bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical and optical properties of Cr and Fe implanted n-GaN
Authors: Polyakov A. Y. , Smirnov N. B. , Govorkov A. V. , Pashkova N. V. , Shlensky A. A. , Pearton S. J. , Overberg M. E. , Abernathy C. R. , Zavada J. M. , Wilson R. G.
Published: April 2003

Deep levels introduced into n-GaN films by Fe and Cr implantation have been studied by means of optical absorption and microcathodoluminescence spectroscopy measurements and by deep level transient spectroscopy, admittance spectroscopy, and capacitance-voltage profiling. The results are compared with previous measurements on Mn and Co implanted GaN. It is shown that the acceptor levels of substitutional Mn, Co, Fe, and Cr in n-GaN are located, respectively, near Ev+1.6 eV, Ev+1.7 eV, Ev+1.8 eV, and Ev+2 eV, the trend being similar to that observed in GaAs, GaP, and InP. The Fermi level in the implanted region is pinned near deep electron traps at Ec−0.5 eV that are tentatively attributed to complexes between substitutional transition metal ions and native defects such as nitrogen vacancies. It is shown that for all implanted species after 700 °C annealing a damaged region with relatively high resistivity is formed down to the depth of about 1 μm much, exceeding the projected range of implanted ions. This region is enriched with radiation-damage-related defects and is most likely formed by outdiffusion of these defects from the implanted region during annealing. The thickness of this damaged region is shown to be the lowest for Cr implantation.
Sulfur-doping of rutile-titanium dioxide by ion implantation: Photocurrent spectroscopy and first-principles band calculation studies
Authors: Umebayashi T. , Yamaki T. , Yamamoto S. , Miyashita A. , Tanaka S. , Sumita T. , Asai K.
Published: April 2003

Sulfur (S)-doped titanium dioxide (TiO2) was synthesized by ion implantation and subsequent thermal annealing. The S ions were implanted into the single crystals of rutile TiO2 at a fluence of 8×1015 ions/cm2. According to the results of Rutherford backscattering spectroscopy and ion channeling analysis, the irradiation damage recovered by annealing at 600 °C in air. In the annealed crystal, the S atoms occupied oxygen sites for form Ti-S bonds, as confirmed by x-ray photoelectron spectroscopy. Compared to the pure TiO2, a photocurrent was observed in the lower-energy regions for the S-doped TiO2. Based on the theoretical analyses by the first-principles band calculations using the full potential linearized augmented plane-wave methods within the generalized gradient approximation, the mixing of the S 3p states with the valence band (VB) was found to contribute to the increasing width of the VB. This leads to the band gap narrowing in the S-doped TiO2. Therefore, the photon-to-carrier conversion was induced during irradiation by visible light above 420 nm (<2.9 eV).
Excitation and propagation characteristics of magnetostatic backward volume wave in a double-layered film structure with magnetic damping
Authors: Zhang Wen-Kang , Liu Gong-Qiang
Published: April 2003

The excitation and propagation characteristics of magnetostatic backward volume wave in a double-layered magnetic film structure with magnetic damping are investigated theoretically. The dispersion, the attenuation constant, and the insertion loss can be decreased and the excitation bandwidth can be increased significantly by using a double-layered structure. The propagation constant and the attenuation constant depend strongly on the physical and geometrical parameters of the magnetic film with large thickness. The excitation characteristics are associated not only with the physical and geometrical parameters of the two magnetic layers and the separation layer, but also with the location and geometrical parameters of the microstrip transducer. The effects of the magnetic damping on the radiation resistance and the propagation constant of the magnetostatic wave (MSW) are weak, and the presence of the magnetic damping mainly leads to the propagation loss of the MSW. In addition, the excitation of the MSW is the main bandwidth-limiting mechanism in a double-layered structure.
Phonon spectrum and thermal properties of cubic Si3N4 from first-principles calculations
Authors: Fang C. M. , de Wijs G. A. , Hintzen H. T. , de With G.
Published: April 2003

The phonon spectrum of cubic Si3N4 was calculated by first-principles techniques. The results permit an assessment of important mechanical and thermo-dynamical properties such as the bulk modulus, lattice specific heat, vibration energy, thermal expansion coefficient, and thermal Grüneisen parameter for this compound. The calculated phonon spectrum shows a gapless spectrum extending to a cutoff energy of ∼1030 cm−1. The calculated Raman- and infrared-active phonon frequencies are compared with measured data in the literature.
Analysis of recombination centers in epitaxial silicon thin-film solar cells by temperature-dependent quantum efficiency measurements
Authors: Wagner T. A. , Rau U.
Published: April 2003

Temperature-dependent quantum efficiency (TQE) measurements are used to investigate recombination in epitaxial silicon thin-film solar cells grown by ion-assisted deposition. Analysis of the experimental results unveils that the diffusion length in this material is dominated by Shockley–Read–Hall recombination via relatively shallow defects with activation energies of 70–110 and 160–210 meV, respectively. The device performance at room temperature is controlled by the concentration of the deeper one of those two defects. The TQE method proves to be a reliable variation of lifetime spectroscopy allowing for the quantitative identification of recombination active defects in completed solar cells.
Charge tunable ErAs islands for backgate isolation in AlGaAs heterostructures
Authors: Dorn A. , Peter M. , Kicin S. , Ihn T. , Ensslin K. , Driscoll D. , Gossard A. C.
Published: April 2003

