bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Growth Temperature on Structural and Magneto-Transport Properties of Co-Doped In2O3 Diluted Magnetic Semiconductors
Authors: Ghosh A , Gupta R K , Kahol P K , Ghosh K
Published: February 2009

Thin films of Co-doped In2O3 diluted magnetic semiconductor have been grown on c-plane sapphire single crystals using pulsed laser deposition technique. Different characterizations such as x-ray diffraction, atomic force microscopy, and magneto-transport have been carried out to study the effect of growth temperature on structural, electrical, and magneto-transport properties of these films. Crystalinity of the films increases with the growth temperature. The films grown at high temperature have preferred orientation along (222) direction, while films grown at low temperature behave more like to nanocrystaline. It is observed that electrical properties of the films strongly depend on growth temperature. The resistivity and magnetoresistance of the films decreases with increase in growth temperature. On the other hand, mobility of the films increases with increase in growth temperature. This could be due to improvement in crystalinity of the films.
A Trade Study for Waste Concepts to Minimize HLW Volume
Authors: Gombert Dirk , Carter Joe , Ebert Bill , Piet Steve , Trickel Tim , Vienna John
Published: February 2009

Advanced nuclear fuel reprocessing can partition wastes into groups of common chemistry. This enables new waste management strategies not possible with the plutonium, uranium extraction (PUREX) process alone. Combining all of the metallic fission products in an alloy and the balance as oxides in glass minimizes high level waste (HLW) volume. Implementing a waste management strategy using state-of-the-art combined waste forms and storage to allow radioactive decay and heat dissipation prior to placement in a repository makes it possible to place almost 10x the HLW equivalent of spent nuclear fuel (SNF) in the same repository space. However, using generic costs based on preliminary studies for waste stabilization facilities and separations modules, this analysis shows that combining the non-actinide wastes and using only one glass waste form is the most cost-effective.
Experimental and Atomistic Modelling Study of Ion Irradiation Damage in Thin Crystals of the TiO2 Polymorphs
Authors: Lumpkin Gregory R , Smith Katherine L , Blackford Mark G , Thomas Bronwyn S , Whittle Karl Rhys , Attard Darren J , Zaluzec Nestor J , Marks Nigel A
Published: February 2009

Thin crystals of rutile, brookite, and anatase were irradiated in-situ with 1.0 MeV Kr using the IVEM-TANDEM facility. Synthetic rutile and cassisterite (SnO2, rutile structure) remained crystalline up to 5 × 1015 ion cm-2 at 50 K. Natural brookite and anatase with low impurity levels became amorphous at 8.1 ± 1.8 × 1014 and 2.3 ± 0.2 × 1014 ions cm-2, respectively, at 50 K. Irradiation at higher temperature revealed Tc = 170 K for brookite and 242 K for anatase. Natural rutile with about 2 wt% impurities became amorphous at 9.4 ± 1.8 × 1014 ions cm-2 at 50 K and has a Tc = 207 K. The available data reveal both a structural effect in the polymorphs with low levels of chemical impurities and a chemical effect in natural rutile specimens containing up to about 1.7 wt% impurities.
Diffusion of 60Co, 137Cs and 152Eu in Opalinus Clay
Authors: García-Gutiérrez Miguel , Cormenzana José Luis , Missana Tiziana , Mingarro Manuel , Alonso Ursula
Published: February 2009

This study addresses the diffusion of representative sorbing elements, cobalt, cesium and europium in the Opalinus Clay (OPA). The methodology used here to determine diffusion coefficients is the ‘instantaneous planar source’ method. In this setup, a paper filter impregnated with tracer is introduced between two clay samples, avoiding contact between the tracer and the experimental vessels.
The apparent diffusion coefficients (Da) perpendicular to the bedding plane, obtained with this experimental method and fitting the experimental results with an analytical solution, were Da(Co) = (2.4-3.5)·10-14 m2/s, Da(Cs) = (5.9-8.0)·10-14 m2/s, and Da(Eu) = (1.0-2.1)·10-15 m2/s. With cobalt and cesium, classical in-diffusion experiments were also performed for comparison, and similar Da values were obtained but with a large dispersion.
To analyze the possible effects of the paper filter impregnated with the tracer on the determinations of Da with the analytical solution, one experiment was also analyzed using a detailed stochastic model of the setup. The good agreement between the two modeling approaches confirms the validity of this experimental setup and the analytical model fitting procedure.
In Situ Radiation Damage Studies of Ca3Zr2FeAlSiO12 and Ca3Hf2FeAlSiO12
Authors: Whittle Karl R , Blackford Mark , Lumpkin Gregory R , Smith Katherine L , Zaluzec Nestor J
Published: February 2009

Garnets, A3B2C3O12, are considered to be potential host phases for the immobilization of high-level nuclear waste as they can accommodate a number of elements of interest, including Zr, Ti and Fe. The naturally occurring garnet, kimzeyite, Ca3(Zr,Ti)2(Si,Al,Fe)3O12, can contain ˜30wt% Zr. An understanding of the radiation tolerance of these materials is crucial to their potential use in nuclear waste immobilization. In this study two synthetic analogues of kimzeyite of composition Ca3Zr2FeAlSiO12 and Ca3Hf2FeAlSiO12 were monitored in situ during irradiation with 1.0 MeV Kr ions using the intermediate voltage electron microscope-Tandem User Facility (IVEM) at Argonne National Laboratory. The structure of these materials was previously determined by neutron diffraction and 57Fe Mössbauer spectroscopy. Ca3Zr2FeAlSiO12 and Ca3Hf2FeAlSiO12 have very similar structural properties with cubic Ia3d symmetry, the only significant difference being the presence of Zr and Hf, respectively, on the 6 coordinated B sites.
Diffusion Behavior of Organic Carbon and Iodine in Low-heat Portland Cement Containing Fly Ash
Authors: Chida Taiji , Sugiyama Daisuke
Published: February 2009

