bluuebunny/crossref_metadata_2025 huggingface dataset:
Co-rich cobalt platinum nanowire arrays: Effects of annealing
Authors: Li Wuxia , Peng Yong , Jones Grenville A. , Shen Tiehan H. , Hill Geoff
Published: January 2005

The effects of annealing on the crystal structure and magnetic properties of Co-rich cobalt platinum nanowire arrays embedded in anodic aluminium oxide membranes have been investigated. For this purpose, a rapid thermal annealing to temperatures of 300°Cto800°C has been used. Transmission electron microscopy and scanning electron microscopy show that the nanowires have a mean diameter of 14nm and an estimated wire density of 7.8×1010cm−2. From x-ray diffraction patterns, we find that the nanowires are hcp and possess a preferred texture in which the c axis of the grains tends to lie along the major axis of the wire. Vibrating sample magnetometry measurements indicate that the easy axis is along the nanowire axis direction. Hysteresis loops, saturation magnetization, squareness ratio (Mr∕Ms), and coercivity (perpendicular and parallel to the nanowire axis) have all been investigated as a function of the annealing temperature (TA). Coercivity parallel to the wire axis first increases with TA, attains a maximum at 600°C (which is 150% of the as-deposited sample), and then decreases. By contrast there is relatively little change in the coercivity measured perpendicular to the wires. The saturation magnetization for the as-deposited sample is 1360emu∕cc and remains almost constant for annealing temperatures up to 500°C: for TA>500°C it decreases significantly. The maximum (Mr∕Ms) ratio attained in this study is 0.99, the highest value reported thus far for cobalt platinum alloy nanowires. The data suggest that these materials are potential candidates for high-density magnetic recording media.
Evidence of spin-wave demagnetization in Fe–Cr giant magnetoresistance multilayers
Authors: Patel R. S. , Majumdar A. K. , Hebard A. F. , Temple D.
Published: January 2005

The temperature dependence of the saturation magnetization of Xe ion-beam sputtered Fe–Cr multilayers has been measured between 5 and 300K in the presence of a field greater than the saturation field (Hsat). With the application of Hsat, the zero-field antiferromagnetically coupled ferromagnetic Fe layers are forced to align ferromagnetically. We find that the thermal demagnetization of such magnetically composite structure follows the Bloch formula for spin waves with anharmonic term in the magnon dispersion relation, viz., M(T)=M(0)[1+AT3∕2+BT5∕2]. Comparisons are presented between the multilayers and bulk crystalline Fe.
Theoretical study of the band-gap anomaly of InN
Authors: Carrier Pierre , Wei Su-Huai
Published: January 2005

Using a band-structure method that includes the correction to the band-gap error in the local-density approximation (LDA), we find that the band gap for InN is 0.8±0.1eV, in good agreement with recent experimental data, but is much smaller than previous experimental value of ∼1.9eV. The unusually small band gap for InN is explained in terms of the high electronegativity of nitrogen and, consequently, the small band-gap deformation potential of InN. The possible origin of the measured large band gaps is discussed in terms of the nonparabolicity of the bands, the Moss–Burstein shift, and the effect of oxygen. Based on the error analysis of our LDA-corrected calculations we have compiled the band-structure parameters for wurtzite AlN, GaN, and InN.
Experimental investigations into the formation of nanoparticles in a∕nc-Si:H thin films
Authors: Thompson S. , Perrey C. R. , Carter C. B. , Belich T. J. , Kakalios J. , Kortshagen Uwe
Published: January 2005

Hydrogenated amorphous silicon thin films with nanocrystalline silicon inclusions (a∕nc-Si:H) have received considerable attention due to reports of electronic properties comparable to hydrogenated amorphous silicon (a-Si:H) coupled with an improved resistance to the light-induced formation of defects. In this study, a∕nc-Si:H thin films are synthesized via radio-frequency plasma-enhanced chemical-vapor deposition with helium and hydrogen diluted silane. The plasma conditions were chosen to simultaneously deposit both Si nanocrystallites and an amorphous silicon matrix. This structure has been confirmed by transmission electron microscopy (TEM) studies. Both plasma electronic diagnostics and TEM image analysis of a∕nc-Si:H films deposited with and without a temperature gradient between the capacitively coupled reactor electrodes suggest nanoparticle formation in the plasma, as opposed to solid-state nucleation of the nanoparticles in the film. Optical-absorption studies of the a∕nc-Si:H films indicate electrical properties comparable to a-Si:H. In particular, the evolution of the films’ photoconductivity over light exposure time shows a Staebler–Wronski effect similar to a-Si:H.
Anisotropic distribution of stacking faults in (Ga,Mn)As digital ferromagnetic heterostructures grown by low-temperature molecular-beam epitaxy
Authors: Kong X. , Trampert A. , Guo X. X. , Däweritz L. , Ploog K. H.
Published: January 2005

