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AbstractMarine macroinvertebrate fossils from two petroleum exploration cores, Apium-1 and Redback-2, are described, and found to contain two separate assemblages. The assemblage from the Apium-1 core was recovered from an ca5-m-thick interval (2756.35–2751.28 m) in the basal Hovea Member (‘inertinitic interval’) of the Kockatea Shale and includes the following forms: ?Spinomarginiferasp., Cimmeriellasp., ?Etherilosiasp., Elivinasp., Cleiothyridinasp., and Paeckelmanelloidea gen. et. sp. indet. (all brachiopods). The age of this assemblage is interpreted as Changhsingian, as constrained by its association with the palynofloral Dulhuntyispora parvitholaZone. The assemblage from the Redback-2 core was recovered from the ‘sapropelic interval’ of the Hovea Member of the Kockatea Shale between 3806 m and 3786 m and comprises the following forms: Lingulidae gen. et sp. indet. (brachiopod), Claraia perthensisDickins & McTavish, Crittendeniacf. australasiatica(Krumbeck), ?Paralledonsp. (bivalves), ?Otocerassp. (ammonoid), Microconchus utahensisZatoń, Taylor & Vinn (microconchid) and Magniestheria mangaliensis(Jones) (spinicaudatan). Among these, the first local appearances of the lingulid species, ?Otocerassp. and M. mangaliensisare associated with the palynofloral Protohaploxypinus microcorpusZone and are interpreted as latest Changhsingian in age. Other occurrences of the Redback-2 fossil assemblage overlap with the palynofloral Kraeuselisporites saeptatusZone and are considered to be of earliest Triassic (Griesbachian) age.G.R. Shi [guang@uow.edu.au] and Sangmin Lee [sangminlee76@gmail.com], School of Earth, Atmospheric and Life Sciences, University of Wollongong, Northfields Ave, Wollongong, NSW 2522, Australia; Ian Metcalfe [imetcal2@une.edu.au], Earth Sciences, Earth Studies Building C02, School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia; Daoliang Chu [chudl@cug.edu.cn], State Key Laboratory of Biogeology and Environmental Geology, School of Earth Sciences, China University of Geosciences, Wuhan 430074, PR China; Huiting Wu [ht_wu415@163.com], College of Geoscience and Surveying Engineering, China University of Mining & Technology, Beijing, PR China; Tinglu Yang [yang@geology.hk], Faculty of Geosciences, East China University of Technology, Nanchang 330013, PR China; Yuri D. Zakharov [yurizakh@mail.ru], Far East Geological Institute, Far East Branch, Russian Academy of Sciences, Vladivostok, 690022 Russia.

Silicon nanowires can be successfully grown by applying the vapor – liquid – solid process. In the case of the commonly used chemical vapor deposition technique, a Si containing gas/precursor is cracked at Au droplets acting as seeds. Si adatoms are subsequently dissolved in the liquid metal. Due to a supersaturation within this droplet, Si precipitates predominantly at the liquid – solid interface – a nanowire grows. A different situation occurs if nanowires are grown by molecular beam epitaxy via the vapor– liquid – solid mechanism. The difference consists, for example, of the role of the metal seed, the morphology of the nanowires and their aspect ratio. In particular, surface diffusion including the metal used as well as Si, strongly influences the growth process. This article describes molecular beam epitaxy growth experiments of Si nanowires under ultra-high vacuum conditions and compares the results with other growth techniques.

