bluuebunny/crossref_metadata_2025 huggingface dataset:
Proteomic analysis of shoot tissue during photoperiod induced growth cessation in V. riparia Michx. grapevines
Authors: Victor Kim J , Fennell Anne Y , Grimplet Jérôme
Published: August 2010

Background

Growth cessation, cold acclimation and dormancy induction in grapevines and other woody perennial plants native to temperate continental climates is frequently triggered by short photoperiods. The early induction of these processes by photoperiod promotes winter survival of grapevines in cold temperate zones. Examining the molecular processes, in particular the proteomic changes in the shoot, will provide greater insight into the signaling cascade that initiates growth cessation and dormancy induction. To begin understanding transduction of the photoperiod signal, Vitis riparia Michx. grapevines that had grown for 35 days in long photoperiod (long day, LD, 15 h) were subjected to either a continued LD or a short photoperiod (short day, SD, 13 h) treatment. Shoot tips (4-node shoot terminals) were collected from each treatment at 7 and 28 days of LD and SD for proteomic analysis via two-dimensional (2D) gel electrophoresis.

Results

Protein profiles were characterized in V. riparia shoot tips during active growth or SD induced growth cessation to examine physiological alterations in response to differential photoperiod treatments. A total of 1054 protein spots were present on the 2D gels. Among the 1054 proteins, 216 showed differential abundance between LD and SD (≥ two-fold ratio, p-value ≤ 0.05). After 7 days, 39 protein spots were more abundant in LD and 30 were more abundant in SD. After 28 days, 93 protein spots were more abundant in LD and 54 were more abundant in SD. MS/MS spectrometry was performed to determine the functions of the differentially abundant proteins.

Conclusions

The proteomics analysis uncovered a portion of the signal transduction involved in V. riparia grapevine growth cessation and dormancy induction. Different enzymes of the Calvin-Benson cycle and glutamate synthetase isoforms were more abundant either in LD or SD treatments. In LD tissues the significantly differentially more abundant proteins included flavonoid biosynthesis and polyphenol enzymes, cinnamyl alcohol dehydrogenase, and TCP-1 complexes. In the SD tissue photorespiratory proteins were more abundant than in the LD. The significantly differentially more abundant proteins in SD were involved in ascorbate biosynthesis, photosystem II and photosystem I subunits, light harvesting complexes, and carboxylation enzymes.
Colorectal carcinoma associated with schistosomiasis: a possible causal relationship
Authors: Salim Omer E H , Hamid Hytham K S , Mekki Salwa O , Suleiman Suleiman H , Ibrahim Shakir Z
Published: August 2010

The association between schistosomiasis and colorectal malignancy has long been suggested in the literature, but it is not uniformly accepted. In the Far East, considerable evidence supports an etiological link between Schistosoma japonicum and colorectal cancer. However, the available data regarding the role of Schistosoma mansoni in colorectal carcinogenesis are conflicting and most often do not show causality. We report on a patient with sigmoid colonic cancer coexisting with schistosomiasis, and we provide a comprehensive review of the literature regarding the epidemiology and pathobiology of this association.
Detection of viral antigen, IgM and IgG antibodies in cerebrospinal fluid of Chikungunya patients with neurological complications
Authors: Kashyap Rajpal S , Morey Shweta H , Chandak Nitin H , Purohit Hemant J , Taori Girdhar M , Daginawala Hatim F
Published: August 2010

Background

During Chikungunya virus (CHIKV) epidemic in Nagpur, India, we identified some suspected Chikungunya patients with neurological complications. Early and cost-effective diagnosis of these patients remains problematic despite many new advanced diagnostic methods. A reliable diagnostic test, which could be performed in any standard pathology laboratory, would help to obtain definitive early diagnosis of CHIKV patients with neurological complications. In our laboratory, in-house ELISA protocol for viral antigen, immunoglobulin M (IgM) and IgG detection has been developed and assessed for the diagnosis of CHIKV patients with neurological complications.

Method

Cerebrospinal fluid samples of forty-six patients who developed neurological symptoms within two months of CHIKV infections along with control subjects were included in the study and were analyzed for the presence of antigens and of IgM and IgG using an ELISA protocol.

Results

The ELISA method for antigen detection yielded 80% sensitivity and 87% specificity for the diagnosis of CHIKV patients with neurological complications. The sensitivity for detection of IgM 48% or IgG 63% was significantly lower than the antigen assay (80%).

Conclusion

The detection of viral antigen in CSF of CHIKV patients with neurological complications by ELISA method gave a more reliable diagnosis than antibodies detection that can be used to develop an immunodiagnostic assay with increased sensitivity and specificity.
The last piece in the cellulase puzzle: the characterisation of β-glucosidase from the herbivorous gecarcinid land crab Gecarcoidea natalis
Authors: Allardyce Benjamin J. , Linton Stuart M. , Saborowski Reinhard
Published: August 2010

