bluuebunny/crossref_metadata_2025 huggingface dataset:
Time dependent current in a nonstationary environment: A microscopic approach
Authors: Bhattacharya Satyabrata , Banik Suman Kumar , Chattopadhyay Sudip , Chaudhuri Jyotipratim Ray
Published: June 2008

Based on a microscopic system reservoir model, where the associated bath is not in thermal equilibrium, we simulate the nonstationary Langevin dynamics and obtain the generalized nonstationary fluctuation dissipation relation (FDR) which asymptotically reduces to the traditional form. Our Langevin dynamics incorporates non-Markovian process also, the origin of which lies in the decaying term of the nonstationary FDR. We then follow the stochastic dynamics of the Langevin particle based on the Fokker–Planck–Smoluchowski description in ratchet potential to obtain the steady and time dependent current in an analytic form. We also examine the influence of initial excitation and subsequent relaxation of bath modes on the transport of the Langevin particle to show that the nonequilibrium nature of the bath leads to both strong nonexponential dynamics as well as nonstationary current.
Photocarrier radiometric and ellipsometric characterization of ion-implanted silicon wafers
Authors: Liu Xianming , Li Bincheng , Zhang Xiren
Published: June 2008

The photocarrier radiometry (PCR) responses of heavily implanted silicon wafers (As+ ion 1×1013–1×1016cm−2) were reported. The experimental dependence of the PCR amplitude on the implant dose was in good agreement with the theoretical prediction calculated with a three-layer PCR model, in which the implanted silicon wafer was assumed to be consisted of an amorphous, a polycrystalline, and a single-crystalline Si layer. The structural, optical, and transport properties of all layers used in the calculations were determined experimentally with spectroscopic ellipsometry (SE), spectrophotometry, and laterally resolved modulated free-carrier absorption to minimize the uncertainties of the theoretical calculations. The dose dependence of the PCR amplitude showed a nonmonotonicity at high dose implantation, as confirmed by the SE measurements.
Grain boundary effects in the granular high-Tc superconductor RuSr2Gd1.4Ce0.6Cu2O10+δ
Authors: Lv Z. M. , Wu H. Y. , Li M. , Zhang J. L. , Wei Z. , Cao L. Z. , Ruan K. Q. , Ni M. Y.
Published: June 2008

We studied the electric transport property of four granular samples RuSr2Gd1.4Ce0.6Cu2O10+δ in different annealing conditions and the results show that the annealing processes gradually destroy the bulk superconductivity with the increase of annealing temperature. However, based on the thermopower and ac susceptibility measurements, the intragranular superconductivity in this Ru-based cuprate is robust as in the other high-Tc superconductors, but the bulk superconductivity is so fragile due to the grain boundary effects. The vanish of bulk superconductivity possibly results from the breaking down of the weak Josephson coupling between grains, as the concentration of oxygens at the grain boundaries decreases during the annealing.
Substrate characteristics beneath self-aligned carbon-nanotube forests
Authors: Dai Xiujuan Jane , Skourtis Chris
Published: June 2008

The catalyst has been examined before and after heating as well as after forest removal. This has revealed the importance of FeO and an additional role for a SiO2 buffer layer in the production of higher-quality faster-growing carbon-nanotube (CNT) forests. Our results, together with the literature, show that oxidation during heating (even when an inert gas is used) breaks up the Fe layer into small Fe2O3 islands. A suitable SiO2 buffer layer (either deposited or formed during the process) acts to inhibit Fe2O3 reduction past FeO, even in the presence of hydrogen from catalytic breakdown of the hydrocarbon during CNT growth. It is suggested that FeO is a more active catalyst than Fe and is more strongly bound to the surface. The interaction appears crucial for faster-growing, self-aligned forests and also for avoiding tip growth, disoriented layers, and included metal particles, which would be toxic in biomedical applications.
Spin-orbit coupling in an In0.52Ga0.48As quantum well with two populated subbands
Authors: Simmonds P. J. , Holmes S. N. , Beere H. E. , Ritchie D. A.
Published: June 2008

Structural inversion asymmetry controls the magnitude of Rashba spin-orbit coupling in the electron energy spectrum of a narrow band gap semiconductor. We investigate this effect for a series of two-dimensional electron gases in In0.52Ga0.48As quantum wells, surrounded by In0.52Al0.48As barriers, where either one or two electric subbands are populated. Structural inversion asymmetry does not exist at low carrier density while at higher carrier densities (above (4–5)×1011cm−2), a finite spin splitting is observed. The spin orbit coupling coefficients (α) are determined from the power spectrum of the oscillatory magnetoresistance, although this is complicated by magnetointersubband scattering in the region where two subbands are occupied. In the lowest subband, α1≈(0.6–1.0)×10−11eVm over a range of (4–9)×1011cm−2 total carrier density. In the second subband, α2≈2.2×10−11eVm, and this reduces with increasing carrier density. The spin-orbit coupling effect disappears at high carrier density although a strong structural inversion asymmetry still exists. We discuss these results with the consequences for spintronic devices operating on the principle of charge density dependent or electric field dependent spin manipulation in narrow band gap semiconductors.
Higher-order resonant modes in a photonic heterostructure nanocavity
Authors: Takahashi Yasushi , Tanaka Yoshinori , Hagino Hiroyuki , Asano Takashi , Noda Susumu
Published: June 2008

We investigated the optical characteristics of higher-order resonant modes for a heterostructure nanocavity formed in a two-dimensional photonic-crystal silicon slab. Two kinds of resonant modes were observed, the nanocavity modes and the Fabry–Pérot modes. High quality factors of more than 1.0×106 were obtained not only for the nanocavity mode but also for the Fabry–Pérot modes.
A density functional theory study of shake-up satellites in photoemission of carbon fullerenes and nanotubes
Authors: Gao Bin , Wu ZiYu , Luo Yi
Published: June 2008

