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Biomedical subjects

W Craig Carter

Publications and source records attributed to W Craig Carter.

9 recordsLinked to original sources
PubMed2006

Grain boundary transitions in binary alloys.

A thermodynamic diffuse interface analysis predicts that grain boundary transitions in solute absorption are coupled to localized structural order-disorder transitions. An example calculation of a planar grain boundary using a symmetric binary alloy shows that first-order boundary transitions can be predicted as a function of the crystallographic grain boundary misorientation and empirical gradient coefficients. The predictions are compared to published experimental observations.

Journal Article↗
PubMed2006

Numerical analysis of the shapes and energies of droplets on micropatterned substrates.

The shapes and energies of drops on substrates patterned with either holes or posts are computed using Surface Evolver software. The holes and posts are cylindrical in shape and distributed in a 6-fold symmetric pattern. The wetting conditions are such that the liquid does not fill the holes and the interface between the drop and the substrate is composite, i.e., partly solid/liquid and partly liquid/vapor. The sequence of stable drop configurations with increasing volume is analyzed and provides, in part, an explanation for superhydrophobic drop spreading.

Journal Article↗
PubMed2006

Ionic colloidal crystals: Ordered, multicomponent structures via controlled heterocoagulation.

We propose a new type of ordered colloid, the "ionic colloidal crystal" (ICC), which is stabilized by attractive electrostatic interactions analogous to those in atomic ionic materials. The rapid self-organization of colloids via this method should result in a diversity of orderings that are analogous to ionic compounds. Most of these complex structures would be difficult to produce by other methods. We use a Madelung summation approach to evaluate the conditions where ICC's are thermodynamically stable. Using this model, we compare the relative electrostatic energies of various structures showing that the regions of ICC stability are determined by two dimensionless parameters representing charge balance and the spatial extent of the electrostatic interactions. Parallels and distinctions between ICC's and classical ionic crystals are discussed. Monte Carlo simulations are utilized to examine the glass transition and melting temperatures, between which crystallization can occur, of a model system having the rocksalt structure. These tools allow us to make a first-order prediction of the experimentally accessible regions of surface charge, particle size, ionic strength, and temperature where ICC formation is probable.

Biophysics↗
PubMed2006

Managed care, inter-agency linkages, and outpatient substance abuse treatment.

: Although treatment of co-occurring behavioral and physical health problems could be facilitated by the linkages between health care providers, it is uncertain how such inter-agency linkages are affected by managed care. We used a sample of 167 service linkages to examine the effects of managed care arrangements on inter-agency communication, coordination, and perceived effectiveness. These linkages were identified based on interviews with 62 outpatient substance abuse treatment units in 2000. Results indicate that frequency of communication and inter-agency coordination are positively related to several managed care arrangements and may moderate the relationships between managed care arrangements and perceived effectiveness.

Ambulatory Care↗
PubMed2006

Assessing the service linkages of substance abuse agencies with mental health and primary care organizations.

Fragmentation of substance abuse treatment represents a major barrier to effective treatment for individuals with cooccurring substance abuse and mental and physical health disorders. Linkages of substance abuse treatment organizations with primary care and mental health agencies are widely considered to be a feasible way to integrate services. In this study, we analyzed information collected from a national sample of 62 outpatient substance abuse treatment units (OSATs) to understand the extent of services linkages in these organizations and to identify facilitators and barriers to service linkages. Results showed that OSATs had limited service linkages with primary care and mental health providers. The cited barriers to linkages included clients' financial problems, managed care restrictions, and limited organizational capacity. Onsite service provision was implemented in some OSATs. The pattern of service linkages in OSATs appeared to reflect the health needs of substance abuse clients.

Humans↗
PubMed2005

Application of the homogenization approximation to rough one-dimensional photonic crystals.

As previously reported [Opt. Lett. 29, 2791 (2004)], one-dimensional photonic crystals exhibit a decrease in their normal reflectivity if their interfaces are not flat. We show that the homogenization approximation accurately predicts this diminished optical response by comparing results with finite-difference time-domain (FDTD) simulations applied to the same roughened structures. Within the parameter range tested (rms roughness < 20% and rms wavelengths < 100% of the photonic crystal periodicity), the homogenization approximation accurately reproduces the reflectivities obtained by the FDTD simulations, which are much more computationally expensive.

Comment↗
PubMed2004

Diminished normal reflectivity of one-dimensional photonic crystals due to dielectric interfacial roughness.

Dielectric reflectors that are periodic in one dimension, also known as one-dimensional photonic crystals (1DPCs), have become extremely useful tools in the optics industry due to the presence of wavelength-tunable photonic bandgaps. However, little is known about the practical effects of manufacturing defects, such as interfacial roughness, on this technologically useful property of 1DPCs. We employ a finite-difference time-domain code to gain further insight into the effect of interfacial roughness on the reflectivity of quarter-wave-tuned 1DPCs in the center of the bandgap at normal incidence. This provides an estimate of the magnitude of the effect of the roughness for even the most-robust incidence conditions.

Journal Article↗
PubMed2003

Exploring for 3D photonic bandgap structures in the 11 f.c.c. space groups.

The promise of photonic crystals and their potential applications has attracted considerable attention towards the establishment of periodic dielectric structures that in addition to possessing robust complete bandgaps, can be easily fabricated with current techniques. A number of theoretical structures have been proposed. To date, the best complete photonic bandgap structure is that of diamond networks having Fd3m symmetry (2-3 gap). The only other known complete bandgap in a face-centred-cubic (f.c.c.) lattice structure is that of air spheres in a dielectric matrix (8-9 gap; the so called 'inverse-opal' structure). Importantly, there is no systematic approach to discovering champion photonic crystal structures. Here we propose a level-set approach based on crystallography to systematically examine for photonic bandgap structures and illustrate this approach by applying it to the 11 f.c.c. groups. This approach gives us an insight into the effects of symmetry and connectivity. We classify the F-space groups into four fundamental geometries on the basis of the connectivity of high-symmetry Wyckoff sites. Three of the fundamental geometries studied display complete bandgaps--including two: the F-RD structure with Fm3m symmetry and a group 216 structure with F43m symmetry that have not been reported previously. By using this systematic approach we were able to open gaps between the 2-3, 5-6 and 8-9 bands in the f.c.c. systems.

Journal Article↗