bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental observation of dominant propagation of the ion-acoustic slow mode in a negative ion plasma and its application
Authors: Ichiki Ryuta , Yoshimura Shinji , Watanabe Tsuguhiro , Nakamura Yoshiharu , Kawai Yoshinobu
Published: October 2002

Different characteristics of ion acoustic waves were experimentally observed in two types of Xe+–F− double plasmas at different electron temperatures. For the lower electron temperature (around 0.15 eV), the slow mode, which had been considered not to dominate the wave propagation, was found to be dominant rather than the fast mode, which was observed to be dominant for the higher electron temperature (around 1.5 eV). According to the previous numerical investigation [Phys. Plasmas 8, 4275 (2001)], the new wave characteristic appeared when the ratio of negative ion mass to positive ion mass and to the ratio of electron temperature to ion temperature are lower than certain critical values. Further, a method of evaluating both the positive ion temperature and the negative ion temperature in a negative ion plasma by observing the dominant slow mode is described. Using this method, the positive and negative ion temperatures in the former plasma were estimated to be 0.075 eV at the highest and 0.1 eV at the lowest, respectively.
Negatively curved spongy carbon
Authors: Barborini E. , Piseri P. , Milani P. , Benedek G. , Ducati C. , Robertson J.
Published: October 2002

We describe the production and characterization of a form of nanostructured carbon consisting of fully connected, three-dimensional (3D) sp2 networks. This form of carbon is characterized by interconnected thin layers forming a spongy structure with meso- and macroporosity. It is produced by a pulsed microplasma cluster source in the presence of a very low concentration of metallorganic catalyst. The unique 3D structure and topology of the spongy carbon are very interesting for catalysis and electrochemical applications and for the investigation of negatively curved forms of carbon such as schwarzites.
Lifetime of nonequilibrium zone-center longitudinal optical phonons in zinc-blende materials
Authors: Barman Saswati , Srivastava G. P.
Published: October 2002

We employ a theoretical model to assess the importance of Ridley’s channel in limiting the lifeitime of nonequilibrium zone-center LO phonons in zinc-blende materials. For comparison, we also present results for the decay through Klemens’s channel as well as via Vallée–Bogani’s intraband combination channel.
Nanowires of metal borates
Authors: Ma Renzhi , Bando Yoshio , Sato Tadao
Published: October 2002

Nanowires of metal borates Al18B9O33 and MgB4O7 were synthesized by thermal evaporation of mixed powders containing metal oxide (Al2O3 or MgO) and boron oxide. Typical widths of these nanowires are in the range of 10 to ∼100 nm and lengths are in the range of several to several tens of micrometers. The nanowires were studied using a high-resolution transmission electron microscope equipped with electron energy loss spectrometer and energy dispersive x-ray spectrometer. The metal borate nanowires fabricated in this way are single crystals. It is proposed that these metal borate nanowires are grown in a vapor–solid process, in which both the metal oxide and boron oxide vapors were simultaneously involved.
Nanofabrication of integrated magnetoelectronic devices using patterned self-assembled copolymer templates
Authors: Bal M. , Ursache A. , Tuominen M. T. , Goldbach J. T. , Russell T. P.
Published: October 2002

Conventional lithographic exposure is used to selectively degrade regions of a self-assembled diblock copolymer film to obtain a honeycomblike nanoporous array template with arbitrary lateral design. Combined with other lithographic process steps, this enables the fabrication of arrays of nanostructures interfaced to electrical probes for device applications. To demonstrate, a unique magnetotransport device is fabricated, consisting of an array of electrodeposited Co nanowires standing atop a thin gold film patterned into a four-probe resistor configuration. Magnetoresistance measurements, performed at various temperatures and magnetic field orientations, reveal the coexistence of anisotropic magnetoresistance and giant magnetoresistance.
Numerical simulation analysis of a near-field optical virtual probe
Authors: Hong Tao , Wang Jia , Sun Liqun , Li Dacheng
Published: October 2002

A near-field optical virtual probe based on the principle of near-field evanescent wave interference can be used in optical data storage, nanolithography, near-field optical imaging, and optical manipulation. This letter gives the numerical simulation results of the optical distribution of a near-field virtual probe and analyzes the dependence of the virtual probe’s on the aperture, the polarization, etc. The simulation results reveal that the transmission efficiency is higher than that of a nanoaperture metal-coated fiber probe. The size of the virtual probe is constant when the distance between the lens and recording media increases within a certain range so that the critical nanoseparation control in near-field system can be relaxed.
Antiferromagnetic hysteresis in magnetoresistive multilayers investigated by x-ray resonant scattering
Authors: Spezzani Carlo , Torelli Piero , Sacchi Maurizio , Delaunay Renaud , Hague Coryn F. , Cros Vincent , Petroff Frédéric
Published: October 2002

We have used resonant scattering of polarized soft x rays as a direct probe of the magnetic order in a weakly coupled Co/Cu multilayer. Our field dependent results, combined with in situ resistance measurements, show a direct correlation between magnetoresistance and antiparallel magnetic ordering in reversible and irreversible processes.
Enhanced luminescence of pulsed-laser-deposited Y2O3:Eu3+ thin-film phosphors by Li doping
Authors: Yi Soung-soo , Bae Jong Seong , Moon Byung Kee , Jeong Jung Hyun , Park Jung-Chul , Kim Ill Won
Published: October 2002

