bluuebunny/crossref_metadata_2025 huggingface dataset:
Uncertainty estimation in measurement of micromechanical properties using random-fuzzy variables
Authors: Zhu Qiang , Jiang Zhuangde , Zhao Zexiang , Wang Hairong
Published: March 2006

Instrumented indentation testing mechanical properties of small volume materials can be affected by various factors during the measurement process, either in random or nonrandom characteristics, which can induce much uncertainty in the evaluation results. The traditional uncertainty estimation method, which is based on probability theory, is ineffective for the cases where some nonrandom effects are present. In this article, uncertainty estimation in measurement of hardness and elastic modulus by tester for micromechanical properties associated with random-fuzzy variables (RFVs) is presented. Uncertainty estimation results from both the traditional and RFV methods are derived and compared. Results show that the measurement uncertainties in hardness and elastic modulus can be effectively expressed in terms of RFVs under different levels of confidence, and all possible influencing effects on the uncertainties can be involved.
Compact pulse power device for generation of one-dimensional strong shock waves
Authors: Kondo Kotaro , Nakajima Mitsuo , Kawamura Tohru , Horioka Kazuhiko
Published: March 2006

A compact pulse power device is proposed for generation of one-dimensional strong shock waves, and preliminary experimental results are reported. The cross section of the discharge area is decreased by tapered electrodes to prevent the decay of the shock wave. This new device drives a quasi-one-dimensional strong shock with the front speed 45km∕s in the acrylic guiding tube filled with Xe gas. When the front speed is more than the critical speed Drad, an interesting structure is observed at the shock front, which indicates that the radiative energy transport affects the shock structure.
Fabrication of a Boersch phase plate for phase contrast imaging in a transmission electron microscope
Authors: Schultheiß K. , Pérez-Willard F. , Barton B. , Gerthsen D. , Schröder R. R.
Published: March 2006

The Boersch phase plate for a transmission electron microscope (TEM) offers major advantages over other phase plate concepts. However, due to its miniature dimensions, it could not be constructed and implemented so far. We report the first successful fabrication of a Boersch phase plate, which was produced by a combination of electron-beam and focused ion-beam lithography on a freestanding silicon nitride membrane. The manufactured multilayer electrode structure was tested for its functionality as an electrostatic einzel lens in a TEM. First experiments show that it can be used as a phase shifting device, as proposed by Boersch, to optimize phase contrast transfer in transmission electron microscopy.
Ionic conduction, rectification, and selectivity in single conical nanopores
Authors: Cervera Javier , Schiedt Birgitta , Neumann Reinhard , Mafé Salvador , Ramírez Patricio
Published: March 2006

Modern track-etching methods allow the preparation of membranes containing a single charged conical nanopore that shows high ionic permselectivity due to the electrical interactions of the surface pore charges with the mobile ions in the aqueous solution. The nanopore has potential applications in electrically assisted single-particle detection, analysis, and separation of biomolecules. We present a detailed theoretical and experimental account of the effects of pore radii and electrolyte concentration on the current-voltage and current-concentration curves. The physical model used is based on the Nernst-Planck and Poisson equations. Since the validity of continuum models for the description of ion transport under different voltages and concentrations is recognized as one of the main issues in the modeling of future applications, special attention is paid to the fundamental understanding of the electrical interactions between the nanopore fixed charges and the mobile charges confined in the reduced volume of the inside solution.
Layered photoconductive polymers: Anisotropic morphology and correlation with photorefractive reflection grating response
Authors: Kwon O-Pil , Kwon Seong-Ji , Jazbinsek Mojca , Günter Peter , Lee Suck-Hyun
Published: March 2006

We demonstrate that the mesophase morphology of the layered photorefractive polymers has a substantial influence on the photorefractive properties, especially in reflection grating geometries with a minimal grating spacing. The layered morphology of the photoconductive polymers based on poly(p-phenyleneterephthalate) (PPT) with pendent carbazole (CZ) groups can be efficiently controlled by changing their molecular weight. Photorefractive composites based on PPT-CZ polymers with different chromophores, diethylaminodicyanostyrene (DDCST) or piperidinodicyanostyrene (PDCST), show anisotropic morphology induced by the squeezing flow during sample preparation. The contributions of the highest occupied molecular orbital levels of the chromophores and of the degree and anisotropy of the layered crystalline structure to the charge transport and trapping result in a high efficiency of the PDCST composite and a similar response speed in DDCST and PDCST composites in the reflection grating geometry, although of about six times lower photoconductivity in the less-ordered PDCST composite.
Translational velocity measurement for single floating cell based on optical Fourier transform theory
Authors: Ishizaki Katsumi , Ishimaru Ichirou , Yoshida Makoto , Inoue Yusuke , Yasokawa Toshiki , Kuriyama Shigeki , Masaki Tsutomu , Nakai Seiji , Takegawa Kaoru , Tanaka Naotaka
Published: March 2006

This letter reports on translational velocity measurement, which is needed for tracking a low contrast cell. We propose a new optical spatial filtering method that is based on the optical Fourier transform theory. In this method, a pinhole is installed as a spatial filter on the optical Fourier transform plane. By means of this spatial filter, the arbitrary component of the spatial frequency is derived from the random refractive index distribution as the periodic light intensity distribution. By observing the changes of this light intensity, we can obtain the translational velocity of a low-contrast cell by means of a high-response photodiode.
Morphological variations as nonstandard test parameters for the response to pollutant gas concentration: An application to Ruthenium Phthalocyanine sensing films
Authors: Generosi A. , Paci B. , Albertini V. Rossi , Perfetti P. , Paoletti A. M. , Pennesi G. , Rossi G. , Caminiti R.
Published: March 2006

