bluuebunny/crossref_metadata_2025 huggingface dataset:
DNA Targets for Certain bZIP Proteins Distinguished by an Intrinsic Bend
Authors: Paolella David N. , Palmer C. Rodgers , Schepartz Alanna
Published: October 2006

In spite of the large amount of sequence conservation among the DNA binding segments of basic region leucine zipper (bZIP) proteins, these proteins can discriminate differently between target sequences that differ in half-site spacing. Here it is shown that the half-site spacing preferences of bZIP proteins are the result of (i) the differential intrinsic curvature in target binding sites that differ by insertion or deletion of a single base pair and (ii) the ability of some bZIP proteins to overcome this intrinsic curvature through a mechanism dependent on basic segment residues.
Antibody Catalyzed Cationic Cyclization
Authors: Li Tingyu , Janda Kim D. , Ashley Jon A. , Lerner Richard A.
Published: October 2006

Two major goals for the design of new catalysts are the facilitation of chemical transformations and control of product outcome. An antibody has been induced that efficiently catalyzes a cationic cyclization in which an acyclic olefinic sulfonate ester substrate is converted almost exclusively (98 percent) to a cyclic alcohol. The key to the catalysis of the reaction and the restriction of the product complexity is the use of antibody binding energy to rigidly enforce a concerted mechanism in accord with the design of the hapten. Thus, the ability to direct binding energy allows the experimenter to dictate a reaction mechanism which is an otherwise difficult task in chemistry. New catalysts for cationic cyclization may be of general use in the formation of carbon-carbon and carbon-heteroatom bonds leading to multi-ring molecules including steroids and heterocyclic compounds.
Liquid-Crystalline Mesophases of Plasmid DNA in Bacteria
Authors: Reich Ziv , Wachtel Ellen J. , Minsky Abraham
Published: October 2006

Bacterial plasmids may often reach a copy number larger than 1000 per cell, corresponding to a total amount of DNA that may exceed the amount of DNA within the bacterial chromosome. This observation highlights the problem of cellular accommodation of large amounts of closed-circular nucleic acids, whose interwound conformation offers negligible DNA compaction. As determined by x-ray scattering experiments conducted on intact bacteria, supercoiled plasmids segregate within the cells into dense clusters characterized by a long-range order. In vitro studies performed at physiological DNA concentrations indicated that interwound DNA spontaneously forms liquid crystalline phases whose macroscopic structural properties are determined by the features of the molecular supercoiling. Because these features respond to cellular factors, DNA supercoiling may provide a sensitive regulatory link between cellular parameters and the packaging modes of interwound DNA in vivo.
Noradrenergic Regulation of Cholinergic Differentiation
Authors: Habecker Beth A. , Landis Story C.
Published: October 2006

When the sympathetic nerves that innervate rat sweat glands reach their targets, they are induced to switch from using norepinephrine as their neurotransmitter to acetylcholine. Catecholamines (such as norepinephrine) released by nerves growing to the sweat gland induce this phenotypic conversion by stimulating production of a cholinergic differentiation factor [sweat gland factor (SGF)] by gland cells. Here, culture of gland cells with sympathetic, but not sensory, neurons induced SGF production. Blockage of α
1
- or β-adrenergic receptors prevented acquisition of the cholinergic phenotype in sympathetic neurons co-cultured with sweat glands, and sweat glands from sympathectomized animals lacked SGF. Thus, reciprocal instructive interactions, mediated in part by small molecule neurotransmitters, direct the development of this synapse.
The Mating of a Fly
Authors: Hall Jeffrey C.
Published: October 2006

Courtship in
Drosophila
is influenced by a wide variety of genes, in that many different kinds of pleiotropic mutations lead to defective courtship. This may seem to be a truism, but the broad temporal and spatial expression of most of the fly's "neuro genes" makes it difficult to exclude elements of such genes' actions as materially underlying reproductive behavior. "Courtship genes" that seem to play more particular roles were originally identified as sensory, learning, or rhythm mutations; their reproductive abnormalities have been especially informative for revealing components of male or female actions that might otherwise have gone unnoticed. Further behavioral mutations seemed originally to be courtship-specific, turned out not to have that property, and have led to a broadened perspective on the nature and action of Drosophila's sex-determination genes.
Forward and Reverse Genetic Approaches to Behavior in the Mouse
Authors: Takahashi Joseph S. , Pinto Lawrence H. , Vitaterna Martha Hotz
Published: October 2006

Modern molecular genetic and genomic approaches are revolutionizing the study of behavior in the mouse. "Reverse genetics" (from gene to phenotype) with targeted gene transfer provides a powerful tool to dissect behavior and has been used successfully to study the effects of null mutations in genes implicated in the regulation of long-term potentiation and spatial learning in mice. In addition, "forward genetics" (from phenotype to gene) with high-efficiency mutagenesis in the mouse can uncover unknown genes and has been used to isolate a behavioral mutant of the circadian system. With the recent availability of high-density genetic maps and physical mapping resources, positional cloning of virtually any mutation is now feasible in the mouse. Together, these approaches permit a molecular analysis of both known and previously unknown genes regulating behavior.
Target of the Transcriptional Activation Function of Phage λ cl Protein
Authors: Li Mei , Moyle Henry , Susskind Miriam M.
Published: October 2006

