bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural and chemical phase transitions in tungsten carbide films evidenced by the analysis of their stiffness tensors
Authors: Wittkowski T. , Jung K. , Hillebrands B. , Comins J. D.
Published: October 2006

Brillouin light scattering (BLS) is used to provide a comprehensive study of thin tungsten carbide films deposited on single crystal silicon substrates whose distinctive nature depends critically on the deposition parameters. The use of stepped films in these slow-on-fast systems provides enhanced data sets and allows the velocity dispersion of the observed surface excitations, including the discrete Rayleigh and Sezawa modes to be studied in detail. Comprehensive and powerful methods of data analysis and interpretation including the recently developed Monte Carlo (MC) method, the surface Green’s function, and classical approaches are applied to extract the effective elastic constants and density of each of the films. The MC and Green’s function methods are used to remove ambiguities in Sezawa mode assignments and to identify a mode-crossing event. Auger electron spectroscopy and x-ray diffraction investigations confirm conclusions about chemical composition and microstructure obtained by BLS including a structural phase transition, thus leading to a consistent description of elastic, structural, and chemical properties of tungsten carbide films as a function of their deposition conditions. The anisotropic elastic tensors of the various films are employed for an analysis of the angular dependent Young’s modulus and the shear modulus, suggesting implications for the film performance in wear protection. Finally, an estimate of the elastic anisotropy of the α-W2C single crystal is provided on the basis of the effective elastic constants of a nanocrystalline W2C film.
Exact results for noise power spectra in linear biochemical reaction networks
Authors: Warren Patrick B. , Tănase-Nicola Sorin , ten Wolde Pieter Rein
Published: October 2006

We present a simple method for determining the exact noise power spectra and related statistical properties for linear chemical reaction networks. The method is applied to reaction networks which are representative of biochemical processes such as gene expression. We find, for example, that a post-translational modification reaction can reduce the noise associated with gene expression. Our results also indicate how to coarse grain networks by the elimination of fast reactions. In this context we have discovered a breakdown of the sum rule which relates the noise power spectrum to the total noise. The breakdown can be quantified by a sum rule deficit, which is found to be universal, and can be attributed to the high-frequency noise in the fast reactions.
Optoelectronic properties of GaN epilayers in the region of yellow luminescence
Authors: Grazzi C. , Strunk H. P. , Castaldini A. , Cavallini A. , Schenk H. P. D. , Gibart P.
Published: October 2006

We studied a GaN epitaxial wafer grown by metal organic chemical vapor deposition, in which a lateral variation in the density of dislocations and associated defects was induced by a special preparation of the GaN buffer layer. Electron beam induced current and photocurrent measurements reveal lateral variations in the electrical properties of the GaN epilayer corresponding to the gradient in the defect density. The photocurrent spectra show four well distinct peaks separating the well known defect related yellow band in a blue, a green, a yellow, and a red component. In particular, we observe a strong dependence of the green component on the density of the a-type threading dislocations. There is evidence that the green and the yellow components are also significantly influenced by point defects.
Active planar optical waveguides with silicon nanocrystals: Leaky modes under different ambient conditions
Authors: Luterová K. , Skopalová E. , Pelant I. , Rejman M. , Ostatnický T. , Valenta J.
Published: October 2006

We study both experimentally and theoretically the propagation of light emitted from silicon nanocrystals forming planar waveguides buried in SiO2. Photoluminescence spectra detected from the sample facet show significant spectral narrowing—leaky modes—with respect to the spectra measured in standard photoluminescence configuration. The spectral position of the leaky modes responds strongly to a local change of refractive index (liquid drop) on the sample surface. Higher refractive index of the liquid induces higher redshift of the mode position. Experimental data agree with the previously proposed leaky mode model.
Time delayed collection field experiments on polymer: Fullerene bulk-heterojunction solar cells
Authors: Offermans Ton , Meskers Stefan C. J. , Janssen René A. J.
Published: October 2006

The recombination of photogenerated charge carriers in poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylene vinylene]:1-(3-methoxycarbonyl)-propyl-1-phenyl-[6,6]C61 bulk-heterojunction solar cells is investigated using the time delayed collection field technique. Here the lifetime of photogenerated electrons and holes that have escaped charge recombination can be determined from current measurements using a pulsed collection voltage that is delayed with respect to the excitation pulse. At 80K, the number of long lived charge carriers decays in time according to t−α with α=0.2, practically independent of laser fluence in the range of 1–1000μJ∕cm2. For excitation density <4μJ∕cm2 the number of long lived carriers (nL) depends linearly on the fluence. At higher fluence, nL is limited by a process that occurs in the time span between generation and carrier extraction under a constant bias (−4V). Continuous background illumination reduces the lifetime of long lived carriers, probably by filling the low energy trap sites, for which a number density of 1017cm−3 is estimated. Recombination of long lived carriers at 80K in the 1–1000μs range is not limited by the (bimolecular) rate of nongeminate electron and hole encounter. Instead, the rate is limited by a monomolecular process, which may be the detrapping of one type of carrier or the recombination within a Coulombically bound electron-hole pair.
Effect of surface tension and surface elasticity of a fluid-fluid interface on the motion of a particle immersed near the interface
Authors: Felderhof B. U.
Published: October 2006

