bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of uterine EMG and cervical LIF in monitoring pregnant patients
Authors: Garfield Robert E. , Maner William L. , Maul Holger , Saade George R.
Published: February 2005

Objectives  Review the uterine electromyography (EMG) and cervical light‐induced fluorescence (LIF) devices and their role in the evaluation of uterine and cervical function in comparison with present methods.

Design  Review of recent studies.

Setting  University of Texas Medical Branch Labour and Delivery Clinics.

Population  Various groups of pregnant women.

Methods  We have developed and recently improved non‐invasive methods to evaluate quantitatively uterine electrical signals from the abdominal surface and cervical collagen.

Main outcome measures  Uterine EMG utilised power density spectrum (PDS) peak frequency and total power (P0) and cervical LIF utilising LIF ratio.

Results  Human studies indicate that uterine and cervical performance can be successfully monitored during pregnancy using EMG and LIF, respectively, and the assessment of uterine and cervical function can both be used to influence patient management in a variety of conditions associated with labour, more than can currently available methods.

Conclusions  The potential benefits of the proposed instrumentation include the following: a reduction in the rate of preterm birth, improved maternal and perinatal outcome, better monitoring of treatment, decreased caesarean section rate and better research methods for understanding uterine and cervical function.
Glutathione depletion resulting in selective mitochondrial complex I inhibition in dopaminergic cells is via an NO‐mediated pathway not involving peroxynitrite: implications for Parkinson's disease
Authors: Hsu Michael , Srinivas Bharath , Kumar Jyothi , Subramanian Rajagopalan , Andersen Julie
Published: February 2005

An early biochemical change in the Parkinsonian substantia nigra (SN) is reduction in total glutathione (GSH + GSSG) levels in affected dopaminergic neurons prior to depletion in mitochondrial complex I activity, dopamine loss, and cell death. We have demonstrated using dopaminergic PC12 cell lines genetically engineered to inducibly down‐regulate glutathione synthesis that total glutathione depletion in these cells results in selective complex I inhibition via a reversible thiol oxidation event. Here, we demonstrate that inhibition of complex I may occur either by direct nitric oxide (NO) but not peroxinitrite‐mediated inhibition of complex I or through H2O2‐mediated inhibition of the tricarboxylic acid (TCA) cycle enzyme α‐ketoglutarate dehydrogenase (KGDH) which supplies NADH as substrate to the complex; activity of both enzymes are reduced in PD. While glutathione depletion causes a reduction in spare KGDH enzymatic capacity, it produces a complete collapse of complex I reserves and significant effects on mitochondrial function. Our data suggest that NO is likely the primary agent involved in preferential complex I inhibition following acute glutathione depletion in dopaminergic cells. This may have major implications in terms of understanding mechanisms of dopamine cell death associated with PD especially as they relate to complex I inhibition.
Retinal‐specific ATP‐binding cassette transporter (ABCR/ABCA4) is expressed at the choroid plexus in rat brain
Authors: Bhongsatiern Jiraganya , Ohtsuki Sumio , Tachikawa Masanori , Hori Satoko , Terasaki Tetsuya
Published: February 2005

ATP‐binding cassette (ABC) transporter A4 is a member of the ABC transporter subfamily A which has been reported to be exclusively expressed in the retina. In contrast, a previous report has suggested a possible relationship between ABCA4 and CNS function. The purpose of the present study was to investigate the localization of ABCA4 mRNA and protein in rat brain. In situ hybridization analysis revealed that ABCA4 mRNA was localized in the lateral ventricles. RT–PCR analysis detected ABCA4 mRNA in isolated rat choroid plexus and conditionally immortalized rat choroid plexus epithelial cells (TR‐CSFB). Furthermore, ABCA4 protein was also detected in the isolated rat choroid plexus at about 250 kDa by western blot analysis, and its apparent molecular size was reduced by N‐glycosidase F treatment. These results suggest that glycosylated ABCA4 protein is expressed in rat choroid plexus epithelial cells. ABCA4 may play a role in the function of the blood–cerebrospinal fluid barrier and affect CSF conditions.
Differential regulation of multiple populations of granules in rat adrenal chromaffin cells by culture duration and cyclic AMP
Authors: Tang Kim San , Tse Amy , Tse Frederick W.
Published: February 2005

We employed carbon fiber amperometry to measure the amount of catecholamine released from individual granules (i.e. the quantal size, Q) of rat chromaffin cells. The distribution of Q1/3 of amperometric events could be reasonably described by the summation of at least three Gaussians, suggesting that rat chromaffin cells contained at least three distinct populations of granules, with a small, medium or large modal Q. After 3 days of culture, the mean cellular Q reduced by ∼14%, which did not arise from a uniform percentage decrease in the Q of every granule. Instead, the rundown involved a > 11% decrease in the proportional release from large Q granules and a > 19% decrease in the modal Q‐value of small Q granules. In contrast, when cells were cultured with dibutyryl‐cAMP (dBcAMP) for 3 days, their mean cellular Q increased by ∼38% (relative to time‐matched controls). This increase in Q was not associated with any shift in the proportional release from the three populations of granules. Instead, cAMP increased the average amount of catecholamines released from all three populations of granules. Our data raise the possibility that distinct populations of granules in rat chromaffin cells can be regulated either differentially or uniformly.
A domain at the C‐terminus of PS1 is required for presenilinase and γ‐secretase activities
Authors: Brunkan A. L. , Martinez M. , Wang J. , Walker E. S. , Goate A. M.
Published: February 2005

