bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of the optical and electronic properties of Ge2Sb2Te5 phase change material in its amorphous, cubic, and hexagonal phases
Authors: Lee Bong-Sub , Abelson John R. , Bishop Stephen G. , Kang Dae-Hwan , Cheong Byung-ki , Kim Ki-Bum
Published: April 2005

Ge – Sb – Te alloys are widely used for data recording based on the rapid and reversible amorphous-to-crystalline phase transformation that is accompanied by increases in the optical reflectivity and the electrical conductivity. However, uncertainties about the optical band gaps and electronic transport properties of these phases have persisted because of inappropriate interpretation of reported data and the lack of definitive analytical studies. In this paper we characterize the most widely used composition, Ge2Sb2Te5, in its amorphous, face-centered-cubic, and hexagonal phases, and explain the origins of inconsistent or unphysical results in previous reports. The optical absorption in all of these phases follows the relationship αhν∝(hν−Egopt)2, which corresponds to the optical transitions in most amorphous semiconductors as proposed by Tauc, Grigorovici, and Vancu [Tauc et al., Phys. Status Solidi 15, 627 (1966)], and to those in indirect-gap crystalline semiconductors. The optical band gaps of the amorphous, face-centered-cubic, and hexagonal phases are 0.7, 0.5, and 0.5eV, respectively. The subgap absorption in the amorphous phase shows an exponential decay with an Urbach slope of 81meV. We measured the photoconductivity of amorphous Ge2Sb2Te5 and determined a mobility-lifetime product of 3×10−9cm2∕V. The spectral photoconductivity shows a threshold at about 0.7eV, in agreement with our analysis of the optical band gap. The face-centered-cubic and hexagonal phases are highly conductive and do not show freeze-out; even at 5K the density of free carriers remains at 1019–1020cm−3, so these are degenerate semiconductors in which the Fermi level resides inside a band. In the hexagonal phase, the effect of free electrons on the Hall coefficient is significant at high temperatures. When the Hall data are fitted using the two-carrier analysis, the hole mobility is found to decrease slowly with temperature, as expected. The considerations discussed in this paper can be readily applied to study related chalcogenide materials.
Equation-of-motion coupled-cluster methods for ionized states with an approximate treatment of triple excitations
Authors: Bomble Yannick J. , Saeh Jamal C. , Stanton John F. , Szalay Péter G. , Kállay Mihály , Gauss Jürgen
Published: April 2005

The accuracy of geometries and harmonic vibrational frequencies is evaluated for two equation-of-motion ionization potential coupled-cluster methods including CC3 and CCSDT-3 triples corrections. The first two Σ states and first Π state of the N2+,CO+, CN, and BO diatomic radicals are studied. The calculations show a tendency for the CC3 variant to overestimate the bond lengths and to underestimate the vibrational frequencies, while the CCSDT-3 variant seems to be more reliable. It is also demonstrated that the accuracy of such methods is comparable to sophisticated traditional multireference approaches and the full configuration interaction method.
Depth analysis of the in-plane lattice constants in compressively strained La0.67Ca0.33MnO3 thin films
Authors: Petit M. , Rajeswari M. , Biswas A. , Greene R. L. , Venkatesan T. , Martínez-Miranda L. J.
Published: April 2005

We have performed depth profile analyses of the lattice parameters in epitaxial thin films of La0.67Ca0.33MnO3 to understand the evolution of strain relaxation processes in these materials. The analyses were done using grazing incidence x-ray scattering on films of different thicknesses on (100)-oriented LaAlO3 with a lattice mismatch of −2%. We find that such films exhibit two and sometimes up to three in-plane strained lattice constants, corresponding to a slight orthorhombic distortion of the crystal, as well as near-surface lattice relaxation. As a function of film thickness, we find that the strain is in the same order of magnitude up to a thickness of 70–80nm, after which the strain begins to relax towards the bulk value of the lattice parameters. In addition, we find a depth behavior in the strain which is consistent with the formation of nonuniformly strained islands in the sample.
Shear softening and structure in a simulated three-dimensional binary glass
Authors: Albano Fabio , Falk Michael L.
Published: April 2005

Three-dimensional model binary glasses produced by quenching from a range of liquid temperatures were tested in shear over a range of strain rates using molecular-dynamics techniques. Tests were performed under constant volume and constant pressure constraints. The simulations revealed a systematic change in short-range order as a function of the thermal and strain history of the glass. While subtle signs of differences in short-range order were evident in the pair distribution function, three-body correlations were observed to be markedly more sensitive to the changes in structure. One particular structural parameter, the number of aligned three-atom clusters, was analyzed as a function of the degree of supercooling, the strain and the strain rate. The glasses quenched from the supercooled liquid regime were observed to contain an initally higher number of such clusters, and this number decreased under shear. Those quenched from high-temperature equilibrium liquids contained lower numbers of such clusters and these increased or remained constant under shear. The glasses quenched from the supercooled liquid regime showed higher strength, more marked shear softening, and an increased propensity toward shear localization. The evolution of this structural parameter depended both on its initial value and on the imposed shear rate. These results were observed to hold for simulations performed under both constant density and constant pressure boundary conditions.
Response to “Comment on ‘Exact solutions of cylindrical and spherical dust ion acoustic waves’” [Phys. Plasmas 12, 054701 (2005)]
Authors: Sahu Biswajit , Roychoudhury Rajkumar
Published: April 2005

