bluuebunny/crossref_metadata_2025 huggingface dataset:
Hypotheses for the origin and early evolution of triterpenoid cyclases
Authors: FISCHER W. W. , PEARSON A.
Published: February 2007

Hopanes and steranes are found almost universally in the sedimentary rock record where they often are used as proxies for aerobic organisms, metabolisms, and environments. In order to interpret ancient lipid signatures confidently we require a complementary understanding of how these modern biochemical pathways evolved since their conception. For example, generally it has been assumed that hopanoid biosynthesis was an evolutionary predecessor to steroid biosynthesis. Here we re‐evaluate this assumption. Using a combined phylogenetic and biochemical perspective, we address the evolution of polycyclic triterpenoid biosynthesis and suggest several constraints on using these molecules as aerobic biomarkers. Amino acid sequence data show that the enzymes responsible for polycyclic triterpenoid biosynthesis (i.e. squalene and 2,3‐oxidosqualene cyclases) are homologous. Numerous conserved domains correspond to active sites in the enzymes that are required to complete the complex cyclization reaction. From these sites we develop an evolutionary analysis of three independent characters to explain the evolution of the major classes of polycyclic triterpenoids. These characters are: (i) the number of unfavourable anti‐Markovnikov ring closures, (ii) all‐chair (CCC) or chair‐boat‐chair (CBC) substrate conformation, and (iii) the choice between squalene and 2,3‐oxidosqualene as the substrate. We use these characters to construct four competing phylogenies to describe the evolution of polycyclic triterpenoid biosynthesis. The analysis suggests that malabaricanoids would be the most ancient polycyclic triterpenoids. The two most parsimonious evolutionary trees are the ones in which hopanoid and steroid cyclases diverged from a common ancestor. The transition from a CCC‐ to CBC‐fold marks the major divergence in the evolution of these pathways, and it is diagnosable in the geological record. However, this transition does not require the simultaneous adoption of the aerobic substrate, 2,3‐oxidosqualene, because these characters are controlled by independent parts of the enzyme.
Increased polyploidy in aortic vascular smooth muscle cells during aging is marked by cellular senescence
Authors: Yang Dan , McCrann Donald J. , Nguyen Hao , Hilaire Cynthia St. , DePinho Ronald A. , Jones Matthew R. , Ravid Katya
Published: February 2007

We previously reported that the frequency of polyploid aortic vascular smooth muscle cells (VSMC) serves as a biomarker of aging. Cellular senescence of somatic cells is another marker of aging that is characterized by the inability to undergo cell division. Here, we examined whether polyploidy is associated with the development of cellular senescence in vivo. Analysis of aortic tissue preparations from young and old Brown Norway rats showed that expression of senescence markers such as p16INK4a and senescence‐associated β‐galactosidase activity are detected primarily in the old tissues. VSMC from p16INK4a knockout and control mice display similar levels of polyploid cells. Intriguingly, senescence markers are expressed in most, but not all, polyploid VSMC. Moreover, the polyploid cells exhibit limited proliferative capacity in comparison to their diploid counterparts. This study is the first to demonstrate in vivo that polyploid VSMC adopt a senescent phenotype.
Apartheid spatial engineering and land use change in Mankweng, South Africa: 1963–2001
Authors: McCUSKER BRENT , RAMUDZULI MARUBINI
Published: February 2007

Land use change studies permeate the geographic literature. While these studies have helped researchers understand the dynamics and importance of such changes, they have less often taken a deeper historical approach in combination with their traditional strengths of geographic information analysis. In this study, we explore historical land use changes in one of South Africa's former bantustans, Lebowa, from 1963 to 2001. We argue that changes in land use arise from both current socioeconomic dynamics but also from historical precedent established by the apartheid regime. Our methods couple historical aerial photography to recent household surveys to elucidate the national, regional and local influences over land use change. We conducted extensive field research in the study site between 2003 and 2006. Our findings show a high degree of urbanization, a loss of grassland and agricultural land and a dramatic pattern of increasing spatial concentration near growth points. We outline three recommendations for policymakers planning post‐apartheid rural spaces and conclude with future research needs.
The karstlands of Antigua, their land use and conservation
Authors: DAY MICHAEL
Published: February 2007

The northeastern 110 km2, or nearly 40%, of Antigua is underlain by impure limestones of the Oligocene‐aged Antigua Formation, on which has developed a subdued karst landscape consisting essentially of shallow enclosed depressions (dolines), intermittently active stream valleys and widely scattered residual hills. The dispersed dolines are broad, shallow and clustered, especially in the central and southeastern sections of the limestone belt, where they attain densities of 7/km2. The widely spaced residual hills attain heights of up to 40 m and localized densities of over 4/km2. Five main valley systems up to 6 km in length traverse the limestone in a broadly northeast direction, carrying both autogenic drainage from within the karst area and allogenic drainage from the non‐carbonate Central Plain. Karst and cave development has been constrained by the low purity of the limestones. Of the four types of carbonate islands identified within the Carbonate Island Karst Model, Antigua most closely resembles the Composite Island type. The karst has been much influenced by human activities, particularly agriculture and quarrying, and is now a focus of the burgeoning tourism industry. Virtually none of the karst is designated as protected areas, but several sites warrant protection, and several conservation strategies have been suggested.
Coastal dune conservation on an Irish commonage: community‐based management or tragedy of the commons?
Authors: MC KENNA JOHN , O’HAGAN ANNE MARIE , POWER JAMES , MACLEOD MICHAEL , COOPER ANDREW
Published: February 2007

