bluuebunny/crossref_metadata_2025 huggingface dataset:
Processing and mechanical properties of Al, Al–2Mg and Al–4Cu alloy base short steel fibre reinforced composites prepared by vortex method
Authors: Mandal D. , Dutta B. K. , Panigrahi S. C.
Published: January 2007

In the present work commercially pure Al, Al–2Mg and Al–4Cu alloy base short steel fibre reinforced composites were prepared by vortex method, and poured into cast iron mould. The steel fibres were coated with copper and nickel by electroless deposition techniques to avoid intermetallic formation and improve wettability. The microstructure observation revealed almost uniform fibre distribution with random orientation in matrixes. Density and hardness increased with addition of short steel fibres. Density measurement shows some interesting aspect on the influence of the coating. Coating with copper gives the best fibre distribution among composites with minimum porosity. Mg addition gives better fibre distribution because it reduced surface energy of steel fibre. Alloying element such as copper addition to the matrix improved hardness but increased porosity. The mechanical properties of these composites were measured and the results were correlated with the observed microstructure; the copper coated short steel fibre reinforced composites showed maximum improvement in strength with good ductility. Fracture surface of tensile specimen was examined under SEM, which revealed fracture mechanism dominated by dimple formation and fibre pull-out. Copper coating on steel fibre improved mechanical properties owing to better interface bonding. Mg and copper addition to the matrix helps to improve strength of different fibre reinforced composites with reduce ductility.
Strain summation in finite element modelling of multipass hot rolling
Authors: Mukhopadhyay A. , Higginson R. L. , Howard I. C. , Sellars C. M.
Published: January 2007

The shear strain distributions in two pass forward–forward (FF) and forward–reverse (FR) rolling have been modelled using plane strain finite element models of individual passes and then summing the results from the individual passes. This method gives excellent agreement with the average shear strain, defined by the net shear angle, and with the distribution of shear strain through the thickness, measured from the distortion of mild steel pins inserted through the thickness of experimentally rolled type 316L stainless steel slabs. The spread in breadth of the experimental slabs has little effect on the shear strain distribution or on the net equivalent strain at any position in the rolled slabs. For a given total reduction, the shear strain for FF two pass rolling is less than that for a single pass and is reduced when a smaller first pass and larger second pass reduction is applied. For FR two pass rolling, the shear strain of the first pass is essentially removed for 30%+30% reductions, but not for 50%+50% reductions. For the experimental conditions studied, the recrystallisation kinetics and recrystallised grain size produced by annealing after FF and FR two pass rolling are satisfactorily correlated by the net equivalent strain, with no evidence of any effect of the different strain paths to achieve the same value of equivalent strain.
Effect of Al and C on structure and mechanical properties of Fe–Al–C alloys
Authors: Baligidad R. G. , Prasad K. Satya
Published: January 2007

Effect of aluminium and carbon content on the microstructure and mechanical properties of Fe–Al–C alloys has been investigated. Alloys were prepared by combination of air induction melting with flux cover (AIMFC) and electroslag remelting (ESR). The ESR ingots were hot forged and hot rolled at 1373 K. As rolled alloys were examined using optical microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to understand the microstructure of these alloys. The ternary Fe–Al–C alloys containing 10·5 and 13 wt-%Al showed the presence of three phases: FeAl with disordered bcc structure, Fe3Al with ordered DO3 structure and Fe3AlC0·5 precipitates with L′12 structure. Addition of high concentration of carbon to these alloys resulted in excellent hot workability and superior tensile at room temperature as well as tensile and creep properties at 873 K. An increase in Al content from 9 to 13 wt-% in Fe–Al–C alloys containing the same levels of carbon has no significant influence on strength and creep properties at 873 K, however resulted in significant improvement in room temperature strength accompanied by a reduction in room temperature ductility.
Plain fatigue and fretting fatigue behaviour of AISI 304 austenitic stainless steel
Authors: Raman S. Ganesh Sundara , Jayaprakash M.
Published: January 2007

The present work deals with the influence of deformation induced martensite formation and grain size on plain fatigue (PF) (without fretting) and fretting fatigue (FF) behaviour of AISI 304 austenitic stainless steel at room temperature. Two grain sizes, namely 43 and 277 μm, were developed via suitable solution annealing treatments. The martensitic transformation was studied using a ferrite scope, X-ray diffractometry, optical and transmission electron microscopy. More martensite formed in coarse grained (CG) material and at higher cyclic stress levels. Owing to the additional influence of contact stress, more martensite formed in the fretting scar region of FF tested samples compared with that in the PF tested specimens. In PF tests conventional behaviour was observed at higher cyclic stress levels, i.e. fine grained material showed superior fatigue lives. But at lower cyclic stress levels CG material exhibited superior fatigue lives. This was explained in terms of amount and time of martensite formation and whether crack initiation or propagation controlled the fatigue life at a given stress level. Fretting fatigue test results indicated a tendency for cross-over in the stress life plots corresponding to two grain sizes.
Microstructure and dynamic material performance of high strength and ultra high strength strip steels
Authors: Oliver S. , Jones T. B. , Fourlaris G.
Published: January 2007

