bluuebunny/crossref_metadata_2025 huggingface dataset:
Self-determination as non-domination
Authors: Young Iris Marion
Published: May 2005

This article conceptualizes self-determination as non-domination, and distinguishes this from the more standard concept of self-determination as noninterference. Principles of non-domination imply relationships between self-determining units and the joint regulation of such relationships. To understand the application of this model, I suggest that we should assume the situation and claims of indigenous people as the norm rather than the exception. This model of self-determination implies federalism as a mode of being together with other self-determining units. Many discussions of federalism, however, assume that autonomous units are large, homogeneously occupied, contiguous territories. Suspending this assumption opens ways of conceiving federal relations as more local, plural, and horizontal. I suggest that this model of self-determination as non-domination and the patchwork federalism it sometimes implies may enable a vision of Israeli Jews and Palestinians dwelling peacefully together in bi-national federation.
Hurley on egalitarianism and the luck-neutralizing aim
Authors: Lippert-Rasmussen Kasper
Published: May 2005

Susan Hurley’s admirable new book, Justice, Luck, and Knowledge, brings together recent developments in the fields of responsibility and egalitarian justice. This article focuses on Hurley’s critique of luck-neutralizing egalitarianism. The article concludes that the bad-luck-neutralizing aim serves better as a justificatory basis for egalitarianism than the more general luck-neutralizing aim. Since the former does not simply assume that we should aim for equality, Hurley has not demonstrated (nor indeed does she claim to have shown) that this concern cannot form the justificatory basis of egalitarianism in a non-question-begging way. This, however, does not detract from the fact that Hurley’s book provides a very insightful discussion of the relationship between luck and justice.
Poetry and Photography
Authors: Szto Peter , Furman Rich , Langer Carol
Published: May 2005

This study explores the use of photography and poetry as tools of qualitative social research. The question guiding this exploration is how might the visual representation of reality (photography) and the compression of experiences expressed in words (poetry) provide insight and understanding into human behavior and the social world? The authors address this question through an extended conversation to critically examine the nature of poetry and photography in the gathering, organizing, and interpretation of data. In particular, both mediums are discussed in relation to the history of social research, methodological issues, and implications for social work. A subsequent thematic analysis is conducted by a third researcher and is presented as a means of treating the conversation itself as data for qualitative research. This exploration therefore demonstrates the use of a creative medium as research and as data for research.
Negative Trends, Possible Selves, and Behavior Change
Authors: Abrams Laura S. , Aguilar Jemel P.
Published: May 2005

This study uses Stein and Markus’ (1996) self-concept and behavior change framework to examine youth offenders’ responses to individual-level treatment in a residential correctional facility. The authors analysed transcripts collected from 10 male offenders, aged 15-17, who were interviewed at least three times over a period of four to six months. Results showed that while many offenders were able to identify negative trends in their life that led to their criminal behavior, other cognitively filtered out self-defeating information and did not identify troubling life patterns. Offenders also articulated visions of hoped for selves that were anchored in their lived experiences with positive role models and feared the selves that they might become if they continued down a criminal path. However, nearly all of the offenders had loosely organized or vague strategies for achieving their hoped for or idealized selves. Based on these findings, the authors pose implications for self-concept theory and for treatment practices with this population group.
Activity and Reflection
Authors: Sanders Jackie , Munford Robyn
Published: May 2005

There is a growing interest in expanding the agendas of research, policy and practice by the direct inclusion of young people so that these groups can contribute meaningfully to developments and decision-making. This article outlines a strategy for generating information with young people about their daily lives and the intersection between these sorts of experiences and broader patterns of inclusion and exclusion. Discussion applies eco-map and social network techniques from social work practice, city mapping strategies from geography and interview strategies from qualitative methods. It also includes a new strategy: the daily life story technique developed in conjunction with young people. These strategies provide a framework for managing conversations about experience, meaning and possible futures. Discussion illustrates the way in which a range of different strategies can be combined so that an interview can become a rich source of varied information about meaning, context, experience, events, places and the intersections and interactions between them can be explained.
Does the Truth Matter in Science?
Authors: Lipton Peter
Published: May 2005

Is science in the truth business, discovering ever more about an independent and largely unobservable world? Karl Popper and Thomas Kuhn, two of the most important figures in science studies in the 20th century, gave accounts of science that are in some tension with the truth view. Their central claims about science are considered here, along with two arguments that bear directly on the truth question. One argument makes an appeal to past scientific failures to argue against the truth view; the other makes an appeal to present scientific successes to argue for it. Both arguments are problematic.
Why/How Does Classics Matter?
Authors: Cartledge Paul
Published: May 2005

Classics is in the news - or on the screen: Gladiator a few years ago, Troy very recently, Alexander as I write. How significant is this current Hollywood fascination with the ancient Greeks and Romans? Or should we take far more seriously the decline of the teaching of the Classical languages in schools, a decline so grave as to prompt a recent debate in the House of Commons? My answer is that both are in their different ways equally significant. Our culture cannot do without proper appreciation of its classical roots, and Hollywood is as objective a barometer as any of our culture’s contemporary pressure points. This article explores six aspects of antiquity - its representation in cinema, athletics, theatre, architecture, literature, and politics - that are still palpably salient for modernity.
Three microarray platforms: an analysis of their concordance in profiling gene expression
Authors: Petersen David , Chandramouli GVR , Geoghegan Joel , Hilburn Joanne , Paarlberg Jonathon , Kim Chang Hee , Munroe David , Gangi Lisa , Han Jing , Puri Raj , Staudt Lou , Weinstein John , Barrett J Carl , Green Jeffrey , Kawasaki Ernest S
Published: May 2005

Background

Microarrays for the analysis of gene expression are of three different types: short oligonucleotide (25–30 base), long oligonucleotide (50–80 base), and cDNA (highly variable in length). The short oligonucleotide and cDNA arrays have been the mainstay of expression analysis to date, but long oligonucleotide platforms are gaining in popularity and will probably replace cDNA arrays. As part of a validation study for the long oligonucleotide arrays, we compared and contrasted expression profiles from the three formats, testing RNA from six different cell lines against a universal reference standard.

