bluuebunny/crossref_metadata_2025 huggingface dataset:
Subtype I BK polyomavirus strains grow more efficiently in human renal epithelial cells than subtype IV strains
Authors: Nukuzuma Souichi , Takasaka Tomokazu , Zheng Huai-Ying , Zhong Shan , Chen Qin , Kitamura Tadaichi , Yogo Yoshiaki
Published: June 2006

BK polyomavirus (BKPyV) is ubiquitous in human populations, infecting children without obvious symptoms and persisting in the kidney. BKPyV isolates have been classified into four subtypes (I–IV) using either serological or genotyping methods. In general, subtype I occurs most frequently, followed by subtype IV, with subtypes II and III rarely detected. As differences in growth capacity in human cells possibly determine the proportion of the four subtypes of BKPyV in human populations, here the growth properties of representative BKPyV strains classified as subtype I or IV in renal proximal tubule epithelial cells (HPTE cells) of human origin were analysed. HPTE cells were transfected with four and three full-length BKPyV DNAs belonging to subtypes I and IV, respectively, and cultivated in growth medium. Virus replication, detected using the haemagglutination assay, was observed in all HPTE cells transfected with subtype I BKPyV DNAs, whereas it was markedly delayed or not detected in those transfected with subtype IV BKPyV DNAs. It was confirmed that the transfected viral DNAs induced virus replication in HPTE cells. Furthermore, it was found that BKPyVs with archetypal transcriptional control regions replicated in HPTE cells, with only the occasional emergence of variants carrying rearranged transcriptional control regions. Essentially the same results as described above were obtained with renal epithelial cells derived from whole kidney. Thus, it was concluded that subtype I BKPyV replicates more efficiently than subtype IV BKPyV in human renal epithelial cells, supporting the hypothesis that growth capacity in human cells is related to the proportion of BKPyV subtypes in human populations.
Novel subtypes (subgenotypes) of hepatitis B virus genotypes B and C among chronic liver disease patients in the Philippines
Authors: Sakamoto Tomoyuki , Tanaka Yasuhito , Orito Etsuro , Co Jonard , Clavio Joseph , Sugauchi Fuminaka , Ito Kiyoaki , Ozasa Atsushi , Quino Alvin , Ueda Ryuzo , Sollano Jose , Mizokami Masashi
Published: June 2006

Several hepatitis B virus (HBV) subtypes (subgenotypes), HBV/Aa (A1 : Asia/Africa), Ae (A2 : Europe), Bj (B1 : Japan) and Ba (B2 : Asia), have been reported with respect to clinical differences between patients infected with these subtypes (subgenotypes). HBV genotype distribution among patients with chronic liver diseases was investigated in the Philippines, where such studies have not been carried out previously. One hundred sera were obtained from such patients, consisting of 32 chronic hepatitis (CH), 37 cirrhosis and 31 hepatocellular carcinoma (HCC) patients. Nine complete genomes and 100 core promoter/precore genes of HBV were sequenced directly. Phylogenetic analyses revealed 51 HBV/A (Aa/A1), 22 HBV/B and 27 HBV/C strains. Interestingly, most HBV/C strains in the Philippines formed a specific cluster distinct from previous HBV/C strains (C1–4), indicating a novel subtype (subgenotype), HBV/C5. Moreover, most HBV/B strains fell within the specific cluster of the HBV/B subtype (subgenotype) B5, with viral characteristics of HBV/Ba (B2) carrying a recombination with HBV/C over the precore and core genes. Of the three genotypes, HBV/B and HBV/C were significantly more prevalent than HBV/A in cirrhosis and HCC patients (P<0.02). The prevalence of the core promoter mutations T1762/A1764 was higher in HCC patients with HBV/B and HBV/C. Multivariate analysis indicated that age [odds ratio (OR) 3.43; 95 % confidence interval (CI) 1.04–11.36; P=0.044] and the core promoter mutation (OR 14.08; 95 % CI 3.62–4.74; P<0.001) were significant factors for HCC development. In conclusion, novel HBV subtypes (subgenotypes) C5 and B5 are prevalent in the Philippines, as well as HBV/Aa (A1).
Pathogenesis of Dugbe virus infection in wild-type and interferon-deficient mice
Authors: Boyd Amanda , Fazakerley John K. , Bridgen Anne
Published: June 2006

In 129 mice, infection with the nairovirus Dugbe virus (DUGV) was lethal following intracerebral but not intraperitoneal inoculation. Following both routes of inoculation, immunostaining of tissue sections demonstrated virus-positive cells in the brain, indicating that DUGV is neuroinvasive in mice. Many brain areas were affected and neurones were the main cell type infected. Infected cells showed punctate accumulations of viral nucleoprotein in the cytoplasm, indicative of virus replication sites. Immunostaining for activated caspase 3 demonstrated no evidence of apoptosis. The type I interferon (IFN) system plays a significant role in defence against DUGV, as 129 IFN-α/β R−/− mice died rapidly following both intraperitoneal and intracerebral inoculations. Studies were undertaken to determine whether the IFN-inducible proteins, protein kinase R (PKR) and MxA, were important for protection; neither PKR nor constitutively expressed human MxA played significant roles.
Unravelling the complexities of respiratory syncytial virus RNA synthesis
Authors: Cowton Vanessa M. , McGivern David R. , Fearns Rachel
Published: June 2006

