bluuebunny/crossref_metadata_2025 huggingface dataset:
Endosomally Stored MHC Class II Does Not Contribute to Antigen Presentation by Dendritic Cells at Inflammatory Conditions
Authors: ten Broeke Toine , van Niel Guillaume , Wauben Marca H. M. , Wubbolts Richard , Stoorvogel Willem
Published: April 2011

Major histocompatibility complex (MHC) class II (MHCII) is constitutively expressed by immature dendritic cells (DC), but has a short half‐life as a consequence of its transport to and degradation in lysosomes. For its transfer to lysosomes, MHCII is actively sorted to the intraluminal vesicles (ILV) of multivesicular bodies (MVB), a process driven by its ubiquitination. ILV have, besides their role as an intermediate compartment in lysosomal transfer, also been proposed to function as a site for MHCII antigen loading and temporal storage. In that scenario, DC would recruit antigen‐loaded MHCII to the cell surface in response to a maturation stimulus by allowing ILV to fuse back with the MVB delimiting membrane. Other studies, however, explained the increase in cell surface expression during DC maturation by transient upregulation of MHCII synthesis and reduced sorting of newly synthesized MHCII to lysosomes. Here, we have characterized the relative contributions from the biosynthetic and endocytic pathways and found that the vast majority of antigen‐loaded MHCII that is stably expressed at the plasma membrane by mature DC is synthesized after exposure to inflammatory stimuli. Pre‐existing endosomal MHCII contributed only when it was not yet sorted to ILV at the moment of DC activation. Together with previous records, our current data are consistent with a model in which passage of MHCII through ILV is not required for antigen loading in maturing DC and in which sorting to ILV in immature DC provides a one‐way ticket for lysosomal degradation.
K182G substitution in DevR or C8G mutation in the Dev box impairs protein–DNA interaction and abrogates DevR‐mediated gene induction in Mycobacterium tuberculosis
Authors: Gupta Rajesh Kumar , Chauhan Santosh , Tyagi Jaya Sivaswami
Published: April 2011

The DevR response regulator mediates adaptation of Mycobacterium tuberculosis to various signals that are likely to be encountered within the host such as hypoxia, nitric oxide, carbon monoxide and ascorbic acid. DevR is proposed as a promising target for developing drugs against dormant bacteria. It induces the expression of target genes by interacting with DNA motifs located in their promoter regions. An understanding of DNA–protein interactions is expected to facilitate the development of inhibitors targeting DevR. Only three amino acids in DevR, namely Lys179, Lys182 and Asn183, directly contact nucleotide bases in the DNA motif. The present study was designed to decipher the contribution of Lys182 in DevR function. M. tuberculosis fdxA (Rv2007c), a member of the DevR regulon, was selected for this analysis. Its transcriptional start point was mapped at −1 or −2 with respect to the putative translational start site suggesting that fdxA is expressed as a leaderless mRNA. DNase I footprinting led to the discovery of a secondary binding site and induction of the fdxA promoter is explained by the cooperative binding of DevR to two binding sites. Mutation of Lys182 lowers the DNA binding affinity of DevR and abrogates induction of fdxA and other regulon genes. Mutational analyses also highlight the singular importance of Lys182–G13 nucleotide interaction for DevR binding and regulon induction. Our findings demonstrate that impairment of Lys182‐mediated interactions alone abolishes DevR function and provide valuable insights for designing molecules that interfere with DevR‐mediated dormancy adaptation.
Opened‐Ring Adducts of 5‐Methylcytosine and 1,5‐Dimethylcytosine with Amines and Water and Evidence for an Opened‐Ring Hydrate of 2′‐Deoxycytidine
Authors: Shetlar Martin D. , Chung Janet
Published: April 2011

A variety of nucleic acid components and related compounds undergo photoreaction with water to form so‐called “photohydrates” (e.g. uracil forms 6‐hydroxy‐5,6‐dihydrouracil). However, the corresponding hydrates of 5‐methylcytosine (a minor nucleobase in eukaryotic DNA) and related compounds have not been characterized. We report the preparation of opened‐ring forms of such products for 5‐methylcytosine (m5C) and 1,5‐dimethylcytosine (DMC). This was accomplished via thermal reaction of ring‐opened amine adducts (e.g. N‐carbamoyl‐3‐amino‐2‐methylacrylamidine (IVa) or N‐(N′‐methylcarbamoyl)‐3‐amino‐2‐methylacrylamidine (IVb)) produced by photo‐induced reactions of m5C with ammonia or methylamine. When these adducts were treated with dilute trifluoroacetic acid, the amino group at the 3‐position was replaced with a hydroxyl group; with IVa, N‐carbamoyl‐3‐hydroxy‐2‐methylacrylamidine (Va) was formed, while reaction of IVb led to N‐(N′‐methylcarbamoyl)‐3‐hydroxy‐2‐methylacrylamidine (Vb). These compounds are ring‐opened isomers of 5,6‐dihydro‐6‐hydroxy‐5‐methylcytosine (Ia and IIa) and 5,6‐dihydro‐6‐hydroxy‐1,5‐dimethylcytosine (Ib and IIb). Compounds Va and Vb each undergo thermal ring closure reactions to form two unstable compounds with chemical and UV spectral properties expected for Ia and IIa (or Ib and IIb). The latter compounds have been identified as minor products in UV‐irradiated aqueous solutions of m5C and DMC. Evidence is also presented that the 2′‐deoxycytidine photohydrates coexist with an opened‐ring form, possibly similar in nature to Vb.
Early Cambrian Mollusc Watsonella crosbyi: A Potential GSSP Index Fossil for the Base of the Cambrian Stage 2
Authors: LI Guoxiang , ZHAO Xin , GUBANOV Alexander , ZHU Maoyan , NA Lin
Published: April 2011