The combined need for weight reduction and increased safety in modern vehicles has led automobile manufacturers to utilise the unique properties of high strength steels in their vehicles. Standard quasi-static tensile tests allow the static mechanical properties to be evaluated for any given steel grade. However, automobile designers require more advanced data, including high strain rate tensile data to fully understand the performance of a steel grade during deformation. Knowledge of the role of strain rate on a given strip steel grades deformation characteristics is essential to fully predict the behaviour of the steel during a crash event to help ensure the safety of the vehicle passengers. In the present study, three commercial strip steel grades were subjected to room temperature deformation at variable strain rates, ranging from quasi-static to dynamic loading conditions, where their obtained mechanical properties were measured. The steel grades studied were a HSLA grade (XF450), a carbon manganese grade (CMn800) and an advanced high strength steel grade (DP1400), each with very different microstructures. The present study showed that the XF450 with a ferrite (97%)-pearlite microstructure exhibited superior elongation and was the most strain rate sensitive grade. This was the only grade where energy absorption until 10% elongation could be measured. The DP1400 with a mainly martensitic microstructure showed very little change in strength or ductility properties over the tested strain rates.
Influence of nitride formers on strength and impact behaviour of hot rolled steel
Authors: Mintz B. , Williamson A. , Su H. , Morrison W. B.
Published: January 2007

The extent to which the nitride formers B, Zr, Ti and Al can be used to improve the properties of C–Mn hot rolled steels has been investigated. Of these nitride formers, a high aluminium addition, ∼0·2%, was the most effective, giving extremely good impact properties with no loss in strength. An impact transition temperature as low as −100°C can be obtained with this Al addition in a silicon killed 0·1%C, 1·4%Mn steel. It is believed that the aluminium may be behaving in a similar manner to silicon and that the improvement in impact behaviour is most likely due to a reduction in the gradient of the Hall–Petch strength–impact relationship, i.e. the ky value, owing to the removal of the interstitials which segregate to the ferrite grain boundaries. Further work is required to examine this hypothesis.
Microstructural characterisation of intercritically annealed 0·5 wt-%Ni and Mn added steels prepared by powder metallurgy method
Authors: Tekeli S. , Gu¨ral A.
Published: January 2007

In the present study, atomised iron powder (Ancorsteel 1000) was mixed with 0·3% graphite, 0·3% graphite + 0·5%Ni and 0·3% graphite + 0·5%Mn. After sintering at 1120°C, specimens were intercritically annealed at different temperatures (724, 735 and 760°C) and water quenched. Through this heat treatment, it was intended to produce a ferrite + martensite (dual phase structure) microstructure in powder metallurgy processed steels. It was seen that all specimens were sensitive to the intercritical annealing (ICA) temperatures. While Ni rich martensite phase in ferrite matrix was produced in Ni added specimens, Ni concentration of martensite phase decreased with increasing ICA temperatures. Martensite phase with high porosity content in ferrite matrix was produced in Mn added specimens. It was observed that in all specimens, martensite volume fraction increased with increasing ICA temperature and the most effective alloying element on martensite volume fraction was found to be Mn.
Strain hardening behaviour of an Fe–Ni–Cr–Al alloy
Authors: Satyanarayana D. V. V. , Prasad K. Satya , Malakondaiah G. , Sarma D. S.
Published: January 2007

Strain hardening behaviour of Fe–Ni–Cr–Al alloys, in both solution treated and aged conditions, has been investigated at ambient temperature. The alloy in both solution treated and aged conditions exhibits three fairly distinct stages of strain hardening. The strain hardening rate decreases in regime I, remains constant in regime II and begins to fall again in regime III. The three regimes shift to lower strain levels upon ageing and then shift to higher strain levels with over-ageing. While interaction of slip and deformation twinning is responsible for the constant strain hardening rate in solution treated specimens, dislocation–dislocation interaction (forest interaction) leading to the formation of dislocation tangled networks contributes to such a behaviour in aged specimens. Although the precipitate size effects on work hardening behaviour are clearly discernible for both θ versus σ and θd σd versus σd plots, as compared to θ versus ϵ plots, the hybrid model ( θd σd versus σd plots) provides a quantitative description of precipitate size effects on the work hardening behaviour of the alloy in aged conditions.
Effect of Ti on TLP bonding of SiCp/2618Al composites using interlayers of mixed Al–Ag–Cu system powders
Authors: Huang J. H. , Wan Y. , Zhao H. T. , Cheng D. H. , Zhang H.
Published: January 2007

Transient liquid phase diffusion bonding of SiC particulate reinforced 2618 aluminium alloy matrix composite (SiCp/2618Al MMC) was carried out by using interlayers of mixed Al–Ag–Cu and Al–Ag–Cu–Ti powders. The effects of Ti on formation, microstructure and properties of the joints were investigated. The results show that adding a certain amount of Ti can obviously improve the TLP bonding quality of SiCp/2618Al MMC by using an Al–Ag–Cu interlayer with the eutectic composition. Besides improving the wettability of Al–Ag–Cu eutectic liquid to surfaces of the parent materials during bonding, the Ti added into interlayers has an effect of shortening the solidification time of the joining layer, thus decreasing SiC particles from the parent materials entering into the joining layer. The joints bonded using Al–Ag–Cu–Ti interlayers have a maximum shear strength of 101 MPa when 2·1%Ti is added.
Transformation characteristics, microstructure and mechanical properties of austempered ductile iron welds
Authors: Sun D. Q. , Wang W. Q. , Xuan Z. Z. , Ren Z. A. , Sun D. X.
Published: January 2007