The motion of a particle immersed in a fluid near a fluid-fluid interface is studied on the basis of the linearized Navier-Stokes equations. The motion is influenced by surface tension, dilatational surface elasticity modulus, and surface shear modulus, as well as by gravity. The backflow at the location of the particle after a sudden impulse has some universal features that are the same as for a rigid wall with stick boundary conditions. At short times the flow depends only on the mass densities of the two fluids. The nature of the short-time flow is calculated from potential flow theory. At a somewhat later time the particle shows a pronounced rebound. The maximum value of the rebound and the time at which the maximum occurs depend on the elastic properties of the interface.
Deformation stacking fault probability and dislocation microstructure of cold worked Cu–Sn–5Zn alloys by x-ray diffraction line profile analysis
Authors: Dey S. N. , Chatterjee P. , Sen Gupta S. P.
Published: October 2006

Plastically deformed (hand-filed) Cu–Sn–5Zn ternary alloys with Sn concentrations 1, 2.5, and 5wt% are investigated. Microstructural parameters are studied in terms of x-ray diffraction profile fitting analysis. It is observed by Dey et al. [Acta. Mater. 53, 4635 (2005)] that the change in stacking fault probability (α) with Sn concentration for ternary Cu–Sn–5Zn alloys is similar to Cu-based binary alloy (Cu–Sn) system but behaves in a different manner from Cu–1Sn–Zn ternary alloy systems. The crystallite size distribution is broader for alloy with 1wt% Sn and becomes narrower with increasing Sn concentration. Value of dislocation density (ρ) is of the order of 1015m−2 and shows a compositional dependence. Type of dislocation is found to be predominantly screw; ⟨100⟩-type dipoles may also be present in the cold-worked alloys. The dislocation arrangement is found to be more correlated in case of 1wt% Sn compared to other alloys of higher Sn concentration. The stacking fault energy (γ) is obtained from modified Reed-Schramm equation and is of the order of 20mJm−2 with no significant compositional dependence.
Photonic band gap of two-dimensional triangular photonic crystals with broken structural and rotational symmetries
Authors: Chang K. P. , Yang S. L.
Published: October 2006

Three deformed and two rotational structures are constructed to study the effect of structural and rotational symmetries on the gap widths of E- and H-polarization bands in photonic crystals. The band structures and field patterns of a triangular lattice of hollow tellurium (Te) rods are calculated using the plane-wave method. The H-polarization band gaps are strongly affected by the interaction between the fields of the rods as the rods are deformed and affected by the reduction in the rotational symmetry as whole rods are rotated. Only the shapes of the rods affect the E-polarization band gaps as the rods are either deformed or rotated. Moreover, H-polarization modes determine the absolute photonic band gap (PBG) width as the rods are rotated, whereas E-polarization modes determine the absolute PBG width as the rods are deformed.
High Curie point CaBi2Nb2O9 thin films: A potential candidate for lead-free thin-film piezoelectrics
Authors: Simões A. Z. , Ries A. , Riccardi C. S. , Gonzalez A. H. M. , Longo E. , Varela J. A.
Published: October 2006

Ca Bi 2 Nb 2 O 9 (CBNO) thin films deposited on platinum coated silicon substrates by the polymeric precursor method exhibited good structural, dielectric, and piezoelectric characteristics. Capacitance-voltage measurements indicated good ferroelectric polarization switching characteristics. Remanent polarization and drive voltage values were 4.2μC∕cm2 and 1.7V for a maximum applied voltage of 10V. The film has a piezoelectric coefficient d33 equal to 60pm∕V, current density of 0.7μA∕cm2, and Curie temperature of 940°C. The polar-axis-oriented CBNO is a promising candidate for use in lead-free high Curie point in ferroelectric and piezoelectric devices.
Strong anisotropy in single atomic layer of Co and Fe on Pt(997)
Authors: Cheng Ruihua , Pearson J. , Li Dongqi , Fradin F. Y.
Published: October 2006

We explore the magnetic properties of Co and Fe on a Pt(997) vicinal single crystal by means of reflection high energy electron diffraction and the surface magneto-optical Kerr effect. Both Co and Fe are grown at room temperature as wedges with thickness ranging from 0 to 3.5 ML (monolayer). We find that Co and Fe show layer-by-layer growth followed by three dimensional growth as the coverage increases due to the large lattice mismatch. Co and Fe exhibit ferromagnetism down to 0.2 ML coverage due to the strong anisotropy. The symmetry breaking at the surface results in the magnetic easy axis of the atomic layers along the surface normal direction. The coercivity of both Fe and Co atomic layers fit an exponential decay with temperature that can be understood as being due to thermally activated, nonequilibrium spin dynamics. The magnetic anisotropy energy per atom is extracted by fitting the experimental data.
Observations of a hysteresis loss valley in yttrium barium copper oxide superconductors
Authors: Çelebi S. , Öztürk A. , Kolemen U. , LeBlanc M. A. R.
Published: October 2006

We present measurements of the ac susceptibility of sintered yttrium barium copper oxide pellets prepared by a melt processed solid state reaction method, with different amounts of ZnO added. The measurements were performed versus temperature T for several different ac magnetic field amplitudes Hac in the presence of static bias magnetic fields Hb directed along Hac. For all our samples, for each choice of Hac, the imaginary part of the ac susceptibility versus T traces a peak, denoted by χ″max, centered at a temperature denoted by Tmax.We also find that plots of the values of χ″max vs Hac and of χ″max vs Tmax generate curves that display a valley. Calculations of hysteresis losses, exploiting a critical-state model where the critical current density jc=α(T)∕Bn, reproduce the experimental data quite well.
Counterpoise corrected geometries of hydrated complexes
Authors: Garden Anna L. , Lane Joseph R. , Kjaergaard Henrik G.
Published: October 2006