Human respiratory syncytial virus(RSV) is the leading cause of paediatric respiratory disease and is the focus of antiviral- and vaccine-development programmes. These goals have been aided by an understanding of the virus genome architecture and the mechanisms by which it is expressed and replicated. RSV is a member of the orderMononegaviralesand, as such, has a genome consisting of a single strand of negative-sense RNA. At first glance, transcription and genome replication appear straightforward, requiring self-contained promoter regions at the 3′ ends of the genome and antigenome RNAs, shortcis-acting elements flanking each of the genes and one polymerase. However, from these minimal elements, the virus is able to generate an array of capped, methylated and polyadenylated mRNAs and encapsidated antigenome and genome RNAs, all in the appropriate ratios to facilitate virus replication. The apparent simplicity of genome expression and replication is a consequence of considerable complexity in the polymerase structure and its cognatecis-acting sequences; here, our understanding of mechanisms by which the RSV polymerase proteins interact with signals in the RNA template to produce different RNA products is reviewed.
Simultaneous mutations in translation initiation factors eIF4E and eIF(iso)4E are required to prevent pepper veinal mottle virus infection of pepper
Authors: Ruffel Sandrine , Gallois Jean-Luc , Moury Benoît , Robaglia Christophe , Palloix Alain , Caranta Carole
Published: June 2006

Capsicumresistance toPepper veinal mottle virus(PVMV) results from complementation between thepvr2andpvr6resistance genes: recessive alleles at these two loci are necessary for resistance, whereas any dominant allele confers susceptibility. In line with previous results showing thatpvr2resistance alleles encode mutated versions of the eukaryotic translation initiation factor 4E (eIF4E), the involvement of other members of theeIF4Emultigenic family in PVMV resistance was investigated. It was demonstrated thatpvr6corresponds to aneIF(iso)4Egene, predicted to encode the second cap-binding isoform identified in plants. Comparative genetic mapping in pepper and tomato indicated thateIF(iso)4Emaps in the same genomic region aspvr6. Sequence analysis revealed an 82 nt deletion ineIF(iso)4EcDNAs from genotypes with thepvr6resistance allele, leading to a truncated protein. This deletion was shown to co-segregate withpvr6in doubled haploid and F2progeny. Transient expression in a PVMV-resistant genotype ofeIF(iso)4Ederived from a genotype with thepvr6+susceptibility allele resulted in loss of resistance to subsequent PVMV inoculation, confirming thatpvr6encodes the translation factor eIF(iso)4E. Similarly, transient expression ofeIF4Efrom a genotype with thepvr2+-eIF4Esusceptibility allele also resulted in loss of resistance, demonstrating that wild-type eIF4E and eIF(iso)4E are susceptibility factors for PVMV and that resistance results from the combined effect of mutations in the two cap-binding isoforms. Thus, whilst most potyviruses specifically require one eIF4E isoform to perform their replication cycle, PVMV uses either eIF4E or eIF(iso)4E for infection of pepper.
Expression and Characterization of a Redox-Sensing Green Fluorescent Protein (Reduction-Oxidation-Sensitive Green Fluorescent Protein) in Arabidopsis
Authors: Jiang Keni , Schwarzer Christian , Lally Elizabeth , Zhang Shibo , Ruzin Steven , Machen Terry , Remington S. James , Feldman Lewis
Published: June 2006

Arabidopsis (Arabidopsis thaliana) was transformed with a redox-sensing green fluorescent protein (reduction-oxidation-sensitive green fluorescent protein [roGFP]), with expression targeted to either the cytoplasm or to the mitochondria. Both the mitochondrial and cytosolic forms are oxidation-reduction sensitive, as indicated by a change in the ratio of 510 nm light (green light) emitted following alternating illumination with 410 and 474 nm light. The 410/474 fluorescence ratio is related to the redox potential (in millivolts) of the organelle, cell, or tissue. Both forms of roGFP can be reduced with dithiothreitol and oxidized with hydrogen peroxide. The average resting redox potentials for roots are −318 mV for the cytoplasm and −362 mV for the mitochondria. The elongation zone of the Arabidopsis root has a more oxidized redox status than either the root cap or meristem. Mitochondria are much better than the cytoplasm, as a whole, at buffering changes in redox. The data show that roGFP is redox sensitive in plant cells and that this sensor makes it possible to monitor, in real time, dynamic changes in redox in vivo.
The risk society at work in the Sydney ‘Tar Ponds’
Authors: Haalboom Bethany , Elliott Susan J. , Eyles John , Muggah Henry
Published: June 2006

This paper explores the implications of environmental contamination on the perceived health impacts, effects on daily life and coping mechanisms of residents living near the Tar Ponds in Sydney, Nova Scotia. The site contains over 700,000 tonnes of contaminated sediments and is considered one of the most contaminated commercial–industrial sites in Canada [Canadian British Consultants Limited (CBCL) and Conestoga Rovers and Associates (CRA) 1999 Phase 1 Site Assessment: Muggah Creek Watershed, Sydney, Nova Scotia]. Resident fears regarding perceived health risks, as well as other concerns related to property values and the viability of the local economy have been reinforced by distrust of government and of science. These concerns have been sustained by clean‐up delays. In response, many residents have engaged in forms of activism as a prominent form of coping, while several residents have kept well‐informed and sought social support. These findings indicate that the process of remediation and site clean‐up must be sensitive to local context.
Genetic population structure of red snappers (Lutjanus malabaricusBloch & Schneider, 1801 andLutjanus erythropterusBloch, 1790) in central and eastern Indonesia and northern Australia
Authors: Salini J. P. , Ovenden J. R. , Street R. , Pendrey R. , Haryanti  , Ngurah
Published: June 2006

