bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of Gallium gallium adsorbate on SiC(0001) surface for GaN by MBE
Authors: Jeganathan K. , Shimizu M. , Ide T. , Okumura H.
Published: November 2003

The adsorption of Gallium gallium (Ga) (Ga) on SiC(0001) reveals a well‐ordered $\sqrt 3 \times \sqrt 3$ − R30° and 3 × 3 surface reconstructions with respect to different Ga adatom coverage. The GaN nucleation behaviours on $\sqrt 3 \times \sqrt 3$ R30° and 3 × 3 surfaces are significantly different. The GaN nucleates randomly in three‐dimensional 3D islands on the $\sqrt 3 \times \sqrt 3$ R30° surface due to unoccupied surface states of dangling bonds. In contrast the 3 × 3 surface was found to be highly suitable for two‐dimensional (2D) GaN nuclei which promotes a step‐flow growth subsequently. The GaN growth kinetics is found to depend on the Ga atomistic process of SiC (0001). (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Impact of exciton localization on the optical properties of non‐polar M‐plane In0.1Ga0.9N/GaN multiple quantum wells
Authors: Jun Sun Yue , Brandt Oliver , Cronenberg Sven , Grahn Holger T. , Ploog Klaus H.
Published: November 2003

Localized states in M‐plane In0.1Ga0.9N/GaN multiple quantum wells without the influence of internal electrostatic fields along the growth direction are studied. The recombination dynamics originates from simultaneous exciton relaxation towards a band of localized states and radiative recombination. The presence of localized states further manifests itself in the anomalous temperature dependence of the photoluminescence line width. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical and magnetic properties of the DyN/GaN superlattice
Authors: Zhou Y. K. , Kim M. S. , Teraguchi N. , Suzuki A. , Nanishi Y. , Asahi H.
Published: November 2003

Ferromagnet/semiconductor DyN/GaN superlattice structures were grown on SiC substrate by radio frequency molecular beam epitaxy. Formation of DyN was confirmed by X‐ray diffraction measurements. The temperature dependence of the photoluminescence (PL) spectra for the DyN/GaN superlattice and GaDyN samples was studied. Sharp PL peaks from two samples showed no shift with temperature, indicating the intra‐atomic f–f transition at Dy ions. Comparison of the PL spectra for the DyN/GaN superlattice and GaDyN suggests that GaDyN is formed at the GaN/DyN interface. The DyN/GaN superlattice exhibited two ferromagnetic components; one is major at low temperatures (<50 K) and the other is major at high temperatures (>350 K). The former shows large coercivity Hc of about 1800 Oe at 7 K, which was originated from DyN layers. The latter may come from GaDyN, which was formed at the GaN/DyN interface. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structure analysis of ELO‐GaN using a 2 × 4 μm2 micro‐beam X‐ray of an 8‐GeV storage ring
Authors: Miyajima T. , Takeya M. , Goto S. , Tomiya S. , Takeda S. , Kurihara H. , Watanabe K. , Kato M. , Hara N. , Tsusaka Y. , Matsui J.
Published: November 2003

We investigated the micrometer‐scale structure of epitaxially laterally overgrown GaN (ELO‐GaN) using a 2 × 4 μm2 micro‐beam X‐ray of an 8‐GeV storage ring. The GaN (0 0 0 12) rocking curve of the wing region had a sharp peak with a FWHM of 46 arcsec, but that of the seed region had several broad peaks. This peak‐narrowing corresponds to the reduction of the threading dislocation (TD) density and to the increase of grain size. The grain in the wing region was typically 5 μm × 5 μm and extended along the ELO stripe of GaN 〈100〉. On the other hand, a larger grain with a 10 μm × 10 μm was observed in the wing region of another ELO‐GaN sample which did not coalesce during the growth. We conclude that the homogeneity of the GaN c‐surface tilting can be declined by coalescence of the wing regions. We believe that this inhomogeneity of the GaN c‐surface tilting and the grain size strongly affect the performance of GaN‐based laser diodes grown on ELO‐GaN. Moreover, GaN c‐surface tilting of 81.5 arcsec was observed in the wing region of ELO‐GaN although no SiO2 mask was used. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of heavy nitrogen doping in III–V semiconductors – How well does the conventional wisdom holdfor the dilute nitrogen “III–V‐N alloys”?
Authors: Zhang Yong , Fluegel B. , Hanna M. C. , Geisz J. F. , Wang L.‐W. , Mascarenhas A.
Published: November 2003

Although heavily N doped III–V semiconductors are frequently referred to as dilute nitrogen III–V‐nitride alloys in general, it is important to realize that there are some subtle but important differences among them. In the indirect gap semiconductor GaP, since even a single N impurity can have a bound state, as far as the absorption near the band gap is concerned, it is difficult to describe GaP:N as an alloy. The N induced bound states (a hierarchy of impurity complexes) can in fact give rise to rather strong absorption below the indirect band gap, which effectively reduced the energy of the “absorption edge”, but the position of the absorption edge cannot be defined in a conventional way. In the direct gap semiconductor GaAs, a single N impurity does not form a bound state but instead has a resonant state above the conduction band edge. In this aspect, GaAs:N is similar to the situation in a conventional alloy, say, GaAs:P, except that the perturbation of N to the host is much stronger than that of P. However, because in reality N incorporation is typically in a random manner and a cluster as small as one N pair can generate bound states, the permissible region for GaAs:N to behave as a regular alloy is in fact rather limited, i.e., only when the N concentration is low enough so that the N pair and cluster states do not significantly interact with the host. In this study, a precise tracking of the evolution of the host and N induced impurity states will be offered for the two prototype systems, GaAs:N and GaP:N, with x varying from as low as ∼10−5 to ∼10−2. Such a study gives valuable insight to the underlying physics of the material evolution, sets up a bench‐mark for testing the theoretical modeling of this type of system, and serves to enhance our understanding of the behavior of isoelectronic impurities in semiconductors in general. The dissimilarity between GaP:N and GaAs:N indicates that seeking a unified model for all the isoelectronic doping systems is unrealistic. Our study also indicates that for strongly perturbed systems like GaP:N and GaAs:N, certain materials properties could be less well defined or not uniquely defined, as compared to those in other conventional semiconductor alloys. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermal conductivity of GaN crystals grown by high pressure method
Authors: Jeżowski A. , Stachowiak P. , Plackowski T. , Suski T. , Krukowski S. , Boćkowski M. , Grzegory I. , Danilchenko B. , Paszkiewicz T.
Published: November 2003