We report on the microstructure of (Ga,Mn)As-based digital ferromagnetic heterostructures, which nominally consist of 40 periods of 0.75-monolayer (ML) Mn sheets between 17-ML GaAs spacer layers grown on GaAs(001) substrates by low-temperature molecular-beam epitaxy. Transmission electron microscopy studies reveal mainly stacking faults, which are preferentially coupled in V-shaped pairs with short intersecting lines along the [11¯0] direction. With increasing the V/III beam equivalent pressure ratio, a stronger laterally inhomogeneous distribution of the Mn atoms is detected along the sheets resulting in a larger local strain and thus in a higher density of stacking fault pairs. Their anisotropic distribution is explained by the energetically favorable Mn–As bonding configuration that is induced by the specific surface morphology appearing at the low growth temperature.
Photonic states deep into the waveguide cutoff frequency of metallic mesh photonic crystal filters
Authors: Sang Hong-Yi , Li Zhi-Yuan , Gu Ben-Yuan
Published: January 2005

We examine the optical properties of three-dimensional metallic photonic crystals made from a periodic stacking of thin metallic mesh layers separated by homogeneous dielectric films by means of a combination of the plane-wave-based transfer-matrix method and analytical modal solution approach. Although each metallic mesh layer can serve as a frequency-selective surface and involves an intrinsic long-wavelength waveguide cutoff to electromagnetic waves, pass bands and new band gaps can exist far below the cutoff frequency due to the global coupling effect among different mesh layers. The results for the transmission spectra and photonic band structures are in good agreement with existing experimental measurements. It is found that the position of the pass bands and band gaps strongly depends on the thickness and composite of the separation layer between the adjacent metallic mesh layers.
Destruction of spin cycloid in (111)c-oriented BiFeO3 thin films by epitiaxial constraint: Enhanced polarization and release of latent magnetization
Authors: Bai Feiming , Wang Junling , Wuttig M. , Li JieFang , Wang Naigang , Pyatakov A. P. , Zvezdin A. K. , Cross L. E. , Viehland D.
Published: January 2005

In BiFeO3 films, it has been found that epitaxial constraint results in the destruction of a space modulated spin structure. For (111)c films, relative to corresponding bulk crystals, it is shown (i) that the induced magnetization is enhanced at low applied fields; (ii) that the polarization is dramatically enhanced; whereas, (iii) the lattice structure for (111)c films and crystals is nearly identical. Our results evidence that eptiaxial constraint induces a transition between cycloidal and homogeneous antiferromagnetic spin states, releasing a latent antiferromagnetic component locked within the cycloid.
Accuracy improvement of protrusion angle of carbon nanotube tips by precision multiaxis nanomanipulator
Authors: Young Song Won , Young Jung Ki , O Beom-Hoan , Park Byong Chon
Published: January 2005

In order to manufacture a carbon nanotube (CNT) tip in which the attachment angle and position of CNT were precisely adjusted, a nanomanipulator was installed inside a scanning electron microscope (SEM). A CNT tip, atomic force microscopy (AFM) probe to which a nanotube is attached, is known to be the most appropriate probe for measuring the shape of high aspect ratio. The developed nanomanipulator has two sets of modules with the degree of freedom of three-directional rectilinear motion and one-directional rotational motion at an accuracy of tens of nanometers, so it enables the manufacturing of more accurate CNT tips. The present study developed a CNT tip with the error of attachment angle less then 10° through three-dimensional operation of a multiwalled carbon nanotube and an AFM probe inside a SEM.
Active clipping system for transversely exited CO2 lasers
Authors: Bellecci C. , Gaudio P. , Martellucci S. , Penco E. , Richetta M.
Published: January 2005

A simple intracavity system, based on electrical discharge, is used to control the shape and duration of transverse electric CO2 laser pulses. The clipping mechanism is based on active locking at the same frequency of the laser. The clipping apparatus can deliver gain switched spikes pulses between the temporal range of 100–110ns. The peak power of the clipped signal is not reduced. The system is optimized to obtain a maximum efficiency equal to 1, and a jitter value of about 10ns. In the article the characteristics of electrical system are described. Finally a scheme of the apparatus and experimental results are presented.
Ca
F
2
∕
Si
∕
Ca
F
2
resonant tunneling diodes grown by B surfactant-mediated epitaxy
Authors: Wang C. R. , Bierkandt M. , Paprotta S. , Wietler T. , Hofmann K. R.
Published: January 2005