Y 2 O 3 : Eu 3+ and Li-doped Y2O3:Eu3+ luminescent thin films have been grown on sapphire substrates using pulsed-laser deposition. The films grown under different deposition conditions have been characterized using microstructural and luminescent measurements. The photoluminescence (PL) brightness data obtained from Li-doped Y2O3:Eu3+ films grown under optimized conditions have indicated that sapphire is a promising substrate for the growth of high-quality Li-doped Y2O3:Eu3+ thin-film red phosphor. In particular, the incorporation of Li+ ions into Y2O3 lattice could induce a remarkable increase of PL. The highest emission intensity was observed with LiF-doped Y1.84Li0.08Eu0.08O3, whose brightness was increased by a factor of 2.7 in comparison with that of Y2O3:Eu3+ films. This phosphor may promise for application to the flat panel displays.
Explanation for the leakage current in polycrystalline-silicon thin-film transistors made by Ni-silicide mediated crystallization
Authors: van der Zaag P. J. , Verheijen M. A. , Yoon S. Y. , Young N. D.
Published: October 2002

The source of the leakage current in polycrystalline-silicon (poly-Si) thin-film transistors (TFTs) made by Ni-mediated crystallization has been investigated. Studies of TFTs and of the crystallization process by in situ transmission electron microscopy show that the crystallization process is a two-stage process and that the cause of the leakage problem is associated with incomplete crystallization of amorphous-Si. By removing the last pockets of amorphous-Si, for instance, by long anneals, poly-Si TFTs can be made with adequately low leakage current <1 pA/μm (at a source–drain voltage of 5 V) for display applications, despite the presence of Ni up to 2.5×1019 atoms/cm3.
Strained M-plane GaN for the realization of polarization-sensitive photodetectors
Authors: Ghosh Sandip , Brandt O. , Grahn H. T. , Ploog K. H.
Published: October 2002

We theoretically investigate the oscillator strengths of the three band-edge transitions and the resulting polarization anisotropy of the absorption coefficient for an M-plane ([11̄00] oriented) GaN film as a function of an arbitrary in-plane strain. Light incident normally on an M-plane film can be completely polarized parallel or perpendicular to the unique c axis of wurtzite GaN. We show that for a particular range of M-plane strain, both the wavelength range, over which the polarization anisotropy in the absorption occurs, and its magnitude are enhanced. Consequently, strained M-plane GaN becomes a promising candidate for realizing polarization-sensitive photodetectors. For such an application, we also determine the strain dependence of the operating wavelength characteristics.
Magnetization dependence of training effect of exchange coupling in ferromagnet/FeMn bilayers
Authors: Yuan S. J. , Wang L. , Zhou S. M. , Lu M. , Du J. , Hu A.
Published: October 2002

The exchange coupling and its training effect are studied as a function of the ferromagnetic layer magnetization by using various ferromagnet/FeMn bilayers with ferromagnetic materials Ni, Ni81Fe19, Ni50Fe50, Co, and Fe. The exchange coupling energy Jex increases with increasing MFM as Jex∝MFM. The training effect of the exchange field is related to both the ferromagnet magnetization and the magnetization reversal mechanism. For ferromagnet/FeMn bilayers with similar magnetization reversal mechanisms, the relative change of the exchange field decreases with increasing magnetization in an exponential manner.
Domain switching characteristics and fabrication of periodically poled potassium niobate for second-harmonic generation
Authors: Kim Joong Hyun , Yoon Choon Sup
Published: October 2002

We report on the 180° domain switching characteristics and fabrication of periodically poled KNbO3 for second-harmonic generation. Using a modified triangular pulse, a periodically poled KNbO3 of very high quality was fabricated with dimensions of 3×4×0.925 (a×b×c) mm3 and a period of 32.5 μm to utilize the d31 component of the second-order nonlinear optical coefficient tensor. An efficient second-harmonic generation of a mode-locked Nd:YAG laser, operated at 1064 nm with a pulse width of 35 ps, was achieved with a maximum conversion efficiency of 34.8%. The effective nonlinear coefficient, measured in the limit of undepleted pump approximation, was 5.2 pm/V, which is 68% of the theoretical value.
Ultrathin silicon dioxide layers with a low leakage current density formed by chemical oxidation of Si
Authors: Asuha  , Kobayashi Takuya , Maida Osamu , Inoue Morio , Takahashi Masao , Todokoro Yoshihiro , Kobayashi Hikaru
Published: October 2002

Chemical oxidation of Si by use of azeotrope of nitric acid and water can form 1.4-nm-thick silicon dioxide layers with a leakage current density as low as those of thermally grown SiO2 layers. The capacitance–voltage (C–V) curves for these ultrathin chemical SiO2 layers have been measured due to the low leakage current density. The leakage current density is further decreased to ∼1/5 (cf. 0.4 A/cm2 at the forward gate bias of 1 V) by post-metallization annealing at 200 °C in hydrogen. Photoelectron spectroscopy and C–V measurements show that this decrease results from (i) increase in the energy discontinuity at the Si/SiO2 interface, and (ii) elimination of Si/SiO2 interface states and SiO2 gap states.
Field emission properties of porous diamond-like films produced by chemical vapor deposition
Authors: Mammana V. P. , Santos T. E. A. , Mammana A. P. , Baranauskas V. , Ceragioli Helder J. , Peterlevitz A. C.
Published: October 2002