A systematic time-resolved energy dispersive x-ray reflectometry study was performed in situ on Ruthenium Phthalocyanine thin fims to estimate the morphological detection limits of this material as NO2 transducer and the influence of the gas concentration on the gas-film interaction mechanisms. The work validates the use of this unconventional method—based on the observation of the morphological parameters change—for evaluating the response of novel sensing materials in alternative to more standard procedures. Indeed, the morphological monitoring is shown to be sensitive to the gas concentration in a range comparable to the usual electroresistive measurements. Moreover, while the latter is only able to give the information on whether the gas is interacting with the sensor, the former is also able to discriminate among interaction processes of a different nature (in the present case the interaction limited to the film surface and the one involving the material bulk).
Nature of the transient BaF2-related phases in the “BaF2” processing of Ba2YCu3O7−x superconductors
Authors: Wong-Ng W. , Levin I. , Cook L. P. , Feenstra R.
Published: March 2006

Transient BaF2-based oxyfluoride phases are thought to play a critical role in the formation of the c-textured Ba2YCu3O7−x layers of coated conductors. In situ high-temperature x-ray diffraction from the precursor films containing pure BaF2 as well as pseudobinary BaF2–Y, BaF2–Cu, and Y–Cu mixtures and heat treated in water vapor under reduced conditions revealed that the transient BaF2-based superstructures, similar to those observed during formation of Ba2Cu3O7−x, develop even from the pure BaF2 precursor. These superstructures results from the dissolution of oxygen in BaF2 leading to formation of the oxyfluoride phase, Ba(F2−2x◻x)Ox, with an ordered arrangement of O, F, and F vacancies.
Fabrication and electronic transport properties of Bi nanotube arrays
Authors: Li L. , Yang Y. W. , Huang X. H. , Li G. H. , Ang R. , Zhang L. D.
Published: March 2006

Bi nanotubes embedded in anodic alumina membranes were fabricated by pulsed electrodeposition. Scanning electron microscope, x-ray diffraction, and high-resolution transmission electron microscope analyses revealed that the Bi nanotubes are highly oriented and single crystalline. Electronic transport measurements proved that there is a metal–semiconductor transition of Bi nanotube arrays with the decrease of the wall thickness of the nanotubes, and this transition depends only on the wall thickness and is independent of the diameter of the nanotubes. The quantum confinement effect is believed to play an important role in determining transport properties. The Bi nanotubes may find applications in thermoelectric nanodevices.
Multilayer organic electrophosphorescent white light-emitting diodes without exciton-blocking layer
Authors: Lei Gangtie , Wang Liduo , Qiu Yong
Published: March 2006

We demonstrate high-efficiency white organic light-emitting diodes with two emissive layers, in which different hosts are employed. With the energy gap of the two hosts, there was no exciton-blocking layer between the emissive layers to confine the diffusion of excitons. The phosphorescent dye, bis[(4,6-difluorophenyl)-pyridinato-N, C2′] (picolinato) Ir(III) and bis (1-phenyl-isoquinoline) (acetylacetonate) iridium (III) [Ir(pic)2acac] were employed as guests, while N,N′-dicarbazolyl-1, 4-dimethene-benzene and 4, 4′-N, N′-dicarbazole-biphenyl were employed as hosts, respectively. The device exhibited white emission by controlling the thickness of the emissive layers and the maximum current efficiency and luminance were 10.5cd∕A and 22000cd∕m2, respectively.
Alternating layers of vacancy-type and interstitial-type defects in Ge ion implanted silicon
Authors: Kögler R. , Peeva A. , Mücklich A. , Eichhorn F. , Skorupa W.
Published: March 2006

The defect structure of Ge-implanted and annealed silicon was investigated. A stacked structure of alternating layers of vacancy-type defects (cavities) and interstitial-type defects (dislocation loops) was detected. These defects form a substructure within the basic dual structure consisting of a near surface vacancy-dominated and a deeper interstitial-dominated region. The appearance of vacancy clusters in the interstitial-dominated region and of dislocation loops in the vacancy-dominated region indicates significant vacancy-vacancy and interstitial-interstitial clustering in addition to the vacancy-interstitial defect recombination. The observed defect structure is in contrast to the widely accepted +1 model which predicts the complete local recombination of ion-generated vacancies and interstitials. Limits of the +1 model are discussed.
Poly(N-vinyl-2-pyrrolidone)-capped platinum nanoclusters on indium-tin oxide glass as counterelectrode for dye-sensitized solar cells
Authors: Wei T. C. , Wan C. C. , Wang Y. Y.
Published: March 2006

Poly(N-vinyl-2-pyrrolidone)-capped platinum nanoclusters were deposited on indium tin oxide glass as a counterelectrode for dye-sensitized solar cells using a “two-step dip coating” process at room temperature. Compared to sputtered-Pt electrodes, an electrode produced by this technique exhibited ultralow Pt-loading at 4.89μg∕cm2 and an acceptable charge-transfer resistance of 5.66Ωcm2. Current-voltage characteristics of the DSSC at this stage stand at 0.66V on VOC, 10.5mA∕cm2 on ISC, 0.41 on fill factor, and 2.84% cell efficiency under AM1.5, 100mW∕cm2 illumination.
Polarization fatigue and frequency-dependent recovery in Pb(Zr,Ti)O3 epitaxial thin films with SrRuO3 electrodes
Authors: Pintilie L. , Vrejoiu I. , Hesse D. , Alexe M.
Published: March 2006