The genetic population structure of red snapperLutjanus malabaricusandLutjanus erythropterusin eastern Indonesia and northern Australia was investigated by allozyme electrophoresis and sequence variation in the control region of mtDNA. Samples were collected from eight sites in Indonesia and four sites in northern Australia for both species. A total of 13 allozyme loci were scored. More variable loci were observed inL. malabaricusthan inL. erythropterus. Sequence variation in the control region (left domain) of the mitochondrial genome was assessed by RFLP and direct sequencing. MtDNA haplotype diversity was high (L. erythropterus, 0·95 andL. malabaricus, 0·97), as was intraspecific sequence divergence, (L. erythropterus, 0·0–12·5% andL. malabaricus, 0·0–9·5%). The pattern of mtDNA haplotype frequencies grouped both species into two broad fisheries stocks with a genetic boundary either between Kupang and Sape (L. malabaricus) or between Kupang and Australian Timor Sea (L. erythropertus). The allozyme analyses revealed similar boundaries forL. erythropterus. Seven allozymes stocks compared to two mtDNA stocks ofL. malabaricusincluding Ambon, which was not sampled with mtDNA, however, were reported. Possible reasons for differences in discrimination between the methods include: i) increased power of multiple allozyme loci over the single mtDNA locus, ii) insufficient gene sampling in the mtDNA control region and iii) relative evolutionary dynamics of nuclear (allozyme loci) and mitochondrial DNA in these taxa. Allozyme and haplotype data did not distinguish separate stocks among the four Australian locations nor the central Indonesian (Bali and Sape locations) for bothL. malabaricusandL. erythropterus.
Evidence of extensive mitochondrial introgression with nearly complete substitution of the typical Squalius pyrenaicus‐like mtDNA of the Squalius alburnoides complex (Cyprinidae) in an independent Iberian drainage
Authors: Sousa‐Santos C. , Collares‐Pereira M. J. , Almada V. C.
Published: June 2006

The first occurrence of massive mitochondrial introgression of Squalius aradensis genes in Squalius alburnoides, a hybridogenetic complex that usually carries mtDNA of its maternal ancestor (Squalius pyrenaicus) is reported. Possible implications of such introgressions for the history of the complex are discussed.
Sexual size dimorphism in seabirds: sexual selection, fecundity selection and differential niche‐utilisation
Authors: Serrano‐Meneses Martín‐Alejandro , Székely Tamás
Published: June 2006

Seabirds exhibit a range of sexual size dimorphism (SSD) that includes both male‐biased (males>females) and female‐biased SSD (males<females). Here we use phylogenetic comparative methods to test the selective processes that may influence their SSD. Using phylogenetically independent contrasts we show that the sizes of males and females are scaled isometrically in seabirds. We also test three functional hypotheses of SSD: sexual selection, fecundity selection and differential niche‐utilisation. First, we found support for the sexual selection hypothesis, even though seabirds are socially monogamous and, as a consequence one might expect sexual selection to be weak. We show that SSD is correlated with an aspect of sexual selection, the agility of male displays, since in species that exhibit aerial displays the males are smaller (relative to the female) than in species in which the males display on the ground. Second, our results are not consistent with the fecundity selection hypothesis, since contrary to the predicted trend, female seabirds lay larger eggs in male‐biased species than in female‐biased ones. Finally, our results are not consistent with a previous study of the differential niche‐utilisation hypothesis, since we found no relationship between SSD and ocean primary productivity in the breeding areas. Taken together, we suggest that seabird SSD is most consistent with the sexual selection hypothesis via the agility of male displays. Nevertheless, further data and tests are required to establish whether different resource utilisation by males and females may also select for SSD.
Eccrine angiomatous hamartoma with elements of an arterio‐venous malformation: a newly recognized variant
Authors: Chien Andy J. , Asgari Maryam , Argenyi Zsolt B.
Published: June 2006

Abstract:  We present the case of a 54‐year‐old man with a brown‐red nodule on the hand that had been present since early adulthood. Histology of the excisional biopsy revealed hyperplasia and proliferation of eccrine, apocrine, lipomatous, and vascular structures. These findings were most characteristic of the entity known as eccrine angiomatous hamartoma (EAH), an uncommon tumor that may present variable clinical and histological features. In addition, this particular case exhibited a prominent component of arterio‐venous malformation that distinguishes it from other EAHs described in the literature and adds to the spectrum of histologic findings that can be seen with this entity.
In situ hybridization in cutaneous deep fungal infections: a valuable diagnostic adjunct to fungal morphology and tissue cultures
Authors: Abbott Jared J. , Hamacher Kirsten L. , Ahmed Iftikhar
Published: June 2006

