bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative evaluation of the octadecylamine-assisted bulk separation of semiconducting and metallic single-wall carbon nanotubes by resonance Raman spectroscopy
Authors: Samsonidze Ge. G. , Chou S. G. , Santos A. P. , Brar V. W. , Dresselhaus G. , Dresselhaus M. S. , Selbst A. , Swan A. K. , Ünlü M. S. , Goldberg B. B. , Chattopadhyay D. , Kim S. N. , Papadimitrakopoulos F.
Published: August 2004

The selective stabilization of octadecylamine (ODA) on semiconducting (S) single-wall carbon nanotubes (SWNTs) has been reported to provide a means for the bulk separation of S from metallic (M) SWNTs. Utilizing resonance Raman spectroscopy and, in particular, the relative changes in the integrated intensities of the radial-breathing mode region, a generic method has been developed to provide quantitative evaluation of the separation efficiency between M and S SWNTs along with diameter separation. The ODA-assisted separation is shown to provide S enrichment by a factor of 5 for SWNTs prepared by high pressure CO decomposition and greater S enrichment for SWNTs with diameters below 1nm.
Decay mechanisms of a blue organic light emitting diode
Authors: Ni S. Y. , Wang X. R. , Wu Y. Z. , Chen H. Y. , Zhu W. Q. , Jiang X. Y. , Zhang Z. L. , Sun R. G.
Published: August 2004

A blue organic light-emitting diode employing perylene as light emitting dopant and 9,10-bis(3’5’-diaryl)phenyl anthracene (DPA) as host has been studied for its decay mechanisms. The device structure is ITO(indium tin oxide)∕CuPc(copper phthalocyanine)∕NPD(α-naphthylphenylbiphenyl diamine)∕DPA:perylene∕Alq3 (8-hydroxy-quinoline aluminum)∕MgAg. In this device, CuPc and NPD are used as hole injection and transporting layers, DPA as a blue host, perylene as a blue emitting dopant, Alq3 as an electron transport layer, MgAg as cathode, respectively. A luminance of 4359cd∕m2 at 15V and a current efficiency of 3cd∕A at 5V have been achieved. The breakdown of the interfaces in the device is found to be one of the factors for the decay and the decomposition of the light emitter is not significantly studied by current–voltage–luminance, photoluminescence, and electroluminescence measurements. The lifetime is not intrinsic for this type of device.
Dielectric and ferroelectric behaviors in Pb(Mg1∕3Nb2∕3)O3–PbTiO3 rhombohedral∕tetragonal superlattices
Authors: Lu Yalin
Published: August 2004

Artificial superlattices composing of alternatively stacked tetragonal (T) and rhombohedral (R) (1−x)Pb(Mg1∕3Nb2∕3)O3−xPbTiO3 phases have been grown. Large dielectric constant enhancement, strong structural dependences of ferroelectric properties including remnant polarization, coercive field, phase transition temperature, and large nonlinear dielectric property enhancement, were measured. These enhancements were explained by the long-range spontaneous polarization coupling and by the increased internal strains inside the superlattices.
Quantum-confined Stark effect of GaInNAs(Sb) quantum wells at 1300–1600nm
Authors: Lordi Vincenzo , Yuen Homan B. , Bank Seth R. , Harris James S.
Published: August 2004

We report the measurement of electroabsorption spectra from GaInNAs and GaInNAsSb quantum wells grown on GaAs showing quantum-confined Stark effect behavior suitable for optical modulation at 1300 and 1550nm wavelength, respectively. The high quality of our material is evidenced by sharp exciton resonances with a full width at half maximum <25meV at 295K, and peak absorption coefficient of 18 000cm−1 for GaInNAs and 34 800cm−1 for GaInNAsSb. Changes in absorption coefficient 10 000cm−1 with an applied electric field were measured. Device performance from these materials is expected to be comparable to or better than the competing material grown on InP.
Voltage-controlled multiguide directional coupler formed in a planar nematic liquid crystal film
Authors: Tsai Ming-Shan , Kuo Chie-Tong , Huang Shuan-Yu , Shih Chia-Chi , Jiang I-Min
Published: August 2004

A voltage-controllable multiguide directional coupler is designed with a nematic liquid crystal cell, comprising a grating-like indium-tin-oxide electrode. An incident polarized laser beam can couple into adjacent channels by periodic distribution of the refractive index. This capability is attributed to the reorientation of the periodic liquid crystal caused by the application of a voltage. The coupling variation of the optical power in the transverse direction parallel to the waveguide surface is investigated. This work presents a promising coupling function for potential applications of optical communication devices.
Chirality selection of single-walled carbon nanotubes by laser resonance chirality selection method
Authors: Maehashi Kenzo , Ohno Yasuhide , Inoue Koichi , Matsumoto Kazuhiro
Published: August 2004

We propose a laser resonance chirality selection method to select single-walled carbon nanotubes (SWNTs) with specific chirality from mass of SWNTs by intense laser irradiation. This technique exploits the multiple Van Hove singularities in the density of states of SWNTs expected for one-dimensional confinement. Absorption of the exciting laser beam can be strongly enhanced for SWNTs with specific chirality when the energy of the incident photon matches the energy of the allowed electronic transitions. As a result of the resonance effect, when the excitation power density of the laser beam increases in an atmosphere of air, at a certain threshold excitation power density, only these SWNTs are oxidized and are removed selectively. With Raman scattering measurements, we have demonstrated that SWNTs with specific chirality are selectively removed after intense laser irradiation.
An electroactive polymer-ceramic hybrid actuation system for enhanced electromechanical performance
Authors: Su Ji , Xu Tian-Bing , Zhang Shujun , Shrout Thomas R. , Zhang Qiming
Published: August 2004

