bluuebunny/crossref_metadata_2025 huggingface dataset:
Contaminated Sediment as a Source of PCBs in a River System
Authors: Larsson Per , Okla Lennart , Ryding Sven-Olof , Westöö Bengt
Published: November 2008

The transport of PCBs (Aroclor 1242) in a river system in southern Sweden was governed by outflow from sediment in a 26-ha contaminated lake. Experiments in the lake revealed that 14 g PCBs/d escaped from the sediment, while sedimentation was 3 g PCB/d. Volatilization of PCBs from the lake surface was 0.02 g/d, which was considerably higher than the atmospheric fallout [Formula: see text]. The majority of the sediment-desorbed compounds (80%) remained at the river mouth, 60 km downstream, and entered the Baltic Sea. Desorption increased the ratio of tetrachlorobiphenyls to pentachlorobiphenyls in the water. Transport across the water/air interface was higher for trichlorobiphenyls, while atmospheric deposition was dominated by penta- and hexachlorobiphenyls. Therefore, the sediment of the lake acted as a source of PCBs entering the river system as well as the atmosphere.
Effects of Extended Daylength on Autumn Growth Dynamics of Juvenile Atlantic Salmon, Salmo salar
Authors: Stewart Mark W. , Saunders Richard L. , Wiggs A. J.
Published: November 2008

The growth and growth dynamics of juvenile Atlantic salmon (Salmo salar) exposed from mid-August to mid-December to either a normal light:dark cycle (LDN) or a constant 16-h light:8-h dark (LD 16:8) photoperiod were compared. Exposure to the LD 16:8 resulted in 38.1% of the fish entering the upper modal group (UMG) of the length–frequency distribution, while only 15.4% entered the UMG under LDN. The length at which fish entered the UMG (critical fork length) did not differ between photoperiods. Fish in the small (5.8–6.7 cm) and middle (6.8–7.7 cm) size-ranges under LD 16:8 had greater growth rates than fish in the same size-ranges under LDN. Fish in the large (8.3–9.2 cm) size-range showed no significant variation in growth rates between photoperiods. At the end of the experiment, mean thyroxine (T4) levels were significantly (P < 0.05) lower in fish from the LD 16:8 photoperiod (1.69 ng/mL) in comparison with LDN fish (3.96 ng/mL). Triiodothyronine (T3) levels and the T3/T4 ratio were elevated under LD 16:8.
Phase Differences between Check Ring Locations in the Orange Roughy Otolith (Hoplostethus atlanticus)
Authors: Gauldie R. W.
Published: November 2008

Orange roughy (Hoplostethus atlanticus) otoliths were shown to have two different mineral phases of aragonite in the upper (anti-sulcul) and lower (sulcul) parts of medio-lateral sections of otoliths. The difference in mineral phase was characterised by differences in the direction of crystal growth, crystal size and crystal jointing. The effect of the difference in mineral phase was to change the patterns of homologous check rings observed in both the upper (anti-sulcul) and lower (sulcul) parts of the otolith. On average, about 24% of the information contained in check ring pattern of the upper (anti-sulcul) part of the otolith was retained in the lower (sulcul) part of the otolith. The loss of information may explain the difficulty in reconciling age interpretations made from sulcul check rings with age interpretations made from ultrastructural patterns in the anti-sulcul parts of medio-lateral sections of otoliths.
Use of Artificial Substrates to Estimate Prey Resources available to a Visually Feeding Benthivorous Fish
Authors: Konkle Blake R. , Collins Nicholas C. , Baker Robert L.
Published: November 2008

Empirically derived estimates of prey resources using conventional sampling methods are generally poor indices of actual food available to visually feeding benthivorous fish. We preferentially sampled the most active fraction of the benthos (presumably that most detectable by fish) utilizing short-term (4 d) colonization of artificial substrates, and used colonist biomass to explain temporal variation in stomach contents of bluegill sunfish (Lepomis macrochirus) in Lake Opinicon, Ontario. Simple linear regressions showed that total biomass of colonists explained 75% of the variance in the biomass of stomach contents. Independent variables using a limited taxonomic range or size range of colonists explained less variance in stomach contents. The convenience and simplicity of this methodology, and its ability to explain within-lake variation in food exploitation by visual benthivores, suggest that artificial substrate colonization could be useful for surveys of prey availability to benthivorous fishes.
Estimation of Submergent Plant Bed Biovolume using Acoustic Range Information
Authors: Thomas G. L. , Thiesfeld S. L. , Bonar S. A. , Crittenden R. N. , Pauley G. B.
Published: November 2008

Acoustic measurements of the distance between the water surface, top of the aquatic plants, and bottom of the water column were made using chart recording echosounders. The vertical cross sectional area (m2), height (m), biovolume (m3), of aquatic plant beds and variances were computed for three surveys of Devils Lake, Oregon, in May, July, and September, 1986 when coefficients of variation for the plant bed biovolume estimates were 0.18, 0.05, and 0.06, respectively (n = 14). Coefficients of variation for plant biomass estimates (g/m2) computed from SCUBA quadrat samples collected concurrently with the acoustic surveys, were 0.98 (n = 48), 0.81 (n = 90), and 1.05 (n = 90), respectively. The higher precision of the biovolume estimates allow for a 5- to 18-fold greater capability to detect a change in the mean. The lower costs of the biovolume estimates allow for a 10- to 33-fold greater precision-for-cost. The plant bed biovolume variable contains ecologically different information than the biomass variable in that it provides a direct estimate of the amount of aquatic habitat in a lake that is influenced by plants; it should prove useful for evaluating plant control practices and possibly for studying plant-fish interactions.
Effects of Temperature on Metabolism of Benzo[a]pyrene by Toadfish (Opsanus beta) Hepatocytes
Authors: Gill Kenneth A. , Walsh Patrick J.
Published: November 2008

