bluuebunny/crossref_metadata_2025 huggingface dataset:
Background reduction by a getter pump around the ionization volume of a Lamb-shift polarimeter and possible improvements of polarized ion sources
Authors: Engels R. , Emmerich R. , Grigoryev K. , Schieck H. Paetz gen. , Ley J. , Mikirtychyants M. , Rathmann F. , Sarkadi J. , Seyfarth H. , Tenckhoff G. , Vasilyev A.
Published: April 2005

The Köln–Jülich Lamb-shift polarimeter is used to measure the nuclear polarization of the hydrogen or deuterium beam produced with the atomic-beam source for the polarized target at the ANKE spectrometer at COSY-Jülich. The precision of the earlier results had been dominated by the recombination of atoms in the ionizer. Protons or deuterons from the dissociative ionization of unpolarized recombined H2 or D2 molecules had strongly contributed to the extracted ion beam. To suppress this effect, in the new ionizer a nonevaporable getter pump of about 2000l∕s H2 or D2 pumping speed surrounds the ionization volume. It reduces the extracted current of unpolarized ions, produced from the recombined molecular gas, by a factor of about 20 compared with the earlier value, which reduces the error of the polarization measurements to about 0.5%. Now the H2 or D2 molecules in the ionization volume predominantly are those which are contained in the incoming beam from the atomic beam source. This allows the measurement of the fraction of unpolarized molecules in the polarized atomic H⃗ or D⃗ beam. The improvement achieved is a valuable step toward the measurement of the nuclear polarization of a gas sample, extracted from the storage cell of the polarized internal gas target for the spectrometer ANKE in the COSY-Jülich storage ring with the Lamb-shift polarimeter. Furthermore, the results show that the polarization of proton or deuteron beams would be increased by the installation of such a pump around the ionization volume of atomic-beam ion sources with an electron-impact ionizer. For ECR ionizers the recombined H2 or D2 molecules would be absorbed, whereas the noble gases, used as buffer, are not pumped by the getter material.
Quaternary InAlGaN-based high-efficiency ultraviolet light-emitting diodes
Authors: Hirayama Hideki
Published: April 2005

In order to realize 250–350-nm-band high-efficiency deep ultraviolet (UV) emitting devices using group-III-nitride materials, it is necessary to obtain high-efficiency UV emission from wide-band-gap (In)AlGaN. The use of the In-segregation effect, which has already been used for InGaN blue emitting devices, is quite effective for achieving high-efficiency deep UV emission. We have demonstrated high-efficiency UV emission from quaternary InAlGaN-based quantum wells in the wavelength range between 290 and 375 nm at room temperature (RT) using the In-segregation effect. Emission fluctuations in the submicron region due to In segregation were clearly observed for quaternary InAlGaN epitaxial layers. An internal quantum efficiency as high as 15% was estimated for a quaternary InAlGaN-based single quantum well at RT. Such high-efficiency UV emission can even be obtained on high threading-dislocation density buffer layers. A comparison of electroluminescence is made between light-emitting diodes (LEDs) with InAlGaN, AlGaN, and GaN active regions fabricated on SiC substrates with emission wavelengths between 340 and 360 nm. The emission intensity from the quaternary InAlGaN UV-LED was more than one order of magnitude higher than that from the AlGaN or GaN UV-LEDs under RT cw operation. We therefore fabricated 310–350-nm-band deep UV-LEDs with quaternary InAlGaN active regions. We achieved submilliwatt output power under RT pulsed operation for 308–314-nm LEDs. We also demonstrated a high output power of 7.4 mW from a 352-nm quaternary InAlGaN-based LED fabricated on a GaN substrate under RT cw operation. The maximum external quantum efficiency (EQE) of the 352-nm InAlGaN-based LED was higher than that obtained for an AlGaN-based LED with the same geometry. From these results, the advantages of the use of quaternary InAlGaN in 350-nm-band UV emitters were revealed.
The Parr formula for the superheating field in a semi-infinite film
Authors: Del Castillo Pierre
Published: April 2005

Di Bartolo, Dolgert, and Dorsey [Phys. Rev. B 53, 5650–5660 (1996)] have constructed asymptotic matched solutions at order 2 for the half-space Ginzburg–Landau model in the weak-κ limit. These authors deduced a formal expansion for the superheating field hsh(κ) up to order 4, extending the de Gennes formula [Proceedings of the Eighth Latin American School of Physics, Caracas, 1966] and the two terms in Parr’s formula [Z. Phys. B 25, 359–361 (1976)]. On the other hand, the present author [Eur. J. Appl. Math 13, 519–547 (2002)] obtained two terms in the lower bound for hsh(κ). In this paper, we prove rigorously that the second term of the expansion of hsh(κ) is of the order of O(κ1∕2) and we get the Parr formula. We improve the upper bound obtained by Bolley and Helffer [Ann. Inst. Henri Poincaré, Anal. Non Linéaire 14, 597–613 (1997)] and we get κ(hsh(κ))2⩽2−3∕2=1532κ+O(κ1+ρ), ρ>0. The proof is based on new estimates for f′, A, and A′. To achieve this, we are guided by the analysis of the properties of the approximate solution constructed previously in [Del Castillo, Math Modell. Numer. Anal. 36, 971–973 (2002); J. Math. Phys. 44, 2416–2450 (2003); Dolgert et al., Phys. Rev. B 53, 5650–5660 (1996)].
Direct detection and time-locked subsampling applied to pulsed electron paramagnetic resonance imaging
Authors: Pursley Randall H. , Salem Ghadi , Pohida Thomas J. , Devasahayam Nallathamby , Subramanian Sankaran , Krishna Murali C.
Published: April 2005

