bluuebunny/crossref_metadata_2025 huggingface dataset:
Rapid mobilization of murine and human hematopoietic stem and progenitor cells with AMD3100, a CXCR4 antagonist
Authors: Broxmeyer Hal E. , Orschell Christie M. , Clapp D. Wade , Hangoc Giao , Cooper Scott , Plett P. Artur , Liles W. Conrad , Li Xiaxin , Graham-Evans Barbara , Campbell Timothy B. , Calandra Gary , Bridger Gary , Dale David C. , Srour Edward F.
Published: April 2005

Improving approaches for hematopoietic stem cell (HSC) and hematopoietic progenitor cell (HPC) mobilization is clinically important because increased numbers of these cells are needed for enhanced transplantation. Chemokine stromal cell derived factor-1 (also known as CXCL12) is believed to be involved in retention of HSCs and HPCs in bone marrow. AMD3100, a selective antagonist of CXCL12 that binds to its receptor, CXCR4, was evaluated in murine and human systems for mobilizing capacity, alone and in combination with granulocyte colony-stimulating factor (G-CSF). AMD3100 induced rapid mobilization of mouse and human HPCs and synergistically augmented G-CSF–induced mobilization of HPCs. AMD3100 also mobilized murine long-term repopulating (LTR) cells that engrafted primary and secondary lethally-irradiated mice, and human CD34+ cells that can repopulate nonobese diabetic-severe combined immunodeficiency (SCID) mice. AMD3100 synergized with G-CSF to mobilize murine LTR cells and human SCID repopulating cells (SRCs). Human CD34+ cells isolated after treatment with G-CSF plus AMD3100 expressed a phenotype that was characteristic of highly engrafting mouse HSCs. Synergy of AMD3100 and G-CSF in mobilization was due to enhanced numbers and perhaps other characteristics of the mobilized cells. These results support the hypothesis that the CXCL12-CXCR4 axis is involved in marrow retention of HSCs and HPCs, and demonstrate the clinical potential of AMD3100 for HSC mobilization.
IL-7 receptor signaling is necessary for stage transition in adult B cell development through up-regulation of EBF
Authors: Kikuchi Kazu , Lai Anne Y. , Hsu Chia-Lin , Kondo Motonari
Published: April 2005

Cytokine receptor signals have been suggested to stimulate cell differentiation during hemato/lymphopoiesis. Such action, however, has not been clearly demonstrated. Here, we show that adult B cell development in IL-7−/− and IL-7Rα2/− mice is arrested at the pre–pro-B cell stage due to insufficient expression of the B cell–specific transcription factor EBF and its target genes, which form a transcription factor network in determining B lineage specification. EBF expression is restored in IL-7−/− pre–pro-B cells upon IL-7 stimulation or in IL-7Rα−/− pre–pro-B cells by activation of STAT5, a major signaling molecule downstream of the IL-7R signaling pathway. Furthermore, enforced EBF expression partially rescues B cell development in IL-7Rα−/− mice. Thus, IL-7 receptor signaling is a participant in the formation of the transcription factor network during B lymphopoiesis by up-regulating EBF, allowing stage transition from the pre–pro-B to further maturational stages.
Anaphylaxis during Anesthesia in Norway
Authors: Harboe Torkel , Guttormsen Anne Berit , Irgens Aagot , Dybendal Turid , Florvaag Erik
Published: April 2005

Background

Several studies have recognized neuromuscular blocking agents as the most common cause of anaphylaxis during general anesthesia, but the reported frequencies vary considerably between countries. In Norway, the issue has raised special concern because of reports from the Norwegian Medicines Agency that suggest a high prevalence. This article presents the results from a standardized allergy follow-up examination of 83 anaphylactic reactions related to general anesthesia performed at one allergy center in Bergen, Norway.

Methods

Eighty-three cases were examined during the 6-yr period of 1996-2001. The diagnostic protocol consisted of case history, serum tryptase measurements, specific immunoassays, and skin tests.

Results

Immunoglobulin E-mediated anaphylaxis was established in 71.1% of the cases, and neuromuscular blocking agents were by far the most frequent allergen (93.2%). Suxamethonium was the most frequently involved substance, followed by rocuronium and vecuronium. The few reactions in which other allergies could be detected were mainly linked to latex (3.6%).

Conclusions

Neuromuscular blocking agents were the dominating antigens causing immunoglobulin E-mediated anaphylaxis in this study. The data could not be used for estimation of the incidence of allergy toward neuromuscular blocking agents in Norway. Larger patient samples, standardization of reporting, and diagnostic protocols should be pursued by network formation to produce data more suitable for epidemiologic research.
Influence of Hypovolemia on the Electroencephalographic Effect of Isoflurane in a Swine Model
Authors: Kurita Tadayoshi , Morita Koji , Fukuda Kazushige , Uraoka Masahiro , Takata Kotaro , Sanjo Yoshimitsu , Sato Shigehito
Published: April 2005

Background

Hypovolemia alters the effect of several intravenous anesthetics by influencing pharmacokinetics and end-organ sensitivity. The authors investigated the influence of hypovolemia on the effect of an inhalation anesthetic, isoflurane, in a swine hemorrhage model.

