bluuebunny/crossref_metadata_2025 huggingface dataset:
There's (Always) Something about Cuba: Security and States of Exception in a Fundamentally Unsafe World
Authors: Goldman Dara E.
Published: March 2008

Recent events have led critics to speculate about whether “everything changed” in the wake of 9/11. Drawing on the work of Giorgio Agamben, this essay examines current rhetoric and practices in both the United States and Cuba. The U.S.-Cuban relationship, especially as manifested in popular depictions of the contested terrain of Guantánamo Bay, provides a curious case study of how state power is exercised at the margins, in nonspaces that lie beyond the national imaginary. These depictions point to a larger history of disenfranchisement, displacement, and suppression. In the end, I argue that the case of Guantánamo constitutes an example of the underlying interdependence between the state and the suspension of the rule of law. It points to how the rhetoric of safety has been deployed by the current administration in the United States to justify an expansion and intensification of established practices that are fundamentally undemocratic.
Role of Budget Impact in Drug Reimbursement Decisions
Authors: Cohen Joshua Parsons , Stolk Elly , Niezen Maartje
Published: March 2008

There are three known criteria that underlie drug reimbursement decisions: therapeutic value, cost-effectiveness, and burden of disease. However, evidence from recent reimbursement decisions in several jurisdictions points to residual, unexplained variables, among which is budget impact. Budget impact refers to the total costs that drug reimbursement and use entail with respect to one part of the health care system, pharmaceutical care, or to the entire health care system, taking into account the possible reallocation of resources across budgets or sectors of the health care system. The economic and equity rationale for carrying out budget impact analyses is opportunity cost, or benefits forgone, measured in terms of utility or equitable distribution, by using resources in one way rather than another. In other words, by choosing to draw down the budget in one way, decision makers forgo other opportunities to use the same resources. Under a set of unrealistic assumptions, cost-effectiveness analysis accounts for opportunity cost while conveying to the decision maker the price of maximizing health gains, subject to a budget or resource constraint. However, the underlying assumptions are implausible, particularly in the context of pharmaceutical care. Moreover, budget impact analysis is more useful to the decision maker than cost-effectiveness analysis if the objective is not to maximize health gains subject to a budget or resource constraint, but to reduce variance in health gains. With respect to equitable distribution, budget impact analyses lay bare the individuals or groups who lose out — those who bear the opportunity cost of spending resources in accordance with one decision rule rather than another.
Alaska Public Health Law Reform
Authors: Meier Benjamin Mason , Hodge James G. , Gebbie Kristine M.
Published: March 2008

The Turning Point Model State Public Health Act (Turning Point Act), published in September 2003, provides a comprehensive template for states seeking public health law modernization. This case study examines the political and policy efforts undertaken in Alaska following the development of the Turning Point Act. It is the first in a series of case studies to assess states' consideration of the Turning Point Act for the purpose of public health law reform. Through a comparative analysis of these case studies and ongoing legislative tracking in all fifty states, researchers can assess (1) how states codify the Turning Point Act into state law and (2) how these modernized state laws influence or change public health practice, leading to improved health outcomes.
Misleading Congress About Drug Development: Reply
Authors: DiMasi Joseph A. , Hansen Ronald W. , Grabowski Henry G.
Published: March 2008

The review essay by Donald Light about a Congressional Budget Office report on pharmaceutical research and development (R&D) (Light 2007) contains factual errors, leaves the reader uninformed about rebuttal responses to criticisms made in the review about studies of R&D costs, and draws erroneous conclusions about the nature of industry economics.
Reply to DiMasi, Hansen, and Grabowski
Authors: Light Donald W.
Published: March 2008

Besides critiquing the Congressional Budget Office for failing to cite and discuss evidence from independent sources that suggest that the net corporate costs of pharmaceutical research and development costs are much lower than industry advocates claim, Light's review showed how these high estimates are constructed realities that one can reconstruct by using different assumptions, data, or calculations and come up with much lower estimates. In their reply here, DiMasi, Hansen, and Grabowski unwittingly reinforce that point.
Drosophilafragile X mental retardation protein developmentally regulates activity-dependent axon pruning
Authors: Tessier Charles R. , Broadie Kendal
Published: March 2008

Fragile X Syndrome (FraX) is a broad-spectrum neurological disorder with symptoms ranging from hyperexcitability to mental retardation and autism. Loss of the fragile X mental retardation 1 (fmr1) gene product,the mRNA-binding translational regulator FMRP, causes structural over-elaboration of dendritic and axonal processes, as well as functional alterations in synaptic plasticity at maturity. It is unclear, however,whether FraX is primarily a disease of development, a disease of plasticity or both: a distinction that is vital for engineering intervention strategies. To address this crucial issue, we have used the Drosophila FraX model to investigate the developmental function of Drosophila FMRP (dFMRP). dFMRP expression and regulation of chickadee/profilincoincides with a transient window of late brain development. During this time,dFMRP is positively regulated by sensory input activity, and is required to limit axon growth and for efficient activity-dependent pruning of axon branches in the Mushroom Body learning/memory center. These results demonstrate that dFMRP has a primary role in activity-dependent neural circuit refinement during late brain development.
Energy Destruction in Iran's Natural Gas Pipe Line Network
Authors: Farzaneh-Gord Mahmood , Hashemi Shahram , Sadi Meisam
Published: March 2008