A hybrid actuation system (HYBAS) utilizing advantages of a combination of electromechanical responses of an electrostrictive copolymer and an electroactive single crystal has been developed. The system employs the contributions of the actuation elements cooperatively. The theoretical modeling of the performances of the HYBAS is in good agreement with experimental observation. The consistency between the theoretical modeling and the experimental tests makes the design concept an effective route for tailoring and maximizing electrically driven displacement of the hybrid actuation system.
Pentacene nanotransistor with carbon nanotube electrodes
Authors: Tsukagoshi Kazuhito , Yagi Iwao , Aoyagi Yoshinobu
Published: August 2004

A pentacene nanocrystal transistor with carbon nanotube electrodes as a nanosize source and drain was realized. In the device fabrication, the evaporated pentacene selectively grew around the nanotube electrodes. This may be caused by the common nanounit combination of the carbon six-membered ring contained in the pentacene and the nanotube. The nanotransistor showed controllable transistor operation at room temperature and Coulomb blockade oscillations at 4.2K in gate voltage characteristics.
Effects of aluminum cathodes prepared by ion-beam-assisted deposition in organic light-emitting devices
Authors: Jeong Soon Moon , Koo Won Hoi , Choi Sang Hun , Jo Sung Jin , Baik Hong Koo , Lee Se-Jong , Song Kie Moon
Published: August 2004

We have fabricated highly stable organic electroluminescent devices based on spin-coated soluble phenyl-substituted poly-p-phenylene-vinylene (Ph-PPVs) thin films. The electrical properties of aluminum cathode, prepared by ion-beam-assisted deposition, on Ph-PPV have been investigated and compared to those prepared by thermal evaporation. Although energetic particles of Al assisted by Ar+ ion may damage the organic material, I–V–L characteristics are improved by evaporating a thin Al buffer layer prior to ion-beam-assisted deposition. In addition, a dense Al cathode inhibits the permeation of H2O and O2 into Ph-PPV film by suppressing pinhole defects, and thus retards dark spot growth. This may be deduced from highly packed structure of Al cathode with smaller contact resistance between Al and Ph-PPV. The lifetime of an organic light-emitting device has been extended by dense Al film through an ion-beam-assisted deposition process.

At the request of the authors, this article is being retracted effective 24 April 2006.
Field-dependent charge carrier dynamics in GaN: Excitonic effects
Authors: van de Lagemaat J. , Vanmaekelbergh D. , Kelly J. J.
Published: August 2004

The electric-field dependence of the charge-carrier dynamics in GaN was studied by measuring excitation spectra of the sub-band-gap (yellow) luminescence as a function of bias using a Schottky junction formed at the interface between the semiconductor and an electrolyte solution. At large bias, the contribution of free electrons and holes to the photoluminescence is significantly reduced due to the dead-layer effect. As a result, striking features are revealed in the spectra close to the fundamental absorption. These features are attributed to exciton decay via yellow luminescence centers.
Tunable and multiple-wavelengths/temporal output from gain-switched diode laser and a four Bragg-grating Fiber
Authors: Rafailov E. U. , Cormack I. G. , Floreani F. , Zhang L. , Bennion I. , Sibbett W.
Published: August 2004

We demonstrate spectral narrowing and selective tuning of the picosecond pulse outputs from an injection-seeded, gain-switched diode laser that is simultaneously coupled to four output fibers with different Bragg-grating resonators. A single-, dual-, and triple-wavelength and temporal pulse operation from all four outputs is presented.
Ultralong coherence times in the purely electronic zero-phonon line emission of single molecules
Authors: Kiraz Alper , Ehrl Moritz , Bräuchle Christoph , Zumbusch Andreas
Published: August 2004

We report the observation of ultralong coherence times in the purely electronic zero-phonon line emission of single terrylenediimide molecules at 1.4K. Vibronic excitation and spectrally resolved detection with a scanning Fabry–Perot spectrum analyzer were used to measure a linewidth of 65MHz. This is within a factor of 1.6 of the transform limit. It therefore indicates that single molecule emission may be suited for applications in linear optics quantum computation. Additionally, it is shown that high-resolution spectra taken with the spectrum analyzer allow for the investigation of fast spectral dynamics in the emission of a single molecule.
Ultrathin gate oxide with a reduced transition layer grown by plasma-assisted oxidation
Authors: Hyun S. , Buh G. H. , Hong S. H. , Koo B. Y. , Shin Y. G. , Jung U. I. , Moon J. T. , Cho M.-H. , Chang H. S. , Moon D. W.
Published: August 2004

Ultrathin SiO2 grown by plasma-assisted oxidation (plasma oxide) has been investigated by high-resolution x-ray photoemission spectroscopy and medium energy ion scattering spectroscopy. We found that the plasma oxide grown at the low temperature of 400°C has a thinner transition layer than conventional thermal oxide. This thinner transition layer in the plasma oxide not only decreased the gate leakage current effectively, but also enhanced the reliability of the gate oxide. We attribute these electrical properties of the plasma oxide to the reduction of the transition layer.
Photoenhanced injection currents in organic solar cells
Authors: Frohne Holger , McNeill Christopher R. , Dastoor Paul C.
Published: August 2004