Fatigue is investigated in epitaxial Pb(Zr,Ti)O3 films grown on SrRuO3∕SrTiO3 substrates with Pt or SrRuO3 (SRO) top electrodes. It was experimentally determined that fatigue occurs irrespective of whether the top electrode is Pt or SRO. The fatigue behavior is strongly dependent on the frequency. A polarization recovery was observed for both types of top electrodes, but the recovery is almost complete for a SRO top electrode and only about 40% from the initial polarization value for Pt top electrodes. The results are tentatively explained by the frequency response of the deep traps and by migration of oxygen vacancies.
In situ monitoring of internal strain and height of InAs nanoislands grown on GaAs(001)
Authors: Takahasi Masamitu , Kaizu Toshiyuki , Mizuki Jun’ichiro
Published: March 2006

A monitoring technique for molecular beam epitaxial growth of InAs∕GaAs(001) nanoislands is presented. With the help of synchrotron radiation, x-ray diffraction intensity mapping in reciprocal space has been measured during growth. The internal strain distribution and height of the Stranski-Krastanov islands were monitored at a temporal resolution of 9.6s. The relaxation process of internal strain inside the Stranski-Krastanov islands displayed significant dependence on the growth temperature.
Thermally stable optical characteristics of sol-gel hybrid material films
Authors: Moujoud Abderrafia , Kim Woo-Soo , Bae Byeong-Soo , Shin Sang-Yung
Published: March 2006

Thermo-optic (TO) coefficients for transverse-electric and transverse-magnetic polarized light (dnTE∕dT and dnTM∕dT, respectively) were measured for sol-gel-derived, new organic-inorganic hybrid materials. The absolute values of dnTE∕dT are comparable to those of dnTM∕dT, indicating low anisotropy (dnTE∕dT-dnTM∕dT) in the TO coefficients. The low anisotropy is evidenced by the very small polarization dependence of the refractive index (nTE−nTM). The high stability of these materials is consistent with a high glass transition temperature (Tg>150°C), and evidenced by an absence of hysteresis in the refractive index and in film thickness during temperature cycling between 30 and 150°C.
Influence of nanobubbles on the bending of microcantilevers
Authors: Jeon Sangmin , Desikan Ramya , Tian Fang , Thundat Thomas
Published: March 2006

Young’s equation, which is commonly used for determining the contact angle of liquid drops on a solid surface, ignores the vertical component of the surface energy. Although this force is extremely small and its effect on the solid can be ignored, it plays a significant role for flexible surfaces such as microcantilevers. A gold-coated silicon microcantilever and a dodecanethiol coated silicon microcantilever were used to detect real-time formation of nanobubbles on their surfaces when exposed to air-rich water. As air nanobubbles form on the surfaces of the cantilever, the cantilever undergoes bending, and we relate this to the vertical component of surface energy in Young’s equation. This implies that the vertical component of the surface tension should be considered for flexible solid surfaces, and the formation of nanobubbles should be avoided when cantilevers are used as sensors to avoid artifacts.
Edge effects in intermetallic compound crystal growth between Nb and molten 52In–48Sn solder
Authors: Li J. F. , Mannan S. H. , Clode M. P.
Published: March 2006

A solder/substrate couple consisting of a Nb substrate and eutectic 52In–48Sn solder shows promise for high-temperature liquid solder interconnects. In this letter, the intermetallic compound (IMC) crystal growth between vacuum-sputtered Nb film and molten 52In–48Sn solder at four temperatures; 192, 220, 240, and 260°C, was investigated employing samples with a solder/substrate interface area of 7mm by 7mm. It was found that at all four temperatures, the IMC crystals nucleated and grew first at the corners of the substrate, followed by the edges, and then gradually covered the entire interface. This result, can be explained if the initiation of IMC crystal growth is diffusion controlled, and the value of the Nb diffusion coefficient is estimated with the aid of a three-dimensional numerical simulation.
Band-edge electroluminescence from N+-implanted bulk ZnO
Authors: Wang Hung-Ta , Kang B. S. , Chen Jau-Jiun , Anderson T. , Jang S. , Ren F. , Kim H. S. , Li Y. J. , Norton D. P. , Pearton S. J.
Published: March 2006

N + ion implantation at moderate doses (1013–1014cm−2) into nominally undoped (n∼1017cm−3) bulk single-crystal ZnO substrates followed by annealing in the range 600–950°C was used to fabricate diodes that show visible luminescence at 300K and band-edge electroluminescence at 120K (∼390nm) under forward bias conditions. The current-voltage behavior of the diodes are characteristic of metal-insulator-semiconductor devices and suggest the implantation creates a more resistive region in the n-ZnO in which holes are created by impact ionization during biasing, similar to the case of electroluminescence in ZnO varistors. The series resistance is only 25Ω due to the use of the conducting ZnO substrate.
Corner-pumped Yb: yttrium aluminum garnet slab laser emitted up to 1kW
Authors: Liu Qiang , Gong Mali , Lu Fuyuan , Gong Wupeng , Li Chen , Ma Dongdong
Published: March 2006

We have developed a slab laser design based on conduction cooling and a novel pumping geometry called corner pumping. The design uses a slab crystal configuration with the pump light incident from the slab corners. A maximum output power of over 1kW was achieved from a 1mm thick Yb:YAG/YAG (YAG=yttrium aluminum garnet) structure with a 0.5at.%-doped Yb:YAG. The slope efficiency and optical-to-optical efficiency with respect to the total pump power were 42.8% and 33.6%, respectively. At this pump power the electrical-to-optical conversion efficiency of the system was 16.8%.
Circadian clock genes
frequency
and
white collar-1
are not essential for entrainment to temperature cycles in
Neurospora crassa
Authors: Lakin-Thomas Patricia L.
Published: March 2006

