bluuebunny/crossref_metadata_2025 huggingface dataset:
A multipurpose torsional magnetometer with optical detection
Authors: Schaapman M. R. , Christianen P. C. M. , Maan J. C. , Reuter D. , Wieck A. D.
Published: September 2002

We have developed a sensitive, multipurpose torsional magnetometer with optical detection of the torque. The use of a feedback system with a current coil mounted with the sample allows direct, quantitative determination of the magnetization with a sensitivity of 10−12 J/T in a Bitter-magnet and 2×10−13 J/T at 15 T in a superconducting magnet. The system can be used over a wide range of temperatures and up to high magnetic fields. To demonstrate the sensitivity and versatility of our magnetometer, we present magnetization measurements of a multisubband two-dimensional electron gas (3×1011 spins) and of a 0.13 mg crystal of the organic conductor κ-(BEDT-TTF)2Cu(NCS)2.
Scalable programmable quantum gates and a new aspect of the additivity problem for the classical capacity of quantum channels
Authors: Winter Andreas
Published: September 2002

We consider two apparently separated problems: in the first part of the article we study the concept of a scalable (approximate) programmable quantum gate (SPQG). These are special (approximate) programmable quantum gates, with nice properties that could have implications on the theory of universal computation. Unfortunately, as we prove, such objects do not exist in the domain of usual quantum theory. In the second part the problem of noisy dense coding (and generalizations) is addressed. We observe that the additivity problem for the classical capacity obtained is of apparently greater generality than for the usual quantum channel (completely positive maps): i.e., the latter occurs as a special case of the former, but, as we shall argue with the help of the nonexistence result of the first part, the former cannot be reduced to an instance of the latter. We conclude by suggesting that the additivity problem for the classical capacity of quantum channels, as posed until now, may conceptually not be in its appropriate generality.
Conditional entropies and their relation to entanglement criteria
Authors: Vollbrecht Karl Gerd H. , Wolf Michael M.
Published: September 2002

We discuss conditional Rényi and Tsallis entropies for bipartite quantum systems of finite dimension. We investigate the relation between the positivity of conditional entropies and entanglement properties. It is in particular shown that any state having a negative conditional entropy with respect to any value of the entropic parameter is distillable since it violates the reduction criterion. Moreover, we show that the entanglement of Werner states in odd dimensions can neither be detected by entropic criteria nor by any other spectral criterion.
Ultrahigh boron doping of nanocrystalline diamond films and their electron field emission characteristics
Authors: Jiang X. , Au Frederick C. K. , Lee S. T.
Published: September 2002

Heavily boron-doped nanocrystalline (nc) diamond films were deposited using microwave plasma chemical vapor deposition process in which the growing film surface was continuously bombarded by H+ and hydrocarbon ions. The dependency of grain size and phase purity on the process parameters and boron incorporation was investigated. Due to boron incorporation the grown nc diamond films show a lower intrinsic compressive stress, which is due to a compensation effect between the boron doping-induced tensile stress and the ion subplantation-induced compressive stress. The nc films show strongly improved electron emission properties. Low-field electron emission and high emission current have been achieved from the films consisting of nanosized diamond grains, showing a long-term stability.
The interface screening model as origin of imprint in PbZrxTi1−xO3 thin films. II. Numerical simulation and verification
Authors: Grossmann M. , Lohse O. , Bolten D. , Boettger U. , Waser R.
Published: September 2002

In this article, the interface screening model is theoretically discussed which explains imprint in ferroelectric thin films caused by a large electric field within a surface layer with deteriorated ferroelectric properties. During aging this field is gradually screened by electronic charges. Different screening mechanisms such as charge injection from the electrodes into the film as well as charge separation within the surface layer are considered by implementing a numerical simulation based on the different screening mechanisms. A comparison between experimental and simulation results is presented. The best agreement between experiment and simulation is obtained for a Frenkel–Poole type charge separation mechanism within the surface layer. The simulation results indicate relatively shallow trap states (0.35 eV) and a surface layer extension of approximately 5 nm.
Critical concentration for the doping-induced metal–nonmetal transition in cubic and hexagonal GaN
Authors: Ferreira da Silva A. , Persson C.
Published: September 2002

The critical concentration for the metal–nonmetal transition has been calculated for n-type and p-type GaN. Both cubic and hexagonal structures of GaN have been considered. Three different computational methods have been utilized: the first is the original Mott model, the second is an extended Mott–Hubbard model, and the third method is based on total energy of the metallic and the nonmetallic phases. All three methods show a similar value of the critical concentration, about 1018 and 1020 cm−3 for n-type and p-type doped materials, respectively.
Band-tail profiling in microcrystalline silicon by photoconductivity analysis
Authors: Brüggemann R.
Published: September 2002

This article provides information about localized states in microcrystalline silicon which interact with carriers in the conduction band and it gives an account of their density-of-states profile. Analysis of the photogeneration-rate dependent photocurrent at different temperatures results in a value of the band tail parameter for an exponential band tail of 20 meV between about 0.18 and 0.28 eV below the conduction band. The overall profile is of hybrid form and is less steep at shallower and deeper energies.
Influence of Se on the electron mobility in extruded Bi2(Te1−xSex)3 (x⩽0.125) thermoelectric alloys
Authors: Vasilevskiy D. , Sami A. , Simard J.-M. , Masut R.
Published: September 2002