Bulk heterojunction organic solar cells with the general structure: indium tin oxide/polyethylenethioxythiophene (PEDOT)/bulk-heterojunction layer/Al with built-in fields between −0.1 and 1V have been fabricated by electrochemically doping the PEDOT electrode. The active bulk-heterojunction layer consisted of a blend of MDMO-PPV (poly(2-methoxy-5-(3′,7′-dimethyl)octyloxy-1,4-phenylenevinylene)) and PCBM ((6,6)-phenyl-C61-butyric-acid methyl ester)). Measurements of the current–voltage curves with varying light intensities for these devices reveal the presence of light-dependent currents in addition to those from the photogenerated charge carriers. Equivalent circuit modeling indicates that these light-dependent currents most likely originate from photoenhanced injection at the electrodes.
Thin-film tunneling transistors on flexible plastic substrates based on stress-assisted lateral growth of polycrystalline germanium
Authors: Hekmatshoar Bahman , Mohajerzadeh Shams , Shahrjerdi Davood , Robertson Michael D.
Published: August 2004

Stress-assisted Cu-induced lateral growth of polycrystalline germanium (poly-Ge) at temperatures as low as 150 °C has been exploited to fabricate thin-film tunneling transistors on flexible plastic substrates. Applying external compressive stress during annealing, leads to the lateral growth of poly-Ge from Cu-seeded drain/source regions, progressing into the channel area. A potential barrier is formed midway in the channel where the two lateral growth frontiers, emanating from source and drain seeded areas, meet each other. As confirmed by electrical measurements, the barrier is controlled by the gate bias. An ON/OFF ratio of 104 has been measured for these transistors, which shows the potential of these devices for switching applications.
Ga
In
N
∕
Ga
N
growth optimization for high-power green light-emitting diodes
Authors: Wetzel C. , Salagaj T. , Detchprohm T. , Li P. , Nelson J. S.
Published: August 2004

Two different approaches to optimize the growth conditions for high-power green light-emitting diodes (LEDs) using Ga1−xInxN∕GaN metalorganic vapor phase epitaxy are discussed. We compare typical results in terms of morphology, photo-, and electroluminescence properties. We find good results for an optimization of the lateral morphological homogeneity of the active region. An extension of growth conditions for the active layers of blue LEDs was misleading. This suggests that different emission processes are involved in blue and green LEDs. We achieve die performances of 2.5mW at 523nm (526nm dominant) for low forward voltages of 3.4V at a typical drive current of 20mA.
Characteristics of nondegenerate four-wave mixing in electroabsorption modulator
Authors: Mori Takashi , Kawaguchi Hitoshi
Published: August 2004

The characteristics of nondegenerate four-wave mixing (FWM) in an electroabsorption modulator are reported. The input power dependence of FWM intensity agrees well with theoretical results based on third-order nonlinearity over a wide input power range of 16dB. The detuning characteristics of FWM have a −6dB∕octave response based on the carrier-density pulsation effect. The experimental results show that a higher reverse voltage brings about a faster carrier recombination. The asymmetricity of positive and negative detuning is the reverse of that of the semiconductor optical amplifier and is explained through a rate equation simulation.
Correlation between the 1∕f noise parameters and the effective low-field mobility in HfO2 gate dielectric n-channel metal–oxide–semiconductor field-effect transistors
Authors: Simoen E. , Mercha A. , Claeys C. , Young E.
Published: August 2004

In this work, the parameters extracted from the 1∕f noise in silicon n-channel metal–oxide–semiconductor field-effect transistors with different HfO2∕SiO2 gate stacks, corresponding with different equivalent oxide thickness (EOT) are reported and their relationship with the effective low-field mobility is studied. It is found that the 1.5nm EOT transistors show lower 1∕f noise, from which a lower effective trap density is derived, compared with their 2nm EOT counterparts. In addition, the gate stack with the higher trap density yields a lower mobility and a lower mobility scattering coefficient.
Ca
2.7
Bi
0.3
Co
4
O
9
∕
La
0.9
Bi
0.1
Ni
O
3
thermoelectric deviceswith high output power density
Authors: Funahashi R. , Urata S. , Mizuno K. , Kouuchi T. , Mikami M.
Published: August 2004

Different versions of a thermoelectric unicouple composed of p-type Ca2.7Bi0.3Co4O9 (Co-349) and n-type La0.9Bi0.1NiO3 (Ni-113) bulks were constructed using Ag paste containing p- and n-type oxide powders, prepared from the same bulks, for connection of the p and n legs, respectively. Internal resistance (RI) of the unicouple corrected using Ag paste containing 6 wt. % of the oxide powders is 26.2mΩ at 1073K in air and decreases with increasing temperature. Maximum output power (Pmax), evaluated using the formula Pmax=VO2∕4RI, (VO is open-circuit voltage), is 94mW at 1073K (ΔT=500K) and increases with temperature. This value corresponds to a volume power density of 0.66W∕cm3.
Modified metal-induced lateral crystallization using amorphous Ge∕Si layered structure
Authors: Kanno Hiroshi , Kenjo Atsushi , Sadoh Taizoh , Miyao Masanobu
Published: August 2004

Modified metal-induced lateral crystallization (MILC) using a-Ge∕a-Si∕Ni∕SiO2 layered structures has been investigated. MILC growth velocity in the a-Ge∕a-Si layered structures was enhanced by three times compared with that in the a-Si single layers. As a result, poly-Si films with large areas (∼10μm) were obtained in a short time annealing (<5h) at 550°C. It is speculated that crystal nucleation in the a-Ge layers stimulated the bond rearrangement in the a-Si layers, which enhanced the MILC velocity. This will be a powerful tool for realizing large poly-Si areas on insulating films for future system-in-displays.
Noise reduction in GaN-based radio frequencysurface acoustic wave filters
Authors: Petroni S. , Tripoli G. , Combi C. , Vigna B. , De Vittorio M. , Todaro M. T. , Epifani G. , Cingolani R. , Passaseo A.
Published: August 2004

