bluuebunny/crossref_metadata_2025 huggingface dataset:
A rational approach for optimization of road upgrading
Authors: Mouratidis Anastasios , Papageorgiou Grigorios
Published: October 2010

Roads designed and constructed in the 1950s and 1960s far from cover present-day traffic needs and require maintenance and renewal. A common practice of upgrading aged two-lane roads consists of pavement resurfacing, but this practice often proves insufficient at providing a high serviceability level and risks being inefficient. An existing aged and distressed road may need more radical upgrading operations. The optimum upgrading strategy must be envisaged with regards to prevailing operational criteria such as road safety, ride comfort, and serviceability. In this context, a systematic approach to the upgrading issue has been elaborated aiming at introducing all significant factors to the processing algorithm designating the optimal intervention in each case. The proposed model is meant to determine and recommend the appropriate strategy for each part of the road network and provide a high level of service and avoid unnecessary expenses. Within this scope, this rational strategy proceeds to an exhaustive assessment of examined roads with respect to their performance and defines improvement priorities in accordance with an innovative management policy. The model distinguishes four levels of “upgrading” activities, with each adopted with respect to the road condition, traffic features, ride quality, and environmental considerations. The option derived is supposed to provide the best cost–benefit upgrading solution.
A study on composite end-plate connections with flexible tensile reinforcements and shear connectors
Authors: Wang Aaron J.
Published: October 2010

A comprehensive parametric study is presented in this paper, which examines numerically the structural behaviour of composite end-plate connections with different material properties and geometrical configurations adopting a two-dimensional finite element model. The study is closely related to the determination of the moment capacities of composite structural flexural members that are partially continuous at the supports. Both ductile and non-ductile shear connectors are covered to investigate the effect of flexibility of the shear connectors on the overall structural behaviour of composite end-plate connections. Moreover, the effect of the elongation limits of tensile reinforcement is also studied. It is concluded that steel beam sizes have significant effects on the structural behaviour of composite end-plate connections with non-ductile shear connectors or the tensile reinforcement with normal ductility.
Analysis of the representativeness and relative severity of ASTM C672 and NQ 2621-900 standard procedures in evaluating concrete scaling resistance
Authors: Houehanou Ernesto , Gagné Richard , Jolin Marc
Published: October 2010

The aim of this study is to gain an understanding of the representativeness and relative severity of ASTM C672 and NQ 2621-900 standard test procedures in evaluating the scaling resistance of concrete incorporating various proportions of fly ash (25% and 35%), slag (25% and 35%), and silica fume (1% and 2%). Length of curing and presaturation of samples were varied before starting the freeze–thaw tests. Laboratory durability of tested concrete was compared with that of similar concrete after 4 years of service life. Results show that the length of the moist pretreatment period is a key parameter in scaling resistance of laboratory-tested concrete. A 28-day period of moist curing appears to be optimal and leads to more realistic assessment of the actual scaling resistance of concrete. The use of a draining-bottom mold had no significant effect on the scaling resistance of the concretes in this study.
Diverting electron fluxes towards sulfate reduction using linoleic acid in a mixed anaerobic culturePaper submitted to the Journal of Environmental Engineering and Science.
Authors: Sharma Mamata , Biswas Nihar
Published: October 2010

Sulfate (1500 mg/L) reduction and glucose (1870 mg/L) degradation was examined in the presence of five varying linoleic acid (LA) levels (100–1000 mg/L) at 37 ± 2 °C and pH 7.0–7.2. The sulfate reduction and methane formation data suggest that LA selectively inhibited methane producing bacteria (MPB). The quantity of sulfate removed increased with increasing LA dosage. Approximately 1375 mg/L (92%) sulfate was removed in cultures fed with high concentrations of LA (1000 mg/L), which was 68% more than that removed in glucose and sulfate controls. The quantity of sulfate removed in cultures fed with 100, 300, 500 and 700 mg/L LA were 62%, 66%, 77%, and 84%, respectively. Initial sulfate degradation rates increased with increasing LA levels in the cultures. High LA levels (1000 mg/L) attributed to approximately a sevenfold increase in the initial sulfate degradation rates compared to cultures containing sulfate plus glucose. The highest initial sulfate removal rate (0.19 µg/(mgVSS min)) was observed in cultures receiving 1000 mg/L LA. Initial glucose degradation rates decreased with increasing LA concentrations. The rates for the cultures receiving 1000 mg/L LA were 2.53 µg/(mgVSS min) while the degradation rate for cultures containing 100 mg/L LA was 5.40 µg/(mgVSS min). Methane formation decreased when sulfate and LA were added. Methane formation was lowest in cultures receiving elevated LA concentrations. The percent electron flow fluxes increased towards sulfidogenesis and decreased towards methanogenesis with increasing LA levels. Less than 0.6% electron flow was diverted to methanogenesis in cultures containing high levels of LA (≥700 mg/L) while ≤ 45% was diverted to sulfidogenesis. Acetate and propionate were the major volatile fatty acids (VFAs) detected during glucose degradation. The amount of sulfate reduced in the cultures receiving only LA or sulfate and no other carbon source was comparable (approximately 10%), which suggests that LA did not contribute to electrons during the course of experiment for sulfate reduction.
Compost stability and maturity evaluation — a literature reviewA paper submitted to the Journal of Environmental Engineering and Science.
Authors: Wichuk Kristine M. , McCartney Daryl
Published: October 2010