We present the electrical transport properties of thermoelectric n-type Bi2(Te1−xSex)3 (x⩽0.125) polycrystalline alloys obtained by mechanical alloying and extrusion. It was determined that the charge carrier mobility decreases in the temperature range 90–300 K as the content (x) of Bi2Se3 is increased. The observed decrease is larger than what could be predicted by the introduction of an alloy scattering mechanism due to the electronegativity difference between Se and Te atoms. It can be explained by the introduction of additional defects induced by the Se incorporation, whose concentration is reduced by thermal annealing following extrusion. In the extrinsic regime, the observed temperature dependence of the mobility [μ=μ0(T/T0)r] of as extruded alloys apparently indicates that charge carrier scattering is mostly limited by acoustic phonons (temperature coefficient r near −1.5). Annealing after extrusion changes the temperature coefficient to values near −1.7 which is closer to what has been reported for pure crystalline Bi2Te3.
On the nature of ion implantation induced dislocation loops in 4H-silicon carbide
Authors: Persson P. O. Å. , Hultman L. , Janson M. S. , Hallén A. , Yakimova R. , Panknin D. , Skorupa W.
Published: September 2002

Transmission electron microscopy was used to investigate B11, C12, N14, Al27, Si28, and Ar37 ion-implanted 4H-SiC epilayers and subsequent defect formation after high temperature annealing. During the annealing process extrinsic dislocation loops of interstitial type are formed on the SiC basal plane with a depth distribution roughly corresponding to the distribution of the implanted ions. The investigation reveals that in samples where the implanted ions are substituting for a position in the silicon sublattice, generating an excess of interstitial silicon, the dislocation loops are more readily formed than in a sample implanted with an ion substituting for carbon.
Accurate identification of the band gap of photonic crystals from transmission spectra
Authors: Yamamoto Noritsugu , Noda Susumu
Published: September 2002

The transmission spectra of a three-dimensional photonic crystal for various incident angles was examined. When the incident angle is not normal to the surface of the crystal, the direction of the wave vector of light is sensitive to the frequency. In order to compare the experimental band edge with the theoretical band diagram, we calculated the band diagram of the frequency versus the incident angle by converting the ordinary band diagram, which is ordinarily expressed as the diagram of the frequency versus the internal wave vector. As a result of the comparison, the changes of the band edge which was obtained in the experimental transmission measurement agreed well with the theoretical changes. It became clear that the two-step attenuation of transmission which is at large incident angles is caused by the split of the first and the second band edge (also the third and the fourth band edge) at large incident angles.
Use of polarization sensitivity for three-dimensional optical data storage in polymer dispersed liquid crystals under two-photon illumination
Authors: McPhail Dennis , Gu Min
Published: September 2002

We report on the use of the polarization-dependent fluorescence property in photorefractive polymer dispersed liquid crystals for three-dimensional (3D) optical data storage under two-photon absorption. The liquid crystals, which have optical anisotropy, exhibit an alignment-based fluorescence feature that depends on the polarization state of an excitation field. Such a polarization sensitivity can be confined to the small focal region under two-photon excitation, allowing the stable recording of a 3D bit array. A 3D data density of 204.8 Gbits/cm3 is achieved using ultrashort pulsed illumination at a wavelength of 900 nm. It is also demonstrated that the recorded data can be erased in bulk or as single bits and then rerecorded.
Photoacoustic trace gas detection of ethane using a continuously tunable, continuous-wave optical parametric oscillator based on periodically poled lithium niobate
Authors: van Herpen M. M. J. W. , Li Shaocheng , Bisson S. E. , Harren F. J. M.
Published: September 2002

A 1.2 W, continuous-wave, continuously-tunable, singly-resonant optical parametric oscillator (OPO) (idler tuning range 3.0–3.8 μm), pumped by a 10 W continuous-wave Nd:YAG laser, is used in combination with a photoacoustic cell for the detection of ethane. An intracavity solid-state etalon (thickness 400 μm) was used to stabilize the OPO cavity and could be used to mode-hop tune the idler wavelength over 10 cm−1. The usefulness of the system was demonstrated by determining a detection limit for ethane down to 10 parts per trillion. The selectivity was achieved by making a 24 GHz wide pump laser scan over the ethane absorption line at 2996.9 cm−1, after which a Lorentzian fit determined the total area of the absorption signal. Both area value and peak value proved to be linearly depending on the ethane concentration.
Defect study of GaInP/GaAs based heterojunction bipolar transistor emitter layer
Authors: Cherkaoui K. , Murtagh M. E. , Kelly P. V. , Crean G. M. , Cassette S. , Delage S. L. , Bland S. W.
Published: September 2002

Defects in the emitter region of Ga0.51In0.49P/GaAs heterojunction bipolar transistors (HBTs) were investigated by means of deep-level transient spectroscopy. Both annealed (635 °C, 5 min) and as grown metalorganic chemical vapor deposition epitaxial wafers were investigated in this study, with an electron trap observed in the HBT emitter space-charge region from both wafers. The deep-level activation energy was determined to be 0.87±0.05 eV below the conduction band, the capture cross section 3×10−14 cm2 and the defect density of the order of 1014 cm−3. This defect was also found to be localized at the emitter–base interface.
Hydrogenated amorphous silicon carbide deposition using electron cyclotron resonance chemical vapor deposition under high microwave power and strong hydrogen dilution
Authors: Chew K. , Rusli  , Yoon S. F. , Ahn J. , Ligatchev V. , Teo E. J. , Osipowicz T. , Watt F.
Published: September 2002