Self-assembled ErAs islands on GaAs embedded between a backgate electrode and a two-dimensional electron gas (2DEG) were grown by molecular-beam epitaxy. The nanometer-sized islands form Schottky barriers with overlapping depletion regions, which insulate the backgate from the 2DEG. From temperature-dependent measurements and charging experiments the effective barrier height between the islands and the Schottky barrier height onto the islands could be determined. In addition, the effects of illumination were studied.
Transparent-cathode for top-emission organic light-emitting diodes
Authors: Han S. , Feng X. , Lu Z. H. , Johnson D. , Wood R.
Published: April 2003

A transparent-charge-injection layer consisting of LiF/Al/Al-doped SiO has been developed as (i) a cathode for top-emitting organic light-emitting diodes and as (ii) a buffer layer against damages induced by energetic ions generated during deposition of other functional thin films by sputtering, or plasma-enhanced chemical vapor deposition. A luminance of 1900 cd/m2 and a current efficiency of 4 cd/A have been achieved in a simple testing device structure of indium tin oxide (ITO) N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (60 nm)/Alq3 (40 nm)/LiF (0.5 nm)/Al (3 nm)/Al-doped SiO (30 nm). A minimum thickness of 30 nm of Al-doped SiO is also found to protect organic layers from ITO sputtering damage.
Structural behavior of Pd40Cu30Ni10P20 bulk metallic glass below and above the glass transition
Authors: Mattern Norbert , Hermann Helmut , Roth Stefan , Sakowski Jan , Macht Michael-Peter , Jovari Pal , Jiang Jianzhong
Published: April 2003

The thermal behavior of the structure of Pd40Cu30Ni10P20 bulk metallic glass has been investigated in situ through the glass transition by means of high-temperature x-ray synchrotron diffraction. The dependence of the x-ray structure factor S(q) of the Pd40Cu30Ni10P20 glass on temperature follows the Debye theory up to the glass transition with a Debye temperature θ=296 K. Above the glass transition temperature Tg, the temperature dependence of S(q) is altered, pointing to a continuous development of structural changes in the liquid with temperature. The atomic pair correlation functions g(r) indicate changes in short-range-order parameters of the first and the second neighborhood with temperature. The temperature dependence of structural parameters is different in glass and in supercooled liquid, with a continuous behavior through the glass transition. The nearest-neighbor distance decreases with temperature, changing the slope at Tg. The interatomic distances of higher coordination shells expand analogously to the macroscopic linear thermal expansion.
Nonclassical effects in liquid-phase nuclear magnetic resonance spectra of 9-methyltriptycene derivatives
Authors: Czerski I. , Bernatowicz P. , Jaźwiński J. , Szymański S.
Published: April 2003

The dynamics of strongly hindered methyl groups in 9-methyltriptycene derivatives, monitored by liquid-phase nuclear magnetic resonance spectra, were investigated using an iterative, least-squares method of line shape analysis. For two of the compounds, apart from nonclassical effects in the stochastic dynamics, anomalously strong dependence on temperature (ca. 0.05 and 0.08 Hz/K) of the J coupling between the methyl protons was observed. The latter effect was attributed to the occurrence of coherent quantum tunneling of the methyl rotor. For methyl group, this would be the first observation of coherent tunneling above cryogenic temperatures.
Silica waveguides fabricated by oxidization of selectively anodized porous silicon
Authors: Nagata Seiichi , Matsushita Shinobu , Saito Kazuya , Ohshita Yoshio , Maeda Yoshinobu , Yamaguchi Masafumi , Ikushima Akira J.
Published: April 2003

To keep the current density at the porous silicon (PS) and Si interface constant, independent of anodization depth, a pulse anodization method has been developed. In this method, a pulse current is controlled to be proportional to the PS/Si interface area. This method was applied to produce two-layered PS with different pore sizes. Titanium organic molecules were selectively doped into larger sized pores. By oxidization, the PS was transformed into a densified silica waveguide and its core, and cladding was automatically formed, without significant volume change. Very few breaking defects have been found in the waveguides. In addition, bends in the Si substrates were small. Optical loss in the slab waveguides was 0.3 dB/cm at 632.8 nm.
Probing the polymer-electrode interface using neutron reflection
Authors: Mitchell William J. , Burn Paul L. , Thomas Robert K. , Fragneto Giovanna
Published: April 2003

We demonstrate that neutron reflection (NR) can be used to characterize polymer films deposited on indium tin oxide (ITO). When the chloro precursor to poly[2-(2′-ethylhexyloxy)5-methoxy-1,4-phenylenevinylene] (MEHPPV) was spin-coated onto ITO NR revealed that between the ITO and the uniform polymer layer was a 20 Å thick low contact zone. We found that the conversion of the chloro precursor to MEHPPV at 180 °C under vacuum gave a uniform film of MEHPPV with the layer of low contact between the polymer and ITO remaining. Finally, the NR profile suggests that the blueshift in the MEHPPV absorption spectrum on ITO when compared to quartz is due to polymer morphology and not incomplete conversion.
Role of aperiodic surface defects on the intensity of electron diffraction spots
Authors: Bullock D. W. , Ding Z. , Thibado P. M. , LaBella V. P.
Published: April 2003