Activation of transcription initiation by the cI protein of phage λ is thought to be mediated by a direct interaction between cI and RNA polymerase at the
P
RM
promoter. Two negatively charged amino acid residues in the DNA binding domain of cI play a key role in activation, suggesting that these residues contact RNA polymerase. The subunit of RNA polymerase involved was identified by selecting polymerase mutants that restored the activation function of a mutant form of cI protein. Although previous studies suggest that several activators interact with the α subunit of RNA polymerase, the results here suggest that cI interacts with the σ subunit. An arginine to histidine change near the carboxyl terminus of σ specifically suppresses an aspartic acid to asparagine change in the activation region of cI. This finding supports the direct-contact model and suggests that a cluster of positively charged residues near the carboxyl terminus of σ is the target of the negatively charged activation region of cI.
Location of cAMP-Dependent Protein Kinase Type I with the TCR-CD3 Complex
Authors: Skålhegg Bjørn S. , Taskén Kjetil , Hansson Vidar , Huitfeldt Henrik S. , Jahnsen Tore , Lea Tor
Published: October 2006

Selective activation of cyclic adenosine 3′,5′-monophosphate (cAMP)-dependent protein kinase type I (cAKI), but not type II, is sufficient to mediate inhibition of T cell replication induced through the antigen-specific T cell receptor-CD3 (TCR-CD3) complex. Immunocytochemistry and immunoprecipitation studies of the molecular mechanism by which cAKI inhibits TCR-CD3-dependent T cell replication demonstrated that regulatory subunit Iα, along with its associated kinase activity, translocated to and interacted with the TCR-CD3 complex during T cell activation and capping. Regulatory subunit IIα did not. When stimulated by cAMP, the cAKI localized to the TCR-CD3 complex may release kinase activity that, through phosphorylation, might uncouple the TCR-CD3 complex from intracellular signaling systems.
Hin Recombinase Bound to DNA: the Origin of Specificity in Major and Minor Groove Interactions
Authors: Feng Jin-An , Johnson Reid C. , Dickerson Richard E.
Published: October 2006

The structure of the 52-amino acid DNA-binding domain of the prokaryotic Hin recombinase, complexed with a DNA recombination half-site, has been solved by x-ray crystallography at 2.3 angstrom resolution. The Hin domain consists of a three-α-helix bundle, with the carboxyl-terminal helix inserted into the major groove of DNA, and two flanking extended polypeptide chains that contact bases in the minor groove. The overall structure displays features resembling both a prototypical bacterial helix-turn-helix and the eukaryotic homeodomain, and in many respects is an intermediate between these two DNA-binding motifs. In addition, a new structural motif is seen: the six-amino acid carboxyl-terminal peptide of the Hin domain runs along the minor groove at the edge of the recombination site, with the peptide backbone facing the floor of the groove and side chains extending away toward the exterior. The x-ray structure provides an almost complete explanation for DNA mutant binding studies in the Hin system and for DNA specificity observed in the Hin-related family of DNA invertases.
Stereospecific Acyl Transfers on the Erythromycin-Producing Polyketide Synthase
Authors: Marsden Andrew F. A. , Caffrey Patrick , Aparicio Jesus F. , Loughran Mark S. , Staunton James , Leadlay Peter F.
Published: October 2006

During assembly of complex polyketide antibiotics like erythromycin A, molecular recognition by the multienzyme polyketide synthase controls the stereochemical outcome as each successive methylmalonyl-coenzyme A (CoA) extender unit is added. Acylation of the purified erythromycin-producing polyketide synthase has shown that all six acyltransferase domains have identical stereospecificity for their normal substrate, (2
S
)-methylmalonyl-CoA. In contrast, the configuration of the methyl-branched centers in the product, that are derived from (2
S
)-methylmalonyl-CoA, is different. Stereoselection during the chain building process must, therefore, involve additional epimerization steps.
Nanometer Spatial Resolution Achieved in Hard X-Ray Imaging and Laue Diffraction Experiments
Authors: Bilderback Donald H. , Hoffman Stephen A. , Thiel Daniel J.
Published: October 2006

Tapered glass capillaries have successfully condensed hard x-ray beams to ultrasmall dimensions providing unprecedented spatial resolution for the characterization of materials. A spatial resolution of 50 nanometers was obtained while imaging a lithographically prepared gold pattern with x-rays in the energy range of 5 to 8 kiloelectron volts. This is the highest resolution scanning x-ray image made to date with hard x-rays. With a beam 360 nanometers in diameter, Laue diffraction was observed from the smallest sample volume ever probed by x-ray diffraction, 5 × 10
-3
cubic micrometers.
Degeneration of a Nonrecombining Chromosome
Authors: Rice William R.
Published: October 2006

Comparative studies suggest that sex chromosomes begin as ordinary autosomes that happen to carry a major sex determining locus. Over evolutionary time the Y chromosome is selected to stop recombining with the X chromosome, perhaps in response to accumulation of alleles beneficial to the heterogametic but harmful to the homogametic sex. Population genetic theory predicts that a nonrecombining Y chromosome should degenerate. Here this prediction is tested by application of specific selection pressures to
Drosophila melanogaster
populations. Results demonstrate the decay of a nonrecombining, nascent Y chromosome and the capacity for recombination to ameliorate such decay.
Meiosis-Induced Double-Strand Break Sites Determined by Yeast Chromatin Structure
Authors: Wu Tzu-Chen , Lichten Michael
Published: October 2006

Double-strand DNA breaks (DSBs) occur at recombination hotspots during
Saccharomyces cerevisiae
meiosis and are thought to initiate exchange at these loci. Analysis of DSB sites in three regions of the yeast genome indicated that breaks occur at or near many potential transcription promoters and that DSBs initiate most, if not all, meiotic recombination. DSB sites displayed deoxyribonuclease I hypersensitivity in chromatin from mitotic and meiotic cells, and changes in chromatin structure produced parallel changes in the occurrence of DSBs. Thus, features of chromatin structure that are established before meiosis play a role in determining where meiotic recombination events initiate.
Parallel Neuronal Mechanisms for Short-Term Memory
Authors: Miller Earl K. , Desimone Robert
Published: October 2006