We have investigated the growth of a-Si1−xCx:H using the electron cyclotron resonance chemical vapor deposition (ECR-CVD) technique, under the conditions of high microwave power and strong hydrogen (H2) dilution. The microwave power used is 900 W and a gas mixture of CH4 and SiH4 diluted in H2 is varied to give carbon (C) fractions x ranging from 0 to 1. We aim to understand the effects of these deposition conditions on the characteristics of ECR-CVD grown a-Si1−xCx:H films at different x. Their microstructure and optical properties are investigated using infrared absorption, Raman scattering, UV-visible spectrophotometry, and photothermal deflection spectroscopy. Information on the atomic fraction x is obtained with Rutherford backscattering spectrometry. The B parameter in the Tauc relation is found to decrease and the Urbach energy Eu increase with x, which are indicative of a higher degree of disorder with C incorporation. At intermediate x, the presence of Si–C bonds can be clearly seen from the IR absorption and Raman scattering results. The T peak around 1200 cm−1 is observed in the Raman spectra of the C-rich samples, with a redshift noted at increasing x. This suggests an increased presence of sp3 C–C bonds in these films, which is attributed to the high microwave power and strong H2 dilution that enhance C sp3 bonding and indirectly limit the number of C sp2 sites. This accounts for the large E04 gaps of more than 3.2 eV observed in such films, which are nearly saturated at large x, instead of exhibiting a maximum at an intermediate x as are commonly reported. Blue photoluminescence (PL) is observed, and the PL peak energies (EPL) are correlated to the E04 gap. The full width at half maximum of the PL are also correlated to the Urbach energy Eu. These results support that the PL broadening is attributed to the disorder broadening arising from the broad band tails.
Temporally resolved cavity ring-down spectroscopy in a pulsed nitrogen plasma
Authors: Yalin A. P. , Zare R. N. , Laux C. O. , Kruger C. H.
Published: September 2002

Cavity ring-down spectroscopy (CRDS) has enabled temporally resolved measurements of the N2+ ion concentration in a pulsed atmospheric pressure nitrogen plasma. A 10 ns voltage pulse is applied to a dc-sustained plasma to change the ionization fraction rapidly. Our measurements show that the pulse increases the N2+ ion concentration from 3.9×1012 to more than 1.5×1013 cm−3, and that the N2+ concentration returns to the dc level in about 10 μs. We also determine the electron density by measuring the electrical conductivity of the plasma. Because N2+ is the dominant ion, the good agreement between electrical and CRDS measurements provides validation of the temporally resolved CRDS technique.
Intervalley scattering in GaAs–AlAs quantum cascade lasers
Authors: Wilson L. R. , Carder D. A. , Cockburn J. W. , Green R. P. , Revin D. G. , Steer M. J. , Hopkinson M. , Hill G. , Airey R.
Published: September 2002

We have investigated the importance of intervalley (Γ–Χ) electron transfer between Γ-point quantum well states and X-point barrier states in GaAs-based quantum cascade lasers with indirect band gap AlAs barriers. A series of samples has been studied in which the energy separation between the coupled injector/upper laser levels and the lowest confined X state in the injection barrier is varied. We demonstrate that for lasing to occur, electron injection into the upper laser level must proceed via Γ states confined below the lowest X state in the injection barrier. The limit this places on the minimum operating wavelength (λ≈8 μm) for the present laser design is overcome by utilizing a double injection barrier to achieve lasing at λ=7.2 μm.
Capacitance and conductance characterization of ferrocene-containing self-assembled monolayers on silicon surfaces for memory applications
Authors: Li Qiliang , Mathur Guru , Homsi Mais , Surthi Shyam , Misra Veena , Malinovskii Vladimir , Schweikart Karl-Heinz , Yu Lianhe , Lindsey Jonathan S. , Liu Zhiming , Dabke Rajeev B. , Yasseri Amir , Bocian David F. , Kuhr Werner G.
Published: September 2002

Self-assembled monolayers of 4-ferrocenylbenzyl alcohol attached to silicon provided the basis for electrolyte-molecule-silicon capacitors. Characterization by conventional capacitance and conductance techniques showed very high capacitance and conductance peaks near ∼0.6 V associated with charging and discharging of electrons into and from discrete levels in the monolayer owing to the presence of the redox-active ferrocenes. The reversible charge trapping of these molecules suggest their potential application in memory devices. Due to the molecular scalability and low-power operation, molecular-silicon hybrid devices may be strong candidates for next-generation electronic devices.
Local magnetostrictive response of small magnetic entities in artificial Fe–Cr composites
Authors: Polushkin Nikolay I. , Wittborn J. , Canalias C. , Rao K. V. , Alexeev A. M. , Popkov A. F.
Published: September 2002

Nanoscale ferromagnetic entities are directly patterned in superparamagnetic Fe–Cr layers by interfering laser beams. To characterize the formed entities, in addition to the conventional methods, we used a technique for magnetic imaging based on the atomic force microscopy (AFM) with nonmagnetic tips and an ac magnetic field applied in situ. The observed AFM dynamic response is interpreted in terms of magnetostriction and a related quantity, the ac susceptibility.
Impact of annealing-induced compaction on electronic properties of atomic-layer-deposited Al2O3
Authors: Afanas’ev V. V. , Stesmans A. , Mrstik B. J. , Zhao C.
Published: September 2002