The application of direct time-locked subsampling (TLSS) to Fourier transform electron paramagnetic resonance (FT-EPR) spectroscopy at radio frequencies (rf) is described. With conventional FT-EPR spectroscopy, the high Larmor frequencies (Lf) often necessitate the use of intermediate frequency (IF) stages to down convert the received free induction decay (FID) signal to a frequency that can be acquired with common data acquisition technology. However, our research focuses on in vivo studies, and consequently utilizes a FT-EPR system with a Lf of 300 MHz. This relatively low frequency Lf, in conjunction with the advent of bandpass sampling analog–to–digital conversion and signal processing technologies, has enabled us to omit the IF stage in our FT-EPR system. With this in mind, TLSS techniques have been developed to directly sample the 300 MHz FID signal at a sampling rate of 80 MHz providing a signal bandwidth of 20 MHz. The required modifications to the data acquisition and processing system specific to this application are described. Custom software developed to control the EPR system setup, acquire the signals, and post process the data, is outlined. Data was acquired applying both coherent averaging and stochastic excitation sequences. The results of these experiments demonstrate digital down conversion of the 300 MHz FID signal to quadrature baseband. Direct FID TLSS eliminates many noise sources common in EPR systems employing traditional analog receiver techniques, such as the IF mixer stage in single channel systems, and the quadrature baseband mixer stage in dual channel systems.
Single-crystalline alpha silicon–nitride nanowires: Large-scale synthesis, characterization, and optic properties
Authors: Zou Guifu , Hu Biao , Xiong Kan , Li Hui , Dong Chao , Liang Jiangbo , Qian Yitai
Published: April 2005

Single-crystalline alpha silicon–nitride nanowires have been achieved with large scale by the reaction of Mg3N2 and SiCl4 at 600 °C. Electron microscopy analyses have revealed that the nanowires have only ∼35nm in diameter, up to 5 μm in length, and a preferred [001] growth direction. The nanowires exhibit the quantum size effect in optical properties, showing the redshift of an infrared band and the blueshift of the photoluminescence band. The growth mechanism of the nanowires have been properly discussed.
Pd/Ag and Pd/Au interface specific resistances and interfacial spin flipping
Authors: Galinon C. , Tewolde K. , Loloee R. , Chiang W.-C. , Olson S. , Kurt H. , Pratt W. P. , Bass J. , Xu P. X. , Xia Ke , Talanana M.
Published: April 2005

We measured the specific resistances, 2ARPd∕Ag and 2ARPd∕Au (sample area A times resistance R), and spin-flip probabilities δPd∕Ag and δPd∕Au for Pd/Ag and Pd/Au interfaces with current perpendicular to the interfaces. 2ARPd∕Ag=0.7±0.15fΩm2 and 2ARPd∕Au=0.45±0.15fΩm2 are smaller than our revised estimate of 2ARPd∕Cu=0.85±0.15fΩm2, and lie further from no-free-parameter calculations. Our estimates of δPd∕Ag=0.15±0.08 and δPd∕Ag=0.08±0.08 are less than our prior estimate of δPd∕Cu∼0.24.
Microcavity single-photon-emitting diode
Authors: Bennett A. J. , Unitt D. C. , See P. , Shields A. J. , Atkinson P. , Cooper K. , Ritchie D. A.
Published: April 2005

We show that a planar semiconductor cavity can be used to enhance by a factor of ten the efficiency with which photons are collected from an electrically driven single InAs∕GaAs quantum dot. Under a fixed bias we observe that the photon statistics change when the injection current is modified. The observed bunching of photons from the biexciton state can be explained by the presence of charged states or dark states within the quantum dot with lifetimes greater than 4ns. Single-photon emission from both the exciton and biexciton states is demonstrated under pulsed electrical injection.
Bandwidth-enhanced volume grating for dense wavelength-division multiplexer using a phase-compensation scheme
Authors: Gu Lanlan , Chen Xiaonan , Shi Zhong , Howley Brie , Liu Jian , Chen Ray T.
Published: April 2005

A phase-compensation scheme is proposed and demonstrated to overcome the intrinsic tradeoff between the dispersion and the bandwidth of a volume grating. Its application to a volume grating-based dense wavelength-division multiplexing (DWDM) device is explored. A DWDM device is fabricated by using a 45°/82° configuration. To achieve phase compensation of the Bragg condition, a wavelength-dependent incident angle for a dispersion-enhanced holographic grating at 82° is generated through a prestaged volume hologram at 45°. The 3dB dispersion bandwidth is increased five times by using such a device configuration. A 21-channel DWDM device centered at 1555nm with 200GHz spacing is demonstrated within its 3dB bandwidth.
Low angular-dispersion microwave absorption of a metal dual-period nondiffracting hexagonal grating
Authors: Lockyear Matthew J. , Hibbins Alastair P. , Sambles J. Roy , Lawrence Christopher R.
Published: April 2005

The microwave (11.3<λ0<16.7mm) reflectivity response of a nondiffracting dual-period hexagonal grating is explored. In three directions at 60° to each other, the aluminum grating has a repeat period of 7.2mm in which are three equally spaced grooves, one being slightly shallower than the other two. This dual-period (λg and λg∕3) structure exhibits strong microwave absorption at several different frequencies. In addition, some of the absorptions are almost completely independent of the angle of incidence and polarization of the microwave radiation.
Temporal correlation scheme for spectroscopic gas analysis using multimode diode lasers
Authors: Somesfalean G. , Sjöholm M. , Persson L. , Gao H. , Svensson T. , Svanberg S.
Published: April 2005