The isothermal transformation of austempered ductile iron (ADI) weld at 370°C for a time period ranging from 0·5 to 1440 min involves three stages. The welding process has the effect of accelerating the subsequent transformation during austempering to bainitic ferrite and high carbon austenite (stage 1) and delaying the transformation to carbide (Fe3C) and ferrite (stage 3). Within the austempering time range 15–240 min, the ADI welds consisting of bainitic ferrite and retained austenite had superior properties (namely tensile strengths between 1030 and 1060 MPa and elongations between 8·0 and 8·5%). As the austempering temperature increased from 310 to 400°C, the tensile strength of ADI weld decreased from 1141 to 1040 MPa and its elongation increased from 4·0 to 9·1%. Under tensile loading a large number of slip bands appeared in the retained austenite and the austenite/ferrite interfaces behaved as obstacles limiting the movement of dislocations. The superior properties of ADI weld are mainly associated with the presence of large amount of retained austenite (30–32%), grain boundary strengthening effect and solid solution strengthening effect.
Anti-microbial activity of doped anatase titania coated nickel ferrite composite nanoparticles
Authors: Rawat J. , Rana S. , Sorensson M. M. , Misra R. D. K.
Published: January 2007

In the previous paper (S. Rana, R. S. Srivastava, M. M. Sorensson and R. D. K. Misra, Materials Science & Engineering B, 2005, 119, 144–151), the processing of composite nanoparticles consisting of a photocatalytic shell of anatase titania and a magnetic core of nickel ferrite by combining reverse micelle and chemical hydrolysis techniques was described. The present study demonstrates the anti-microbial performance of undoped and doped as synthesised composite nanoparticles. The doping process involved heat treatment at ∼400°C for 20 min. Heat treatment of the composite nanoparticles does not influence the magnetic characteristics of the nickel ferrite core.
Evaluation of dimensional changes from as received dilatometric sintering plot
Authors: Panigrahi B. B.
Published: January 2007

During the dilatometric study, powder compact initially shows the expansion before the onset of sintering. This expansion was found to be influenced strongly by the factors such as gases, stresses, phase change, etc. The present work demonstrates a systematic method to eliminate the influence of these factors from the dilatometric plot and to estimate true shrinkage, in different metal powders [microsize Ni, Fe, Ti, Ti–2Al (at.-%) and nanosize Ti and Ni]. First, the coefficient of thermal expansion αc of the sintered sample from the cooling curve was estimated and the expansion of green compact from room temperature to final temperature was calculated based on αc, assuming that there was no shrinkage during heating. Finally, from this expansion, the shrinkage was measured. The necessary corrections were incorporated where the volumetric changes occurred owing to phase transformations.
Effects of annealing on structure, resistivity and transmittance of Ga doped ZnO films
Authors: Yim K. , Kim H. W. , Lee C.
Published: January 2007

Effects of annealing on the electrical resistivity and transmittance properties of Ga doped ZnO (GZO) thin films deposited on glass by radio frequency (RF) magnetron sputtering were investigated. The electrical resistivity of a GZO thin film is effectively decreased by annealing in a reducing atmosphere such as N2 + 5%H2. This is attributed to passivation of grain boundaries and zinc ions by hydrogen atoms resulting in increases in carrier concentration and mobility. However, annealing at a temperature >400deg;C is less effective. The lowest resistivity of 2·3 × 10−4 Ω cm is obtained by annealing at 400°C in an N2 + 5%H2 atmosphere. The optical transmittance of the GZO film is improved by annealing regardless of the annealing atmosphere. Annealing in an N2 + 5%H2 atmosphere widens the optical band gap, while annealing in an O2 atmosphere makes the band gap narrower, which can be explained as a blue shift phenomenon.
Characterisation of phase segregation during back extrusion of ZA27 semisolid alloy
Authors: Mola J. , Aashuri H. , Amirkhiz B. Shalchi
Published: January 2007

Effort was made to characterise segregation tendency of mechanically stirred ZA27 alloy with back extrusion as a thixoforming process. At sufficiently high ram speeds, at which liquid phase flows forcefully, pooling of the heavy liquid phase owing to gravitational segregation contributes to homogeneity of back extruded products in terms of solid phase distribution. The amount of this contribution depends on the contact time of this liquid with solid skeleton during liquid exertion to the clearance. Hence, at high ram speeds, small rams which demand taller initial slugs are more efficient in minimising the segregation. However, in the case of low speed back extrusion tests, liquid impotency gives rise to higher performance of the ram which sooner induces combined flow of both phases and thus, thick rams are advantageous over thin ones.
SiC/Cu composites with tungsten coating prepared by powder metallurgy
Authors: Gan K. K. , Chen N. , Wang Y. , Gu M. Y.
Published: January 2007