Atomic-layer-deposited layers of Al2O3 on (100)Si are shown to transform into γ-Al2O3 when treated at temperatures above 800 °C. The compaction process leads to widening of the alumina band gap and causes an ≈0.5 eV upward shift of the oxide conduction band with respect to the Fermi level of Au and Al. In the case of incomplete transformation of the Al2O3 film, large leakage currents across the oxide are observed, which are explained by the formation of conducting grain boundaries similar to those formed on γ-alumina surfaces.
Lattice-matched HfN buffer layers for epitaxy of GaN on Si
Authors: Armitage R. , Yang Qing , Feick H. , Gebauer J. , Weber E. R. , Shinkai Satoko , Sasaki Katsutaka
Published: September 2002

Gallium nitride is grown by plasma-assisted molecular-beam epitaxy on (111) and (001) silicon substrates using sputter-deposited hafnium nitride buffer layers. Wurtzite GaN epitaxial layers are obtained on both the (111) and (001) HfN/Si surfaces, with crack-free thickness up to 1.2 μm. Initial results for GaN grown on the (111) surface show a photoluminescence peak width of 17 meV at 11 K, and an asymmetric x-ray rocking curve width of 20 arcmin. Wurtzite GaN on HfN/Si(001) shows reduced structural quality and peculiar low-temperature luminescence features. However, growth on the (001) surface results in nearly stress-free films, suggesting that much thicker crack-free layers could be obtained.
Fast polymer integrated circuits
Authors: Fix W. , Ullmann A. , Ficker J. , Clemens W.
Published: September 2002

Using soluble polymers for the active layer and insulating layer, we report on a concept for the fabrication of fast integrated circuits based on p-type organic transistors only. Ring oscillators with frequencies above 100 kHz and propagation stage delays below 0.7 μs are presented. They show a very stable performance over time even without encapsulation, when stored and measured under ambient conditions. Regioregular poly(3-alkylthiophen) is used as the active semiconducting layer, a polymer blend as the insulator, a flexible polyester film as the substrate and metal electrodes. To enable vertical interconnects, the insulating layer is patterned.
Nanotomography based on hard x-ray microscopy with refractive lenses
Authors: Schroer C. G. , Meyer J. , Kuhlmann M. , Benner B. , Günzler T. F. , Lengeler B. , Rau C. , Weitkamp T. , Snigirev A. , Snigireva I.
Published: September 2002

Based on parabolic refractive x-ray lenses we have built a hard x-ray microscope that allows one to image the interior of opaque samples with submicrometer resolution. We have combined magnified imaging with tomography to obtain the three-dimensional structure of the sample at a resolution well below 1 μm. Using an aluminum lens to record a magnified tomogram of a test sample (microprocessor), a resolution of slightly above 400 nm was found for the three-dimensional reconstruction. Lenses made of beryllium are expected to improve this resolution to well below 100 nm. The resulting challenges concerning instrumentation and numerical methods are discussed.
Depth-profiling plasma-induced densification of porous low-k thin films using positronium annihilation lifetime spectroscopy
Authors: Sun Jia-Ning , Gidley David W. , Hu Yifan , Frieze William E. , Ryan E. Todd
Published: September 2002

Positronium annihilation lifetime spectroscopy (PALS) has been used to depth profile the densification induced in a porous low-dielectric constant (k) thin film by typical device integration processing, including exposure to plasmas and oxygen ashing. Such “integration damage” has previously been observed as an undesirable increase in k accompanied by shrinkage in the porous film thickness. PALS confirms that the structural damage is confined to a surface layer of collapsed pores with the underlying pores being undamaged. The dense layer thickness determined by PALS increases with plasma exposure time.
Pulsed laser-assisted surface structuring with optical near-field enhanced effects
Authors: Huang S. M. , Hong M. H. , Luk’yanchuk B. S. , Zheng Y. W. , Song W. D. , Lu Y. F. , Chong T. C.
Published: September 2002

The effects of optical resonance and near field in the interaction of transparent particles on a substrate with laser light have been examined experimentally and theoretically. It is found that pits can be created at the contacting point between the particle and the metallic surface by laser irradiation (KrF,λ=248 nm) with a single pulse. The influence of the particle size and the laser fluence on the structuring of the surface has been investigated. The size of the particle ranges from 1.0 μm to 140 nm in diameter. The morphologies of the holes created have been characterized by an atomic force microscope and a scanning electron microscope. For constant laser fluence, the created hole is sensitive to the particle size. For higher-laser fluence, the corresponding hole becomes larger and deeper. With a low fluence of 300 mJ/cm2 and for 140 nm particles, the lateral dimensions of created pits can be down to 30 nm. With a high fluence of 750 mJ/cm2 and 1.0 μm particles, the diameter and the depth of created holes are about 350 and 100 nm, respectively. Theoretical calculations and an accurate solution of a boundary problem indicate that incident light could excite some resonance modes inside the particle and produce enhanced light intensities on the contacting area (substrate surface). The light intensity on the contacting area is nonuniform and sensitive to the particle size parameter. Experimental results are explained and are very consistent with those of theoretical calculations. The experimental results also provide direct evidence of the optical resonance and near-field effects in the interaction of transparent particles on the substrate with laser light.
Preparation and characterization of a- and b-axis-oriented epitaxially grown Bi4Ti3O12-based thin films with long-range lattice matching
Authors: Watanabe Takayuki , Funakubo Hiroshi , Saito Keisuke , Suzuki Toshimasa , Fujimoto Masayuki , Osada Minoru , Noguchi Yuji , Miyayama Masaru
Published: September 2002

