bluuebunny/crossref_metadata_2025 huggingface dataset:
Variability in morphology, hygroscopicity, and optical properties of soot aerosols during atmospheric processing
Authors: Zhang Renyi , Khalizov Alexei F. , Pagels Joakim , Zhang Dan , Xue Huaxin , McMurry Peter H.
Published: July 2008

The atmospheric effects of soot aerosols include interference with radiative transfer, visibility impairment, and alteration of cloud formation and are highly sensitive to the manner by which soot is internally mixed with other aerosol constituents. We present experimental studies to show that soot particles acquire a large mass fraction of sulfuric acid during atmospheric aging, considerably altering their properties. Soot particles exposed to subsaturated sulfuric acid vapor exhibit a marked change in morphology, characterized by a decreased mobility-based diameter but an increased fractal dimension and effective density. These particles experience large hygroscopic size and mass growth at subsaturated conditions (<90% relative humidity) and act efficiently as cloud-condensation nuclei. Coating with sulfuric acid and subsequent hygroscopic growth enhance the optical properties of soot aerosols, increasing scattering by ≈10-fold and absorption by nearly 2-fold at 80% relative humidity relative to fresh particles. In addition, condensation of sulfuric acid is shown to occur at a similar rate on ambient aerosols of various types of a given mobility size, regardless of their chemical compositions and microphysical structures. Representing an important mechanism of atmospheric aging, internal mixing of soot with sulfuric acid has profound implications on visibility, human health, and direct and indirect climate forcing.
Fc receptor engagement mediates differentiation of cardiac fibroblast precursor cells
Authors: Haudek Sandra B. , Trial JoAnn , Xia Ying , Gupta Damon , Pilling Darrell , Entman Mark L.
Published: July 2008

We previously described a critical role for a fibroblast precursor population in the development of a murine fibrotic cardiomyopathy model (I/RC). These precursors arose from circulating bone marrow-derived cells of monocytic origin. Administration of serum amyloid P (SAP) prevented the presence of this cell population in the heart and the cardiomyopathy. Because SAP binds to Fc receptors (FcRs) expressed on monocytes, we investigated the involvement of FcR signaling. We chose mice lacking the FcRγ chain protein (FcRγ
−/−
), a common membrane-signaling component of activating FcRs. Like wild-type mice, FcRγ
−/−
mice developed fibrosis and cardiac dysfunction when subjected to I/RC. However, unlike wild-type mice, SAP in FcRγ
−/−
mice failed to inhibit the development of fibrosis and cardiac dysfunction and did not diminish the numbers of α-smooth muscle actin
+
and CD34
+
, CD45
+
fibroblasts that were typical for I/RC. To further examine the role of SAP in monocyte-to-fibroblast transition, we performed
in vitro
assays in which human peripheral blood mononuclear cells (PBMCs) migrated through human umbilical vein endothelial cells (HUVECs). We found that MCP-1-dependent transendothelial migration of monocytes markedly accelerated their differentiation into fibroblasts. This monocyte differentiation to fibroblasts was eliminated when SAP was added to the PBMC suspension before endothelial transmigration. Adding SAP to cells after successful migration did not inhibit fibroblast maturation. These data indicate that SAP inhibits the differentiation of a blood-borne, myeloid cell population into fibroblasts by signaling through activating FcRs before transendothelial migration has occurred. We suggest that FcR activation of circulating precursor cells may represent a new treatment target for adverse remodeling and cardiac fibrosis.
Hormone-dependent nuclear export of estradiol receptor and DNA synthesis in breast cancer cells
Authors: Lombardi Maria , Castoria Gabriella , Migliaccio Antimo , Barone Maria Vittoria , Di Stasio Rosina , Ciociola Alessandra , Bottero Daniela , Yamaguchi Hiroshi , Appella Ettore , Auricchio Ferdinando
Published: July 2008

In breast cancer cells, cytoplasmic localization of the estradiol receptor α (ERα) regulates estradiol-dependent S phase entry. We identified a nuclear export sequence (NES) in ERα and show that its export is dependent on both estradiol-mediated phosphatidylinositol-3-kinase (PI3K)/AKT activation and chromosome region maintenance 1 (CRM1). A Tat peptide containing the ERα NES disrupts ERα–CRM1 interaction and prevents nuclear export of ERα- and estradiol-induced DNA synthesis. NES-ERα mutants do not exit the nucleus and inhibit estradiol-induced S phase entry; ERα-dependent transcription is normal. ERα is associated with Forkhead proteins in the nucleus, and estradiol stimulates nuclear exit of both proteins. ERα knockdown or ERα NES mutations prevent ERα and Forkhead nuclear export. A mutant of forkhead in rhabdomyosarcoma (FKHR), which cannot be phosphorylated by estradiol-activated AKT, does not associate with ERα and is trapped in the nucleus, blocking S phase entry. In conclusion, estradiol-induced AKT-dependent phosphorylation of FKHR drives its association with ERα, thereby triggering complex export from the nucleus necessary for initiation of DNA synthesis and S phase entry.
Outbreak ofShewanella algaeandShewanella putrefaciensInfections Caused by a Shared Measuring Cup in a General Surgery Unit in Korea
Authors: Oh Hyang Soon , Kum Kyung Ah , Kim Eui-Chong , Lee Hoan-Jong , Choe Kang Won , Oh Myoung Don
Published: July 2008

Objective.

To control an outbreak ofShewanella algaeandS. putrefaciensinfections by identifying the risk factors for infection and transmission.

Design.

Matched case-control study.

Setting.

A university-affiliated tertiary acute care hospital in Seoul, Republic of Korea, with approximately 1,600 beds.

Patients.

From June 20, 2003, to January 16, 2004, a total of 31 case patients withShewanellacolonization or infection and 62 control patients were enrolled in the study.