AbstractThe South Primorye area of Far East Russia has long been recognized for its highly diverse mid-Permian brachiopod fauna; however, a taxonomic and palaeobiogeographical reassessment is overdue. This paper describes two brachiopod assemblages from the Barabash and Pilnikov section localities in South Primorye. The Barabash section assemblage was collected from the lower part of the Barabashevka Formation and includes 18 brachiopod species associated with other marine faunas indicative of the late Wordian. Alternatively, the Pilnikov section assemblage derives from the Pilnikov Formation and yields four brachiopod species consistent with the mid-Kungurian (Irenian). The palaeobiogeographical composition of the Barabash assemblage is distinguished by a conspicuous admixture of cool-water Boreal Realm elements and palaeoequatorial warm-water Cathaysian Province elements, together with genera that have antitropical distributions. Comparisons with analogous Neogene faunas from the Sea of Japan/East Sea suggest that the Barabash section might have been situated in the eastern part of the Sino-Mongolian seaway, which was located in an equivalent mid-latitude northern temperate confluence of warm- and cold-water ocean currents.G. R. Shi* [guang@uow.edu.au] and Sangmin Lee[sangminlee76@gmail.com], School of Earth, Atmospheric and Life Sciences, University of Wollongong, Northfields Ave, Wollongong, NSW 2522, Australia; Galina V. Kotlyar[galina_kotlyar@vsegei.ru], Karpinsky All Russian Research Geological Institute (VSEGEI), Srednii pr. 74, St. Petersburg, 199106 Russia; Yuri D. Zakharov[yurizakh@mail.ru], Far East Geological Institute, Far East Branch, Russian Academy of Sciences, Vladivostok, 690022 Russia.

In Gram-negative bacteria, outer membrane transporters import nutrients by coupling to an inner membrane protein complex called the Ton complex. The Ton complex consists of TonB, ExbB, and ExbD, and uses the proton motive force at the inner membrane to transduce energy to the outer membrane via TonB. Here, we structurally characterize the Ton complex from Escherichia coli using X-ray crystallography, electron microscopy, double electron–electron resonance (DEER) spectroscopy, and crosslinking. Our results reveal a stoichiometry consisting of a pentamer of ExbB, a dimer of ExbD, and at least one TonB. Electrophysiology studies show that the Ton subcomplex forms pH-sensitive cation-selective channels and provide insight into the mechanism by which it may harness the proton motive force to produce energy.

The mechanism by which the drug export protein TolC is utilized for import of the cytotoxin colicin E1 across the outer membrane and periplasmic space is addressed. Studies of the initial binding of colicin E1 with TolC, occlusion of membrane-incorporated TolC ion channels, and the structure underlying the colicin–TolC complex were based on the interactions with TolC of individual colicin translocation domain (T-domain) peptides from a set of 19 that span different segments of the T-domain. These studies led to identification of a short 20-residue segment 101–120, a “TolC box”, located near the center of the colicin T-domain, which is necessary for binding of colicin to TolC. Omission of this segment eliminated the ability of the T-domain to occlude TolC channels and to co-elute with TolC on a size-exclusion column. Far-ultraviolet circular dichroism spectral and thermal stability analysis of the structure of T-domain peptides implies (i) a helical hairpin conformation of the T-domain, (ii) the overlap of the TolC-binding site with a hinge of the helical hairpin, and (iii) a TolC-dependent stage of colicin import in which a central segment of the T-domain in a helical hairpin conformation binds to the TolC entry port following initial binding to the BtuB receptor. These studies provide the first structure-based information about the interaction of colicin E1 with the unique TolC protein. The model inferred for binding of the T-domain to TolC implies reservations about the traditional model for colicin import in which TolC functions to provide a channel for translocation of the colicin in an unfolded state across the bacterial outer membrane and a large part of the periplasmic space.

