Magnetic field induced assembling of nanoparticles in ferrofluidic liquid thin films based on NixFe1?xFe2O4

Ultra fine precursors for ferrofluid synthesis, belonging to the series, Ni _x Fe_1−x Fe₂O₄ (where ‘x’ varies from ‘0’ to ‘0.6’ in steps of 01), were synthesized. Ferrofluids based on these fine particles were prepared with oleic acid as surfactant and kerosene as carrier. Ferrofluidic thin films were made on glass substrates and magnetic field induced laser transmission was studied. The pattern exhibited by the films under the influence of a magnetic field was observed with the help of a CCD camera. The analysis of results confirms the chain formation of particles in the presence of an applied magnetic field and their saturation at higher applied fields.     

Crack growth in structural adhesive joints in aqueous environments

The adhesive fracture energy, G _c , of metallic joints, bonded with a rubber-toughened epoxy adhesive, has been measured using monotonically-loaded tests. Such tests have been conducted in various relative humidities and in water, at 21 °C. Two surface pretreatments have been employed for the substrates prior to bonding: a simple grit-blast and degrease (‘GBD’) pretreatment or a grit-blast, degrease and silane primer (‘GBS’) pretreatment. The joints were formed using metallic substrates which were either (a) aluminium-alloy substrates, (b) steel substrates, or (c) ‘dissimilar’ substrates (i.e. one substrate being aluminium-alloy with the other one being steel). For both test environments, when G _c was plotted against the crack velocity, three regions of fracture behaviour could be distinguished. At low rates of displacement the crack grew in a stable manner, visually along the interface, and relatively low crack velocities could be readily measured. This was termed ‘Region I’ and here the value of G _c measured in the aqueous environment was relatively low compared to that measured in a relatively dry environment of 55% relative humidity. On the other hand, at relatively high rates of displacement the crack always grew in a stick-slip manner mainly cohesively in the adhesive layer at approximately 20 km/min. This was termed ‘Region III’, and here the value of G _c was relatively high and independent of the environmental test conditions employed. In this region the crack was considered to grow faster than the water molecules were able to reach the crack tip, which explains the independence of G _c upon the test environment. In between ‘Region I’ and ‘Region III’, a transition region was observed which was designated as ‘Region II’. The major effect of the ‘GBS’ pretreatment, compared to the ‘GBD’ pretreatment, was to increase the value of G _c both in ‘Regions I and III’, although the presence of the silane primer had the far greater effect in ‘Region I’.     

Template and template-free preparation of one-dimensional metallic nanostructures

In this article, we have studied and developed two approaches for organizing metallic nanoparticles into one-dimensional assemblies. The first uses DNA as a ‘template’ and allows the preparation of various silver nanostructures (‘beads-on-a-string’ or rod-like wires). The conductance of such nanostructures was demonstrated by employing a powerful technique, Electrostatic Force Microscopy (EFM). This technique gave us ‘contactless’ information about the electrical properties of silver nanostructures, aligned on a SiO₂/Si surface. Additionally, I–V characteristics of a single silver nanowire crossing two microelectrodes were recorded. The nanowire resistivity was estimated at 1.46 × 10⁻⁷ Ω m (at 300 K), which is one order of magnitude higher than that of bulk silver (1.6 × 10⁻⁸ Ω m). The second approach is a ‘template-free’ one, and exploits the binding ability of l-arginine, which favours the self-assembling of capped gold nanoparticles into gold nanochains. The results suggest that gold nanochains were formed due to dipole–dipole interaction between adjacent nanoparticles, which fuse together through an oriented attachment mechanism. Atomic force microscopy, TEM, UV–vis spectroscopy and X-ray diffraction were used to characterize the morphological, optical and structural properties of these metallic nanostructures.     