In Ireland ‘commonage’ refers to lands jointly owned by several individuals who have grazing rights. Commonage can provide the low‐intensity grazing regime regarded as optimal for habitat conservation, and it is also unlikely to suffer the negative impacts of building development or coastal engineering. Today, however, the traditional control systems of coastal commonage are generally moribund, leading to habitat degradation. The only viable future management model is likely to be one based on local community control. Community management would have the legitimacy to counter the negative perceptions of external authority that generate environmental degradation.
Land‐cover change and human–environment interactions in a rural cultural landscape in South Africa
Authors: GIANNECCHINI MONICA , TWINE WAYNE , VOGEL COLEEN
Published: February 2007

This paper presents an historical analysis (1974–97) of associations between land‐cover change and socio‐economic factors for three villages in a former bantustan region of South Africa. The notion of social–ecological systems is used as the conceptual framework for this analysis, in which the former bantustan region of Bushbuckridge is posited as a cultural landscape. The local landscape showed distinctive modifications over the study period, broad trends including the growth of human settlements and the decrease in woodland cover. However, changes were not uniform across sites, and the direction and magnitude of changes in land cover were often nonlinear and site‐specific. Analysis of associations between biophysical and socio‐economic changes at different scales revealed a range of important interacting forces such as population growth, drought, shortages of land, grazing and wood resources, weakening institutional governance of natural resources, and the diversification of livelihood strategies, including the sale of fuelwood, concurrent with declining employment security and cattle ownership. Evidence suggests a possible erosion of resilience in these social–ecological systems at various scales, with important implications for socio‐economic development and sustainable resource management.
Developing KaNgwane: geographies of segregation and integration in the new South Africa
Authors: KING BRIAN H
Published: February 2007

This paper examines social, political and economic processes within the former KaNgwane bantustan to understand the changing relationships between society and space in the post‐apartheid era. Research on rural development and reconstruction in South Africa attest to the spatial legacy of apartheid while suggesting that dynamic transformations are occurring within the former bantustans. A central concern of this paper is the ways the apartheid government constructed and presented KaNgwane as a development project in order to justify racial segregation and control. While the bantustans have been effectively erased from the popular imagination, these spaces continue to be framed developmentally in ways that provide limited attention to local context and change. In order to consider the shifts in environment and development discourses within these territories, a case study is employed to evaluate livelihood production systems, environmental change, and governance institutions. It is argued that these patterns reveal the simultaneously static and dynamic nature of the bantustans while demonstrating that their reincorporation will remain an ongoing process in the post‐apartheid era.
Resilient geographies: land, boundaries and the consolidation of the former bantustans in post‐1994 South Africa
Authors: RAMUTSINDELA MAANO
Published: February 2007

This paper focuses on the spatial impact of land reform and the redrawing of internal boundaries on South Africa's former bantustans. It argues that, in contrast to the democratic government's intention to use land reform and boundary demarcation to effectively change the spatial legacy of apartheid, these processes tend to cement the geography of the former bantustans. Though earlier research correctly projected that post‐apartheid policies could result in the enlargement of the areas of the former bantustans, the ways in which this could happen were still unclear. This paper draws on experiences of land reform and boundary demarcation to demonstrate how and why the areas of the former bantustans have been enlarged over the 12 years of democracy in South Africa.
ANALYST BEHAVIOR SURROUNDING TENDER OFFER ANNOUNCEMENTS
Authors: Bradley Daniel J. , Morgan Angela G. , Wolf Jack G.
Published: February 2007

We examine the usefulness and credibility of analyst recommendations by focusing on their behavior surrounding tender offer announcements. For our 1998–2001 sample, we find analysts did not identify takeover targets through their recommendations nor did they distinguish between wealth‐increasing and wealth‐decreasing tender offers. We find some evidence of conflicts of interest in analyst recommendations, but it is confined to the 1999–2000 dot‐com period. However, the long‐run performance following recommendations suggests that these conflicts have little ultimate cost to investors.
ABNORMAL PERFORMANCE IN SMALL PORTFOLIOS WITH EVENT‐INDUCED VOLATILITY: THE CASE OF STOCK SPLITS
Authors: Baixauli J. Samuel
Published: February 2007

In this article I present a test for detecting abnormal returns when the event analyzed induces volatility and the portfolio is small. The results show that the test is well specified and leads to significant gains in power. I subsequently analyze the abnormal returns around the stock split ex date according to the split factor and find significant abnormal returns only when the factor is greater than 2. The varying motives behind the splits may explain this finding.
WHAT'S IN A NICKNAME? PRICE AND VOLUME EFFECTS OF A PURE TICKER SYMBOL CHANGE
Authors: Kadapakkam Palani‐Rajan , Misra Lalatendu
Published: February 2007