Results of measurements of thermal conductivity κ of bulk GaN crystals in the temperature interval4.2–300 K are reported. Experiments were performed on three types of GaN material: (i) single, high‐pressure grown GaN crystals showing highly n‐type conductivity, (ii) on bulk Mg doped GaN crystals with slightly p‐type conductivity, (iii) on homoepitaxial GaN layer grown by hydride vapour phase epitaxy (HVPE) on bulk GaN crystal. For the n‐GaN crystals, the record thermal conductivity value κmax is equal to 1600 W/m × K at Tmax = 45 K, and κ ≅ 230 W/m K at 300 K. It is suggested that for this crystal and for T ≥ Tmax the contribution of Umklapp phonon scattering processes dominate in the heat transport processes. A heavily Mg doped crystal and HVPE GaN layer on bulk GaN show much lower thermal conductivity in the whole applied temperature region. The temperature dependence of κ shows the importance of point defects (impurities, vacancies) in determination of the thermal resistance of GaN bulk crystals. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Control of electron density in InN by Si doping and optical properties of Si‐doped InN
Authors: Higashiwaki M. , Inushima T. , Matsui T.
Published: November 2003

We have studied Si‐doping profiles of InN films grown by plasma‐assisted molecular‐beam epitaxy and their photoluminescence (PL) properties. We confirmed experimentally that Si acts as a donor in InN. Undoped and Si‐doped InN films with electron densities (n) of 1.6 × 1018 − 1.4 × 1019 cm−3 showed clear n dependences of PL properties. The PL peak shifted to the higher energy side with increasing n, and the PL intensity decreased with increasing n. These were characteristics of degenerated semiconductors with a large density of defects and/or dislocations. The band‐gap energy of degenerated InN films with n = 1.6 × 1018 − 4.7 × 1018 cm−3 was estimated to be about 0.6 eV by assuming a nonparabolic conduction band and a constant band‐renormalization effect. By taking the band‐gap shrinkage of about 20 meV due to the conduction‐band renormalization into account, we suggest that the band‐gap energy of intrinsic InN is 0.6–0.65 eV. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimization of the growth of Ga1− xMnxN epilayers using plasma‐assisted MBE
Authors: Kuroda S. , Bellet‐Amalric E. , Biquard X. , Cibert J. , Giraud R. , Marcet S. , Mariette H.
Published: November 2003

A systematic compositional and structural study of GaN : Mn epilayers grown by molecular beam epitaxy (MBE) was performed, with a special attention to the dependence on the growth conditions. The “growth diagram” related to the Ga/N flux ratio for GaN was modified by adding Mn flux. In particular, the stable Ga‐bilayer coverage on the surface for the Ga‐rich condition was reduced in the presence of Mn. The Mn incorporation in the epilayers was found to be strongly dependent on the Ga/N flux ratio. The X‐ray diffraction (XRD) and extended X‐ray absorption fine structure (EXAFS) measurements revealed a clear contrast between the precipitation of a perovskite compound GaMn3N at Mn compositions higher than 1.7%, and the single phase of the wurtzite Ga1−xMnxN at lower Mn compositions. The single‐phase epilayers (x ≤ 1.7%) exhibited intrinsic ferromagnetic behaviors at room temperature. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of GaN on a‐plane sapphire: in‐plane epitaxial relationships and lattice parameters
Authors: Paskova T. , Darakchieva V. , Valcheva E. , Paskov P. P. , Monemar B. , Heuken M.
Published: November 2003

We have studied GaN films grown on a‐plane sapphire substrates by both hydride vapor phase epitaxy (HVPE) and metalorganic vapor phase epitaxy (MOVPE). The in‐plane orientation relationships between the epitaxial films and the substrate are determined to be [11–20]GaN ∥ [0001]sapphire and [1–100]GaN ∥ [1–100]sapphire in the HVPE growth, while [1–100]GaN ∥ [0001]sapphire and [11–20]GaN ∥ [1–100]sapphire are found in the MOVPE growth. The different orientation preferences are attributed to the atom termination of the sapphire surface determined by the substrate treatment used in the different growth methods. The effect of the lattice matches on the in‐plane lattice parameters and strain anisotropy in the two cases is studied. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carrier capture times in InGaN/GaN multiple quantum wells
Authors: Fan W. H. , Olaizola S. M. , Wang T. , Parbrook P. J. , Wells J.‐P. R. , Mowbray D. J. , Skolnick M. S. , Fox A. M.
Published: November 2003