Carbon 1s shake-up spectra of fullerenes C60, C70, and C82 and single-walled carbon nanotubes (SWCNTs) of (5,5), (6,5), and (7,6) have been investigated by using equivalent core hole Kohn–Sham density functional theory approach, in which only one-electron transition between molecular orbitals within core-hole potential is considered. The calculated spectra are generally in good agreement with results of equivalent core-hole time-dependent density functional theory calculations and available experiments, and reliable assignments for the complicated shake-up spectra of such large systems are provided. Calculations have also been performed for endohedral metallofullerene Gd@C82 to demonstrate the possible use of shake-up processes to identify the charge transfer between the metal ion and the carbon cage. It is found that the exciton binding energy of all systems under investigation is around 0.5eV.
Fluorescence lifetime of Mn-doped ZnSe quantum dots with size dependence
Authors: Gan Chenli , Zhang Yanpeng , Battaglia David , Peng Xiaogang , Xiao Min
Published: June 2008

Radiative lifetimes of high quality Mn:ZnSe nanocrystals synthesized by nucleation-doping method are experimentally measured at wavelength near 580nm. The slow decay rate in millisecond time scale is identified as the radiative decay from the T14 metastable excited state of Mn2+ ions embedded in the ZnSe nanocrystals. Also, two fast decay components are measured at this wavelength with much lower intensities, which can be attributed to the emission tails from the host ZnSe nanocrystals and from the surface-trap states or the self-activated luminescence due to Mn ion pairs, respectively. Size dependences of the radiative decay rates for the Mn:ZnSe samples are measured.
Ultrafast reset time of superconducting single photon detectors
Authors: Tarkhov M. , Claudon J. , Poizat J. Ph. , Korneev A. , Divochiy A. , Minaeva O. , Seleznev V. , Kaurova N. , Voronov B. , Semenov A. V. , Gol’tsman G.
Published: June 2008

We have measured the ultrafast reset time of NbN superconducting single photon detectors (SSPDs) based on a design consisting of N parallel superconducting stripes. Compared to a standard SSPD of identical active area, the parallel SSPD displays a similar detection efficiency and a kinetic inductance, which is divided by N2. For N=12, the duration of the voltage detection pulse is reduced by nearly two orders of magnitude down to 200ps. The timing jitter associated with the rising front is only 16ps. These results open a way to efficient detectors with ultrahigh counting rate exceeding 1 GHz.
Simple fabrication technique of distributed-feedback polymer laser by direct photonanoimprint lithography
Authors: Yamashita K. , Arimatsu M. , Takayama M. , Oe K. , Yanagi H.
Published: June 2008

This paper describes a fabrication technique of polymeric distributed-feedback lasers using the photonanoimprint lithography. In devices with a grating structure, which was imprinted directly onto the active layer surface in vacuum, single-mode laser oscillations were easily obtained. The emission color of the distributed-feedback laser can be controlled only by changing doping material and grating period of the master mold. It was demonstrated that the nanoimprint lithography would be a key technology for development of a multicolor light source.
Cold microplasma plume produced by a compact and flexible generator at atmospheric pressure
Authors: Ni T. L. , Ding F. , Zhu X. D. , Wen X. H. , Zhou H. Y.
Published: June 2008

In this letter, we report a cold microplasma generator at atmospheric pressure excited at 1kHz in a pin to hole-electrode configuration by using soft materials partly. A nitrogen plasma plume with a length of more than 5cm can be produced at low electrical power of 0.7W without high feed gas pressure. The generator exhibits a compact structure with flexible property, which is suitable for treating thermally sensitive materials and biomedical materials, especially for delicate objects in an irregular confined space. Optical emission spectroscopy is used to spatially identify excited species in plasma plume.
Nanoscale deformation in TiC∕a-C multilayered nanocomposite coatings
Authors: Chen C. Q. , Pei Y. T. , Shaha K. P. , De Hosson J. Th. M.
Published: June 2008

Nanoscale deformation in TiC∕a-C nanocomposite coatings is revealed by combined nanoindentation and high resolution cross-sectional transmission electron microscopy. A process characterized by rearrangement of TiC nanocrystallites and the displacement of a-C matrix is found to dominate the deformation mechanism at length scales ranging from tens of nanometers down to 1nm and contributes to toughening of the nanocomposite coatings by delocalizing local plastic deformations.
Time dependent degradation of photovoltaic modules by ultraviolet light
Authors: Zimmermann Claus G.
Published: June 2008

For high efficiency silicone encapsulated solar modules for concentrator photovoltaic systems or space applications, the question of performance degradation due to long term exposure to ultraviolet (UV) light is addressed. The transparent silicones DC93-500 and Elastosil S690 and S695 were subjected to a time and wavelength resolved UV test with a total accumulated dose of 10 000 equivalent sun hours. Based on a model for the kinetics of photodegradation, it is shown that the measured decrease in transmittance translates into a universal logarithmic time dependence for the module short circuit current. The UV related performance impact over 15years under the AM0 spectrum in space and the terrestrial AM1.5 spectrum with 500× concentration is quantified.
Study of in-plane orientation of epitaxial AlN films grown on (111) SrTiO3
Authors: Yao Z. Q. , Fan X. , He B. , Zhang W. J. , Bello I. , Lee S. T. , Meng X. M.
Published: June 2008

