Highly sensitive and selective dynamic light-scattering assay for TNT detection using p-ATP attached gold nanoparticle

TNT is one of the most commonly used nitro aromatic explosives for landmines of military and terrorist activities. As a result, there is an urgent need for rapid and reliable methods for the detection of trace amount of TNT for screenings in airport, analysis of forensic samples, and environmental analysis. Driven by the need to detect trace amounts of TNT from environmental samples, this article demonstrates a label-free, highly selective, and ultrasensitive para-aminothiophenol (p-ATP) modified gold nanoparticle based dynamic light scattering (DLS) probe for TNT recognition in 100 pico molar (pM) level from ethanol:acetonitile mixture solution. Because of the formation of strong π-donor-acceptor interaction between TNT and p-ATP, para-aminothiophenol attached gold nanoparticles undergo aggregation in the presence of TNT, which changes the DLS intensity tremendously. A detailed mechanism for significant DLS intensity change has been discussed. Our experimental results show that TNT can be detected quickly and accurately without any dye tagging in 100 pM level with excellent discrimination against other nitro compounds.     

A constraint consensus memetic algorithm for solving constrained optimization problems

Constraint handling is an important aspect of evolutionary constrained optimization. Currently, the mechanism used for constraint handling with evolutionary algorithms mainly assists the selection process, but not the actual search process. In this article, first a genetic algorithm is combined with a class of search methods, known as constraint consensus methods, that assist infeasible individuals to move towards the feasible region. This approach is also integrated with a memetic algorithm. The proposed algorithm is tested and analysed by solving two sets of standard benchmark problems, and the results are compared with other state-of-the-art algorithms. The comparisons show that the proposed algorithm outperforms other similar algorithms. The algorithm has also been applied to solve a practical economic load dispatch problem, where it also shows superior performance over other algorithms.     

Effect of molecular weight and concentration of poly(acrylic acid) on the formation of a polymeric calcium phosphate cement

Previous investigations have noted that the tetracalcium phosphate (TTCP)/dicalcium phosphate anhydrous (DCPA) apatite forming calcium phosphate cement (CPC) possesses many favorable properties from a biomaterials standpoint. Despite these positive properties various shortcomings have limited clinical usage of these materials and fostered investigations into the effect of numerous additives. The present study concerns the effect of poly(acrylic acid) (PAA) addition and the influence of factors such as molecular weight and concentration of the additive on the properties of the set cement. One-way ANOVA was conducted using all results obtained, to firstly derive the influence of concentration within each molecular weight group, and secondly to derive the influence of molecular weight within each concentration group. All investigated mechanical properties were influenced by both molecular weight and concentration of the additive. Higher molecular weights tended to result in cements with shorter setting times and higher compressive, diametral and biaxial flexural strengths than their lower molecular weight counterparts. The effect of concentration on the properties of the set cement however was somewhat more complex, a negative correlation was observed between the initial setting time and PAA concentration. In regards to the final setting time, any correlation with concentration was difficult to derive as a consequence of the highly brittle nature of cements made with low concentrations. In regard to mechanical properties, intermediate concentrations tended to give higher strengths than both their higher and lower counterparts, however the exact pattern was largely specific to the mechanical strength test employed. We conclude that molecular weight and concentration of PAA influence the setting behavior and final mechanical properties of the TTCP/DCPA cement, and that selection of an appropriate PAA solution can lead to the production of cements with properties superior to those formed in the absence of the polymer.     

Green synthesis of copper sulfide (CuS) nanostructures for heterojunction diode applications

Copper sulfide (CuS) rod shaped nanostructures with an average length 8 to 10 nm are synthesized through green chemical route using biodegradable starch as a capping agent under a nitrogen environment. Owing to the presence of a large number of glucose units linked by glycosidic bonds, starch can cap copper sulfide (CuS) nanoparticles. The preparation of CuS under nitrogen atmosphere produces fine quality CuS nanostructures by minimizing oxidation. XRD pattern reveals pure hexagonal covellite type CuS nanostructure with prime diffraction planes along (101), (102), (103), (006), (008), and (110) directions. The lattice parameters estimated as a?=?3.790 Å and c?=?16.51 Å. HRTEM studies show a well distribution of CuS nanorods. It shows prominent d-value of 0.28 nm corresponding to (103) hexagonal plane of CuS. The optical absorption extended up to 364 nm which is fairly blue shifted over bulk owing to the quantum confinement brought by starch. The photoluminescence emission is observed at 525 nm. The I–V measurements in planar geometry exhibit the linearity that reveals the ohmic behavior of carrier transport in CuS nanostructures. CuS nanostructures have been successfully used as effective p-type layer to fabricate sandwiched heterojunction devices with zinc chalcogenides (ZnO/ZnS and ZnS/ZnO) core/shell nanocomposites. The p-CuS/n-(zinc chalcogenides) heterojunction devices show good diode characteristics with an increase of ideality factor that may be attributed to surface defects and inhomogeneity in the barrier height. The photodetector also exhibits promising characteristics in terms of responsivity and quantum efficiency which are significant corresponding to material properties.

