Chemico-physical modifications induced by plasma and ozone sterilizations on shape memory polyurethane foams

Thermally activated shape memory polyurethane foams are promising materials for minimally invasive surgical procedures. Understanding their physical and chemical properties, in vitro response and effects of sterilization is mandatory when evaluating their potential as biomaterials. In this work, we report on the characterization of two Cold Hibernated Elastic Memory (CHEM) foams before and after two novel low-temperature sterilization techniques (plasma and ozone). Foams have different transition temperatures (T_trans), as determined by Tanδ peaks in DMA tests, that depend on their chemical composition: both foams possess excellent shape recovery ability (Recovery Rate up to 99%) in conventional shape recovery tests. Plasma sterilization (Sterrad^® sterilization system) resulted in a slight increase of open porosity, but no effects on bulk chemical and thermo-mechanical properties were observed. Ozone sterilization had a stronger effect on foams morphology, both in terms of an evident rupture of pore walls and surface oxidation. These modifications affected both thermomechanical and shape recovery behavior. Furthermore, plasma sterilized foams cytocompatibility was investigated with L929 fibroblast cell line in vitro, showing a good adhesion and proliferation, as confirmed by SEM observation and Alamar blue assay. The obtained results contribute to define the role of shape memory foams as biomaterials and open novel questions on the role of sterilization technique effects on cellular solids.     

Porous scaffolds of polycaprolactone reinforced with in situ generated hydroxyapatite for bone tissue engineering

Polycaprolactone/hydroxyapatite (PCL/HA) composites were prepared by in situ generation of HA in the polymer solution starting from the precursors calcium nitrate tetrahydrate and ammonium dihydrogen phosphate via sol–gel process. Highly interconnected porosity was achieved by means of the salt-leaching technique using a mixture of sodium chloride and sodium bicarbonate as porogens. Structure and morphology of the PCL/HA composites were investigated by scanning electron microscopy, and mechanical properties were determined by means of tensile and compression tests. The possibility to employ the developed composites as scaffolds for bone tissue regeneration was assessed by cytotoxicity test of the PCL/HA composites extracts and cell adhesion and proliferation in vitro studies.     

Characterization of angled tapered superluminescent LEDs

We present a detailed analysis of the output beam of high-power edge-emitting angled tapered superluminescent LEDs (A-TSLEDs). A device model, including spontaneous and stimulated emission processes as well as the typical nonuniform carrier-density distribution due to current spreading and carrier diffusion, has been developed and used to interpret the experimentally obtained characteristics of inhouse-fabricated A-TSLEDs. The good match between measured and theoretical results indicates that the model reproduces the A-TSLED operation very satisfactorily and clearly explains the role of the collecting lens on the pronounced asymmetry of some of the measured optical intensity profiles.     

Advances in single-molecule magnet surface patterning through microcontact printing

We present an implementation of strategies to deposit single-molecule magnets (SMMs) using microcontact printing microCP). We describe different approaches of microCP to print stripes of a sulfur-functionalized dodecamanganese (III, IV) cluster on gold surfaces. Comparison by atomic force microscopy profile analysis of the patterned structures confirms the formation of a chemically stable single layer of SMMs. Images based on chemical contrast, obtained by time-of-flight secondary ion mass spectrometry, confirm the patterned structure.     

Multiregion bicentric-spheres models of the head for the simulation of bioelectric phenomena

Equations are derived for the electric potentials [electroencephalogram (EEG)] produced by dipolar sources in a multiregion bicentric-spheres volume-conductor head model. Being the equations valid for an arbitrary number of regions, our proposal is a generalization of many spherical models presented so far in literature, each of those regarded as a particular case of our multiregion model. Moreover, our approach allows considering new features of the head volume-conductor to better approximate electrical properties of the real head.     