Results

The three platforms had 6430 genes in common. In general, correlation of gene expression levels across the platforms was good when defined by concordance in the direction of expression difference (upregulation or downregulation), scatter plot analysis, principal component analysis, cell line correlation or quantitative RT-PCR. The overall correlations (r values) between platforms were in the range 0.7 to 0.8, as determined by analysis of scatter plots. When concordance was measured for expression ratios significant at p-values of <0.05 and at expression threshold levels of 1.5 and 2-fold, the agreement among the platforms was very high, ranging from 93% to 100%.

Conclusion

Our results indicate that the long oligonucleotide platform is highly suitable for expression analysis and compares favorably with the cDNA and short oligonucleotide varieties. All three platforms can give similar and reproducible results if the criterion is the direction of change in gene expression and minimal emphasis is placed on the magnitude of change.
Vitamin supplementation for prevention of mother-to-child transmission of HIV and pre-term delivery: a systematic review of randomized trial including more than 2800 women
Authors: Mills Edward J , Wu Ping , Seely Dugald , Guyatt Gordon H
Published: May 2005

Background

Observational studies have suggested that low serum vitamin levels are associated with increased mother-to-child transmission (MTCT) of HIV and increased preterm delivery. We aimed to determine the efficacy of vitamins on the prevention of MTCT and preterm delivery by systematically reviewing the available randomized controlled trials [RCTs]. We conducted systematic searches of 7 electronic databases. We extracted data from the RCTs independently, in duplicate.

Results

We included 4 trials in our review. Of the three trials on Vitamin A, two suggested no difference in MTCT, while the third and largest trial (n = 1078) suggested an increased risk of MTCT (Relative Risk 1.35, 95% Confidence Interval [CI], 1.11–1.66, P = 0.009). Two of the vitamin A trials addressed the impact of supplementation on pre-term delivery; one suggested a benefit (RR 0.65, 95% CI, 0.44–0.94) and the other no difference. All three vitamin A trials found no significant effect on infant mortality at 1 year. Of the two trials that looked at multivitamin use, only one addressed the prevention of MTCT, and found a non-significant RR of 1.04 (95% CI, 0.82–1.32). Two of the multivitamin trials found no significant effects on pre-term delivery. The single multivitamin trial examining children's mortality at 1 year yielded a non-significant RR of 0.91 (95% CI, 0.17–1.17).

Conclusion

Randomized trials of vitamins to prevent MTCT have yielded conflicting results without strong evidence of benefit and have failed to exclude the possibility of harm.
Adeno-associated virus: from defective virus to effective vector
Authors: Gonçalves Manuel AFV
Published: May 2005

The initial discovery of adeno-associated virus (AAV) mixed with adenovirus particles was not a fortuitous one but rather an expression of AAV biology. Indeed, as it came to be known, in addition to the unavoidable host cell, AAV typically needs a so-called helper virus such as adenovirus to replicate. Since the AAV life cycle revolves around another unrelated virus it was dubbed a satellite virus. However, the structural simplicity plus the defective and non-pathogenic character of this satellite virus caused recombinant forms to acquire centre-stage prominence in the current constellation of vectors for human gene therapy. In the present review, issues related to the development of recombinant AAV (rAAV) vectors, from the general principle to production methods, tropism modifications and other emerging technologies are discussed. In addition, the accumulating knowledge regarding the mechanisms of rAAV genome transduction and persistence is reviewed. The topics on rAAV vectorology are supplemented with information on the parental virus biology with an emphasis on aspects that directly impact on vector design and performance such as genome replication, genetic structure, and host cell entry.
Mutation analysis of the ATRgene in breast and ovarian cancer families
Authors: Heikkinen Katri , Mansikka Virpi , Karppinen Sanna-Maria , Rapakko Katrin , Winqvist Robert
Published: May 2005

Introduction

Mutations in BRCA1, BRCA2, ATM, TP53, CHK2 and PTEN account for only 20–30% of the familial aggregation of breast cancer, which suggests the involvement of additional susceptibility genes. The ATR (ataxia-telangiectasia- and Rad3-related) kinase is essential for the maintenance of genomic integrity. It functions both in parallel and cooperatively with ATM, but whereas ATM is primarily activated by DNA double-strand breaks induced by ionizing radiation, ATR has been shown to respond to a much broader range of DNA damage. Upon activation, ATR phosphorylates several important tumor suppressors, including p53, BRCA1 and CHK1. Based on its central function in the DNA damage response, ATR is a plausible candidate gene for susceptibility to cancer.

Methods

We screened the entire coding region of the ATR gene for mutations in affected index cases from 126 Finnish families with breast and/or ovarian cancer, 75 of which were classified as high-risk and 51 as moderate-risk families, by using conformation sensitive gel electrophoresis and direct sequencing.

Results

A large number of novel sequence variants were identified, four of which – Glu254Gly, Ser1142Gly, IVS24-48G>A and IVS26+15C>T – were absent from the tested control individuals (n = 300). However, the segregation of these mutations with the cancer phenotype could not be confirmed, partly because of the lack of suitable DNA samples.

