bluuebunny/crossref_metadata_2025 huggingface dataset:
The Rise and Fall of Small Worlds: Exploring the Dynamics of Social Structure
Authors: Gulati Ranjay , Sytch Maxim , Tatarynowicz Adam
Published: December 2010

This paper explores the interplay between social structure and economic action by examining some of the evolutionary dynamics of an emergent network that coalesces into a small-world system. The study highlights the small-world system's evolutionary dynamics at both the macro level of the network and the micro level of an individual actor. This dual analytical lens helps establish that, in competitive and information-intensive settings, a small-world system could be a highly dynamic structure that follows an inverted U-shaped evolutionary pattern, wherein an increase in the small-worldliness of the system is followed by its later decline as a result of three factors: (1) the recursive relationship between the evolving social structure and individual actors' formation of bridging ties, which eventually homogenizes the information space and decreases actors' propensity to form bridging ties, creating a globally separated network; (2) self-containment of the small-world network, or increasing homogenization of the social system, which makes the small world less accepting of and less attractive to new actors, thereby limiting formation of bridging ties to outside clusters; and (3) fragmentation of the small-world network, or the small-world system's inability to retain current clusters. The study uses data on interorganizational tie formation in the global computer industry in the period from 1996 to 2005 to test the hypothesized relationships.
Text Me! New Consumer Practices and Change in Organizational Fields
Authors: Ansari Shahzad (Shaz) , Phillips Nelson
Published: December 2010

While scholars have provided increasingly well-developed theoretical frameworks for understanding the role of institutional entrepreneurs and other purposeful actors in bringing about change in organizational fields, much less attention has been paid to the role of unorganized, nonstrategic actors in catalyzing change. In particular, the role of consumers remains largely uninvestigated. In this article, we draw on a case of the introduction of text messaging in the United Kingdom to explore the role of consumers in catalyzing change in organizational fields. Text messaging has become a widely diffused and institutionalized communication practice, in part changing mobile telephony from a voice-based, aural, and synchronous experience to a text-based, visual, and asynchronous experience. As consumers innovated and diffused new practices around this product, their actions led to significant changes in the field. We suggest how and under what conditions consumers are likely to innovate at the micro level and, with the subsequent involvement of other actors, catalyze change at the field level. Our primary contribution is to show how the cumulative effect of the spontaneous activities of one important and particularly dispersed and unorganized group can lead to changes in a field. By showing how change can result from the uncoordinated actions of consumers accumulating and converging over time, we provide an alternative explanation of change in organizational fields that does not privilege purposeful actors such as institutional entrepreneurs.
Putting the Teeth into the UK Biobank
Authors: Galloway John
Published: December 2010

The author of this article has been involved in the development of the UK Biobank, and was instrumental in ensuring that dentistry has been included in the project. He describes what the UK Biobank is, what the project involves and aims to achieve, and how by July 2010 some 500,000 UK citizens aged from 40–69 years had been recruited. He then details the events that led to the inclusion of dentistry in the project, the key role that stored saliva samples will have, and how the project will link to data stored by the Dental Practice Board and now the National Health Service Business Services Authority. The article ends with a brief look into the future of the project.
Dental Tooth Surface Loss and Quality of Life in University Students
Authors: Daly Blanaid , Newton J Timothy , Fares Joumana , Chiu Katherine , Ahmad Norasmatul , Shirodaria Soha , Bartlett David
Published: December 2010

Aim

To determine the relationship between toothwear into dentine and oral health-related quality of life impacts in a sample of university students not attending for dental treatment.

Methods

A cross-sectional survey of 1010 university students was undertaken. Clinical examination, including the Smith & Knight (1984) index of tooth erosion, was performed and completion of the Oral Health Impact Profile-49 (OHIP-49) measure of oral health-related quality of life was arranged.

Results

Seventy-seven per cent of the students had at least one tooth with tooth surface loss into dentine. Overall OHIP scores were similar for individuals with different levels of severity of tooth surface loss. Individuals with severe tooth surface loss were more likely to report that their appearance had been affected by, and that they had felt self-conscious because of, the condition of their mouth and teeth.

Conclusions

Tooth surface loss into dentine was prevalent among the young adults who were examined in this study. They reported that it had little impact on oral health-related quality of life at the non-clinical levels seen in this study.
Factors that Dentists use to Decide Whether or Not to Render a Patient Edentulous
Authors: Pearce Mark , Gedling Catherine , Whittle Gary , Tickle Martin , Mallinson Sara
Published: December 2010

Aims

To identify the factors that dentists use to decide whether to render a patient edentulous, prior to developing a questionnaire to investigate the factors that dentists use when making this decision.

Method

This was a qualitative study involving two groups of seven dentists practising in primary care in East Lancashire who were given scenarios involving patients of different types to facilitate discussion and identify all factors. Audio recordings were used during the focus groups and were subsequently fully transcribed. Two members of the research team independently coded the transcripts and then used thematic analysis to identify key themes.

Results

Analysis of the results identified 12 factors that the dentists considered when making a patient edentulous. These were caries, periodontal disease, position of the teeth, aesthetics, bone support, the transition from partial dentures, patient motivation, medicolegal issues, age of the patient, patient choice, cost of treatment, and the dentist's attitude and skills.