The structural requirements for presenilin (PS) to produce active presenilinase and γ‐secretase enzymes are poorly understood. Here we investigate the role the cytoplasmic C‐terminal region of PS1 plays in PS1 activity. Deletion or addition of residues at the PS C‐terminus has been reported to inhibit presenilinase endoproteolysis of PS and alter γ‐secretase activity. In this study, we use a sensitive assay in PS1/2KO MEFs to define a domain at the extreme C‐terminus of PS1 that is essential for both presenilinase and γ‐secretase activities. Progressive deletion of the C‐terminus demonstrated that removal of nine residues produces a PS1 molecule (458ST) that lacks both presenilinase processing and γ‐secretase cleavage of Notch and APP substrates. In contrast, removal of four or five residues had no effect (462ST, 463ST), while intermediate truncations partially inhibited PS1 activity. The 458ST mutant was unable to replace endogenous wtPS1 in HEK293 cells. Although 458ST was able to form a γ‐secretase complex, this complex was not matured, illustrated by mutant PS1 instability, lack of endoproteolysis, and little production of mature Nicastrin. These data indicate that the C‐terminal end of PS1 is essential for Nicastrin trafficking and modification as well as the replacement of endogenous PS1 by PS1 transgenes.
A complementary peptide approach applied to the design of novel semaphorin/neuropilin antagonists
Authors: Williams Gareth , Eickholt Britta J. , Maison Patrick , Prinjha Rabinder , Walsh Frank S. , Doherty Patrick
Published: February 2005

Semaphorin 3A can inhibit axonal growth and induce neuronal apoptosis following binding to neuropilin‐1, with the membrane proximal MAM (meprin, A5, mu) domain in neuropilin‐1 playing a key role in the formation of a higher order receptor complex. If functional motifs on semaphorin 3A and/or the MAM domain can be identified, then small‐constrained peptides might be developed as antagonists. We have scored peptide pairs for complementary hydropathy and antisense homology to identify a candidate functional motif in the Ig domain of semaphorin 3A, and in the MAM domain of neuropilin‐1. Synthetic peptides corresponding to these sequences fully inhibit growth cone collapse induced by semaphorin 3A. A number of smaller peptides derived from the parental sequence also inhibited the response, particularly after they were constrained by a disulfide bond. Finally, we have used an algorithm to design a peptide that is a near‐perfect hydropathic complement of the candidate functional site in the MAM domain; this also inhibits the semaphorin 3A response. Thus, an algorithm‐driven methodology has led to the identification of three independent semaphorin 3A antagonists. Semaphorin 3F stimulates growth cone collapse following binding to the closest relative to neuropilin‐1 in the genome, neuropilin‐2. Where tested, the peptides that antagonise semaphorin 3A failed to inhibit the semaphorin 3F response.
Differences in serotonergic neurotransmission between rats displaying high or low anxiety/depression‐like behaviour: effects of chronic paroxetine treatment
Authors: Keck Martin E. , Sartori Simone B. , Welt Tobias , Müller Marianne B. , Ohl Frauke , Holsboer Florian , Landgraf Rainer , Singewald Nicolas
Published: February 2005

Disturbances in serotonergic neurotransmission have been suggested to be closely interlinked with hyperactivity of the hypothalamic‐pituitary‐adrenocortical (HPA) system, and are likely to be involved in the pathophysiology of anxiety disorders and major depression. We therefore investigated markers of serotonergic transmission and their modulation by chronic paroxetine in rats selectively bred for high (HAB) or low (LAB) anxiety‐related behaviour, both under basal conditions and in response to emotional stress. Hippocampal serotonin 1 A (5‐HT1A) receptor mRNA expression was reduced in HAB rats, whereas 5‐HT concentrations in hippocampal microdialysates did not differ between HAB and LAB rats under basal conditions. In the hippocampus, overall expression of serotonin transporter binding sites was increased in HAB compared with LAB rats. Exposure to emotional stress failed to increase intrahippocampal 5‐HT release in HAB rats whereas LAB rats displayed a physiological, albeit small rise. Chronic paroxetine treatment markedly increased the stress‐induced rise in hippocampal 5‐HT in HAB, but not LAB rats. This effect may be (at least in part) related to a greater down‐regulation of hippocampal serotonin transporter binding sites by paroxetine in HABs compared with LABs, while 5‐HT1A receptor expression remained unaffected in this brain area. The findings indicate reduced hippocampal serotonergic transmission in HAB rats as compared with LAB rats, which is evident both at the presynaptic (5‐HT release) and the postsynaptic (5‐HT1A receptor) level. Chronic paroxetine enhanced the presynaptic responsivity in HAB rats, but not LAB rats, pointing to a preferential efficacy of paroxetine in rats with enhanced anxiety/depression‐related behaviour.
Protective autoimmunity: interferon‐γ enables microglia to remove glutamate without evoking inflammatory mediators
Authors: Shaked I. , Tchoresh D. , Gersner R. , Meiri G. , Mordechai S. , Xiao X. , Hart R. P. , Schwartz M.
Published: February 2005