Prior in vivo studies of the effects of temperature on uptake, metabolism and excretion of benzo[a]pyrene (BaP) by the gulf toadfish (Opsanus beta) suggested that metabolism of BaP may be partially temperature insensitive under certain conditions. In the present study, hepatocytes were isolated from toadfish acclimated to 18 or 28 °C, and then cells were exposed to BaP at 18, 23, and 28 °C in vitro to more directly examine the effects of temperature on metabolism. Toadfish hepatocytes metabolized BaP to a variety of Phase I and Phase II metabolites in similar proportions to toadfish in vivo, with the exception that fewer Phase I metabolites were detected. A marked temperature dependence of metabolism of BaP to Phase II metabolites was noted between 18 and 28 °C at near saturating concentration of BaP (13 μg∙mL−1). Warm-acclimated toadfish displayed a lower temperature sensitivity than cold-acclimated toadfish (Q10, the ratio of the rate at T + 10 °C: rate at T = 1.85 and 2.65, respectively). However, at a lower, subsaturating concentration of BaP (5 μg∙mL−1), production of all metabolites showed a marked temperature independence. We speculate that this independence is the result of temperature effects on the kinetic properties of the enzymes of xenobiotic metabolism.
Cyclic Dominance and Optimal Escapement of Adams River Sockeye Salmon (Oncorhynchus nerka)
Authors: Welch D. W. , Noakes D. J.
Published: November 2008

We examined escapement policies for a stock-recruitment model with negative between-year interactions. Regardless of the degree of interaction present, the optimal policy is to always equalize escapement. Parameter estimates obtained for the Adams River sockeye salmon (Oncorhynchus nerka) indicate that between-year interactions may occur, but confidence regions include the null hypothesis of no interaction at all (the Ricker model). We conclude that the extreme amplitude of the current recruitment cycle in this stock frustrates statistical identification of interaction. It seems unlikely that between-year interactions will be measurable until the off year runs increase by at least two to three orders of magnitude. Comparison of total yields for the Adams River sockeye shows that an equal escapement policy could increase yields by at least 35% over that obtained by the current cyclic escapement pattern. This is equivalent to obtaining an additional $27 million in total yield per annum from the Adams River stock alone and, assuming a discount rate of 4%, translates into an increase in net present value of $675 million. If between-year interactions do not exist, the potential benefits of moving to an equal escapement policy are even larger, on the order of $3 to $4 billion.
DNA Transfer from Organelles to the Nucleus: The Idiosyncratic Genetics of Endosymbiosis
Authors: Kleine Tatjana , Maier Uwe G. , Leister Dario
Published: November 2008

In eukaryotes, DNA is exchanged between endosymbiosis-derived compartments (mitochondria and chloroplasts) and the nucleus. Organelle-to-nucleus DNA transfer involves repair of double-stranded breaks by nonhomologous end-joining, and resulted during early organelle evolution in massive relocation of organelle genes to the nucleus. A large fraction of the products of the nuclear genes so acquired are retargeted to their ancestral compartment; many others now function in new subcellular locations. Almost all present-day nuclear transfers of mitochondrial or plastid DNA give rise to noncoding sequences, dubbed nuclear mitochondrial DNAs (NUMTs) and nuclear plastid DNAs (NUPTs). Some of these sequences were recruited as exons, thus introducing new coding sequences into preexisting nuclear genes by a novel mechanism. In organisms derived from secondary or tertiary endosymbiosis, serial gene transfers involving nucleus-to-nucleus migration of DNA have also occurred. Intercompartmental DNA transfer therefore represents a significant driving force for gene and genome evolution, relocating and refashioning genes and contributing to genetic diversity.
Biomechanical Research of TiNb Alloys with Electrochemical Treatment Using Finite Element Method
Authors: Cheng Hsin-Chung , Shih Yung-Hsun , Peng Pei-Wen , Pan Yung-Ning , Ou Keng-Liang
Published: November 2008

In the present study, atomic force microscopy, contact angle instrument and the nano-indentation were conducted to evaluate the effects of oxide layers on TiNb alloys with and wiout surface treatment (TiNb, A-TiNb and AC-TiNb). In addition, the biomechanical properties of TiNb, A-TiNb and AC-TiNb were evaluated by finite element (FE) computer simulations. The results revealed that the rough surface and wettability property of TiNb alloy could be obtained after surface treatments. Furthermore, the surface properties of TiNb, A-TiNb and AC-TiNb are all relative the surface treatments. The elastic modulus of AC-TiNb was reduced to be closed to that of bone tissue. The gradual mechanical properties existed on the TiNb treated samples. The phenomena that more stress shared by bone tissue with treated metallic screws were showed in FEM models. In conclusion, the oxide layers formed by anodization with cathodical pretreatment played an important role in enhancing the biocompatibility and biomechanical ability of TiNb alloys. These results demonstrated that new AC-TiNb alloys not only contain nontoxic constituents but have relatively surperior biomechanical capability as well.
High Frequency Surface Acoustic Wave Devices Based on Multilayered LiNbO3/Diamond/AlN Substrates: A Finite Element Study
Authors: Sankaranarayanan Subramanian K. , Cular Stefan , Bhethanabotla Venkat
Published: November 2008