Conclusion

The dentists identified a large number of factors that they might consider before making a patient edentulous. There was a consensus that the change should be made gradually, if possible.
Tagging by Lobster Fishermen to Estimate Abundance of the Discarded Portions of Their Catch
Authors: Miller Robert J.
Published: December 2010

The cost of tagging studies can be greatly reduced if fishermen tag, release, and recapture during fishing operations. Some population components captured during fishing can not be legally retained. If these components are returned to the sea unharmed, their abundance can be estimated. Lobster tag, release, and recapture data were obtained by fishermen during their fishing activities over a 9-week season. Tags were inexpensive and easy to apply to cable ties. Abundance of ovigerous females and window females (non-ovigerous females, 114–124 mm carapace length) were estimated for seven and three fishing grounds respectively. When lobster fecundity was included in the calculations, annual egg production was also estimated. Fishery management applications include measuring the benefits of a regulation, and setting reference points to the numerical abundance of a life history stage. Experimental and area-specific management are more affordable if fishermen can collect data for stock assessment during their fishing operations. Data quality depends on carefully communicating the purpose and procedures to fishermen, and on designing a data sheet to reduce recording errors.

Resumen

el costo de los estudios de marcado puede reducirse sustancialmente si los pescadores mismos marcan, liberan y recapturan a los animales durante las operaciones de pesca. Algunos componentes poblacionales que son capturados durante las faenas no pueden ser retenidos legalmente. Si estos componentes se regresan intactos al mar, entonces es posible estimar su abundancia. Los datos de marcado, liberación y recaptura de langosta fueron tomados por los pescadores durante las actividades de pesca a lo largo de una temporada de nueve semanas. Las marcas fueron poco costosas y fáciles de aplicar. Se estimó la abundancia de hembras ovígeras y no ovígeras (éstas últimas con longitudes de carapacho de 114 mm a 124 mm) para siete y tres zonas de pesca, respectivamente. Cuando la fecundidad de las langostas fue incluida en los cálculos, también se estimó la producción anual de huevos. Las aplicaciones para el manejo pesquero incluyeron la medición de los beneficios de una regulación y el establecimiento de puntos de referencia para la abundancia numérica de los estadios de vida. El manejo experimental y por áreas es más costeable si los pescadores, durante las operaciones de pesca, pueden colectar datos útiles para la evaluación de los stocks. La calidad de los datos depende de que a los pescadores se les comunique cuidadosamente el propósito y procedimiento que implica el estudio así como del diseñ una hoja de captura que reduzca el error en los registros.
Efficiency Measurement of Housing Sector in Iran
Authors: Sepehrdoust Hamid
Published: December 2010

The present research provides a critical review of the housing industry efficiency and its future in Iran. Data Envelopment Analysis (DEA) is used to evaluate housing industry performance in different states based on the relevant data collected from Statistical Centres of Iran during 2006-2009. The research found that only 30 percent of the states operate as technically efficient and the average efficiency score obtained by all states is 0.90. Most of the technically efficient states have the opportunity to employ illegally migrated workers of neighboring countries in building construction activities using the advantages of lower level of payments and less commitment to the worker's insurance regulations in the country. Providing subsidy assistance to disadvantaged states and stimulating legal employment of building workers will supplement the government in finding a solution to the current housing problem.
Cardiovascular risk factors affect hippocampal microvasculature in early AD
Authors: Schwartz Elizabeth , Wicinski Bridget , Schmeidler James , Haroutunian Vahram , Hof Patrick
Published: December 2010

There is growing clinical and neuropathologic evidence suggesting that cognitive decline in early Alzheimer’s disease (AD) is aggravated by a synergistic relationship between AD and cerebrovascular disease associated with cardiovascular risk factors such as diabetes and hypertension. Here we used the stereologic “Space Balls” method to investigate the relationships between AD pathology and cardiovascular risk factors in postmortem human brains of patients with hypertension and diabetes in two groups — one consisting of cases with AD diagnosis and one of cases without. Hippocampal CA1 and CA3 microvasculature length density estimates were generated to characterize quantitatively the contribution of cardiovascular risk factors to the severity of neuropathologic changes. Our main finding is that the mean and variance of length density values in the AD group were significantly increased from the non-AD group, regardless of the absence or presence of a cardiovascular risk factor. An additional finding is that in the AD group without a risk factor, dementia severity correlated with amount of length density change in the CA1 field—this correlation did not exist in the AD groups with risk factors. Our findings suggest a role for cardiovascular risk factors in quantifiable change of hippocampal CA1 field microvasculature, as well as suggest a possible role of cardiovascular risk factors in altering microvasculature pathology in the presence of AD.
A note on the sea-horse in the human brain
Authors: Judaš Miloš , Pletikos Mihovil
Published: December 2010

It is commonly believed that the term hippocampus represents a shining example of inappropriate and fanciful anatomical naming, because this brain structure supposedly does not display any resemblance, striking or remote, to the little sea-horse fish known as hippocampus. The aim of this short historical notice is to demonstrate that, in fact, the hippocampus looks very much like the little sea-horse fish, as demonstrated by Gustav Retzius more than a century ago. However, to note this striking resemblance, one has to apply a proper method of anatomical dissection.
Impacts of Gasoline Prices on New Jersey Transit Ridership
Authors: Yanmaz-Tuzel Ozlem , Ozbay Kaan
Published: December 2010