The reliability of diode lasers used in spectroscopic applications is limited by their intrinsic multimode and mode-jump behavior when wavelength-tuned by current or temperature. We report on a scheme for gas analysis based on temporal correlation between absorption signals from an unknown external and a known reference gas concentration, simultaneously recorded when the diode laser wavelength is temperature-tuned across absorption features of the gas of interest. This procedure, which does not require any knowledge of the exact spectrum, also eliminates light intensity fluctuations due to mode competition. The method is illustrated for atmospheric oxygen absorption applied to diffusion measurements.
Backward quasi-phase-matched second-harmonic generation in submicrometer periodically poled flux-grown KTiOPO4
Authors: Canalias C. , Pasiskevicius V. , Fokine M. , Laurell F.
Published: April 2005

A 1mm thick flux-grown KTiOPO4 sample was poled with a 720nm domain period by employing deep-UV laser lithography, chemical patterning, and electric field poling. An atomic force microscope was used to characterize the periodic domain structure. The sample was used to demonstrate sixth and seventh order quasi-phase-matched backward second-harmonic generation.
Microfluidic detection and analysis by integration of thermocapillary actuation with a thin-film optical waveguide
Authors: Valentino Joseph P. , Troian Sandra M. , Wagner Sigurd
Published: April 2005

We demonstrate a nonintrusive optical method for microfluidic detection and analysis based on evanescent wave sensing. The device consists of a planar thin-film waveguide integrated with a microfluidic chip for directed surface flow. Microliter droplets are electronically transported and positioned over the waveguide surface by thermocapillary actuation. The attenuated intensity of propagating modes is used to detect droplet location, to monitor dye concentration in aqueous solutions, and to measure reaction rates with increasing surface temperature for a chromogenic biochemical assay. This study illustrates a few of the capabilities possible by direct integration of optical sensing with surface-directed fluidic devices.
Resonant-tunneling electron emitter in an AlN∕GaN system
Authors: Ishida A. , Inoue Y. , Fujiyasu H.
Published: April 2005

An AlN∕GaN multiple-barrier resonant-tunneling electron emitter is proposed in this letter, utilizing polarization fields in the AlN∕GaN heterostructure. The resonant-tunneling voltage is extremely high, compared with usual resonant-tunneling devices, due to the polarization field in the heterostructure, and this high resonant voltage enables practical use of the devices. Selective and high-density electron emission is to be expected through the resonant-tunneling layer and GaN surface accelerating layer.
Generation of high-confinement step-like optical waveguides in LiNbO3 by swift heavy ion-beam irradiation
Authors: Olivares J. , García G. , García-Navarro A. , Agulló-López F. , Caballero O. , García-Cabañes A.
Published: April 2005

We demonstrate a swift ion-beam irradiation procedure based on electronic (not nuclear) excitation to generate a large index jump step-like optical waveguide (Δn0≈0.2,Δne≈0.1) in LiNbO3. The method uses medium-mass ions with a kinetic energy high enough to assure that their electronic stopping power Se(z) reaches a maximum value close to the amorphous (latent) track threshold inside the crystal. Fluorine ions of 20 and 22MeV and fluences in the range (1–30)×1014 are used for this work. A buried amorphous layer having a low refractive index (2.10 at a wavelength of 633nm) is then generated at a controlled depth in LiNbO3, whose thickness is also tuned by irradiation fluence. The layer left at the surface remains crystalline and constitutes the core of the optical waveguide which, moreover, is several microns far from the end of the ion range. The waveguides show, after annealing at 300°C, low propagation losses (≈1dB∕cm) and a high second-harmonic generation coefficient (50%–80% of that for bulk unirradiated LiNbO3, depending on the fluence). The formation and structure of the amorphous layer has been monitored by additional Rutherford backscattering/channeling experiments.
Substitution mechanism of ZnO-doped lithium niobate crystal determined by powder x-ray diffraction and coercive field
Authors: Chia C.-T. , Lee C.-C. , Chang P.-J. , Hu M.-L. , Hu L. J.
Published: April 2005

ZnO-doped lithium niobate crystals with a doped concentration of up to 8.3mol% were grown by the Czochralski technique. The effects of incorporating Zn2+ ions into LiNbO3 crystals were studied by powder x-ray diffraction and taking polarization hysteresis loop measurements. When the Li-site vacancy model is adopted, the coercive fields obtained from the polarization reversal measurement depend strongly on the number of NbLi4−+4VLi−. However, the coercive field of Zn-doped ions into LiNbO3 is insensitive to the ZnLi2++VLi−. Experimental results indicate that four distinct substitutions of Zn−2 ions incorporated into ions into LiNbO3 crystals for doping concentrations from 0to8.3mol%. The extent of Zn substitution is quantitatively determined for doping of below 7.5mol%.
Electronic temperature and density of the plasma produced by nanosecond ultraviolet laser ablation of LiF
Authors: Gordillo-Vázquez F. J. , Perea A. , McKiernan A. P. , Afonso C. N.
Published: April 2005

Optical emission spectroscopy is used to investigate the spatial evolution of the electron temperature (Te) and electron density (Ne) in the plasma generated by laser ablation in a vacuum of a wide-band-gap material, such as LiF, with a pulsed 193 nm excimer laser operating at a fluence of 1.5Jcm−2 close to the threshold. It is found that, whereas Ne (in the range of 1016cm−3) decreases by a factor of 2 as the distance to the target increases, Te exhibits a sharp decrease (from 1.85 eV to 0.66 eV) between 1 and 2 mm from the target and it remains practically constant for longer distances from the target. These results provide direct measurements of the electron temperature and density during nanosecond laser ablation of LiF.
Functional analysis of the pseudoknot structure in human telomerase RNA
Authors: Chen Jiunn-Liang , Greider Carol W.
Published: April 2005