In this work we have fabricated and characterized GaN based surface acoustic wave (SAW) delay lines grown by metal organic chemical vapor deposition (MOCVD) on sapphire substrate. The acoustic wave velocity of 0th Rayleigh and Sezawa modes, and the piezoelectric electromechanical coupling constant have been measured for different wave numbers in a 2μm-thick layer. The acoustic velocity resulted to be independent from the layer resistivity, which strongly affects the noise level. Through the introduction of a highly resistive GaN buffer layer, a noise level as low as −70dB has been measured. This result has been attributed to a reduced coupling between the input and output terminals.
Mn-doped InAs self-organized diluted magnetic quantum-dot layers with Curie temperatures above 300K
Authors: Holub M. , Chakrabarti S. , Fathpour S. , Bhattacharya P. , Lei Y. , Ghosh S.
Published: August 2004

The magnetic and structural properties of InAs:Mn self-organized diluted magnetic quantum dots grown by low-temperature (∼270°C), solid-source molecular-beam epitaxy using a very low InAs growth rate (<0.1ML∕s) are investigated. A Curie temperature (TC) of ∼350K is measured in a sample grown with a Mn∕In flux ratio of 0.15. Electron energy-loss spectroscopy confirms that most of the Mn remains within the InAs quantum dots. We propose as a possible explanation for this high TC the effects of magnetic and structural disorder introduced by a random incorporation and inhomogeneous distribution of Mn atoms amongst the InAs quantum dots.
Dielectric tunability of (Ba0.90Ca0.10)(Ti0.75Zr0.25)O3 ceramics
Authors: Tang X. G. , Chew K.-H. , Wang J. , Chan H. L. W.
Published: August 2004

We have performed a study on the dielectric properties of (Ba0.90Ca0.10)(Ti0.75Zr0.25)O3 bulk ceramics prepared by a sol–gel technique in the cooling temperature range from 400to213K. The ceramics are found to exhibit an interesting dielectric response under the presence of a dc bias field. The field dependence of dielectric constant is stronger at T≈Tm (Tm is the temperature of dielectric maximum) and the field-induced variation of dielectric constant Δε is nonzero for T−Tm<150K. One striking feature of these ceramics is that they possess a broad optimum value of figure of merit (as high as 200 at 30kV∕cm) between the temperature range from 295 and 330K. At room temperature, the high tunability (K=60%), low-loss tangent (≈0.003), and large figure of merit (200), clearly indicate that these ceramics are suitable candidates for microwave applications.
Ca
2+
/calmodulin-dependent protein kinase II potentiates ATP responses by promoting trafficking of P2X receptors
Authors: Xu Guang-Yin , Huang Li-Yen Mae
Published: August 2004

To elucidate the functional link between Ca
2+
/calmodulin protein kinase II (CaMKII) and P2X receptor activation, we studied the effects of electrical stimulation, such as occurs in injurious conditions, on P2X receptor-mediated ATP responses in primary sensory dorsal root ganglion neurons. We found that endogenously active CaMKII up-regulates basal P2X3 receptor activity in dorsal root ganglion neurons. Electrical stimulation causes prolonged increases in ATP currents that lasts up to ≈45 min. In addition, the total and phosphorylated CaMKII are also up-regulated. The enhancement of ATP currents depends on Ca
2+
and calmodulin and is completely blocked by the CaMKII inhibitor, 2-[
N
-(2-hydroxyethyl)]-
N
-(4-methoxybenzenesulfonyl)]amino-
N
-(4-chlorocinnamyl)-
N
-methylbenzylamine). Western analyses indicate that electrical stimulation enhances the expression of P2X3 receptors in the membrane and that the enhancement is blocked by the inhibitor. These results suggest that CaMKII up-regulated by electrical stimulation enhances ATP responses by promoting trafficking of P2X receptors to the membrane and may play a key role in the sensitization of P2X receptors under injurious conditions.
Detection of the mycophenolate-inhibited form of IMP dehydrogenase
in vivo
Authors: McPhillips Christine C. , Hyle Judith W. , Reines Daniel
Published: August 2004

IMP dehydrogenase (IMPDH) is the rate-limiting enzyme for
de novo
GMP synthesis. Its activity is correlated with cell growth, and it is the target of a number of proven and experimental drug therapies including mycophenolic acid (MPA). MPA inhibits the enzyme by trapping a covalent nucleotide-enzyme intermediate.
Saccharomyces cerevisiae
has four IMPDH genes called
IMD1
—
IMD4
.
IMD2
is transcriptionally regulated and is the only one that enables yeast to grow in the presence of MPA. We show here that
de novo
synthesis of the
IMD2
-encoded protein is strongly induced upon MPA treatment. We also monitor the
in vivo
formation of a covalent nucleotide-enzyme intermediate for Imd2, Imd3, and Imd4 that accumulates in the presence of MPA. Complete formation of the Imd2 intermediate requires drug concentrations manyfold higher than that required to quantitatively trap the Imd3- or Imd4-nucleotide adducts. Purification of the tagged
IMD
gene products reveals that the family of polypeptides coassemble to form heteromeric IMPDH complexes, suggesting that they form mixed tetramers. These data demonstrate that
S. cerevisiae
harbor multiple IMPDH enzymes with varying drug sensitivities and offer an assay to monitor the inhibition of IMPDH in living cells. They also suggest that mixed inhibition profiles may result from heteromeric complexes in cell types that contain multiple IMPDH gene products. The mobility shift assay could serve as a tool for the detection of drug-inactivated IMPDH in the cells of patients receiving MPA therapy.
Genome-wide discovery of loci influencing chemotherapy cytotoxicity
Authors: Watters James W. , Kraja Aldi , Meucci Melissa A. , Province Michael A. , McLeod Howard L.
Published: July 2004