This study analyzes the impacts of changes in gasoline prices on New Jersey Transit facility ridership on the basis of observed ridership data between 1980 and 2008. Two separate gasoline price increases are considered: (a) summer 2005 because of Hurricane Katrina and (b) spring 2008 because of oil price increases. New Jersey has been among the nation's leaders in transit investment, with ridership growth that exceeds the national average. Thus, investigating transit ridership trends in the New Jersey area is crucial. To understand the ridership behavior in New Jersey, after controlling for seasonal fluctuation and economic growth factors, cross-elasticity values with respect to gasoline prices are calculated with time-series regression models. Estimation results show that several months elapse before travelers respond to gasoline price changes. Moreover, correlations between transit ridership and employment rate, transit fare, and service rate are statistically significant. Cross-elasticity values with respect to gasoline prices are quite low and range from 0.12 to 0.22 in the short term and from 0.028 to 0.176 in the medium term. The findings of this study are important from an empirical point of view because they are based on real data that contain rarely found significant fluctuations in gas prices along with employment rate and give an opportunity to test the effect of these two factors on transit ridership. These results are also important from an application perspective because transit agencies can use them to make better decisions about transportation system investments, pricing, and deployment of new transit services.
Quantifying the Benefits: Application of Customer Loyalty Modeling in Public Transportation Context
Authors: Minser Jason , Webb Valerie
Published: December 2010

This paper provides a demonstration of potential applications of customer loyalty modeling in the public transportation industry. Customer loyalty modeling investigates the cumulative effects of influencing factors on customers’ tendencies to choose one service or product over another for a particular need. Industries, such as airlines and telecommunications, model customer loyalty extensively to better understand and improve customer retention. A review of the literature returned only one direct application of this approach in the public transportation industry. The influencing factors of public transportation customer loyalty are explored with the use of structural equation modeling and other empirical tests to demonstrate the appropriateness of this application. A comprehensive set of hypotheses explores the relationships between public image, problem experience, service quality, service value, customer satisfaction, and customer loyalty. Initial findings suggest that service quality and customer satisfaction positively and directly influence customer loyalty. In addition, public image and problem experience exert a stronger influence on service quality, customer satisfaction, and service value than initially predicted. Recommendations and managerial implications based on experiences and challenges during the research are offered for this technique.
Operationalizing Place Making in a Choice Experiment Context
Authors: Yannes Craig D. , Lownes Nicholas E. , Garrick Norman W. , Johnston Robert J.
Published: December 2010

The ability to interpret and understand public perception of public transit and the built environment that it can create is imperative to the creation of a successful transit system. This research uses stated preference choice surveys in a hypothetical bond referendum to investigate public response to transit systems with particular service and place-making attributes. The survey asks each participant to compare and choose one of two new transit service options or a “none of the above” option. The options are described by six attributes: service type, stop environment, travel time, fare, comfort, and the corresponding increase in taxes. Fitting a conditional logit model to these data allows the quantitative comparison of transit system configurations to ascertain the public's willingness to pay for the specific attributes. This study finds that people place a significant value on the quality of public spaces created by public transit, captured here through the use of digitally rendered built environments that capture several aspects of good public spaces: wide sidewalks, narrow streets, greenery, reduced building setbacks, multistory development, and human activity.
Insight into a Novel p53 Single Point Mutation (G389E) by Molecular Dynamics Simulations
Authors: Pirolli Davide , Carelli Alinovi Cristiana , Capoluongo Ettore , Satta Maria Antonia , Concolino Paola , Giardina Bruno , De Rosa Maria Cristina
Published: December 2010

The majority of inactivating mutations of p53 reside in the central core DNA binding domain of the protein. In this computational study, we investigated the structural effects of a novel p53 mutation (G389E), identified in a patient with congenital adrenal hyperplasia, which is located within the extreme C-terminal domain (CTD) of p53, an unstructured, flexible region (residues 367–393) of major importance for the regulation of the protein. Based on the three-dimensional structure of a carboxyl-terminal peptide of p53 in complex with the S100B protein, which is involved in regulation of the tumor suppressor activity, a model of wild type (WT) and mutant extreme CTD was developed by molecular modeling and molecular dynamics simulation. It was found that the G389E amino acid replacement has negligible effects on free p53 in solution whereas it significantly affects the interactions of p53 with the S100B protein. The results suggest that the observed mutation may interfere with p53 transcription activation and provide useful information for site-directed mutagenesis experiments.
Targeting Cell Entry of Enveloped Viruses as an Antiviral Strategy
Authors: Teissier Elodie , Penin François , Pécheur Eve-Isabelle
Published: December 2010

