bluuebunny/crossref_metadata_2025 huggingface dataset:
Airborne geophysical data leveling based on line-to-line correlations
Authors: Huang Haoping
Published: March 2008

A new technique removes the leveling errors in airborne geophysical data based on an assumption that the data are continuous (i.e., not renulled or recalibrated) from line to line. A single flight line is selected as a reference to level and tie all survey lines to this continuously varying datum. The leveling errors are determined in a least-squares sense from the reference line and the adjacent line to be leveled. The technique markedly improves the quality of the unleveled, raw data and works best if the reference line overlaps most of the line being leveled. This method cannot distinguish a linear geologic feature in the direction of flight lines from a leveling error. The technique initially was developed for airborne electromagnetic (EM) data in cases where tie-line leveling works poorly. However, it may also be used for airborne-magnetic and other data, in which case tie-lines used in conventional leveling techniques are not needed.
Efficacy, Toxicity, and Quality of Life in Older Women With Early-Stage Breast Cancer Treated With Letrozole or Placebo After 5 Years of Tamoxifen: NCIC CTG Intergroup Trial MA.17
Authors: Muss Hyman B. , Tu Dongsheng , Ingle James N. , Martino Silvana , Robert Nicholas J. , Pater Joseph L. , Whelan Timothy J. , Palmer Michael J. , Piccart Martine J. , Shepherd Lois E. , Pritchard Kathleen I. , He Zhi , Goss Paul E.
Published: March 2008

Purpose

National Cancer Institute of Canada Clinical Trials Group trial MA.17 randomly assigned 5,187 postmenopausal, hormone-receptor–positive patients with early breast cancer who completed 5 years of tamoxifen to receive either letrozole or placebo. At 30 months median follow-up, letrozole significantly improved disease-free survival (DFS) in all patients and overall survival (OS) in node-positive patients. Breast cancer incidence increases with age and more than 1,300 women age 70 years or older were enrolled onto MA.17, making it ideal to explore the benefits, toxicities, and quality of life (QOL) impact of letrozole on older women.

Patients and Methods

In this study, 5,169 randomly assigned patients were divided into three age groups: younger than 60 years (n = 2,152), 60 to 69 years (n = 1,694), and ≥ 70 years (n = 1,323). Log-rank test was used to compare differences in DFS, distant-disease–free survival, and OS between age and treatment groups, and Cox models were used to estimate hazard ratios and associated 95% CIs. QOL was measured using the Medical Outcomes Short Form-36 and the Menopause-Specific Quality-of-Life questionnaire.

Results

At 4 years, DFS demonstrated statistically significant differences favoring letrozole only in patients age younger than 60 years (hazard ratio = 0.46; P = .0004); there was no interaction between age and treatment, indicating a similar effect of letrozole among all age groups. There was no difference in toxicity or QOL at 24 months among letrozole- and placebo-treated patients age ≥ 70 years.

Conclusion

Healthy patients age 70 years and older completing 5 years of tamoxifen should be considered for extended adjuvant therapy with letrozole.
Letrozole Compared With Tamoxifen for Elderly Patients With Endocrine-Responsive Early Breast Cancer: The BIG 1-98 Trial
Authors: Crivellari Diana , Sun Zhuoxin , Coates Alan S. , Price Karen N. , Thürlimann Beat , Mouridsen Henning , Mauriac Louis , Forbes John F. , Paridaens Robert J. , Castiglione-Gertsch Monica , Gelber Richard D. , Colleoni Marco , Láng István , Del Mastro Lucia , Gladieff Laurence , Rabaglio Manuela , Smith Ian E. , Chirgwin Jacquie H. , Goldhirsch Aron
Published: March 2008

Purpose

To explore potential differences in efficacy, treatment completion, and adverse events (AEs) in elderly women receiving adjuvant tamoxifen or letrozole for five years in the Breast International Group (BIG) 1-98 trial.

Methods

This report includes the 4,922 patients allocated to 5 years of letrozole or tamoxifen in the BIG 1-98 trial. The median follow-up was 40.4 months. Subpopulation Treatment Effect Pattern Plot (STEPP) analysis was used to examine the patterns of differences in disease-free survival and incidences of AEs according to age. In addition, three categoric age groups were defined: “younger postmenopausal” patients were younger than 65 years (n = 3,127), “older” patients were 65 to 74 years old (n = 1,500), and “elderly” patients were 75 years of age or older (n = 295).

Results

Efficacy results for subpopulations defined by age were similar to the overall trial results: Letrozole significantly improved disease-free survival (DFS), the primary end point, compared with tamoxifen. Elderly patients were less likely to complete trial treatment, but at rates that were similar in the two treatment groups. The incidence of bone fractures, observed more often in the letrozole group, did not differ by age. In elderly patients, letrozole had a significantly higher incidence of any grade 3 to 5 protocol-specified non-fracture AE compared with tamoxifen (P = .002), but differences were not significant for thromboembolic or cardiac AEs.