We examine the effect of a voluntary change in ticker symbol without other contemporaneous corporate events such as a name change. We find significant declines in trading volume and prices on the effective date of the ticker change. We segment the sample by exchange listing, share turnover activity, and subperiod. We observe declines in trading volume in all subsamples and negative abnormal returns in recent years.
Clinicopathological findings and results of bone marrow aspiration in dogs with cutaneous mast cell tumours: 157 cases (1999–2002)*
Authors: Endicott M. M. , Charney S. C. , McKnight J. A. , Loar A. S. , Barger A. M. , Bergman P. J.
Published: February 2007

Bone marrow aspiration for routine staging of canine cutaneous mast cell tumour is not consistently performed, and the overall incidence of bone marrow infiltration and predictive value of the complete blood count (CBC) is unknown. This study evaluated a series of 157 dogs presented for cutaneous mast cell tumours in which a CBC and bone marrow aspiration were performed. The incidence of bone marrow infiltration at initial staging was low at 2.8%, and 4.5% overall. Factors significantly associated with bone marrow infiltration included increased age, leucocytosis, anaemia, neutrophilia, monocytosis, eosinophilia, thrombocytopenia, being purebred and staging at the time of recurrent or progressive disease. Our study suggests that a bone marrow sample is not indicated for routine staging but maybe indicated for those dogs with mast cell tumours having either an abnormal haemogram (neutrophilia, monocytosis, eosinophilia, basophilia, anaemia and thrombocytopenia) or presenting for tumour regrowth, progression or new occurrence.
Icodextrin Peritoneal Transport In Vitro: Effect of Sodium Deoxycholate, Glucose, and Methylglyoxal
Authors: Szary Beata , Grzelak Teresa , Czyzewska Krystyna
Published: February 2007

Abstract:  The aim of the in vitro studies was to examine the effect of sodium deoxycholate, glucose, and methylglyoxal on icodextrin peritoneal transfer. The rabbit peritoneum in a modified Ussing chamber was an experimental model. Transport and morphometric analyses were performed. In the first of them, the icodextrin (7.5 g/dL) diffusion from the mesothelial to the interstitial side of the membrane, expressed as a diffusive permeability coefficient (P), was evaluated in the control stage, after chemical modification of the membrane using sodium deoxycholate (104 mg/dL), after the addition of glucose (1.8 g/dL) and methylglyoxal (1 mg/dL), in the separate experimental series. In the second morphometric studies, the thickness and transverse cross‐section surface area of native tissue, in 75 min of experiment and after application of sodium deoxycholate, were investigated. In the control conditions, the rate of glucose polymer passage remained constant. A mean value of P ± SD was 0.194 ± 0.126 (×10−4, cm/s) during 120 min of the study. The transfer of icodextrin was enhanced by 224% after 3 min of incubation of the peritoneum with sodium deoxycholate. The introduction of glucose into the circulating medium with icodextrin caused the increase of P values for glucose polymer by 94% during 60 min. In the same conditions, the usage of methylglyoxal did not change transport parameters. Both thickness and transverse cross‐section surface area of the native tissue in 75 min of the study did not differ. It was 4.87 µm and 12.50 × 102 µm2 for the mesothelial layer, and 63.83 µm and 208.10 × 102 µm2 for the whole peritoneal membrane. The application of sodium deoxycholate caused the decrease of mesothelium thickness by 20% but the increase of thickness and transverse cross‐section surface area of the peritoneum by 37% in comparison with 75 min of experiment. In conclusion, sodium deoxycholate and glucose, but not methylglyoxal, intensify peritoneal transport of icodextrin in vitro. These modifications are probably connected with the exfoliation of the mesothelium and looseness of the interstitium caused by sodium deoxycholate as well as the physical and metabolic influence of glucose on the peritoneum.
Right Axillary Vein Cannulation for Percutaneous Cardiopulmonary Support
Authors: Tochii Masato , Ando Motomi , Yamashita Mitsuru , Sato Masato , Hattori Koji , Hoshino Ryo , Akita Kiyotoshi
Published: February 2007

Abstract:  A 34‐year‐old male with a past history of permanent inferior vena cava (IVC) filter placement was referred to us for chronic thromboembolic pulmonary hypertension. Percutaneous cardiopulmonary support (PCPS) was required for the lung hemorrhage and reperfusion injury, although the thromboendarterectomy was successfully completed. The arterial cannula was inserted into the femoral artery, and the venous cannula was inserted into the right axillary vein. The patient was weaned from PCPS 1 day after the operation and was discharged 35 days after the operation. Axillary vein cannulation is thought to be a feasible method when PCPS is required for a patient with previous IVC filter placement.
The Origins of Modern Divorce
Authors: COONTZ STEPHANIE
Published: February 2007

High rates of marital dissolution and easy access to divorce are not unprecedented, historically or cross‐culturally. But contemporary divorce in North America and Western Europe has different origins and features than divorce in previous cultures. The origins of modern divorce patterns date back more than 200 years, to the invention of the historically unprecedented idea that marriage should be based on love and mutual affection. Ironically, then, the fragility of modern marriage stems from the same values that have elevated the marital relationship above all other personal and familial commitments: the concentration of emotion, passion, personal identity, and self‐validation in the couple relationship and the attenuation of emotional attachments and obligations beyond the conjugal unit. The immediate causes of divorce may range from factors as diverse as the personal psychological characteristics of one or both spouses to the stresses of economic hardship and community disintegration. But in a larger perspective, the role of divorce in modern societies and its relatively high occurrence both flow from the same complex of factors that have made good marriages so much more central to people's happiness than through most of the past, and deterioration of a marital relationship so much more traumatic.
Framing Divorce Reform: Media, Morality, and the Politics of Family
Authors: ADAMS MICHELE , COLTRANE SCOTT
Published: February 2007