Interventions.

Requirement to use single-use measuring cups and standard precautions (including hand washing before and after patient care and use of gloves).

Results.

S. algaeorS. putrefacienswas isolated from blood, for 9 (29.0%) of 31 patients who acquired one of the organisms; from bile, for 8 (25.8%), and from ascitic fluid, for 8 (25.8%). The attack rate of this outbreak was 5.8% (31 patients infected or colonized, of 534 potentially exposed on ward A) and the pathogenicity of the two species together was 77.4% (24 patients infected, of 31 who acquired the pathogens). The estimated incubation period forShewanellaacquisition was 3–49 days. Using logistic analysis, we identified the following risk factors: presence of external drainage catheters in the hepatobiliary system (odds ratio [OR], 20;P< .001), presence of hepatobiliary disease (OR, 6.4;P< .001), admission to the emergency department of the hospital (OR, 2.9;P= .039), wound classification of “contaminated” or “dirty or infected” (OR, 16.5;P= .012), an American Society of Anesthesiologists score of 3 or higher (OR, 8.0;P= .006), duration of stay in ward A (OR, 1.1;P< .001), and, for women, an age of 60–69 years (OR, 13.3;P= .028). AShewanellaisolate was recovered from the surface of a shared measuring cup, and 12 isolates ofS. algaeshowed the same pulsed-field gel electrophoresis pattern.

Conclusions.

ThisShewanellaoutbreak had a single-source origin and spread by contact transmission via a contaminated measuring cup.Shewanellaspecies are emerging as potentially serious human pathogens in hospitals and could be included in hospital infection surveillance systems.
A rough differentiable function
Authors: Kirchheim Bernd , Müller Paul
Published: July 2008

A real-valued continuously differentiable function

f
f

on the unit interval is constructed such that
\[

∑

k
=
1

∞

β
f

(
x
,

2

−
k

)
=
∞

\sum _{k=1}^\infty \beta _f (x, 2^{-k} ) = \infty

\]
holds for every

x
∈
[
0
,
1
]
.

x \in [0,1].

Here

β
f

(
x
,

2

−
k

)

\beta _f (x, 2^{-k} )

measures the distance of

f
f

to the best approximating linear function at scale

2

−
k

2^{-k}

around

x
x

.
Self-similar sets with an open set condition and great variety of overlaps
Authors: Bandt Christoph , Hung Nguyen
Published: July 2008

For a very simple family of self-similar sets with two pieces, we prove, using a technique of Solomyak, that the intersection of the pieces can be a Cantor set with any dimension in

[
0
,
0.2
]

[0,0.2]

as well as a finite set of any cardinality

2
m

2^m

. The main point is that the open set condition is fulfilled for all these examples.
Sign changes of Hecke eigenvalues of Siegel cusp forms of degree 2
Authors: Pitale Ameya , Schmidt Ralf
Published: July 2008

Let

μ
(
n
)

\mu (n)

,

n
>
0

n>0

, be the sequence of Hecke eigenvalues of a cuspidal Siegel eigenform

F
F

of degree

2
2

. It is proved that if

F
F

is not in the Maaß space, then there exist infinitely many primes

p
p

for which the sequence

μ
(

p
r

)

\mu (p^r)

,

r
>
0

r>0

, has infinitely many sign changes.
Poincaré series of subsets of affine Weyl groups
Authors: Viswanath Sankaran
Published: July 2008

In this note, we identify a natural class of subsets of affine Weyl groups whose Poincaré series are rational functions. This class includes the sets of minimal coset representatives of reflection subgroups. As an application, we construct a generalization of the classical length-descent generating function and prove its rationality.
On the Néron-Severi group of surfaces with many lines
Authors: Boissière Samuel , Sarti Alessandra
Published: July 2008

For a binary quartic form

ϕ
\phi

without multiple factors, we classify the quartic

K
3

K3

surfaces

ϕ
(
x
,
y
)
=
ϕ
(
z
,
t
)

\phi (x,y)=\phi (z,t)

whose Néron-Severi group is (rationally) generated by lines. For generic binary forms

ϕ
\phi

,

ψ
\psi

of prime degree without multiple factors, we prove that the Néron-Severi group of the surface

ϕ
(
x
,
y
)
=
ψ
(
z
,
t
)

\phi (x,y)=\psi (z,t)

is rationally generated by lines.
Transcription-coupled DNA Double-Strand Breaks Are Mediated via the Nucleotide Excision Repair and the Mre11-Rad50-Nbs1 Complex
Authors: Guirouilh-Barbat Josée , Redon Christophe , Pommier Yves
Published: July 2008

The cellular activity of Yondelis (trabectedin, Ecteinascidin 743, Et743) is known to depend on transcription-coupled nucleotide excision repair (TCR). However, the subsequent cellular effects of Et743 are not fully understood. Here we show that Et743 induces both transcription- and replication-coupled DNA double-strand breaks (DSBs) that are detectible by neutral COMET assay and as γ-H2AX foci that colocalize with 53BP1, Mre11, Ser1981-pATM, and Thr68-pChk2. The transcription coupled-DSBs (TC-DSBs) induced by Et743 depended both on TCR and Mre11-Rad50-Nbs1 (MRN) and were associated with DNA-PK–dependent γ-H2AX foci. In contrast to DNA-PK, ATM phosphorylated H2AX both in NER-proficient and -deficient cells, but its full activation was dependent on H2AX as well as DNA-PK, suggesting a positive feedback loop: DNA-PK-γ-H2AX-ATM. Knocking-out H2AX or inactivating DNA-PK reduced Et743's antiproliferative activity, whereas ATM and MRN tended to act as survival factors. Our results highlight the interplays between ATM and DNA-PK and their impacts on H2AX phosphorylation and cell survival. They also suggest that γ-H2AX may serve as a biomarker in patients treated with Et743 and that molecular profiling of tumors for TCR, MRN, ATM, and DNA-PK might be useful to anticipate tumor response to Et743 treatment.
The wisdom of the commons: ensemble tree classifiers for prostate cancer prognosis
Authors: Koziol James A. , Feng Anne C. , Jia Zhenyu , Wang Yipeng , Goodison Seven , McClelland Michael , Mercola Dan
Published: July 2008

Motivation: Classification and regression trees have long been used for cancer diagnosis and prognosis. Nevertheless, instability and variable selection bias, as well as overfitting, are well-known problems of tree-based methods. In this article, we investigate whether ensemble tree classifiers can ameliorate these difficulties, using data from two recent studies of radical prostatectomy in prostate cancer.