a- and b-axis-oriented epitaxial Bi4Ti3O12 films were prepared on (101)TiO2 (rutile) substrates at 630 °C by metalorganic chemical vapor deposition and their perfect epitaxial growths were confirmed by several x-ray diffraction measurements. As the bottom electrode, (101)-oriented conductive materials with the same rutile-type structure as the TiO2, RuO2, and IrO2, were epitaxially grown on (101)TiO2, (012)Al2O3, and (110)Al2O3 substrates. Finally, a- and b-axis-oriented Bi4Ti3O12-based materials, (Bi4−xNdx)(Ti3−yVy)O12, were epitaxially grown on these conductive substrates with high reproducibility and a well-saturated P–E hysteresis loop with a remanent polarization above 20 μC/cm2 was observed. These results open the long-range lattice matching growth (the c-axis lattice parameter is about 3.3 nm) of a- and b-axis-oriented bismuth layer-structured ferroelectrics on conductive electrodes.
A Comparison between Human and Machine Labelling of Image Regions
Authors: Clark Angus A , Troscianko Tom , Campbell Neill W , Thomas Barry T
Published: September 2002

In previous work (Campbell et al, 1997 Pattern Recognition30 555–563) a vision system was developed which is capable of classifying objects in outdoor scenes. The approach involves segmenting the image into regions, obtaining a feature-based description of each region, and then passing this description on to an artificial neural network (ANN) which has been trained to label the region with one of eleven possible object types. The question addressed here is: how important is each of these features to overall performance, both in human and machine vision?

A set of experiments was conducted in which human subjects were trained in the same labelling task as the ANN. The stimuli, each depicting a single image region, were generated from a large database of urban and rural images. The subjects were then tested on both intact and degraded stimuli. The results suggest that certain features are particularly influential in mediating overall labelling performance.

An equivalent experiment was carried out with the ANN. A method is presented which allows individual features to be corrupted in such a way as to simulate the loss of certain forms of visual information. The results, which are broadly similar to those found in the previous experiment, imply that the ANN can provide a useful model of human image region labelling. It is anticipated that the methodology, which draws on both computational and psychophysical techniques, will be of use to other areas of investigation.
Microtubule-associated protein 1B
Authors: Ding Jianqing , Liu Jia-Jia , Kowal Anthony S. , Nardine Timothy , Bhattacharya Priyanka , Lee Arthur , Yang Yanmin
Published: September 2002

Giant axonal neuropathy (GAN), an autosomal recessive disorder caused by mutations in GAN, is characterized cytopathologically by cytoskeletal abnormality. Based on its sequence, gigaxonin contains an NH2-terminal BTB domain followed by six kelch repeats, which are believed to be important for protein–protein interactions (Adams, J., R. Kelso, and L. Cooley. 2000. Trends Cell Biol. 10:17–24.). Here, we report the identification of a neuronal binding partner of gigaxonin. Results obtained from yeast two-hybrid screening, cotransfections, and coimmunoprecipitations demonstrate that gigaxonin binds directly to microtubule-associated protein (MAP)1B light chain (LC; MAP1B-LC), a protein involved in maintaining the integrity of cytoskeletal structures and promoting neuronal stability. Studies using double immunofluorescent microscopy and ultrastructural analysis revealed physiological colocalization of gigaxonin with MAP1B in neurons. Furthermore, in transfected cells the specific interaction of gigaxonin with MAP1B is shown to enhance the microtubule stability required for axonal transport over long distance. At least two different mutations identified in GAN patients (Bomont, P., L. Cavalier, F. Blondeau, C. Ben Hamida, S. Belal, M. Tazir, E. Demir, H. Topaloglu, R. Korinthenberg, B. Tuysuz, et al. 2000. Nat. Genet. 26:370–374.) lead to loss of gigaxonin–MAP1B-LC interaction. The devastating axonal degeneration and neuronal death found in GAN patients point to the importance of gigaxonin for neuronal survival. Our findings may provide important insights into the pathogenesis of neurodegenerative disorders related to cytoskeletal abnormalities.
Mycobacterium and the coat of many lipids
Authors: Russell David G. , Mwandumba Henry C. , Rhoades Elizabeth E.
Published: September 2002

Pathogenic Mycobacterium reside inside vacuoles in their host macrophages. These vacuoles fail to fuse with lysosomes yet interact with early endosomes. Glycoconjugates released by the intracellular bacilli traffic through the host cell and are released through exocytosis. These molecules represent both antigens for immune recognition and modulators of immune function. The molecules play key roles in the induction and maintenance of the granuloma, a tissue response that limits bacterial spread yet ensures persistence of the infection.
Uncoupling of Gating Charge Movement and Closure of the Ion Pore During Recovery from Inactivation in the Kv1.5 Channel
Authors: Wang Zhuren , Fedida David
Published: September 2002

Both wild-type (WT) and nonconducting W472F mutant (NCM) Kv1.5 channels are able to conduct Na+ in their inactivated states when K+ is absent. Replacement of K+ with Na+ or NMG+ allows rapid and complete inactivation in both WT and W472F mutant channels upon depolarization, and on return to negative potentials, transition of inactivated channels to closed-inactivated states is the first step in the recovery of the channels from inactivation. The time constant for immobilized gating charge recovery at −100 mV was 11.1 ± 0.4 ms (n = 10) and increased to 19.0 ± 1.6 ms (n = 3) when NMG+o was replaced by Na+o. However, the decay of the Na+ tail currents through inactivated channels at −100 mV had a time constant of 129 ± 26 ms (n = 18), much slower than the time required for gating charge recovery. Further experiments revealed that the voltage-dependence of gating charge recovery and of the decay of Na+ tail currents did not match over a 60 mV range of repolarization potentials. A faster recovery of gating charge than pore closure was also observed in WT Kv1.5 channels. These results provide evidence that the recovery of the gating elements is uncoupled from that of the pore in Na+-conducting inactivated channels. The dissociation of the gating charge movements and the pore closure could also be observed in the presence of symmetrical Na+ but not symmetrical Cs+. This difference probably stems from the difference in the respective abilities of the two ions to limit inactivation to the P-type state or prevent it altogether.
Minimal structures: from the classroom to management structures
Authors: Pina e Cunha Miguel , Vieira da Cunha João
Published: September 2002