It is shown that the similarity solution of cylindrical Korteweg–de Vries equation given by Tian and Gao in their Comment on our paper can be obtained by the group analysis method using the same generators given in the paper by Sahu and Roychoudhury.
Fractional Fokker–Planck equation for fractal media
Authors: Tarasov Vasily E.
Published: April 2005

We consider the fractional generalizations of equation that defines the medium mass. We prove that the fractional integrals can be used to describe the media with noninteger mass dimensions. Using fractional integrals, we derive the fractional generalization of the Chapman–Kolmogorov equation (Smolukhovski equation). In this paper fractional Fokker–Planck equation for fractal media is derived from the fractional Chapman–Kolmogorov equation. Using the Fourier transform, we get the Fokker–Planck–Zaslavsky equations that have fractional coordinate derivatives. The Fokker–Planck equation for the fractal media is an equation with fractional derivatives in the dual space.
Temperature dependence of Nd3+↔Yb3+ energy transfer in the YAl3(BO3)4 nonlinear laser crystal
Authors: Ramirez M. O. , Jaque D. , Bausá L. E. , Martín I. R. , Lahoz F. , Cavalli E. , Speghini A. , Bettinelli M.
Published: April 2005

The temperature dependence of the Nd3+→Yb3+ energy-transfer rate in the YAl3(BO3)4 nonlinear laser crystal has been investigated from the analysis of fluorescence decay curves recorded in the 10–600 K range. Three different regimes, independent on the dopant concentration, have been observed in the thermal behavior of the Nd3+→Yb3+ energy-transfer rate. By comparing experimental results with theoretical predictions based on the Dexter model [J. Chem. Phys. 21, 836 (1953)], the origin of these different regimes has been explained. In addition, the influence of temperature and of both Nd3+ and Yb3+ concentrations on the Nd3+←Yb3+ energy back-transfer rate has been also investigated, concluding that it is a migration-assisted energy-transfer process. Finally, the populations of both Nd3+ and Yb3+ metastable states achieved after continuous-wave Nd3+ excitation have been calculated and measured and results have been explained in terms of the thermal behavior of both forward- and back-transfer rates.
Manipulation of luminescence from CdSe nanoparticles by three-dimensional photonic crystal
Authors: Chuang C. M. , Lu W. B. , Su W. F. , Lin C. M. , Chen Y. F.
Published: April 2005

We have demonstrated that the luminescence properties of CdSe nanoparticles can be manipulated by self-assembled silica photonic crystal. When the emitting wavelength of nanoparticles matches the stop band of the photonic crystal, the photoluminescence of the CdSe nanoparticles can be greatly enhanced by up to five times. By changing the collection angle of photoluminescence measurements, the photoluminescence intensity of CdSe embedded in photonic crystal can also be controlled.
Photochromic silver nanoparticles fabricated by sputter deposition
Authors: Okumu J. , Dahmen C. , Sprafke A. N. , Luysberg M. , von Plessen G. , Wuttig M.
Published: April 2005

In this study a simple route to preparing photochromic silver nanoparticles in a TiO2 matrix is presented, which is based upon sputtering and subsequent annealing. The formation of silver nanoparticles with sizes of some tens of nanometers is confirmed by x-ray diffraction and transmission electron microscopy. The inhomogeneously broadened particle-plasmon resonance of the nanoparticle ensemble leads to a broad optical-absorption band, whose spectral profile can be tuned by varying the silver load and the annealing temperature. Multicolor photochromic behavior of this Ag–TiO2 system upon irradiation with laser light is demonstrated and discussed in terms of a particle-plasmon-assisted electron transfer from the silver nanoparticles to TiO2 and subsequent trapping by adsorbed molecular oxygen. The electron depletion in the nanoparticles reduces the light absorption at the wavelength of irradiation. A gradual recovery of the absorption band is observed after irradiation, which is explained with a slow thermal release of electrons from the oxygen trapping centers and subsequent capture into the nanoparticles. The recovery can be accelerated by ultraviolet irradiation; the explanation for this observation is that electrons photoexcited in the TiO2 are captured into the nanoparticles and restore the absorption band.
Mechanical force sensors using organic thin-film transistors
Authors: Darlinski Grzegorz , Böttger Ulrich , Waser Rainer , Klauk Hagen , Halik Marcus , Zschieschang Ute , Schmid Günter , Dehm Christine
Published: April 2005

The pressure dependence of pentacene (C22H14) transistors with solution-processed polyvinylphenol gate dielectric on glass substrates is investigated by applying uniaxial mechanical pressure with a needle. We found that organic thin-film transistors are sensitive to applied pressure inherently. The measurements reveal a reversible current dependence of the transfer characteristics where the drain current is switching between two states. Experimental and simulation results suggest that switch-on voltage and interface resistance are affected. The change takes seconds, hinting at trap states being responsible for the effect.
Versatile force–feedback manipulator for nanotechnology applications
Authors: Jobin Marc , Foschia Raphael , Grange Sébastien , Baur Charles , Gremaud Gérard , Lee Kyumin , Forró Laszlo , Kulik Andrzej
Published: April 2005