A tungsten coating on SiC particles was produced using a sol–gel technique followed by reduction treatment in hydrogen for the first time. The microstructure and properties of Cu composites reinforced with as received and W coated SiC particles were studied. Experimental results showed that the W coating could effectively improve the wettability and increase the interfacial bonding between SiC and Cu. The fracture mechanism of SiC/Cu composites was found to change from interface debonding to matrix tearing owing to the introduction of W coating. The W coating also increased the thermal conductivity of SiC/Cu composites.
Transformation of ZrO2 crystal structure under hydrothermal conditions
Authors: Qin D.-K. , Chen H.-L.
Published: January 2007

The preparation of ZrO2 powders under hydrothermal conditions has been extensively studied, but the details of the transformation in crystal structure associated with hydrothermal treatment, which will be discussed in the present paper, are unclear. The present results indicate that the t-ZrO2 phase formed from the precursor in the early stages of hydrothermal treatment is converted to m-ZrO2 as hydrothermal treatment proceeds. The pure m-ZrO2 phase was formed after 18 h at 180°C. These results differ from those reported by Stefanic et al., which probably refer to an intermediate stage in the transformation during hydrothermal treatment at 95°C, reflecting the kinetics of the crystallisation process. The present results indicate that the kinetics of crystallisation is significantly delayed at this relatively low temperature when compared with the transformation at the relatively high temperature of 180°C.
Effect of active flux addition on laser welding of austenitic stainless steel
Authors: Kaul R. , Ganesh P. , Singh N. , Jagdheesh R. , Bhagat M. S. , Kumar H. , Tiwari P. , Vora H. S. , Nath A. K.
Published: January 2007

The use of active flux in tungsten inert gas (TIG) welding is known to increase its weld depth. The present paper involves study of active flux laser beam welding (ALBW) of austenitic stainless steel sheets with respect to its effect on plasma plume, microstructure and mechanical properties of the resultant weldments. ALBW performed with SiO2 as the flux significantly modified shape of the fusion zone (FZ) to produce narrower and deeper welds. Plasma plume associated with the process was considerably smaller and of lower intensity than that produced during bead on plate laser beam welding (LBW). Flux addition during LBW produced thin and rough weld bead associated with humping. The development of such a weld bead is cause by reversal in the direction of Marangoni flow by oxygen induced inversion of surface tension gradient, widely fluctuating plasma plume and presence of oxides on the weld pool surface preventing free flow of the melt. Active flux laser weldments exhibited lower ductility than that of bead on plate laser weldments.
Resistance and friction stir spot welding of DP600: A comparative study
Authors: Khan M. I. , Kuntz M. L. , Su P. , Gerlich A. , North T. , Zhou Y.
Published: January 2007

Efforts to reduce vehicle weight and improve crash performance have resulted in increased application of advanced high strength steels (AHSS) and a recent focus on the weldability of these alloys. Resistance spot welding (RSW) is the primary sheet metal welding process in the manufacture of automotive assemblies. Friction stir spot welding (FSSW) was invented as a novel method to spot welding sheet metal and has proven to be a potential candidate for spot welding AHSS. A comparative study of RSW and FSSW on spot welding AHSS has been completed. The objective of this work is to compare the microstructure and mechanical properties of Zn coated DP600 AHSS (1·2 mm thick) spot welds conducted using both processes. This was accomplished by examining the metallurgical cross-sections and local hardnesses of various spot weld regions. High speed data acquisition was also used to monitor process parameters and attain energy outputs for each process. Results show a correlation found among microstructure, failure loads, energy requirements and bonded area for both spot welding processes.
Effects of flux containing fluorides on TIG welding process
Authors: Leconte S. , Paillard P. , Chapelle P. , Henrion G. , Saindrenan J.
Published: January 2007

The mechanisms of the inorganic powders, named activating flux and used in ATIG welding process, are not well identified. Oxides and fluorides usually compose activating fluxes. The present paper studies the fluoride activating effect. The analysis of the arc energy influence on the weld bead geometry allows determining the mechanisms that occur during ATIG welding with fluorides. It seems that fluoride activating effect could depends on the fluoride lattice energy and/or the ionic radius of the element. Fluorides act on the arc physics only. An arc energy densification is observed. Furthermore, an arc temperature increase, find out with optical emission spectrometry, characterises the fluoride activating effect. The fluorides do not affect the weld bead surface chemistry. Marangoni convection movements stay centrifugal as in TIG welding and do not favour a penetration increase.
Effects of electron beam oscillation techniques on solidification behaviour and stress rupture properties of Inconel 718 welds
Authors: Madhusudhana Reddy G. , Srinivasa Murthy C. V. , Viswanathan N. , Prasad Rao K.
Published: January 2007

Effects of electron beam oscillation techniques (sinusoidal, square, triangular, ramp, circle and elliptical) in controlling Nb segregation, Laves formation and stress rupture behaviour of Inconel 718 electron beam welds are studied. Effects of various post-weld heat treatments on stress rupture behaviour are compared. Elliptical beam oscillation technique resulted in less Nb segregation and discontinuous and fine Laves in the interdendritic regions compared with other welds and unoscillated beam weld. Response to aging was better for welds made with elliptical oscillated beam compared with welds made with unoscillated beam. Oscillated beam welds exhibited longer rupture life than unoscillated beam welds in both solution treated and aged and directly aged conditions.
Hardness changes on pass by pass basis in mild steel gas metal arc welds
Authors: Metzbower E. A. , Moon D. W.
Published: January 2007

