death, angina, stroke, peripheral vascular disease).1 This was achieved without hypoglycaemia or weight gain. As a result, metformin is now regarded as the oral hypoglycaemic agent of choice in the treatment of overweight people with type 2 diabetes.

Telepaediatrics and diabetic retinopathy screening of young people with diabetes in Queensland

We have examined the feasibility of a telemedicine-enabled screening service for children and adolescents with diabetes in Queensland. There are approximately 1400 young people with diabetes in Queensland and only about two-thirds of them are screened in accordance with international guidelines. A regional retinal screening service was established using a non-mydriatic digital retinal camera. Seven centres volunteered to participate in the study. During a five-month pilot trial, 83 of the young people with diabetes who attend these centres underwent digital retinal screening (3.7%). Retinal images were sent via email to a paediatric ophthalmologist for review and results were returned via email. A copy of each participant's results was forwarded by mail to the referring diabetes doctor and the participant and family. The majority of the image files (96%) were rated as excellent or good. Only one participant was identified as having an abnormal result. Participants and their families expressed satisfaction with the digital retinal screening process.

Randomised controlled trial of health assessments for older Australian veterans and war widows

Objective: To assess the effect of home-based health assessments for older Australians on health-related quality of life, hospital and nursing home admissions, and death. Design: Randomised controlled trial of the effect of health assessments over 3 years. Participants and setting: 1569 community-living veterans and war widows receiving full benefits from the Department of Veterans' Affairs and aged 70 years or over were randomly selected in 1997 from 10 regions of New South Wales and Queensland and randomly allocated to receive either usual care (n = 627) or health assessments (n = 942). Intervention: Annual or 6-monthly home-based health assessments by health professionals, with telephone follow-up, and written report to a nominated general practitioner. Main outcome measures: Differences in health-related quality of life, admission to hospital and nursing home, and death over 3 years of follow-up. Results: 3-year follow-up interviews were conducted for 1031 participants. Intervention-group participants who remained in the study reported higher quality of life than control-group participants (difference in Physical Component Summary score, 0.90; 95% CI, 0.05-1.76; difference in Mental Component Summary score, 1.36; 95% CI, 0.40-2.32). There was no significant difference in the probability of hospital admission or death between intervention and control groups over the study period. Significantly more participants in the intervention group were admitted to nursing homes compared with the control group (30 v 7; P < 0.01). Conclusions: Health assessments for older people may have small positive effects on quality of life for those who remain resident in the community, but do not prevent deaths. Assessments may increase the probability of nursing-home placement.

The other side of the coin: safety of complementary and alternative medicine

Most consumers consider complementary and alternative medicine (CAM) products inherently safe. The growing simultaneous use of CAM products and pharmaceutical drugs by Australian consumers increases the risk of CAM-drug interactions. The Therapeutic Goods Administration (TGA) has a two-tier, risk-based regulatory system for therapeutic goods - CAM products are regulated as low risk products and are assessed for quality and safety; and sponsors of products must hold the evidence for any claim of efficacy made about them. Adverse reactions to CAM products can be classified as intrinsic (innate to the product), or extrinsic (where the risk is not related to the product itself, but results from the failure of good manufacturing practice). Adverse reactions to CAM practices can be classified as risks of commission (which includes removal of medical therapy) and risks of omission (which includes failure to refer when appropriate). While few systematic studies of adverse events with CAM exist, and under-reporting is likely, most CAM products and practices do not appear to present a high risk; their safety needs to be put into the perspective of wider safety issues. A priority for research is to rigorously define the risks associated with both CAM products and practices so that their potential impact on public health can be assessed.

Factors influencing the number needed to excise: excision rates of pigmented lesions by general practitioners

Objective: To identify doctor and patient characteristics associated with excision of benign versus malignant pigmented skin lesions. Design, setting and participants: Retrospective audit of data on 4741 pigmented skin lesions excised from November 1998 to February 2000 by 468 general practitioners (39% response rate) from 223 practices in Perth, WA. (The data used were from the baseline period of a randomised controlled trial of a diagnostic aid for pigmented skin lesions.) Main outcome measure: The number needed to treat (NNT), defined as the number of pigmented lesions needed to be excised to identify one melanoma, in relation to demographic characteristics of GPs and patients. Results: Relatively more benign lesions were excised per melanoma (NNT = 83) in the youngest patients (aged 10-19 years) compared with the oldest (aged greater than or equal to 70) (NNT = 11) (P [trend]

Seronegative spondyloarthropathies: To lump or split?

The advent of novel biological therapies for the treatment of rheumatic disease has renewed interest in the seronegative spondyloarthropathies (SpAs). International efforts are redefining disease classification and measures of disease activity, outcome, metrology, and imaging. However, opinion is divided between those who propose that the SpA group represents the same disease with variable expression (the lumpers) and those who consider these to be separate diseases with shared clinical features (the splitters). This review presents the evidence for both approaches.

Empiric management of community-acquired pneumonia in Australian emergency departments

Objective: To describe empiric community-acquired pneumonia (CAP) management in Australian hospital emergency departments (EDs) and evaluate this against national guidelines, including use of the pneumonia severity index and antibiotic selection. Design: A multicentre, cross-sectional, retrospective audit, April 2003 to February 2005. Setting: 37 Australian hospitals: 22 principal referral hospitals, six large major city hospitals, four large regional hospitals, four medium hospitals and one private hospital. Participants: Adult patients with a diagnosis of CAP made in the ED. Data on 20 consecutive CAP ED presentations were collected in participating hospitals. Outcome measures: Documented use of the pneumonia severity index, initial antibiotic therapy prescribed in the ED, average length of stay, inpatient mortality, and concordance with national guidelines. Results: 691 CAP presentations were included. Pneumonia severity index use was documented in 5% of cases. Antibiotic therapy covering common bacterial causes of CAP was prescribed in 67% of presentations, although overall concordance with national guidelines was 18%. Antibiotic prescribing was discordant due to inadequate empiric antimicrobial cover, allergy status (including contraindication to penicillin), inappropriate route of administration and/or inappropriate antibiotic choice according to recommendations. There was no significant difference between concordant and discordant antibiotic prescribing episodes in average length of stay (5.0 v 5.7 days; P=0.22) or inpatient mortality (1.6% v 4.1%; chi(2) = 1.82; P=0.18). Conclusions: Antibiotic therapy for CAP prescribed in Australian EDs varied. Concordance with national CAP guidelines was generally low. Targeted interventions are required to improve concordance.