Glutamate in excessive amounts is a major contributor to neuronal degeneration, and its removal is attributed mainly to astrocytes. Traumatic injury to the central nervous system (CNS) is often accompanied by disappearance of astrocytes from the lesion site and failure of the remaining cells to withstand the ensuing toxicity. Microglia that repopulate the lesion site are the usual suspects for causing redox imbalance and inflammation and thus further exacerbating the neurotoxicity. However, our group recently demonstrated that early post‐injury activation of microglia as antigen‐presenting cells correlates with an ability to withstand injurious conditions. Moreover, we found that T cells reactive to CNS‐specific self‐antigens protected neurons against glutamate toxicity. Here, we show that antigen‐specific autoimmune T cells, by tailoring the microglial phenotype, can increase the ability of microglia‐enriched cultures to remove glutamate. This T‐cell‐mediated effect could not be achieved by the potent microglia‐activating agent lipopolysaccharide (LPS), but was dose‐dependently reproduced by the Th1 cytokine interferon (IFN)‐γ and significantly reduced by neutralizing anti‐IFN‐γ antibodies. Under the same conditions, IFN‐γ had no effect on cultured astrocytes. Up‐regulation of glutamate uptake induced by IFN‐γ activation was not accompanied by the acute inflammatory response seen in LPS‐activated cultures. These findings suggest that T cells or their cytokines can cause microglia to adopt a phenotype that facilitates rather than impairs glutamate clearance, possibly contributing to restoration of homeostasis.
Extracellular release of newly synthesized sphingosine‐1‐phosphate by cerebellar granule cells and astrocytes
Authors: Anelli Viviana , Bassi Rosaria , Tettamanti Guido , Viani Paola , Riboni Laura
Published: February 2005

Sphingosine‐1‐phosphate (S1P) is a potent biomediator that can act as either an intracellular or an intercellular messenger. In the nervous system it exerts a wide range of actions, and specific membrane receptors for it have been identified in various regions. However, the physiological origin of extracellular S1P in the nervous system is largely unknown. We investigated cerebellar granule cells at different stages of differentiation and astrocytes in primary cultures as possible origins of extracellular S1P. Although these cells show marked differences in S1P metabolism, we found that they can all release S1P and express mRNAs for S1P specific receptors. Extracellular S1P derives from the export of newly synthesized intracellular S1P, and not from the action of a released sphingosine kinase. S1P release is rapid, efficient, and can be regulated by exogenous stimuli. Phorbol ester treatment resulted in an increase in sphingosine kinase 1 activity in the membranes, accompanied by a significant increase in extracellular S1P. S1P release in cells from the cerebellum emerges as a regulated mechanism, possibly related to a specific pool of newly synthesized S1P. To our knowledge, this is the first evidence of the extracellular release of S1P by primary cells from the CNS, which supports a role of S1P as autocrine/paracrine physiological messenger in the cerebellum.
Role of the autophagic‐lysosomal system on low potassium‐induced apoptosis in cultured cerebellar granule cells
Authors: Canu Nadia , Tufi Roberta , Serafino Anna Lucia , Amadoro Giuseppina , Ciotti Maria Teresa , Calissano Pietro
Published: February 2005

Apoptotic and autophagic cell death have been implicated, on the basis of morphological and biochemical criteria, in neuronal loss occurring in neurodegenerative diseases and it has been shown that they may overlap. We have studied the relationship between apoptosis and autophagic cell death in cerebellar granule cells (CGCs) undergoing apoptosis following serum and potassium deprivation. We found that apoptosis is accompanied by an early and marked proliferation of autophagosomal–lysosomal compartments as detected by electron microscopy and immunofluorescence analysis. Autophagy is blocked by hrIGF‐1 and forskolin, two well‐known inhibitors of CGC apoptosis, as well as by adenovirus‐mediated overexpression of Bcl‐2. 3‐Methyladenine (3‐MA) an inhibitor of autophagy, not only arrests this event but it also blocks apoptosis. The neuroprotective effect of 3‐MA is accompanied by block of cytochrome c (cyt c) release in the cytosol and by inhibition of caspase‐3 activation which, in turn, appears to be mediated by cathepsin B, as CA074‐Me, a selective inhibitor of this enzyme, fully blocks the processing of pro‐caspase‐3. Immunofluorescence analysis demonstratesd that cathepsin B, normally confined inside the lysosomal‐endosomal compartment, is released during apoptosis into the cytosol where this enzyme may act as an execution protease. Collectively, these observations indicate that autophagy precedes and is causally connected with the subsequent onset of programmed death.
Potentiation of ATP‐induced currents due to the activation of P2X receptors by ubiquitin carboxy‐terminal hydrolase L1
Authors: Manago Yoshimasa , Kanahori Yoshiko , Shimada Aki , Sato Ayumi , Amano Taiju , Sato‐Sano Yae , Setsuie Rieko , Sakurai Mikako , Aoki Shunsuke , Wang Yu‐Lai , Osaka Hitoshi , Wada Keiji , Noda Mami
Published: February 2005

Mammalian neuronal cells abundantly express a de‐ubiquitinating isozyme, ubiquitin carboxy‐terminal hydrolase L1 (UCH L1). Loss of UCH L1 function causes dying‐back type of axonal degeneration. However, the function of UCH L1 in neuronal cells remains elusive. Here we show that overexpression of UCH L1 potentiated ATP‐induced currents due to the activation of P2X receptors that are widely distributed in the brain and involved in various biological activities including neurosecretion. ATP‐induced inward currents were measured in mock‐, wild‐type or mutant (C90S)‐UCH L1‐transfected PC12 cells under the conventional whole‐cell patch clamp configuration. The amplitude of ATP‐induced currents was significantly greater in both wild‐type and C90S UCH L1‐transfected cells, suggesting that hydrolase activity was not involved but increased level of mono‐ubiquitin might play an important role. The increased currents were dependent on cAMP‐dependent protein kinase (PKA) and Ca2+ and calmodulin‐dependent protein kinase (CaMKII) but not protein kinase C. In addition, ATP‐induced currents were likely to be modified via dopamine and cyclic AMP‐regulated phosphoprotein (DARPP‐32) that is regulated by PKA and phosphatases. Our finding shows the first evidence that there is a relationship between UCH L1 and neurotransmitter receptor, suggesting that UCH L1 may play an important role in synaptic activity.
In vitroandin vivoanalyses of human embryonic stem cell‐derived dopamine neurons
Authors: Park Chang‐Hwan , Minn Yang‐Ki , Lee Ji‐Yeon , Choi Dong Ho , Chang Mi‐Yoon , Shim Jae‐Won , Ko Ji‐Yun , Koh Hyun‐Chul , Kang Min Jeong , Kang Jin Sun , Rhie Duck‐Joo , Lee Yong‐Sung , Son Hyeon , Moon Shin Yong , Kim Kwang‐Soo , Lee Sang‐Hun
Published: February 2005