We have used 3-D coupled field structural finite element models to study the acoustic wave propagation characteristics of diamond/AlN/LiNbO3 multi-layered piezoelectric surface acoustic wave devices under the influence of fluid loading for applications in chemical and biological sensing. These devices were studied as a method to increase device frequency and sensitivity, and maintain standard fabrication procedures. Although recent experimental investigations have realized GHz frequency devices based on such multilayered substrates, very little is known about the acoustic wave propagation characteristics in these devices. Identifying the optimum configuration and thickness of the various layers involved still represents a challenge which is addressed in this work.
Dual FFPI Strain Sensor with Low-Cost LED Light Source
Authors: Wang Mu-Chun , Hsieh Zhen-Ying , Wang Jon-En , Huang Heng-Sheng
Published: November 2008

Seeking an accurate, reliable, highly sensitive, and low-cost detector is always an exciting challenge for sensor researchers. Here, a dual fiber-optic Fabry-Perot interferometer (FFPI) for strain sensors with a low-cost communication light-emitting diode (LED) replacing expensive laser diode was experimentally implemented. Both an expensive light source and costly Faraday isolator were waived in this system. The dynamic strain modulation in the sensing FFPI was with a piezoelectric transducer (PZT). The characteristic performance showing both modulation and detection is almost identical. The temperature variation in the sensing part was simultaneously detected with demodulation of a reference FFPI.
Electroreduction of Nitrocyclopropanes and Nitroaryl Cyclopropanes
Authors: Sardashti Alireza , Nassi Achille , Couture-Martin Frédéric , Cristea Cecilia , Chapuzet Jean Marc , Lessard Jean
Published: November 2008

The electrochemical behavior of the substituted nitrocyclopropanes 3 (n = 1) as well as of the nitrophenylcyclopropanes 7 (n = 1) have been studied at a Pt electrode by cyclic voltammetry, microcoulometry, and preparative electrolysis in DMF-(n-Bu)4PF6. Electroreduction of 8 consumes one electron to give radical anion 8•−, which undergoes a homolytic C-N bond cleavage leading to the formation of the corresponding cyclopropyl radical and the nitrite ion. Electroreduction of 11 consumes 2 electrons. The radical anion 11•− is formed first followed by C-C bond cleavage (homolytic and/or heterolytic) of the cyclopropane ring leading to a distonic radical anion 5•−. The latter is reduced to the corresponding distonic dianion, which is protonated in the aqueous work up.
Synthesis and Characterization of Nanosized Calcium Zincate Powder and it Application to the Zn Electrodes
Authors: Yang Chun-Chen , Chen Po-Wei
Published: November 2008

The nanosized calcium zincate powders used as active materials for the secondary Zn electrodes were prepared by a chemical co-precipitation method. The characteristic properties of nanosized calcium zincate powders were examined by thermal gravimetric analysis (TGA), X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) mapping system, transmission electron microscope (TEM) and micro-Raman spectroscopy. For comparison, the secondary Zn electrodes prepared by both chemical precipitation (CP) and ball-milled (BM) calcium zincate powders, so-called CP-ZnCa and BM-ZnCa powders, respectively, were obtained and examined. The electrochemical performances of the secondary Zn electrodes were systematically investigated by galvanostatic charge/discharge measurements. It was shown that the electrochemical properties of the secondary Zn electrode composed of nanosized CP-ZnCa powders were greatly enhanced. Especially, the best performance for the CP-ZnCa powders were synthesized at pH 12 with a mole ratio of Zn:Ca = 2.5:1. For comparison, it was found that the secondary Zn electrode based on the CP-ZnCa powders exhibited better charge/discharge reversibility and longer life-cycle performance, as compared with that based on the BM-ZnCa powders.
Preparation and Characterization of the PVA/TiO2 Composite Polymer Membrane and its Application on Alkaline DMFC
Authors: Yang Chun-Chen , Lin Che-Tseng
Published: November 2008

A novel poly(vinyl alcohol)/titanium dioxide (PVA/TiO2) composite polymer membrane was prepared by a sol-gel method. The characteristic properties of PVA/TiO2 nanocomposite polymer membranes were systematically investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA), methanol permeability and AC impedance spectroscopy. It was found that the addition of the TiO2 fillers into the PVA polymer matrix was improved their ionic conductivities, thermal and mechanical properties, and dimensional stability. It was also found that alkaline DMFC with the PVA/TiO2 composite polymer membrane showed excellent electrochemical performance at ambient temperature and atmospheric pressure. As a result, the maximum power density of alkaline DMFC in a mixture solution of 8M KOH + 2M CH3OH is 18.42 mW cm-2 at 60oC and ambient air.
Electrochemical Investigations of the Fries Rearrangement in Ionic Liquids
Authors: Cheek Graham T.
Published: November 2008

The Fries rearrangement of phenyl benzoate has been studied in the AlCl3 : 1-butyl-1-methylpyrrolidinium chloride buffered neutral ionic liquid, giving results similar to those found in the analogous 1-ethyl-3-methylimidazolium chloride system. In the former system, it is possible to observe the reduction of sodium ion, allowing assessment of the buffer level in the system. Further work involves the Fries rearrangement of phenyl benzoate in 1-butyl-1-methylpyrrolidinium triflate ionic liquid. In contrast to the 1-ethyl-3-methylimidazolium tetrafluoroborate system, addition of Lewis acids such as aluminum chloride and boron trifluoride does not result in extensive complexation of the ester in 1-butyl-1-methylpyrrolidinium triflate. An enhancement of the ester reduction processs is, however, observed, indicating that the added acids can interact with the ester to produce an ECE process. These results suggest that the Lewis acids form adducts with the triflate anion, preventing the full activity toward the ester.
Electrochemical Reactivity and Anodic Cyanation of Germatranes
Authors: Soualmi Saida , Ignatovich Lubova , Lukevics Edmunds , Ourari Ali , Jouikov Viatcheslav V.
Published: November 2008