A series of welds were fabricated in mild (ASTM A36) steel. The first pass was the entire length of the plate and each subsequent pass was indented ∼25 mm. This allowed us to determine the change in hardness on a pass by pass basis by mapping the hardness over each weld pass.
Actual application of FEM to analysis of large scale mechanical problems in welding
Authors: Nishikawa H. , Serizawa H. , Murakawa H.
Published: January 2007

The finite element method is a powerful tool for predicting welding distortion. However, the mechanical phenomena are strongly non-linear and transient and thus, thermo–elastic–plastic finite element analyses of the phenomena require very long computational time. To overcome this problem, an interactive substructure method was developed as an approach to reduce the computational time in three-dimensional analyses. In this paper, in order to confirm calculation efficiency for a large scale problem, a pipe model with 538 200 degrees of freedom was computed. Furthermore, the residual distortion in an engine component was computed and the applicability of the calculation for problems in welding practices was demonstrated.
Plasma augmented laser welding of 6 mm steel plate
Authors: Swanson P. T. , Page C. J. , Read E. , Wu H. Z.
Published: January 2007

A hybrid laser arc welding system incorporating a plasma arc in a triangulated configuration (plasma augmented laser welding – PALW) was used to produce bead on plate welds in 6 mm low carbon steel. Laser powers up to 5 kW and arc currents up to 150 A were investigated. Plasma augmented laser welding allowed an increase in full penetration welding speed of 100% or an increase in penetration of between 25 and 100%, compared with the laser alone. At speeds of 2 m min−1 and above, PALW and laser alone were found to be equal with respect to fusion zone area per kW (mm2 kW−1). Plasma augmented laser welding was equivalent in terms of welding energy utilisation (mm3 J−1 of fusion zone) at 2 m min−1 and superior above 2 m min−1. Full penetrating PALW allows significant energy losses via the keyhole root exit. Only when the keyhole root closes can the full benefits of the hybrid process be manifested in the workpiece.
Effects of silver based filler metals on microstructure and properties of laser brazed joints between TiNi shape memory alloy and stainless steel
Authors: Li M. G. , Sun D. Q. , Qiu X. M. , Liu J. B. , Miao K. , Wu W. C.
Published: January 2007

The effects of silver based filler metals on the microstructure and properties of laser brazed joints between TiNi shape memory alloy (SMA) and stainless steel (SS) have been investigated and potentially desirable filler metal has been demonstrated. All of the filler metals, Ag–20Cu–12Zn, Ag–20Cu–16Zn–5Sn and Ag–22Cu–18Zn–8Sn filler metals, have good wettability on SS but Ag–20Cu–12Zn and Ag–20Cu–16Zn–5Sn filler metals exhibit worse wettability on TiNi SMA. The laser brazed joints using three different filler metals primarily consists of a α-Ag solid solution, a 9 αα-Cu solid solution and eutectic structures but the phase composition of the joint using Ag–20Cu–12Zn filler metal is a little different from that using other two filler metals. Part of the two base metals melts and enters the brazing seams during laser brazing when the joints were brazed with Ag–20Cu–12Zn and Ag–20Cu–16Zn–5Sn filler metals but only part of SS melts when the joint was brazed with Ag–22Cu–18Zn–8Sn filler metal. The tensile strength of the laser brazed joint using Ag–22Cu–18Zn–8Sn filler metal, superelasticity and shape memory effect of TiNi SMA in the heat affected zone are obviously higher than those using other two filler metals. From the standpoint of wettability on TiNi SMA and SS, as well as the microstructure and properties of the laser brazed joint, Ag–22Cu–18Zn–8Sn filler metal shows potential for application in comparison with the other two filler metals.
Numerical simulation of columnar dendritic grain growth during weld solidification process
Authors: Wei Y. H. , Zhan X. H. , Dong Z. B. , Yu L.
Published: January 2007

A numerical model based on cellular automaton algorithm is developed to simulate dendrite growth at the edge of weld molten pool and the solute diffusion during grain growing process in weld solidification is analysed too. By means of two-dimensional square cells and von Neumann neighbourhood, the growing morphologies of the columnar dendritic grains with different cooling rates and different numbers of seeds are simulated. The growth of secondary dendrite arms, tertiary dendrite arms and their competitive growth are also presented. The results illustrate that the final primary dendrite spacing depends on the number of seeds that initially generated. With increasing cooling rate, the growing speed is increasing obviously. It is also indicated that competitive growth exists between different dendrite arms. The tendency of competitive growth in high cooling rate conditions is weaker than the one in relatively small cooling rate conditions.
Characterisation of electron beams at different focus settings and work distances in multiple welders using the enhanced modified Faraday cup
Authors: Palmer T. A. , Elmer J. W.
Published: January 2007

