bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultraviolet amplified spontaneous emission from zinc oxide ridge waveguides on silicon substrate
Authors: Yu S. F. , Yuen Clement , Lau S. P. , Wang Y. G. , Lee H. W. , Tay B. K.
Published: November 2003

Zinc oxide (ZnO) thin-film waveguides with ridge structures have been fabricated on n-type (100) silicon substrates. The deposition of high-crystal-quality ZnO thin films on the lattice-mismatched silicon substrate was achieved by using the filtered cathodic vacuum arc technique. A ridge structure is defined on the ZnO thin film by plasma etching. Room temperature amplified spontaneous emission with peak wavelength at 385 nm is observed under 355 nm optical excitation. The pump threshold is found to be around 0.45 MW/cm2. The maximum net optical gain of the ZnO waveguide is larger than 120 cm−1 at a pump intensity of 1.9 MW/cm2.
Effects of in-plane compressive stress on electrical properties of (Ba,Sr)TiO3 thin film capacitors prepared by on- and off-axis rf magnetron sputtering
Authors: Park Woo Young , Ahn Kun Ho , Hwang Cheol Seong
Published: November 2003

This study investigated the structural and electrical properties of (Ba,Sr)TiO3 (BST) thin film capacitors with thicknesses ranging from 18 to 215 nm, which were prepared by on- and off-axis rf magnetron sputtering technique on Pt/SiO2/Si substrates. The deposition rate and cation composition ratios of the films were controlled to be the same regardless of the sputtering geometry. All the films show elongations in the out-of-plane lattice spacing, suggesting the presence of compressive stress with a smaller value by on-axis sputtering than by the off-axis system. There was no thickness dependence of the strain in the polycrystalline BST films. The BST films deposited using the on-axis system showed a higher bulk dielectric constant with a higher interfacial capacitance and a lower leakage current level than the films produced by the off-axis system. The strain effect was proposed to explain the correlations between the structural and electrical properties.
Smooth relaxed Si0.75Ge0.25 layers on Si(001) via in situ rapid thermal annealing
Authors: Hong S. , Foo Y. L. , Bratland K. A. , Spila T. , Ohmori K. , Sardela M. R. , Greene J. E. , Yoon E.
Published: November 2003

Atomically flat, fully strained Si1−xGex layers with thicknesses ranging from 8 to 180 nm were grown on Si(001) at 450 °C by gas-source molecular beam epitaxy from Ge2H6/Si2H6 mixtures. We show that smooth, relaxed alloy layers are obtained, without the necessity of using several-microns-thick compositionally graded layers, via in situ rapid thermal annealing of fully strained Si1−xGex(001) layers at 1000 °C for 10 s. Relaxed Si0.75Ge0.25(001) layers with thicknesses of 100–180 nm were found to have surface widths of ≃5 nm, comparable to the best results obtained using thick graded buffer layers.
Ion beam-induced anisotropic plastic deformation at 300 keV
Authors: van Dillen T. , Polman A. , van Kats C. M. , van Blaaderen A.
Published: November 2003

Contrary to earlier predictions, ion irradiation at energies as low as 300 keV causes dramatic anisotropic plastic deformation of silica glass. Spherical colloidal silica particles with diameters of 125, 305, and 1030 nm were irradiated with Xe ions at energies in the range 0.3–4.0 MeV at temperatures between 85 and 380 K. Irradiation-induced anisotropic plastic deformation changes the colloid shape from spherical into oblate ellipsoidal at a rate that strongly increases with ion energy. At a fixed fluence, the transverse diameter increases with electronic energy loss. Even at an energy as low as 300 keV large particle anisotropy was found (size aspect ratio of 1.43 at 1×1015 cm−2). The transverse plastic strain gradually decreases with increasing irradiation temperature: it decreases by a factor 4.5 between 85 and 380 K. The data are in agreement with a viscoelastic thermal spike model for anisotropic deformation.
Direct measurement of the refractive index profile of phase gratings, recorded in silver halide holographic materials by phase-contrast microscopy
Authors: Bányász I.
Published: November 2003

Plane-wave phase holograms recorded in Agfa-Gevaert 8E75HD emulsions and processed by the combination of AAC developer and the R-9 bleaching agent were studied by phase-contrast microscopy, using high-power immersion (100×) objective. Thus the modulation of the refractive index as a function of the bias exposure and the visibility of the recording interference pattern can also be determined. Measured diffraction efficiencies were compared to those predicted by coupled wave theory, using the measured refractive index modulations. Direct measurement of the phase profile of the gratings can be used for optimizing processing.
Magnetic coercivity patterns for magnetic recording on patterned media
Authors: Albrecht M. , Rettner C. T. , Best M. E. , Terris B. D.
Published: November 2003

Magnetic patterns were created by locally altering the magnetic coercivity of a perpendicular anisotropy film by ion irradiation. The resulting pattern, after dc magnetizing, consists of regions having alternating up/down magnetization patterns in remanence. In this case, the magnetization of the soft magnetic material in the exposed segments is reversed and stabilized by the demagnetization fields of the adjacent unexposed media. A magnetic pattern generated in this manner can be used as a type of servo pattern for recording head positioning. An accuracy in positioning of better than 10 nm was demonstrated and deliberate magnetic patterns were written and read back by addressing individual 80 nm single-domain nanostructures.
Doped thin films of two organic molecules for light-emitting diodes
Authors: Giovanella Umberto , Botta Chiara , Pasini Mariacecilia , Porzio William , Destri Silvia
Published: November 2003