The electrooxidation of germatranes with different R groups at Ge was studied in CH3CN and DMF solutions. The results of cyclic voltammetry supported by DFT B3LYP/6-311G calculations suggest that donor activity of the N atom is substantially reduced by the dative N-Ge coordination compared to parent trialkylamino derivatives, Et3N and (HOCH2CH2)3N. The electro chemical reactivity of these compounds is well described by the generalized additive inductive model including mesomeric interactions. The oxidation of germatranes follows classical scheme for tertiary amines - reversible electron transfer with the ensuing deprotonation of alpha-carbon atom; last reaction was used for anodic cyanation of m-bromobenzyl germatrane.
Performance of Lithium Ion Cell Anode Graphites Under Various Cycling Conditions
Authors: Ridgway Paul , Zheng Honghe , Liu Gao , Song Xiangyun , Guerfi Abdelbast , Charest Patrick , Zaghib K. , Battaglia Vincent
Published: November 2008

Graphites MCMB-2810 and OMAC-15 (made by Osaka Gas Inc.), and SNG12 (Hydro Quebec, Inc.) were evaluated in lithium half-cells as anode materials for lithium-ion cells intended for use in hybrid electric vehicles. Though the reversible capacity obtained for SNG was slightly higher than that of OMAC or MCMB, its 1st cycle efficiency was considerably lower. Voltage vs capacity plots of cycling data show that the discharge and charge limits shift to higher capacity values due to continuation of anode side reactions. Varying the cycle charge and discharge limits was found to have an insignificant effect on fractional capacity shift per cycle.
Model Reduction via Proper Orthogonal Decomposition for the Lithium Ion Battery
Authors: Cai Long , White Ralph E.
Published: November 2008

An efficient and first-principles based reduced order model is presented using proper orthogonal decomposition for online prediction and control of lithium ion battery performance. The methodology to calculate the proper orthogonal modes and to analyze their optimality is introduced. The analysis of the dynamic properties indicates that the POD-based ROM is sensitive to the model parameters; therefore, more attention should be paid to the application of ROM while estimating parameters. The POD-based ROM for a lithium ion battery is successfully used to simulate a charge/discharge process, battery cycling and behavior of a battery pack. Compared to the rigorous model, the computational time to solve the ROM is significantly lesser and the two models show an agreement to within at least three digits.
Rechargeable Li-S Battery with Specific Energy 350 Wh/kg and Specific Power 3000 W/kg.
Authors: Mikhaylik Yuriy , Kovalev Igor , Xu Jason , Schock Riley
Published: November 2008

Rate capability improvements of Li-S cells are reported. The main goal of this work, to achieve the maximum high power benefit from the liquid polysulfide cathode system, was realized. Higher rate capability has been achieved through reduction of the electrode stack Area Specific Resistance (ASR) to below 10 Ohm*cm2, contact design improvements, and better current distribution uniformity along the electrodes and current collectors. Maximal specific power delivered by 2.5 Ah cells at 30 A pulses was 3500 W/kg. At a continuous discharge, with specific power at ~1500 W/kg, the 2.5 Ah cells delivered specific energy in excess of 200 Wh/kg.
Electrochemical Performance of Electrospun ACNF Electrodes Using Polymer Blend
Authors: Ju Young-Wan , Na Min-Young , Jung Hong-ryun , Lee Wan-Jin
Published: November 2008

The blended fibers were prepared by electrospinning using polymer blend solution of polyacrilonitrile (PAN) and cellulose acetate (CA). Various types of activated carbon nanofibers (ACNF) were synthesized through the process of stabilization, short-time carbonization, and activation using the blended fibers. The CA-free ACNF (CN) showed smooth surface, while the CA-blended ACNF appeared to be rough surface or small holes with increasing CA content. All ACNFs had aligned structure and good electrical conductivity. The specific surface area and average pore diameter of CN were 742 m2/g and 2.0 nm, respectively, while those of 15 wt.% CA-blended ACNF (CN15) were 1160 m2/g and 2.8 nm, respectively. The capacitance of CN was 141 F/g at 1 mA/cm2, whilst that of CN15 increased to 245 F/g. This is why the CN was predominated by microporosity, whereas the CN15 was formed as morphology of mesoporous high surface area by the effect of blending and electrospinning.
Electrochemical Kinetics and Perforamcne of 2-Volt Class Li-Ion Battery System with Safety, Quick-Charging, and High-Power
Authors: Takami Norio , Inagaki Hiroki , Kishi Takashi , Harada Yasuhiro , Fujita Yumi , Hoshina Keigo
Published: November 2008

Microvoltammograms of a single particle of Li4/3Ti5/3O4 (LTO) spinel were interpreted using a core shell model in the spinel/rock-salt two-phase transition process. Lithium insertion into the particle was controlled by the diffusion in Li7/3Ti5/3O4 rock-salt structure out-layer. Lithium extraction from the particle was significantly affected by the charge transfer on the LTO spinel out-layer rather than by the diffusion of lithium ions. The discharge speed during the internal short circuit abuse test connecting with the LTO anode was three orders of magnitude slower than that with graphite anode. At the internal short circuit point, transformation to the low electron-conductive LTO spinel phase will work to suppress the rapid extension of internal short circuit reaction. It was demonstrated that the 2-volt class lithium-ion battery system using the LTO anode exhibited excellent high-power and quick-charging with outstanding safety characteristics by using the LTO anode.
Coated Porous Carbon Cathodes for Lithium Ion Batteries
Authors: Kercher Andrew K. , Dudney Nancy , Kiggans Jim , Klett James
Published: November 2008