Conclusion

Adjuvant treatment with letrozole had superior efficacy (DFS) compared with tamoxifen in all age groups. On the basis of a small number of patients older than 75 years (6%), age per se should not unduly affect the choice of adjuvant endocrine therapy.
Integrin-Mediated Expression of Bone Formation-Related Genes in Osteoblast-Like Cells in Response to Fluid Shear Stress: Roles of Extracellular Matrix, Shc, and Mitogen-Activated Protein Kinase
Authors: Lee Ding-Yu , Yeh Chiuan-Ren , Chang Shun-Fu , Lee Pei-Ling , Chien Shu , Cheng Cheng-Kung , Chiu Jeng-Jiann
Published: March 2008

Integrins play significant roles in mechanical responses of cells on extracellular matrix (ECM). We studied the roles of integrins and ECM proteins (fibronectin [FN], type I collagen [COL1], and laminin [LM]) in shear-mediated signaling and the expression of bone formation-related genes (early growth response-1 [Egr-1], c-fos, cyclooxygenase-2 [Cox-2], and osteopontin [OPN]) in human osteosarcoma MG63 cells. MG63 cells on FN, COL1, and LM were kept as controls or subjected to shear stress (12 dynes/cm2), and the association of αvβ3 and β1 integrins with Shc, phosphorylation of mitogen-activated protein kinases (MAPKs, i.e., extracellular signal-regulated kinase [ERK], c-jun-NH2-terminal kinase [JNK], and p38), and expressions of Egr-1, c-fos, Cox-2, and OPN were determined. In MG63 cells, shear stress induces sustained associations of αvβ3 and β1 with Shc when seeded on FN, but sustained associations of only β1 with Shc when seeded on COL1/LM. Shear inductions of MAPKs and bone formation-related genes were sustained (24 h) in cells on FN, but some of these responses were transient in cells on COL1/LM. The shear activations of ERK, JNK, and p38 were mediated by integrins and Shc, and these pathways differentially modulated the downstream bone formation-related gene expression. Our findings showed that β1 integrin plays predominant roles for shear-induced signaling and gene expression in osteoblast-like MG63 cells on FN, COL1, and LM and that αvβ3 also plays significant roles for such responses in cells on FN. The β1/Shc association leads to the activation of ERK, which is critical for shear induction of bone formation-related genes in osteoblast-like cells.
Die Aussetzung als strafrechtsdogmatischer Mikrokosmos
Authors: Heger Martin
Published: March 2008

I. Einleitung

Seit jeher ist der Straftatbestand der Aussetzung vor allem Gegenstand wissenschaftlicher Kontroversen. Seine praktische Bedeutung war bis zur Neufassung durch das 6. Strafrechtsreformgesetz (StrRG) gering: und obwohl die tatbestandliche Ausweitung von § 221 eigentlich das Gegenteil erwarten ließ, spricht das weitgehende Fehlen veröffentlichter Rechtsprechung zur Neufassung des § 221 für eine weiterhin geringe praktische Relevanz. Vielleicht lassen die bereits unmittelbar nach der Neufassung zutage getretenen dogmatischen Kontroversen die Strafjustiz bei der Anwendung von § 221 zögern. So wäre in einem kürzlich in Berlin entschiedenen Fall, als ein Vater seine dreijährige Tochter vier Stunden im Strandbad Weißensee in einem eingezäunten Spielbereich zurückgelassen hat, um währenddessen ein Fitnessstudio aufzusuchen, neben einer Verurteilung wegen Verletzung der Fürsorge- und Erziehungspflicht (§ 171) auch eine Strafbarkeit wegen Aussetzung denkbar gewesen, zumal § 171 durch § 221 verdrängt wird.
Thermal conversion of gels to YBa2Cu3Ox, Bi2Sr2CaCu2Ox, and (Bi, Pb)2Sr2Ca2Cu3Ox and their decarbonization by low-temperature treatment with nitric acid
Authors: Deptula A. , Olczak T. , Lada W. , Goretta K. C. , Di Bartolomeo A. , Brignocchi A.
Published: March 2008

Thermal conversion of acetate-derived gels to YBa2Cu3Ox (Y–123), Bi2Sr2CaCu2Ox (Bi–2212), and (Bi, Pb)2Sr2Ca2Cu3Ox (Bi-2223) has been studied by thermal analysis, x-ray diffraction, and infrared spectroscopy. Carbonates formed above 200 °C during thermal treatment of all gels. Decomposition of the carbonates proved to be more difficult for Y-123 than for Bi-2212 or Bi-2223. However, all of the gels that were heated contained significant amounts of carbon after calcination. Complete decarbonization of materials was attained by treating the intermediate phases (e.g., those formed after calcination at 600 °C) with nitric acid and then subjecting them to a final thermal treatment. Removal of carbonates from the intermediate phases strongly accelerated formation of the superconducting compounds.
Solid-state processing and phase development of bulk (MgO)w/BPSCCO high-temperature superconducting composite
Authors: Yuan Y. S. , Wong M. S. , Wang S. S.
Published: March 2008

The inherently weak mechanical properties associated with monolithic high-temperature superconductors (HTS) can be improved by introducing properly selected strong ceramic whiskers into the HTS materials. In this research, processing and superconducting properties of monolithic Pb-doped Bi-2223 (BPSCCO) and MgO whisker-reinforced BPSCCO HTS composite materials have been systematically studied. A solid-state processing method is successfully developed to fabricate the (MgO)w/BPSCCO composite. The HTS composite contains a dense and highly pure BPSCCO matrix phase with a preferred grain orientation, which is reinforced by MgO whiskers randomly oriented in the plane perpendicular to the hot-pressing direction. The HTS composite material is shown to exhibit excellent superconducting properties. For example, a transport Jc measured at 77 K in a zero field has been obtained to exceed 5000 A/cm2 in a (MgO)w/BPSCCO composite with 10% MgO whiskers by volume. Relationships among solid-state processing variables, HTS phase development, and superconducting properties of the monolithic BPSCCO and the HTS composite are established in the paper.
Development of novel microstructures in zirconia-toughened alumina using rapid solidification and shock compaction
Authors: Freim John , McKittrick J. , Nellis W. J. , Katz J. D.
Published: March 2008