We have investigated the temperature and carrier density dependence of the carrier capture time of two optically pumped InGaN/GaN multiple quantum well laser structures by subpicosecond time‐resolved differential transmission spectroscopy. We find that the carrier capture time varies significantly with both the temperature and the carrier density. The carrier density dependence is consistent with screening of piezoelectric fields, in agreement with theoretical predictions. The sample with the lower threshold for stimulated emission has a faster carrier capture rate, which highlights the importance of carrier capture for the lasing process. At room temperature the capture time is less than 1.2 ps in both samples. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sub‐microscopic transient lens spectroscopy of InGaN/GaN quantum wells
Authors: Okamoto Koichi , Fujita Shigeo , Kawakami Yoichi , Scherer Axel
Published: November 2003

Transient lens (TL) spectroscopy was developed with sub‐micrometer spatial resolution to observe the temporal and special behavior of the nonradiative processes of carrier dynamics in InGaN/GaN quantum wells (QW). We have observed the carrier density dynamics and the thermal dynamics in the TL signals with a nanosecond pulsed laser. We have also observed TL and photoluminescence (PL) signals by using near‐field scanning optical microscopy (NSOM), and find that both PL and TL images are correlated and exhibit submicron scale spatial inhomogeneity. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Shallow donors in GaN
Authors: Freitas J. A. , Moore W. J. , Shanabrook B. V. , Braga G. C. B. , Koleske D. D. , Lee S. K. , Park S. S. , Han J. Y.
Published: November 2003

High‐resolution, variable temperature PL experiments were performed in the spectral region associated with recombination processes involving the ground and excited states of the neutral donor bound excitons. High‐resolution infrared measurements in combination with high‐sensitive SIMS unambiguously identified Si and O shallow donors and yield their ground state binding energies. These binding energies are in excellent agreement with values obtained by the analysis of the two‐electron‐satellite PL spectra considering the participation of ground and excited state donor bound excitons. This work clarifies conflicting aspects existing in donor identification and the binding energies of the impurities and excitons. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of AlN buffer layer on the growth of InN epitaxial film on Si substrate
Authors: Yamaguchi T. , Saito Y. , Morioka C. , Yorozu K. , Araki T. , Suzuki A. , Nanishi Y.
Published: November 2003

InN films were grown on Si(111) substrates by RF‐MBE, and an AlN buffer layer was inserted between Si substrates and a low‐temperature InN buffer layer. The AlN buffer layer suppressed the formation of amorphous‐like SiNx layer on the Si substrate surface, which led to the improvement of the crystallinity of the low‐temperature InN buffer layer. High‐quality InN films could then be realized on the low‐temperature InN buffer layer with the AlN buffer layer inserted. The best value of the XRC‐FWHM was 31.3 arcmin for InN films with a thickness of 300 nm. In addition, a surface reconstruction of InN was observed for the first time. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stranski–Krastanow growth of stacked GaN quantum dots with intense photoluminescence
Authors: Hoshino K. , Kako S. , Arakawa Y.
Published: November 2003

Multiple‐layer stacked GaN quantum dots (QDs) with intense photoluminescence (PL) have been grown by the Stranski–Krastanow growth mode in metalorganic chemical vapor deposition. Scanning transmission electron microscopy (STEM) analysis shows that the vertical aligned QDs are formed, which results from a strain field induced by buried islands. We have also investigated PL spectra at room temperature. The PL intensity increases with increasing number of the stacked layer. This indicates that the carriers can be injected into each layer of GaN quantum dots. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Recombination dynamics in low‐dimensional nitride semiconductors
Authors: Kawakami Y. , Kaneta A. , Omae K. , Shikanai A. , Okamoto K. , Marutsuki G. , Narukawa Y. , Mukai T. , Fujita Sg.
Published: November 2003

Optical properties induced by two major effects, potential fluctuation and piezoelectric fields, have been assessed to interpret the emission mechanism in low‐dimensional nitride semiconductors because the former leads to the exciton/carrier localization, and the latter to the quantum confined Stark effect (QCSE). Degenerated white‐light pump‐and‐probe spectroscopy has been employed to assess which factor plays an important role in the series of InxGa1−xN multiple quantum well (MQW) structures whose well widths are 3 nm, 5 nm and 10 nm. Moreover, photoluminescence (PL) mapping with scanning near‐field optical microscopy (SNOM) has revealed the dense distribution of island‐like structures, the size of which ranges from 20 nm to 70 nm in a 3 nm‐thick InxGa1−xN single quantum well (SQW) structure emitting at blue spectral region. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoluminescence and optical absorption edge for MOVPE‐grown InN
Authors: Sugita K. , Takatsuka H. , Hashimoto A. , Yamamoto A.
Published: November 2003

This paper reports the photoluminescence (PL) spectra and the optical absorption edge at room temperature for MOVPE grown InN films as a function of growth temperature and background carrier concentration. A strong PL band with a peak energy in the range 0.7–0.9 eV is observed at room temperature. A sample grown at around 600 °C shows the highest PL intensity and the lowest peak energy. With decreasing the growth temperature from 600 °C, the PL intensity is markedly decreased and the peak energy is shifted toward the higher energy side. The absorption edge shows a similar change with the PL peak energy when the growth temperature is decreased. The difference between absorption edge and the PL peak energy is 50–100 meVand it increases with increasing the carrier concentration. The changes in PL peak energy and absorption edge with carrier concentration are not so steep compared to the absorption edge change predicted by Davydov et al. This may be explained by the increase in electron effective mass with increasing the carrier concentration reported by Wu et al. [Phys. Rev. B 66, 201403 (2002)]. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improvement of luminescence capability of Tb3+‐related emission by AlxGa1−xN
Authors: Nakanishi Y. , Wakahara A. , Okada H. , Yoshida A. , Ohshima T. , Itoh H.
Published: November 2003