The field emission properties of “porous diamond-like” carbon structures have been characterized. A hot filament chemical vapor deposition system fed with ethyl alcohol vapor diluted in helium was used to deposit the samples. Morphological analysis by field emission scanning electron microscopy revealed that they had a highly porous structure, which was attributed to the modification of the kinetics of the carbon deposition process due to the presence of helium as a buffer gas. Micro-Raman spectroscopy showed two peaks in the graphene and microcrystalline graphite frequencies and a new peak at 1620 cm−1. Low threshold fields (Et) and hysteresis in the current versus voltage characteristic have been observed, and a model to explain the hysteresis is proposed.
Electron transport studies on In0.30Ga0.70As/GaAs-quantum-well infrared photodetectors using time-resolved photocurrent measurements
Authors: Steinkogler S. , Schneider H. , Rehm R. , Walther M. , Koidl P.
Published: October 2002

We report on the time-resolved photocurrent response of an InGaAs/GaAs quantum-well infrared photodetector stimulated by infrared fs-laser pulses (∼9 μm wavelength). We observe two dynamic photocurrent components, which are driven by the optical excitation and by the photoinduced space charge, respectively. The ratio of the time-averaged values of these two components allows us to determine the photoconductive gain. These gain values exhibit a good quantitative agreement with the gain obtained from continuous waves measurements of the peak responsivity. Furthermore, we present a detailed study of the decay time constant of the slow component as a function of the temperature and the bias voltage and compare our results with a recent theoretical model.
Magnetocaloric effect in layered perovskite manganese oxide La1.4Ca1.6Mn2O7
Authors: Zhu Hong , Song Hao , Zhang YuHeng
Published: October 2002

We report the discovery of a large magnetic entropy change in La1.4Ca1.6Mn2O7, a bilayered perovskite manganese oxide that has a Curie temperature (TC) of about 270 K and which allows magnetic refrigeration at room temperature. The magnetic entropy changes reach values of 11.3 J K−1 kg−1 and 16.8 J K−1 kg−1 for field changes of 2 T and 5 T, respectively. The refrigerant capacity of our material is much larger than that of Gd. The large entropy change can be attributed to the fact that the ferromagnetic transition enhances the effect of the applied magnetic field greatly.
Flexoelectric polarization of barium strontium titanate in the paraelectric state
Authors: Ma Wenhui , Cross L. Eric
Published: October 2002

The strain-gradient-induced polarization (flexoelectric effect) was investigated in Ba0.67Sr0.33TiO3 (BST) ceramic at temperatures above the 21 °C Curie point. At 23 °C the flexoelectric coefficient μ12 was more than one order of magnitude greater than the highest value measured in lead magnesium niobate ceramic. Over the temperature range of linear Curie–Weiss behavior, the coefficient μ12 was roughly proportional to the dielectric permittivity; however, the constant of proportionality was higher than predicted for simple ionic solids. The unexpected behavior in the BST ceramic suggests the need for a broader database of flexoelectric coefficients.
Frequency characterization and modeling of interface traps in HfSixOy/HfO2 gate dielectric stack from a capacitance point-of-view
Authors: Masson Pascal , Autran Jean-Luc , Houssa Michel , Garros Xavier , Leroux Charles
Published: October 2002

A time-resolved analysis of the capacitance–voltage (C–V) technique and an inverse modeling approach have been developed to determine the energy distribution and the capture cross section of interface traps in the silicon band gap from multifrequency C–V measurements. In this work, our method is performed on n-type metal-oxide-semiconductor capacitors with HfSixOy/HfO2 gate dielectric stack and polysilicon gate. From the frequency dispersion of C–V data, we evidence a peak of acceptor states in the upper half of the band gap at 0.81 eV above the valence band and characterized by a capture cross section of 1.5×10−17 cm2. This value is approximately ten times lower than typical capture cross sections relative to the dangling bonds (Pb centers) at the Si/SiO2 interface, which is in good agreement with a Coulombic center model predicting a capture cross section inversely proportional to the square of the dielectric permittivity.
On–off switching of edge direct tunneling currents in metal-oxide-semiconductor field-effect transistors
Authors: Chen Ming-Jer , Lu Ming-Pei
Published: October 2002

On–off switching behaviors or two-level random telegraph signals (RTS) are measured in the low voltage (−1.40 V<VG<−0.88 V) edge direct tunneling currents in ultrathin gate stack (10 Å oxide+10 Å nitride) n-channel metal-oxide-semiconductor field-effect transistors. The plausible origin is the process-induced defects in terms of localized gate stack thinning (or equivalently the conductive filament). In such extrinsic case, the current trapping–detrapping theories can adequately elucidate the data, particularly the RTS magnitude as large as 18%. The current–voltage characteristic associated with a certain defective spot is assessed straightforwardly, showing remarkable compatibility with existing oxide thinning case. Systematic measurements of RTS in the terminal currents allow for determining the occurrence probability as well as locations of defects, and may be treated as a sensitive process monitor.
Noninvasive magnetic imaging and magnetization measurement of isolated mesoscopic Co rings
Authors: Bekaert J. , Buntinx D. , Van Haesendonck C. , Moshchalkov V. V. , De Boeck J. , Borghs G. , Metlushko V.
Published: October 2002