Conclusion

The present study does not support a major role for ATR mutations in hereditary susceptibility to breast and ovarian cancer.
Investigation of the Properties of Polyoxyethylene (10) Lauryl Ether: C12E10 in Aquo-n-Alcohol Mediums
Authors: Sharma Kshatrapati Shivaji , Rakshit Animesh Kumar
Published: May 2005

The effect of the concentration and the nature of different n-alcohols (C2–C5) on the growth of C12E10 [CH3(CH2)11(OCH2CH2)10OH] micelles has been studied by tensiometric, viscometric, and proton NMR techniques. Critical micelle concentrations (CMC) were determined by surface-tension measurements in the presence of different concentrations of n-alcohols (C2–C4) and at different temperatures. The Gibbs free energy, enthalpy, and entropy of micellization ( , , ) and adsorption at an air/water interface ( , , ) were computed and discussed. An enthalpy–entropy compensation effect was observed at an isostructural temperature of about 300 K for both micellization and interfacial adsorption. The transfer enthalpies and heat capacities of the micelle from water to aqueous n-alcohol solutions were also computed. The intrinsic viscosity gave the hydrated micellar volume (Vh), volume of the hydrocarbon core (Vc), and the volume of the palisade layer of the OE unit (VOE). The spin–lattice proton relaxation time (T1) in the aqueous micellar region and 1H NMR were also used to study the behavior of OE micelles in both the absence and presence of alcohols. There was a slight rise in the cloud point (CP) when using lower alcohols. However a decrease was seen for n-BuOH and n-PenOH.
Theoretical Study on the Transformation of Bis(acetylene)cobalt to Cobaltacyclopentadiene and the Regioselectivity in this Transformation
Authors: Dahy AbdelRahman A , Koga Nobuaki
Published: May 2005

The transformation of bis(acetylene)cobalt complex to cobaltacyclopentadiene complex was studied using a hybrid density functional theory method. B3LYP calculations showed that the reaction of an unsubstituted system, bis(η2-acetylene)cobalt complex, on a singlet potential energy surface is an easy reaction with a small activation energy of 11.2 kcal/mol and an exothermicity of −19.2 kcal/mol. The low activation barrier was as expected for a symmetry-allowed reaction. Because the product of cobaltacyclopentadiene has a low-lying unoccupied orbital, the two Co–Cα bonds are different in distance due to the second-order Jahn–Teller effect, and the triplet cobaltacyclopentadiene is more stable than the singlet cobaltacyclopentadiene, different from the reactant and transition state. In addition, we performed calculations for the reactions of acetylenes substituted by methyl and/or methoxycarbonyl groups, in order to investigate the factors that control the regioselectivity observed in this type of reaction. The calculations for the mono- and disubstituted reactions showed that these substituents prefer α-carbon to β-carbon. We analyzed the origin of this regioselectivity based on the relative stability of the products, to find that it is closely related to the site preference in the substituted butadienes. This suggests that the site preference of substituents is an important factor of regioselectivity.
High Magnetic Field Effects on Biradical Lifetimes: Evaluation of Magnetic Field Dependence and Chain Length Dependence Using Calculated g and Hyperfine Tensors
Authors: Mouri Yutaka , Fujiwara Yoshihisa , Aoki Takeshi , Yoshida Hiroshi , Naka Kazunari , Aoki Yuriko , Yonemura Hiroaki , Yamada Sunao , Haino Takeharu , Fukazawa Yoshimasa , Tanimoto Yoshifumi
Published: May 2005

The g and hyperfine tensors of radicals were theoretically estimated by quantum chemical calculations, and compared with experimentally obtained ones. From the comparison, it was found that the theoretically calculated tensors can reproduce the experimental ones with accuracy. By using those tensors, therefore, high magnetic field dependences of the lifetimes of biradicals, which were generated by a photo-induced electron transfer in α-cyclodextrin inclusion complexes of chain-linked molecules of phenothiazine–(CH2)n–viologen (PhnV2+, n = 12, 10, and 8) and carbazole–(CH2)12–viologen (Cz12V2+), were quantitatively analyzed on the basis of the relaxation mechanism of the generated bi-cationic biradicals (Ph•+nV•+ and Cz•+12V•+). The analysis conclusively showed that two extremely small correlation times of each radical motion were still necessary for reversals characteristic of the high magnetic field dependences, and also that the order of the obtained correlation time was Cz•+ > V•+ > Ph•+. The order in the correlation time was discussed while referring to the rigidity of the radical frameworks.
Facile Reductive Coupling Reaction of Bis(ruthenocenylethynyl)titanocene Complexes via Visible Light-Activation of the Ruthenocenyl Terminal
Authors: Hayashi Yukiko , Kobayashi Kimiko , Hashizume Daisuke , Osawa Masahisa , Wakatsuki Yasuo
Published: May 2005

The irradiation of (η5-C5H4R)2Ti(C≡CRc)2 (R = Me, SiMe3 (= TMS); Rc = ruthenocenyl) at the band assignable to CT from Rc to Ti in the presence of equimolar amounts of RcC≡CH and MeO2CC≡CCO2Me smoothly gave titanacyclic complexes (η5-C5H4R)2Ti{–C(Rc)=C(C≡CRc)–CH=C(Rc)–} and (η5-C5H4TMS)2Ti{–C(C≡CRc)=C(Rc)–C(OMe)(C≡CCO2Me)–O–}, respectively, two of which were structurally characterized. The formation of these complexes has been explained by the extremely easy reductive coupling in (η5-C5H4R)2Ti(C≡CRc)2, brought about by photo-excitation at the Rc group, followed by metallacycle formation that involves the resulting diyne unit and the externally added alkynes.
Differential Pulse Voltammetry Determination of l-Cysteine with Ferrocene-Modified Carbon Paste Electrode
Authors: Raoof Jahan Bakhsh , Ojani Reza , Kolbadinezhad Mansoure
Published: May 2005

