Development and application of spherically curved charge-coupled device imagers.

Operation of a CCD imager on a curved focal surface offers advantages to flat focal planes, especially for lightweight, relatively simple optical systems. The first advantage is that the modulation transfer function can approach diffraction-limited performance for a spherical focal surface employed in large field-of-view or large-format imagers. The second advantage is that a curved focal surface maintains more uniform illumination as a function of radius from the field center. Examples of applications of curved imagers, described here, include a small compact imager and the large curved array used in the Space Surveillance Telescope. The operational characteristics and mechanical limits of an imager deformed to a 15 mm radius are also described.

Modeling the response time of an in vivo glucose affinity sensor.

A mathematical model was developed to describe the dose-response relationship of an optical glucose sensor. The basis for glucose detection is the reversible competitive displacement of a ligand from a receptor protein with specific binding sites for certain carbohydrates. Detection of glucose is based on measurements of the change in fluorescent lifetime of the donor-labeled protein, as it binds to the acceptor-labeled ligand. The sensor was modeled as a hollow fiber membrane, permeable to glucose, which encapsulates a solution of the receptor protein and competing ligand. Model equations that describe the diffusion of glucose through the fiber membrane and the subsequent displacement reactions within the fiber lumen were solved numerically to predict the response time of the sensor following a step change in bulk glucose concentration. The incorporation of an external mass transfer boundary layer was found to increase the response time by a factor of 3.7 over the well-stirred case. On the basis of the results of a parametric study, the response time of the sensor was found to be most sensitive to the diffusion coefficient of glucose in the membrane. When compared to experimental response times for an intensity-based affinity sensor using Concanavalin A as the receptor protein and dextran as the competing ligand, the model predictions were found to be significantly shorter than those observed. The effect of the in vivo environment on the performance of the sensor was also investigated through the incorporation of a fibrotic capsule layer. The additional diffusional resistance offered by the capsular tissue resulted in a 5-fold increase in the response time of the sensor.

How do parents' child-feeding behaviours influence child weight? Implications for childhood obesity policy.

BACKGROUND: Parents have some responsibility for children's dietary habits and they are often the focus of public health interventions designed to improve children's diets and thereby reduce the prevalence of childhood obesity. The current UK interventions promote awareness of healthy food choices, but offer little guidance for parents on child-feeding behaviours. METHODS: A review of recent literature regarding child-feeding behaviours and child weight. RESULTS: Parents report using a wide range of child-feeding behaviours, including monitoring, pressure to eat and restriction. Restriction of children's eating has most frequently and consistently been associated with child weight gain. Furthermore, there is substantial evidence for a causal relationship between parental restriction and childhood overweight. CONCLUSIONS: Parents may inadvertently promote excess weight gain in childhood by using inappropriate child-feeding behaviours. We recommend the development of interventions to increase awareness of the possible consequences of inappropriate child-feeding behaviours. Parents who are concerned about their child's weight will also require guidance and support in order to adopt more appropriate child-feeding behaviours.

Ionic permeability of K, Na, and Cl in crayfish nerve. Regulation by membrane fixed charges and pH.

Teorell's fixed charge theory for membrane ion permeability was utilized to calculate specific ionic permeabilities from measurements of membrane potential, conductance, and specific ionic transference numbers. The results were compared with the passive ionic conductances calculated from the branched equivalent circuit membrane model of Hodgkin Huxley. Ionic permeabilities for potassium, sodium, and chloride of crayfish (Procambarus clarkii) medial giant axons were examined over an external pH range from 3.8 to 11.4. Action potentials were obtained over this pH range. Failures occurred below pH 3.8 during protonation of membrane phospholipid phosphate and carboxyl, and above pH 11.4 from calcium precipitation. In general, chloride permeability increases with membrane protonation, while cation permeability decreases. At pH 7.0, PK = 1.33 X 10(-5), PCl = 1.49 X 10(-6), PNa = 1.92 X 10(-8) cm/s. PK: PCl: PNa = 693:78:1. PCl is zero above pH 10.6 and is opened predominately by protonation of epsilon-amino, and partially by tyrosine and sulfhydryl groups from pH 10.6 to 9. PK is activated in part by ionization of phospholipid phosphate and carboxyl around pH 4, then further by imidazole from pH 5 to 7, and then predominately from pH 7 to 9 by most probably phosphatidic acid. PNa permeability parallels that of potassium from pH 5 to 9.4. Below pH 5 and above pH 9.4, PNa increases while PK decreases. Evidence was obtained that these ions possibly share common passive permeable channels. The data best support the theory of Teorell, that membrane fixed charges regulate permiability and that essentially every membrane ionizable group appears involved in various amounts in ionic permeability control.

Adolescent bunions treated by the modified Lapidus procedure.

The modified Lapidus procedure with rigid internal fixation was used to correct adolescent bunion deformities in 20 patients (32 feet). All patients were female and skeletally mature at surgery. Their average age was 18 years. Preoperatively, 100% had bunion pain and trouble with shoe wear, and 93% had a hypermobile first ray. Sixteen patients (24 feet) were available for follow-up examination and radiographs. The average follow-up time for the entire group was 24.3 months (range 3-72 months). Excellent or good results were obtained in 91% of patients. One recurrence required reoperation with first metatarsal osteotomy and MTP joint debridement. In our experience, the modified Lapidus procedure is the procedure of choice for the adolescent bunion with a hypermobile first ray.

Wide-field-of-view heterodyne receiver at 1.06 microm with photorefractive InP:Fe.

Photorefractive InP:Fe with an applied dc field was used to construct a wide-field-of view heterodyne receiver in a double phase-conjugate mirror configuration. Large double phase-conjugate mirror diffraction efficiencies (>20%) and stable (as a function of signal-beam angle) intermediate-frequency powers were measured over an approximately 8 degrees field of view with a minimum rise time of approximately 65 ms. The influence of electric-field strength and sample temperature on rise time was measured.