Results: Using time to progression following prostatectomy as the relevant clinical endpoint, we found that ensemble tree classifiers robustly and reproducibly identified three subgroups of patients in the two clinical datasets: non-progressors, early progressors and late progressors. Moreover, the consensus classifications were independent predictors of time to progression compared to known clinical prognostic factors.

Contact:  dmercola@uci.edu
PathCluster: a framework for gene set-based hierarchical clustering
Authors: Kim Tae-Min , Yim Seon-Hee , Jeong Yong-Bok , Jung Yu-Chae , Chung Yeun-Jun
Published: July 2008

Motivation: Gene clustering and gene set-based functional analysis are widely used for the analysis of expression profiles. The development of a comprehensive method jointly combining the two methods would allow for greater biological insights.

Results: We developed a software package, PathCluster for gene set-based clustering via an agglomerative hierarchical clustering algorithm. The distances between predefined gene sets are illustrated in a dendrogram in which the relationships between gene sets can be visually assessed. Valuable biological insights can be obtained according to the type of gene sets, e.g. coordinated action of molecular functions (functional gene sets) and putative motif synergy (promoter gene set) in a biological process. The combined use of gene sets further enables the interrogation of different biological themes and their putative relationships, such as function-versus-regulatory motif or drug-versus-function. PathCluster can also be used for knowledge-based sample partitioning or class categorization for clinical purposes. With extended applicability, PathCluster will facilitate the gleaning of meaningful biological insights and testable hypotheses in the contexts of given expression profiles.

Availability: PathCluster executable files can be freely downloaded at http://www.systemsbiology.co.kr/PathCluster/.

Contact:  yejun@catholic.ac.kr
Specific ligation to double-stranded RNA for analysis of cellular RNA::RNA interactions
Authors: Faridani Omid R. , McInerney Gerald M. , Gradin Katarina , Good Liam
Published: July 2008

Double-stranded RNA (dsRNA) is formed in cells as intra- and intermolecular RNA interactions and is involved in a range of biological processes including RNA metabolism, RNA interference and translation control mediated by natural antisense RNA and microRNA. Despite this breadth of activities, few molecular tools are available to analyse dsRNA as native hybrids. We describe a two-step ligation method for enzymatic joining of dsRNA adaptors to any dsRNA molecule in its duplex form without a need for prior sequence or termini information. The method is specific for dsRNA and can ligate various adaptors to label, map or amplify dsRNA sequences. When combined with reverse transcription–polymerase chain reaction, the method is sensitive and can detect low nanomolar concentrations of dsRNA in total RNA. As examples, we mapped dsRNA/single-stranded RNA junctions within Escherichia coli hok mRNA and the human immunodeficiency virus TAR element using RNA from bacteria and mammalian cells.
Demographic mechanism of a historical bird population collapse reconstructed using museum specimens
Authors: Green Rhys E
Published: July 2008

Long-term studies of demographic rates provide clues about the external causes of animal population declines, but systematic monitoring is rarely in place until after the decline has occurred. This study evaluates alternative hypotheses about the demographic mechanisms underlying the historical collapse of corncrake (Crexcrex) populations in Britain and Ireland in the late nineteenth and early twentieth centuries using characteristics of museum specimens. The proportion of adult corncrakes that are 1-year old was estimated from feather characteristics of birds collected before, during and after the population decline and showed a marked transitory reduction during the decline. This pattern would be expected if the decline was caused by a large reduction in the recruitment of young birds to the breeding population and is the opposite of what would be expected if a change in adult survival had caused the decline. These results are consistent with previous suggestions that the corncrake population decline was caused by adverse effects on breeding productivity caused by the mechanization of the harvesting of hay crops.
Expression of arginine vasotocin in distinct preoptic regions is associated with dominant and subordinate behaviour in an African cichlid fish
Authors: Greenwood Anna K , Wark Abigail R , Fernald Russell D , Hofmann Hans A
Published: July 2008

Neuropeptides have widespread modulatory effects on behaviour and physiology and are associated with phenotypic transitions in a variety of animals. Arginine vasotocin (AVT) is implicated in mediating alternative male phenotypes in teleost fish, but the direction of the association differs among species, with either higher or lower AVT related to more territorial behaviour in different fishes. To clarify the complex relationship between AVT and alternative phenotype, we evaluated AVT expression in an African cichlid in which social status is associated with divergent behaviour and physiology. We compared AVT mRNA expression between territorial and non-territorial (NT) males in both whole brains and microdissected anterior preoptic areas using transcription profiling, and in individual preoptic nuclei usingin situhybridization. These complementary methods revealed that in the posterior preoptic area (gigantocellular nucleus), territorial males exhibit higher levels of AVT expression than NT males. Conversely, in the anterior preoptic area (parvocellular nucleus), AVT expression is lower in territorial males than NT males. We further correlated AVT expression with behavioural and physiological characteristics of social status to gain insight into the divergent functions of individual AVT nuclei. Overall, our findings highlight a complex association between AVT and social behaviour.
Convergence and divergence are mostly reciprocated properties of the connections in the network of cortical areas
Authors: Négyessy László , Nepusz Tamás , Zalányi László , Bazsó Fülöp
Published: July 2008