The preparation of ferrocene-modified carbon paste electrode by incorporation of a mediator into a graphite powder–paraffin oil matrix is described. The suitability of this chemically modified electrode for electrocatalytic oxidation of l-cysteine was studied in buffered solution by cyclic voltammetry and double potential step chronoamperometry. It has been found that, under optimum conditions (pH = 7.00), the oxidation of l-cysteine at the surface of such an electrode occurs at a potential about 500 mV less positive than on an unmodified carbon paste electrode. The kinetic parameters such as electron transfer coefficient α and catalytic reaction rate constant K′h were determined using various electrochemical approaches. The electrocatalytic oxidation peak current of l-cysteine at the surface of this modified electrode was used for determination of l-cysteine by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Linear analytical curves were obtained in the ranges of 10−5 M (= mol dm−3) – 10−3 M and 8.9 × 10−6 M – 2 × 10−4 M of l-cysteine concentration with CV and DPV methods, respectively. The detection limits were determined as 6.5 × 10−6 M and 4.7 × 10−6 M by CV and DPV methods. This method was also examined for determination of l-cysteine in samples, such as Soya protein powder, serum and plasma of human blood, using recovery and standard addition methods.
μ-Hydroxo-μ-phenolato Dinuclear Zinc(II) and Nickel(II) Complexes Derived from Dinucleating Compartmental Ligands of “End-off” Type: Synthesis, Structures, and Properties
Authors: Matsufuji Kanako , Shiraishi Hitomi , Miyasato Yuji , Shiga Takuya , Ohba Masaaki , Yokoyama Takushi , Okawa Hisashi
Published: May 2005

Some dinucleating compartmental ligands of “end-off” type, 2,6-bis{N-[(2-dimethylamino)ethyl]iminomethyl}-4-methylphenol (HL1), 2,6-bis{N-(2-pyridylethyl)iminomethyl}-4-methylphenol (HL2), and 2,6-bis{N,N-di(2-pyridylmethyl)aminomethyl}-4-methylphenol (HL3), have afforded the following dinuclear Zn(II) and Ni(II) complexes: [Zn2(L1)(OH)(py)2](ClO4)2 (1), [Zn2(L2)(OH)(py)3](ClO4)2 (2), [Zn2(L3)(OH)](ClO4)2 (3), [Ni2(L1)(OH)(py)2](ClO4)2 (4), and [Ni2(L2)(OH)(py)4](ClO4)2 (5). X-ray crystallographic studies for 1·Pr2OH, 2·0.5Pr2OH, 3·MeCN, 4·py, and 5 indicate that they have a dinuclear core doubly bridged by the endogenous phenolic oxygen of each compartmental ligand and by exogenous hydroxide oxygen. Physicochemical properties of 1–5 are studied.
Molecular Arrangement in the Cocrystals of 1,1′,3,3′-Tetramethyl-2,2′-bi-1H-imidazolium Bis(tetraphenylborate) with Ketone, Aldehyde, and Nitrile as Guest Molecules
Authors: Ono Katsuhiko , Iwao Takeshi , Uchiumi Hideki , Suzuki Takahisa , Tomura Masaaki , Ohkita Masakazu , Saito Katsuhiro
Published: May 2005

1,1′,3,3′-Tetramethyl-2,2′-bi-1H-imidazolium bis(tetraphenylborate), an ion-association compound, afforded inclusion crystals with a variety of guest molecules, such as ketone, aldehyde, and nitrile. X-ray crystallographic analyses revealed intermolecular interactions between the biimidazolium dication and the guest molecules in the inclusion crystals. Their contact modes depended on the molecular structures of the guest molecules, resulting in various molecular arrangements.
Structure and Chiral Recognition Ability of endo-3-Benzamidonorborn-5-ene-2-carboxylic Acid
Authors: Wang Zhaohui , Hirose Takuji , Shitara Hiroaki , Goto Midori , Nohira Hiroyuki
Published: May 2005

The absolute configuration of endo-3-benzamidonorborn-5-ene-2-carboxylic acid was determined by X-ray single crystal analysis of the diastereomeric salt with cis-2-(benzylamino)cyclohexylmethanol. It was demonstrated that the CH–π interaction between the vinylic hydrogen atom of the acid and the aromatic ring of the amine worked as an additional interaction for the stabilization of the structure formed by the hydrogen bond network. The chiral recognition ability was studied using a 1H NMR titration technique and the intermolecular interactions were discussed based on the results of its saturated counterpart, endo-3-benzamidonorbornane-2-carboxylic acid.
A Computational Study of Lithium Dialkylamide Mixed Aggregates with Lithium Chloride
Authors: Pratt Lawrence M
Published: May 2005

Lithium dialkylamides form several mixed aggregates with lithium chloride in ethereal solvents. The relative amounts of mixed dimer, trimer, and tetramer are dependent on the steric strain of the lithium dialkylamide homodimer and on solvent effects. Microsolvation with coordinating THF ligands generated results in qualitative agreement with available experimental data.
Catalysis by Calcined Zn2+/Al3+ Layered Double Hydroxides in Friedel–Crafts Alkylation of Benzene with Benzyl Chloride
Authors: Shimada Hiroshi , Ogoshi Tomokazu
Published: May 2005

