Compact Polyelectrolyte Complexes: “Saloplastic” Candidates for Biomaterials

Precipitates of polyelectrolyte complexes were transformed into rugged shapes suitable for bioimplants by ultracentrifugation in the presence of high salt concentration. Salt ions dope the complex, creating a softer material with viscous fluid-like properties. Complexes that were compacted under the centrifugal field (CoPECs) were made from poly(diallyldimethyl ammonium), PDADMA, as polycation, and poly(styrene sulfonate), PSS, or poly(methacrylic acid), PMAA, as polyanion. Dynamic mechanical testing revealed a rubbery plateau at lower frequencies for PSS/PDADMA with moduli that decreased with increasing salt concentration, as internal ion pair cross-links were broken. CoPECs had significantly lower modulii compared to similar polyelectrolyte complexes prepared by the “multilayering ” method. The difference in mechanical properties was ascribed to higher water content (located in micropores) for the former and, more importantly, to their nonstoichiometric polymer composition. The modulus of PMAA/PDADMA CoPECs, under physiological conditions, demonstrated dynamic mechanical properties that were close to those of the nucleus pulposus in an intervertebral disk

Determination of reference values for optical properties of liquid phantoms based on Intralipid and India ink

A multi-center study has been set up to accurately characterize the optical properties of diffusive liquid phantoms based on Intralipid and India ink at near-infrared (NIR) wavelengths. Nine research laboratories from six countries adopting different measurement techniques, instrumental set-ups, and data analysis methods determined at their best the optical properties and relative uncertainties of diffusive dilutions prepared with common samples of the two compounds. By exploiting a suitable statistical model, comprehensive reference values at three NIR wavelengths for the intrinsic absorption coefficient of India ink and the intrinsic reduced scattering coefficient of Intralipid-20% were determined with an uncertainty of about 2% or better, depending on the wavelength considered, and 1%, respectively. Even if in this study we focused on particular batches of India ink and Intralipid, the reference values determined here represent a solid and useful starting point for preparing diffusive liquid phantoms with accurately defined optical properties. Furthermore, due to the ready availability, low cost, long-term stability and batch-to-batch reproducibility of these compounds, they provide a unique fundamental tool for the calibration and performance assessment of diffuse optical spectroscopy instrumentation intended to be used in laboratory or clinical environment. Finally, the collaborative work presented here demonstrates that the accuracy level attained in this work for optical properties of diffusive phantoms is reliable

New trends in soil micromorphology

The book contains state of the art new research results in micromorphology as well as other disciplines of soil science. It provides very useful up-to-date information for researchers, educators, graduate students interested in microscopic and submicroscopic studies of soils and sediments. In the past, micromorphology has been considered almost solely as a descriptive and interpretative branch of science. Attempts are now made to obtain quantitative data. There has been much progress in applying soil micromorphology in Quaternary geology, in particular identifying and characterizing palaeosols. The new areas for soil micromorphology are soil ecology, materials sciences and archaeology. © 2008 Springer-Verlag Berlin Heidelberg. All rights are reserved

Physical fractionation and cryo-coupe analysis of mormoder humus

Soil micromorphology plays a key role in the research of the decomposition, storage, and mineralisation of soil organic matter. It is often difficult to study the internal fabrics and stability of soil aggregates, based on soil micromorphological properties. Similar to physical fractionation of soil inorganic particles organic matter from ectorganic and endorganic horizons can also be fractionated. Quantification of aggregate stability can be achieved, by the weight percentage of such fractions. Also the micromorphological properties of soil particles can be studied using cryo-coupes from gelatin suspensions prepared in a cryostat. The results of physical fractionation and cryo-coupe analysis improve our knowledge on the development of the humus form in the soil

Effects of interferon-gamma on bone remodeling during experimental tooth movement

PubMedID: 17029552Objective: To determine the effects of interferon-gamma (IFN-?) on bone remodeling during orthodontic tooth movement. Materials and Methods: Thirty adult male Sprague Dawley rats were randomly categorized into five groups. IFN-? was administered in three different doses (0.01, 0.02, and 0.05 µg/20 µL) and the remaining two groups served as control. Mandibular first molars were moved mesially by means of Ni-Ti closed coil springs in all groups. The results were evaluated histomorphometrically, and parameters of trabecular bone volume (BV/TV), trabecular bone number (Tr.N), and trabecular separation (Tr.Sep) were observed at the interradicular bone area of the mandibular first molars. Results: Increases in BV/TV and Tr.N and decreases in Tr.Sep revealed the antiosteoclastic activity of IFN-?. Conclusion: IFN-? administration may be useful clinically for anchorage control. © 2006 by The EH Angle Education and Research Foundation, Inc