Methods

Eleven swine were studied. After animal preparation with inhalation of 2% isoflurane anesthesia, the inhalation concentration was decreased to 0.5% and maintained at this level for 25 min before being returned to 2% (control). After 25 min, hypovolemia was induced by removing 14 ml/kg of the initial blood volume via an arterial catheter. After a 25-min stabilization period, the inhalation concentration was decreased to 0.5%, maintained at this level for 25 min, and then returned to 2% (20% bleeding). After another 25 min, a further 7 ml/kg blood was collected, and the inhalation concentration was altered as before (30% bleeding). End-tidal isoflurane concentrations and an electroencephalogram were recorded throughout the study. Spectral edge frequency was used as a measure of the isoflurane effect, and pharmacodynamics were characterized using a sigmoidal inhibitory maximal effect model for the spectral edge frequency versus end-tidal concentration.

Results

There was no significant difference in the effect of isoflurane among the conditions used. Hypovolemia did not shift the concentration-effect relation (the effect site concentration that produced 50% of the maximal effect was 1.2 +/- 0.2% under control conditions, 1.2 +/- 0.2% with 20% bleeding, and 1.1 +/- 0.2% with 30% bleeding).

Conclusions

Hypovolemia does not alter the electroencephalographic effect of isoflurane, in contrast to several intravenous anesthetics.
Effect of Bupivacaine and Levobupivacaine on Exocytotic Norepinephrine Release from Rat Atria
Authors: Joseph Antony , Montiague Raul , Effendi Ali R. , Urbanska Renata A. , Vogel Stephen , Winnie Alon P. , Rabito Sara F.
Published: April 2005

Background

The cardiotoxic mechanism of local anesthetics may include interruption of cardiac sympathetic reflexes. The authors undertook this investigation to determine if clinically relevant concentrations of bupivacaine and levobupivacaine interfere with exocytotic norepinephrine release from cardiac sympathetic nerve endings.

Methods

Rat atria were prepared for measurements of twitch contractile force and [H]-norepinephrine release. After nerve endings were loaded with [H]-norepinephrine, the tissue was electrically stimulated in 5-min episodes during 10 10-min sampling periods. After each period, a sample of bath fluid was analyzed for radioactivity and [H]-norepinephrine release was expressed as a fraction of tissue counts. Atria were exposed to buffer alone during sampling periods 1 and 2 (S1 and S2). Control atria received saline (100 microl each, n = 6 atria) in S3-S10. Experimental groups (n = 6 per group) received either bupivacaine or levobupivacaine at concentrations (in microM) of 5 (S3-S4), 10 (S5-S6), 30 (S7-S8), and 100 (S9-S10).

Results

Bupivacaine and levobupivacaine decreased stimulation-evoked fractional [H]-norepinephrine release with inhibitory concentration 50% values of 5.1 +/- 0.5 and 6.1 +/- 1.3 microM. The inhibitory effect of both local anesthetics (approximately 70%) approached that of tetrodotoxin. Local anesthetics abolished the twitch contractions of atria with inhibitory concentration 50% values of 12.6 +/- 5.0 microM (bupivacaine) and 15.7 +/- 3.9 microM (levobupivacaine). In separate experiments, tetrodotoxin inhibited twitch contractile force by only 30%.

Conclusions

The results indicate that clinically relevant cardiotoxic concentrations of bupivacaine and levobupivacaine markedly depress cardiac sympathetic neurotransmission. A possible mechanism of local anesthetics in reducing evoked norepinephrine release from sympathetic endings is blockade of tetrodotoxin-sensitive fast sodium channels.
Intravenous versus Nebulized Ceftazidime in Ventilated Piglets with and without Experimental Bronchopneumonia
Authors: Tonnellier Marc , Ferrari Fabio , Goldstein Ivan , Sartorius Alfonso , Marquette Charles-Hugo , Rouby Jean-Jacques
Published: April 2005

Background

Lung deposition of intravenous cephalosporins is low. The lung deposition of equivalent doses of ceftazidime administered either intravenously or by ultrasonic nebulization using either nitrogen-oxygen or helium-oxygen as the carrying gas of the aerosol was compared in ventilated piglets with and without experimental bronchopneumonia.

Methods

Five piglets with noninfected lungs and 5 piglets with Pseudomonas aeruginosa experimental bronchopneumonia received 33 mg/kg ceftazidime intravenously. Ten piglets with noninfected lungs and 10 others with experimental P. aeruginosa bronchopneumonia received 50 mg/kg ceftazidime by ultrasonic nebulization. In each group, the ventilator was operated in half of the animals with a 65%/35% helium-oxygen or nitrogen-oxygen mixture. Animals were killed, and multiple lung specimens were sampled for measuring ceftazidime lung tissue concentrations by high-performance liquid chromatography.