Amorphous oxides formed upon the calcination of Zn2Al layered double hydroxide chloride or carbonate intercalates showed high catalytic efficiency in the benzylation of benzene with benzyl chloride. The IR spectra of pyridine adsorbed on amorphous oxides suggest that the benzylation activity is due to the formation of zinc chloride on the surface.
Periodic Twinning in Crystal Quartz for Optical Quasi-Phase Matched Secondary Harmonic Conversion
Authors: Harada Masaki , Muramatsu Ken-Ichi , Iwasaki Yutaka , Kurimura Sunao , Taira Takunori
Published: May 2005

We show here the possibility of optical quasi-phase matched secondary harmonic generation in crystal quartz that is a non-ferroelectric crystal. By utilizing a twinning phenomenon, for the first time, we have succeeded in fabricating periodic modulation of the nonlinear coefficient by hot pressing. In this method, stress is applied vertically on a quartz surface. We also devised a special press system. The numbers of twins we have achieved are 10 for 500 μm and 17 for 250 μm periods, and the depth of the twinned area is about 50 μm. Our results suggest that the twinned regions can be controlled artificially, and over a few tens of microns of twinned depth can be realized.
On the Atomistic Simulation of Plastic Deformation and Fracture in Crystals
Authors: Shen Y-L.
Published: May 2005

Tensile stretching of a two-dimensional model crystal was computationally studied using molecular statics simulations. Attention was directed to the atomistics of defect activities throughout the deformation history. It is shown that the incorporation of an initial point defect is able to trigger dislocation slip in a repetitive and controlled manner. The initial defect is also seen to have potential bearing on the formation of voiding damage that leads to ductile fracture of the crystal. Implications to the nanoscale mechanical behavior and its modeling are discussed.
Microwave-Induced Combustion Synthesis of Nanocrystalline TiO2–SiO2 Binary Oxide Material
Authors: Ganesh I. , Johnson R. , Mahajan Y.R. , Khan A. , Madhavendra S.S. , Reddy B.M.
Published: May 2005

A nanocrystalline titania–silica (1:1 molar ratio) binary oxide material was synthesized by microwave-induced combustion process in a modified domestic microwave oven (operated at 2.45 GHz frequency and 700 W power) in approximately 60 min from in situ synthesized titanyl nitrate and siliconyl nitrate using urea as fuel. For the sake of comparison, two different types of TiO2–SiO2 powders were also synthesized by the sol-gel and the co-precipitation methods. All the synthesized powders were characterized with the help of thermogravimetriy/differential thermal analysis, x-ray diffraction, transmission electron microscopy (TEM), and Brunauer–Emmett–Teller surface area measurements and the results compared. The as-synthesized TiO2–SiO2 powder obtained by the combustion process showed an average crystallite size of 10 nm and the specific surface area of 115 m2g-1. Among the three differently synthesized TiO2-SiO2 powders, only the microwave-induced combustion synthesis yielded crystalline material. TEM in particular confirmed the presence of nano-sized particles in the microwave-induced combustion-synthesized powder. Among the three analogies, microwave synthesis was found to be superior in terms of ease of processing leading to time and power savings.
Liquid-Phase Siliconizing and Aluminizing at the Surface of a Ti3Al-Based Alloy and Improvement in Oxidation Resistance
Authors: Xiong Hua-Ping , Xie Yong-Hui , Mao Wei , Chen Yun-Feng , Li Xiao-Hong
Published: May 2005

A simple and inexpensive method to modify the surface of a Ti3Al-based alloy, liquid-phase siliconizing and aluminizing by an Al-Si alloy, has been proposed. The surface modification at 1013 K for 10 min using Al-10 wt% Si melt resulted in a modified layer with a thickness of about 21 μm, composed of TiAl3 and TiSi2. The coating improved the isothermal oxidation resistance of the Ti3Al-based alloy at 1073 K. A continuous alumina-rich scale was formed at the outermost surface after oxidation. SiO2 was detectable in the oxide scale. The results of x-ray diffraction and x-ray energy dispersive spectrometer analysis showed that during oxidation, some of the TiSi2 in the coating was oxidized to SiO2. In the meantime, the TiSi2 was reduced to a lower silicide, Ti5Si4. The change of the surface microstructure after oxidation and the diffusion reaction between the coating and the Ti3Al substrate were also discussed.
Formation of Al3Ni Nanofibers in an Al-Based Metal Matrix Composite Fabricated by Reaction Sintering
Authors: Yu Peng , Deng Cheng-Ji , Ma Nan-Gang , Ng Dickon H.L.
Published: May 2005

We developed an Al2O3 and Al3Ni intermetallic reinforced Al-based metal matrix composite by sintering an Al-20 wt% NiO powder compact at 1000 °C. Differential thermal analysis showed that a two-step reaction took place between Al and NiO in the temperature range 600–650 °C. The initial stage was a solid-state reaction, but it was soon paused by the newly formed Al2O3 and Al3Ni phases that separated the Al and NiO grains. A liquid–solid reaction was later resumed as the temperature was increased above the eutectic temperature of Al–Al3Ni at 640 °C when molten Al–Ni appeared. When the molten sample was quenched to room temperature, a two-phase Al–Al3Ni eutectic was found in the sample. In comparison with the air-quenched and the oil-quenched samples, the sizes of proeutectic Al3Ni grains and Al–Al3Ni eutectic phases in the salt-solution-quenched sample were much finer. The eutectic contained Al3Ni nanofibers with a diameter of approximately 50 nm. A reaction model of Al and NiO was proposed. A thermodynamic model was also proposed to describe the formation of the composite.
Influence of Capping Groups on the Synthesis of γ-Fe2O3 Nanocrystals
Authors: Yin Ming , Willis Amanda , Redl Franz , Turro Nicholas J. , O’Brien Stephen P.
Published: May 2005