Cognition is based on the integrated functioning of hierarchically organized cortical processing streams in a manner yet to be clarified. Because integration fundamentally depends on convergence and the complementary notion of divergence of the neuronal connections, we analysed integration by measuring the degree of convergence/divergence through the connections in the network of cortical areas. By introducing a new index, we explored the complementary convergent and divergent nature of connectional reciprocity and delineated the backward and forward cortical sub-networks for the first time. Integrative properties of the areas defined by the degree of convergence/divergence through their afferents and efferents exhibited distinctive characteristics at different levels of the cortical hierarchy. Areas previously identified as hubs exhibit information bottleneck properties. Cortical networks largely deviate from random graphs where convergence and divergence are balanced at low reciprocity level. In the cortex, which is dominated by reciprocal connections, balance appears only by further increasing the number of reciprocal connections. The results point to the decisive role of the optimal number and placement of reciprocal connections in large-scale cortical integration. Our findings also facilitate understanding of the functional interactions between the cortical areas and the information flow or its equivalents in highly recurrent natural and artificial networks.
Equilibrium Shape of Internal Cavities in Sapphire
Authors: Choi* Jung‐Hae , Kim* Doh‐Yeon , Hockey Bernard J. , Wiederhorn* Sheldon M. , Handwerker Carol A. , Blendell John E. , Carter W. Craig , Roosen Andrew R.
Published: July 2008

The equilibrium shape of internal cavities in sapphire was determined through the study of submicrometer internal cavities in single crystals. Cavities formed from indentation cracks during annealing at 1600°C. Equilibrium could be reached only for cavities that were smaller than is approximately100 nm. Excessive times were required to achieve equilibrium for cavities larger than is approximately 1μm. Five equilibrium facet planes were observed to bound the cavities: the basal (C) {0001}, rhombohedral (R) {1¯012}, prismatic (A) {12¯10}, pyramidal (P) {112¯3}, and structural rhombohedral (S) {101¯1}. The surface energies for these planes relative to the surface energy of the basal plane were γR = 1.05, γA = 1.12, γP = 1.06, γS = 1.07. These energies were compared with the most recent theoretical calculations of the surface energy of sapphire. The comparison was not within experimental scatter for any of the surfaces, with the measured relative surface energies being lower than the calculated energies. Although the prismatic (M) {101¯0} planes are predicted to be a low‐energy surface, facets of this orientation were not observed.
Polarization Dependence of the Cr3+ R‐Line Fluorescence from Sapphire and Its Application to Crystal Orientation and Piezospectroscopic Measurement
Authors: He Jun , Clarke David R.
Published: July 2008

The room‐temperature polarization characteristics of the ruby R lines have been studied by monitoring the fluorescence intensity as a function of excitation direction relative to the crystallographic axes of the ruby crystal. The R lines are strongly polarized in the basal plane but have no preferred vibration direction within the basal plane. However, the degree of polarization, P, of the R1 and R2 lines is not the same, being PR1=87% and PR2=62%. The phenomenon is explained in terms of the absorption anisotropy and the probability of spontaneous emission. The findings provide the basis for a high‐spatial‐resolution spectrophotometric method to determine the optical c‐axis of chromium‐doped Al2O3 crystals using the angular dependence of the intensity ratio of the R2 line to the R1 line. The application to the orientation determination of sapphire fibers embedded in composites and the corresponding residual stress components are discussed together with the possibility of measuring the texture in the Al2O3 polycrystalline thin films such as oxidation scales. Furthermore, the consequences of polarization orientation on piezospectroscopic measurements are discussed.
Compressive Creep and Creep Failure of 8Y2O3/3Al2O3‐Doped Hot‐Pressed Silicon Nitride
Authors: Crampon Jacques , Duclos Richard , Peni Fation , Guicciardi Stefano , de Portu Goffredo
Published: July 2008

The compressive creep properties of hot‐pressed Si3N48Y2O3—3Al2O3 (wt%) have been investigated in the temperature range of 1543–1603 K in air. The stress exponent, n, of the power creep law was determined to be 1.5, and the activation energy was determined to be 650 kJ/mol. Transmission electron microscopy observations showed that grain‐boundary sliding occurred with cavitation formation in the grain‐boundary glassy phase. The quasi‐steady‐state creep results were consistent with that of the diffusion‐controlled solution—diffusion—precipitation creep mechanism, and the distinguished failure mechanism was cavitation creep damage controlled by the viscosity of the boundary glassy phase. The compressive creep failure time, obtained at 1573 K, in the stress range of 175–300 MPa, followed the MonkmanGrant relation, indicating that cavity growth was mainly controlled by the creep response of the material.
Mullite/SiAlON/Alumina Composites by Infiltration Processing
Authors: Albano Mara P. , Scian Alberto N.
Published: July 2008

The formation of mullite/SiAlON/alumina composites was studied by infiltrating a SiAlON/alumina‐base composite with two different solutions, followed by thermal treatment. The base composite was prepared from a mixture of tabular Al2O3 grains, fume SiO2, and aluminum powders. The mixture was pressed into test bars and nitrided in a nitrogen‐gas (N2) atmosphere at 1480°C. The infiltrants were prehydrolyzed ethyl polysilicate solution and ethyl polysilicatealuminum nitrate solution. The composites were infiltrated under vacuum, cured at 100°C, and precalcined in air at 700°C. This infiltration process was repeated several times to produce bars that had been subjected to multiple infiltrations, then the bars were calcined in a N2 atmosphere at 1480°C to obtain mullite/SiAlON/alumina composites. The infiltration process increased the percentage of nitrogenous crystalline and mullite phases in the matrix; therefore, a decrease of the composite microporosity was observed. The infiltration increased the mechanical strength of the composites. Of the two composites, the one produced using prehydrolyzed ethyl polysilicate as the infiltrant had a higher mechanical strength, before and after being subjected to a severe thermal shock.
Joining of Carbon—Carbon Composites Using Boron and Titanium Disilicide Interlayers
Authors: Dadras Parviz , Ngai Thomas T. , Mehrotra Gopal M.
Published: July 2008