Substrate temperature and chemical etching were demonstrated to be dominant factors in determining the in-plane orientation of AlN films grown epitaxially on SrTiO3 (STO) (111) substrates by magnetron sputtering. Single-domain epitaxial AlN films were grown at moderate temperatures of 270–370°C with a sharp interface and orientation relationship of [21¯1¯0]AlN∥[01¯1]STO and (0002)AlN∥(111)STO. At temperature above 470°C, an additional 30° in-plane-rotated AlN domain appeared, and increased in percentage with increasing temperature. A model based on the reconstruction of STO (111) surfaces from (1×1) to (3×3)R30° was proposed to account for the formation of this new domain.
Bending-stress-driven phase transitions in pentacene thin films for flexible organic field-effect transistors
Authors: Yang Chanwoo , Yoon Jinhwan , Kim Se Hyun , Hong Kipyo , Chung Dae Sung , Heo Kyuyoung , Park Chan Eon , Ree Moonhor
Published: June 2008

The effects of bending strain on the structure and electrical characteristics of pentacene films in flexible devices were investigated. It was found that the volume fraction of bulk phase in the pentacene film increases from 10.7% to 27.7% under 1.1% of tensile strain but decreases to 3.5% under 1.0% of compressive strain. These bending-stress-driven phase transitions between the bulk phase and the thin-film phase in the pentacene film resulted in the changes in field-effect mobility, and were driven by the differences between the in-plane dimensions of the crystal unit cells of the two phases to reduce the external bending stress.
Pure-tin microdroplets irradiated with double laser pulses for efficient and minimum-mass extreme-ultraviolet light source production
Authors: Fujioka Shinsuke , Shimomura Masashi , Shimada Yoshinori , Maeda Shinsuke , Sakaguchi Hirokazu , Nakai Yuki , Aota Tatsuya , Nishimura Hiroaki , Ozaki Norimasa , Sunahara Atsushi , Nishihara Katsunobu , Miyanaga Noriaki , Izawa Yasukazu , Mima Kunioki
Published: June 2008

Laser-driven expansion of pure-tin microdroplets was demonstrated to produce an efficient and low-debris extreme-ultraviolet (EUV) light source. The pre-expansion is indispensable for resolving the considerable mismatch between the optimal laser spot diameter (∼300μm) and the diameter (∼20μm) of microdroplets containing the minimum-mass Sn fuel for generating the required EUV radiant energy (∼10mJ/pulse). Explosive expansion of microdroplets was attained by using a laser prepulse, whose intensity was at least 3×1011W∕cm2. The expanded microdroplet was irradiated with a CO2 laser pulse to generate EUV light. A combination of low density and long-scale length of the expanded microdroplet leads to a higher EUV energy conversion efficiency (4%) than that (2.5%) obtained from planar Sn targets irradiated by a single CO2 laser pulse. This scheme can be used to produce a practical EUV light source system.
ZnO quasibicrystals formed by thermal annealing
Authors: Yan Zijie , Zhu Kan , Chen Wan-Ping
Published: June 2008

Atmospheric annealing could melt the nanorods with diameters of ∼10nm at ∼600°C, and completely change them into jointed grains at 610°C. Most of the jointed grains are quasibicrystals with nearly symmetric morphologies but twinning free structures, much different from the commonly observed ZnO twinning crystals. The quasibicrystals would also be formed when annealing ZnO nanoparticles, which may be a common thermal behavior of ZnO low dimensional nanostructures and should be considered when preparing ZnO nanoscale devices and ceramics.
Preparation and Surface Modification of Poly(acrylonitrile-co-acrylic acid) Electrospun Nanofibrous Membranes
Authors: Che Ai-Fu , Huang Xiao-Jun , Wang Zhen-Gang , Xu Zhi-Kang
Published: June 2008

Poly(acrylonitrile-co-acrylic acid) (PANCAA) was synthesized and fabricated into nanofibrous membranes by an electrospinning technique. Scanning electron microscopy revealed that membranes composed of uniformly thin and smooth nanofibres were obtained under optimized processing parameters. Surface modification with chitosan on these nanofibrous membranes was accomplished by a coupling reaction between the carboxylic groups of PANCAA and the primary amino groups of chitosan. Fluorescent labelling, weight measurement, FT-IR/ATR spectroscopy, and X-ray photoelectron spectroscopy (XPS) were used to confirm the modification process and determine the immobilization degree of chitosan. Platelet adhesion experiments were further carried out to evaluate the hemocompatibility of the studied nanofibrous membranes. Preliminary results indicated that the immobilization of chitosan on the PANCAA nanofibrous membranes was favourable for platelet adhesion.
Direct-Current Methods for the Estimation of Corrosion Rates in Aqueous Timber Preservatives
Authors: Kear Gareth , Wú Hãi-Zhèn , Jones Mark S. , Walsh Frank C.
Published: June 2008

As part of a program to assess the durability of metals in timber preservatives, direct-current electrochemical analyses have been carried out using mild steel, American Iron and Steel Institute 316 stainless steel and galvanized steel immersed in three liquid timber preservatives containing dissolved copper as a biocide. The aqueous preservatives examined were copper–chrome–arsenate (Cu–Cr–As), copper azole (Cu-Tebucanazole), and alkaline copper quaternary (Cu-didecylthyl ammonium chloride). These preservatives are known commercially as CCA, CuAz, and ACQ-B, respectively. Despite previous assumptions, neither polarization resistance- nor Tafel slope-based analyses are suitable methodologies for the universal derivation of absolute values of corrosion rate. An alternative approach is suggested based on anodic linear sweep voltammetry. The results show that the hot-dipped zinc coating was found to be the most active material in terms of the polarization behaviour, especially within the CCA-based electrolyte. There is a strong qualitative correlation between the electrochemical data and corrosion rates estimated using the American Wood Preservers’ Association E-17 standard test for aqueous treatment solutions.
How to Analyze Ionic Liquid Anions? Investigation into the Application of Suppressed and Non-Suppressed Ion Chromatography
Authors: Stepnowski Piotr , Markowska Aleksandra
Published: June 2008