Although objects that have just been seen may persist in memory automatically for a time and interact passively with incoming stimulation, some tasks require that the memory be actively maintained and used. To test for the existence of separate automatic and volitional mechanisms of short-term memory, recordings were made from neurons in the inferior temporal cortex of monkeys while the monkeys held a sample picture "in mind" and signaled when it was repeated in a sequence of pictures, ignoring other stimulus repetitions. Some neurons were suppressed by any picture repetition, regardless of relevance, whereas others were enhanced, but only when a picture matched the sample. Short-term memory appears to reflect the parallel operation of these two mechanisms—one being automatic and the other active.
Phospholipase D: a Downstream Effector of ARF in Granulocytes
Authors: Cockcroft Shamshad , Thomas Geraint M. H. , Fensome Amanda , Geny Blandine , Cunningham Emer , Gout Ivan , Hiles Ian , Totty Nicholas F. , Truong Oanh , Hsuan J. Justin
Published: October 2006

Activation of the phospholipase D (PLD) pathway is a widespread response when cells are activated by agonists that bind receptors on the cell surface. A 16-kD cytosolic component can reconstitute guanosine triphosphate (GTP)-mediated activation of phospholipase D in HL60 cells depleted of their cytosol by permeabilization. This factor was purified and identified as two small GTP-binding proteins, ARF1 and ARF3. Recombinant ARF1 substituted for purified ARF proteins in the reconstitution assay. These results indicate that phospholipase D is a downstream effector of ARF1 and ARF3. The well-established role of ARF in vesicular traffic would suggest that alterations in lipid content by PLD are an important determinant in vesicular dynamics.
Lack of Acidification in
Mycobacterium
Phagosomes Produced by Exclusion of the Vesicular Proton-ATPase
Authors: Sturgill-Koszycki Sheila , Schlesinger Paul H. , Chakraborty Prasanta , Haddix Pryce L. , Collins Helen L. , Fok Agnes K. , Allen Richard D. , Gluck Stephen L. , Heuser John , Russell David G.
Published: October 2006

The success of
Mycobacterium
species as pathogens depends on their ability to maintain an infection inside the phagocytic vacuole of the macrophage. Although the bacteria are reported to modulate maturation of their intracellular vacuoles, the nature of such modifications is unknown. In this study, vacuoles formed around
Mycobacterium avium
failed to acidify below pH 6.3 to 6.5. Immunoelectron microscopy of infected macrophages and immunoblotting of isolated phagosomes showed that
Mycobacterium
vacuoles acquire the lysosomal membrane protein LAMP-1, but not the vesicular proton-adenosine triphosphatase (ATPase) responsible for phagosomal acidification. This suggests either a selective inhibition of fusion with proton-ATPase-containing vesicles or a rapid removal of the complex from
Mycobacterium
phagosomes.
Antigenic Diversity and the Transmission Dynamics of
Plasmodium falciparum
Authors: Gupta Sunetra , Trenholme Katharine , Anderson Roy M. , Day Karen P.
Published: October 2006

The average age of humans at their first infection with
Plasmodium falciparum
is typically less than 1 year in most endemic areas. This has been interpreted as evidence of the high transmissibility of the parasite, with the implication that control of malaria will require high levels of coverage with a potential vaccine. This interpretation is challenged by mathematical models that demonstrate that the long period required to develop immunity to malaria permits a high risk (or low average age) of infection even when parasite transmissibility is low. Patterns of seroconversion to five antigenically distinct isolates of
P. falciparum
in a highly malarious area of Papua New Guinea indicate that each is only mildly transmissible and that malaria, as a construct of several such independently transmitted strains, has a basic reproductive rate (or transmissibility) that is an order of magnitude lower than other estimates.
Assessment of Analysis of Urinary Pneumococcal Antigen by Immunochromatography for Etiologic Diagnosis of Community-Acquired Pneumonia in Adults
Authors: Briones Maria Luisa , Blanquer José , Ferrando David , Blasco Maria Luisa , Gimeno Concepción , Marín Julio
Published: October 2006

The limitations of conventional microbiologic methods (CMM) for etiologic diagnosis of community pneumococcal pneumonia have made faster diagnostic techniques necessary. Our aim was to evaluate the usefulness of the immunochromatography (ICT) technique for detecting urinary
Streptococcus pneumoniae
antigen in the etiologic diagnosis of community-acquired pneumonias (CAP). This was a prospective study on in-patients with CAP in a tertiary hospital conducted from October 2000 to March 2004. Apart from using CMM to reach an etiologic diagnosis, we determined pneumococcal antigen in concentrated urine by ICT. We also determined the urinary pneumococcal antigen (UPA) content in patients from two control groups to calculate the specificity of the technique. One group was comprised of in-patients diagnosed with chronic obstructive pulmonary disease (COPD) or asthma, with respiratory infection, and without pneumonia; the other group included fractures. We studied 959 pneumonia patients and determined UPA content in 911 (95%) of them. We diagnosed the etiology of 253 cases (28%) using CMM;
S. pneumoniae
was the most common etiologic agent (57 cases). ICT analysis was positive for 279 patients (31%). Using this technique, the percentage of diagnoses of pneumococcal pneumonias increased by 26%, while the overall etiologic diagnosis increased from 28 to 49%. The technique sensitivity was 81%; the specificity oscillated between 80% in CAP with nonpneumococcal etiology and 99% for patients with fractures without infections. Determination of UPA is a rapid, simple analysis with good sensitivity and specificity, which increased the percentage of etiologic diagnoses. Positive UPA may persist in COPD patients with probable pneumococcal colonization or recent pneumococcal infections.
Induction of Long-Term Lipopolysaccharide Tolerance by an Agonistic Monoclonal Antibody to the Toll-Like Receptor 4/MD-2 Complex
Authors: Ohta Shoichiro , Bahrun Uleng , Shimazu Rintaro , Matsushita Hidetomo , Fukudome Kenji , Kimoto Masao
Published: October 2006