Thermal quenching of the trivalent Tb (Tb3+)‐related luminescence in AlxGa1−xN (x: 0.00–0.15) is investigated. Tb ions are introduced into AlxGa1−xN epitaxial layers, which are grown by organometallic vapor phase epitaxy, by implantation at 200 keV. For all samples, strong and sharp emission peaks attributed to the 4f‐4f transition of Tb3+ are observed around 490–600 nm. The thermal quenching of the luminescence intensity and the decay time related to Tb3+ transitions strongly depend on the Al contents, and the luminescence is suppressed by introducing Al into GaN. For AlxGa1−xN with x > 0.10, the Tb3+‐related green photoluminescence can be observed at room temperature. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microstructure and electronic properties of InGaN alloys
Authors: Ponce F. A. , Srinivasan S. , Bell A. , Geng L. , Liu R. , Stevens M. , Cai J. , Omiya H. , Marui H. , Tanaka S.
Published: November 2003

The InxGa1−xN system has electronic band gaps extending from under 1eV to 3.4 eV, and as such they are used as the active layer in commercially available visible‐light emitting devices. There are many interesting features that make these nitride semiconductor alloys especially useful for efficient light emitters. It has been conjectured that the combination of piezoelectric fields and local composition inhomogeneities may be responsible for the observed high emission efficiencies, in spite of their characteristic high dislocation densities. But it is very difficult to grow InxGa1−xN layers with high indium composition. This paper presents an overview of the properties of InxGa1−xN epilayers based on a systematic study of thick layers and of quantum well structures. We find that the microstructure of thick films varies significantly with indium composition. For x < 0.08, the composition is uniform and unperturbed by dislocations. For 0.10 < x < 0.20, secondary phases nucleate at threading dislocations. For x > 0.20, spontaneous phase separation occurs resulting in a polycrystalline, inhomogeneous layer. A correlation between optical properties and microstructure is presented. It is observed that the misfit strain is affected by threading dislocations. Mechanisms of misfit strain relaxation are presented for InxGa1−xN layers grown on standard GaN on sapphire and on epitaxial‐lateral‐overgrowth GaN layers. In addition, we have studied the properties of quantum well structures using several novel techniques. The electrostatic fields across the wells have been profiled using electron holography in the TEM. The effect of well thickness on the strength of the fields is reported. The effects of localization by compositional fluctuations and of internal field screening have been studied using time‐resolved cathodoluminescence spectroscopy. In spite of significant progress that has been made in the last ten years, much work remains ahead in order to master the science and technology of these alloys. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Field‐compensated quaternary InAlGaN/GaN quantum wells
Authors: Kalaïtzakis F. , Androulidaki M. , Pelekanos N. T. , Dimakis E. , Bellet‐Amalric E. , Jalabert D. , Cengher D. , Tsagaraki K. , Aperathitis E. , Konstantinidis G. , Georgakilas A.
Published: November 2003

We demonstrate that it is possible to reduce significantly the internal polarisation fields in InAlGaN/GaN quantum wells (QWs), provided that the composition of the quaternary layer is appropriate. We have experimentally estimated an internal field of 2.65 mV/Å in In0.085Al0.285Ga0.63N/GaN QWs, which is a factor of four smaller than in “equivalent” GaN/Al0.15Ga0.85N QWs. Preliminary optical pumping experiments on laser structures using as active medium In0.085Al0.285Ga0.63N/GaN QWs have shown lower threshold than GaN/AlGaN laser structures at room temperature. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nitrides as spintronic materials
Authors: Dietl Tomasz
Published: November 2003

The Guest Editors of the Proceedings of the 5th International Conference on Nitride Semiconductors (ICNS‐5), Hiroshi Amano and Takashi Udagawa, have nominated the invited presentation by Tomasz Dietl [1] as Editor's Choice of the present issue of physica status solidi (b). This paper is a progress report on spintronics‐related issues in Mn‐based III‐nitrides as potential diluted magnetic semiconductors.

The cover picture shows the computed values of the Curie temperature for various p‐type III–V compounds containing 5% of Mn in the S = 5/2 high spin state and 3.5 × 1020 holes per cm3, predicting that TC should exceed room temperature in the Mn‐based nitrides.

Thomas Dietl is head of the Low‐Temperature Physics Group and professor at the Institute of Physics of the Polish Academy of Sciences. He is one of the most experienced researchers in the area of ferromagnetic semiconductors, spin‐related phenomena and other current topics of semiconductor physics with many publications and invited talks at conferences and seminars world‐wide.

The full Proceedings of the 5th International Conference on Nitride Semiconductors (ICNS‐5) are published in physica status solidi (c) – conferences and critical reviews, Vol. 0, No. 7 (November 2003) (ISBN 3‐527‐40489‐9). Conference papers can also be found in phys. stat. sol. (a) 200, No. 1 (2003).
Experimental Studies on the Carboxymethylation of Arrowroot Starch in Isopropanol‐Water Media
Authors: Kooijman Laura M. , Ganzeveld Klaassien J. , Manurung Robbert M. , Heeres Hero J.
Published: November 2003