A random distribution of two-dimensional gallium arsenide (GaAs) islands is found to effect the intensity of the electron diffraction pattern from the GaAs(001) surface. By utilizing the spontaneous island formation phenomenon as well as submonolayer deposition, the island coverage is systematically changed. It is found that the intensities of the one-, two-, and three-quarter-order diffraction spots of the [11̄0] azimuth decrease as the concentration of islands increases. In addition, only in the presence of islands, does the intensity of the half-order spot decrease as the grazing angle of the electron beam is decreased. A simple quantitative model is developed that provides insight into how an aperiodic arrangement of islands effects the electron diffraction patterns.
Phase switching of ordered arrays of liquid crystal emulsions
Authors: Rudhardt D. , Fernández-Nieves A. , Link D. R. , Weitz D. A.
Published: April 2003

We report a fabrication method for producing interference-based electro-optic phase gratings that switch between diffracting and transparent states. The phase grating consists of a hexagonal-close-packed array of monodisperse emulsion drops of nematic liquid crystal, embedded in a polymer matrix. Monodisperse droplet size allows for fast switching at low electric fields.
Magnetic field tuning of the effective g factor in a diluted magnetic semiconductor quantum dot
Authors: Chang Kai , Xia J. B. , Peeters F. M.
Published: April 2003

The spin interaction and the effective g factor of a magnetic exciton (ME) are investigated theoretically in a diluted magnetic semiconductor (DMS) quantum dot (QD), including the Coulomb interaction and the sp–d exchange interaction. At low magnetic field, the ME energy decreases rapidly with increasing magnetic field and saturates at high magnetic field for high Mn concentration. The ground state of the ME exhibits an interesting crossing behavior between σ+-ME and σ−-ME for low Mn concentration. The gex factor of the ME in a DMS QD displays a monotonic decrease with increasing magnetic field and can be tuned to zero by an external magnetic field.
Composite deposition of Co and Si clusters by rf/dc plasma-gas-codensation
Authors: Katoh R. , Hihara T. , Peng D. L. , Sumiyama K.
Published: April 2003

A double-glow discharge cluster source system has been made by modification of a conventional co-sputter-deposition apparatus. Using this equipment, we tried to produce Co clusters generated by a dc glow discharge mode, Si clusters by an rf glow discharge mode, and deposit them simultaneously on a substrate. Putting a separate plate between these two glow discharge rooms, we have obtained a mixture of Co and Si clusters. Here, the Co clusters are distributed rather at random, while the Si clusters are aggregated to form a larger group. Taking off the separate plate, we have obtained core–shell clusters, in which small Si clusters surround Co core clusters. These features are quite different from the instantaneous alloying and/or very rapid atom diffusion that has been expected at contact interfaces between nanometer-sized small Co and Si clusters. They suggest that this double-cluster source system is useful to fabricate various sorts of cluster composites that cannot be prepared by thermodynamical methods, such as co-evaporation and precipitation.
Spatially selective flash sublimation of small organic molecules for organic light-emitting diodes and display applications
Authors: Becker E. , Riedl T. , Dobbertin T. , Schneider D. , Heithecker D. , Metzdorf D. , Johannes H. H. , Kowalsky W.
Published: April 2003

A flash-sublimation technique for the spatially selective deposition of small organic molecules is presented. Single-pulse electrically heated copper stripes (width 100 μm) serve as heating elements. The relevant time scale of our technique is on the order of milliseconds. Under high vacuum conditions, the heating elements are used to locally flash-sublimate small-molecule material from a previously coated polyimide foil onto a (ITO-)glass substrate, positioned at a vertical distance of 60 μm. The spatial resolution in our nonoptimized experiments was 250 μm. Organic light-emitting diode (OLED) devices with flash-deposited tris-(8-hydroxyquinoline)aluminum (Alq3) as the active material are demonstrated with satisfying electrical and optical properties. Flash sublimation of a stacked nonintermixed Alq3 (30 nm) [2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5Hbenzo[ij]quinolizin-9-yl)ethenyl]-4H-pyran-4-ylidene]propane-dinitrile (DCM2) (1 nm)/Alq3 (30 nm) layer is shown to yield a red-emitting (λ=624 nm) DCM2-doped Alq3 layer. Our technique presents a simple alternative to the use of shadow masks for full-color small-molecule OLED displays.
Structure determination of individual single-wall carbon nanotubes by nanoarea electron diffraction
Authors: Gao M. , Zuo J. M. , Twesten R. D. , Petrov I. , Nagahara L. A. , Zhang R.
Published: April 2003

In this letter, we report an electron diffraction determination of chiral vectors (n,m) of individual single-wall carbon nanotubes (SWNTs). Electron diffraction patterns from individual SWNTs were recorded on imaging plates using a parallel electron beam over a section of tube of ∼50 nm long. Using two tubes of 1.39 and 3.77 nm in diameter, we show that the details of electron diffuse scattering can be detected for both the small and large tubes. The quality of diffraction patterns allows the accurate measurement of both the diameters and chiral angles of SWNTs for a direct determination of chiral vectors. The electron diffraction technique is general and applicable to other forms of individual nanostructures.
Direct current field and temperature dependent behaviors of antiferroelectric to ferroelectric switching in highly (100)-oriented PbZrO3 thin films
Authors: Zhai Jiwei , Chen Haydn
Published: April 2003