The mollusc Watsonella crosbyi was studied on the basis of material from the lower Cambrian Dahai Member of the Zhujiaqing Formation in eastern Yunnan, China and the Pestrotsvet Formation of the Aldan River region in the Siberian Platform. This fossil had been excessively described under different names in the literature, such as Heraultia varensalensis Cobbold, 1935, H. sibirica Missarzhevsky, 1974, Heraultipegma yunnanensis He and Yang, 1982, H. yannanese He and Yang, 1982, Watsonella yunnanensis, W. crosbyi Grabau, 1900, etc. Taxonomic revision shows that other species are junior synonyms of W. crosbyi. Analysis of functional morphology implies that W. crosbyi may be rather a helcionelloid than a rostroconch since its univalved conch is untorted endogastric and lacks a rostrum and a true internal pegma. Replicas of the original microstructures preserved on the surfaces of phosphatic internal moulds confirm that the shell consists of two layers. The inner layer is lamello‐fibrillar, and the outer layer is spherulitic prismatic. The widespread geographical occurrences in both siliciclastic and carbonate rocks of the late Terreneuvian indicate that W. crosbyi is an important index fossil for global correlations and subdivision of the Cambrian Series 1 (Terreneuvian). The first appearance datum (FAD) of W. crosbyi is suggested to be a potential GSSP (Global Boundary Stratotype Section and Point) candidate marker for defining the base of the Cambrian Stage 2.
A Potential Global Standard Stratotype‐Section and Point of the Moscovian Stage (Carboniferous)
Authors: WANG Xiangdong , QI Yuping , LAMBERT Lance , WANG Zhihao , WANG Yue , HU Keyi , LIN Wei , CHEN Bo
Published: April 2011

Conodonts and fusulinids are the two most widely used biotic groups for subdividing and correlating Bashkirian and Moscovian strata. The definition of the base of the Global Moscovian Stage is undecided because there are many disagreements among existing boundary definition proposals, each of which has disadvantages. Declinognathodus donetzianus is easily recognized but somewhat limited in its paleogeographic distribution. Idiognathoides postsulcatus is slightly more widespread, but it is less easily identified and its occurrences may be diachronous from region to region. Diplognathodus ellesmerensis is easily recognized and even more widespread, but it is usually rare and its ancestry is not adequately known. The Naqing Section of South Guizhou, South China contains diverse conodont evolutionary lineages among different taxa, including Idiognathoides, Idiognathodus, Diplognathodus, Neognathodus, Gondolella and Mesogondolella. There are numerous transitional forms in almost every lineage of the Naqing section, which shows that the prospects for South China to play a critical role in determining the basal Moscovian Stage definition are good.
Lower Triassic and Induan‐Olenekian Boundary in Chaohu, Anhui Province, South China
Authors: TONG Jinnan , ZHAO Laishi
Published: April 2011

Since the West Pingdingshan Section in Chaohu was proposed as the candidate of the Global Stratotype Section and Point of the Induan‐Olenekian boundary in 2003, the Lower Triassic of Chaohu has been extensively studied. Based on the studies on the Lower Triassic of Chaohu, (1) a continuous conodont zonation is established, which has become an important reference for Lower Triassic stratigraphic correlation over the world; (2) the First Appearance Datum of conodont Neospathodus waageni was suggested and has been basically accepted as the primary marker to define the Induan‐Olenekian boundary; (3) a characteristic Lower Triassic excursion of carbon isotopes was brought to light and has been proven to be not only an excellent index for the stratigraphic correlation but also a unique indication for the perturbation of ecological environments in the aftermath of the end‐Permian mass extinction; (4) a magnetostratigraphic sequence is constituted with a certain biostratigraphic control in the low‐latitude region and it presents an important correlation to the Boreal sequence; (5) a cyclostratigraphic study provides an alternative method to constrain the age of the chronostratigraphic units; and (6) a scheme of the Olenekian subdivision is recently suggested to define the boundary between the Smithian and Spathian Substages. In addition, Chaohu is also the type locality of the Chaohuan Stage, the upper stage of the Lower Triassic in the China Chronostratigraphic System. Thus, the Lower Triassic of Chaohu is not only a classic sequence in South China, but also a key reference sequence to the investigation of the corresponding stratigraphy and geological events over the world. The recent achievements are viewed here for an overall understanding of the sequence. Then the current situation of the Induan‐Olenekian and Smithian‐Spathian boundaries is discussed to provide a reference for later works.
Conodont Biostratigraphy and Age Determination of the Lower‐Middle Triassic Boundary in South Guizhou Province, China
Authors: YAO Jianxin , JI Zhansheng , WANG Liting , WANG Yanbin , WU Zhenjie , LIU Dunyi , WU Guichun , ZHANG Jianwei , LI Suping
Published: April 2011