A high-resolution scanning Hall probe microscope was used as a noninvasive technique to visualize the magnetization reversal in an array of micron-size Co rings. Two stable “onion” states at remanence and “vortex” states at switching fields were found. To rule out a possible influence of dipole–dipole interaction between ring elements on remagnetization processes, an isolated Co ring was deposited on top of a Hall magnetometer and extremely sharp transitions from onion to vortex and from vortex to onion state of opposite polarity were resolved. Our results were supported by MOKE magnetization measurements and micromagnetic simulations.
Vacuum ultraviolet luminous efficiency and plasma ion density in alternating current plasma display panels
Authors: Choi Eun Ha , Ahn Jeong Chull , Moon Min Wug , Jung Yoon , Choi Myung Chul , Seo Yoonho , Cho Guangsup , Uhm Han Sup , Tachibana Kunihide , Whang Ki Woong , Kristiansen Magne
Published: October 2002

The correlation between the vacuum ultraviolet (VUV) luminous efficiency and the plasma ion density has been investigated in terms of the xenon mole fraction in the neon filling gas for alternating current plasma display panels. The VUV luminous efficiency and plasma ion density are found to have strong correlation and to be saturated at xenon mole fractions greater than 7% and gas pressures of 400 Torr.
Voronoi diagrams in barrier gas discharge
Authors: Zanin A. L. , Liehr A. W. , Moskalenko A. S. , Purwins H.-G.
Published: October 2002

Voronoi diagrams are essential topics of modern physics, chemistry, biology and other fields. There is a great interest in generating Voronoi diagrams for real-time applications that can be made by means of parallel analog computation. We report the observation of self-organized Voronoi diagrams as a pattern arising in a barrier gas-discharge system. It is shown experimentally that this phenomenon provides an opportunity to generate Voronoi diagrams in a parallel way for a given set of reference points on submillisecond time scale.
Light-controlled photon tunneling
Authors: Smolyaninov Igor I. , Davis Christopher C. , Zayats Anatoly V.
Published: October 2002

Recent measurements of photon tunneling through individual subwavelength pinholes in a gold film covered with a layer of polydiacetylene [Phys. Rev. Lett. 88, 187402 (2002)] has provided strong indication of “photon blockade” effects similar to Coulomb blockade phenomena observed in single-electron tunneling experiments. Here we report the observation of photon tunneling being blocked (gated) by light at a different wavelength. This suggests the possibility of building a class of “gated” photon tunneling devices for all-optical signal processing.
Photoelectron spectroscopy of ClH2− and ClD2−: A probe of the Cl+H2 van der Waals well and spin–orbit excited states
Authors: Ferguson Michael J. , Meloni Giovanni , Gomez Harry , Neumark Daniel M.
Published: October 2002

Photoelectron (PE) spectra of ClH2− and ClD2− were measured at 299 nm (4.154 eV). Photodetachment of these anions accesses the prereactive van der Waals well on the ground state Cl+H2 potential energy surface, as well as the low-lying spin–orbit excited states resulting from the interaction of Cl and Cl* with H2. The PE spectra are dominated by two relatively narrow peaks corresponding to transitions to the neutral Cl⋅H2 and Cl*⋅H2 complexes. The energetics and widths of these features are interpreted in terms of the properties of the anion and neutral potential energy surfaces.
Dissociative adsorption of NO upon Al(111): Orientation dependent charge transfer and chemisorption reaction dynamics
Authors: Komrowski Andrew J. , Ternow Ho̊kan , Razaznejad Behrooz , Berenbak Bart , Sexton Jonathon Z. , Zoric Igor , Kasemo Bengt , Lundqvist Bengt I. , Stolte Steven , Kleyn Aart W. , Kummel Andrew C.
Published: October 2002

The dissociative and abstractive chemisorption dynamics of NO on Al(111) were studied. A higher sticking probability for the N end-on of NO onto Al(111) was measured. In contrast, Auger electron experiments reveal stepped surfaces to be oxygen rich at low coverage after exposure to NO. Density functional theory calculations show (i) a few angstroms from the surface, an N end-on first collision geometry results in electronic structures consistent with charge transfer; (ii) there is stabilization on the surface for N end-on or side-on orientations; (iii) dissociation is enhanced by a partial or full flip of the molecule.
Intersubband transitions in proton irradiated In0.52Ga0.48As/In0.52Al0.48As multiple quantum wells grown on semi-insulating InP substrate
Authors: Zhou Qiaoying , Manasreh M. O. , Weaver B. D. , Missous M.
Published: October 2002

Intersubband transitions in In0.52Ga0.48As/In0.52Al0.48As multiple quantum wells (MQWs) were investigated as a function of 1 MeV proton irradiation dose and thermal annealing temperature. It is observed that proton doses as high as 1×1014 cm−2 do not have a measurable effect on the intensity or the peak position energy of the intersubband transitions. While a dose of 1×1014 cm−2 has shown a detrimental effect on the intersubband transitions in the GaAs/AlGaAs MQWs, the intersubband transitions in InGaAs/InAlAs MQWs withstood proton doses as high as 1×1015 cm−2 and completely depleted after irradiation with a dose of 3×1015 cm−2. Furnace thermal annealing of the heavily irradiated samples shows that the depleted intersubband transitions in InGaAs/InAlAs MQW samples were almost completely recovered.
Modeling Recruitment Maneuvers with a Variable Compliance Model for Pressure Controlled Ventilation
Authors: Crooke P. S. , Marini J. J. , Hotchkiss J. R.
Published: October 2002