The reaction between granular arrowroot starch and sodium monochloroacetate (SMCA) in isopropanol‐water mixtures has been studied in a systematic way using experimental design strategies. The effect of six factors, i.e. the theoretical degree of substitution (DSt), reaction time, weight fraction of water in the mixture, NaOH/SMCA ratio, temperature and weight fraction of starch on three responses, i.e. the degree of substitution (DS), the conversion of SMCA and the selectivity of SMCA towards carboxymethyl starch, has been determined in a systematic manner. Granular carboxymethyl arrowroot starch with a maximum DS of 1.4 could be prepared in a singlestep procedure. The results are compared with data obtained for potato starch. Similar trends for all responses were observed, suggesting close similarities between the chemical composition and the topochemistry of granular arrowroot‐ and potato‐starch.
The spatial restrictions of 5′HoxC genes expression are maintained in adult newt spinal cord
Authors: Nicolas S. , Papillon D. , Perez Y. , Caubit X. , Le Parco Y.
Published: November 2003

Abstract Urodele amphibians are the only adult vertebrates possessing the capacity to regenerate their limbs and tail after amputation. Epimorphic regeneration is characterized by the accumulation of undifferentiated and dividing mesenchymal cells originating from the tissues of the stump, which form a blastema. It has been proposed that the ability to regenerate precisely the amputated structures depends on a ‘positional memory’ of the cells at the level of amputation plane and that a continuum of positional value would be present in adult urodeles along the appendages able to regenerate. Hox genes are good candidates for playing a role in providing the capacity for regeneration and for carrying positional information. Here, we report the cloning of four AbdB‐like genes (Hoxa9, Hoxc10, Hoxc12 and Hoxc13) in the newt Pleurodeles waltl (Pw). To analyse their expression pattern along the antero‐posterior (AP) axis of adult urodele central nervous system (CNS), we used the reverse transcription‐polymerase chain reaction (RT‐PCR) and showed that the 5’HoxC genes expression pattern conforms to the usual spatial colinearity rule. In addition, the expression level in tail regenerates of PwHoxc13, PwHoxc12, and PwHoxc10 was respectively 20, 7 and 2 fold higher than in adult tail. These last results suggest that 5′HoxC genes could specify positional memory in adult spinal cord (SC) and could be involved in axial patterning of the tail during regeneration.
Integrative molecular and developmental biology of adult stem cells
Authors: Bunting Kevin D , Hawley Robert G
Published: November 2003

Abstract Stem cells are believed to be important for regeneration of several adult tissues. Recently, adult stem cells with very broad differentiation potential have been identified although whether they represent vestigial primitive pluripotent stem cells or products of extremely rare de‐differentiation events involving tissue‐specific stem cells is not known. Transdifferentiation of tissue‐specific stem cells across lineage boundaries has also been demonstrated but the relative inefficiency of the process in vivo, even in the presence of tissue damage, questions whether such a mechanism is of physiologic relevance. Interestingly, among adult stem cells, the capacity for lineage switching appears to be greatest in stem cells that can be cultured ex vivo for extended periods. If the normal cell fate decisions of diverse adult stem cell types could be reliably redirected at high frequency in situ, possible regenerative therapies for a wide variety of diseases could be envisioned. An integrated understanding of the transcriptional regulatory networks that comprise the various adult stem cell entities as well as the signaling pathways governing their differentiation into therapeutically useful cell types will facilitate clinical application of these exciting findings.
Different regulation of the Trio Dbl‐Homology domains by their associated PH domains
Authors: Bellanger J.‐M. , Estrach S. , Schmidt S. , Briançon‐Marjollet A. , Zugasti O. , Fromont S. , Debant A.
Published: November 2003

Abstract Guanine nucleotide exchange factors for Rho‐GTPases (Rho‐GEFs) invariably share a catalytic Dbl‐Homology (DH) domain associated with a Pleckstrin Homology (PH) domain, whose function in Rho‐GEF activation is not well understood. Trio is the first member of an emerging family of Dbl proteins containing two Rho‐GEF domains (GEFD1 and GEFD2). TrioGEFD1 activates the GTPases RhoG and Rac1, while TrioGEFD2 acts on RhoA. In this study, we have investigated the roles of the two PH domains of Trio in Rho‐GEF activity. We show that TrioPH1 is required for GEFD1‐mediated induction of actin cytoskeleton remodeling and JNK activation. TrioPH1 is involved both in the catalytic activity and in the subcellular localization of its associated DH domain, by acting as a cytoskeletal targeting signal. Moreover, TrioPH1 in association with DH2 activates the JNK pathway, by an unknown mechanism independent of DH2 catalytic activity. TrioPH2 does not behave as a targeting module in intact cells. TrioPH2 inhibits DH2‐dependent stress fiber formation, which correlates with the TrioPH2‐mediated inhibition of DH2 GEF activity. In addition, expression in the neuron‐like PC12 cell line of the intact Trio protein deleted of each PH domain shows that only TrioPH1 is required for Trio‐induced neurite outgrowth. Taken together, these data demonstrate that the two PH domains play a different role in the control of Trio Rho‐GEF function.
Hydrogen peroxide‐induced apoptosis in pc12 cells and the protective effect of puerarin
Authors: Jiang B. , Liu J. H. , Bao Y. M. , An L. J.
Published: November 2003