Results

As compared with intravenous administration, nebulization of ceftazidime significantly increased lung tissue concentrations (17 +/- 13 vs. 383 +/- 84 microg/g in noninfected piglets and 10 +/- 3 vs. 129 +/- 108 microg/g in piglets with experimental bronchopneumonia; P < 0.001). The use of a 65%/35% helium-oxygen mixture induced a 33% additional increase in lung tissue concentrations in noninfected piglets (576 +/- 141 microg/g; P < 0.001) and no significant change in infected piglets (111 +/- 104 microg/g).

Conclusion

Nebulization of ceftazidime induced a 5- to 30-fold increase in lung tissue concentrations as compared with intravenous administration. Using a helium-oxygen mixture as the carrying gas of the aerosol induced a substantial additional increase in lung deposition in noninfected piglets but not in piglets with experimental bronchopneumonia.
The development of electronic journals in the United Arab Emirates University (UAEU)
Authors: Dualeh Abdulla Ali
Published: April 2005

Purpose

This case study seeks to reflect upon the short history and rapid development of electronic journals (e‐journals) at the United Arab Emirates University (UAEU). It describes the scope of the journal migration project and its impact on library operations. UAEU (with over 16,000 students) is the flagship university in the UAE, and much farther along in the transition to electronic‐only access to journal literature than most libraries in the Arab world.

Design/methodology/approach

The article begins with background information on UAE and its academic institutions, then discusses the development of e‐journals at UAEU starting with the rationale and decision to cancel print journals and move to an all‐e‐journal collection.

Findings

The author shows that e‐journals have added enormous resources to the collection, improved service, enhanced access to journal literature, increased its usage, and decreased the demand for document delivery of single articles. The author also indicates the challenges of offering e‐journals as “bundled” packages and UAEU's concern about the library's inability to remove irrelevant titles, control cost, and retain the freedom to make changes on its journal collection.

Originality/value

Since there has been little or no discussion in the library literature on the impact that the increasing use of e‐journals has on academic institutions in developing countries, this case study of the UAEU experience should be useful to others in the Gulf region and in other parts of developing countries, as well as the library community in general.
Report on the 6th International Conference on Grey Literature
Authors: Cassell Kay Ann
Published: April 2005

Purpose

To report on the 6th International Conference on Grey Literature held December 6 and 7, 2004, at the New York Academy of Medicine in New York City.

Design/methodology/approach

A summary of the main points of the conference.

Findings

Grey literature has been affected by the trends in the field of information and publishing that include more electronic information, information as a commodity and not as a public good, publishers who want more security for their information, the hypertexualization of information, the lack of infrastructures for the information community, the ability to search information, the currency of information online, and the researchability of digital information.

Originality/value

This report is of interest to library and information management professionals and those interested in how grey literature had been transformed in recent years.
The importance of marketing
Authors: Leventhal Richard C.
Published: April 2005

Purpose

To gain insight into what marketing entails and how a marketer can begin to employ the basic fundamentals in order to become more customer focused.

Design/methodology/approach

Provides guidelines to enhancing and strengthening your marketing efforts.

Findings

Posits that a more successful and innovative marketing strategy can be attained by following the guidelines outlined in this paper.

Originality/value

Helps a marketer to understand the keys to developing a more successful and innovative marketing strategy and respond to the challenges that they face.
High‐speed cameras and laser Doppler vibrometers
Authors: Connolly Christine
Published: April 2005

Purpose

To present two non‐contact methods of measuring vibrations and impact events.

Design/methodology/approach

The paper concentrates on the practical capabilities and underlying technology of commercial high‐speed CMOS cameras and laser Doppler vibrometers.

Findings

The instruments are used to analyse modes of failure and to test quality in a very wide range of products. They are also used to develop safety and protective devices, and to study natural phenomena.

Originality/value

A practical guide to the tools available, with some example applications of interest to production engineers.
Chance discovery of terahertz waveguides by US research group
Authors: Bogue Robert
Published: April 2005

Purpose

This paper describes the discovery of waveguides capable of transmitting electromagnetic radiation at terahertz (THz) frequencies. Until now this has not been possible, despite extensive research.

Design/methodology/approach

The discovery was made by a research group at Rice University whilst working on apertureless, near‐field THz microscopy. By chance, the group found that bare metal wires are capable of transmitting THz radiation to and from remote samples with virtually no dispersion and little attenuation.

Findings

This discovery allows THz waves to be taken directly to and from the source and detector and eliminates the need for objects to be positioned directly in the THz beam. It also overcomes problems associated with shock and vibration. Subsequently, the group used this phenomenon to develop the world's first prototype THz‐frequency endoscope, which was used to examine a glass flask.

Originality/value

The availability of THz waveguides will allow many new applications to be realised. A major use is expected to be security, where systems could be used for checking passengers and baggage at airports, etc. for concealed weapons, drugs and explosives. Uses in product quality control and healthcare are also anticipated.
Metallic resonant strain gauges with high overload capability
Authors: Yan T. , Jones B.E. , Rakowski R.T. , Tudor M.J. , Beeby S.P. , White N.M.
Published: April 2005

Purpose

This paper reports on a novel load cell and a novel torque transducer having stiffness and potential overload capability some ten times that of existing load cells and torque transducers based on the resistance strain gauges.