The entry of enveloped viruses into their host cells involves several successive steps, each one being amenable to therapeutic intervention. Entry inhibitors act by targeting viral and/or cellular components, through either the inhibition of protein-protein interactions within the viral envelope proteins or between viral proteins and host cell receptors, or through the inhibition of protein-lipid interactions. Interestingly, inhibitors that concentrate into/onto the membrane in order to target a protein involved in the entry process, such as arbidol or peptide inhibitors of the human immunodeficiency virus (HIV), could allow the use of doses compatible with therapeutic requirements. The efficacy of these drugs validates entry as a point of intervention in viral life cycles. Strategies based upon small molecule antiviral agents, peptides, proteins or nucleic acids, would most likely prove efficient in multidrug combinations, in order to inhibit several steps of virus life cycle and prevent disease progression.
Relationship between Oversulfation and Conformation of Low and High Molecular Weight Fucoidans and Evaluation of Their in Vitro Anticancer Activity
Authors: Cho Myoung Lae , Lee Boo-Yong , You Sang Guan
Published: December 2010

Low and high molecular weight fucoidans (F5-30K and F>30K) were chemically modified through the addition of sulfate groups, and the effect of oversulfation on the in vitro anticancer activity was investigated. After the addition of sulfate groups, a considerable increase of 35.5 to 56.8% was observed in the sulfate content of the F5-30K fraction, while the sulfate content of the F>30K fraction increased to a lesser extent (from 31.7 to 41.2%). Significant differences in anticancer activity were observed between the oversulfated F5–30K and F>30K fractions, with activities of 37.3–68.0% and 20.6–35.8%, respectively. This variation in the anticancer activity of oversulfated fucoidan derivatives was likely due to differences in their sulfate content. The results suggest that the molecular conformation of these molecules is closely related to the extent of sulfation in the fucan backbones and that the sulfates are preferably substituted when the fucoidan polymers are in a loose molecular conformation.
On-Demand Information Retrieval in Sensor Networks with Localised Query and Energy-Balanced Data Collection
Authors: Teng Rui , Zhang Bing
Published: December 2010

On-demand information retrieval enables users to query and collect up-to-date sensing information from sensor nodes. Since high energy efficiency is required in a sensor network, it is desirable to disseminate query messages with small traffic overhead and to collect sensing data with low energy consumption. However, on-demand query messages are generally forwarded to sensor nodes in network-wide broadcasts, which create large traffic overhead. In addition, since on-demand information retrieval may introduce intermittent and spatial data collections, the construction and maintenance of conventional aggregation structures such as clusters and chains will be at high cost. In this paper, we propose an on-demand information retrieval approach that exploits the name resolution of data queries according to the attribute and location of each sensor node. The proposed approach localises each query dissemination and enable localised data collection with maximised aggregation. To illustrate the effectiveness of the proposed approach, an analytical model that describes the criteria of sink proxy selection is provided. The evaluation results reveal that the proposed scheme significantly reduces energy consumption and improves the balance of energy consumption among sensor nodes by alleviating heavy traffic near the sink.
Spatially Explicit Analysis of Water Footprints in the UK
Authors: Feng Kuishuang , Hubacek Klaus , Minx Jan , Siu Yim Ling , Chapagain Ashok , Yu Yang , Guan Dabo , Barrett John
Published: December 2010

The Water Footprint, as an indicator of water consumption has become increasingly popular for analyzing environmental issues associated with the use of water resources in the global supply chain of consumer goods. This is particularly relevant for countries like the UK, which increasingly rely on products produced elsewhere in the world and thus impose pressures on foreign water resources. Existing studies calculating water footprints are mostly based on process analysis, and results are mainly available at the national level. The current paper assesses the domestic and foreign water requirements for UK final consumption by applying an environmentally extended multi-regional input-output model in combination with geo-demographic consumer segmentation data. This approach allows us to calculate water footprints (both direct and indirect) for different products as well as different geographies within the UK. We distinguished between production and consumption footprints where the former is the total water consumed from the UK domestic water resources by the production activities in the UK and the latter is the total water consumed from both domestic and global water resources to satisfy the UK domestic final consumption. The results show that the production water footprint is 439 m3/cap/year, 85% of which is for the final consumption in the UK itself. The average consumption water footprint of the UK is more than three times bigger than the UK production water footprint in 2006. About half of the UK consumption water footprints were associated with imports from Non-OECD countries (many of which are water-scarce), while around 19% were from EU-OECD countries, and only 3% from Non-EU-OECD countries. We find that the water footprint differs considerably across sub-national geographies in the UK, and the differences are as big as 273 m3/cap/year for the internal water footprint and 802 m3/cap/year for the external water footprint. Our results suggest that this is mainly explained by differences in the average income level across the UK. We argue that the information provided by our model at different spatial scales can be very useful for informing integrated water supply and demand side management.
Child Soldiery as a Tool of Modern Warfare (?): the Role of Child Soldiers in New Wars Causes and Consequences
Authors: Szijj Dóra
Published: December 2010

The hardly-known but regrettably prevalent phenomenon of child soldiery, which can be considered as a new development of modern warfare, might affect approximately 250,000 - 300,000 children worldwide. According to the estimates, 40% of our planet's armed forces or armed groups deploy "child combatants" for different tasks, while the international community is still struggling against this form of the abuse of children. The global nature of child soldiery raises many questions in many fields, because it has deep political, social, economic, military, environmental, ethnic and religious etc. roots and far reaching consequences in the so-called Third World. Moreover, if we focus on the African peacekeeping missions of the European Union, child soldiery might also have indirect impacts on the European community. The aim of this study is to offer a comprehensive approach in connection with child soldiery, and pointing out the links between the post-colonial conflicts and this form of human rights breaches.
High Temperature Wear of Ti3AlC2 Sliding against Al2O3
Authors: Jiang Feng , Ren Shu Fang , Meng Jun Hu , Lu Jin Jun
Published: December 2010