Natural gas is transported from production sites to end users through high pressure (5-7 MPa) transmission pipelines. At a consumption point or when passing into a lower pressure pipeline, the pressure of the gas must be reduced. This pressure reduction takes place at City Gate Stations (CGS). Currently in all of Iran's CGSs, valuable pressure exergy (potential energy) contained by the high-pressure natural gas is lost to the environment in throttling valves (expansion valves). In this study, based on a comprehensive program, the inlet and outlet properties and daily flow rates of natural gas through Khorasan province (Iran) CGSs were measured and recorded for a whole year. Based on these data, the amount of energy lost to the environment was calculated. It was found that the yearly average mass flow rate in Khorasan CGSs is 90.5 kg/s, and average energy destruction is 13,240 kW. Assuming a conversion efficiency of 75%, one can extract 9,930 kW of electrical power. Based on Iran's average daily natural gas consumption of 336 × 106 m3/day and assuming the same conditions at all CGSs as at Khorasan, 762 MW of electrical power could be generated by capturing the lost pressure exergy flowing through all of Iran's CGSs.
Cation mass-valence sum (CM-VS) approach to assigning OH-bending bands in dioctahedral smectites
Authors: Gates Will P.
Published: March 2008

The assignments of OH-bending bands in the infrared (IR) spectra of dioctahedral smectites (montmorillonites, ferruginous smectites, and nontronites) have been revisited using a cation mass-valence sum (CM-VS) approach to quantify octahedral cation occupancy. The CM-VS approach enabled prediction of OH-bending band positions (in wavenumbers) related to OH-sharing octahedral cation pairs that had valence sums of 4 and 5, and cation masses associated with Fe(II) and Mg. Application of rules for the relationship enabled determination of the location of OH-sharing octahedral cation pairs containing Mg and Fe(II) for which previous assignments have been considered controversial, e.g. Fe(III)Mg-OH and MgMg-OH, or for which assignments have been missing due to lack of spectroscopic evidence, e.g. AlFe(II)-OH, Fe(III)Fe(II)-OH, Fe(II)Mg-OH, and Fe(II)Fe(II)-OH. Examples of these bands from several natural ferruginous smectites and nontronites are discussed. Quantification of IR spectra was used to develop a better understanding of the octahedral cation occupancy of this important class of Fe(III)-enriched smectites. While Fe(II) contents may be somewhat overestimated by the IR technique, those for four of the six ferruginous smectites studied here agree well with data from Mössbauer spectroscopy.
Geochemical records of a bentonitic acid-tuff succession related to a transgressive systems tract — Indication of changes in the volcanic sedimentation rate
Authors: Püspöki Z. , Kozák M. , Kovács-Pálffy P. , Szepesi J. , McIntosh R. , Kónya P. , Vincze L. , Gyula G.
Published: March 2008

A detailed stratigraphic and facies reconstruction of a bentonitized acid-tuff succession, deposited within the transgressive systems tract of the Upper Miocene-Sarmatian Ser-3 eustatic cycle, at Sajóbábony, northern Hungary, was performed via petrographic, mineralogical and geochemical analyses. The purpose of the work was to analyze the degree of alteration of the volcanogenic sediments, as an indicator of the relative volcanic sedimentation rate. This may have an important role in indicating volcanic periods synchronous with sedimentation or reconstructing the volcanosedimentary paleoconditions. Sample pairs were collected from each bentonite and tuff layer, and, to facilitiate microstratigraphic relations, samples were collected every 10 cm within bentonite layers. Mineralogical analyses were performed by X-ray diffraction and geochemical analyses by inductively coupled plasma-mass spectroscopy.

The CaO/K2O and Eu/La ratios correlate with each other and with a montmorillonite/X-ray-amorphous phase ratio, reflecting Ca and Eu incorporation associated with devitrification and smectite formation. In accordance with the current literature, these mineralogical and geochemical proxies can be related primarily to the weathering processes. Considering vertical distributions in a sequence-stratigraphic context, the Ca content and Eu/La values show that local peaks and Eu anomalies characteristic of acid tuffs show minima at flooding surfaces (FS). Within a bentonite layer, representing a single transgressive period, the repeated events of dust-tuff accumulations have been determined by K2O/CaO and La/Eu peaks, confirmed also by the Eu anomalies in the rare earth element (REE) patterns, thus leading to the conclusion that the level of alteration is closely correlated with the elimination of terrigenous input and a minimum in volcanic sedimentation rate allowing more intensive alteration of the deposited volcanic material. In the case of fine tuff beds, Eu anomalies on REE patterns reflect limited alteration at the bottom and more intensive alteration in the upper parts of the beds, reflecting the effect of infiltration of sea water into the pores.
The viscosity of organic liquid suspensions of trimethyldococylammonium-montmorillonite complexes
Authors: Minase Makoto , Kondo Mitsuji , Onikata Masanobu , Kawamura Katsuyuki
Published: March 2008