We have calculated the equilibrium geometries of the hydrated complexes, H2O∙CO2, H2O∙CS2,H2O∙OCS, H2O∙SO2, and H2O∙SO3, in the electronic ground state. We have used the coupled cluster with singles, doubles, and perturbative triples ab initio method with a correlation consistent augmented triple-zeta basis set. We find that a counterpoise corrected optimization scheme is important for an accurate description of the geometries. These high level ab initio calculated geometries are of comparable quality to those obtained experimentally.
Detection of multiple-quantum coherences with projective nuclear magnetic resonance measurement
Authors: Lee Jae-Seung , Khitrin A. K.
Published: October 2006

It is shown that in nuclear magnetic resonance, multiple-quantum (MQ) coherences can be detected “instantly” by exploiting the principle of quantum-mechanical projective measurement. Therefore, the mixing period, which involves collective multispin dynamics and converts MQ coherences into observable single-quantum coherence (magnetization), is not necessary. The experimental examples are given for two finite clusters: benzene in liquid crystal and liquid crystal 4′-n-pentyl-4-cyanobiphenyl, and for solid adamantane with an infinite network of dipolar couplings.
Growth mechanism of Si nanowhiskers and SiGe heterostructures in Si nanowhiskers: X-ray scattering and electron microscopy investigations
Authors: Dujardin R. , Poydenot V. , Devillers T. , Favre-Nicolin V. , Gentile P. , Barski A.
Published: October 2006

Silicon nanowhiskers have been grown by molecular beam epitaxy on Si (111) by vapor-liquid-solid mechanism induced by gold droplets. Very thin Ge containing layers have been incorporated in Si nanowhiskers in order to grow SiGe heterostructures. Si and Ge growth rate in nanowhiskers, shape, and sidewall facets of nanowhiskers have been investigated by scanning electron microscopy and grazing incidence small angle x-ray scattering. Anomalous grazing incidence x-ray diffraction and transmission electron microscopy observations show a strong intermixing of Si with Ge in nanowhiskers and formation of SiGe heterostructures which are highly strained to Si.
Influence of Ag particle size on ethanol sensing of SnO1.8:Ag nanoparticle films: A method to develop parts per billion level gas sensors
Authors: Joshi Rakesh K. , Kruis F. Einar
Published: October 2006

The influence of Ag particle size on ethanol sensing of SnO1.8:Ag films composed of size-selected nanoparticles with independently controlled size and concentration of Ag is reported in the present study. The study shows that Ag nanoparticles are acting as catalyst for chemical sensitization through a spillover effect. The catalyst particles are observed to be more active on decreasing their size, resulting into an improved sensor response. A response time of 2s for 1000ppm ethanol has been achieved. Detection of 100ppb ethanol in air has been demonstrated using this well-defined technique.
Continuous light-shift correction in modulated coherent population trapping clocks
Authors: Shah V. , Gerginov V. , Schwindt P. D. D. , Knappe S. , Hollberg L. , Kitching J.
Published: October 2006

The authors demonstrate a simple technique to significantly improve the long-term frequency stability of atomic clocks based on coherent population trapping (CPT). In this technique, the CPT fields are created by a modulated diode laser and a slow servo is used to actively tune the laser modulation index to a value where the light shift vanishes. The observed clock frequency at this modulation index is given by the rubidium hyperfine frequency when no light fields are present, and this makes the clock frequency largely insensitive to variations in laser properties. In addition to reducing stringent requirements on the long-term stabilities of laser temperature, laser frequency, and rf modulation power, this technique may also significantly reduce frequency drifts related to laser aging. In the experiment, they demonstrate improvement by over one order of magnitude in the stability of a clock that is limited by light-shift-induced frequency drifts.
Ionic contrast terahertz time resolved imaging of frog auricular heart muscle electrical activity
Authors: Masson Jean-Baptiste , Sauviat Martin-Pierre , Gallot Guilhem
Published: October 2006

The authors demonstrate the direct, noninvasive and time resolved imaging of functional frog auricular fibers by ionic contrast terahertz (ICT) near field microscopy. This technique provides quantitative, time-dependent measurement of ionic flow during auricular muscle electrical activity, and opens the way of direct noninvasive imaging of cardiac activity under stimulation. ICT microscopy technique was associated with full three-dimensional simulation enabling to measure precisely the fiber sizes. This technique coupled to waveguide technology should provide the grounds to development of advanced in vivo ion flux measurement in mammalian hearts, allowing the prediction of heart attack from change in K+ fluxes.
Magnetoelectric properties of the lead–free cofired BaTiO3–(Ni0.8Zn0.2)Fe2O4 bilayer composite
Authors: Islam Rashed A. , Priya Shashank
Published: October 2006

In this letter the authors report the ferroelectric and magnetoelectric (ME) properties of the cofired bilayer composite targeting low cost lead-free magnetic field sensor. The ME response was characterized as a function of the magnetic field direction and as a function of the dc bias. It was found that when the ac magnetic field is applied at 90° to the ferroelectric polarization axis of the sample, a ME response of 72mV∕cmOe was obtained without any dc bias. The magnitude of the ME coefficient reached the saturation at dc bias of 1000Oe having magnitude of 152mV∕cmOe. The scanning electron microscopy analysis showed the presence of clear interface boundary between the strained BaTiO3∕(Ni0.8Zn0.2)Fe2O4 region.
Memory effect of a mechanical anomaly related to ferroelastic domain switching in rhombohedral lead zirconate titanate ceramics
Authors: Wang Can , Redfern Simon A. T. , Daraktchiev Maren , Harrison Richard J.
Published: October 2006

