Characterisation of DLC films deposited using titanium isopropoxide (TIPOT) at different flow rates

In recent years, there has been growing interest in the search for advanced biomaterials for biomedical applications, such as human implants and surgical cutting tools. It is known that both carbon and titanium exhibit good biocompatibility and have been used as implants in the human body. It is highly desirable to deposit biocompatible thin films onto a range of components in order to impart biocompatibility and to minimise wear in implants. Diamond like carbon (DLC) is a good candidate material for achieving biocompatibility and low wear rates. In this study, thin films of diamond-like-carbon DLC were deposited onto stainless steel (316) substrates using C2H2, argon and titanium isopropoxide (TIPOT) precursors. Argon was used to generate the plasma in the plasma enhanced vapour deposition (PECVD) system. A critical coating feature governing the performance of the component during service is film thickness. The as-grown films were in the thickness range 90-100 nm and were found to be dependent on TIPOT flow rate. Atomic force microscopy (AFM) was used to characterise the surface roughness of the samples. As the flow rate of TIPOT increased the average roughness was found to increase in conjunction with the film thickness. Raman spectroscopy was used to investigate the chemical structure of amorphous carbon matrix. Surface tension values were calculated using contact angle measurements. In general, the trend of the surface tension results exhibited an opposite trend to that of the contact angle. The elemental composition of the samples was characterised using a VG ToF SIMS (IX23LS) instrument and X-ray photoelectron spectroscopy (XPS). Surprisingly, SIMS and XPS results showed that the DLC samples did not show evidence of titanium since no peaks representing to titanium appeared on the SIMS/XPS spectra.

Magnetic properties of barium ferrite dispersed within polystyrene-butadiene-styrene block copolymers

Magnetic properties of nanocomposite materials obtained by dispersing barium ferrite nanoparticles within polystyrene-butadiene-styrene block copolymer, in the temperature range, 300 to 500 K are reported. The temperature dependence of the magnetization at saturation, averaged uniaxial magnetocrystalline anisotropy, and coercive field of thick films are analyzed. A "matrix effect" was noticed within the glass transition range of the hard component (polystyrene) of the polymeric matrix. The reported modifications of the magnetic properties were assigned to the competition between the magnetic and mechanical reorientation of nanoparticles within the polymeric matrix. Such modifications were not observed in barium ferrite dispersed in cement.

Azurophilic inclusions in plasma cells

We report a 45-year-old man with complaints of chest pain and weight loss who was referred for a bone marrow/trephine procedure to the Aga Khan University Hospital. Bone marrow examination showed plasmacytosis of 95% with plasma cells containing coarse Auer rod-like azurophilic inclusions, which failed to stain positively with Sudan Black B or periodic acid Schiff stain. These inclusions have rarely been previously reported as they are more significant morphologically rather than having a prognostic value.

The potential of oil-utilizing bacterial consortia associated with legume root nodules for cleaning oily soils

The surfaces of root nodules of Vicia faba and Lupinus albus (legume crops), were colonized with bacterial consortia which utilized oil and fixed nitrogen. Such combined activities apparently make those periphytic consortia efficient contributors to bioremediation of oily nitrogen-poor desert soils. This was confirmed experimentally in this study. Thus, cultivating V. faba, L. albus and, for comparison, Solanum melongena, a nonlegume crop, separately in oily sand samples resulted in more oil attenuation than in an uncultivated sample. This effect was more pronounced with the legume crops than with the nonlegume crop. Furthermore, in flask cultures, V. faba plants with nodulated roots exhibited a higher potential for oil attenuation in the surrounding water than plants with nodule-free roots. Denaturation gradient gel electrophoresis (DGGE) of polymerase chain reaction amplified 16S rRNA coding genes revealed that periphytic bacteria had DGGE bands not matching those of the oil-utilizing rhizospheric bacteria. Legume nodules also contained endophytic bacteria whose 16S rDNA bands did not match those of Rhizobium nor those of all other individual periphytic and rhizospheric strains. It was concluded that legume crops host on their roots bacterial consortia with a satisfactory potential for oil phytoremediation.

Intraocular pressure following intravitreal injection of triamcinolone acetonide

Background:

To investigate the intraocular pressure (IOP) response following intravitreal injection of triamcinolone acetonide.

Methods:

This retrospective consecutive non-comparative case series study included 41 patients (52 eyes) (19 male, 22 female, mean age 64.1 ± 13.44; range 22 – 85 years) with progressive exudative ARMD (n = 10 eyes) or diffuse diabetic macular oedema (42 eyes), who received one or more intravitreal injection(s) of 4 mg triamcinolone acetonide.

Results:

IOP increased significantly (p<0.001) from 16.08 (±3.28) mm Hg (range 12-26 mm Hg) preoperatively to a mean maximum of 26.1 (±11.79) mmHg (range 15-80 mm Hg) postoperatively (p<0.001). An IOP rise to values higher than 21 mm Hg was observed in 28 (53.8%) eyes. Elevation of IOP occurred 7.5 weeks (±7.07) after the injection. All five patients (11.9%) with a family history of glaucoma developed an IOP rise above the mean maximum level. The post-injection rise of IOP was statistically independent of gender (p=0.37), but the presence of diabetes mellitus demonstrated a marked influence on the rate of a postoperative elevation of IOP (p=0.05).

Conclusion:

The IOP response following IVTA was consistent with previous studies. A family history of glaucoma and a history of diabetes mellitus may predispose patients to a greater than average IOP rise following IVTA. Careful IOP assessment for at least 6 months post injection is recommended.