A 160 kDa enzyme with β-glucosidase activity was purified from the midgut gland of the land crab Gecarcoidea natalis. The enzyme was capable of releasing glucose progressively from cellobiose, cellotriose or cellotetraose. Although β-glucosidases (EC 3.2.1.21) have some activity towards substrates longer than cellobiose, the enzyme was classified as a glucohydrolase (EC 3.2.1.74) as it had a preference for larger substrates (cellobiose<cellotriose=cellotetraose). It was able to synthesise some cellotetraose by the transglycosylation of smaller substrates – another common feature of glucohydrolases. The interaction between the glucohydrolase described here and the endo-β-1,4-glucanases described previously for G. natalis provides a complete model for cellulose hydrolysis in crustaceans and possibly in other invertebrates. After mechanical fragmentation by the gastric mill, multiple endo-β-1,4-glucanases would initially cleave β-1,4-glycosidic bonds within native cellulose, releasing small oligomers, including cellobiose, cellotriose and cellotetraose. The glucohydrolase would then attach to these oligomers, progressively releasing glucose. The glucohydrolase might also attach directly to crystalline cellulose to release glucose from free chain ends. This two-enzyme system differs from the traditional model, which suggests that total cellulose hydrolysis requires the presence an endo-β-1,4-glucanse, a cellobiohydrolase and a β-glucosidase.
Variation in innate immunity in relation to ectoparasite load, age and season: a field experiment in great tits (Parus major)
Authors: De Coster Greet , De Neve Liesbeth , Martín-Gálvez David , Therry Lieven , Lens Luc
Published: August 2010

It remains largely unknown which factors affect the innate immune responses of free-living birds. Nevertheless, the degree of innate immunity may play a crucial role in an individual's survival as it procures the first defence against pathogens. We manipulated the ectoparasite load of great tit (Parus major) nests by infesting them with hen fleas (Ceratophyllus gallinae) before egg laying. We subsequently quantified natural antibody (NAb) concentration and complement activation in nestlings and adult females during breeding and post-breeding periods. NAb concentrations increased in nestlings and adult females breeding in flea-infested nest boxes during the nestling provisioning period, but not in breeding females during incubation. In contrast, parasite abundance did not affect levels of complement activity in females. NAb levels of nestlings were already fully developed at the end of the nestling stage, but complement activation was only observed post-fledging. Concentrations of NAbs and complement activation of adult females were significantly lower during the breeding season compared with post-breeding levels, but did not differ between incubation and chick rearing. Further experimental studies in species that vary in life-history strategies will allow us to unravel the mechanisms underlying the observed variation in innate immune defences.
View-based strategy for reorientation by geometry
Authors: Pecchia Tommaso , Vallortigara Giorgio
Published: August 2010

Human and non-human animals can use geometric information (metric information and left–right discrimination sense) to reorient themselves in an environment. The hypothesis that in so doing they rely on allocentric (map-like) representations has received wide consensus. However, theoretical models suggest that egocentric representations may represent efficient strategies for visuo-spatial navigation. Here, we provide, for the first time, evidence that a view-based strategy is effectively used by animals to reorient themselves in an array of landmarks. Domestic chicks were trained to locate a food-reward in a rectangular array of either four indistinguishable or distinctive pipes. In the key experimental series, the pipes had four openings, only one of which allowed the chicks to access the reward. The direction of the open access relative to the array was either maintained stable or it was changed throughout training. The relative position of the pipes in the array was maintained stable in both training conditions. Chicks reoriented according to configural geometry as long as the open access pointed in the same direction during training but failed when the positions of the openings was changed throughout training. When the correct pipe was characterized by a distinctive featural cue, chicks learnt to locate the reward irrespective of the stability of the direction to openings, indicating that place-navigation was dissociated from non-spatial learning. These findings provide evidence that view-based strategies to reorient by geometry could be used by animals.
The neuronal proteins CIPP, Cypin and IRSp53 form a tripartite complex mediated by PDZ and SH3 domains
Authors: Barilari Manuela , Dente Luciana
Published: August 2010

Here we report the dissection of a tripartite complex formed by CIPP (channel-interacting PDZ protein), IRSp53 (insulin receptor tyrosine kinase substrate protein) and Cypin (cytosolic PSD-95 interactor) in cultured cells. The three proteins are expressed in similar neuronal districts, where CIPP binds to different membrane channels and receptors, IRSp53 regulates the morphogenesis of actin-rich dendritic spines, and Cypin promotes dendrite branching and patterning by binding to tubulin heterodimers. We observed that the interaction among the three proteins is mediated by small binding domains: CIPP works as a bridge, linking the carboxy-termini of IRSp53 and Cypin with its PDZ domains; IRSp53 connects Cypin, through an unusual SH3-mediated association, which can be impaired by substituting two crucial positively charged residues of Cypin. The observation that the three engineered proteins co-localize in the cytoplasm, and at the tip of induced neurites in neuronal cells, raises the interesting possibility that they work together in the formation of neuronal protrusions.
Synthesis and Characterization of Bimetallic Pd-Co Nano Magnetic Materials in Mesoporous Silica
Authors: Tatineni Balaji , Kumar Dhananjay , Perkins Joslyn , Yarmolenko Sergey , Kuila Debasish
Published: August 2010

An one-pot procedure was developed for the synthesis of mesoporous silica containing bimetallic PdCo using Pd(NO3)2 and CoCl2, and cetyl trimethyl ammonium bromide (CTAB) as the templating agent, and tetramethoxy silane (TMOS) as the precursor. The materials were characterized using high resolution scanning transmission electron microscopy (HRSTEM), elemental analysis, X-ray diffraction (XRD), and magnetic measurements. The data indicate that the bimetallic Pd-Co nanoparticles are uniformly distributed on the inner pore walls of silica. The magnetic measurements of reduced Pd-Co nanoparticles (4-5 nm) in mesoporous silica reveal a typical ferromagnetic behavior up to 20 K and exhibit superparamagnetic properties above 30 K.
Oxygen vacancy migration in CSZ using density functional theory
Authors: Lee Byeong-Eon , Kim Dae-Hee , Kim Yeong-Cheol
Published: August 2010