Design/methodology/approach

Describes the practical capabilities and technology – the design, construction and characterisation.

Findings

Both the load cell and the torque transducer use recently developed metallic triple beam resonators with thick‐film lead zirconate titanate (PZT) drives and pickups. The advantages of this technology are frequency output, high overload capability, high sensitivity, high resolution, and low‐cost manufacture. Both the load cell and torque transducer output large changes in frequency (>500 Hz for relatively low changes in strain level i.e. <200 microstrain for the load cell and <400 microstrain for the torque transducer), providing high sensitivity and high overload capability.

Practical implications

Load cells and torque transducers employing the new metallic resonators are expected to be far more robust than those using metallic resistance strain gauges.

Originality/value

Focuses on an instrument with important features of use in many applications.
On the design and implementation of an instrumented grinding testbed
Authors: Marsh Eric R. , Knapp Byron R.
Published: April 2005

Purpose

The need for an instrumented grinding system that addresses the requirements of ductile regime machining of brittle materials is implemented. The static and dynamic stiffness of the structural loop of the grinding system meets or exceeds those of previous researchers. An instrumented spindle is introduced which features capacitance gages embedded in the stator of an air bearing spindle.

Design/methodology/approach

The instrumented spindle is demonstrated to provide valuable force feedback for fine grinding and is capable of resolving intra‐revolution force components. Tests are performed to demonstrate the use of the instrumented spindle for ductile grinding of brittle materials with superabrasive wheels.

Findings

The results of the test show that the instrumented spindle is capable of determining intra‐revolution force components for square alumina‐titanium carbide wafers.

Originality/value

Outlines some important work developing and building instrumented spindles to aid the precision grinding industry.
Customer size and customer profitability in non‐contractual relationships
Authors: van Triest Sander
Published: April 2005

Purpose

The profitability of individual customers can show substantial variation, both in money amounts and in margins (percentages). The literature suggests that larger customers have a higher customer profitability margin: a dollar in revenue from a large customer generates more profit than a dollar in revenue from a small customer. The purpose of this paper is to explore the relationship between customer size and the customer profitability margin.

Design/methodology/approach

Draws up a model with five variables (customer size, product margin, exchange efficiency, support, customer profitability margin) and hypothesizes the relationships between the variables. Uses LISREL to test the relationships on a database from a business‐to‐business setting.

Findings

The relationship between customer size and customer profitability margin is not direct, but runs through other variables, mainly exchange efficiency. It is not the result of larger customers paying higher product margins or having fewer customer support demands.

Research limitations/implications

Adds to the empirical literature on customer profitability. Ideally, this would be done using panel data rather than the cross‐sectional data used in this paper.

Practical implications

Profitability data at the level of individual customers provide useful insights. Customer size as such is not a driver of the customer profitability margin. Identify the trade‐offs between customer size, product margins (discounts), support demands, and exchange costs that ultimately lead to customer profitability.

Originality/value

Adds to the empirical literature on customer profitability and offers practical implications for managing customer relationships.
Communal deliberation: the art of learning schools
Authors: Schechter Chen
Published: April 2005

Purpose

To illuminate the importance of the communal deliberative process, as a form of collective thinking, in overcoming the growing complexities of schoolwork in uncertain and turbulent environments.

Design/methodology/approach

Introduces the notion of deliberation as evolved from Dewey's moral theory, the essential phases and elements of deliberative activities and the principal's role in facilitating this communal process.

Findings

Provides information on the stepping‐stones towards communal deliberation, while recognizing its major impediments.

Originality/value

In light of structural restructuring efforts that have not yielded significant effects in issues of teaching and learning, this paper offers the rhetorical process of communal deliberation as a means for developing schools that learn.
Evaluation of section heads’ performance at Kuwait secondary schools
Authors: Al‐Hamdan Jasem M. , Al‐Yacoub Ali M.
Published: April 2005

Purpose

The study attempts to examine the viewpoints of those involved in evaluating the performance of section heads in Kuwait secondary schools; mainly section heads themselves, supervisors and principals. It sets out to determine the strength and weaknesses in the performance evaluation form designed for section heads.

Design/methodology/approach

A study was conducted on a sample of section heads, principals, and supervisors at secondary schools, six educational districts in Kuwait via a 15‐item questionnaire.

Findings

The sample believe that the performance evaluation form designed for the section head: enables self‐evaluation; contributes by content to the principle of self‐evaluation; encourages discipline at work by minimizing absence; enables them to develop their performance in the next semester of the study year; contributes to defining training requirement; and encourages taking training courses.