Human embryonic stem (hES) cells, due to their capacity of multipotency and self‐renewal, may serve as a valuable experimental tool for human developmental biology and may provide an unlimited cell source for cell replacement therapy. The purpose of this study was to assess the developmental potential of hES cells to replace the selectively lost midbrain dopamine (DA) neurons in Parkinson's disease. Here, we report the development of anin vitrodifferentiation protocol to derive an enriched population of midbrain DA neurons from hES cells. Neural induction of hES cells co‐cultured with stromal cells, followed by expansion of the resulting neural precursor cells, efficiently generated DA neurons with concomitant expression of transcriptional factors related to midbrain DA development, such as Pax2, En1 (Engrailed‐1), Nurr1, and Lmx1b. Using our procedure, the majority of differentiated hES cells (> 95%) contained neuronal or neural precursor markers and a high percentage (> 40%) of TuJ1+ neurons was tyrosine hydroxylase (TH)+, while none of them expressed the undifferentiated ES cell marker, Oct 3/4. Furthermore, hES cell‐derived DA neurons demonstrated functionalityin vitro,releasing DA in response to KCl‐induced depolarization and reuptake of DA. Finally, transplantation of hES‐derived DA neurons into the striatum of hemi‐parkinsonian rats failed to result in improvement of their behavioral deficits as determined by amphetamine‐induced rotation and step‐adjustment. Immunohistochemical analyses of grafted brains revealed that abundant hES‐derived cells (human nuclei+ cells) survived in the grafts, but none of them were TH+. Therefore, unlike those from mouse ES cells, hES cell‐derived DA neurons either do not survive or their DA phenotype is unstable when grafted into rodent brains.
Effects of hyperglycaemia on ocular development in rabbit: refraction and biometric changes
Authors: Herse Peter
Published: February 2005

Aim:  To determine the effect of acute and chronic hyperglycaemia on the refraction and development of the rabbit eye.

Methods:  Ocular dimensions of five alloxan‐induced hyperglycaemic and six control rabbits were measured over 9 weeks using A scan biometry. Refraction was measured using retinoscopy. The animals were 10 weeks of age at the start of the experiment.

Results:  The acute onset of hyperglycaemia was associated with a fast and stable 2 D hyperopic shift in refraction. Lens thickness increased during the first 2 weeks of hyperglycaemia, returned to near normal thickness after 3–5 weeks of hyperglycaemia and then decreased in thickness in the last 4 weeks of the study. The hyperopic refraction remained unchanged during changes in lens thickness. Nine weeks of hyperglycaemia was associated with a 25% reduction in the growth of both the globe and the lens and a 17% decrease in body mass compared with the controls.

Conclusion:  The hyperopic refraction change of acute hyperglycaemia is likely to be because of a change in the refractive index of the cortical fibres of the lens and is the probable source of the fluctuating refraction seen in diabetic patients. Chronic hyperglycaemia reduced the axial development of the eye and is the probable source of the chronic hyperopic refraction seen in children with Type I diabetes.
The Dubbelman eye model analysed by ray tracing through aspheric surfaces
Authors: Norrby Sverker
Published: February 2005

Dubbelman and co‐workers have determined intraocular spacings and surface shapes in living eyes by means of corrected Scheimpflug images in a large number of subjects of different age at several levels of accommodation. They give relationships for key anterior segment parameters as a function of age and level of accommodation. These are used in this paper to build a schematic eye incorporating aspheric surfaces. This eye model is analysed by means of ray tracing with a technique developed for use with a common spreadsheet computer program. The Dubbelman eye model appears to be well corrected for spherical aberration. Compared with measurements on real eyes it agrees well in general, but spherical aberration is negative, while in real eyes it tends to be positive.
Vasovagal syncope evoked by needle phobia when inserting a contact lens*
Authors: Mimura Tatsuya , Funatsu Hideharu , Yamagami Satoru , Usui Tomohiko , Ono Kyoko , Araie Makoto , Amano Shiro
Published: February 2005

Purpose:  To report a patient who fell unconscious because of vasovagal syncope evoked by needle phobia when he tried to wear contact lenses.

Case reports:  A 16‐year‐old healthy boy had sometimes experienced dizziness when looking at the tips of pens. When he put his finger and the lens close to his eye to insert a soft contact lens, he felt sick and dizzy and fell unconscious.

Conclusion:  Our experience suggests that patients with needle phobia may develop vasovagal syncope by concentrating on a fingertip when inserting a contact lens. We need to be aware of unconsciousness because of phobia when trying to insert contact lenses.
Impact of Adolescents' Filial Self‐Efficacy on Quality of Family Functioning and Satisfaction
Authors: Caprara Gian Vittorio , Pastorelli Concetta , Regalia Camillo , Scabini Eugenia , Bandura Albert
Published: February 2005

In this prospective study, we tested a structural model in which adolescents' perceived self‐efficacy to manage parental relationships affected their satisfaction with family life both directly, and indirectly, through its impact on family practices. Findings based on 380 Italian adolescents showed that perceived filial self‐efficacy was linked directly and indirectly to satisfaction with family life, and that these relations held both concurrently and longitudinally. In particular, the greater adolescents perceived their self‐efficacy, the more they reported open communication with their parents, the more accepting they were of their parents' monitoring of their own activities outside the home and the less inclined they were to get into escalative discord over disagreements. Regardless of whether perceived filial self‐efficacy was placed in the conceptual structure as a contributor to the quality of family interactions or as a partial product of family functioning, it consistently predicted satisfaction with family life.
Structured Methods and Striking Moments: Using Question Sequences in “Living” Ways
Authors: Lowe Roger
Published: February 2005