A nanoscale manipulation system has been designed and built through the integration of a force–feedback haptic device and a commercial atomic force microscope. The force–feedback interaction provides a very intuitive, efficient and reliable way for quick manipulation of nanoscale objects. Unlike other nanomanipulators, ours allows the user to feel the actual tip–sample interaction during the manipulation process. Various modes of manipulation have been implemented and evaluated. As a proof of concept, we show a contact-mode nanomanipulation of a carbon nanotube and a noncontact manipulation of silicon beads. In addition to nanomanipulation itself, all relevant signals can be recorded during the manipulation process which allows quantitative interpretation of nanomechanics experiments.
Synchrotron beamline for extreme-ultraviolet multilayer mirror endurance testing
Authors: Tarrio C. , Grantham S.
Published: April 2005

The lifetime of multilayer mirrors is an outstanding problem on the road to commercialization of extreme-ultraviolet (EUV) lithography. The mirrors are exposed to high-intensity EUV radiation in a vacuum with traces of water vapor and hydrocarbons. The combination of EUV and reactive species leads to chemical degradation of the mirror surfaces—carbon deposition and/or oxidation of the Si surface. In order to understand and quantify these processes, as well as to study mitigation schemes, we have constructed a dedicated synchrotron-based facility with the capability to deliver high-intensity EUV radiation in a variety of trace-gas atmospheres. The facility features a spherical Mo–Si coated mirror and a thin Be foil captured in a gate valve, which serves as both a spectral filter and vacuum seal. We will describe this facility and its performance.
Algebraic methods for diagonalization of a quaternion matrix in quaternionic quantum theory
Authors: Jiang Tongsong
Published: April 2005

By means of complex representation and real representation of a quaternion matrix, this paper studies the problem of diagonalization of a quaternion matrix, gives two algebraic methods for diagonalization of quaternion matrices in quaternionic quantum theory.
Preparation of nonconducting infrared-absorbing thin films
Authors: Gradhand Martin , Breitenstein Otwin
Published: April 2005

A simple procedure for preparing colloidal “black” bismuth films is introduced, which leaves the target cold and does not pollute the recipient. The Bi evaporation occurs in a closed box in the evaporation chamber with an internal radiation shield. The bismuth is evaporated from a tantalum boat at a residual air pressure of 2×102Pa. The resulting films with a thickness of about 10μm are structureless down to a spatial resolution of 5.6μm, they become electrically insulating after 48h storage time in air, and they show an IR absorbance of above 70% in the 3–5μm wavelength range. The films are easily removable in an ultrasonic water bath. Thus, these films are ideally appropriate to increase the IR emissivity of microelectronic structures in microthermal infrared failure analysis investigations such as lock-in thermography, as is demonstrated in an application example. The application of this film may improve the thermographic detection limit of heat sources below metallized areas by up to a factor of 10, leading to a saving in acquisition time by a factor of 100.
Direct sample positioning and alignment methodology for strain measurement by diffraction
Authors: Ratel N. , Hughes D. J. , King A. , Malard B. , Chen Z. , Busby P. , Webster P. J.
Published: April 2005

An ISO (International Organization for Standardization) TTA (Technology Trends Assessment) was published in 2001 for the determination of residual stress using neutron diffraction which identifies sample alignment and positioning as a key source of strain measurement error. Although the measurement uncertainty by neutron and synchrotron x-ray diffraction for an individual measurement of lattice strain is typically of the order of 10–100×10−6, specimens commonly exhibit strain gradients of 1000×10−6mm−1 or more, making sample location a potentially considerable source of error. An integrated approach to sample alignment and positioning is described which incorporates standard base-plates and sample holders, instrument alignment procedures, accurate digitization using a coordinate measuring machine and automatic generation of instrument control scripts. The methodology that has been developed is illustrated by the measurement of the transverse residual strain field in a welded steel T-joint using neutrons.
Development of low noise cantilever deflection sensor for multienvironment frequency-modulation atomic force microscopy
Authors: Fukuma Takeshi , Kimura Masayuki , Kobayashi Kei , Matsushige Kazumi , Yamada Hirofumi
Published: April 2005

We have developed a low noise cantilever deflection sensor with a deflection noise density of 17fm∕Hz by optimizing the parameters used in optical beam deflection (OBD) method. Using this sensor, we have developed a multienvironment frequency-modulation atomic force microscope (FM-AFM) that can achieve true molecular resolution in various environments such as in moderate vacuum, air, and liquid. The low noise characteristic of the deflection sensor makes it possible to obtain a maximum frequency sensitivity limited by the thermal Brownian motion of the cantilever in every environment. In this paper, the major noise sources in OBD method are discussed in both theoretical and experimental aspects. The excellent noise performance of the deflection sensor is demonstrated in deflection and frequency measurements. True molecular-resolution FM-AFM images of a polydiacetylene single crystal taken in vacuum, air, and water are presented.
Scheme for precise correction of orbit variation caused by dipole error field of insertion device
Authors: Nakatani T. , Agui A. , Aoyagi H. , Matsushita T. , Takao M. , Takeuchi M. , Yoshigoe A. , Tanaka H.
Published: April 2005