Little is known about the heritability of chemotherapy activity or the identity of genes that may enable the individualization of cancer chemotherapy. Although numerous genes are likely to influence chemotherapy response, current candidate gene-based pharmacogenetics approaches require
a priori
knowledge and the selection of a small number of candidate genes for hypothesis testing. In this study, an
ex vivo
familial genetics strategy using lymphoblastoid cells derived from Centre d'Etude du Polymorphisme Humain reference pedigrees was used to discover genetic determinants of chemotherapy cytotoxicity. Cytotoxicity to the mechanistically distinct chemotherapy agents 5-fluorouracil and docetaxel were shown to be heritable traits, with heritability values ranging from 0.26 to 0.65 for 5-fluorouracil and 0.21 to 0.70 for docetaxel, varying with dose. Genome-wide linkage analysis was also used to map a quantitative trait locus influencing the cellular effects of 5-fluorouracil to chromosome 9q13-q22 [logarithm of odds (LOD) = 3.44], and two quantitative trait loci influencing the cellular effects of docetaxel to chromosomes 5q11–21 (LOD = 2.21) and 9q13-q22 (LOD = 2.73). Finally, 5-fluorouracil and docetaxel were shown to cause apoptotic cell death involving caspase-3 cleavage in Centre d'Etude du Polymorphisme Humain lymphoblastoid cells. This study identifies genomic regions likely to harbor genes important for chemotherapy cytotoxicity using genome-wide linkage analysis in human pedigrees and provides a widely applicable strategy for pharmacogenomic discovery without the requirement for
a priori
candidate gene selection.
Hematopoietic cells and osteoblasts are derived from a common marrow progenitor after bone marrow transplantation
Authors: Dominici Massimo , Pritchard Colin , Garlits John E. , Hofmann Ted J. , Persons Derek A. , Horwitz Edwin M.
Published: July 2004

Bone and bone marrow are closely aligned physiologic compartments, suggesting that these tissues may represent a single functional unit with a common bone marrow progenitor that gives rise to both osteoblasts and hematopoietic cells. Although reports of multilineage engraftment by a single marrow-derived stem cell support this idea, more recent evidence has challenged claims of stem cell transdifferentiation and therefore the existence of a multipotent hematopoietic/osteogenic progenitor cell. Using a repopulation assay in mice, we show here that gene-marked, transplantable marrow cells from the plastic-nonadherent population can generate both functional osteoblasts/osteocytes and hematopoietic cells. Fluorescent
in situ
hybridization for the X and Y chromosomes and karyotype analysis of cultured osteoblasts confirmed the donor origin of these cells and excluded their generation by a fusion process. Molecular analysis demonstrated a common retroviral integration site in clonogenic hematopoietic cells and osteoprogenitors from each of seven animals studied, establishing a shared clonal origin for these ostensibly independent cell types. Our findings indicate that the bone marrow contains a primitive cell able to generate both the hematopoietic and osteocytic lineages. Its isolation and characterization may suggest novel treatments for genetic bone diseases and bone injuries.
DNA vaccines to attack cancer
Authors: Stevenson Freda K. , Ottensmeier Christian H. , Johnson Peter , Zhu Delin , Buchan Sarah L. , McCann Katy J. , Roddick Joanne S. , King Andrew T. , McNicholl Feargal , Savelyeva Natalia , Rice Jason
Published: August 2004

Delivery of antigens by injection of the encoding DNA allows access to multiple antigen-presenting pathways. Knowledge of immunological processes can therefore be used to modify construct design to induce selected effector functions. Expression can be directed to specific intracellular sites, and additional genes can be fused or codelivered to amplify responses. Therapeutic vaccination against cancer adds a requirement to overcome tolerance and to activate a weakened immune repertoire. Induction of CD4+T helper cells is critical for both antibody and T cell effector responses. To activate immunity against tumor antigens, we fused the tumor-derived sequences to genes encoding microbial proteins. This strategy engages T helper cells from the large antimicrobial repertoire for linked help for inducing antibody against cell-surface tumor antigens. The principle of linked T cell help also holds for induction of epitope-specific antitumor CD8+T cells, but the microbial sequence has to be minimized to avoid competition with tumor antigens. Epitope-specific DNA vaccination leads to powerful antitumor attack and can activate immunity from a profoundly tolerized repertoire. Vaccine designs validated in preclinical models are now in clinical trial with immune responses detected against both tumor antigens and fused microbial antigens. DNA priming is highly efficient, but boosting may benefit from increased antigen expression. Physical methods including electroporation provide increased expression without introducing additional competing antigens. A wide range of cancers can be targeted, and objective assays of response will determine efficacy.
Golgi Enzymes Are Enriched in Perforated Zones of Golgi Cisternae but Are Depleted in COPI Vesicles
Authors: Kweon Hee-Seok , Beznoussenko Galina V. , Micaroni Massimo , Polishchuk Roman S. , Trucco Alvar , Martella Oliviano , Di Giandomenico Daniele , Marra Pierfrancesco , Fusella Aurora , Di Pentima Alessio , Berger Eric G. , Geerts Willie J. C. , Koster Abraham J. , Burger Koert N. J. , Luini Alberto , Mironov Alexander A.
Published: July 2004