The feasibility of joining of 3‐D carbon—carbon (C–C) composites by using B and TiSi2 interlayers has been investigated. The optimum temperature for joining with a B interlayer was determined to be about 1995°C and that for joining with a TiSi2 interlayer was about 1490°C. The shear strengths of the joints made at these optimum temperatures were found to increase with the shear testing temperature up to a point, followed by a decrease at higher temperatures. For C–C specimens bonded at 1995°C with a B interlayer, the maximum joint shear strength (average value 18.35 MPa) was observed at the test temperature of 1660°C. The shear strength of joints produced with a TiSi2 interlayer showed a maximum at the test temperature of 1164°C, with an average value of 34.41 MPa. The B interlayers reacted with C–C composite pieces during joining, and the product of reaction was identified as B4C. In specimens joined with TiSi2 interlayers, the reaction between TiSi2 and C did not go to completion, and the bond interlayer contained TiC, SiC, and TiSi2.
Low‐Temperature Chemical Synthesis of Lanthanum Monoaluminate
Authors: Taspinar Ercan , Tas A. Cuneyt
Published: July 2008

One of the promising candidates for ferroelectric substrate materials, lanthanum monoaluminate (LaAlO3), was successfully synthesized by two separate chemical powder preparation techniques: (i) homogeneous precipitation from aqueous solutions containing urea (CH4N2O) in the presence of nitrate salts, and (ii) self‐propagating combustion synthesis from aqueous solutions containing CH4N2O and the respective nitrate salts of lanthanum and aluminum. The submicrometer, spherical‐like particles of the precursors were completely converted to pure LaAlO3 at 850C in the homogeneous precipitation route, and the same conversion temperature was observed to be 750C, which becomes the lowest temperature ever reported for the powder synthesis of a pure LaAlO3 phase. The materials were characterized by powder X‐ray diffractometry, simultaneous thermogravimetric/differential thermal analysis, scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy. Structural refinements by Rietveld analysis showed that LaAlO3 was isostructural with BaTbO3 and had the space group R‐3c, in contrast to the previously assumed space group of R‐3m for this phase. The atomic positions in the structure of LaAlO3 were refined and presented for the first time, with respect to the present space group.
In‐Situ Measurement of Emissivities of Ceramic—Polymer Composite Materials
Authors: Yang Thomas C. K. , Viswanath Dabir S.
Published: July 2008

Emissivities of high‐dielectric ceramic composites used in microelectronic packaging were measured by a modified hot‐filament ASTM method and infrared thermometry; total hemispherical emissivities were measured using the hot‐filament method, and effective band emissivities were measured using infrared thermometry. Two ceramics—5μm alumina and 2–3μm aluminum nitride—were chosen as the base of the substrate. They were blended with poly(vinyl butyral) (PVB) with proper amounts of solvents and cast on a 304‐stainless‐steel strip used as the heating filament. Emissivity measurements in the temperature range of 380–1000 K were performed using three different sets of experiments. In the first set of experiments, the emissivities of unfired polymer composites were measured in the temperature range of 380–450 K, a temperature at which thermal degradation starts to occur. In the second set, the specimens were heated overnight in a furnace at 673 K for binder burnout, and measurements were conducted on fired composites in the temperature range of 380–1000 K. In the last set, the emissivity of the specimens were measured in situ in the temperature range of 380–1000 K by condensing the degradation products using a liquid‐nitrogen cryogenic jacket on‐line before the pump line to avoid contamination of the turbomolecular pump. The system pressure was controlled below 5 × 10−5 torr (}6.7 × 10−3 Pa) in all experiments to constrain nonradiative types of heat transfer inside the bell jar.
Tape Casting of Lanthanum Chromite
Authors: Murphy Michael W. , Armstrong Timothy R. , Smith Peter A.
Published: July 2008

The effects of process additives, ball milling, and solids loading were evaluated for tape casting suspensions of glycinenitrate‐synthesized La0.7Ca0.31CrO3 powder. An optimized formulation was obtained based on rheological characterization, electrokinetic sonic amplitude measurements, qualitative examination of green tapes, and the sintered microstructure. The tape casting formulation incorporated 66:34 methyl ethyl ketone/ethyl alcohol solvent, an aliphatic phosphate ester dispersant, and 80 wt% (35 vol%) solids. The best binder/plasticizer system was 12 wt% (15 vol%) poly(isobutyl methacrylate) and 5 wt% (6.3 vol%) benzyl butyl phthalate plasticizer (binder:plasticizer = 2.3). Cast tapes were sintered at 1300°C for 2 h, producing a bulk density of 96.2% theoretical, with linear shrinkage of 22% and an approximate grain size of 1.3 μm.
30 kbar Phase Equilibria of the La2O3–SrO–CuO System at 950°C
Authors: Geny Joel , Meen James K. , Elthon Don
Published: July 2008