Finished compost should be both stable (resistant to decomposition) and mature (ready for a particular end-use) so that it can safely be packaged and transported, and not cause adverse effects during its end use. A variety of methods for evaluating stability and maturity are available; this paper contains a review of the effectiveness of a number of the most commonly used tests, to determine the most reliable approach(es). In the literature reviewed, it was generally agreed that a single, stand-alone test for both compost stability and maturity does not yet exist; therefore, it is best to use a combination of tests. However, there is disagreement in the literature as to what the best combination for evaluation should be, and guidelines and regulations around the world employ a variety of approaches.
Survival of phosphate-solubilizing bacteria against DNA damaging agents
Authors: Shrivastava Manoj , Rajpurohit Yogendra S. , Misra Hari S. , D’Souza S. F.
Published: October 2010

Phosphate-solubilizing bacteria (PSBs) were isolated from different plant rhizosphere soils of various agroecological regions of India. These isolates showed synthesis of pyrroloquinoline quinone (PQQ), production of gluconic acid, and release of phosphorus from insoluble tricalcium phosphate. The bacterial isolates synthesizing PQQ also showed higher tolerance to ultraviolet C radiation and mitomycin C as compared to Escherichia coli but were less tolerant than Deinococcus radiodurans . Unlike E. coli, PSB isolates showed higher tolerance to DNA damage when grown in the absence of inorganic phosphate. Higher tolerance to ultraviolet C radiation and oxidative stress in these PSBs grown under PQQ synthesis inducible conditions, namely phosphate starvation, might suggest the possible additional role of this redox cofactor in the survival of these isolates under extreme abiotic stress conditions.
Molecular analyses of the diversity in marine bacterioplankton assemblages along the coastline of the northeastern Gulf of Mexico
Authors: Olapade Ola A.
Published: October 2010

Bacterial community diversity in marine bacterioplankton assemblages were examined in 3 coastal locations along the northeastern Gulf of Mexico (GOM) using 16S rRNA gene libraries and fluorescence in situ hybridization approaches. The majority of the sequences (30%–60%) were similar to the 16S rRNA gene sequences of unknown bacteria; however, the operational taxonomic units from members of the Cyanobacteria, Proteobacteria, and Bacteroidetes were also present at the 3 GOM sites. Overall, sequence diversity was more similar between the Gulf sites of Carrabelle and Ochlockonee than between either of the Gulf sites and Apalachicola Bay. Fluorescence in situ hybridization analyses revealed the quantitative predominance of members of the Alphaproteobacteria subclass and the Cytophaga – Flavobacterium cluster within the bacterioplankton assemblages. In general, the study further reveals the presence of many bacterial taxa that have been previously found to be dominant in coastal marine environments. Differences observed in the representation of the various bacterial phylogenetic groups among the GOM coastal sites could be partly attributed to dynamic variations in several site-specific conditions, including intermittent tidal events, nutrient availability, and anthropogenic influences.
Quantitative PCR assay of sewage-associatedBacteroidesmarkers to assess sewage pollution in an urban lake in Dhaka, Bangladesh
Authors: Ahmed Warish , Yusuf Rita , Hasan Imtiaj , Goonetilleke Ashantha , Gardner Ted
Published: October 2010

This paper aimed to assess the magnitude of sewage pollution in an urban lake in Dhaka, Bangladesh, by using quantitative PCR of sewage-associated Bacteroides HF183 markers. PCR was also used for the quantitative detection of ruminant wastewater-associated CF128 markers along with the enumeration of traditional fecal indicator bacteria, namely enterococci. The number of enterococci in lake water samples ranged from 1.1 × 104to 1.9 × 105colony-forming units/100 mL water. From the 20 water samples tested, 14 (70%) and 7 (35%) were PCR positive for HF183 and CF128 markers, respectively. The numbers of HF183 and CF128 markers in lake water samples were 3.9 × 104to 6.3 × 107and 9.3 × 103to 6.3 × 105genomic units/100 mL water, respectively. The high numbers of enterococci and HF183 markers are indicative of sewage pollution and potential health risks to those who use the lake water for nonpotable purposes such as bathing and washing clothes. This is the first study that investigated the presence of microbial source tracking markers in Dhaka, Bangladesh, where diarrhoeal disease is one of the major causes of childhood mortality. The molecular assay used in this study can provide valuable information on the extent of sewage pollution, thus facilitating the development of robust strategies to minimize potential health risks.
Selection of genetically diverse Trichoderma spp. isolates for suppression of Phytophthora capsici on bell pepper
Authors: Roberts Daniel P. , Maul Jude E. , McKenna Laurie F. , Emche Sarah E. , Meyer Susan L.F. , Collins Ronald T. , Bowers John H.
Published: October 2010

Environmentally compatible control measures are needed for suppression of Phytophthora capsici on pepper. Twenty-three isolates of Trichoderma were screened for suppression of a mixture of 4 genetically distinct isolates of this pathogen on bell pepper ( Capsicum anuum ) in greenhouse pot assays. Of these 23 isolates, GL12, GL13, and Th23 provided significant suppression of P. capsici in at least 2 assays. These isolates were then compared with Trichoderma virens isolates GL3 and GL21 for suppression of this disease in the presence and absence of the harpin-based natural product Messenger. Isolates GL3 and Th23 provided significant disease suppression (P ≤ 0.05) in 3 of 4 assays, while GL12, GL13, and GL21 provided significant suppression in 2 of 4 assays. There was no apparent benefit from the application of Messenger. Phylogenetic analysis of these 5 isolates (based on the ITS1 region of the nuclear rDNA cluster and tef1), and an additional 9 isolates that suppressed P. capsici in at least 1 assay, separated isolates into 2 clades, with 1 clade containing GL3, GL12, GL13, and GL21. There were also 2 more distantly related isolates, one of which was Th23. We report here the identification of genetically distinct Trichoderma isolates for potential use in disease management strategies employing isolate combinations directed at suppression of P. capsici on pepper.
Calculation of muscle maximal shortening velocity by extrapolation of the force–velocity relationship: afterloaded versus isotonic release contractions
Authors: Bullimore Sharon R. , Saunders Travis J. , Herzog Walter , MacIntosh Brian R.
Published: October 2010