Antiferroelectric PbZrO3 films had been grown on LaNiO3/Pt/Ti/SiO2/Si wafers using a sol-gel process. The electric field-induced antiferroelectric (AFE) to ferroelectric (FE) phase switching behaviors was examined by the polarization versus electrical field measurements as a function of temperature and film thickness. The AFE to FE phase switching was found to shift to lower temperature under a dc bias field. With increasing dc bias field, the FE phase region was enlarged and the FE to paraelectric phase transformation temperature shifted to higher temperature. The adjustability of the AFE phase to FE in temperature was weakened if the thickness of thin film decreased.
Vacancy–oxygen complex in Si1−xGex crystals
Authors: Markevich V. P. , Peaker A. R. , Murin L. I. , Abrosimov N. V.
Published: April 2003

Electronic properties of the vacancy–oxygen complex in unstrained Si1−xGex crystals (0<x⩽0.055) grown by the Czochralski method were studied by means of capacitance transient techniques. The enthalpy of electron ionization for the single acceptor level of the defect relative to the conduction band edge, ΔHn, was found to increase from 0.16 to 0.19 eV with the increase in Ge content. The change of the lattice parameter in Si1−xGex alloys is argued to be one of the main reasons of the observed ΔHn change.
Conduction and magnetoresistance in doped manganite grain boundaries
Authors: Blamire M. G. , Schneider C. W. , Hammerl G. , Mannhart J.
Published: April 2003

Grain boundary diffusion has been used to increase selectively the doping in grain boundaries of doped lanthanum manganite thin films. We show that this doping strongly modifies the temperature dependence of the grain boundary resistance and the form of the conductance versus voltage characteristic. The low field magnetoresistance associated with the grain boundary is altered following doping, but is not necessarily enhanced. This behavior is interpreted in terms of a doping-induced suppression of the local Curie temperature in the region of the grain boundary.
Fault-tolerant, scalable organic light-emitting device architecture
Authors: Duggal Anil R. , Foust Donald F. , Nealon William F. , Heller Christian M.
Published: April 2003

High performance organic light emitting diodes (OLEDs) become problematic as emitting area increases due to the high resistivity of the transparent electrode and the increasing probability of encountering a catastrophic short-circuit defect during fabrication. In this letter, a monolithic series-connected OLED architecture is demonstrated. It is shown that such devices exhibit the same power efficiency as traditional small area OLEDs but are, in addition, relatively insensitive to electrode resistivity and tolerant to normally catastrophic short-circuit defects. This architecture should enable applications such as lighting where scalability to large emitting area without high fabrication cost or design complexity is required.
Spectroscopy of individual silicon nanowires
Authors: Qi Jifa , Belcher Angela M. , White John M.
Published: April 2003

Photoluminescence (PL) spectroscopy of individual silicon nanowires has been investigated. A narrow emission band (85 meV) was observed associated with a fast luminescence decay in the picosecond region and is considered due to the recombination relaxation of confined electronic states. The optical anisotropy was found in the individual nanowires. When a wire was excited by linearly polarized light, the maximum intensity of linearly polarized PL was along the axis direction of the wire, and the maximum degree of polarization was determined to be 0.5. The value agrees well with the calculated one, which suggests that the polarization arise from the dielectric contrast between the crystalline cores and the silicon oxide sheathes of the nanowires.
Chemical reactivity of metcar Ti8C12, nanocrystal Ti14C13 and a bulk TiC(001) surface: A density functional study
Authors: Liu Ping , Rodriguez José A. , Hou Hua , Muckerman James T.
Published: April 2003

Density functional calculations show that the “magic” structures of titanium carbide nanoparticles display an unexpected high reactivity toward CO, NH3, and H2O when compared to the bulk TiC(001) surface. In spite of the large C/Ti ratio in Ti8C12, our results show that the bulk surface is much more tightly bonded than the nanocluster, and thus the nanocluster has a much higher chemical activity.
A multiplicative property of quantum flag minors
Authors: Caldero Ph.
Published: April 2003

We study the multiplicative properties of the quantum dual canonical basis

B

∗

{\mathcal B}^*

associated to a semisimple complex Lie group

G
G

. We provide a subset

D
D

of

B

∗

{\mathcal B}^*

such that the following property holds: if two elements

b
b

,

b
′

b’

in

B

∗

{\mathcal B}^*

q
q

-commute and if one of these elements is in

D
D

, then the product

b

b
′

bb’

is in

B

∗

{\mathcal B}^*

up to a power of

q
q

, where

q
q

is the quantum parameter. If

G
G

is SL

n

_n

, then

D
D

is the set of so-called quantum flag minors and we obtain a generalization of a result of Leclerc, Nazarov and Thibon.
Targeted recruitment of a histone H4-specific methyltransferase by the transcription factor YY1
Authors: Rezai-Zadeh Natalie , Zhang Xiaohong , Namour Fares , Fejer Gyorgy , Wen Yu-Der , Yao Ya-Li , Gyory Ildiko , Wright Kenneth , Seto Edward
Published: April 2003