Monodisperse and uniform γ-Fe2O3 (maghemite) nanocrystals of variable size were prepared by thermal decomposition of iron pentacarbonyl [Fe(CO)5] in the presence of surfactants, following controlled oxidation with trimethylamine N-oxide as a mild oxidant. The influence of carboxylic acids with variable alkyl carbon chain lengths on the synthesis of γ-Fe2O3 nanocrystals was investigated. The effect of the molar ratios of surfactant to iron precursor was also studied. The nanocrystals were characterized by x-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD showed the particles were highly crystalline at the nanometer scale. The results showed that the size and shape of the nanocrystal is strongly influenced by the decomposition temperature of iron pentacarbonyl and closely related to the length of carbon chain of the capping groups and the molar ratio of surfactant to iron precursor. Following controlled evaporation from nonpolar solvents, self-assembly into two-dimensional arrays could be observed by TEM. It was also found that the distance between the nanocrystals in self-assembled structures matched the length of the capping molecules very well.
Relaxation of Thermal Stress by Dislocation Motion in Passivated Metal Interconnects
Authors: Nicola Lucia , Giessen Erik Van der , Needleman Alan
Published: May 2005

The development and relaxation of stress in metal interconnects strained by their surroundings (substrate and passivation layers) is predicted by a discrete dislocation analysis. The model is based on a two-dimensional plane strain formulation, with deformation fully constrained in the line direction. Plastic deformation occurs by glide of edge dislocations on three slip systems in the single-crystal line. The substrate and passivation layers are treated as elastic materials and therefore impenetrable for the dislocations. Results of the simulations show the dependence of the stress evolution and of the effectiveness of plastic relaxation on the geometry of the line. The dependence of stress development on line aspect ratio, line size, slip plane orientation, pitch length, and passivation layer thickness are explored.
Strain Determination Around Vickers Indentation on Silicon Surface by Raman Spectroscopy
Authors: Puech Pascal , Demangeot François , Sergio Pizani Paulo
Published: May 2005

We used Raman spectroscopy to characterize indentations on silicon. We focused our attention on the strain field around several indentations made on an (001) oriented silicon wafer with loads ranging from 100 mN to 10 N. Micro-Raman spectroscopy was used for the analysis of the indentation strain field. By multiplying the frequency shift of the optical phonon of silicon by the distance from the center of the fingerprint to the point under investigation, we were able to determine the strained zone extension accurately with the boundary between the strained area and the unperturbed area, which becomes clearly visible. This method allowed us to propose an equation valid over a large range of loads (0.1–10 N), which allowed us to estimate the size of the strained zone. We show that even in the absence of visible defects, the strain field extended to a region relatively far from the imprint in between cracks. The analysis of the radial and lateral cracks gives information where the proposed equations are valid.
Ion-beam synthesis of epitaxial Au nanocrystals in MgO
Authors: Thevuthasan S. , Shutthanandan V. , Wang C.M. , Weber W.J. , Jiang W. , Cavanagh A. , Lian J. , Wang L.M.
Published: May 2005

The formation of Au nanoclusters in MgO using ion implantation and subsequent annealing was investigated. Approximately 1200 and 1400 Au2+ ions/nm2 were implanted in MgO(100) substrates at 300 and 975 K, respectively. Subsequent annealing in air for 10 h at 1275 K promoted the formation of Au nanostructures in MgO. The sample implanted at 300 K showed severe radiation damage. In addition, two-dimensional plateletlike structures with possible composition of Au and MgO were formed during implantation in the sample that was implanted at 300 K. In contrast, Au implantation at 975 K promoted the nucleation of Au nanostructures during implantation. Subsequent annealing of both samples show three-dimensional clusters in MgO. However, the 975 K implanted sample shows clean, high-quality, single-crystal Au clusters that have an epitaxial relationship to MgO(100).
Ion-beam irradiation of Gd2Sn2O7 and Gd2Hf2O7 pyrochlore: Bond-type effect
Authors: Lian Jie , Ewing Rodney C. , Wang L.M. , Helean K.B.
Published: May 2005

Ceramics with III-IV pyrochlore compositions, A3+2B4+2O7 (A = Y and rare earth elements; B = Ti, Zr, Sn, or Hf), show a wide range of responses to ion-beam irradiation. To evaluate the role of the B-site cations on the radiation stability ofthe pyrochlore structure-type, Gd2Sn2O7 and Gd2Hf2O7 have been irradiated by1 MeV Kr+. The results are discussed in terms of the ionic size and type ofbonding of Sn4+ and Hf4+ and compared to previous results for titanate andzirconate pyrochlores. Gd2Sn2O7 is sensitive to ion beam–induced amorphizationwith a critical amorphization dose of approximately 3.4 displacements per atom(dpa) (2.62 × 1015 ions/cm2) at room temperature and a critical amorphization temperature of approximately 350 K. Gd2Hf2O7 does not become amorphous at adose of approximately 4.54 displacement per [lattice] atom (3.13 × 1015 ions/cm2) at room temperature, but instead is transformed to a disordered fluorite structure upon ion-beam irradiation. Although the radius ratio of the A- to B-site cations provides a general indication of the type of radiation response of different pyrochlore compositions, the results for Gd2Sn2O7 emphasize the importance of bond type, particularly the covalency of the 〈Sn–O〉 bond in determining the radiation response.
Colloidal processing of chemically prepared zinc oxide varistors. Part I: Milling and dispersion of powder
Authors: Bell Nelson S. , Cesarano Joe , Voigt James A. , Lockwood Steve J. , Dimos Duane B.
Published: May 2005