An anomaly in the temperature dependent mechanical properties of a lead zirconate titanate ferroelectric ceramic has been observed by dynamic mechanical analysis. The anomaly, seen as a rise in modulus, accompanied by a decrease in internal friction, occurs in the low-temperature phase below TC. The temperature of the anomalies varies systematically with the applied forces and the anomaly does exhibit a memory effect. The corresponding static bending deformation, mainly from remnant strain by ferroelastic domain switching, is analyzed, and a critical remnant strain value for triggering the anomaly is obtained. The anomaly is thought to be induced by pinning and depinning of domain walls. The results confirm that the memory effect and the occurrence of the anomaly are controlled by ferroelastic domain switching.
Tunability and permittivity-temperature characteristics of highly (100) oriented compositionally graded (Ba0.7Sr0.3)(SnxTi1−x)O3 thin films grown by pulse-laser deposition
Authors: Lu S. G. , Xu Z. K.
Published: October 2006

Compositionally graded (Ba0.7Sr0.3)(SnxTi1−x)O3 (BSSnT) (x=0.1, 0.2, 0.3, and 0.4) thin films were prepared by pulse-laser deposition on (La0.7Sr0.3)CoO3∕LaAlO3 substrates. A highly (100) oriented structure was obtained for both the upgraded (x increased from the bottom layer) and downgraded (x decreased from the bottom layer) configurations. The tunabilities are 31% and 35% for up- and downgraded BSSnT thin films at 300kV∕cm, respectively. Both the up- and downgraded BSSnT thin films exhibit near linear permittivity-temperature characteristics in the temperature range of −150to150°C. Fine grain size and graded configuration are believed to be responsible for this dielectric behavior.
Structural investigation of CuIn5Se8 single crystals by optical second harmonic generation, ellipsometry, and photoluminescence
Authors: Kulyuk L. , Mirovitskii V. , Arushanov E. , Tezlevan V. , Leon M. , Mishina E. , Sherstyuk N. , Dumouchel T. , Fortin E. , Rasing Th.
Published: October 2006

Cu In 5 Se 8 bulk single crystals were characterized using ellipsometry, photoluminescence (PL), and optical second harmonic generation (SHG). The refractive n(E) and absorption k(E) indices as functions of photon energy E are determined. The structure of the PL spectrum suggests the presence of the Cu-rich nonstoichiometric phases at the natural surfaces of the CuIn5Se8 sample. The best fit of the experimental SHG data is achieved by assuming that CuIn5Se8 belongs to the 4¯2m symmetry group. This result is in contradiction with x-ray analysis (6¯2m group), which testifies to the difference in surface and bulk structure.
Quantum asymmetry of switching in laterally coupled quantum wires with tunable coupling strength
Authors: Ramamoorthy A. , Bird J. P. , Reno J. L.
Published: October 2006

The authors study switching in laterally coupled quantum wires under conditions where their sidewall confinement strongly influences the transmission properties of their coupling region. Their analysis suggests that the low-temperature behavior of the currents in this regime results from the influence of inevitable structural asymmetry on the quantum-level structure of the quantum wires.
Computational investigation of B-site donor doping effect on fatigue behavior of lead zirconate titanate
Authors: Zhang Zhen , Lu Li , Shu Chang , Wu Ping
Published: October 2006

The effect of the B-site donor on the fatigue behavior of lead zirconate titanate (PZT) was studied. Seven elements were considered. The formation energies of oxygen vacancies and band structures of these doped systems were investigated. It was found that the Nb, Ta, and W doped PZT systems have the highest formation energy of oxygen vacancies as well as reduced occupations of Ti 3d states by the electrons released from oxygen vacancies. Therefore, the systems respectively doped with Nb, Ta, and W can effectively improve the fatigue property of PZT.
The systematic relationships of Brunonia.
Authors: Carolin RC
Published: October 2006

Although Brunonia has had a long separate history from the other Goodeniaceae, they
do appear to be related, and it remains a matter of personal preference whether one
places it in a subfamily of Goodeniaceae or in a separate family. Since I prefer large
families to give easily recognizable groups, I opt for the first alternative.
The long separate history of Brunonia may be the result of its early entry into the arid
areas, possibly before other goodeniads, with secondary invasions of the higher rainfall
zones only much later. The relationship between Goodeniaceae and Campanulaceae is
not very close, and it seems they must both have arisen quite early in the evolution of
the Metachlamydeae. The evolution of the Goodeniaceae as a whole and the Campanulaceae
occurred after the break up of Gondwanaland, in the temperate areas of each
continent. The Stylidiaceae are primitively a cool to cold montane group of southern
Gondwanaland.
The genus Whiteochloa C.E. Hubbard (Poaceae, Paniceae)
Authors: Lazarides M
Published: October 2006

In the previously monotypic genus Whiteochloa, two new species are
described and two transferred from Panicum. The original circumscription of the genus
is revised to accommodate the five constituent species, which are described in detail and
identified by a key.
The genus Calogyne R.Br. in Australia.
Authors: Carolin RC
Published: October 2006

The genus
is considered to contain nine species in Australia of which four, C. porphvrea, C. neglecta,
C. symonii and C. quadrifida are described for the first time. Distylis berardiana Gaud.,
which has been previously placed in Calogyne, is here transferred to Goodenia as
G. berardiana.
Micraira F.Muell. (Poaceae, Micrairoideae)
Authors: Lazarides M
Published: October 2006