A rapidly solidified alumina-zirconia eutectic material containing nanocrystalline t-ZrO2 has been synthesized. When heated, the microstructure contained a mixture of t-ZrO2 and m-ZrO2, each of which can facilitate toughening of the composite. Dynamic shock compaction was used to accelerate densification of the material, producing crack-free specimens with high green densities. After sintering to densities measuring ∼95% of theoretical, the shock-compacted specimens fabricated with unstabilized alumina-zirconia were extensively microcracked due to an overabundance of the m-ZrO2 phase. Experiments employing Y2O3 as a chemical stabilizer have shown that the extent of the phase transformation can be controlled, and the microstructure that developed in the stabilized material contained an acceptable level of the microcrack generating m-ZrO2 phase.
Sol-gel synthesis of phosphate ceramic composites I
Authors: Lee Burtrand I. , Samuels William D. , Wang Li-Qiong , Exarhos Gregory J.
Published: March 2008

Monolithic gels of phosphate ceramics were synthesized using PO(OH)3−x(OR)x and alkoxides of silicon and titanium. The PO(OH)3−x(OR)x species were synthesized from the reaction of P2O5 and ethanol or n-butanol, and the products consisted of approximately equal molar amounts of mono- and dialkyl phosphate. The phosphate gels containing titanium lost less phosphorus than from the gels of silicon/phosphorus upon firing of gels in air. At phosphorus contents above 60 mole %, the gels were completely crystallized upon firing at temperatures above 700 °C, while the gels containing zinc and alkali metals remained amorphous after firing at 850 °C. Solid state nuclear magnetic resonance spectroscopy showed that all of the silicon is hexacoordinated in the phosphate gels containing silicon and titanium upon firing at temperatures above 520 °C
Electrical properties of sol-gel derived films containing composites of glass-ceramics and nanocrystalline silver
Authors: Kundu T. K. , Chakravorty D.
Published: March 2008

Sol-gel-derived films containing BaTiO3 crystallites have been grown on suitable substrates using a precursor composition in the system Li2O-BaO-TiO2. Silver particles of diameters in the range 4.9 to 16.2 nm have been synthesized within these films by ion exchange and reduction technique. Electrical resistivities are found to vary from ∼102 to 105 ohm-cm, depending on the silver particle diameter. A low activation energy, approximately a few millielectron volts, is found to characterize the electrical properties of most of the samples. A quantum size effect is invoked to explain the results.
Damage-resistant alumina-based layer composites
Authors: An Linan , Chan Helen M. , Padture Nitin P. , Lawn Brian R.
Published: March 2008

A new philosophy for tailoring layer composites for damage resistance is developed, specifically for alumina-based ceramics. The underlying key to the approach is microstructural control in the adjacent layers, alternating a traditionalhomogeneousfine-grain alumina (layerA) for hardness and wear resistance with aheterogeneousalumina : calcium-hexaluminate composite (layerC) for toughness and crack dispersion, with strong bonding between the interlayers. Two trilayer sequences,ACAandCAC, are investigated. Hertzian indentation tests are used to demonstrate the capacity of the trilayers to absorb damage. In the constituent materials, the indentation responses are fundamentally different: ideally brittle in materialA, with classical cone cracking outside the contact; quasi-plastic in materialC, with distributed microdamage beneath the contact. In theACAlaminates, shallow cone cracks form in the outerAlayer, together with a partial microdamage zone in the innerClayer. A feature of the cone cracking is that it is substantially shallower than in the bulkAspecimens and does not penetrate to the underlayer, even when the applied load is increased. This indicates that the subsurface microdamage absorbs significant energy from the applied loads, and thereby “shields” the surface cone crack. Comparative tests onCAClaminates show a constrained microdamage zone in the outerClayer, with no cone crack, again indicating some kind of shielding. Importantly, interlayer delamination plays no role in either layer configuration; the mechanism of damage control is by crack suppression rather than by deflection. Implications for the design of synergistic microstructures for damage-resistant laminates are considered.
Phase development of Bi-2212 superconductor: A time-resolved neutron powder diffraction investigation
Authors: Argyriou Dimitri N. , Garcia Julie A. , Mitchell John F. , Jorgensen J. D. , Hinks D. G.
Published: March 2008

Time-resolved in situ neutron powder diffraction and Rietveld refinement have been used to study the synthesis of Bi-2212 from hydroxide precursors in a 2% O2 atmosphere. Bi-2212 was found to form within the temperature range 770–800 °C. Studies at 800 °C show that Bi-2212 grows rapidly at the expense of Bi-2201. Upon lowering the temperature to 500 °C and changing the atmosphere to Ar, a rapid increase in the lattice parameters was observed. We attribute this change to the loss of oxygen from the Bi-2212 lattice. The final material exhibited a Tc of 94 K.
Air oxidation of undoped and B-doped polycrystalline diamond films at high temperature
Authors: Miyata Koichi , Kobashi Koji
Published: March 2008

Air oxidation of undoped and B-doped polycrystalline diamond films was investigated at temperatures between 500 and 700 °C. Diamond (111) facets were etched for both undoped and B-doped films after 1 h at 700 °C. The etching rate of (111) facet due to oxidation was approximately 50% lower by B-doping of 1 × 1019 cm−3, presumably because of the decrease of sp2 bands and lattice defects that were identified by Raman and photoluminescence spectroscopy. X-ray photoelectron and electron energy loss spectroscopy revealed that by the high temperature treatment, the diamond surface was initially converted into graphite and successively etched by oxygen.
Fullerenic nanostructures in flames
Authors: Das Chowdhury K. , Howard Jack B. , VanderSande John B.
Published: March 2008