Abstract:  Dimorphic fungal infections (histoplasmosis, blastomycosis, coccidioidomycosis, and cryptococcosis) can occur in immunocompromised and healthy individuals. Cutaneous involvement is often secondary and may be the presenting sign of systemic disease. These ominous infections are frequently clinically indistinct, and patient prognosis is influenced by a timely diagnosis and treatment. Morphologic differentiation between these organisms is not definitive, and tissue cultures represent the diagnostic gold standard in current day practice. However, tissue cultures are rarely obtained and merely represent an afterthought in seemingly unsuspecting cases. Furthermore, when performed, they may take several days or weeks for completion. In situ hybridization (ISH) utilizing oligonucleotide probes directed against fungal ribosomal RNA is a rapid and accurate assay for the identification of dimorphic fungi in paraffin‐embedded tissue sections. We present five patients in whom ISH both prospectively and retrospectively confirmed the presence of a cutaneous infection (histoplasmosis, blastomycosis, coccidioidomycosis, and cryptococcosis). In all of the skin sections analyzed, dimorphic fungi were morphologically apparent but not diagnostically discernible. In summary, ISH is a valuable tool in the prompt diagnosis of cutaneous deep fungal infections.
Condition factor and hepatosomatic index as estimates of energy status in male three‐spined stickleback
Authors: Chellappa S. , Huntingford F. A. , Strang R. H. C. , Thomson R. Y.
Published: June 2006

Seasonal variation in direct and indirect measures of energy status was examined using estimates of glycogen, lipid and protein levels in a single cohort of male three‐spined sticklebacks from an annual population collected each month over one complete year. Condition factor, somatic condition factor and hepatosomatic index (HSI) were calculated as indirect indices of energy status and the accuracy of these indirect measures as predictors of energy status was investigated. Results indicate that both condition factors were significant predictors of energy reserves (lipid, protein, glycogen and total energy), but that the proportion of variance accounted for was small. Both condition factors perform better as predictors of energy content per unit body weight. The HSI was a significant, but a weak predictor of total glycogen levels over the whole year. On a seasonal basis the relationship between HSI and energy reserves was highly variable. These indices are therefore poor predictors of energy reserves in male three‐spined sticklebacks.
Evidence supporting the paraphyly of Hucho (Salmonidae) based on ribosomal DNA restriction maps
Authors: Phillips R. B. , Oakley T. H. , Davis E. L.
Published: June 2006

Relationships among the less derived genera in the subfamily Salmoninae were investigated by phylogenetic analysis of data from restriction maps of the ribosomal DNA using Osmerus mordax (rainbow smelt), Coregonus hoyi (bloater), and Thymattus arcticus (Arctic grayling) as outgroups. Analysis of the results suggests that Hucho h. taimen is more closely related to Brachymystax lenok (lenok) than to Hucho perryi (Sakhalin taimen) and that B. lenok and Hucho h. taimen (Eurasian taimen) form the most ancestral clade of the Salmoninae.
Computer‐assisted motion analysis of sperm from the common carp
Authors: Toth G. P. , Christ S. A. , McCarthy H. W. , Torsella J. A. , Smith M. K.
Published: June 2006

Computer‐assisted semen analysis (CASA) technology was applied to the measurement of sperm motility parameters in the common carp Cyprinus carpio. Activated sperm were videotaped at 200 frames s−1 and analysed with the CellTrak/S CASA research system. The percentage of motile cells and both sperm head curvilinear velocity and straight‐line velocity were measured following exposure of carp sperm to three predilution conditions and activation in media of differing ionic strengths and osmotic pressures. The highest percentage of motile sperm was obtained following predilution of sperm in seminal plasma and activation in Na‐HEPES buffer pH 8.0. This level of motility was equalled after predilution in 200 mm KCl for 2 h. Straight‐line velocities and curvilinear velocities of 130 μm s−1 and 210 μm s−1, respectively, were observed. Duration of motility was higher under seminal plasma predilution conditions (over 50% motile sperm at 55 s post‐activation). The application provides a sound basis for the assessment of Sperm Characteristics in fish.
Transgenic salmon: tailoring the genome for food production
Authors: Hew C. L. , Fletcher G. L. , Davies P. L.
Published: June 2006

The production of transgenic salmon using gene transfer technology is described. Both antifreeze proteins and growth hormone genes have been successfully transferred. The expression, inheritance and phenotypes are examined using a wide variety of techniques. The development of new transgenics will be beneficial to aquaculture.
Immunization of Atlantic salmon against the salmon louse: identification of antigens and effects on louse fecundity
Authors: Grayson T. H. , John R. J. , Wadsworth S. , Greaves K. , Cox D. , Roper J. , Wrathmell A. B. , Gilpin M. L. , Harris J. E.
Published: June 2006

Injection of extracts derived from adult caligid copepods induced a partial immunity to Lepeophtheirus salmonis in Atlantic salmon. Antigens were derived from the supernatant of adult lice extracts and were partially purified by Con A affinity chromatography. The antigens were also present in the pellet derived from adult lice extracts, Immunohistochemistry showed that antibodies present in the serum of rats immunized with the Con A purified extract bound predominantly to the gut of L. salmonis. Components of apparent sizes > 205 000, 165 000, 133 000, 130 000, 125 000, 114 000, 110 000, 96 000, 82 000, 78 000, 65 000, 46 000, 35 000, 31 000 and < 29 000 were present in the extract. Although the numbers of attached lice were initially higher on those fish in the immunized group, throughout the course of the challenge experiment the total numbers of lice did not vary greatly between the immunized or control groups of fish. Initially, an overall average of about 17 attached stages were recorded from each fish sampled and by the end of the experiment this figure had fallen to about five adult lice per fish. However, compared with control fish fewer gravid female lice were present on immunized fish and furthermore these lice possessed fewer eggs (P<0.01). No major differences in egg hatching success were recorded. Further exploitation of this would require the isolation and purification of the antigens responsible for the observed effects. The possibilities for the development of a salmon louse vaccine are promising.
Low stocking incidence in brown trout populations from northwestern Spain monitored by LDH‐5* diagnostic marker
Authors: Arias J. , Sánchez L. , Martínez P.
Published: June 2006