The fungus
Neurospora crassa
is a model system for investigating the mechanism of circadian rhythmicity, and the core of its circadian oscillator is thought to be a transcription/translation feedback loop involving the products of the
frq
(frequency),
wc-1
(white-collar-1) and
wc-2
(white-collar-2) genes. Several reports of rhythmicity in
frq
and
wc
null mutants have raised questions about how central the FRQ/WC loop is to the circadian system of
Neurospora
. Several research groups have attempted to answer this question by looking for entrainment of the conidiation banding rhythm in
frq
null mutants. Because the
frq
mutants are blind to light and cannot be entrained to light/dark cycles, these groups have used symmetric temperature cycles of equal-duration cool and warm phases to entrain the rhythm. Under these conditions, the direct effects of temperature on conidiation (masking effects) can compromise observations of the endogenous rhythm. I have reexamined this question by using short heat pulses to clearly separate masking from endogenous rhythms, and I have assayed entrainment in both
frq
and
wc-1
null mutants. I found similar patterns of entrainment in the wild type and both mutant strains. Strong masking effects were found in the
frq
mutant but not in the
wc-1
mutant. I conclude that a rapidly damping temperature-entrainable oscillator is present in the null mutants. A single temperature-entrainable oscillator may drive the conidiation rhythm in all strains, and additional properties such as light sensitivity and temperature compensation may be conferred by the intact FRQ/WC loop in the WT strain.
Inadvertent social information and the avoidance of parasitized male mice: A role for oxytocin
Authors: Kavaliers Martin , Choleris Elena , Ågmo Anders , Braun W. John , Colwell Douglas D. , Muglia Louis J. , Ogawa Sonoko , Pfaff Donald W.
Published: March 2006

Social information can be acquired either directly or indirectly from cues inadvertently produced by individuals with similar interests and requirements (“inadvertent social information,” ISI). These inadvertent cues provide “public information” that other individuals can use to guide their behavior. We show here that female mice use olfactory ISI to determine their choice of, and responses to, males and that the use of this ISI involves the gene for oxytocin (OT). Female mice (OT wild type and CF-1 strain) displayed a significant interest in, and choice of, the odors of uninfected males of varying sexual status that were associated with the odors of an another estrous female. This recognition of, and choices for, specific, individual male odors was evident 24 h later. Female mice also distinguished between males subclinically infected with the gastrointestinal nematode parasite,
Heligimosomoides polygyrus
, and nonparasitized males, displaying aversive responses (analgesia, increased corticosterone) to, and avoidance of, the odors of infected males. The presence of the odors of another estrous female with that of the infected male, which are indicative of potential mate interests, attenuated these aversive responses and resulted in a choice for the odors of infected male. OT gene-deficient (knockout) females were impaired in their use of this ISI to modulate their responses to either uninfected males of differing sexual states or infected males. These findings suggest that OT genes are necessary for the processing of inadvertent social information and likely the integration of both direct and indirect social information.
Is the Hygiene Hypothesis an Example of Hormesis?
Authors: Bukowski John A. , Lewis R. Jeffrey
Published: March 2006

The “hygiene hypothesis” has been suggested to explain the rising incidence of allergic disorders in developed countries. The postulated mechanism is that infectious and/or microbial agents stimulate the immune system toward Th1 (allergy fighting) rather than Th2 (allergy promoting) response. This paper reviews the evidence related to early life infectious/microbial exposures and subsequent atopic disorders and evaluates whether these data suggest a hormetic effect. Our review indicates an insufficient and contradictory association for bacterial/viral infections, with protective effects being either absent or specific to certain infections and/or populations. Chronic, heavy parasitic burdens appear to confer protection against atopic disorders, but are associated with considerable pathology. Moreover, light parasitic burden may increase allergic responses (i.e., no “low dose” beneficial effect). In contrast, there is consistent evidence that general microbial exposures, particularly gut commensals, may be protective against allergy development, which is consistent with a hormetic effect (i.e., potentially beneficial effects at low doses and detrimental effects at high levels).

Conclusion:

General microbial exposures in relation to the “hygiene hypothesis” may represent a hormetic effect, although further research with more rigorous study methods (i.e., prospective designs and measurement of exposure timing, dose, route, etc.) are needed.
Effect of Low Doses of Guaiacol and Ethanol on Enzymatic Activity of Fungal Cultures
Authors: Malarczyk Elżbieta , Jarosz-Wilkołazka Anna , Kochmanska-Rdest Janina
Published: March 2006

The influence of low doses of guaiacol and ethanol, the natural effectors of lignin and phenolics transformations, on laccase and peroxidase activities produced by two strains of Basidiomycetes, Pleurotus sajor-caju and Trametes versicolor, was evaluated. Fungal mycelia were grown for 2 weeks on liquid media containing serial dilutions of guaiacol or ethanol ranging from 100−1 to 100−20 mol/L. Laccase and peroxidase activities in the medium were measured at the end of 2 weeks. The effect of low doses of guaiacol and ethanol on enzyme activities was manifested in an oscillating manner. Similar response patterns were observed when pure enzymes were exposed to the same serial dilutions of guaiacol and ethanol. T. versicolor cultures enriched with 40 mmol guaiacol (simulating natural environmental conditions) also displayed oscillating enzyme activity patterns in response to serial dilutions of guaiacol, but the maximum enzyme activity values were increased compared to those observed in cultures not receiving 40 mmol guaiacol. The differences between maxima and minima varied among the experimental groups and depended on the species of fungus, type of effector, and kind of enzyme. The results suggest the possibility of subtle regulation of enzymatic activity on the molecular level.
An Analysis of the Role of Tobacco-Specific Nitrosamines in the Carcinogenicity of Tobacco Smoke
Authors: Brown Buddy G. , Borschke August J. , Doolittle David J.
Published: March 2006