The diffusion of radionuclides in cementitious materials used as an engineered barrier is an important parameter in the performance assessment of the sub-surface repository system used for low-level radioactive waste disposal in Japan. In particular, organic carbon-14 and iodine-129 would provide large contributions to the dose evaluation, because of their low ability to be adsorbed on cementitious materials. In this study, the diffusion of acetate and iodide in hardened cement pastes was examined by through-diffusion experiments. Low-heat Portland cement containing 30 wt% fly ash (FAC), which is a candidate cement material for the construction of the sub-surface repository, was prepared for the diffusion experiments. The effective diffusion coefficients, De, of the trace ions for hardened FAC cement pastes were estimated to be on the order of 10-13 m2 s-1 at the beginning of the diffusion experiments. Then, the rate of diffusion of the trace ions decreased over the experimental period of 1-15 months. This is probably due to the change in the microstructure of the FAC as the result of a pozzolanic reaction. After a few months, the values of De were estimated to be on the order of 10-14 m2 s-1. These results suggest that an engineered barrier made of FAC can act as an effective barrier inhibiting the diffusion of trace ions such as organic carbon and iodine.
Current Status of Mo-Si-B Silicide Alloys for Ultra-high Temperature Applications
Authors: Heilmaier Martin , Saage Holger , Krüger Manja , Jehanno Pascal , Böning Mike , Kestler Heinrich
Published: February 2009

We review the current development status of molybdenum borosilicide (Mo-Si-B) alloys for ultra-high temperature applications in air. The assessment of several ingot and powder metallurgy approaches revealed that (i) the presence of a continuous Mo solid solution matrix is mandatory for adequate low temperature toughness and (ii) wrought processing of such alloys at temperatures established for refractory metals requires the presence of an ultrafine (sub-micron) microstructure. Both prerequisites could be fulfilled using mechanical alloying (MA) as the crucial processing step , however, values for the ductile-to-brittle transition temperature (DBTT) below 800°C could not be obtained due to grain boundary embrittlement by Si segregation. First results on the effect of different microalloying additions on a reduction of this segregation exemplified for the Mo solid solution will be presented and discussed.
In Situ Observation of Nucleation and Growth of Carbon Nanotubes from Iron Carbide Nanoparticles
Authors: Yoshida Hideto , Takeda Seiji , Uchiyama Tetsuya , Kohno Hideo , Homma Yoshikazu
Published: February 2009

Nucleation and growth processes of carbon nanotubes (CNTs) in iron catalyzed chemical vapor deposition (CVD) have been observed by means of in-situ environmental transmission electron microscopy. Our atomic scale observations demonstrate that solid state iron carbide (Fe3C) nanoparticles act as catalyst for the CVD growth of CNTs. Iron carbide nanoparticles are structurally fluctuated in CVD condition. Growth of CNTs can be simply explained by bulk diffusion of carbon atoms since nanoparticles are carbide.
Self-aligned growth of single-walled carbon nanotubes using optical near-field effects
Authors: Zhou Y.S. , Xiong W. , Mahjouri-Samani M. , Yang W.Q. , Yi K.J. , He X.N. , Lu Yong Feng
Published: February 2009

By applying optical near-field effects in a laser-assisted chemical vapor deposition (LCVD) process, self-aligned growth of ultra-short single-walled carbon nanotubes (SWNTs) was realized in a well controlled manner at a relatively low substrate temperature due to the nanoscale heating enhancement induced by the optical near-field effects. Bridge structures containing single suspending SWNT channels were successfully fabricated. Ultra-sharp tip-shaped metallic electrodes were used as optical antennas in localizing and enhancing the optical fields. Numerical simulations using High Frequency Structure Simulator (HFSS) reveal significant enhancement of electrical fields at the metallic electrode tips under laser irradiation, which induces localized heating at the tips. Numerical simulations were carried out to optimize SWNT growth conditions, such as electrode tip sharpness and film thickness, for maximal enhancement of electrical near field and localized heating.
Gate Controlled Negative Differential Resistance and Photoconductivity Enhancement in Carbon Nanotube Addressable Intra-connects
Authors: Lee Seon Woo , Rotkin Slava , Sirenko Andrei , Lopez Daniel , Kornblit Avi , Grebel Haim
Published: February 2009