The structure of Si:Er layers grown by MBE on Si(001) substrates was investigated by transmission electron microscopy. We studied the dependence of the layer structure on the erbium concentration [Er] (8 × 1018 – 4 × 1019 cm–3) as well as the epitaxial growth temperature (400–700 °C). In general, ErSi2 platelets and spherical metallic precipitates are formed during the epitaxial growth through the layer and in the near-interface region, respectively. For [Er] ≥2 × 1019 cm–3, an oscillation of platelet density with periodicity approximately 200–250 nm was observed. A new type of complex structural defect was observed in a specimen with [Er] = 4 × 1019 cm–3. In the layers grown at 400 °C, complexes of extended defects consisting of partial dislocations, stacking faults and twins are generated. The formation of silicides and Er precipitates is accompanied by emission of vacancies, which leads to the formation of pores in the layer. A high concentration of vacancies should also result in formation of V–V and V–Er complexes. The presence of these point-defect complexes can explain the appearance of deep acceptor levels with an activation energy of 360 meV, which can be responsible for nonradiative paths. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Abstract:Paleoclimatic settings have been reconstructed for the Campanian using original oxygen‐isotopic analyses of well‐preserved molluskan and foraminifera shells from Russian Far East, Hokkaido, USA, Belgium and some DSDP holes (95,98,102, 390A, and 392A) in North Atlantic. Early Early Campanian climatic optimum has been recognized from data on high bottom shelf water paleotemperatures in middle latitudes of both the western circum‐Pacific (to 24.2°C) and the eastern circum‐Pacific (to 26.4°C) areas and high bottom shallow water paleotemperatures in high latitudes of the Koryak Upland (22.4–25.5°C), which agrees with the data on the Campanian Barykovskaya flora in high latitudes (Golovneva and Herman, 1998) and Jonker flora and its equivalents in middle latitudes. Judging from the data on comparatively high bottom shallow water paleotemperature values in high latitudes, South Alaska (19.4°C) and the Koryak Upland (22.4–25.5°C), we also expect Latest Campanian temperature maximum, which has not been confirmed, however, for low and middle latitudes by neither of isotopic nor paleobotanic data now. Main climatic tendency during the Campanian (with the exception of Latest Campanian) has been learned from isotopic composition of Campanian aragonitic ammonoid shells from the Hokkaido‐South Sakhalin (Krilyon) marine basin. In contrary to Huber's et al. (2002) assumption, we expect warm greenhouse conditions during the most part of the Campanian.

A mathematical model is proposed for describing the temperature dependence of the photoluminescence spectrum of self-ordered arrays of quantum dots with due regard for the electron-phonon interaction and different transfer processes in the “quantum dot-wetting layer-barrier” system. This model, as applied to analysis of the experimental spectra of InAs quantum dots grown on GaAs vicinal substrates, makes it possible to separate the manifestations of different mechanisms of excitation transfer in the photoluminescence spectra and to relate the observed temperature dependences of the spectra to the structural features of the quantum-dot array.

Silicon nanowires can be successfully grown by applying the vapor–liquid–solid process. In the case of the commonly used chemical vapor deposition technique, a Si containing gas/precursor is cracked at Au droplets acting as seeds. Si adatoms are subsequently dissolved in the liquid metal. Due to a supersaturation within this droplet, Si precipitates predominantly at the liquid–solid interface – a nanowire grows. A different situation occurs if nanowires are grown by molecular beam epitaxy via the vapor–liquid–solid mechanism. The difference consists, for example, of the role of the metal seed, the morphology of the nanowires and their aspect ratio. In particular, surface diffusion including the metal used as well as Si, strongly influences the growth process. This article describes molecular beam epitaxy growth experiments of Si nanowires under ultra-high vacuum conditions and compares the results with other growth techniques.