Using the enhanced modified Faraday cup (EMFC), the differences in the beams produced by two electron beam welders are characterised at different focus settings and work distances. For example, EMFC measurements show that sharply focused beams display different shapes and peak power densities which vary by nearly 20% for the same welding parameters on these two welders. Increases in work distance on each machine were shown to result in decreases in both the peak power density and the resulting weld size and shape. Because of the differences in machine performance, additional differences also arise when comparing the welds produced by each machine. These different weld dimensions are attributed to differences in the beam shape and a 70 mm difference in the theoretical beam crossover location in the upper column of the two welders. The crossover location, which can not be physically measured, is determined using the EMFC by analysing the beam distribution parameters of sharply focused beams over a range of work distances. By combining these results with simplified optics calculations, the magnification of the beam optics can be determined and the machine performance of each welder characterised. The work distance on each machine at which beams with similar peak power density values will be produced can then be determined. With this knowledge, changes in either the beam focus or work distance can be made to attain similar beams from different welders, thus providing a baseline for developing modern weld transfer procedures.
On the occurrence of Cotunnite, Anglesite, Leadhillite, and Galena on fused lead from the wreck of the fire-ship ‘Firebrand‘ in Falmouth Harbour, Cornwall
Authors: Russell Arthur
Published: February 2007

The specimens which form the subject of the present notes were contained ill a collection of minerals formed by the late Mr. Alfred Fox, of Falmouth, and which was acquired by myself in 1909. According to an old label with them, they are described as 'Murio-carbonate of lead taken up the 4th March, 1846, flora the wreck of the fire-shlp Firebrand, which was burnt in Falmouth Harbour about the year 1780. They were found under the lead pump, most of which appeared to be melted and mixed with charcoal.'
The detection of rotatory polarization in an orthorhombic crystal exhibiting crossed axial dispersion
Authors: Greenwood Gilbert
Published: February 2007

The existence of rotatory polarization is comparatively easy to detect in isotropic crystals and in uniaxial crystals in the direction of the optic axis ; but in a biaxial crystal the problem presents far greater difficulties, since in general the rotatory polarization is obscured by the double refraction. The possibility of its existence in a biaxial crystal was denied by É. Mallard (Traité de Cristallographie, 1884, vol. 2, p. 818). However, the persistence of rotatory polarization in a quartz crystal , made biaxial by pressure, brought this conclusion into doubt. Later work, both experimental and theoretical, by H. C. Pocklington (Phil. Mag., 1901, ser. 6, vol. 2, p. 861) established its presence in certain biaxial crystals.
Temperature Dependence of Erythromelalgia Mutation L858F in Sodium Channel Nav1.7
Authors: Han Chongyang , Lampert Angelika , Rush Anthony M , Dib-Hajj Sulayman D , Wang Xiaoliang , Yang Yong , Waxman Stephen G
Published: January 2007

Background:

The disabling chronic pain syndrome erythromelalgia (also termed erythermalgia) is characterized by attacks of burning pain in the extremities induced by warmth. Pharmacological treatment is often ineffective, but the pain can be alleviated by cooling of the limbs. Inherited erythromelalgia has recently been linked to mutations in the gene SCN9A, which encodes the voltage-gated sodium channel Nav1.7. Nav1.7 is preferentially expressed in most nociceptive DRG neurons and in sympathetic ganglion neurons. It has recently been shown that several disease-causing erythromelalgia mutations alter channel-gating behavior in a manner that increases DRG neuron excitability.

Results:

Here we tested the effects of temperature on gating properties of wild type Nav1.7 and mutant L858F channels. Whole-cell voltage-clamp measurements on wild type or L858F channels expressed in HEK293 cells revealed that cooling decreases current density, slows deactivation and increases ramp currents for both mutant and wild type channels. However, cooling differentially shifts the midpoint of steady-state activation in a depolarizing direction for L858F but not for wild type channels.

Conclusion:

The cooling-dependent shift of the activation midpoint of L858F to more positive potentials brings the threshold of activation of the mutant channels closer to that of wild type Nav1.7 at lower temperatures, and is likely to contribute to the alleviation of painful symptoms upon cooling in affected limbs in patients with this erythromelalgia mutation.
POU-domain factor Brn3a regulates both distinct and common programs of gene expression in the spinal and trigeminal sensory ganglia
Authors: Eng S Raisa , Dykes Iain M , Lanier Jason , Fedtsova Natalia , Turner Eric E
Published: January 2007

Background

General somatic sensation is conveyed to the central nervous system at cranial levels by the trigeminal ganglion (TG), and at spinal levels by the dorsal root ganglia (DRG). Although these ganglia have similar functions, they have distinct embryological origins, in that both contain neurons originating from the neural crest, while only the TG includes cells derived from the placodal ectoderm.

Results

Here we use microarray analysis of E13.5 embryos to demonstrate that the developing DRG and TG have very similar overall patterns of gene expression. In mice lacking the POU-domain transcription factor Brn3a, the DRG and TG exhibit many common changes in gene expression, but a subset of Brn3a target genes show increased expression only in the TG. In the wild-type TG these Brn3a-repressed genes are silent, yet their promoter regions exhibit histone H3-acetylation levels similar to constitutively transcribed gene loci. This increased H3-acetylation is not observed in the DRG, suggesting that chromatin modifications play a role in cell-specific target gene regulation by Brn3a.