The photoluminescence and electroluminescence of doped organic materials are reported for thin films prepared by ultrahigh-vacuum coevaporation and by spin coating from solution of two emitting molecules. For both films, efficient energy transfer from the donor to the acceptor molecules is observed without relevant dopant segregation for molar concentrations up to 10%. In spin-coated films the energy transfer from the matrix to the dopant is due to purely resonant energy transfer processes while the cosublimated films show the presence of additional thermally activated hopping processes. Light-emitting diodes fabricated with coevaporated films yield electroluminescence with higher efficiency and stability.
Influence of interfacial bonding on giant magnetoelectric response of multiferroic laminated composites of Tb1−xDyxFe2 and PbZrxTi1−xO3
Authors: Nan Ce-Wen , Liu Gang , Lin Yuanhua
Published: November 2003

The influence of interfacial bonding on the magnetoelectric response in multiferroic laminated composites of Tb1−xDyxFe2 (Terfenol-D) and lead–zirconate–titanate (PZT) by using the recent Green’s function technique was studied. Numerical results demonstrate that a giant magnetoelectric response is produced in the simple sandwiched composites of thick Terfenol-D layers and thin PZT layers. The interfacial epoxy binders used for bonding PZT and Terfenol-D together are very critical to the giant magnetoelectric response of the composites. A thicker interfacial epoxy film and, in particular, a sliding interfacial bonding by a very flexible epoxy would result in a significant drop in the magnetoelectric response.
Thermal stability of internal gettering of iron in silicon and its impact on optimization of gettering
Authors: Zhang Peng , Väinölä Hele , Istratov Andrei A. , Weber Eicke R.
Published: November 2003

The redissolution behavior of gettered iron was studied in p-type Czochralski-grown silicon with a doping level of 2.5×1014 cm−3 and an oxide precipitate density of 5×109 cm−3. The concentrations of interstitial iron and iron–boron pairs were measured by deep level transient spectroscopy. It was found that the dependence of redissolved iron concentration on annealing time can be fitted by the function C(t)=C0[1−exp(−t/τdiss)], and the dissolution rate τdiss−1 has an Arrhenius-type temperature dependence of τdiss−1=4.01×104×exp[−(1.47±0.10) eV/kBT] s−1. Based on this empirical equation, we predict how stable the gettered iron is during different annealing sequences and discuss implications for optimization of internal gettering.
Truly bistable twisted nematic liquid crystal display using photoalignment technology
Authors: Yeung Fion S. Y. , Kwok H. S.
Published: November 2003

Truly bistable twisted nematic liquid crystal display has been fabricated using photoalignment. This display can be switched between the −22.5° and 157.5° twist states by breaking the anchoring condition on one of the substrates. The application of a photoalignable polymer SDA-1 was able to achieve the weak anchoring energy necessary for switching. Both theoretical and experimental results show that this mode has excellent contrast ratio and wide viewing angles.
Ultrafast patterning of nanostructures in polymers using laser assisted nanoimprint lithography
Authors: Xia Qiangfei , Keimel Chris , Ge Haixiong , Yu Zhaoning , Wu Wei , Chou Stephen Y.
Published: November 2003

We propose and demonstrate a nanopatterning technique, laser-assisted nanoimprint lithography (LAN), in which the polymer is melted by a single excimer laser pulse and then imprinted by a mold made of fused quartz. LAN has been used to pattern nanostructures in various polymer films on a Si or quartz substrate with high fidelity over the entire mold area. Here we show 200 nm pitch gratings with 100 nm linewidth and 90 nm height. The entire imprint from melting the polymer to completion of the imprint is less than 500 ns. The mold has been used multiple times without cleaning between each imprint. LAN not only greatly shortens the imprint processing time, but also significantly reduces the heating and expansion of the substrate and mold, leading to better overlay alignment between the two.
Stress-induced effects on depletion-layer capacitance of metal–oxide–semiconductor capacitors
Authors: Matsuda Kazunori , Kanda Yozo
Published: November 2003

Depletion-layer capacitance of n-type metal–oxide–semiconductor capacitors is investigated under a uniaxial 〈110〉 stressed condition, by means of a high-frequency sweep measurement at room temperature. Abrupt large shifts of the depletion-layer capacitance by the stress are observed. Gauge factors of the effects are approximately 13–33 at 500 ppm strain, which are almost comparable with the piezoresistance effect, and have an opposite sign in tension and compression. The capacitance shifts could be explained with the intrinsic Fermi level which lifts and drops by a change in the ratio of the density-of-states effective masses of holes to electrons due to the band splitting.
In-plane polarization anisotropy and polarization rotation for M-plane GaN films on LiAlO2
Authors: Misra Pranob , Sun Yue Jun , Brandt Oliver , Grahn Holger T.
Published: November 2003

We investigate the dependence of the transmittance spectra of strained M-plane GaN films on the angle of the linear in-plane polarization, with the c axis of the underlying wurtzite crystal structure in the film plane. Because of the reduced in-plane symmetry and the large in-plane anisotropic strain, the transmission spectra for an arbitrary in-plane polarization angle can be directly derived from two transitions with polarizations parallel and perpendicular to the c axis. Since the energy gap for these two polarizations is shifted by more than 50 meV, the M-plane GaN film becomes dichroic, resulting in a polarization rotation after transmission for energies between the two gaps for an initial angle of 45° by as much as 40° towards the c axis.
Crystal structure and polarization phenomena of epitaxially grown Pb(Zr,Ti)O3 thin-film capacitors
Authors: Tsukada M. , Yamawaki H. , Kondo M.
Published: November 2003