Originality/value

This study is important for several reasons. First, according to researchers, this is the first field study that examines the viewpoints of section heads, supervisors and principals collectively about the performance evaluation form designed for section heads at secondary schools in the State of Kuwait. Second, it provides recommendations and proposals for designing an evaluation form for section heads based on the outcome of a field survey and previous studies. Third, it helps lay down criteria for selecting and training section heads. Finally, it examines the viewpoints of researched participants involved in the evaluation of section heads, showing potential differences of opinion with regard to the performance evaluation form designed for section heads.
Natural monopoly privatisation under different regulatory regimes
Authors: Domney Mark D. , Wilson Heather I.M. , Chen Er
Published: April 2005

Purpose

To compare the profitability and technical efficiency of firms in a monopoly industry, airports, operating with different degrees of market power and under differing regulatory regimes, minimalist in New Zealand and interventionist in Australia.

Design/methodology/approach

Unlike previous privatisation studies, this study measures efficiency and profitability separately. Using data envelopment analysis (DEA), the technical efficiency of privatised airports is assessed, and this independent measure is used in regression analyses to determine whether efficiency, regulation or privatisation is related to airport profitability.

Findings

For firms with monopolistic characteristics operating under minimalist regulation, profitability is related to market power, not efficiency improvements. For firms operating in a regulated environment, profitability is related to regulation, which constrains market power but does not impede efficiency.

Research limitations/implications

This study is limited by its small sample size and its generalisability due to its single industry and regional focus. However, the findings support assertions that the impact of privatisation cannot be assessed independently of industry structure and regulation.

Practical implications

Policy makers considering SOE privatisation in non‐competitive markets should introduce either competition or regulation if firm efficiency is a desired outcome.

Originality/value

Academics and policy makers should be aware that privatisation and competition are not only complementary, as per the extant literature, but they are essential bedfellows. In the absence of competition, regulation is required to control for market power.
A sequence analysis of consumers’ online searches
Authors: Ylikoski Teemu
Published: April 2005

Purpose

To describe consumers’ heuristic and analytical searches for a pre‐purchase information acquisition, and to assess the correspondence of flexibility of information task and the information found with a search.

Design/methodology/approach

Propositions based on current research in web use and consumer studies. Tracked records of searches are used for descriptive analysis of transitional patterns in the data. Regression is used for statistical verification of the information provided by searches.

Findings

Consumer searches center on chaining events, indicating heavy reliance on hyperlink navigation between web sites. Formal searches are seldom used, although when employed, tend to have a high level of diagnosticity. The emphasis on heuristic behavior is logical, as the way consumer information is currently presented on the internet rewards for this type of behavior. Use of heuristic search increases the likelihood of access to flexibly presented information.

Research limitations/implications

Consumers favor heuristic trial‐and‐error searches even in focused fact‐finding search tasks, which are typically considered the domain of analytical seeking. Consumers seem to benefit most from apparently inefficient, reactive and heuristic searches, because these are more likely to provide information in a format that the consumer can adapt. Convenience sample limits generalizability of findings.

Originality/value

While there is an increasing body of knowledge concerning internet use for finding information, fewer studies have focused on consumer uses of the web in search. This paper provides new information of online consumers, an increasingly important topic.
Effects of temperature on life history variables in perch
Authors: Sandström O. , Neuman E. , Thoresson G.
Published: April 2005

Population structure, recruitment, mortality, life expectancy, age at maturity, gonad development, fecundity, net reproductive rate and energy storage were studied in a perch population exposed to thermal discharge. The experiment was conducted during 1978–1990 in an artificial enclosure at a nuclear power plant on the Baltic Sea coast. Abundance increased after the plant started operating, although the proportion of larger perch dropped to a low level. Recruitment improved, but adult mortality increased. This effect was accentuated as the fishes matured very early and at a very small size, reducing their ability to support a growing gonad in high winter temperatures. During the spawning period, condition dropped to very low levels accompanied by increased mortality. Surviving fish delayed the next spawning by one or more years and reduced their fecundity. Body condition thus improved in large perch at the end of the study period. Life‐time fecundity was reduced, and reproductive performance shifted to youner ages.
Three‐dimensional imaging of walleye pollock otoliths: reconstruction from serial sections and fluorescent laser cytometry
Authors: Bailey K. M. , Brown A. L. , Nishimura A. , Reilly M. T.
Published: April 2005

Two techniques have been developed to examine the three‐dimensional internal structure of otoliths. In the first, otoliths were sectioned serially, images were digitized, and the otolith was reconstructed as a computer model. In the second method growth increments were marked in vivo during their formation by immersing the fish in a fluorescent dye, and then the internal structure of the otolith visualized using laser cytometry. The results are useful for evaluating the potential for bias in otolith measurements and for determining the sectional plane with the least bias.
Simulation of Segregation to Free Surfaces in Cubic Oxides
Authors: Battaile Corbett C. , Najafabadi Reza , Srolovitz David J.
Published: April 2005

Segregation of isovalent solute cations to (001) and (001) free surfaces in cubic metal oxides is investigated using atomistic computer simulations. Solute concentrations are represented by a mean‐field approximation, and equilibrium distributions of solute are calculated by minimizing the free energy. Surface energy effects are found to dominate segregation behavior, even when in competition with misfit strain energy effects. Results are compared with a conventional Langmuir‐McLean (LM) analysis. The two approaches are found to agree well in certain cases, but the LM treatment fails to reproduce important phenomena revealed using the free energy method (i.e., segregation to subsurface atomic layers).
Electrically Induced Shape Changes in Hardened Cement Pastes and Porous Silica Gels: The Dynamic Nature of Gel Pore Structures during Water Transport
Authors: Yuan Lijian , Li Jie‐Fang , Viehland Dwight
Published: April 2005