Telomerase is essential for maintaining telomere length and chromosome stability in stem cells, germline cells, and cancer cells. The telomerase ribonucleoprotein complex consists of two essential components, a catalytic protein component and an RNA molecule that provides the template for telomeric repeat synthesis. A pseudoknot structure in the human telomerase RNA is conserved in all vertebrates and is essential for telomerase activity. It has been proposed that this highly conserved structure functions as a dynamic structure with conformational interchange between the pseudoknot and a hairpin with intraloop base pairings. To examine the structural and functional requirements of the pseudoknot structure, we made mutations in the proposed base-paired regions in the pseudoknot. Although mutations that disrupted the pseudoknot P3 helix abolished activity as predicted, mutations that disrupted the intraloop hairpin base pairings did not reduce telomerase activity, indicating that the intraloop hairpin is not required for telomerase function. This functional study thus provides evidence against the previous proposed molecular-switch model of telomerase pseudoknot function and supports a static pseudoknot structure. The mutational analysis further suggests that telomerase RNA can function independent of the proposed intermolecular pairings between pseudoknot regions on two RNA molecules.
Prion protein recruits its neuronal receptor NCAM to lipid rafts to activate p59fyn and to enhance neurite outgrowth
Authors: Santuccione Antonella , Sytnyk Vladimir , Leshchyns'ka Iryna , Schachner Melitta
Published: April 2005

In spite of advances in understanding the role of the cellular prion protein (PrP) in neural cell interactions, the mechanisms of PrP function remain poorly characterized. We show that PrP interacts directly with the neural cell adhesion molecule (NCAM) and associates with NCAM at the neuronal cell surface. Both cis and trans interactions between NCAM at the neuronal surface and PrP promote recruitment of NCAM to lipid rafts and thereby regulate activation of fyn kinase, an enzyme involved in NCAM-mediated signaling. Cis and trans interactions between NCAM and PrP promote neurite outgrowth. When these interactions are disrupted in NCAM-deficient and PrP-deficient neurons or by PrP antibodies, NCAM/PrP-dependent neurite outgrowth is arrested, indicating that PrP is involved in nervous system development cooperating with NCAM as a signaling receptor.
A developmentally regulated Na-H exchanger in Dictyostelium discoideum is necessary for cell polarity during chemotaxis
Authors: Patel Hitesh , Barber Diane L.
Published: April 2005

Increased intracellular H+ efflux is speculated to be an evolutionarily conserved mechanism necessary for rapid assembly of cytoskeletal filaments and for morphological polarity during cell motility. In Dictyostelium discoideum, increased intracellular pH through undefined transport mechanisms plays a key role in directed cell movement. We report that a developmentally regulated Na-H exchanger in Dictyostelium discoideum (DdNHE1) localizes to the leading edge of polarized cells and is necessary for intracellular pH homeostasis and for efficient chemotaxis. Starved DdNHE1-null cells (Ddnhe1−) differentiate, and in response to the chemoattractant cAMP they retain directional sensing; however, they cannot attain a polarized morphology, but instead extend mislocalized pseudopodia around the cell and exhibit decreased velocity. Consistent with impaired polarity, in response to chemoattractant, Ddnhe1− cells lack a leading edge localization of F-actin and have significantly attenuated de novo F-actin polymerization but increased abundance of membrane-associated phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P3). These findings indicate that during chemotaxis DdNHE1 is necessary for establishing the kinetics of actin polymerization and PI(3,4,5)P3 production and for attaining a polarized phenotype.
Deep-etch EM reveals that the early poxvirus envelope is a single membrane bilayer stabilized by a geodetic “honeycomb” surface coat
Authors: Heuser John
Published: April 2005

Three-dimensional “deep-etch” electron microscopy (DEEM) resolves a longstanding controversy concerning poxvirus morphogenesis. By avoiding fixative-induced membrane distortions that confounded earlier studies, DEEM shows that the primary poxvirus envelope is a single membrane bilayer coated on its external surface by a continuous honeycomb lattice. Freeze fracture of quick-frozen poxvirus-infected cells further shows that there is only one fracture plane through this primary envelope, confirming that it consists of a single lipid bilayer. DEEM also illustrates that the honeycomb coating on this envelope is completely replaced by a different paracrystalline coat as the poxvirus matures. Correlative thin section images of infected cells freeze substituted after quick-freezing, plus DEEM imaging of Tokuyasu-type cryo-thin sections of infected cells (a new application introduced here) all indicate that the honeycomb network on immature poxvirus virions is sufficiently continuous and organized, and tightly associated with the envelope throughout development, to explain how its single lipid bilayer could remain stable in the cytoplasm even before it closes into a complete sphere.
The β Subunit of the Na+/K+-ATPase Follows the Conformational State of the Holoenzyme
Authors: Dempski Robert E. , Friedrich Thomas , Bamberg Ernst
Published: April 2005