Coated porous carbons for cathodes in automotive lithium batteries are being developed with the goal of overcoming the problems with capacity fade and poor thermal management in conventional polymer-bonded cathodes. The active cathode material (lithium iron phosphate nanoparticles) is carbon-bonded to the porous carbon support material. Cathodes have been developed with high specific energy and power and with good cycling behavior.
Electrochemical and Structural Investigations of xLi[Li0.33Mn0.66]O2 (1-x)Li[Ni0.8Co0.15Zr0.05]O2 (0.0{{less than or equal to}} x {{less than or equal to}} 1.0) Composite Layered Oxide Cathode for Rechargeable Lithium Ion Batteries
Authors: Sundaresan Sivaprakash , Katiyar Ram , Majumder Subhasish
Published: November 2008

The potential for high power lithium ion batteries have made them one of the most attractive candidates for electric as well as hybrid electric vehicles. As a cathode material for lithium ion rechargeable batteries, the lithium based layered as well as spinel oxides remain attractive candidates. The capacity of these cathodes has so for been limited to 160 mAhg-1 in most cases and their electrochemical performance strongly depended on the synthesis conditions. With the aim to increase the discharge capacity beyond 160 mAhg-1 with the improved cycleability and rate capabilities, in the present work, we have synthesized a solid solution series of layered xLi[Li0.33Mn0.66]O2 (inactive) (1-x)Li[Ni0.8Co0.15Zr0.05]O2 (active) (0.0{less than or equal to} x {less than or equal to} 1.0) by wet chemical route. The X-ray diffraction pattern analysis has been utilized to characterize the structural changes of the active component as a function of the inactive layered oxide component and ESCA spectroscopy has been used to find oxidation/ reduction behavior over the surface of cathode material. The mechanism of Li overcapacity during electrochemical charging is believed to be due to oxygen loss and the conversion of inactive material to active one.
In-situ Spatial Analysis of RF Voltage during Plasma Etching
Authors: Milenin Alexey P. , De Marneffe Jean-Francois , Struyf Herbert , Boullart Werner
Published: November 2008

In-situ plasma characterization was performed in industrial equipment using 300-mm PlasmaTemp and PlasmaVolt sensor wafers from OnWafer/KLA-Tencor. It was shown that the local characteristics of RF voltage collected with 7 detectors provide additional information to the generally used power and DC Bias readouts. Thus, the magnitude of the RF voltage as well as the noise level were shown to be influenced by the temperature of the dual zone chuck in TCP reactor, demonstrating a higher level of both at high temperature. Dependence of the RF voltage on pressure was studied in both CCP and TCP reactors, showing an increase of the RF voltage with pressure for CCP and the opposite trend for TCP. Finally, a simple description of the experimental data was proposed based on the equivalent scheme of plasma reactor and on the dominating part of a plasma impedance.
Damage-free Pattern Transfer by Low Energy Electron Enhanced Etching (LE4): Mechanisms and Applications
Authors: Gillis H.P. , Anz Samir , Demine Matthew
Published: November 2008

The conventional ion-enhanced dry etch methods inflict 2 nm or more of "etch process damage" through surface ion bombardment, and this inherent surface damage creates a potentially limiting condition for IC manufacturing at feature sizes below 45 nm. As an alternative we describe the LE4 dry etch method, in which electrons with energies below about 200 eV stimulate anisotropic etching for high-resolution feature definition. Features as small as 20 nm have been etched with no damage. Line edge roughness (LER) in poly-silicon etching with LE4 is substantially less than with ion-enhanced etching. LE4 avoids trenching, bowing, and notching effects in etched profiles. In addition to control of critical dimensions, LE4 gives atomically smooth etched surfaces and maintains stoichiometry of compound materials. The absence of ion bombardment damage and the ability to tune the process to specific material energy thresholds, enable very high selectivity in LE4.
Enhancement of Bioelectrocatalytic Oxidation of Glucose by Application of Tetrathiafulvalene Modified Carbon Nanotubes as Mediating System
Authors: Kowalewska Barbara , Kulesza Pawel J.
Published: November 2008

Combination of tetrathiafulvalene (TTF)-modified multi-walled carbon nanotubes and glucose oxidase within the film produces a bio-electrocatalytic system capable of effective oxidation of glucose in 0.1 mol dm-3 phosphate buffer (pH=7.0). An important function of carbon nanotubes is to improve transport of electrons within the film. Here carbon nanotubes have been modified with ultra-thin layers of TTF to form stable colloidal suspensions of carbon nanostructures. They have been utilized to produce Nafion-containing inks for sequential deposition of components. The presence of TTF is expected to facilitate an effective flow of electrons from the redox centers of glucose oxidase to the glassy carbon electrode. TTF constitutes a group of redox molecules that were successfully used as redox mediators in enzyme electrochemistry. Our highly porous film of carbon nanotubes on the electrode surface have presumably acted as three-dimensional network of nanowires around the enzyme molecules and have promoted the efficient electron transfers.
Feasibility Study on Electrochemical Impedance Spectroscopy for Microbial Fuel Cells: Measurement Modes & Data Validation
Authors: Strik David P. , Ter Heijne Annemiek , Hamelers Hubertus V. M. , Saakes Michel , Buisman Cees
Published: November 2008