In the previously monotypic genus Micraira, seven new species are described, all from the
Arnhem Land plateau or closely adjoining areas, Northern Territory. All the new species
are based on first collections made chiefly in the past 6 years. In distribution the genus
is recorded from Western Australia for the first time and the original species
(M. subulifolia), previously recorded from Queensland and the Northern Territory, is con-
fined to Queensland. A key to the identity of the eight described species is provided.
Plants of the genus are considered to have revival properties.
The Malesian species of Serianthes Bentham (Fabaceae-Mimosoideae)
Authors: Kanis A
Published: October 2006

The Malesian representatives of Serianthes are revised and
the relationships with those from nearby Pacific islands are discussed. A key is provided
to all relevant taxa as well as maps showing their respective distributions.
S. minahassae (Koord.) Merr. & ~ e r r y is reinstated here and newly subdivided with
ssp. rninahassae in central Malesia, ssp. ledermannii (Harms) Kanis, stat. nov.. in New
Guinea and ssp. fosbergii Kanis. nom. & stat. nov. (based on Albizia melanesica Fosb.),
in the Bismarck Archipelago and the Solomon Islands. S. dilmyi Fosb. reaches from
Sumatra and the Philippines to western New Guinea and the Admiralty Islands. S. robinsonii
Fosb, is restricted to the southern Moluccas. S. hooglandii (Fosb.) Kanis, stat. nov.,
occurs in eastern New Guinea, with ssp. floridensis Kanis, ssp. nov.. in the Solomon
Islands. S. kanehirae Fosb. is excluded, being restricted to the western Caroline Islands.
Taxonomic revisions in Theaceae in Papuasia. 1. Gordonia, Ternstroemid, Adinandra and Archboldiodendron.
Authors: Barker WR
Published: October 2006

The revisions cover all genera
of Theaceae in Papuasia except Eurya and the single Australian representative.
Descriptions and keys at all levels are provided, including a key to all genera of Theaceae
in the region. Gordonia is represented by a single species G. papuana Kobuski; G. brassii
Kobuski and Kobuski's varieties of G.papuana are reduced to synonymy. Five species
of Ternstroemia occur; T. britteniana FvM. encompasses eight previously recognized
species; T. meiocarpa Kobuski is maintained as a distinct species with some reservation;
T. cherryi (F. M. Bailey) Merr., extending into north-eastern Queensland, has T. rehderana
Kobuski and probably T. nabirensis Kurata as synonyms; T. monostigma, a new species
from north-westem and north-central lowland Papuasia, is unique in the genus by its
single 2-ovulate carpel with a single stigma; T. merrilliana Kobuski has close affinities
to west Malesian species. Adinandra consists of one species Ad. forbesii Bak.f., with
Ad. brassii Kobuski reduced to synonymy. Endemic Archboldiodendron has one species
Archb. calosericeum Kobuski (1940) with taxonomic synonym Adinandra calosericea Diels
(1922); it has been reconstituted to comprise three subspecies, with ssp. merrillianum based
on Archb. merrillianum Kobuski, and ssp, kaindiensis a new subspecies confined to the
Wau area; the first documentation of its succulent indehiscent fruit with many seeds
borne on fleshy placentas supports its affinities being near Adinandra. Ploiarium sessile
(Scheff.) Hall.f., usually considered to belong in Bonnetiaceae, is briefly treated and
included in the generic key.
A revision of Vittadinia A.Rich. (Compositae) together with reinstatement of Eurybiopsis DC. and description of a new geunus, Camptacra.
Authors: Burbidge NT
Published: October 2006

It is
reported that Gaudichaud was correct in describing, under Brachycome Cass., three species,
B. triloba, B. dentata and B. spathulata. Reference is made to the nomenclatural status of
these species in accordance with the results of a revision of Brachycome by Davis (1948). De
Candolle erred in transferring the species to Vittadinia A. Rich, for which the New Zealand
V. australis is the type. Reasons are given for regarding V. triloba (Gaudich.) DC. as
synonymous with V. australis var. dissecta Benth., and the variety is raised to specific rank.
Included with V. australis and V. dissecta in Vittadinia s. str. (i.e. in Vittadinia subgenus
Vittadinia) are V. cuneata DC. (a name which can be applied to a complex group of taxa
widespread in southern and eastern Australia) and a further 17 species of which the
following are new: V. cervicularis (with four varieties), V. constricta, V. condyloides, V.
decora, V. eremaea, V. humerata, V. nullarborensis, V. pustulata, V. simulans and V. sulcata,
while V. gracilis (J. D. Hook.) N. Burbidge and V. australasica (Turcz.) N. Burbidge
are new combinations. V. scabra DC. and a group of taxa which have been referred to it
or, incorrectly, to V. macrorhiza (DC.) A. Gray have been placed in a new subgenus
of Vittadinia under the name Peripleura. Within this subgenus nine species are recognized:
V. scabra DC., V, hispidula F. Muell. ex A. Gray (with two varieties), and the new
species V. arida, V. bicolor, V. diffusa, V. obovata, V. sericea, V. spechtii (with two varieties)
and V. virgata. With the exception of V. australis which is endemic to New Zealand and V.
simulans, a New Caledonian species, all are endemic to Australia; however, V. hispidula has
been reported for New Caledonia where it is deemed to be an alien and V. gracilis and
possibly V. muelleri appear to have become naturalized in New Zealand. V. brachycomoides
(F. Muell.) Benth. becomes the type of a new genus, Camptacra, with two species, both
distributed in northern and north-eastern Australia. Eurybiopsis DC. is reinstated, with its
single species, E. macrorhiza DC., found only in northern Australia.
Supplement to a revision of the Loranthaceae of Australia
Authors: Barlow B.A
Published: October 2006

