Polycystic ovary syndrome (PCOS) is associated with altered lipid profile and increased small, dense LDL particles (sdLDL). Considering that paraoxonase 1 (PON1) is an antioxidative enzyme located on HDL particles, the aim of this study was to investigate the connection between oxidative stress (OS) and PON1 activity with lipoprotein subclasses in PCOS depending on obesity. In 115 PCOS patients, lipoprotein subclasses distributions were determined by gradient gel electrophoresis. OS status was assessed by total oxidative status (TOS), advanced oxidation protein products, malondialdehyde (MDA), prooxidant-antioxidant balance (PAB), total antioxidative status (TAS) and superoxide dismutase (SOD) and PON1 activity. Overweight/obese PCOS patients (n 55) had increased OS compared with normal weight patients (n 60). In addition, overweight/obese group had lower HDL size and higher proportion of HDL 3a subclasses (P < 0·05). PAB was in negative correlation with HDL 2a (P < 0·001), whereas MDA and SOD correlated positively with HDL 3 subclasses (P < 0·05). Serum PON1 activity was positively associated with proportions of PON1 activity on HDL 2b (P < 0·05) and 2a (P < 0·01), but negatively with the proportion on HDL 3 particles (P < 0·01). LDL B phenotype patients had increased TAS, SOD and PON1 activity on HDL 2b, but decreased PON1 activity on HDL 3 subclasses. OS is associated with altered lipoprotein subclasses distribution in PCOS patients. Obesity in PCOS affects the profile of HDL subclasses, reflected through the reduced proportion of PON1 activity on HDL 3 subclasses in the presence of sdLDL particles.

Measurements of the complex, frequency dependent susceptibility, χ(ω) = χ′ (ω) − i χ′′ (ω) over the frequency range 50 MHz to 15 GHz, of a surfacted ferrofluid comprising MnFe204 ferrite particles in dibutylphthalat (DBP), as a function of a biasing magnetic field arepresented. The biasing field was varied over the range 0 to 100 kAm−1, and has enabledaverage values of anisotropy constant, $\bar{K}$ , and anisotropy field $\bar{H}_{\rm A}$ forthe sample to be determined. Ferromagnetic resonance was exhibited for all values of the biasing field, covering the range 1.2 to 8.5 GHz, with the χ′ (ω) component of the susceptibility going negative in the GHz region.

The composition of an Fe-Mn-Si-Cr-Ni stainless steel with shape memory effect was altered in this work in order to increase the strength of the alloy. The alloy possessed a low yield strength which is a major draw back for structural applications.

Nitrogen alloying, using nitrogen pressurized melting (P=l–10 atm), was employed to introduce a nitrogen concentration of up to 0.36 wt%. The effect of nitrogen alloying on shape memory effect was studied through mechanical testing. It was found that nitrogen alloying increased the hardness; however, nitrogen as an interstitial alloying element suppressed the γ⇒ε transformation and therefore decreased the shape memory effect.

Introducing small amount of Nb (e. g., 0.36 wt%) to the nitrogen containing alloys caused formation of NbN. The NbN compound was in the form of globular dispersed particles (200 nm) which increased the strength of the alloy without significantly changing the shape memory effect.

The effect of annealing in air on internal structure and optical properties of hot filament CVD nanocrystalline diamond films was investigated. Oxidation of the films lead to selective removal of intercrystallite layers with formation of highly porous structure with characteristic dimensions of several nanometers. Dramatic changes in optical transmission and Raman spectra were also observed. The origin of the two Raman spectrum maxima at 1140 and 500 cm−1 is discussed. Hydrogen absorption and desorption processes in porous diamond were studied.

We report the first chemical vapor deposition growth and systematic photoluminescence study of strained Si1–xGex alloy layers on < 110 > Si substrates. Compared to < 100 > Si substrates, the same growth conditions yielded a slightly lower Ge composition, but a much lower growth rate. For thick layers, the relaxation along [110] direction is insufficient and lead to predominantly uniaxial strain in the the films. From the photoluminescence, the bandgap of strained Si1–x.Gex on < 110 > Si for 0.16 ≤ x ≤ 0.43 is determined and compared to theory. A strong “no-phonon” emission process in photoluminescence spectra of strained < 110 > Si/Si1–x.Gex/Si was observed as compared with that observed in < 100 > layers. Finally, quantum confinement shift of Si/Si0.71 Ge0.29/Si wells with a confinement energy up to 110 meV has been observed by varying the well width from 133 Å to 17 Å.