We studied oxygen migration in calcia-stabilized cubic zirconia (CSZ) using density functional theory. A Ca atom was substituted for a Zr atom in a 2×2×2 ZrO2 cubic supercell, and an oxygen vacancy was produced to satisfy the charge neutrality condition. We found that the formation energies of an oxygen vacancy, as a function of its location with respect to the Ca atom, were varied. The relative formation energies of the oxygen vacancies located at the first-, second-, third-, and fourth-nearest-neighbors were 0.0, −0.07, 0.19, and 0.19 eV, respectively. Therefore, the oxygen vacancy located at the second-nearest-neighbor site of the Ca atom was the most favorable, the oxygen vacancy located at the first-nearest-neighbor site was the second most favorable, and the oxygen vacancies at the third- and fourth-nearest-neighbor sites were the least favorable. We also calculated the energy barriers for the oxygen vacancy migration between oxygen sites. The energy barriers between the first and the second nearest sites, the second and third nearest sites, and the third and fourth nearest sites were 0.11, 0.46, and 0.23 eV, respectively. Therefore, the oxygen vacancies favored the first- and second-nearest-neighbor oxygen sites when they drifted under an electric field.
Real Structure - Oxygen Mobility Relationship in Nanocrystalline Doped Ceria-Zirconia Fluorite-Like Solid Solutions Promoted by Pt
Authors: Sadykov Vladislav , Mezentseva N. , Muzykantov V. , Efremov D. , Gubanova E. , Sazonova N. , Bobin A. , Paukshtis E. , Ishchenko A. , Voronin V. , Ross J. , Mirodatos C. , van Veen A.
Published: August 2010

This work considers effect of type and content of dopant on the real structure, state of surface Pt species and oxygen mobility of nanocrystalline Lnx(Ce0.5Zr0.5)1-xO2-δ (Ln=La3+, Gd3+, Pr3+/4+) solid solutions prepared by Pechini route. For the reactions of methane selective oxidation and dry reforming into syngas, catalytic activity correlates rather well with either surface (in diluted feeds) or bulk (in realistic feeds) oxygen mobility as well as Pt dispersion controlled by the type and content of a dopant.
Thickness Dependent Effects of Thermal Annealing and Solvent Vapor Treatment of Poly (3-hexylthiophene) and Fullerene Bulk Heterojunction Photovoltaics
Authors: Zhao Zhouying , Rice Lynn , Efstathiadis Harry , Haldar Pradeep
Published: August 2010

We have utilized room-temperature solvent vapor treatment followed by thermal annealing to process bulk heterojunction (BHJ) photovoltaic devices based on blends of poly (3-hexylthiophene) (P3HT) and phenyl-C61-butyric acid methyl ester (PCBM) of varied active layer thickness. The morphological and photovoltaic performance characteristics of the cells subject to these treatments were found to be dependent on active layer thickness. The devices were characterized using atomic force microscopy (AFM) and opto-electrical and external quantum efficiency measurements in order to analyze the mechanism underlying the observed trend. Performance indicators including fill factor, short-circuit current and power conversion efficiency were correlated to the ordering of device active layers and morphology. The maximum power conversion efficiency achieved was 4.1 %.
Modeling of pH Elevation Due to the Reaction of Saline Groundwater with Hydrated Ordinary Portland Cement Phases
Authors: Honda Akira , Masuda Kenta , Nakanishi Hiroshi , Fujita Hideki , Negishi Kumi
Published: August 2010

Thermodynamic calculations of the reaction between hydrated OPC phases and saline groundwater indicate an elevated pH > 13, which is not associated with the well known initial release of the alkalis. Instead, the pH elevation is attributed to the generation of OH− accompanied with the precipitation of Friedel's salt (Ca3Al2O6·CaCl2·10H2O; AFm-Cl2) from the reaction of portlandite (Ca(OH)2;CH) and hydrogarnet (Ca3Al2O6·6H2O; C3AH6) with chloride ions from the saline groundwater. If such a reaction mechanism were to occur in the context of the geological disposal of radioactive wastes, the impact of a hyper alkaline plume on other barrier components, such as a bentonite buffer, could be significant. Experimental investigations were therefore conducted using only portlandite and hydrogarnet to represent hydrated OPC and NaCl solution to represent a saline groundwater. The pH elevation was confirmed and showed good agreement with the thermodynamic calculations. The experiments were repeated using hardened OPC paste to confirm this reaction mechanism in the presence of other hydrated OPC phases. In this case, however, the pH elevation was not as high as expected. This deviation can be explained by the residual aluminum, after being partially consumed by AFt and/or AFm, not being wholly assigned to hydrogarnet and a better agreement between the thermodynamic calculations and the experimentally measured results can be made assuming a fraction of aluminum is incorporated into the C-S-H gel phase.
Release of Colloids from Injection Grout Silica Sol
Authors: Hölttä Pirkko L , Hakanen Martti , Lahtinen Mari , Leskinen Anumaija , Lehto Jukka , Juhola Piia
Published: August 2010