Additions and supplementary notes to a revision of Australian
Loranthaceae published by the present author in 1966 are presented. Six species,
Decaisnina congesta, Lysiana filifolia, Amyema dolichopodum, Amyema microphyllum,
Amyema subcapitatum and Amyema tridactylum, are described as new. Three subspecies,
Decaisnina brittenii subsp. speciosa, Decaisnina petiolata subsp. angustata and Amyema
congener subsp. diver gens, are described as new. One variety, Amyema bifurcatum var.
eburnum, is described as new. Two genera, Cecarria and Dactyliophora, are recorded
as new for Australia, where each is represented by one species. One other species, Amyema
friesianum, is recorded as new for Australia. Change of rank of two taxa necessitate the
following new combinations: Lysiana maritima and Dendrophthoe acacioides subsp.
longifolia.
Nomenclatural History of Hibbertia grossulariifolia (Dilleniaceae)
Authors: Stearn W.T
Published: October 2006

The generic name Burtonia Salisb. was validly published
in 1807 and based on the species now known as Hibbertia grossulariifolia (Salisb.) Salisb.,
probably the first species from Western Australia to flower in England. Burtonia R. Br.
(1811) has been proposed for conservation.
A revision of Dodonaea Miller (Sapindaceae) in Australia.
Authors: West JG
Published: October 2006

A taxonomic revision of the genus Dodonaea Miller (Sapindaceae) in Australia
is presented. A total of 61 native species are recognized in six infrageneric groups. Seven
new species are described and illustrated: D. falcata, D. glandulosa, D. intricata, D. rigida,
D. sinuolata, D. subglandulifera and D. uncinata. Two new subspecies and two new
varieties are described: D. sinuolata ssp. acrodentata, D. viscosa ssp. mucronata, D.
lanceolata van subsessilifolia and D. microzyga var. acrolobata. D. cuneata and D.
angustissima are reduced to subspecific level in the polymorphic D. viscosa and the
following subspecies are also recognized within D. viscosa: ssp. viscosa, ssp. burmanniana,
spp. angustifolia and ssp. spatulata.
A general key to the species, another based on vegetative features and keys to the
infraspecific taxa are provided. Fruits and leaf outlines of all recognized taxa are
illustrated.
Cyperochloa, a new genus in the Arundinoideae Dumortier (Poaceae).
Authors: Lazarides M , Watson L
Published: October 2006

Cyperochloa (type species: C. hirsuta Lazarides &
L. Watson), a new monotypic grass genus from Western Australia, is described and illus-
trated. It is sedge-like in appearance, with filiform basal leaves and a terminal, solitary,
bracteate spike subtended by a spathaceous leaf sheath. Detailed comparisons of its mor-
phology and anatomy with 728 generic descriptions in an automated database place it in
the Arundinoideae, where it occupies a rather isolated position among the relatives of
Danthonia.
Isolation, characterization, and genetic complementation of a cellular mutant resistant to retroviral infection
Authors: Agarwal Sumit , Harada Josephine , Schreifels Jeffrey , Lech Patrycja , Nikolai Bryan , Yamaguchi Tomoyuki , Chanda Sumit K. , Somia Nikunj V.
Published: October 2006

By using a genetic screen, we have isolated a mammalian cell line that is resistant to infection by retroviruses that are derived from the murine leukemia virus, human immunodeficiency virus type 1, and feline immunodeficiency virus. We demonstrate that the cell line is genetically recessive for the resistance, and hence it is lacking a factor enabling infection by retroviruses. The block to infection is early in the life cycle, at the poorly understood uncoating stage. We implicate the proteasome at uncoating by completely rescuing the resistant phenotype with the proteasomal inhibitor MG-132. We further report on the complementation cloning of a gene (
MRI
, modulator of retrovirus infection) that can also act to reverse the inhibition of infection in the mutant cell line. These data implicate a role for the proteasome during uncoating, and they suggest that MRI is a regulator of this activity. Finally, we reconcile our findings and other published data to suggest a model for the involvement of the proteasome in the early phase of the retroviral life cycle.
Microsporidian mitosomes retain elements of the general mitochondrial targeting system
Authors: Burri Lena , Williams Bryony A. P. , Bursac Dejan , Lithgow Trevor , Keeling Patrick J.
Published: October 2006

Microsporidia are intracellular parasites that infect a variety of animals, including humans. As highly specialized parasites, they are characterized by a number of unusual adaptations, many of which are manifested as extreme reduction at the molecular, biochemical, and cellular levels. One interesting aspect of reduction is the mitochondrion. Microsporidia were long considered to be amitochondriate, but recently a tiny mitochondrion-derived organelle called the mitosome was detected. The molecular function of this organelle remains poorly understood. The mitosome has no genome, so it must import all its proteins from the cytosol. In other fungi, the mitochondrial protein import machinery consists of a network series of heterooligomeric translocases and peptidases, but in microsporidia, only a few subunits of some of these complexes have been identified to date. Here, we look at targeting sequences of the microsporidian mitosomal import system and show that mitosomes do in some cases still use N-terminal and internal targeting sequences that are recognizable by import systems of mitochondria in yeast. Furthermore, we have examined the function of the inner membrane peptidase processing enzyme and demonstrate that mitosomal substrates of this enzyme are processed to mature proteins in one species with a simplified processing complex,
Antonospora locustae
. However, in
Encephalitozoon cuniculi
, the processing complex is lost altogether, and the preprotein substrate functions with the targeting leader still attached. This report provides direct evidence for presequencing processing in mitosomes and also shows how a complex molecular system has continued to degenerate throughout the evolution of microsporidia.
Unusual mechanical stability of a minimal RNA kissing complex
Authors: Li Pan T. X. , Bustamante Carlos , Tinoco Ignacio
Published: October 2006