This article draws together two seemingly incompatible practices in social constructionist therapies: the use of structured questioning methods (associated with solution‐focused and narrative therapies) and the poetic elaboration of “striking moments” (associated with conversational therapies). To what extent can we value and use both styles of practice? Beginning with practitioners' concerns about the use of structured question sequences, I explore possibilities for resituating these methods in different conceptual and metaphorical frames, selectively drawing on ideas from the philosophy of striking moments. The aim is not to reduce one therapeutic style to another, but to encourage the teaching and practice of structured methods in more creative, improvisational, and “living” ways.
Family Ties: Constructing Family Time in Low‐Income Families
Authors: Tubbs Carolyn Y. , Roy Kevin M. , Burton Linda M.
Published: February 2005

“Family time” is reflected in the process of building and fortifying family relationships. Whereas such time, free of obligatory work, school, and family maintenance activities, is purchased by many families using discretionary income, we explore how low‐income mothers make time for and give meaning to focused engagement and relationship development with their children within time constraints idiosyncratic to being poor and relying on welfare. Longitudinal ethnographic data from 61 low‐income African American, European American, and Latina American mothers were analyzed to understand how mothers construct family time during daily activities such as talking, play, and meals. We also identify unique cultural factors that shape family time for low‐income families, such as changing temporal orientations, centrality of television time, and emotional burdens due to poverty. Implications for family therapy are also discussed.
Microstructural Evolution of Titania Nanocrystallites by a Hydrothermal Treatment: A HRTEM study
Authors: Daoud Walid A. , Xin John H. , Pang G. K. H.
Published: February 2005

Nanocrystalline anatase titanium dioxide films were formed by a hydrothermal treatment at temperatures below 100°C. The microstructural evolution of the crystallites was monitored by high‐resolution transmission electron microscopy (HRTEM). HRTEM analysis of the as‐grown film revealed the presence of nanocrystalline brookite TiO2 within an amorphous matrix. After 90 min of the hydrothermal treatment, the TiO2 nanoparticles remained of brookite form and a small increase in grain size was observed. Intergranular amorphous TiO2 between the nanoparticles was observed in both as‐grown and 90‐min‐treated films. However, after further 90 min of the treatment, TiO2 nanoparticles were transformed into anatase phase with a rapid growth in grain size.
Preparation of Transparent Conductive (ZnO)mIn2O3 Fine Powder by Gel‐Combustion Reaction
Authors: Kikkawa Shinichi , Hosokawa Shoji , Ogawa Hidetoshi
Published: February 2005

A fine powder of (ZnO)mIn2O3 (m=3, 4) was obtained by the self‐combustion reaction, under firing at a furnace temperature of 350°C in a nitrogen atmosphere, of a gel prepared from a mixed zinc and indium nitrate aqueous solution peptized with citric acid. A (ZnO)3In2O3 single‐phase product was obtained when citric acid was substituted by glycine, because the combustion temperature of glycine mixture is >1260°C. The highest electrical conductivity, 0.2 S cm−1, was obtained in a tin‐substituted, transparent conducting (ZnO)mIn2O3 product, where m=3 and 4.
Stress Corrosion Cracking and Hydrogen‐Induced Cracking of an Alumina Ceramic
Authors: Shi B. , Chu W. Y. , Su Y. J. , Gao K. W. , Qiao L. J.
Published: February 2005

Stress corrosion cracking (SCC) in water and hydrogen‐induced cracking (HIC) of an alumina ceramic during dynamical charging with various current densities were investigated using constant load specimens. The results showed that hydrogen‐induced intergranular failure occurred, and the normalized threshold stress intensity of HIC, KIH/KIC, decreased linearly with the logarithm of hydrogen concentration C0, i.e., KIH/KIC=1.1–0.36 lnC0. The normalized threshold stress intensity of SCC in water was KISCC/KIC=0.64, which was below that of HIC during charging with i≤20 mA/cm2.
Crystallization Kinetics of the LiBO2–Nb2O5 Glass Using Differential Thermal Analysis
Authors: Prasad N. Syam , Varma K. B. R.
Published: February 2005

The crystallization kinetics in the glass system (100−x)LiBO2−xNb2O5 (5≤x≤20, in molar ratio) prepared via the conventional metal‐plate quenching technique have been studied by isothermal and non‐isothermal methods using differential thermal analyses. X‐ray powder diffraction studies carried out on heat‐treated (500°C) glasses reveal the evolution of lithium niobate crystalline phase along with a minor phase of LiBO2. The exponent n in the Jhonson–Mehl–Avrami (JMA) equation applied to the isothermal process is 2.62, which is in excellent agreement with that obtained under the non‐isothermal process (2.67). The activation energies for crystal growth obtained from JMA equation under isothermal condition, modified Ozawa and Kissinger equations under non‐isothermal conditions, are 293, 311, and 306 kJ/mol, respectively.
High Strain, 〈001〉 Textured 0.675Pb(Mg1/3Nb2/3)O3–0.325PbTiO3Ceramics: Templated Grain Growth and Piezoelectric Properties
Authors: Kwon Seongtae , Sabolsky Edward M. , Messing Gary L. , Trolier‐McKinstry Susan
Published: February 2005