Brown trout Salmo trutta is one of the most valuable species inhabiting river drainages in Galicia (northwestern Spain). The influence of man, through overfishing and pollution, is thought to have caused the decline of trout in Galician rivers. To balance the possible population decline, Galician rivers have been stocked extensively with a brown trout stock of German origin during the last 30 years. In this study, the incidence of stocking practices has been investigated by an LDH‐5* genetic marker. A very low number of stocked individuals have been observed within river populations, despite the long period of repopulation. Only eight out of the 44 populations analysed showed a limited number of individuals of hatchery origin. Most stocked individuals detected were 0+ age, and showed a poor condition factor (K < 1). Environmental factors (muscular stamina and food habits) and genetic factors (different selective conditions in hatchery medium) are invoked to explain the low viability of hatchery fish Observed in this Study.
Population genetics of tunas
Authors: Ward R. D.
Published: June 2006

Population genetic studies on tunas are reviewed. These studies have focused on phylogenetic reconstructions, species identifications and stock delineation, and have used tools ranging from blood group and allozyme analysis to PCR‐aided examination of mitochondrial DNA variation. Both allozyme and mtDNA approaches show tunas in the genus Thunnus to be very closely related to one another, but also indicate that the two presently recognized subspecies of northern bluefin tuna, Thunnus thynnus thynnus and T. t. orientalis, in fact may be worthy of species status. These techniques also permit the unequivocal recognition of specimens, which is not always possible on morphological grounds. However, it is arguable that, until recently, tunas have not received their due attention from geneticists given their commercial significance and the need for information on stock structure to ensure sustainable management. This may be because tunas are known to be highly vagile and therefore levels of population differentiation are expected to be low. None the less, population subdivision has been recorded in several species (skipjack, yellowfin, albacore), although this tends to be on a broad (intra‐ or inter‐oceanic) rather than on a more local scale. New molecular tools, including the PCR‐based analyses of nuclear genes and microsatellite loci, are yielding new, highly polymorphic markers, and will enable more powerful analyses of stock structure than have hitherto been possible.
SELENIUM RUBY GLASS*
Authors: Sullivan John D. , Austin Chester R.
Published: June 2006

This paper presents the results of an experimental study on the production of selenium ruby glass, particularly on the retention of the colorants during the melting and fining operations. Selenium, cadmium, and sulfur are necessary in the final glass to get a ruby color. Reducing conditions are conducive to the retention of a large percentage of the selenium in the glass, but when conditions are highly reducing, cadmium is eliminated almost completely. The writers believe that too little attention has been given in the past to the chemistry of the entire glass batch, and as a result operators and research workers have often failed to get a ruby glass not because the loss of selenium was too high but because they eliminated the cadmium by maintaining too strongly reducing conditions.

A balance must be maintained so that the batch and the atmosphere above it are sufficiently reducing to hold enough selenium in the melt but not so strongly reducing as to eliminate the cadmium.

Most of the work reported in this paper was done on soda‐lime‐silica glasses similar to those melted in continuous tanks for the production of machine‐made ware. A glass of this composition, containing 0.03% of selenium, 0.06% of cadmium, and 0.03% of sulfur, will produce a ruby color. The writers have found that if the cadmium is added as cadmium sulfide the final glass will have sufficient sulfur for color development. The use of silicon as a reducing agent is suggested.

An arrested‐cooling procedure for developing color is described briefly.
Factors Affecting Thermal Stress Resistance of Ceramic Materials
Authors: KINGERY W. D.
Published: June 2006

The sources and calculation of thermal stresses are considered, together with the factors involved in thermal stress resistance factors. Properties affecting thermal stress resistance of ceramics are reviewed, and testing methods are considered.
Thermal Fracture of Ceramic Materials Under Quasi‐Static Thermal Stresses (Ring Test)
Authors: BUESSEM W. R. , BUSH E. A.
Published: June 2006

The ring test consists in heating a pile of ceramic rings, each 2 in. in outside diameter, 1 in. in inside diameter, and 1½2 in. long, from the inside by a heating element and cooling it from the outside by a calorimetric chamber. The center rings of the pile have radial heat flow. The radial temperature gradient in these center rings can be measured and also the number of calories flowing through their unit surface area. Under equilibrium conditions these measurements yield the thermal conductivity of the ring material. The radial temperature gradient produces thermal stresses in the rings. If the gradient is increased slowly so as to maintain always approximate equilibrium conditions, there will be a maximum gradient which causes failure. The maximum gradient determined by thermal fracture and the thermal conductivity can be used to compute the two thermal stress resistivity constants,RandR1, of the material.RandR1have been determined for five ceramic materials: porous TiO2, dense TiO2, steatite, cordierite, and spodumene.
Effect of Shape on Thermal Fracture
Authors: BAROODY E. M. , SIMONS E. M. , DUCKWORTH W. H.
Published: June 2006

