bluuebunny/crossref_metadata_2025 huggingface dataset:
Geochemical Processes During Five Years of Aquifer Storage Recovery
Authors: Herczeg Andrew L. , Rattray Karen J. , Dillon Peter J. , Pavelic Paul , Barry Karen E.
Published: December 2005

A key factor in the long‐term viability of aquifer storage recovery (ASR) is the extent of mineral solution interaction between two dissimilar water types and consequent impact on water quality and aquifer stability. We collected geochemical and isotopic data from three observation wells located 25, 65, and 325 m from an injection well at an experimental ASR site located in a karstic, confined carbonate aquifer in South Australia. The experiment involved five major injection cycles of a total of 2.5 × 105 m3 of storm water (total dissolved solids [TDS] ∼ 150 mg/L) into the brackish (TDS ∼2400 mg/L) aquifer. ∼60% of the mixture was pumped out during the fifth year of the experiment. The major effect on water quality within a 25 m radius of the injection well following injection of storm water was carbonate dissolution (35 ± 6 g of CaCO3 dissolved/m3 of aquifer) and sulfide mineral oxidation (50 ± 10 g as FeS2/m3 after one injection). < 0.005% of the total aquifer carbonate matrix was dissolved during each injection event, and ∼0.2% of the total reduced sulfur. Increasing amounts of ambient ground water was entrained into the injected mixture during each of the storage periods. High 14CDIC activities and slightly more negative δ13CDIC values measured immediately after injection events show that substantial CO2(aq) is produced by oxidation of organic matter associated with injectant. There were no detectable geochemical reactions while pumping during the recovery phase in the fifth year of the experiment.
Hydraulic Conductivity Prediction for Sandy Soils
Authors: Cronican Amy E. , Gribb Molly M.
Published: December 2005

The potential for petroleum‐contaminated soils to impact ground water is evaluated using the soil leachability model in South Carolina and Georgia. In this model, the Green and Ampt (1911) equation is used to estimate unsat‐urated flow with saturated hydraulic conductivity (Ks) values obtained using the Rawls and Brakensiek (1989) equation from inputs of percent sand‐ and clay‐sized particles. However, many soils have > 70% sand‐sized particles, which is the maximum amount for which the Rawls and Brakensiek equation is valid. Therefore, 70 sets of Ks and particle‐size data from the literature for southeastern United States sandy soils were analyzed to develop a new equation for estimating Ks. A multiple linear regression model with an adjusted R2= 0.65 (p < 0.0001) was developed from percent clay‐ and sand‐sized particle data. Eight additional sets of data were used to validate the model. The root mean square deviation and maximum squared difference, (yi‐ŷi2), values for the new model are smaller than those obtained using the Rawls and Brakensiek equation, or Rosetta, a neural network‐based model (Schaap 1999). The new model provides estimates that are within an order of magnitude for all but one of the test data sets. Rosetta predicts Ks within one order of magnitude of measured values for six test data, and predicts Ks within two orders of magnitude for the other two. The Rawls and Brakensiek predictions are within one order of magnitude for four test data, but are two or more orders of magnitude too high for the remaining four points. The new equation is recommended for estimating Ks for sandy southeastern United States soils for which inputs are limited to percent sand and clay.
SecA Dimer Cross-Linked at Its Subunit Interface Is Functional for Protein Translocation
Authors: Jilaveanu Lucia B. , Oliver Donald
Published: December 2005

SecA facilitates protein transport across the eubacterial plasma membrane by its association with cargo proteins and the SecYEG translocon, followed by ATP-driven conformational changes that promote protein translocation in a stepwise manner. Whether SecA functions as a monomer or a dimer during this process has been the subject of considerable controversy. Here we utilize cysteine-directed mutagenesis along with the crystal structure of the SecA dimer to create a cross-linked dimer at its subunit interface, which was normally active for in vitro protein translocation.
“UnPAKing” Human Immunodeficiency Virus (HIV) Replication: Using Small Interfering RNA Screening To Identify Novel Cofactors and Elucidate the Role of Group I PAKs in HIV Infection
Authors: Nguyen Deborah G. , Wolff Karen C. , Yin Hong , Caldwell Jeremy S. , Kuhen Kelli L.
Published: December 2005

In order to identify novel proviral host factors involved in human immunodeficiency virus (HIV) infection, we performed a screen of a small interfering RNA (siRNA) library targeting 5,000 genes with the highest potential for being targets for therapeutics. Many siRNAs in the library against known host factors, such as TSG101, furin, and CXCR4, were identified as inhibitors by the screen and thus served as internal validation. In addition, many novel factors whose knockdown inhibited infection were identified, including Pak3, a member of the serine/threonine group I PAK kinases. The HIV accessory factor Nef has been shown to associate with a PAK kinase, leading to enhanced viral production; however, the exact identity of the kinase has remained controversial. Prompted by the Pak3 screen hit, we further investigated the involvement of group I PAK kinases in HIV using siRNA. Contrary to the current literature, Pak1 depletion strongly inhibited HIV infection in multiple cell systems and decreased levels of integrated provirus, while Pak2 depletion showed no effect. Overexpression of a constitutively active Pak1 mutant also enhanced HIV infection, further supporting its role as the dominant PAK involved.
Severe Acute Respiratory Syndrome Coronavirus 3a Protein Is Released in Membranous Structures from 3a Protein-Expressing Cells and Infected Cells
Authors: Huang Cheng , Narayanan Krishna , Ito Naoto , Peters C. J. , Makino Shinji
Published: December 2005

