A sensitive procedure for the quantitation of free and N-(2-hydroxypropyl) methacrylamide polymer-bound doxorubicin (PK1) and some of its metabolites, 13-dihydrodoxorubicin, 13-dihydrodoxorubicinone and doxorubicinone, in human plasma and urine by reversed-phase HPLC with fluorimetric detection

A high-performance liquid chromatographic assay has been developed and validated for the determination in plasma and urine of doxorubicin (DXR) and some of its metabolites released in vivo from an N-(2-hydroxypropyl)methacrylamide (HPMA) polymer containing DXR linked through its aminosugar moiety to the polymer via an oligopeptide spacer (PK1). The method also allows measurement of the DXR still bound to the polymer. Following addition of two internal standards, the free compounds were extracted twice with isopropanol-chloroform (25:75, v/v). The first extraction was performed at physiological pH and the second after buffering at pH 8.4, in order to extract the aglycones and the glycosides, respectively. Determination of total DXR (polymer-bound plus free DXR) was performed, after quantitative acid hydrolysis to release doxorubicinone from free or polymer-bound DXR, by extraction with the same solvent mixture at pH 7.4. In both cases the organic phase was evaporated to dryness; the compounds were then separated by reversed-phase high-performance liquid chromatography (HPLC) under isocratic conditions and quantitated by fluorimetric detection. In the chromatograms all the analytes appeared to be separated at the baseline and no interference from blank human plasma and urine was observed. The suitability of the method for in vivo samples was checked by the analysis of plasma and urine samples obtained from a cancer patient who had received a single intravenous dose of the test compound.     

Omental transfer for salvage of the moribund lower extremity

Use of omental flaps is well documented in soft tissue reconstruction of the head and neck, chest wall, and abdomen. Three cases of omental transfer for soft tissue reconstruction of the lower extremities are presented. In two patients, free vascularized omental flaps were used to cover deep soft tissue defects over the lower leg and in one patient, a pedicle flap was used to cover a deep groin defect extending into the hip joint. In all patients, use of an omental graft allowed revascularization and subsequent wound healing with good cosmetic results.     

Low and high‐cycle fatigue properties of an ultrahigh‐strength TRIP bainitic steel

The scope of this study is to characterize the mechanical properties of a novel Transformation‐Induced Plasticity bainitic steel grade TBC700Y980T. For this purpose, tensile tests are carried out with loading direction 0, 45 and 90° with respect to the L rolling direction. Yield stress is found to be higher than 700 MPa, ultimate tensile strength larger than 1050 MPa and total elongation higher than 15%. Low‐cycle fatigue (LCF) tests are carried out under fully reverse axial strain exploring fatigue lives comprised between 10² and 10⁵ fatigue cycles. The data are used to determine the parameters of the Coffin–Manson as well as the cyclic stress–strain curve. No significant stress‐induced austenite transformation is detected. The high‐cycle fatigue (HCF) behaviour is investigated through load controlled axial tests exploring fatigue tests up to 5 × 10⁶ fatigue cycles at two loading ratios, namely R = ?1 and R = 0. At fatigue lives longer than 2 × 10⁵ cycles, the strain life curve determined from LCF tests tends to greatly underestimate the HCF resistance of the material. Apparently, the HCF behaviour of this material cannot be extrapolated from LCF tests, as different damage, cyclic hardening mechanisms and microstructural conditions are involved. In particular, in the HCF regime, the predominant damage mechanism is nucleation of fatigue cracks in the vicinity of oxide inclusions, whereby mean value and scatter in fatigue limit are directly correlated to the dimension of these inclusions.     

Mechanisms of nucleation and crystallization of lithium disilicate in Li-Zn-silicate glass-ceramic fibres

The preferred crystal orientation of Li₂Si₂O₅ crystallites has been evaluated in several partially crystallized glass fibres with the following chemical composition in mol %: 66.75 SiO₂; 23.45 Li₂O; 8.00 ZnO; 1.00 K₂O and 0.80 P₂O₅. The crystallites were shown to be grown radially with thec-axis directed from the surface towards the core of the fibre. When glass fibres have been subjected to a nucleation treatment step, this preferred orientation slightly increases in the temperature range 590 to 620° C, by increasing the crystallinity content. This behaviour was attributed to the presence of active nuclei. A kinetic study on the crystalline volume coarsening, carried out according to the Johnson-Mehl-Avrami equations, showed a mechanism of linear growth for the lithium disilicate phase with the (00/) growing planes moved inward from the surface to the core of the fibre. The small-angle X-ray scattering results were obtained by using a masking liquid with an electron density close to that of the glass fibres investigated, in order to eliminate the total external reflection and surface scattering. Results indicated that two distinct particle fractions are precipitated inside the fibres after glass-in glass phase separation and nucleation at 500° C for various periods of time. The fraction of the largest particles,13 to20 nm in size, is probably constituted with vitreous SiO₂-rich droplets, whereas the smallest particles, 2.5 to 6.5 nm in size, are probably Li₂O-rich clusters containing P₂O₅.     