We have observed gate-controlled N-shaped negative differential resistance (NDR) and photoconductivity enhancement in carbon nanotube (CNT) based addressable intra-connects. The intra-connects – bridges spanning across planar electrodes – were measured at room temperature. Individual single-walled CNT (SWCNT) channels were grown using chemical vapor deposition (CVD) precisely between very sharp metal tips on the pre-fabricated electrodes without post-processing. The electrodes were made of cobalt. Methane and H2 gas mixture were introduced into quartz tube for an hour at 900 C, with flow rate of 1900 sccm for methane and 20 sccm for H2. We have investigated two different cases: in one case, the source-drain current-voltage, Ids-Vds, characteristics were linear. The other case exhibited nonlinear Ids-Vds characteristics. Raman scattering of the intra-connects indicated that each were made of SWCNT with radial breathing mode (RBM) at 191.9 cm-1 and 176.2 cm-1, respectively. Current-voltage Ids-Vds characteristics were measured for various Vgs from -10 V to +10 V. Negative differential resistance (NDR) was found in the Ids-Vgs curves for gate bias in the region of -3>Vgs>-6 V. The NDR peak was shifted to the negative side as the source-drain voltage was increased from Vds=0 to 0.75 V. Otherwise, the intra-connects exhibited characteristics of an ordinary p-type channel. The experiments were repeated under white light illumination. The light increases the carrier density in the channel but not in the metal electrodes and allowed us to study the effective doping of the channel without affecting the work function of the SWCNT/metal contact. The overall channel conductance increased under the light irradiation. Under illumination, the devices became more stable, as well. In summary, we have investigated contact properties between a SWCNT intra-connect and metal electrodes in a well controlled layout settings.
A New Thermionic Cathode Based on Carbon Nanotubes with a Thin Layer of Low Work Function Barium Strontium Oxide Surface Coating
Authors: Jin Feng , Liu Yan , Little Scott A , Day Chris M
Published: February 2009

We have created a thermionic cathode structure that consists of a thin tungsten ribbon; carbon nanotubes (CNTs) on the ribbon surface; and a thin layer of low work function barium strontium oxide coating on the CNTs. This oxide coated CNT cathode was designed to combine the benefits from the high field enhancement factor from CNTs and the low work function from the emissive oxide coating. The field emission and thermionic emission properties of the cathode have been characterized. A field enhancement factor of 266 and a work function of 1.9 eV were obtained. At 1221 K, a thermionic emission current density of 1.22A/cm2 in an electric field of 1.1 V/μm was obtained, which is four orders of magnitude greater than the emission current density from the uncoated CNT cathode at the same temperature. The high emission current density at such a modest temperature is among the best ever reported for an oxide cathode.
Thermo- and chemo-electrical behavior of carbon nanotube filled co-continuous conductive polymer nanocomposites (CPC) to develop amperometric sensors
Authors: Lu Jianbo , Castro Mickaël , Kumar Bijandra , Feller Jean-François
Published: February 2009

The conductive polymer nanocomposite (CPC) of multiwall carbon nanotubes (MWNT) filled Polycaprolactone (PCL) was formulated by melt mixing method. PCL based conductive phase served as disperse phase, blended with polypropylene (PP) and polyamide 12 (PA12) respectively. The thermo- and chemo-electrical properties of mono- and bi-component CPC have been investigated independently. Results show that PP/PCL-CNT CPC is a good temperature sensor whereas no significant response was observed while exposing to toluene vapor. In contrast, PA12/PCL-CNT exhibits good vapor sensing capability instead of temperature sensor. It is assumed that PP phase prevents the diffusion of vapor molecules within PCL conductive phase. The vapor sensing results indicated that PP external matrix provides the CPC with higher barrier effects than PA12.
Aligned-Crystalline Si Films on Non-Single-Crystalline Substrates
Authors: Findikoglu Alp , Holesinger Terry G. , Niemeyer Alyson , Matias Vladimir , Ugurlu Ozan
Published: February 2009

We summarize recent progress in growth and characterization of aligned-crystalline silicon (ACSi) films on polycrystalline metal and amorphous glass substrates. The ACSi deposition process uses, as a key technique, ion-beam-assisted deposition (IBAD) texturing on a non-single-crystalline substrate to achieve a biaxially-oriented (i.e., with preferred out-of-plane and in-plane crystallographic orientations) IBAD seed layer, upon which homo- and hetero-epitaxial buffer layers and hetero-epitaxial silicon (i.e., ACSi) films with good electronic properties can be grown. We have demonstrated the versatility of our approach by preparing ACSi films on customized architectures, including fully insulating and transparent IBAD layer and buffer layers based on oxides on glass and flexible metal tape, and conducting and reflective IBAD layer and buffer layers based on nitrides on flexible metal tape. Optimized 0.4-μm-thick ACSi films demonstrate out-of-plane and in-plane mosaic spreads of 0.8° and 1.3°, respectively, and a room-temperature Hall mobility of ∼90 cm2/V.s (∼50% of what is achievable with epitaxial single-crystalline Si films, and ∼1000 times that of amorphous Si films) for a p-type doping concentration of ∼4×1016 cm−3. By using various experimental techniques, we have confirmed the underlying crystalline order and the superior electrical characteristics of low-angle (<5°) grain boundaries in ACSi films. Forming gas anneal experiments indicate that Si films with low-angle grain boundaries do not need to be passivated to demonstrate improved majority carrier transport properties. Measurements on metal-insulator-semiconductor structures using ACSi films yield near-electronic-grade surface properties and low surface defect densities in the ACSi films. A prototype n+/p/p+–type diode fabricated using a 4.2-μm-thick ACSi film shows minority carrier lifetime of ∼3 μs, an estimated diffusion length of ∼30 μm in the p-Si layer with a doping concentration of 5×1016 cm−3, and external quantum efficiency of ∼80% at 450 nm with the addition of an MgO film anti-reflector.
Improvement and innovation through collaborative partnerships
Authors: Wamuziri S. , Madan S.
Published: February 2009