In the present study, two reliable and accurate methods have been developed for the quantitative and qualitative determination of ionic liquid anions based on suppressed and non-suppressed ion chromatography. They were applied to the separation and analysis of chloride, bromide, p-tosylate, tetrafluoroborate, hexafluorophosphate, dicyanamide, and bis(trifluoromethanesulfonyl)imide. In the non-suppressed mode, the influence of the concentration of phthalic acid, acetonitrile, and pH of the mobile phase on the retention and separation of analytes were investigated; 8 mM solution of phthalic acid with 20% v/v of acetonitrile (pH = 4) can be regarded as the optimal mobile phase in this separation mode. In the suppressed mode, various compositions of a carbonate/bicarbonate buffer solution with and without acetonitrile were also assessed; 3.2 mM Na2CO3/1 mM NaHCO3 and 25% acetonitrile were found to act as the optimal mobile phase. Under the analytical conditions developed, both methods provided very good separation and symmetrical peak shapes of all compounds within the reasonable time-frame of 30 min. The analytical performance parameters of both methods were good; however sensitivity will be further improved in future studies. Moreover, the suppressed separation mode was successfully applied to the analysis of tetrafluoroborate in a soil aquifer.
Synthesis of α-Aminoalkyl Phosphonate Derivatives of Resveratrol as Potential Antitumour Agents
Authors: Shi Lei , Huang Xian-Feng , Zhu Zhen-Wei , Li Huan-Qiu , Xue Jia-Yu , Zhu Hai-Liang , Liu Chang-Hong
Published: June 2008

Several α-aminoalkyl phosphonate derivatives of resveratrol were first prepared by partial synthesis from resveratrol. Antitumour activities of the synthesized compounds were determined against a human nasopharyngeal epidermoid tumour cell line KB and a human normal cell line L02 in vitro. The results indicated that these compounds showed good cytotoxic activity against KB but weak cytotoxic activity against L02. Compounds 5c and 5d showed significant cytotoxic activity against KB, with median inhibition concentration (IC50) values of 0.4 μM and 0.9 μM, respectively. On the basis of the biological results, the structure–activity relationship is discussed concisely. The potent antitumour activities shown by 5c and 5d make these resveratrol phosphonate derivatives of great interest for further investigations.
Convenient Synthesis and Purification of [Bu4N]2[Ru(4-carboxy-4-carboxylate-2,2′-bipyridine)2(NCS)2]: a Landmark DSC Dye
Authors: Rawling Tristan , Buchholz Florian , McDonagh Andrew M.
Published: June 2008

We present here a convenient synthesis of the landmark dye-sensitized solar cell dye [Bu4N]2[Ru(4-carboxy-4-carboxylate-2,2′-bipyridine)2(NCS)2] (N719). Key to this synthetic procedure is the protection of the carboxyl functionalities with iso-butyl ester groups. This strategy allows the use of silica chromatography to remove the less efficient S-bound isomers and significantly reduces the time and difficulty of the synthesis.
Synthesis and In-Vivo Evaluation of [11C]p-PVP-MEMA as a PET Radioligand for Imaging Nicotinic Receptors
Authors: Dollé Frédéric , Langle Sandrine , Roger Gaëlle , Fulton Roger R. , Lagnel-de Bruin Béatrice , Henderson David J. , Hinnen Françoise , Paine Taliesha , Coster Mark J. , Valette Heric , Bottlaender Michel , Kassiou Michael
Published: June 2008

Within the class of (4-pyridinyl)vinylpyridines developed by Abbott laboratories as potent neuronal nicotinic acetylcholine receptor ligands, p-PVP-MEMA ({(R)-2-[6-chloro-5-((E)-2-pyridin-4-ylvinyl)pyridin-3-yloxy]-1-methylethyl}methylamine) is the lead compound of a novel series that do not display the traditional nicotinic-like pyrrole-ring but still possessing high subnanomolar affinity (Ki 0.077 nm—displacement of [3H](–)cytisine from whole rat brain synaptic membranes). In the present study, p-PVP-MEMA and its nor-derivative ({(R)-2-[6-chloro-5-((E)-2-pyridin-4-ylvinyl)pyridin-3-yloxy]-1-methylethyl}methylamine) as precursor for labelling with the short-lived positron-emitter carbon-11 (T1/2 20.4 min) were synthesized in 10 chemical steps from 2-hydroxy-5-nitropyridine and Boc-d-alanine. N-Alkylation of nor-p-PVP-MEMA with [11C]methyl iodide afforded [11C]p-PVP-MEMA (>98% radiochemically pure, specific activity of 86.4 GBq μmol–1) in 2% (non-decay corrected and non-optimized) radiochemical yield, in 34 min (including HPLC purification and formulation). Preliminary positron emission tomography (PET) results obtained in a Papio hamadryas baboon showed that [11C]p-PVP-MEMA is not a suitable PET-radioligand.
Solvent-Induced Chirality in the Hydroboration of Ketones
Authors: Baldauf Christoph , Dickerhof Nina , Hüttenhain Stefan H. , Kern Stefanie , Krummrich Nancy , Kruse Friedrich , May Janine , Meister Melanie , Müller Kristina , Rauer Sabine , Salwig Isabelle , Scharfenecker Nico , Spitznagel Birgit
Published: June 2008