High resolution transmission electron microscopy (HRTEM) was used to characterize nanostructures in soots produced in flames of benzene, acetylene, or ethylene premixed with oxygen and an inert diluent gas. The nanostructures ranged from ∼2 nm to ∼30 nm in size with a hollow core measuring about ∼ 1 nm to ∼10 nm in diameter and containing 5 to 20 shells. The shapes of the nanostructures included spherical, spheroidal, tubular, and trigonous.
Characterization of boron nitride thin films prepared from a polymer precursor
Authors: Chan V. Z-H. , Rothman J. B. , Palladino P. , Sneddon L. G. , Composto R. J.
Published: March 2008

Excellent quality boron nitride (BN) thin films on silicon have been produced by a simple procedure involving spincoating solutions of the “single-source” polymeric-precursor polyborazylene, (B3N3H∼4)x, on a silicon substrate, followed by pyrolysis at 900 °C. Rutherford backscattering spectrometry (RBS) indicates that the B/N ratios are 1.37 and 1.09 for conversions carried out in a vacuum oven at 900 and 1250 °C, respectively. Forward recoil spectrometry (FRES) showed that the atomic percent of residual hydrogen is 10 and 9%, respectively. Plain-view and cross-sectional scanning electron microscopy (SEM) studies showed that the samples annealed at 900 °C were clean and uniform in thickness. A thickness of 800 × 1015 atoms/cm2 was determined by ion scattering. Films annealed to 1250 °C likewise showed a continuous unbroken boron nitride layer, but also exhibited morphological features resulting from reactions of the underlying silicon oxide-silicon interface in the substrate. Auger electron spectroscopy and atomic force microscopy showed that the BN coating produced at this higher temperature remained unbroken but had a surface area of ∼15% covered by dimples 2–7 nm in depth. Compared to typical films made by chemical vapor deposition, BN films produced from this “single-source” method have lower hydrogen and carbon concentrations.
Size distribution of ultrafine particles in KDP aqueous solutions
Authors: Lian Li , Taijing Lu , Zaizu Yasushi , Ogawa T.
Published: March 2008

Quantitative and qualitative investigations on the size distribution of ultrafine particles in KDP solutions were performed by a laser light scanning particle counter and by comparing with scattering polystyrene particles of standard size. The ultrafine particles are of a size distribution from <70 nm to 2000 nm, and the density of the particles sharply decreased with increasing particle size. Most of them were smaller than 100 nm, and almost no particles were >1000 nm. The size of the visual particles, which are distinguished individually by a laser light-scattering technique,3 was estimated in the size range from 200 nm to 1000 nm. The reliability of the results was evaluated.
Chemical influence of inert gas on the thin film stress in plasma-enhanced chemical vapor deposited a-SiN: H films
Authors: Loboda M. J. , Seifferly J. A.
Published: March 2008

The growth of amorphous hydrogenated silicon nitride (a-SiN:H) films by plasma enhanced chemical vapor deposition (PECVD) of SiH4−NH3−N2 reactive gas mixtures has been studied. Films were deposited at low temperature (T < 250 °C) in a commercial PECVD system commonly used to grow a-SiN: H for semiconductor integrated circuit passivation. It has been observed that the stress of the a-SiN: H film can be controlled through dilution of the film precursors with an inert gas. Experiments indicate that the influence of the inert gas on the process extends from growth kinetics and plasma chemistry to hydrogen bonding, elemental composition, and biaxial elastic modulus. The stress in films deposited without dilution is tensile. When argon is added to the plasma, Si–Hx plasma chemistry and film hydrogen bond density change producing a reduction in the amount of tensile stress. Dilution with helium can be used to shift the film stress from tensile to compressive with minimum change in growth rate. The observed helium/film stress relationship is associated with helium-based Penning ionization processes, which create metastable reactive gas species. In turn, the metastables influence nitrogen and hydrogen incorporation into the film. Nitrogen incorporation produces volume expansion of the film, increasing the compressive character of the film stress. This effect is similar to that observed when the RF power is varied or when low or multifrequency plasma excitation is used during PECVD growth of a-SiN: H.
Mechanical properties of nanocrystalline copper produced by solution-phase synthesis
Authors: Suryanarayanan R. , Frey Claire A. , Sastry Shankar M. L. , Waller Benjamin E. , Bates Susan E. , Buhro William E.
Published: March 2008

Nanocrystalline copper powder was produced by a NaBH4 reduction of CuCl in a simple solution phase room temperature reaction. Uniaxial hot pressing in a closed tungsten die was used to compact powder into dense specimens. Samples were analyzed by x-ray diffraction, precision densitometry, electron microscopy, energy dispersive x-ray analysis, and selected area diffraction. Mechanical properties of the consolidated samples were determined by microhardness measurements, three-point bending of rectangular specimens, and compression tests. Yield strength measured for nanocrystalline Cu in the present work was over two times that reported in literature for Cu with comparable grain size and over five times that of conventional Cu. Restricted grain growth observed in the hot-pressed samples and improved mechanical properties are attributed to the presence of boron. A unique method of obtaining homogeneous in situ nanosized reinforcements to strengthen the grain boundaries in nanocrystalline materials is identified.
Deformation, recovery, and recrystallization behavior of nanocrystalline copper produced from solution-phase synthesized nanoparticles
Authors: Suryanarayanan R. , Frey Claire A. , Sastry Shankar M. L. , Waller Benjamin E. , Buhro William E.
Published: March 2008