Non-cementitious grouts have been tested in Olkiluoto for the sealing of fractures with the small hydraulic aperture. A promising non-cementitious inorganic grout material for sealing the fractures of the apertures less than 0.05 mm is commercial colloidal silica called silica sol. The use of colloidal material has to be considered in the long-term safety assessment of a spent nuclear fuel repository. Objective of this work was to determine colloid release from the silica sol gel and stability of silica colloids in different groundwater conditions. To use silica sol as a grout, the injected colloids have to aggregate and form a gel within a predictable time by using a saline solution as an accelerator. Silica sol gel samples were stored in contact with medium salinity and low salinity groundwater simulates. Release of silica colloids and colloid stability was followed by analyzing the colloid concentration, particle size distribution, concentration of reactive silicon, solution pH and zeta potential after one month, half a year and one year. Malvern Zetasizer Nano ZS equipment was used to determine colloidal particle size distributions applying the dynamic light scattering method and zeta potential based on dynamic electrophoretic mobility. The colloidal particle concentration was estimated from Zetasizer measurements applying a standard series. Dissolved reactive silica concentration was determined using the molybdate blue method and total silica concentrations were determined using ICP–MS.
The release and stability of silica colloids were found to be dependent significantly on groundwater salinity. Zeta potential values near zero and the increase in particle size at first and then the disappearance of large particles indicated particle flocculation or coagulation and instable colloidal dispersion in a saline groundwater simulate. In low salinity ground water simulate high negative zeta potential values, small particle size and constant size distribution indicate the existence of stable silica colloids. The concentrations of the released colloids were slightly higher than determined in natural granitic ground waters. Under prevailing saline groundwater conditions in Olkiluoto no significant release of colloids from silica sol is expected but the possible influence of low salinity glacial melt waters has to be considered.
Mechanism of Decarburization of Alloy 617 at 1000°C in Helium Containing CO and CO2 as impurities
Authors: Kumar Deepak , Was Gary S.
Published: August 2010

The objective of this study was to determine the mechanism of decarburization of alloy 617 by investigating the surface and bulk stabilities of the alloy in helium gas containing only CO and CO2 impurities over the temperature range 900-1000°C. For this purpose, the alloy was pre-oxidized at 900°C for 150h in He + 15 ppm CO + 1.6 ppm CO2 gas mixture and subsequently decarburized at 1000°C for additional 100h. The reaction mechanism was corroborated through gas phase analysis, microstructural examination and micro-probe measurements. It was determined that decarburization of the alloy occurred via a reaction between the porous Cr2O3 scale (formed during pre-oxidation) and carbon in the alloy, resulting in chromium metal and carbon monoxide. The chromium diffused back into the matrix, whereas the carbon monoxide escaped the sample through existing cracks and pores in the oxide. Therefore, this study shows that decarburization of alloy 617 occurs in a helium gas containing only CO and CO2 impurities.
Effects of hydrogen permeation on W, Mo and Cu Langmuir probes at ISTTOK
Authors: Nunes D. , Carvalho P.A. , Mateus R. , Nogueira I.D. , Deus A. Moita de , Correia J.B. , Shohoji N. , Gomes R.B. , Fernandes H. , Silva C. , Franco N. , Alves E.
Published: August 2010

The microstructures of tungsten, molybdenum and copper wires used as Langmuir probes at ISTTOK edge plasma have been investigated. The probes cross-sections evidenced extensive grain growth, intergranular bubbles and increased hardness at the plasma exposed regions. Internal surfaces of large bubbles exhibited slip bands resulting from plastic deformation induced by high H2 pressure. Elastic recoil detection analysis was used to measure H concentration profiles. The present results suggest that H2 bubble formation in first wall components under long-term high thermal loads should be closely monitored in nuclear fusion devices. Strategies for H damage mitigation are proposed and discussed.
Catalytic Property of Chemically Pretreated Ni3Al/Ni Two-phase Alloy Foils for Methane Steam Reforming
Authors: Kamikihara Daisuke , Xu Ya , Demura Masahiko , Hirano Toshiyuki
Published: August 2010

We have found that Ni3Al intermetallics shows catalytic activity for H2 production reaction, such as methane steam reforming. In addition to the single-phase Ni3Al, we recently studied the catalytic property of the Ni3Al/Ni two-phase alloy in foil form, and have found that the catalytic activity is not so high in the cold-rolled state. In case of atomized Ni3Al powder with a NiAl/Ni3Al two-phase structure in fact, it is possible to improve the catalytic activity for methane steam reforming by chemical pretreatment in acid and subsequent alkali solutions [1]. The reason was similarly due to the formation of fine Ni particles on the porous surface. These results show a possibility to improve the catalytic activity of Ni3Al/Ni two-phase alloy foils by the two-step chemical treatment similar as powder. In this study we carried out this chemical pretreatment on the surface of Ni3Al/Ni two-phase alloy foil and the catalytic properties for methane steam reforming were evaluated. Ni3Al/Ni two-phase alloy foil (Ni-18 at% Al) with a thickness of 30 μm was used. The chemical pretreatment consisted of two steps, the first step was acid leaching (HCl + HNO3, vol. ratio 3:1) and the second step was alkali leaching (NaOH solution, 20 wt%). Methane steam reforming was carried out in a conventional fixed-bed flow reactor as described in previous reports [1]. Prior to the reaction, the foil was reduced at 873 K for 1 hour by H2. Then isothermal test was carried out at 1123 K for 50 hours under steam-to-carbon ratio of 1. The surface morphology was analyzed using SEM and EDS. The chemically pretreated foil showed much higher catalytic activity for methane steam reforming than the non-treated foil. Especially, the catalytic activity rapidly increased during in the first several hours, and then slowly increased during the subsequent reaction. The maximum H2 production rate was about 30 L/min/m2. This value was 40 times higher than the non-treated foil. This result indicated that the catalytic activity can be improved by chemical pretreatment in acid and subsequent alkali solutions. The surface morphology observation revealed that acid leaching dissolved Ni3Al phase and alkali leaching dissolved Al mainly, resulting in the Ni-enriched surface structure. We consider that this Ni-enriched surface introduced by the two-step chemical treatment attributed to the initial catalytic activity. It also revealed that many fine Ni particles were formed on the surface during the reaction, and the amount of fine Ni particles increased with time. We consider that these Ni particles produced during reaction, contributed to the increase of catalytic activity during reaction. [1] Y. Ma, Y. Xu, M. Demura, D.H. Chun, G.Q. Xie, T. Hirano, Catal. Lett. 112 (2006) 31
Transmission Electron Microscopy of Fe2Nb Laves Phase with C14 structure in Fe-Nb-Ni Alloys
Authors: Takata Naoki , Ishikawa Shigehiro , Matsuo Takashi , Takeyama Masao
Published: August 2010