We developed a scheme for precisely correcting the orbit variation caused by a dipole error field of an insertion device (ID) in a storage ring and investigated its performance. The key point for achieving the precise correction is to extract the variation of the beam orbit caused by the change of the ID error field from the observed variation. We periodically change parameters such as the gap and phase of the specified ID with a mirror-symmetric pattern over the measurement period to modulate the variation. The orbit variation is measured using conventional wide-frequency-band detectors and then the induced variation is extracted precisely through averaging and filtering procedures. Furthermore, the mirror-symmetric pattern enables us to independently extract the orbit variations caused by a static error field and by a dynamic one, e.g., an error field induced by the dynamical change of the ID gap or phase parameter. We built a time synchronization measurement system with a sampling rate of 100Hz and applied the scheme to the correction of the orbit variation caused by the error field of an APPLE-2-type undulator installed in the SPring-8 storage ring. The result shows that the developed scheme markedly improves the correction performance and suppresses the orbit variation caused by the ID error field down to the order of submicron. This scheme is applicable not only to the correction of the orbit variation caused by a special ID, the gap or phase of which is periodically changed during an experiment, but also to the correction of the orbit variation caused by a conventional ID which is used with a fixed gap and phase.
Ultralow-power all-optical switching
Authors: Soljačić Marin , Lidorikis Elefterios , Joannopoulos J. D. , Hau Lene Vestergaard
Published: April 2005

Using analytical modeling and detailed numerical simulations, we investigate properties of hybrid systems of photonic crystal microcavities which incorporate a highly nonlinear ultraSlow light medium. We demonstrate that such systems, while being miniature in size (order wavelength), and integrable, could enable ultrafast nonlinear all-optical switching at ultralow (even single photon) energy levels.
Optical properties of GaN quantum dots grown on nonpolar (11-20) SiC by molecular-beam epitaxy
Authors: Founta S. , Rol F. , Bellet-Amalric E. , Bleuse J. , Daudin B. , Gayral B. , Mariette H. , Moisson C.
Published: April 2005

We report on nonpolar GaN quantum dots embedded in AlN, grown on (11-20) 6H–SiC by plasma-assisted molecular-beam epitaxy. These dots are aligned in the growth plane and present a constant aspect ratio of 10. Their optical properties were studied as a function of GaN coverage. Especially, the variation of their emission energy as compared to that of (0001) GaN quantum dots is a clear fingerprint of the reduced internal electric field present in these nonpolar nanostructures. Time-resolved spectroscopy confirmed this result by revealing lifetimes in the few 100 ps range in contrast to the much longer ones obtained for the (0001) GaN quantum dots.
Characteristics of unannealed ZnMgO∕ZnO p-n junctions on bulk (100) ZnO substrates
Authors: Yang Hyucksoo , Li Y. , Norton D. P. , Pearton S. J. , Jung Soohwan , Ren F. , Boatner L. A.
Published: April 2005

Zn 0.9 Mg 0.1 O ∕ Zn O  p-n junctions were grown by pulsed laser deposition at ⩽500°C on bulk n-type, (100), nonpolar, a-plane ZnO substrates. No postgrowth annealing was performed, with the P-doped ZnMgO showing p-type conductivity (hole density ∼1016cm−3, mobility ∼6cm2V−1s−1) in the as-grown state. Front-to-back p-n junctions were fabricated with Ni∕Au used as the p-Ohmic contact and Ti∕Au as the backside n-Ohmic contact. The p contacts showed improved characteristics after annealing up to 400°C, but the n contacts were Ohmic as deposited. The junctions showed rectifying behavior up to 200°C. The forward turn-on voltage was ∼6.5V at 25°C. The simple, low-temperature growth and processing sequence show the promise of ZnO for applications in transparent electronics and UV light emitters.
Self-heating study of an AlGaN∕GaN-based heterostructure field-effect transistor using ultraviolet micro-Raman scattering
Authors: Ahmad I. , Kasisomayajula V. , Holtz M. , Berg J. M. , Kurtz S. R. , Tigges C. P. , Allerman A. A. , Baca A. G.
Published: April 2005

We report micro-Raman studies of self-heating in an AlGaN∕GaN heterostructure field-effect transistor using below (visible 488.0nm) and near (UV 363.8nm) GaN band-gap excitation. The shallow penetration depth of the UV light allows us to measure temperature rise (ΔT) in the two-dimensional electron gas (2DEG) region of the device between drain and source. Visible light gives the average ΔT in the GaN layer, and that of the SiC substrate, at the same lateral position. Combined, we depth profile the self-heating. Measured ΔT in the 2DEG is consistently over twice the average GaN-layer value. Electrical and thermal transport properties are simulated. We identify a hotspot, located at the gate edge in the 2DEG, as the prevailing factor in the self-heating.
Nitride deep-ultraviolet light-emitting diodes with microlens array
Authors: Khizar M. , Fan Z. Y. , Kim K. H. , Lin J. Y. , Jiang H. X.
Published: April 2005

