bluuebunny/crossref_metadata_2025 huggingface dataset:
PRELIMINARY COMMUNICATION Occlusive power evaluation of O/W/O multiple emulsions on gelatin support cells
Authors: FILHO R.
Published: May 2007

The water content of the stratum corneum plays an important role in providing skin suppleness and smoothness. The diffusion of water through the skin is limited primarily by the stratum corneum and the noncornified part of the epidermis has negligible water barrier properties. Multiple emulsions are vesicular systems utilized for the prolonged liberation of active ingredients. The O/W/O multiple emulsion type is employed in cosmetics because its high oil content is able to maintain an occlusive film (barrier) on the skin surface. The objective of this study was to determine the occlusive power of O/W/O multiple emulsions on gelatin support cells. The results showed that occlusive products form a uniform layer on the surface of gelatin after the test, whereas nonocclusive products form two layers: an aqueous phase on the gelatin, and an oil phase above the aqueous phase. Thus, the different occlusive powers are due to the homogeneity of this layer and to its ability to prevent water evaporation. Resume. La fonction principale de la couche cornee est proteger le corp human de la deshydratation, ainsi que des attaques des agents chymiques et biologiques. Le contenu d'eau de la couche cornee est responsable par la douceur et suavite de la peau. La diffusion de l'eau vers la peau est limitee par la couche cornee et la partie cellulaire que n'est pas keratinisee, ne represent pas une barriere pour la diffusion d'eau. Les emulsions multiples sont de systemes vesiculaires utilises pour obtenir liberation prolongee de principes actives. L'emulsion multiple L/H/L est employe dans la cosmetologie a cause de la taux tres elevee d'huile qui peut former une barriere occlusive sur la peau. Le principal but de cet article est determiner le pouvoir occlusive des emulsions multiples L/H/L sur les cellules de gelatine. Les resultats montrent que les produits assez occlusives forment une couche uniforme sur la surface de gelatine tandis que ceux moins occlusives forment une couche aqueuse inferieur en contact avec la gelatine et une autre superieure de caracteristique huileuse au dessus de la couche aqueuse. L'occlusivite des emulsions multiples est due a l'integrite de l'emulsion multiple, donc la couche aqueuse intermediare, et a leur capacite en retenir l'evaporation d'eau a la surface de la peau.
The use of block copolymer stabilizers for controlling dispersion stability
Authors: COSGROVE T.
Published: May 2007

The role of block copolymers in stabilizing colloidal dispersions against flocculation or coalescence is discussed in terms of the detailed structure of the interface. Both particulate dispersions and liquid/liquid interfaces are used as examples. Two novel experimental methods are introduced, small‐angle neutron scattering and neutron reflection. Comparison with the Scheutjens Fleer theory for block copolymers is also presented. Strategies for the optimum design of the stabilizing polymer are introduced. Le role de copolymeres blocs dans la stabilisation de dispersions colloidales contre la flocculation ou la coalescence est commente en fonction de la structure precise de l'interface. On utilise comme exemples a la fois des dispersions particulaires et des interfaces liquide/liquide. Deux nouvelles methodes experimentales sont introduites, la diffusion de neutrons a angle faible et la reflexion de neutrons. On presente aussi une comparaison avec la theorie des copolymeres blocs de Scheutjens Fleer. On introduit des orientations strategiques pour la conception optimale du polymere stabilisateur.
The use of radiolabelling techniques to measure substantivity to, and penetration into, hair of protein hydrolysates
Authors: JONES R.T. , CHAHAL S.P.
Published: May 2007

The use of 14C‐labelled amino acids enables the measurement of both the total substantivity to hair and the degree of penetration into the hair shaft of amino acid mixtures derived from complete hydrolysis of proteins. The technique utilizes the fact that direct measurement of 14C radioactivity of the treated hair detects only the surface substantivity. Total substantivity can be determined following solubilization of the hair. Data obtained for wheat amino acids show significant penetration when used to treat hair from a shampoo or conditioner formulation. A similar technique has been investigated for a wheat protein partial hydrolysate using 14CNO for radiolabelling purposes and shows that significant penetration into hair can occur. L'utilisation d'amino‐acides marques au 14C permet la mesure a la fois de l'absorption totale par les cheveux et du degre de penetration dans la fibre du cheveu de melanges d'amino‐acides obtenus a partir d'une hydrolyse totale de proteines. La technique utilise le fait que la mesure directe de la radioactivite du 14C des cheveux traites ne detecte que l'absorption en surface. L'absorption totale peut etre determinee apres solubilisation des cheveux. Les donnees obtenues a partir d'amino‐acides de ble montrent une penetration significative lors d'une utilisation pour traiter des cheveux a partir d'une formulation de shampoing ou d'apres‐shampoing. Une technique similaire a ete exploree vis‐a‐vis d'un hydrolysat partiel d'une proteine de ble utilisant 14CNO a des fins de marquage, et montre qu'une penetration significative dans les cheveux peut avoir lieu.
Antiperspirant compositions based on titanium salts
Authors: HAGAN D.B. , LENG F.J. , SMITH P.M. , SNOW M. , WATSON A.
Published: May 2007