We have established an agonistic monoclonal antibody, UT12, that induces stimulatory signals comparable to those induced by lipopolysaccharide (LPS) through Toll-like receptor 4 and MD-2. UT12 activated nuclear factor κB and induced the production of proinflammatory cytokines such as tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6) in peritoneal exudative cells. In addition, mice injected with UT12 rapidly fell into endotoxin shock concomitant with the augmentation of serum TNF-α and IL-6 levels, followed by death within 12 h. On the other hand, when the mice were pretreated with a sublethal dose of UT12, the mice survived the subsequent lethal LPS challenges, with significant suppression of serum TNF-α and IL-6, indicating that UT12 induced tolerance against LPS. This effect of UT12 was maintained for at least 9 days. In contrast, the tolerance induced by LPS continued for less than 3 days. These results illuminate a novel potential therapeutic strategy for endotoxin shock by the use of monoclonal antibodies against the Toll-like receptor 4/MD-2 complex.
Field Evaluation of a Novel Differential Diagnostic Reagent for Detection of
Mycobacterium bovis
in Cattle
Authors: Cockle P. J. , Gordon S. V. , Hewinson R. G. , Vordermeier H. M.
Published: October 2006

In the search for improved tools with which to control bovine tuberculosis, the development of enhanced immunodiagnostic reagents is a high priority. Such reagents are required to improve the performance of tuberculin-based reagents and allow the discrimination of vaccinated cattle from those infected with
Mycobacterium bovis
. In this study, we identified the immunodominant, frequently recognized peptides from Rv3873, Rv3879c, Rv0288, and Rv3019c, which, together with peptides comprising the current lead diagnostic antigens, ESAT-6 and CFP-10, were formulated into a peptide cocktail. In a test of naturally infected cattle, this cocktail was significantly better than tuberculin was for identifying skin test-negative animals with confirmed bovine tuberculosis. In addition, the specificity of this cocktail was not compromised by
Mycobacterium bovis
BCG vaccination. In summary, our results prioritize this peptide-based, fully synthetic reagent for assessment in larger trials.
Limited Diagnostic Capacities of Two Commercial Assays for the Detection of
Leptospira
Immunoglobulin M Antibodies in Laos
Authors: Blacksell Stuart D. , Smythe Lee , Phetsouvanh Rattanaphone , Dohnt Michael , Hartskeerl Rudy , Symonds Meegan , Slack Andrew , Vongsouvath Manivanh , Davong Viengmone , Lattana Olay , Phongmany Simmaly , Keolouangkot Valy , White Nicholas J. , Day Nicholas P. J. , Newton Paul N.
Published: October 2006

The diagnostic utility of immunochromatographic (Leptotek) and enzyme-linked immunosorbent assay (ELISA; Panbio) tests for the detection of
Leptospira
immunoglobulin M antibodies was assessed in febrile adults admitted in Vientiane, Laos. Both tests demonstrated poor diagnostic accuracy using admission serum (Leptotek sensitivity of 47.3% and specificity of 75.5%: ELISA sensitivity of 60.9% and specificity of 65.6%) compared to the
Leptospira
“gold standard” microscopic agglutination test.
Serologic Evaluation of Patients from Missouri with Erythema Migrans-Like Skin Lesions with the C
6
Lyme Test
Authors: Philipp Mario T. , Masters Edwin , Wormser Gary P. , Hogrefe Wayne , Martin Dale
Published: October 2006

Southern tick-associated rash illness (STARI), also known as Masters disease, affects people predominantly in the Southeast and South Central United States. These patients exhibit skin lesions that resemble erythema migrans (EM), the characteristic skin lesion in early Lyme disease. The etiology of STARI remains unknown, and no serologic test is available to aid in its diagnosis. The C
6
Lyme enzyme-linked immunosorbent assay was used to evaluate coded serum specimens from patients with STARI at two laboratory sites. The specimens tested at one site consisted of acute- and convalescent-phase samples that were obtained from nine STARI patients from Missouri and from one patient with documented
Borrelia lonestari
infection who acquired this infection in either North Carolina or Maryland. All of these samples were C
6
negative. Seventy acute- or convalescent-phase specimens from 63 STARI patients from Missouri were C
6
tested at the second site. All but one of these STARI specimens were also negative. In contrast, of nine acute- and nine convalescent-phase serum specimens obtained from culture-confirmed Lyme disease patients with EM from New York state, seven were C
6
positive at the acute stage, and eight were positive at convalescence. The C
6
test is negative in patients with STARI, providing further evidence that
B. burgdorferi
is not the etiologic agent of this disease.
Enhancement of Post-Cu-Chemical Mechanical Polishing Cleaning Process for Low-k Substrate
Authors: Miyamoto Makoto , Hirano Shinya , Chibahara Hiroyuki , Watadani Takashi , Akazawa Moriaki , Furukawa Seiji
Published: October 2006