In this paper, we discuss the topic of participation in the classroom and explore its implications for management development. We suggest that participation is triggered when there is motivation (interest in course content) and potential (resources) for it. The success of participation depends on the presence of a minimal interaction structure and results in higher levels of perceived learning and perceived class quality. The paper advances a process approach to organizational participation and highlights the necessity of a dialectical approach to organizational phenomena.
People management in SMEs: an analysis of human resource strategies in family and non‐family businesses
Authors: Reid Renee , Morrow Trevor , Kelly Bridgita , McCartan Pat
Published: September 2002

This paper examines the findings of a large‐scale postal survey based on an adaptation of the Cranfield Network (CRANET) Survey of International Strategic Human Resource Management (SHRM) to facilitate the analysis of HRM practices in the SME business environment. These findings are considered in light of a review of HRM literature. The survey utilised a sample of 1,369 organisations representing every company employing between 20‐100 people in Northern Ireland. This paper analyses key issues emerging from the 219 (16 per cent) responses received and provides a comparison of HRM practices in family and non‐family businesses. Overall, the findings suggest that family business practices within HRM are different than their non‐family counterparts.
Site‐specific DNA cleavage of synthetic NarL sites by an engineered Escherichia coli NarL protein–1,10‐phenanthroline cleaving agent
Authors: Xiao Gaoping , Cole Daniel L. , Gunsalus Robert P. , Sigman David S. , Chen Chi‐Hong B.
Published: September 2002

The NarL response regulatory protein of Escherichia coli has been engineered by covalent modification with 1,10‐phenanthroline (OP) to create a set of site‐specific DNA‐cleaving agents. This was accomplished by introducing single cysteine amino acid replacements at selected locations within the carboxy‐terminal DNA‐binding domain in or nearby the helix 8 to helix 9 region of the NarL protein using site‐directed mutagenesis. Of 18 modified NarL‐OP proteins made, 13 retained the ability to bind DNA as evidenced by gel mobility assays, whereas 10 of the 1,10‐phenanthroline‐modified proteins also exhibited specific cleavage activity for a synthetic NarL recognition sequence. These DNA‐cleaving agents were divided into two groups based on the location of the cleavage sites. The first class set cleaved the DNA nearby the center of a synthetic 7–2–7 sequence composed of two NarL heptamer sites separated by a 2‐bp spacer element. The second class cut the DNA at the periphery of the 7–2–7 sequence. The cleavage data are consistent with the ability of two NarL monomers to recognize and bind to the DNA in a head‐to‐head orientation. A second set of DNA‐cleaving agents was constructed using the carboxy‐terminal domain of NarL called NarLC. Similar cleavage patterns were observed whether full‐length NarL or NarLC was used. The availability of 1,10‐phenanthroline‐modified NarL and NarLC proteins opens up the possibility to explore the position, orientation, and number of NarL recognition sites at E. coli promoters predicted to contain multiple and complex arrangements of NarL‐binding sites.
Quantitation of Human Immunodeficiency Virus Type 1 DNA Forms with the Second Template Switch in Peripheral Blood Cells Predicts Disease Progression Independently of Plasma RNA Load
Authors: Kostrikis Leondios G. , Touloumi Giota , Karanicolas Rose , Pantazis Nikos , Anastassopoulou Cleo , Karafoulidou Anastasia , Goedert James J. , Hatzakis Angelos
Published: September 2002

There are several forms of human immunodeficiency virus type 1 (HIV-1) DNA in peripheral blood T cells and lymph nodes in untreated HIV-1-infected individuals and in patients whose plasma HIV-1 RNA levels are suppressed by long-term combination antiretroviral therapy. However, it remains to be established whether the concentration of HIV-1 DNA in cells predicts the clinical outcome of HIV-1 infection. In this report, we measured the concentration of HIV-1 DNA forms which has undergone the second template switch (STS DNA) and 2-long-terminal-repeat DNA circles in peripheral blood mononuclear cell (PBMC) samples. To do this, we used molecular-beacon-based real-time PCR assays and studied 130 patients with hemophilia in the Multicenter Hemophilia Cohort Study. We assessed the influence of baseline HIV-1 STS DNA levels on the progression of HIV-1 disease in the absence of combination antiretroviral therapy by Kaplan-Meier and Cox regression analysis. Among the patients who progressed to AIDS, the median levels (interquartile ranges) of STS HIV-1 DNA in PBMC were significantly higher than those of patients who remained AIDS free during the 16 years of follow-up (1,017 [235 to 6,059] and 286 [31 to 732] copies per 10
6
PBMC, respectively;
P
< 0.0001). Rates of progression to death and development of AIDS varied significantly (log rank
P
< 0.001) by quartile distribution of HIV-1 STS DNA levels. After adjustment for age at seroconversion, baseline CD4
+
T-cell counts, plasma viral load, and T-cell-receptor excision circles, the relative hazards (RH) of death and AIDS were significantly increased with higher HIV-1 STS DNA levels (adjusted RH, 1.84 [95% confidence interval {CI}, 1.30 to 2.59] and 2.62 [95% CI, 1.75 to 3.93] per 10-fold increase per 10
6
PBMC, respectively). HIV-1 STS DNA levels in each individual remained steady in longitudinal PBMC samples during 16 years of follow-up. Our findings show that the concentration of HIV-1 STS DNA in PBMC complements the HIV-1 RNA load in plasma in predicting the clinical outcome of HIV-1 disease. This parameter may have important implications for understanding the virological response to combination antiretroviral therapy.
Signal Transduction and Transcription Factor Modification during Reactivation of Epstein-Barr Virus from Latency
Authors: Bryant Helen , Farrell Paul J.
Published: September 2002