Phase equilibria of the La2O3–SrO–CuO system have been determined at 950°C at 30 kbar (3 GPa). Stable phases at the apexes of the ternary phase diagram are CuO, La2O3, and SrO. Stable intermediate phases are La2, CuO4 and La2Cu2O5 in the LaO1.5–CuO binary and Sr2CuO3, SrCuO2, and Sr14Cu24O41 in the CuO–SrO binary. The La2–xSrx‐CuO4–δ solid solution is stable for 0.00 is ≤x≤ 1.29, the La2–xSr1+xCu2O6+δ solid solution is stable for 0.03 ≤x≤0.20, the La2–xSrxCu2O5–δ solid solution is stable for 0.00 ≤x≤1.08, and the LaxSr14–xCu24O41 solid solution is stable for 0.00 ≤x≤ 6.15. The 30 kbar phase diagram differs from the 1 atm (0.1 MPa) and 10 kbar (1 GPa) results principally in the absence of La1–xSr2+xCu2O5.5+δ as a stable phase and the extended range of the La2–xSrxCu2O5–δ solid solution at 30 kbar.
Fracture Energy of GlassAlumina Interfaces via the Bimaterial Bend Test
Authors: Cazzato Anthony , Faber K. T.
Published: July 2008

The fracture energies of glassalumina interfaces were measured using the bimaterial bend test. These experiments comprise one of the few studies in which the bimaterial bend test has been applied to an all‐ceramic materials system. The experiment was used to evaluate the effect of materials purity, processing and environmental conditions on the interface toughness. Changes in interface fracture energy were measured as a function of glass content, interface roughness, phase angle, and testing atmosphere. Alumina glass content and testing atmosphere had the greatest effect on the interface toughness and the overall mechanical behavior of the composite. The effect of phase angle of loading on the interface fracture energy was assessed over several degrees by varying the relative heights of the two layers. The results from these interface fracture experiments offer insight into the fracture behavior of multiphase and composite ceramics where deflection of cracks at bimaterial interfaces is an important concern.
Improvement of Cutting Performance of Silicon Nitride Tool by Adherent Coating of Thick Diamond Film
Authors: Itoh Hideaki , Shimura Sadanori , Sugiyama Kazuyoshi , Iwahara Hiroyasu , Sakamoto Hiromichi
Published: July 2008

A thick diamond film was coated using two‐stage microwave plasma CVD in the COH, system on a pretreated silicon nitride substrate for a cutting tool. The effects of acid treatment and microflawing treatment of the substrate on adherence of the film and cutting performance were investigated as well as the effects of two‐stage CVD conditions. The combination of substrate pretreatment in a hot, strong acid solution of HF and HNO3 and subsequent ultrasonic microflawing pretreatment with diamond grains resulted in the anchored deposition of CVD diamond into the micropores in the silicon nitride substrate. An excellent adherence of the diamond film to the substrate was attained by the two‐stage CVD, which consists of a first CVD of fine diamond grains into the micropores and a second higher rate CVD of thick diamond film (thickness >30 pm). A dense layer composed of diamond‐like carbon and silicon nitride was formed deep in the boundary region of the substrate during long CVD treatment. Long tool life of the silicon nitride chip coated with a thick diamond film was verified by a milling test using Al‐20 wt% Si alloy as the work material.
Paralinear Oxidation of CVD SiC in Water Vapor
Authors: Opila Elizabeth J. , Hann Raiford E.
Published: July 2008

The oxidation kinetics of CVDSiC were monitored by thermogravimetric analysis (TGA) in a 50% H2O/50% O2 gas mixture flowing at 1.4 cm/s for temperatures between 1200” and 1400°C. Paralinear weight change kinetics were observed as the water vapor oxidized the SiC and simultaneously volatilized the silica scale. The long‐term degradation rate of SiC is determined by the volatility of the silica scale. Rapid SiC surface recession rates were estimated from these data for actual aircraft engine combustor conditions.
Joining of Carbon‐Carbon Composites for Thermonuclear Fusion Applications
Authors: Salvo Milena , Lemoine Patrick , Ferraris Monica , Montorsi Margherita , Merola Mario
Published: July 2008

Carbon‐fiber‐reinforced carbon (CfC) composites have been joined by using different joining agents: metals (silicon, aluminum, and titanium), an intermetallic compound (magnesium silicide, Mg2Si), and glasses (borosilicates and zinc borates). These joining agents have been chosen by considering their possible use in a thermonuclear fusion reactor, as suggested by their low‐activation properties, reasonably high working temperature, industrial feasibility, and potential scale‐up of the joined carboncarbon structures using pressureless‐processing techniques. Each joined structure (CfC composite–joining material‐CfC composite) has been first morphologically characterized by scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and X‐ray diffractometry. Then, single‐lap shear tests have been performed on the most‐promising joined structures, i.e., silicon‐ and aluminum‐joined CfC‐composite samples, which have shown an average shear strength of 22 and 10 MPa, respectively.
Sliding Wear of Al2O3–SiC–(Al,Si) Composites against a Steel Counterface
Authors: Ravikiran A. , Jayaram Vikram , Biswas Sanjay K.
Published: July 2008

The sliding‐wear behavior of Al2O3–SiC–Al composites prepared by melt oxidation against a steel counterface has been recorded in a pin‐on‐disk machine. At high speeds and pressures (10 m/s, 20 MPa), friction and wear appear to be principally controlled by the in‐situ formation of an interfacial film that consists of a layer of Fe3O4. The formation of this film is examined as a function of sliding speed, lubrication, and composite microstructure. A model is proposed in which high surface temperatures cause the preferential extrusion of aluminum from the composite onto the pin/disk interface. This promotes the adhesive pickup of iron and its oxidation to form a stable tribologically beneficial layer of Fe3O4.
Modeling the Elastic‐Plastic Deformation of Al/Al2O3 Particulate Composites
Authors: Nan Ce‐Wen , Clarke David R.
Published: July 2008