The introduction of low-dielectric-constant (low-k) materials as interlayer dielectrics (ILD) to support Cu interconnects causes poor slurry removal efficiency and watermark generation in post Cu-chemical mechanical polishing (CMP) cleaning because low-k dielectric films are hydrophobic. To address these problems, the authors performed basic studies using low-k (SiOC) blank (unpatterned) substrates. Our studies have revealed that it is important to control the wettability of the SiOC surface by using a surfactant-spiked cleaning solution in order to effectively remove the large number of slurry particles adhering to the SiOC surface due to hydrophobic interaction. For watermark generation, our study has found that even the combination of ultrapure water (UPW) spin rinsing and spin drying causes a watermark to be generated on a clean SiOC surface. It is revealed that watermark generation is attributed mainly to oxygen diffusion into microdroplets left on the SiOC surface after spin drying. Fourier transform IR (FTIR) analysis indicates this watermark to be composed of silicon oxides or silicon hydrates. The authors have also proven that watermark generation can be suppressed by using ultrapure water with N2 gas dissolved to its saturated concentration (N2-UPW).
Origin of Room Temperature Magnetism in Thin (ZnO)1-x(MnO2)xFilms and ZnO/MnO2Multilayers
Authors: López-Ponce E. , Wennberg A. , Martín-González M. S. , Costa-Krämer J. L. , García M. A. , Quesada A. , Hernando A. , Caballero A. C. , Villegas M. , Fernández J. F.
Published: October 2006

The reactivity of the Zn–Mn–O system prepared by conventional ceramic routes using ZnO and MnO2as starting materials and in thin film form by pulsed-laser deposition is described and correlated with the system's magnetic response. Structural analysis is performed using X-ray diffraction analysis, X-ray photoelectron spectroscopy and Raman spectroscopy. The ferromagnetic phase is determined to be due to the presence of both Mn+3and Mn+4ions at the Zn diffusion front of the manganese oxide grain. Thus, it is demonstrated that Mn is not incorporated into the ZnO lattice, but that Zn diffuses into manganese oxide grains. Zn diffusion delays the total manganese reduction, i.e., Mn+4→Mn+3. At the diffusion front both manganese ions coexist and their spins couple ferromagnetically through a double-exchange mechanism. This mechanism explains the origin of the room-temperature ferromagnetism that has been recently discovered in the Zn–Mn–O system, and suggests that it is a unique and promising material for spintronic devices.
Silicon-Based Solar Cell Fabricated by Metal-Induced Lateral Crystallization of Amorphous Silicon Film
Authors: Hwang Jun-Dar , Chi Tzu-Yi , Liu Jun-Chin , Kung Chung-Yuan , Hsein In-Cha
Published: October 2006

Silicon-based polycrystalline solar cells are first fabricated by metal-induced lateral crystallization in which n-type polycrystalline-silicon (poly-Si) films, processed using nickel-induced amorphous silicon, are grown on p-silicon substrate at 550 °C by furnace annealing. The fabricated n-type poly-Si/p-substrate solar cell exhibits a conversion efficiency of 10.4% and an open-circuit voltage of 0.54 V without any passivation or antireflection coating layers.
Thermal and Electrical Properties of High-Quality Freestanding GaN Wafers with High Carrier Concentration
Authors: Oshima Yuichi , Yoshida Takehiro , Eri Takeshi , Shibata Masatomo , Mishima Tomoyoshi
Published: October 2006

The thermal and electrical properties of high-quality bulk GaN crystals fabricated by hydride vapor phase epitaxy were investigated in the high-carrier-concentration region between 1.0×1018 and 1.24×1019 cm-3. The carrier concentration was almost identical to the Si doping concentration. An electrical resistivity as low as 2.5 mΩ cm was obtained at the carrier concentration n=1.24×1019 cm-3. The electron mobilities from Hall measurements were 441 and 200 cm2 V-1 s-1 for n=1.0×1018 and 1.24×1019 cm-3, respectively, which are significantly higher than those reported in the literature. The thermal conductivity measured by the laser flash method was consistently high in the measured carrier concentration range, i.e., about 2.0 W cm-1 K-1 for n=1.0×1018 cm-3 and 1.87 W cm-1 K-1 for n=1.24×1019 cm-3.
Magnetic Properties of Mn-Doped ZnO Nanostructures Synthesized by Chemical Vapor Transport
Authors: Zhang Hua-Wei , Shi Er-Wei , Chen Zhi-Zhan , Liu Xue-Chao , Xiao Bing
Published: October 2006

Mn-doped ZnO nanostructures have been fabricated by chemical vapor transport (CVT). Nanobelts, nanorods and nanowires have different growth directions because of their different growth environments. X-ray diffraction, electron paramagnetic resonance and Raman spectrum methods have been used to identify the substitution of a Zn site with Mn ions. Despite their different morphologies, these nanostructures possess the same magnetic properties. Magnetization was paramagnetic and antiferromagnetic. No ferromagnetism was observed even at T=5 K.
Enhanced Light Output in Double Roughened GaN Light-Emitting Diodes via Various Texturing Treatments of Undoped-GaN Layer
Authors: Peng Wei Chih , Wu YewChung Sermon
Published: October 2006

An InGaN–GaN light-emitting diodes (LEDs) with double roughened (p-GaN and undoped-GaN) surfaces were successfully fabricated by surface-roughening, wafer-bonding and laser lift-off technologies. The effect of the roughness of the undoped-GaN layer on the performance of double roughened LEDs was investigated. It was found that the rms roughness of the undoped-GaN layer increased from 18.6 to 146.7 nm, the output power increased from 7.2 to 10.2 mW, and view angle decreased from 133.6 to 116°.
Optical Amplifier Using Nonlinear Nanodefect Cavity in Photonic Crystal
Authors: Kawashita Yoshiyuki , Haraguchi Masanobu , Okamoto Hiroyuki , Fujii Masamitsu , Fukui Masuo
Published: October 2006