The lattice structure of the C14 Fe2Nb Laves phase with Ni in solution in Fe-Nb-Ni ternary alloys was examined by transmission electron microscopy. Binary stoichiometric Fe2Nb (Fe-33.3 at.% Nb) exhibits a featureless morphology with a low dislocation density. A similar morphology was observed in stoichiometric Fe2Nb containing 20 at.% Ni and in binary Fe-rich Fe2Nb (Fe-27.5 at.% Nb). In contrast, many planar faults parallel to the basal plane of the C14 structure were observed in Fe-rich Fe2Nb with Ni in solution, and the fault density increases with increasing Ni content up to 33.1 at.%. The high resolution transmission electron microscope (HRTEM) analysis revealed that the planar faults are related to the local change in the stacking sequence of the three 36-nets (triple layer) of the C14 structure. These results suggest that the presence of both, the point defects (Fe sublattice sites occupied by Ni atoms) and the anti-site defects (Nb sublattice sites occupied by excess Fe atoms), facilitate the formation of the planar faults.
Wireless Remote 2-D Strain Sensor using SAW Delay Line
Authors: Nomura Toru , Saitoh Atushi
Published: August 2010

Two-dimensional (2-D) strain sensor utilizing surface acoustic wave (SAW) devices is demonstrated. SAW devices offer many attractive features for applications as chemical and physical sensors. In this paper, a novel SAW strain sensor that employs SAW delay lines has been designed. Two crossed delay lines were used to measure the two-dimensional strain. A wireless sensing system is also proposed for effective operation of the strain sensor.
Study the Conduction Mechanism and the Electrical Response of Strained Nano-thin 3C-SiC Films on Si used as Surface Sensors
Authors: Rahimi Ronak , Miller Christopher M , Munger Alan , Raghavan Srikanth , Stinespring C D , Korakakis D
Published: August 2010

Various superior properties of SiC such as high thermal conductivity, chemical and thermal stability and mechanical robustness provide the basis for electronic and MEMS devices of novel design [1]. This work evaluates heterostructures that consist of a few nanometers-thick 3C-SiC films on silicon substrates. Nano-thin SiC films differ significantly in their electrical behavior compared to the bulk material [2], a finding that gives rise to a potential use of these films as surface sensors. To gain a better understanding of the effect of surface states on the electrical response of these thin, strained films, several metal-semiconductor-metal heterostructures have been examined under variable conditions. The nano-thin, strained films were grown using gas source molecular beam epitaxy. Reflection high-energy electron diffraction patterns obtained from several 3C-SiC films indicate that these films are strained nearly 3% relative to the SiC lattice constant. Al, Cr and Pt contacts to a nano-thin film 3C-SiC were deposited and characterized. I-V measurements of the strained nano-thin films demonstrate metal-semiconductor-metal characteristics. Band offsets due to biaxial tensile strain introduced within the 3C-SiC films were calculated and band diagrams incorporating strain effects were simulated. Electron affinity of 3C-SiC has been extracted from experimental I-V curves and is in good agreement with the value that has been calculated for a strained 3C-SiC film [3]. On the basis of experimental and simulation results, an empirical model for the current transport has been proposed. Fabricated devices have been characterized in a controlled environment under hydrogen flow and also in a reactive ambient, while heating the sample and oxidizing the surface, to investigate the effects of the environment on the surface states. Observed changes in I-V characteristics suggest that these nano-thin films can be used as surface sensors.
Degradation of Vertically Aligned Carbon Nanotubes at Growth Interface Joints at High Temperatures and Its Impact on Electron Emission Properties
Authors: Jin Feng , Liu Yan , Day Chris , Little Scott
Published: August 2010

Degradation of carbon nanotubes (CNTs) significantly affects CNT's electron emission capability and limits their applications as electron emitters. In this study, CNTs were placed in controlled environment and their degradations were studied. Two types of CNT degradations, thermal and chemical degradations were identified and their effects on electron emission were studied. It was found that CNTs placed in low vacuum environment at high temperature were subject to oxidation that led to severe degradation of CNTs and their electron emission ability, whereas, CNTs treated at the same high temperatures in an ultrahigh vacuum environment only suffered from morphological changes that had minor impact on electron emission. The CNT samples used in this study were grown on tungsten substrates via plasma enhanced chemical vapor deposition (PE-CVD). The surface morphology changes of the CNT emitters were examined using scanning electron microscopy (SEM). The field emission properties of the CNTs were measured and correlated to the morphology changes.
High Yield and High Throughput Reactive IBAD MgO Process for Long-length, HTS Wire Production at SuperPower
Authors: Xiong Xuming , Zdun karol , Kim Sunjing , Rar Andrei , Sambandam Senthil , Schmidt Robert , Chen Yimin , Lenseth Kenneth , Selvamanickam Venkat
Published: August 2010