Lead magnesium niobate–lead titanate, 0.675Pb(Mg1/3Nb2/3)O3–0.325PbTiO3(PMN–32.5PT) ceramics were textured (grain‐oriented) in the 〈001〉‐crystallographic direction by the templated grain growth process. The textured PMN–32.5PT ceramics were produced by orienting {001}‐SrTiO3(ST) platelets (∼10 μm in diameter and ∼2‐μm thickness) in a submicron PMN–32.5PT matrix. The templated growth of 〈001〉‐oriented PMN–32.5PT grains on the ST platelets resulted in textured ceramics with ∼70% Lotgering factor and >98% theoretical density. Unlike most lead‐based ceramics, excess PbO was not needed for sintering or grain growth. Based on unipolar stain‐field measurements at 0.2 Hz, the textured samples displayed >0.3% strain at 50 kV/cm. Low‐fieldd33‐coefficients of >1600 pC/N (<5 kV/cm) were measured directly from unipolar measurements. The low drive fieldd33‐piezoelectric coefficient of the highly textured samples is two times greater than polycrystalline PMN–32.5PT.
Effects of Ionic Size in the Tetrahedral and Octahedral Sites on the Thermal Expansion of Low‐Temperature Cordierite
Authors: Miyake Akira
Published: February 2005

The effects of ionic size in octahedral and two kinds of tetrahedral sites (M, T1, and T2) on the thermal expansion of cordierite were systematically investigated by means of molecular dynamics simulations. Thermal expansion along the a axis could be controlled by varying the ionic size in the M‐site, and expansion along the c axis could be controlled by varying the ionic size in the M‐ and T2‐sites. However, the ionic sizes in the M‐ and T2‐sites had opposite effects.
Li6ALa2Nb2O12 (A=Ca, Sr, Ba): A New Class of Fast Lithium Ion Conductors with Garnet‐Like Structure
Authors: Thangadurai Venkataraman , Weppner Werner
Published: February 2005

Garnet‐like structured metal oxides with the general formula Li6ALa2Nb2O12 (A=Ca, Sr, Ba) have been prepared by solid‐state reaction using appropriate amounts of corresponding metal oxides, nitrates, and hydroxides. The powder X‐ray diffraction data reveal that Li6ALa2Nb2O12 compounds are isostructural with the parent compound Li5La3Nb2O12. The cubic lattice parameter was found to increase with increasing size of the alkaline earth ions. The grain size decreases considerably with the substitution of La by the alkaline earth elements under the same preparation conditions. The Ca‐substituted compound exhibits both bulk and major grain boundary contributions to the total resistance, while the Sr‐ and Ba‐substituted compounds show mainly bulk resistance with a rather small grain boundary contribution (∼14% of the total resistance at 20°C) with further decrease with increasing temperature. In comparison, the ionic conductivity decreases with decreasing ionic radius of the alkaline earth elements. Among the investigated compounds, the Ba‐compound Li6BaLa2Nb2O12 shows the highest ionic conductivity of 6 × 10−6 S/cm at room temperature (22°C) and lowest activation energy of 0.44 eV compared with 0.55 and 0.50 eV for the corresponding Ca‐ and Sr‐ compounds, respectively. The ionic conductivity is comparable with that of parent Li5La3Nb2O12 and other fast lithium ion conductors known so far.
Dielectric Properties of (1−x)CaTiO3–xCa(Zn1/3Nb2/3)O3 Ceramic System at Microwave Frequency
Authors: Liu Hanxing , Yu Hongtao , Tian Zhongqing , Meng Zhenghua , Wu Zhaohui , Ouyang Shixi
Published: February 2005

The microwave dielectric properties of the (1−x)CaTiO3–xCa(Zn1/3Nb2/3)O3 ceramic system have been investigated. The ceramic samples sintered at 1300°–1450°C for 4 h in air exhibit orthorhombic pervoskite and form a complete solid solution for different x value. When the x value increased from 0.2 to 0.8, the permittivity ɛr decreased from 115 to 42, the unloaded quality factor Q×f increased from 5030 to 13 030 GHz, and the temperature coefficient τf decreased from 336 to −28 ppm/°C. When x=0.7, the best combination of dielectric properties, a near zero temperature coefficient of resonant frequency of τf∼−6 ppm/°C, Q×f∼10 860 GHz and ɛr∼51 is obtained.
Rheology of Hydroxyapatite Dispersions
Authors: Gardini Davide , Galassi Carmen , Lapasin Romano
Published: February 2005

Hydroxyapatite (HA) is an interesting ceramic material for orthopedic applications, in particular for implant operations and bone regeneration, owing to its bioactivity and biocompatibility with the surrounding tissues. Even if different shaping processes can be used in order to obtain porous ceramic bodies with optimal final properties, the sponge impregnation method with aqueous HA dispersions is particularly suitable to achieve an appropriate macroporosity to bone regeneration. As for conventional slip or tape casting, the rheological behavior of HA suspensions must be properly fitted to process conditions and controlled through a satisfactory stabilization of the disperse phase, i.e., through an appropriate dispersant dosage and an accurate homogenization of dispersed powder. In the present work, HA powders with different crystallinity degree were used to prepare aqueous dispersions with different contents of solids and dispersant (ammonium polyacrylate). The specific surface area of HA powders is very high, and then special attention must be dedicated to the dispersant selection and the dispersion process since the rheology of HA suspensions is strongly influenced by the structural conditions of the disperse phase. Even small differences in dispersant concentration can lead to dramatic changes in the rheological properties also at relatively low values of solids volume concentration. Above a critical concentration, the viscosity drop associated with the apparently plastic behavior is confined within a very narrow stress range, a neat transition is observed in the linear viscoelastic properties, and the time‐dependent effects induced by the shear history become quite important and crucial for the experimental characterization.
Synthesis of Single‐Crystalline Silicon Nitride Nanobelts Via Catalyst‐Assisted Pyrolysis of a Polysilazane
Authors: Yang Weiyou , Xie Zhipeng , Miao Hezhuo , Zhang Ligong , Ji Hang , An Linan
Published: February 2005