Reaction mechanism,kinetics and high temperature transformations of geopolymers

The reaction kinetics and mechanism of geopolymers are studied. The dissolved silicate concentration decreases from the beginning of the reaction. A characteristic time ‘t _0,vit’ for the setting of the reaction mixture is derived from isothermal Dynamic Mechanical Analysis experiments. ‘t _0,vit’ increases with SiO₂/R₂O but goes through a minimum for increasing water content. The reaction is slower for K compared to Na-silicate based systems. ²⁹Si and ²⁷Al solution NMR are used to probe the molecular changes. ²⁷Al NMR and FTIR reveal that an ‘intermediate aluminosilicate species’ (IAS) is formed from the start of the reaction. The concentration decrease of OH⁻ during low-temperature reaction is related to the formation of IAS. The rate law of this process seems to be obeyed by a total reaction order of 5/3, with a partial order of 1 for OH⁻ and 0 for Na⁺ in the silicate solution. During first heating after polymerization water is lost leading to a distortion of the Al environment. According to XRD, no crystallization occurs below 900 °C. However, between 950 and 1100 °C a crystallization exotherm of nepheline is observed with DSC for a geopolymer with SiO₂/Na₂O = 1.4. Neither T _g of the amorphous geopolymer, nor the shrinkage and expansion around T _g during first heating, cause a measurable heat effect.     

Growth and physico chemical characterization of lanthanum neodymium oxalate single crystals

Single crystals of lanthanum neodymium oxalate (LNO) are grown in sodium meta silicate gels, by the diffusion of a mixture of aqueous solutions of lanthanum nitrate and neodymium nitrate into the test tube having the set gel containing oxalic acid. The bluish pink coloured tabular crystals of LNO having well defined hexagonal basal planes appear either as ‘foggy’ or ‘clear’, the latter at the greater depths inside the gel. The colouration of LNO visually observed is evidenced in UV-visible spectrum, by the revelation of well pronounced characteristic peaks in the visible region (500–900 nm). X-ray diffraction (XRD) of powdered LNO is ordered, meaning crystalline in nature, besides its ‘isostructurality’ with similarly grown lanthanum samarium oxalate crystals. The single crystallinity of LNO is established by its oscillation XRD pattern. Thermogravimetric analysis (TGA) and differential scanning colorimetry (DSC) support that LNO loses water of crystallization around 120°C and CO and CO₂ around 350–450°C, while the infrared absorption (IR) spectrum of LNO establishes the presence of oxalate (C₂O₄)²⁻ ions. Energy dispersive X-ray analysis (EDAX) confirms the presence of La and Nd in the sample. X-ray photoelectron spectroscopic (XPS) studies of LNO establish the presence of La and Nd in their respective oxide states. An empirical structure for LNO has been proposed on the basis of these findings. The ‘smokiness’ in the foggy LNO crystal has been attributed due to the ‘gel inclusion’ during the growth process.     

Studies on ionic transport properties of a new Ag+ ion conducting composite electrolyte system (1−x)[0·75 AgI: 0·25 AgCl]:xSnO2

A new Ag⁺ ion conducting composite electrolyte system (1−x)[0·75 AgI: 0·25 AgCl]:xSnO₂ using a quenched/annealed [0·75 AgI: 0·25 AgCl] as host compound in place of conventional host AgI, has been investigated. The effects of various preparation methods and soaking time are reported. The composition 0·8[0·75 Agl: 0·25 AgCl]:0·2SnO₂ exhibited optimum conductivity (σ = 8·4 × 10⁻⁴S/cm) with conductivity enhancement of ∼ 10¹ from the annealed host at room temperature. Transport property studies such as electrical conductivity (σ) as a function of temperature using impedance spectroscopy technique, ionic transference number (t _ion) using Wagner’s d.c. polarization method and ionic mobility (μ) by transient ionic current technique were carried out on the optimum conducting composition. The mobile ion concentration (n) was calculated from ‘σ’ and ‘μ’ data.     

Effect of KCl and KNO<Subscript>3</Subscript> on Partial Molal Volumes and Partial Molal Compressibilities of Some Amino Acids at Different Temperatures