Conclusion

These results demonstrate that one developmental role of Brn3a is to repress potential differences in gene expression between sensory neurons generated at different axial levels, and to regulate a convergent program of developmental gene expression, in which functionally similar populations of neurons are generated from different embryological substrates.
Near infrared spectroscopy in the development of solid dosage forms
Authors: Räsänen Eetu , Sandler Niklas
Published: January 2007

The use of near infrared (NIR) spectroscopy has rapidly grown partly due to demands of process analytical applications in the pharmaceutical industry. Furthermore, newest regulatory guidelines have advanced the increase of the use of NIR technologies. The non-destructive and non-invasive nature of measurements makes NIR a powerful tool in characterization of pharmaceutical solids. These benefits among others often make NIR advantageous over traditional analytical methods. However, in addition to NIR, a wide variety of other tools are naturally also available for analysis in pharmaceutical development and manufacturing, and those can often be more suitable for a given application. The versatility and rapidness of NIR will ensure its contribution to increased process understanding, better process control and improved quality of drug products. This review concentrates on the use of NIR spectroscopy from a process research perspective and highlights recent applications in the field.
Determination of amorphous content in the pharmaceutical process environment
Authors: Savolainen Marja , Jouppila Kirsi , Pajamo Outi , Christiansen Leena , Strachan Clare , Karjalainen Milja , Rantanen Jukka
Published: January 2007

The amorphous state has different chemical and physical properties compared with a crystalline one. Amorphous regions in an otherwise crystalline material can affect the bioavailability and the processability. On the other hand, crystalline material can function as nuclei and decrease the stability of an amorphous system. The aim of this study was to determine amorphous content in a pharmaceutical process environment using near infrared (NIR) and Raman spectroscopic techniques together with multivariate modelling tools. Milling was used as a model system for process-induced amorphization of a crystalline starting material, α-lactose monohydrate. In addition, the crystallization of amorphous material was studied by storing amorphous material, either amorphous lactose or trehalose, at high relative humidity conditions. The results show that both of the spectroscopic techniques combined with multivariate methods could be applied for quantitation. Preprocessing, as well as the sampling area, was found to affect the performance of the models. Standard normal variate (SNV) transformation was the best preprocessing approach and increasing the sampling area was found to improve the models. The root mean square error of prediction (RMSEP) for quantitation of amorphous lactose using NIR spectroscopy was 2.7%, when a measuring setup with a larger sampling area was used. When the sampling area was smaller, the RMSEPs for lactose and trehalose were 4.3% and 4.2%, respectively. For Raman spectroscopy, the RMSEPs were 2.3% and 2.5% for lactose and trehalose, respectively. However, for the optimal performance of a multivariate model, all the physical forms present, as well as the process environment itself, have to be taken into consideration.
Process analytical applications of Raman spectroscopy
Authors: Rantanen Jukka
Published: January 2007

There is an increasing demand for new approaches to understand the chemical and physical phenomena that occur during pharmaceutical unit operations. Obtaining real-time information from processes opens new perspectives for safer and more efficient manufacture of pharmaceuticals. Raman spectroscopy provides a molecular level insight into processing, and therefore it is a future process analytical tool. In this review, different applications of Raman spectroscopy in the field of process analysis of pharmaceutical solid dosage forms are summarized. In addition, pitfalls associated with interfacing to the process environment and challenges within data management are discussed.
Raman spectroscopy for quantitative analysis of pharmaceutical solids
Authors: Strachan Clare J , Rades Thomas , Gordon Keith C , Rantanen Jukka
Published: January 2007

Raman spectroscopy is experiencing a surge in interest in solid-state pharmaceutical applications. It is rapid, non-destructive, no sample preparation is required and measurements can be made in aqueous environments. It can be used for not only qualitative, but also quantitative, analysis. In this paper, the use of Raman spectroscopy for quantitative analysis of pharmaceutical solids is reviewed. The technique has been used for chemical and physical form analysis. Physical form analysis has involved quantification of polymorphism, hydrates, the amorphous form and, recently, protein conformation. Initially, simple powder systems were quantified, although this has since extended to complex pharmaceutical formulations, including tablets, capsules, microspheres and suspensions. Formulations have also been analysed through packaging. The characteristics of the technique make it ideal for process monitoring and it has been used to quantify changes in-situ during processes such as wet granulation and batch crystallisation. The theoretical basis of quantitative Raman spectroscopy, common data analysis approaches, including multivariate analysis, and sources of error in quantitative analysis are also discussed.
The influence of various excipients on the conversion kinetics of carbamazepine polymorphs in aqueous suspension
Authors: Tian Fang , Saville Dorothy J , Gordon Keith C , Strachan Clare J , Zeitler J Axel , Sandler Niklas , Rades Thomas
Published: January 2007