Antiperspirant compositions have traditionally relied upon aluminium‐based active compounds to reduce sweating. Titanium is a physiologically inert metal, and titanium metal chelates appear to induce superficial physical pore blockage to provide effective antiperspirancy in a variety of product types. Titanium metal chelates can be formed from titanium alkoxides and organic acids. Conflicting opinions as to the salt structure exist and, in the case of part‐neutralized ammonium titanium lactate (ATL) salt, evidence has been seen for a range of ligands bound to different strengths at different stages of hydrolysis. Aluminium is thought to work by ductal diffusion to give antiperspirancy via neutralization to a polymeric, relatively superficial gel obstruction. ATL mimics conventional alumiunium salts in that it is mainly a topical antiperspirant active, with ATL‐treated skin restored to normal patterns of sweating activity after a few tape‐strips. Under acidic and near‐neutral pH conditions, the ATL active is relatively stable to hydrolysis and can be formulated into topical compositions as either an aqueous solution of the active or as a free‐flowing powder in anhydrous systems. When judged by an in vitro efficacy technique which is thought to predict in vivo performance, ATL functions as an effective antiperspirant. Les compositions antitranspiration reposent habituellement sur des principes actifs a base d'aluminium pour reduire la sudation. Le titane est un metal physiologiquement inoffensif, et les chelates du metal titane peuvent induire un blocage physique superficiel des pores pour donner une propriete antitranspiration efficace apartir de divers types de produits. Les chelates du metal titane peuvent etre formes a partir d'alkoxydes de titane et d'acides organiques. Les avis divergent quant a la structure du sel et, dans le cas du lactate d'ammonium et de titane partiellement neutralise (ATL), on a trouve des signes de divers ligands lies par des liaisons de forces differentes lors des differentes etapes de l'hydrolyse. On pense que l'aluminium fonctionne par diffusion le long du canal pour mener a l'antitranspiration via neutralisation jusqu'a obstruction par un gel polymerique relativement superficiel. L'ATL imite les sels d'aluminium classiques dans la mesure ou il s'agit principalement d'un principe actif antitranspiration topique, une peau traitee a l'ATL revenant a des schemas normaux de transpiration apres quelques pelages. Sous conditions de pH acide et presque neutre, le principe actif ATL, est relativement stable vis‐a‐vis de l'hydrolyse et peut etre formule en des compositions topiques soit en solution aqueuse du principe actif soit comme poudre libre dans des systemes anhydres. Lors de l'evaluation par une technique de test de l'activite in vitro qui renseigne sur le comportement in vivo, l'ATL agit comme un antitranspirant efficace.
Adaptation and the Set-Point Model of Subjective Well-Being
Authors: Lucas Richard E.
Published: May 2007

Hedonic adaptation refers to the process by which individuals return to baseline levels of happiness following a change in life circumstances. Dominant models of subjective well-being (SWB) suggest that people can adapt to almost any life event and that happiness levels fluctuate around a biologically determined set point that rarely changes. Recent evidence from large-scale panel studies challenges aspects of this conclusion. Although inborn factors certainly matter and some adaptation does occur, events such as divorce, death of a spouse, unemployment, and disability are associated with lasting changes in SWB. These recent studies also show that there are considerable individual differences in the extent to which people adapt. Thus, happiness levels do change, and adaptation is not inevitable.
Rough-and-Tumble Play and the Development of the Social Brain
Authors: Pellis Sergio M. , Pellis Vivien C.
Published: May 2007

Social play—that is, play directed toward others—is a readily recognizable feature of childhood. In nonhuman animals, social play, especially seemingly competitive rough-and-tumble play or play fighting, has been the most studied of all forms of play. After several decades of study, researchers of play fighting in laboratory rats have pieced together the rudiments of the neural mechanisms that regulate the expression of this behavior in the mammalian brain. Furthermore, the understanding of the organization, development, and neural control of play in rats has provided a model with which to examine how the experiences accrued during play fighting can lead to organizational changes in the brain, especially those areas involved in social behavior.
Emerging Patterns of EU Membership: Drawing Lessons from Slovakia's First Two Years as a Member State
Authors: Haughton Tim , Malová Darina
Published: May 2007

The 2004 enlargement of the European Union has provided political scientists with 10 additional cases to examine national preference formation and behaviour in the EU. The first two years of Slovakia's membership suggest that while unique historical experiences and size contribute to explaining Slovakia's stance on further integration, ideology, powerful societal interests and the opportunities of membership (as opposed to accession) hold the key. These findings not only feed into broader debates surrounding preference formation and related theories of European integration, but also cast light on the behaviour of new Member States following the period shaped by accession conditionality.
Unquestioned Answers/Unanswered Questions in IPE: A Rejoinder to ‘Non-Marxist’ Historical Materialism
Authors: Morton Adam David
Published: May 2007

This rejoinder to Randall Germain's promotion of a ‘non-Marxist’ historical materialism focuses on a number of weaknesses revealed by his ‘resistance’ to the recovery of the concept of class in international political economy. Most notable is the binary line he draws throughout his argument between class identity, on the one hand, and the formation of collective subjectivities on the other, which results in the very effacing of class in IPE that was so central to my original concerns. Flowing from this, my rejoinder reveals a series of unquestioned answers he provides from his philosophically idealist posture as well as a series of unanswered questions that are left hanging for future debate.
Moral Outrage Mediates the Dampening Effect of System Justification on Support for Redistributive Social Policies
Authors: Wakslak Cheryl J. , Jost John T. , Tyler Tom R. , Chen Emmeline S.
Published: May 2007