Severe acute respiratory syndrome coronavirus (SCoV) accessory protein 3a is a virus structural protein. We demonstrate here that 3a protein was released efficiently in membranous structures from various cell lines expressing 3a protein. A subpopulation of the released 3a protein is associated with detergent-resistant membranes. The presence of the YxxΦ and diacidic motifs, located within the cytoplasmic tail of the 3a protein, was not required for its efficient release. Analysis of supernatant from SCoV-infected cells with sucrose gradient sedimentation and virus capture assay indicated that the 3a protein was released from infected cells in two distinct populations, as a component of SCoV particles, and in membrane structures with a lower buoyant density. These data provide new insights into the biological properties of SCoV 3a protein.
Lack of Intrinsic CTLA-4 Expression Has Minimal Effect on Regulation of Antiviral T-Cell Immunity
Authors: Homann Dirk , Dummer Wolfgang , Wolfe Tom , Rodrigo Evelyn , Theofilopoulos Argyrios N. , Oldstone Michael B. A. , von Herrath Matthias G.
Published: December 2005

CTLA-4 is considered one of the most potent negative regulators of T-cell activation. To circumvent experimental limitations due to fatal lymphoproliferative disease associated with genetic ablation of CTLA-4, we have used radiation chimeras reconstituted with a mixture of CTLA-4+/+and CTLA-4−/−bone marrow that retain a normal phenotype and allow the evaluation of long-term T-cell immunity under conditions of intrinsic CTLA-4 deficiency. Following virus infection, we profiled primary, memory, and secondary CD8+and CD4+T-cell responses directed against eight different viral epitopes. Our data demonstrate unaltered antigen-driven proliferation, acquisition of effector functions, distribution of epitope hierarchies, T-cell receptor repertoire selection, functional avidities, and long-term memory maintenance in the absence of CTLA-4. Moreover, regulation of memory T-cell survival and homeostatic proliferation, as well as secondary responses, was equivalent in virus-specific CTLA4+/+and CTL-A-4−/−T-cell populations. Thus, lack of CTLA-4 expression by antigen-specific T cells can be compensated for by extrinsic factors in the presence of CTLA-4 expression by other cells. These findings have implications for the physiologic, pathological, and therapeutic regulation of costimulation.
Neither the RNA nor the Proteins of Open Reading Frames 3a and 3b of the Coronavirus Infectious Bronchitis Virus Are Essential for Replication
Authors: Hodgson Teri , Britton Paul , Cavanagh Dave
Published: December 2005

Gene 3 of infectious bronchitis virus is tricistronic; open reading frames (ORFs) 3a and 3b encode two small nonstructural (ns) proteins, 3a and 3b, of unknown function, and a third, structural protein E, is encoded by ORF 3c. To determine if either the 3a or the 3b protein is required for replication, we first modified their translation initiation codons to prevent translation of the 3a and 3b proteins from recombinant infectious bronchitis viruses (rIBVs). Replication in primary chick kidney (CK) cells and in chicken embryos was not affected. In chicken tracheal organ cultures (TOCs), the recombinant rIBVs reached titers similar to those of the wild-type virus, but in the case of viruses lacking the 3a protein, the titer declined reproducibly earlier. Translation of the IBV E protein is believed to be initiated by internal entry of ribosomes at a structure formed by the sequences corresponding to ORFs 3a and 3b. To assess the necessity of this mechanism, we deleted most of the sequence representing 3a and 3b to produce a gene in which ORF 3c (E) was adjacent to the gene 3 transcription-associated sequence. Western blot analysis revealed that the recombinant IBV produced fivefold less E protein. Nevertheless, titers produced in CK cells, embryos, and TOCs were similar to those of the wild-type virus, although they declined earlier in TOCs, probably due to the absence of the 3a protein. Thus, neither the tricistronic arrangement of gene 3, the internal initiation of translation of E protein, nor the 3a and 3b proteins are essential for replication per se, suggesting that these proteins are accessory proteins that may have roles in vivo.
Characterization of the Vaccinia Virus A35R Protein and Its Role in Virulence
Authors: Roper Rachel L.
Published: December 2005

The vaccinia virus A35R gene is highly conserved among poxviruses and encodes a previously uncharacterized hydrophobic acidic protein. Western blotting with anti-A35R peptide antibodies indicated that the protein is expressed early in infection and resolved as a single sharp band of ∼23 kDa, slightly higher than the 20 kDa predicted from its sequence. The protein band appeared to be the same molecular weight on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, whether expressed in an in vitro transcription/translation system without microsomes or expressed in infected cells, suggesting that it was not glycosylated. A mutant virus with the A35R gene deleted (vA35Δ) formed wild-type-sized plaques on all cell lines tested (human, monkey, mouse, and rabbit); thus, A35R is not required for replication and does not appear to be a host range gene. Although the A35R protein is hydrophobic, it is unlikely to be an integral membrane protein, as it partitioned to the aqueous phase during TX-114 partitioning. The protein could not be detected in virus-infected cell supernatants. A35R localized intracellularly to the virus factories, where the first stages of morphogenesis occur. The vA35Δ mutant formed near-normal levels of the various morphogenic stages of infectious virus particles and supported normal acid-induced fusion of virus-infected cells. Despite normal growth and morphogenesis in vitro, the vA35Δ mutant virus was attenuated in intranasal challenge of mice compared to wild-type and A35R rescue virus. Thus, the intracellular A35R protein plays a role in virulence. The A35R has little homology to any protein outside of poxviruses, suggesting a novel virulence mechanism.
Role for nsP2 Proteins in the Cessation of Alphavirus Minus-Strand Synthesis by Host Cells
Authors: Sawicki Dorothea L. , Perri Silvia , Polo John M. , Sawicki Stanley G.
Published: December 2005