Electrically induced strain studies of hardened cement pastes were performed using an inductance technique. Investigations were done as a function of electrical history, measurement frequency, moisture content, and initial water to cement ratio (w/c) during hydration. Expansive strains as large as 4.5 × 10−4 were observed under field strengths of ∼0.5 kV/cm in specimens which had been saturated with water. Both switchable and nonswitchable strains were observed under cycling with an ac electrical field. Evidence was observed that the switchable strains are due to redistribution of water within the specimen, whereas the nonswitchable strains are related to long‐range water transport toward the surface of the specimen. Investigations as a function of measurement frequency revealed a strong relaxation of the induced strain in the frequency range of 6.67 × 10−3 to 1 Hz. It is believed that ions in the diffuse double layer move under an electrical field and that water is transported by electro‐osmosis. Electrically induced strains then develop because of local swelling effects associated with a saturation gradient. Investigations as a function of w/c ratio revealed that the induced strains are related to the volume fraction of gel porosity. Electrically induced strain measurements of porous silica gels with average pore sizes of 25 and 50 Å were then performed. The characteristics of the electrically induced strains were found to be nearly identical to those for portland cement. It is believed that the characteristics of the electrically induced strains are controlled by the entry and removal of physically absorbed water within the gel pore structures.
Observation of Cell Structures Developed by Marangoni Convection in Glass Thick Films
Authors: Yamaguchi Takashi , Takada Tomoyuki
Published: April 2005

Cell structures developed by convection in glass thick films have been studied with special emphasis on the effects of material parameters and heating conditions on the cell structure. Borosilicate glass films from 10 to 30 μm thick were prepared on alumina substrates by printing and firing at temperatures between 750° and 950°C up to 2 h, and surface flow patterns were observed with an optical microscope under dark‐field illumination. In most cases a flow pattern developed and changed with time, finally reaching a steady state. Cell structures with regular polygons of four to seven sides from 15 to 150 μm across developed, depending on the glass composition. The effects of heating time, temperature, film thickness, and glass chemistry on the cell structure have been examined. From observations of cell structures, the driving force for the convection in glass thick films has been identified to be the gradient in surface tension due to small temperature fluctuations on the surface. Hence, it is concluded that the convection in glass thick films is of Marangoni type.
Measurement of Biaxial Displacement by a Speckle Correlation Method at High Temperature
Authors: Uchimura Hiroshi , Takenoshita Takeshi , Kaji Masaki
Published: April 2005

Biaxial displacement of a buttonhead tensile‐torsional specimen surface was measured by a speckle correlation method at 800°C. A high‐power argon gas laser of 488 nm wavelength and band‐pass filters were used to improve the signal/noise ratio at high temperature. In the case of displacement parallel to a specimen axis, calculated values by the speckle correlation agreed with the displacement measured with a dial gauge. For the perpendicular direction, agreement was also obtained, taking into account an additional correction. These biaxial displacements were measured in real time.
Liquid Precursor Infiltration Processing of Powder Compacts: II, Fracture Toughness and Strength
Authors: Tu Wen‐Chiang , Lange Fred F.
Published: April 2005

Si3N4 powder compacts were infiltrated with liquid precursors which produce either Zr(Y)O2 (3 mol% Y2O3) solid solution or amorphous Si3N4 after pyrolysis at relative low temperatures and without shrinkage. Results show that cracks which occur within a thin, surface layer of the precursor during pyrolysis can extend into the powder compact. As suggested by theory, this cracking phenomenon could be avoided either by making the powder compact stronger before infiltration or by removing the thin precursor layer before pyrolysis. The mechanical properties of these materials were studied as a function of residual porosity. It was observed that crack extension occurred within the second phase produced by infiltration and pyrolysis. The second phase appeared to govern the critical stress intensity factor (Kc) of the material. Kc was found to be a linear function of the change in residual, relative porosity divided by the initial, relative porosity in the powder compact. Reasonable flexural strengths (∼300 MPa) could be achieved despite considerable residual porosity.
Graded Casting: Process Control for Producing Tailored Profiles
Authors: Tuffé Stéphane , Marple Basil R.
Published: April 2005

The concept of graded casting for processing composite materials having a smooth through‐the‐thickness transition in composition is further developed and refined. An empirical model is presented that uses data from the casting of constant composition slips to predict casting rates for slips of changing composition. The model was tested by producing A12O3–ZrO2 composites having tailored composition profiles. Both linear‐ and nonlinear‐graded compositions were processed, and it was shown that the model could correctly predict the changes necessary during casting to produce the selected contours. Analysis of the composites by EDS and SEM revealed a smooth transition in composition through the thickness of sintered bodies and a relatively good distribution of the phases.
AI2O3 Coatings as Diffusion Barriers Deposited from Particulate‐Containing Sol‐Gel Solutions
Authors: Shaw Leon , Abbaschian Reza
Published: April 2005