The maximal shortening velocity of a muscle (Vmax) provides a link between its macroscopic properties and the underlying biochemical reactions and is altered in some diseases. Two methods that are widely used for determining Vmaxare afterloaded and isotonic release contractions. To determine whether these two methods give equivalent results, we calculated Vmaxin 9 intact single fibres from the lumbrical muscles of the frog Xenopus laevis (9.5–15.5 °C, stimulation frequency 35–70 Hz). The data were modelled using a 3-state cross-bridge model in which the states were inactive, detached, and attached. Afterloaded contractions gave lower predictions of Vmaxthan did isotonic release contractions in all 9 fibres (3.20 ± 0.84 versus 4.11 ± 1.08 lengths per second, respectively; means ± SD, p = 0.001) and underestimated unloaded shortening velocity measured with the slack test by an average of 29% (p = 0.001, n = 6). Excellent model predictions could be obtained by assuming that activation is inhibited by shortening. We conclude that under the experimental conditions used in this study, afterloaded and isotonic release contractions do not give equivalent results. When a change in the Vmaxmeasured with afterloaded contractions is observed in diseased muscle, it is important to consider that this may reflect differences in either activation kinetics or cross-bridge cycling rates.
The impact of tannins on protein, dry matter, and energy digestion in moose (Alces alces)
Authors: Spalinger D. E. , Collins W. B. , Hanley T. A. , Cassara N. E. , Carnahan A. M.
Published: October 2010

Recent work suggests that moose ( Alces alces (L., 1758)) in the boreal ecoregion may be nutritionally limited by the availability of protein as a consequence of both low nitrogen (N) concentrations and high tannin levels in their principal foods. However, the ability of moose to digest protein in the presence of tannins is unknown. We undertook a series of digestion trials with captive moose to quantify the effects of tannins and compare the digestive capabilities of moose to other browsing cervids. We fed four moose 14 single-species diets including 10 native tannin-containing forages and 4 non-tanniferous foods over four winters. True protein digestibility in moose was 92%, and metabolic fecal N excretion was estimated at 0.389 g N/100 g dry matter (DM) intake. Tannins reduced protein digestion, on average, by 38%, and the rate of reduction in protein digestion was estimated to be 8.28 g protein/100 g DM per unit protein-precipitating capacity. The digestion of protein, neutral detergent fiber, DM, and energy of tanniferous foods was not significantly different between moose and mule ( Odocoileus hemionus (Rafinesque, 1817)) or white-tailed deer ( Odocoileus virginianus (Zimmermann, 1780)). However, our experiments provide refined assays for evaluating the nutritional quality of browses for moose.
Polyandry and tibial spur chewing in the Carolina ground cricket (Eunemobius carolinus)
Authors: Piascik Edyta K. , Judge Kevin A. , Gwynne Darryl T.
Published: October 2010

During mating, the female Carolina ground cricket ( Eunemobius carolinus (Scudder, 1877)) chews specialized spurs on the male’s hind tibia for access to his hemolymph. One potential benefit to spur chewing includes nutritional acquisition from male hemolymph. A method for testing this hypothesis is to manipulate food quality or quantity, with the prediction that mating rate will increase as food quality or quantity decreases. We manipulated diet quality in adult females and provided them with four consecutive mating opportunities. We measured four aspects of mating behaviour (mating rate, latency to copulate, copulation duration, and spur chewing duration) and three of female fitness (egg number, egg-laying rate, and life span). Females of the two diet treatments did not differ significantly in any of the measured mating behaviours, although females fed a low-quality diet lived longer. Male life span did not correlate with any measured variable, although males that experienced more matings and longer total times of copulation and spur chewing lost more mass. These results suggest that spur chewing may be costly for males, although we detected no evidence that this behaviour was a benefit to the female or represented a form of male coercion.
Seasonally contrasting life-history strategies in the land snail Cornu aspersum: physiological and ecological implications
Authors: Nicolai A. , Filser J. , Briand V. , Charrier M.
Published: October 2010

When a life history is characterized by both seasonality in reproduction and seasonality in offspring fitness, trade-offs in reproductive traits might be adjustments to seasonal time constraints to optimize reproductive success. Therefore, we compared in the laboratory the trade-offs in reproductive traits between early (after maturity) and delayed (after dormancy) reproduction in young land snails Cornu aspersum (Müller, 1774) (syn. Helix aspersa ), depending on food energy content. We also investigated the maternal investment in reproductive output in both breeding periods. After attaining maturity, snails produced single clutches with many small eggs, which resulted, in contrast to previous studies, in large offspring with a low hatching rate owing to high within-clutch cannibalism. The young cannibals may have a higher survival probability in the following hibernation. Snails starting to reproduce after hibernation had smaller clutches of larger eggs, resulting in high quantity of lighter offspring. The clutch mass was positively correlated with maternal mass in snails reproducing after having attained maturity and negatively correlated in snails reproducing after hibernation. Multiple oviposition occurred only after hibernation, thereby enhancing reproductive success. An energy-rich diet did not affect reproductive strategies. Further studies should focus on seasonal plasticity of reproductive strategies in natural populations of C. aspersum and investigate survival probabilities of breeders and juveniles in an evolutionary context.
Lack of behavioral responses of moose (Alces alces) to high ambient temperatures near the southern periphery of their range
Authors: Lowe Stacey J. , Patterson Brent R. , Schaefer James A.
Published: October 2010