Proposed corrections for the quantification of coupling patterns by recurrence plots

The aim of this paper is to quantify the coupling during phase-locking patterns by using the recurrence plot quantification approach. We found that the percent determinism of the recurrences and the entropy of recurrences--corrected for border effect induced by finite data lenght--succeeded in distinguishing three coupling conditions both in simulation signals and in real data from cardiorespiratory synchronization experiments.     

Mucilaginous aggregates in the northern Adriatic in the period 1999-2002: typology and distribution

The spatial and temporal distributions of different types of visible mucilaginous aggregates were investigated monthly by underwater video cameras in the northern Adriatic (NA) from June 1999 to July 2002. Small aggregates (flocs, macroflocs and stringers) were observed in all seasons with higher values in autumn and winter. Larger aggregates (ribbons, cobwebs, clouds, and false bottoms) formed only during late-spring and summer, particularly in 2000 and 2002, when the seasonal thermohaline stratification was marked. In fact, the process of mucilage formation took place mainly in the upper water column, above the main pycnocline. The spatial distribution shows that higher concentrations of small aggregates occur in the more productive coastal waters. The larger aggregates form or accumulate mainly in coastal waters in the southern part of the NA and in the central part of the Po River delta-Rovinj transect, where a gyre greatly influences the aggregates distribution. The fronts between low salinity coastal waters and high salinity waters of southern origin play an important role for accumulation and aggregation of the mucilage during spring and summer. Most of the aggregates accumulate in correspondence with strong pycnoclines with differences in density anomaly of 2 kg m(-3) or higher. False bottoms formed in correspondence with strong haloclines (DeltaS congruent with 2), while cobwebs and ribbons also occurred when the halocline was less marked (DeltaS<0.5). Meteorological conditions greatly influenced the aggregate formation. Calm weather and weak winds favour aggregation processes, while strong north-easterly winds, causing intense mixing, result in the dispersion of the mucilaginous aggregates, as occurred during the Bora event in July 2000.     

Development of a biotic ligand model and a regression model predicting acute copper toxicity to the earthworm Aporrectodea caliginosa

The purpose of this study was to develop a terrestrial biotic ligand model (BLM) for predicting acute copper toxicity to the earthworm Aporrectodea caliginosa. To overcome the basic problems hampering development of BLMs for terrestrial organisms, an artificial flow-through exposure system was developed consisting of an inert quartz sand matrix and a nutrient solution, of which the composition was univariately modified. A. caliginosa was exposed for 7 days under varying concentrations of copper and the major cations modifying toxicity: H+, Ca2+, Mg2+, and Na+. In addition copper speciation was modulated by means of EDTA or dissolved organic carbon (DOC). An increase in pH or pNa resulted in a linear decrease of 7-days median lethal concentrations. Increasing Ca2+ and Mg2+ activities had inconsistent effects. EDTA addition decreased toxicity when the total copper concentration in the pore water was kept the same. This is attributed to the strong complexation capacity of EDTA and shows that total copper is not the toxic species. DOC was more protective than could be explained by its metal complexing properties. The BLM developed incorporates the effects of H+ and Na+. This BLM was validated with the results of a set of bioassays with artificial pore water in quartz sand and by a set of bioassays in spiked field soils. Prediction error was within a factor of 2, but some predictions were not within the 95% confidence interval. Therefore a more widely applicable regression type model was developed that was able to explain >95% of the (lack of) toxicity observed. To our knowledge this is the first report of the successful development of a terrestrial BLM.     

A system for securing push-based distribution of XML documents

Push-based systems for distributing information through Internet are today becoming more and more popular and widely used. The widespread use of such systems raises non trivial security concerns. In particular, confidentiality, integrity and authenticity of the distributed data must be ensured. To cope with such issues, we describe here a system for securing push distribution of XML documents, which adopts digital signature and encryption techniques to ensure the above mentioned properties and allows the specification of both signature and access control policies. We also describe the implementation of the proposed system and present an extensive performance evaluation of its main components.