Nanocrystalline copper produced by a solution-phase chemistry approach and compacted by hot pressing was subjected to room temperature deformation. Uniaxial compression and rolling were used to deform the samples to °90% reduction in thickness. Samples were subjected to several heat treatments to study microstructure and property evolution as a function of heat treatment. Thermal response of the as-pressed and deformed nanocrystalline Cu was also studied by differential scanning calorimetry. Optical metallography, scanning and transmission electron microscopy, and selected area diffraction were used to characterize microstructures after heat treatments. Samples exhibited an endotherm upon heating at 322 °C which was reversible upon cooling. This was attributed to either dissolution and formation of Cu–B precipitates or the diffusion of B from the grain boundaries to the bulk and back to the grain boundaries. Exaggerated recrystallization occurs in the temperature range of 399–422 °C. Samples maintained high dislocation density, deformation bands, and fine grain size up to 322 °C. Beyond the recrystallization temperature, grains grew at a faster rate to submicron or micron levels. The strain hardening observed in the samples of the present study is attributed to the presence of boron. Two mechanisms are suggested for the role of B: (i) segregation of B to the grain boundaries leading to strengthening of grain boundaries, and (ii) formation of Cu–B nanoprecipitates leading to precipitation strengthening.
Residual strain energy in composites containing particles
Authors: Mizutani Toshiaki
Published: March 2008

Selsing's formula for radial tension at the particle-matrix interface is extended into a general formula which includes the effects of the amount of dispersed particles. A relationship is derived between individual volumes of strained unit cells in the crystal lattices of the particles and of the surrounding matrix. These relationships are used to predict the effect of the particles (2H−TiB2, 2H−ZrB2, and t−WB) on their unit cells and on the unit cell of the surrounding 6H–SiC matrix. The precision of these predictions was 7.1% or better. Hence, in principle, it is possible to investigate the distributions of residual bulk stress/strain. Estimates of characterizing values of the three composite systems are attempted on the rough basis of the elastic constants of the SiC matrix, confirming the physical validity of this approach as a first approximation. Further, the residual bulk strain energies of the particles and the matrix are discussed in connection with the elastic term involved in the fracture energy of such composites.
Stimulated surface crystallization of β–barium borate on glass due to ultrasonic treatment and second harmonic generation
Authors: Ding Yong , Miura Yoshinari , Osaka Akiyoshi
Published: March 2008

A glass of 47.5BaO · 47.5B2O3 · 5Al2O3 (in mol%) having a shorter optical absorption edge (∼236 nm) and suitable glass formation was selected as the mother glass for studying the surface crystallization of β−BaB2O4 · β−BaB2O4 was not the main surface crystallized phase when only a conventional heat treatment was applied. Crystallization of β−BaB2O4 was stimulated due to ultrasonic surface treatment with an ethanol suspension of β−BaB2O4 particles and subsequent heat treatment. After the ultrasonic treatment, β−BaB2O4 was the main crystallized phase. Transparent and dense β−BaB2O4 thin films/glass showed second harmonic generation. The tensor components of the second-order nonlinear optical susceptibility were estimated.
A method of monitoring water absorption in polymers using a depth sensing indentation system
Authors: Ashcroft I. A. , Spinks G. M.
Published: March 2008

The mechanical properties of many polymers are known to change as they absorb water. This fact has been used to monitor the absorption of water into the surface layers of an epoxy adhesive with a depth sensing indentation system. Two methods have been demonstrated. The sample can be immersed in water for a period of time and then removed and tested in air. Alternatively, the sample can be tested in in situ. In the second method the transport of water through the adhesive can clearly be seen in hardness/depth profiles. Hardness, elastic modulus, and creep strain of the adhesive change with time until a stable value is reached, which corresponds to full plasticization of the adhesive to the influence depth of the indenter. The initial mechanical properties of the epoxy are mostly recovered on drying.
Scanning electron microscopy observations of misfit dislocations in epitaxial In0.25Ga0.75As on GaAs(001)
Authors: Keller R. R. , Phelps J. M.
Published: March 2008

Dislocations in the misfit epitaxial film system In0.25Ga0.75As on GaAs(001) were imaged using a modified electron channeling contrast technique in a LaB6 SEM. We obtained images at an incident beam energy of 30 keV, a beam divergence of less than 1 mrad and a specimen tilt of 70° in conjunction with a movable scintillator detector mounted at a takeoff angle of approximately 3° to 5°. We achieved a spatial resolution of approximately 80 to 100 nm with this technique. Such resolution allowed rapid imaging of clusters consisting of only a few closely spaced dislocations in a 55 nm thick film. At such small film thicknesses, we did not require accurate knowledge of the incident beam direction in order to obtain sufficiently strong channeling contrast for qualitative characterization. The observed defect arrangements included features that we believe represent clustered threading segments.
Controlled decomposition and reformation of the 2223 phase in Ag-clad (Bi, Pb)2Sr2Ca2Cu3Ox tapes and its influence on the microstructure and critical current density
Authors: Parrell J. A. , Feng Y. , Dorris S. E. , Larbalestier D. C.
Published: March 2008

The decomposition of almost fully reacted (Bi, Pb)2Sr2Ca2Cu3Ox (BSCCO-2223) tapes caused by heating in 1 atm of pure O2 at 825 °C has been studied. It was found that partially decomposing 2223 tapes to a mixture of Bi2Sr2Ca1Cu2Oy, (Ca, Sr)2PbO4, and other secondary phases reduced the critical current density (77 K, 0 T) from ∼20 kA/cm2 to nearly zero. Reheating the tapes in 7.5% O2 restored the 2223 phase and, while there was some degradation of the 2223 grain alignment due to residual secondary phase growth, the critical current density was also restored to nearly its original value. We hypothesize that such a decomposition/reformation process can be useful in increasing the connectivity and relative density of polycrystalline 2223, by encouraging the formation of a liquid phase which heals residual cracks in the BSCCO core.
The demonstration of Y2BaCuO5 particle segregation in melt-processed YBa2Cu3O7−x through a computer visualization model
Authors: Varanasi C. , Black M. A. , McGinn P. J.
Published: March 2008

