Infrared radiative properties and thermal modeling of ceramic-embedded textile fabrics.

The infrared optical properties of textiles are of great importance in numerous applications, including infrared therapy and body thermoregulation. Tuning the spectral response of fabrics by the engineering of composite textile materials can produce fabrics targeted for use in these applications. We present spectroscopic data for engineered polyester fabric containing varying amounts of ceramic microparticles within the fiber core and report a spectrally-dependent shift in infrared reflectance, transmittance and absorptance. A thermal transport model is subsequently implemented to study the effect of these modified properties on the spectral distribution of infrared radiation incident upon the wearer of a garment constructed of this fabric.

Solventless fabrication of porous-on-porous materials.

Here we fabricate patterned porous polymer membranes on porous substrates by a combination of physical masking and chemical vapor deposition. This all-dry technique eliminates solvent-related issues and allows for the fabrication of hierarchical porous-on-porous structures with a wide range of chemical compositions and shapes. The porous polymer membranes are made by operating at unconventional processing conditions to simultaneously deposit and polymerize monomer. The solid monomer serves as a porogen and creates microstructures around which polymer forms. Membranes with thicknesses ranging from a few hundred micrometers to a millimeter are fabricated on porous paper substrates. The resolution of the patterning process and the structure of the resulting membranes are analyzed as a function of the deposition time. It was found that the patterned membranes exhibit a tapered structure and the dimensions are in good agreement with the dimensions of the mask. One potential application of these patterned polymer membranes is demonstrated for the selective separation of analytes for diagnostic applications on paper-based microfluidic devices. The ability to pattern porous-on-porous structures can be useful for the development of hierarchical membranes for water purification and gas separation, and for sensing, patterned tissue scaffolding, and other lab-on-a-chip applications.

Self-assembly of pillars modified with vapor deposited polymer coatings.

In this paper, we demonstrate that thin layers of polymer coatings can be used to self-assemble pillars into stable microstructures. Polymer coatings are deposited onto elastomeric pillars using solventless initiated chemical vapor deposition and capillary forces are used to collapse the coated pillars into microstructures. The location of pillar collapse can be controlled by patterning regions of hydrophilicity and hydrophobicity. Poly(hydroxyethyl methacrylate) and poly(methacrylic acid) coatings stabilize the self-assembled microstructures by providing an adhesive force through solvent bonding. These solvent bonds allow the response of the microstructures to be tuned by varying the thickness of the polymer coating and the solubility parameter of the solvent. The coating process described in this paper is substrate-independent and therefore can be applied to pillars composed of any material.

Polymer nanocomposites with nanowhiskers isolated from microcrystalline cellulose.

The ability to produce polymer nanocomposites, which comprise a percolating, three-dimensional network of well-individualized nanofibers, is important to maximize the reinforcing effect of the nanofibers. While microcrystalline cellulose (MCC) has been previously shown to improve the mechanical properties of polymer composites, the formation of fibrous percolating networks within the nanocomposites has been stifled. Through the utilization of a template approach, nanocomposites based on an ethylene oxide/epichlorohydrin copolymer and nanowhiskers isolated from MCC were produced that display the maximum mechanical reinforcement predicted by the percolation model.

How many patients with infrarenal aneurysms are candidates for endovascular repair? The Northern California experience.

PURPOSE: To determine how many patients with abdominal aortic aneurysms (AAA) meet the anatomical selection criteria for AneuRx stent-graft repair in community hospitals of Northern California. METHODS: The records were reviewed of 220 AAA patients (171 men, 49 women) who were considered for endovascular repair by the treating vascular surgeon at 28 community hospitals in Northern California between January and October 2001. Contrast computed tomographic angiography (CTA) and selective arteriography were performed at each institution and reviewed by a centralized, independent image-reading center. Selection criteria determined by the manufacturer and published in the indications for use were applied to each set of imaging studies. The number of patients who met inclusion criteria were recorded, as were the anatomical characteristics of each aneurysm. RESULTS: The mean aneurysm size in the 220 patients was 55.3 +/- 0.7 mm. Among these patients, 122 (55%) were judged to be candidates for endovascular repair and 98 (45%) were considered ineligible. The primary anatomical reason for ineligibility was a short infrarenal neck in 43 (44%) patients, followed by a large proximal neck diameter (25, 25%), iliac aneurysms (10, 10%), extremely tortuous or calcified neck (7, 7%), iliac occlusion (6, 6%), and small distal aortic bifurcation and accessory renal arteries (5, 5%). Four (4%) patients were classified as non-candidates due to poor quality imaging. There was no difference in aneurysm diameter (54.0 +/- 0.8 versus 57.1 +/- 1.2 mm, p=NS) or age (72.2 +/- 1.2 versus 74.6 +/- 2.2 years, p=NS) between candidates and non-candidates. However, proportionally more men (60%) than women (39%) were eligible for endovascular repair with the AneuRx stent-graft (p<0.05). All 122 patients who were considered candidates for endovascular repair were treated, with successful stent-graft placement achieved in 121 (99%). CONCLUSIONS: Fifty-five percent of patients considered for endovascular AAA repair in community hospitals in Northern California met the anatomical selection criteria for the AneuRx stent-graft. Men appeared to be twice as likely to meet the eligibility requirements as women. Unfavorable infrarenal neck anatomy was the primary exclusion criterion for endovascular repair in this community setting.

Superficial femoral-popliteal vein as a conduit for brachiocephalic arterial reconstructions.

Revascularization of brachiocephalic arteries with prosthetic graft offers excellent patency for most reconstructions. For complex brachiocephalic reconstructions, such as redo operations or reconstructions for infection, autogenous conduit may be preferable. Occasionally saphenous vein is inadequate or absent. The purpose of this study was to evaluate the indications and intermediate-term outcomes of superficial femoral-popliteal vein (SFPV) as an alternative conduit for brachiocephalic reconstructions. Over a 6-year period, 71 patients underwent carotid, subclavian, or axillary artery bypass. In 18 (25%) of these reconstruction SFPV was used as the conduit. Ten bypasses (55%) were redo operations. Three bypasses (17%) were performed after failed prosthetic grafts. Three grafts (17%) were required in infected patients. Indications for the use of SFPV included inadequate saphenous vein (n = 13), infection (n = 3), and failed prosthetic bypass (n = 3). Thirty-day mortality was 5.5%. The neurologic event rate was 5.5%. During a mean follow-up of 26 +/- 5 months, there were no graft thromboses or graft infections. Revision-free primary patency was 92% at 48 months. Assisted primary patency was 100%. These data suggest that SFPV is a safe, durable conduit for brachiocephalic reconstructions. SFPV yielded excellent results for a disadvantaged patient population.