{100} oriented Pb(Zr,Ti)O3 (PZT) thin films were deposited by metalorganic chemical vapor deposition on both Ir/MgO(100) and Ir/MgAl2O4/SiO2/Si(100) substrates. The x-ray Φ-scan spectra for the (202) reflections revealed each film had fourfold symmetry, which was epitaxially grown as cube-on-cube. The switchable polarization (Qsw) of the PZT capacitor on the MgO substrate attained 100 μC/cm2 at 1.8 V; however, PZT capacitors on Si had a Qsw of 23 μC/cm2. This difference in Qsw is attributed to the volume fraction of (001) orientation of each PZT film. The difference in orientation between the two kinds of PZT films does not seem to depend on misfit of lattice parameters between PZT and Ir, but on the stress caused by the difference in the thermal expansion coefficients of MgO and Si.
Microshaping metal surfaces by wave-directed self-organization
Authors: Yoo Pil J. , Park S. Young , Kwon S. Joon , Suh Kahp Y. , Lee Hong H.
Published: November 2003

Self-organization in the shaping of a metal surface is dictated by an internal wave that selects the type of modes from an externally imposed periodic pattern. An elastomeric mold, when placed on a thin bilayer of metal on polymer and heated, provides periodic nodes that give rise to a periodic wave of harmonic series. The internal wave in the bilayer selects the type, number of harmonic modes, and the fractional magnitude that each allowed harmonic mode contributes to the overall surface shape, thereby permitting shape engineering of the metal surface.
Combined first-principles calculation and neural-network correction approach for heat of formation
Authors: Hu LiHong , Wang XiuJun , Wong LaiHo , Chen GuanHua
Published: November 2003

Despite their success, the results of first-principles quantum mechanical calculations contain inherent numerical errors caused by various intrinsic approximations. We propose here a neural-network-based algorithm to greatly reduce these inherent errors. As a demonstration, this combined quantum mechanical calculation and neural-network correction approach is applied to the evaluation of standard heat of formation ΔfH⊖ for 180 small- to medium-sized organic molecules at 298 K. A dramatic reduction of numerical errors is clearly shown with systematic deviation being eliminated. For example, the root-mean-square deviation of the calculated ΔfH⊖ for the 180 molecules is reduced from 21.4 to 3.1 kcal mol−1 for B3LYP/6-311+G(d,p) and from 12.0 to 3.3 kcal mol−1 for B3LYP/6-311+G(3df,2p) before and after the neural-network correction.
Real-time observation of the energy band diagram during microcrystalline silicon p–i interface formation
Authors: Fujiwara Hiroyuki , Kondo Michio , Matsuda Akihisa
Published: November 2003

We have performed real-time infrared attenuated total reflection spectroscopy to characterize free-carrier absorption during microcrystalline silicon (μc-Si:H) p–i interface formation. In the μc-Si:H i-layer growth on the p layer, a free-carrier concentration in the p layer showed a large variation, in accordance with a built-in potential present at the p/i interface. We demonstrate that real-time observation of the energy band diagram is possible during semiconductor thin-film growth by employing free carriers in a doped layer as a probe.
Characterization of intra-framework and guest/host interactions in the AlPO4-15 molecular sieve by charge-density analysis
Authors: Aubert Emmanuel , Porcher Florence , Souhassou Mohamed , Lecomte Claude
Published: November 2003

The electron-density distribution of AlPO4-15 has been determined using high-resolution single-crystal X-ray diffraction, and the topological properties of the charge density have been calculated using the `atoms in molecules' (AIM) theory. Analysis of the topological properties at the bond critical points has been used to characterize the interactions within the framework, and between the framework and the extra-framework species (ammonium ions and water molecules), and to define atomic properties, such as volume and net charges, uniquely. A comparison between procrystal and multipolar representations of the density was performed in order to explore to what extent the former representation is likely to reflect the interactions in the solid. Correlation with geometrical properties (P—O and Al—O bond lengths, and Al—O—P angle) is found for topological charges obtained from the multipolar model, but not for the results from the procrystal representation.
Devonian Vertebrates From Colombia
Authors: Janvier P. , Villarroel C.
Published: November 2003

Vertebrate remains are reported from the Emsian–Eifelian Floresta Formation and the Late Devonian (?Frasnian) Cuche Formation of north‐eastern Colombia. The material from the Floresta Formation is associated with a marine invertebrate fauna and includes an arthrodire and probably a rhenanid. Several vertebrate‐bearing localities are recorded from the Cuche Formation; vertebrates occur with plant remains and lingulid fragments. They include an acanthodian (Cheiracanthoides? sp.), a chondrichthyan (Antarctilamna? sp.), placoderms (Bothriolepis sp., Asterolepis? sp. and an undetermined groenlandaspidid or primitive brachythoracid arthrodire), a stegotrachelid actinopterygianand three sarcopterygians (a cosmine‐covered form tentatively referred to an osteolepidid, the porolepiform Holoptychiussp., and the rhizodontid Strepsodus? sp.). This assemblage suggests a Late Frasnian age and is surprisingly similar to Late Devonian vertebrate assemblages found in similar facies of Europe and North America, notwithstanding the presence of the Gondwanan chondrichthyan Antarctilamna?. key words: Vertebrata, Devonian, Colombia, South America, biostratigraphy, palaeobiogeography.
Scoyenia burrows from Ordovician palaeosols of the Juniata Formation in Pennsylvania
Authors: Retallack Gregory J.
Published: November 2003