By using optical tweezers, we have investigated the mechanical unfolding of a minimal kissing complex with only two G·C base pairs. The loop–loop interaction is exceptionally stable; it is disrupted at forces ranging from 7 to 30 pN, as compared with 14–20 pN for unfolding hairpins of 7 and 11 bp. By monitoring unfolding/folding trajectories of single molecules, we resolved the intermediates, measured their rate constants, and pinpointed the rate-limiting steps. The two hairpins unfold only after breaking the intramolecular kissing interaction, and the kissing interaction forms only after the folding of the hairpins. At forces that favor the unfolding of the hairpins, the entire RNA structure is kinetically stabilized by the kissing interaction, and extra work is required to unfold the metastable hairpins. The strong mechanical stability of even a minimal kissing complex indicates the importance of such loop–loop interactions in initiating and stabilizing RNA dimers in retroviruses.
UV irradiation induces a postreplication DNA damage checkpoint
Authors: Callegari A. John , Kelly Thomas J.
Published: October 2006

Eukaryotic cells irradiated with high doses of UV exhibit cell-cycle responses referred to as G
1
/S, intraS, and G
2
/M checkpoints. After a moderate UV dose that approximates sunlight exposure and is lethal to fission yeast checkpoint mutants, we found unexpectedly that these cell-cycle responses do not occur. Instead, cells at all stages of the cell cycle carry lesions into S phase and delay cell-cycle progression for hours after the completion of bulk DNA synthesis. Both DNA replication and the checkpoint kinase, Chk1, are required to generate this cell-cycle response. UV-irradiation of Δ
chk1
cells causes chromosome damage and loss of viability only after cells have replicated irradiated DNA and entered mitosis. These data suggest that an important physiological role of the cell-cycle response to UV is to provide time for postreplication repair.
An intramolecular folding sensor for imaging estrogen receptor–ligand interactions
Authors: Paulmurugan Ramasamy , Gambhir Sanjiv S.
Published: October 2006

Strategies for high-throughput analysis of interactions between various hormones and drugs with the estrogen receptor (ER) are crucial for accelerating the understanding of ER biology and pharmacology. Through careful analyses of the crystal structures of the human ER (hER) ligand-binding domain (hER–LBD) in complex with different ligands, we hypothesized that the hER–LBD intramolecular folding pattern could be used to distinguish ER agonists from selective ER modulators and pure antiestrogens. We therefore constructed and validated intramolecular folding sensors encoding various hER–LBD fusion proteins that could lead to split
Renilla
/firefly luciferase reporter complementation in the presence of the appropriate ligands. A mutant hER–LBD with low affinity for circulating estradiol was also identified for imaging in living subjects. Cells stably expressing the intramolecular folding sensors expressing wild-type and mutant hER–LBD were used for imaging ligand-induced intramolecular folding in living mice. This is the first hER–LBD intramolecular folding sensor suited for high-throughput quantitative analysis of interactions between hER with hormones and drugs using cell lysates, intact cells, and molecular imaging of small living subjects. The strategies developed can also be extended to study and image other important protein intramolecular folding systems.
Wild-type microglia extend survival in PU.1 knockout mice with familial amyotrophic lateral sclerosis
Authors: Beers David R. , Henkel Jenny S. , Xiao Qin , Zhao Weihua , Wang Jinghong , Yen Albert A. , Siklos Laszlo , McKercher Scott R. , Appel Stanley H.
Published: October 2006

The most common inherited form of amyotrophic lateral sclerosis (ALS), a neurodegenerative disease affecting adult motoneurons, is caused by dominant mutations in the ubiquitously expressed Cu
2+
/Zn
2+
superoxide dismutase (SOD1). Recent studies suggest that glia may contribute to motoneuron injury in animal models of familial ALS. To determine whether the expression of mutant SOD1 (mSOD1
G93A
) in CNS microglia contributes to motoneuron injury, PU.1
−/−
mice that are unable to develop myeloid and lymphoid cells received bone marrow transplants resulting in donor-derived microglia. Donor-derived microglia from mice overexpressing mSOD1
G93A
, an animal model of familial ALS, transplanted into PU.1
−/−
mice could not induce weakness, motoneuron injury, or an ALS-like disease. To determine whether expression of mSOD1
G93A
in motoneurons and astroglia, as well as microglia, was required to produce motoneuron disease, PU.1
−/−
mice were bred with mSOD1
G93A
mice. In mSOD1
G93A
/PU.1
−/−
mice, wild-type donor-derived microglia slowed motoneuron loss and prolonged disease duration and survival when compared with mice receiving mSOD1
G93A
expressing cells or mSOD1
G93A
mice.
In vitro
studies confirmed that wild-type microglia were less neurotoxic than similarly cultured mSOD1
G93A
microglia. Compared with wild-type microglia, mSOD1
G93A
microglia produced and released more superoxide and nitrite+nitrate, and induced more neuronal death. These data demonstrate that the expression of mSOD1
G93A
results in activated and neurotoxic microglia, and suggests that the lack of mSOD1
G93A
expression in microglia may contribute to motoneuron protection. This study confirms the importance of microglia as a double-edged sword, and focuses on the importance of targeting microglia to minimize cytotoxicity and maximize neuroprotection in neurodegenerative diseases.
Effect of force on mononucleosomal dynamics
Authors: Mihardja Shirley , Spakowitz Andrew J. , Zhang Yongli , Bustamante Carlos
Published: October 2006