In order to establish nonlytic persistent infections (PI) of BHK cells, replicons derived from Sindbis (SIN) and Semliki Forest (SFV) viruses have mutations in nsP2. Five different nsP2 PI replicons were compared to wild-type (wt) SIN, SFV, and wt nsPs SIN replicons. Replicon PI BHK21 cells had viral RNA synthesis rates that were less than 5% of those of the wt virus and ∼10% or less of those of SIN wt replicon-infected cells, and, in contrast to wt virus and replicons containing wt nsP2, all showed a phenotype of continuous minus-strand synthesis and of unstable, mature replication/transcription complexes (RC+) that are active in plus-strand synthesis. Minus-strand synthesis and incorporation of [
3
H]uridine into replicative intermediates differed among PI replicons, depending on the location of the mutation in nsP2. Minus-strand synthesis by PI cells appeared normal; it was dependent on continuous P123 and P1234 polyprotein synthesis and ceased when protein synthesis was inhibited. The failure by the PI replicons to shut off minus-strand synthesis was not due to some defect in the PI cells but rather was due to the loss of some function in the mutated nsP2. This was demonstrated by showing that superinfection of PI cells with wt SFV triggered the shutdown of minus-strand synthesis, which we believe is a host response to infection with alphaviruses. Together, the results indicate alphavirus nsP2 functions to engage the host response to infection and activate a switch from the early-to-late phase. The loss of this function leads to continuous viral minus-strand synthesis and the production of unstable RC+.
Prostate Tumor Cells Infected with a Recombinant Influenza Virus Expressing a Truncated NS1 Protein Activate Cytolytic CD8
+
Cells To Recognize Noninfected Tumor Cells
Authors: Efferson Clay L. , Tsuda Naotake , Kawano Kouichiro , Nistal-Villán Estanislao , Sellappan Shankhar , Yu Dihua , Murray James L. , García-Sastre Adolfo , Ioannides Constantin G.
Published: December 2005

Many viral oncolytic approaches against cancer are based on the ability of specific viruses to replicate in tumors expressing components of the constitutively activated Ras/mitogen-activated protein kinase (MAPK) pathways and/or inhibited or dysregulated alpha/beta interferon (IFN-α/β) response pathways. A major issue when considering these approaches is their applicability to tumors that lack activated Ras. To identify the effector mechanisms activated by oncolytic viruses, we investigated inhibition of proliferation of the prostate cancer line LNCap by the recombinant TR-NS1 influenza A virus, a genetically attenuated influenza A/PR8/34 virus expressing a truncated nonstructural protein (NS1) of 126 amino acids. LNCap cells lack constitutively activated MAPK, extracellular signal-regulated kinase (ERK), and p38 and are resistant to death by IFN-α. Truncation of the NS1 protein of influenza viruses is known to result in viral attenuation due to a reduced ability of the NS1 to inhibit the IFN-α/β response. Infection with TR-NS1 virus rapidly activated ERK-1 more than ERK-2 in LNCap cells. Importantly, TR-NS1 virus infection transiently inhibited cell proliferation and induced apoptosis in LNCap cells. Addition of peripheral blood mononuclear cells (PBMC) and interleukin 12 (IL-12) to TR-NS1 virus-infected LNCap cells (TR-NS1-LNCap) resulted in faster elimination of TR-NS1-LNCap cells compared with LNCap cells. Moreover, TR-NS1-LNCap cells induced IFN-γ in PBMC. The levels of IFN-γ were amplified by IL-12. TR-NS1-LNCap cells also induced tumor-lytic cytotoxic T lymphocytes (CTL). These CTL lysed noninfected LNCap cells in a CD8-dependent manner. Activation of cellular immunity to tumor cells by viruses is an intriguing effector pathway, which should be especially significant for elimination of human tumors that lack activated Ras.
Point Mutations in Herpes Simplex Virus Type 1 oriL, but Not in oriS, Reduce Pathogenesis during Acute Infection of Mice and Impair Reactivation from Latency
Authors: Balliet John W. , Schaffer Priscilla A.
Published: December 2005

In vitro studies of herpes simplex virus type 1 (HSV-1) viruses containing mutations in core sequences of the viral origins of DNA replication, oriL and oriS, that eliminate the ability of these origins to initiate viral-DNA synthesis have demonstrated little or no effect on viral replication in cultured cells, leading to the conclusion that the two types of origins are functionally redundant. It remains unclear, therefore, why origins that appear to be redundant are maintained evolutionarily in HSV-1 and other neurotropic alphaherpesviruses. To test the hypothesis that oriL and oriS have distinct functions in the HSV-1 life cycle in vivo, we determined the in vivo phenotypes of two mutant viruses, DoriL-I
LR
and DoriS-I, containing point mutations in oriL and oriS site I, respectively, that eliminate origin DNA initiation function. Following corneal inoculation of mice, tear film titers of DoriS-I were reduced relative to wild-type virus. In all other tests, however, DoriS-I behaved like wild-type virus. In contrast, titers of DoriL-I
LR
in tear film, trigeminal ganglia (TG), and hindbrain were reduced and mice infected with DoriL-I
LR
exhibited greatly reduced mortality relative to wild-type virus. In the TG explant and TG cell culture models of reactivation, DoriL-I
LR
reactivated with delayed kinetics and, in the latter model, with reduced efficiency relative to wild-type virus. Rescuant viruses DoriL-I
LR
-R and DoriS-I-R behaved like wild-type virus in all tests. These findings demonstrate that functional differences exist between oriL and oriS and reveal a prominent role for oriL in HSV-1 pathogenesis.
Herpes Simplex Virus Type 1 Infection Induces Activation and Recruitment of Protein Kinase C to the Nuclear Membrane and Increased Phosphorylation of Lamin B
Authors: Park Richard , Baines Joel D.
Published: December 2005