Bulk Ti3AlC2 was prepared via hot pressing TiC, Ti and Al powders in vacuum. The sliding wear of Ti3AlC2 against Al2O3 at room temperature up to 800°C was investigated on a SRV-IV oscillating friction and wear tester. Reduced wear and wear transition of Ti3AlC2/Al2O3 tribo-couple were found by increasing temperature. The worn surfaces of both Ti3AlC2 and Al2O3 were analyzed by scanning electron microscope and X-ray photoelectron spectrometer. It was found that the severe wear of Ti3AlC2 and Al2O3 from room temperature to 200°C was related to mechanical wear, i.e. grain fracture and pullout of Ti3AlC2. At temperature higher than 400°C, the tribo-oxidation layer on the worn surface of Ti3AlC2 containing TiO2 and Al2O3 was beneficial for reducing wear of both Ti3AlC2 and Al2O3.
Formation Mechanism of SrBi2Nb2O9 Prepared by Melting Salt Method
Authors: Li Bao Rang , Liu Xing Tao , Zheng Yang Sheng , Chang Hui Bin
Published: December 2010

In this paper SrBi2Nb2O9 was prepared by molten salt synthesis method and KCl chosen as molten medium. In order to disclose possible formation mechanism of SrBi2Nb2O9, a simple route was established for comparison by dividing the starting precursors into four groups. With the help of XRD, possible synthesis route was analyzed. The results showed that pure SrBi2Nb2O9 powders could be obtained at temperature higher than 700oC by molten salt synthesis. Intense synthesis reaction happened in the temperature range from 500 to 700oC. The reaction mechanisms of SrBi2Nb2O9 included four steps, namely the formation of 1) SrBi2O4 at close to 600oC,2) BiNbO4 from the reaction of at 600-700 oC, 3) SrBi2Nb2O9 from the reaction of SrBi2O4 and Nb2O5 and 4)SrBi2Nb2O9 from the reaction of BiNbO4 and SrCO3. The molten salt could improve distribution and reactivity of the precursors and significant formation of SrBi2Nb2O9.
DEM Simulation of Machining Damage in SiC Pre-Stressing Cutting Process
Authors: Jiang Sheng Qiang , Tan Yuan Qiang , Zhang Gao Feng , Yang Dong Min
Published: December 2010

Based on the theory of metal pre-stressing machining, the method of pre-stressing suitable for ceramic materials machining was presented. Using the cluster method, the discrete element method (DEM) model of ceramic materials machining was established. The DEM simulations of cutting process of SiC ceramic under different machining parameters were carried out by orthogonal test design method, and the effects of machining parameters on the number of surface cracks and maximum crack depth after processing were also analyzed. The results showed that the tool edge radius influenced greatly on the number of surface cracks, while the pre-stress influenced greatly on the maximum crack depth.
Binding Performance of a Zirconia Framework Material and Veneering Porcelain
Authors: Shao Long Quan , Deng Bin , Yi Yuan Fu , Liu Qi , Zhang Wei Wei , Wen Ning
Published: December 2010

In this study, the binding performance of a Cercon-based zirconia framework material and special Cercon Ceram S zirconia veneering porcelain is discussed. Rectangular 30 mm × 20 mm × 2 mm porcelain blocks were made from zirconia using the CAD/CAM system. The 2 mm veneering porcelain was then sintered onto blocks at a temperature of 850-800°C with a loading speed of l mm/min. The shear bond strength of the interface was tested. Sintering was studied by visual observation, scanning electron microscopy, energy dispersive spectroscopy (EDS), thermal shock test and other methods. Excellent sintering results of the zirconia framework material and veneering porcelain can be achieved. The cross-sectional morphology of the samples, observed by SEM, shows a uniform, fine, and smooth texture for the veneering porcelain, whereas that of the zirconia framework material shows a rough surface with a uniform and compact texture. EDS results indicate that a small amount of A12O3 and SiO2 is present in the zirconia area, and no ZrO2 or Y2O3 is detected in the veneering porcelain area. No interlayer radial crack or flaw is found throughout the entire thermal shock test of the samples at 60-240°C. Thus, the cracking temperature of the samples is pegged at T>240°C. The shear bond strength of the interface is 32.62±5.77 MPa. Chemical element infiltration exists between zirconia and the veneering porcelain, indicating the chemical bond between the two. An excellent match between the Cercon-based zirconia framework and the special veneering porcelain can be achieved, which can satisfy clinical requirements.
Fabrication of Silicon Nitride Ceramics with Magnesium Silicon Nitride and Yttrium Oxide as Sintering Additives
Authors: Jiang Guo Jian , Xu Jia Yue , Shen Hui , Zhang Yan , Peng Gui Hua , Zhuang Han Rui , Li Wen Lan , Xu Su Ying , Mao Yong Jun
Published: December 2010