In the most widely accepted version of the cisternal maturation/progression model of intra-Golgi transport, the polarity of the Golgi complex is maintained by retrograde transport of Golgi enzymes in COPI-coated vesicles. By analyzing enzyme localization in relation to the three-dimensional ultrastructure of the Golgi complex, we now observe that Golgi enzymes are depleted in COPI-coated buds and 50- to 60-nm COPI-dependent vesicles in a variety of different cell types. Instead, we find that Golgi enzymes are concentrated in the perforated zones of cisternal rims both in vivo and in a cell-free system. This lateral segregation of Golgi enzymes is detectable in some stacks during steady-state transport, but it was significantly prominent after blocking endoplasmic reticulum-to-Golgi transport. Delivery of transport carriers to the Golgi after the release of a transport block leads to a diminution in Golgi enzyme concentrations in perforated zones of cisternae. The exclusion of Golgi enzymes from COPI vesicles and their transport-dependent accumulation in perforated zones argues against the current vesicle-mediated version of the cisternal maturation/progression model.
Targets of Fibroblast Growth Factor 1 (FGF-1) and FGF-2 Signaling Involved in the Invasive and Tumorigenic Behavior of Carcinoma Cells
Authors: Billottet Clotilde , Elkhatib Nadia , Thiery Jean-Paul , Jouanneau Jacqueline
Published: July 2004

Fibroblast growth factor (FGF)-1 and -2 have potent biological activities implicated in malignant tumor development. Their autocrine and nonautocrine activity in tumor progression of carcinoma was investigated in the NBT-II cell system. Cells were manipulated to either produce and be autocrine for FGF-1 or -2 or to only produce but not respond to these factors. The autocrine cells are highly invasive and tumorigenic and the determination of specific targets of FGF/fibroblast growth factor receptor (FGFR) signaling was assessed. In vitro studies showed that nonautocrine cells behave like epithelial parental cells, whereas autocrine cells have a mesenchymal phenotype correlated with the overexpression of urokinase plasminogen activator receptor (uPAR), the internalization of E-cadherin, and the redistribution of β-catenin from the cell surface to the cytoplasm and nucleus. uPAR was defined as an early target, whereas E-cadherin and the leukocyte common antigen-related protein-tyrosine phosphatase (LAR-PTP) were later targets of FGF signaling, with FGFR1 activation more efficient than FGFR2 at modulating these targets. Behavior of autocrine cells was consistent with a decrease of tumor-suppressive activities of both E-cadherin and LAR-PTP. These molecular analyses show that the potential of these two growth factors in tumor progression is highly dependent on specific FGFR signaling and highlights its importance as a target for antitumor therapy
PAK Kinases Ste20 and Pak1 Govern Cell Polarity at Different Stages of Mating inCryptococcus neoformans
Authors: Nichols Connie B. , Fraser James A. , Heitman Joseph
Published: July 2004

Sexual identity and mating are linked to virulence of the fungal pathogen Cryptococcus neoformans. Cells of the α mating type are more prevalent and can be more virulent than a cells, and basidiospores are thought to be the infectious propagule. Mating in C. neoformans involves cell-cell fusion and the generation of dikaryotic hyphae, processes that involve substantial changes in cell polarity. Two p21-activated kinase (PAK) kinases, Pak1 and Ste20, are required for both mating and virulence in C. neoformans. We show here that Ste20 and Pak1 play crucial roles in polarized morphogenesis at different steps during mating: Pak1 functions during cell fusion, whereas Ste20 fulfills a distinct morphogenic role and is required to maintain polarity in the heterokaryotic mating filament. In conclusion, our studies demonstrate that PAK kinases are necessary for polar growth during mating and that polarity establishment is necessary for mating and may contribute to virulence of C. neoformans.
Mediation of Endogenous β‐Endorphin by Tetrandrine to Lower Plasma Glucose in Streptozotocin‐Induced Diabetic Rats
Authors: Hsu Jen-Hao , Wu Yang-Chang , Liou Shorong-Shii , Liu I-Min , Huang Lee-Wen , Cheng Juei-Tang
Published: July 2004

The role of β‐endorphin in the plasma glucose‐lowering action of tetrandrine in streptozotocin‐induced diabetic rats (STZ‐diabetic rats) was investigated. The plasma glucose concentration was assessed by the glucose oxidase method. The enzyme‐linked immunosorbent assay was used to determine the plasma level of β‐endorphin‐like immunoreactivity (BER). The mRNA levels of glucose transporter subtype 4 (GLUT4) in soleus muscle and phosphoenolpyruvate carboxykinase (PEPCK) in the liver of STZ‐diabetic rats were detected by Northern blotting analysis. The expressed protein of GLUT4 or PEPCK was characterized by Western blotting analysis. Tetrandrine dose‐dependently increased plasma BER in a manner parallel to the decrease of plasma glucose in STZ‐diabetic rats. Moreover, the plasma glucose‐lowering effect of tetrandrine was inhibited by naloxone and naloxonazine at doses sufficient to block opioid μ‐receptors. Further, tetrandrine failed to produce plasma glucose‐lowering action in opioid μ‐receptor knockout diabetic mice. Bilateral adrenalectomy eliminated the plasma glucose‐lowering effect and plasma BER‐elevating effect of tetrandrine in STZ‐diabetic rats. Both effects were abolished by treatment with hexamethonium or pentolinium at doses sufficient to block nicotinic receptors. Tetrandrine enhanced BER release directly from the isolated adrenal medulla of STZ‐diabetic rats and this action was abolished by the blockade of nicotinic receptors. Repeated intravenous administration of tetrandrine (1.0 mg/kg) to STZ‐diabetic rats for 3 days resulted in an increase in the mRNA and protein levels of the GLUT4 in soleus muscle, in addition to the lowering of plasma glucose. Similar treatment with tetrandrine reversed the elevated mRNA and protein levels of PEPCK in the liver of STZ‐diabetic rats. The obtained results suggest that tetrandrine may induce the activation of nicotinic receptors in adrenal medulla to enhance the secretion of β‐endorphin, which could stimulate opioid μ‐receptors to increase glucose utilization or/and reduce hepatic gluconeogenesis to lower plasma glucose levels in STZ‐diabetic rats.
Tissue-Specific Expression of Head-to-Tail Cyclized Miniproteins in Violaceae and Structure Determination of the Root CyclotideViola hederacearoot cyclotide1[W]
Authors: Trabi Manuela , Craik David J.
Published: August 2004