Comparison is made between experimental measurements of the elasticplastic deformation of a series of Al/Al2O3 particulate composites with a rather simple hybrid modeling method combining an effective medium approximation with the essential features of dislocation plasticity. Two different effective approximationsa simple, non‐self‐consistent and a self‐consistent effective medium approximationare employed depending on the volume fraction of particles. For a wide range of volume fractions of Al2O3 particles, there is good agreement between the full stressstrain curves measured and the predictions of the hybrid model.
Reactive Coating of Zircon on Mullite and Mullite—Alumina Substrates
Authors: Sainz Maria A. , Caballero Angel , Moya Jos S.
Published: July 2008

A stable zirconia coating of 20–30 pm thickness on a mullite substrate with a different alumina/silica ratio was obtained by reactive coating of zircon. It is shown that the Al2O3/ SiO2 ratio of the mullite substrate drastically affects the morphology of the zirconia coating. The results are explained on the basis of the Al2O3–SiO2–ZrO2 phase equilibria.
Immobilization of Sodium‐Bearing High‐Level Radioactive Waste in Synroc Containing (Na0.5Nd0.5)TiO3‐Type Perovskite
Authors: Li Liyu , Luo Shanggeng , Tang Baolong , Wang Dexi
Published: July 2008

This study on the immobilization of high‐sodium‐bearing HLW in synroc indicates that (Na0.5Nd0.5)TiO3‐type perovskite can be used to incorporate a high content of sodium in synroc. Synroc samples containing 13.0 wt% waste oxide and 5.7 wt% Na2O show very well chemical durability and physical properties. The standard Synroc‐C formulation can incorporate only 2 wt% Na2O, so this study greatly improved the immobilization ability of sodium in Synroc‐related material.
Phase Equilibria in the Ga2O3In2O3 System
Authors: Edwards Doreen D. , Folkins Pollyanna E. , Mason Thomas O.
Published: July 2008

Subsolidus phase relationships in the Ga2O3–In2O3 system were studied by X‐ray diffraction and electron probe microanalysis (EPMA) for the temperature range of 800°–1400°C. The solubility limit of In2O3 in the β‐gallia structure decreases with increasing temperature from 44.1 ± 0.5 mol% at 1000°C to 41.4 ± 0.5 mol% at 1400°C. The solubility limit of Ga2O3 in cubic In2O3 increases with temperature from 4.X ± 0.5 mol% at 1000°C to 10.0 ± 0.5 mol% at 1400°C. The previously reported transparent conducting oxide phase in the Ga‐In‐O system cannot be GaInO3, which is not stable, but is likely the In‐doped β‐Ga2O3 solid solution.
Phase Relations and Lattice Constants in the MgO‐Al2O3‐Ga2O3 System at 1550°C
Authors: Stalder Roland , Nitsch Karl‐Heinz
Published: July 2008

Phase relations and lattice constants in the MgO–Al2O3–Ga2O3 system at 1550°C have been determined experimentally. In a large part of this system, only a nonstoichiometric spinel is stable. Compositions as extreme as 12.5 mol% MgO–20.5 mol% Ga2O3–67 mol% Al2O3 for a homogeneous spinel are possible. In the bordering phase diagrams of MgO–Al2O3 and MgO–Ga2O3, the composition of the spinel is as high as 63 mol% Al2O3 or Ga2O3, respectively. The contributions of all simple ionic exchange reactions on the lattice constant of the spinel have been deduced from X‐ray diffractometry data.
Fabrication, Mechanical Properties, and Electrical Conductivity of Co3O4 Ceramics
Authors: Sakamoto Shinichi , Yoshinaka Masaru , Hirota Ken , Yamaguchi Osamu
Published: July 2008

Well‐densified Co3O4 ceramics (98.3% of theoretical) have been fabricated by the combined use of hot pressing (800°C/I h/30 MPa) and hot isostatic pressing (880°C/2 h/196 MPa). Their Vickers hardness and fracture toughness are 10.3 GPa and 4.2 MPa·m1/2, respectively. They exhibit a high electrical conductivity of 3.35 × 10′ S·cm−1 at 800°C.
Reaction‐Bonding Preparation of Si3N4/MoSi2 and Si3N4/WSi2 Composites from Elemental Powders
Authors: Zhang Bing‐Rong , Marino Francesco
Published: July 2008

Si3N4/MoSi2 and Si3N4/WSi2 composites were prepared by reaction‐bonding processes using as starting materials powder mixtures of Si‐Mo and Si‐W, respectively. A presintering step in an At‐base atmosphere was used before nitriding for the formation of MoSi2 and WSi2; the nitridation in a N2‐base atmosphere was followed after presintering with the total stepwise cycle of 1350°C × 20 h +1400°C × 20 h +1450°C × 2 h. The final phases obtained in the two different composites were Si3N4 and MoSi2 or WSi2; no free elemental Si and Mo or W were detected by X‐ray diffraction.
Powder Preparation and Sintering Characteristics of Rare‐Earth Sesquisulfide Ceramics
Authors: Vaughan‐Forster Cheryl M. , White William B.
Published: July 2008

Dense ceramics were prepared from rare‐earth sesquisulfides. Extremely fine‐grained precursor oxides were synthesized by evaporative decomposition of solutions. The sesquisulfides were synthesized by direct reaction of the oxides with flowing H2S in the presence of graphite. These reactive, fine‐grained, EDS‐derived sulfides could be sintered into ceramic compacts that achieved 92–98% of theoretical density. In comparison, the same processing conditions with 25–50 m stock powder produced ceramics with only 70–80% of theoretical density.
Oxide Superconductors
Authors: Cava Robert J.
Published: July 2008

This article briefly reviews ceramic superconductors from historical and materials perspectives. It describes the factors that distinguish high‐temperature cuprate superconductors from most electronic ceramics and places them in the context of other families of superconducting materials. Finally, it describes some of the scientific issues presently being actively pursued in the search for the mechanism for high‐temperature superconductivity and the directions of research into new superconducting ceramics in recent years.
Corrosion of Aluminum Nitride (AlN) in Aqueous Cleaning Solutions
Authors: Svedberg Lynne M. , Arndt Kenneth C. , Cima Michael J.
Published: July 2008