Si3N4 ceramics have been fabricated through pressureless sintering and hot-pressing sintering with MgSiN2-Y2O3 or only MgSiN2 as sintering additive, respectively. The effects of MgSiN2 and Y2O3 and sintering methods on sintering properties of Si3N4 ceramics were studied. The results indicate that the bend strength of Si3N4 ceramic with 5.6wt.%MgSiN2-15.8wt.%Y2O3 sintered at 1820°C for 4h could achieve 839MPa. The bend strength of Si3N4 ceramic with 4.76wt.%MgSiN2 produced by hot-pressing sintering at 1750°C for 1h under uniaxial pressure of 20MPa is 1149MPa. The thermal conductivity of the Si3N4 ceramic was 92Wm-1K-1 and could remarkably increase to 129Wm-1K-1 by prolonging the sintering time from 1 h to 12 h. The present work demonstrated that MgSiN2 additives and hot-pressing sintering were effective to improve the thermal conductivity of Si3N4 ceramic.
Structure and Luminescence Characteristics of Yttrium Hydroxide Nanosheets Doped with Eu3+
Authors: Zhang Lin , Jiang Dan Yu , Liu Zhan Lian , Li Qiang
Published: December 2010

Eu3+ doped yttrium hydroxide nanosheets were successfully synthesized from layer compound of Y2(OH)5NO3 doped by Eu3+. Firstly layer compound of Y2(OH)5NO3 doped by Eu3+ was obtained by hydrothermal reaction. After ion exchange reaction with SDS, the layer space became lager. Furthermore stable nanosheet sol was prepared after exfoliation. The structure of layer compound and nanosheets were determined by XRD, TEM. The luminescence properties of yttrium hydroxide nanosheets doped with Eu3+ were examined; the relationship between structure and spectra was discussed.
Structural and Optical Properties of 6H-SiC Helium and Oxygen Implanted at 700 K
Authors: Zhang Hong Hua , Gao Wei Min , Shen Y.L. , Li B.S.
Published: December 2010

Raman scattering spectroscopy, ultraviolet and visible absorption spectroscopy and Rutherford backscattering spectrometry were employed to analyze the annealing behavior of defects and the optimistic effect of cavities to oxygen. It was found that the cavities had strong getting effect to oxygen and captured its neighboring implanted oxygen atom, and enhanced the formation of SixOy compound, thus helped shaping the buried oxide in a well defined region. In addition, it also minished the damage level in lattice. The interface between damage layer and crystalline layer was estimated to be 198 nm below surface of 6H-SiC. The implanted oxygen was pegged in the compressed and serried cavity layer, making the amorphous layer narrower than that of reference samples
Microwave Hydrothermal Preparation of Uniform Nanocrystalline Anatase
Authors: Chen Zhi Qin , Zeng Wei Jun , Li Wen Kui , Zhou Ze Hua , Yu Hong Ying
Published: December 2010

The synthesis of nanocrystalline pure anatase at low temperature and short time is not an easy achievement, as the synthetic processes generally lead to amorphous, moreover some processes normally require harsh reaction. Uniform nanocrystalline pure anatase has been obtained using tetrabutyl titanate and normal butyl alcohol under microwave irradiation condition at low temperature 120 °C for 3 h. This process simplication will lower production cost and make continuous process possible. It was revealed that the as-synthesized TiO2 products without any heat treatment were uniformly dispersed and granulous single-phase anatase, with the average grain size of 10 nm, by means of XRD and TEM.
Preparation and Properties of 3Y-TZP Ceramic Tools
Authors: Chen Zhi Wei , Feng Liu , Niu Jin Ye
Published: December 2010

Fully densitified 3Y-TZP (>98% of theoretical density) ceramic tools have been prepared by gelcasting and sintered with conventional pressureless at 1500 ~ 1600°C. The microstructure and mechanical properties as a function of sintering temperature were investigated. The experiment results indicate that the samples with a range of grain size from 300nm to700nm have high mechanical properties. With the sintering temperature rising, the hardness show no obvious change, the average value is 13.2GPa; while the bending strength have a trend of first increasing then decreasing. The optimal sintering temperature is 1550°C, the bending strength and the fracture toughness all reach the maximum, which is 947 MPa and 8.9MPa.M1/2.
Influences of Argon Atmosphere on Ceramic Coatings on Ti Alloy by Micro-Arc Oxidation in Na2SiO3 Solutions
Authors: Zhang Jin Xue , Hao Guo Dong , Ji Jin Li
Published: December 2010

Ceramic coatings with the main crystalline of TiO2 were prepared on Ti-6Al-4V alloy by pulsed bi-polar Micro-arc Oxidation (MAO) in Na2SiO3 solution. The coated samples were calcined in argon under 1000oC. The phase composition, morphology and element content of the ceramic coatings were investigated by XRD, SEM and EDS. The results showed that the main components of the coatings are TiO2 and amorphous substances, after oxidation in argon, SiO2 was crystalized in coating. The content of elements in the coatings both changed a little.
Fabrication and Microstructure of the Fe3Al/Al2O3 Composites by Pressureless Sintering
Authors: Jiang Tao , Pan Ke Wei
Published: December 2010