An organophilic bentonite was prepared by means of a reaction of natural Na-montmorillonite with trimethyldococylammonium which has an especially longn-alkyl chain. The addition of trimethyldococylammonium to montmorillonite was in the range 0.25–3.0 times the cation exchange capacity (CEC) of the clay (i.e.0.23–2.82 mmol/g clay). The particle morphology in organic liquid suspensions of organoclay complexes was studied by measuring the viscosity based on Eyring’s rate process and Robinson’s relative sediment volume. In toluene, montmorillonite with 1.17 mmol/g clay trimethyldococylammonium (1.25 times the CEC) had the largest specific gel volume, relative sediment volume, andK-factor. The results of the stoichiometry for trimethyldococylammonium-montmorillonite show that practically all of the quaternary ammonium was adsorbed to montmorillonite. Maximum half widths of 001 reflections from X-ray diffraction patterns were obtained in the range 0.74–1.17 mmol/g clay, indicating a disordered arrangement of the organic cation molecules intercalated between the layers. Appreciable shifts to lower-frequency regions in the Fourier transform infrared absorption spectra as a result of CH2-stretching vibrations were observed with increasing amounts of the organic cation. When increasing the amount of organic cation added to the clay from 0.94 to 1.41 mmol/g clay, a large shift occurred to the lower-frequency side, approaching the frequency of the organic cation alone. This indicates that the interaction between adjacent hydrocarbon chains becomes progressively stronger, due to van der Waals attraction, with increases in the amount of organic cation. Interactions of the alkyl chains in trimethyldococylammonium-montmorillonite complexes with irregularly distributed and randomly arranged alkyl chains between the silicate layers were weak, and, as a result, solvation with external organic liquids occurred and gel formation developed through macroscopic swelling of the organoclay.
Ionic liquids-kaolinite nanostructured materials. Intercalation of pyrrolidinium salts
Authors: Letaief Sadok , Detellier Christian
Published: March 2008

Ionic liquids intercalated in kaolinite constitute a novel class of nanostructured material. Kaolinite-pyrrolidinium halide intercalates have been prepared successfully by reacting the pyrrolidinium salts with kaolinite which was preintercalated with dimethyl sulfoxide (DMSO) using the melt condition under N2. X-ray diffraction, 13C magic angle spinning nuclear magnetic resonance, differential thermal analysis (DTA)-thermal gravimetric analysis, and Fourier transform infrared spectroscopy confirm the displacement of DMSO during the intercalation process. Based on results from the various characterization techniques, a structural model is proposed in which one mole of the pyrrolidinium salt covers two or three structural units of kaolinite, depending on the structure and size of the salt. The thermal stability was improved remarkably after intercalation of the pyrrolidinium salts, compared to the pre-intercalate. The DTA-TGA data show that the largest number of organic units released and decomposed, occurs under N2 flow, at temperatures ranging from 260 to 340°C, depending on the nature of the intercalated organic salts.
NMR spectroscopy of naturally occurring surface-adsorbed fluoride on Georgia kaolinite
Authors: Cochiara Stacey G. , Phillips Brian L.
Published: March 2008

Using 19F magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy, we show that most of the fluoride present in the KGa-lb reference kaolinite from Washington County, Georgia, occurs as a surface-adsorbed species bonded to Al. This surface fluoride can be removed from the <2 µm fraction by acid wash, but is largely retained in the coarse fraction. Correlation of integrated 19F NMR peak intensities with fluoride sorption experiments indicates a bulk F content of ∼144 ppm for KGa-1b, of which ∼30% substitutes for hydroxyl sites in the mineral structure and the remaining 70% occurs adsorbed on particle surfaces, corresponding to an edge surface fluoride density of ∼0.7 F− nm−2. 19F{27Al} TRAPDOR (TRAnsfer of Populations in DOuble Resonance) NMR data for the original kaolinite and for products of F− sorption experiments at pH 4 show that all of the observed 19F signals arise from fluoride bonded to Al atoms. Furthermore, bridging Al-F-Al sites and terminal Al-F give distinctly different TRAPDOR fractions allowing assignment of resolved peaks based on the number of Al in the first coordination sphere. This result was confirmed for fluoride adsorbed to the surface of gibbsite from aqueous suspension. No evidence was found for Si-F-type environments on the kaolinite surfaces.
Diagenetic reorientation of phyllosilicate minerals in Paleogene mudstones of the Podhale Basin, southern Poland
Authors: Day-Stirrat Ruarri J. , Aplin Andrew C. , Środoń Jan , van der Pluijm Ben A.
Published: March 2008

We used high-resolution X-ray texture goniometry to quantify changes in the mm-scale orientation of phyllosilicate minerals in a suite of Paleogene mudstones from the Podhale Basin in southern Poland. The sample set covers an estimated range of burial depths between 2.4 and 7.0 km, corresponding to a temperature range of 60–160°C. Although mechanical compaction has reduced porosities to ∼10% in the shallowest samples, the phyllosilicate fabric is only modestly aligned. Coarser-grained (>10 µm) detrital chlorite and mica appear to be more strongly aligned with (001) parallel to bedding, suggesting their deposition as single grains rather than as isotropic flocs or aggregates. From 2.4 to 4.6 km, R0 illite-smectite with 40–50% illite layers changes to R1 illite-smectite with 70–80%) illite layers. At the same time kaolinite is lost and diagenetic chlorite is formed. The mineralogical changes are accompanied by a strong increase in the alignment of illite-smectite, chlorite, and detrital illite, parallel to bedding and normal to the presumed principal effective stress. We propose that the development of a more aligned I-S fabric results from the dissolution of smectite and the growth of illite with (001) normal to the maximum effective stress. Water released by illitization may act as a lubricant for the rotation of all platy minerals into nanoporosity transiently formed by the illitization reaction. At greater depths and temperatures, further illitization is inhibited through the exhaustion of K-feldspar. After the cessation of illitization, a further 2.4 km of burial only results in a small increase in phyllosilicate alignment. At such small values for porosity and pore size, increasing stress does not substantially reorient phyllosilicates in the absence of mineralogical change.
Dendritic cell subtypes as primary targets of vaccines: the emerging role and cross-talk of pattern recognition receptors
Authors: Benkő Szilvia , Magyarics Zoltán , Szabó Attila , Rajnavölgyi Éva
Published: March 2008

