The double-reversing Z-plasty in primary palatoplasty: operative experience and early results

The double-reversing Z-plasty of Furlow for closure of the soft palate was used in 34 children with various types of cleft palate. Mean age at repair was 12.8 months. Intraoperative experience was favorable, with acceptable operating time and blood loss. Length of hospitalization averaged 1.9 days. Postoperatively, two children experienced temporary stridor, which resolved within 24 to 48 hours. One child had dehiscence of the hard palate (Von Lagenbeck repair) 4 weeks postoperatively, and three children developed small oronasal fistulae. Early speech evaluation demonstrated adequate soft palate mobility in 33 of 34 patients, with observable velopharyngeal function. Twelve children had mild velar compromise, with eight exhibiting slight nasal air escape.     

Simulations of the mobile phase of polyethylene

Results are presented from atomistic molecular dynamics simulations of the mobile pseudo-hexagonal phase of polyethylene, which occurs under conditions of elevated pressure and temperature. Three different types of model are considered, all of which employ periodic boundary conditions. The first model consists of n-alkane sequences (48×-C₂₄H₄₈-) that are bonded across the simulation box boundaries to produce chains that are effectively infinite in extent. On heating, at high pressure, this system displays a rotator phase, in which the chains retain an all-trans conformation, and rotate as semi-rigid units. A second model, consisting of finite n-alkanes (48×C₂₄H₅₀) displays the same behaviour at low temperatures, but at high temperature and pressure forms a conformationally disordered rotator phase, characterised by a large proportion of gauche defects and a significant lattice expansion. The final model considered contains long n-alkanes (24×C₁₀₂H₂₀₆) which contain jog defects and each pass twice through the simulation box. This model forms a conformationally disordered rotator phase at high temperature and ambient pressure. The behaviour of the three models, in terms of the variations in chain conformation and rotational and translational dynamics, are compared. The conformationally disordered phases provide useful representations of the experimentally observed mobile phase.     

Effects of manufacturing defects on the mechanical properties of carbon fibre reinforced polyethersulphone laminates

The effects of defects on the mechanical properties of carbon fibre reinforced polyethersulphone laminates have been measured. The defects studied were cut fibre plies, omission of polymer films and local delamination produced by the inclusion of foreign matter. Of these it was found that only cut plies had a significant detrimental effect on the strength of a laminate. For specimens with two cut plies, the failure stress, tensile, flexural and compressive in the remaining continuous plies was the same as in the defect-free material, provided that the cut plies were widely separated. However the failure stresses were 15–18% lower in the continuous plies in the specimens containing two cut plies which were more closely spaced and in specimens containing four cut plies.     

Stochastic model for a wavelike exothermal reaction in condensed heterogeneous systems

The labile protons of two 32-base-pair, four-arm models of immobile Holliday junctions have been studied by two-dimensional 1H nuclear magnetic resonance (NMR) spectroscopy. Overlap of resonances in the imino-imino region of two-dimensional nuclear Overhauser enhancement (NOE) spectra necessitates the use of a multi-pathway approach for obtaining sequence-specific assignments wherein all possible NOE connectivities to the labile protons are utilized, including those from the 2H of adenine, 5CH3 of thymine, and 5H of cytosine. Resonance assignments are obtained for all slowly exchanging imino and cytosine amino protons. Base-pairing up to and including the junction point is found in all four arms of both Holliday junctions. Several cross-arm NOE connectivities are identified and can be used to infer the geometry of the helical stacking domains. The two Holliday junctions studied, which differ only by the exchange of two base pairs at the branch point, appear to have opposite arm stacking geometries. These assignments form an important part of the critical background for detailed NMR analysis of Holliday junction structure and dynamics.     

Transconductance and mobility of Si:B delta MOSFETs

Delta-doped MOSFETs have been fabricated in MBE-grown silicon using for the first time boron as the dopant within the delta layer. Current-voltage characteristics have been measured, and secondary ion mass spectrometry (SIMS) is used to confirm the location of the delta layer and the extent of layer broadening by diffusion during processing. Precise threshold voltages of the devices are difficult to determine since the devices (which all operate in depletion mode) take several volts to switch off. Transconductances of the devices have been measured, and it is shown how analysis of these results can yield estimates of the carrier mobility for transport along the delta layers despite the uncertainty in the threshold voltage. A clear transition is observed in the results which is attributed to the formation of a parasitic surface-channel field-effect transistor, providing conclusive evidence that the devices are conducting along a delta channel for part of the measured range of applied gate biases     

Antigenic variants of Plasmodium chabaudi chabaudi AS and the effects of mosquito transmission

Previous results, using a passive transfer assay, have shown that recrudescences of Plasmodium chabaudi chabaudi AS strain are antigenically different from the infecting parental population and also that the recrudescence appears to be a mix of antigenic types. This present study examines further these recrudescent populations using an indirect fluorescent antibody test on live, schizont-infected red blood cells. This analysis shows that ten clones derived from a recrudescence are all antigenically different from the parent population and that some are different from each other. The use of this method to examine the antigenic types of recrudescent clones after transmission through mosquitoes also demonstrates a resulting change in antigenicity. Such results showing a link between mosquito transmission and varying antigenicity may have important implications in terms of immunity and vaccine development.     

Effect of crosslinking agent content, monomer functionality, and repeat unit chemistry on properties of unfilled resins

Seven mechanical/physical properties were used to evaluate 10 unfilled resins: eight aromatic dimethacrylates and two urethane dimethacrylates. Physical property tests included compressive strength, Young's modulus in compression, uniaxial tensile strength, intrinsic yield point, toothbrush abrasion, Knoop hardness, and water sorption. Controlled changes were made in the following four material parameters: amount of crosslinking diluent present in the uncured monomer, functionality of the monomer, repeat unit chemistry of the monomer (urethane vs. aromatic structure) and mode of activation (chemical vs. visible light). Polymers containing a high concentration of crosslinking agent (50 wt%) were found to be tougher and to possess lower hardness than materials containing lesser amounts of crosslinking agent. This was attributed to the flexible nature of the triethylene glycol dimethacrylate crosslinking molecule. Exposure to water plasticized the highly crosslinked materials to the degree that the yield point and elastic modulus were effectively lowered. Most of the tested properties were unaffected by differences in functionality except resistance to toothbrush abrasion, which was enhanced for polymers derived from high functionality monomers. The urethane-based polymers sorbed substantially more water than the aromatic-based materials, which presumably resulted in lower values for surface hardness. However, the urethane resins were very tough, and excellent resistance to toothbrush abrasion was observed. Property differences caused by differences in activation mode were small, although the visible light materials did sorb more water.