Cigarette smoke is a complex mixture consisting of more than 4500 chemicals, including several tobacco-specific nitrosamines (TSNA). TSNA typically form in tobacco during the post-harvest period, with some fraction being transferred into mainstream smoke when a cigarette is burned during use. The most studied of the TSNA is 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). NNK has been shown to be carcinogenic in laboratory animals. Studies examining the carcinogenicity of NNK frequently are conducted by injecting rodents with a single dose of 2.5 to 10 μmol of pure NNK; the amount of NNK contained in all of the mainstream smoke from about 3700 to 14,800 typical U.S. cigarettes. Extrapolated to a 70-kg smoker, the carcinogenic dose of pure NNK administered to rodents would be equivalent to the amount of NNK in all of the mainstream smoke of 22 to 87 million typical U.S. cigarettes. Furthermore, extrapolating results from rodent studies based on a single injection of pure NNK to establish a causative role for NNK in the carcinogenicity of chronic tobacco smoke exposure in humans is not consistent with basic pharmacological and toxicological principles. For example, such an approach fails to consider the effect of other smoke constituents upon the toxicity of NNK. In vitro studies demonstrate that nicotine, cotinine, and aqueous cigarette “tar” extract (ACTE) all inhibit the mutagenic activity of NNK. In vivo studies reveal that the formation of pulmonary DNA adducts in mice injected with NNK is inhibited by the administration of cotinine and mainstream cigarette smoke. Cigarette smoke has been shown to modulate the metabolism of NNK, providing a mechanism for the inhibitory effects of cigarette smoke and cigarette smoke constituents on NNK-induced tumorigenesis. NNK-related pulmonary DNA adducts have not been detected in rodents exposed to cigarette smoke, nor has the toxicity of tobacco smoke or tobacco smoke condensate containing marked reductions in TSNA concentrations been shown to be reduced in any biological assay. In summary, there is no experimental evidence to suggest that reduction of TSNA will reduce the mutagenic, cytotoxic, or carcinogenic potential of tobacco smoke.
An averaging process for unipotent group actions
Authors: Yekutieli Amnon
Published: March 2006

We present an averaging process for sections of a torsor under a unipotent group. This process allows one to integrate local sections of such a torsor into a global simplicial section. The results of this paper have applications to deformation quantization of algebraic varieties.
Adenomatous Polyposis Coli on Microtubule Plus Ends in Cell Extensions Can Promote Microtubule Net Growth with or without EB1
Authors: Kita Katsuhiro , Wittmann Torsten , Näthke Inke S. , Waterman-Storer Clare M.
Published: March 2006

In interphase cells, the adenomatous polyposis coli (APC) protein accumulates on a small subset of microtubules (MTs) in cell protrusions, suggesting that APC may regulate the dynamics of these MTs. We comicroinjected a nonperturbing fluorescently labeled monoclonal antibody and labeled tubulin to simultaneously visualize dynamics of endogenous APC and MTs in living cells. MTs decorated with APC spent more time growing and had a decreased catastrophe frequency compared with non-APC-decorated MTs. Endogenous APC associated briefly with shortening MTs. To determine the relationship between APC and its binding partner EB1, we monitored EB1-green fluorescent protein and endogenous APC concomitantly in living cells. Only a small fraction of EB1 colocalized with APC at any one time. APC-deficient cells and EB1 small interfering RNA showed that EB1 and APC localized at MT ends independently. Depletion of EB1 did not change the growth-stabilizing effects of APC on MT plus ends. In addition, APC remained bound to MTs stabilized with low nocodazole, whereas EB1 did not. Thus, we demonstrate that the association of endogenous APC with MT ends correlates directly with their increased growth stability, that this can occur independently of its association with EB1, and that APC and EB1 can associate with MT plus ends by distinct mechanisms.
Akt Binds to and Phosphorylates Phospholipase C-γ1 in Response to Epidermal Growth Factor
Authors: Wang Yi , Wu Jiliang , Wang Zhixiang
Published: March 2006

Both phospholipase (PL) C-γ1 and Akt (protein kinase B; PKB) are signaling proteins that play significant roles in the intracellular signaling mechanism used by receptor tyrosine kinases, including epidermal growth factor (EGF) receptor (EGFR). EGFR activates PLC-γ1 directly and activates Akt indirectly through phosphatidylinositol 3-kinase (PI3K). Many studies have shown that the PLC-γ1 pathway and PI3K–Akt pathway interact with each other. However, it is not known whether PLC-γ1 binds to Akt directly. In this communication, we identified a novel interaction between PLC-γ1 and Akt. We demonstrated that the interaction is mediated by the binding of PLC-γ1 Src homology (SH) 3 domain to Akt proline-rich motifs. We also provide a novel model to depict how the interaction between PLC-γ1 SH3 domain and Akt proline-rich motifs is dependent on EGF stimulation. In this model, phosphorylation of PLC-γ1 Y783 by EGF causes the conformational change of PLC-γ1 to allow the interaction of its SH3 domain with Akt proline-rich motifs. Furthermore, we showed that the interaction between PLC-γ1 and Akt resulted in the phosphorylation of PLC-γ1 S1248 by Akt. Finally, we showed that the interaction between PLC-γ1 and Akt enhanced EGF-stimulated cell motility.
Arl2 and Arl3 Regulate Different Microtubule-dependent Processes
Authors: Zhou Chengjing , Cunningham Leslie , Marcus Adam I. , Li Yawei , Kahn Richard A.
Published: March 2006