In this study, the effect of puerarin on hydrogen peroxide‐induced apoptosis in PC12 cells was studied. Exposure of cells to 0.5 mM H2O2may cause significant viability loss and apoptotic rate increase. When c‐Myc, Bcl‐2 and Bax expression and caspase‐3 activity were measured, using Ac‐DEVD‐AMC as a substrate, the changes in these apoptosis regulatory and effector proteins suggested that the elevation of c‐Myc, decrease in Bcl‐2: Bax protein ratio, and caspase‐3 activation all play a key role in apoptosis. When cells were treated with puerarin prior to 0.5 mM H2O2treatment, a reduction in viability loss and apoptotic rate was seen. In addition, c‐Myc expression decreased and Bcl‐2: Bax ratio increased. Puerarin also reduced the H2O2‐induced elevation of caspase‐3 activation. These results suggest that puerarin can protect neurons against oxidative stress. It can block apoptosis in its early stages via the regulation of anti‐ and pro‐apoptotic proteins, as well as by the attenuation of caspase‐3 activation in H2O2‐induced PC12 cells.
Distigmine bromide induced acute psychotic disorder in a patient with multiple sclerosis
Authors: Himmerich Hubertus , Szegedi Armin , Klawe Christoph , Anghelescu Ion , Müller Matthias J.
Published: November 2003

A female patient with multiple sclerosis (MS) suffered from an acute psychotic disorder after taking distigmine bromide for detrusor dysfunction. She showed a dramatic relief of her symptoms after the medication, distigmine bromide, was stopped. Distigmine is not supposed to penetrate the blood-brain barrier (BBB). However, in MS patients a leakage of the BBB could be hypothesized.
Number of dementia sufferers in Europe between the years 2000 and 2050
Authors: Wancata Johannes , Musalek M. , Alexandrowicz R. , Krautgartner M.
Published: November 2003

Several authors have pointed out that in the next few decades dementia will affect a considerably increasing number of the elderly. To our knowledge there exist no calculations of the number of demented persons for the whole European region. We made calculations on the number of dementia cases for the period 2000–2050 based on the population projections of the United Nations. For this purpose, we used the results of several meta-analyses of epidemiological studies. The number of prevalent dementia cases in the year 2000 was 7.1 million. Within the next 50 years, this number will rise to about 16.2 million dementia sufferers. The number of new dementia cases per year will increase from about 1.9 million in the year 2000 to about 4.1 million in the year 2050. Contrarily, the working-age population will considerably decrease during the next 50 years. In the year 2000, 7.1 million dementia cases faced 493 million persons in working-age. This equals a ratio of 69.4 persons in working-age per one demented person. Until the year 2050, this ratio will decrease to only 21.1. Thus, the financial and emotional burden placed by dementia on the working-age population will markedly rise.
Determinants of burden in caregivers of patients with exacerbating schizophrenia
Authors: Lauber Christoph , Eichenberger Adrian , Luginbühl Peter , Keller Christian , Rössler Wulf
Published: November 2003

Purpose

Restriction in involuntary hospital admission and reduced lengths of inpatient stay increase burden on relatives of individuals with schizophrenia. This study aims at assessing the relationship between caregiver burden and behavioural disturbances of the affected, e.g. threats, nuisances, but also substance use and aggression. Two weeks before the last hospitalisation of the affected are considered as being the most burdensome period for relatives.

Subjects and methods

Sixty-four relatives of schizophrenic patients were assessed by the semi-structured “Interview for Measuring the Burden on the Family”. Subscales and total scales of burden were calculated. Predictors were identified by regression analyses.

Results

The most important predictor of burden is burden in the relationship between caregiver and the affected representing the changes in the relationship occurring in acute illness. Threats, nuisances, time spent with the affected, and burden due to restricted social life and leisure activities were additional predictors, but not aggression or substance abuse. Eighty-five percent of the cases could be assigned correctly.

Discussion and conclusions

To better encounter burden, relatives should learn to cope with disturbing behaviour of and altered relationship to the affected, but also with their own needs. Finally, relatives must be included in the decision whether or not an affected person should be hospitalised.
Involuntary medication in psychiatric inpatient treatment
Authors: Kaltiala-Heino R. , Välimäki M. , Korkeila J. , Tuohimäki C. , Lehtinen V.
Published: November 2003

The aim of this study was to examine involuntary medication in psychiatric inpatient treatment. A retrospective chart review of 1543 consecutive admissions of working aged civil patients from well-defined catchment areas to three psychiatric centres were evaluated regarding events of involuntary medication. 8.2% of the admissions included involuntary medication episode(s). Involuntary medication was associated with a diagnosis of schizophrenia, involuntary legal status and having previously been committed. One of the studied centres used less involuntary medication than the other two, even if patients with schizophrenia were over-represented in that centre. Although involuntary medication mainly takes places in the treatment of patients who are conceptualised most ill and perhaps resist treatment most, treatment culture obviously also plays a role. In future, it is important to study the aspects of treatment culture to fully understand the use of involuntary medication in psychiatry.
Growth‐related changes in cell body size and succinate dehydrogenase activity of spinal motoneurons innervating the rat soleus muscle
Authors: Ishihara Akihiko , Kawano Fuminori , Ishioka Noriaki , Oishi Hirotaka , Higashibata Akira , Shimazu Toru , Ohira Yoshinobu
Published: November 2003

Cell body sizes and oxidative enzyme (succinate dehydrogenase) activities of spinal motoneurons innervating the soleus muscle were determined in rats ranging in postnatal age from 3 to 13 weeks. The soleus motoneurons were labeled by a retrograde neuronal tracer, nuclear yellow. The mean cell body sizes of motoneurons increased from 3 to 7 weeks of age, while the mean succinate dehydrogenase activities of motoneurons decreased from 3 to 7 weeks of age. There were no changes in mean cell body size or mean succinate dehydrogenase activity of motoneurons from 7 to 13 weeks of age. An inverse relationship between cell body size and succinate dehydrogenase activity of motoneurons was observed, irrespective of age. These results indicate that motoneurons innervating the rat soleus muscle show the adult pattern of cell body size and succinate dehydrogenase activity at an earlier stage of postnatal growth, 7 weeks of age.
Mouse polyomavirus large T antigen inhibits cell growth and alters cell and colony morphology in Saccharomyces cerevisiae
Authors: Adamec T. , Palková Z. , Forstová J.
Published: November 2003