Scoyenia beerboweri is a new ichnospecies of burrow from the late Ordovician (Ashgill) Juniata Formation in central Pennsylvania, USA. The burrows are abundant in red calcareous palaeosols, and were created by animals living at the time of soil formation, because they are filled with red sediment like that of the palaeosol matrix, and both cut across, and are cut by, nodules of pedogenic carbonate. The isotopically light carbon and oxygen of carbonate in the palaeosols indicate a terrestrial ecosystem of well‐drained floodplains in a tropical seasonally‐dry semi‐arid palaeoclimate. Backfill layering within the burrows is evidence of a bilaterally symmetrical animal. Size distribution of the burrows reveals discontinuous growth, as found in arthropods. Ferruginized faecal pellets in the burrows indicate that they ingested sediment. For these reasons the burrows of Scoyenia beerboweri are most likely to be the work of millipedes. The nature of vegetation supporting them is unknown, although a single problematic plant‐like fossil cast was found, and liverwort spores are widespread in rocks of this age. Vegetative biomass was limited judging from the degree of chemical weathering, extent of burial gleization and isotopic composition of carbon in the palaeosols. These distinctive respiration‐dominated liverwort‐millipede polsterlands lived at a time of global greenhouse climate, following Precambrian–Cambrian lichen‐algal microbial earths and supplanted by Silurian brakelands of early vascular land plants.
Hindlimb of a giant terrestrial bird from the upper Eocene, Fayum, Egypt
Authors: Rasmussen D. T. , Simons E. L. , Hertel F. , Judd A.
Published: November 2003

Eremopezus eocaenus Andrews, 1904 is a giant groundbird from upper Eocene deposits of the Fayum, Egypt, which has hitherto been known from non‐diagnostic fragmentary material. New fossils collected from quarry L‐41 of the Jebel Qatrani Formation include two well‐preserved distal tarsometatarsi and an associated whole tarsometatarsus and distal tibiotarsus that allow a more precise evaluation of the phylogenetic position and tarsal function of Eremopezus. Unlike most ratites, the distal tarsometatarsus has a patent distal foramen and a slight hallucal digit. The trochlea for digits II and IV are only slightly reduced in size, are splayed to the right, and the heads lack deep grooving. These features resemble the condition seen in BalaenicepsSagittarius, suggesting active use of the toes in grasping or manipulation, rather than the condition in graviports and cursors, which have reduced medial and lateral trochleae often with distinct grooving of the heads. The limb is relatively long and gracile, another difference from graviports. There is no compelling evidence to link Eremopezus to any known ratite lineage, to the Phorusrhacoidea, or to the extinct predatory birds of the Eocene (e.g. Diatryma, Gastornis). We suggest that Eremopezus represents an endemic African group that independently attained large size and flightlessness.
Taxonomy and phylogeny of cementing Triassic bivalves (families Prospondylidae, Plicatulidae, Dimyidae and Ostreidae)
Authors: Hautmann Michael
Published: November 2003

Based on new material from the Upper Triassic Nayband Formation of east‐central Iran and on type material from the Alpine Triassic, the taxonomy of the cementing bivalve families Prospondylidae, Plicatulidae, Dimyidae and Ostreidae is examined and their phylogenetic relations are discussed. The Prospondylidae are characterized by the presence of an early pectiniform stage in their Palaeozoic genera which disappeared in most later forms due to ontogenetic pre‐displacement of cementation. The Plicatulidae probably evolved from an ancestor within the Prospondylidae by the formation of strong crura, which allowed the reduction of the lateral part of the ligament. Their hinge was later modified by shifting resilifer and crura in a ventral direction and by forming a secondary ligament dorsally. The emended genera EoplicatulaPseudoplacunopsis represent different early stages of this development. The species Eoplicatula parvadehensis sp. nov. and Pseudoplacunopsis asymmetrica sp. nov. from the Nayband Formation are described. The shell of some early Ostreidae is characterized by the lack of structural chambers and by the presence of an originally aragonitic inner shell layer. For such forms, the new genus Umbrostrea is proposed, and the new species Umbrostrea emamiiUmbrostrea iranica are described. The available data on shell microstructure as well as most conchological characters do not support a close relationship between Ostreidae, Plicatulidae and Dimyidae.
Integrated Silurian Chitinozoan and Graptolite Biostratigraphy of the Banwy River Section, Wales
Authors: Mullins Gary L. , Loydell David K.
Published: November 2003