Methylation of specific residues within the N-terminal histone tails plays a critical role in regulating eukaryotic gene expression. Although great advances have been made toward identifying histone methyltransferases (HMTs) and elucidating the consequences of histone methylation, little is known about the recruitment of HMTs to regulatory regions of chromatin. Here we report that the sequence-specific DNA-binding transcription factor Yin Yang 1 (YY1) binds to and recruits the histone H4 (Arg 3)-specific methyltransferase, PRMT1, to a YY1-activated promoter. Our data confirm that histone methylation does not occur randomly but rather is a targeted event and provides one mechanism by which HMTs can be recruited to chromatin to activate gene expression.
NQK1/NtMEK1 is a MAPKK that acts in the NPK1 MAPKKK-mediated MAPK cascade and is required for plant cytokinesis
Authors: Soyano Takashi , Nishihama Ryuichi , Morikiyo Kayoko , Ishikawa Masaki , Machida Yasunori
Published: April 2003

The tobacco protein kinase NPK1 is a MAPKKK that regulates formation of the cell plate during cytokinesis. In the present study, we have identified tobacco NQK1/NtMEK1 and NRK1 as a MAPKK and a MAPK, respectively, downstream of NPK1. NQK1/NtMEK1 complements the mutation in thePBS2MAPKK gene of yeast in a manner that depends on both NPK1 and its activator, NACK1, a kinesin-like protein. Active NPK1 and NQK1/NtMEK1 phosphorylate and activate NQK1/NtMEK1 and NRK1, respectively. Both NQK1/NtMEK1 and NRK1, as well as NPK1, are activated at the late M phase of the cell cycle in tobacco cells, and they are rapidly inactivated by depolymerization of phragmoplast microtubules. These results suggest the existence of a MAPK cascade that consists of NPK1, NQK1/NtMEK1, and NRK1 and functions in a process related to the architecture of phragmoplasts at the late M phase of the cell cycle. Overexpression of kinase-negative NQK1/NtMEK1 in tobacco cells generates multinucleate cells with incomplete cross-walls.Arabidopsisplants with a mutation in theANQ1gene, an ortholog ofNQK1/NtMEK1, display a dwarf phenotype, with unusually large cells that contain multiple nuclei and cell-wall stubs in various organs. In addition,anq1homozygotes set fewer flowers and produce large and malformed pollen grains with a tetrad structure. Thus, NQK1/NtMEK1 (ANQ1) MAPKK appears to be a positive regulator of plant cytokinesis during meiosis as well as mitosis.
The microRNAs ofCaenorhabditis elegans
Authors: Lim Lee P. , Lau Nelson C. , Weinstein Earl G. , Abdelhakim Aliaa , Yekta Soraya , Rhoades Matthew W. , Burge Christopher B. , Bartel David P.
Published: April 2003

MicroRNAs (miRNAs) are an abundant class of tiny RNAs thought to regulate the expression of protein-coding genes in plants and animals. In the present study, we describe a computational procedure to identify miRNA genes conserved in more than one genome. Applying this program, known as MiRscan, together with molecular identification and validation methods, we have identified most of the miRNA genes in the nematodeCaenorhabditis elegans. The total number of validated miRNA genes stands at 88, with no more than 35 genes remaining to be detected or validated. These 88 miRNA genes represent 48 gene families; 46 of these families (comprising 86 of the 88 genes) are conserved inCaenorhabditis briggsae, and 22 families are conserved in humans. More than a third of the worm miRNAs, including newly identified members of thelin-4andlet-7gene families, are differentially expressed during larval development, suggesting a role for these miRNAs in mediating larval developmental transitions. Most are present at very high steady-state levels—more than 1000 molecules per cell, with some exceeding 50,000 molecules per cell. Our census of the worm miRNAs and their expression patterns helps define this class of noncoding RNAs, lays the groundwork for functional studies, and provides the tools for more comprehensive analyses of miRNA genes in other species.
XOL-1, primary determinant of sexual fate inC. elegans, is a GHMP kinase family member and a structural prototype for a class of developmental regulators
Authors: Luz John Gately , Hassig Christian A. , Pickle Catherine , Godzik Adam , Meyer Barbara J. , Wilson Ian A.
Published: April 2003

InCaenorhabditis elegans, an X chromosome-counting mechanism specifies sexual fate. Specific genes termed X-signal elements, which are present on the X chromosome, act in a concerted dose-dependent fashion to regulate levels of the developmental switch genexol-1. In turn,xol-1levels determine sexual fate and the activation state of the dosage compensation mechanism. The crystal structure of the XOL-1 protein at 1.55 Å resolution unexpectedly reveals thatxol-1encodes a GHMP kinase family member, despite sequence identity of 10% or less. Because GHMP kinases, thus far, have only been characterized as small molecule kinases involved in metabolic pathways, for example, amino acid and cholesterol synthesis, XOL-1 is the first member that controls nonmetabolic processes. Biochemical investigations demonstrated that XOL-1 does not bind ATP under standard conditions, suggesting that XOL-1 acts by a mechanism distinct from that of other GHMP kinases. In addition, we have cloned a XOL-1 ortholog fromCaenorhabditis briggsae, a related nematode that diverged fromC. elegans∼50–100 million years ago. These findings demonstrate an unanticipated role for GHMP kinase family members as mediators of sexual differentiation and dosage compensation and, possibly, other aspects of differentiation and development.
Translational control of SCL-isoform expression in hematopoietic lineage choice
Authors: Calkhoven Cornelis F. , Müller Christine , Martin Richard , Krosl Goradz , Hoang Trang , Leutz Achim
Published: April 2003