Recently, one‐dimensional nanostructures have attracted extensive attention since they are potentially important for both applications and fundamental research. In this paper, we report the synthesis of ultra‐long single crystal Si3N4 nanobelts via catalyst‐assisted pyrolysis of polymeric precursors. The obtained products contain both α‐ and β‐Si3N4 nanobelts, which are 50–100 nm in thickness, 400–1000 nm in width, and a few hundreds of micrometers to several millimeters in length. Different from previous techniques for synthesizing one‐dimensional structures, the current nanobelts are synthesized through confined crystallization of an amorphous phase. A solid–liquid–gas–solid reaction/crystallization growth mechanism is proposed. The formation of nanobelts instead of nanowires is attributed to the anisotropy growth at an earlier stage.
Processing and Surface Flaw Tolerance of Alumina Bilayers
Authors: Montgomery John K. , Faber K. T.
Published: February 2005

Alumina bilayers of different relative thicknesses and densities were produced with a strong interface using a modified gel‐casting technique. Tolerance to surface damage is examined using biaxial flexure of disks damaged with a single Vickers indentation at various loads. The greatest surface flaw tolerance is seen in bilayers consisting of a thin porous layer on the tensile surface coupled to a thick dense layer. Here, the modulus mismatch causes redistribution of the applied stress, and fracture initiates at the internal porous‐dense interface rather than at the surface from the introduced indentation flaw.
Improved High‐Temperature Strength of Silicon Nitride Toughened with Aligned Whisker Seeds
Authors: Park Dong‐Soo , Hahn Byung‐Dong , Bae Byoung‐Chan , Park Chan
Published: February 2005

The effect of the amount of the sintering additives, i.e., yttria and alumina, on the microstructure and the high‐temperature flexural strengths of silicon nitride with and without the aligned whisker seeds was examined. As the amount of the sintering additives was increased, both width and length of the grains were increased. The high‐temperature strengths of silicon nitride with and without the aligned seeds were increased and decreased, respectively, according to the increase of the amount of the sintering additives. When both 4.8 wt% yttria and 2.2 wt% alumina were added to silicon nitride with the aligned whisker seeds, the experimental results indicated that it had three times the flexural strength as silicon nitride without the seeds at 1673 K. During the high‐temperature flexure testing, observations did not indicate yielding present in the samples with the aligned whisker seeds, while it was present in samples without the whisker seeds. The reinforcing grains growing from the whisker seeds aligned perpendicular to the crack propagation direction acted as effective obstacles to the crack propagation and improved the fracture toughness.
Yttrium Silicate Coatings on Chemical Vapor Deposition‐SiC‐Precoated C/C–SiC: Thermodynamic Assessment and High‐Temperature Investigation
Authors: Seifert Hans J. , Wagner Sigrid , Fabrichnaya Olga , Lukas Hans L. , Aldinger Fritz , Ullmann Thomas , Schmücker Martin , Schneider Hartmut
Published: February 2005

Yttrium silicates are promising materials for improved oxidation and erosion protection for carbon fiber‐reinforced composites. A two‐layer coating system of low‐pressure plasma‐sprayed yttrium silicate on chemical vapor deposition‐SiC‐precoated C/C–SiC was tested under atmospheric re‐entry conditions simulated within a plasma wind tunnel test facility. The thermal expansion behavior of Y2SiO5 and Y2Si2O7 was investigated. The chemical compatibility with and without increasing oxygen partial pressure at the interface of the two‐layer system was calculated by the CALPHAD method. The calculations were compared with experimental results. Furthermore, a thermodynamic explanation is presented to understand and predict the observed coating failure mechanism, identified as blister formation.
Early Stage of Phase Separation in Aluminoborosilicate Glass for Liquid Crystal Display Substrate
Authors: Kato Y. , Yamazaki H. , Watanabe T. , Saito K. , Ikushima A. J.
Published: February 2005

The early stage of phase separation in aluminoborosilicate glass for liquid crystal display substrates was investigated using a scanning electron microscope (SEM) and small‐angle X‐ray scattering measurement device (SAXS). The phase‐separated particles were detected with SAXS in samples in which no particle was observed with SEM. The particle diameter in an as‐formed sample was 2 nm. The relationship between the diameter and heat‐treatment time indicates that the phase separation proceeds by a diffusion‐controlled process. Based on the results of Fourier‐transform infrared spectroscopy, fast compositional change may occur in the early stage of phase separation.
Comparison of Aqueous and Non‐Aqueous Tape Casting of Aluminum Nitride Substrates
Authors: Luo Xiao‐Jun , Zhang Bao‐Lin , Li Wen‐Lan , Zhuang Han‐Rui
Published: February 2005

A direct comparison of aqueous and non‐aqueous tape casting was investigated. Aqueous and non‐aqueous formulations were developed for tape casting of aluminum nitride (AlN) powder. The oxygen content of the AlN powder in aqueous ball‐milling media had a slight increase, but it did not almost influence the thermal conductivity of AlN substrate. The solid loading of aqueous AlN slurry was higher than that of the non‐aqueous one, but its viscosity was lower than that of non‐aqueous AlN slurry. Under the same burnout program, the residual carbon content in aqueous AlN green sheet was lower than that of the non‐aqueous one. The thermal conductivity of the aqueous AlN substrate sintered at 1850°C for 3 h was 138 W·(m·K)−1, which was close to 142 W·(m·K)−1 of the non‐aqueous AlN substrate.
Epitaxial Growth of Cuprous Oxide Electrodeposited onto Semiconductor and Metal Substrates
Authors: Oba Fumiyasu , Ernst Frank , Yu Yeonseop , Liu Run , Kothari Hiten M. , Switzer Jay A.
Published: February 2005