Preventive vaccination is the most successful approach against infectious diseases and has a great impact on world health. Vaccines operate through the activation of innate immunity that helps to stimulate antigen-specific T- and B-lymphocytes. These events are orchestrated by dendritic cells (DCs) that are able to sample foreign structures and concomitantly sense ‘danger signals’. Thus, DCs provide a functional link between innate and acquired immunity, and due to their regulatory potential are referred to as natural adjuvants. Human conventional and plasmacytoid DCs express different sets of well-characterized Toll-like membrane receptors (TLRs) that recognize a broad range of conserved molecular patterns of pathogens. The recently discovered cytosolic Nod-like receptors (NLRs) and RIG-like helicases (RLHs) also turned out to participate in pathogen recognition and modulation of immune responses through interacting signaling pathways. As a result of their collaboration, the TLR, NLR and RLH recognition systems induce the secretion of different combinations of cytokines that play a fundamental role in T-cell activation and instruction. Ligands of the innate recognition systems emerge as new adjuvants for vaccine design, whereas manipulation of the signaling pathways mediated by these receptors offers new avenues for fine tuning immune responses and optimizing immunotherapies.
Modeling of variant copies of subunit D1 in the structure of photosystem II from Thermosynechococcus elongatus
Authors: Loll Bernhard , Broser Matthias , Kós Peter B. , Kern Jan , Biesiadka Jacek , Vass Imre , Saenger Wolfram , Zouni Athina
Published: March 2008

In the cyanobacterium Thermosynechococcus elongatus BP-1, living in hot springs, the light environment directly regulates expression of genes that encode key components of the photosynthetic multi-subunit protein-pigment complex photosystem II (PSII). Light is not only essential as an energy source to power photosynthesis, but leads to formation of aggressive radicals which induce severe damage of protein subunits and organic cofactors. Photosynthetic organisms develop several protection mechanisms against this photo-damage, such as the differential expression of genes coding for the reaction center subunit D1 in PSII. Testing the expression of the three different genes (psbAI, psbAII, psbAIII) coding for D1 in T. elongatus under culture conditions used for preparing the material used in crystallization of PSII showed that under these conditions only subunit PsbA1 is present. However, exposure to high-light intensity induced partial replacement of PsbA1 with PsbA3. Modeling of the variant amino acids of the three different D1 copies in the 3.0 Å resolution crystal structure of PSII revealed that most of them are in the direct vicinity to redox-active cofactors of the electron transfer chain. Possible structural and mechanistic consequences for electron transfer are discussed.
Analysis of the human cytomegalovirus pp65-directed T-cell response in healthy HLA-A2-positive individuals
Authors: Schalich Juliane , Vytvytska Oresta , Zauner Wolfgang , Fischer Michael B. , Buschle Michael , Aichinger Gerald , Klade Christoph S.
Published: March 2008

Human cytomegalovirus (HCMV) is contained by T-lymphocyte responses focused towards the major tegument protein pp65. To systematically identify T-cell epitopes, we applied the following strategy: 441 overlapping 15mer peptides spanning the entire HCMV pp65 antigen in 1-aa steps were screened in enzyme-linked immunospot (ELIspot) assays for interferon gamma (IFN-γ) secretion by peripheral blood mononuclear cells (PBMCs) from nine healthy HCMV-seropositive subjects expressing human leukocyte antigen (HLA)-A2. This analysis confirmed a number of previously known epitopes and revealed several new ones. A total of 26 epitopes were identified, including 14 HLA-A2, four HLA-B7, -B35, -B12 and -B44 restricted class I epitopes, six class II epitopes, and two epitopes of unknown restriction. Three novel HLA-A2 epitopes were confirmed using T2-cells, and one peptide for which only binding data had been published so far was verified. Two novel class II epitopes were confirmed by intracellular cytokine staining. Responses were usually oligoclonal against up to seven HLA-A2 epitopes, albeit with a few dominating epitopes. Clusters of overlapping epitopes (hot-spots) were identified. These and the newly identified T-cell epitopes may be of great value for epitope-based immunotherapeutic approaches, including peptide vaccines.
Maintenance of serological memory
Authors: Wrammert Jens , Ahmed Rafi
Published: March 2008

Long-lived plasma cells are key to maintaining long-term humoral immunity after infection or vaccination. Some vaccines and/or infections induce antibody levels that remain stable for the life of the individual. However, the mechanism whereby these long-lived plasma cells are maintained over long periods of time remains an open question. Furthermore, given a finite number of sustainable plasma cells within the bone marrow, it is also unclear how space for newly induced plasma cells is generated without compromising the pre-existing repertoire. Here we review the current understanding of these important issues.
Dynamisches Verfahren zur Messung von elektostriktiven und elektrooptischen Effekten. Beispiel: Tinkalkonit Na2B4O5(OH)4 · 3 H2O
Authors: Bohatý Ladislav
Published: March 2008

A method for the dynamic measurement of electrostrictive and electrooptical effects basing on the principle of a Michelson interferometer has been developed. Changes of optical pathways as small as 0.1 Å can be determined with good accuracy. The linear electrostrictive and the linear electrooptical tensors of tincalconite, Na2B4O5(OH)4 · 3 H2O have been measured.
Crystallographic aspects of the linear electro-optic effect
Authors: Bohatý Ladislav
Published: March 2008

Aspects of symmetry and crystal chemistry of the linear electrooptic effect are analyzed on the basis of new experimental results.