No‐fault statutes changed divorce from an adversarial system pitting victims against victimizers, with the state acting as enforcer of marital norms, to a private decision between unhappily married but legally blameless partners. Divorce reform following no‐fault primarily focused on making divorce more fair for the parties involved. Over the last several decades, divorce reform has transitioned from making divorce better to making marriage healthier. The good divorce has slipped from policy attention, elevating the potential for restigmatization of divorced couples and their children. We trace the trajectory of media framing of divorce reform discourse in three general circulation newspapers from the start of the no‐fault revolution, noting how media framing parallels and naturalizes the transition in divorce reform policy. We conclude by observing the prevalence of divorce and the related need for therapists to be cognizant of this naturalization process, thereby keeping the good divorce as a goal for those who desire to end their marriages.
Re‐visioning, Restructuring, and Reconciliation: Clinical Practice With Complex Postdivorce Families
Authors: BERNSTEIN ANNE C.
Published: February 2007

I address three themes in therapeutic interventions with complex postdivorce families: I begin by deconstructing the “Child of Divorce” as a dispositive narrative, or “script,” that restricts possibilities and becomes a self‐fulfilling prophecy for children and parents in divorcing families and for therapists who work with them. I then discuss the gap between preconceptions and possibilities in the “new extended family” created by divorce and new partnerships, addressing such questions as family membership, restructuring workable postdivorce family forms, and how therapists can assist families in building both “good fences” and “good bridges.” I conclude by examining the potential for repairing relationships that have become strained by marital transitions, examining the application of such concepts as “accusatory suffering,”“self‐defeating spite,” and “witnessing” to family therapy with this population, with especial emphasis on the relationship between parents and their adult children.
Integrative Family Therapy for High‐Conflict Divorce With Disputes Over Child Custody and Visitation
Authors: LEBOW JAY , NEWCOMB REKART KATHLEEN
Published: February 2007

A growing number of divorcing families become locked in intractable disputes over child custody and visitation. This article describes an integrative family therapy approach targeted toward such families. Aspects of this treatment include negotiating a clear therapy contract, creating a multipartial alliance with all parties, assessing through the lens of specific understandings about these cases, incorporating multiple therapy session formats, holding both systemic and individual focused perspectives, incorporating a solution‐oriented focus, and drawing upon a wide range of intervention techniques. The treatment aims to create a good‐enough postdivorce climate in which a new family structure can be constituted in which parents maintain distance from one another, and conflict and triangulation can be minimized.
An Approach to Preventing Coparenting Conflict and Divorce in Low‐Income Families: Strengthening Couple Relationships and Fostering Fathers' Involvement
Authors: COWAN CAROLYN PAPE , COWAN PHILIP A. , KLINE PRUETT MARSHA , PRUETT KYLE
Published: February 2007

In the context of current concern about levels of marital distress, family violence, and divorce, the SFI study is evaluating the effectiveness of an intervention to facilitate the positive involvement of low‐income Mexican American and European American fathers with their children, in part by strengthening the men's relationships with their children's mothers. The study design involves a randomized clinical trial that includes assignment to a 16‐week couples group, a 16‐week fathers group, or a single‐session control group. Couples in both group interventions and the control condition include partners who are married, cohabiting, and living separately but raising a young child together. This article presents the rationale, design, and intervention approach to father involvement for families whose relationships are at risk because of the hardships of their lives, many of whom are manifesting some degree of individual or relationship distress. We present preliminary impressions and qualitative findings based on our experience with 257 families who completed the pretest, and the first 160 who completed one postintervention assessment 9 months after entering the study. Discussion centers on what we have learned and questions that remain to be answered in mounting a multisite preventive intervention to strengthen relationships in low‐income families.
Effects of the Dads for Life Intervention on Interparental Conflict and Coparenting in the Two Years After Divorce
Authors: COOKSTON JEFFREY T. , BRAVER SANFORD L. , GRIFFIN WILLIAM A. , DE LUSÉ STEPHANIE R. , MILES JONATHAN C.
Published: February 2007

The ability of parents to forge harmonious coparenting relationships following divorce is an important predictor of their children's long‐term well‐being. However, there is no convincing evidence that this relationship can be modified through intervention. A preventive intervention that we developed, Dads for Life (DFL), which targeted noncustodial parents as participants, has previously been shown in a randomized field trial to favorably impact child well‐being. We explore here whether it also has an impact on mothers' and fathers' perceptions of coparenting and interparental conflict in the 2 years following divorce. Results of the latent growth curve models we evaluated showed that both mothers and fathers reported less conflict when the father participated in DFL as compared with controls. For the fathers, perceptions of coparenting did not change over time in either the DFL or control conditions. Alternatively, mothers' perceptions of support declined over time in the control group, whereas those whose ex‐husbands participated in the DFL program reported significant positive growth change toward healthier coparenting. The positive findings for mothers' reports are particularly compelling because mothers were not the participants, and thus common alternative explanations are ruled out. The DFL intervention, then, offers courts a promising program to improve families' functioning after divorce.
Description of Rhynchopus euleeides n. sp. (Diplonemea), a Free‐Living Marine Euglenozoan
Authors: ROY JOANNIE , FAKTOROVÁ DRAHOMÍRA , BENADA OLDŘICH , LUKEŠ JULIUS , BURGER GERTRAUD
Published: February 2007