The influence of the systematic variation of chiral solvents and of diverse Lewis acids on the asymmetric induction of the hydroboration of acetophenone has been studied. None of the solvents used could surpass lactic acid methyl ester, and for the Lewis acids, ZnCl2 and ZnI2 showed positive effects on the enantiomeric excess (ee) and the conversion. Also, the effect of the substrate structure was investigated by comparing the conversion and ee of eight different ketones. Apparently, the achievable asymmetric induction was higher with aromatic ketones.
Environmentally Friendly Organic Synthesis Using Bismuth Compounds. Bismuth Trifluoromethanesulfonate-Catalyzed Allylation of Dioxolanes
Authors: Spafford Matthew J. , Christensen James E. , Huddle Matthew G. , Lacey Joshua R. , Mohan Ram S.
Published: June 2008

A bismuth trifluoromethanesulfonate (triflate)-catalyzed (2.0 mol-%) multicomponent reaction involving the allylation of dioxolanes followed by in situ derivatization with anhydrides to generate highly functionalized esters has been developed under solvent-free conditions. Most reagents used to date for allylation of dioxolanes are highly corrosive and are often required in stoichiometric amounts. In contrast, the use of a relatively non-toxic and non-corrosive bismuth(iii)-based catalyst makes this methodology especially attractive for scale-up.
Regioselective 1,3-Dipolar Cycloaddition Reactions of 4-Methylene-2-oxazolidinones with Benzonitrile Oxide
Authors: Newton Rebecca , Savage G. Paul
Published: June 2008

Substituted 4-methylene-2-oxazolidinones were prepared in two steps by cyclizing O-propargyl carbamates, which in turn were prepared from propargyl alcohols and phenyl isocyanate. The 4-methylene-2-oxazolidinones underwent a 1,3-dipolar cycloaddition reaction with benzonitrile oxide to give the corresponding spiro heterocycles. Where the substitution pattern on the oxazolidinone engendered facial asymmetry, the cycloadditon reaction proceeded with 5:1 selectivity for the less hindered face of the dipolarophile.
Systematics and natural history of the Australian genus Metoligotoma Davis (Embioptera:Australembiidae)
Authors: Miller Kelly B. , Edgerly Janice S.
Published: June 2008

Members of the order Embioptera (webspinners) are among the least known groups of insects, but have a relatively well-developed, phylogenetically unique, and biologically interesting fauna in portions of Australia. The genus Metoligotoma Davis (Australembiidae) is a well-defined group occurring in south-eastern Australia where species are especially distinctive in that they occupy extremely small endemic areas. Additionally, both males and females are wingless, thereby severely limiting opportunities for dispersal. Hypotheses of relationships among these species are not available in a modern phylogenetic context and little is known of their natural history and biogeography. A new species of Embioptera, Metoligotoma rooksi Miller & Edgerly, sp. nov. is described from a male specimen from near Bombala, New South Wales, Australia. A phylogenetic analysis of the genus (including 10 of the 16 known species of Metoligotoma) was conducted using morphological and molecular data from 16S, 28S, COI+COII and H3. The new species is most closely related to M. begae, from which it is geographically separated by the high coastal mountains. The natural history of the genus is reviewed, including descriptions of the silk galleries, habitats and eggs. The biogeography of the genus is examined in light of the phylogeny. No obvious vicariance model supports the current distribution and small endemic areas exhibited by members of the genus. Instead, it is speculated that periodic, rare dispersal events from north to south, and inland over the coastal mountains, resulted in the current distribution of the species. This is the first modern phylogenetic analysis of the Australembiidae, and the first extensive analysis of any group of Embioptera to include molecular data.
Molecular phylogeny and historical biogeography of the cosmopolitan parasitic wasp subfamily Doryctinae (Hymenoptera:Braconidae)
Authors: Zaldivar-Riverón Alejandro , Belokobylskij Sergey A. , León-Regagnon Virginia , Briceño-G. Rosa , Quicke Donald L. J.
Published: June 2008

The phylogenetic relationships among representatives of 64 genera of the cosmopolitan parasitic wasps of the subfamily Doryctinae were investigated based on nuclear 28S ribosomal (r) DNA (~650 bp of the D2–3 region) and cytochrome c oxidase I (COI) mitochondrial (mt) DNA (603 bp) sequence data. The molecular dating of selected clades and the biogeography of the subfamily were also inferred. The partitioned Bayesian analyses did not recover a monophyletic Doryctinae, though the relationships involved were only weakly supported. Strong evidence was found for rejecting the monophylies of both Doryctes Haliday, 1836 and Spathius Nees, 1818. Our results also support the recognition of the Rhaconotini as a valid tribe. A dispersal–vicariance analysis showed a strong geographical signal for the taxa included, with molecular dating estimates for the origin of Doryctinae and its subsequent radiation both occurring during the late Paleocene–early Eocene. The divergence time estimates suggest that diversification in the subfamily could have in part occurred as a result of continental break-up events that took place in the southern hemisphere, though more recent dispersal events account for the current distribution of several widespread taxa.
Social organisation and den utilisation of painted spiny lobster (Panulirus versicolor) on a coral reef at Northwest Island, Australia
Authors: Frisch Ashley J.
Published: June 2008