We report that herpes simplex virus type 1 (HSV-1) infection leads to the recruitment of protein kinase C (PKC) to the nuclear rim. In HEp-2 cells, PKC recruitment to the nuclear rim was initiated between 8 h and 12 h postinfection. PKCδ, a proapoptotic kinase, was completely recruited to the nuclear rim upon infection with HSV-1. PKCα was less dramatically relocalized mostly at the nuclear rim upon infection, although some PKCα remained in the cytoplasm. PKCζ-specific immunofluorescence was not significantly relocated to the nuclear rim. The U
L
34 and U
L
31 proteins, as well as their association, were each required for PKC recruitment to the nuclear rim. The HSV-1 U
S
3 protein product, a kinase which regulates the phosphorylation state and localization of U
L
34, was not required for PKC recruitment to the nuclear rim; however, it was required for proper localization along the nuclear rim, as PKC appeared unevenly distributed along the nuclear rim of cells infected with U
S
3 null and kinase-dead mutants. HSV-1 infection induced the phosphorylation of both lamin B and PKC. Elevated lamin B phosphorylation in HSV-1-infected cells was partially reduced by inhibitors of PKC. The data suggest a model in which kinases that normally disassemble the nuclear lamina during apoptosis are recruited to the nuclear membrane through functions requiring U
L
31 and U
L
34. We hypothesize that the recruitment of PKC functions to phosphorylate lamin B to help modify the nuclear lamina and promote budding of nucleocapsids at the inner nuclear membrane.
Betanodavirus B2 Is an RNA Interference Antagonist That Facilitates Intracellular Viral RNA Accumulation
Authors: Fenner Beau J. , Thiagarajan Rekha , Chua Hui Kheng , Kwang Jimmy
Published: December 2005

Betanodaviruses are small positive-sense bipartite RNA viruses that infect a wide variety of fish species and are notorious for causing lethal outbreaks in juvenile fish hatcheries worldwide. The function of a small nonstructural protein, B2, encoded by the subgenomic RNA3 of betanodaviruses, has remained obscure. Greasy grouper nervous necrosis virus, a betanodavirus model, was used to develop a facile DNA-based reverse genetics system that recapitulated the virus infection cycle, and we used this system to show that B2 is a small nonstructural protein that is essential for high level accumulation of viral RNA1 after RNA transfection of fish, mammalian, and avian cells. The defect in RNA1 accumulation in a B2 mutant was partially complemented by supplying B2 RNA in
trans
. Confocal analysis of the cellular distribution of B2 indicated that B2 is able to enter the nucleus and accumulates there during the late stages of GGNNV infection. Using human HeLa cells as a cellular RNA interference model, we found that B2 could efficiently antagonize RNA interference, which is a property shared by the distantly related alphanodavirus B2 proteins. This function provides appears to provide an explanation, at least in part, for why B2 mutant RNA1 is severely impaired in its intracellular accumulation.
SIMULATIONS OF THE GENERATION OF TERAHERTZ RADIATION BY PHOTOMIXING IN LASER-ASSISTED FIELD EMISSION TO OPTIMIZE THE SIGNAL-TO-NOISE RATIO
Authors: HAGMANN MARK J.
Published: December 2005

Quantum simulations and experiments show that photomixing in laser-assisted field emission has promise as a new method for wide-band tunable sources of radiation at terahertz frequencies. The tunable bandwidth is only limited by the means for coupling power from the oscillations in the field emission current from photomixing, and not by the processes that generate this current. Photomixing is simulated as a stationary stochastic process in which the frequencies and phases of the incident optical radiation are random variables. The waveform of the current is determined by solving the Schrödinger equation at discrete time steps for which the effective potential barrier is a superposition of the incident radiation field and the static barrier. These samples satisfy the criteria of a Poisson process to allow for the discrete emission of electrons at a specified total current. The one-sided power spectral density for this current is calculated with the FFT to produce periodogram estimates. The simulations show that the signal-to-noise ratio may be increased by (1) raising the power flux density of each laser, (2) raising the DC static current, (3) reducing the linewidth of each laser, and (4) using a static current density of no more than 1010 A/m.
LONG-TERM CORRELATIONS AND FRACTAL DIMENSION OF BEAT-TO-BEAT BLOOD PRESSURE DYNAMICS
Authors: BAUMERT MATHIAS , BAIER VICO , VOSS ANDREAS
Published: December 2005

Arterial blood pressure is modulated by several physiological regulatory processes. The analysis of beat-to-beat blood pressure dynamics provides information about cardiovascular control and patho-physiological conditions. In this paper we investigated the long-term correlations and fractal dimension of systolic blood pressure time series applying detrended fluctuation analysis (DFA) and Higuchi's algorithm (HFD). Thirty-minute blood pressure recordings in 25 patients with dilated cardiomyopathy (DCM) and 27 healthy controls (CON) were analyzed. The DFA and HFD revealed multifractal features in the blood pressure dynamics of CON as well as of DCM. At small scales, DFA and HFD of CON were significantly different from those of CON, reflecting patho-physiological changes. In conclusion, scaling analysis of blood pressure dynamics might lead to an enhanced assessment of autonomic cardiovascular control in patients with DCM.
COMMUNITY INDICATOR PROGRAMS: THEIR CONSTRUCTION, LOGIC AND CONSISTENCY BASED ON A PROGRAM EVALUATION OF THE SANTA MONICA CIP, CALIFORNIA
Authors: BLAIR JOHN M.
Published: December 2005

Some 200–300 local government agencies (LGAs) in the United States (US) use suites of indicators to monitor economic and environmental trends and social well-being, often against goals. Many reservations have been expressed about these community indicator programs (CIPs) including their internal logic such as the validity of indicators in relation to goals, the measurability and plausibility of goals and data reliability.