A nonlinear mathematical model for pressure controlled, variable compliance ventilation is proposed, solved, and analyzed. The effect of the variable compliance on the key outcome variables, tidal volume, average lung volume, total PEEP, and mean alveolar pressure, is presented. Using human data, the
variable compliance model is used to investigate effects of recruitment maneuvers on the key outcome variables.
Why do Complications Accumulate in Individual Patients?
Authors: Sonnenberg Amnon
Published: October 2002

It appears as if the failure of one organ system precipitates the subsequent failure of other organ systems. The aim of the present analysis is to model such system behavior and understand why medical complications accumulate in individual patients. The human body is first modeled as being comprised of multiple subsystems, with the health of each subsystem dependent on input regarding its own health status and that of all other subsystems. In a second step, the discrete model is generalized into a continuous model that captures system failure, as well as system repair, by a first order differential equation. Failure is approximated by a logistic decline and repair is approximated by a logistic rise in health. A small drop in health of a single subsystem spreads throughout the entire system and affects its overall health. Unless counteracted by measures of therapy or repair, any time‐related loss in health of individual subsystems leads to a decline in health of the entire system. The delay in onset of therapy represents the most crucial factor to influence the overall cumulative decline in health. The model suggests that medical management needs to be expeditious to minimize the cumulative time‐dependent toll of illness on the entire body.
Public works and municipal government in two Italian capital cities: Comparing technical bureaucracies in Turin and Rome, 1848–88
Authors: Bocquet Denis , de Pieri Filippo
Published: October 2002

The article draws a comparison between nineteenth-century Turin and Rome, linking the growth of technical bureaucracies in the municipal institutions of both cities to the local struggles for control over urban space. In both post-1848 Turin and post-1870 Rome, the implementation of new institutional reforms offered local city councils an opportunity to gain more power and autonomy than they had enjoyed in the recent past. The organization and the role of municipal technical services were therefore affected, with quite opposite results, by the conflicts opened with the state about the redefinition of the province of local government
The centre and the suburbs: Social protest and modernization in Milan and Turin, 1898–1917
Authors: Levy Carl
Published: October 2002

This article focuses on two points of disorder and social-political tension in the histories of Milan and Turin: 1898 and 1917. It examines the reasons for different shapes of protest during the ‘ Fatti di Maggio ‘ in 1898 and the events in the summer of 1917. Both cities are the hubs of Italian industrialization and modernization but in 1898, 1917 and later in 1919-20, ‘pre-modern’ protests about the price of bread were melded together with modern political mobilization. This article also examines the growth of working-class suburbs in each city and their relationship to the ‘historic city centres’ on the one hand and the rural hinterland on the other. The uniqueness of protest in each city is related to the political economy and politics of Milan and Turin and the specific relationships between city centre, suburbs and hinterlands in each. The importance of municipal history for the national historical narrative of modern Italy is thus emphasized in this article.
Conquering the city: The representation of Milan in Massimo Bontempelli's La vita operosa
Authors: Storchi Simona
Published: October 2002

The article focuses on the representation of Milan in Massimo Bontempelli's 1920 short novel La vita operosa. In this novel the protagonist-narrator, a writer and journalist returning to Milan after the end of the war, is confronted with a city which has lost all its points of reference and has turned into a place dominated by the ethics of speed and profit. In this context, the protagonist's adventures in Milan assume the features of an ironic and self-ironic journey of discovery for the letterato who finds himself having to redefine his identity and role in a society whose taste and values have profoundly changed.
Karyopherins in nuclear pore biogenesis
Authors: Lusk C. Patrick , Makhnevych Taras , Marelli Marcello , Aitchison John D. , Wozniak Richard W.
Published: October 2002

The mechanisms that govern the assembly of nuclear pore complexes (NPCs) remain largely unknown. Here, we have established a role for karyopherins in this process. We show that the yeast karyopherin Kap121p functions in the targeting and assembly of the nucleoporin Nup53p into NPCs by recognizing a nuclear localization signal (NLS) in Nup53p. This karyopherin-mediated function can also be performed by the Kap95p–Kap60p complex if the Kap121p-binding domain of Nup53p is replaced by a classical NLS, suggesting a more general role for karyopherins in NPC assembly. At the NPC, neighboring nucleoporins bind to two regions in Nup53p. One nucleoporin, Nup170p, associates with a region of Nup53p that overlaps with the Kap121p binding site and we show that they compete for binding to Nup53p. We propose that once targeted to the NPC, dissociation of the Kap121p–Nup53p complex is driven by the interaction of Nup53p with Nup170p. At the NPC, Nup53p exists in two separate complexes, one of which is capable of interacting with Kap121p and another that is bound to Nup170p. We propose that fluctuations between these two states drive the binding and release of Kap121p from Nup53p, thus facilitating Kap121p's movement through the NPC.
Distinct cell cycle–dependent roles for dynactin and dynein at centrosomes
Authors: Quintyne Nicholas J. , Schroer Trina A.
Published: October 2002