We investigated the translational regulation of SCL protein expression and its role in hematopoietic lineage choice. We show that the expression of different SCL protein isoforms is regulated by signal transduction pathways that modulate translation initiation factor (eIF) function. A conserved small upstream open reading frame (uORF) in SCL transcripts acts as acis-regulatory element for isoform expression. At the onset of erythroid differentiation, truncated SCL protein isoforms arise by alternative translation initiation and favor the erythroid lineage. In comparison, full-length SCL proteins are more efficient at enhancing the megakaryocyte lineage. Together, our studies unravel translational control as a novel mechanism regulating hematopoietic outcome.
Raster space with relativity
Authors: Li Yongli , Li Zhilin , Chen Yong‐qi , Li Xiaoxia , Lin Yi
Published: April 2003

Practical needs in geographical information systems (GIS) have led to the investigation of formal, sound and computational methods for spatial analysis. Since models based on topology of R2 have a serious problem of incapability of being applied directly for practical computations, we have noticed that models developed on the raster space can overcome this problem. Because some models based on vector spaces have been effectively used in practical applications, we then introduce the idea of using the raster space as our platform to study spatial entities of vector spaces. In this paper, we use raster spaces to study not only morphological changes of spatial entities of vector spaces, but also equal relations and connectedness of spatial entities of vector spaces. Based on the discovery that all these concepts contain relativity, we then introduce several new concepts, such as observable equivalence, strong connectedness, and weak connectedness. Additionally, we present a possible method of employing raster spaces to study spatial relations of spatial entities of vector spaces. Since the traditional raster spaces could not be used directly, we first construct a new model, called pansystems model, for the concept of raster spaces, then develop a procedure to convert a representation of a spatial entity in vector spaces to that of the spatial entity in a raster space. Such conversions are called approximation mappings.
Adaptive dual control in one biomedical problem
Authors: Nechval Konstantin N. , Nechval Nicholas A. , Vasermanis Edgars K.
Published: April 2003

In this paper, the following biomedical problem is considered. People are subjected to a certain chemotherapeutic treatment. The optimal dosage is the maximal dose for which an individual patient will have toxicity level that does not cross the allowable limit. We discuss sequential procedures for searching the optimal dosage, which are based on the concept of dual control and the principle of optimality. According to the dual control theory, the control has two purposes that might be conflicting: one is to help learning about unknown parameters and/or the state of the system (estimation); the other is to achieve the control objective. Thus the resulting control sequence exhibits the closed‐loop property, i.e. it anticipates how future learning will be accomplished and how it can be fully utilized. Thus, in addition to being adaptive, this control also plans its future learning according to the control objective. Results are obtained for a priori uniform distribution of the unknown dosage. Because answers can be obtained analytically without approximation, the optimum policy can be compared with the non‐optimum policy of optimizing stage by stage. An illustrative example is given.
Autocorrelation and frequency analysis differentiate cardiac and economic bios from 1/f noise
Authors: Patel M. , Sabelli H.
Published: April 2003

Mathematical bios and heartbeat series show an inverse relation between frequency and power; the time series of differences between successive terms of cardiac and mathematical chaos shows a direct relation between frequency and power. Other statistical analyses differentiate these biotic series from stochastically generated 1/f noise. The time series of complex biological and economic processes as well as mathematical bios show asymmetry, positive autocorrelation, and extended partial autocorrelation. Random, chaotic and stochastic models show symmetric statistical distributions, and no partial autocorrelation. The percentage of continuous proportions is high in cardiac, economic, and mathematical biotic series, and scarce in pink noise and chaos. These findings differentiate creative biotic processes from chaotic and stochastic series. We propose that the widespread 1/f power spectrum found in natural processes represents the integration of the fundamental relation between frequency and energy stated in Planck's law. Natural creativity emerges from determined interactions rather than from the accumulation of accidental random changes.
A holistic approach towards the validation and legitimisation of information systems
Authors: Petkova O. , Petkov D.
Published: April 2003

The research aims to show that validation and legitimisation of an information systems (IS) project need to be treated simultaneously to improve software project management. A starting assumption is that traditional aspects of model validity and legitimisation in operational research can be applicable to the field of IS. However, non‐traditional types of IS are more suitable to be viewed from an interpretive viewpoint. Validation is explored both from hard systems and also from soft systems point of view. Some extensions on the notion of validation for soft systems are provided for that purpose. Issues regarding both validation and legitimisation in IS are illustrated on a case study regarding the management of an academic research management IS project. Issues related both validation and legitimisation in IS are illustrated on a case study regarding the management of an academic research IS project. The latter had eventually to be abandoned. The case study shows how the non‐adherence to the principles of validation and legitimisation lead to that situation.
Development of an autonomous spacecraft for planetary exploration
Authors: Radice Gianmarco
Published: April 2003