Relations between the linear electro-optic effect [r
σ
ijk] (unclamped) and the linear electrostrictive effect [d
ijk] are investigated by comparison of the longitudinal effects r'111 and d'111; The relation |d'111|max/|r'111|max≥1 is valid for 41 of the hitherto available data of 49 crystals.

Guidelines for the search of crystals with high electro-optic effects are reviewed. The most important keywords for a “chemical engineering” of new electro-optic materials are: pyroelectric symmetry groups; “polar” structural units; structures with strongly asymmetric bonds; molecules with high hyperpolarizabilities; structures tending towards a dielectric instability.
Electro-optic and electrostrictive properties of the low-temperature phase of barium borate BaB2O4
*
Authors: Bohatý Ladislav , Liebertz J.
Published: March 2008

All components of the linear electro-optic tensor [r
σ
ijk] (unclamped) of low-temperature BaB2O4 and the liner electrostrictive tensor [d
ijk] were determined (T= 293 K; λ= 633 nm). In its electro-optic and electrostrictive behaviour low-temperature BaB2O4 resembles the tetraborates Li2B4O7 and PbB4O7. The maximum value of the longitudinal and transversal electro-optic effects is only one fourth of that in KDP. This reduces the importance of BaB2O4 for electro-optic applications.
Mechanics of shaped crystal growth from the melt
Authors: Lambropoulos John C. , Wu Chien-Hsing
Published: March 2008

We present the numerical formulation of the thermal stress driven steady-state dislocation generation during the growth of shaped crystals from the melt, with Czochralski (CZ) growth of solid cylinder III–V compound semiconductors as an example. We use and compare the Haasen–Alexander model, coupling dislocation multiplication and creep strain rates, and the Jordan model, based on thermoelastic stresses. Growth parameters may be chosen so as to produce an overall approximately flat interface, leading to reduced dislocation density in the majority of the crystal's cross section. Calculation of final dislocation density requires the initial dislocation density and all stress components along the solid-liquid interface, microstructural features which depend on the physical processes leading to solidification. The final dislocation density is not sensitive to the initial dislocation density along the solid-liquid interface, but strongly depends on the interface stress. Significant stress relaxation at the interface is required to produce experimentally observed “W” shaped dislocation patterns. Crystal growth direction and crystalline anisotropy couple elastic (lattice) and plastic (slip systems) crystalline anisotropy.
Influence of in-process copper incorporation on the quality of diamond-like carbon films deposited by pulsed laser deposition technique
Authors: Dikshit S. J. , Lele Pramada , Ogale S.B. , Kshirsagar S. T.
Published: March 2008

Copper-incorporated carbon films have been prepared on Si(100) and Corning (7059) glass substrates by the pulsed excimer laser deposition technique using KrF radiation (λ = 248 nm). Cold-pressed composite pellets, having compositions from 2 at. % to 11 at. % copper in carbon, were used as targets for ablation. Good quality, scratch-proof films were obtained at a laser energy density of 2−3 J/cm2 and a substrate temperature of 50 °C. The films were characterized by x-ray diffraction (XRD), Raman spectroscopy, x-ray photoelectron spectroscopy (XPS), UV-visible spectrometry, ellipsometry, and four-point probe resistivity measurements. Under similar deposition conditions, films obtained from composite targets of lower copper concentration are seen to have better diamond-like character as compared to those obtained from a pure graphite target. At such low concentrations, copper is seen to cluster in the form of nanoparticles. As the copper concentration increases in the films, they tend to acquire disordered graphitic network with degraded DLC characteristics, and the size of copper agglomerates increases from about 5 nm (for the 2 at. % case) to 85 nm (for the 11 at. % case). It is seen that an increase in the copper content leads to modifications in the carbon network, additional interband transitions, and reduction of the band gap.
Microstructure and 90° domain assemblages of Pb(Zr, Ti)O3//RuO2 capacitors as a function of Zr-to-Ti stoichiometry
Authors: Tuttle B. A. , Headley T. J. , Al-Shareef H.N. , Voigt J. A. , Rodriguez M. , Michael J. , Warren W. L.
Published: March 2008

Planar microstructure, 90° domain configurations, and cross-sectional perovskite grain morphology were characterized for a series of Pb(Zr, Ti)O3//RuO2 thin film capacitors. Perovskite grain size increased substantially with increasing Zr concentration of the Pb(Zr, Ti)O3 (PZT) films, being on the order of 0.15 μm for PZT 20/80 films and 2.5 μm for PZT 50/50 films. While PZT 20/80 and PZT 30/70 films were single phase perovskite, the PZT 40/60 and 50/50 films contained a second phase with fluorite structure. The second phase matrix consisted of two nanophases, one having fluorite structure while the other was amorphous. Both the amorphous nanophase and the fluorite nanophase were Pb deficient compared to the perovskite phase. Differences in cross-sectional perovskite grain morphology were substantial for these materials, with the PZT 40/60 film being almost entirely columnar and the PZT 20/80 film exhibiting almost entirely granular morphology. Differences in 90° domain wall density were essentially negligible among the films, suggesting that if 90° domains were responsible for the differences in electrical properties, it is not due to 90° domain population.
Synthesis of yttria-stabilized zirconia nanoparticles by decomposition of metal nitrates coated on carbon powder
Authors: Jiang Shusheng , Stangle Gregory C. , Amarakoon Vasantha R. W. , Schulze Walter A.
Published: March 2008