ABSTRACT. We describe Rhynchopus euleeides n. sp., using light and electron microscopy. This free‐living flagellate, which was isolated earlier from a marine habitat, can be grown axenically in a rich medium based on modified seawater. In the trophic stage, cells are predominantly elliptical and laterally flattened, but frequently change their shape (metaboly). Gliding is the predominant manner of locomotion. The two flagella, which are typically concealed in their pocket, are short stubs of unequal length, have conventional axonemes, but apparently lack a paraxonemal rod. Swarmer cells, which form only occasionally, are smaller in size and carry two conspicuous flagella of more than 2 times the body length. Cells are decorated with a prominent apical papillum. Both the flagellar pocket and the adjacent feeding apparatus seem to merge together into a single sub‐apical opening. The mitochondrion, which is most likely single, is located peripherally. It is reticulated in shape and contains only a few lamellar cristae. Mitochondrial DNA is abundant and evenly distributed throughout the organelle. Morphological synapomorphies confirm the affiliation of the species with the genus Rhynchopus (Diplonemea, Euglenozoa). We discuss the characters that distinguish Rhynchopus from Diplonema corroborating the validity of the two genera.
Modeling of Thermal Behavior of Ancient Metallurgical Ceramics
Authors: Hein Anno , Kilikoglou Vassilis
Published: February 2007

The finite element method is used to examine the thermal properties of functional ceramics, which were used in metallurgical processes during antiquity. Based on the ceramics' microstructure a model is developed considering the impact of porosity and inclusions and the heat transfer from ceramics to environment. An example of a Bronze Age copper smelting furnace from Cyprus is presented. Particularly the influence of pore shape and pore orientation on the thermal conductivity is investigated. Temperature development in the entire furnace is simulated and compared with estimations of the firing temperature in particular areas of the furnace.
Effect of Molybdenum on the Structure and on the Crystallization of SiO2–Na2O–CaO–B2O3 Glasses
Authors: Caurant Daniel , Majérus Odile , Fadel Edward , Lenoir Marion , Gervais Christel , Pinet Olivier
Published: February 2007

Crystallization of the poorly durable Na2MoO4 phase able to incorporate radioactive cesium must be avoided in SiO2–Al2O3–B2O3–Na2O–CaO glasses developed for the immobilization of Mo‐rich nuclear wastes. Increasing amounts of B2O3 and MoO3 were added to a SiO2–Na2O–CaO glass, and crystallization tendency was studied. Na2MoO4 crystallization tendency decreased with the increase of B2O3 concentration whereas the tendency of CaMoO4 to crystallize increased due to preferential charge compensation of BO4− entities by Na+ ions. 29Si MAS NMR showed that molybdenum acts as a reticulating agent in glass structure. Trivalent actinides surrogate (Nd3+) were shown to enter into CaMoO4 crystals formed in glasses.
Application of In Situ High‐Temperature Techniques to Investigate the Effect of B2O3 on the Crystallization Behavior of Aluminosilicate E‐Glass
Authors: Hillers Maike , Matzen Guy , Véron Emmanuel , Dutreilh‐Colas Maggy , Douy André
Published: February 2007

Using classical ex situ techniques (optical microscopy, Raman spectroscopy), differential scanning calorimetry, and two new in situ techniques for characterization during crystallization (high‐temperature environmental scanning electron microscopy and high‐temperature X‐ray diffraction with a fast detector), the addition of B2O3 to SiO2–Al2O3–CaO glasses was examined to understand its impact on crystallization behavior. The conventional ex situ characterization reveals that B2O3 addition reduces crystal growth rate and also decreases the liquidus temperature. The in situ techniques provide complementary information on the crystallization kinetics.
Dielectric Properties of Low Loss (1–x)(Mg0.95Zn0.05)TiO3–xSrTiO3 Ceramic System at Microwave Frequency
Authors: Huang Cheng‐Liang , Wang Jun‐Jie , Chang Yu‐Pin
Published: February 2007

The microstructures and the microwave dielectric properties of the (1–x)(Mg0.95Zn0.05)TiO3–xSrTiO3 ceramic system were investigated. (Mg0.95Zn0.05)TiO3 possesses high dielectric constant (ɛr∼17.05), high quality factor (Q×f value∼264 000 at 9 GHz), and negative τf value (−40.31 ppm/°C). In order to achieve a temperature‐stable material, SrTiO3, having a large positive τf value of 1700 ppm/°C, was added to (Mg0.95Zn0.05)TiO3. Two‐phase system was confirmed by the X‐ray diffraction patterns and the measured lattice parameters. Evaporation of Zn occurred at temperatures higher than 1300°C and caused an increase in the dielectric loss of the system. As the x value varies from 0 to 0.1, (1–x)(Mg0.95Zn0.05)TiO3–xSrTiO3 ceramic system has the dielectric properties as follows: 17.05<ɛr<26.35, 20 000<Q×f<264 000, and −41<τf<140. By appropriately adjusting the x value in the (1–x)(Mg0.95Zn0.05)TiO3–xSrTiO3 ceramic system, zero τf value can be achieved. A new microwave dielectric material, 0.96(Mg0.95Zn0.05)TiO3–0.04SrTiO3 applicable in microwave devices is suggested and possesses the dielectric properties of a dielectric constant ɛr∼20.96, a Q×f value∼135 000 GHz (at 9 GHz), and a τf value ∼0 ppm/°C. A compact band‐pass filter using two open‐loop ring resonators with asymmetric tapping feed lines is designed and fabricated using the proposed dielectric to study its performance.
Importance of Crystallization Hierarchies in Microstructural Evolution of Silicate Glass–Ceramics
Authors: Lee W. E. , Arshad S. E. , James P. F.
Published: February 2007

