Emerging methods and tools for environmental risk assessment, decision-making, and policy for nanomaterials: summary of NATO Advanced Research Workshop

Nanomaterials and their associated technologies hold promising opportunities for the development of new materials and applications in a wide variety of disciplines, including medicine, environmental remediation, waste treatment, and energy conservation. However, current information regarding the environmental effects and health risks associated with nanomaterials is limited and sometimes contradictory. This article summarizes the conclusions of a 2008 NATO workshop designed to evaluate the wide-scale implications (e.g., benefits, risks, and costs) of the use of nanomaterials on human health and the environment. A unique feature of this workshop was its interdisciplinary nature and focus on the practical needs of policy decision makers. Workshop presentations and discussion panels were structured along four main themes: technology and benefits, human health risk, environmental risk, and policy implications. Four corresponding working groups (WGs) were formed to develop detailed summaries of the state-of-the-science in their respective areas and to discuss emerging gaps and research needs. The WGs identified gaps between the rapid advances in the types and applications of nanomaterials and the slower pace of human health and environmental risk science, along with strategies to reduce the uncertainties associated with calculating these risks.     

An improved boundary element method for the charge density of a thin electrified plate in ℝ3

A weakly singular integral equation of the first kind on a plane surface piece Γ is solved approximately via the Galerkin method. The determination of the solution of this integral equation (with the single-layer potential) is a classical problem in physics, since its solution represents the charge density of a thin, electrified plate Γ loaded with some given potential. Using piecewise constant or piecewise bilinear boundary elements we derive asymptotic estimates for the Galerkin error in the energy norm and analyse the effect of graded meshes. Estimates in lower order Sobolev norms are obtained via the Aubin–Nitsche trick. We describe in detail the numerical implementation of the Galerkin method with both piecewise-constant and piecewise-linear boundary elements. Numerical experiments show experimental rates of convergence that confirm our theoretical, asymptotic results.     

new simple and one-pot synthetic routes to polyfunctionally substituted imidazo-[1,2-a]pyridines, pyrido[1,2-a]pyrimidines, pyrido-[1,2-a]-1,3-diazepines, and imidazo[1,2-a]pyrimidines

Reactions of arylidenemalononitriles with 2-nitromethylene-substituted imidazolidine, hexahydropyrimidine, and hexahydro-1,3-diazepine afforded the title derivatives. Reaction of 2-nitromethylenehexahydropyrimidine with benzylamine or n-butylamine and formalin in a molar ratio of 1:1:2 gave the hexahydro-1H-imidazo[1,2-c]pyrimidine derivatives. Treatment of 2-nitromethyleneimidazolidine and hexahydropyrimidine with secondary aliphatic amines and formalin in a molar ratio of 1:1:1 afforded the corresponding methylene bis-compounds. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1850–1853, December, 2005.     

Testing the thermooxidation of lubricating oils via differential thermal analysis

Two DTA programmes have been developed to differentiate between the thermooxidation stabilities of lubricating oils. Measurements were carried out either by heating the oil sample at a rate of 10 deg/min (direct programme) or by keeping it at 250° (isothermal programme). The selected optimum conditions for these two programmes included the use of 40 mg of sample under oxygen at a flow rate of 150 cm³/min until oxodegradation of the sample. These conditions were found to give precise and repeatable results. The procedures can be recommended as simple and fast quality control methods. Thermooxidation parameters from the DTA curves were correlated with results from the standard routine method IP 306.     

Effect of temperature and absorbed ionizing radiation doses on the electric and electronic properties of copper(II) complexes

A large number of copper(II) complexes derived from their related pyridine derivatives were prepared, crystallized and their characteristics established. The temperature dependence of d.c. electronic (electrical) conductivity and the electronic absorption properties of the materials under investigation were studied before and after exposure to various absorbed gamma does up to 10⁷ rads using a ⁶⁰Co gamma cell. The effect of gamma absorbed doses on the d.c. electrical conductivity and electronic absorption spectra of γ-irradiated samples are discussed on the basis of the effect of ionizing radiation firstly on metal—oxygen, and secondly on CC bonds regarding the substituent effect on their electronic delocalization and their geometrical structures.     