Weakly agglomerated nanoparticles of yttria-stabilized zirconia (YSZ) were synthesized by a novel process which involved the decomposition of metal nitrates that had been coated on ultrafine carbon black powder, after which the carbon black was gasified. The use of ultrafine, high-surface-area carbon black powder apparently allowed the nanocrystalline oxide particles to form and remain separate from each other, after which the carbon black was gasified at a somewhat higher temperature. As a result, the degree of agglomeration was shown to be relatively low. The average crystallite size and the specific surface area of the as-synthesized YSZ nanoparticles were 5−6 nm and 130 m2/g, respectively, for powder synthesized at 650 °C. The as-synthesized YSZ nanoparticles had a light brown color and were translucent, which differs distinctly from conventional YSZ particles which are typically white and opaque. The mechanism of the synthesis process was investigated, and indicated that the gasification temperature had a direct effect on the crystallite size of the as-synthesized YSZ nanoparticles. High-density and ultrafine-grained YSZ ceramic articles were prepared by fast-firing, using a dwell temperature of 1250 °C and a dwell time of two minutes or less.
Microstructure development in furfuryl resin-derived microporous glassy carbons
Authors: Constant Kristen Persels , Lee Jonq-Ren , Chiang Yet-Ming
Published: March 2008

The processing of microporous glassy carbon derived from furfuryl alcohol and ethylene glycol mixtures has been studied, with emphasis on understanding and controlling microstructure development. It is shown that this system exhibits a polymerization-dependent miscibility gap, and that the carbon microstructure is determined by phase separation in the liquid state. Variations in carbon microstructure with composition and thermal history can be understood in terms of the time-dependent immiscibility and resulting phase separation.
An elastic-plastic indentation model and its solutions
Authors: Yu Weiping , Blanchard James P.
Published: March 2008

An analytical model of hardness has been developed. Four major indentation tests, namely indentation by cones, wedges, spheres, and flat-ended, axisymmetric cylinders have been analyzed based on the model. Analytical relationships among hardness, yield stress, elastic modulus, Poisson's ratio, and indenter geometries have been found. These results enable hardness to be calculated in terms of uniaxial material properties and indenter geometries for a wide variety of elastic and plastic materials. These relationships can also be used for evaluating other mechanical properties through hardness measurements and for converting hardness from one type of hardness test into those of a different test. Comparison with experimental data and numerical calculations is excellent.
Peritectic solidification model for Y-system superconductive oxides
Authors: Nakamura Y. , Shiohara Y.
Published: March 2008

A peritectic solidification growth model considering both solute diffusion in the liquid and interface kinetics is developed for the growth of YBa2Cu3O61x (123) superconductive oxide. The effect of interface kinetics on the growth rate and the rate control process is discussed using this model. The growth rate of the 123 crystal is evaluated as a function of the undercooling using the proper kinetic equation. The evaluated results by this model show good agreement with the experimental results. As a result of this evaluation, the growth of the 123 crystal is predicted to be limited by a mixed control process in general.
Growth and electronic properties of epitaxial TiN thin films on 3C-SiC(001) and 6H-SiC(0001) substrates by reactive magnetron sputtering
Authors: Hultman L. , Ljungcrantz H. , Hallin C. , Janzén E. , Sundgren J-E. , Pécz B. , Wallenberg L. R.
Published: March 2008

Epitaxial TiN films were grown on cubic (3C)-SiC(001) and hexagonal (6H)-SiC(0001) substrates by ultrahigh vacuum reactive magnetron sputtering from a Ti target in a mixed Ar and N2 discharge at a substrate temperature of 700 °C. Cross-sectional transmission electron microscopy, including high-resolution imaging, showed orientational relationships TiN(001)‖3C-SiC(001), and TiN[110]‖3C-SiC[110], and TiN(111)‖6H-SiC(0001) and . In the latter case, twin-related TiN domains formed as the result of nucleation on SiC terraces with an inequivalent stacking sequence of Si and C. The TiN/SiC interface was locally atomically sharp for both SiC polytypes. Defects in the TiN layers consisted of threading double positioning domain boundaries in TiN(111) on 6H-SiC. Stacking faults in 3C-SiC did not propagate upon growth of TiN. Room-temperature resistivity of TiN films was ρ = 14 μΩ cm for 6H-SiC(0001) and ρ = 17 μΩ cm for 3C-SiC(001) substrates. Specific contact resistance of TiN to 6H-SiC(0001) was 1.3 3 10−3 Ω cm2 for a 6H-SiC substrate with an n-type doping of 5 × 1017 cm−3.
Highly resistive sputtered ZnO films implanted with copper
Authors: Puchert M. K. , Hartmann A. , Lamb R. N. , Martin J. W.
Published: March 2008