The demarcation of the Lower–Middle Triassic boundary is a disputed problem in global stratigraphic research. Lower–Middle Triassic strata of different types, from platform to basin facies, are well developed in Southwest China. This is favorable for the study of the Olenekian–Anisian boundary and establishing a stratotype for the Qingyan Stage. Based on research at the Ganheqiao section in Wangmo county and the Qingyan section in Guiyang city, Guizhou province, six conodont zones have been recognized, which can be correlated with those in other regions, in ascending order as follows: 1, Neospathodus cristagalli Interval‐Zone; 2, Neospathodus pakistanensis Interval‐Zone; 3, Neospathodus waageni Interval‐Zone; 4, Neospathodus homeri‐N. triangularis Assemblage‐Zone; 5, Chiosella timorensis Interval‐Zone; and 6, Neogongdolella regalis Range‐Zone. An evolutionary series of the Early–Middle Triassic conodont genera Neospathodus‐Chiosella‐Neogongdolella discovered in the Ganheqiao and Qingyan sections has an intermediate type named Neospathodus qingyanensis that appears between Neospathodus homeri and Chiosella timorensis in the upper part of the Neospathodus homeri‐N. triangularis Zone, showing an excellent evolutionary relationship of conodonts near the Lower–Middle Triassic boundary. The Lower–Middle Triassic boundary is located at 1.5 m below the top of the Ziyun Formation, where Chiosella timorensis Zone first appears in the Qingyan section, whereas this boundary is located 0.5 m below the top of the Ziyun Formation, where Chiosella timorensis Zone first appears in the Ganheqiao section. There exists one nearly 6‐m thick vitric tuff bed at the bottom of the Xinyuan Formation in the Ganheqiao section, which is usually regarded as a lithologic symbol of the Lower–Middle Triassic boundary in South China. Based on the analysis of high‐precision and high‐sensitivity Secondary Ion Mass Spectrum data, the zircon age of this tuff has a weighted mean 206Pb/238U age of 239.0 ± 2.9 Ma (2σ), which is a directly measured zircon U‐Pb age of the Lower–Middle Triassic boundary. The Ganheqiao section in Wangmo county can therefore provide an excellent section through the Lower–Middle Triassic because it is continuous, the evolution of the conodonts is distinctive and the regionally stable distributed vitric tuff near the Lower–Middle Triassic boundary can be regarded as a regional key isochronal layer. This section can be regarded not only as a standard section for the establishment of the Qingyan Stage in China, but also as a reference section for the GSSP of the Lower–Middle Triassic boundary.
Stratigraphy of the Triassic–Jurassic Boundary Successions of the Southern Margin of the Junggar Basin, Northwestern China
Authors: SHA Jingeng , VAJDA Vivi , PAN Yanhong , LARSSON Linda , YAO Xiaogang , ZHANG Xiaolin , WANG Yaqiong , CHENG Xiansheng , JIANG Baoyu , DENG Shenghui , CHEN Siwei , PENG Bo
Published: April 2011

The Triassic–Jurassic (Tr–J) boundary marks a major extinction event, which (∼200 Ma) resulted in global extinctions of fauna and flora both in the marine and terrestrial realms. There prevail great challenges in determining the exact location of the terrestrial Tr–J boundary, because of endemism of taxa and the scarcity of fossils in terrestrial settings leading to difficulties in linking marine and terrestrial sedimentary successions. Investigation based on palynology and bivalves has been carried out over a 1113 m thick section, which is subdivided into 132 beds, along the Haojiagou valley on the southern margin of the Junggar Basin of the northern Xinjiang, northwestern China. The terrestrial Lower Jurassic is conformably resting on the Upper Triassic strata. The Upper Triassic covers the Huangshanjie Formation overlaid by the Haojiagou Formation, while the Lower Jurassic comprises the Badaowan Formation followed by the Sangonghe Formation. Fifty six pollen and spore taxa and one algal taxon were identified from the sediments. Based on the key‐species and abundance of spores and pollen, three zones were erected: the Late Triassic (Rhaetian)Aratrisporites‐AlisporitesAssemblage, the Early Jurassic (Hettangian)Perinopollenites–PinuspollenitesAssemblage, and the SinemurianPerinopollenites–CycadopitesAssemblage. The Tr–J boundary is placed between bed 44 and 45 coincident with the boundary between the Haojiagou and Badaowan formations. Beds withFerganoconcha(?),Unio–FerganoconchaandWaagenoperna–Yananoconchabivalve assemblages are recognized. TheFerganoconcha(?) bed is limited to the upper Haojiagou Formation,Unio–FerganoconchaandWaagenoperna–Yananoconchaassemblages are present in the middle and upper members of the Badaowan Formation. The sedimentary succession is interpreted as terrestrial with two mainly lake deposit intervals within Haojiagou and Badaowan formations, yielding fresh water algae and bivalves. However, the presence of brackish water algaeTasmanitesand the marine‐littoral facies bivalveWaagenopernafrom the Badaowan Formation indicate that the Junggar Basin was influenced by sea water caused by transgressions from the northern Tethys, during the Sinemurian.
On the Lower Cretaceous in Yixian County of Jinzhou City, Western Liaoning, China
Authors: JI Qiang , LIU Yongqing , JIANG Xiaojun
Published: April 2011

Traditionally, the lacustrine deposits in Yixian County of Western Liaoning have been assigned to either “the Dakangpu Bed” of the Yixian Formation or the Jiufotang Formation. However, a 206Pb/238U age of 126.47 ± 0.87 Ma is newly obtained from the tuff sample (06051) of the lacustrine deposits in the Baitaigou fossil site of Potaizi village, Yixian County, indicating that the lacustrine deposits in Potaizi area are approximately equivalent to the Wumingshan volcanics of the Sihetun Bed of the Yixian Formation in Beipiao. From our new dating data have arisen some new problems: Where could we find the Jiufotang Formation in Yixian County? How widely distributed is the Jiufotang Formation in Western Liaoning? Could the traditionally named Jiufotang Formation somewhere in Western Liaoning be the synchronous deposits of other litho‐units (e.g. the Yixian Formation) in different facies? Could some lacustrine deposits somewhere in Western Liaoning have been assigned to the Jiufotang Formation?
Chinese Continental Paleocene‐Eocene Boundary and Its Correlation
Authors: WANG Yuanqing , TONG Yongsheng , LI Qian
Published: April 2011

