Parametric Characterization of Porous 3D Bioscaffolds Fabricated by an Adaptive Foam Reticulation Technique

Commercially pure titanium (Ti) and its alloys, in particular, titanium-vanadium-aluminium (Ti-6Al-4V), have been used as biomaterials due to their mechanical similarities to bone, good biocompatibility, and inertness in vivo. The introduction of porosity to the scaffolds leads to optimized mechanical properties and enhanced biological activity. The adaptive foam reticulation (AFR) technique has been previously used to generate hydroxyapatite bioscaffolds with enhanced cell behavior due to the generation of macroporous structures with microporous struts that provided routes for cell infiltration as well as attachment sites. Sacrificial polyurethane templates of 45 ppi and 90 ppi were coated in biomaterial-based slurries containing either Ti or Ti-6Al-4V as the biomaterial and camphene as the porogen. The resultant macropore sizes of 100–550 μm corresponded well with the initial template pore sizes while camphene produced micropores of 1–10 μm, with the level of microporosity related to the amount of porogen inclusion.     

SERFing the web: The Re-Web approach for web re-structuring

In our emerging digital paper-less society, massive amount of information is being maintained in on-line repositories and diverse web site representations of this information must be served over the Internet to different user groups. E-commerce and digital libraries are two representative sample applications with such needs. In this paper we present a database-centric approach called Re-Web that addresses this need for flexible web site generation, re-structuring, and maintenance. Re-Web is based on two key ideas. First, we exploit the web site structure by associating web semantics (XML equivalents) with the modeling constructs of the ODMG object model to aid the web site generation process. By capturing the logical structure of web views within the OODB system, we can efficiently maintain the web views using standard database techniques. Secondly, to ease the process of specification and construction of multiple customized web view sites, we also propose the notion of generic web view transformations that are encapsulated into re-usable templates. Thus desired new web view sites can be generated simply by applying the corresponding transformations on the underlying database to produce web view classes and then by applying the web semantics on the newly built view classes. The Re-Web system has been implemented using PSE by Object Design Inc. as object repository, ODMG as object model, OQL as transformation language, SERF as OODB evolution facility and IBM XML parser and LotusXSL processor to aid the web site generation. A case study using Re-Web is also presented to illustrate the working of the system. To the best of our knowledge, Re-Web is the first web site management system focusing on the issue of re-usable view generation templates at the content and not at the presentation style level of abstraction. This revised version was published online in August 2006 with corrections to the Cover Date.     

Investigation of structural dependence of host erbium-doped triangular-lattice PCF on lasing properties and design of high performance laser

A detailed study is presented on the lasing properties of an erbium-doped photonic crystal fiber (PCF) laser. The effects of the host PCF’s structure and laser parameters on continuous-wave laser emission are analyzed by considering the confinement and overlap of pump and signal fields in the gain medium for varying values of pitch, hole diameter, and doping radius. For analysis, we used a finite-difference mode-calculation algorithm devised with standard population and propagation rate-equation solver. Our analysis, applied to an experimentally realized PCF laser, reproduces the observed/reported data, thereby showing the efficacy of our analysis. Finally, a fiber geometry to realize a laser with threshold as low as 6?mW using a short fiber length of 0.52?m is prescribed. The aim of the design is to greatly reduce splice loss with standard single-mode SM28/G.652 fiber while maintaining the optimum performance. These results are new in PCF laser research and should be useful in realizing high performance PCF-based laser devices.     

Selective enrichment of n−3 polyunsaturated fatty acids with C18–C20 acyl chain length from sardine oil using Pseudomonas fluorescens MTCC 2421 lipase

An extracellular lipase purified from Pseudomonas fluorescens MTCC 2421 was used to enrich sardine oil triglycerides with eicosapentaenoic acid (20:5 n−3) and linolenic acid (18:3 n−3) to 35.28% and 8.25%, respectively, after 6 h of hydrolysis. The corresponding n−6 fatty acids (18:2 n−6 and 20:4 n−6) exhibit a reduction (54.93% and 50%, respectively). Structure–bioactivity relationship analyses revealed that the lower hydrophobic (log P values) constants of 18:3 n−3 and 20:5 n−3 (5.65 and 5.85, respectively) result in their higher hydrolytic resistance towards lipase, leading to their enrichment in the triglyceride fraction after lipase-catalysed hydrolysis. Lipase-catalysed hydrolysis of sardine oil for 6 h followed by urea fractionation at 4 °C with methanol provided free fatty acids containing 42.50% 20:5 n−3 and 10.31% 18:3 n−3, respectively. Argentation neutral alumina column chromatography, using n-hexane/ethylacetate (2:1, v/v) resulted in 20:5 n−3 of high purity (83.62%), while 18:3 n−3 was found to be eluted with n-hexane/dichloromethane (4:1, v/v) as eluting solvent with a final purity of 75.31%.     