The succession of 38 upper Llandovery–lower Wenlock chitinozoan taxa from graptolitic horizons in the Banwy River section (Powys, Wales) is described. Five new species are named: Bursachitina nestoraeConochitina leviscapulaeConochitina mathrafalensisBelonechitina caveiBelonechitina meifodensis. A further ten taxa are described under open nomenclature. Seven chitinozoan biozones are recognized in the Banwy River section, three of which (Cingulochitina bouniensisConochitina acuminataSalopochitina bella) are new. The base of each biozone is correlated with the graptolite biostratigraphical scheme as follows: Angochitina longicollis Biozone — upper spiralis Biozone; Conochitina acuminata Biozone — lowermost lapworthi Biozone; Margachitina banwyensis Biozone — upper lapworthi Biozone; Margachitina margaritana Biozone — lowermost insectus Biozone; Cingulochitina bouniensis Biozone — upper murchisoni Biozone; Salopochitina bella Biozone — upper firmus Biozone. The succession of chitinozoan biozones in the Banwy River section is compared with that in other sections which have graptolite biostratigraphical control. This has highlighted the following: (1) the correlation of the base of the dolioliformis Biozone with the graptolite biozonation is imprecise; (2) E. dolioliformis is recorded only from levels after the first A. longicollis in Sweden (although this may reflect previously unrecognized synonymies); (3) the longicollis Biozone may be diachronous, its base correlating with levels low in the Telychian in Sweden, Norway and Estonia and with the upper Telychian spiralis Biozone in Wales and the Prague Basin; (4) data herein and from the Prague Basin indicate that the base of the margaritana Biozone correlates with a level low in the insectus Biozone.
Underground Vendobionta From Namibia
Authors: Grazhdankin Dmitri , Seilacher Adolf
Published: November 2003

The late Precambrian fossils from Namibia have generally been regarded as soft‐bodied organisms whose three‐dimensional preservation resulted from smothering in fluidized sand. The sedimentological context of Pteridinium and Namalia within a sandstone bed, however, allows us to distinguish between two taphocoenoses: (1) winnowed, laterally collapsed, current‐transported specimens accumulated as a lag deposit of turbidite‐like flows, and (2) specimens ‘floating’ in the top part of an event bed with their vanes extending upwards to the upper bedding surface. The second taphocoenosis is interpreted as an in situ preserved ‘infaunal’ community. The immobile underground life habit and the bizarre modes of growth of Pteridinium and Namalia do not fit any extinct or modern group of multicellular organisms. Similar statements can be made for Ernietta and Rangea, thus reviving the Vendobionta hypothesis.
A New Species of Goniopholis from the Upper Jurassic of Portugal
Authors: Schwarz Daniela
Published: November 2003

The new goniopholidid crocodile Goniopholis baryglyphaeus sp. nov. from the Kimmeridgian of Guimarota/Leiria, Portugal is based on the oldest known relatively complete skeleton of Goniopholis from Europe and consists of a nearly complete skull together with a mandible and various postcranial remains. G. baryglyphaeus shows characters that hitherto have only been described for Goniopholis simus: a caudal expansion of the prefrontal that excludes the frontal from the medial margin of the orbit; and the loss of contact between the paroccipital process and the lateral surface of the squamosal and the quadrate, which exposes the cranioquadrate canal laterally. This new species can be distinguished from other European Goniopholis species by an articular facet placed ventral to the retroarticular process, and directed slightly medioventrally; a caudal margin of the mandible forming almost a right angle at its caudoventral corner; an almost square rostrolateral corner of the cranial table; a straight transverse suture between the parietal and the frontal with a median rostral process; a rostrally tapering wedge‐like lacrimal, and a regular heavy skull‐sculpturing. The new find of Goniopholis in Portugal shows that this genus was distributed in a larger area, and was present much earlier, than hitherto reported in south‐western Europe.
Apparatus Composition, Growth, And Survivorship Of The Lower Ordovician Conodont paracordylodus Gracilis Lindström, 1955
Authors: Tolmacheva Tania Yu. , Purnell Mark A.
Published: November 2003

Analysis of numerous conodont element clusters from the Lower Ordovician cherts of the Burubaital Formation in central Kazakhstan reveals that the apparatus of Paracordylodus gracilis Lindstro¨m, 1955 consisted of 15 elements: two M elements, nine S elements (including 1 S0), and four P elements (2 P1, 2 P2). The clusters probably originated as faecal pellets, but the best preserved indicate that the architecture of the apparatus of P. gracilis was comparable to that of ozarkodinid conodonts, providing strong support for the hypothesis that the 15‐element 2M‐9S‐4P apparatus plan was plesiomorphic for conodonts with morphologically complex elements. All the elements within the P. gracilis clusters appear to be at a similar stage of ontogeny, and there is no evidence for late addition or replacement of elements. Analysis of element growth suggests that the relative dimensions of some elements changed during ontogeny, but the available data support the hypothesis that the growth of the apparatus as a whole was isometric. The size distribution of P. gracilis in the Burubaital Formation suggests that individuals in a particular size range were preferentially selected for consumption by predators. The identity of these predators is unknown, but they may have included other P. gracilis.
An Evaluation of the Recently Proposed Palaeozoic Gastropod Subclass Euomphalomorpha
Authors: Nützel Alexander
Published: November 2003

The recently proposed subclass Euomphalomorpha Bandel and Frýda, 1998 was primarily based on an openly coiled, planispiral initial whorl. Here, the protoconch of Carboniferous euomphalids is described and figured in detail previously unknown. This protoconch comprises distinctly less than one planispiral whorl with an abrupt transition to the telecoconch. It is umbilicate or openly coiled. Umbilicate or bilaterally symmetrical protoconchs are still present in Recent species of the Cocculiniformia, the Neomphalidae and the Docoglossa. A previously suggested close phylogenetic relationship between the euomphalids and primitive gastropod limpets is therefore corroborated by the protoconch morphology. The fact that several Palaeozoic gastropods, unlike most modern gastropods, have an openly coiled initial whorl is highly remarkable, but the meaning of this feature for the phylogeny and the systematics of the Gastropoda is not yet clear.
Spiders in Upper Cretaceous Amber from New Jersey (Arthropoda: Araneae)
Authors: Penney David
Published: November 2003