Electrochemical impedance spectroscopy (EIS) is in potential a powerful tool for the in depth analysis of microbial fuels cells (MFCs). To prevent the risk of drawing false conclusions from invalid EIS measurements we investigated the feasibility of this method on an MFC by checking: linearity, causality, stability and finiteness. EIS application under steady state conditions was partly feasible. For further application EIS on MFCs we recommend to: (1) use the constant anode or cathode potential measurement mode with a fast couple at the counter electrode; (2) record the polarization curve and measure at different amplitudes to check the linearity condition; (3) perform preliminary measurements to reveal measurement presets; (4) apply prolonged pretreatment to facilitate the stability criterion; (5) perform duplicate measurements to examine the stability; (6) use a broad frequency range to validate the finiteness criterion; (7) use a statistical based validation check based on the Kramers-Kronig transformation.
Multiscale Carbon Materials as Supports for Bioelectrodes
Authors: Wen Hao , Ramanujam Kothandraman , Calabrese Barton Scott
Published: November 2008

A quantitative study of transport and reaction in multiscale porous biocatalytic electrodes is presented, using glucose oxidation catalyzed by glucose oxidase as a model system. Kinetic parameters determined from planar electrodes are applied to porous electrodes to determine utilization and transport properties. In a multiscale porous electrode containing multi-wall carbon nanotubes supported on carbon fibers, surface area increases 100-fold over bare fibers, but catalyst utilization of about 10% is observed. Hence, improving the dispersion of active material over the entire nanoscale area is expected to further improve electrode performance.
Synthesis and Phase Stability in Ultra-thin Solid Electrolytes: The Case of Zirconia Thin Films
Authors: Tsuchiya Masaru , Minor Andrew , Ramanathan Shriram
Published: November 2008

Phase stability in 9.5 mol % yttria doped zirconia (YDZ) and pure zirconia thin films have been studied by transmission electron microscopy (TEM). Through detailed in-situ TEM analysis, we found that phase stability in nanoscale zirconia thin film depends on film thickness, grain size, and annealing ambient. Pure zirconia thin films of ~ 52 nm thickness were stabilized without any dopants at room temperature, while it transformed into a tetragonal phase upon heating to 400 oC. On the other hand, 9.5 % Yttria doping enables stabilization of the cubic structure regardless of grain growth. Annealing of poor crystalline YDZ films in air (oxygen rich) leads to tetragonal phase formation, while ultra-high vacuum (oxygen-deficient) annealed samples display cubic phase at high temperature.
Investigating Oxygen Surface Exchange Kinetics of La0.8Sr.20MnO3 and La0.6Sr0.4Co0.2Fe0.8O3-δ Using an Isotopic Tracer
Authors: Kan Cynthia C. , Kan Heywood H. , Van Assche F. Martin , Armstrong Eric N. , Wachsman E. D.
Published: November 2008

The kinetics and mechanisms of oxygen surface exchange on La0.8Sr.20MnO3-δ and La0.6Sr0.4Co0.2Fe0.8O3-δ were investigated using temperature programmed desorption, reaction and isothermal switching. Using oxygen isotope 18O2 as a tracer, the total gas exchange behavior can be separated into surface and bulk oxygen components without disturbing the total oxygen concentration. LSM is less catalytically active towards oxygen exchange than LSCF, with exchange onset occurring at 350åC in LSM and 200åC in LSCF. A two-step model is proposed consisting of dissociative adsorption of oxygen onto the surface followed by adsorbed oxygen incorporation into the material. By extracting the overall reaction order with respect to oxygen, it is found that LSCF is limited by dissociative adsorption at all temperatures while LSM is mostly incorporation limited at 600åC and becomes more dissociative adsorption limited at 800åC. The formation of oxygen vacancies in LSM at high temperatures may facilitate the incorporation step.
Effect of Coal Gas Contaminants on Solid Oxide Fuel Cell Operation
Authors: Marina Olga , Pederson Larry R. , Edwards Danny J. , Coyle Chris A. , Templeton Jared , Engelhard Mark H. , Zhu Zihua
Published: November 2008

The operation of solid oxide fuel cells (SOFC) was evaluated on simulated coal gas in the presence of several coal gas impurities that are expected to remain in low concentration after warm gas cleanup. Phosphorus, arsenic and sulfur were considered in this study. The presence of phosphorus and arsenic in low, 1-2 ppm, concentrations led to the slow and irreversible SOFC degradation due to the formation of the secondary phases with nickel in the upper part of the nickel-based anode close to the gas inlet. Sulfur interactions with the nickel were limited to the surface only. Cell performance losses due to sulfur exposure were reversible and independent of the presence of other impurities.
Impedance Analysis of Phosphorous Impurity Effect on Performance of Ni-YSZ Anode of SOFC
Authors: Zhi Mingjia , Madhiri Nicholas , Finklea Harry , Celik Ismail , Kang Bruce , Liu Xingbo , Bajura Richard , Wu Nick
Published: November 2008

Electrochemical impedance analysis was performed on a Ni-YSZ/YSZ/Ni-YSZ (8 mol.% Yttria Stabilized Zirconia) half cell in order to evaluate the effects of a phosphorous impurity on the performance of the Ni-YSZ cermet anode of a solid oxide fuel cell (SOFC). 20 ppm PH3 was introduced into the simulated coal-derived syngas (30.6% H2, 30% CO, 11.8% CO2, and 27.6% H2O). Both the charge transfer resistance and the diffusion resistance increased with time during exposure to the P-containing syngas. The diffusion resistance increased faster than the charge transfer resistance. Both the charge transfer resistance and the diffusion resistance values under load (DC current flow) were larger the corresponding values at open circuit.
Oxygen Generation from Carbon Dioxide for Advanced Life Support
Authors: Bishop Sean R. , Duncan Keith , Hagelin-Weaver Helena , Neal Luke , Sanchez Jose , Paul Heather , Wachsman E. D.
Published: November 2008