We report on the fabrication of 280-nm AlGaN-based deep-ultraviolet light-emitting diodes (UV LEDs) on sapphire substrates with an integrated microlens array. Microlenses with a diameter of 12μm were fabricated on the sapphire substrate by resist thermal reflow and plasma dry etching. LED devices were flip-chip bonded on high thermal conductive AlN ceramic submounts to improve the thermal dissipation, and the emitted UV light was extracted through the sapphire substrates. With the integrated microlens array, a 55% enhancement in the output power at 20-mA dc driving was achieved compared with the same LED without microlens. The light extraction enhancement is the result of the reduced internal reflections of the light caused by the microlens surface profile.
Size dependence of initial polarization direction in nanosized epitaxial PbTiO3 islands fabricated by hydrothermal epitaxy below Curie temperature
Authors: Ahn S. H. , Jung W. W. , Choi S. K.
Published: April 2005

Nanosized epitaxial PbTiO3 (PTO) islands with a mono c domain were fabricated via self-assembly on a Nb-SrTiO3 (NSTO) substrate at 160 °C by hydrothermal epitaxy without undergoing the paraelectric to ferroelectric phase transition. The direction of the polarization at the as-fabricated state was observed with an island size up to a lateral area of 104nm2 and thickness of 12 nm (determined by atomic force microscope) using a piezoresponse force microscope. We found a critical size below which the negative polarization is stable at the as-fabricated state and above which the positive polarization is stable. This phenomenon was discussed under two assumptions: that the PTO islands are grown initially with positive polarization during fabrication, and the energy barrier for the transition from the positive polarization state to the negative polarization state is dependent on the ferroelectric island size.
Detection of halide ions with AlGaN∕GaN high electron mobility transistors
Authors: Kang B. S. , Ren F. , Kang M. C. , Lofton C. , Tan Weihong , Pearton S. J. , Dabiran A. , Osinsky A. , Chow P. P.
Published: April 2005

Al Ga N ∕ Ga N high electron mobility transistors (HEMTs) both with and without a Au gate are found to exhibit significant changes in channel conductance upon exposing the gate region to various halide ions. The polar nature of the halide ions leads to a change of surface charge in the gate region on the HEMT, producing a change in the surface potential at the semiconductor∕liquid interface. HEMTs with a Au-gate electrode not only doubled the sensitivity of changing the channel conductance as compared to gateless HEMT, but also showed the opposite conductance behavior. When anions adsorbed on the Au, they produced a counter charge for electrovalence. These anions drag some counter ions from the bulk solution or create an image positive charge on the metal for the required neutrality. The gateless HEMTs can be used as sensors for a range of chemicals through appropriate modification with covalently bonded halide functional groups on the Au surface. This creates many possibilities to functionalize the surface for a wide range of integrated biological, chemical, and fluid monitoring sensors.
Effector CD8+T cells recovered from an influenza pneumonia differentiate to a state of focused gene expression
Authors: Marshall Dana R. , Olivas Elvia , Andreansky Samita , La Gruta Nicole L. , Neale Geoff A. , Gutierrez Astrid , Wichlan David G. , Wingo Suzette , Cheng Cheng , Doherty Peter C. , Turner Stephen J.
Published: April 2005

The restriction of influenza A virus replication to mouse respiratory epithelium means that this host response is anatomically compartmentalized, on the one hand, to sites of T cell stimulation and proliferation in the secondary lymphoid tissue and, on the other hand, to the site of effector T cell function and pathology in the pneumonic lung. Thus, it is hardly surprising that virus-specific CD8+T cells recovered by bronchoalveolar lavage (BAL) from the infected respiratory tract seem more “activated” in terms of both cytolytic activity and cytokine production than those cells isolated from the spleen. The present analysis uses Affymetrix microarray technology to compare profiles of gene expression in these two lineage-related, yet anatomically separate, lymphocyte populations. Ninety differentially expressed genes were identified for influenza-specific CD8+DbNP366+T cells obtained directlyex vivoby BAL or spleen disruption, with nine genes being further analyzed by quantitative, real-time PCR at the population level. Integrin αE, for example, was shown by Affymetrix and real-time mRNA analyses and then by single-cell PCR and protein staining to be present at a much higher prevalence on the BAL CD8+DbNP366+set. The unpredicted finding, however, was that mRNA expression for 75% of the 90 genes was lower in T cells from the BAL than from the spleen. Apparently, the localization of virus-specific CD8+T cells to the site of virus-induced pathology is associated with a narrowing, or “focusing,” of gene expression that favors enhanced effector function in the damaged, “high-antigen load” environment of the pneumonic lung.
Direct activation of fission yeast adenylate cyclase by the Gpa2 Gα of the glucose signaling pathway
Authors: Ivey F. Douglas , Hoffman Charles S.
Published: April 2005

G protein-mediated signaling is implicated in yeast and fungal cAMP pathways. By two-hybrid screens and pull-down experiments, we show that the fission yeast Gpa2 Gα binds an N-terminal domain of adenylate cyclase, comprising a moderately conserved sequence within a region otherwise poorly related to other fungal adenylate cyclases. Overexpressing this domain in yeast perturbs cAMP signaling, which is restored by Gpa2 coexpression. Mutations affecting this domain, over 1,100 residues from the catalytic domain, alter glucose-triggered cAMP signaling. This is evidence for direct activation of adenylate cyclase by a fungal G protein and suggests a distinct activation mechanism from that of mammals.
Evaluation of perennial herbaceous legumes with different phosphorus sources and levels in a Brazilian Ultisol
Authors: Espindola J.A.A. , Guerra J.G.M. , Almeida D.L. , Teixeira M.G. , Urquiaga S.
Published: April 2005