This paper provides a conceptual background for future research in the area of innovation and continuous improvement (CI) in the facilities management supply chain. In a modern, rapidly changing business environment, it is important for businesses to sustain innovation and continuous improvement through active collaboration with suppliers and service providers. The paper provides a synthesis of the theories of CI and an evaluation of the practical implications of its implementation and management. It also provides further insights into the different levels of CI capabilities of organisations as well as the critical success factors in forming collaborative alliances between clients, suppliers and other service providers.
Development of a simulated earthworm gut for determining bioaccessible arsenic, copper, and zinc from soil
Authors: Ma Wai K. , Smith Ben A. , Stephenson Gladys L. , Siciliano Steven D.
Published: February 2009

Soil physicochemical characteristics and contamination levels alter the bioavailability of metals to terrestrialinvertebrates. Current laboratory-derived benchmark concentrations used to estimate risk do not take into account site-specific conditions, such as contaminant sequestration, and site-specific risk assessment requires a battery of time-consuming and costly toxicity tests. The development of an in vitro simulator for earthworm bioaccessibility would significantly shorten analytical time and enable site managers to focus on areas of greatest concern. The simulated earthworm gut (SEG) was developed to measure the bioaccessibility of metals in soil to earthworms by mimicking the gastrointestinal fluid composition of earthworms. Three formulations of the SEG (enzymes, microbial culture, enzymes and microbial culture) were developed and used to digest field soils from a former industrial site with varying physicochemical characteristics and contamination levels. Formulations containing enzymes released between two to 10 times more arsenic, copper, and zinc from contaminated soils compared with control and 0.01 M CaCl2 extractions. Metal concentrations in extracts from SEG formulation with microbial culture alone were not different from values for chemical extractions. The mechanism for greater bioaccessible metal concentrations from enzyme-treated soils is uncertain, but it is postulated that enzymatic digestion of soil organic matter might release sequestered metal. The relevance of these SEG results will need validation through further comparison and correlation with bioaccumulation tests, alternative chemical extraction tests, and a battery of chronic toxicity tests with invertebrates and plants.
A quasiclassical approach to strongly correlated quantum dots
Authors: Matulis Algirdas , Jarema Denis , Anisimovas Egidijus
Published: February 2009

The adiabatic approximation and reaction-coordinate method is applied to the quasiclassical description of nanostructures. In a two-electron model quantum dot, the Schrödinger equation is solved in the vicinity of the transition path connecting two equivalent potential-energy minima. The obtained results demonstrate the formation of a Wigner crystallite.
Stochastic resonance induced by a multiplicative periodic signal in a logistic growth model with correlated noises
Authors: Bai Chunyan , Du Luchun , Mei Dongcheng
Published: February 2009

The stochastic resonance (SR) phenomenon induced by a multiplicative periodic signal in a logistic growth model with correlated noises is studied by using the theory of signal-to-noise ratio (SNR) in the adiabatic limit. The expressions of the SNR are obtained. The effects of multiplicative noise intensity α and additive noise intensity D, and correlated intensity λ on the SNR are discussed respectively. It is found that the existence of a maximum in the SNR is the identifying characteristic of the SR phenomena. In comparison with the SR induced by additive periodic signal, some new features are found: (1) When SNR as a function of λ for fixed ratio of α and D, the varying of α can induce a stochastic multi-resonance, and can induce a re-entrant transition of the peaks in SNR vs λ; (2) There exhibits a doubly critical phenomenon for SNR vs D and λ, i.e., the increasing of D (or λ) can induce the critical phenomenon for SNR with respect to λ (or D); (3) The doubly stochastic resonance effect appears when α and D are simultaneously varying in SNR, i.e., the increment of one noise intensity can help the SR on another noise intensity come forth.
Stochastic dynamics and mean field approach in a system of three interacting species
Authors: Valenti Davide , Spagnolo Bernardo
Published: February 2009

The spatio-temporal dynamics of three interacting species, two preys and one predator, in the presence of two different kinds of noise sources is studied, by using Lotka-Volterra equations. A correlated dichotomous noise acts on the interaction parameter between the two preys, and a multiplicative white noise affects directly the dynamics of the three species. After analyzing the time behaviour of the three species in a single site, we consider a two-dimensional spatial domain, applying a mean field approach and obtaining the time behaviour of the first and second order moments for different multiplicative noise intensities. We find noise-induced oscillations of the three species with an anticorrelated behaviour of the two preys. Finally, we compare our results with those obtained by using a coupled map lattice (CML) model, finding a good qualitative agreement. However, some quantitative discrepancies appear, that can be explained as follows: i) different stationary values occur in the two approaches; ii) in the mean field formalism the interaction between sites is extended to the whole spatial domain, conversely in the CML model the species interaction is restricted to the nearest neighbors; iii) the dynamics of the CML model is faster since an unitary time step is considered.
Interface resistive switching effects in bulk manganites
Authors: Belogolovskii Mikhail
Published: February 2009

A physical mechanism driving the resistance switching in heterocontacts, formed by a metal counterelectrode and electrically conducting bulk perovskite manganites, is discussed. The nature of the inelastic, charge-hopping transport inside insulating and strongly inhomogeneous metal/manganite interfaces is studied theoretically. Comparison with measured current-voltage characteristics for a La0.67Ca0.33MnO3/Ag heterostructure in a high-resistance state reveals the presence of one or more charge traps along a conduction path within the interface. In a low-resistance state the main charge-transferring events are direct tunneling ones. The analysis of electrical noise measurements for a La0.82Ca0.18MnO3 single crystal in three different charge-transport regimes shows scattering centers with a broad, flat spectrum of excitation states, independent of manganite electrical and/or magnetic characteristics. All of these results are consistent with an oxygen-drift model for a bistable resistance state in perovskites.
Vitrification of a monatomic 2D simple liquid
Authors: Mizuguchi Tomoko , Odagaki Takashi
Published: February 2009