Centrosomal dynactin is required for normal microtubule anchoring and/or focusing independently of dynein. Dynactin is present at centrosomes throughout interphase, but dynein accumulates only during S and G2 phases. Blocking dynein-based motility prevents recruitment of dynactin and dynein to centrosomes and destabilizes both centrosomes and the microtubule array, interfering with cell cycle progression during mitosis. Destabilization of the centrosomal pool of dynactin does not inhibit dynein-based motility or dynein recruitment to centrosomes, but instead causes abnormal G1 centriole separation and delayed entry into S phase. The correct balance of centrosome-associated dynactin subunits is apparently important for satisfaction of the cell cycle mechanism that monitors centrosome integrity before centrosome duplication and ultimately governs the G1 to S transition. Our results suggest that, in addition to functioning as a microtubule anchor, dynactin contributes to the recruitment of important cell cycle regulators to centrosomes.
Assembly of centrosomal proteins and microtubule organization depends on PCM-1
Authors: Dammermann Alexander , Merdes Andreas
Published: October 2002

The protein PCM-1 localizes to cytoplasmic granules known as “centriolar satellites” that are partly enriched around the centrosome. We inhibited PCM-1 function using a variety of approaches: microinjection of antibodies into cultured cells, overexpression of a PCM-1 deletion mutant, and specific depletion of PCM-1 by siRNA. All approaches led to reduced targeting of centrin, pericentrin, and ninein to the centrosome. Similar effects were seen upon inhibition of dynactin by dynamitin, and after prolonged treatment of cells with the microtubule inhibitor nocodazole. Inhibition or depletion of PCM-1 function further disrupted the radial organization of microtubules without affecting microtubule nucleation. Loss of microtubule organization was also observed after centrin or ninein depletion. Our data suggest that PCM-1–containing centriolar satellites are involved in the microtubule- and dynactin-dependent recruitment of proteins to the centrosome, of which centrin and ninein are required for interphase microtubule organization.
Myosin Va binding to neurofilaments is essential for correct myosin Va distribution and transport and neurofilament density
Authors: Rao Mala V. , Engle Linda J. , Mohan Panaiyur S. , Yuan Aidong , Qiu Dike , Cataldo Anne , Hassinger Linda , Jacobsen Stephen , Lee Virginia M-Y. , Andreadis Athena , Julien Jean-Pierre , Bridgman Paul C. , Nixon Ralph A.
Published: October 2002

The identification of molecular motors that modulate the neuronal cytoskeleton has been elusive. Here, we show that a molecular motor protein, myosin Va, is present in high proportions in the cytoskeleton of mouse CNS and peripheral nerves. Immunoelectron microscopy, coimmunoprecipitation, and blot overlay analyses demonstrate that myosin Va in axons associates with neurofilaments, and that the NF-L subunit is its major ligand. A physiological association is indicated by observations that the level of myosin Va is reduced in axons of NF-L–null mice lacking neurofilaments and increased in mice overexpressing NF-L, but unchanged in NF-H–null mice. In vivo pulse-labeled myosin Va advances along axons at slow transport rates overlapping with those of neurofilament proteins and actin, both of which coimmunoprecipitate with myosin Va. Eliminating neurofilaments from mice selectively accelerates myosin Va translocation and redistributes myosin Va to the actin-rich subaxolemma and membranous organelles. Finally, peripheral axons of dilute-lethal mice, lacking functional myosin Va, display selectively increased neurofilament number and levels of neurofilament proteins without altering axon caliber. These results identify myosin Va as a neurofilament-associated protein, and show that this association is essential to establish the normal distribution, axonal transport, and content of myosin Va, and the proper numbers of neurofilaments in axons.
Central role of α7 nicotinic receptor in differentiation of the stratified squamous epithelium
Authors: Arredondo Juan , Nguyen Vu Thuong , Chernyavsky Alexander I. , Bercovich Dani , Orr-Urtreger Avi , Kummer Wolfgang , Lips Katrin , Vetter Douglas E. , Grando Sergei A.
Published: October 2002

Several ganglionic nicotinic acetylcholine receptor (nAChR) types are abundantly expressed in nonneuronal locations, but their functions remain unknown. We found that keratinocyte α7 nAChR controls homeostasis and terminal differentiation of epidermal keratinocytes required for formation of the skin barrier. The effects of functional inactivation of α7 nAChR on keratinocyte cell cycle progression, differentiation, and apoptosis were studied in cell monolayers treated with α-bungarotoxin or antisense oligonucleotides and in the skin of Acra7 homozygous mice lacking α7 nAChR channels. Elimination of the α7 signaling pathway blocked nicotine-induced influx of 45Ca2+ and also inhibited terminal differentiation of these cells at the transcriptional and/or translational level. On the other hand, inhibition of the α7 nAChR pathway favored cell cycle progression. In the epidermis of α7−/− mice, the abnormalities in keratinocyte gene expression were associated with phenotypic changes characteristic of delayed epidermal turnover. The lack of α7 was associated with up-regulated expression of the α3 containing nAChR channels that lack α5 subunit, and both homomeric α9- and heteromeric α9α10-made nAChRs. Thus, this study demonstrates that ACh signaling through α7 nAChR channels controls late stages of keratinocyte development in the epidermis by regulating expression of the cell cycle progression, apoptosis, and terminal differentiation genes and that these effects are mediated, at least in part, by alterations in transmembrane Ca2+ influx.
Visualization of replication initiation and elongation in Drosophila
Authors: Claycomb Julie M. , MacAlpine David M. , Evans James G. , Bell Stephen P. , Orr-Weaver Terry L.
Published: October 2002