The separation of pure oxygen from the atmosphere using ce- ramic oxygen generators (COGs) is well known and widely stud- ied. However, complete reduction of metabolically produced CO2 (into carbon and oxygen) has not received as much at- tention. This technology has the potential of reducing oxygen storage weight for life support if the oxygen can be recovered. Recently, we developed novel ceramic oxygen generators em- ploying a bilayer electrolyte of gadolinia-doped ceria and erbia- stabilized bismuth oxide for NASA's future exploration of Mars. The results showed that oxygen could be reliably produced from CO2 at temperatures as low as 400 °. The strategy discussed here for advanced life support systems employs a catalytic layer combined with a COG cell so that CO2 is reduced all the way to solid carbon and oxygen without carbon buildup on the COG cell and subsequent deactivation.
Low Temperature NOx Decomposition Using Electrochemical Reactor
Authors: Hamamoto Koichi , Fujishiro Yoshinobu , Awano Masanobu
Published: November 2008

We attempted to fabricate and evaluate a new electrochemical reactor with an additional NOx adsorption layer on a multilayer catalytic cathode and investigated a cell operating method to achieve a low temperature operation. To clarify the capability of a NOx adsorption layer, we carried out the NOx decomposition measurements of the cell. As a result, NOx adsorption layers have improved the NOx decomposition properties though the current values of each cell were almost the same. The NO decomposition by a GDC (10mol% Gd doped CeO2) -based cell with a Pt/K/Al2O3 adsorbent took onset around 225°. It was clarified that the starting temperature and the efficiency of the NOx decomposition are heavily dependent on the adsorptivity of NOx adsorbent and the cell operating voltage mode.
The Effect of LSGM Nanoparticle Dispersion in Ag-LSGM Composite Thin Film Cathode for LSGM Electrolyte Solid Oxide Fuel Cells
Authors: Muranaka Minoru , Sasaki Kazuya , Suzuki Akihiro , Terai Takayuki
Published: November 2008

Different amounts of LSGM nanoparticles were dispersed in the silver thin film cathode using the RF magnetron sputtering method. The nanostructure of the Ag-LSGM composite thin film cathode was observed using a field emission scanning electron microscope, and the area specific resistance of the Ag-LSGM composite thin film cathodes was measured by the three-probe AC impedance method. The silver grains became smaller as the amount of the LSGM nanoparticles increased after annealing at 600 ° in air for 100 h. The non-charge-transfer resistance decreased and became constant with an increase in the amount of the LSGM nanoparticles dispersed in the Ag-LSGM composite thin film cathode.
Estimation of the Surface Potential and Concentration of Surface Defects in Superionic Oxides
Authors: Uvarov Nikolai F.
Published: November 2008

The Stern model was used for estimation of the surface potential fi(S) and concentration of the surface defects in superionic oxides M(1-c)Me(c)O(2-c/2). Accordingly, the surface charge is defined by the Langmuir adsorption isotherm determined by fi(S) value and adsorption energies of positive and negative defects. Gouy-Chapman or Mott-Schottky equations were employed for taking into account potential distribution in the space charge layer (SCL). Calculations show that at high temperatures fi(S) values obtained using both the models of SCL are close. The Stern model explains the experimentally observed effect of a strong segregation of impurity cations on the surface in spite of positive surface potential even at zero value of the segregation energy.
Evaluation and Analysis of PEM-FC Performance using Non-Platinum Cathode Catalysts based on Pyrolysed Fe- and Co-Porphyrins - Influence of a Secondary Heat-treatment
Authors: Koslowski Ulrike , Herrmann Iris , Bogdanoff Peter , Barkschat Christa , Fiechter Sebastian , Iwata Naoko , Takahashi Hiroaki , Nishikori Hidetaka
Published: November 2008

Porphyrin based catalysts were prepared by the pyrolysis of transition metal-macrocycles in the presence of iron oxalate as foaming-agent and by the addition of sulfur. Characterization was performed using N2 and H2O sorption measurements, XPS, Raman and 57Fe-Mößbauer spectroscopy, RRDE and PEM Fuel Cell experiments. ORR-activity of already pyrolysed material was found to be significantly enhanced by a secondary heat-treatment in either N2, CO2 or NH3. Additionally, the specific surface area was found to increase and in case of NH3, catalytic centers were also generated. The final catalysts exhibit 2-5 wt% metal, 3-6 wt % nitrogen and 1-5 wt% sulfur integrated in an in-situ formed graphene network. However, despite the high efficiency in RDE measurements, in FC tests only 2 % of electrical power compared to a 45 wt% Pt/C catalyst is reached. An unsuitable morphology of the GDE and a high hydrophilicity of the catalyst were identified as limiting factors.
Application of Inorganic Redox-Conducting Solids As Charge Relays in Dye-Sensitized Solar Cell
Authors: Rutkowska Iwona A. , Skunik Magdalena , Miecznikowski Krzysztof , Kulesza Pawel J.
Published: November 2008