Recent paleontological, paleomagnetic and carbon isotopic investigations have provided new evidence supporting placement of the Chinese terrestrial Paleocene–Eocene boundary at the base of the Lingcha Formation in the Hengyang Basin, Hunan Province, and within the upper part of the Nomogen Formation in the Erlian Basin, Inner Mongolia. Based on mammalian and ostracod biostratigraphic data, the boundary can also be roughly correlated with the contacts between the Baoyue and Huayong formations in the Sanshui Basin of Guangdong, the Qingjiang and Xinyu formations of Jiangxi, the Fourth Formation of the Funing Group and the Dainan Formation in northern Jiangsu, and the Dabu and Shisanjianfang formations in the Turfan Basin of Xinjiang.
Special Lateral Increase in a Permian Rugose Coral Kepingophyllum aksuence Wu et Chow
Authors: ZHANG Feng , WANG Xiangdong
Published: April 2011

Well‐preserved specimens of Kepingophyllum aksuence Wu et Chow were collected from Early Permian strata in western Tarim Basin, Xinjiang. More than 100 serial thin sections were made for this study. Kepingophyllum aksuence displays a unique increase pattern. The bud appears in lonsdaleoid dissepiments between the corallites where the wall of parent corallite disappears and the area becomes aphroid. This increase pattern is different from other lateral increases of most colonial rugose corals, and therefore has taxonomic significance to differentiate Kepingophyllidae from other compound rugose corals. It is also discussed that Kepingophyllum aksuence has a high “reproductive integration”, which means a rapid growth of buds during the offsetting process. Kepingophyllum was possibly originated from Ivanovia and was also a probable ancestor of Wentzellophyllum, which is supported here by more or less the similarity of the blastogeny in different stages of three taxa.
First Description of Fossil Naucoridae (Heteroptera: Nepomorpha) from Late Mesozoic of China
Authors: ZHANG Weiting , YAO Yunzhi , REN Dong , ZHAO Yunyun
Published: April 2011

Herein the description and illustration of two new fossil genera and species of Naucoridae, Exilcrus cameriferus gen. & sp. Nov. and Miroculus laticephlus gen. & sp. Nov., are provided. Both species were collected from the Late Jurassic to Early Cretaceous Yixian Formation of western Liaoning, China. The complete preservation of the new specimens enable us to determine the characters of the specimens reported here. This finding represents the first record of fossil Naucoridae from China, which includes well‐preserved nymphs. The possibility of a predatory habit of these specimens is discussed.
A New Cockroach Genus of the Family Fuziidae from Northeastern China (Insecta: Blattida)
Authors: GUO Yinxia , REN Dong
Published: April 2011

A new genus and two new species of fossil Fuziidae are described and illustrated: Parvifuzia gen. nov., P. marsa sp. nov. and P. brava sp. nov. Both species were collected from the Middle Jurassic Jiulongshan, Formation of Daohugou, Inner Mongolia of China. In conjunction with Fuzia Vršanský, Liang et Ren, 2009, the present findings allow us to demonstrate that members of the family were morphologically diverse, with body length ranging from medium (17 mm) in Fuzia to small (9.7 mm) in the present genus. Wing venation of F. dadao is complicated, but simple in the present species, and apex of male's cerci are sharp and forceps‐like in F. dadao, but strongly curved inward and round in the new genus.
The epidemiology of osteoarthritis in Asia
Authors: FRANSEN Marlene , BRIDGETT Lisa , MARCH Lyn , HOY Damian , PENSERGA Ester , BROOKS Peter
Published: April 2011

Worldwide, osteoarthritis (OA) is estimated to be the fourth leading cause of disability. Most of this disability burden is attributable to the involvement of the hips or the knees. OA is strongly associated with ageing and the Asian region is ageing rapidly. Further, OA has been associated with heavy physical occupational activity, a required livelihood for many people living in rural communities in developing countries. Unfortunately, joint replacement surgery, an effective intervention for people with severe OA involving the hips or knees, is inaccessible to most people in these regions. On the other hand, obesity, another major risk factor, may be less prevalent, although it is on the increase. Determining region‐specific OA prevalence and risk factor profiles will provide important information for planning future cost‐effective preventive strategies and health care services. An update of what is currently known about the prevalence of hip and knee OA from population‐based studies conducted in the Asian region is presented in this review. Many of the recent studies have conducted comparisons between urban and rural areas and poor and affluent communities. The results of Asian‐based studies evaluating risk factors from population‐based cohorts or case–control studies, and the current evidence on OA morbidity burden in Asia is also outlined.
Improving care for people with osteoarthritis of the hip and knee: How has national policy for osteoarthritis been translated into service models in Australia?
Authors: BRAND Caroline , HUNTER David , HINMAN Rana , MARCH Lyn , OSBORNE Richard , BENNELL Kim
Published: April 2011