We have proposed a new optical amplifier in a photonic crystal. The amplifier consists of a nonlinear nanodefect cavity and a cross waveguide. The input–output characteristics have been simulated for the amplifier with three- or four-port cross waveguide in a two-dimensional photonic crystal by the finite-difference time-domain method. In the amplifier, a signal light can be amplified by an energy transfer from a control light to the signal light at the nonlinear nano-defect cavity. The calculated amplification factor of the amplifier was 2.33×104. When optical transistor was used with an amplifier with a three-port cross waveguide in a two-dimensional photonic crystal, the calculated switching rate, the on–off ratio and the amplification factor of the transistor were 12 Gbit/s, 1.95×105 and 2.29×104, respectively. The transistor can work well even under a low power input in the signal port and can be utilized as a small amplifier and an optical sensor with a fast response.
Enhancement of Optical Parametric Chirped Pulse Amplification by Controlling Idler Laser Pulse
Authors: Harimoto Tetsuo , Nagata Hiroshi , Yamakawa Koichi
Published: October 2006

We present a novel method for optical parametric chirped pulse amplification to enhance the spectral bandwidth of amplified signal pulses by suppressing reconversion in a collinear degenerate geometry using a sequence of crystal pairs. The scheme consists of a conventional crystal pair used for achieving saturated amplification at the peak portion of the seed laser pulse, and a number of additional crystal pairs for optimizing the amplified seed laser pulse, especially in its spectral range and output stability. Numerical results showed that the proposed scheme can be used to produce a stable amplified seed laser pulse with a broader spectral bandwidth than the input spectrum under ordinary conditions.
Influence of Fe 3d Orbitals on Quadrupole Splittings of β-FeSi2
Authors: Kondo Shin-ichiro , Hasaka Masayuki , Morimura Takao
Published: October 2006

We have investigated the influence of Fe 3d orbitals on the quadrupole splittings (QS) of two different Fe sites (Fe I and II sites) of β-FeSi2, mainly focusing on the ratio of the QS value of the Fe I site to that of the Fe II site. When calculating QS value, we assume that the charges from the surrounding Si atoms have little influence on electric field gradient (EFG) at iron nuclei because of Thomas–Fermi and inner core screenings and that the distortion of 3d wave functions caused by outside charges plays an important role in determining the QS value of each iron site. From the analysis, the Fe 3d orbitals appear to expand in comparison with those in metal iron, which suggests the presence of covalent Fe–Si bonds.
Effect of Stress on Phase Transition of Ferroelectric Films
Authors: Chung Wing Yee Winnie , Lo Veng Cheong
Published: October 2006

The effect of stress on the ferroelectric–paraelectric phase transition temperature of ferroelectric thin films has been evaluated using a modified planar-type four-state Potts model. In this model, it is assumed that the electromechanical effect is induced by the association between the dipole orientation and the strain state in individual perovskite cells. The mechanical energy density, which is equal to the product of stress and strain, gives rise to the additional contribution to the system Hamiltonian. The rotation of dipoles, governed by the change in Hamiltonian as in the usual Metropolis algorithm, gives rise to various ferroelectric properties. The shift in phase transition in the presence of transverse stress is demonstrated and compared with experimental results based on the position of the susceptibility peak [T. R. Taylor et al.: Appl. Phys. Lett. 80 (2002) 1978; K. Abe et al.: J. Appl. Phys. 77 (1995) 6461].
Dielectric Breakdown Phenomena during Secondary Electron Emission Measurement of Sputter-Deposited MgO Films
Authors: Nakano Takeo , Fujimoto Takashi , Nakada Daisuke , Baba Shigeru
Published: October 2006

The ion-induced secondary electron emission (SEE) characteristics of sputter-deposited magnesium oxide (MgO) films have been investigated. Using an RF magnetron sputtering apparatus, MgO films of 50–200 nm thickness were deposited on Si substrates from a sintered MgO target. Under irradiation of 1 keV of Ar+ ions, secondary electrons were collected at a positively biased electrode. The secondary electron current increased as the bias voltage increased, and saturated to give an SEE coefficient of 2–2.5 in all samples. The deposition condition (gas pressure 2–20 Pa) did not strongly affect this current–voltage (I–V) characteristic of the SEE, while an increase in film thickness resulted in an increase in the voltage at which the SEE current began to rise. This rising voltage depended neither on the energy nor on the current of the primary ion beam. We concluded that the rising voltage was governed by an electric breakdown phenomenon by which the positive charge accumulating on the surface was compensated from the substrate. The field strength was estimated to be as high as 109 V/m.
Characteristics of Secondary Electron Emission Coefficient and Sputtering Yield for MgAl2O4/MgO Protective Layer in AC-Plasma Display Panels
Authors: Jeoung Jin-Man , Ko Byung-Doc , Lee Hye-Jung , Jung Yong-Whan , Jung Kang-Won , Kang Seung-Oun , Choi Eun Ha
Published: October 2006

The secondary electron emission coefficient (γ) and sputtering yield of the MgAl2O4/MgO protective layer has been investigated using γ-focused ion beam (γ-FIB) and focused ion beam (FIB) systems, respectively. The MgAl2O4/MgO protective layer has higher γ values (from 0.09 to 0.12) than the single MgAl2O4 protective layer (from 0.06 to 0.07) at Ne+ ion energies ranging from 90 to 200 eV. Also it has been found that the secondary electron emission coefficient (γ) of the MgAl2O4/MgO protective layer is similar to that of the MgO protective layer. Moreover, the MgAl2O4/MgO protective layer has been found to have lower sputtering yields (from 0.25 to 0.35) than the MgO protective layer (from 0.36 to 0.44) for Ga+ ion energies ranging from 10 to 14 keV.
Spectroscopic Study on Vibrational Distribution of N2 C3Π and B3Π States in Microwave Nitrogen Discharge
Authors: Sakamoto Takeshi , Matsuura Haruaki , Akatsuka Hiroshi
Published: October 2006