Quench studies of in‐house melted glasses were used to study the microstructural evolution in Macor‐type and Corning Code 9606‐type glass–ceramics to elucidate the microstructures of the commercial products. They reveal that phase separation initiates crystallization in both systems which then proceeds via formation of several phases at different scales of size, the first phases to form being those containing the most rapidly diffusing species. This study highlights the concept of crystallization hierarchies whereby crystals form, sometimes simultaneously, sometimes sequentially, on heating glasses, but at different length scales. This is illustrated by the simultaneous nucleation of μ‐cordierite nanocrystals and ∼0.2 μm MgAl2Ti3O10 rosettes in Corning 9606‐type compositions and of ∼0.3 μm chondrodite and 3–4 μm fluorophlogopite laths in Macor‐type compositions.
On the Vickers Indentation Fracture Toughness Test
Authors: Quinn George D. , Bradt Richard C.
Published: February 2007

The Vickers indentation fracture toughness test, or VIF, is addressed by considering its origins and the numerous equations that have been applied along with the technique to estimate the fracture resistance, or the KIc of ceramics. Initiation and propagation of cracks during the VIF test are described and contrasted with the pre‐cracking and crack growth for internationally standardized fracture toughness tests. It is concluded that the VIF test technique is fundamentally different than standard fracture toughness tests. The VIF test has a complex three‐dimensional crack system with substantial deformation residual stresses and damage around the cracks. The VIF test relates to an ill‐defined crack arrest condition as opposed to the rapid crack propagation of the standardized fracture toughness tests.

Previously published fracture toughness results employing the VIF technique are reviewed. These reveal serious discrepancies in reported VIF fracture toughness values. Finally, recent fracture resistance measurements by the VIF technique for the Standard Reference Material SRM 2100 are presented. These are compared with standardized test results for the same material. It is concluded that the VIF technique is not reliable as a fracture toughness test for ceramics or for other brittle materials. What the VIF actually measures in terms of fracture resistance cannot be readily defined. It is recommended that the VIF technique no longer be acceptable for the fracture toughness testing of ceramic materials.
Preparation of 200 nm BaTiO3 Particles with their Tetragonality 1.010 Via a Solid‐State Reaction Preceded by Agglomeration‐Free Mechanical Activation
Authors: Yanagawa Rui , Senna Mamoru , Ando Chie , Chazono Hirokazu , Kishi Hiroshi
Published: February 2007

Well‐dispersed barium titanate (BaTiO3; BT) with an average primary particle size <200 nm and lattice tetragonality 1.010, being very close to that of a BT single crystal, was obtained via a solid‐state route with the aid of preliminary dry mechanical processing. The latter treatment not only activates the starting mixture but also decreases the particle sizes of individual ingredients and increases the homogeneity. All these favor to suppress grain growth of the product BT due to increasing nucleation site density, easing the nucleation at the given nucleation site, and decreasing the diffusion paths. These were confirmed by (i) microscopy and particle size analysis to observe downsizing of individual particulates without causing agglomeration; (ii) electron probe microanalysis to reveal increase in the homogeneity in a few micrometer regime; and (iii) X‐ray photoelectron spectroscopy to reveal mechanochemical effects across the solid–solid boundary of dissimilar particles.
Densification of the PLZT Films Derived from Polymer‐Modified Solution by Tailoring Annealing Conditions
Authors: Du Z. H. , Ma J. , Zhang T. S.
Published: February 2007

The Pb0.91La0.09(Zr0.65,Ti0.35)0.9775O3 films were prepared from the solution containing polyvinylpyrrolidone, with Mw of 360 000. A fast heating rate of 40°C/min was used to heat our samples to temperatures in the range of 550°–750°C for different durations. Both a rapid heating rate and isothermal holding at a proper temperature are found to be essential for obtaining dense and crack‐free PLZT films. The TG‐DTA and Fourier‐transform infrared results indicated that the fast heating rate could keep a certain amount of polyvinylpyrrolidone residues undecomposed to a higher temperature (<700°C), which was found to be beneficial for the densification of the films during subsequent isothermal hold. The possible mechanisms responsible for the enhanced densification have been discussed. In addition, the effects of annealing temperature on the electrical and optical properties were also investigated.
Precipitation of Carbonated Calcium Phosphate Powders from a Highly Supersaturated Simulated Body Fluid Solution
Authors: Hofmann Ingo , Müller Lenka , Greil Peter , Müller Frank A.
Published: February 2007