There is strong rationale for improving care for people with chronic conditions, including osteoarthritis (OA). Successful implementation of healthcare reform requires new concepts and directions that are strongly supported by policy, new models of care (service redesign) and changes in day‐to‐day practice (healthcare provider and patient practice). In this paper we discuss the extent to which policy about management of OA of the hip and knee has been translated into new service models in Australia. A structured search of government and other key health websites in Australia was performed to identify policy, funding initiatives and new services models for managing OA of the hip and knee. This search was supported by a literature review. Musculoskeletal conditions were designated a National Health Priority in Australia in 2002. Under the Better Arthritis and Osteoporosis Care initiative, Australia has developed a national policy for OA care and national evidence‐based clinical practice guidelines for management of OA of the hip and knee. Only two well‐described examples of new chronic disease management service models, the Osteoarthritis Clinical Pathway (OACP) model and the Osteoarthritis Hip and Knee Service (OAHKS) were identified. Primarily focused within acute care public hospital settings, these have been shown to be feasible and acceptable but have limited data on clinical impact and cost‐effectiveness. While policy is extant, implementation has not been systematic and comprehensive. Clinicians have evidence‐based recommendations for OA management but are poorly supported by service models to deliver these effectively and efficiently.
An overview of OA research in two urban APLAR populations
Authors: LEUNG Ying Y. , THUMBOO Julian
Published: April 2011

Osteoarthritis (OA), the most prevalent type of arthritis in the elderly, is also among the first five leading causes of disability in developed countries. With the ‘Westernized’ living environment and lifestyle among Southeast Asian urbanized cities, where obesity is on the rise and the populations are ageing, the incidence of OA is expected to rise in the next decades. There is need to summarize research work within these places. This article summarizes some of the research aspects of OA in Southeast Asian cities. These data may form a useful basis for future planning of medical resource and needs.
Update in surgery for osteoarthritis of the knee
Authors: CHOONG Peter F. M. , DOWSEY Michelle M.
Published: April 2011

Osteoarthritis is a leading cause of disability with incidence and prevalence rising in most nations. Management to address the degenerative joint is stratified according to degree of severity of involvement and always begins with non‐surgical modalities before progressing through a range of surgeries, including arthroscopy, osteotomy, unicompartmental and total knee replacement. Predictability of results depends on the type of procedure with total joint replacement giving the most sustainable relief from symptoms, improvement of function and longevity of construct. Obesity is a health priority in developed countries where it is overrepresented in patients presenting for joint replacement. Complications, poor patient satisfaction and joint function can be directly attributable to obesity. Efforts to address obesity should be considered as part of the approach to managing osteoarthritis.
Micro‐X‐ray diffraction assessment of shock stage in enstatite chondrites
Authors: IZAWA Matthew R. M. , FLEMMING Roberta L. , BANERJEE Neil R. , McCAUSLAND Philip J. A.
Published: April 2011

Abstract– A new method for assessing the shock stage of enstatite chondrites has been developed, using in situ micro‐X‐ray diffraction (μXRD) to measure the full width at half maximum (FWHMχ) of peak intensity distributed along the direction of the Debye rings, or chi angle (χ), corresponding to individual lattice reflections in two‐dimensional XRD patterns. This μXRD technique differs from previous XRD shock characterization methods: it does not require single crystals or powders. In situ μXRD has been applied to polished thin sections and whole‐rock meteorite samples. Three frequently observed orthoenstatite reflections were measured: (020), (610), and (131); these were selected as they did not overlap with diffraction lines from other phases. Enstatite chondrites are commonly fine grained, stained or darkened by weathering, shock‐induced oxidation, and metal/sulfide inclusions; furthermore, most E chondrites have little olivine or plagioclase. These characteristics inhibit transmitted‐light petrography, nevertheless, shock stages have been assigned MacAlpine Hills (MAC) 02837 (EL3) S3, Pecora Escarpment (PCA) 91020 (EL3) S5, MAC 02747 (EL4) S4, Thiel Mountains (TIL) 91714 (EL5) S2, Allan Hills (ALHA) 81021 (EL6) S2, Elephant Moraine (EET) 87746 (EH3) S3, Meteorite Hills (MET) 00783 (EH4) S4, EET 96135 (EH4–5) S2, Lewis Cliff (LEW) 88180 (EH5) S2, Queen Alexandra Range (QUE) 94204 (EH7) S2, LaPaz Icefield (LAP) 02225 (EH impact melt) S1; for the six with published shock stages, there is agreement with the published classification. FWHMχ plotted against petrographic shock stage demonstrates positive linear correlation. FWHMχ ranges corresponding to shock stages were assigned as follows: S1 < 0.7°, S2 = 0.7–1.2°, S3 = 1.2–2.3°, S4 = 2.3–3.5°, S5 > 3.5°, S6—not measured. Slabs of Abee (EH impact‐melt breccia), and Northwest Africa (NWA) 2212 (EL6) were examined using μXRD alone; FWHMχ values place both in the S2 range, consistent with literature values. Micro‐XRD analysis may be applicable to other shocked orthopyroxene‐bearing rocks.
What’s up? Preservation of gravitational direction in the Larkman Nunatak 06299 LL impact melt breccia
Authors: RUBIN Alan E. , MOORE William B.
Published: April 2011