Although fundamental factors limiting geographic ranges are understood for many animal species, there is less certainty regarding how such factors influence the behavior of individuals near distributional edges. We tested the hypothesis that climate limits the southern distribution of moose ( Alces alces (L., 1758)) by documenting space use and behavior of 36 females at the margin of the species’ range in Ontario, Canada. We assessed temperature differences among habitats and related changes in seasonal habitat use and daily movement patterns in response to temperature. Ambient temperatures frequently exceeded the thresholds of –5 °C (winter) and 14 °C (summer), above which moose are supposed to be thermally stressed. We detected no differences in habitat use relative to thermoregulation thresholds. However, moose exhibited reduced movement when snow was deep and were more active at dawn and dusk. Low variability in temperature among habitat types implied that functional thermal shelters were absent. We suggest that moose in their southern range either ameliorate heat stress at a finer resolution than we measured or are more resilient to temperature than previously thought. Additional evidence linking temperatures with negative responses is necessary before the prevalent hypothesis of heat stress limiting the southern distribution of moose can be fully assessed.
ON THE CONNECTION BETWEEN TWO QUASILINEAR ELLIPTIC PROBLEMS WITH SOURCE TERMS OF ORDER 0 OR 1
Authors: ABDEL HAMID HAYDAR , BIDAUT-VERON MARIE FRANÇOISE
Published: October 2010

We establish a precise connection between two elliptic quasilinear problems with Dirichlet data in a bounded domain of ℝN. The first one, of the form [Formula: see text] involves a source gradient term with natural growth, where β is non-negative, λ > 0, f(x) ≧ 0, and α is a non-negative measure. The second one, of the form [Formula: see text] presents a source term of order 0, where g is non-decreasing, and μ is a non-negative measure. Here β and g can present an asymptote. The correlation gives new results of existence, non-existence, regularity and multiplicity of the solutions for the two problems, without or with measures. New informations on the extremal solutions are given when g is superlinear.
MINIMAX PROBABILITIES FOR AUBRY–MATHER PROBLEMS
Authors: GOMES DIOGO A. , JUNG NARA , LOPES ARTUR O.
Published: October 2010

In this paper, we study minimax Aubry–Mather measures and its main properties. We consider first the discrete time problem and then the continuous time case. In the discrete time problem, we establish existence, study some of the main properties using duality theory and present some examples. In the continuous time case, we establish both existence and non-existence results. First, we give some examples showing that in continuous time stationary minimax Mather measures are either trivial or fail to exist. A more natural definition in continuous time are T-periodic minimax Mather measures. We give a complete characterization of these measures and discuss several examples.
PERSISTENCE IN A RATIO-DEPENDENT PREDATOR-PREY-RESOURCE MODEL WITH STAGE STRUCTURE FOR PREY
Authors: AGARWAL MANJU , DEVI SAPNA
Published: October 2010

This paper deals with a ratio-dependent predator-prey model where the prey population is stage-structured consisting of immature and mature stages and the predator population is influenced by the resource biomass. By means of a transformation of variables, we transform the model into a dynamical system in such a way that there is one-to-one correspondence between the positive values of the original model and the positive values of the transformed model, so that the results which are true for the transformed model are also true for the original model. Dynamical behaviors such as positivity, boundedness, stability, bifurcation and persistence of the model are studied analytically using theory of differential equations. Computer simulations are carried out to substantiate the analytical findings. It is noted that the influence of the resource biomass on the predator population may lead to the extinction of prey population at a lesser value of maturity time in comparison to the absence of the resource biomass.
Current Status of Nonvolatile Semiconductor Memory Technology
Authors: Fujisaki Yoshihisa
Published: October 2010

In this report, an overview of the current status of nonvolatile semiconductor memory technology is presented. We are reaching the integration limit of flash memories, and many new types of memories to replace conventional flash memories have been proposed. Unlike flash memories, new nonvolatile memories do not require electric charge storing. The possibility of phase-change random access memory (PRAM) or resistive-change RAM (ReRAM) replacing ultrahigh-density NAND flash memories has been discussed; however, there are many issues to overcome, making the replacement difficult. Nonetheless, ferroelectric RAMs (FeRAMs) and MRAMs are gradually penetrating into fields where the shortcomings of flash memories, such as high operating voltage, slow rewriting speed, and limited number of rewrites, make their use inconvenient. For the successful application of new nonvolatile semiconductor memories, they must be practically utilized in new fields in which flash memories are not applicable, and the technology for them must be developed.
Deep Electronic Levels of AlxGa1-xN with a Wide Range of Al Composition Grown by Metal–Organic Vapor Phase Epitaxy
Authors: Ooyama Kimihito , Sugawara Katsuya , Okuzaki Shinya , Taketomi Hiroyuki , Miyake Hideto , Hiramatsu Kazumasa , Hashizume Tamotsu
Published: October 2010