     

The effect of surface treatment of hydroxyapatite on the properties of a bioactive bone cement

Bioactive bone cements based on a paste-paste system for orthopaedic applications have been developed. They consist of hydroxyapatite (HA) filler particles in a methacrylate matrix comprising urethane dimethacrylate (UDMA) and triethylene glycol dimethacrylate (TEGDMA). To improve the interface between inorganic filler and organic matrix the HA particles were subjected to two different surface treatment methods, using polyacrylic acid (PAA) and gamma-methacryloxypropyltrimethoxy silane (gammaMPS). The aim of the present study was to determine the influence of surface treatment on the mechanical properties, namely compressive strength (CS), diametral tensile strength (DTS) and three-point flexural strength (FS) of the cements and the effect of ageing in simulated body fluid (SBF). Comparing the mechanical properties of the two cements after fabrication, the gammaMPS-HA cement showed higher strength values for all tests conducted (CS = 185+/-19.6 MPa, DTS = 27+/-2.5 MPa, FS=50.2+/-4.9 MPa), whereas PAA-HA containing cement had strength values around 20% lower. However, poly(acrylic acid) surface treatment was found to be more effective in improving the interface, and PAA-HA cements maintained their mechanical properties after immersion in SBF whereas gammaMPS-HA cement showed a reduction in strength values post ageing. From the results of this study, it is concluded that PAA treatment of the HA filler is a viable alternative to silanation with gammaMPS which may provide increased durability in aqueous environments.     

Poly(acrylic acid) modified calcium phosphate cements: the effect of the composition of the cement powder and of the molecular weight and concentration of the polymeric acid

Polymer modified calcium phosphate cements made with cement powders of varying tetracalcium phosphate [TTCP] content were prepared using two different molecular weight fractions of poly(acrylic acid) at four different concentrations. The ratio of the precursors (TTCP:DCPA) in the cement powder was found to influence the initial setting which decreased with increasing concentration of TTCP in the powder phase. It was also observed that cements derived from the higher molecular weight containing PAA yielded significantly (P < 0.05) shorter initial setting time (Ti) than cements containing the lower molecular weight, poly(acrylic acid) [GE7 PAA] The effect of the varying the TTCP content in the three different cement types PCPC-A, PCPC-B and PCPC-C showed that the trends of the compressive strength were specific to the concentration and molecular weight of the poly (acrylic acid). A 20% concentration of Glascol-E7 with a cement powder composed of an equimolar ratio of precursors (PCPC-B) resulted in optimal compressive strength within the range investigated. The TTCP content of the cement powder could also be varied to improve the diametral tensile strengths of the cements; the specific effects however, were again governed by both the concentration and molecular weight of the constituent poly (acrylic acid). The influence of TTCP on both the initial setting time and diametral tensile strength was related to the Ca ²⁺ ion concentration, which determined the rate and amount of cross-linking in the cement.     

Mapping the dynamics of knowledge base of innovations of R&;D in Bangladesh: triple helix perspective

Triple helix (TH) collaborations involving university, industry and government provide a networked infrastructure for shaping the dynamic fluxes of knowledge base of innovations locally and these fluxes remain emergent within the domains. This study maps these emergence dynamics of the knowledge base of innovations of Research & Development (R&D) by exploring the longitudinal trend of systemness within the networked research relations in Bangladesh on the TH model. The bibliometric data of publications collected from the Science Citation Index (SCI), the social sciences and the arts and humanities for analysis of science indicators and the patent data collected from the US Patent Office to analyze the patent success ratio as a measure of innovation within TH domains. The findings show that the network dynamics have varied considerably according to the R&D policies of the government. The collaboration patterns of co-authorship relations in the SCI publications prominently increased, with some variation, from 1996 to 2006. Nevertheless, inter-institutional collaboration negatively influenced by the national science and technology (S&T) research policies in the last 5 years due to their evaluation criteria. Finally, the findings reveal that the R&D system of Bangladesh is still undergoing a process of institutionalizing S&T and has failed to boost its research capacity for building the knowledge base of innovations by neglecting the network effects of TH dynamics.     

