Biomedical subjects
Publications and source records attributed to Christopher Harrison.
The BEACH program, a continuous national study of general practice activity in Australia, gives us an overview of encounters at which malignant neoplasms were managed. This synopsis provides a backdrop against which the articles in this issue of Australian Family Physician can be further considered.
Irritable colon, spastic colon syndrome, mucous colitis, splenic flexure syndrome and functional diarrhoea were included with irritable bowel syndrome (IBS), however these related conditions accounted for only 3% of total IBS problems managed.
INTRODUCTION: Universal infant heptavalent pneumococcal conjugate vaccine (PCV-7) immunization, dosed near to the originally recommended schedule of a 3-dose series in the first 6 months of life, then a booster between 12 and 15 months, should reduce nasopharyngeal (NP) carriage of Streptococcus pneumoniae (Spn) PCV-7 types. The reduced availability of PCV-7 altered immunization schedules, particularly for third and fourth PCV-7 doses. We evaluated NP colonization in relation to originally recommended intervals and numbers of PCV-7 doses. METHODS: Spn from NP cultures of a cohort of 106 normal children, obtained during 20 months of PCV-7 shortage, were identified and serotyped by standard methods. RESULTS: Spn was detected in 153 of 418 cultures (37%). Age, >1 sibling, day-care attendance and prolonged PCV-7 dosing intervals were univariate risks for NP detection of PCV-7 types. PCV-7 strains comprised 7 of 15 (47%) of Spn before the first dose, 28 of 36 (78%) and 27 of 41 (66%), respectively, after the first and second dose and then 16 of 36 (44%) and 11 of 25 (44%) after the third and fourth doses. The risk of NP colonization with PCV-7 types was higher with intervals of >3 months between second and third doses and intervals of >8 months between the third and fourth doses. Multivariate analysis showed prolonged interval after the second and third PCV-7 doses and day-care attendance as risk factors for NP detection of PCV-7 strains. CONCLUSION: Although PCV-7 serotypes were detected less after third and fourth PCV-7 doses, longer dosing intervals, particularly in day-care attendees, were associated with higher risk of PCV-7 detection in the NP.
Frontal photopolymerization (FPP) offers numerous advantages for the rapid prototyping of microfluidic devices. Quantitative utilization of this method, however, requires a control of the vertical dimensions of the patterned resist material. To address this fundamental problem, we study the ultraviolet (UV) photopolymerization of a series of multifunctional thiolene resists through a combination of experiments and analytical modeling of the polymerization fronts. We describe this nonlinear spatio-temporal growth process in terms of a "minimal" model involving an order parameter phi(x, t) characterizing the extent of monomer-to-polymer conversion, the optical attenuation T(x, t), and the solid front position h(t). The latter exhibits an induction time (or equivalent critical UV dose) characterizing the onset of frontal propagation. We also observe a novel transition between two logarithmic rates of growth, determined by the Beer-Lambert attenuation constants mu(0) and mu(infinity) of the monomer and fully polymerized material, respectively. The measured frontal kinetics and optical transmission of the thiolene resist materials are consistent with our photopolymerization model, exhibiting both "photodarkening" and "photoinvariant" polymerization. This is apparently the first observation of photodarkening reported in FPP. On the basis of these results, multilevel fluidic devices with controlled height are readily fabricated with modulated illumination. A representative two-level microfluidic device, incorporating a chaotic mixer, a T junction, and a series of controlled flow constrictions, illustrates the practical versatility of this fabrication method.
As technology continues towards smaller, thinner and lighter devices, more stringent demands are placed on thin polymer films as diffusion barriers, dielectric coatings, electronic packaging and so on. Therefore, there is a growing need for testing platforms to rapidly determine the mechanical properties of thin polymer films and coatings. We introduce here an elegant, efficient measurement method that yields the elastic moduli of nanoscale polymer films in a rapid and quantitative manner without the need for expensive equipment or material-specific modelling. The technique exploits a buckling instability that occurs in bilayers consisting of a stiff, thin film coated onto a relatively soft, thick substrate. Using the spacing of these highly periodic wrinkles, we calculate the film's elastic modulus by applying well-established buckling mechanics. We successfully apply this new measurement platform to several systems displaying a wide range of thicknessess (nanometre to micrometre) and moduli (MPa to GPa).
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We have followed the coarsening dynamics of a single layer of cylindrical block copolymer microdomains in a thin film. This system has the symmetry of a two-dimensional smectic. The orientational correlation length of the microdomains was measured by scanning electron microscopy and found to grow with the average spacing between +/-1/2 disclinations, following a power law xi2(t) approximately t(1/4). By tracking disclinations during annealing with time-lapse atomic force microscopy, we observe dominant mechanisms of disclination annihilation involving tripoles and quadrupoles (three and four disclinations, respectively). We describe how annihilation events involving multiple disclinations result in similarly reduced kinetic exponents as observed here. These results map onto a wide variety of physical systems that exhibit similarly striped patterns.
We describe a method for using polynomial mapping to correct scanning probe microscope images for distortion due to piezoelectric creep. Because such distortion varies from image to image, this method can be used when the actual locations of some features within an image are known absolutely, or in a series of images in which the actual locations of some features are known not to vary. While the general case of polynomial mapping of degree N requires the determination of 2(N+ 1)2 matrix elements by regression, we find that by understanding the mechanism by which piezoelectric creep distorts scanning probe microscope images, we can fix most of these coefficients at 0 or 1 a priori, leaving only 2(N+ 1) coefficients to be determined by regression. We describe our implementation of this strategy using the Interactive Data Language (IDL) programming language, and demonstrate our technique on a series of atomic force microscopy (AFM) images of diblock copolymer microdomains. Using our simplified scheme, we are able to reduce the effects of distortion in an AFM image from 5% of the scan width to a single pixel, using only five reference points.