In melt-processed YBa2Cu3O7−x (123) microstructures, often unreacted Y2BaCuO5 (211) particles are observed to be present in an inhomogeneous manner delineating distinguishable patterns. The presence of these patterns in 123 is more clearly observed in the case of low 211 volume concentration and also when the 211 particle size is small. The observed patterns are believed to be due to 211 particle segregation in 123 domains in specific planes during melt texture growth. In the present paper a software program is used to draw a three-dimensional visualization model to demonstrate a possible structure of 211 particle segregation in 123 domains and to explain the presence of observed patterns in the microstructures. The formation of such a 211 particle segregation is explained in the light of previously proposed 123 growth mechanisms.
Effects of lanthanum modification on rhombohedral Pb(Zr1−xTix)O3 ceramics: Part II. Relaxor behavior versus enhanced antiferroelectric stability
Authors: Dai Xunhu , Xu Z. , Li Jie-Fang , Viehland Dwight
Published: March 2008

Lanthanum-modified lead zirconate titanate ceramics Pb1−3/2xLax(Zr1−yTiy)O3 [PLZT 100x/100(1 − y)/100y] with Zr/Ti ratios close to the antiferroelectric-ferroelectric (AFE-FE) phase boundary were investigated by dielectric spectroscopy, Sawyer–Tower polarization techniques, and electron microscopy. An incommensurate antiferroelectric (AFEIn) phase was found to be stabilized from the rhombohedral FE state in the compositional series 100x/90/10 for x ≥ 0.02. The La content required to induce the AFEIn state increased as the Ti content was increased. For 100x/85/15, a state with relaxor-like dielectric behavior and nanodomains was observed to develop with increasing La content; however, the double-loop-like P-E curves were suggestive of antiferroelectric behavior. Investigations for the composition 6/85/15 revealed the formation of nanodomains from the AFEIn modulation, where the size of the nanodomains equaled the value of the AFEIn modulation wavelength. For this composition, P-E studies revealed double hysteresis characteristics, whereas dielectric investigations revealed relaxor-like behavior. It is suggested that the order within the nanodomain state may be antipolar over a range of compositions in high La content rhombohedral PLZT ceramics.
Preparation of NiFe2O4 powder by spray pyrolysis of nitrate aerosols in NH3
Authors: Yu Hsuan-Fu , Gadalla Ahmed M.
Published: March 2008

To avoid the formation of hollow spheres during spray pyrolysis, NH3 was employed to change the mechanism of forming NiFe2O4 from aerosols, containing Ni(II) and Fe(III) nitrates in the required stoichiometric ratio. Nearly spherical, solid submicron NiFe2O4 particles with narrow size distribution were produced in one step using a dilute aqueous solution at pyrolysis temperatures as low as 823 K. However, higher pyrolysis temperatures (≥1023 K) reduced the oxides to metallic alloy of Ni and Fe due to dissociation of NH3. The forming steps and possible reaction mechanisms for aerosol droplets involved in the process were discussed.
Microstructural development of ZnO using a rate-controlled sintering dilatometer
Authors: Agarwal Gaurav , Speyer Robert F. , Hackenberger Wesley S.
Published: March 2008

Rate-controlled sintering (RCS) of isostatically pressed particulate compacts of ZnO showed lower average grain sizes and intragranular pore densities than constant heating rate temperature controlled sintering. Valid comparisons of this form could only be made after corrections to hardware and software which reduced specimen creep under dilatometer pushrod load, nonuniform pushrod expansion, reproducible specimen temperature determination, thermal expansion during sintering, and instantaneous termination of sintering at the specified end of RCS. The improved microstructures from RCS were attributed to maximized efficiency of densification, optimizing the time and temperatures permitted for grain growth.
Synthesis of stoichiometric lead molybdate PbMoO4: An x-ray diffraction, Fourier transform infrared spectroscopy, and differential thermal analysis study
Authors: Zeng H. C.
Published: March 2008

The PbO/MoO3 system with 47%: 53%, 53%: 47%, and 50%: 50% molar ratios at various processing temperatures has been studied with x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and differential thermal analysis (DTA) methods. It is found that in addition to the crystallization of primary PbMoO4 phase, subphases such as Pb2MoO5 and PbMo2O7 are also formed. The remaining PbO and MoO3 are detected at certain stages of the thermal process due to localized powder inhomogeneity. Physical processes, such as sublimation, eutectic melting, solid to liquid, and liquid to vapor transformations are also investigated. In particular, evaporations of excessive PbO or MoO3 in the nonstoichiometric PbO/MoO3 can be correlated to thermal processing parameters. The current study has led to the following three processing guidelines to obtain stoichiometric PbMoO4: (i) for high temperature application, such as the Czochralski melt growth, it is suggested an excessive MoO3 (a few mol %) must be included and a slow heating rate should be employed; (ii) for low temperature synthesis, the stoichiometric PbO–MoO3 can be used, but with a fast heating rate; and (iii) PbO-rich PbO/MoO3 system is not recommended in PbMoO4 synthesis.
The extent of solid solubility in the RuO2–TiO2 system
Authors: Hrovat Marko , Holc Janez , Samardžija Zoran , Dražič Goran
Published: March 2008