Arl2 and Arl3 are closely related members of the Arf family of regulatory GTPases that arose from a common ancestor early in eukaryotic evolution yet retain extensive structural, biochemical, and functional features. The presence of Arl3 in centrosomes, mitotic spindles, midzones, midbodies, and cilia are all supportive of roles in microtubule-dependent processes. Knockdown of Arl3 by siRNA resulted in changes in cell morphology, increased acetylation of α-tubulin, failure of cytokinesis, and increased number of binucleated cells. We conclude that Arl3 binds microtubules in a regulated manner to alter specific aspects of cytokinesis. In contrast, an excess of Arl2 activity, achieved by expression of the [Q70L]Arl2 mutant, caused the loss of microtubules and cell cycle arrest in M phase. Initial characterization of the underlying defects suggests a defect in the ability to polymerize tubulin in the presence of excess Arl2 activity. We also show that Arl2 is present in centrosomes and propose that its action in regulating tubulin polymerization is mediated at centrosomes. Somewhat paradoxically, no phenotypes were observed Arl2 expression was knocked down or Arl3 activity was increased in HeLa cells. We conclude that Arl2 and Arl3 have related but distinct roles at centrosomes and in regulating microtubule-dependent processes.
Rac1-null Mouse Embryonic Fibroblasts Are Motile and Respond to Platelet-derived Growth Factor
Authors: Vidali Luis , Chen Feng , Cicchetti Gregor , Ohta Yasutaka , Kwiatkowski David J.
Published: March 2006

Previous studies of Rac1 in fibroblasts have used dominant negative constructs, which may have nonspecific effects. We used a conditional Rac1 allele to critically examine Rac1 function in mouse fibroblasts. Lack of Rac1 had dramatic effects on nonconfluent cells, which were elongated and had extensive blebbing, but no lamellipodia or ruffle formation. However, Rac1-null fibroblasts translocated using pseudopodia-like protrusions without lamellipodia, migrating toward a platelet-derived growth factor (PDGF) gradient as efficiently as their wild-type counterparts. Rac1-null fibroblasts closed wounds in vitro and spread on a fibronectin substrate, although at a slower rate than wild-type cells. However, Rac1-null cells were markedly impaired in proliferation, with a defect in G1 to S transition, although they were capable of surviving in culture for more than 2 wk. These results refine our understanding of the functions of Rac1, indicate that lamellipodia formation is not required for cell motility, and show that PDGF-induced chemotaxis can occur in the absence of both lamellipodia and Rac1.
Protein Kinase Cζ Mediates Insulin-induced Glucose Transport through Actin Remodeling in L6 Muscle Cells
Authors: Liu Li-Zhong , Zhao Hai-Lu , Zuo Jin , Ho Stanley K.S. , Chan Juliana C.N. , Meng Yan , Fang Fu-De , Tong Peter C.Y.
Published: March 2006

Protein kinase C (PKC) ζ has been implicated in insulin-induced glucose uptake in skeletal muscle cell, although the underlying mechanism remains unknown. In this study, we investigated the effect of PKCζ on actin remodeling and glucose transport in differentiated rat L6 muscle cells expressing myc-tagged glucose transporter 4 (GLUT4). On insulin stimulation, PKCζ translocated from low-density microsomes to plasma membrane accompanied by increase in GLUT4 translocation and glucose uptake. Z-scan confocal microscopy revealed a spatial colocalization of relocated PKCζ with the small GTPase Rac-1, actin, and GLUT4 after insulin stimulation. The insulin-mediated colocalization, PKCζ distribution, GLUT4 translocation, and glucose uptake were inhibited by wortmannin and cell-permeable PKCζ pseudosubstrate peptide. In stable transfected cells, overexpression of PKCζ caused an insulin-like effect on actin remodeling accompanied by a 2.1-fold increase in GLUT4 translocation and 1.7-fold increase in glucose uptake in the absence of insulin. The effects of PKCζ overexpression were abolished by cell-permeable PKCζ pseudosubstrate peptide, but not wortmannin. Transient transfection of constitutively active Rac-1 recruited PKCζ to new structures resembling actin remodeling, whereas dominant negative Rac-1 prevented the insulin-mediated PKCζ translocation. Together, these results suggest that PKCζ mediates insulin effect on glucose transport through actin remodeling in muscle cells.
Genome-wide Analysis of Re-replication Reveals Inhibitory Controls That Target Multiple Stages of Replication Initiation
Authors: Tanny Robyn E. , MacAlpine David M. , Blitzblau Hannah G. , Bell Stephen P.
Published: March 2006

DNA replication must be tightly controlled during each cell cycle to prevent unscheduled replication and ensure proper genome maintenance. The currently known controls that prevent re-replication act redundantly to inhibit pre-replicative complex (pre-RC) assembly outside of the G1-phase of the cell cycle. The yeast Saccharomyces cerevisiae has been a useful model organism to study how eukaryotic cells prevent replication origins from reinitiating during a single cell cycle. Using a re-replication-sensitive strain and DNA microarrays, we map sites across the S. cerevisiae genome that are re-replicated as well as sites of pre-RC formation during re-replication. Only a fraction of the genome is re-replicated by a subset of origins, some of which are capable of multiple reinitiation events. Translocation experiments demonstrate that origin-proximal sequences are sufficient to predispose an origin to re-replication. Origins that reinitiate are largely limited to those that can recruit Mcm2-7 under re-replicating conditions; however, the formation of a pre-RC is not sufficient for reinitiation. Our findings allow us to categorize origins with respect to their propensity to reinitiate and demonstrate that pre-RC formation is not the only target for the mechanisms that prevent genomic re-replication.
Mutations of theDrosophilaZinc Finger-encoding GenevielfältigImpair Mitotic Cell Divisions and Cause Improper Chromosome Segregation
Authors: Staudt Nicole , Fellert Sonja , Chung Ho-Ryun , Jäckle Herbert , Vorbrüggen Gerd
Published: March 2006