For radial steady‐state heat flow through hollow circular cylinders, the usual application of thermoelastic theory indicates that the heat flow per unit length to cause fracture (Wmax) is simply the product of two factors: M, characterizing the material, and S, the shape. Studies sponsored by the Atomic Energy Commission are in progress at Battelle Memorial Institute to evaluate the practical worth of this relationship. In this paper, attention is given to its validity for cylinders with both circular and noncircular cross sections and to measuring the effect of dimensions on S for circular cylinders. Thermal fracture experiments on circular cylinders of two ceramics indicated the manner in which S varies with the ratios of dimensions which define the shape. Changing all dimensions by factors up to 1.6, with these ratios constant, had no noticeable effect on S. Using theorems derived by Biot, it is shown that the product relationship is expected to hold for a considerably wider variety of shapes than the simple circular tube. Experimental results from tubes having cross sections with a circular inner boundary and a circular or square outer boundary support the product relation. Information was obtained on the shape factor for these cross sections and for similar tubes with a triangular outer boundary.
Effect of Porosity on Physical Properties of Sintered Alumina
Authors: COBLE R. L. , KINGERY W. D.
Published: June 2006

Porous structures having a continuous solid phase with isolated pores were prepared by the addition of different amounts of crushed naphthalene to an alumina casting slip. Samples of from 5 to 50% porosity were fired together for comparable grain development, eliminating structural variables except porosity. Effects of porosity and temperature on strength, elastic modulus, modulus of rigidity, and coefficient of thermal expansion were investigated. Effects of porosity on thermal stress resistance and tor‐sional creep properties were studied at constant temperature.
Moisture Expansion of Clay Products
Authors: YOUNG JAMES E. , BROWNELL WAYNE E.
Published: June 2006

The phenomenon of moisture expansion as related to structural clay products was studied to obtain information on the magnitude of expansion in commercial brick and to determine the phases in the fired body which are responsible for the expansion. Many commercial brick were tested and analyzed, and the results were expanded by laboratory tests on specimens prepared from the crude clays. Pure kaolin specimens, with and without controlled additions of impurities, were employed to study the mechanism and causes of moisture expansion. Information was gathered to substantiate the theory of moisture expansion proposed by Smith in 1955. The results produced considerable doubt about the reliability of an accelerated autoclave test as a measure of moisture expansion under service conditions. At the end of this study, several factors came to light which would assist the brick manufacturer in producing a more stable product with respect to moisture expansion.
Thermal Conductivity: XIV, Conductivity of Multicomponent Systems
Authors: KINGERY W. D.
Published: June 2006

The thermal conductivity of a number of multi‐component systems has been determined as a function of composition and temperature. These were silicate glasses, MgO‐NiO, Al2O3‐Cr2O3, UO2‐UO2+x‐ThO2, ZrO2‐HfO2‐CaO, MgO‐Mg2‐SiO4, MgO‐BeO, Al2O3‐mullite, MgO‐MgAl2O4, Al2O3‐ZrO2, Al2O3‐glass, and Si‐Sic. Analyses of these results indicate that a second component in solid solution markedly lowers the thermal conductivity. The second‐component scattering mean free path is inversely proportional to concentration at low concentrations and independent of temperature at the temperatures studied (above room temperature). The conductivity of polyphase ceramics can be predicted if the conductivity of each phase, amount of each phase, and phase distribution (including pore phase) are known.
Spectral Emittance of Ceramic‐Coated and Uncoated Specimens of Inconel and Stainless Steel
Authors: RICHMOND JOSEPH C. , STEWART JAMES E.
Published: June 2006

The normal spectral emittance of Inconel and type 321 stainless steel specimens with six different surface treatments, including application of National Bureau of Standards ceramic coatings A418 and N‐143, was determined at 900°, 1200°, 1500°, and 1800°F. over the wave‐length range 1.5 to 15 μ. The specimens with different surface treatments had markedly different spectral emittance curves. The bare polished specimens had the lowest spectral emittarce at all wave lengths, and the specimens coated with A–418 had the highest spectral emittarce over most of the range 5 to 15 μ. The spectral emittance of all specimens increased with temperature at all wave lengths.
Effect of Minor Additions on Sintering of MgO
Authors: LAYDEN G. K. , McQUARRIE M. C.
Published: June 2006

Fourteen selected metal ions were added to magnesium basic carbonate, and the MgO obtained after calcining was fired at various temperatures to determine the effect of the additives on the sintering behavior. The magnesia without additives showed rapid increase in density with firing temperature near 1200° C. The majority of the additives caused increased density, at a given firing treatment, but some were without effect and one (Cr) dramatically inhibited sintering in certain percentages. It is believed that most of the additives which aided sintering did so by entering into the magnesia lattice and creating defects, although at least one (V) clearly promoted sintering by liquid formation.
Surface Tension of Alkaline‐Earth Borates Containing 3 Mole % Potassium Oxide
Authors: SHARTSIS L. , SHERMER H. F. , BESTUL A. B.
Published: June 2006

The surface tensions of a series of barium, strontium, and calcium borates, each containing 3 mole % of K2O to counteract immiscibility, were measured by a ring detachment method. The order Ca < Sr < Ba was established for surface tensions of melts containing up to 40 mole % MO (alkaline‐earth oxide). Positive temperature coefficients of surface tension were observed for melts of low MO content. An interpretation of the observed inversions of surface tension from the order of ionic potential of the cations for these systems, as well as for other systems previously studied, is presented in terms of the Gibbs adsorption equation. A connection is indicated between inversions in the order of surface‐tension values and the presence of positive temperature coefficients.
Young's Modulus of Various Refractory Materials as a Function of Temperature
Authors: WACHTMAN J. B. , LAM D. G.
Published: June 2006