The oldest described fossils of the extant spider families Segestriidae, Oonopidae, Oecobiidae, Dictynidae and Linyphiidae, previously known from the Tertiary, are presented from Upper Cretaceous amber of New Jersey. The third and oldest known specimen of the fossil spider family Lagonomegopidae is also described and provides further palaeontological evidence of a common Laurasian fauna. The extant genera Segestria and Oecobius are taken back a further 52 and 69–74 myr respectively in the fossil record. These fossils predict the presence of the Caponiidae, Tetrablemmidae, Orsolobidae, Dysderidae, Hersiliidae, Eresidae, Pimoidae, Scytodoidea s.l., cyatholipoids, theridioids and symphytognathoids in the Cretaceous. They also extend the known geological range of extant spider families through and beyond the end–Cretaceous extinction. This event, which affected numerous marine and some terrestrial organisms, probably had little effect on the Araneae.
Ecology And Growth Habit Of Laveineopteris: A Gymnosperm from the Late Carboniferous Tropical Rain Forests
Authors: Shute C. H. , Cleal C. J.
Published: November 2003

Cyclopterid leaves were borne on the same Late Carboniferous medullosalean plants that bore the pinnate fronds currently known as Laveineopteris. They were morphologically and anatomically different from the pinnate foliage, and presumably were also physiologically different. The cyclopterids are here interpreted as having been shade leaves and the pinnate foliage sun leaves. The juvenile Laveineopteris plant probably consisted of a monopole sapling bearing only cyclopterid leaves, which optimized growth in canopy shade conditions. On reaching the canopy level, the plant produced a crown of pinnate sun leaves. Cyclopterids were also borne epiphyllously in the proximal parts of the pinnate fronds; this may have represented a transitional light–level between canopy and subcanopy conditions. Thus, in this reconstruction, the cyclopterid leaves were complementary to the pinnate foliage of the adult Laveineopteris plant, and played a key role in its growth habit and ecology.
Jurassic soft–bottom oyster Crassostrea from Japan
Authors: Komatsu Toshifumi , Chinzei Kiyotaka , Zakhera Mohamed S. , Matsuoka Hiroshige
Published: November 2003

A new species of oyster, Crassostrea tetoriensis, is described from the lower part of the Middle Jurassic–Cretaceous Tetori Group. This is the oldest record of the genus and one of the earliest muddy–bottom–dwelling oysters. Characteristics of the species include an elongate spatulate outline and narrow attachment area, an elongate hinge area with deep umbonal cavity, a reniform adductor muscle scar, and a smooth commissural margin without chomata. The oysters are cemented to each other and constitute bouquet–like aggregates or colonies of shells in muddy deposits of inferred brackish–water origin. The shells contain lenticular or blister–like chambers filled with a chalky deposit. These ecological and structural properties are characteristic of Crassostrea, and may be regarded as the result of adaptation of the sessile, suspension feeding animals to soft muddy substrates. Oysters are a group of bivalves that have lost mobility and live cemented mostly to hard substrates. Crassostrea and its allies returned secondarily to soft bottoms. The find of C. tetoriensis indicates that the return occurred early in the history of oysters, 60 myr after the first appearance of ostreid oysters in Late Triassic.
Reinvestigation of Nystroemia pectiniformis Halle, an enigmatic seed plant from the Upper Permian of China
Authors: Hilton Jason , Li Cheng–Sen
Published: November 2003

Reinvestigation of Nystroemia pectiniformis Halle from the Upper Shihhotze Formation of Shanxi Province, China, has led to the identification of new and important features of this enigmatic Late Permian seed plant, permitting its typification and diagnosis. After reassembling several of the previously studied specimens to form a single articulated branching system comprising at least four orders of branching, previously unknown features of its branching pattern and morphology have been characterized. First–order axes are wide and branch to one side only, bearing second–order branches either singly or in pairs and of two kinds: one fertile and bearing characteristic ovulate branching systems and the other presumably vegetative. Ovulate second–order axes are narrow and branch to one side only, producing numerous, closely spaced lateral branches in two alternate to sub–opposite rows. Lateral branches are slender and produce numerous ovulate branching systems to one side of the axis only. Ovulate branching systems divide unequally to produce 3–15 ultimate axes of different lengths that are planated. Each ultimate axis bears a single terminal ovule with 180 degree rotational symmetry and two horn–like integumentary projections distally. The other kind of second–order axes are distinct from those bearing ovules; they are wider and longer and branches occur on both sides of the secondary axis, lacking divisions in close proximity to the first–order axis. These have only been observed incomplete although their distinct morphology indicates they are unlikely to be ovulate branches from which ovules/seeds have been shed. Additional organs of the Nystroemia plant are considered, including pollen organs previously assigned by Halle to the same species (displaying its characteristic branching style), and also leaves of Chiropteris reniformis Halle that were probably borne on the larger kind of second–order branches. Implications of Nystroemia on seed plant evolution and distribution are discussed, and it is concluded that this most likely represents a late stratigraphic occurrence of a plesiomorphic hydrasperman–type seed plant with affinities closely allied to members of the Lyginopteridales.
The oldest in situ hermit crab from the Lower Cretaceous of Speeton, UK
Authors: Fraaije René H. B.
Published: November 2003