Density (ρ) and ultrasonic velocity (u) values of amino acids l-alanine, l-proline, l-valine, and l-leucine in 2M aqueous KCl and 2M aqueous KNO₃ solutions have been measured as a function of amino acid concentration at different temperatures (298.15 K, 303.15 K, 308.15 K, 313.15 K, 318.15 K, and 323.15 K). Using the ρ and u data, partial molal volume () and partial molal isentropic compressibility () values have been computed. The increase in partial molal volume with temperature has been attributed to the volume expansion of hydrated zwitterions. The and values of l-alanine, l-proline, l-valine, and l-leucine in 2M aqueous KCl and KNO₃ solutions have been found to be larger than the corresponding values in water. The larger partial molal volumes of l-alanine, l-proline, l-valine, and l-leucine in 2M aqueous KCl and KNO₃ solutions have been ascribed to the formation of ‘zwitterion-K⁺/Cl⁻/NO₃⁻’ and ‘K⁺/Cl⁻/NO₃⁻–water dipole’ aggregates in solutions. The formation of these entities in solutions causes the release of water associated with zwitterions to the bulk water. The larger partial molal compressibilities of l-alanine-/l-proline-/l-valine-/l-leucine–2M aqueous KCl/KNO₃ solutions than the corresponding values in water have been attributed to the formation of ‘zwitterion–ion’ and ‘ion–water dipole’ incompressible entities in solutions.     

Mechanical failure of a Thompson’s hemiarthoplasty stem 28 years post-implantation: an investigation with electron microscopy

Τhe authors would like to report a mechanical failure of a Thompson’s prosthesis, 28 years post-implantation. A detailed examination of the specimen revealed no defects in the prosthesis and a dominating ‘brittle component’ fracture of the stem. In this context the detailed fractographic study by scanning electron microscopy (SEM) revealed no detrimental manufactural defects that may have produced microcracks and consequently risked initiating the fracture propagation. In contrast, the fracture was mainly a fatigue one with a mixed mode of microscopic trans- and intergranular crack propagation. To the best of our knowledge, such a mechanism of implant failure in a cementless stem has never before reached 28 years neither in a Thompson’s nor any other type of prosthesis, and in the already reported case, it exceeded 30 years [N. Wolson and J. P. Waadell, Can. J. Surg. 38(6) (1995) 542], however the stem’s ultrastructure has never been investigated under electron microscopy, which arguably can provide a useful assessment of a fatigue fracture. Τhe authors introduce the question of revising our standards when evaluating the newly designed and expensive implants and propose re-focusing on surgical technique, rather than purely on implant properties.     

Influence of crystallographic textures on tensile properties of 316L austenitic stainless steel

Role of cold rolling texture on the tensile properties of the cold rolled and cold rolled and annealed AISI 316L austenitic stainless steel is described here. The solution-annealed stainless steel plates were unidirectionally cold rolled to 50, 70 and 90% of reduction in thickness. The cold rolled material was annealed at 500–900 °C annealing temperatures. X-ray diffraction technique was employed to study the texture evolution in cold rolled as well as cold rolled and annealed conditions. The texture components that evolved were translated into slip transmission number ‘λ’ and Schmid factor ‘μ’. These two parameters were correlated with the tensile properties of the material. The tensile properties were evaluated under all processing conditions. Softening of the cold rolled material was observed after annealing with increasing annealing temperatures. From the stress–strain curves, strain hardening coefficient ‘n’ and strain hardening rate ‘θ’ were determined. It was found that the effect of texture on tensile behaviour could be understood clearly by strain hardening rate. Out of the two parameters, ‘n’ and ‘θ’, strain hardening rate was found to be more sensitive to type of texture in the material.     

Active anion manipulation for emergence of active functions in the nanoporous crystal 12CaO·7Al<Subscript>2</Subscript>O<Subscript>3</Subscript>: a case study of abundant element strategy

This article reviews our approach to render 12CaO · 7Al₂O₃ (C12A7) electronically active using a new concept of ‘active anion manipulation’, where nanostructures embedded within the C12A7 crystal lattice are intentionally utilized to generate chemically unstable (‘water-free active’) anions. Anionic active oxygen radicals, O⁻ and O₂⁻, are formed efficiently in C12A7 cages under high oxygen activity conditions. The configuration and dynamics of O₂⁻ in cages are revealed by a combination of continuous-wave and pulsed electron paramagnetic resonance (EPR). It is demonstrated that metal-loaded C12A7 is a promising oxidation catalyst for syngas (CO + H₂) formation from methane. Furthermore, the O⁻ ion, the strongest oxidant among active oxygen species, can be extracted from the cage into an external vacuum by applying an electric field with thermal assistance, generating a high-density O⁻ beam in the order of μA cm⁻². In contrast, heat treatment of C12A7 in a hydrogen atmosphere forms H⁻ ions in the cages. The resultant C12A7:H⁻ exhibits a persistent insulator-conductor conversion upon ultraviolet-light or electron-beam irradiation. The irradiation-induced conversion mechanism is examined by first-principle theoretical calculations. Furthermore, the presence of a severely reducing environment causes the complete substitution of electrons for anions in the cages. The resulting C12A7:e⁻, which exhibits excellent stability and an electrical conductivity greater than 100 S cm⁻¹, is regarded as an ‘electride’, an ionic compound in which electrons serve as anions. The C12A7 electride exhibits a high potential for applications involving cold cathode and thermal field electron emissions due to its small work function. Electride fabrication methods suitable for large-scale production via melt processing are described. It is also demonstrated that proton or inert gas ion implantations into C12A7 thin films at elevated temperatures are effective for both H⁻ and electron doping.     