Carbonated hydroxy apatite (CHA) powders were prepared by precipitation from a modified simulated body fluid (5 × M‐SBF). The ionic concentrations were five times higher than in human blood plasma with the exception of Mg2+ and HCO3− concentrations that were reduced in order to accelerate crystal growth. Spheroaggregates of CHA platelets with molar (Ca+Mg)/P ratios ranging from 1.44 to 1.56 were obtained after precipitation at 50°C. The crystallite size in the c direction was approximately 31 nm and depending on the precipitation time, a CO32− content of 1.8–5.2 wt% was determined. Using this low‐temperature precipitation method, CHA powders with a high specific surface area of 83 m2/g and a composition and crystallite size close to those of the mineral phase of human bone were obtained.
Synthesis of Ti3SiC2 Powders: Reaction Mechanism
Authors: Córdoba José M. , Sayagués María J. , Alcalá María D. , Gotor Francisco J.
Published: February 2007

Titanium silicon carbide (Ti3SiC2) and Ti3SiC2‐based composite powders were synthesized by isothermal treatment in an inert atmosphere as a function of initial compositions (mixtures). A high content of TiC was obtained in the final product when the initial mixtures contained free carbon. The use of TiC as a reagent was unsuccessful in obtaining Ti3SiC2. High Ti3SiC2 conversion was found for the initial mixtures containing SiC as the main source for silicon and carbon. An initial mixture with a large excess of silicon, 3Ti/1.5SiC/0.5C, was needed to obtain high‐purity Ti3SiC2. A reaction mechanism, where Ti3SiC2 nucleates on Ti5Si3C crystals and grows by long‐range diffusion of Ti and C, is proposed. The reaction mechanism was proposed to be based on silicon loss during the formation of Ti3SiC2.
Synthesis and Characterization of Nanoscale Ce(x)Ru(1−x)O2 Coatings With Electrochemical Activity
Authors: Zhang Teng , Tang Dian , Shao Yanqun , Ke Xuebiao , You Shaoxin
Published: February 2007

The nanoscale coatings of CexRu1−xO2 (x=0, 0.25, 0.5, and 0.75 mol%) with electrochemical activity were investigated. The characterization of the resulting materials was conducted by X‐ray diffraction (XRD), scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET), and cyclic voltammetry test (CV). It is shown through XRD analysis that there is no metallic ruthenium in those samples containing more than 50 mol% Ce. The results of SEM and BET show that the presence of CeO2 changes the morphology as well as the surface areas of the coatings in electrodes. The electrochemical activity also shows a strong dependence on the CeO2 content in the coatings under the CV test. The electrode of Ce0.5Ru0.5O2 has the highest surface area (19.13 m2/g) and the best electrochemical property (voltammetric charge of 180.64 mC/cm2) among the binary compositions.
Template‐Free Self‐Assembly of a Nanoporous TiO2 Thin Film
Authors: Gao Yanfeng , Nagai Masayuki , Seo Won‐Seon , Koumoto Kunihito
Published: February 2007

We report a nanoporous TiO2 thin film prepared using a supersaturated aqueous solution containing peroxotitanium complex ions. The film morphology can be regulated by chemical kinetics, which was partially controlled by solution conditions such as the concentrations of starting materials, pH values, and the temperatures of the solutions. Porous films with various morphologies from particulate to curved sheet shaped were prepared on different substrates including Si, polymers, and glass. Porous microstructures of films permitted us to prepare a crack‐free film 2–3 μm in thickness. These films were still amorphous under the present treatment conditions. Dye‐sensitized solar cells using annealed (anatase) films of different morphologies as electrodes yielded conversion efficiency ranging from 1.3% to 3.1%. Improvement in performance may be achieved by either increasing the film thickness or inducing crystallization in solutions.
Soft‐Chemistry Synthesis, Characterization, and Stabilization of CGO/Al2O3/Pt Nanostructured Composite Powders
Authors: Levy Caroline , Guizard Christian , Julbe Anne
Published: February 2007

Soft‐chemistry routes were used to synthesize Ce0.9Gd0.1O1.95‐based powders with attractive and stable structural, morphological, and textural properties. In the intermediate temperature range between 500° and 700°C, the average Gd‐doped CeO2 (CGO) crystallite size is in the range 9–22 nm and the specific surface area varies from 43.4 to 8 m2/g. Above 700°C, a phase separation occurs between ceria and gadolinium oxide. Addition of alumina was found to be useful in stabilizing the CGO nanocrystallites at a high temperature and to avoid phase separation. A homogeneous dispersion of Pt nanoparticles (<10 nm at 1000°C) in the CGO materials was found to be possible by post‐impregnation, although direct insertion of the Pt precursors during the synthesis led to aggregated particles, with less potential for catalytic applications.
Controlled Synthesis and Stability of Co@SiO2 Aqueous Colloids
Authors: Aslam M. , Li S. , Dravid V. P.
Published: February 2007

