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Biomedical subjects

A L Gonzalez

Publications and source records attributed to A L Gonzalez.

6 recordsLinked to original sources
PubMed2005

Optical absorbance of colloidal suspensions of silver polyhedral nanoparticles.

The optical absorption of colloidal suspensions made of silver nanoparticles with polyhedral shapes is studied experimentally and theoretically. The influence of the shape on the optical response is investigated by comparing the measured absorbance with theoretical results for icosahedral, decahedral, and cuboctahedral silver nanoparticles. The theoretical spectra are obtained within the discrete dipole approximation. We find that colloidal suspensions of silver nanoparticles with a small dispersion of size distribution show very few structural shapes.

Journal Article↗
PubMed2002

Energy response of an imaging plate exposed to standard beta sources.

Imaging plates (IPs) are a reusable media, which when exposed to ionizing radiation, store a latent image that can be read out with a red laser as photostimulated luminescence (PSL). They are widely used as a substitute for X-ray films for diagnostic studies. In diagnostic radiology this technology is known as computed radiography. In this work, the energy response of a commercial IP to beta-particle reference radiation fields used for calibrations at the National Institute of Standards and Technology was investigated. The absorbed dose in the active storage phosphor layer was calculated following the scaling procedure for depth dose for high Z materials with reference to water. It was found that the beta particles from Pm-147 and Kr-85 gave 68% and 24% higher PSL responses than that induced by Sr-90, respectively, which was caused by the different PSL detection efficiencies. In addition, normalized response curves of the IPs as a function of depth in polystyrene were measured and compared with the data measured using extrapolation chamber techniques. The difference between both sets of data resulted from the continuous energy change as the beta particle travels across the material, which leads to a different PSL response.

Brachytherapy↗
PubMed1993

Autoimmune syndrome after induction of neonatal tolerance to I-E antigens.

Neonatal injection of semiallogeneic spleen cells induces a state of specific tolerance to the parental alloantigens, but also the development of an autoimmune syndrome known as host-versus-graft disease (HVGD). The autoimmune features are a consequence of the allogeneic cooperation between persisting alloreactive host T helper type 2 (TH2) cells and donor semiallogeneic B cells. It has been established that I-A alloantigens play a central role in the triggering of this HVGD. Here it was investigated if I-E antigens, which have shown functional differences, regarding autoimmunity and alloreactivity, with respect to I-A antigens, are also able to trigger this autoimmune syndrome. The injection of spleen cells from [B10.A(4R) x B10.A(2R)]F1 (I-E+) hybrid mice into newborn B10.A(4R) (I-E-) mice was accompanied by the establishment of chimerism and also by the development of a characteristic, but moderated, HVGD. The weak intensity of this HVGD is likely due to the moderation of the alloreactive responses induced against I-E molecules. Moreover, the marked increase in the levels of IgE and in the titers of anti-DNA IgG1 antibodies strongly suggest that alloreactive TH2 cells play also a main role in the autoimmune syndrome following tolerization to I-E antigens. Therefore, it is concluded that the I-E and I-A isotypes are functionally similar with respect to the allogeneic cellular interactions that account for the HVGD.

Animals↗