The gene for mouse polyomavirus large tumor (LT) antigen, a potent oncoprotein, was expressed in Saccharomyces cerevisiae from the inducible GAL1 promoter. Substantial cell growth inhibition as well as colony and cell morphology changes dependent on cyclic adenosine monophosphate (cAMP) were observed. In contrast to cell and colony morphology alterations, the growth inhibition appeared to be transient, thus indicating the existence of an active adaptation of yeast cells to the LT antigen presence.
Distinctive binding and structural properties of piscine transthyretin
Authors: Folli Claudia , Pasquato Nicola , Ramazzina Ileana , Battistutta Roberto , Zanotti Giuseppe , Berni Rodolfo
Published: November 2003

The thyroid hormone binding protein transthyretin (TTR) forms a macromolecular complex with the retinol‐specific carrier retinol binding protein (RBP) in the blood of higher vertebrates. Piscine TTR is shown here to exhibit high binding affinity for L‐thyroxine and negligible affinity for RBP. The 1.56 Å resolution X‐ray structure of sea bream TTR, compared with that of human TTR, reveals a high degree of conservation of the thyroid hormone binding sites. In contrast, some amino acid differences in discrete regions of sea bream TTR appear to be responsible for the lack of protein–protein recognition, providing evidence for the crucial role played by a limited number of residues in the interaction between RBP and TTR. Overall, this study makes it possible to draw conclusions on evolutionary relationships for RBPs and TTRs of phylogenetically distant vertebrates.
Investigation of cytokinin‐deficient phenotypes in Arabidopsis by ectopic expression of orchid DSCKX1
Authors: Yang Shuhua , Yu Hao , Xu Yifeng , Goh Chong Jin
Published: November 2003

The plant hormone cytokinin plays a major role in regulating plant growth and development. Here we generated cytokinin‐reduction Arabidopsis plants by overexpressing a heterologous cytokinin oxidase gene DSCKX1 from Dendrobium orchid. These transgenic plants exhibited reduced biomass, rapid root growth, decreased ability to form roots in vitro, and reduced response to cytokinin in growing calli and roots. Furthermore, the expression of KNAT1, STM, and CycD3 genes was significantly reduced in the transgenic plants, suggesting that cytokinin may function to control the cell cycles and shoot/root development via regulation of these genes.
p53 down‐regulation: a new molecular mechanism involved in ischaemic preconditioning
Authors: Mocanu Mihaela M , Yellon Derek M
Published: November 2003

Ischaemic preconditioning is associated with the activation of prosurvival mechanisms. Here we demonstrate that following a preconditioning protocol, the proapoptotic p53 is inactivated possibly via phosphatidylinositol 3‐kinase (PI3K)‐protein kinase B (Akt)‐murine double minute 2 (Mdm2) phosphorylation. Our data show that in preconditioned hearts Mdm2 was significantly phosphorylated, and wortmannin (a PI3K inhibitor) abrogated this effect (Western blotting). Also in preconditioned hearts p53 was shown to be bound to phospho‐Mdm2 (co‐immunoprecipitation). Furthermore, pifithrin α (a p53 inhibitor), administered to isolated perfused hearts prior to ischaemia, significantly attenuated the infarction. In conclusion our results suggest that p53 is implicated in ischaemia/reperfusion injury and that preconditioning counterbalances this effect via PI3K‐Akt‐Mdm2 phosphorylation.
Insulin stimulates glucose metabolism via the pentose phosphate pathway in Drosophila Kc cells
Authors: Ceddia Rolando B. , Bikopoulos George J. , Hilliker Arthur J. , Sweeney Gary
Published: November 2003

Drosophila melanogaster has become a prominent and convenient model for analysis of insulin action. However, to date very little is known regarding the effect of insulin on glucose uptake and metabolism in Drosophila. Here we show that, in contrast to effects seen in mammals, insulin did not alter [3H]2‐deoxyglucose uptake and in fact decreased glycogen synthesis (∼30%) in embryonic Drosophila Kc cells. Insulin significantly increased (∼1.5‐fold) the production of 14CO2 from D‐[1‐14C]glucose while the production of 14CO2 from D‐[6‐14C]glucose was not altered. Thus, insulin‐stimulated glucose oxidation did not occur via increasing Krebs cycle activity but rather by stimulating the pentose phosphate pathway. Indeed, inhibition of the oxidative pentose phosphate pathway by 6‐aminonicotinamide abolished the effect of insulin on 14CO2 from D‐[U‐14C]glucose. A corresponding increase in lactate production but no change in incorporation of D‐[U‐14C]glucose into total lipids was observed in response to insulin. Glucose metabolism via the pentose phosphate pathway may provide an important source of 5′‐phosphate for DNA synthesis and cell replication. This novel observation correlates well with the fact that control of growth and development is the major role of insulin‐like peptides in Drosophila. Thus, although intracellular signaling is well conserved, the metabolic effects of insulin are dramatically different between Drosophila and mammals.
FasL‐induced downregulation of CD28 expression on jurkat cells in vitro is associated with activation of caspases
Authors: Ma Shibin , Ochi Hirotomo , Cui Lianxian , He Wei
Published: November 2003