Fe3Al/Al2O3 composites were fabricated by pressureless sintering in this research. Fe3Al intermetallics compounds powders were fabricated by mechanical alloying and heat treatment. The Fe3Al powders and Al2O3 powders were mixed together, then the Fe3Al/Al2O3 composites were fabricated by pressureless sintering process at 1700oC for 2h. The phase composition and microstructure of the Fe3Al intermetallics compounds powders and the phase composition and microstructure of the sintered Fe3Al/Al2O3 composites were investigated. The XRD patterns results showed that the Fe-Al intermetallics compounds powders were prepared by mechanical alloying for 60h, and the Fe-Al intermetallics compounds powders transformed into Fe3Al intermetallics compounds powders after heat treatment at 800oC and 1000oC. The XRD patterns results showed that there existed Fe3Al phase and Al2O3 phase in the sintered composites. The microstructure showed that the mean particles size of the Fe3Al intermetallics compounds powders produced by mechanical alloying and heat treatment was rather fine and about 2-3μm. The sintered Fe3Al/Al2O3 composites exhibited homogenous and compact microstructure, the Fe3Al particles were homogenously distributed in the Al2O3 matrix. The mean particles size of Fe3Al was about 3-5μm. The sintered Fe3Al/Al2O3 composites exhibited more homogenous and compact microstructure with the increase of Fe3Al content in the Al2O3 matrix.
Pyramid Shaped Pyrolysis Flame Catalyst Synthesis of Carbon Nanotubes
Authors: Ding Zhao Yong , Sun Bao Min , Liu Yuan Chao , Xu Bing Hao , Guo Yong Hong
Published: December 2010

Pyramid sharped pyrolysis flame is a new method for carbon nanotubes synthesis. Oxy-acetylene flame outside the frustum of pyramid sharped reactor provides the necessary high temperature environment, while CO is used as the source of carbon, iron pentacarbonyl (Fe(CO)5) as the source of catalyst precursor in reactor. Inside, the mixture of CO, H2, and Fe(CO)5 will burn incompletely after initial reaction under high temperature. Immerging a sampling substrate into the incomplete burning flame can gain carbon nanotubes. Field emission scanning electron microscope and High resolution transmission electron microscopy were used to illustrate the results of experimental. By adjusting the distance between the oxy-acetylene flame jet and the synthesis zone, the purpose that only changing one factor of synthesis or pyrolysis temperature while the other one constant was achieved, then respectively studied the effects of them on experimental. The best synthesis temperature in experimental is about 590°C and pyrolysis temperature is about 1000°C. Effects of sampling time were also studied. 300s is economic for carbon nanotubes synthesis. Synthesis process of carbon nanotubes was discussed starting from the sampling time. The first 60s is the time for the temperature rise of sampling substrate. After the decalescence and thermal dissipation of substrate is balance, the temperature of substrate is fixed, and the main synthesis phase of carbon nanotubes begin.
Characterization of Ultrafine Glassy Powder for Al-Si-Ca-P-O-F Polynary System by Liquid Precipitation
Authors: Yuan G.C. , Wu Q.G. , Zeng Guo Xun , Ling Z.Y.
Published: December 2010

The ultrafine glassy powder of Al-Si-Ca-P-O-F polynary system was prepared by liquid precipitation method with several inorganic compounds as reactants containing the ions such as Al3+, SiO32-, P3O105-, Ca2+, F-, respectively. The powder was heat-treated in the range of temperature from 773 to 1173K and its crystallized processes were ascertained. The morphology, composition, bonding state and structure, crystallized behavior of the glassy powder were characterized by means of TEM, XRD, EDAX, IR, DSC etc methods. The results show that the powder containing Al, Si, Ca, P, O, F elements belongs to typical amorphous state, and the particles appeared hollow and near spherical morphology with the size from 30 to 70nm. The hollow particles collapsed as plate like conglutination state and a series of crystallized phases CaF2, Al2SiO5, Ca2SiO4, and Ca3(PO4)2 were separated sequentially during heat treatment in the range of temperature above. The characteristics of the glassy powder are similar to those of popular melting-quenched glass of the system. The network structure of the glass was mainly formed by the tetrahedrons of [SiO4], [AlO4] and [PO4], which were linked by the oxygen atoms of the angle in the tetrahedrons.
A New Type of Colored Alumina/Glass Composite Biological Safety Assessment - Oral Mucous Membrane Irritation and Skin Sensitivity Tests
Authors: Lu Huai Xiu , Deng Bin , Shao Long Quan , Yi Yuan Fu , Liu Jie , Zhang Wei Wei , Wen Ning
Published: December 2010

Objective: to describe and demonstrate an oral mucosa irritation and a skin sensitivity test for evaluation of the biological safety of a colored alumina/glass composite (AGC). Methods: colored alumina/glass composite and control materials were sutured to mucine bilateral cheek pouch mucosa, in a position for gross observation and for histological and cytological examination; skin irritation activity of the composite was tested by intradermal injection of a guinea pig test solution, by inducing, enhancing, and stimulating the allergic response observed after local tissue exposure. Results: colored AGC in mouse cheek pouch mucosa stimulated the same reaction as the control, with no significant inflammatory reaction or infiltration of inflammatory cells. Guinea pigs showed no obvious erythema or edema from the irritation test, such that the assessment of colored AGC skin allergy response in mice was 0%. Conclusion: colored AGC was benign towards mouse oral mucosa and elicited no allergic skin inflammation response, indicating that in these aspects this material had good biological safety.
Determination of SiO2 Content in Boron-Containing Silica Refractories by Hydrofluoric Acid Gravimetry
Authors: Xu Jian Ping
Published: December 2010