To understand how and why people tolerate ongoing social and economic inequality, we conducted two studies investigating the hypothesis that system justification is associated with reduced emotional distress and a lack of support for helping the disadvantaged. In Study 1, we found that the endorsement of a system-justifying ideology was negatively associated with moral outrage, existential guilt, and support for helping the disadvantaged. In Study 2, the induction of a system-justification mind-set through exposure to “rags-to-riches” narratives decreased moral outrage, negative affect, and therefore intentions to help the disadvantaged. In both studies, moral outrage (outward-focused distress) was found to mediate the dampening effect of system justification on support for redistribution, whereas existential guilt (Study 1) or negative affect in general (Study 2; inward-focused distress) did not. Thus, system-justifying ideology appears to undercut the redistribution of social and economic resources by alleviating moral outrage.
Immigrants in the Political Process
Authors: Bäck Henry , Soininen Maritta
Published: May 2007

Immigrants, who comprise a growing group in many European countries, are usually under‐represented in the political process. Sweden's immigrant policy, with its far‐reaching social and political rights, liberal citizenship laws and respect for cultural differences, is often regarded as an exemplary model of how to integrate immigrants in society. The 1975 electoral reform in Sweden gave immigrants the opportunity to become active in the democratic process by allowing foreign citizens to vote in local political elections. This article examines the political and organizational participation of immigrants. The findings indicate widespread and significant exclusion and under‐representation of immigrants in political and organizational life. We argue that immigrant political participation is best understood in terms of a tension between individual characteristics and institutional and organizational factors. In particular, the long‐term exclusion of large numbers of immigrants from labor related organizations is shown to be an important obstacle to their further social and political participation.
Occupational Class and Vote in the 1949 Norwegian Election. Research Note
Authors: Barton Allen H.
Published: May 2007

In 1948–49 the Sociology Office of the University of Oslo, under the guidance of Prof. Paul Lazarsfeld of Columbia University, initiated a series of studies on the Norwegian economic planning system. Part of this Planning Project was a national election survey in the fall of 1949, on a modified probability sample of 2600 people. The results show the paramount influence of economic class on voting, interpreting class as a combination of employer/employee relationship, property ownership, prestige‐status, and income. Indicators of the homogeneity of class environment also played a role. Given the occupational structure of Norway, the Labor party had to win over part of the non‐working‐class population to obtain control of the government. They did this by winning about 1/3 of the white‐collar vote, and about 1/4 of the farmers and fishermen. The policies of economic stabilization ‐ control of inflation through price controls, wage controls, food subsidies, and rationing, and maintenance of full employment under conditions of “suppressed inflation” ‐ were crucial to winning over these white‐collar and farm voters.
Majoritarian and Consensus Democracy: the Swedish Experience
Authors: Lewin Leif
Published: May 2007

According to the classical parliamentary doctrine of majoritarian rule, governments should be large, united and accountable to the voters. Since the introduction of proportional representation in the beginning of this century, these requirements have seldom been fulfilled in Continental politics. In this article the Swedish experience of minority parliamentarism is analyzed. The conclusion is drawn that the consensus model of democracy that has been practiced in this country comes closer to the ideal of the Conservatives who a hundred years ago opposed the parliamentary system.
Laser-Evoked Cortical Potentials in Cluster Headache
Authors: Ellrich J , Jung K , Ristic D , Yekta S Said
Published: April 2007

Craniofacial nociceptive processing in patients ( n = 25) suffering from unilateral cluster headache was assessed by laser-evoked cortical potentials (LEPs). Latencies and amplitudes of late (N2, P2) and middle-latency (N1) LEPs were measured in chronic (CCH, n = 9) and episodic cluster headache (ECH, n = 17). In CCH patients on headache side N1c occurred later and P2 amplitude was smaller than on the healthy control side. In active periods of ECH patients P2 latency was shorter on the headache side. In remission periods of ECH patients the N2P2 ratio was lower on the headache side. In 19 out of 26 examinations in 25 headache patients LEP deviated from normative data in healthy controls ( n = 10) without any specific pattern of altered parameters. LEPs document pathological changes in craniofacial nociception in cluster headache. However, there seems to be no pathognomonic deviation pattern that enables reliable diagnosis of cluster headache and application of LEPs in further studies of pathophysiological mechanisms.
A Multicentre, Double-Blind, Randomized, Placebo-Controlled, Parallel Group Study of Multiple Treatments of Botulinum Toxin Type A (BoNTA) for the Prophylaxis of Episodic Migraine Headaches
Authors: Relja M , Poole AC , Schoenen J , Pascual J , Lei X , Thompson C
Published: April 2007

Our aim was to evaluate the safety and efficacy of botulinum toxin type A (BoNTA; BOTOX®) for prophylaxis of episodic migraine. In this double-blind, placebo-controlled study, patients were randomized to 225, 150 or 75 U of BoNTA or placebo after a 30-day placebo run-in for three 90-day treatment cycles. The primary efficacy end-point was the mean reduction from baseline in the frequency of migraine episodes at day 180 in the placebo non-responder stratum. All groups ( N = 495) improved, with no significant differences. At day 180, the frequency of migraine episodes was reduced from baseline means of 4.3, 4.7, 4.7 and 4.4 by 1.6, 1.7, 1.5 and 1.4 for BoNTA 225 U, 150 U and 75 U and placebo, respectively. The primary end-point was not met. Treatment-related adverse events were transient and mild to moderate. BoNTA treatment was safe and well tolerated but did not result in significantly greater improvement than placebo in this study. Several factors may have confounded the results.
Prevalence of Trigeminal Autonomic Symptoms in Migraine: A Population-Based Study
Authors: Obermann M , Yoon M-S , Dommes P , Kuznetsova J , Maschke M , Weimar C , Limmroth V , Diener HC , Katsarava Z
Published: April 2007