Deep electronic levels of Al
x
Ga1-x
N (0.25<x<0.60) were investigated by deep level transient spectroscopy (DLTS) and photocapacitance methods. Si-doped AlGaN layers were grown on an AlN/sapphire template by metal–organic vapor phase epitaxy. DLTS analysis using a sampling time window of up to 100 s showed two dominant deep levels with activation energies (ΔE) higher than 1.0 eV in Al
x
Ga1-x
N with x=0.25 and 0.37. The densities of those levels were higher than 1×1016 cm-3. For the Al0.60Ga0.40N sample, the deeper levels (ΔE>1.5 eV) were detected by photocapacitance measurement. It was found that the energy position of the dominant deep level closely followed the Fermi level stabilization energy reported by Walukiewicz et al. [J. Cryst. Growth 269 (2004) 119], indicating that the origin of the dominant deep level in AlGaN is related to a defect complex including anti-site defects and divacancies.
Dielectric Properties of Zr–Al Anodized Thin Film Capacitors Prepared Using Al-Doped Zr Alloy Films
Authors: Kimizaki Hidefumi , Shinkai Satoko , Sasaki Katsutaka , Yanagisawa Hideto , Yamane Misao , Abe Yoshio
Published: October 2010

We have examined the dielectric properties of Zr–Al anodized thin film capacitors prepared using Al-doped Zr alloy films to improve the thermal stability and capacitance density of pure-Zr anodized thin film capacitors. The Al content of the Zr–Al anodized film was varied from 0 to 24 at. %. It was revealed that the capacitance densities of the Zr–Al anodized capacitors increase with increasing Al content to 17 at. %, because the tetragonal ZrO2 phase grows and the monoclinic ZrO2 phase disappears, although pure-Zr anodized films consist of a mixture of monoclinic and tetragonal ZrO2 phases. In addition, it was confirmed that the thermal stability of the Zr–Al(17 at. %) anodized film is superior to that of the pure-Zr anodized film. We infer that this is due to the formation of the tetragonal ZrO2 phase by Al doping.
Effect of Trap Profile on Device Characteristics of Metal–Oxide–Semiconductor Field Effect Transistors with Hafnium-Based Dielectrics
Authors: Jang Tae-Young , Kim Tea Wan , Kim Dong-Hyoub , Kim Jung-Woo , Jeong Jae Kyeong , Choi Rino
Published: October 2010

The trap properties and performance of metal–oxide–semiconductor field effect transistors (MOSFETs) with either a HfSiO or HfO2 dielectric were determined using single-pulse I
d–V
g and charge pumping measurements. The HfSiO dielectric shows a lower bulk trap density and a lower interface trap density than the HfO2 dielectric. Particularly, the trap depth profile as a function of distance from the Si/SiO
x
interface, which is obtained using frequency-dependent charge pumping measurements, shows a marked reduction in trap density in the HfSiO dielectric, unlike in the HfO2 dielectric. This significant reduction in trap density close to the Si/SiO
x
interface can contribute to the improvement in the carrier mobility of MOSFETs with a HfSiO dielectric.
Performance Enhancement of Organic Thin-Film Transistors Using Bathophenanthroline:Cs Electron Injection Layer
Authors: Kim Myunghwan , Kim Jeongsoo , Son Heegeun , Jang Ji-Hyang , Yi Moonsuk
Published: October 2010

In this study, we fabricated an organic thin-film transistor (OTFT) with a bathophenanthroline (Bphen):Cs electron injection layer between an organic semiconductor (C60) and a metal electrode. We compared the electrical characteristics of OTFTs with and without Bphen:Cs insertion layer which depend on the insertion layer thickness. We found that the Bphen:Cs layer inserted between the active layer (C60) and the metal electrode played an important role in improving the electrical characteristics of the devices. When the OTFT with 5-Å-thick Bphen:Cs was compared with that without Bphen:Cs, the mobility and the output current were determined to increase from 0.029 cm2 V-1 s-1 and 4.32×10-7 A to 0.127 cm2 V-1 s-1 and 1.67×10-6 A, respectively. This improvement was attributed to the reduction in contact resistance between C60 and the Al electrode layer when a Bphen:Cs electron injection layer of optimum thickness was applied.
Optical Properties of Blue-Light-Emitting (Ca,Sr)Mg2Si3O9:Eu2+ Phosphor
Authors: Lee Hyun Ju , Choi Sung Hwan , Kim Kyung Pil , Shin Hyun Ho , Yoo Jae Soo
Published: October 2010

For light-emitting diode (LED) excitation at 400 nm, the optical properties of a Eu2+-activated CaO–SrO–MgO–SiO2 material system were investigated. All the materials were synthesized by solid state reaction. In particular, (Ca,Sr)Mg2Si3O9:Eu2+, which has the same crystal structure as CaMgSi2O6, was found to be promising as a blue-light-emitting phosphor for near UV LED application. The luminance intensity was optimized by controlling the Eu2+ concentration and the composition of the host lattice. The ratio of calcium ions to strontium ions was a convenient parameter for adjusting the maximum excitation peak to 400 nm, which is favorable for near UV LED excitation. The highest luminance intensity of Ca1-x-y
Sr
y
Mg2Si3O9:Eu
x

2+ under 405 nm excitation was achieved at the Eu2+ concentration of x=0.01 and a Sr2+ concentration of y=0.3. The luminance intensity of (Ca,Sr)Mg2Si3O9:Eu2+ was found to be superior to that of a commercial blue-light-emitting BaMgAl10O17:Eu2+ phosphor, which is used for near-UV LED excitation.
Low-Voltage, Simple-Structure, High-Efficiency p–i–n-Type Electrophosphorescent Blue Organic Light-Emitting Diodes
Authors: Yu Jae Hyung , Jeon Woo Sik , Park Jung Soo , Pode Ramchandra , Kwon Jang Hyuk
Published: October 2010