This study was carried out under field conditions with the aim of evaluating the period of time necessary for soil cover, dry matter production and accumulation of nutrients by perennial herbaceous legumes with different phosphorus sources at different levels. Four legumes were evaluated: calopo (Calopogonium mucunoidesDesv.), forage groundnut (Arachis pintoiKrap. & Greg.), siratro (Macroptilium atropurpureum(OC.) Urb.) and tropical kudzu (Pueraria phaseoloides(Roxb.) Benth.). Each of these species received different phosphorus (P) sources and levels: no phosphate fertilization; 44 and 88 kg of P ha−1applied as rock phosphate; and 44 kg of P ha−1as triple superphosphate. Calopo, siratro and tropical kudzu completely covered the soil surface 129 days before forage groundnut. Phosphate fertilization did not increase the dry matter production of any species. The legumes forage groundnut, siratro and tropical kudzu showed desirable characteristics that promote their use as cover crops, such as high dry matter production and shoot accumulation of nitrogen (N) and potassium (K). Forage groundnut had the highest proportion of N derived from the atmosphere at the end of the rainy season, while there were no significant differences between the legumes at the end of the dry season. There was an elevation of soil pH and calcium+magnesium (Ca+Mg) contents, associated with a reduction of aluminum (Al) content, in the surface soil layer (0–5 cm) for siratro in relation to groundnut and tropical kudzu. Tropical kudzu promoted higher soil organic C contents when compared to groundnut.
Perennial crops and endogenous nutrient supplies
Authors: Crews T.E.
Published: April 2005

Perennial cropping systems may achieve significant improvement over annual systems in the synchrony between crop nutrient demands and nutrient supplies. Improvements in nutrient synchrony would result in the reduction of nutrient losses and their associated environmental impacts. A perennial system with high levels of synchrony would also require fewer nutrient inputs, such that it may be possible to develop an agriculture that functions mostly, if not entirely, on nutrient inputs from endogenous sources (i.e., weathering of primary and secondary minerals and biological nitrogen fixation). In this paper I describe three realms of research that will inform the development of relatively high-yielding grain production systems grown on endogenous nutrient supplies: (1) improvement of nutrient synchrony through the development of perennial crops; (2) identification of soils that are in a high nutrient release phase of pedogenesis, which could balance the export of rock-derived nutrients in crop harvests; and (3) optimization of legume density, harvest index and percent nitrogen derived from the atmosphere (%Ndfa) to achieve adequate nitrogen inputs through biological fixation.
Single cell analysis shows decreasing FoxP3 and TGFβ1 coexpressing CD4+CD25+ regulatory T cells during autoimmune diabetes
Authors: Pop Shannon M. , Wong Carmen P. , Culton Donna A. , Clarke Stephen H. , Tisch Roland
Published: April 2005

Natural CD4+CD25+ regulatory T (CD4+CD25+ T reg) cells play a key role in the immunoregulation of autoimmunity. However, little is known about the interactions between CD4+CD25+ T reg cells and autoreactive T cells. This is due, in part, to the difficulty of using cell surface markers to identify CD4+CD25+ T reg cells accurately. Using a novel real-time PCR assay, mRNA copy number of FoxP3, TGFβ1, and interleukin (IL)-10 was measured in single cells to characterize and quantify CD4+CD25+ T reg cells in the nonobese diabetic (NOD) mouse, a murine model for type 1 diabetes (T1D). The suppressor function of CD4+CD25+CD62Lhi T cells, mediated by TGFβ, declined in an age-dependent manner. This loss of function coincided with a temporal decrease in the percentage of FoxP3 and TGFβ1 coexpressing T cells within pancreatic lymph node and islet infiltrating CD4+CD25+CD62Lhi T cells, and was detected in female NOD mice but not in NOD male mice, or NOR or C57BL/6 female mice. These results demonstrate that the majority of FoxP3-positive CD4+CD25+ T reg cells in NOD mice express TGFβ1 but not IL-10, and that a defect in the maintenance and/or expansion of this pool of immunoregulatory effectors is associated with the progression of T1D.
Detection of Airborne Severe Acute Respiratory Syndrome (SARS) Coronavirus and Environmental Contamination in SARS Outbreak Units
Authors: Booth Timothy F. , Kournikakis Bill , Bastien Nathalie , Ho Jim , Kobasa Darwyn , Stadnyk Laurie , Li Yan , Spence Mel , Paton Shirley , Henry Bonnie , Mederski Barbara , White Diane , Low Donald E. , McGeer Allison , Simor Andrew , Vearncombe Mary , Downey James , Jamieson Frances B. , Tang Patrick , Plummer Frank
Published: April 2005

Severe acute respiratory syndrome (SARS) is characterized by a risk of nosocomial transmission; however, the risk of airborne transmission of SARS is unknown. During the Toronto outbreaks of SARS, we investigated environmental contamination in SARS units, by employing novel air sampling and conventional surface swabbing. Two polymerase chain reaction (PCR)–positive air samples were obtained from a room occupied by a patient with SARS, indicating the presence of the virus in the air of the room. In addition, several PCR-positive swab samples were recovered from frequently touched surfaces in rooms occupied by patients with SARS (a bed table and a television remote control) and in a nurses’ station used by staff (a medication refrigerator door). These data provide the first experimental confirmation of viral aerosol generation by a patient with SARS, indicating the possibility of airborne droplet transmission, which emphasizes the need for adequate respiratory protection, as well as for strict surface hygiene practices
Wnt signaling in the intestinal epithelium: from endoderm to cancer
Authors: Gregorieff Alex , Clevers Hans
Published: April 2005