A procedure for the formation of A12O3 coatings as diffusion barriers between ductile reinforcements (e.g., Nb and Ta) and intermetallic matrices (e.g., MoSi2 and NiAl) is described. The coating technique involved sol‐gel processing of alumina ‐forming sols with the addition of submicrometer‐sized A12O3 particles. Cracking in the coatings, a typical shortcoming of alumina sol‐gel coating, was overcome by the addition of the fine particles into the sols. The surface charge of the A12O3 particles was adjusted to be the same as the AIO(OH) colloids in the sols and electrophoresis was used to codeposit A12O3 and AIO(OH) onto the surfaces of the reinforcements. The alumina gel derived from the sols acted as binder for the alumina particles, while the particles reduced the shrinkage of the sol‐gel coatings and promoted the formation of dense coatings. The thickness of the coatings could be easily controlled without cracking and the effectiveness of the coatings as diffusion barriers was improved substantially.
Effect of Growth and Coalescence of Multisurface Cracks on Static Fatigue Behavior of Glass Ceramics
Authors: Ikeda Kiyohiko , Yoshikawa Akira , Adachi Katsushige , Kaizu Koichi , Igaki Hisashi
Published: April 2005

In order to study the effect of the interaction and coalescence of multisurface cracks on the static fatigue behavior of brittle materials such as glass and ceramics, a single crack and three collinear cracks were introduced on the surfaces of plate specimens of glass ceramics by Vickers microhardness indentation and were subjected to a constant four‐point bending load. It was found that time‐to‐failure for a certain applied stress significantly decreased with the decrease in the crack center distance of indentation cracks, and the effect of interaction and coalescence of multicracks was shown to be significant. On the basis of the crack growth parameters for a single crack, time‐to‐failure for multicracks was predicted by taking the interaction and coalescence into consideration. It was demonstrated that the proposed multicrack coalescence model gives better predictions.
Synthesis of Diamond from Carbon Disulfide in Hydrogen
Authors: Barber Greg D. , Yarbrough Walter A.
Published: April 2005

The synthesis of diamond has been accomplished from carbon disulfide (CS2) in hydrogen (H2) using tungsten hot filament chemical vapor deposition. A continuous layer was deposited on silicon and characterized using Raman spectroscopy, X‐ray diffraction (XRD), and scanning electron microscopy. The polycrystalline film exhibited a sharp Raman peak at 1331.4 cm−1 and a broad low–intensity peak at approximately 1500 cm−1. X–ray diffraction analysis showed peaks corresponding to the {111}, {220}, and {311} reflections of diamond with evidence of (110) texture. Diamond growth from CS2 in H2 was observed to be highly faceted by scanning electron microscopy.
Fine Structural Features in α‐Silicon Nitride Powder Particles and Their Implications
Authors: Wang Chong‐Min
Published: April 2005

Commercial Si3N4 powder particles have been studied with transmission electron microscopy. A vacancy type of dislocation loop is revealed to be a typical feature of as–grown α‐Si3N4 particles fabricated through the imide decomposition method. As a result of vacancy agglomeration on the (0001) plane, a stacking fault which is distinctively situated in the very middle of an individual particle with respect to the c‐axis can be seen within some particles. In combination with three other recent publications reporting dislocation loops in α‐Si3N4 but produced by different methods, it seems that dislocation loops are a common feature of as—grown α‐Si3N4 even produced by distinctively different methods. Of the most relevance to the present observation, the controversy over the structural nature of α‐Si3N4 is discussed.
Creep Behavior of a Pitch‐Based Carbon Filament
Authors: Kogure Kei , Sines George , Lavin J. Gerard
Published: April 2005

New fabrication techniques were developed for uniaxial creep specimens of high‐strength, high elastic modulus, pitch‐based, carbon filaments, with a matrix‐free test section. Experiments show that pitch‐based carbon filaments with a tensile modulus of 896 GPa can exhibit, under high stress, large creep deformation without necking. The stress exponent for the pitch‐based fibers in the Dorn equation is much lower than that for PAN‐based fibers, while the activation energy is the same. The activation energies and activation volumes determined from the experiments suggest mechanisms of creep deformation.
Strain Fields and Damage around Notches in Ceramic‐Matrix Composites
Authors: Mackin T. J. , Perry K.E. , Epstein J. S. , Cady C. , Evans A. G.
Published: April 2005

Strain development in several notched ceramic‐matrix composites (CMCs) has been monitored over a broad range of load. This was achieved by using phase‐shifting moire interferometry, which provides a map of the surface strains. A sequence of fringe patterns was used to chart the evolution of strain redistribution as a function of load. The ensuing strains were related to the micromechanical damage mechanisms. Stress concentrations were estimated from the strains by using stress/strain curves. Implications for the notch sensitivity of CMCs are discussed.
Spontaneous Infiltration of Aluminum‐Silicon Alloy into Silicon Carbide Preforms in Air
Authors: Xi Xiao Mei , Yang Xiao Feng
Published: April 2005