Using single-molecule optical-trapping techniques, we examined the force-induced dynamic behavior of a single nucleosome core particle. Our experiments using the DNA construct containing the 601 nucleosome-positioning sequence revealed that the nucleosome unravels in at least two major stages. The first stage, which we attributed to the unraveling of the first DNA wrap around the histone octamer, could be mechanically induced in a reversible manner, and when kept at constant force within a critical force range, exhibited two-state hopping behavior. From the hopping data, we determined the force-dependent equilibrium constant and rates for opening/closing of the outer wrap. Our investigation of the second unraveling event at various loading rates, which we attributed to the inner DNA wrap, revealed that this unraveling event cannot be described as a simple two-state process. We also looked at the behavior of the mononucleosome in a high-salt buffer, which revealed that the outer DNA wrap is more sensitive to changes in the ionic environment than the inner DNA wrap. These findings are needed to understand the energetics of nucleosome remodeling.
Distance measurements reveal a common topology of prokaryotic voltage-gated ion channels in the lipid bilayer
Authors: Richardson Jessica , Blunck Rikard , Ge Pinghua , Selvin Paul R. , Bezanilla Francisco , Papazian Diane M. , Correa Ana M.
Published: October 2006

Voltage-dependent ion channels are fundamental to the physiology of excitable cells because they underlie the generation and propagation of the action potential and excitation–contraction coupling. To understand how ion channels work, it is important to determine their structures in different conformations in a membrane environment. The validity of the crystal structure for the prokaryotic K
+
channel, K
V
AP, has been questioned based on discrepancies with biophysical data from functional eukaryotic channels, underlining the need for independent structural data under native conditions. We investigated the structural organization of two prokaryotic voltage-gated channels, NaChBac and K
V
AP, in liposomes by using luminescence resonance energy transfer. We describe here a transmembrane packing representation of the voltage sensor and pore domains of the prokaryotic Na channel, NaChBac. We find that NaChBac and K
V
AP share a common arrangement in which the structures of the Na and K selective pores and voltage-sensor domains are conserved. The packing arrangement of the voltage-sensing region as determined by luminescence resonance energy transfer differs significantly from that of the K
V
AP crystal structure, but resembles that of the eukaryotic K
V
1.2 crystal structure. However, the voltage-sensor domain in prokaryotic channels is closer to the pore domain than in the K
V
1.2 structure. Our results indicate that prokaryotic and eukaryotic channels that share similar functional properties have similar helix arrangements, with differences arising likely from the later introduction of additional structural elements.
Global aggregation of newly translated proteins in an
Escherichia coli
strain deficient of the chaperonin GroEL
Authors: Chapman Eli , Farr George W. , Usaite Renata , Furtak Krystyna , Fenton Wayne A. , Chaudhuri Tapan K. , Hondorp Elise R. , Matthews Rowena G. , Wolf Sharon G. , Yates John R. , Pypaert Marc , Horwich Arthur L.
Published: October 2006

In a newly isolated temperature-sensitive lethal
Escherichia coli
mutant affecting the chaperonin GroEL, we observed wholesale aggregation of newly translated proteins. After temperature shift, transcription, translation, and growth slowed over two to three generations, accompanied by filamentation and accretion (in ≈2% of cells) of paracrystalline arrays containing mutant chaperonin complex. A biochemically isolated inclusion body fraction contained the collective of abundant proteins of the bacterial cytoplasm as determined by SDS/PAGE and proteolysis/MS analyses. Pulse–chase experiments revealed that newly made proteins, but not preexistent ones, were recruited to this insoluble fraction. Although aggregation of “stringent” GroEL/GroES-dependent substrates may secondarily produce an “avalanche” of aggregation, the observations raise the possibility, supported by
in vitro
refolding experiments, that the widespread aggregation reflects that GroEL function supports the proper folding of a majority of newly translated polypeptides, not just the limited number indicated by interaction studies and
in vitro
experiments.
Late Archean rise of aerobic microbial ecosystems
Authors: Eigenbrode Jennifer L. , Freeman Katherine H.
Published: October 2006

We report the
13
C content of preserved organic carbon for a 150 million-year section of late Archean shallow and deepwater sediments of the Hamersley Province in Western Australia. We find a
13
C enrichment of ≈10‰ in organic carbon of post-2.7-billion-year-old shallow-water carbonate rocks relative to deepwater sediments. The shallow-water organic-carbon
13
C content has a 29‰ range in values (−57 to −28‰), and it contrasts with the less variable but strongly
13
C-depleted (−40 to −45‰) organic carbon in deepwater sediments. The
13
C enrichment likely represents microbial habitats not as strongly influenced by assimilation of methane or other
13
C-depleted substrates. We propose that continued oxidation of shallow settings favored the expansion of aerobic ecosystems and respiring organisms, and, as a result, isotopic signatures of preserved organic carbon in shallow settings approached that of photosynthetic biomass. Facies analysis of published carbon-isotopic records indicates that the Hamersley shallow-water signal may be representative of a late Archean global signature and that it preceded a similar, but delayed,
13
C enrichment of deepwater deposits. The data suggest that a global-scale expansion of oxygenated habitats accompanied the progression away from anaerobic ecosystems toward respiring microbial communities fueled by oxygenic photosynthesis before the oxygenation of the atmosphere after 2.45 billion years ago.