Deposition of Na2WO4 films by ultrasonic spray pyrolysis: effect of thickness on the crystallographic and sensing properties

Na₂WO₄ films have been grown on Si (1 0 0) and glass substrate using ultrasonic spray pyrolysis. The films are prepared from aqueous solution containing Na₂WO₄·2H₂O at 475 °C temperature and characterized by XRD and SEM techniques and the chemical composition of the films have been verified by EDX and PIXE and its formula Na₂WO₄ is confirmed by XRD. The evolution of the crystallinity was studied as a function of film thickness ranging from 2500 to 4200 nm, which corresponds to a deposition time from 10 to 30 min, respectively. The crystalline quality was found to improve, where the grain size values increased with increasing thickness. Atomic Force Microscopy (AFM) was used to study the morphology evolution with the deposition time, where porous films were found due to the synthesis parameters, and a better sensing response to gases was developed with increasing thickness. Thus, this study demonstrates the possibility of utilizing Na₂WO₄ thick films as a sensor element for the detection of ethanol vapor at room temperature, where thicker films exhibit excellent ethanol vapor sensing properties with a maximum sensitivity at 25 °C in air atmosphere with fast response time.     

Direct correlation of microstructure and device performance of liquid phase crystallized Si thin film solar cells on glass

Si thin films on glass grown by liquid phase crystallization (LPC) exhibit large grains resembling those in multicrystalline Si wafers. The present work gives direct insight into how planar defects in LPC‐Si thin films influence the device performance of the corresponding solar cells by acquiring electron‐backscatter diffraction maps and measuring solar cell parameters on the same identical positions. By this approach, it was possible to demonstrate how low scanning velocities of the laser line during the crystallization lead to lower densities of grain boundaries, to improved charge‐carrier diffusion lengths, and hence to improved device performances.

     

Synthetic Routes to Selected Heterocycles Containing Antipyrine Moiety

This review deals with the synthetic potentiality and utility of antipyrine and its derivatives in the synthesis of 4‐substituted antipyrine and other heterocycles containing antipyrine moiety such as thiazole, pyrazolopyridines, pyrazolopyrimidines, and pyrazolotriazines. The reactions that cover the methods of synthesizing the aforementioned heterocycles such as addition, condensation, and cyclization were also reviewed.     

Pharmacological Evaluation of Novel Organoiron Dendrimers as Antimicrobial and Anti‐Inflammatory Agents

The synthesis of a novel and attractive class of nonsteroidal anti‐inflammatory and antimicrobial organoiron dendrimers attached to the well‐known drug ibuprofen is achieved. The structures of these dendrimers are established by spectroscopic and analytical techniques. The antimicrobial activity of these dendrimers is investigated and tested against five human pathogenic Gram‐positive and Gram‐negative bacteria, and minimum inhibitory concentrations are reported. Some of these synthesized dendrimers exhibit higher inhibitory activity against methicillin‐resistant Staphylococcus aureus, vancomycin‐resistant Enterococcus faecium, and Staphylococcus warneri compare to the reference drugs. As well, the in vitro and in vivo anti‐inflammatory activities of these dendrimers are evaluated. The results of in vivo anti‐inflammatory activity and histopathology of inflamed paws show that all dendrimers display considerable anti‐inflammatory activity; however, second‐generation dendrimer ( G2‐D6 ) shows the best anti‐inflammatory activity, which is more potent than the commercial drug ibuprofen at the same tested dose. Results of the toxicity study reveal that G2‐D6  is the safest drug on biological tissues.     

Spectrophotometric determination of gatifloxacin in pure form and in pharmaceutical formulation

Simple, rapid, and extractive spectrophotometric methods were developed for the determination of gatifloxacin (GT) in bulk and pharmaceutical dosage form. These methods are based on the formation of yellow ion-pair complexes between the basic nitrogen of the drug and three sulphonphthalein acid dyes, namely; bromocresol green (BCG), bromocresol purple (BCP), bromophenol blue (BPB) and bromothymol blue (BTB) in phthalate buffer pH 3.0, 3.4 and 3.2, using BCG, BCP and (BPB or BTB), respectively. The formed complexes were extracted with chloroform and measured at 415, 417, 412 and 414 nm for BCG, BPB, BCP and BTB, respectively. The analytical parameters and their effects on the reported systems are investigated. The reactions were extremely rapid at room temperature and the absorbance values remains unchanged at 48 h for all reactions. Beer's law was obeyed in the ranges 2.0-20, 2.0-14 and 2.0-16 microg mL(-1) for BCG, BCP and (BPB or BTB), respectively. The composition of the ion pairs was found 1:1 by Job's method. Beer's law validation, accuracy, precision, limits of detection, limits of quantification. The proposed methods have been applied successfully for the analysis of the drug bulk form and its dosage form. The results were in good agreement with those obtained by the official and reported methods.