A special solid-phase epitaxy technique utilizing the surfactant B for the growth of crystalline Si-QWs on CaF2∕Si(111) enabled us to grow CaF2∕Si∕CaF2 double-barrier diodes exhibiting resonant tunneling effects from 77K up to room temperature with peak voltages at 0.2eV, which is very close to simple resonant tunneling model predictions. The peak voltages and currents were virtually independent of temperature. No trapping or hysteresis effects were found in the I–V characteristics which exhibited 2–7 orders of magnitude larger peak current densities than previously reported CaF2∕Si∕CaF2 RTDs.
Hf
O
2
high-κ gate dielectrics on Ge (100) by atomic oxygen beam deposition
Authors: Dimoulas A. , Mavrou G. , Vellianitis G. , Evangelou E. , Boukos N. , Houssa M. , Caymax M.
Published: January 2005

Thin insulator films of the high-κ dielectric HfO2 are deposited on Ge(100) substrates by evaporating Hf in atomic oxygen beams after in situ thermal desorption of the native oxide in ultrahigh vacuum and subsequent treatment of the clean Ge surface in oxygen and nitrogen. It is shown that HfO2 forms atomically sharp interfaces with Ge and behaves as an excellent insulator with dielectric permittivity κ∼25, which is close to the expected bulk value. Very low equivalent oxide thickness of 0.75 (±0.1) nm with a low gate leakage current of ∼4.5×10−4A∕cm2 at 1 V in accumulation is achieved. Strong frequency dispersion of the inversion capacitance and low frequency behavior of the high frequency capacitance–voltage curves is observed. This is attributed to a combined effect of a high generation rate of minority carriers due to impurity traps and the high intrinsic carrier concentration in Ge, which result in a short minority carrier response time.
Ablation of organic polymers by 46.9-nm-laser radiation
Authors: Juha L. , Bittner M. , Chvostova D. , Krasa J. , Otcenasek Z. , Präg A. R. , Ullschmied J. , Pientka Z. , Krzywinski J. , Pelka J. B. , Wawro A. , Grisham M. E. , Vaschenko G. , Menoni C. S. , Rocca J. J.
Published: January 2005

We report results of the exposure of poly(tetrafluoroethylene) -(PTFE), poly(methyl methacrylate) -(PMMA), and polyimide -(PI) to intense 46.9-nm-laser pulses of 1.2-ns-duration at fluences ranging from ∼0.1 to ∼10J∕cm2. The ablation rates were found to be similar for all three materials, ∼80–90nm∕pulse at 1J∕cm2. The results suggest that the ablation of organic polymers induced by intense extreme ultraviolet laser radiation differs from that corresponding to irradiation with longer wavelengths.
Ultrasound radiating performances of piezoelectric micromachined ultrasonic transmitter
Authors: Wang Zhihong , Zhu Weiguang , Tan Ooi Kiang , Chao Chen , Zhu Hong , Miao Jianmin
Published: January 2005

This letter reports on a membrane-type piezoelectric micromachined ultrasonic transducer (pMUT). It consists of 3.5 or 7μm thick composite lead zirconate titanate (PZT) film on a multilayered membrane and works as an ultrasonic transmitter. The ultrasound-radiating performance of the transmitter, in response to a continuous ac driving voltage, has been tested systematically. The generated sound pressure level at resonance frequency of the transmitter varies with the applied dc bias and driving voltage and can exceed 110dB at a measuring distance of 12mm. For a given square membrane with the same multilayer structure and thickness, the resonance frequency of the transmitter is inversely proportional to the area of the membrane, and can be further tuned by control of the poling conditions of the PZT film or the applied dc bias.
Selective surface modification and patterning by a micro-plasma discharge
Authors: Chai Jinan , Li Baoming , Kwok Daniel Y.
Published: January 2005

We demonstrate a selective surface patterning method by a micro-plasma discharge. In this method, argon plasma is ignited through a hole of copper clad polyimide microstructure electrodes. We described here experiments in which an octadecanethiol [CH3(CH2)17SH] self-assembled monolayer (SAM) on a gold film is exposed to a microdischarge, followed by immersion of the sample in 16-mercaptohexadecanoic acid solution. The octadecanethiol SAM is desorbed upon Ar plasma exposure, allowing the formation of a second SAM on the damaged region. The spatial resolution in the present experiments is limited by the dimension of microstructure electrodes. The patterned samples are viewed by using optical microscope and scanning electron microscopy. The advantage of this approach is that it is noncontact and eliminates the need of photolithography.
Laser-induced nanowelding of gold nanoparticles
Authors: Kim Seol Ji , Jang Du-Jeon
Published: January 2005