An Early Cretaceous (Hauterivian) hermit crab perfectly preserved within an ammonite is described. Palaeontologists have focused too much on the wrong class of molluscs in their attempt to analyse the evolution of the pagurids. The shift of mollusc habitation during the Cretaceous, from ammonites to gastropods, affected the morphology of the aperture–blocking hermit–crab claws.
ACARYOCHLORIS MARINA GEN. ET SP. NOV. (CYANOBACTERIA), AN OXYGENIC PHOTOSYNTHETIC PROKARYOTE CONTAINING CHL D AS A MAJOR PIGMENT1
Authors: Miyashita Hideaki , Ikemoto Hisato , Kurano Norihide , Miyachi Shigetoh , Chihara Mitsuo
Published: November 2003

The phylogenetic position of an oxygenic photosynthetic prokaryote containing chl d as a major pigment, which have been tentatively named “Acaryochloris marina,” was analyzed using small subunit rDNA sequences. Phylogenetic relationships inferred among A. marina, selected strains from the Cyanobacteria, and plastids showed that A. marina was within the cyanobacterial radiation. The A. marina lineage diverged independently from other phylogenetic subgroups of the Cyanobacteria. No organism was found to be identical or related closely to A. marina by a similarity search and phylogenetic analysis. Based on these results, in addition to the reported characteristics of the cell morphology, pigment composition, and photosynthesis, a new taxon, Acaryochloris marina Miyashita et Chihara gen. et sp. nov., is formally proposed for the oxy‐genic photosynthetic prokaryote.
Sample preparation technique and white cell content influence the detectable levels of growth factors in platelet concentrates
Authors: Zimmermann R. , Arnold D. , Strasser E. , Ringwald J. , Schlegel A. , Wiltfang J. , Eckstein R.
Published: November 2003

Background and Objectives  Autologous platelet concentrate (PC) is applied locally to improve wound healing and tissue repair. Previous measurements of the growth factor content of platelets have given conflicting results. To date, there is no information on the influence of different preanalytical sample‐preparation methods on the detectable amount of growth factors.

Materials and Methods  We measured the level of growth factors in PCs obtained by plateletpheresis and by leukapheresis. We subjected aliquots of these components to six different preparation methods: freezing/thawing once or twice; dissolution in 0·5% Triton‐X‐100; and clot formation by the addition of calcium and thrombin with subsequent incubation for 1 h, for 24 h, or for 1 h followed by freezing and thawing.

Results  In samples dissolved in Triton‐X‐100, higher levels of growth factors were detected than in the other specimens. In comparison to clot formation, freezing and thawing platelets twice was equivalent with respect to the release of platelet‐derived growth factor (PDGF) but superior with respect to the release of transforming growth factor‐β1 (TGF‐β1). Overall, mean levels of 4·77 × 10−16 g of PDGF‐AB, 2·2 × 10−17 g of PDGF‐BB, and 2·41 × 10−16 g of TGF‐β1 were found per single human platelet in white blood cell (WBC)‐poor samples dissolved in Triton‐X‐100.

Conclusions  Dissolving PC in Triton‐X‐100 releases maximum quantities of growth factors from platelets. The release of each growth factor by any sample preparation method should be investigated and interpreted separately. The preanalytical sample‐preparation method, as well as the platelet and WBC content, influence the measurable levels of growth factors in PCs. The results implicate the need to correct, considerably upwards, previous estimations of the PDGF content of platelets.
Influence of specimen diameter on the relationship between subsurface depth and hardness of a light‐cured resin composite
Authors: Asmussen Erik , Peutzfeldt Anne
Published: November 2003

In pilot studies of the relationship between subsurface depth and hardness of a light‐cured resin composite, it was found that the resin composite was softer at a depth of 0.5 mm than at, for example, a depth of 1.0 mm. It is possible that the increase in hardness at intermediate subsurface depths compared with the hardness at small depths is due to the heat of polymerization, causing a greater increase in temperature at intermediate depths than at small depths. As the temperature rise increases with volume of the test specimen, it was hypothesized that the increase in hardness would increase with the diameter of the irradiated specimen. The hardness of a resin composite was measured as a function of subsurface depth for cylindrical specimens of 3, 4, and 6 mm diameter. It was found that the resin composite was softer at 0.5 mm than at 1.0–1.5 mm depth independent of specimen diameter. Possible explanations are oxygen inhibition of polymerization and high rate of cure of material at small subsurface depth. It was also found that, corresponding with increasing specimen diameters, the specimens became significantly softer at depths of 3.0 mm, 3.5 mm, and 4.0 mm, respectively. The heat production and reflection of light from the walls of the molds may explain the latter, but not the former finding.
Coping and optimism in relation to dental health behaviour – a study among Finnish young adults
Authors: Ylöstalo Pekka , Ek Ellen , Knuuttila Matti
Published: November 2003

Our aim in this paper was to investigate active coping in relation to optimism, dental health behavior and self‐reported dental health among 31‐yr‐old men and women born in Northern Finland in 1966. Connecting coping strategies and optimism with health behavior is an unexplored approach in dentistry, even though both coping strategies and optimism are known to be associated with many health outcomes. The data were based on a postal questionnaire, which was sent to the Northern Finland 1966 Birth Cohort at age 31 yr (n = 11 541). The number of replies was 8690, with a 75.3% response rate. Active coping was measured using the Ways of Coping Checklist and optimism using a revised Life Orientation Test. Prevalence proportion ratios were estimated by applying a log‐binomial regression models. The results showed a correlation between active coping and optimism. Both active coping and optimism were related to different dental health behaviors. The effect of active coping on dental health behavior disappeared by adjusting for optimism, education and gender. The results support the previous findings that active coping acts as a mediator between optimism and health. Optimism was also related to self‐reported dental health, which supports the comprehensiveness of optimism as a determinant for health.
The effect of oestrogen and testosterone on the urethral seam of the developing male mouse genital tubercle
Authors: Yucel S. , Cavalcanti A.G. , Desouza A. , Wang Z. , Baskin L.S.
Published: November 2003