The Na+/K+-ATPase is a ubiquitous plasma membrane ion pump that utilizes ATP hydrolysis to regulate the intracellular concentration of Na+ and K+. It is comprised of at least two subunits, a large catalytic α subunit that mediates ATP hydrolysis and ion transport, and an ancillary β subunit that is required for proper trafficking of the holoenzyme. Although processes mediated by the α subunit have been extensively studied, little is known about the participation of the β subunit in conformational changes of the enzyme. To elucidate the role of the β subunit during ion transport, extracellular amino acids proximal to the transmembrane region of the sheep β1 subunit were individually replaced for cysteines. This enabled sulfhydryl-specific labeling with the environmentally sensitive fluorescent dye tetramethylrhodamine-6-maleimide (TMRM) upon expression in Xenopus oocytes. Investigation by voltage-clamp fluorometry identified three reporter positions on the β1 subunit that responded with fluorescence changes to alterations in ionic conditions and/or membrane potential. These experiments for the first time show real-time detection of conformational rearrangements of the Na+/K+-ATPase through a fluorophore-labeled β subunit. Simultaneous recording of presteady-state or stationary currents together with fluorescence signals enabled correlation of the observed environmental changes of the β subunit to certain reaction steps of the Na+/K+-ATPase, which involve changes in the occupancy of the two principle conformational states, E1P and E2P. From these experiments, evidence is provided that the β1-S62C mutant can be directly used to monitor the conformational state of the enzyme, while the F64C mutant reveals a relaxation process that is triggered by sodium transport but evolves on a much slower time scale. Finally, shifts in voltage dependence and kinetics observed for mutant K65C show that this charged lysine residue, which is conserved in β1 isoforms, directly influences the effective potential that determines voltage dependence of extracellular cation binding and release.
Antisense Suppression of a (+)-δ-Cadinene Synthase Gene in Cotton Prevents the Induction of This Defense Response Gene during Bacterial Blight Infection But Not Its Constitutive Expression
Authors: Townsend Belinda J. , Poole Andrew , Blake Christopher J. , Llewellyn Danny J.
Published: April 2005

In cotton (Gossypium hirsutum) the enzyme (+)-δ-cadinene synthase (CDNS) catalyzes the first committed step in the biosynthesis of cadinane-type sesquiterpenes, such as gossypol, that provide constitutive and inducible protection against pests and diseases. A cotton cDNA clone encoding CDNS (cdn1-C4) was isolated from developing embryos and functionally characterized. Southern analysis showed that CDNS genes belong to a large multigene family, of which five genomic clones were studied, including three pseudogenes and one gene that may represent another subfamily of CDNS. CDNS expression was shown to be induced in cotton infected with either the bacterial blight or verticillium wilt pathogens. Constructs for the constitutive or seed-specific antisense suppression of cdn1-C4 were introduced into cotton by Agrobacterium-mediated transformation. Gossypol levels were not reduced in the seeds of transformants with either construct, nor was the induction of CDNS expression affected in stems of the constitutive antisense plants infected with Verticillium dahliae Kleb. However, the induction of CDNS mRNA and protein in response to bacterial blight infection of cotyledons was completely blocked in the constitutive antisense plants. These results suggest that cdn1-C4 may be involved specifically in the bacterial blight response and that the CDNS multigene family comprises a complex set of genes differing in their temporal and spatial regulation and responsible for different branches of the cotton sesquiterpene pathway.
Cloning and Characterization of GLOSSY1, a Maize Gene Involved in Cuticle Membrane and Wax Production
Authors: Sturaro Monica , Hartings Hans , Schmelzer Elmon , Velasco Riccardo , Salamini Francesco , Motto Mario
Published: April 2005

The cuticle covering the aerial organs of land plants plays a protective role against several biotic and abiotic stresses and, in addition, participates in a variety of plant-insect interactions. Here, we describe the molecular cloning and characterization of the maize (Zea mays) GLOSSY1 (GL1) gene, a component of the pathway leading to cuticular wax biosynthesis in seedling leaves. The genomic and cDNA sequences we isolated differ significantly in length and in most of the coding region from those previously identified. The predicted GL1 protein includes three histidine-rich domains, the landmark of a family of membrane-bound desaturases/hydroxylases, including fatty acid-modifying enzymes. GL1 expression is not restricted to the juvenile developmental stage of the maize plant, pointing to a broader function of the gene product than anticipated on the basis of the mutant phenotype. Indeed, in addition to affecting cuticular wax biosynthesis, gl1 mutations have a pleiotropic effect on epidermis development, altering trichome size and impairing cutin structure. Of the many wax biosynthetic genes identified so far, only a few from Arabidopsis (Arabidopsis thaliana) were found to be essential for normal cutin formation. Among these is WAX2, which shares 62% identity with GL1 at the protein level. In wax2-defective plants, cutin alterations induce postgenital organ fusion. This trait is not displayed by gl1 mutants, suggesting a different role of the maize and Arabidopsis cuticle in plant development.
Identification and Characterization of Endoplasmic Reticulum-Associated Degradation Proteins Differentially Affected by Endoplasmic Reticulum Stress
Authors: Kirst Mariana E. , Meyer David J. , Gibbon Bryan C. , Jung Rudolf , Boston Rebecca S.
Published: April 2005

The disposal of misfolded proteins from the lumen of the endoplasmic reticulum (ER) is one of the quality control mechanisms present in the protein secretory pathway. Through ER-associated degradation, misfolded substrates are targeted to the cytosol where they are degraded by the proteasome. We have identified four maize (Zea mays) Der1-like genes (Zm Derlins) that encode homologs of Der1p, a yeast (Saccharomyces cerevisiae) protein implicated in ER-associated degradation. Zm Derlins are capable of functionally complementing a yeast Der1 deletion mutant. Such complementation indicates that the Der1p function is conserved among species. Zm Derlin genes are expressed at low levels throughout the plant, but appear prevalent in tissues with high activity of secretory protein accumulation, including developing endosperm cells. Expression of three of the four Zm Derlin genes increases during ER stress, with Zm Derlin1-1 showing the strongest induction. Subcellular fractionation experiments localized Zm Derlin proteins to the membrane fraction of microsomes. In maize endosperm, Zm Derlin proteins were found primarily associated with ER-derived protein bodies regardless of the presence of an ER stress response.
Are Knowledge Spillovers Driving the Convergence of Productivity among Firms?
Authors: Fung Michael K.
Published: April 2005