Details of silicon diodes with Ge/Si multilayer quantum dot heterostructures embedded in the Si p–n junction grown by molecular beam epitaxy emitting in the range of 1.4–1.7 µm at room temperature and continuous injection pumping are discussed. Output power of the light emitting diode reaches 1 µW/cm2 at applied current density of 2 A/cm2. Photoluminescence and transmission electron microscopy show that the origin of intense luminescence is defect free stacked Ge quantum dot array formed inside the structure. It is shown that doping by antimony improves structure quality and increases photoluminescence efficiency at room temperature. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The interaction of colicins with target cells is a paradigm for protein import. To enter cells, bactericidal colicins parasitize Escherichia coli outer membrane receptors whose physiological purpose is the import of essential metabolites. Colicins E1 and E3 initially bind to the BtuB receptor, whose β-barrel pore is occluded by an N-terminal globular “plug”. The x-ray structure of a complex of BtuB with the coiled-coil BtuB-binding domain of colicin E3 did not reveal displacement of the BtuB plug that would allow passage of the colicin (Kurisu, G., S. D. Zakharov, M. V. Zhalnina, S. Bano, V. Y. Eroukova, T. I. Rokitskaya, Y. N. Antonenko, M. C. Wiener, and W. A. Cramer. 2003. Nat. Struct. Biol. 10:948–954). This correlates with the inability of BtuB to form ion channels in planar bilayers, shown in this work, suggesting that an additional outer membrane protein(s) is required for colicin import across the outer membrane. The identity and interaction properties of this OMP were analyzed in planar bilayer experiments.OmpF and TolC channels in planar bilayers were occluded by colicins E3 and E1, respectively, from the trans-side of the membrane. Occlusion was dependent upon a cis-negative transmembrane potential. A positive potential reversibly opened OmpF and TolC channels. Colicin N, which uses only OmpF for entry, occludes OmpF in planar bilayers with the same orientation constraints as colicins E1 and E3. The OmpF recognition sites of colicins E3 and N, and the TolC recognition site of colicin E1, were found to reside in the N-terminal translocation domains. These data are considered in the context of a two-receptor translocon model for colicin entry into cells.

Cellular import of colicin E3 is initiated by the Escherichia coli outer membrane cobalamin transporter, BtuB. The 135-residue 100-Å coiled-coil receptor-binding domain (R135) of colicin E3 forms a 1:1 complex with BtuB whose structure at a resolution of 2.75 Å is reported. Binding of R135 to the BtuB extracellular surface (ΔG° = −12 kcal mol−1) is mediated by 27 residues of R135 near the coiled-coil apex. Formation of the R135–BtuB complex results in unfolding of R135 N- and C-terminal ends, inferred to be important for unfolding of the colicin T-domain. Small conformational changes occur in the BtuB cork and barrel domains but are insufficient to form a translocation channel. The absence of a channel and the peripheral binding of R135 imply that BtuB serves to bind the colicin, and that the coiled-coil delivers the colicin to a neighboring outer membrane protein for translocation, thus forming a colicin translocon. The translocator was concluded to be OmpF from the occlusion of OmpF channels by colicin E3.

We study the spectral and polarization properties of acoustic waves propagating in nematic liquid–crystalline rubber materials. We apply the viscoelastic theory of nematic elastomers in the low–frequency (hydrodynamic) limit. Dynamic soft elasticity, exhibited by ideal nematic elastomers under certain geometries of shear at low frequencies, leads to anomalous anisotropy of energy transfer and attenuation of transverse waves. The results suggest an application of this class of materials as an acoustic polarizer medium.

An external electric field acts on the mass transport in ionic solids as a second driving force in addition to the chemical potential gradient. The acceleration of a spinel-forming reaction between two binary oxides under the influence of an external electric field is studied in the model system MgOMgIn2O4In2O3. A simple kinetic model based on defect thermodynamics and linear transport theory is presented. The results indicate that the morphology during the early stages of growth of MgIn2O4in the electric field is determined mainly by the initial grain structure of the In2O3layer. The reaction front advances faster in the vicinity of grain boundaries. Morphological instabilities predicted by a continuum model of the different transport properties of MgO, MgIn2O4and In2O3are less important. The grain boundaries act as fast diffusion paths, resulting in large MgIn2O4thickness variations along the interface. Accordingly the MgIn2O4MgO interface adopts a highly curved morphology. Depending on the curvature of the MgIn2O4MgO interface, the advancement of the interface proceeds either viaa dislocation mechanism or viaa ledge mechanism. Most probably, these two mechanisms result again in locally different growth rates, so that a feedback mechanism is established viathe local micromorphology of the interface.