SuperPower's IBAD (ion beam assisted deposition) MgO process has been changed to reactive ion beam sputtering of Mg metal target instead of MgO ceramic target, which gives ∼ 60 % increase in deposition rate. The process speed was increased from 195 m/h to 360 m/h. Texture of IBAD MgO tapes by this reactive process was found to degrade faster during long length run. This uniform issue was resolved with feedback control during long run and from run to run. The bottleneck of alumina layer process due to slow ion beam sputtering deposition was removed by new high rate reactive magnetron sputtering at transition mode. The new alumina process speed can be as high as 3,000 m/h in our Pilot Buffer system. The yttria layer process was also changed to high rate reactive magnetron sputtering at transition mode with achievable speed as high as 10,000 m/h in our Pilot Buffer system. The routine production speed of alumina and yttria is 750 m/h due to limitation of tape driving system. The high rate magnetron-sputtered alumina/yttria yields the same texture of IBAD MgO as ion beam sputtered alumina/yttria. Now we are routinely producing IBAD MgO template tapes of ∼ 1.4 km with a uniform in-plane texture ∼ 6-7 degrees. Record high critical current of 813 A/cm over a one meter length and a world record critical current times length value of > 233,8100A-m was obtained with our routinely-produced high throughput IBAD MgO buffers. The requirements for a better IBAD texturing layer than IBAD MgO are also suggested.
Light Trapping effects in Thin Film Silicon Solar Cells
Authors: Haug Franz-Josef , Söderström Thomas , Dominé Didier , Ballif Christophe
Published: August 2010

We present advanced light trapping concepts for thin film silicon solar cells. When an amorphous and a microcrystalline absorber layers are combined into a micromorph tandem cell, light trapping becomes a challenge because it should combine the spectral region from 600 to 750 nm for the amorphous top cell and from 800 to 1100 for the microcrystalline bottom cell. Because light trapping is typically achieved by growing on textured substrates, the effect of interface textures on the material and electric properties has to be taken into account, and importantly, how the surface textures evolve with the thickness of the overgrowing layers. We present different scenarios for the n-i-p configuration on flexible polymer substrates and p-i-n cells on glass substrate, and we present our latest stabilized efficiencies of 9.8% and 11.1%, respectively.
Defect Study of Polycrystalline–silicon Seed Layers made by Aluminum Induced Crystallization
Authors: Venkatachalam Srisaran , Van Gestel Dries , Gordon Ivan
Published: August 2010

A polycrystalline silicon (pc-Si) thin film with large grains on a low-cost non-Si substrate is a promising material for thin-film solar cells. One possibility to grow such a pc-Si layer is by aluminum-induced crystallization (AIC) followed by epitaxial thickening. The best cell efficiency we have achieved so far with such an AIC approach is 8%. The main factor that limits the efficiency of our pc-Si solar cells at present is the presence of many intra-grain defects. These intra-grain defects originate within the AIC seed layer. The defect density of the layers can be determined by chemical defect etching. This technique is well suited for our epitaxial layers but relatively hard to execute directly on the seed layers. This paper presents a way to reveal the defects present in thin and highly-aluminum-doped AIC seed layers by using defect etching. We used diluted Schimmel and diluted Wright etching solutions. SEM pictures show the presence of intra-grain defects and grain boundaries in seed layers after defect etching, as verified by EBSD analyses. The SEM images of diluted Wright etched pc-Si seed layer shows that grain boundaries become much better visible than with diluted Schimmel etch.
First-principles Modeling of Structure, Vibrations, Electronic Properties and Bond Dynamics in Hydrogenated Amorphous Silicon: Theory versus Experiment
Authors: Shkrebtii Anatoli , Kupchak Ihor , Gaspari Franco
Published: August 2010

We carried out extensive first-principles modeling of microscopic structural, vibrational, electronic properties and chemical bonding in hydrogenated amorphous silicon (a-Si:H) in a wide range of hydrogen concentration and preparation conditions. The theory has been compared with experimental results to comprehensively characterize this semiconductor material. The computer modeling includes ab-initio Molecular Dynamics (MD), atomic structure optimization, advanced signal processing and computer visualization of dynamics. We extracted parameters of hydrogen and silicon bonding, electron charge density and calculated electron density of states (EDOS) and hydrogen diffusion. A good agreement of the theory with various experiments allowed us to correlate microscopic processes at the atomic level with macroscopic properties. Here we focus on correlation of the amorphous structure of the material, atom dynamics and electronic properties. These results are of increasing interest due to extensive application of a-Si:H in modern research and technology and to the significance of detailed understanding of the material structure, bonding, disordering mechanisms and stability.
Single and Mixed Self-Assembled Monolayers of Phenyl Species on SiO2 with Various Ring to Ring Interactions
Authors: Gadenne Virginie , Desbief Simon , Patrone Lionel
Published: August 2010