A monatomic simple liquid in two dimensions, where atoms interact isotropically through the Lennard-Jones-Gauss potential [M. Engel, H.-R. Trebin, Phys. Rev. Lett. 98, 225505 (2007)], is vitrified by the use of a rapid cooling technique in a molecular dynamics simulation. Transformation to a crystalline state is investigated at various temperatures and the time-temperature-transformation (TTT) curve is determined. It is found that the transformation time to a crystalline state is the shortest at a temerature 14% below the melting temperature T
m and that at temperatures below T
v ≡ 0:6T
m the transformation time is much longer than the available CPU time. This indicates that a long-lived glassy state is realized for T ≤ T
v.
Anatomical characteristics and antioxidant properties of Euphorbia nicaeensis ssp. glareosa
Authors: Luković Jadranka , Malenčić Djordje , Zorić Lana , Kiprovski Biljana , Merkulov Ljiljana , Boža Pal
Published: February 2009

Anatomical analyses found that leaves of Euphorbia nicaeensis ssp. glareosa are isolateral, amphistomatous, with two layers of palisade cells on the adaxial and one on the abaxial side. Laticifers are present by vascular bundles, in palisade and spongy tissue. Stem laticifers are located in the pericyclic ring, adjacent to the phloem, in cylinder parenchyma and medullar rays. The structure of pleiochasium and dichasium peduncle is similar to the stem structure. Plants from typical steppe habitat show more xeromorphic features. Phytochemical screening of extracts showed presence of catecholes, flavonoids, tannins, saponins, free quinone derivatives and absence of anthocyanins, leucoanthocyanins, alkaloids, steroid compounds and essential oils. Our results showed that the examined taxon was partially susceptible to the action of reactive oxygen species, such as O2·− and ·OH. The higher quantities of ROS thus provoked an antioxidative response from the plant, both in an enzymatic and non-enzymatic manner. Stable anatomical structure, presence and distribution of laticifers and effective antioxidant properties when exposed to ROS, make Euphorbia nicaeensis subsp. glareosa potentially interesting for further pharmaceutical and phytochemical examinations.
Seasonal dynamics of macrophyte abundance in two regulated streams
Authors: Hrivnák Richard , Oťaheľová Helena , Gömöry Dušan
Published: February 2009

This study analysed seasonal dynamics of macrophyte abundance in two perennial lowland regulated streams (Stream 1 and 2) in the Danube basin (Slovakia). Assessments of macrophyte abundance and environmental characteristics were accomplished 7 times during the vegetation period in 2005 within a 100 m long section. Statistically significant differences in total abundance of macrophytes as well as an abundance of macrophyte groups (hydrophytes, amphiphytes, helophytes) and Potamogeton nodosus were detected among months within the vegetation period. Abundance fluctuations for individual macrophyte groups and species were moderate in Stream 1 and much stronger in Stream 2. Only amphiphytes showed bimodal temporal distribution in Stream 1, but the abundance of this group was low, reflecting more or less random occurrence of species in vegetation period. Multiple linear regression revealed that water depths and air temperature are the most significant environmental variables affecting the seasonal pattern of total as well as dominating group abundance in Stream 1 and 2, respectively. In all cases, abundances are significantly influenced by the abundance of the respective group in the preceding month. Culmination time differed between streams for all macrophyte groups except helophytes. Total abundance culminated 0.57 month later in the Stream 1 compared to Stream 2.
The effects of markedly raised intracellular sphingosine kinase-1 activity in endothelial cells
Authors: Limaye Vidya , Vadas Mathew , Pitson Stuart , Gamble Jennifer
Published: February 2009

The enzyme sphingosine kinase-1 (SK1) promotes the formation of sphingosine-1-phosphate (S1P), which is an important survival factor for endothelial cells (EC). Modest increases in intracellular SK1 activity in the EC are known to confer a survival advantage upon the cells. Here, we investigated the effects of more dramatic increases in intracellular SK1 in the EC. We found that these cells show reduced cell survival under conditions of stress, enhanced caspase-3 activity, cell cycle inhibition, and cell-cell junction disruption. We propose that alterations in the phosphorylation state of the enzyme may explain the differential effects on the phenotype with modest versus high levels of enforced expression of SK1. Our results suggest that SK1 activity is subject to control in the EC, and that this control may be lost in conditions involving vascular regression.
Chronic increases in sphingosine kinase-1 activity induce a pro-inflammatory, pro-angiogenic phenotype in endothelial cells
Authors: Limaye Vidya , Xia Pu , Hahn Chris , Smith Malcolm , Vadas Mathew , Pitson Stuart , Gamble Jennifer
Published: February 2009