This study evaluates the impact of knowledge spillovers on the convergence of productivity among firms. With the use of patent citation data, knowledge spillovers are decomposed into intra‐ and inter‐industry spillovers, and internal knowledge flows. The findings from this study suggest that each firm is converging to its own steady‐state productivity growth rate, which is conditional on the firm's R&D efforts and the intensity of intra‐industry spillovers it receives. Moreover, if technology followers and leaders invest equally in R&D activities, the followers will eventually catch up with the leaders because the former tend to be the ones who receive knowledge spillovers from the latter.
Is the Investment–Uncertainty Relationship Nonlinear? An Empirical Analysis for the Netherlands
Authors: Bo Hong , Lensin Robert
Published: April 2005

We examine the investment–uncertainty relationship for a panel of Dutch non‐financial firms. The system generalized method of moments (GMM) estimates suggest that the effect of uncertainty on investment is nonlinear: for low levels of uncertainty an increase in uncertainty has a positive effect on investment, while for high levels of uncertainty an increase in uncertainty lowers investment. This result is in line with a number of theoretical studies, but has never been documented empirically.
UV‐induced DNA damage in human keratinocytes: Quantitation and correlation with long‐term survival
Authors: Lisby Steen , Gniadecki Robert , Wulf Hans Christian
Published: April 2005

Abstract:  Ultraviolet (UV) radiation has a major role in the pathogenesis of skin cancer due to its capacity to induce immunosuppression and DNA damage in cells. In this study, we describe the use of a novel extra‐long polymerase chain reaction (XL‐PCR) assay for detection of UV‐inducible DNA lesions in a human keratinocyte line (HaCaT cells). Ultraviolet B (UVB), in doses from 4 to 50 mJ/cm2 resulted in a linear increase in the number of DNA lesions in the genome [range 0.3 ± 0.2 lesions−3.6 ± 0.7 lesions (mean ± SD)/10 kb]. At lower doses of UVB (<10 mJ/cm2), 89 ± 13% lesions were repaired within 24 h of culture. At higher doses, more lesions remained unrepaired, but the repair efficacy expressed as a proportion of repaired lesions to the total amount of DNA lesions remained constant in the range 0–50 mJ/cm2. Moreover, we demonstrated a correlation between the dose of UV and cell survival. The D37 (dose that reduced clonogenic survival to 37%) of UVB equaled 19 mJ/cm2, corresponding to the introduction of 1.4 lesions/10 kb. In contrast to UVB, UVA1 irradiation neither induced measurable DNA damage nor induced cell death in the doses up to 15 J/cm2. In conclusion, the non‐radioactive extra‐long (XL)‐based real‐time (RT)‐PCR assay system can be used to quantify the UV‐induced DNA damage in intact cells. The DNA lesions detected by this assay are mainly induced by short‐waved radiation in the UVB range, and unrepaired DNA lesions cause keratinocyte death or permanent cell‐cycle block.
Dopa oxidase activity in the hair, skin and ocular melanocytes is increased in the presence of stressed fibroblasts
Authors: Balafa Chariklia , Smith‐Thomas Linda , Phillips Jennifer , Moustafa Manar , George Elizabeth , Blount Margaret , Nicol Scott , Westgate Gillian , MacNeil Sheila
Published: April 2005

Abstract:  We previously reported that mesenchymal cells (dermal fibroblasts and dermal papilla cells) can stimulate dopa oxidase activity in the skin melanocytes. This study extends the investigation of the influence of the fibroblast in a comparative study of melanogenesis in melanocytes from the hair, the skin and the eye. Culture of melanocytes with normal proliferative dermal fibroblasts slightly increased dopa oxidase activity of the hair, skin and ocular melanocytes (by 17, 11 and 28%, respectively), but co‐culture with fibroblasts recovering from storage in liquid nitrogen or growth‐arrested by means of gamma radiation showed much greater effects. Most dramatic results were obtained with fibroblasts, which had been both gamma‐irradiated and then frozen in liquid nitrogen, where increases in dopa oxidase activity of 125, 227 and 185% for melanocytes of the hair, the skin and the eye, respectively, were seen. Experiments by using transwell cultures of melanocytes and fibroblasts and by using fibroblast‐conditioned medium showed that a large proportion of this fibroblast influence could be mediated by diffusible factors, of which a good proportion was attributable to basic Fibroblast Growth Factor (bFGF). The addition of bFGF significantly increased dopa oxidase activity of the skin melanocytes, when fibroblasts were present, but not in their absence. These data show that fibroblasts in vitro, particularly when deliberately stressed, have the ability to increase dopa oxidase activity in melanocytes of the hair, the skin and the eye and further suggest that this effect is mediated by bFGF acting in combination with some other fibroblast‐derived factors.
Apoptosis in CD30‐positive lymphoproliferative disorders of the skin
Authors: Greisser Johannes , Doebbeling Udo , Roos Malgorzata , Mueller Beatrix , Schmid Mirka , Burg Günter , Kadin Marshall E. , Kempf Werner
Published: April 2005