The Wnt pathway controls cell fate during embryonic development. It also persists as a key regulator of homeostasis in adult self-renewing tissues. In these tissues, mutational deregulation of the Wnt cascade is closely associated with malignant transformation. The intestinal epithelium represents the best-understood example for the closely linked roles of Wnt signaling in homeostatic self-renewal and malignant transformation. In this review, we outline current understanding of the physiological role of Wnt signaling in intestinal biology. From this perspective, we then describe how mutational subversion of the Wnt cascade leads to colorectal cancer.
Medial floor plate formation in zebrafish consists of two phases and requires trunk-derived Midkine-a
Authors: Schäfer Matthias , Rembold Martina , Wittbrodt Joachim , Schartl Manfred , Winkler Christoph
Published: April 2005

The medial floor plate (MFP) organizes the specification of neurons and outgrowth of axons in the ventral spinal cord of vertebrates. We show that the growth factor Midkine-a, expressed in the paraxial mesoderm, is required for formation of the MFP in zebrafish. Our epistatic analyses demonstrate that development of MFP comprises two independent sequential phases. Following initial MFP induction in the gastrula organizer, Midkine-a regulates allocation of MFP cells during subsequent development. Thus in zebrafish, trunk-derived signals are required for complete MFP formation from a common pool of organizer-derived midline precursor cells.
Investment Decisions for Robotics Development
Authors: Kim Jae , Kleiner Brian H.
Published: April 2005

Discusses the factors involved in the decision‐making process about
investment in robotics. Examines levels of automation in organizations,
financial analysis tools such as ROI and NPV, competitive benefits of
robotics, and non‐financial aspects of automation. Concludes that the
decision will depend on the organization′s strategic goals, since
financial analysis provides incomplete consideration of all factors.
An introduction to a simple modelling tool to evaluate the annual energy consumption and carbon dioxide emissions from non‐domestic buildings
Authors: Frame Ian
Published: April 2005

Purpose

This paper describes an introduction to a simple modelling tool for designers of environmentally sensitive buildings.

Design/methodology/approach

The theoretical basis of the program is explained with examples given of typical program output.

Findings

The package can be used as an environmental simulator of a building's energy consumption and energy‐related carbon dioxide emissions. It is specifically designed to help meet the more stringent requirements of the Building Regulations for Fuel and Power L2 Approved Document, April 2002.

Practical implications

The designer can explore building size, shape, fenestration, orientation and fabric thermal properties to minimise a buildings' environmental effect. Aspects of heating, lighting, and natural and mechanical ventilation with heat recovery systems can also be investigated. The spreadsheet is best used to check that buildings will comply with the regulations or used as an early design aid rather than a detailed design simulator of building performance. The program should therefore be of particular interest to architects, building surveyors and building control officers rather than building service engineers.

Originality/value

Describes an innovative approach to thermal design.
Developing a new understanding of markets: reinterpreting the 4Ps
Authors: Håkansson Håkan , Waluszewski Alexandra
Published: April 2005

Purpose

Arising from systematic empirical observations' aims to fulfil the need to review and refine existing market models and tools.

Design/methodology/approach

The article includes a critical analysis of existing marketing models, which mainly originate from the marketing mix (the 4Ps) model, which in turn has a clear micro economic “allocation of resources” background. Today, it is argued there are important changes in how markets work and what kind of marketing problems companies meet. Marketing is much more about dealing with dynamic issues where interaction is a key mechanism and where the value of resources are not given but can be developed. The basic marketing problem in many situations is consequently more about the development of resources than the allocation of them.

Findings

The 4Ps can still be a useful starting‐point in many analyses but then the model has to be reframed including how the 4Ps are conceptualized. In a first reinterpretation attempt, promotion (in terms of interaction) and place appear to be more essential for the creation of value, and product and price more an outcome of the same process.

Originality/value

The paper is a strong argument for an increased interest in developing new and alternative approaches to marketing where dynamic processes, including creation of resources and value, are focused.
The impact of horizontal and vertical connections on relationships' commitment and trust
Authors: Hadjikhani Amjad , Thilenius Peter
Published: April 2005

Purpose

While an ever‐increasing body of research on business networks has commented on vertically connected relationships, this study embeds the horizontally connected relationships. Constructed on business network theories the paper aims to add more knowledge on business networks by developing a connection model including both vertical and horizontal connections. The model aims to explore the impact of connections on focal business relationships. It differentiates connected relationships on the basis of their vertical and horizontal natures. The purpose is to grasp the impact of these different connected relationships on the focal business relationship. The focal relationship elements are defined by commitment and trust, which capture their properties from the dyadic interaction and the two types of connected relationships.

Design/methodology/approach

The paper tests the theoretical construction empirically. The empirical study is based on the IMP2 survey, utilizing information from extensive interviews with 138 firms regarding their relationships with important foreign customers.