To test these criticisms, a formal evaluation of a CIP has been done using the well-respected Santa Monica, California, CIP as the case study. The research tests the plausibility of a CIP as well as its effectiveness. It is done using program evaluation techniques, in particular, the tool of evaluability assessment. Using Likert rating techniques against several criteria, the author finds that plausibility of the CIP is reasonably robust and that it is a particularly effective tool of governance. More important, the research yields an evaluative methodology for assessing all goal-based CIPs. It is a framework that can help strengthen existing CIPs and it is transferable to appraising similar documents. Lastly, the research offers several lessons of value to urban planners and managers including discussion of targets, regionalism and the nature of "success" in urban management.
OPTIMAL UTILIZATION OF RECLAIMED WASTEWATER FOR IRRIGATION PURPOSES: CASE OF AS-SAMRA WASTEWATER TREATMENT PLANT
Authors: MRAYYAN BASSAM
Published: December 2005

Due to the rapid population growth and industrial development in Jordan, the demand on water resources for different purposes, mainly agriculture has been elevated. The shortage of fresh water resources and the high demand make the reclaimed wastewater a key factor in the water budget. This paper examines both positive and negative impacts of wastewater reuse for agriculture. Currently, Jordan has more than 27 wastewater treatment plants all over the country; the largest is As-Samra treatment plant. The objective of this article is to set a framework for optimal utilization of the said reclaimed water taking into consideration the technical, financial, economical and social aspects at the end user demand centers and the new upgrading project at the study area, in addition to promoting the anticipated findings for other similar regional cases in terms of knowledge disseminations and setting a pilot cases for neighboring countries.
TiO2 Photocatalysis: A Historical Overview and Future Prospects
Authors: Hashimoto Kazuhito , Irie Hiroshi , Fujishima Akira
Published: December 2005

Photocatalysis has recently become a common word and various products using photocatalytic functions have been commercialized. Among many candidates for photocatalysts, TiO2 is almost the only material suitable for industrial use at present and also probably in the future. This is because TiO2 has the most efficient photoactivity, the highest stability and the lowest cost. More significantly, it has been used as a white pigment from ancient times, and thus, its safety to humans and the environment is guaranteed by history. There are two types of photochemical reaction proceeding on a TiO2 surface when irradiated with ultraviolet light. One includes the photo-induced redox reactions of adsorbed substances, and the other is the photo-induced hydrophilic conversion of TiO2 itself. The former type has been known since the early part of the 20th century, but the latter was found only at the end of the century. The combination of these two functions has opened up various novel applications of TiO2, particularly in the field of building materials. Here, we review the progress of the scientific research on TiO2 photocatalysis as well as its industrial applications, and describe future prospects of this field mainly based on the present authors' work.
Effect of Indium on Photoluminescence Properties of InGaPN Layers Grown by Solid Source Molecular Beam Epitaxy
Authors: Kim Sung Man , Furukawa Yuzo , Yonezu Hiroo , Umeno Kazuyuki , Wakahara Akihiro
Published: December 2005

The effect of indium on photoluminescence properties of InGaPN layers was investigated and compared with that of GaPN layers. Two phenomena involving photoluminescence properties were observed in the InGaPN layers: (i) an S-shape of photoluminescence (PL) peak energy as a function of temperature, caused by spatial fluctuation of bandgap energy related to In and N content; and (ii) red shifts of the PL peak energy at 18 K in the InGaPN layers after rapid thermal annealing (RTA), caused by the increase of N- and In-rich region with increasing RTA temperature. It was also found that integrated PL intensity in the InGaPN layers was higher than that in the GaPN layers, and that PL quenching became more insensitive to the change in temperature resulting from the decrease in nonradiative centers with increasing RTA temperature.
New Two-Diode Model for Detailed Analysis of Multicrystalline Silicon Solar Cells
Authors: Kurobe Ken-ichi , Matsunami Hiroyuki
Published: December 2005

In order to extract electrical properties of multicrystalline silicon (Mx-Si) solar cells precisely, current–voltage (I–V) measurement in the dark condition was carried out. A new two-diode model, which includes a diffusion-current dominant area (DCA) and a recombination-current dominant area (RCA), with nonequivalent series resistances, was proposed as a new equivalent circuit. Electrical properties as fitting parameters were successfully extracted using a successive approximation method. This characterization derived J
01 and J
02, which are the diode saturation current densities for n=1 and 2 diodes, respectively. To ensure this diode model, temperature characteristics were measured, and the validity of this model was shown through calculation of the energy band gap from J
01. J
01 and J
02 indicate a power factor and a loss factor of solar cells, respectively, which are newly proposed to classify solar cell performance.
Simulation Study of the Dependence of Submicron Polysilicon Thin-Film Transistor Output Characteristics on Grain Boundary Position
Authors: Walker Philip M. , Uno Shigeyasu , Mizuta Hiroshi
Published: December 2005