Sphingosine kinase-1 (SK1) promotes the formation of sphingosine-1-phosphate (S1P), which has potent pro-inflammatory and pro-angiogenic effects. We investigated the effects of raised SK1 levels on endothelial cell function and the possibility that this signaling pathway is activated in rheumatoid arthritis. Human umbilical vein endothelial cells with 3- to 5-fold SK1 (ECSK) overexpression were generated by adenoviral and retroviralmediated gene delivery. The activation state of these cells and their ability to undergo angiogenesis was determined. S1P was measured in synovial fluid from patients with RA and OA. ECSK showed an enhanced migratory capacity and a stimulated rate of capillary tube formation. The cells showed constitutive activation as evidenced by the induction of basal VCAM-1 expression, and further showed a more augmented VCAM-1 and E selectin response to TNF compared with empty vector control cells (ECEV). These changes had functional consequences in terms of enhanced neutrophil binding in the basal and TNFstimulated states in ECSK. By contrast, over-expression of a dominant-negative SK inhibited the TNF-induced VCAM-1 and E selectin and inhibited PMN adhesion, confirming that the observed effects were specifically mediated by SK. The synovial fluid levels of S1P were significantly higher in patients with RA than in those with OA. Small chronic increases in SK1 activity in the endothelial cells enhance the ability of the cells to support inflammation and undergo angiogenesis, and sensitize the cells to inflammatory cytokines. The SK1 signaling pathway is activated in RA, suggesting that manipulation of SK1 activity in diseases of aberrant inflammation and angiogenesis may be beneficial.
The expression of COX-2, hTERT, MDM2, LATS2 and S100A2 in different types of non-small cell lung cancer (NSCLC)
Authors: Stražišar Mojca , Mlakar Vid , Glavač Damjan
Published: February 2009

Several studies have reported different expression levels of certain genes in NSCLC, mostly related to the stage and advancement of the tumours. We investigated 65 stage I-III NSCLC tumours: 32 adenocarcinomas (ADC), 26 squamous cell carcinomas (SCC) and 7 large cell carcinomas (LCC). Using the real-time reverse transcription polymerase chain reaction (RT-PCR), we analysed the expression of the COX-2, hTERT, MDM2, LATS2 and S100A2 genes and researched the relationships between the NSCLC types and the differences in expression levels. The differences in the expression levels of the LATS2, S100A2 and hTERT genes in different types of NSCLC are significant. hTERT and COX-2 were over-expressed and LATS2 under-expressed in all NSCLC. We also detected significant relative differences in the expression of LATS2 and MDM2, hTERT and MDM2 in different types of NSCLC. There was a significant difference in the average expression levels in S100A2 for ADC and SCC. Our study shows differences in the expression patterns within the NSCLC group, which may mimic the expression of the individual NSCLC type, and also new relationships in the expression levels for different NSCLC types.
Kinetic and morphological differentiation of ettringites in plain and blended Portland cements with metakaolin and the ASTM C 452-68 test. Part II: Morphological differentiation by SEM and XRD analysis
Authors: Talero R.
Published: February 2009

The same cementitious materials (OPCs, SRPCs and matekaolin, MK), the same blended cements and the same ASTM C 452-68 test than in Part I, were used. Other complementary determinations were: chemical analysis of cementing materials, SEM and XRD analysis of ettringites and specific properties of some cement tested and of their pastes.The experimental results have also demonstrated that when 7.0% SO3, equivalent to 15.05% of gypsum, was added to the M pozzolan-containing Portland cement and tested with the ASTM C 452-68 method, it was not found to behave aggressively but rather as “setting regulator ”, because the increase in mechanical strengths over time and setting times in these mixes were, therefore, similar to the pattern observed in any PC. However, when the gypsum content was raised to triple than that amount (21.0% SO3), it behaved aggressively. In both cases, logically, ettringite from both origins were involved in the resulting beneficial or adverse behavior.
Brick durability and conservation treatment (Santa María de Jesús chapel portal, Seville, Spain)
Authors: Alejandre F. J. , Villegas R.
Published: February 2009

Durability differences of 2 types of brick from Santa María de Jesús Chapel (Sevilla) and 2 treatments for its restoration have been studied. They have been characterizad using XRD and SEM, as well as their physical, hydric and mechanical properties. Samples prepared with bricks from the chapel have been submitted to salt crystallization test, to identify decay causes and mechanisms.The red brick present the lowest firing temperature, lower porosity and a great proportion of micropores. Physical and mechanical properties don’t change significantly with the treatments, only hygric properties vary with the water repellent. The accelerated aging test revealed significant improvement in the behaviour of yellow brick, but no change in the decay mechanism of red brick (Typical of microporous materials) or its durability is observed.
Biocalcarenites as construction materials in Santa Marina de Aguas Santas Church at Cordoba, Spain
Authors: Barrios Neira J. , Montealegre L. , Ortega A. , Meroño J. E. , Aguilera M. J.
Published: February 2009

This study consisted in characterizing the materials used to build Santa Marina de Aguas Santas Church at Cordoba and locating the original quarries. The techniques used in the lithological and chemical characterization included XRD, petrographic microscopy and electron dispersive scanning microscopy. The chemical index of weathering (CIW) was used to quantify the state of stone decay. The lithology and different types of alterations observed were mapped. A comparison of the material on the building to ancient quarries identified “Naranjo” as the possible site where the stone was originally quarried.
Use of Medaka in Toxicity Testing
Authors: Padilla Stephanie , Cowden John , Hinton David E. , Yuen Bonny , Law Sheran , Kullman Seth W. , Johnson Rodney , Hardman Ronald C. , Flynn Kevin , Au Doris W.T.
Published: February 2009