Mapping inventive activity and technological change through patent analysis: A case study of India and China

The characteristics of Indian and Chinese patenting activity in the US patent system are examined by delineating two categories of patents; ‘nationally assigned’, and ‘invented not nationally assigned’ patents (not-nationally assigned patents in short). Further within the above two categories, patents are distinguished and analysed in terms of patent types: utility, design, and plant patents. Indian patents are mainly of utility type whereas China's activity falls in both utility and design.In the ‘nationally assigned’ patents, the different types of institutions involved and linkages are much higher for China. However, ‘not-nationally assigned’ patents of both the countries are dominated by industry and inter-institutional collaborations are sparse. Patents addressing technology sectors (analysis based on utility patents) do not exhibit major differences between the two categories in Chinese patents and address with varying degree all technology sectors. Unlike China, India's ‘nationally assigned’ patents are concentrated in chemical and drugs & medical whereas their ‘not-nationally assigned’ patents are similar to that of China in addressing technology sectors. In design patents, Chinese ‘nationally assigned’ patents mainly cover ornamental design of lighting equipments whereas their ‘not-nationally assigned’ patents are mainly in design equipment for production, distribution or transformation of energy. Further, few firms are active in design patents in both the categories. India's design activity is insignificant in both the categories. The paper concludes by examining the results in the policy context. This revised version was published online in June 2006 with corrections to the Cover Date.     

UK Research Assessment Exercises: Informed judgments on research quality or quantity?

A longitudinal analysis of UK science covering almost 20 years revealed in the years prior to a Research Assessment Exercise (RAE 1992, 1996 and 2001) three distinct bibliometric patterns, that can be interpreted in terms of scientists’ responses to the principal evaluation criteria applied in a RAE. When in the RAE 1992 total publications counts were requested, UK scientists substantially increased their article production. When a shift in evaluation criteria in the RAE 1996 was announced from ‘quantity’ to ‘quality’, UK authors gradually increased their number of papers in journals with a relatively high citation impact. And during 1997–2000, institutions raised their number of active research staff by stimulating their staff members to collaborate more intensively, or at least to co-author more intensively, although their joint paper productivity did not. This finding suggests that, along the way towards the RAE 2001, evaluated units in a sense shifted back from ‘quality’ to ‘quantity’. The analysis also observed a slight upward trend in overall UK citation impact, corroborating conclusions from an earlier study. The implications of the findings for the use of citation analysis in the RAE are briefly discussed.     

Isotopic Composition of Water Used in Triple-Point Cells

Isotopic analysis of the water used in KRISS triple point of water (TPW) cells was performed by three separate laboratories. The δD and δ ¹⁸O isotopic composition of six ampoules, made from two TPW cells, were analyzed by isotope ratio mass spectrometers. The analysis data showed that δD and δ ¹⁸O were − 62.17‰ and − 9.41‰ for the KRISS-2002-Jan cell, and − 36.42‰ and − 4.08‰ for the KRISS-2005-Jun cell. The temperature deviation of the triple point of water for these cells calculated from Kiyosawa’s data and the definition of the TPW were + 45.07μK for the KRISS-2002-Jan cell, and + 25.49μK for the KRISS-2005-Jun cell. The KRISS TPW temperature was + 92μK higher than the CCT-K7 KCRV after correcting for the deviation of the isotopic composition from Vienna Standard Mean Ocean Water.     