Findings

The statistical findings in the form of a LISREL‐model clearly expose the impact of the horizontal connections and verify the validity of the theoretical model. It depicts that trust increase by vertical connections leading to increased commitment, thus strengthening the relationship while horizontal connection, on the contrary, weakens it. The facts also demonstrate how the horizontal connections impose effects on technological long‐term investments.

Originality/value

Marketing researchers advocating certain theoretical views are thereby required to observe respect for the market realities with which managers are confronted.
The changing nature of work in the age of e‐business
Authors: Landry Brett J.L. , Mahesh Sathi , Hartman Sandra
Published: April 2005

Purpose

This paper reviews recent discussions in the information technology (IT) and management literatures in order to consider their implications and to make a series of predictions about organizational life in the coming e‐business era.

Design/methodology/approach

A wide variety of recent discussions, ranging from comments by political/governmental figures to scholarly reports in the academic literature, are reviewed to consider their implications for the structure and shape of jobs and the job market.

Findings

The review provides evidence that developments in IT suggest that significant levels of job loss will occur in routine jobs, coupled with a pronounced movement towards a job market of flexible, fluid groups of highly‐skilled, entrepreneurial, consultant‐like employees.

Practical implications

Should this transition take place, there will be little place in the coming workforce for low‐skilled employees and a significant decrease in the overall size of the workforce. The jobs which remain will be those, which by their very nature, are creative and cannot be automated. Managers, governmental policy makers and the workforce in general will need to consider these implications.

Originality/value

Discussion and debate of the prospects need to begin immediately. This paper represents an effort to begin this process.
Adoption of virtual organization by Taiwanese electronics firms
Authors: Lin Liang‐Hung , Lu Iuan‐Yuan
Published: April 2005

Purpose

This empirical study aims to examine an organizational response to the needs of e‐business, virtual organization, and associated determinants of its successful adoption in the Taiwanese electronics industry.

Design/methodology/approach

The research examined a large sample of Taiwanese electronics companies. A research population of Taiwanese electronics companies was drawn from firms listed on both the TAIEX and the OTC markets and included 305 firms. Questionnaires were sent to firm administrators who were asked the degree to which the company had undertaken virtual organizational structuring that was enabled by information technologies.

Findings

The findings of this research reveal significant impacts of individual and organizational factors, but no effect for environmental variables on virtual organization adoption.

Research limitations/implications

While the results might provide clues for understanding the adoption of virtual organization structure in the manufacturing sector, there still remains uncertainty in generalizing to service industries. The variety of types of service firms and their outputs makes any generalization to services from this study difficult.

Practical implications

First, information technologies may provide the potential means to implement innovative organization structures, such as virtual organization, to respond to the pressures of change. Second, the adoption and diffusion of virtual organization might transform firms to meet the demands of e‐commerce.

Originality/value

The study identifies factors which may impact on the successful use of information technologies to implement innovative organization structures, such as virtual organizations, to respond to the pressures of change.
Mobile advertising adoption by multinationals
Authors: Okazaki Shintaro
Published: April 2005

Purpose

Although the wireless internet attracts more and more interest from marketers and researchers, there is little empirical evidence of multinational corporations’ (MNCs) adoption of push‐type mobile advertising in global markets. The aim of this study is to fill this research gap, by conducting an empirical survey of the perceptions of MNCs operating in Europe regarding SMS‐based mobile advertising adoption.

Design/methodology/approach

The study proposes six basic constructs which are thought to influence MNCs’ decision‐making process on mobile advertising adoption. On this base, a structured questionnaire is developed. The data are obtained by telephone interviews from 53 senior executives of MNCs’ subsidiaries in Spain.

Findings

Hierarchical regression analysis reveals that branding strategy, facilitating conditions, and security and costs are the strongest determinants of MNCs’ mobile advertising adoption. Furthermore, discriminant analysis indicates that Japanese, American, and European firms are statistically classifiable according to their cultural affiliation in terms of their perceptions of mobile advertising adoption. Japanese firms are the least willing to use mobile advertising, while their American counterparts are the most motivated in this regard.

Originality/value

While SMS‐based mobile marketing has been receiving an increasing attention from both academics and practitioners, there exists little empirical research on this area. In this vein, this study contributes to the literature in two ways. First, the study proposes a conceptual research model based on six basic constructs, which incorporate both theoretical and practical perspectives. Second, the model is tested by empirical data obtained from top managers of MNCs’ subsidiaries operating in a European market. The findings of this study thus offer useful insights based on their “hands‐on” experience.
Building an Effective Office Space
Authors: Rudolph Philip A. , Kleiner Brian H.
Published: April 2005

Considers the personal needs of workers to be taken into
consideration when the physical work environment is changed. Argues that
most office environments are detrimental to productivity because they
ignore the requirements of those who work in them. Surmizes that office
layout can be improved by considering changes to office furniture,
lighting and noise control.
Factory and Office Layout Using Functional Planning
Authors: Wilde Edwin
Published: April 2005

Examines the factors to be considered when developing a functional
layout for new factories or offices. Considers the importance of gaining
information from work studies, and developing an ideal layout before
construction starts if the building is new. Concludes that factors such
as travel times, facilities, communications, and location of equipment,
and the opinions of employees are all worthy of consideration.