We investigate the impact of varying the grain boundary (GB) position on the output (I
d–V
d) characteristics of submicron single GB polysilicon thin film transistors (TFTs), by two-dimensional (2D), drift-diffusion based, device simulation. We employ a localized GB trapping model with a distribution of both donor-like and acceptor-like trap states over the forbidden energy gap of the GB region. We show that for devices with channel lengths in the deep submicron regime, significant variations in output conductance (g
d) occur as the GB position is varied. Specifically, we find that output conductance increases as the GB approaches the drain edge. Furthermore, the sensitivity of output conductance to the GB position increases as channel length decreases. The findings have important implications for any future analogue three-dimensional (3D) IC design that uses polysilicon as a device material.
Excess Carrier Lifetime Measurement of Bulk SiC Wafers and Its Relationship with Structural Defect Distribution
Authors: Mori Tatsuhiro , Kato Masashi , Watanabe Hideki , Ichimura Masaya , Arai Eisuke , Sumie Shingo , Hashizume Hidehisa
Published: December 2005

Excess carrier lifetime in bulk 2-in. SiC wafers was measured by microwave photoconductivity decay (µ-PCD). The mapping technique was used to obtain the lifetime distribution in the entire wafer. We observed the birefringence image and X-ray topograph of the wafers in order to determine the structural defect distribution, and the net donor concentration distribution was also observed by capacitance–voltage measurements. By comparison of lifetime maps with the structural defect distribution, it was found that relatively long lifetime regions correspond to regions with high-density structural defects. The net donor concentration did not show a clear influence on the carrier lifetimes. We confirmed that surface recombination has a negligible effect on the carrier lifetimes, and therefore the lifetimes obtained from mapping measurements are mainly dominated by carrier recombination behavior in the bulk of the wafers.
Electroreflectance Observation of Transformation Processes of the First and Second Minibands to Wannier–Stark Localization States in a GaAs/AlAs Superlattice
Authors: Hasegawa Takayuki , Nakayama Masaaki
Published: December 2005

We have investigated the transformation processes of the first (n=1) and second (n=2) minibands to the Wannier–Stark (WS) localization states in a GaAs (6.8 nm)/AlAs (0.9 nm) superlattice embedded in a p–i–n structure by electroreflectance spectroscopy. The high sensitivity of electroreflectance enabled us to observe the interband optical transitions associated with the n=2 minibands in addition to those associated with the n=1 minibands. The systematic results of the electroreflectance spectra as a function of electric field strength demonstrate that the electric field strength for the formation of the WS-localization state of the n=2 miniband is higher than that of the n=1 miniband, which reflects a difference in the energy widths of the n=1 and n=2 minibands. The experimental results are quantitatively discussed on the basis of the electric-field-strength dependence of the energies and envelope functions of the n=1 and n=2 minibands calculated using a transfer-matrix method. We find a clear correlation between the miniband widths and the critical electric field strengths for the formation of the WS-localization states.
Antireflective Coating Design of Spherical Silicon Solar Cell with Reflector Cup by Ray-Tracing Simulation
Authors: Minemoto Takashi , Ikuta Tomohiro , Takakura Hideyuki , Hamakawa Yoshihiro
Published: December 2005

An optimum design of an antireflective (AR) coating for a spherical Si solar cell with a reflector cup has been analyzed with a three-dimensional (3D) ray-tracing simulation. The 3D ray tracing is required to estimate the short-circuit current density (J
sc) because of an incident light angle distribution on a solar cell surface. In the simulation, the solar cell consists of a spherical Si solar cell with a diameter of 1 mm covered by an AR coating without surface texturing, and a hemispherical reflector cup with an aperture of 2 mm. The calculations of AR coating thickness (t) and refractive index (n) dependences on J
sc revealed that an optimum J
sc of 39.7 mA/cm2 can be obtained at t=78 nm and n=2.0. Also, a higher design tolerance in an optical film thickness of the AR coating is demonstrated, which is especially advantageous for spherical Si solar cells which inherently have some technical difficulties in a uniform AR coating formation.
2.4 and 5.2 GHz Dual-Band Antenna Fabricated on Flexible Parylene Membrane
Authors: Huang Chuen-Uan , Chen I-Yu , Chen Henry J. H. , Jou Christina F. , Huang Star Ruey-Shing
Published: December 2005

A 2.4 and 5.2 GHz dual-band monopole antenna fabricated on a flexible parylene membrane for Bluetooth and wireless local area network (WLAN) modules was designed and fabricated. The measured results show a good antenna performance and agree very well with the design simulations in both return loss and radiation characteristics. Parylene is a flexible polymer film; it can be deposited on various substrates and peeled off after completing device processes as stand-alone thin-and-flexible-substrate-containing devices. Owing to its excellent physical and chemical properties such as its low dielectric constant, light weight, low conductivity, and inertness to chemicals, parylene is also suitable for fabrication of many other RF devices.
Simulation of Band Diagram for Chemical-Vapor-Deposition Diamond Surface Conductivity
Authors: Kono Shozo , Koide Yasuo
Published: December 2005

One-dimensional energy band simulation has been performed in order to understand chemical-vapor-deposition (CVD) diamond surface conductivity. It was found that the presence of shallow-level acceptors in the subsurface region and defect states at the surface causes a steep rise in the valence band toward the Fermi level, which causes accumulation of holes in the valence band in the subsurface and near-surface regions. An artificial negative charge accumulation (NCA) layer is introduced in the simulation to examine the effect of possible negatively charged adsorbates on surface conductivity. By adjusting the thickness of NCA layers, we have reproduced quantitatively both the surface conductivity change and Fermi-level change found in previous experiments [Kono et al.: Diamond Relat. Mater. 14 (2005) 459; Riedel et al.: ibid.13 (2004) 746].
Relationship between Excess Ga and Residual Oxides in Amorphous GaN Films Deposited by Compound Source Molecular Beam Epitaxy
Authors: Obinata Naoyuki , Sugimoto Koichi , Ijima Kazuyuki , Ishibiki Masaya , Egawa Shinichi , Honda Tohru , Kawanishi Hideo
Published: December 2005

