No abstract

Hyaluronic acid (HA) was electrospun. The effects of flow rate, spin length, and the applied voltage on the diameter of the HA nanofibers were analyzed. The average thickness of the webs was 0.041 cm. The air permeability of sterilized HA nanofiber wound dressing was much higher than that of gauze with Vaseline. The degree of crystallinity of HA nanofibers was characterized using powder X-ray technique and was found to be 20.6%. A preclinical study was conducted to compare healing of wounds covered by an adhesive bandage, a sterilized solid HA, gauze with Vaseline, an antibiotic dressing, and a sterilized HA nanofiber wound dressing. Results of the two methods of appraisal showed that the sterilized HA nanofiber wound dressing was the best type of dressing out of the five types of dressings compared.

Biaxially stretched composite polyethylene naphthalate (PEN) films (BSCPF) embedded with submicron lithium fluoride ( 6 LiF) particles and luminescent molecules were fabricated to make large area scintillation films (%1 m  1 m) for thermal neutron detection. BSCPF had 20.2% higher neutron light yield as compared to unstretched composite film (UCPF), and were 2.46 AE 1.47 times more efficient for detecting thermal neutrons than lithiated glass GS20 above lower level discriminator corresponding to an intrinsic efficiency for gamma <10 À6 . MCNPX simulations for a layered BSCPF detector resulted 6.1 cps for 1 ng 252 Cf, thus meeting the Pacific Northwest National Laboratory criteria for absolute neutron detection efficiency and intrinsic gamma-neutron discrimination. BSCPF have alpha to beta ratio of 0.25, which is higher than that for UCPF (0.11), and also for GS20 (0.22), which offers the possibility of excellent neutron/gamma discrimination.

An equation was developed to predict the morphology of aramid fibers using dissolution time (t) data of Kevlar and Nomex multifilament yarns, which were heat set at various temperatures. The degree of crystallinity of the fibers was characterized by WAXS and the dissolution time of the samples was measured. The degree of crystallinity and dissolution time of the fibers increases with both heat treatment time and heat treatment temperature. The coefficient of correlation between 1/t and the X-ray degree of crystallinity was found to be À0.88 for Nomex aramid and À0.95 for Kevlar aramid multifilament yarns. The dissolution times of completely amorphous and fully crystalline fibers can be predicted using regression and were substituted in a novel equation to characterize the morphology of the aramid fibers. New equations were proposed to assess the degree of crystallinity of the aramid multifilament yarns. For Nomex, the equation is c = [(0.053) À (1/t)]/(0.00054). For Kevlar, the equation is c = [(0.12) À (1/t)]/(0.0015).

Flame retardant treated gray cotton fibers were blended with antibacterial treated gray cotton fibers and polyester/polyester sheath/core bicomponent fibers to form high-loft fabrics. The high flame retardancy (FR) and antibacterial property of these high lofts were evaluated by limiting oxygen index, vertical flame testing, and antimicrobial tests against S. aureus (ATCC 6538), a Gram-positive bacterium, and K. pneumonia (ATCC 4352), a Gram-negative bacterium. The blended high-loft nonwoven fabrics, apart from the control blend number 5, had high LOI values greater than 24.7. Samples should have a higher LOI value than the threshold value of 20.95. All the blended high-loft nonwoven fabrics passed the vertical flame test and the char length increased with the decrease in the proportion of the SRRC FR cotton in the blends. The blended high-loft nonwoven fabrics were effective in reducing the bacteria by 99.9% for both types of bacteria tested. FR gray cotton fiber obtained from the treatment of SRRC 2 formulation (blend number 4) also showed good antibacterial properties.

No abstract

Thin polymeric films are evaluated in this research as a potential replacement technology for radiation portal monitors where specific attention is given to the physical basis for neutron-photon discrimination. It is shown that the difference in the energy deposition mechanics from charged particle reaction products and from the Compton scattered electrons allows for the effective discrimination between neutrons and gammas. One goal of this study was to establish optimal thickness for polymeric films that maximize the neutron interactions and simultaneously minimize the measured interaction of photons. Polymeric films ranging from m to m containing were fabricated and tested for their capability to satisfy criteria established by the Department of Homeland Security. Results from Monte Carlo simulations with the GEANT4 code and data from measurements confirm the technical basis for our proposed understanding of neutron-photon discrimination characteristics for thin films.

In order to manufacture cellulose submicron fibers, electrospinning of cellulose was tried with different solvents. Alpha-cellulose did not dissolve in 6% (w/w) sodium hydroxide/4%urea aqueous solution. Alpha-cellulose solution in 85% phosphoric acid was not spinnable at an applied voltage between 15kV to 25 kV and at a spin length of 4 to 6 inches. Electrospinning of alpha-cellulose in Nmethylmorpholine-N-oxide/N-methylpyrrolidinone/water solvent mixture could be performed at an applied voltage of 28 kV and at a spin length of seven inches during spinning and at an ambient temperature of 38 0 C. The degree of crystallinity of the cellulose submicron fibers was found to be 37.88%. The number average fiber diameter of cellulose submicron fibers from 1.25% (w/w) cellulose solution in the N-methylmorpholine-N-oxide/N-methyl-pyrrolidinone/water solvent was found to be 207 nm and the number average fiber diameter of cellulose submicron fibers from 2.5% (w/w) cellulose solution in the N-methylmorpholine-N-oxide/N-methyl-pyrrolidinone/water solvent mixture was found to be 243 nm.