An external electric field acts on the mass transport in ionic solids as a second driving force in addition to the chemical potential gradient. The acceleration of a spinel-forming reaction between two binary oxides under the influence of an external electric field is studied in the model system MgO/MgIn₂O₄/In₂O₃. A simple kinetic model based on defect thermodynamics and linear transport theory is presented. The results indicate that the morphology during the early stages of growth of MgIn₂O₄ in the electric field is determined mainly by the initial grain structure of the In₂O₃ layer. The reaction front advances faster in the vicinity of grain boundaries. Morphological instabilities predicted by a continuum model of the different transport properties of MgO, MgIn₂O₄ and In₂O₃ are less important. The grain boundaries act as fast diffusion paths, resulting in large MgIn₂O₄ thickness variations along the interface. Accordingly the MgIn₂O₄/MgO interface adopts a highly curved morphology. Depending on the curvature of the MgIn₂O₄/MgO interface, the advancement of the interface proceeds either via a dislocation mechanism or via a ledge mechanism. Most probably, these two mechanisms result again in locally different growth rates, so that a feedback mechanism is established via the local micromorphology of the interface.

The optical and structural properties of the Ge submonolayer nano-inclusions in a Si matrix grown by molecular beam epitaxy are investigated. It is shown that at relatively high growth temperatures >600° C new features appear in the photoluminescence spectra. It is found that these features correspond to formation of the germanium nano-inclusions in a silicon matrix.

Exact solutions are obtained in the framework of the classical theory of laminates subjected to the action of normal moments, double forces, double moments or momentless double dipoles. Seven cases of such loads are considered and completed by considering the case of given transversal discontinuity of normal deflection. It is shown that, in contrast to the case of infinite straight dislocations in a pure in-plane problem, the energy of this eighth solution depends on the discontinuity orientation. Some numerical examples are presented. Besides the formal value, the obtained double-force and double-moment solutions, as well as dimensionless double dipoles, can be used to construct kernels of additional boundary integral equations (BIE). Due to the coupling phenomena in the BIE system for the region with a corner point, additional variable such as corner forces appear and require the mentioned equation.

Thermodynamic properties, stability, and structure of the toxin-like molecule colicin E1 were analyzed by differential scanning calorimetry and circular dichroism to determine the number of structurally independent domains, and the interdomain interactions necessary for colicin import into the Escherichia coli cell. Analysis of denaturation profiles of the 522 residue colicin E1, together with fragments of 342 and 178 residues that contain subsets of the domains, showed three stable cooperative blocks that differ in thermal stability and correspond to three major functional domains of the colicin: (i) the COOH-terminal channel-forming (C) domain with the highest thermal stability; (ii) the BtuB receptor binding (R) domain; and (iii) the N-terminal translocation (T) domain that has the smallest stabilization enthalpy and thermal stability. Interdomain interactions were described in which T-R interactions stabilize R, and T-C and R-C interactions stabilize R and T, but destabilize C. The R and T domains behaved in a similar way as a function of pH and ionic strength. Interacting extended helices of the R domain, possibly a coiled-coil, were implied by: (i) the very high (>90 %) α-helical content of the R domain, (ii) cooperative decreases in α-helical content near the Ttr of thermal denaturation of the R domain; (iii) a large denaturation enthalpy, implying extensive H-bond and van der Waals interactions.The R domain was inferred, from the extended network of interacting helices, large ΔH, and steep temperature dependence of its stabilization energy to have a dominant role in determining the conformation of other domains. It is proposed that cellular import starts with the R domain binding to the BtuB receptor, followed by unfolding of the R domain coiled-coil and thereby of the T domain, which then interacts with the TolC receptor-translocator.