The social ecology of spiny lobsters (Palinuridae) is poorly known but important for understanding their evolution and interpreting the behavioural basis of their catchability. Visual surveys of 60 ha of coral reef at North-west Island revealed 34 shelters (dens) occupied by painted spiny lobster (Panulirus versicolor). Eighty-five lobsters were tagged with highly visible external tags and moult-resistant internal tags. Most dens contained only a single lobster, but the distribution of lobsters was aggregated; most lobsters occurred in groups of 2–7 individuals. Daily visits to each den revealed that lobsters moved frequently to and from nearby dens and the composition of groups changed often. However, groups were not random mixtures of individuals since two male lobsters never occupied the same den simultaneously. Surprisingly, there was no significant relationship between body size and male social status (number of co-habiting females). Experimental translocation of single male and female lobsters to occupied dens did not result in eviction, regardless of body size, indicating that subtle mechanisms drive this social system. Most lobsters congregated in the same 10–15 dens. This renders P. versicolor easy to find and vulnerable to over-exploitation, but suggests that marine reserves may be useful for protecting this highly sought-after species.
Environmental predictors of macroinvertebrate communities in coastal wetlands of southern Brazil
Authors: Stenert Cristina , Bacca Roberta C. , Mostardeiro Carolina C. , Maltchik Leonardo
Published: June 2008

The rapid degradation of wetlands worldwide accentuates the urgent need for ecological data to help manage and protect the threatened biodiversity in the remaining often-fragmented wetlands. In the Neotropics where fragmentation is common, environmental factors structuring aquatic macroinvertebrate communities are poorly known. We tested the hypothesis that physical features, such as wetland area, habitat diversity, water depth and temperature, and water and sediment chemistry are important correlates with richness, density and composition of wetland macroinvertebrate assemblages in Brazil. If so, do these correlations differ between summer and winter? A total of 16 895 individuals across 61 families were collected. Richness was positively associated with habitat diversity and water depth and negatively associated with water temperature. Macroinvertebrate density was negatively associated with water depth, and positively correlated with habitat diversity, percentage of sediment organic matter and water conductivity. Macroinvertebrate composition was associated mainly with wetland area and habitat diversity in the wetlands studied; these relationships persisted in both seasons. Our data illustrate environmental factors that potentially structure and maintain aquatic macroinvertebrate biodiversity in southern Brazil wetlands, and should be managed because 90% of these ecosystems have already been lost as a result of human activities.
Modelling wave-induced disturbance in highly biodiverse marine macroalgal communities: support for the intermediate disturbance hypothesis
Authors: England Phillip R. , Phillips Julia , Waring Jason R. , Symonds Graham , Babcock Russell
Published: June 2008

As biodiversity declines globally, it is becoming increasingly important to understand the processes that create and maintain biodiverse communities. We examined whether the extraordinarily high species diversity of macroalgal communities in shallow coastal waters off south-west Western Australia is related to wave-induced physical disturbance. We used the numerical wave model SWAN to estimate the hydrodynamic forces generated by waves in bathymetrically complex coastal reefs. Oscillatory water motion at the seabed during extreme wave events was used as an index of physical disturbance in macroalgal communities. There was a significant curvilinear relationship between species diversity and disturbance index, consistent with the intermediate disturbance hypothesis (IDH). Diversity was lower at exposed offshore sites where disturbance is likely to be highest and at very sheltered sites with the least disturbance. Our results match those from some other highly diverse habitats, including rainforests, grasslands and coral reefs in which patchy, stochastic disturbance regimes have been hypothesised to prevent the development of homogeneous climax communities, promoting spatiotemporal heterogeneity and increasing total system diversity. Our results represent important evidence in support of a role for the IDH in driving diversity in marine plant communities.
Reciprocal patterns of methylation of H3K36 and H3K27 on proximal vs. distal IgV
H
genes are modulated by IL-7 and Pax5
Authors: Xu Cheng-Ran , Schaffer Lana , Head Steven R. , Feeney Ann J.
Published: June 2008

The usage of >100 functional murine Ig heavy chain V
H
genes, when rearranged to D
H
J
H
genes, generates a diverse antibody repertoire. The V
H
locus encompasses 2.5 Mb, and rearrangement of V
H
genes in the D
H
-distal half of the locus are controlled very differently from the V
H
genes in the proximal end of the locus. The rearrangement of distal but not proximal V
H
genes is impaired in mice deficient in the cytokine IL-7 or its receptor, in the transcription factor Pax5, or in Ezh2, a histone methyltransferase for Lys-27 of histone H3 (H3K27). The relative role of IL-7, Pax5, and Ezh2 in regulating distal vs. proximal V
H
rearrangement is not clear. Here, we show by ChIP and ChIP-on-chip that the active histone modification H3K36me2 is most highly associated with distal V
H
segments and the repressive histone modification H3K27me3 is exclusively present on proximal V
H
segments. We observed an absence of H3K27me3 in fetal pro-B cells, which predominantly rearrange proximal V
H
genes. Absence of IL-7 signaling reduces H3K36me2, and overexpression of IL-7 increases H3K36me2. In contrast, the major effect of the absence of Pax5 is the reduction in H3K27me3. Our data indicate that the cytokine IL-7 and the transcription factor Pax5 influence the rearrangement of the two regions of the V
H
locus by differentially modulating two reciprocal histone modifications during B lymphocyte development.
Cyclic adenosine monophosphate differentiated β-endorphin neurons promote immune function and prevent prostate cancer growth
Authors: Sarkar Dipak K. , Boyadjieva Nadka I. , Chen Cui Ping , Ortigüela María , Reuhl Kenneth , Clement E. Michael , Kuhn Peter , Marano Jason
Published: June 2008