We examined the vibrational and rotational temperatures of the C3Π and B3Π states of N2 by optical emission spectroscopy. We measured the band spectra (first and second positive systems) of N2 compared the experimentally measured and the calculated spectra to determine the actual vibrational and rotational temperatures of the generated plasma. We generated a microwave discharge nitrogen plasma in a cylindrical quartz tube (26 mm i.d.) with a discharge pressure of 0.5–1.0 Torr. The microwave frequency was 2.45 GHz and the output power was set at 600 W. It was found that T
v≈0.5–0.7 eV and T
r≈0.07–0.15 eV at B3Π (v=7, 8 and 9), whereas T
v≈0.65–0.9 eV and T
r≈0.06–0.16 eV at C3Π (v=0 and 1). We also discussed the measured vibrational populations using theoretical calculations, in which the variation in the number density was expressed in terms of molecular processes.
Why Is the Mach Probe Formula Expressed as R=Jup/Jdn=exp [KM∞]?
Authors: Chung Kyu-Sun
Published: October 2006

The normalized drift velocity of flowing plasmas can be deduced using a Mach probe, which has two directional probes at opposite sides. The relationship between the ratio (R) of upstream ion saturation current density (Jup) to downstream current density (Jdn) and the normalized drift velocity (M∞=Vd/√Te/mi) of plasma has generally been fitted into an exponential form asR=Jup/Jdn=exp [KM∞], whereKis a calibration factor depending on the magnetic flux density, collisionality, viscosity, and ion temperature of plasmas. Without going into detailed theories for various conditions of plasmas and probes, a simple explanation is given in terms of decaying current density in the downstream region. Existing theories and experiments of Mach probes in magnetized and unmagentized flowing plasmas are summarized along with key physics and comments.
High Mobility Pentacene Thin-Film Transistors on Photopolymer Modified Dielectrics
Authors: Chou Wei-Yang , Kuo Chia-Wei , Cheng Horng-Long , Chen Yi-Ren , Yang Feng-Yu , Shu Dun-Yin , Liao Chi-Chang , Tang Fu-Ching
Published: October 2006

An innovative technique for surface modification of pentacene thin-film transistors (TFTs) with mobility greater than 1.92 cm2 V-1 s-1 is reported in this paper. Photosensitive polyimide was used as a modification layer presenting a nonpolar interface on which the semiconductor, pentacene, could grow. The surface of the modification layer was exposed to a polarized ultraviolet light with a dose of 1 J to achieve a nonpolar surface on which high-performance TFTs have been fabricated. The experiment showed that the parasitic contact resistances of silver electrodes could be extracted by the gated-transfer length method, and the corrected field-effect mobility of pentacene TFTs in the linear region was as high as 2.25 cm2 V-1 s-1.
Interface Resistivity of Directly Bonded Si Wafers
Authors: Kanno Ikuo , Yamashita Makoto , Nomiya Seiichiro , Onabe Hideaki
Published: October 2006

To study the interface resistivity of bonded Si wafers, every combination of three kinds of Si wafers (1.86×10-2, 1.91×10-1, and 2.44 Ω cm in resistivity) was bonded by surface activation bonding. Thermal treatments up to 1100 °C were performed and the resistivities of bonded Si wafers were measured by a four-probe method. The interface resistivities were estimated with calculations based on a model of the composite resistivity of bonded Si wafers.
Development of Multilayer Resist Technology for Halftone Mask in Liquid Crystal Display Manufacturing
Authors: Horibe Hideo , Ichikawa Tomokazu , Takamatsu Shinya
Published: October 2006

A halftone mask was used in a lithography process to reduce the number of steps required in liquid crystal display (LCD) manufacturing. Three thicknesses of resist films were produced using the halftone mask. Since the resist is exposed in the area where the sensitivity curve rises, a problem arises in that the thickness of the resist film fluctuates drastically when the exposure dose to the resist fluctuates slightly. We tried to stabilize the film thickness using two kinds of resists having different sensitivities. We used a low-sensitivity resist as a lower layer and a high-sensitivity resist as an upper layer. However, it was not possible to produce a stable film thickness because the two resists blended at the interface. Therefore, we added an aqueous polymer solution as an intermediate layer between the resists which were dissolved in a solvent. This solved the blending problem and a stable film thickness was obtained.
Etching of Poly(tetrafluoroethylene) Sheet by Synchrotron Radiation Exposure in Soft X-ray Region
Authors: Kato Yuri , Kanda Kazuhiro , Haruyama Yuichi , Matsui Shinji
Published: October 2006

The reaction mechanism for the direct photoetching of poly(tetrafluoroethylene) (PTFE) using synchrotron radiation (SR) in the soft X-ray region, which is important for the microfabrication of PTFE nanoparts, was investigated by varying the photon flux irradiated to a PTFE sheet by changing the electron current of the storage ring. The etching depth of the PTFE sheet by SR exposure at 100 mA·h was measured at room temperature, 120 and 200 °C. Etching depth increased with photon flux despite of setting the SR exposure on the same quantity at each substrate temperature. It was found that the etching of PTFE proceeds not only via the first-order reaction but also via the second-order reaction whether substrate temperature was higher than glass transition temperature.
InAs/GaAs Quantum-Dot Laser Diode Lasing at 1.3 µm With Triple-Stacked-Layer Dots-in-a-Well Structure Grown by Atomic Layer Epitaxy
Authors: Kim Kwang Woong , Cho Nam Ki , Ryu Sung Phil , Song Jin Dong , Choi Won Jun , Lee Jung Il , Park Jung Ho
Published: October 2006