Polycrystalline (0001)-oriented thin films of ZnO (thickness 120 nm) were deposited by rf magnetron sputtering and post-deposition annealed at 500 °C in oxygen (1 atm). The films were subsequently implanted with copper at doses over the range 1016 to 1017 ions/cm2. X-ray diffraction (XRD) indicates the compressive intrinsic film stress is largely relieved by the preimplantation anneal, and does not change when implanted or when further annealed after implantation, suggesting that the dominant cause of intrinsic stress is the atomic packing density rather than the crystallographic defect density. Resistivity measurements indicate that annealing of pure ZnO films causes the perpendicular resistivity to increase from 1.3 × 105 Ω · cm to 5 × 1010 Ω · cm. Copper implantation results in a lower resistivity of the order of 107 Ω · cm, but subsequent annealing actually increases resistivity beyond that of annealed nonimplanted ZnO to 3 × 1012 Ω · cm. It is proposed that copper increases the resistivity of those annealed films by trapping free electrons with the Cu 3d hole state occurring in CuO (formed predominantly during annealing). In order to check this, the oxidation state of the implanted copper was studied before and after annealing by x-ray photoelectron spectroscopy (XPS) and extended x-ray absorption fine structure (EXAFS). Three oxidation states of copper (Cu0, Cu1+, Cu2+) are detected in the implanted films, and postimplantation annealing results in oxidation of copper to the Cu2+ state, confirming that the presence of CuO in ZnO is associated with increased resistivity.
Circumferential permeability in nonmagnetostrictive amorphous wires
Authors: Sanchez M. L. , Valenzuela R. , Vazquez M. , Hernando A.
Published: March 2008

Real and imaginary components of the impedance response on Co68.1Fe4.4B15Si12.5 amorphous as-cast wires were measured in the 100 Hz-100 kHz frequency range and 0.05–30 mA (RMS) current amplitude, at axial dc fields of 0 and 4800 A/m. From these data, plots of circumferential complex permeability as a function of circular field, as well as magnetization curves, were derived. Results are analyzed in terms equivalent circuits, which allows a resolution of domain wall and rotational contributions to the circumferential magnetization processes.
Dynamic convection-driven thermal gradient chemical vapor infiltration
Authors: Ofori John Y. , Sotirchos Stratis V.
Published: March 2008

The operation of the process of chemical vapor infiltration using a combination of pressure pulsing and thermal gradients is theoretically investigated in this study. Past studies had shown that pulsing of the pressure in the gas phase can lead to a dramatic reduction of the density gradients in the densifying structure, in comparison to those seen in isobaric diffusion-driven Pinfiltration, with significant gradients present only in the vicinity of the external surface of the preforms. Using a detailed model for chemical vapor infiltration under unsteady nonisothermal conditions, we show that temperature gradients, created in our study through microwave heating, can, in conjunction with pressure pulsing, eliminate the density gradients in the final product. Moreover, appropriate tuning of the operational parameters can lead to a situation where densification proceeds from the interior of the preform toward the external surface.
Processing and characterization of Pb(Zr, Ti)O3films, up to 10 μm thick, produced from a diol sol-gel route
Authors: Tu Y. L. , Milne S. J.
Published: March 2008

A recently developed diol sol-gel route has been modified in order to produce multilayer PbZr0.53Ti0.47O3films on platinized sapphire substrates. Up to 20 depositions of a 1.1 M sol were carried out leading to a final film thickness of 10 μm. A similar thickness could be achieved from 12 coatings of a more concentrated 1.6 M sol. Decomposition and crystallization of the multilayer coatings were performed using a two-stage prefiring sequence, at 350 °C and 600 °C, followed by a final firing step at 700 °C. Ferroelectric remanant polarization increased with increasing film thickness to a value of 40 μC cm−2for a 10 μm film, with a corresponding coercive field of 30 kV cm−1; the relative permittivity of this film was ∼1000 and the dissipation factor 0.04. The thickness dependence of relative permittivity could be modeled on a simple series capacitor circuit representing the ferroelectric Pb(Zr, Ti)O3(PZT) film and low-permittivity interface layers; but other possible contributory factors are also discussed.
Phase transformation and characterization of TiO2 and ZrO2 addition in the Li2O–Al2O3-SiO2 gels
Authors: Lin Ming-Hong , Wang Moo-Chin
Published: March 2008

Glass-ceramic powders with a composition of Li2O · Al2O3 · 4SiO2 (LAS) have been synthesized by the sol-gel technique using LiOCH3, Al(OC2H5)3, Si(OC2H5)4, Ti(OC2H5)4, and Zr(OC2H5)4 as starting materials and the phase transformation behavior during calcination has been investigated. Differential thermal analysis (DTA), x-ray diffraction (XRD), and scanning electron microscopy (SEM) were utilized to determine the thermal behavior of the gels. Considering the LAS gels with 6.0 wt. % TiO2 and various wt. % ZrO2 content, and peak position of the β-spodumene phase formation in DTA curves was shifted to a higher temperature when the ZrO2 content was increased. The activation energy of β-spodumene crystallization was 283.8 kcal/mol for LAS gels with 6.0 wt. % TiO2 and 2.0 wt. % ZrO2. Unlike foregoing studies for LAS gels, during calcination of the dried LASTZ gels from 800 °C to 1200 °C neither β-eucryptite nor γ-spodumene was noted to be present. The crystallized phases comprised of β-spodumenes as the major phase and rutile (TiO2) together with zirconia (ZrO2) are precipitated as minor phases.
Effect of temperature gradient in the solution on spiral growth of YBa2Cu3O7−x bulk single crystals
Authors: Kanamori Y. , Shiohara Y.
Published: March 2008

Bulk single crystals of Y123 are required to clarify the superconductivity phenomena and develop electronic devices using unique superconductive properties. Only the Solute-Rich Liquid–Crystal Pulling (SRL-CP) method has succeeded in continuous growth of the Y123 single crystal. In this paper, we investigated the growth of Y123 single crystals under different temperature gradients in the solution in order to understand the growth mechanism of Y123. It was revealed that Y123 single crystals grow with a spiral growth mode, which is in good agreement with the BCF theory.
Oxidation and crystallization of an amorphous Zr60Al15Ni25 alloy
Authors: Sun X. , Schneider S. , Geyer U. , Johnson W. L. , Nicolet M-A.
Published: March 2008