Long wavelength approximation to peristaltic motion of an Oldroyd 4-constant fluid in a planar channel

An analysis is carried out to study the peristaltic motion of an incompressible Oldroyd 4-constant fluid in a planar channel. The flow modeling is first developed in dimensionless form and the governing problem is then simplified by adopting a long wavelength assumption. It is found that unlike Oldroyd 3-constant fluid, the governing problem of an Oldroyd 4-constant fluid under a long wavelength approximation contains the rheological parameters. The resulting non-linear problem has been solved numerically using a combination of the finite difference scheme and the iterative method. In addition, an analytical solution is presented for the domain near the channel center. The effect of material parameters on the pumping and trapping is discussed. A comparison with the corresponding results for a viscous Newtonian fluid is also made.

Endothelial cell growth on silicon modified hydrogenated amorphous carbon thin films

The biological response of human microvascular endothelial cells (HMEC-1) seeded on Si-DLC films and on control surfaces was evaluated in terms of initial cell enhancement, growth, and cytotoxicity. The microstructure of the films was characterised by Raman spectroscopy and X-ray photoelectron spectroscopy. The effect of changes in microstructure, surface energy, surface electronic state, and electronic conduction, on the biological response of the films to endothelial cells was investigated. Endothelial cell adhesion and growth was found to be affected by changes in the microstructure of the films induced by silicon doping and thermal annealing. We observed a significant statistical difference in endothelial cell count between the as-deposited DLC and Si-DLC films using the one sample t-test at a p-value of 0.05. We also found a statistically significant difference between the adhesion of HMEC films on DLC and Si-DLC films at various annealing temperatures using the one-way ANOVA F statistic test at p < 0.05 and the post-hoc Tukey test. One sample t-test at p < 0.05 of MTT-assay results showed the endothelial cells to be viable when seeded on DLC/Si-DLC films. We suspect that the increased adhesion of endothelial cells induced by increasing the amount of silicon in the Si-DLC films is associated with the development of a suitable surface energy due to silicon addition, which neither favored cell denaturing nor preferential water spreading before cellular attachment on the film surface. The presence of an external positively charged dipole on the Si-DLC films confirmed by our Kelvin probe measurements is also expected to enhance the adhesion of endothelial cells that are well known to carry a negative charge. The Si-DLC films investigated hold potential promise as coatings for haemocompatible artificial implants.

Molecular genetic studies of Anopheles stephensi in Pakistan

Anopheles stephensi Liston s.l. (Diptera: Culicidae) is one of the major vectors of malaria in Pakistan, India, Iran and Afghanistan. In parts of its range this species has shown increases in both relative and absolute abundance in what is hypothesized to be a response to human-mediated environmental change resulting from extensive irrigation. We attempted to detect the molecular genetic signatures of this population instability based on three samples obtained from two villages (149/6R and 111/6R) within an irrigation zone in Punjab Province and from one village (Azakhel) outside the irrigation scheme in Northwest Frontier Province (NWFP), Pakistan, using seven microsatellite loci and 682 basepairs of the mitochondrial CO1 gene. For microsatellite loci, high levels of genetic diversity were observed within populations (mean alleles per locus 10.71-11.57; mean heterozygosity 0.703-0.733). Deviation from Hardy-Weinberg expectations was observed for only two microsatellite loci in 21 tests. No genetic differentiation was observed between populations and average pairwise F(ST) values did not differ significantly from zero for any population pair or either marker system. Tests of population expansion for both mitochondrial and microsatellite loci were inconclusive.

Surface engineering of artificial heart valve disks using nanostructured thin films deposited by chemical vapour deposition and sol-gel methods

Pyrolytic carbon (PyC) is widely used in manufacturing commercial artificial heart valve disks (HVD). Although PyC is commonly used in HVD, it is not the best material for this application since its blood compatibility is not ideal for prolonged clinical use. As a result thrombosis often occurs and the patients are required to take anti-coagulation drugs on a regular basis in order to minimize the formation of thrombosis. However, anti-coagulation therapy gives rise to some detrimental side effects in patients. Therefore, it is extremely urgent that newer and more technically advanced materials with better surface and bulk properties are developed. In this paper, we report the mechanical properties of PyC-HVD, i.e. strength, wear resistance and coefficient of friction. The strength of the material was assessed using Brinell indentation tests. Furthermore, wear resistance and coefficient of friction values were obtained from pin-on-disk testing. The micro-structural properties of PyC were characterized using XRD, Raman spectroscopy and SEM analysis. Also in this paper we report the preparation of freestanding nanocrystalline diamond films (FSND) using the time-modulated chemical vapour deposition (TMCVD) process. Furthermore, the sol-gel technique was used to uniformly coat PyC-HVD with dense, nanocrystalline-titanium oxide (nc-TiO2) coatings. The as-grown nc-TiO2 coatings were characterized for microstructure using SEM and XRD analysis.

Peristaltic flow of a couple stress fluid in an asymmetric channel

This paper presents an analysis of the peristaltic flow of a couple stress fluid in an asymmetric channel. The asymmetric nature of the flow is introduced through the peristaltic waves of different amplitudes and phases on the channel walls. Mathematical modelling corresponding to a two-dimensional flow has been carried out. The flow analysis is presented under long wavelength and low Reynolds number approximations. Closed form solutions for the axial velocity, stream function and the axial pressure gradient are given. Numerical computations have been carried out for the pressure rise per wavelength, friction forces and trapping. It is noted that there is a decrease in the pressure when the couple stress fluid parameter increases. The variation of the couple stress fluid parameter with the size of the trapped bolus is also similar to that of pressure. Furthermore, the friction force on the lower channel wall is greater than that on the upper channel wall.