Epidemiological data on trigeminal unilateral autonomic symptoms in patients with migraine are scarce. The authors wanted to provide a population-based evaluation of the prevalence of unilateral autonomic features in migraine patients and an assessment of the expression of unilaterality of autonomic symptoms and head pain in patients with UAs compared to other migraine patients. A population based sample of 6000 inhabitants of the city of Essen in Germany was screened using a previously validated standard questionnaire. Three thousand three hundred and sixty subjects (56% of a total 6000) responded. 841 subjects had migraine, out of which 226 reported accompanying unilatral auetonomic symptoms (26.9%, CI 95% [23.9-30%]). Unilateral autonomic symptoms in patients with migraine are common and have been widely underestimated in the past. One out of four migraine patients regularly experiences one or more unilateral autonomic symptoms during their attack. Migraine patients with accompanying autonomic symptoms seem to experience their pain more unilateral and more severe than non-UA patients.
Lactational State Modifies Alcohol Pharmacokinetics in Women
Authors: Pepino Marta Yanina , Steinmeyer Allison L. , Mennella Julie A.
Published: May 2007

Background: Given the physiological adaptations of the digestive system during lactation, the present study tested the hypothesis that lactation alters alcohol pharmacokinetics.

Methods: Lactating women who were exclusively breastfeeding a 2‐ to 5‐month‐old infant and 2 control groups of nonlactating women were studied. The first control group consisted of women who were exclusively formula‐feeding similarly aged infants, whereas the other consisted of women who had never given birth. A within‐subjects design study was conducted such that women drank a 0.4 g/kg dose of alcohol following a 12‐hour overnight fast during one test session (fasted condition) or 60 minutes after consuming a standard breakfast during the other (fed condition). Blood alcohol concentration (BAC) levels and mood states were obtained at fixed intervals before and after alcohol consumption.

Results: Under both conditions, the resultant BAC levels at each time point were significantly lower and the area under the blood alcohol time curve were significantly smaller in lactating women when compared with the 2 groups of nonlactating women. That such changes were due to lactation per se and not due to recent parturient events was suggested by the finding that alcohol pharmacokinetics of nonlactating mothers, who were tested at a similar time postpartum, were no different from women who had never given birth. Despite lower BAC levels in lactating mothers, there were no significant differences among the 3 groups of women in the stimulant effects of alcohol. However, lactating women did differ in the sedative effects of alcohol when compared with nulliparous but not formula‐feeding mothers. That is, both groups of parous women felt sedated for shorter periods of time when compared with nulliparous women.

Conclusions: The systemic availability of alcohol was diminished during lactation. However, the reduced availability of alcohol in lactating women did not result in corresponding changes in the subjective effects of alcohol.
Incidence of Atrial Arrhythmias Detected by Permanent Pacemakers (PPM) Post‐Pulmonary Vein Antrum Isolation (PVAI) for Atrial Fibrillation (AF): Correlation with Symptomatic Recurrence
Authors: VERMA ATUL , MINOR STEPHEN , KILICASLAN FETHI , PATEL DIMPI , HAO STEVEN , BEHEIRY SALWA , LAKKIREDDY DHANUMJAYA , ELAYI S. CLAUDE , CUMMINGS JENNIFER , MARTIN DAVID O. , BURKHARDT J. DAVID , SCHWEIKERT ROBERT A. , SALIBA WALID , TCHOU PATRICK J. , NATALE ANDREA
Published: April 2007

Background: Studies examining AF recurrences post‐PVAI base recurrence on patient reporting of symptoms. However, whether asymptomatic recurrences are common is not well known.

Objective: To assess the incidence of atrial tachycardia/fibrillation post‐PVAI as detected by a PPM and whether these recurrences correlate to symptomatic recurrence.

Methods: Eighty‐six consecutive patients with symptomatic AF and PPMs with programmable mode‐switch capability underwent PVAI. Mode switching was programmed post‐PVAI to occur at an atrial‐sensed rate of >170 bpm. Patients were followed with clinic visits, ECG, and PPM interrogation at 1, 3, 6, and 9 months post‐PVAI. The number and duration of mode‐switching episodes (MSEs) were recorded at each visit and is presented as median (interquartile range).

Results: The patients (age 57 ± 8 years, EF 54 ± 10%) had paroxysmal (65%) and persistent (35%) AF pre‐PVAI. Sensing, pacing, and lead function were normal for all PPMs at follow‐up. Of the 86 patients, 20 (23%) had AF recurrence based on symptoms. All 20 of these patients had appropriate MSEs detected. Of the 66 patients without symptomatic recurrence, 21 (32%) had MSEs detected. In 19 of these patients, MSEs were few in number, compared with patients with symptomatic recurrence (16 [4–256] vs 401 [151–2,470], P < 0.01). The durations were all <60 seconds. All of these nonsustained MSEs occurred within the first 3 months post‐PVAI, gradually decreasing over time. The other 2 of 21 remaining patients had numerous (1,343 [857–1,390]) and sustained (18 ± 12 minutes) MSEs that also persisted beyond 3 months (1 beyond 6 months). Therefore, the incidence of numerous, sustained MSEs in asymptomatic patients post‐PVAI was 2 of 66 (3%).