We studied the formation of phenylalkyltrichlorosilane self-assembled monolayers on native oxide covered silicon. After a first chemisorption step in the monolayer growth, the presence of the short alkyl chain (3-4 carbon atoms) is responsible for a second growth step which corresponds to the arrangement between molecules. We found that this packing step is accelerated by replacing phenyl by pentafluoro-phenyl rings, possibly due to quadrupolar interactions between fluorinated cycles. Furthermore we demonstrate that mixing phenyl and pentafluoro-phenyl molecules leads to an even faster packing step which is accounted for by hydrogen bonding CH...FC in a face to face phenyl/pentafluoro-phenyl arrangement. We believe these results allow improving charge delocalization over conjugated molecular domains. In a second part, we studied the phase separation between phenyl-alkyltrichlorosilane and octadecyltrichlorosilane (OTS) molecules. Improving the phase separation was studied using ring to ring interactions afore-analyzed. We show phase separation is improved and OTS islands are smaller with phenyl species that involve stronger ring to ring interactions. The best case is obtained with mixing phenyl and pentafluoro-phenyl rings using hydrogen bonds for packing together the aromatic species. These results demonstrate improved control of SAM composition and morphology essential to further use the obtained islands for building molecular devices.
Towards Greatly Improved Efficiency of Polymer LED
Authors: Zhou Zhang-Lin , Sheng Xia , Zhao Lihua , Gibson Gary , Lam Sity , Nauka K. , Brug James
Published: August 2010

Polymer light-emitting diodes (PLEDs) show great promise of revolutionizing display technologies. The archetypical multilayer PLED heterostructure introduces numerous chemical and physical challenges to the develoment of efficient and robust devices. These layered structure are formed from solution based spin-casting or printing with subsequesnt removal of the solvent. However, solvent from the freshly deposited film may dissolve or partially dissolve the underlying layer resulting in loss of the desired structure and corresponding device functionality. Undesirable changes in the morphology and interfaces of the polymer films are another detrimental effect associated with solvent removal. Herein, we demonstrated that by embedding hole transporting materials (HTLs) in a cross-linked polymer matrix, the total luminance and external quantum efficiency were greatly improved over devices without this HTL layer.
Degradation of Ir(ppy)2(dtb-bpy)PF6 iTMC OLEDs
Authors: Goldberg Velda , Kaplan Michael D. , Soltzberg Leonard , Armira Dolly , Bigelow Megan , Bitzas Stephanie , Brady Rachel , Browne Shannon , Dichiaro Bianca , Foley Heather , Hutchinson Lauren , Inglis Alison , Kawamoto Nicole , McLaughlin Amanda , Millett Caitlin , Nasri Hanah , Newsky Sarah , Pham Tram , Saikin Cassandra , Scharpf Mary , Trieu Melissa , Malliaras George G. , Bernhard Stefan
Published: August 2010

Simplicity of construction and operation are advantages of iTMC (ionic transition metal complex) OLEDs compared with multi-layer OLED devices. Unfortunately, lifetimes do not compare favorably with the best multi-layer devices. We have previously shown for Ru(bpy)3(PF6)2 based iTMC OLEDs that electrical drive produces emission-quenching dimers of the active species. We report evidence here that a chemical process may also be implicated in degradation of devices based on Ir(ppy)2(dtb-bpy)PF6 albeit by a very different mechanism. It appears that degradation of operating devices made with this Ir-based complex is related to current-induced heating of the organic layer, resulting in loss of the dtb-bpy ligand. (The dtb-bpy ligand is labile compared with the cyclometallated ppy ligands.) Morphological changes observed in electrically driven Ir(ppy)2(dtb-bpy)PF6 OLEDs provide evidence of substantial heating during device operation. Evidence from UV-vis spectra in the presence of an electric field as well as MALDI-TOF mass spectra of the OLED materials before and after electrical drive add support for this model of the degradation process.
Stress Gradients Observed in Cu Thin Films Induced by Capping Layers
Authors: Murray Conal E. , Besser Paul R. , Witt Christian , Jordan-Sweet Jean L.
Published: August 2010

Glancing-incidence X-ray diffraction (GIXRD) has been applied to the investigation of depth-dependent stress distributions within electroplated Cu films due to overlying capping layers. 0.65 μm thick Cu films plated on conventional barrier and seed layers received a CVD SiCxNyHz cap, an electrolessly-deposited CoWP layer, or a CoWP layer followed by a SiCxNyHz cap. GIXRD and conventional X-ray diffraction measurements revealed that strain gradients were created in Cu films possessing a SiCxNyHz cap, where a greater in-plane tensile stress was generated near the film / cap interface. The constraint imposed by the SiCxNyHz layer during cooling from the cap deposition temperature led to an increase in the in-plane stress of approximately 180 MPa from the value measured in the bulk Cu. However, Cu films possessing a CoWP cap without a SiCxNyHz layer did not exhibit depth-dependent stress distributions. Because the CoWP capping deposition temperature was much lower than that employed in SiCxNyHz deposition, the Cu experienced elastic deformation during the capping process. Cross-sectional transmission electron microscopy indicated that the top surface of the Cu films exhibited extrusions near grain boundaries for the samples undergoing the thermal excursion during SiCxNyHz deposition. The conformal nature of these caps confirmed that the morphological changes of the Cu film surface occurred prior to capping and are a consequence of the thermal excursions associated with cap deposition.
Research Progress in the Resistance Switching of Transition Metal Oxides for RRAM Application: Switching Mechanism and Properties Optimization
Authors: Wang Qun , Li Xiaomin , Chen Lidong , Cao Xun , Yang Rui , Yu Weidong
Published: August 2010

Electric-induced resistance switching (EIRS) effect based on transition metal (TM) oxides, such as perovskite manganites (Pr1-xCaxMnO3, La1-xCaxMnO3) and binary oxides (NiO, TiO2 and CoO) etc, has attracted great interest for potential applications in next generation nonvolatile memory known as resistance random access memory (RRAM). Compared with other nonvolatile memories, RRAM has several advantages, such as fast erasing times, high storage densities, and low operating consumption. Up to date, the switching mechanism, property improvement and new materials exploitation are still the hotspots in RRAM research.