Ligation of CD28, which is present on the majority of CD4+T cells, promotes proliferation and immune responses. However, expression of CD28 declines with aging, and apoptosis may contribute to this decline. We have investigated the molecular mechanism underlying the decrease in CD28 expression in Jurkat T cells cultured with FasL. FasL blocks expression of CD28 at the transcriptional level. This correlates with activation of caspase cascades: active caspase‐3 can be detected and inhibitors of caspase‐3 and caspase‐8 increase CD28 promoter activity and CD28 expression. These findings are consistent with the hypothesis that apoptosis plays a key role in the age‐related decline of CD28 expression and hence in immunosenescence.
Winter mesoscale variations of carbonate system parameters and estimates of CO2 fluxes in the Gulf of Cadiz, northeast Atlantic Ocean (February 1998)
Authors: González‐Dávila Melchor , Magdalena Santana‐Casiano J. , Dafner Evgeny V.
Published: November 2003

Further observations with small spatial and temporal resolutions conducted during different seasons are required in order fully to understand the role that shelves play in the global carbon cycle. The components of the carbonate system (total alkalinity, pH in the total scale, total dissolved inorganic carbon, and CO2 fugacity), and dissolved oxygen, nutrients, and phytopigments were studied along the mesoscale section over the continental shelf and slope in the Gulf of Cadiz in February 1998. All the chemical properties clearly distinguish four different water masses: Gulf of Cadiz Water, North Atlantic Surface Water, North Atlantic Central Water, and Mediterranean Water. From the thermohaline properties and applied chemical conservative tracers for each water mass, a mixing model has been established which explains more than 96% of the variability in the distribution of chemical properties. The relative variation of nutrients and carbon concentrations resulting from the regeneration of organic matter was estimated. The contribution of Mediterranean water to the waters at the traverse of Cadiz varies from 15% to 40% according to this model. The difference of fCO2 between seawater and atmosphere (ΔfCO2 = −35 μatm) shows that the surface seawater in the Gulf of Cadiz is a sink for atmospheric CO2 during winter with an average calculated net CO2 flux across the air‐sea interface of about −19.5 ± 3.5 mmol m−2 d−1. We estimate that at the traverse of Cadiz the shallow core of Mediterranean outflow carries out 1.2 • 104 to 2.4 • 104 mol inorganic carbon s−1. This estimate is 1 order of magnitude lower than that calculated for the Mediterranean outflow in the Strait of Gibraltar.
Coseismic and long‐term vertical displacement due to back arc shortening, central Vanuatu: Offshore and onshore data following the Mw 7.5, 26 November 1999 Ambrym earthquake
Authors: Lagabrielle Yves , Pelletier Bernard , Cabioch Guy , Régnier Marc , Calmant Stéphane
Published: November 2003

This paper presents a combined analysis of data collected both onshore and offshore in the epicentral region of the Mw 7.5, 26 November 1999, Ambrym earthquake. This offshore event occurred at the southern end of the back‐arc thrust belt of the Vanuatu subduction zone, east of the island of Ambrym and resulted in permanent uplift of the eastern tip of the island. The data presented include (1) interpretation of older seismic lines across the tectonic front, (2) compilation of aftershock sequences, (3) postseismic bathymetry from multibeam surveys, (4) measurements of permanent coseismic ground motion using desiccated red algae, uplifted beaches, and uplifted coral colonies, and (5) dating of raised corals exposed along the coastal cliff. The active scarp of the main fault appears 13 km east of the eastern tip of Ambrym (40 km long, 2 km depth, 950 m maximum step). Uplift rates of 3.5–4 mm/yr for the past 8000 years are calculated by dating raised corals. This leads to a longer seismic recurrence interval of 375 years for events similar to that of 1999, assuming no interseismic subsidence. Postseismic ground motion was monitored using stainless steel marks set at three sites along the uplifted coast in January 2000. No significant motion could be recorded during the 2 years following the event, but slight subsidence cannot be ruled out. Finally, our results confirm that the back‐arc belt of central Vanuatu is an active tectonic crustal wedge propagating eastward that accommodates more shortening than the Vanuatu subduction zone to the west.
Impact of remote oceanic forcing on Gulf of Alaska sea levels and mesoscale circulation
Authors: Melsom Arne , Metzger E. Joseph , Hurlburt Harley E.
Published: November 2003

We examine the relative importance of regional wind forcing and teleconnections by an oceanic pathway for impact on interannual ocean circulation variability in the Gulf of Alaska. Any additional factors that contribute to this variability, such as freshwater forcing from river runoff, are disregarded. The study is based on results from numerical simulations, sea level data from tide gauge stations, and sea surface height anomalies from satellite altimeter data. At the heart of this investigation is a comparison of ocean simulations that include and exclude interannual oceanic teleconnections of an equatorial origin. Using lagged correlations, the model results imply that 70–90% of the interannual coastal sea level variance in the Gulf of Alaska can be related to interannual sea levels at La Libertad, Equador. These values are higher than the corresponding range from sea level data, which is 25–55%. When oceanic teleconnections from the equatorial Pacific are excluded in the model, the explained variance becomes about 20% or less. During poleward propagation the coastally trapped sea level signal in the model is less attenuated than the observed signal. In the Gulf of Alaska we find well‐defined sea level peaks in the aftermath of El Niño events. The interannual intensity of eddies in the Gulf of Alaska also peaks after El Niño events; however, these maxima are less clear after weak and moderate El Niño events. The interannual variations in eddy activity intensity are predominantly governed by the regional atmospheric forcing.