Pituitary adenylate cyclase-activating peptide (PACAP), a cAMP-activating agent, is highly expressed in the hypothalamus during the period when many neuroendocrine cells become differentiated from the neural stem cells (NSCs). Activation of the cAMP system in rat hypothalamic NSCs differentiated these cells into β-endorphin (BEP)-producing neurons in culture. When these
in vitro
differentiated neurons were transplanted into the paraventricular nucleus (PVN) of the hypothalamus of an adult rat, they integrated well with the surrounding cells and produced BEP and its precursor gene product, proopiomelanocortin (POMC). Animals with BEP cell transplants demonstrated remarkable protection against carcinogen induction of prostate cancer. Unlike carcinogen-treated animals with control cell transplants, rats with BEP cell transplants showed rare development of glandular hyperplasia, prostatic intraepithelial neoplasia (PIN), or well differentiated adenocarcinoma with invasion after
N
-methyl-
N
-nitrosourea (MNU) and testosterone treatments. Rats with the BEP neuron transplants showed increased natural killer (NK) cell cytolytic function in the spleens and peripheral blood mononuclear cells (PBMCs), elevated levels of antiinflammatory cytokine IFN-γ, and decreased levels of inflammatory cytokine tumor necrosis factor-α (TNF-α) in plasma. These results identified a critical role for cAMP in the differentiation of BEP neurons and revealed a previously undescribed role of these neurons in combating the growth and progression of neoplastic conditions like prostate cancer, possibly by increasing the innate immune function and reducing the inflammatory milieu.
Evidence for fractional crystallization of wadsleyite and ringwoodite from olivine melts in chondrules entrained in shock-melt veins
Authors: Miyahara Masaaki , El Goresy Ahmed , Ohtani Eiji , Nagase Toshiro , Nishijima Masahiko , Vashaei Zahra , Ferroir Tristan , Gillet Philippe , Dubrovinsky Leonid , Simionovici Alexandre
Published: June 2008

Peace River is one of the few shocked members of the L-chondrites clan that contains both high-pressure polymorphs of olivine, ringwoodite and wadsleyite, in diverse textures and settings in fragments entrained in shock-melt veins. Among these settings are complete olivine porphyritic chondrules. We encountered few squeezed and flattened olivine porphyritic chondrules entrained in shock-melt veins of this meteorite with novel textures and composition. The former chemically unzoned (Fa
24–26
) olivine porphyritic crystals are heavily flattened and display a concentric intergrowth with Mg-rich wadsleyite of a very narrow compositional range (Fa
6
–Fa
10
) in the core. Wadsleyite core is surrounded by a Mg-poor and chemically stark zoned ringwoodite (Fa
28
–Fa
38
) belt. The wadsleyite–ringwoodite interface denotes a compositional gap of up to 32 mol % fayalite. A transmission electron microscopy study of focused ion beam slices in both regions indicates that the wadsleyite core and ringwoodite belt consist of granoblastic-like intergrowth of polygonal crystallites of both ringwoodite and wadsleyite, with wadsleyite crystallites dominating in the core and ringwoodite crystallites dominating in the belt. Texture and compositions of both high-pressure polymorphs are strongly suggestive of formation by a fractional crystallization of the olivine melt of a narrow composition (Fa
24–26
), starting with Mg-rich wadsleyite followed by the Mg-poor ringwoodite from a shock-induced melt of olivine composition (Fa
24–26
). Our findings could erase the possibility of the resulting unrealistic time scales of the high-pressure regime reported recently from other shocked L-6 chondrites.
In vivo
iron–sulfur cluster formation
Authors: Raulfs Estella C. , O'Carroll Ina P. , Dos Santos Patricia C. , Unciuleac Mihaela-Carmen , Dean Dennis R.
Published: June 2008

It has been proposed that iron–sulfur [Fe-S] clusters destined for the maturation of [Fe-S] proteins can be preassembled on a molecular scaffold designated IscU. In the present article, it is shown that production of the intact
Azotobacter vinelandii
[Fe-S] cluster biosynthetic machinery at levels exceeding the amount required for cellular maturation of [Fe-S] proteins results in the accumulation of: (
i
) apo-IscU, (
ii
) an oxygen-labile [2Fe-2S] cluster-loaded form of IscU, and (
iii
) IscU complexed with the S-delivery protein, IscS. It is suggested that these species represent different stages of the [Fe-S] cluster assembly process. Substitution of the IscU Asp
39
residue by Ala results in the
in vivo
trapping of a stoichiometric, noncovalent, nondissociating IscU–IscS complex that contains an oxygen-resistant [Fe-S] species. In aggregate, these results validate the scaffold hypothesis for [Fe-S] cluster assembly and indicate that
in vivo
[Fe-S] cluster formation is a dynamic process that involves the reversible interaction of IscU and IscS.
Sir2 mediates apoptosis through JNK-dependent pathways in
Drosophila
Authors: Griswold Anthony J. , Chang Karen T. , Runko Alexander P. , Knight Melanie A. , Min Kyung-Tai
Published: June 2008

Increased expression of the histone deacetylase
sir2
has been reported to extend the life span of diverse organisms including yeast,
Caenorhabditis elegans
, and
Drosophila melanogaster
. A small molecule activator of Sir2, resveratrol, has also been suggested to extend the fitness and survival of these simple model organisms as well as mice fed high calorie diets. However, other studies in yeast have shown that Sir2 itself may prevent life extension, and high expression levels of Sir2 can be toxic to yeast and mouse cells. This conflicting evidence highlights the importance of understanding the mechanisms by which Sir2 expression or activation affects survival of organisms. To investigate the downstream signaling pathways affected by Sir2 in
Drosophila
, we generated transgenic flies expressing
sir2
. Here, we show that overexpression of
sir2
in
Drosophila
promotes caspase-dependent but p53-independent apoptosis that is mediated by the JNK and FOXO signaling pathways. Furthermore, we find that a loss-of-function
sir2
mutant partially prevents apoptosis induced by UV irradiation in the eye. Together, these results suggest that Sir2 normally participates in the regulation of cell survival and death in
Drosophila
.
Sequence analysis of GerM and SpoVS, uncharacterized bacterial ‘sporulation’ proteins with widespread phylogenetic distribution
Authors: Rigden Daniel J. , Galperin Michael Y.
Published: June 2008