The plant cyclotides are a family of 28 to 37 amino acid miniproteins characterized by their head-to-tail cyclized peptide backbone and six absolutely conserved Cys residues arranged in a cystine knot motif: two disulfide bonds and the connecting backbone segments form a loop that is penetrated by the third disulfide bond. This knotted disulfide arrangement, together with the cyclic peptide backbone, renders the cyclotides extremely stable against enzymatic digest as well as thermal degradation, making them interesting targets for both pharmaceutical and agrochemical applications. We have examined the expression patterns of these fascinating peptides in various Viola species (Violaceae). All tissue types examined contained complex mixtures of cyclotides, with individual profiles differing significantly. We provide evidence for at least 57 novel cyclotides present in a single Viola species (Viola hederacea). Furthermore, we have isolated one cyclotide expressed only in underground parts of V. hederacea and characterized its primary and three-dimensional structure. We propose that cyclotides constitute a new family of plant defense peptides, which might constitute an even larger and, in their biological function, more diverse family than the well-known plant defensins.
Global Transcription Profiling Reveals Multiple Sugar Signal Transduction Mechanisms in Arabidopsis[W]
Authors: Price John , Laxmi Ashverya , St. Martin Steven K. , Jang Jyan-Chyun
Published: August 2004

Complex and interconnected signaling networks allow organisms to control cell division, growth, differentiation, or programmed cell death in response to metabolic and environmental cues. In plants, it is known that sugar and nitrogen are critical nutrient signals; however, our understanding of the molecular mechanisms underlying nutrient signal transduction is very limited. To begin unraveling complex sugar signaling networks in plants, DNA microarray analysis was used to determine the effects of glucose and inorganic nitrogen source on gene expression on a global scale in Arabidopsis thaliana. In whole seedling tissue, glucose is a more potent signal in regulating transcription than inorganic nitrogen. In fact, other than genes associated with nitrate assimilation, glucose had a greater effect in regulating nitrogen metabolic genes than nitrogen itself. Glucose also regulated a broader range of genes, including genes associated with carbohydrate metabolism, signal transduction, and metabolite transport. In addition, a large number of stress responsive genes were also induced by glucose, indicating a role of sugar in environmental responses. Cluster analysis revealed significant interaction between glucose and nitrogen in regulating gene expression because glucose can modulate the effects of nitrogen and vise versa. Intriguingly, cycloheximide treatment appeared to disrupt glucose induction more than glucose repression, suggesting that de novo protein synthesis is an intermediary event required before most glucose induction can occur. Cross talk between sugar and ethylene signaling may take place on the transcriptional level because several ethylene biosynthetic and signal transduction genes are repressed by glucose, and the repression is largely unaffected by cycloheximide. Collectively, our global expression data strongly support the idea that glucose and inorganic nitrogen act as both metabolites and signaling molecules.
Comparison of the Preisach and Jiles‐Atherton models to take hysteresis phenomenon into account in finite element analysis
Authors: Benabou Abdelkader , Clénet Stéphane , Piriou Francis
Published: July 2004

In this communication, the Preisach and Jiles‐Atherton models are studied to take hysteresis phenomenon into account in finite element analysis. First, the models and their identification procedure are briefly developed. Then, their implementation in the finite element code is presented. Finally, their performances are compared with an electromagnetic system made of soft magnetic composite. Current and iron losses are calculated and compared with the experimental results.
Reliability‐based topology optimization for electromagnetic systems
Authors: Kang Jenam , Kim Chwail , Wang Semyung
Published: July 2004

This paper presents a probabilistic optimal design for electromagnetic systems. A 2D magnetostatic finite element model is constructed for a reliability‐based topology optimization (RBTO). Permeability, coercive force, and applied current density are considered as uncertain variables. The uncertain variable means that the variable has a variance on a certain design point. In order to compute reliability constraints, a performance measure approach is widely used. To find reliability index easily, the limit‐state function is linearly approximated at each iteration. This approximation method is called the first‐order reliability method, which is widely used in reliability‐based design optimizations. To show the effectiveness of the proposed method, RBTO for the electromagnetic systems is applied to magnetostatic problems.
2D harmonic analysis of the cogging torque in synchronous permanent magnet machines
Authors: Lukaniszyn M. , Jagiela M. , Wróbel R. , Latawiec K.
Published: July 2004

Presents an approach to determine sources of cogging torque harmonics in permanent magnet electrical machines on the basis of variations of air‐gap magnetic flux density with time and space. The magnetic flux density is determined from the two‐dimensional (2D) finite element model and decomposed into the double Fourier series through the 2D fast Fourier transform (FFT). The real trigonometric form of the Fourier series is used for the purpose to identify those space and time harmonics of magnetic flux density whose involvement in the cogging torque is the greatest relative contribution. Carries out calculations for a symmetric permanent magnet brushless machine for several rotor eccentricities and imbalances.
Electromagnetic forming
Authors: Giannoglou A. , Kladas A. , Tegopoulos J. , Koumoutsos A. , Manolakos D. , Mamalis A.
Published: July 2004