Abstract– Larkman Nunatak (LAR) 06299 is a vesicular LL chondrite impact melt breccia that cooled rapidly (0.1–0.3 °C s−1) during crystallization. Ar‐Ar data from the literature indicate that the impact event that formed this rock occurred approximately 1 Ga ago. About 30 vol% of the meteorite consists of a melt matrix containing faceted and intergrown mafic silicate grains (mainly 4–11 μm size olivine phenocrysts) partially to completely surrounded by 2–20 μm size patches of plagioclase. Suspended in the melt are 30–370 μm size ellipsoidal to spheroidal metal‐sulfide nodules (several hundred per thin section), many connected to 8–600 μm size ellipsoidal to spheroidal vesicles. Most of the metal‐sulfide nodules contain a large oblate metallic Fe‐Ni bleb at one end of the nodule. For approximately 90% of the nodules, the metal blebs are aligned on the same side of the nodules; for approximately 80% of the nodules that are adjacent to vesicles, the vesicles are attached to the opposite end of the nodules from the oblate metal blebs. Most of the oblate metal blebs themselves are flattened in a direction perpendicular to the long axis of the nodule/vesicle. These features result from alignment in the gravitational field on the LL parent asteroid, making LAR 06299 the first known chondrite to indicate gravitational direction. Using reasonable estimates of the cooling rate, viscosity of the metal‐sulfide melt, and asteroid density, as well as the observed sizes of constituent phases in LAR 06299, we obtain a lower limit of approximately 1.5 km for the radius of the LAR 06299 parent body. The body was probably substantially larger.
Correlation of Structure and Photoelastic Response in Tin Phosphate Glass
Authors: Martin Vincent , Werner‐Zwanziger Ulrike , Zwanziger Josef W. , Dunlap Richard A.
Published: April 2011

Recently an empirical model was established to predict the photoelastic response of a glass based on its composition and the crystalline structure of its constituents. In the present work the model was tested in detail by comparing the local structure assessed by a combination of nuclear magnetic resonance and Mössbauer spectroscopy with the model predictions and the measured photoelastic response. The system investigated was (SnO)x(P2O5)1−x. It was found that while the original simple model based on data on the pure components predicted the composition of the zero stress‐optic glass to within about 15 mol%, inclusion of data on mixed systems, more reflective of the true glass structure, gave substantial improvement of the prediction. This finding further confirms the relation of local bonding structure to the photoelastic response of glass.
Unsteady Forces of Rotor Blades in Full and Partial Admission Turbines
Authors: Hushmandi Narmin Baagherzadeh , Fridh Jens E. , Fransson Torsten H.
Published: April 2011

A numerical and experimental study of partial admission in a low reaction two-stage axial air test turbine is performed in this paper. In order to model one part load configuration, corresponding to zero flow in one of the admission arcs, the inlet was blocked at one segmental arc, at the leading edge of the first stage guide vanes. Due to the unsymmetrical geometry, the full annulus of the turbine was modeled numerically. The computational domain contained the shroud and disk cavities. The full admission turbine configuration was also modeled for reference comparisons. Computed unsteady forces of the first stage rotor blades showed cyclic change both in magnitude and direction while moving around the circumference. Unsteady forces of first stage rotor blades were plotted in the frequency domain using Fourier analysis. The largest amplitudes caused by partial admission were at first and second multiples of rotational frequency due to the existence of single blockage and change in the force direction. Unsteady forces of rotating blades in a partial admission turbine could cause unexpected failures in operation; therefore, knowledge about the frequency content of the unsteady force vector and the related amplitudes is vital to the design process of partial admission turbine blades. The pressure plots showed that the nonuniformity in the static pressure field decreases considerably downstream of the second stage’s stator row, while the nonuniformity in the dynamic pressure field is still large. The numerical results between the first stage’s stator and rotor rows showed that the leakage flow leaves the blade path down into the disk cavity in the admitted sector and re-enters downstream of the blocked channel. This process compensates for the sudden pressure drop downstream of the blockage but reduces the momentum of the main flow.
Optimization of the Aerodynamic Flame Stabilization for Fuel Flexible Gas Turbine Premix Burners
Authors: Burmberger Stephan , Sattelmayer Thomas
Published: April 2011

A frequently employed method for aerodynamic flame stabilization in modern premixed low emission combustors is the breakdown of swirling flows; with carefully optimized tailoring of the swirler, a sudden transition in the flow field in the combustor can be achieved. A central recirculation zone evolves at the cross-sectional area change located at the entrance of the combustion chamber and anchors the flame in a fixed position. In general, premixed combustion in swirling flows can lead to flame flashback that is caused by combustion induced vortex breakdown near the centerline of the flow. In this case, the recirculation zone suddenly moves upstream and stabilizes in the premix zone (Kröner , 2007, “Flame Propagation in Swirling Flows—Effect of Local Extinction on the Combustion Induced Vortex Breakdown,” Combust. Sci. Technol., 179, pp. 1385–1416). This type of flame flashback is caused by a strong interaction between the flame chemistry and vortex dynamics. The analysis of the vorticity transport equation shows that the axial gradient of the azimuthal vorticity is of particular importance for flame stability. A negative azimuthal vorticity gradient decelerates the core flow and finally causes vortex breakdown. Based on fundamental fluid mechanics, guidelines for a proper aerodynamic design of gas turbine combustors are given. These guidelines summarize the experience from several previous aerodynamic and combustion studies of the authors.
A Study of Combined Effects of Surface Roughness and Lubricant Rheology on the Hydrodynamic Contact Behavior Using the Homogenized Method
Authors: Mouassa Ahcene , Lahmar Mustapha , Bou-Said Benyebka
Published: April 2011