Black Africa in the science citation index

According to a quantitative analysis of the publications of the Black African Countries indexed in the SCI between 1992 to 1998, Nigeria seems to be the leader in scientific production on the black continent during that period (the term ‘Black Africa’ refers to all African countries excluding South Africa, Maghrebi, and Egypt). However, an analysis that only takes into account the number of publications does not necessarily disclose very much about neither the dynamics of the respective scientific community nor about the representativity of the country’s production with respect to its total population. Therefore, the number of publications per country is compared with the respective total population. According to this method, Kenya turns out to be the leader in scientific-publication production and several other countries get higher ranks. Additionally, any evaluation of scientific production in that part of the world should also take into account the specific features of these countries, e.g. the difficulties in publication and the existence of a large number of unpublished texts.     

Analysis of Copper Pitting Failure in Drinking Water Distribution System

Electrochemical tests, as well as surface and chemical analysis were used to investigate the cause of pitting failure of copper tubing in a drinking water distribution system. The results show that localized pitting was the cause of failure and copper corrosion problems were observed under a green deposit. The pitting corrosion was associated with the Cl⁻ and SO₄ ²⁻ ions introduced by the water softening treatment. These ions promoted the corrosion and the influence of Cl⁻ ion was much greater than that of the SO₄ ²⁻ ion.     

The effect of caesium on barium hollandites studied by neutron diffraction and magic-angle spinning (MAS) nuclear magnetic resonance

The structural effects of incorporating Cs into the monoclinic and tetragonal hollandites Ba_1.2−x Cs _x Mg_1.2−x/2Ti_6.8+x/2O₁₆ and Ba_1.2−x Cs _x Al_2.4−x Ti_5.6+x O₁₆ have been studied using powder neutron diffraction and ¹³³Cs and ²⁷Al MAS NMR. Addition of Cs to the monoclinic structure induces a ‘shear-type collapse’, in agreement with previously published results. NMR spectra show that the addition of Cs does not change the local structure around the Al cations within the tunnel walls. An algorithm is given that allows a prediction of unit cell parameters to be made for tetragonal hollandites containing barium.     

Comparison of the dimensions of electrical resistance units, supported on the basis of the hall quantum effect, in the All-Russia Research Institute of Metrological Service and the Czech Metrological Institute

VNIIMS (Russia) and CMI (Czech Republic) quantum Hall resistance standards are compared using a VNIIMS portable resistance standard of 1 and 10 kΩ. Conformity is established for the dimensions of units within the limits of relative expanded (k = 2) uncertainty of 10⁻⁷. Translated from Izmeritel’naya Tekhnika, No. 12. pp. 58–61, December, 2008.     

Properties of GaInAsSb solid solutions obtained from antimony fluxes by liquid-phase epitaxy in the spinodal decay region

The growth of epitaxial layers of GaSb lattice-matched Ga_1−x In_xAs_ySb_{1− y} solid solutions by liquid-phase epitaxy from Sb-enriched liquid phases within the spinodal decay region is reported. The highest value of the composition (x=0.4) was achieved for growth on a GaSb(111)B substrate. Results of investigations of the luminescence and structural properties of these solid solutions are presented. Pis’ma Zh. Tekh. Fiz. 24, 58–62 (March 26, 1998)     

Design Support Using Distributed Web-Based AI Tools

Currently, designers are faced with searching through a ‘sea’ of on-line knowledge to support their decision making activities. This paper describes WebCADET, which is a reimplementation of the stand-alone CADET – a Knowledge-Based System (KBS) for product design evaluation. WebCADET aims to provide effective and efficient support for designers during their searches for design knowledge. WebCADET uses the ‘AI as text’ approach, where KBSs can be seen as a medium to facilitate the communication of design knowledge between designers. The development of WebCADET to include practical support via World Wide Web-based functionality, which illustrates the potential of the ‘AI as text’ approach, is described in the paper.     

Sleeping Beauties in science

A ‘Sleeping Beauty in Science’ is a publication that goes unnoticed (‘sleeps’) for a long time and then, almost suddenly, attracts a lot of attention (‘is awakened by a prince’). We here report the -to our knowledge- first extensive measurement of the occurrence of Sleeping Beauties in the science literature. We derived from the measurements an ‘awakening’ probability function and identified the ‘most extreme Sleeping Beauty so far’. This revised version was published online in June 2006 with corrections to the Cover Date.