Chorion gene amplification in the ovaries of Drosophila melanogaster is a powerful system for the study of metazoan DNA replication in vivo. Using a combination of high-resolution confocal and deconvolution microscopy and quantitative realtime PCR, we found that initiation and elongation occur during separate developmental stages, thus permitting analysis of these two phases of replication in vivo. Bromodeoxyuridine, origin recognition complex, and the elongation factors minichromosome maintenance proteins (MCM)2–7 and proliferating cell nuclear antigen were precisely localized, and the DNA copy number along the third chromosome chorion amplicon was quantified during multiple developmental stages. These studies revealed that initiation takes place during stages 10B and 11 of egg chamber development, whereas only elongation of existing replication forks occurs during egg chamber stages 12 and 13. The ability to distinguish initiation from elongation makes this an outstanding model to decipher the roles of various replication factors during metazoan DNA replication. We utilized this system to demonstrate that the pre–replication complex component, double-parked protein/cell division cycle 10–dependent transcript 1, is not only necessary for proper MCM2–7 localization, but, unexpectedly, is present during elongation.
Identification of amino acid residues lining the pore of a gap junction channel
Authors: Skerrett I.M. , Aronowitz J. , Shin J.H. , Cymes G. , Kasperek E. , Cao F.L. , Nicholson B.J.
Published: October 2002

Gap junctions represent a ubiquitous and integral part of multicellular organisms, providing the only conduit for direct exchange of nutrients, messengers and ions between neighboring cells. However, at the molecular level we have limited knowledge of their endogenous permeants and selectivity features. By probing the accessibility of systematically substituted cysteine residues to thiol blockers (a technique called SCAM), we have identified the pore-lining residues of a gap junction channel composed of Cx32. Analysis of 45 sites in perfused Xenopus oocyte pairs defined M3 as the major pore-lining helix, with M2 (open state) or M1 (closed state) also contributing to the wider cytoplasmic opening of the channel. Additional mapping of a close association between M3 and M4 allowed the helices of the low resolution map (Unger et al., 1999. Science. 283:1176–1180) to be tentatively assigned to the connexin transmembrane domains. Contrary to previous conceptions of the gap junction channel, the residues lining the pore are largely hydrophobic. This indicates that the selective permeabilities of this unique channel class may result from novel mechanisms, including complex van der Waals interactions of permeants with the pore wall, rather than mechanisms involving fixed charges or chelation chemistry as reported for other ion channels.
Tuberous sclerosis complex tumor suppressor–mediated S6 kinase inhibition by phosphatidylinositide-3-OH kinase is mTOR independent
Authors: Jaeschke Anja , Hartkamp Joerg , Saitoh Masao , Roworth Wendy , Nobukuni Takahiro , Hodges Angela , Sampson Julian , Thomas George , Lamb Richard
Published: October 2002

The evolution of mitogenic pathways has led to the parallel requirement for negative control mechanisms, which prevent aberrant growth and the development of cancer. Principally, such negative control mechanisms are represented by tumor suppressor genes, which normally act to constrain cell proliferation (Macleod, K. 2000. Curr. Opin. Genet. Dev. 10:81–93). Tuberous sclerosis complex (TSC) is an autosomal-dominant genetic disorder, characterized by mutations in either TSC1 or TSC2, whose gene products hamartin (TSC1) and tuberin (TSC2) constitute a putative tumor suppressor complex (TSC1-2; van Slegtenhorst, M., M. Nellist, B. Nagelkerken, J. Cheadle, R. Snell, A. van den Ouweland, A. Reuser, J. Sampson, D. Halley, and P. van der Sluijs. 1998. Hum. Mol. Genet. 7:1053–1057). Little is known with regard to the oncogenic target of TSC1-2, however recent genetic studies in Drosophila have shown that S6 kinase (S6K) is epistatically dominant to TSC1-2 (Tapon, N., N. Ito, B.J. Dickson, J.E. Treisman, and I.K. Hariharan. 2001. Cell. 105:345–355; Potter, C.J., H. Huang, and T. Xu. 2001. Cell. 105:357–368). Here we show that loss of TSC2 function in mammalian cells leads to constitutive S6K1 activation, whereas ectopic expression of TSC1-2 blocks this response. Although activation of wild-type S6K1 and cell proliferation in TSC2-deficient cells is dependent on the mammalian target of rapamycin (mTOR), by using an S6K1 variant (GST-ΔC-S6K1), which is uncoupled from mTOR signaling, we demonstrate that TSC1-2 does not inhibit S6K1 via mTOR. Instead, we show by using wortmannin and dominant interfering alleles of phosphatidylinositide-3-OH kinase (PI3K) that increased S6K1 activation is contingent upon the suppression of TSC2 function by PI3K in normal cells and is PI3K independent in TSC2-deficient cells.
Information needs and information seeking behaviour of rural dwellers in Nigeria: a case study of Ekpoma in Esan West local government area of Edo State, Nigeria
Authors: Momodu Margaret O.
Published: October 2002

The extent and nature of rural populations in Nigeria is described. A study is reported which examined the information needs of rural populations in the Ekpoma district and its conclusions are discussed. These include information needs and information sources, and the information gathering habits discovered.
African universities and the challenge of knowledge creation and application in the information age
Authors: Abdul Kargbo John
Published: October 2002