The combined effects of surface roughness and lubricant rheology on the performance characteristics of a hydrodynamic inclined slider bearing are investigated by means of the homogenized method. The pad surface is rough and stationary while the lower surface is assumed to be smooth and moving. The V. K. Stokes couple stress fluid model is adopted to describe the rheological behavior of the lubricant flowing between the two surfaces. The numerical simulations are performed by considering three roughness patterns (transverse, longitudinal and anisotropic), and various values of the couple stress parameter. It is found that the homogenization method is rigorous and efficient for the three roughness patterns considered. It is also found that the combined effects of the surface roughness as well as the couple stress due to the presence of polymer additives on the hydrodynamic performance characteristics such as load carrying capacity, friction factor are significant.
A Numerical Study of Friction in Isothermal EHD Rolling-Sliding Sphere-Plane Contacts With Spinning
Authors: Vergne P. , Dormois H. , Doki Thonon Th. , Fillot N. , Habchi W. , Morales-Espejel G. E.
Published: April 2011

This paper presents a study of the spinning influence on film thickness and friction in EHL circular contacts under isothermal and fully-flooded conditions. Pressure and film thickness profiles are computed with an original Full-System FEM approach. Friction was thereafter investigated using a classical Ree-Eyring model to calculate the longitudinal and transverse shear stresses. An analysis of both the velocity and shear stress distributions at every point of the contact surfaces has allowed explaining the fall of the longitudinal friction coefficient. Moreover in the transverse direction, spinning favors large shear stresses of opposite signs, decreasing the fluid viscosity by non-Newtonian effects. These effects have direct consequences on the friction reduction that is observed in presence of spinning. They are expected to further decrease friction in real situations due to shear heating.
Analysis of 100 and 700 rpm Cycles in Boundary Lubrication Using Fluorinated Mix Interactions Under Extreme Boundary Lubrication
Authors: Nehme Gabi
Published: April 2011

Tribology and solid mechanics are essential when studying engine lubrications. Very reproducible boundary lubrication tests were conducted as part of Design of Experiment software (DOE) to study the behavior of fluorinated mix in developing environmentally friendly (reduced P and S) anti-wear additives for future engine oil formulations using ball on cylinder testing protocol. In this study fully formulated oil and ZDDP plain oils were tested under the protocol of two cycles. A 100 rpm cycle was used for the first 5000 revolutions and a 700 rpm cycle was used until failure or 100000 revolutions whichever comes first. All tests were generated under extreme boundary lubrication (Hertzian contact pressure of 2.72 GPa). Design of Experiment (DOE) with 2 level factorial was used to investigate the failure and wear responses with respect to fluorinated mix interactions in plain and fully formulated oils. The two cycle’s tests indicate better performance than the one cycle test. Findings indicate that the most significant factors, affecting friction and wear are fluorinated mix concentrations together with oil formulation.
Influence of Position Errors on EHD Lubrication in Spiral Bevel Gears
Authors: Simon Vilmos
Published: April 2011

The thermal elastohydrodynamic analysis of lubrication is applied to investigate the influence of misalignments of the meshing members on lubrication in spiral bevel gears. The calculation is based on the simultaneous solution of the Reynolds, elasticity, energy, and Laplace’s equations. The full thermal EHD lubrication analysis is applied, therefore, the oil viscosity variation with respect to pressure and temperature and the density variation with respect to pressure are included. By using the corresponding computer program, the influence of pinion’s running offset and axial adjustment errors, and angular position error of pinion axis on maximum oil film pressure and temperature, EHD load carrying capacity, and on power losses in the oil film is investigated. On the basis of the obtained results it can be concluded that the EHD load carrying capacity and the friction factor are very sensitive to misalignments of the mating members in the spiral bevel gear pair, the friction factor is reduced by the increase of EHD load carrying capacity and vise versa, and the maximum inlet oil temperature is almost insensitive to the misalignments.
Numerical Analysis on Dynamic Characteristics of Flying Magnetic Head Under Ultra Thin Spacing
Authors: Yao Hua-ping , Ping Huang , Chen Yang-zhi
Published: April 2011

This paper presents numerical analysis of the dynamic characteristics of an air bearing system of a magnetic head under ultra-thin spacing. First, the static pressure distribution is numerically calculated by using up-wind scheme for a very large bearing number and a harmonic algorithm to calculate the flux factor for the abrupt change of film thickness. Then, the dynamic characteristics are analyzed in frequency domain by a perturbation method and finite difference method. The varying tendencies of the stiffness and damping coefficient in the translation, pitch and rolling directions with the frequency and the minimum film height are obtained.
Modeling Non-Newtonian Piston Skirts EHL in the Initial Engine Start Up
Authors: Qasim Syed Adnan , Chaudhri Usman F. , Malik M. Afzaal , Mufti Riaz A.
Published: April 2011

In the normal high speed engine operation at small piston-to-bore radial clearance, elastohydrodynamic lubrication (EHL) of skirts and non-Newtonian lubricant behavior prevent adhesive wear, but in the initial engine start up, the large clearance, low speed and absence of EHL, cause start up wear. This study models 2-D upper convected Maxwell viscoelastic EHL of piston skirts at small radial clearance in a few initial low speed engine start up cycles by solving the Reynolds equation and using the inverse solution technique. The numerical analysis incorporate characteristic lubricant relaxation times and a perturbation method to predict and compare hydrodynamic and EHL pressures and film profiles. The effects of viscoelasticity on the lubricant characteristics, transverse eccentricities of piston, film thickness, and pressure fields in the hydrodynamic and EHL regimes are investigated. This study suggests that EHL film is formed at very small piston-to-bore radial clearance at low start up speed under assumed conditions to prevent start up wear as viscoelasticity produces a beneficial effect on piston skirts lubrication in the initial engine start up.
Impact of Sulfur Pollution Silver Cage on Bearing Operating Performance
Authors: Yang Qingxiang , Qi Yulin , Gu Le
Published: April 2011