Chemically prepared zinc oxide powders are fabricated for the production of high aspect ratio varistor components. Colloidal processing was performed to reduce agglomerates to primary particles, form a high solids loading slurry, and prevent dopant migration. The milled and dispersed powder exhibited a viscoelastic to elastic behavioral transition at a volume loading of 43–46%. The origin of this transition was studied using acoustic spectroscopy, zeta potential measurements, and oscillatory rheology. The phenomenon occurs due to a volume fraction solids dependent reduction in the zeta potential of the solid phase. It is postulated to result from divalent ion binding within the polyelectrolyte dispersant chain and was mitigated using a polyethylene glycol plasticizing additive. This allowed for increased solids loading in the slurry and a green body fabrication study to be presented in our companion paper.
Colloidal processing of chemically prepared zinc oxide varistors. Part II: Near-net-shape forming and fired electrical properties
Authors: Bell Nelson S. , Voigt James A. , Tuttle Bruce A. , Dimos Duane B.
Published: May 2005

Chemically prepared zinc oxide powders were processed for the production of high aspect ratio varistor components (length/diameter >5). Near-net-shape casting methods including slip casting and agarose gelcasting were evaluated for effectiveness in achieving a uniform green microstructure that densifies to near theoretical values during sintering. The structure of the green parts was examined by mercury porisimetry. Agarose gelcasting produced green parts having low solids loading values and did not achieve high fired density. Isopressing the agarose cast parts after drying raised the fired density to greater than 95%, but the parts exhibited catastrophic shorting during electrical testing. Slip casting produced high green density parts, which exhibit high fired density values. The electrical characteristics of slip-cast parts are comparable with dry-pressed powder compacts.
Phase diagram, optical, nonlinear optical, and physicochemical studies of the organic monotectic system: Pentachloropyridine–succinonitrile
Authors: Rai R.N.
Published: May 2005

The two immiscible liquid phases in equilibrium with a single liquid phase have been observed during the phase diagram study of an organic analog of a metal–nonmetal system involving pentachloropyridine (PCP)–succinonitrile (SCN). The phase equilibrium shows the formation of a monotectic and a eutectic, with large miscibility gap in the system, containing 0.0456 and 0.9658 mole fractions of SCN, respectively, and the consolute temperature being 99.0 °C above the monotectic horizontal line. The heat of mixing, entropy of fusion, roughness parameter, interfacial energy, and excess thermodynamic functions were calculated based on enthalpy of fusion data determined via the differential scanning calorimetry method. The effects of solid–liquid interfacial energy on morphology of monotectic structure as well as the variation of interfacial energies with temperature have been discussed. The microstructures of monotectic and eutectic show peculiar characteristic features. The material properties of PCP and PCP doped with SCN crystals, grown by the Bridgman–Stockbarger method, have been studied via studying second harmonic generation efficiency, transparency range, and mechanical hardness.
Degradation and failure mechanisms in thermally exposed Au–Al ball bonds
Authors: Noolu Naren J. , Murdeshwar Nikhil M. , Ely Kevin J. , Lippold John C. , Baeslack William A.
Published: May 2005

During the manufacturing and the service life of Au–Al wire bonded electronic packages, the ball bonds experience elevated temperatures and hence accelerated interdiffusion reactions that promote the transformation of the Au–Al phases and the growth of creep cavities. In the current study, these service conditions were simulated by thermally exposing Au–Al ball bonds at 175 and 250 °C for up to 1000 h. The Au–Al phase transformations and the growth of cavities were characterized by scanning electron microscopy. The volume changes associated with the transformation of the intermetallic phases were theoretically calculated, and the effect of the phase transformations on the growth of cavities was studied. The as-bonded microstructure of a Au–Al ball bond typically consisted of an alloyed zone and a line of discontinuous voids (void line) between the Au bump and the bonded Al metallization. Thermal exposure resulted in the nucleation, growth, and the transformation of the Au–Al phases and the growth of cavities along the void line. Theoretical analysis showed that the phase transformations across and lateral to the ball bond result in significant volumetric shrinkage. The volumetric shrinkage results in tensile stresses and promotes the growth of creep cavities at the void line. Cavity growth is higher at the crack front due to stress concentration, which was initially at the edge of the void line. The crack propagation occurs laterally by the coalescence of sufficiently grown cavities at the void line resulting in the failure of the Au–Al ball bonds.
Silver-nanoparticle dispersion from the consolidation of Ag-attached silica colloid
Authors: Kim Tae-Gon , Kim Young Woon , Kim Jong Soon , Park Byungwoo
Published: May 2005

Silver nanoparticles dispersed in a silica matrix were made by the consolidation of a Ag-attached silica colloid, which was synthesized via the electrolysis of a pure Ag electrode, the reduction of Ag+ ions by H2, and the nucleation and growth of Ag particles on the silica nanoparticles in water. This simple process produced Ag/silica nanocomposites with a high concentration and narrow size distribution of nanoparticles, which was confirmed by transmission electron microscopy and x-ray diffraction. As estimated by Raman and photoluminescence measurements, the quantity of broken oxygen bonds was increased with increasing Ag concentration due to the intervention of Ag ions as structural modifiers in the silica network structure. Ag ions in the matrix are probably a residue of the Ag+ ions that could not be reduced by H2 during the electrolysis/reduction reaction. The optical-absorption spectra and the HCl-soaking test suggested that a chemical-interface damping effect, which was caused by electron transfer from the metal particles to the oxide matrix, dominates the optical-absorption properties in this system.
Transmission electron microscopy study of YNi2B2C thin film growth on MgO(001)
Authors: Cao G.H. , Simon P. , Skrotzki W.
Published: May 2005