Amorphous GaN (a-GaN) films were deposited at a low temperature below 500°C by compound-source molecular beam epitaxy (CS-MBE). The relationship between excess Ga and its oxidation in the deposited GaN films is reported. X-ray photoelectron spectroscopy (XPS) revealed that the excess Ga in deposited films was oxidized in the air and converted to gallium oxide. By increasing the substrate temperature, the total amount of gallium oxide in the deposited films decreased due to the reduction of the excess Ga. Cathodoluminescence (CL) intensity from the UV to the blue spectral regions increased with as the amount of gallium oxide in the deposited films decreased.
Effect of Epitaxial Layer Crystal Quality on DC and RF Characteristics of AlGaN/GaN Short-Gate High-Electron-Mobility Transistors on Sapphire Substrates
Authors: Shiojima Kenji , Makimura Takashi , Suemitsu Tetsuya , Shigekawa Naoteru
Published: December 2005

The DC and RF characteristics of short-gate high-electron-mobility transistors (HEMTs) formed on four AlGaN/GaN wafers grown on sapphire substrates with different crystal quality have been investigated. Atomic force microscopy observation revealed many pits and trenches on the AlGaN surface, and the morphology of each sample was distinct. There were also differences in electron mobility and sheet carrier concentration. However, the gate length dependences of the measured transconductance and cut-off frequency were virtually the same. For a more detailed investigation, we subtracted the source resistance and AlGaN thickness contributions from measured DC and performed a delay time analysis for the RF characteristics. The results indicate that the intrinsic performance of HEMTs was independent of the surface morphology and that effective electron velocity ranged from 1.4 to 1.8×107 cm/s.
Effect of SiO2(1.2 µm)/Ti-Foil Substrate Nitridation on GaN Thin Films Grown by Reactive Evaporation Method
Authors: Zhu Yongfu , Sato Yuichi , Sato Susumu , Jiang Qing
Published: December 2005

The effect of the plasma nitridation of the SiO2(1.2 µm)/Ti-foil substrate on the quality of the GaN thin films grown by the reactive evaporation method was investigated. Highly c-axis oriented GaN(0002) thin films were obtained. In contrast to the case without nitridation, the quality of GaN(0002) crystals with substrate nitridation was improved. This can be attributed to the flattened surface of the intermediate SiO2 layer and the passivation of Si and O dangling bonds during the substrate nitridation. Photoluminescence measurements show that the emission at the near-band edge (about 3.15 eV) is detected when nitridation occurs whereas only deep level emission is observed when no nitridation occurs.
Evolution of Magnetic State of Ultrathin Co Films with Volmer–Weber Growth
Authors: Shiratsuchi Yu , Murakami Tatsuya , Endo Yasushi , Yamamoto Masahiko
Published: December 2005

The surface structure and magnetic state of ultrathin Co films with Volmer–Weber growth (V–W growth) on α-Al2O3(0001) have been investigated as a function of Co thickness. Due to V–W growth, Co forms particles with a diameter of approximately 5 nm. Originating from the particle structure, the magnetic state of Co is superparamagnetism below a thickness of 1.1 nm, and evolves to ferromagnetism as the Co thickness increases. The transition occurs for a wide thickness range, i.e., 1 to 3 nm. Due to the wide-range transition, it enables to observe the coexistence of superparamagnetism and ferromagnetism at a thickness of around 2 nm. The wide range transition of the magnetic state is explained by the slow coalescence of Co particles. The structural transition would be dominated by the large interface energy between Co and α-Al2O3(0001).
Blue Light Tuning Output of Picosecond Optical Parametric Generation and Amplification in Intelligent Controller
Authors: Wang Li , Huang Liu , Zhou Jinfeng
Published: December 2005

A blue light 420–485 nm output with a linewidth of 0.3 nm and a pump-to-signal energy conversion efficiency of up to 29% at an injected seeding energy of 400 µJ has been achieved. The optimum crystal length from 4 to 2 mm at a pump intensity of 500 MW/cm2 is studied using computer simulation. The experimental designs of the optical parametric generation of type-II noncritical-phase-matched LiB3O5 and the amplification of type-I critical-phase-matched β-BaB2O4 are presented in detail. The experimental setup is pumped using the 355 nm 30 ps-duration output pulse of an active-passive model-locked Nd:YAG laser, is reported.
Second-Harmonic Generation Studies on Thermoreversible Helix–Helix Transition between Right-Handed αR- and Left-Handed ωL-Helices in Solid Film of Poly(β-phenylpropyl L-aspartate)
Authors: Yen Chu-Chun , Sakajiri Koichi , Park Byoungchoo , Takezoe Hideo , Watanabe Junji
Published: December 2005