Sulfur pollution on the silver cage leads to discoloration. Depot rework of silvered bearing cage caused by discoloration leads to great financial losses. In this paper, using a self-made high speed bearing bench test apparatus and the ball disc friction test machine assess the impact of sulfur pollution silver cage on bearing operating performance. The friction property of cage study on the ball disc friction test machine shows that the friction coefficient of silver sulfide film bearing cage is lower than that without pollution. The results from bearing bench test illustrates that the system power loss with sulfur pollution is slightly lower than that without pollution, and the sulfur pollution has little effect on bearing temperature rise. From the experimental results obtained, there is no necessary depot rework for the sulfur pollution sliver bearing cage from the perspective of the use of performance.
Experiments on Grease Performance in Aircraft Landing Gear Pin Joints
Authors: Pugh Steven Daniel , Zhu Juan Juan , Dwyer-Joyce Rob S.
Published: April 2011

A pin joint simulation machine has been built to test a real landing gear pin joint under realistic loading and reciprocation conditions. The pin is loaded hydraulically using a hydraulic actuator to apply a fixed displacement cycle whilst measuring the reactive torque. The machine was used to measure the torque cycle (and hence friction coefficient) required to operate the joint. In this work a method of evaluating different formulation greases has been proven. This involved measuring their frictional torque and also evaluating performance using a Sommerfeld type approach that displays the different lubrication regimes in the joint for different conditions. Measured friction coefficients were in the region of 0.02 to 0.12 depending on the joint load and articulating speed. In actual gear the surface sliding speed is low and so the joint operates in the boundary regime. The required torque and coefficient of friction have been related to the lubrication mechanisms occurring as a function of articulation angle, reciprocal frequency and applied axial load for lubrication starvation in a reciprocating journal bearing.
Characterizing and Comparing Fretting Fatigue and Pitting in Low-Amplitude Reciprocating Contact
Authors: Sandoz-Rosado Emil , Terrell Elon
Published: April 2011

Fretting fatigue has consistently been described as an “insidious” fracture process due to the difficulty in modeling and predicting fretting-induced crack initiation. Components can develop fretting fatigue cracks even when they are designed for minimal relative motion, as in the case of a turbine blade root. Vibrations that are typically small enough to be considered negligible in engineering analysis can cause cracks that will lead to component failure. The sliding distance for fretting to occur is loosely defined as tens to hundreds of micrometers. To date, there has not been a good delineation between the fretting motion and gross-sliding regimes. Likewise, it is not well understood when a given component will experience fretting fatigue or pitting (which is associated with gross sliding and is often seen in gear components). Preliminary data suggest that pitting-like cracks can initiate in a hemisphere-on-flat linear reciprocating configuration at a low number of cycles (104) and fretting-sized displacements (200–300μm). Because of the differences between the mechanisms for failure in fretting and pitting, new insight must be developed to determine parameters under which to expect either failure mode. This work seeks to characterize these two forms of failure and to determine the conditions under which fretting or pitting becomes dominant to develop a new tool for the prediction and prevention of moving components.
Predicting Micro-Pitting Occurrence in Wind Turbine Gearbox Roller Bearings
Authors: Harris Tedric A. , Kotzalas Michael N.
Published: April 2011

The standard rolling contact fatigue life calculations currently in use by the rolling bearing industry is based on the first occurrence of subsurface-initiated spalling of a raceway or roller surface. However, wind turbine gearbox roller bearings have been suffering from another damage mode, which manifests itself as micro-pitting. The micro-pitting, which is spalling on a micro scale, by itself can be tolerated in its early stages; i.e. the roller bearing will still function properly. As the damaged bearing continues to operate, the micro-pitting propagates and at the later stages, often termed peeling, the pitting becomes deep enough to reach the appearance of traditional subsurface-initiated spalling. To better understand the phenomenon micro-pitting and its causes, this study was conducted to review published literature on the topic as it relates to bearing operation. The key findings were the need for a low specific lubricant film thickness parameter, and some component of sliding velocity in the contacting surface. With this knowledge, a proposed test scheme including these variables could be created from which a method to predict the risk of micro-pitting may be determined.
Post-Angioplastic Contact Mechanics With Different Levels of Artherosclerotic Plaque
Authors: Teodorescu M. , Rahnejat H. , Brand Moshe , Rosen Jacob
Published: April 2011

The main goal of balloon angioplasty is to extend the active cross-section of a partly blocked artery. In the last stage of the medical operation, a metallic frame (stent) is introduced in the open space of the artery (lumen) and expanded to the desired diameter. It is generally accepted that some of the main causes of post-angioplasty restenosis are the global stresses induced in the artery by the expanding stent and the local interaction between the stent and the arterial wall. In a blocked artery a thick layer of hard plaque deposition usually covers a significant section of the wall. Therefore, to choose an appropriate stent and improve upon the angioplasty success rate, a fundamental understanding of the local interaction between the stent and the plaque, as well as between the stent and the healthy wall is vital. The goal of the present study is to find a correlation between the local thickness of the plaque layer, contact geometry and the stent/artery radial mismatch.