It is demonstrated that cuprous oxide (Cu2O) can be electrodeposited epitaxially onto silicon (Si) and indium phosphide (InP) (001) single‐crystalline substrates from aqueous solution. Epitaxial electrodeposition under these conditions is remarkable considering the strong driving force for the formation of amorphous native oxide layers on Si and InP substrates. To elucidate the growth mechanisms, the microstructure of the interfaces between the Cu2O layer and the two different substrates was investigated by TEM (transmission electron microscopy) in conjunction with XEDS (X‐ray energy‐dispersive spectroscopy) and EELS (electron energy‐loss spectroscopy). In both heteroepitaxial systems, the Cu2O layers have a unique but non‐trivial crystallographic orientation relationship (OR) with the substrate, which can be described as a 45° rotation around the common [001] axis representing the substrate normal. We show that this relationship minimizes the overall misfit between corresponding interatomic spacings of the two adjacent crystals. In apparent contradiction to the unique OR, TEM revealed that in both hetero‐systems the Cu2O layer is separated from the substrate by an amorphous interlayer. The thickness of the interlayer typically is a few nanometers. The presence of an amorphous interlayer contrasts with our experimental results on electrodeposited Cu2O on Au (001) single‐crystal substrates, also included in this article, where TEM shows the Cu2O epilayer in direct contact with the substrate. XEDS and EELS analysis of the chemical composition and bonding at Cu2O/Si and Cu2O/InP interfaces in the as‐grown state as well as after tempering revealed that the interlayer is mainly composed of SiO2 and InPO4, respectively. Most likely, the observed epitaxial layers on top of an amorphous interlayer evolve by nucleation of epitaxial Cu2O directly on the substrate. While simultaneous oxidation of the substrate leads to the formation of an amorphous layer, the epitaxial nuclei can laterally overgrow the oxide. Consequently, the local composition of the amorphous layer varies with the nature of the substrate.
A comparison of colour micrographs obtained with a charged couple device (CCD) camera and a 35‐mm camera
Authors: Pedersen Mads Møller , Smedegaard Jesper , Jensen Peter Koch , Heegaard Steffen , Jensen Ove Aksel , Prause Jan Ulrik
Published: February 2005

Purpose:  The purpose of this study was to determine if micrographs produced with a colour charged couple device (CCD) camera were comparable in quality to micrographs obtained with a 35‐mm colour film camera. The Axiocam (Zeiss, Jena, Germany) CCD camera produced images of 3900 × 3090 pixels.

Methods:  Each picture in a series of 50 pairs of film and digital micrographs was rated independently by each of three observers on the categories of colour, detail and overall impression. A total of 28 of the 50 pairs of micrographs were discarded due to colour differences.

Results:  Digital micrographs were rated lower on colour and higher on detail compared to film micrographs. The film and digital micrographs were rated equally on overall impression. The difference in colour between film and digital micrographs can be compensated for using image processing software on the digital image. However, such manipulation was not carried out as part of the present study. The study originally included 50 digital micrographs and 50 film micrographs. The micrographs were paired and 22 of the 50 pairs of micrographs were assessed. Thus 28 pairs were not evaluated due to colour differences in the non‐manipulated pictures. The interobserver difference on colour in the remaining 22 pairs given as mean square ± standard error of the mean was − 0.27 ± 0.10, 0.62 ± 0.10 and 0.90 ± 0.11. The interobserver difference on detail was − 0.48 ± 0.10, 0.95 ± 0.10 and 1.43 ± 0.10. The interobserver difference on overall impression was − 0.70 ± 0.10, 0.57 ± 0.10 and 1.27 ± 0.10. All the results differed significantly (p < 0.001).

Conclusion:  Digital micrographs are sufficient in detail, colour and overall impression to replace the traditional 35‐mm film recordings for use in histopathology.
Reduction of asthenopia related to accommodative relaxation by means of far point stimuli
Authors: Iwasaki Tsuneto , Tawara Akihiko , Miyake Nobuyuki
Published: February 2005

Purpose:  To conduct an experimental investigation of the effect of accommodative relaxation using far point shift stimuli for the reduction of asthenopia.

Methods:  Twenty‐two female students accommodated to a far point shift stimuli during a 2‐min period immediately after a 15‐min sustained task on a three‐dimensional display. Before and after the trial, their accommodative step response and symptoms were assessed. The far point shift stimuli in the optical system, which were presented on a refractometer, were created by moving the target scenery images from far to near, lineally centred about the far point position of each eye. During 2 min of fixating on the far point shift stimuli, changes in refraction were recorded in the same eye.

Results:  While looking at the far point shift stimuli, 10 of 22 subjects had changes in refraction that showed a hypermetropic shift, and the other 12 subjects had changes in refraction that showed a myopic shift. The time taken for the accommodative step response from far to near post‐trial in the myopic shift group was markedly prolonged, and the accommodative lag at the far target in the optometer was significantly increased. In the myopic shift group, the symptoms of ‘eye fatigue’, ‘eye pain’, ‘eye heaviness’, and ‘eye dryness’ also increased after the trial. In the hyperopic shift group, however, only the symptom of ‘eye dryness’ increased, with no reduction of accommodation function.

Conclusions:  We suggest that accommodative relaxation by accommodative far point shift stimuli is effective in the reduction of asthenopia.