Small aquarium fishes are increasingly used as animal models, and one of these, the Japanese Medaka (Oryzias latipes), is frequently utilized for toxicity testing. While these vertebrates have many similarities with their terrestrial counterparts, there are differences that must be considered if these organisms are to be used to their highest potential. Commonly, testing may employ either the developing embryo or adults; both are easy to use and work with. To illustrate the utility and breadth of toxicity testing possible using medaka fish, we present protocols for assessing neurotoxicity in developing embryos, evaluating toxicant effects on sexual phenotype after treatment with endocrine‐disrupting chemicals by sexual genotyping, and measuring hepatotoxicity in adult fish after treatment with a model hepatotoxicant. The methods run the gamut from immunohistology through PCR to basic histological techniques. Curr. Protoc. Toxicol. 39:1.10.1‐1.10.36. © 2009 by John Wiley & Sons, Inc.
Glutamate Cysteine Ligase (GCL) Transgenic and Gene‐Targeted Mice for Controlling Glutathione Synthesis
Authors: Mohar Isaac , Botta Dianne , White Collin C. , McConnachie Lisa A. , Kavanagh Terrance J.
Published: February 2009

The tripeptide glutathione (GSH) has important antioxidant properties, scavenges free radicals, and serves as a cofactor for glutathione S‐transferase conjugation of many xenobiotics. GSH is synthesized in two steps. The first and, often, rate‐limiting step is the formation of γ‐glutamylcysteine, which is catalyzed by the inducible heterodimeric enzyme glutamate cysteine ligase (GCL). The two subunits of GCL are the catalytic subunit (GCLC) and the modifier subunit (GCLM). In this unit, the generation and basic characterization methodologies of transgenic mouse models that have been developed to (1) conditionally over express both GCL subunits; (2) lack GCLM (Gclm null); and (3) create a hybrid between Gclm conditional over‐expressing mice on a Gclm null genetic background are discussed. These models can be used to explore the fundamental role of GCLC and GCLM in GSH synthesis, as well as the toxicological role of GSH and its synthesis in xenobiotic metabolism and response to oxidative stress. Curr. Protoc. Toxicol. 39:6.16.1‐6.16.20. © 2009 by John Wiley & Sons, Inc.
Microvolume Spectrophotometric and Fluorometric Determination of Protein Concentration
Authors: Desjardins Philippe , Hansen Joel B. , Allen Michael
Published: February 2009

Methods for determining protein concentration that use progressively smaller amounts of material are continually being developed. A new way of minimizing the amount of sample used for spectroscopic analysis is providing more opportunities for greater quality control. Traditional spectrophotometric and fluorometric methods for determination of protein concentrations have long required placing samples into containment devices such as cuvettes or capillaries. A microsample retention system is changing that paradigm by using natural surface tension properties to capture and hold microvolume samples in place during measurement without traditional containment devices. The advantage of such a system is to dramatically reduce the amount of sample required (1 to 2 µl) while greatly increasing the dynamic range of protein concentrations that can be measured. Modifications to classic protein concentration determination protocols are presented to provide a microvolume alternative to traditional cuvette‐based methods. Curr. Protoc. Protein Sci. 55:3.10.1‐3.10.16. © 2009 by John Wiley & Sons, Inc.
Overview on Concepts and Applications of Fab Antibody Fragments
Authors: Rader Christoph
Published: February 2009

In this overview, the Fab molecule is introduced and discussed as the first generated antibody fragment, which still dominates basic research and clinical applications. The unit contains a concepts section and an applications section. In the concepts section, the two principal methods for producing Fab, as well as the generation and directed evolution of Fab by phage display, are described. The applications section discusses Fab in clinical applications, as well as their increasingly important role in the determination of the three‐dimensional structures of transmembrane proteins. Curr. Protoc. Protein Sci. 55:6.9.1‐6.9.14. © 2009 by John Wiley & Sons, Inc.
E. coli Expression and Purification of Fab Antibody Fragments
Authors: Kwong Ka Yin , Rader Christoph
Published: February 2009

The Fab molecule was the first generated antibody fragment and still dominates basic research and clinical applications. This unit describes the E. coli expression and purification of Fab antibody fragments with and without a His tag, and is designed to yield sufficient protein for the evaluation and characterization of a panel of Fab selected from a Fab library by phage display. Curr. Protoc. Protein Sci. 55:6.10.1‐6.10.14. © 2009 by John Wiley & Sons, Inc.
Analysis of Protein Acylation
Authors: Zeidman Ruth , Jackson Caroline S. , Magee Anthony I.
Published: February 2009

Proteins can be acylated with a variety of fatty acids attached by different covalent bonds, influencing, among other things, their function and intracellular localization. This unit describes methods to analyze protein acylation, both levels of acylation and also the identification of the fatty acid and the type of bond present in the protein of interest. Protocols are provided for metabolic labeling of proteins with tritiated fatty acids, for exploitation of the differential sensitivity to cleavage of different types of bonds, in order to distinguish between them, and for thin‐layer chromatography to separate and identify the fatty acids associated with proteins.Curr. Protoc. Protein Sci. 55:14.2.1‐14.2.12. © 2009 by John Wiley & Sons, Inc.
Use of the Intracellular Fluorescent Dye CFSE to Monitor Lymphocyte Migration and Proliferation
Authors: Parish Christopher R. , Glidden Megan H. , Quah Ben J. C. , Warren Hilary S.
Published: February 2009