RuO2 single crystals were obtained by evaporation of PbO from Pb2Ru2O6.5 at high temperatures and were verified as good standards for WDS analysis. They were used for the investigation of phase equilibria and the extent of solid solubility in the RuO2–TiO2 system by WDS quantitative microanalysis. The solid solubility at 1350 °C was determined to be 16.5% TiO2 in RuO2 and 13.5% RuO2 in TiO2.
Amorphization of graphite induced by mechanical milling and subsequent crystallization of the amorphous carbon upon heat treating
Authors: Tang J. , Zhao W. , Li L. , Falster A. U. , Simmons W. B. , Zhou W. L. , Ikuhara Y. , Zhang J. H.
Published: March 2008

The effects of mechanical milling (MM) on the phase transformation of graphite carbon were investigated using high resolution electron microscopy (HREM), x-ray diffraction, and differential thermal analysis (DTA). Amorphization of graphite as a result of prolonged high-energy ball milling was directly observed with HREM. The exothermic peak in the DTA trace of the ∼200 h ball-milled sample indicated a crystallization onset temperature of about 670 °C and crystallization activation energy of 234 kJ/mole.
Microtexture of highly crystallized graphite as studied by galvanomagnetic properties and electron channeling contrast effect
Authors: Kaburagi Yutaka , Yoshida Akira , Hishiyama Yoshihiro
Published: March 2008

The relationship between microtexture and crystallinity of highly crystallized graphites with the residual resistivity ratio ρ300K/ρ4.2K of 3.45–5.50 was investigated. The graphite crystals studied were kish graphite (KG), highly oriented pyrolytic graphite (HOPG), and highly crystallized graphite films prepared from carbonized aromatic polyimide films. The study was made by the observations of an electron channeling pattern and electron channeling contrast image (ECI) under scanning electron microscope and the measurements of x-ray diffraction, magnetoresistance, and Hall coefficient. The values of the mean free path of the carriers λ, which approximates the mean crystal grain size, were estimated to be 2.6–6.1 μm from the magnetoresistance at 4.2 K for the highly crystallized graphites. The values of the average crystal grain diameter D in the basal plane evaluated from ECI were several hundred microns or more for KG, 60 μm for HOPG, and 6 and 12 μm for the graphite films. The difference between the values of λ and D for each crystallized graphite was discussed in relation to other results obtained.
Fabrication of large grain YBCO by seeded peritectic solidification
Authors: Lo Wai , Cardwell D. A. , Dewhurst C. D. , Dung S-L.
Published: March 2008

The ability to process large grain, uniform high temperature superconducting ceramics that exhibit high critical current densities at 77 K is essential if the enormous potential of these materials for a range of permanent magnet-type applications is to be realized. We report a study of the fabrication of large grain YBa2Cu3O7−δ by seeded peritectic solidification in which key processing parameters such as the peritectic melting process, the seed-YBCO reaction, and the YBCO solidification kinetics are investigated in detail. Evolution of the sample microstructure during various stages of the growth process, in particular, has been studied extensively. The superconducting properties of specimens cut from different regions of large grain samples have been measured using vibrating sample magnetometry, and the results correlated with the microstructure of the materials.
Crystallinity of YBa2Cu3O7−x single crystals grown by the pulling method
Authors: Namikawa Y. , Egami M. , Koyama S. , Shiohara Y. , Kutami H.
Published: March 2008

Large YBa2Cu3O7−x (Y123) single crystals (larger than 13 mm cubed) have been grown along the c-axis reproducibly by the modified pulling method. The crystallinity of Y123 single crystal was investigated by x-ray diffraction and x-ray topography. Crystals grown from an MgO single crystal seed had some low angle subgrain boundaries which tilted 0.1–0.8° from each other. These grain boundaries originated from the seed crystal, and the subgrains were extended along the growth direction from the seed crystal. Y123 single crystals with no marked subgrains in the whole area were obtained by using Y123 single subgrain crystal seeds. FWHM of the x-ray rocking curve for the crystal so produced was about 0.14°, which was much better than the spectrum consisting of several separated peaks obtained from the previous crystals. Tc onset of the annealed sample was about 93.6 K, and the transition width was about 0.9 K. The low angle subgrain boundaries did not seem to be effective pinning centers for the magnetic flux.
Spontaneous solution-sol-gel process for preparing tin oxide monolith
Authors: Wu Nae-Lih , Wu Lih-Fu , Yang Ya-Chin , Huang Shu-Jiuan
Published: March 2008

A sol-gel process for preparing SnO2 monolith of high specific surface area and transparency from chloride solution is described. Without introducing any alkaline precipitating reagent to induce condensation, this new process employs tin chloride (or its hydrate), water, and, optionally, alcohols as the only process reagents. Spontaneous solution-to-sol and sol-to-gel transitions take place upon mixing these reagents under appropriate conditions, and the entire transition processes are carried out under acidic conditions (typically pH ≤ 4.0). The rate of condensation has been found to increase with decreasing SnCl4 concentration, which corresponds to decreasing solution acidity, and with increasing temperature. For fixed starting salt concentration and temperature, there exists an optimum amount of ethanol addition for the fastest condensation. Good performance of thus derived SnO2 monolith has been demonstrated in two applications, including catalytic oxidation and solid-state gas-sensing for carbon monoxide.
Microstructure of a high strength alumina glass composite
Authors: Hornberger Helga , Marquis Peter M. , Christiansen Silke , Strunk Horst P.
Published: March 2008