Magnetic nanoparticles have emerged as an important class of functional nanostructures with potential applications of magnetic resonance imaging, drug targeting, and bio‐conjugation. We have developed a modified sol–gel approach to synthesize stable and well‐dispersed magnetic Co@SiO2 nanoparticles with improved control over shell thickness and larger core diameters. These well‐defined Co@SiO2 core–shell nanoparticles exhibit useful magnetic properties, and the protective silica shell allows them to be surface modified for bioconjugation for various biomedical applications. The core–shell nanoparticles were characterized by transmission electron microscopy, energy‐dispersive spectroscopy, elemental mapping, and the line compositional analyses to demonstrate that uniform individually isolated core–shell nanoparticles are obtained through the improved synthetic route.
Mechanism of “Solid‐State” Single‐Crystal Conversion in Alumina
Authors: Dillon Shen J. , Harmer Martin P.
Published: February 2007

Single crystals of Al2O3 were reproducibly grown from an MgO‐doped polycrystalline precursor. The single crystals were grown through controlled abnormal grain growth at temperatures between 1670° and 1945°C. It was observed that CaO impurities segregated to the boundary between the single crystal and the polycrystalline region, and formed a wetting intergranular film. This type of film is required to produce the highly mobile grain boundaries that facilitate single‐crystal conversion. The measured grain boundary mobilities correspond reasonably well with the mobilities calculated from data for a grain boundary containing a film with properties of the bulk glass, although some deviation from bulk behavior is indicated by the difference in activation energy. The grain boundaries are the most highly mobile alumina grain boundaries measured to date. This suggests that extrinsic effects produce the highest grain boundary mobility, rather than intrinsic behavior, which has conventionally been assumed to be the fastest.
Comparison of the Formation of Calcium and Barium Phosphates by the Conversion of Borate Glass in Dilute Phosphate Solution at near Room Temperature
Authors: Huang Wenhai , Day Delbert E. , Rahaman Mohamed N.
Published: February 2007

The formation of phosphates of calcium or barium at near room temperature by the direct conversion of borate glass in dilute phosphate solution was investigated. Borate glass particles (150–300 μm), with the composition 20Na2O·20AO·60B2O3 (mol%), where A is the alkali‐earth metal Ca or Ba, were prepared by conventional processing, and immersed in 0.25M K2HPO4 solution at 37°C and with a starting pH value of 9.0 or 12.0. The effects of the borate glass composition and the solution pH on the rate of formation, the chemical composition, and the structure of the phosphate products formed in the conversion reaction were investigated using weight loss and pH measurements, X‐ray diffraction, X‐ray fluorescence, scanning electron microscopy, and Brunauer–Emmett–Teller surface area. At both pH values, the calcium borate glass particles were completely converted to hydroxyapatite, Ca10(PO4)6(OH)2, with a high surface area (160–170 m2/g). At pH=9.0, the barium borate glass particles converted completely to a barium phosphate product that was isostructural with BaHPO4, whereas at pH=12.0, the barium phosphate product was isostructural with Ba3(PO4)2, with both products having much lower surface areas (4–8 m2/g). The formation of the phosphate products was pseudomorphic, retaining the external shape of the original glass particles.
Direct Observation of Multilayer Adsorption on Alumina Grain Boundaries
Authors: Dillon Shen J. , Harmer Martin P.
Published: February 2007

Grain‐boundary films 0.6 nm in size have been observed on the grain boundaries of neodymia (Nd2O3)‐doped alumina (α‐Al2O3) sintered at 1800°C. Direct observation by high‐angle annular dark‐field imaging in the aberration‐corrected scanning transmission electron microscope shows that this type of grain‐boundary structure is the result of multilayer adsorption. Neodymium cations adsorb onto the faces of each of the two grains that comprise the grain boundary by substituting for aluminum cations. The positions of these cations are slightly distorted relative to the perfect lattice, and a third atomic layer in the core of the grain‐boundary resides between these two layers. The measurements also confirm that the thickness deduced from high‐resolution transmission electron microscopy lattice images are accurate.
Coronally advanced flap: a modified surgical approach for isolated recession‐type defects: Three‐year results
Authors: De Sanctis M. , Zucchelli G.
Published: February 2007

Background: Various modifications of the coronally displaced flap have been proposed in the literature with the attempt of treating gingival recession with uneven predictable results. The goal of the present study was to evaluate the effectiveness with respect to root coverage of a modification of the coronally advanced flap procedure for the treatment of isolated recession‐type defects in the upper jaw.

Methods: Forty isolated gingival recessions with at least 1 mm of keratinized tissue apical to the defects were treated with a modified approach to the coronally advanced flap. The main change in the surgical procedure consisted in the modification of flap thickness and dimension of surgical papillae during flap elevation. All recessions fall into Miller class I or II. The clinical re‐evaluation was performed 1 year and 3 years after the surgery.

Results: At the 1‐year examination, the average root coverage was 3.72±1.0 mm (98.6% of the pre‐operative recession depth) and 3.64±1.1 mm (96.7%) at 3 years. The gain in probing attachment amounted to 3.65±1.10 mm at 1 year and to 3.70±1.09 mm at 3 years. The average increase of keratinized tissue between the baseline and the 3‐year follow‐up amounted to 1.78±0.90 mm. All changes of keratinized tissue (difference between baseline and 1 year, baseline and 3 years, and between 1 and 3 years) were statistically significant.

Conclusion: The modified coronally advanced surgical technique is effective in the treatment of isolated gingival recession in the upper jaw.