Sporulation in low-G+C gram-positive bacteria (Firmicutes) is an important survival mechanism that involves up to 150 genes, acting in a highly regulated manner. Many sporulation genes have close homologs in non-sporulating bacteria, including cyanobacteria, proteobacteria and spirochaetes, indicating that their products play a wider biological role. Most of them have been characterized as regulatory proteins or enzymes of peptidoglycan turnover; functions of others remain unknown but they are likely to have a general role in cell division and/or development. We have compiled a list of such widely conserved sporulation and germination proteins with poorly characterized functions, ranked them by the width of their phylogenetic distribution, and performed detailed sequence analysis and, where possible, structural modeling aimed at estimating their potential functions. Here we report the results of sequence analysis of Bacillus subtilis spore germination protein GerM, suggesting that it is a widespread cell development protein, whose function might involve binding to peptidoglycan. GerM consists of two tandem copies of a new domain (designated the GERMN domain) that forms phylum-specific fusions with two other newly described domains, GERMN-associated domains 1 and 2 (GMAD1 and GMAD2). Fold recognition reveals a β-propeller fold for GMAD1, while ab initio modeling suggests that GMAD2 adopts a fibronectin type III fold. SpoVS is predicted to adopt the AlbA archaeal chromatin protein fold, which suggests that it is a DNA-binding protein, most likely a novel transcriptional regulator.

Contact:  drigden@liverpool.ac.uk

Supplementary information:  Supplementary data are available at ftp://ftp.ncbi.nih.gov/pub/galperin/Sporulation.html
Dispersal of Munida gregaria (Decapoda: Galatheidae) larvae in Patagonian channels of southern Chile
Authors: León Roxana , Castro Leonardo R. , Cáceres Mario
Published: June 2008

León, R., Castro, L. R., and Cáceres, M. 2008. Dispersal of Munida gregaria (Decapoda: Galatheidae) larvae in Patagonian channels of southern Chile. – ICES Journal of Marine Science, 65: 1131–1143. The dispersal of Munida gregaria larvae in Chilean Patagonian channels was assessed in spring 2002 and 2003, and winter 2003. In winter 2003, zoea I was the most abundant stage in all channels and there were no larval stages older than zoea IV. In spring 2002 and 2003, there were six larval stages in all channels, and the greater abundance of older larvae suggested that reproduction takes place in winter and larval development in spring. Further, analysis of spatial distribution by stage revealed that early zoeae moved seawards. Generalized Additive Models analyses showed that most larval stages were temperature-dependent, and that the salinity range of the youngest zoea was wider than that of older larvae and post-larvae, coinciding with an ontogenetic distribution change from estuary to shelf. Residual flows determined with an acoustic Doppler current profiler revealed two layers of opposite flow: the shallowest layer moved seawards and the deeper layer onshore. The surface layer was wider in spring than in winter because of seasonal increase in fresh-water input. The dispersal pattern of M. gregaria consisted of an inner channel larval release in winter, followed by an along-channel larval drift and subsequent export to the shelf in spring. The mechanism by which juveniles return to the channels seemed to be associated with the onshore subsurface flow.
Buoyancy and vertical distribution of Norwegian coastal cod (Gadus morhua) eggs from different areas along the coast
Authors: Stenevik Erling Kåre , Sundby Svein , Agnalt Ann Lisbeth
Published: June 2008

Stenevik, E. K., Sundby, S., and Agnalt, A. L. 2008. Buoyancy and vertical distribution of Norwegian coastal cod (Gadus morhua) eggs from different areas along the coast. – ICES Journal of Marine Science, 65: 1198–1202. There are significant genetic differences in coastal cod (Gadus morhua) along the Norwegian coast, and in order to maintain these differences, there must be mechanisms that ensure local retention of eggs and larvae in the spawning areas. The buoyancy of eggs from four different areas along the Norwegian coast was measured using a density gradient column, and the results from modelling experiments showed that in three of the groups (Tysfjord, Helgeland, and Øygarden), the buoyancy in combination with local hydrography would place the eggs in subsurface waters where retention is greater than in surface waters.
Arabidopsis ELONGATED MITOCHONDRIA1 Is Required for Localization of DYNAMIN-RELATED PROTEIN3A to Mitochondrial Fission Sites
Authors: Arimura Shin-ichi , Fujimoto Masaru , Doniwa Yoko , Kadoya Naoki , Nakazono Mikio , Sakamoto Wataru , Tsutsumi Nobuhiro
Published: June 2008

Mitochondrial fission is achieved partially by the activity of self-assembling dynamin-related proteins (DRPs) in diverse organisms. Mitochondrial fission in Arabidopsis thaliana is mediated by DRP3A and DRP3B, but the other genes and molecular mechanisms involved have yet to be elucidated. To identify these genes, we screened and analyzed Arabidopsis mutants with longer and fewer mitochondria than those of the wild type. ELM1 was found to be responsible for the phenotype of elongated mitochondria. This phenotype was also observed in drp3a plants. EST and genomic sequences similar to ELM1 were found in seed plants but not in other eukaryotes. ELM1:green fluorescent protein (GFP) was found to surround mitochondria, and ELM1 interacts with both DPR3A and DRP3B. In the elm1 mutant, DRP3A:GFP was observed in the cytosol, whereas in wild-type Arabidopsis, DRP3A:GFP localized to the ends and constricted sites of mitochondria. These results collectively suggest that mitochondrial fission in Arabidopsis is mediated by the plant-specific factor ELM1, which is required for the relocalization of DRP3A (and possibly also DRP3B) from the cytosol to mitochondrial fission sites.