A YNi2B2C thin film deposited on MgO(001) substrate by pulsed laser deposition has been investigated by transmission electron microscopy (TEM). Cross-sectional TEM analyses show that the YNi2B2C film grows in the [001] direction. Y2O3 exists not only as an interlayer at the interface of the YNi2B2C thin film and the MgO substrate but occasionally also in the YNi2B2C thin film near the substrate. The orientation relationships between the YNi2B2C thin film, Y2O3 interlayer, and MgO substrate are determined from electron-diffraction patterns to be MgO(001)[100] ‖ Y2O3(001)[100], YNi2B2C(001)[110] ‖ Y2O3(001)[100] ‖ Y2O3(001)[100, and YNi2B2C(001)[100] ‖ Y2O3(001)[100 1.5‖ Y2O3(001)[100] ‖ Y2O3(001)[100 (the numeral above the “parallel” symbol represents the misorientation (in degrees) between the [100] ‖ Y2O3(001)[100 directions).
Elastic properties, hardness, and indentation fracture toughness of intermetallics relevant to electronic packaging
Authors: Ghosh G.
Published: May 2005

Many intermetallics, such as Ag3Sn, AuSn4, Cu3Sn, Cu6Sn5 (η and η`), Ni3Sn4, and γ–Cu5Zn8 are present in modern solder interconnects as a result of solder chemistry and/or due to the interfacial reaction between solder and metallization scheme. Coarse-grained, single-phase intermetallics are produced by conventional casting followed by annealing for long time. Ambient temperature isotropic elastic moduli (bulk, Young’s, shear, and Poisson’s ratio) and selected plastic properties (hardness and indentation fracture toughness) of these intermetallics are presented. The isotropic elastic moduli of these intermetallics are determined by the pulse-echo technique. The measured bulk, Young’s and shear moduli lie in the range of 6.3 to 11.4 × 1010 N/m2, 7.1 to 12.3 × 1010 N/m2 and 2.7 to 4.5 × 1010 N/m2, respectively. The hardness and fracture toughness are determined by an indentation method. The loads used for indentation experiments were: 100–10,000 g for Ag3Sn and γ–Cu5Zn8, 10–50 g for AuSn4, 200–1000 g for Cu3Sn, 50–100 g for Cu6Sn5, and 100–200 g for Ni3Sn4. The measured Vickers hardness lies in the range of 50 to 470 Kg/mm2, and the measured indentation fracture toughness lies in the range of 2.5 to 5.7 MPa m1/2. Due to coarse grain size of the specimens, the indentation cracks were contained within one grain. In Cu3Sn, Cu6Sn5 (η and η`) and Ni3Sn4 intermetallics, the indentation cracks were found to be nearly straight and run along the indent diagonal. However, the cracks in AuSn4 showed significant zig-zag and branching phenomena, and they seemed to propagate along particular cleavage plane(s). The presence of slip bands are also observed in AuSn4, Ag3Sn, Cu3Sn, γ-Cu5Zn8, and Ni3Sn4. In the case of Ag3Sn and γ–Cu5Zn8, indentation cracks cannot be induced by applying loads up to 10 kg. Rather, extensive plastic deformation occurs resulting in the formation of a large number of shear/kink bands, and possibly twins, that spread across several grains. At a load of 5000 g or higher, Ag3Sn exhibits grain boundary decohesion near the indents. Among the intermetallics studied, Ag3Sn is shown to be the most ductile.
Nanomechanical properties of ordered phthalocyanine Langmuir–Blodgett layers
Authors: Oshiro Tammy , Backstrom Arnie , Cumberlidge Ann-Marie , Hipps K.W. , Mazur Ursula , Pevovar S.P. , Bahr D.F. , Smieja Joanne
Published: May 2005

The mechanical properties of monolayer and multilayer structures of several symmetrically substituted alkoxy copper phthalocyanine, CuPc(OR)8, Langmuir–Blodgett (LB) films were evaluated. One-dimensional compliance of the monolayers was determined from the slopes of the surface pressure–area isotherms. Multilayers were examined using a SPM and a commercial nanoindentation system. The nanomechanical studies show a distinct relationship between the position and length of alkoxy substituents on the Pc macrocycle and the LB film elasticity and hardness. The phthalocyanine complexes with peripheral octabutoxy and octaoctyloxy substituents form stiff LB monolayers and multilayers. The nonperipheral alkoxy derivetized CuPc films were less stiff. For monolayer films, it appears that the extent of π-π interaction determines the strength of the film. In multilayers, significant additional stability can be imparted through interdigitation of long paraffinic chains which play a significant role in determining the interlayer structure of the LB layers.
Control of crystalline texture in polycrystalline alumina ceramics by electrophoretic deposition in a strong magnetic field
Authors: Uchikoshi T. , Suzuki T.S. , Okuyama H. , Sakka Y.
Published: May 2005

Highly crystalline-textured pure dense alumina ceramics were fabricated from spherical alumina powder without any seed particles and sintering additives by electrophoretic deposition (EPD) in a strong magnetic field of 10 T. The crystalline texture was confirmed by x-ray diffraction (XRD) for alumina ceramics deposited at 10 T followed by sintering at 1873 K. The angle between the directions of the magnetic and electric fields (φB-E) was altered to control the dominant crystal faces of the α-alumina monoliths. The average orientation angles estimated from the XRD diagram of the samples prepared at φB-E = 0°, 45°, and 90° were 16.52°, 45.15°, and 84.90°, respectively. Alumina/alumina laminar composites with different crystalline-oriented layers were also fabricated by alternately changing the φB-E layer by layer during EPD in a 10 T magnetic field. It was demonstrated that by using this technique, it is possible to control the crystalline orientation by changing the angle of E versus B during the EPD.