We present simple p–i–n structures with single-emitting and mixed emitting layers for highly efficient phosphorescent blue organic devices. Using a high-triplet-energy-hole-transporting material of 1,1-bis(4-methylphenyl)-aminophenyl-cyclohexane (TAPC) and a high-triplet-energy-electron-transporting material of 1,3,5-tris(m-pyrid-3-ylphenyl)benzene (Tm3PyPB), the p–i–n structure has been realized by doping with MoO3 as a p-dopant and Cs2CO3 as an n-dopant. A very low onset voltage of 3.0 V and a driving voltage of 4.0 V to obtain a brightness of 1000 cd/m2 are achieved in this p–i–n device configuration. A maximum external quantum efficiency of 23.9% and a power efficiency of 36.7 lm/W are reported.
Formation of TiO2Nano Pattern on GaN-Based Light-Emitting Diodes for Light Extraction Efficiency
Authors: Cho Joong-Yeon , Byeon Kyeong-Jae , Park Hyoungwon , Kim Hyeong-Seok , Lee Heon
Published: October 2010

A TiO2nano-structure was formed on the indium-tin-oxide electrode of a GaN-based light-emitting diode (LED) in order to enhance the light extraction efficiency. The UV bi-layer imprinting and lift-off processes were used to form the TiO2nano-structure without any plasma etching process, which can lead to degradation of the electrical properties of the device. As a result, the light output power of the LED on the patterned sapphire substrate (PSS) with the TiO2nano-structure was enhanced up to 12% compared to identical LED formed on the PSS without TiO2nano-structure. No electrical degradation was observed for the patterned LED device.
Observation and Analysis of Molecular Vibration Modes in Polylactide at Terahertz Frequencies
Authors: Fuse Norikazu , Sato Ryo , Mizuno Maya , Fukunaga Kaori , Itoh Koichi , Ohki Yoshimichi
Published: October 2010

Terahertz (THz) spectra were obtained for polylactide, and they were analyzed by numerical calculations based on density functional theory. An absorption band was observed at approximately 50 cm-1, which becomes larger when the THz electric field is parallel to the sample drawing direction. An absorption peak with a similar directional dependence appears at approximately 40 cm-1 in the simulation, which is due to normal-mode molecular vibrations parallel to the molecular helix. Since the 50 cm-1 absorption decreases with an increase in crystallinity and the permittivity shows a step-like decrease, the molecular vibrations responsible for the 50 cm-1 band seem to be subjected to strong damping in amorphous regions. On the other hand, another absorption peak at 65 cm-1 with a positive absorption dependence on the sample's crystallinity is likely to be due to lattice vibration, since it does not appear in the calculations, which only deal with intramolecular vibration.
In situ Mapping of Light-Induced Refractive Index Gratings by Digital Holographic Microscopy
Authors: Lin Yu-Chih , Lee Yi-Ta , Lai Xin-Ji , Cheng Chau-Jern , Tu Han-Yen
Published: October 2010

This work presents a technique forin situmeasurement of light-induced refractive index gratings in epoxy resin using digital holographic microscopy (DHM). The reconstructed phase image derived from a digital hologram can exhibit the grating structure and refractive index profile of an epoxy resin hologram. Reconstruction properties of finite aperture effect in the DHM system are considered and analyzed theoretically. Due to the high spatial frequency components collected by the objective lens, the DHM system can measure fine grating structures and numerically determine the reconstructed images in increased detail. Grating formation and dynamic behavior during the light-induced holographic process can be demonstrated experimentally and characterized using the proposed scheme. Compared with an optical holographic readout, the proposed technique facilitates direct observation and substantial understanding of the holographic recording mechanism in a microscopic view.
Dynamic Nuclear Polarization of 29Si Nuclei Induced by Li and Li–O Centers in Silicon
Authors: Rahman Mohammad R. , Itahashi Tatsumasa , Vlasenko Marina P. , Vlasenko Leonid S. , Haller Eugene E. , Itoh Kohei M.
Published: October 2010

Dynamic nuclear polarization (DNP) of 29Si nuclear spins induced by saturation of electron paramagnetic resonance (EPR) transitions of lithium-related centers in float zone (FZ) grown silicon is reported. Both isolated Li and Li–O complex centers showed strong EPR absorption lines in the temperature range 3.4–10 K and led to very efficient orientation of 29Si nuclear spins. The temperature dependence and time constant of 29Si DNP are investigated in detail. The 29Si DNP of 0.72% was achieved at 3.4 K by excitation of the Li–O forbidden EPR transition under illumination, corresponding to a ∼352 fold increase with respect to the thermal equilibrium polarization.
Negative Differential Resistance in InGaAs/InAlAs Nanoscale In-Plane Structures
Authors: Komatsuzaki Yuji , Higashi Kazuhiro , Kyougoku Tomoteru , Onomitsu Koji , Horikoshi Yoshiji
Published: October 2010