We describe the molecular characterization and function of vielfältig (vfl), a X-chromosomal gene that encodes a nuclear protein with six Krüppel-like C2H2 zinc finger motifs. vfl transcripts are maternally contributed and ubiquitously distributed in eggs and preblastoderm embryos, excluding the germline precursor cells. Zygotically, vfl is expressed strongly in the developing nervous system, the brain, and in other mitotically active tissues. Vfl protein shows dynamic subcellular patterns during the cell cycle. In interphase nuclei, Vfl is associated with chromatin, whereas during mitosis, Vfl separates from chromatin and becomes distributed in a granular pattern in the nucleoplasm. Functional gain-of-function and lack-of-function studies show that vfl activity is necessary for normal mitotic cell divisions. Loss of vfl activity disrupts the pattern of mitotic waves in preblastoderm embryos, elicits asynchronous DNA replication, and causes improper chromosome segregation during mitosis.
FLOATING WITH A LARGE LIFE JACKET: MONETARY AND EXCHANGE RATE POLICIES IN CROATIA UNDER DOLLARIZATION
Authors: ŠOŠIĆ VEDRAN , KRAFT EVAN
Published: March 2006

Even after more than a decade of low inflation, Croatia remains highly dollarized. Commercial banks avoid currency mismatch by indexing loans to the exchange rate. Although this eliminates direct currency risk, it creates credit risk, because any larger depreciation might induce borrower defaults. Monetary and exchange rate policies focus on exchange rate smoothing to safeguard financial stability. Dollarization has prevented the use of monetary policy to stabilize output. Given Croatia's likely entry into the EU and adoption of the Euro, dedollarization seems unfeasible. Rather than attempting to reverse dollarization, the central bank has taken measures to make the banking system more robust to shocks. (JEL E52, E58, F31, G21, P24)
Purification and characterization of infectious myonecrosis virus of penaeid shrimp
Authors: Poulos Bonnie T. , Tang Kathy F. J. , Pantoja Carlos R. , Bonami Jean Robert , Lightner Donald V.
Published: March 2006

The causative agent of myonecrosis affecting culturedPenaeus vannameiin Brazil was demonstrated to be a virus after purification of the agent from infected shrimp tissues. Purified viral particles were injected into specific pathogen-freeP. vannamei, resulting in a disease that displayed the same characteristics as those found in the original shrimp used for purification. The virus was named infectious myonecrosis virus (IMNV). The viral particles were icosahedral in shape and 40 nm in diameter, with a buoyant density of 1·366 g ml−1in caesium chloride. The genome consisted of a single, double-stranded (dsRNA) molecule of 7560 bp. Sequencing of the viral genome revealed two non-overlapping open reading frames (ORFs). The 5′ ORF (ORF 1, nt 136–4953) encoded a putative RNA-binding protein and a capsid protein. The coding region of the RNA-binding protein was located in the first half of ORF 1 and contained a dsRNA-binding motif in the first 60 aa. The second half of ORF 1 encoded a capsid protein, as determined by amino acid sequencing, with a molecular mass of 106 kDa. The 3′ ORF (ORF 2, nt 5241–7451) encoded a putative RNA-dependent RNA polymerase (RdRp) with motifs characteristic of totiviruses. Phylogenetic analysis based on the RdRp clustered IMNV withGiardia lamblia virus, a member of the familyTotiviridae. Based on these findings, IMNV may be a unique member of theTotiviridaeor may represent a new dsRNA virus family that infects invertebrate hosts.
Genome analysis and phylogenetic relationships between east, central and west African isolates of Yellow fever virus
Authors: von Lindern Jana J. , Aroner Sarah , Barrett Nicholas D. , Wicker Jason A. , Davis C. Todd , Barrett Alan D. T.
Published: March 2006

Yellow fever virus (YFV), a reemerging disease agent in Africa and South America, is the prototype member of the genus Flavivirus. Based on examination of the prM/M, E and 3′ non-coding regions of the YFV genome, previous studies have identified seven genotypes of YFV, including the Angolan, east/central African and east African genotypes, which are highly divergent from the prototype strain Asibi. In this study, full genome analysis was used to expand upon these genetic relationships as well as on the very limited full genome database for YFV. This study was the first to investigate genomic sequences of YFV strains from east and central Africa (Angola71, Uganda48a and Ethiopia61b). All three viruses had genomes of 10 823 nt in length. Compared with the prototype strain Asibi (from west Africa) they were approximately 25 % divergent in nucleotide sequence and 7 % divergent in amino acid sequence. Comparison of multiple flaviviruses in the N-terminal region of NS4B showed that amino acid sequences were variable and that west African strains of YFV had an amino acid deletion at residue 21. Additionally, N-linked glycosylation sites were conserved between viral genotypes, while codon usage varied between strains.
293T cells expressing simian virus 40 T antigen are semi-permissive to bovine adenovirus type 3 infection
Authors: Patel Amrutlal K. , Tikoo Suresh K.
Published: March 2006