Conclusions: Detection of atrial tachyarrhythmias by a PPM occurred in 30% of patients without symptomatic AF recurrence. Most of these episodes were <60 seconds and waned within 3 months. Sustained, asymptomatic episodes were uncommon.
Time Course of Esophageal Lesions After Catheter Ablation with Cryothermal and Radiofrequency Ablation: Implication for Atrio‐Esophageal Fistula Formation After Catheter Ablation for Atrial Fibrillation
Authors: RIPLEY KENNETH LAUREN , GAGE ANDREW A. , OLSEN DON B. , VAN VLEET JOHN F. , LAU CHU‐PAK , TSE HUNG‐FAT
Published: April 2007

Background: Atrio‐esophageal fistulas have been described as a consequence of radiofrequency (RF) ablation for the treatment of atrial fibrillation (AF). However, whether cryoablation can avoid this potential fatal complication remains unclear.

Methods and Results: We studied the effects of direct application of RF and cryoablation on the cervical esophagus in 16 calves. Cryoablation was performed with a 6.5‐mm catheter probe using a single 5‐minute freeze at <−80°C, and RF ablation was delivered with an 8‐mm catheter electrode at 50 W and 50°C for 45–60 seconds. Histopathologic assessments were performed at 1, 4, 7, and 14 day(s) after completion of the ablation protocol: four animals were examined each day. A total of 85 direct esophageal ablations were performed: 41 with RF and 44 with cryoablation. There were no significant differences in lesion width, depth, or volume between cryoablation and RF ablation at Day 1, 4, and 14 after the procedure (P > 0.05). However, lesion width and volume were significantly larger with RF than with cryoablation at Day 7. Although acute (Day 1) and chronic (Day 14) RF and cryoablation lesions were of comparable size, histologic evidence of partial‐ to full‐wall esophageal lesion ulceration was observed in 0 of 44 (0%) lesions with cryoablation, compared with 9 of 41 (22%) lesions with RF ablation (P = 0.0025).

Conclusions: Direct application of cryoablation and RF ablation created similar acute and chronic lesion dimensions on the esophagus. However, cryoablation was associated with a significantly lower risk of esophageal ulceration, compared with RF ablation.
Apparent Activation Energy for the Densification of a Commercially Available Granulated Zirconia Powder
Authors: Bernard‐Granger Guillaume , Guizard Christian
Published: April 2007

Sintering in air of a commercially available granulated zirconia powder has been investigated using vertical dilatometer tests. Using several heating rates and the formalism of the constant rate of heating method, it has been possible to determine the apparent activation energy for the mechanism controlling densification, for different values of the relative density. It is shown that the apparent activation energy does not have a single value but depends directly on the relative density.
Design of High‐Quality Pt–CeO2 Composite Anodes Supported by Carbon Black for Direct Methanol Fuel Cell Application
Authors: Takahashi Motoi , Mori Toshiyuki , Ye Fei , Vinu Ajayan , Kobayashi Hidehiko , Drennan John
Published: April 2007

A Pt on nano‐sized CeO2 particles that in turn are supported on carbon black (CB) was synthesized using the co‐impregnation method. This potential anode material for fuel cell applications was synthesized in a stepwise process. The pure CeO2 was synthesized using an ammonium carbonate precipitation method, and the Pt particles dispersed on the CeO2 in such a way that a uniform dispersion with the CB was obtained (Pt–CeO2/CB). The electrochemical activity of the methanol (CH3OH) oxidation reaction on the Pt–CeO2/CB was investigated using cyclic voltammetry and chronoamperometry experimentation. The onset potential of CH3OH oxidation reaction on the Pt–CeO2/CB anode was shifted to a lower potential as compared with that on commercially available Pt–Ru/carbon (C) alloy anode. In addition, the activation energy of the Pt–CeO2/CB anode was much lower than that of the Pt–Ru/C alloy anode. Moreover, the current density of the Pt–CeO2/CB anode was much higher than that of the Pt–Ru/C alloy anode at temperatures between 28° and 60°C. These results suggest that the anode performance of the Pt–CeO2/CB anode at the operating temperature of typical fuel cells (80°C) is superior to that of the more usual Pt–Ru/C alloy anode. Importantly, the rare metal, Ru, is not required in the present anode material and the amount of Pt required is also significantly reduced. As a consequence, we report a promising candidate Pt–CeO2/CB composite anode for application in the development of direct methanol fuel cells.
Dynamic Fracture of Ceramics in Armor Applications
Authors: Chen Weinong W. , Rajendran A. M. , Song Bo , Nie Xu
Published: April 2007

Ceramic materials have been extensively used in armor applications for both personnel and vehicle protection. As the types of threats have diversified recently, e.g., improvised explosive devices and explosively formed projectiles, a proper set of ceramic material selection criteria is needed to design and optimize corresponding mitigating structures. However, the dynamic fracture and failure behavior of engineering ceramics is still not well understood. Using examples of thin ceramic plates and confined thick ceramics subjected to kinetic energy projectile impact, this article provides a brief summary on the current understanding of dynamic failure processes of ceramics under dynamic penetration loading conditions. Laboratory examination of dynamic fracture of ceramics is conducted using split Hopkinson bars with various loading rates, stress states, and loading histories.
Tensile Creep Behavior of SiC‐Based Fibers With a Low Oxygen Content
Authors: Sauder Cédric , Lamon Jacques
Published: April 2007

