The self-diffusion of Niobium.

Report year runs ends June 30.

Self-diffusion of metals and associated phenomena :

"Contract AT-30-1-GEN-367."

The Penny magazine of the Society for the Diffusion of Useful Knowledge.

Title from caption.

On the mental illumination and moral improvement of mankind; or, An inquiry into the means by which a general diffusion of knowledge and moral principle may be promoted. Illustrated with engravings.

Mode of access: Internet.

On the mental illumination and moral improvement of mankind; or, An inquiry into the means by which a general diffusion of knowledge and moral principle may be promoted. Illustrated with engravings.

Mode of access: Internet.

The biographical dictionary of the Society for the diffusion of useful knowledge--

Vols. 1-4 cover only the letter A.

The diffusion of gases through liquids and allied experiments,

Mode of access: Internet.

Popular tales from the Norse : with an introductory essay on the origin and diffusion of popular tales /

Translation of Norske folkeeventyr.

On the improvement of society by the diffusion of knowledge : or, an illustration of the advantages which would result from a more general dissemination of rational and scientific information among all ranks /

Mode of access: Internet.

Jerusalem. Year-Book for the Diffusion of an Accurate Knowledge of Ancient and Modern Palestine

Mode of access: Internet.

NMR imaging of the diffusion of water at 310 K into semi-IPNs of PEM and Poly(HEMA-co-THFMA)

Magnetic resonance imaging has been used to monitor the diffusion of water at 310 K into a series of semi-IPNs of poly(ethyl methacrylate), PEM, and copolymers of 2-hydroxyethyl methacrylate, HEMA, and tetrahydrofurfuryl methacrylate, THFMA. The diffusion was found to be well described by a Fickian kinetic model in the early stages of the water sorption process, and the diffusion coefficients were found to be slightly smaller than those for the copolymers of HEMA and THFMA, P(HEMA-co-THFMA), containing the same mole fraction of HEMA in the matrix. A second stage sorption process was identified in the later stage of water sorption by the PEM/PTHFMA semi-IPN and for the systems containing a P(HEMA-co-THFMA) component with a mole fraction HEMA of 0.6 or less. This was characterized by the presence of Water near the surface of the cylinders with a longer NMR T-2 relaxation time, which would be characteristic of mobile water, such as water present in large pores or surface fissures. The presence of the drug chlorhexidine in the polymer matrixes at a concentration of 5.625 wt % was found not to modify the properties significantly, but the diffusion coefficients for the water sorption were systematically smaller when the drug was present.

Investigation into the diffusion of water into HEMA-co-MOEP hydrogels

Cross-linked homopolymers and copolymers of 2-hydroxyethyl methacrylate, HEMA, and ethylene glycol methacrylate phosphate, MOEP, have been synthesized, and the diffusion of water into these systems has been investigated. Only polymers with 0-20 mot % MOEP exhibited ideal swelling behavior as extensive fracturing occurred in the systems with greater than 20 mot % MOEP as the polymers began to swell during water sorption. Gravimetric studies were used in conjunction with magnetic resonance imaging of the diffusion front to elucidate the diffusion mechanism for these systems. In the case of the cross-linked HEMA homopolymer gets, the water transport mechanism was determined to be concentration-independent Fickian diffusion. However, as the fraction of MOEP in the network increased, the transport mechanism became increasingly exponentially concentration-dependent but remained Fickian until the polymer consisted of 30 mot % MOEP where the water transport could no longer been described by Fickian diffusion.

NMR imaging of the diffusion of water at 37 degrees C into poly(2-hydroxyethyl methacrylate) containing aspirin or vitamin B-12

The ingress of water into poly(2-hydroxyethyl methacrylate), PHEMA, loaded with either one of two model drugs, vitamin B-12 or aspirin, was studied at 37 degreesC using three-dimensional NMR imaging. PHEMA was loaded with 5 and 10 wt % of the drugs. From the imaging profiles, it was observed that incorporation of vitamin B-12 into PHEMA resulted in enhanced crack formation on sorption of water and the crack healing behind the diffusion front was slower than for PHEMA without added drug. This was accounted for by the anti-plasticization of PHEMA by vitamin B-12. Crack formation was inhibited in the P-HEMA-aspirin systems because of the plasticizing effect of the aspirin on the PHEMA matrix. All of the polymers were found to absorb water according to an underlying Fickian diffusion mechanism. For PHEMA loaded with 5 wt % of aspirin or vitamin B-12, the best values of the water diffusion coefficients were both found to be 1.3 +/- 0.1 x 10(-11) m(2) s(-1) at 37 degreesC, while the values for the polymer loaded with 10 wt % of the drugs were slightly higher, 1.5 +/- 0.1 x 10(-11) m(2) s(-1).

Diffusion of linear paraffins in nanoporous silica

The diffusion of hexane, heptane, octane, and decane in nanoporous MCM-41 silica at various temperatures is investigated by the zero-length-column method. The diffusion coefficients are derived by a complete-time-range analysis of desorption curves at different purge flow rates and temperatures. The results show that the calculated low-coverage diffusivity values decrease monotonically, and the derived Henry's law constants increase, as the carbon number of paraffins increases. The study reveals that transport is strongly influenced by intracrystalline diffusion and dominated by the sorbate-sorbent interaction. The diffusion activation energy and adsorption isosteric heat at zero loading increase monotonically with the carbon number of linear paraffins, but their ratio is essentially constant for each adsorbate compound.