Recent studies on strained layer heteroepitaxy in high misfit systems (eg. Ge on Si) have clearly indicated the importance of elastic strain on a number of surface-mediated growth effects. In this work we consider the transition from ideal, 2-D layer-by-layer growth to the initial stages of a 3-D growth morphology as a precursor to misfit dislocation injection in GexSi1−x/Si heterostructures with x as low as 0.15. Experimentally, we have studied a wide range of MBE-and CVD-grown single and multilayer GexSi1−x/Si (x<0.5) structures using transmission electron microscopy and photoluminescence spectroscopy. Firstly, we describe a new mechanism for the heterogeneous nucleation of misfit dislocations in strained epitaxial layers, the ‘double half-loop’ source, which originates from atomic-scale (<1.5 nm) interfacial perturbations. Secondly, the atomic-scale dilatational perturbations, which can exist in areal densities up to ∼109 cm−2, have been identified as the origin of intense, broad-band PL from MBE-grown GexSi1−x/Si strained layers. The change in PL behaviour with increasing strained layer thickness has been used to study the effects of elastic strain-induced surface roughening at low misfits.

Si1−xGex alloys and multilayers synthesized by solid source MBE on Si(100) substrates have been characterized by low temperature photoluminescence (PL) spectroscopy and transmission electron microscopy (TEM). Phonon resolved transitions originating from excitons bound to shallow impurities were observed in addition to a broad band of intense luminescence. PL spectroscopy over the temperature range 2K to 100K has been used to characterize Si1−xGex/Si heterostructures exhibiting both types of PL spectra. Thin alloy layers exhibited phonon-resolved PL spectra, similar to bulk material, but shifted in energy due to strain and hole quantum confinement. In single quantum wells confinement shifts up to ∼200 meV were observed (1.2 nm wells with x = 0.38) and NP linewidths down to 1.37 meV were obtained. However, the broad PL band (peak energy ∼120meV below the strained bandgap) was predominant when the alloy layer thickness was greater than 2 – 10nm, depending on x, growth temperature, and substrate surface preparation. The strength of the broad PL band was correlated with the areal density of strain perturbations (∼109cm−2 per quantum well; local lattice dilation ∼1.5 nm in diameter) observed in plan-view TEM. The role of MBE growth parameters in determining optical properties was investigated by changing growth temperature, substrate preparation procedures and exploring the effect of surface passivation in a hydrogen ambient. In addition, post growth anneals at temperatures in the range 700°C to 1 100°C were carried out, where interdiffusion removes interfacial asperities and the broad luminescence band decays to zero intensity.

This paper reports the incorporation of erbium into MBE Si and Si/Ge alloys with substrate temperatures of 500°C and 700°C. Using a solid source MBE system, concentrations of erbium between 1018 and 1022 cm−3 have been studied by photoluminescence, electrical measurements, SIMS and TEM. We find no shallow donors or acceptors attributable to erbium but we observe a high concentration of deep states with an activation energy of ∼360 meV. The photoluminescence output is of greatest magnitude when [Er] =2 × 1018 cm−3. Above this concentration the onset of erbium precipitates can just be observed using TEM and at even higher concentrations structured growths of erbium suicide are apparent. The effect on the optical activity of Si:Er that has subsequently been implanted with oxygen is also reported.

The structural stability of strained layer superlattices (SLS's) is addressed using an equilibrium model and then compared to the stability of single strained layers. Relaxation mechanisms are described for various superlattice geometries. The application of a critical thickness/strain criterion to define stability limits was found to be very useful in predicting the detailed relaxation process. The competition between relaxation by misfit accommodation at the base of the SLS and at individual strained interfaces is considered for the initial condition of full coherency and after partial relaxation. Experimental data for the Si-Ge strained layer system are presented; as-grown by MBE and after annealing in the temperature range 500°C – 900°C. The extent of relaxation and the detailed dislocation structure within the SLS's were determined by X-ray rocking curve analysis, Nomarski interference microscopy and transmission electron microscopy. The abrupt changes in relaxation behaviour indicate that rigid boundaries between stable and metastable structures do exist, as predicted by the equilibrium models.