Abstract:  The spectrum of CD30‐positive cutaneous lymphoproliferative disorders (CD30+ CLPD) includes lymphomatoid papulosis (LyP), primary cutaneous CD30+ large T‐cell lymphoma (LTCL) and rare borderline patients. Despite their malignant histopathology, CD30+ CLPD exhibit a low‐grade malignant course with an excellent prognosis and a characteristic tendency for spontaneous regression. Apoptosis of tumour cells is considered a principal mechanism of tumour regression. We examined the proliferation and apoptosis rates as well as the expression of apoptosis‐related proteins in various clinical entities, tumour cell lines and evolutional (evolving and regressing) stages of CD30+ CLPD. Skin biopsies of LyP (n = 20) and LTCL (n = 19) and five CD30+ lymphoma cell lines were analysed by means of immunohistochemistry and Western blotting in order to evaluate the proliferation (Ki67), apoptosis (FragEl) and expression of Bax, Bcl‐x, C‐kit and Mcl‐1. A significantly higher apoptotic index (AI) was found in LyP (AI = 12.5%) than in LTCL (AI = 3.1%, P < 0.005). Bax was expressed by the majority of tumour cells in all forms of CD30+ CLPD and CD30+ cell lines. However, no Bax expression was found in tumour cell lines derived from systemic CD30+ lymphomas, which lack spontaneous regression and display an aggressive clinical course. No significant correlation was found between the expression of apoptosis‐related proteins and the tumour type and evolutional stage of CD30+ CLPD. We conclude that the higher AI in LyP may contribute to the regression of LyP lesions and the excellent prognosis of the disease. Pro‐apoptotic protein Bax is expressed at high levels in CD30+ CLPD and may play a crucial role in mediating apoptosis of tumour cells.
In vitro culture of skin‐homing T lymphocytes from inflammatory skin diseases
Authors: Bang Karen , Lund Marianne , Mogensen Søren C. , Thestrup‐Pedersen Kristian
Published: April 2005

Abstract:  We, in this study, describe how T lymphocytes in a skin biopsy can proliferate in vitro for up to 3 months by using T‐cell growth factors – interleukin‐2 (IL‐2) and IL‐4 yielding approximately 100–160 million T lymphocytes within 1 month. We established cell lines from three tuberculin skin tests, four positive patch tests, 15 of 16 biopsies from atopic dermatitis (AD), 15 of 19 biopsies from mycosis fungoides (MF), 12 of 24 biopsies from psoriasis vulgaris, which was significantly less than AD (P < 0.05), and with a reduced cumulative number of lymphocytes (P < 0.05). Omitting IL‐2 and IL‐4 led to immediate halt of proliferation. Blood mononuclear cells from patients and biopsies from healthy persons never gave cell lines. All cells were T lymphocytes expressing CD45RO+, HLA‐DR+ and CD150. The CD7 expression was significantly increased in cell lines from AD (P < 0.05). T‐cell receptor β‐chain studies by using reverse transcription‐polymerase chain reaction showed that all T lymphocytes had access to the skin compartment. Single‐stranded conformational analysis showed clonally expanded T cells numbering between 40 and 60 clones. After approximately 2 months of growth, the mean CD4+ : CD8+ ratio was for AD 1.20, MF 0.65 and psoriasis 0.85. Patients with AD treated with cyclosporin‐A had almost no growth of CD8+ cells in vitro. Our findings indicate a changed homeostasis among skin‐homing lymphocytes for in vitro culture. Our culture system of skin‐homing T lymphocytes leads to a prominent cellular expansion allowing for a range of studies of in vivo activated skin T lymphocytes.
The perception of ward‐based nurses seconded into an Outreach Service
Authors: Plowright Catherine , O'Riordan Bernadette , Scott Glyn
Published: April 2005

A group of ward nurses were seconded into an Outreach Service for a 2‐week period. Following this, the group took part in an evaluation of the placement using a focus group methodology. The aim of this project was to explore the perceptions of a ward‐based nurse recruited into the Outreach Service so that they could function effectively and efficiently in that role.

The intended outcomes of the project were:

– to explore the needs of the new Outreach nurse who was recruited from the ward environment

– to enable the participants of the project to have a better understanding of the role of the Outreach team

– to enable the participants to develop their skills in assessing critically ill patients

– to make recommendations to the Kent Critical Care Network regarding the recruitment of ward staff to Outreach
Assessment of practice using the National Health Service Knowledge and Skills Framework
Authors: McLean Christopher , Monger Eloise , Lally Isabella
Published: April 2005

Current difficulties in the assessment of practice of qualified nurses undertaking courses in critical care nursing are outlined and discussed. The evaluation and development of previously identified core competencies for intensive care nurses is discussed.The use of the National Health Service Knowledge and Skills Framework as a framework for the assessment of practice of nurses undertaking courses in intensive care nursing within one higher education Institution is presented and examined. The potential implications of these developments for practice and education are outlined.
Organ and tissue donation: a trustwide perspective or critical care concern?
Authors: Elding Christine , Scholes Julie
Published: April 2005

Organ donation has become an accepted practice within the critical care setting; however, tissue donation is seldom considered within the ICU environment and even less in other hospital departments.This study describes the results from an early base line audit performed as the first stage in a larger action research project following the implementation of the Donor Liaison Scheme in an NHS trust. It was designed to assess the current level of knowledge, confidence and value system staff have, working in all areas of the hospital setting in relation to organ and tissue donation.The results from this audit highlight key areas for practice development across all areas of this NHS trust.Many healthcare professionals working within this trust are unaware that donation can be considered. The respondents identified a lack of knowledge and confidence to be able to identify and discuss the options of donation with a family, yet the majority believe strongly that a person's wishes should be respected after death.People who have signed on the NHS ODR anticipate that healthcare professionals will access the ODR and support their family in following through their wishes; therefore, all healthcare professionals should receive education on donation issues as an integral part of bereavement and end of life decision training.Education strategies that adopt an experiential approach should be developed in order to create confidence in healthcare professionals to offer choice in donation options
Effects of spaceflight on postnatal development of arterial baroreceptor reflex in rats
Authors: Waki H. , Katahira K. , Yamasaki M. , Nagayama T. , Katsuda S. , Wago H. , Okouchi T. , O‐Ishi H. , Miyake M. , Miyamoto Y. , Shimizu T.
Published: April 2005