The co-volatilization of boron and silicon has been studied for determination of SiO2 content in boron-containing silica refractories. The co-volatilization of boron may cause positive interference for determining of SiO2 content. The interference can be eliminated by the volatilization of boron with 5mL and 2mL of ethanol by separately volatizing, before volatilization of SiO2 with hydrofluoric acid. The method for determination of SiO2 content in boron-containing silica refractories has been established. The scope and precision of this method are equaled to that of the conventional method by hydrofluoric acid gravimetry.
Existence Forms of Magnesium Oxide in Steel Slag by Chemical Phase Separation
Authors: Li Zhao Feng , Zhou Zong Hui , Shan Li Fu
Published: December 2010

Magnesium oxide solid dissolved in silicate phase, mesophase and RO-phase which are the major constituents of steel slag. The MgO exists in the steel slag with complex forms, which results in the bad soundness of the steel slag. In this paper, the silicate phase and mesophase were separated by salicylic acid methanol solution and potassium hydroxide-sucrose solution respectively and were studied combining with the XRD and SEM. The results show that the silicate phase and mesophase can be fully dissolved, however, the RO phase is not influenced by the two solutions in this process. The content of magnesium oxide existed in different minerals can be detected by chemical analysis. It can be found that the magnesium oxide mainly exists as RO-phase in steel slag, and some of them exist as free state, while only a small quantity of solid dissolve in the silicate phase and mesophase.
Effects of Carbonation on Steel Slag Products
Authors: Wu Hao Ze , Chang Jun , Pan Zheng Zhao , Cheng Xin
Published: December 2010

The effects of carbonation on structure and properties of steel slag specimens are evaluated by some different testing technologys in this paper. The experimental results of strength and soundness show that the compressive strength of samples is improved 6-8 times due to carbonation, and carbonated specimens have qualified autoclave soundness. Also the carbonation reactions of steel slag and the reason that why strength and soundness improved are analyzed by chemical titration, XRD, TG, SEM and MIP etc. Experimental results indicate that in steel slag specimens, f-CaO, f-MgO, partial C2S and C3S minerals could be carbonated, and 105～110 gram CO2 gas could be sequestrated after carbonating per kilogram of steel slag specimens.
Synthesis and Characterization of CoO2 Nanosheets
Authors: Li Cai Xia , Xu Hai Fang , Feng Tao , Zhang Na , Li Qiang
Published: December 2010

The layered sodium cobalt oxide Na0.6CoO2 phase has been synthesized from Na2O2 and Co3O4 by solid-state reaction at 550°C for 12h with the heating rate about 2°C /min. The colloidal suspension of exfoliated, layered cobalt oxide nanosheets was prepared through the intercalation of tetrabutyl ammonium hydroxide ions (TBA) into protonated sodium cobalt oxide. The as-obtained composites were analyzed by powder X-ray diffraction (XRD). They were also cross-confirmed by a range of methods including UV/Vis spectroscopy, and Transmission Electron Microscopy (TEM). The Zeta-potential measurements clearly demonstrated the negative surface charge of cobalt oxide nanosheets.
Nuclear Magnetic Resonance Studies on Microstructure of Cement Pastes
Authors: Jin Dan , Yao Wu , She An Ming , Liu Xiao Yan
Published: December 2010

For water filled porous materials, the difference between the relaxation time of molecules at the pore surface and the relaxation time of molecules in the bulk fluid can be interpreted by a fast diffusion model. With this model, the nuclear magnetic resonance (NMR) can be applied to investigate the microstructure of cement pastes. The cement pastes we tested are two series, one is of same water to cement ratio (w/c=0.4) at different curing time (7d, 28d and 90d), the other is of different water to cement ratio (w/c=0.3, 0.4 and0.5, respectively) at the same curing day. Comparing results by NMR method with those by mercury intrusion porosimetry (MIP) shows that NMR is a convenient and nondestructive way to probe pore distribution of cement pastes.
Influence of Cement Coarse Particle on the Self-Healing Ability of Concrete Based on Ultrasonic Method
Authors: Li Zhi Qiang , Zhou Zong Hui , Xu Dong Yu , Yu Jing Hua
Published: December 2010

The influences of particle size and mixing content of coarse cement on the self-healing ability of concrete were researched by ultrasonic method. Damaged degree was measured through the decrease of ultrasonic head wave amplitude (UHA) before and after loading. The relationship between damaged degree and self-healing ratio of concrete was built based on the experimental results as well as the relationship between cement diameter and self-healing ratio of concrete. Analyzing results show that UHA can evaluate the damaged degree of concrete clearly. There exists a damaged threshold of the concrete during loading. Under the same mixing content of coarse cement, when the damaged degree is higher than the threshold, the self-healing ratio of concrete decreases with the increase of damaged degree and increases with the increase of coarse cement diameter, however, while the damaged degree is less than the threshold, the self-healing ratio of concrete increases with both the increase of damaged degree and coarse cement diameter.