The creep behavior of Hi‐Nicalon, Hi‐Nicalon S, and Tyranno SA3 fibers is investigated at temperatures up to 1700°C. Tensile tests were carried out on a high‐capability fiber testing apparatus in which the fiber is heated uniformly under vacuum. Analysis of initial microstructure and composition of fibers was performed using various techniques. All the fibers experienced a steady‐state creep. Primary creep was found to be more or less significant depending on fiber microstructure. Steady‐state creep was shown to result from grain‐boundary sliding. Activation energy and stress exponents were determined. Creep mechanisms are discussed on the basis of activation energy and stress exponent data. Finally, tertiary creep was observed at very high temperatures. Tertiary creep was related to volatilization of SiC. Results are discussed with respect to fiber microstructure.
Core–Shell Structure Analysis of BaTiO3 Ceramics by Synchrotron X‐Ray Diffraction
Authors: Yasukawa Katsumasa , Nishimura Michiaki , Nishihata Yasuo , Mizuki Jun'ichiro
Published: April 2007

The shell thickness of a BaTiO3 ceramic with a core–shell structure has been measured by means of synchrotron X‐ray diffraction (XRD). BaTiO3 ceramic is known from transmission electron microscope (TEM)/energy dispersive X‐ray spectroscopy (EDS) observations to have an inhomogeneous microstructure with cores of a pure BaTiO3 and shells doped with additives. It is also known, from XRD observations, that the BaTiO3 cores have a tetragonal lattice structure and the shells are pseudocubic. We have estimated the shell thickness d from the full‐width at half‐maximum (FWHM) of the cubic (400)c peak, using Scherrer's equation. The shell thickness dcal was also evaluated from the volume fraction of tetragonal BaTiO3 using a spherical core–shell model. The two values thus determined agree well, confirming that the BaTiO3 ceramic specimens have a core–shell structure. Our results show that synchrotron XRD is a simple and effective tool for quantitative analysis of the core–shell structure. It enables us to understand quantitatively the relationship between the microstructure and the dielectric properties of BaTiO3 ceramics.
Novel Low‐Temperature Synthesis of Ferroelectric Neodymium‐Doped Bismuth Titanate Nanoparticles
Authors: Prakash Prem , Garg Ashish , Roy Mukesh Kumar , Verma Harish Chandra
Published: April 2007

In this study, we report on the synthesis of nanopowders of ferroelectric Bi3.5Nd0.5Ti3O12 ceramic at temperatures below 500°C via a simple chemical method using citric acid as a solvent. The calcined powders were characterized using X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). Heating the as‐dried powders in air first leads to crystallization of the Bi2Ti2O7 phase at ∼310°C, followed by crystallization of the perovskite Nd‐doped Bi4Ti3O12 phase at ∼490°C as suggested by the peaks in the DSC analysis and confirmed by the evolution of phases in XRD patterns of the powders calcined at various temperatures. TEM of particles calcined at 550°C for 1 h in air showed an average particle size of 50–60 nm. The temperature dependence of capacitance of nanopowders calcined at 700°C for 1 h in air showed a Curie temperature of ∼615°C evincing a ferroelectric transition.
The Formation Mechanism of the Novel Core–Shell Microstructure in Polyvinyl Alcohol‐Additive Lead Zirconate Titanate Films
Authors: Chang Tien‐I , Lin Chen‐Fu , Huang Jow‐Lay , Wang Sheng‐Chang
Published: April 2007

Crack‐free lead zirconate titanate (PZT) films were fabricated by the sol–gel process using a modified polyvinyl alcohol (PVA) solution, which contained PVA, glycerol, and water. In this study, the modified PVA solution was added to the PZT precursor solution, ranging from 1:2 to 1:6 in weight ratio. The X‐ray diffraction results showed that the addition of the PVA solution still made the PVA‐additive PZT films maintain crystallinity at 600°C for 30 min. The phase transformation of the PVA‐additive PZT films was similar to the PVA‐free PZT films, but the initial formation temperature of the perovskite phase was successfully reduced to 500°C by the enhancement of the PVA solution. Furthermore, the chelating effects of PVA induced to have the novel circular PZT clusters with a lead‐rich core, and a zirconium‐ and titanium‐rich shell. The formation mechanism of the novel core–shell PZT films is discussed. The circular core–shell PZT clusters acted as heterogeneous nucleation sites to reduce the nucleation barrier. Therefore, the PVA‐additive multi‐layer PZT films showed a smaller grain size than PVA‐free PZT films. With this innovative procedure, crack‐free, fine‐grained, multi‐layer PZT films were successfully obtained.
Fabrication of a Nano‐Si3N4/Nano‐C Composite by High‐Energy Ball Milling and Spark Plasma Sintering
Authors: Xu Xin , Nishimura Toshiyuki , Hirosaki Naoto , Xie Rong‐Jun , Tanaka Hidehiko
Published: April 2007

A nano‐Si3N4/5 wt% nano‐C composite was successfully fabricated for the first time via high‐energy ball milling, followed by spark plasma sintering. The milling promoted the amorphization of the starting powders; most of the carbon particles were transformed into nano‐size and embedded in the amorphous phase. This, combined with a low sintering temperature and a rapid densification rate, prevented the reactions between carbon and the other starting powders, leading to a uniform nano/nano‐composite microstructure. Nano‐sized carbon grains with an average diameter of about 10 nm were homogeneously dispersed in nano‐sized (about 70 nm) Si3N4 grain boundaries. The hardness of the obtained nano‐ceramics is comparable with that of conventional Si3N4, whereas Young's modulus is significantly decreased.
Oxygen Non‐Stoichiometry and Thermal–Chemical Expansion of Ce0.8Y0.2O1.9−δ Electrolytes by Neutron Diffraction
Authors: Li Yaping , Maxey Evan R. , Richardson James W. , Ma Beihai , Lee Tae H. , Song Sun‐Ju
Published: April 2007