Reactivation of Epstein-Barr virus (EBV) from latency involves activation of the Zp promoter of the EBV BZLF1 gene. This occurs rapidly and efficiently in response to cross-linking the B-cell receptor on Akata Burkitt's lymphoma cells. After optimizing conditions for induction, signal transduction responses to B-cell receptor cross-linking were observed within 10 min, well before any autoactivation effects of BZLF1 protein. The primary events in reactivation were shown to involve dephosphorylation of the myocyte enhancer factor 2D (MEF-2D) transcription factor via the cyclosporin A-sensitive, calcium-mediated signaling pathway. This and other signal transduction events were correlated with the quantitative promoter analysis reported in the accompanying paper (U. K. Binné, W. Amon, and P. J. Farrell, this issue). Dephosphorylation of MEF-2D is known to be associated with histone acetylase recruitment, correlating with the histone acetylation at Zp during reactivation that we reported previously (Jenkins et al., J. Virol.74:710-720, 2000). Histone deacetylation in response to phosphorylated MEF-2D can be mediated by class I or class II histone deacetylases (HDACs); HDAC 7 was the most readily detected class II HDAC in Akata and Raji cells, suggesting that it may be involved in Zp repression during latency.
Role for Human Immunodeficiency Virus Type 1 Membrane Cholesterol in Viral Internalization
Authors: Guyader Mireille , Kiyokawa Etsuko , Abrami Laurence , Turelli Priscilla , Trono Didier
Published: September 2002

The membrane of human immunodeficiency virus type 1 (HIV-1) virions contains high levels of cholesterol and sphingomyelin, an enrichment that is explained by the preferential budding of the virus through raft microdomains of the plasma membrane. Upon depletion of cholesterol from HIV-1 virions with methyl-β-cyclodextrin, infectivity was almost completely abolished. In contrast, this treatment had only a mild effect on the infectiousness of particles pseudotyped with the G envelope of vesicular stomatitis virus. The cholesterol-chelating compound nystatin had a similar effect. Cholesterol-depleted HIV-1 virions exhibited wild-type patterns of viral proteins and contained normal levels of cyclophilin A and glycosylphosphatidylinositol-anchored proteins. Nevertheless, and although they could still bind target cells, these virions were markedly defective for internalization. These results indicate that the cholesterol present in the HIV-1 membrane plays a prominent role in the fusion process that is key to viral entry and suggest that drugs capable of disturbing the lipid composition of virions could serve as a basis for the development of microbicides.
A Structural Model of Pestivirus E
rns
Based on Disulfide Bond Connectivity and Homology Modeling Reveals an Extremely Rare Vicinal Disulfide
Authors: Langedijk J. P. M. , van Veelen P. A. , Schaaper W. M. M. , de Ru A. H. , Meloen R. H. , Hulst M. M.
Published: September 2002

E
rns
is a pestivirus envelope glycoprotein and is the only known viral surface protein with RNase activity. E
rns
is a disulfide-linked homodimer of 100 kDa; it is found on the surface of pestivirus-infected cells and is secreted into the medium. In this study, the disulfide arrangement of the nine cysteines present in the mature dimer was established by analysis of the proteolytically cleaved protein. Fragments were obtained after digestion with multiple proteolytic enzymes and subsequently analyzed by liquid chromatography-electrospray ionization mass spectrometry. The analysis demonstrates which cysteine is involved in dimerization and reveals an extremely rare vicinal disulfide bridge of unknown function. With the assistance of the disulfide arrangement, a three-dimensional model was built by homology modeling based on the alignment with members of the Rh/T2/S RNase family. Compared to these other RNase family members, E
rns
shows an N-terminal truncation, a large insertion of a cystine-rich region, and a C-terminal extension responsible for membrane translocation. The homology to mammalian RNase 6 supports a possible role of E
rns
in B-cell depletion.
Evolutionary Dynamics of Viral Attenuation
Authors: Badgett Marty R. , Auer Alexandra , Carmichael Leland E. , Parrish Colin R. , Bull James J.
Published: September 2002

The genetic trajectory leading to viral attenuation was studied in a canine parvovirus (CPV) strain grown on dog kidney cells for 115 transfers. Consensus sequences of viral populations at passages 0, 3, 30, 50, 80, and 115 were obtained from PCR products covering 86% of the genome; clones from each of the 80th and 115th passages were also sequenced, covering 69% of the genome. Sixteen changes were fixed in the 115th-passage virus sample. Levels of polymorphism were strikingly different over time, in part because of a plaque-cloning step at passage 112 that reduced variation: passage 80 had 19 variants common among the clones, but passage 115 had only a single common variant. Several mutations increased in the culture at the same time, with most reaching fixation only after the 80th passage. The pattern of evolution was consistent with recombination and not with separate selective sweeps of individual mutations. Thirteen of the changes observed were identical to or at the same positions as changes observed in other isolates of CPV or feline panleukopenia virus.
CENTRAL SEQUENCE SUBFACTORS AND DOUBLE COMMUTANT PROPERTIES
Authors: KAWAMURO KEIKO
Published: September 2002