Nanoscale in-plane structure devices are fabricated by electron beam lithography followed by electron cyclotron resonance reactive ion etching. We investigate the negative differential resistance (NDR) of InGaAs/InAlAs in-plane structure devices. The NDR appears in the current–voltage (I–V) characteristics of simple two-terminal in-plane short-channel devices. NDR characteristics depend on the effective channel width of in-plane gate transistors and become more pronounced when the channel conductance is increased by applying gate voltages. In a short-channel in-plane gate transistor, a more prominent NDR is observed and the NDR appears even at room temperature. In addition, the NDR onset voltage shifts to lower voltages when the channel length decreases. The NDR phenomenon is most likely caused by the real-space transfer of electrons from a high mobility channel to a low mobility layer.
Observation of N-Shaped Negative Differential Resistance in GaAs-Based Modulation-Doped Field Effect Transistor with InAs Quantum Dots
Authors: Li Yueqiang , Wang Xiaodong , Xu Xiaona , Liu Wen , Chen Yanling , Yang Fuhua , Tan Pingheng , Zeng Yiping
Published: October 2010

N-shaped negative differential resistance (NDR) with a high peak-to-valley ratio (PVR) is observed in a GaAs-based modulation-doped field effect transistor (MODFET) with InAs quantum dots (QDs) in the barrier layer (QDFET) compared with a GaAs MODFET. The NDR is explained as the real-space transfer (RST) of high-mobility electrons in a channel into nearby barrier layers with low mobility, and the PVR is enhanced dramatically upon inserting the QD layer. It is also revealed that the QD layer traps holes and acts as a positively charged nano-floating gate after a brief optical illumination, while it acts as a negatively charged nano-floating gate and depletes the adjacent channel when charged by the electrons. The NDR suggests a promising application in memory or high-speed logic devices for the QDFET structure.
Trade-Off Relationship of Size and Density of Platinum Nanocrystal in Nonvolatile Memory Characteristics
Authors: Seo Jungmok , Lee Taeyoon
Published: October 2010

The replacement of metal nanocrystal (NC)-based nonvolatile memories (NVMs) with polycrystalline silicon floating-gate memories is very attractive, since they demonstrate superior capability of charge localization and a reduction in cell-to-cell interference. Varying the size (ranging from 15.1 to 55.2 nm) and density (from 5.6×1011to 3.2×1010cm-2) of the metal NC affects the entire memory properties such as the charging/discharging process, retention characteristic, and charge storage capability. Here, we investigated the effects of the size and density of platinum (Pt) NCs on the aforementioned memory characteristics by fabricating Pt-NC-embedded metal oxide semiconductor (MOS) capacitors using a direct self-assemble method. The flatband voltage shift, a measure of charge storage capability for NC-based NVMs, increased from 5.75 to 13.05 V as the mean size of the NCs was varied from 15.1 to 55.2 nm, which was relatively higher than that of other NC-based NVMs. Our studies revealed that the flatband voltage shift depends on not only the size and density of the NCs, but also the tunneling probability of the electrons, which is closely related to the applied electric field at a tunneling oxide. The relationships among the flatband voltage shift, the size and density of the NCs, and the applied electric field, which are revealed in this study, can be generally applicable to other NVMs based on various metal and semiconducting NCs.
Effect of Source/Drain Doping Gradient on Threshold Voltage Variation in Double-Gate Fin Field Effect Transistors as Determined by Discrete Random Doping
Authors: Moon Dae-hyun , Song Jae-Joon , Kim Ohyun
Published: October 2010

We present a numerical simulation and physical analysis of how a single dopant in the channel region effects the variation of threshold voltage ΔV
th in highly scaled (gate length = 16 nm) and undoped double-gate fin field effect transistors. The presence of a single contaminant dopant in an undoped channel with an abrupt source/drain (S/D) doping gradient can cause a severe change in ΔV
th (140 mV owing to a single acceptor; 100 mV owing to a single donor). To effectively suppress this severe variation, we suggest S/D doping gradient engineering to make the lateral straggle of S/D doping (σS/D) larger than 2 nm to minimize ΔV
th. The distribution of V
th is also estimated by three-dimensional simulation using the position of the dopant.
Growth of ZnO-Nanorod Grating on the Seed Grating Produced by Femtosecond Laser Pulses
Authors: Lee Geon Joon , Nam Hyun Jung , Hwangbo Chang Kwon , Lim Hyunjin , Cheong Hyeonsik , Kim Hee Soo , Yoon Chong Seung , Min Sun-Ki , Han Sung-Hwan , Lee YoungPak
Published: October 2010

In this research, we successfully fabricated ZnO-nanorod grating by carrying out femtosecond-laser modification of the seed layer. First, a Ag-doped ZnO seed layer was deposited on a glass substrate by dc/rf magnetron co-sputtering, in which rf and dc power sources were utilized for the ZnO and the Ag targets, respectively. Next, a seed grating was produced on the seed layer by using the two-beam interference of femtosecond-laser pulses. Finally, a ZnO-nanorod grating was grown on the seed grating by chemical bath deposition in an aqueous solution of Zn(NO3)2and hexamethyltetramine. The scanning-electron-microscopy images indicate that the ZnO-nanorod grating can be regarded as a spatially periodic structure consisting of alternating bands of ZnO nanorods with relatively large and small diameters. The selected-area electron-diffraction patterns of the seed grating reveal that the formation of the ZnO-nanorod grating is attributable to the spatially selective modification of the seed layer produced by femtosecond-laser pulses.
High-Current Reliability of Carbon Nanotube Via Interconnects
Authors: Sato Motonobu , Hyakushima Takashi , Kawabata Akio , Nozue Tatsuhiro , Sato Shintaro , Nihei Mizuhisa , Awano Yuji
Published: October 2010