The amorphous ternary metallic alloy Zr60Al15Ni25 was oxidized in dry oxygen in the temperature range 310 °C to 410 °C. Rutherford backscattering (RBS) and cross-sectional transmission electron microscopy (TEM) studies suggest that during this treatment an amorphous layer of zirconium-aluminum-oxide is formed at the surface. Nickel was depleted in the oxide and enriched in the amorphous alloy near the interface. The oxide layer thickness grows parabolically with annealing duration, with a transport constant of 2.8 × 10−5 m2/s × exp(−1.7 eV/kT). The oxidation rate may be controlled by the diffusion of Ni in the amorphous alloy. At later stages of the oxidation process, precipitates of nanocrystalline ZrO2 appear in the oxide near the interface. Finally, two intermetallic phases nucleate and grow simultaneously in the alloy, one at the interface and one within the alloy. An explanation involving preferential oxidation is proposed.
Etching of polycrystalline diamond films by electron beam assisted plasma
Authors: Kobashi Koji , Miyauchi Shigeaki , Miyata Koichi , Nishimura Kozo , Rocca Jorge J.
Published: March 2008

Polycrystalline diamond films were processed in a direct current plasma produced by a self-focused electron beam using combinations of H2, O2, and He as the processing gas. The film surfaces were observed by scanning electron microscopy, and characterized by x-ray photoelectron spectroscopy. It was found that for the case in which O2 was included in the processing gas, a high density of etch pits appeared on (100) faces of diamond grains, and oxygen was either physisorbed or chemisorbed at the film surface. It was demonstrated that the etching apparatus used was capable of forming at least a 5-μm wide pattern of polycrystalline diamond film.
Tribological properties of fullerenes C60 and C70 microparticles
Authors: Zhao Wei , Tang Jinke , Puri Ashok , Sweany Ray L. , Li Yuxin , Chen Liquan
Published: March 2008

The frictional behaviors of fullerenes C60 and C70 were studied because they were speculated to be solid lubricants. For the sublimated pure C60 films on Si(001), a high friction coefficient (0.55–0.8) was observed under different loads and pin materials. For the C70 film, the friction coefficient showed a pin dependence, which changed from 0.5 with an Al2O3 pin to about 0.9 with a 440 stainless steel pin. The relatively high friction coefficients of C60 and C70 films were due to the tendency of the C60 and C70 particles to clump and compress into high shear strength layers rather than due to the impurities in the fullerenes. The benzene-solvated C60 · 4C6H6 and C70 ·xC6H6 showed a lowered friction coefficient (0.25 for C60 · 4C6H6 and 0.3 for C70 · xC6H6), which might result from the lowered shear strength of the hcp structure of C60 · 4C6H6 and C70 ·xC6H6 molecular crystals in which the benzene molecules were intercalated.
A novel mosaic-like structure in SrTiO3 thin films on a Pt(001) surface revealed by transmission electron microscopy
Authors: Takeno S. , Nakamura S. , Abe K. , Komatsu S.
Published: March 2008

A novel mosaic-like structure in SrTiO3 thin films was discovered and characterized by means of transmission electron microscopy (TEM). The films were deposited on a (001) oriented Pt surface. The orientation relationship between SrTiO3 film and Pt substrate was determined, and four types of growth modes were revealed. These four growth modes formed four types of domains, respectively, and these domains and Pt formed peculiarly ordered interfacial structures, i.e., near coincidence site lattices. Antiphase boundaries between two adjacent domains were also observed by high-resolution imaging.
Optical properties of nanosized gold particles
Authors: Doremus Robert H. , Rao Pratima
Published: March 2008

Gold particles smaller than 2 nm in diameter were grown in glass. Their optical absorption spectrum did not show the usual plasma absorption band for gold particles; this band was spread by the small particle size. The absorption spectrum was calculated from the bulk optical properties of gold, modified for the small particle size; there was good agreement between calculated and measured spectra. The smallest particles containing from 20 to 40 gold atoms showed a λ−4 dependence of absorption on wavelength λ. This result implies that the absorption in these particles was entirely from free electrons at wavelengths above 0.3 μm.
Copper (I) oxide powder generation by spray pyrolysis
Authors: Majumdar D. , Shefelbine T. A. , Kodas T. T. , Glicksman H. D.
Published: March 2008

Copper oxide powders were prepared by the spray pyrolysis of copper nitrate solutions over a range of temperatures (400–1300 °C) and residence times (3–7 s). Phase-pure [by x-ray diffraction (XRD)] copper (I) oxide was obtained at 800–1300 °C in an inert (nitrogen) atmosphere. The particles varied from smooth, solid spheres at 1300 °C to irregularly shaped and hollow particles at 800 °C with dense particles of Cu2O being made only at 1000 °C or higher. The particles were polycrystalline with an average crystallite size of 42 nm at 800 °C, while at 1000–1200 °C, the particles were single crystals. Spray pyrolysis in forming gas (7% H2–N2) atmosphere at 500–700 °C gave Cu while spray pyrolysis in air yielded CuO over 800–1000 °C and a mixture of Cu2O/CuO at 1200 °C. These results show that solid, phase-pure Cu2O particles can be produced by aerosol-phase densification at temperatures below its melting point (1235 °C).