Influence of molecular weight on the crystallization of poly(vinylidene fluoride)

Five samples of Poly (vinylidene fluoride) with a molecular weight from 45,000 to 260,000 were analyzed by means of FT-IR spectroscopy in order to study the influence of molecular weight on the crystallization process. The spectra of films obtained from methylethylketone solutions revealed the prevalence of form II () in the case of lower and of form III () in the higher molecular weight samples. The amount of form III was found to increase as the Mv decreased and as annealing temperatures increased. The deconvolution technique of vibrational spectra allowed detection of small amounts of other forms accompanying the prevailing one.     

High-temperature compressive creep of novel fine-grained orthorhombic ZrO2 ceramics stabilized with 12 mol% Ta doping

A novel fine-grained orthorhombic ZrO₂ ceramic stabilized with 12?mol% Ta doping was fabricated by spark-plasma sintering from home-made powders, and its high-temperature mechanical properties evaluated for the first time by compressive creep tests in both Ar and air. It was found that the high-temperature plasticity of the ceramic deformed in Ar, under which the Ta-doped orthorhombic ZrO₂ is a black suboxide with abundant oxygen vacancies in its crystal structure, is controlled by grain boundary sliding (stress exponent ～2, and activation energy ～780–800?kJ/mol). However, the high-temperature plasticity of the ceramic deformed in air, under which the Ta-doped orthorhombic ZrO₂ is a white oxide due to the elimination in situ of oxygen vacancies, is controlled by recovery creep (stress exponent ～3, and activation energy ～750?kJ/mol). It was also observed that black Ta-doped orthorhombic ZrO₂ is more creep resistant than its white counterpart with the same grain size, and that the former deforms as the more conventional Y₂O₃-stabilized ZrO₂ does.     

Influence of iron addition on the microstructure and the electrochemical corrosion of Al–Zn–Mg alloys

The effect of Fe addition on the microstructural properties and the corrosion resistance of Al–Zn–Mg alloys submitted to different heat treatments (cast, annealed and aged), has been studied in chloride solutions using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), cyclic polarization (CP) and open circuit potential (o.c.p.) measurements. The presence of 0.3% Fe in the alloy limited the growth of the MgZn₂ precipitates, both in the annealed and in the quenched specimens. No effect of Cr on the grain size in the presence of Fe was found because of the accumulation of Cr in the Fe-rich particles. Fe in the Al–Zn–Mg alloys also made them more susceptible to pitting. Pitting occurred mainly near the Fe-rich particles both, under o.c.p. conditions in O₂-saturated solutions and during the CP.     

Morphological and electrochemical characterization of a poly(3-methylthiophene)/PVDF composite

Composite electrodes were prepared via electrochemical polymerization of 3-methylthiophene in porous PVDF membranes of various thicknesses. The electrochemical properties were determined by cyclic voltammetry and charge-discharge tests and the possible correlation of the results with the morphology of the host membranes was examined. The best definition of n- and p-doping/undoping processes and the biggest capacitance (82 F g⁻¹) were obtained with a 27.5 μm-thick composite. Further characterization of this composite using electrochemical impedance spectroscopy revealed three behaviors associated with variation in the oxidation state of poly(3-methylthiophene) during transition from the n-undoping to p-doping states. The behavior of the charge transfer resistance and the double layer capacitance as a function of the applied potential were also determined.     

Densification of ultrafine WC–12Co cermets by Pressure Assisted Fast Electric Sintering

WC–12Co nanopowders have been densified by means of an innovative apparatus belonging to the Field Assisted Sintering Techniques (FAST), named Pressure Assisted Fast Electric Sintering (PAFES). The technique allows to control the electrical parameters in terms of waveforms and frequencies of the applied currents. By means of AC currents different sintering cycles for the consolidation of cemented carbides have been investigated and optimised. The effect of the different sintering cycles on the microstructure and mechanical properties of the final bulks has been analysed. Fully dense WC–12Co has been obtained, characterised by ultrafine grained microstructure and very high hardness combined with good fracture toughness values.