A dense tubular solid electrolyte with the composition Ce0.8Y0.2O1.9−δ (CY20) was prepared. In situ time‐of‐flight neutron powder diffraction (TOF‐ND) was performed at 900°C in the oxygen partial pressure pO2 range from 10−1–10−18 atm, and TOF‐ND data were analyzed by the Rietveld method. Diffraction data showed that the lattice parameter moderately increased with decreasing pO2 in the range of pO2>10−14 atm, while a dramatic expansion (∼0.6%) of the fluorite structure occurred at a pO2 of 10−18 atm. By refining all reasonable structural parameters, an approximately linear relationship between lattice parameter and oxygen vacancy δ was observed, resulting in ɛc/δ=0.08 and corresponding to δ=0.10 at a pO2 of 10−18 atm, all in agreement with the data published in the literature. The relative change in lattice parameter Δa/a followed a −1/4 power relation with pO2 in a low‐pO2 regime. As several (often strongly correlated) structural parameters can affect the intensities in ND profiles, care was taken to select refinement variables. It was found that O atom thermal factors for CY20 increased as the oxygen vacancy concentration and lattice expansion increased.
Non‐Isothermal Decomposition Kinetics of Alkaline Earth Metal Carbonates
Authors: Maitra S. , Bandyopadhyay N. , Das S. , Pal A. J. , Pramanik J.
Published: April 2007

The kinetics of thermal decomposition of four synthetic alkaline earth metal carbonates (MgCO3, CaCO3, SrCO3, and BaCO3) was studied under non‐isothermal conditions using thermo‐gravimetry. The activation energy and the pre‐exponential factor for the decomposition reactions were determined using the Agarwal and Sivasubramanium integral approximation method. A new method was developed using a Turbo‐C‐based computer program to evaluate the integral of the kinetic equation. It was observed that the decomposition reaction of MgCO3 and CaCO3 followed two‐dimensional diffusion‐controlled kinetics and the decomposition reaction of SrCO3 and BaCO3 followed a Ginstling–Brounshtein model‐based diffusion‐controlled kinetics.
Synthesis of Mesoporous Needle‐Shaped Ytterbium Oxide Crystals by Solvothermal Treatment of Ytterbium Chloride
Authors: Hosokawa Saburo , Iwamoto Shinji , Inoue Masashi
Published: April 2007

The reaction of rare‐earth (RE; Y, Er, and Yb) chloride hydrates in 1,4‐butanediol at 300°C for 2 h gave mixtures of RE(OH)2Cl and RE2O3·xH2O, and the products were composed of irregularly shaped particles. A prolonged reaction (10 h) yielded a mixture of RE(OH)2Cl and RE2O3·xH2O for Er or Y, but phase‐pure RE2O3·xH2O was obtained for Yb. The product for Yb comprised needle‐shaped single crystals of Yb2O3·xH2O with a width of 0.2–0.6 μm and a length of 5–15 μm. The Yb2O3·xH2O phase decomposed to Yb2O3 at 350°–500°C, preserving the needle‐shaped morphology; this was maintained even after calcination at 1100°C. Single crystals of Yb2O3 obtained by the calcination of Yb2O3·xH2O at 500°C had very small voids and the voids were enlarged to 35 Å in diameter by calcination at 800°C.
Manganese‐Doped Zinc Orthosilicate‐Bearing Phosphor Microparticles with Controlled Three‐Dimensional Shapes Derived from Diatom Frustules
Authors: Cai Ye , Dickerson Matthew B. , Haluska Michael S. , Kang Zhitao , Summers Christopher J. , Sandhage Kenneth H.
Published: April 2007

Mn‐doped zinc orthosilicate (Zn2SiO4)‐bearing phosphor microparticles were synthesized with controlled three‐dimensional (3‐D) morphologies inherited from the microshells (frustules) of diatoms (unicellular algae). Silica‐based diatom frustules were first coated with manganese and zinc oxide nanoparticles by exposure to an acetate precursor solution and then firing at 700°C. Subsequent reaction of the nanoparticles with the underlying silica at 1050°C yielded compact, continuous, and conformal Mn‐doped Zn2SiO4 coatings on the frustule surfaces. The converted 3‐D microparticles exhibited bright green emission upon stimulation with 275‐nm light. Photoluminescent microparticles with a wide variety of well‐controlled 3‐D morphologies can be mass produced with this simple, low‐cost bioclastic process.
Fabrication and Microwave Properties of Three‐Dimensional Photonic Crystals With a Diamond Structure Composed of Ceramic Spheres in Resin
Authors: Nakagawa Takuji , Kageyama Keisuke , Wada Nobuyuki , Sakabe Yukio , Kirihara Soshu , Miyamoto Yoshinari
Published: April 2007

Three‐dimensional photonic crystals with a diamond structure composed of YSZ (3 mol% Y2O3‐stabilized ZrO2) spheres in a resin matrix were fabricated by using stereolithography. The lattice constant was 12 mm and the diameter of the spheres was 5 mm. These photonic crystals made of ceramic spheres showed complete photonic band gaps at around 12 GHz between the eighth and ninth bands. The propagation characteristics of microwaves agreed well with the calculated results using the plane wave expansion method.
Thermal Behavior of the Raw Materials Forming Porcelain Stoneware Mixtures by Combined Optical andIn SituX‐Ray Dilatometry
Authors: Gualtieri Alessandro F.
Published: April 2007