Aim:  It has been reported that spaceflight attenuates the arterial baroreceptor reflex. As this reflex function changes dramatically during postnatal development, we hypothesized that space flight depresses the developmental changes of the reflex system. To test this hypothesis, we evaluated the baroreceptor reflex function in rats, which were exposed to a microgravity environment on a space shuttle 9–25 days after birth.

Methods:  Baroreceptor reflex sensitivity and the afferent sensitivity were evaluated by measuring heart rate (HR) and aortic nerve activity (ANA) changes in response to an increase in mean arterial pressure (MBP) derived by phenylephrine injection (20–50 μg kg−1) under urethane‐anaesthesia.

Results:  Baroreceptor reflex sensitivity (% change of HR/% change of MBP) was lower in the flight group (FLT: −0.19 ± 0.04, n = 4) than either the asynchronous ground control group (AGC: −0.47 ± 0.06, n = 6, P < 0.01) or the vivarium group (VIV: −0.41 ± 0.07, n = 6, P < 0.05). This was similar to the differences of the afferent sensitivity (% change of ANA/% change of MBP) between FLT (2.07 ± 0.30) and the control groups (AGC: 2.71 ± 0.22, n.s.; VIV: 3.00 ± 0.32, P < 0.05). At the end of 30 days of recovery under normal gravity conditions, however, there were no significant group differences in these parameters.

Conclusion:  These results suggest that the space environment attenuates the postnatal development of the arterial baroreceptor reflex function in rats, which may be partially because of a depression of the postnatal development of the baroreceptor afferents. These functional alterations, however, recover to their normal level on re‐exposure to the Earth's gravity.
Oestrogen influence on myogenic satellite cells following downhill running in male rats: a preliminary study
Authors: Tiidus P. M. , Deller M. , Liu X. L.
Published: April 2005

Aim:  This study examined the effect of oestrogen supplementation in rats on myogenic satellite cell quantities in type I and II muscles following eccentric exercise.

Methods:  Gonad intact adult male rats divided into four groups, oestrogen supplemented (25 mg oestrogen pellet) control (EC), oestrogen supplemented, exercised (EE), sham (no oestrogen) control (SC) and sham, exercised (SE). After 1 week of oestrogen exposure the EE and SE animals performed 90 min of intermittent downhill running (5 min running/2 min rest @−13.5° incline and 17 m min−1 speed). Seventy‐two hours later exercised (EE and SE) and control (EC and SC) animals were killed and blood samples taken and soleus and white (superficial) vastus muscles surgically removed. Histochemical sections of soleus and white vastus muscles were examined for myogenic satellite cell content by use of Pax7 antibody and for neutrophil content by use of haematoxylin and eosin (H and E) staining procedures.

Results:  Downhill running resulted in significant elevations in satellite cells and neutrophils detected in both soleus and white vastus muscle samples (P < 0.01). Interestingly, oestrogen supplementation resulted in significantly greater (P < 0.01) post‐exercise elevations in satellite cells detected in both soleus and white vastus muscle samples compared with sham (no oestrogen) rats. Increases in neutrophils were significantly (P < 0.05) attenuated in oestrogen supplemented rats relative to sham in soleus but not in white vastus muscles.

Conclusions:  Oestrogen supplementation in male rats may have accentuated the 72 h post‐downhill running increase in Pax7 detected myogenic satellite cell number in both soleus and white vastus muscles relative to unsupplemented rats. The mechanisms and physiological consequences of this effect are yet to be determined.
The significance of rectal bleeding after pelvic radiotherapy
Authors: Williams H. R. T. , Vlavianos P. , Blake P. , Dearnaley D. P. , Tait D. , Andreyev H. J. N.
Published: April 2005

Background : Rectal bleeding after pelvic radiotherapy is often attributed to radiation proctitis and patients do not routinely undergo flexible endoscopy.

Aims : To assess the significance of bleeding after radiotherapy.

Methods : We maintained a prospective register of all such patients referred to our endoscopy unit.

Results : One hundred and thirty‐nine men (median age 70 years; range 31–82), and 32 women (median age 61 years; range 30–81) were referred with rectal bleeding (median 2 years; range 0–21) after pelvic radiotherapy. Primary tumour sites were urological (n = 139), gastrointestinal (n = 7) and gynaecological (n = 25). Ninety patients had bleeding alone; 81 had other symptoms. One hundred and forty‐one had typical radiation proctitis; in 65 this was the sole diagnosis; eight had cancer, nine had high‐risk adenomas, and six had three or more small adenomas. Ninety‐five other diagnoses were made. Eleven (73%) patients with advanced polyps or cancer required only flexible sigmoidoscopy to make the diagnosis, while four (27%) diagnoses were made only after colonoscopy; 47% of these patients had no other symptoms apart from rectal bleeding.

Conclusions : After pelvic radiotherapy, clinical symptoms are not reliable in differentiating between radiation proctitis alone or more significant pathology. It is mandatory that all patients with new onset rectal bleeding are investigated with, at least, flexible sigmoidoscopy.