The Impact of Filling an Abandoned Open Cast Mine with Fly Ash on Ground Water Quality: A Case Study

Fly ash has been used to fill an abandoned open cast mine. Ground water samples were collected from the periphery of the ash-filled mine, from within the mine property, and a half kilometer away from the site; the pH and concentrations of total dissolved solids, total hardness, Ca, Mg, Cl, SO₄, F, K, Cu, Cd, Cr, Fe, Pb, Zn, Mn, and Ni were determined. Concentrations of F and Mn were significantly greater in the ground water collected at the ash-filled mine than in the uncontaminated area, and are potentially a matter of concern. The other parameters were found to be affected but not at problematic levels. An erratum to this article can be found at     

Dielectric properties of cobalt substituted M-type barium hexaferrite prepared by co-precipitation

Barium hexaferrite was synthesised via the co-precipitation method using high purity nitrates, oxides and carbonates of iron (III), barium (II) and ammonium hydroxide. Once a phase pure sample of barium hexaferrite was obtained, it was doped, by weight, with 1, 2, 3, 5, 10, 15, 20 and 30% cobalt oxide (Co₃O₄). The addition of cobalt to the BaM had the effect of reducing the permittivity and loss tangent until a doping of 10% whereupon it remained constant at around 9. Thermogravimetric (TG) studies of green bodies showed decarboxilation to occur at around 825°C and the transformation of residual Co₃O₄ to Co₂O₃ at around 900°C. The X-ray diffraction (XRD) studies confirmed the Co ions substituting in the iron sites until a doping level, of 10–15% where the structure underwent a transition to one more closely resembling the W-type hexaferrite. The measured densities were found to vary with doping levels, with a maximum of 4.45 g/cm³ at 1% Co doping.     

Antibacterial labdane diterpenoids of Ulva fasciata Delile from southwestern coast of the Indian Peninsula

Chromatographic purification of the dichloromethane-soluble fraction of alga, on neutral alumina, using increasing concentrations of ethylacetate/n-hexane as eluents, yielded seven labdane diterpenoids (1–7) as major constituents of green alga Ulva fasciata. Structures of these diterpenoids were established using extensive spectroscopic techniques. Antimicrobial assay showed that the compounds labda-14-ene-3α,8α-diol (2) and labda-14-ene-8α-hydroxy-3-one (4) were inhibitory to the growth of Vibrio parahaemolyticus and Vibrio alginolyticus with minimum inhibitory concentrations of 30 μg/ml by 2, and 40 μg/ml by 4, respectively against the former and 30 μg/ml by 2, and 80 μg/ml by 4, respectively, against the latter. Structure–activity relationship analyses revealed that the compounds with electronegative hydroxyl or carbonyl group(s) exhibit greater activities, apparently by proton exchange reaction with the basic aminoacyl residue at the macromolecular receptor site of virulent enzymes of pathogenic bacteria. These might provide promising therapeutic agents against infections with multi-resistant Gram-negative fish pathogenic bacteria.     

Cellular and molecular responses of smooth muscle cells to surface nanotopography

Recent studies have demonstrated that surface nano-topography affect cell responses and activities. However, the molecular mechanism of the nano-structures on cellular behavior is yet to be determined. To bridge this gap, the present study was aimed to investigate the cellular and molecular responses of smooth muscle cells (SMCs) to surface nano-topography in vitro using nano-porous alumina membranes with different sizes (200 nm- and 20 nm-pores). Cellular responses such as cell adhesion, morphology, and proliferation were assessed using scanning electron microscopy (SEM), hematoxylin and eosin (HE) staining, and cell counting. The molecular cell responses were also investigated using cDNA microarrays. Results from these studies showed an unchanged response in cell adhesion, an alteration in cell morphology, and an increase in cell proliferation for cells grown on 200 nm-pore surfaces than on 20 nm-pore surfaces. In addition, exposure of SMCs to larger nano-pores induced the expression of various genes involved in cell cycle, DNA replication, cell proliferation, and signaling transduction pathways. These findings demonstrated that cellular responses of SMCs are dependent on the underlying nano-topography, and thereby suggesting nano-dimensional surface is one of the most important considerations to design of the next generation of medical devices and tissue engineering scaffolds.