We report the first demonstration of room-temperature (RT) lasing at 1.3 µm from the ground state of three-stacked InAs quantum dots (QDs) in an In0.15Ga0.85As quantum well, which was grown by atomic layer epitaxy (ALE). For an as-cleaved device with a 2000-µm-long × 15-µm-wide ridge structure, the threshold current density (J
th) at RT is 155 A/cm2 with the ground state lasing at 1310 nm under pulsed operation. The thermal coefficient of a lasing wavelength shift is 0.53 nm/K and the characteristic temperature is 103 K near RT. The lasing wavelength of the QD laser diodes (LDs) shows simultaneous lasing and the state switching from the ground state at 1310 nm and to the first excited state at 1232 nm with increasing injection current owing to the gain saturation of the ground state. The performance of ALE QD-LD is comparable to that of the conventional Stranski–Krastanov QD-LD.
Synthesis of Single-Wall Carbon Nanotubes from Diesel Soot
Authors: Uchida Takashi , Ohashi Ouji , Kawamoto Hironori , Yoshimura Hirofumi , Kobayashi Ken-ichi , Tanimura Makoto , Fujikawa Naohiro , Nishimoto Tetsuro , Awata Kazuhiko , Tachibana Masaru , Kojima Kenichi
Published: October 2006

We show that diesel soot can be recycled as a carbon source for the synthesis of single-wall carbon nanotubes (SWNTs). The synthesis of SWNTs was carried out by the laser vaporization of diesel soot. The presence of SWNTs was confirmed by Raman spectroscopy and transmission electron microscopy. SWNTs produced in this way should provide economic benefits and also contribute to a cleaner environment.
Stimulation of adenosine A1and A2Areceptors by AMP in the submucosal plexus of guinea pig small intestine
Authors: Gao Na , Hu Hong-Zhen , Liu Sumei , Gao Chuanyun , Xia Yun , Wood Jackie D.
Published: October 2006

Actions of adenosine 5′-monophosphate (AMP) on electrical and synaptic behavior of submucosal neurons in guinea pig small intestine were studied with “sharp” intracellular microelectrodes. Application of AMP (0.3–100 μM) evoked slowly activating depolarizing responses associated with increased excitability in 80.5% of the neurons. The responses were concentration dependent with an EC50of 3.5 ± 0.5 μM. They were abolished by the adenosine A2Areceptor antagonist ZM-241385 but not by pyridoxal-phosphate-6-azophenyl-2,4-disulfonic acid, trinitrophenyl-ATP, 8-cyclopentyl-1,3-dimethylxanthine, suramin, or MRS-12201220. The AMP-evoked responses were insensitive to AACOCF3 or ryanodine. They were reduced significantly by 1) U-73122, which is a phospholipase C inhibitor; 2) cyclopiazonic acid, which blocks the Ca2+pump in intraneuronal membranes; and 3) 2-aminoethoxy-diphenylborane, which is an inositol ( 1 , 4 , 5 )-trisphosphate receptor antagonist. Inhibitors of PKC or calmodulin-dependent protein kinase also suppressed the AMP-evoked excitatory responses. Exposure to AMP suppressed fast nicotinic ionotropic postsynaptic potentials, slow metabotropic excitatory postsynaptic potentials, and slow noradrenergic inhibitory postsynaptic potentials in the submucosal plexus. Inhibition of each form of synaptic transmission reflected action at presynaptic inhibitory adenosine A1receptors. Slow excitatory postsynaptic potentials, which were mediated by the release of ATP and stimulation of P2Y1purinergic receptors in the submucosal plexus, were not suppressed by AMP. The results suggest an excitatory action of AMP at adenosine A2Areceptors on neuronal cell bodies and presynaptic inhibitory actions mediated by adenosine A1receptors for most forms of neurotransmission in the submucosal plexus, with the exception of slow excitatory purinergic transmission mediated by the P2Y1receptor subtype.
Elevated cardiac tissue level of aldosterone and mineralocorticoid receptor in diastolic heart failure: beneficial effects of mineralocorticoid receptor blocker
Authors: Ohtani Tomohito , Ohta Miho , Yamamoto Kazuhiro , Mano Toshiaki , Sakata Yasushi , Nishio Mayu , Takeda Yasuharu , Yoshida Junichi , Miwa Takeshi , Okamoto Mitsuhiro , Masuyama Tohru , Nonaka Yasuki , Hori Masatsugu
Published: October 2006

Cardiac aldosterone levels have not been evaluated in diastolic heart failure (DHF), and its roles in this type of heart failure remain unclear. This study aimed to detect cardiac aldosterone by use of a liquid chromatographic-mass spectrometric method and to assess the effects of mineralocorticoid receptor blockade on hypertensive DHF. Dahl salt-sensitive rats fed 8% NaCl diet from 7 wk (hypertensive DHF model) were divided at 13 wk into three groups: those treated with subdepressor doses of eplerenone (12.5 or 40 mg·kg−1·day−1) and an untreated group. Dahl salt-sensitive rats fed 0.3% NaCl diet served as controls. Cardiac aldosterone was detected in the DHF rats but not in the control rats, with increased ventricular levels of mineralocorticoid receptor. Cardiac levels of 11-deoxycorticosterone, corticosterone, and 11-dehydrocorticosterone were not different between the control and DHF rats, but the tissue level of corticosterone that has an affinity to mineralocorticoid receptor was 1,000 times as high as that of aldosterone. Aldosterone synthase activity and CYP11B2 mRNA were undetectable in the ventricular tissue of the DHF rats. Administration of eplerenone attenuated ventricular hypertrophy, ventricular fibrosis, myocardial stiffening, and relaxation abnormality, leading to the prevention of overt DHF. In summary, the myocardial aldosterone level increased in the DHF rats. However, its value was extremely low compared with corticosterone, and no evidence for enhancement of intrinsic myocardial aldosterone production was found. The upregulation of mineralocorticoid receptor may play a central role in the pathogenesis of DHF, and blockade of mineralocorticoid receptor is likely an effective therapeutic regimen of DHF.