Human cells do not normally support productive bovine adenovirus type 3 (BAdV-3) infection. Here, the outcome of BAdV-3 infection of both 293 cells and 293 cells modified to constitutively express the simian virus 40 (SV-40) T antigen (293T cells) was studied. Whereas BAdV-3 could efficiently infect 293 cells, there was a block in virus DNA replication, late-gene expression and virus production. In contrast, replication and efficient virus production could be detected in 293T cells infected with BAdV-3 or transfected with a replication-competent genomic BAdV-3 clone (pFBAV304). Early-phase gene expression was detected readily in both BAdV-3-infected 293 and 293T cells. However, the progression to efficient viral DNA synthesis and late-phase protein synthesis occurred only in 293T cells. Electron microscopy and virus growth kinetics demonstrated the formation of progeny virus in 293T cells. The SV-40 T antigens act to overcome a barrier in BAdV-3 DNA replication in 293 cells.
Molecular evolution of dengue 2 virus in Puerto Rico: positive selection in the viral envelope accompanies clade reintroduction
Authors: Bennett Shannon N. , Holmes Edward C. , Chirivella Maritza , Rodriguez Dania M. , Beltran Manuela , Vorndam Vance , Gubler Duane J. , McMillan W. Owen
Published: March 2006

Dengue virusis a circumtropical, mosquito-borne flavivirus that infects 50–100 million people each year and is expanding in both range and prevalence. Of the four co-circulating viral serotypes (DENV-1 to DENV-4) that cause mild to severe febrile disease, DENV-2 has been implicated in the onset of dengue haemorrhagic fever (DHF) in the Americas in the early 1980s. To identify patterns of genetic change since DENV-2's reintroduction into the region, molecular evolution in DENV-2 from Puerto Rico (PR) and surrounding countries was examined over a 20 year period of fluctuating disease incidence. Structural genes (over 20 % of the viral genome), which affect viral packaging, host-cell entry and immune response, were sequenced for 91 DENV-2 isolates derived from both low- and high-prevalence years. Phylogenetic analyses indicated that DENV-2 outbreaks in PR have been caused by viruses assigned to subtype IIIb, originally from Asia. Variation amongst DENV-2 viruses in PR has since largely arisenin situ, except for a lineage-replacement event in 1994 that appears to have non-PR New World origins. Although most structural genes have remained relatively conserved since the 1980s, strong evidence was found for positive selection acting on a number of amino acid sites in the envelope gene, which have also been important in defining phylogenetic structure. Some of these changes are exhibited by the multiple lineages present in 1994, during the largest Puerto Rican outbreak of dengue, suggesting that they may have altered disease dynamics, although their functional significance will require further investigation.
Bovine spongiform encephalopathy agent in spleen from an ARR/ARR orally exposed sheep
Authors: Andréoletti Olivier , Morel Nathalie , Lacroux Caroline , Rouillon Virginie , Barc Céline , Tabouret Guillaume , Sarradin Pierre , Berthon Patricia , Bernardet Philippe , Mathey Jacinthe , Lugan Séverine , Costes Pierrette , Corbière Fabien , Espinosa Juan-Carlos , Torres Juan Maria , Grassi Jacques , Schelcher François , Lantier Frédéric
Published: March 2006

Oral contamination with bovine spongiform encephalopathy (BSE) agent in susceptible PRNP genotype sheep results in widespread distribution of prion in the host. Because ARR homozygous sheep are considered to be resistant to transmissible spongiform encephalopathies, they have been selected to eradicate scrapie from sheep flocks and to protect the human food chain from small ruminant BSE risk. However, results presented here show that several months after an oral challenge with BSE agent, healthy ARR/ARR sheep can accumulate significant amounts of PrPScin the spleen.
Origin and evolution of overlapping genes in the family Microviridae
Authors: Pavesi Angelo
Published: March 2006

The possibility of creating novel genes from pre-existing sequences, known as overprinting, is a widespread phenomenon in small viruses. Here, the origin and evolution of gene overlap in the bacteriophages belonging to the family Microviridae have been investigated. The distinction between ancestral and derived frames was carried out by comparing the patterns of codon usage in overlapping and non-overlapping genes. By this approach, a gradual increase in complexity of the phage genome – from an ancestral state lacking gene overlap to a derived state with a high density of genetic information – was inferred. Genes encoding less-essential proteins, yet playing a role in phage growth and diffusion, were predicted to be novel genes that originated by overprinting. Evaluation of the rates of synonymous and non-synonymous substitution yielded evidence for overlapping genes under positive selection in one frame and purifying selection in the alternative frame.
Functional disruption of the prion protein gene in cloned goats
Authors: Yu Guohua , Chen Jianquan , Yu Huiqing , Liu Siguo , Chen Juan , Xu Xujun , Sha Hongying , Zhang Xufeng , Wu Guoxiang , Xu Shaofu , Cheng Guoxiang
Published: March 2006

The cellular prion protein (PrPC), a membrane glycoprotein anchored to the outer surface of neurons, lymphocytes and other cells, is associated directly with the pathogenesis of the transmissible spongiform encephalopathies (TSEs) occurring mainly in humans, cattle, sheep and goats. Although mice lacking PrPC develop and reproduce normally and are resistant to scrapie infection, large animals lacking PrPC, especially those species in which TSE occurs naturally, are currently not available. Here, five live PRNP
+/− goats cloned by gene targeting are reported. Detailed RNA-transcription and protein-expression analysis of one PRNP
+/− goat showed that one allele of the caprine PRNP gene had been disrupted functionally. No gross abnormal development or behaviour could be seen in these PRNP
+/− goats up to at least 3 months of age. These heterozygous PRNP
+/− goats are ready to be used in producing homozygous PRNP
−/− goats in which no PrPC should be expressed.