Polynuclear redox conducting mixed-valent inorganic materials, such as sol-gel processed nanostructured nickel(II) hexacyanoferrate(II,III), have been utilized as redox mediators (charge relays) in dye-sensitized solar cell (DSSC). The systems' granules are likely to penetrate pores of the dye-modified TiO2. An important issue is that the formal potential of nickel(II) hexacyanoferrate(II,III) is more positive (>300 mV) relative to the commonly used iodide/triiodide couple. With the same dye-modified TiO2 used, the above property led to the larger potential output of DSSC. The proposed redox-conducting inorganic materials is in a mixed-valent state in which iron(II) and iron(III) sites are at the 1:1 ratio, and the concentration gradients are maximized. Consequently, the system is characterized by fast dynamics of electron transfers. Since the structures are hydrated, they are also good ionic (K+) conductors. An important feature is high physicochemical stability of such inorganic polynuclear electroactive materials.
Fabrication of Porous Supported MIEC Dense Thin Coating for Hydrogen Separation
Authors: Wang Haibing , Gopalan Srikanth , Pal Uday B.
Published: November 2008

Decomposition of steam under a chemical driving force at moderate temperatures offers a simple and economical way to generate hydrogen. Significant amounts of hydrogen can be separated by splitting steam and removing the oxygen using Gd0.2Ce0.8O1.9-Gd0.08Sr0.88Ti0.95Al0.05O3{plus minus}δ mixed ionic and electronic conductors. Hydrogen generation experiments for the self-standing thick membranes and porous supported thin membranes have been conducted at different oxygen pressure gradients across the membranes and steam contents on the steam side. Experimental results indicate that the hydrogen generation process is controlled by the bulk diffusion for the thick membranes, while the permeation process for the thin membranes is mixed controlled, i.e. the process is controlled by surface exchange reactions and the oxygen bulk diffusion. A mathematical model for the calculation of the area specific hydrogen generation rate is proposed based on the measured oxygen partial pressures, gas compositions of the inlet and outlet gases on the steam side.
Laser-Induced Backside Wet Etching of Transparent Materials with Organic and Metallic Absorbers
Authors: Zimmer K. , Böhme R.
Published: November 2008

Laser-induced backside wet etching (LIBWE) allows the high-quality etching of transparent materials for micro- and nanopatterning. Recent own results of LIBWE with hydrocarbon and metallic absorbers (H- and M-LIBWE) are summarized and compared with selected results of other groups regarding the etching process and the etched surface. Significant results on the impact of the liquid absorber, the material and the wavelength, and the pulse length of the laser to the etching are selected for this comparison. The etching of submicron-sized periodic structures in sapphire and fused silica with interference techniques and the selection of the preferred method in dependence on the material and the processing goal discussed. The experimental results are discussed on a thermal model considering both interface and volume absorption of the laser beam. These results have the conclusion that the etching at M-LIBWE is mainly due to material melting and evaporation whereas at H-LIBWE, a modified near-surface region with a very high absorption is ablated.
GA‐Based Fuzzy Sliding Mode Controller for Nonlinear Systems
Authors: Chen P. C. , Chen C. W. , Chiang W. L.
Published: November 2008

Generally, the greatest difficulty encountered when designing a fuzzy sliding mode controller (FSMC) or an adaptive fuzzy sliding mode controller (AFSMC) capable of rapidly and efficiently controlling complex and nonlinear systems is how to select the most appropriate initial values for the parameter vector. In this paper, we describe a method of stability analysis for a GA‐based reference adaptive fuzzy sliding model controller capable of handling these types of problems for a nonlinear system. First, we approximate and describe an uncertain and nonlinear plant for the tracking of a reference trajectory via a fuzzy model incorporating fuzzy logic control rules. Next, the initial values of the consequent parameter vector are decided via a genetic algorithm. After this, an adaptive fuzzy sliding model controller, designed to simultaneously stabilize and control the system, is derived. The stability of the nonlinear system is ensured by the derivation of the stability criterion based upon Lyapunov′s direct method. Finally, an example, a numerical simulation, is provided to demonstrate the control methodology.
Effect of Edge‐Preserving Adaptive Image Filter on Low‐Contrast Detectability in CT Systems: Application of ROC Analysis
Authors: Okumura Miwa , Ota Takamasa , Kainuma Kazuhisa , Sayre James W. , McNitt-Gray Michael , Katada Kazuhiro
Published: November 2008

Objective. For the
multislice CT (MSCT) systems with a larger
number of detector rows, it is essential to
employ dose‐reduction techniques. As reported in
previous studies, edge‐preserving adaptive image
filters, which selectively eliminate only the
noise elements that are increased when the
radiation dose is reduced without affecting the
sharpness of images, have been developed. In the
present study, we employed receiver operating
characteristic (ROC) analysis to assess the
effects of the quantum denoising system (QDS),
which is an edge‐preserving adaptive filter that we
have developed, on low‐contrast resolution, and
to evaluate to what degree the radiation dose
can be reduced while maintaining acceptable
low‐contrast resolution.
Materials and Methods. The low‐contrast phantoms (Catphan 412) were scanned at various tube current settings, and ROC analysis was then performed for the groups of images obtained with/without the use of QDS at each tube current to determine whether or not a target could be identified. The tube current settings for which the area under the ROC curve (Az value) was approximately 0.7 were determined for both groups of images with/without the use of QDS. Then, the radiation dose reduction ratio when QDS was used was calculated by converting the determined tube current to the radiation dose.
Results. The use of the QDS edge‐preserving adaptive image filter allowed the radiation dose to be reduced by up to 38%.
Conclusion. The QDS was found to be useful for reducing the radiation dose without affecting the low‐contrast resolution in MSCT studies.