In this report, the main results of resistance switching of two kinds of TM oxides including La0.7Ca0.3MnO3 and TiO2 were presented. Based on the I-V characteristics, the field-direction dependence of resistance switching (RS) behavior, and the conduction process analysis, the EIRS mechanisms were studied in detail. For the La0.7Ca0.3MnO3 film, the EIRS mechanism was related to the carrier injected space charge limited current (SCLC) conduction controlled by the traps existing at the interface between top electrode and La0.7Ca0.3MnO3 film. The RS behavior is produced by the trapping/detrapping process of carriers under different voltages. For the TiO2 film, both unipolar and bipolar RS behavior can be obtained in our experiments. The interface controlled filamentary mechanism was proposed to explain the unipolar EIRS in nanocrystalline TiO2 thin films, while the bipolar RS behavior may be related to the charge trapping or detrapping effect. In addition, it was confirmed that the I-V sweeps in vacuum environment, the applying of asymmetry pulse pairs and the oxygen annealing of films can improve the endurance of the EIRS devices. Our researches will provide some meaningful clues to understanding the EIRS mechanism and some useful pathways for the development of RRAM devices.
Investigation of Resistance Switching Properties in Undoped and Indium Doped SrTiO3 Thin Films Prepared by Pulsed Laser Deposition
Authors: Li Xiaomin
Published: August 2010

In this paper, the undoped SrTiO3 (STO) and Indium doped STO (SrTi1-xInxO3: STIO) thin films were grown on Pt/Ti/SiO2/Si substrates by pulsed laser deposition with low substrate temperature. For undoped STO film, the influences of the forming processes on their resistive switching properties were studied by current and voltage controlled I-V sweeps, respectively. An obvious current controlled negative differential conductance phenomenon was found in both polarities of the electrical field. However, for low Indium doped STIO (x=0.1), the filament related resistance switching was observed in both the current and voltage I-V sweeps. And for high Indium doped STIO (x=0.2), a resistance switching with a reverse direction change to that in undoped STO can be obtained by a proper forming process. Based on these results, the reversible change of the Schottky like barrier at the grain boundary by the migration of oxygen vacancies were proposed to interpret the mechanism of the resistance switching.
Growth of Epitaxial ZnO:Mn/ZnO:V Heterostructures and Ferroelectric-ferromagnetic Characterization
Authors: Mukherjee Devajyoti , Dhakal Tara , Srikanth Hariharan , Mukherjee Pritish , Witanachchi Sarath
Published: August 2010

The wide band gap semiconductor ZnO is well known for its multifunctionality in the form of ferromagnetism (FM), piezoelectricity, and magneto optics. ZnO has been found to grow with intrinsic oxygen deficiencies which in turn are believed to give ferromagnetism and high conductivity in this material. Doping Zn2+ sites by V5+ ions creates a mixed valency as well as strain in the original ZnO hexagonal structure because of the reduced ionic size of vanadium. The mixed valency creates charge polarity between Zn-O and V-O bonds. This charge polarity and the rotation of the nonlinear V-O bonds with respect to Zn-O bonds under electric field have been shown to produce ferroelectricity. Furthermore, Mn doping of ZnO has also shown enhancement in ferromagnetic properties in ZnO. For this material to be a viable ferromagnetic material the magnetic properties should not be from segregated phases. In the present study we have grown undoped, Mn, and V doped ZnO thin films using pulsed laser deposition (PLD). ZnO target with 2% atomic Mn doping and a target with 0.5% atomic V doping were prepared by solid state reactions and sintering. Films were grown both epitaxially on sapphire substrates and in polycrystalline form on silicon substrates. Magnetization measurements by the PPMS showed M vs. H hysteresis loops with saturation for all ZnO: Mn films. V doped films showed high saturation polarization for film deposited at high pressures. We have also fabricated epitaxial bilayers of ZnO:V/ZnO:Mn on sapphire substrates. Ferroelectric and ferromagnetic properties of these heterostructures are presented.
Fabrication and Magneto-Capacitance Measurements of PbNb0.02Zr0.2Ti0.8O3/La0.7Sr0.3MnO3/SiO2/Si Structure Grown by Chemical Solution Deposition
Authors: Kotru Sushma , Nampoori Harshan V.
Published: August 2010

Multiferroic composite thin films consisting of PbNb0.02Zr0.2Ti0.8O3 (PNZT) and La0.7 Sr0.3 MnO3 (LSMO) were deposited on SiO2/Si substrates. SiO2 films were deposited by pulsed electron deposition and LSMO and PNZT films were prepared using chemical solution deposition process using a metal organic deposition route. Individual films and the test structure PNZT/LSMO/ SiO2/Si were characterized using various characterizing techniques. Preliminary results of magnetic field dependent capacitance (magneto-capacitance) on the test structure are reported. A change in capacitance from 18.92 pf to 5.49 pf is observed as frequency changes from 50 KHz to 1 MHz, when no external magnetic field is applied. When a magnetic field of 330 Oe (positive or negative) is applied, the change in magneto-capacitance is appreciable, with a maximum change of 37 % being observed at a frequency of 1 MHz.