The purpose of this paper is to present a new approach in the concept and implementation of autonomous micro‐spacecraft. The one true “artificial agent” approach to autonomy requires the micro‐spacecraft to interact in a direct manner with the environment through the use of sensors and actuators. As such, little computational effort is required to implement such an approach, which is clearly of great benefit for limited micro‐satellites. Rather than using complex world models, which have to be updated, the agent is allowed to exploit the dynamics of its environment for cues as to appropriate actions to achieve mission goals. The particular artificial agent implementation used here has been borrowed from studies of biological systems, where it has been used successfully to provide models of motivation and opportunistic behaviour. The so‐called “cue‐deficit” action selection algorithm considers the micro‐spacecraft to be a non‐linear dynamical system with a number of observable states. Using optimal control theory rules are derived which determine which of a finite repertoire of behaviours the satellite should select and perform. The principal benefits of this approach is that the micro‐spacecraft is endowed with self‐sufficiency, defined here to be the ability to achieve mission goals, while never placing itself in an irrecoverable position.
Life‐long creation in the prevention of premature aging
Authors: Sabelli H. , Sugerman A.
Published: April 2003

Aging is a continuous process of growth and decay, both of which start at birth and continue throughout life. Activity develops muscles and neurons; inactivity atrophies them. Here we propose lifelong creative activity as a method to deal with aging. Decreased creative and learning capacity is a self‐fulfilling prophecy. Changing personal perceptions and expectations can promote health care and productive behavior.
Inside communication in nanostructured evolutionary automata — nanophysics and an information concept for viable technologies
Authors: Santoli Salvatore
Published: April 2003

On the background of previous research work concerning a nanoscale approach to a theory of biomimetic evolutionary systems and biomimetic information processing it is shown that strictly formal‐logic based, “hard‐wired” electronic hardware misses the very physical nature of bioevolvability. A new, physics‐base concept of information, and a new concept of hierarchical, open and dissipative “evolware”, much like biosystems “wetware”, are required for developing an actually biomimetic “evolutionary automata” technology, but a basic inter‐ and intra‐level communication problem is shown to affect the whole automaton's nanostructure. The problem consists in the difficulty of setting forth causal links bridging the whole hierarchy, from the nanoscale up to the macroscopic structure‐functions.
Systems dynamics modelling, simulation and optimization of integrated urban systems: a soft computing approach
Authors: Satsangi P.S. , Mishra D.S. , Gaur S.K. , Singh B.K. , Jain D.K.
Published: April 2003

A systems dynamics (SD) simulation model has been developed to analyse dynamics of system behaviour in terms of various performance indicators representing city problems, on one hand, and city development, on the other, with three types of policy interventions: changes in the level of sectoral activities, structural changes in different sectors; and changes in the tolerable city problems index. An artificial neurals network (ANN) model has been successfully trained and used as a quick response model for fast feature extraction of the dynamics of the integrated urban energy‐economy‐environment system such that the outputs are within reasonable acceptable error for values of inputs covered by the input space of training patterns. For the sake of further convenience and effectiveness in policy decision making, optimised simulation trajectories are generated by applying genetic algorithms (GAs) search and optimisation methods for alternative policy scenarios of input variables. An application is shown in the context of the city of Jaipur.
On the criterion of optimal product structure in the micro‐economic system (enterprise) and adjustment of product structure
Authors: Tao Lixin
Published: April 2003

In order to make a thorough inquiry into the criterion of optimal product structure in the micro‐economic system (enterprise), this paper has proposed and demonstrated the benefit‐type linear programming model, and based on it, the concepts of enterprise's product structure, feasible structure and optimal structure have been discussed and the criterion of optimal structure has been revealed. In this paper, the methods of simplex iteration and sensitivity analysis are both used to approach necessarily the adjustment of product structure under the circumstances of varied or invaried environment inside and outside the system, and as a final, it has come to a conclusion that the variation of resource price vector P would not affect the optimal product structure in enterprise, but the variation of resource‐constrained vector b will cause negative effects both on optimal product structure in enterprise and on determination of criterion for optimal structure.
Swarm based study on spatial‐temporal emergence in flood
Authors: Wei Yiming , Zhang Linpeng , Fan Ying
Published: April 2003

In complex adaptive system (CAS), the complex behavior of system is emerged from the bottom, that agents’ adaptability bottom‐up the complexity of the entire system. This idea can be simulated by the method of computer aid simulation. SWARM, which is developed by Santa Fe Institute, is such a tools kit based on the bottom‐up modeling method that can be used in CAS simulation on computer. This paper presented a Swarm based simulation platform for the study on complexity in flood disaster. Its application is illustrated with a SWARM based model and program for simulating spatial and temporal emergence of flooding. This model offers virtually unlimited possibilities to simulate the emergence of flooding. Some rules have been elicited from the experimental results, which could provide useful information for the disaster reduction and management.
On stochastic optimal control for stock price volatility
Authors: Yi‐rong Ying , Yi Lin , Chong‐feng Wu
Published: April 2003

The dynamic measure of risk problem in a incomplete market is discussed when stock appreciation rates are uncertain. Meanwhile, a related stochastic game problem is studied. The value of a stochastic optimal control is regarded as a reasonable measure of the risk. The form of the optimal objective is obtained by employing the tools of BSDE theory.
Pansystems GuanKong technology and information quantization
Authors: Hong‐Yi Yu , Feng Leon (Xiangjun) , Ran Yu
Published: April 2003