Undertakes an analysis of electromagnetic forming process. Despite the fact that it is an old process, it is able to treat current problems of advanced manufacturing technology. Primary emphasis is placed on presentation of the physical phenomena, which govern the process, as well as their numerical representation by means of simplified electrical equivalent circuits and fully coupled fields approach of the electromagnetic‐mechanical‐electric phenomena involved. Compares the numerical results with measurements. Finally, draws conclusions and perspectives for future work.
Optimal shape design of a high‐voltage test arrangement
Authors: Di Barba P. , Galdi R. , Piovan U. , Savini A. , Consogno G.
Published: July 2004

Discusses the automated shape design of the electrodes supplying an arrangement for high‐voltage test. Obtains results that are feasible for industrial applications by means of an optimisation algorithm able to process discrete‐valued design variables.
Structural MR Imaging
Authors: Grant P. Ellen
Published: July 2004

Summary:  Phased‐array imaging at 1.5 and 3 T significantly improves image quality compared with that in routine 1.5‐T head coil studies. These improvements significantly increase lesion detection in patients with focal epilepsy. Semiautomated image‐analysis techniques have the potential to improve lesion detection, assess lesion burden more accurately, characterize cortical abnormalities, and determine the location and extent of associated cortical and deep gray nuclei involvement. With increasing interest in understanding the role white matter plays in epileptogenesis and seizure propagation, diffusion tensor imaging may yield useful information about changes in white matter organization. Our current multimodality imaging combines these structural imaging advances with coregistered neurophysiological information obtained with magnetoencephalography and with simultaneous EEG recordings. Our initial experience suggests that multimodality imaging will improve our ability to detect and define the extent of epileptogenic lesions.
Optical Imaging of Epileptiform Activity in Human Neocortex
Authors: Haglund Michael M. , Hochman Daryl W.
Published: July 2004

Summary:  The surgical outcomes of patients suffering from neocortical epilepsy are not as successful as the surgical outcomes from resections of epilepsy patients with mesial temporal sclerosis. The main difficulty in the treatment of neocortical epilepsy is that current technology has limited accuracy in mapping neocortical epileptogenic tissue. It is known that the optical spectroscopic properties of brain tissue are correlated with changes in neuronal activity. The method of mapping these activity‐evoked optical changes is known as imaging of intrinsic optical signals (IIOS). Activity‐evoked optical changes measured in neocortex are generated by changes in cerebral hemodynamics (i.e., changes in blood oxygenation and blood volume). Our experimental approach was to acquire high‐resolution IIOS maps of epileptiform activity in patients undergoing surgery for medically intractable neocortical epilepsy. Both spontaneous and stimulation‐evoked epileptiform activity was monitored. Imaging of intrinsic optical signals was able to localize neocortical epileptic foci precisely by using changes in blood volume in contrast to changes in blood oxygenation. IIOS has the potential to translate from a purely research tool to a new intraoperative approach for the surgical treatment of neocortical epilepsy.
Nonpharmacologic Treatment of the Catastrophic Epilepsies of Childhood
Authors: Wheless James W.
Published: July 2004

Summary:  The catastrophic epilepsy syndromes of childhood are initially treated with a pharmacologic intervention in most cases. However, due to the poor response patients often have to pharmacologic interventions, nonpharmacologic treatment options are an important part of a comprehensive treatment plan for this group of children. Additionally, nonpharmacologic therapy may offer a method to minimize associated morbidity and mortality. This article discusses the use of epilepsy surgery, the ketogenic diet, and vagus nerve stimulation in the treatment of patients with infantile spasms, Lennox‐Gastaut syndrome, and progressive myoclonic epilepsy. Efficacy of the nonpharmacologic treatment options, as measured by reduction in seizure frequency, as well as by developmental progress or behavioral improvement, varies according to the specific catastrophic epilepsy disorder and the treatment option.
Hand development and sequence of ossification in the forelimb of the European shrew Crocidura russula (Soricidae) and comparisons across therian mammals
Authors: Prochel Jan , Vogel Peter , Sánchez‐Villagra Marcelo R.
Published: August 2004

Hand development in the European shrew Crocidura russula is described, based on the examination of a cleared and double‐stained ontogenetic series and histological sections of a c. 20‐day‐old embryo and a neonate. In the embryo all carpal elements are still mesenchymal condensations, and there are three more elements than in the adult stage: the ‘lunatum’, which fuses with the scaphoid around birth; a centrale, which either fuses with another carpal element or just disappears later in ontogeny; and the anlage of an element that later fuses with the radius. Carpal arrangement in the neonate and the adult is the same. In order to compare the relative timing of the onset of ossification in forelimb bones in C. russula with that of other therians, we built up two matrices of events based on two sets of data and used the event‐pair method. In the first analysis, ossification of forelimb elements in general was examined, including that of the humerus, radius, ulna, the first carpal and metacarpal to ossify, and the phalanges of the third digit. The second analysis included each carpal, humerus, radius, ulna, the first metacarpal and the first phalanx to ossify. Some characters (= event–pairs) provide synapomorphies for some clades examined. There have been some shifts in the timing of ossification apparently not caused by ecological and/or environmental influences. In two species (Oryctolagus and Myotis), there is a tendency to start the ossification of the carpals relatively earlier than in all other species examined, the sauropsid outgroups included.