Young's modulus as a function of temperature was determined by a dynamic method for single‐crystal sapphire and ruby and for polycrystalline aluminum oxide, magnesium oxide, thorium oxide, mullite, spinel, stabilized zirconium oxide, silicon carbide, and nickel‐bonded titanium carbide. For the single crystals, Young's modulus was found to decrease linearly with increasing temperature from 100°C. to the highest temperature of measurement. For all the polycrystalline materials, except silicon carbide, stabilized zirconium oxide, and spinel, Young's modulus was found to decrease approximately linearly with increasing temperature until some temperature range characteristic of the material was reached in which Young's modulus decreased very rapidly and in a nonlinear manner with increasing temperature. This rapid decrease at high temperature is attributed to grain‐boundary slip. Stabilized zirconium oxide and spinel were found to have the same rapid decrease in Young's modulus at high temperature, but they also had a decidedly nonlinear temperature dependence at low temperature.
Retention of Sulfates by Fired Clay Products
Authors: BROWNELL W. E.
Published: June 2006

Sulfate is retained in a fired clay product as adsorbed sulfur trioxide and sulfate salts. These salts react with silicates at temperatures within the firing range of clay products, but the reaction rates and mechanisms may prevent the reaction from going to completion. The mechanism of efflorescence has been clarified by these studies.
Studies in Lithium Oxide Systems: VIII, Application of Silicate Liquid Immiscibility to Development of Opaque Glazes
Authors: HUMMEL F. A. , TIEN T. Y. , KIM K. H.
Published: June 2006

Recent studies have shown that opaque white glasses can be obtained in the systems Li2O‐TiO2‐SiO2 and CaO–TiO2–SiO2, owing to the separation of immiscible liquids. The two phases in the lime system are easily observed under the petrographic microscope, but the dispersion of spheres in the matrix glass in the lithia system can be seen only with the higher resolutions available with the electron microscope. The two systems have been combined to yield a base for opaque glaze compositions which can be fired in the usual maturing range of vitrified whiteware bodies around 1250°C. The thermal expansion behavior of four‐component oxide glazes is discussed in the light of some glaze‐fit problems which might arise. A brief picture of the effect of other oxides such as Na2O, ZnO, BaO, and ZrO2 on the texture and opacity of these immiscible liquid glasses is presented.
Phase Relations in Some Halide Systems
Authors: DEADMORE DANIEL L. , MACHIN JAMES S.
Published: June 2006

Phase relations in the systems LiF‐CdCl2, CdF2‐CdCl2, NaF‐CdCl2, NaCl‐CdCl2, and NaCl‐CdF2were studied by the cooling‐curve technique with visual observations. The systems LiF‐CdCl2and CdF2‐CdCl2 showed simple binary eutectics. The compounds NaFCdCl2 and 2NaClCdCl2were observed in the systems NaF‐CdCl2 and NaCl‐CdCU respectively. It was found that there was reaction between the end members in the system NaCl‐CdF2 to give NaF and CdCl2, which then formed the compound NaF.CdCl2.
Radiation Energy Transfer and Thermal Conductivity of Ceramic Oxides
Authors: LEE D. W. , KINGERY W. D.
Published: June 2006

The heat‐transfer mechanisms in several ceramic oxides have been investigated from room temperature to 1250°C. The conductivity of normal sintered porous polycrystalline oxides results from phonon conduction, and results agree with theoretical expectations for the effect of impurities, structure, and temperature dependence. Single crystals, glasses, and low‐porosity aggregates show deviations from the expected phonon conduction which are attributed to a second mechanism of heat transfer, namely, photon conduction. Measurements of photon conduction are related to infrared transmission, structure, and conditions of the measurements. Photon conduction can be a significant portion of the total heat conduction at high temperatures; however, for normal polycrystalline ceramic oxides of porosities greater than 2%, this contribution is small.
Flexural Strength of Specimens Prepared from Several Uranium Dioxide Powders; Its Dependence on Porosity and Grain Size and the Influence of Additions of Titania
Authors: KNUDSEN F. P. , PARKER H. S. , BURDICK M. D.
Published: June 2006

Flexural strengths of specimens prepared from four uranium dioxide powders were determined at room temperature and at 1000°C. The relation of the strength (S) to porosity (P) and to grain size (G) could be represented by the expression S=kG−ae−bP, where k, a, and b are empirical constants which differed with test temperature but did not differ for the different urania powders used. Additions of titania were very effective in promoting sintering and additions of 0.50 or 0.75% by weight markedly increased the strength of the specimens.
Diffusion of Oxygen from Contracting Bubbles in Molten Glass
Authors: DOREMUS R. H.
Published: June 2006

Some experimental measurements on the rate of contraction of oxygen bubbles in molten glass were compared with an equation for the diffusion‐ controlled contraction of a sphere. This comparison showed that the equation was valid until about 80% of the oxygen had diffused from the bubbles, so that the diffusion coefficient of the oxygen in the molten glass could be calculated from the experimental measurements. These values of the diffusion coefficient were higher than one would expect from the Stokes‐Einstein equation for diffusion in liquids. Thus it was concluded that some short‐circuiting mechanism such as diffusion in channels in the glass was operative. It also appeared that the oxygen diffused in the glass as atoms, rather than as molecules. From contraction measurements on glasses with different fining agents it was concluded that the mechanism of fining by such agents as antimony and arsenic oxides was not discharge of oxygen gas as had been generally supposed but was reduction of the concentration of oxygen in the glass, which caused the oxygen in the bubbles to diffuse into the glass more rapidly.
Studies on Lead Titanate Ceramics Containing Niobium or Tantalum
Authors: SUBBARAO E. C.
Published: June 2006