First, we construct the Jones tower and tunnel of the central sequence subfactor arising from a hyperfinite type II 1 subfactor with finite index and finite depth, and prove each algebra has the double commutant property in the ultraproduct of the enveloping II 1 factor. Next, we show the equivalence between Popa's strong amenability and the double commutant property of the central sequence factor for subfactors as above without assuming the finite depth condition.
THE TENSOR PRODUCT IN THE THEORY OF FROBENNIUS MANIFOLDS
Authors: KAUFMANN RALPH M.
Published: September 2002

We introduce the operation of forming the tensor product in the theory of analytic Frobenius manifolds. Building on the results for formal Frobenius manifolds which we extend to the additional structures of Euler fields and flat identities, we prove that the tensor product of pointed germs of Frobenius manifolds exists. Furthermore, we define the notion of a tensor product diagram of Frobenius manifolds with factorizable flat identity and prove the existence of such a diagram and hence a tensor product Frobenius manifold. These diagrams and manifolds are unique up to equivalence. Finally, we derive the special initial conditions for a tensor product of semi-simple Frobenius manifolds in terms of the special initial conditions of the factors.
NEW EXAMPLES OF CONTINUOUS SPATIAL SEMIGROUPS OF *-ENDOMORPHISMS OF ${\mathfrak B} ({\mathfrak h})$
Authors: POWERS ROBERT T.
Published: September 2002

This paper concerns the structure of continuous spatial semigroups of *-endomorphisms of [Formula: see text]. These are semigroups of *-endomorphisms of [Formula: see text] for which there exist a strongly continuous one parameter semigroup of intertwining isometries. New examples of such semigroups are constructed. Unlike all previous examples these semigroups are not cocycle conjugate to semigroups constructed using the CAR or CCR algebras.
ON THE DEGREE AND THE BIRATIONALITY OF THE SECOND ADJUNCTION MAPPING
Authors: BELTRAMETTI MAURO C. , SOMMESE ANDREW J.
Published: September 2002

Let ℒ be a very ample line bundle on ℳ, a projective manifold of dimension n ≥3. Under the assumption that Kℳ + (n-2) ℒ has Kodaira dimension n, we study the degree of the map ϕ associated to the complete linear system |2(KM + (n-2) L)|, where (M, L) is the first reduction of (ℳ, ℒ). In particular we show that under a number of conditions, e.g. n ≥ 5 or Kℳ + (n-3)ℒ having nonnegative Kodaira dimension, the degree of ϕ is one, i.e. ϕ is birational. We also show that under a mild condition on the linear system |KM + (n-2) L| satisfied for all known examples, ϕ is birational unless (ℳ, ℒ) is a three dimensional variety with very restricted invariants. Moreover there is an example with these invariants such that deg ϕ= 2.
PAIRS OF SIMPLE DIMENSION GROUPS
Authors: KISHIMOTO A.
Published: September 2002

Given a pair of simple dimension groups with isomorphic state spaces we try to express it as the pair K0(A),K0(A×αR) of K0 groups for a C*-algebra A with an action α of R, where both A and the crossed product A×αR are supposed to be simple AT algebras of real rank zero. We solve this when the state spaces are finite-dimensional.
HARMONIC SURFACES IN AFFINE 4-SPACE
Authors: LI JIANGFAN
Published: September 2002

A theorem of Bernstein type is established saying that a complete affinely harmonic graph in R4 is affinely equivalent to {(x,y,xy,y2 - x2)|(x,y)∈ R2}. The structures of flat affinely harmonic surfaces are determined.
THE KOBAYASHI k-METRICS ON COMPLEX SPACES
Authors: THAI DO DUC , DUC PHAM VIET
Published: September 2002

In this article we are going to give a characterization of the hyperbolicity of complex spaces through the Kobayashi k-metrics on complex spaces and to give an integrated representation of the Kobayashi pseudo-distance on any complex space. Moreover, it is shown that a complex space is hyperbolic iff every irreducible branch of this space is hyperbolic.
A ROHLIN TYPE THEOREM FOR AUTOMORPHISMS OF CERTAIN PURELY INFINITE C*-ALGEBRAS
Authors: NAKAMURA HIDEKI
Published: September 2002

We show a noncommutative Rohlin type theorem for automorphisms of a certain class of purely infinite simple C*-algebras. This class consists of the purely infinite unital simple C*-algebras which are in the bootstrap category [Formula: see text] and have trivial K1-groups.
HERMES AND THE SPIN OF THE PROTON
Authors: JACKSON H. E.
Published: September 2002

HERMES is a second generation experiment to study the spin structure of the nucleon, in which measurements of the spin dependent properties of semi-inclusive deep-inelastic lepton scattering are emphasized. Data have been accumulated for semi-inclusive pion, kaon, and proton double-spin asymmetries, as well as for high-pT hadron pairs, and single-spin azimuthal asymmetries for pion electroproduction and deep virtual Compton scattering. These results provide information on the flavor decomposition of the polarized quark distributions in the nucleon and a first glimpse of the gluon polarization, while the observation of the azimuthal asymmetries show promise for probing the tensor spin of the nucleon and isolating the total angular momentum carried by the quarks.