The morphology and microstructure of an Al2O3 glass composite (trade name In-Ceram, Vita Zahnfabrik) were studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The composite was produced by infiltration of a lanthanum-based glass throughout a porous Al2O3 body. This alumina body was formed by three classes of particles differing in size and shape: faceted particles typically ≤4 μm in diameter, platelets of average diameter 8 μm, 1.5 μm thickness, and small spheres 0.4 μm in diameter. The outstanding strength properties of the composite (600 MPa, ball-on-ring test) are a result of the high wetting capability of the glass phase on the Al2O3 surface. In addition, plastic strain relaxation in the faceted particles by dislocation formation compensates partially for residual stresses and impedes crack formation at the glass/Al2O3 interface.
Fullerene-tetracyanoquinodimethane thin film and novel electrical bistability
Authors: Gao H. J. , Xue Z. Q. , Wu Q. D. , Pang S. J.
Published: March 2008

We report the electrical bistability of C60-tetracyanoquinodimethane (TCNQ) thin films fabricated by using an ionized-cluster-beam method in a high vacuum system. The films were characterized by transmission electron microscopy and electronic absorption spectroscopy. The spectroscopic results showed evidence of the formation of the charge-transfer complex system in C60-TCNQ thin films, and the TEM results revealed the microstructure of the films. The film thickness is ∼100 nm. The electromotive intensity at the transition point was of the order of 106 V/m. The possible mechanism of the electrical phenomena of the films is discussed in the paper.
A large angle convergent beam electron diffraction study of the core nature of dislocations in 3C-SiC
Authors: Ning X. J. , Pirouz P.
Published: March 2008

Dislocations produced by 1300 °C indentation of the silicon-terminated (111) face of 3C-SiC were investigated by transmission electron microscopy. They were all found to be either widely separated partial dislocation pairs, or else, arrays of single partial dislocation half-loops on neighboring parallel slip planes and having the same Burgers vector. It was concluded that in the latter case, each array consisted of leading partial dislocations which had nucleated without accompanying trailing partial dislocations. The core nature of both dissociated dislocations and arrays of single partial dislocations has been determined by the technique of large angle convergent beam electron diffraction. The results indicate that the core of all single partial dislocation half-loops constituting an array consists of silicon atoms. It is concluded that, with the present deformation geometry, the Si-core partial dislocations are preferentially nucleated before the C-core partial dislocations. In the case of a dissociated dislocation, when a pair of partials was present, electron microscopy observations revealed that the morphology of the two partial dislocations was very different; while the Si-core partials were smooth, the C-core partial dislocations had a zig-zag morphology.
Effect of high pressure on the preparation of Pd–Si–Cu bulk nanocrystalline material
Authors: Yao B. , Ding B. Z. , Sui G. L. , Wang A. M. , Hu Z. Q.
Published: March 2008

A Pd–Si–Cu bulk nanocrystalline material was prepared by quenching the melted Pd78Si16Cu6 alloy at a cooling rate of 200 K/s under 2–6 GPa. It was found that the nanocrystalline material consists of Pd(Cu) disordered solid solution and a metastable phase-II, Pd4Si. The grain size was found to decrease with increasing pressure. The influence of high pressure on the grain size of bulk nanocrystalline material is discussed, and a possible formation mechanism is proposed.
Role of Bi2O3 in optimizing the dielectric properties of Ba4.5Nd9Ti18O54 based microwave ceramics
Authors: Valant Matjaž , Suvorov Danilo , Kolar Drago
Published: March 2008

Small additions of Bi2O3 or bismuth titanate improve the dielectric properties of Ba4.5Nd9Ti18O54 at microwave frequencies. It was found that Bi3+ can replace Nd3+ up to 15 mol%, the limiting composition of solid solution being Ba4.5(Nd0.85Bi0.15)9Ti18O54. At the solid solution limit the temperature coefficient of resonant frequency attains its minimum value. The modified ceramic is distinguished by high permittivity of 99 and a Q-value of 5500. The temperature coefficient of resonant frequency is low, 15 ppm/K. After exceeding the solid solubility limit, additional Bi2O3 concentrates as a Bi-rich phase at the grain boundaries, causing considerable reduction of the Q-value and an increase of τf.
Fast firing of lead magnesium niobate at low temperature
Authors: Saha Dipika , Sen A. , Maiti H. S.
Published: March 2008

A fast-firing technique for the sintering of lead magnesium niobate relaxor ceramics at relatively low temperature has been described. In this process, the samples containing excess PbO (up to 5 wt. %) are directly introduced into a furnace maintained at a temperature of 950 °C and kept there for 15–80 min, followed by a postsintering annealing treatment at 800 °C for 10 h. The importance of fast heating as well as annealing treatment has been justified. The sintered samples are near-phase-pure perovskite materials showing high bulk densities (>94%), uniform and dense microstructure, and satisfactory dielectric properties (Kmax > 13,000). The technique is simple and economic, does not require any controlled atmosphere, and minimizes hazards from lead volatilization.
Fabrication of TiB2 and TiB2/FeB composites by mechanically activated borothermic reduction of ilmenite
Authors: Millet P. , Hwang T.
Published: March 2008

TiB2 and TiB2/FeB composites have been formed at temperatures below 1000 °C, directly from ilmenite sand by reaction with amorphous boron. The structural transformations occurring during high-energy mechanical milling pretreatment and subsequent annealing of different mixtures of the constituents have been studied. On heating at temperature below 800 °C, complete borothermic reduction of the ilmenite structure is accomplished. The mixture so obtained with an ilmenite-boron ratio equal to 1/6 undergoes a sequence of reactions on further heating to form TiB2, FeB, and the amorphous phase B2O2.