The channel-forming domain of colicin E1 is composed of a soluble helical bundle which, upon membrane binding, unfolds to form an extended, two-dimensional helical net in the membrane interfacial layer. To characterize the pathway of unfolding of the protein and the structure of the surface-bound intermediate, the time-course of intra-protein distance changes and unfolding on a millisecond time-scale were determined from the kinetics of changes in the efficiency of fluorescence resonance energy transfer, and of the donor-acceptor overlap integral, between each of six individual tryptophan residues and a Cys-conjugated energy transfer acceptor (C509-AEDANS). Comparison of the rate constants revealed the following order of events associated with unfolding of the protein at the membrane surface: (A) movement of the hydrophobic core helices VIII-IX, coincident with a small change in Trp-Cys509 distances of the outer helices; (B) unfolding of surface helices in the helical bundle in the order: helix I, helices III, IV, VI, VII, and helix V; (C) a slow (time-scale, seconds) condensation of the surface-bound helices. The rate of protein unfolding events increased with increasing anionic lipid content. Unfolding did not occur below the lipid thermal phase transition, indicating that unfolding requires mobility in the interfacial layer. The structure of the two-dimensional membrane-bound intermediate in the steady-state was inferred to consist of a quasi-circular arrangement of eight helices embedded in the membrane interfacial layer and anchored by the hydrophobic helical hairpin. The pathway of unfolding of the colicin channel at the membrane surface, catalyzed by electrostatic and hydrophobic forces, is the first described for a membrane-active protein. It is proposed that the pathway and principles described for the colicin protein are relevant to membrane protein import.

Ferredoxin-NADP+reductase (FNR) was previously inferred to bind to the cytochrome b6fcomplex in the electron transport chain of oxygenic photosynthesis. In the present study, this inference has been examined through analysis of the thermodynamics of the interaction between FNR and the b6fcomplex. Isothermal titration calorimetry (ITC) was used to characterize the physical interaction of FNR with b6fcomplex derived from two plant sources (Spinacia oleraceaand Zea maize). ITC did not detect a significant interaction of FNR with the b6fcomplex in detergent solution nor with the complex reconstituted in liposomes. A previous inference of a small amplitude but defined FNR-b6finteraction is explained by FNR interaction with micelles of the undecyl β-D maltoside (UDM) detergent micelles used to purify b6f. Circular dichroism, employed to analyze the effect of detergent on the FNR structure, did not reveal significant changes in secondary or tertiary structures of FNR domains in the presence of UDM detergent. However, thermodynamic analysis implied a significant decrease in an interaction between the N-terminal FAD-binding and C-terminal NADP+-binding domains of FNR caused by detergent. The enthalpy, ΔHo, and the entropy, ΔSo, associated with FNR unfolding decreased four-fold in the presence of 1 mM UDM at pH 6.5. In addition to the conclusion regarding the absence of a binding interaction of significant amplitude between FNR and the b6fcomplex, these studies provide a precedent for consideration of significant background protein-detergent interactions in ITC analyses involving integral membrane proteins.

In the northwestern circum-Pacific, two main trends in Late Cretaceous temperatures can be recognized. (1) In general, a recurrent warming trend is thought to have begun in the Turonian–Campanian, reaching temperature maxima in the early Late Santonian and early Late Campanian, and temperature minima in the earliest Santonian and perhaps early Campanian. (2) During the Maastrichtian, temperatures dropped sharply, with only a slight warming in the early Late Maastrichtian. The existence of a thermal maximum at the Coniacian–Santonian transition has previously been expected, but is not confirmed by new isotopic results. Copyright 1999 Academic Press

In the northwestern circum-Pacific, two main trends in Late Cretaceous temperatures can be recognized. (1) In general, a recurrent warming trend is thought to have begun in the Turonian–Campanian, reaching temperature maxima in the early Late Santonian and early Late Campanian, and temperature minima in the earliest Santonian and perhaps early Campanian. (2) During the Maastrichtian, temperatures dropped sharply, with only a slight warming in the early Late Maastrichtian. The existence of a thermal maximum at the Coniacian–Santonian transition has previously been expected, but is not confirmed by new isotopic results.

Scanning force microscopy (SFM) has been used for comparative studies of domain structures in SrBi2Ta2O9 (SBT) thin films grown by sol-gel, Flash MOCVD and pulsed laser deposition (PLD) techniques. Investigation has been focused on establishing microscopic correlation between crystallinity, domain arrangements and switching behavior of the films. It has been shown that the domain contrast of an individual grain and its switchability are strongly dependent on the grain orientation. The remnant polarization value was found to decrease with decrease in the fraction of a-oriented grains which exhibit sharp domain contrast.