The stable incorporation of the intracellular fluorescent dye 5‐(and ‐6)‐carboxyfluorescein diacetate succinimidyl ester (CFSE) into cells provides a powerful tool to monitor cell migration, and to quantify cell division, because of the sequential decrease in fluorescent labeling in daughter cells. CFSE‐labeled lymphocytes have been used to analyze the relationship between cell division and differentiation of cell function, and cell proliferation versus apoptosis, both in vivo and in vitro, and have allowed analysis of the site of response to antigens in vivo.Curr. Protoc. Immunol. 84:4.9.1‐4.9.13. © 2009 by John Wiley & Sons, Inc.
Laboratory Maintenance of Clostridium difficile
Authors: Sorg Joseph A. , Dineen Sean S.
Published: February 2009

Clostridium difficile is a Gram‐positive, spore‐forming, anaerobe and is the leading cause of antibiotic‐associated diarrhea, pseudomembranous colitis, and toxic megacolon. Essential to the lifestyle of C. difficile is the ability to form a metabolically dormant spore, germinate, and grow out upon appropriate signals and elicit disease with the secretion of two toxins. To aid in the study of this organism, this unit describes the growth and maintenance of C. difficile. Included are methods to isolate C. difficile from environmental samples, grow in laboratory medium, and produce and purify spores. Curr. Protoc. Microbiol. 12:9A.1.1‐9A.1.10. © 2009 by John Wiley & Sons, Inc.
Cultivation and Laboratory Maintenance of Chlamydia pneumoniae
Authors: Campbell Lee Ann , Kuo Cho‐Chou
Published: February 2009

Chlamydiae are Gram‐negative obligate intracellular parasites. Chlamydia pneumoniae is a human respiratory pathogen that causes pneumonia, bronchitis, sinusitis, and pharyngitis. C. pneumoniae has also been associated with cardiovascular disease. C. pneumoniae can only be grown in cell culture and is more difficult to isolate from specimens than Chlamydia trachomatis. Commonly used cell lines for isolation of C. trachomatis are not sensitive for C. pneumoniae. The most sensitive cell lines for isolation of C. pneumoniae are HL and HEp‐2. Centrifugation of the inoculum onto the monolayer and inclusion of cycloheximide in the medium enhance isolation. Inclusions are smaller than those of other chlamydiae and are visualized by staining with FITC‐conjugated genus‐ or C. pneumoniae–specific monoclonal antibodies. Slow expansion and use of a small inoculum are key to successful culture. Infectious organisms can be purified by use of Hypaque‐76 gradients to titers >1 × 108/ml. Curr. Protoc. Microbiol. 12:11B.1.1‐11B.1.23. © 2009 by John Wiley & Sons, Inc.
Testing of Transmission of Tobraviruses by Nematodes
Authors: MacFarlane Stuart A. , Neilson Roy
Published: February 2009

Virus diseases often are spread between plants by vector organisms, some of which live below ground (e.g., fungi and nematodes) and feed on the plant root system. Tobraviruses are one of only two groups of plant viruses that have nematode vectors. They are primarily viruses of weed plants but can cause significant economic damage in a range of cultivated crops including potato, peas, beans, and many ornamental species. Identifying these viruses and their nematode vectors is a very important part of the struggle to combat disease in crop plants, and requires specialized techniques that will be discussed further in this unit. Curr. Protoc. Microbiol. 12:16B.5.1‐16B.5.16. © 2009 by John Wiley & Sons, Inc.
Novel Approaches to Bacterial Infection Therapy by Interfering with Cell‐to‐Cell Signaling
Authors: Rasko David A. , Sperandio Vanessa
Published: February 2009

The identification of cell‐to‐cell signaling inhibitors among bacteria is a novel mechanism used to control the virulence of pathogens. Signaling inhibitors have a significant potential to be used as therapeutics in that they will exert less biological pressure to develop resistance than classic antibiotics, which attempt to eradicate or significantly inhibit bacterial growth. Decreasing the virulence of pathogens by inhibiting signaling provides a mechanism by which the bacteria will be “misled” into not activating virulence factors. If virulence factors are not activated, these pathogens will either pass through the host without incidence or be controlled by the host's immune system. In this unit, we discuss the general principles for the design and implementation of a high‐throughput screen to identify inhibitors of bacterial cell‐to‐cell communication. We also provide a detailed protocol using a specific example of signaling inhibitor identification using enterohemorrhagic Escherichia coli as a model system. Curr. Protoc. Microbiol. 12:17.3.1‐17.3.11. © 2009 by John Wiley & Sons, Inc.
Nanoporous Copper with Tunable Nanoporosity for SERS Applications
Authors: Chen Lu‐Yang , Yu Jin‐Shan , Fujita Takeshi , Chen Ming‐Wei
Published: February 2009

Nanostructured materials with designable microstructure and controllable physical and chemical properties are highly desired for practical applications in nanotechnology. In this article, it is reported that nanoporous copper with a tunable nanopore size can be fabricated by controlling the dealloying process. The influence of acid concentration and etching potential on the formation of nanoprosity is systematically investigated. With optimal etching conditions, the nanopore sizes can be tailored from ∼15 to ∼120 nm by controlling the dealloying time. It is found that the tunable nanoporosity leads to significant improvements in surface‐enhanced Raman scattering (SERS) of nanoporous copper and peak values of SERS enhancements for both rhodamine 6G and crystal violet 10B molecules are observed at a pore size of ∼30–50 nm. This study underscores the effect of complex three‐dimensional nanostructures on physical and chemical properties and is helpful in developing inexpensive SERS substrates for sensitive instrumentations in molecular diagnostics.