Adhesion between oppositely charged polyelectrolytes

The adhesion between a grafted polyelectrolyte layer (brush) and a gel of an oppositely charged polyelectrolyte has been measured as a function of applied pressure, and the interface has been traced using neutron reflectometry. The interface (in aqueous medium at pH 6) between the (polycationic) brush and the (polyanionic) gel has a limited pressure dependence, with a small amount of deformation of the interface at the brush–gel contact. Brushes with a dry thickness of up to 13 nm exhibit weak adhesion (measured using a mechanical force tester) with an adhesive failure when the gel is detached. Thicker brushes result in the gel exhibiting cohesive failure. Reversing the geometry, whereby a polycationic brush is replaced with a polyanion and the polyanionic gel is replaced with a polycation, reveals that the pH dependence of the adhesion is moderately symmetric about pH 6, but that the maximum force required to separate the polycation gel from the polyanion brush over the range of pH is greater than that for the polycation brush and polyanion gel. The polyanion used is poly(methacrylic acid) (PMAA) and polycations of poly[2-(diethylamino)ethyl methacrylate] (PDEAEMA) and poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA) were used.     

The cost of caring for end-stage kidney disease patients: an analysis based on hospital financial transaction records

The costs of care for end-stage renal disease patients continue to rise because of increased numbers of patients. Efforts to contain these costs have focused on the development of capitated payment schemes, in which all costs for the care of these patients are covered in a single payment. To determine the effect of a capitated reimbursement scheme on care of dialysis patients (both hemodialysis [HD] and peritoneal dialysis [PD]), complete financial records (all reimbursements for inpatient and outpatient care, as well as physician collections) of dialysis patients at a single medical center over 1 year were analyzed. For the period from July 1994 to July 1995, annualized cost per dialysis patient-year averaged $63,340, or 9.8% higher than the corrected estimate from the U.S. Renal Data Service (USRDS; $57,660). The "most expensive" 25% of patients engendered 44 to 48% of the total costs, and inpatient costs accounted for 37 to 40% of total costs. Nearly half of the inpatient costs resulted from only two categories (room charges and inpatient dialysis), whereas other categories each made up a small fraction of the inpatient costs. PD patients were far less expensive to care for than HD patients, due to reduced hospital days and lower cost of outpatient dialysis. Care for a university-based dialysis population was only slightly more expensive than estimates predicted from the USRDS. These results validate the USRDS spending data and suggest that they can be used effectively for setting capitated rates. Efforts to control costs without sacrificing quality of care must center on reducing inpatient costs, particularly room charges and the cost of inpatient dialysis.     

National curriculum in Australia? A matter of politics, powerful knowledge and the regulation of learning

This article maps the contentious question of 'national curriculum' in Australia. It explains both why there is no national (i.e. Australian) curriculum, and analyses the history of curriculum formation with a view to documenting the changing significance and status of 'national' (i.e. nation-building) curriculum. The analysis is informed by an historical sociology perspective which begins by considering curriculum in relation to the national question in Australia and then moves on to examine the role of curriculum in the contemporary re-design of education as a social institution and a regulatory device within the Australian national jurisdiction.     

Protocell design through modular compartmentalization

De novo synthetic biological design has the potential to significantly impact upon applications such as energy generation and nanofabrication. Current designs for constructing organisms from component parts are typically limited in scope, as they utilize a cut-and-paste ideology to create simple stepwise engineered protein-signalling pathways. We propose the addition of a new design element that segregates components into lipid-bound ‘proto-organelles’, which are interfaced with response elements and housed within a synthetic protocell. This design is inspired by living cells, which utilize multiple types of signalling molecules to facilitate communication between isolated compartments. This paper presents our design and validation of the components required for a simple multi-compartment protocell machine, for coupling a light transducer to a gene expression system. This represents a general design concept for the compartmentalization of different types of artificial cellular machinery and the utilization of non-protein signal molecules for signal transduction.