We have improved the high-current reliability of carbon nanotube (CNT) via interconnects by chemical mechanical polishing (CMP) and vacuum in situ metal deposition processes. These processes enable us to decrease the contact resistance of a CNT via to the upper and lower Cu lines, and also increase the number of CNTs contributing to current flow. Consequently, the current density per CNT was decreased, and current tolerance properties were improved. As a result, the CNTs via interconnects were able to withstand a high current density of 4×107 A/cm2 per via, i.e., 1.7×108 A/cm2 per CNT. In addition, we found that the failure mode of Cu-line/CNT-via/Cu-line interconnects with a CNT density of 3×1011 tubes/cm2 was the slit void formation at the Cu line under the via, which is similar to that of Cu via interconnects. Furthermore, we discussed how to further increase the tolerance of electromigration (EM), taking advantage of their high thermal conductivity.
Local Tunneling Barrier Height at and around Subsurface Dopant Sites on p-GaAs(110)
Authors: Kobayashi Kengo , Kurokawa Shu , Hasegawa Shigehiko , Sakai Akira
Published: October 2010

The local tunneling barrier height at and around subsurface Zn acceptor atoms on GaAs(110) has been investigated by scanning tunneling microscopy (STM) and local barrier height (LBH) imaging. The measured LBH showed the bias dependence, which was in good agreement with the theoretical simulation that takes into account the effect of tip-induced band bending (TIBB). Above the acceptor sites, the bias dependence of LBH shifted to the positive-bias side as compared with that of the area distant from acceptors. We explained the observed shift by the additional local band bending that is induced by ionized acceptors.
Improvement in Crystalline Quality of InGaN-Based Epilayer on Sapphire via Nanoscaled Epitaxial Lateral Overgrowth
Authors: Chiu Ching-Hsueh , Lin Da-Wei , Li Zhen-Yu , Chiu Chin-Hua , Chao Chu-Li , Tu Chia-Cheng , Kuo Hao-Chung , Lu Tien-Chang , Wang Shing-Chung
Published: October 2010

In this study, a high-performance GaN-based light-emitting diode (LED) was achieved using a nanocolumn patterned sapphire substrate (NCPSS) with low-pressure metal-organic chemical vapor deposition (LP-MOCVD). The surface roughness was evaluated by atomic force microscopy (AFM). The mechanisms of carrier localization in the GaN-based LED fabricated on NCPSS were discussed referring to the results obtained from the power-dependent photoluminescence measurements. Moreover, from the transmission electron microscopy (TEM) image, the threading dislocation densities (TDDs) through the GaN-based LED fabricated on NCPSS were found to be about 10 times lower than those fabricated on planar substrates. Finally, the internal quantum efficiency (IQE) of the GaN-based LED fabricated on NCPSS was as high as 48% at 30 mW, corresponding to a current of 20 mA, which is higher than that of a GaN-based LED fabricated on a planar sapphire substrate by 8%. The use of NCPSS is suggested to be effective for elevating the emission efficiency of the GaN-based LED owing to an improvement in crystal quality.
Electrochemical, Optical and Electronic Properties of Iridium Tin Oxide Thin Film as Counter Electrode of Electrochromic Device
Authors: Niwa Tatsuo , Takai Osamu
Published: October 2010

Iridium tin oxide films (IRTOFs) containing dispersed iridium oxide in a tin oxide matrix were prepared by an ion-plating process. The optical, electrochemical, and electronic properties of the films were measured by varying the iridium concentration in the films. The cyclic voltammogram characteristic of the films showed good reproducibility. The coloration efficiency of the IRTOFs increased with an increase in the concentration of iridium. The change ranges of the conductivity become more than 108 times. The activation energy increased with increasing iridium concentration in the iridium concentration range in which the conductivity decreased. The characteristics of an all-solid-state electrochromic device with an IRTOF counter electrode were measured.
Influence of Rapid Thermal Annealing on Raman Scattering of InN Epilayers
Authors: Yang Min-De , Tong Shih-Chang , Chou I-Tin , Shu Gia-Wei , Shen Ji-Lin , Lee Yueh-Chien , Huang Ying-Sheng , Chen Yang-Fang , Lin Tai-Yuan
Published: October 2010

We studied the Raman scattering of the InN epilayers with rapid thermal annealing (RTA). The longitudianl optical (LO) phonon in Raman spectrum shifts toward lower frequency and increases asymmetric broadening as the RTA temperature is increased. We suggest that the formation of indium-related defects, such as metallic indium clusters or indium vacancies, are responsible for the change in the asymmetric ratio in the LO mode. The E2 (high) mode in the Raman spectrum does not exhibit significant change after RTA since the indium atom does not involve the E2 (high) mode.
Interaction between Dielectric Barrier Discharge and Positive Streamer in Helium Plasma Jet at Atmospheric Pressure
Authors: Urabe Keiichiro , Ito Yosuke , Sakai Osamu , Tachibana Kunihide
Published: October 2010

We have investigated the discharge mechanisms in a helium plasma jet with a coaxial dielectric barrier discharge (DBD) configuration, which can generate low-temperature plasma plume mainly by positive corona streamer propagation. In this study, we focused on the relationships between the coaxial DBD inside a glass tube and the positive streamer propagating in the plasma plume, using novel types of electrode configurations composed of insulated electric wires. The discharge characteristics were investigated by measuring plume length, discharge currents of the DBD, and the line-integrated density of helium metastable atoms in the plume. The experimental results indicate that the excited-species density in the plume is largely dependent on surface-charge density accumulated by the DBD. Moreover, we analyzed the spatiotemporal distribution of electrical potential around the tube exit by the finite element method, and discussed the mechanism determining plume length.