OBJECTIVES

To describe the effects of exogenous oestrogens and androgens on urethral formation in the mouse, as the development of the mouse and human urethra have significant similarities, and understanding normal male urethral development may help to identify the causes of abnormal development, e.g. hypospadias.

MATERIALS AND METHODS

Timed‐pregnant C57/6 mice were exposed to synthetic oestrogens and androgens. The morphology of the genital tubercles was examined histologically and with three‐dimensional computer reconstruction. Specific attention was focused on the developing urethral seam.

RESULTS

Microscopic serial analysis confirmed the presence of an arrest in seam formation in about half of oestrogen‐treated male fetuses. In contrast, there was acceleration of urethral fold fusion and a longer urethral tube in those treated with androgens. Oestrogen‐treated fetuses had a thin periurethral spongiosa, in contrast to androgen‐treated fetuses which developed a thicker periurethral spongiosa. The effect of oestrogens on seam area formation did not depend on the dose, but in contrast, in the androgen‐treated fetuses it was.

CONCLUSION

Oestrogens and androgens have a direct effect on the fusion of the urethral fold that leads to seam formation. Normal urethral development depends on the delicate balance of these complementary hormones.
Hypogonadism and erectile dysfunction: pathophysiological observations and therapeutic outcomes
Authors: Morales A. , Heaton J.P.W.
Published: November 2003

Androgens have a profound effect in male sexual function in general and erectile physiology in particular. Despite the common belief that male sexuality is fully dependent on normal androgens, hypogonadal men are capable of sexual erections; almost a third of men receiving effective antiandrogen therapy can develop erections when tested with an erotic challenge. However, successful hormonal supplementation that results in normal testosterone values does not always restore libido and erectile function. Although the primary goal of treatment for hypogonadism may be to restore sexual function, there will be other significant benefits and potential drawbacks. Libido, general well‐being, osteoporosis, muscle strength, mental acuity, and growth hormone levels will all be positively affected by appropriate management of low testosterone levels. Testosterone replacement therapy should maintain not only physiological levels of serum testosterone but also its metabolites, including dihydrotestosterone and oestradiol. The assessment of hypogonadism, its treatment and monitoring, are unavoidable responsibilities of the urologist.
The Use of Kalman Filter and Neural Network Methodologies in Gas Turbine Performance Diagnostics: A Comparative Study
Authors: Volponi A. J. , DePold H. , Ganguli R. , Daguang C.
Published: November 2003

The goal of gas turbine performance diagnositcs is to accurately detect, isolate, and assess the changes in engine module performance, engine system malfunctions and instrumentation problems from knowledge of measured parameters taken along the engine’s gas path. The method has been applied to a wide variety of commercial and military engines in the three decades since its inception as a diagnostic tool and has enjoyed a reasonable degree of success. During that time many methodologies and implementations of the basic concept have been investigated ranging from the statistically based methods to those employing elements from the field of artificial intelligence. The two most publicized methods involve the use of either Kalman filters or artificial neural networks (ANN) as the primary vehicle for the fault isolation process. The present paper makes a comparison of these two techniques.
Engine Torque Nonuniformity Evaluation Using Instantaneous Crankshaft Speed Signal
Authors: Cavina N. , Ponti F.
Published: November 2003

The paper presents the development of a methodology for evaluating the torque nonuniformity between the various cylinders of an internal combustion engine (ICE). This nonuniformity can be due, for example, to pathological operating conditions such as misfires or misfuels, as well as to other abnormal operating conditions. Between the nominal torque production and the one corresponding to the absence of combustion there exist, in fact, a series of possible intermediate conditions. Each of them corresponds to a value of produced torque that lies between the nominal value and the one corresponding to the lack of combustion (due for example to statistical dispersion in manufacturing or aging in the injection system). The diagnosis of this type of nonuniformity is a very important issue in today’s engine control strategies design. The use of the developed methodology should in fact allow the control strategy to adopt the appropriate interventions if the diagnosed nonuniformity is related to different behavior of the injectors. In order to evaluate this torque production variability between the various cylinders, information hidden in the instantaneous crankshaft speed fluctuations has been processed using a suitable methodology. The procedure has been validated running a supercharged 2.0 liters V6 engine, and a 1.2 liters L4 engine, in a test cell. During the tests, the in-cylinder pressure signal has been acquired together with the instantaneous engine speed, in order to determine a correlation between speed fluctuations and the indicated torque produced by each cylinder. The actual cylinder-by-cylinder torque nonuniformity can then be evaluated on-board by processing engine speed. The procedure is able to diagnose the absence of combustion (due for example to a misfire or a misfuel) as well as abnormal combustions that do not necessarily involve lack of combustion, with, the accuracy needed for on-board use. Control interventions to injection and ignition time commands of one or more cylinders should, in most cases, be able to re-establish torque production uniformity.