Fully infiltrated near‐net‐shape composites of SiC‐Al‐Si have been fabricated by dipping carbon‐containing SiC preforms into a molten Al‐40 wt% Si alloy in an open‐air environment at 1500–1600°C for 10 min. The infiltration process operates in two different modes, the reaction‐controlled and the infiltration‐controlled modes. The reaction‐controlled mode operates in the beginning of infiltration and the reaction product between Al‐Si and C is SiC, whereas the infiltration‐controlled mode operates after a certain infiltration depth has been reached, and the reaction product is dominantly Al4SiC4 elongated grains. Typically a fully infiltrated composite consists of a core (the region with Al4SiC4 elongated grain) and a shell (the region without Al4SiC4 elongated grains), and the two regions are separated by an abrupt boundary. The Al4SiC4 in the core is, however, unstable and changes to SiC when the Si concentration in the core increases above a critical value.
Theoretical Description of a Two‐dimensional Compaction Process of Cylinders
Authors: Ikegami Takayasu
Published: April 2005

Two possible two‐dimensional packing cases, one with slippery cylinders and the other with adhesive cylinders, were analyzed both experimentally and theoretically. In both cases, cylinders 10 mm in diameter and 16 mm in height were arranged inside a compaction apparatus in a random manner. The slippery cylinders were compacted to a maximum possible random closed array with little applied pressure, and virtually no further rearrangement was achieved, even by applying large additional pressure on the assembly. Compaction of the adhesive cylinders, on the other hand, occurred more gradually with applied pressure. Compaction of the cylinders resembled three‐dimensional powder compaction.
Space‐Charge‐Controlled Diffusional Creep: Volume Diffusion Case†
Authors: Jamnik Janez , Raj Rishi
Published: April 2005

The diffusive flux of atoms required in Nabarro‐Herring creep can, under certain conditions, become limited by diffusion across the space charge layer that is associated with interfaces in ionic or partly ionic materials. We derive a new equation for volume diffusional creep in such materials. Physically speaking, the creep rate is enhanced when the defect, which controls the self‐diffusivity, is accumulated, and retarded when this defect is depleted, in the space charge region. For the enhanced case the factor by which the strain rate is increased quickly reaches a limit given by 1 +4LD/d, where LD is the Debye length, and d is the grain size. In the other case the retardation factor continues to increase exponentially with the space charge potential: furthermore, the retardation is most severe when the valency of the accumulating defect, which constitutes the space charge region, is small, while the valency of the depleted defect, which controls diffusion, is large. In retardation the grain size dependence of the creep rate changes from d‐2 to d‐1.
Microstructure and Dielectric Characteristics of (PbxBa0.5−xSr0.5)TiO3 Ceramics
Authors: Ganesh Ramaratnam , Goo Edward
Published: April 2005

Microstructural and dielectric properties of the PbxBa0.5_x—Sr0.5TiO3 system have been studied. It is found that this system forms a solid solution in the entire composition range (0.0≤x≤0.5) and is cubic for the x= 0, 0.1, and 0.2 compositions and tetragonal for other compositions. Measurements of the dielectric constant as a function of temperature reveal that this material is ferroelectric at room temperature for the x > 0.2 compositions and has a broad paraelectric‐ferroelectric transition region. No shift in the dielectric maxima was noted; however, there is a slight spread in the dielectric constant with frequency for the x= 0.4 composition. A quantitative model to mathematically analyze the effect of composition fluctuations on the dielectric broadening for a ternary system is presented. Transmission electron microscopic studies reveal the presence of 90° ferroelectric domains oriented along the {01} planes for the x= 0.3 and 0.4 compositions.
Perovskite Phase Formation in the Relaxor System [Pb(Fe1/2Nb1/2)O3]1‐x–[Pb(Zn1/3Nb2/3)O3]x
Authors: Rao Radhika M. V. , Halliyal Arvind , Umarji Arun M.
Published: April 2005

Phase formation and dielectric properties of the compositions in the system [Pb(Fe1/2Nb1/2)O3]1_x–[Pb(Zn1/3Nb2/3)O3]x were investigated as possible materials for multilayer ceramic capacitors. The formation of the phase with perovskite structure and dielectric properties of ceramics at room temperature in the entire composition range are presented. The undesirable pyrochlore phase can be suppressed up to x= 0.6 by adopting calcination of B‐site oxides, followed by reaction with PbO. Compositions in the single‐phase range can be sintered at less than 1000°C.
A test for a regime shift
Authors: SOLOW ANDREW R. , BEET ANDREW R.
Published: April 2005

This note describes a formal statistical approach to testing for a regime shift based on population time series for a system of interacting species or groups. Under this approach, a regime shift is said to occur if the system switches abruptly from varying around one locally stable steady state to varying around another. This allows the problem to be formulated as testing for a changepoint in a vector autoregressive process. The test is illustrated using data from the North Sea covering the period 1963–97.