Information is a resource for development. It is vital for every aspect of our personal and working lives. Libraries have traditionally been among the foremost repositories in the dissemination of information. But the ways in which they fulfil these roles are rapidly altered by modern technologies. African university libraries are gradually embracing these new technologies as an opportunity to extend their information services to their clientele and even beyond. Experience has shown that the various levels of investment by African university libraries in information and communication technologies are inconsistent. This article examines the application of current information and communication technologies in African academic libraries and their implications in academia.
Thermal environment effects on construction workers’ productivity
Authors: Mohamed Sherif , Srinavin Korb
Published: October 2002

This paper reports on a research study that focused on predicting the loss of construction workers’ productivity due to thermal environment variations. The paper utilises a statistical polynomial regression analysis to establish a relationship between productivity and the predicted mean vote (PMV) thermal comfort index. In doing so, it builds upon a substantial amount of data reported in the literature regarding construction productivity and thermal environment. A set of equations reflecting the nature of the construction task being performed as well as the thermal environment are proposed to predict the degree of change in workers’ productivity, according to a change in the thermal environment. The paper also reports on an experimental investigation undertaken to validate the developed equations. Validation results indicate that the developed equations can predict productivity with a reasonable level of accuracy. Furthermore, they show that the workers’ productivity decreases as the PMV index moves away from the optimum range for all the observed tasks.
The myth of continuous improvement
Authors: Bolton Michael , Heap John
Published: October 2002

Suggests that “continuous improvement” is an unworkable approach to organisational transformation; that discontinuity is essential to ensure that gains are consolidated and locked in to baseline performance. Describes a particular organisational transformation methodology – the UPLIFT programme – used to investigate, assess and prepare for “organisational futures” and uses it to demonstrate this need for discontinuity.
Competence, competency and competencies: performance assessment in organisations
Authors: Moore David R. , Cheng Mei‐I , Dainty Andrew R.J.
Published: October 2002

A number of confusions within the area of performance assessment with regard to the use of terminology, and differing interpretations, regarding competence assessment are discussed. A significant difference between the US and UK approaches to performance assessment is identified as being the issue of behaviours. A hierarchy of terms and their specific meanings is proposed as a first step in addressing the identified confusions. A particular aspect of this hierarchy is its relevance to assessment based on behaviours and attitudes rather than simply on the results of functional analysis concerning a particular job. This has implications for the future direction of performance assessment in the UK, particularly with regard to identifying the differences between average and superior performance.
Optimization of replacement stocks using a maintenance programme derived from reliability studies of production systems
Authors: Castán Farrero José Ma , Guitart Tarrés Laura , Bolancé Losilla Catalina
Published: October 2002

This paper is the outcome of a study carried out in a nine‐cell flexible manufacturing unit which produces components for Diesel engine injection pumps. The study involved the monitoring and recording of the various types of failure which led to interruptions in production. The objective of the study was to design a maintenance system for the optimal management of replacement stocks, both from the technical and economic point of view. The design of this programme was based on matching a given statistical distribution (Weibull’s distribution, exponential, normal, log‐normal, or gamma) to the time between failures. By means of this fit, the basic system parameters were determined: average lifetime, failure rate, mean time between failures, mean time between inspections. Knowledge of these variables permits us to determine the frequency of inspections in relation to the level of reliability we require of the system. This information also enables us to establish a programme to determine which elements require inspection, the frequency of these inspections and the operations that need to be carried out.
Impact of JIT on inventory to sales ratios
Authors: Biggart Timothy B. , Gargeya Vidyaranya B.
Published: October 2002

Just‐In‐Time (JIT) production has received a great deal of attention, worldwide, since its introduction in Japan a few decades ago. It has been well documented that some of the main benefits of JIT implementation are reduction of inventories, lead‐time reduction, and cost savings. Most of the previous research on the impact of JIT on firm performance has either been anecdotal (one‐firm studies), or cross‐sectional (comparing JIT firms with non‐JIT firms at one point in time) in nature. This paper focuses on studying the impact of JIT on inventories to sales ratios prior‐ and post‐adoption based on actual performance of 74 firms as reported in COMPUSTAT data. Results show that the total inventory to sales ratio and raw material inventory to sales ratio decreased post‐implementation; however, there has not been any statistically significant change in work‐in‐process inventory to sales ratio and finished goods inventory to sales ratio post‐implementation.
Managing the development of a mainframe‐based inquiry system for the Internet
Authors: Fleming Matthew , Couturier Gordon
Published: October 2002

Although the Internet and the World Wide Web (Web) have existed for several years, it has only been in the past year or two that high‐powered software and infrastructure have been available for a company to web enable legacy mainframe systems (i.e. to provide an Internet front‐end). This paper addresses the management considerations in developing a web‐enabled mainframe using current Internet technologies and without the added cost and maintenance overhead of new hardware and expensive software.
Electronic new product development –‐ a conceptual framework
Authors: Yang Jie , Yu Liming
Published: October 2002

Today’s knowledge economy era is characterized by short product life‐cycles, dynamic customer requirements and complex business processes, knowledge management (KM) is becoming the pivot of new product development. In this article, the interactions between five activities of KM and new product development process are discussed in detail. Then, a novel concept – electronic new product development (E‐NPD) is put forward. E‐NPD is defined as the convergence of customer relationship, business processes, enterprise IT applications, and knowledge management system necessary to perform continuous innovation through new business model in the new knowledge‐based economy. Based on a case study in the high‐tech industry, we demonstrate that the convergence of KM and new product development have greatly enhanced the efficiency of new product development, accordingly led to the success of new product. In the end, it is concluded that competence of NPD is from KM by describing the E‐NPD structure as an organism.