A basic pansystems scientific view about the physical world is presented. The principle and methodology of pansystems GuanKong technology are introduced. Simple metrics for the quantization of information, risk and gain by comparison (GBC) are established and discussed, and the practical and simple membership function which realizes the transformation from qualitative to quantitative order are given, and an example showing the pansystems GuanKong in detail is also given.
Randomization and eventual reordering: a number theoretic approach
Authors: Zeeberg Barry
Published: April 2003

Shuffling a deck of cards is normally used for randomization. An imperfect shuffle would not produce the desired randomization, since there would be residual correlation with the original order. On the other hand, from the classical card magic literature it is known that eight successive perfect riffle shuffles returns the deck to the original order. The question addressed here is whether this observation is in fact unusual and surprising. Although a general closed‐form analytical solution does not appear to be possible, a simple program could be written to determine deck sizes and numbers of shuffles for which eventual reordering occurs. This computational approach correctly predicts the original observation of eight shuffles for a deck of 52 cards; in fact if the trivial solutions of integral multiples of eight shuffles are discarded, eight shuffles appears to be the unique solution for a 52 card deck.
Experimental and Analytical Study of Cold Bending Process for Pipelines
Authors: Fukuda Naoki , Yatabe Hiroshi , Kawaguchi Shinobu , Watanabe Takahito , Masuda Tomoki
Published: April 2003

The behavior during the cold bending of pipelines was experimentally and analytically investigated. Full-scale cold bending experiments were performed on API X60 and X80 grade line pipes. Finite element (FE) analyses simulated the cold bending process by considering the contact interactions between a pipe and the components of the bending machine. The results of the simulation were in good agreement with the full-scale experiments. The stress-strain relationship and yield to tensile ratio (Y/T) had no obvious effect on the strain distribution after cold bending. The tensile tests quantitatively evaluated the decrease in the yield stress along the longitudinal direction on the cold bends due to the Bauschinger effect.
Multiple Stable/Unstable Equilibria of a Cylinder in the Wake of an Upstream Cylinder
Authors: Wu Wusheng , Huang Shan , Barltrop Nigel
Published: April 2003

The static equilibrium position and its associated dynamic stability of a cylinder situated in the wake of an upstream cylinder is investigated in this paper. Both the upstream and downstream cylinders are elastically mounted on springs to allow for streamwise and transverse displacements. Due to the wake effect the downstream cylinder is subject to a lift force as well as a drag. It is shown that under certain flow conditions there exist multiple stable and unstable equilibria for the downstream cylinder. There also exist a critical flow velocity and once this velocity is exceeded no equilibrium positions of the downstream cylinder can be found, which suggests a likely occurrence of clashing between the two cylinders.
The Influence of the Wave Climate on the Design and Annual Production of Electricity by OWC Wave Power Plants
Authors: Sarmento Anto´nio J. N. A. , e Melo Ana Brito , Pontes Maria Teresa
Published: April 2003

The present paper deals with the influence of wave climate on the design specifications of the power take-off equipment and annual production of electricity by OWC wave power plants. A wave-to-wire model of the Pico plant developed in previous studies was used. In addition to the Pico, six other wave climates characteristic of areas in the northeastern Atlantic Ocean were used, with annual wave power levels ranging from about 14 kW/m to 54 kW/m. Apart from Pico, the remaining sites were selected in pairs with similar wave power levels but different variability, thus enabling the influence of these two wave climate parameters to be assessed separately. An analysis of the influence of the detail of wave height and period statistics on the annual production of electricity is also presented.
A Graph-Based Approach for Capturing the Capability Envelope of a Machining Process
Authors: Huang Zhengdong , Yip-Hoi Derek , Zhou Ji
Published: April 2003

In this paper, we present a method to determine the capability envelope of a machining process which consists of a sequence of parameterized machining operations. First, operations as well as workpiece in a machining process are represented using a Parametric Feature Relational Graph (P-FRG). Second, the workpiece P-FRG within a process is updated step-by-step by mixing with operation P-FRGs as the operations in the process are successively applied to it. Since alternative setups may exist for an operation, a tree of workpiece P-FRGs can be generated for a process. All the P-FRGs at the leaf nodes of the tree together form the capability envelope of the machining process, that is, the envelope of the parts that can be produced using the process from a given initial workpiece. The parameter mappings, from the parameters of a machining process to the parameters of a part P-FRG in the capability envelope, are also given in this paper. The capability envelope can be applied to the integration of part design and process planning.
Dynamic Modeling for Machine Tool Thermal Error Compensation
Authors: Yang Hong , Ni Jun
Published: April 2003

This paper proposes a new thermal error modeling methodology called the Dynamic Thermal Error Modeling which improves the accuracy and robustness of the machine tool thermal error model. The characteristics of the thermoelastic system are investigated from the dynamic system viewpoint. The pseudo-hysteresis effect is revealed to be the major factor causing poor robustness of the conventional static thermal error model. System identification theory is applied to build the dynamic thermal error model for machine tool thermal error on-line prediction. The modeling procedure for the linear Output Error (OE) model is illustrated using simulation work for both one-dimensional spindle and two-dimensional machine structure thermal deformations. Model performance evaluation through spindle experiments shows that the thermal error dynamic model has advantages over the conventional static model in terms of model accuracy and robustness.