We prepared an electrically poled film of poly(β-phenylpropyl L-aspartate) and performed second-harmonic generation (SHG) measurements to detect its thermo-reversible helix–helix transition between right-handed αR- and left-handed ωL-helices. In this poled film, the helical molecules are highly oriented and SHG intensity profiles were measured with various angular combinations of polarizer and analyzer. The in-plane anisotropies of SHG were interpreted by the polar C6 symmetry through the temperature region from 25 to 160°C, and then clearly reflected the thermo reversible transformation between the αR-helix and ωL-helix at 155°C on heating and at 142°C on cooling. The β
l
m
n
ratios of molecules evaluated from the χ components were found to be characteristic for each helical conformation; β
X
Z
X,α:β
Z
X
X,α:β
Z
Z
Z,α=8.7:2.0:1.0 for the αR-helix (at 145°C) and β
X
Z
X,ω:β
Z
X
X,ω:β
Z
Z
Z,ω=5.3:3.3:0.7 for the ωL-helix (at 160°C).
Efficiency and Color Coordinate Improvement Using Codopants in Blue Organic Light-Emitting Diode
Authors: Wang Xiu Ru , Chen Jiang Shan , You Han , Ma Dong Ge , Sun Run Guang
Published: December 2005

The codoping method is applied to fabricate efficient blue organic light-emitting diodes (OLEDs). With the same structure of indium–tin oxide (ITO)/N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'diamine (NPB)(80 nm)/light-emitting layer (30 nm)/tris-(8-hydroxy-quinoline)aluminum (Alq3) (20 nm)/LiF (1 nm)/Al (120 nm), a set of three devices was manufactured for comparison. For Devices 1, 2, and 3, the light-emitting layers are 9,10-di(2-naphthyl)anthracene (ADN):4,4'-(1,4-phenylenedi-2,1-ethene diyl)bis[N,N-bis(4-methylphenyl)-benzenamine] (DPAVB) (1 wt %), ADN:2,5,8,11-tetra-(t-butyl)-perylene (TBPE) (1 wt %), and ADN:DPAVB (0.3 wt %):TBPE (0.7 wt %), respectively. It is found that the codoped Device 3 has the highest maximum luminance, Electroluminescence (EL) quantum efficiency and color saturation. Further study on the effect of the codopants was through a relative photoluminescence (PL) quantum efficiency measurement. The result shows that the relative PL efficiencies of Devices 1, 2, and 3 are 15.6, 19.3, and 24%, respectively, as determined using an integrating sphere system excited at 375 nm. The codoping method improves the EL efficiency intrinsically. Codopants of the heterogeneous light-emitting molecules may decrease the possibility of self-quenching from the interaction of the homogenous molecules at the same total doping concentration. Furthermore, the decrease in the interaction of homogenous molecules suppresses the light emission from the aggregations thus narrowing the emission spectrum, and results in saturated blue light emission.
Suppression of Side Fringes in Low-Coherence Interferometric Measurements Using Gain- or Loss-Modulated Multimode Laser Diodes
Authors: Wada Kenji , Sato Hideki , Yoshioka Hiroyuki , Matsuyama Tetsuya , Horinaka Hiromichi
Published: December 2005

We examined three commercially available Fabry–Perot laser diodes with different oscillation wavelengths (660, 800, and 1550 nm) to suppress side fringes appearing under gain- or loss-modulation operation in low-coherence interferometric fringe measurements. For the shorter-wavelength laser diodes (660 and 800 nm), the amplitude of the maximum side fringe was effectively suppressed to 4% of the main fringe amplitude by utilizing the linewidth broadening effect of gain-switched laser diodes due to the generation of frequency chirping, and also by superimposing a multimode spectrum from another laser diode of the same kind. For the 1550 nm laser diode, however, the above approaches were less effective because noticeable gain saturation in the laser diode disturbed the transition of the spectral shape from a characteristic multimode spectrum to a continuum.
A New Four-Ary Run-Length-Limited (2,12) Code for Multilevel Optical Recording Channels
Authors: Hu Hua , Xu Duanyi , Pan Longfa , Hu Heng
Published: December 2005

In this paper, we introduce a new four-ary run-length-limited (d,k)=(2,12) code for multilevel optical recording channels. This code has a simple one-codeword look-ahead encoder and a sliding block decoder. The code rate is 4/5 (bits/symbol), and the density ratio is 2.4 bits/T
min, which is larger than that of binary codes used for typical optical recording systems. The encoding and decoding rules of the proposed code are simple and easy for implementation. With the bit error rate (BER) performance evaluation, this code shows feasible to be applied in high-density multilevel optical storage systems.
Structure and Optical Band-Gap Energies of Ba0.5Sr0.5TiO3 Thin Films Fabricated by RF Magnetron Plasma Sputtering
Authors: Xu Zhimou , Suzuki Masato , Yokoyama Shin
Published: December 2005

The structure and optical band-gap energies of Ba0.5Sr0.5TiO3 (BST0.5) thin films prepared on SiO2/Si and fused quartz substrates by RF magnetron plasma sputtering were studied in terms of deposition temperature and film thickness. Highly (100)-oriented BST0.5 thin films were successfully sputtered on a Si substrate with an approximately 1.0-µm-thick SiO2 layer at a deposition temperature of above 450°C. The optical transmittance of BST0.5 thin films weakly depended on the magnitude of X-ray diffraction (XRD) peak intensity. This is very helpful for monolithic integration of BST0.5 films for electrooptical functions directly onto a SiO2/Si substrate. The band-gap energies showed a strong dependence on the deposition temperature and film thickness. It was mainly related to the quantum size effect and the influence of the crystallinity of thin films, such as grain boundaries, grain size, oriented growth, and the existence of an amorphous phase. The band-gap energy values, which were much larger than those of single crystals, decreased with the increase in the deposition temperature and the thickness of BST0.5 thin films. The band-gap energy of 311-nm-thick amorphous BST0.5 thin film was about 4.45 eV and that of (100)-oriented BST0.5 thin film with a thickness of 447 nm was about 3.89 eV. It is believed that the dependence of the band-gap energies of the thin films on the crystallinity for various values of deposition temperature and film thickness means that there could be applications in integrated optical devices.