The corrosion of aluminum nitride (AlN) in aqueous solutions has been evaluated in situ, using an ammonium/ammonia ion‐selective electrode. The corrosion behavior of AlN over a pH range of 5.5–12 indicates that the corrosion products that are formed act as a protective barrier layer in the pH regime where they have the lowest stability. An insoluble barrier layer is formed via the oxidation of the AlN surface in air at a temperature of 750°C for 10 min. This oxynitride layer, which is 200 Å thick, prevents the corrosion of the AlN in a pH 9.5 aqueous solution; however, the thermal conductivity is reduced by 6.6%.
Mechanochemical Synthesis of 0.9[0.6Pb(Zn1/3Nb2/3)O3·0.4Pb(Mg1/3Nb2/3)O3]·0.1PbTiO3
Authors: Wan Dongmei , Xue Junmin , Wang John
Published: July 2008

Lead zinc niobate–lead magnesium niobate–lead titanate (PZN–PMN–PT) ceramic powders of perovskite structure have been prepared via a mechanochemical processing route. A single‐phase perovskite powder of ultrafine particles in the nanometer range was successfully synthesized when a MZN powder (columbite precursor) was mechanically activated for 10 h together with mixed lead and titanium oxides. The following steps are involved when the ternary oxide mixture is subjected to an increasing degree of mechanical activation. First, the starting materials are significantly refined in particle size as a result of the continuous deformation, fragmentation and then partially amorphized at the initial stage of mechanical activation. This is followed by the formation of perovskite nuclei and subsequent growth of these nuclei in the activated oxide matrix with increasing activation time. When calcined at various temperatures in the range of 500–800°C, pyrochlore phase was not detected by XRD phase analysis in the mechanochemically synthesized powder. Only a minor amount (∼2%) of pyrochlore phase was observed when the calcination temperature was raised to 850°C. The PZN–PMN–PT derived from the mechanochemically synthesized powder can be sintered to ∼98% relative density at a sintering temperature of 950°C. The PZN–PMN–PT sintered at 1100°C for 1 h exhibits a dielectric constant of ∼18 600 and a dielectric loss of 0.015 at the Curie temperature of 112°C when measured at a frequency of 0.1 kHz, together with a d33 value of 323 ×10−12 pC/N.
Reactions in Vapor‐Phase Electrolytic Deposition for Preparing Yttria‐Stabilized Zirconia Thin Films
Authors: Uchimoto Yoshiharu , Tsutsumi Kazushi , Ioroi Tsutomu , Ogumi Zempachi , Takehara Zen‐Ichiro
Published: July 2008

The process of vapor‐phase electrolytic deposition (VED) for the formation of yttria‐stabilized zirconia (YSZ) films has been studied. This technology, which is similar to the electrochemical vapor deposition (EVD) process, is based on electrolytic deposition, using a glow‐discharge plasma as the conductive medium. Radio‐frequency (rf) glow‐discharge plasma is generated in the vapor phase of a metal chloride (ZrCl4 or YCl3). A porous electrode layer, which is deposited on the stabilized zirconia layer, is connected to a dc power source. The grounded electrode, which is located in the plasma, is used as a counter electrode to complete the dc circuit. X‐ray photoemission spectroscopy and electron probe microanalysis measurements identify the deposited layer to be YSZ that contains 8 mol% of Y2O3. This layer is free from pores and cracks, within the scale of scanning electron microscopy observation. The conductivities of the YSZ films that are prepared at different current densities via the VED process are almost equal, and the conductivity values of these thin films are very similar to that of the sintered YSZ pellet. The dependence of the current efficiency on the dc current density is investigated. The current efficiency decreases as the current density increases.
Sintering of Mixtures of Seeded Boehmite and Ultrafine α‐Alumina
Authors: Kwon Seongtae , Messing Gary L.
Published: July 2008

α‐Alumina was fabricated by dry pressing mixtures of seeded boehmite and fine α‐alumina (i.e., 0.2 and 0.3 μm diameter) to reduce the large shrinkage of boehmite‐derived α‐alumina. The maximum green density was obtained with mixtures containing ∼70%α‐alumina for both alumina powders. The ∼15% linear shrinkage and microstructures of these samples were comparable to 100% alumina powder samples. Samples with 0.2 μm alumina sintered to densities >95% at 1300°C whereas 1400°C was needed for samples with 0.3 μm alumina. These results indicate that boehmite can be used as a substitute for relatively expensive ultrafine α‐alumina powders.
Sintering Characteristics in the BaTiO3–Nb2O5–Co3O4 Ternary System: II, Stability of So‐called “Core–Shell” Structure
Authors: Chazono Hirokazu , Kishi Hiroshi
Published: July 2008

The sintering characteristics and the reaction of additives with BaTiO3 (BT) were examined for two materials having Nb‐rich composition (Comp.N) and Co‐rich composition (Comp.C) to elucidate the relation between the stability of the core–shell microstructure and the Nb/Co ratio in the BT–Nb2O5–Co3O4 system. TEM observation revealed that the concentration gradient of Nb and Co existed in the shell region although Nb and Co macroscopically distributed homogeneously. X‐ray diffraction analysis showed that the shell formation preceded the densification and completed at about 1280°C for both Comp.N and Comp.C as determined from differential scanning calorimetry. A diffusion couple experiment disclosed that Co had a larger diffusivity than Nb and that the diffusion of Co was suppressed when the sample was codoped with a sufficient amount of Nb. On the basis of these experimental results, new mechanisms of the formation and collapse of core–shell structure in the BT–Nb2O5–Co3O4 system were proposed.