Dielectric, lattice constant, and thermal‐expansion measurements have been made on solid solution ceramics in the systems PbTiO3Pb0.5NbO3 and PbTiO3‐Pbo.5TaO3. The ferro‐electric Curie temperature is lowered to 465OC. at the solubility limit (2 to 5% Nb or Ta). Replacement of Ti4+ by Nb5+ or Ta5+ in these perovskite‐type solid solutions is accompanied by the creation of cation vacancies. These vacancies seem to facilitate material transport and aid sintering. Thus ceramics were obtained with up to 91% of theoretical density. These compositions have peak dielectric constants of the order of 10,000 with tan δ less than 0.1 in the interval 25° to 525°C.
Phase Equilibria in the System ZnO—TiO2
Authors: DULlN F. H. , RASE D. E.
Published: June 2006

The system ZnO‐Ti02 has been investigated using quenching, hydrothermal, strip‐furnace, and solid‐state‐reaction techniques. Two compounds were found: Zn2Ti04, which melts congruently at 1549 C., and ZnTiO2, which dissociates hydrothermally at 945° C. to give Zn2Ti04and rutile. Two eutectics were found: one between ZnO and Zn2Ti04 at 32 mole % TiO, and 1537°C. and the other between Zn2TiO4and TiO2 at 58 mole % TiO2 and 1418°C. Rutile was the only modification of TiO2 observed. The reported melting points of ZnO and TiO2 are 1975° and 1830°C. respectively; however, data exist which indicate the sublimation of ZnO at atmospheric pressure. Loss of ZnO by volatilization slightly decreased the accuracy of the liquidus relations. Reported solid solutions of TiO2 in Zn2Ti04 and ZnTiO3 were not encountered, and explanations of this discrepancy are proposed.
Vaporization of Rare‐Earth Oxides
Authors: WALSH PATRICK N. , GOLDSTEIN HAROLD W. , WHITE DAVID
Published: June 2006

A study of the vaporization of La2O3, Nd2O3, and Y2O3 at high temperatures has been carried out by the Knudsen effusion technique. The methods employed, the results of the measurements, and the low‐temperature heat capacities of these materials, which were determined for the purpose of calculating thermal functions of the oxides, are discussed. All the foregoing oxides react with tantalum, forming gaseous tantalummonoxide as a principal product. Cubic tantalates of lanthanum and neodymium are also formed in these reactions.
Principles of High‐Temperature Microscopy
Authors: BRENDEN BYRON B. , NEWKIRK H. W. , BATES J. I.
Published: June 2006

An extensive summary of literature is presented which deals with (1) the design of microscope objectives suitable for high‐temperature work, (2) the design of high‐temperature microscope stages and furnaces, and (3) the problems of high‐temperature photomicrography. Designs of microscope systems of long working distance and with numerical apertures of 0 or greater are available and have been shown to be suitable for studying microstructures at temperatures above 750° C. Numerical apertures as low as 0.1 are suitable for the observation of specimens in image‐type furnaces and for the observation of macrostructures. Several types of excellent furnaces are available commercially.
Properties of Pyrolytic Graphite
Authors: PAPPIS J. , BLUM S. L.
Published: June 2006

Pyrolytic graphite is a vapor‐deposited form of carbon which is characterized by strong anisotropic properties. The anisotropy is caused by the tendency of the individual crystallites to align themselves in such a way that their c axes are perpendicular to the surface of deposition. The Individual crystallites are composed of parallel graphitic layers which are randomly oriented with respect to the c axis. The ultimate strength of pyrolytic graphite in tension, bending, and compression has been found to increase considerably with increasing test temperatures. Other properties such as thermal conductivity and electrical resistivity give extremely high and low conduction parallel and perpendicular to the basal planes, respectively, in addition to varying considerably with increasing test temperatures. Properties are also influenced by the as‐deposited microstructure and by the amount of graphitization to which the material has been subjected. The properties and possible uses of this unique material are presented, discussed, and compared with the properties of other high‐temperature materials.
Viscosity‐Temperature Relation for Network Liquids
Authors: MACKENZIE J. D.
Published: June 2006

The viscosity‐temperature relation for the network liquids is considered in the light of the results for associated liquids and polymers. A critical examination of all the data available indicates that for liquid B2O3, SiO2, and BeF2 the energy of activation for flow is temperature dependent. Liquid GeO2 is possibly an anomaly. Empirical equations which satisfactorily describe the viscosity of associated liquids are not applicable to liquid B2O3 and SiO2.
Properties of Aluminoborate Glasses of Group II Metal Oxides: I, Glass Formation and Thermal Expansion
Authors: HIRAYAMA CHIKARA
Published: June 2006

The glass formation of the aluminoborates of Group II metal oxides depends on the atomic weight of the oxide and on the electronic configuration of the metal ion. The participation of zinc, cadmium, and magnesium ions as network formers in the glass is shown from measurements of thermal expansion. The linear thermal expansion of the alkaline‐earth aluminoborates varies from 4.7 × 10−6 to 16 × 10−6 per °C.
Infrared Spectra of Layer‐Structure Silicates
Authors: STUBIČAN V. , ROY RUSTUM
Published: June 2006

The relations between the structure, crystal chemistry, chemical bonds involved, and the infrared spectra of layer‐structure silicates established on the basis of recent experiments are discussed and summarized.