Synthesis and characterization of biocompatible hydroxyapatite coated ferrite

Ferrite particles coated with biocompatible phases can be used for hyperthermia treatment of cancer. We have synthesized substituted calcium hexaferrite, which is not stable on its own but is stabilized with small substitution of La. Hexaferrite of chemical composition (CaO)_0.75(La₂0₃)_0.20(Fe₂O₃)₆ was prepared using citrate gel method. Hydroxyapatite was prepared by precipitating it from aqueous solution of Ca(NO₃)₂ and (NH₄)₂HPO₄ maintaining pH above 11. Four different methods were used for coating of hydroxyapatite on ferrite particles. SEM with EDX and X-ray diffraction analysis shows clear evidence of coating of hydroxyapatite on ferrite particles. These coated ferrite particles exhibited coercive field up to 2 kOe, which could be made useful for hysteresis heating in hyperthermia. Studies by culturing BHK-21 cells and WBC over the samples show evidence of biocompatibility. SEM micrographs and cell counts give clear indication of cell growth on the surface of the sample. Finally coated ferrite particle was implanted in Kasaulli mouse to test its biocompatibility. The magnetic properties and biocompatibility studies show that these hydroxyapatite coated ferrites could be useful for hyperthermia.     

The preparation of high conversion polymeric systems containing eugenol residues and their rheological characterization

Copolymeric systems bearing eugenol covalently linked to the macromolecular chains have been prepared and characterised in terms of thermal, rheological and in vitro behaviour. Eugenyl methacrylate (EgMA) and ethoxyeugenyl methacrylate (EEgMA) were polymerized and copolymerized with ethyl methacrylate (EMA) in a wide range of feed composition by bulk at high conversion. Glass transition temperature (T_g) increased with the content of EgMA in the copolymer whereas T_g decreased with the content of EEgMA. The presence of any of the eugenyl monomers in the copolymer increased the thermal stability of the materials. Rheological analysis showed that EMA-co-EgMA copolymers present a higher density of crosslinking or entanglements among the chains compared with EMA-co-EEgMA materials, and copolymers containing more than 40% EgMA exhibited a pseudo-solid like behaviour with G′ relatively independent of the frequency. The average molecular weight between cross-links (M_c) for the latter copolymers was in the order of 10⁴ Da. For EEgMA copolymers, tan δ was lower than unity and G′ showed a gradual and slight dependency with frequency over the whole range of composition. In vitro behaviour showed a higher hydrophilicity of the EEgMA containing copolymers manifested in higher water sorption values, lower water contact angle values and higher surface free energy due to an increase in polarity. All systems presented a good cytocompatibility with human fibroblasts assessed through direct and indirect assays.     

Variability in rheology of cemented paste backfill with hydration age,binder and superplasticizer dosages

The use of (CPB) material to ameliorate geotechnical stability of underground mine is in nascent stage in India. Rheological properties of CPB change with travelling time as it is transported to underground mine stope through pipeline reticulation. In this paper, rheological properties of CPB based on mill tailings of a carbonate rich mineral processing waste are evaluated for different dosages of polycarboxylate (PC) based (SP). Each CPB sample having 78?wt% solids is mixed separately with 4%, 6% or 8% of binder dosages (ratio of the weight of dry binder to the weight of dry tailings) and, 0%, 0.5%, or 1.0% of SP dosages as weight of dry binder. The paper presents a methodology for determining yield stress, plastic viscosity and thixotropic behaviour of CPB mixture as a function of hydration age, binder and SP dosages. Results from the experimental campaigns indicate that SP content has significant influence on rheological behaviour of CPB and can be suitably exploited to enhance the flow characteristics of the carbonate rich process tailings. The study also develops multivariate linear regression models of yield stress, plastic viscosity and thixotropy of CPB depending on the hydration age, binder and SP dosages.