The influence of various excipients on the conversion of carbamazepine polymorphs to the dihydrate in aqueous suspension has been investigated. Ten excipients having functional groups which were potentially able to form hydrogen bonds with carbamazepine (group 1: methylcellulose, hypromellose (hydroxypropyl methylcellulose), hydroxypropylcellulose (HPC), 2-hydroxyethylcellulose (HEC), carmellose sodium (sodium carboxymethylcellulose), cellobiose; group 2: povidone (polyvinylpyrrolidone), povidone-vinyl acetate copolymer (povidone/VA) and N-methyl-2-pyrrolidone; group 3: macrogol (polyethylene glycol) and polyethylene oxide-polypropylene oxide copolymer (PEO/PPO)) were selected. Carbamazepine polymorphic forms III and I were dispersed separately into each aqueous excipient solution (0.1%, w/v) for 30 min at room temperature. The inhibition effect of each excipient was quantified using Raman spectroscopy combined with multivariate analyses. The solubility parameter of each excipient was calculated and used for categorizing excipients. Excipients in groups 1 and 2, which had both low solubility parameters (< 27.0 MPa½) and strong hydrogen bonding groups, inhibited the conversion completely. With increasing solubility parameter, the inhibition effect decreased for group 1 excipients, especially for carbamazepine form I, which had a higher specific surface area. Also, the excipients of group 3, lacking strong hydrogen bonding groups, showed poor inhibition although they had low solubility parameters (< 21.0 MPa½). This study indicated the importance of both hydrogen bonding interaction and a suitable hydrophobicity (expressed by the solubility parameter) in the inhibition of the conversion of carbamazepine to the dihydrate.
Characterization of silicone elastomer vaginal rings containing HIV microbicide TMC120 by Raman spectroscopy
Authors: Bell Steven E J , Dennis Andrew C , Fido Louise A , Malcolm R Karl , Sirimuthu Narayana M S , Toner Clare F , Woolfson A David
Published: January 2007

Silicone elastomer vaginal rings are currently being pursued as a controlled-release strategy for delivering microbicidal substances for the prevention of heterosexual transmission of HIV. Although it is well established that the distribution of drugs in delivery systems influences the release characteristics, in practice the distribution is often difficult to quantify in-situ. Therefore, the aim of this work was to determine whether Raman spectroscopy might provide a rapid, non-contact means of measuring the concentrations of the lead candidate HIV microbicide TMC120 in a silicone elastomer reservoir-type vaginal ring. Vaginal rings loaded with TMC120 were manufactured and sectioned before either Raman mapping an entire ring cross-section (100 μm resolution) or running line scans at appropriate time intervals up to 30 h after manufacture. The results demonstrated that detectable amounts of TMC120, above the silicone elastomer saturation concentration, could be detected up to 1 mm into the sheath, presumably as a consequence of permeation and subsequent reprecipitation. The extent of permeation was found to be similar in rings manufactured at 25 and 80°C.
Terahertz pulsed spectroscopy and imaging in the pharmaceutical setting - a review
Authors: Zeitler J Axel , Taday Philip F , Newnham David A , Pepper Michael , Gordon Keith C , Rades Thomas
Published: January 2007

Terahertz pulsed spectroscopy (TPS) and terahertz pulsed imaging (TPI) are two novel techniques for the physical characterization of pharmaceutical drug materials and final solid dosage forms, utilizing spectral information in the far infrared region of the electromagnetic spectrum. This review focuses on the development and performance of pharmaceutical applications of terahertz technology compared with other tools for physical characterization. TPS can be used to characterize crystalline properties of drugs and excipients. Different polymorphic forms of a drug can be readily distinguished and quantified. Recent developments towards a better understanding of the fundamental theory behind spectroscopy in the far infrared have been discussed. Applications for TPI include the measurement of coating thickness and uniformity in coated pharmaceutical tablets, structural imaging and 3D chemical imaging of solid dosage forms.
Applications of solid-state NMR to pharmaceutical polymorphism and related matters
Authors: Harris Robin K
Published: January 2007

Magic-angle spinning NMR is now making a significant contribution to our understanding of the structure of polymorphs and solvates of pharmaceutical significance. This personal review article discusses a range of applications, with particular emphasis on information about crystallography, for which NMR can address problems that cannot be readily solved by diffraction techniques (such as dynamic disorder and non-stoichiometric hydration). Unlike diffractograms, NMR spectra yield immediate chemical information. Moreover, heterogeneous samples can be investigated and amorphous content provides no significant barrier to studies. Furthermore, NMR can be an effective technique for quantitation (down to the level of ca. 1%). Additional strength is being derived from computation of chemical shifts in solids, using a code that takes account of the spatial repetition inherent in crystalline materials.
Characterization of the bulk properties of pharmaceutical solids using nonlinear optics - a review
Authors: Lee Chris J , Strachan Clare J , Manson Peter J , Rades Thomas
Published: January 2007

With the development of stable, compact and reliable pulsed laser sources the field of characterizing materials through their nonlinear optical response has bloomed. Second harmonic generation by non-centrosymmetric crystal structures has provided a new spectroscopic tool of potentially great utility in the pharmaceutical field. The nonlinear optical response of various materials provides a very sensitive technique for the characterization of pharmaceutically interesting bulk compounds and dispersions, and determining their concentrations. This work has potential application for in-line monitoring and quality control of pharmaceutical manufacturing. In this article we have presented an extensive review of the spectroscopic techniques that make use of the nonlinear optical response of solid media. Also, we have presented the results of our own work in this field.
Time-of-flight secondary-ion mass spectrometry for the surface characterization of solid-state pharmaceuticals
Authors: Prestidge Clive A , Barnes Timothy J , Skinner William
Published: January 2007

Time-of-flight secondary-ion mass spectrometry (ToF-SIMS) is a highly surface sensitive analytical method for surface chemical identification and surface chemical distribution analysis (mapping). Here we have explored the application of ToF-SIMS for the characterization of solid-state pharmaceuticals and highlight specific case studies concerning the distribution and stability of pharmaceutical actives within solid matrices (pellets and polymeric carriers) and the face-specific properties of pharmaceutical crystals.