The dilatometric behavior of the raw materials forming a porcelain stoneware tile mixture was investigated at a molecular/microscopical scale by combinedin situoptical dilatometry and X‐ray powder diffraction. Each single raw material was investigated separately and mixed with all the others to simulate a standard production mixture. Thus, it was possible to evaluate whether the reaction path taking place during the firing of the raw materials is changed during the firing of the combined mixture. A general classification of the causes of contraction and/or expansion events has been attempted. Causes are subdivided intostructural(S, intra‐mineral) andmicrostructural(M, inter‐mineral). Contractions can be generated by: loss of volatiles (S); structure collapse of the pseudo‐amorphous products of dehydroxylation of clay minerals (S); solid state or viscous sintering (M); crystallization from amorphous precursor (S) and related volume reduction (densification) (M); displacive phase transition with a volume decrease (S); and melting generally atT>800°C (S). Expansion can be generated by thermal expansion (S); displacive phase transition with a volume increase (S); glass transitions (S) and related volume change (M); and overfiring/pyroplastic deformation (M). Many reactions observed in the single raw materials have also been observed in the mixture. The major variations concern (i) crystallization of cristobalite is observed only in the kaolin and not in the mixture, where silica segregated from the reaction of formation of mullite from metakaolinite is readily incorporated in the alkaline amorphous phase; (ii) quartz alone is stable with temperature but tends to be partly decomposed in contact with the alkaline melt in the mixture; and (iii) in the illite‐rich clay, melting of the system and subsequent expansion caused by pyroplastic deformation of the K‐rich melt begins at relatively low temperature (1150°C). This behavior is not observed in the mixture below 1350°C where a presumably less viscous melt is formed.
Synthesis of Bundle‐ and Flake‐Like CeO2 Powders Via a Precursor‐Pyrolysis Approach
Authors: Chen Limiao , Xie Hongbo , Liu Younian , Huang Kelong
Published: April 2007

Micrometer‐sized CeO2 powders with bundle‐ and flake‐like morphologies have been successfully synthesized by a precursor‐pyrolysis approach, in which the precursors are first synthesized by a hydrothermal method and CeO2 powders are finally obtained through a pyrolysis process. Results reveal that the stoichiometric concentration of cerium ion plays an important role in the formation of the final products with different morphologies. The CeO2 powders obtained by pyrolyzing the precursors prepared from the solutions with high concentration (0.05M) and low concentration (0.0125M) exhibit bundle‐ and flake‐like morphology, respectively. The possible growth process is proposed by preparing a series of intermediate morphologies during the shape evolution of bundle‐like CeO2 based on the scanning electron microscopy image observation.
Mechanical Properties and Contact Damage Behavior in Aligned Silicon Nitride Materials
Authors: Belmonte M. , Miranzo P. , Osendi M. I.
Published: April 2007

Aligned Si3N4 microstructures were achieved by seeding, extruding, and laminating methods. The degree of grain alignment was determined by microstructural measurements. Mechanical properties, including toughness, strength, hardness, and elastic modulus, as well as the contact damage response, were addressed and discussed as a function of this anisotropic microstructure. KIC values over 8 MPa·m1/2 and strengths above 900 MPa were achieved for the most favorable planes in the textured material. Contact damage behavior was influenced by grain orientation in two ways, first, by conferring elliptical shape to the radial surface cracks and second, by the multiple twin/slip formation at the large seeds within the high shear strain region.
High‐Temperature Proton Conductivity in Acceptor‐Substituted Rare‐Earth Ortho‐Tantalates, LnTaO4
Authors: Haugsrud Reidar , Norby Truls
Published: April 2007

The electrical properties of 1 mol% Ca‐doped LnTaO4 (Ln=La, Nd, Gd, Er) have been characterized by AC impedance spectroscopy and by the EMF transport number technique as a function of the oxygen pressure and the water vapor pressure from 300° to 1200°C. Protons, oxide ions, electron holes, and electrons contribute to the total conductivity, depending on the conditions. Ionic conductivity predominates under reducing and weakly reducing conditions, with protons prevailing in wet atmospheres up to temperatures of around 1000°C. p‐type electronic conductivity prevails at high temperatures under oxidizing conditions. The conductivity behavior has been interpreted according to a point‐defect model where protons and oxygen vacancies charge compensate the acceptor doping. Thermodynamic and transport parameters have been extracted based on the changes in total conductivity upon variations in the conditions. The hydration enthalpy becomes increasingly negative with increasing oxide ion density from LaTaO4 to ErTaO4.
Preferential Grain Orientation in Hot Pressed TiB2
Authors: Jensen Morten Sundheim , Einarsrud Mari‐Ann , Grande Tor
Published: April 2007

Preferential grain growth is reported for hot pressed titanium diboride (TiB2) prepared at 1800°C and 50 MPa. Orientation imaging microscopy and X‐ray diffraction revealed that the grains in the material were preferentially orientated with the [001] direction parallel to the mechanical field. The experimental findings are discussed, with emphasis on the anisotropic properties of TiB2.
Mitochondria and Ca2+signaling
Authors: Toescu Emil C.
Published: May 2007

Mitochondria play a central role in cell homeostasis. Amongst others, one of the important functions of mitochondria is to integrate its metabolic response with one of the major signaling pathways ‐ the Ca2+signaling. Mitochondria are capable to sense the levels of cytosolic Ca2+and generate mitochondrial Ca2+responses. Specific mechanisms for both Ca2+uptake and Ca2+release exist in the mitochondrial membranes. In turn, the mitochondrial Ca2+signals are able to produce changes in the mitochondrial function and metabolism, which provide the required level of functional integration. This essay reviews briefly the current available information regarding the mitochondrial Ca2+transport systems and some of the functional consequences of mitochondrial Ca2+uptake