Picosecond laser pulses are employed to adjoin, to hold closely, and to weld gold nanoparticles on carbon-coated copper grids. Microscopic images and profiles indicate that gold particles are well connected showing single-phased nanocontact. Our results suggest that laser-induced nanowelding can be achieved in a programmed manner to produce ohmic contact by considering the size-dependent thermodynamic, dynamic, and kinetic properties of metallic nanometerials.
Lithographic patterning of nanoparticle films self-assembled from organic solutions by using a water-soluble mask
Authors: Harnack Oliver , Raible Isabelle , Yasuda Akio , Vossmeyer Tobias
Published: January 2005

A lithographic technique is described that enables the highly selective patterning of thin films from gold nanoparticles and organic linker molecules, which are formed via repetitive self-assembly from organic solution. The key element of this method is the application of a calcium oxide∕hydroxide mask, which withstands the application of organic solvents during film deposition and which prevents deposition of nanoparticles on protected parts of the substrate. After film assembly the mask is removed by dissolution in water at room temperature. The method was used to pattern chemiresistor-type vapor sensors based on gold nanoparticle∕nonanedithiol films. Comparative experiments with nonpatterned reference sensors reveal that the patterning process does not degrade the sensing properties of the films.
Optical forces between metallic particles
Authors: Hallock A. J. , Redmond P. L. , Brus L. E.
Published: January 2005

We calculate the optical attractive forces that occur between 30-nm Au or Ag nanocrystals when irradiated at visible wavelengths. These forces show resonances at dipolar plasmon wavelengths, similar to resonances in the near-field electromagnetic intensities. At MW/cm
2
intensities, optical forces can be stronger than van der Waals forces and could be used to organize metallic particles. We also suggest that photonucleation of organic crystals from supersaturated liquid solutions may be caused by optical forces.
Body sizes of hosts and parasitoids in individual feeding relationships
Authors: Cohen Joel E. , Jonsson Tomas , Müller Christine B. , Godfray H. C. J. , Savage Van M.
Published: January 2005

In a natural community of 49 species (12 species of aphids and 37 species of their parasitoids), body lengths of 2,151 parasitoid individuals were, to an excellent approximation, related to the body lengths of their individual aphid hosts by a power law with an exponent close to 3/4. Two alternative models predict this exponent. One is based on surface area to volume relationships. The other is based on recent developments in metabolic ecology. Both models require a changing ratio (in both host and parasitoid) of length to diameter with increasing body length. These changing ratios are manifested differently in the two models and result in testably different predictions for the scaling of body form with increasing size. The estimated exponent of 3/4 for the relationship between individual host body size and individual parasitoid body size degrades to an exponent of nearly 1/2, and the scatter in the relationship between aphid and parasitoid body length is substantially increased, if the average length of a parasitoid species is examined as a function of the average length of its aphid host species instead of using measurements of individuals.
A saturation screen for cis-acting regulatory DNA in the
Hox
genes of
Ciona intestinalis
Authors: Keys David N. , Lee Byung-in , Di Gregorio Anna , Harafuji Naoe , Detter J. Chris , Wang Mei , Kahsai Orsalem , Ahn Sylvia , Zhang Cindy , Doyle Sharon A. , Satoh Noriyuki , Satou Yutaka , Saiga Hidetoshi , Christian Allen T. , Rokhsar Dan S. , Hawkins Trevor L. , Levine Mike , Richardson Paul M.
Published: January 2005

A screen for the systematic identification of cis-regulatory elements within large (>100 kb) genomic domains containing
Hox
genes was performed by using the basal chordate
Ciona intestinalis
. Randomly generated DNA fragments from bacterial artificial chromosomes containing two clusters of
Hox
genes were inserted into a vector upstream of a minimal promoter and
lacZ
reporter gene. A total of 222 resultant fusion genes were separately electroporated into fertilized eggs, and their regulatory activities were monitored in larvae. In sum, 21 separable cis-regulatory elements were found. These include eight
Hox
linked domains that drive expression in nested anterior–posterior domains of ectodermally derived tissues. In addition to vertebrate-like CNS regulation, the discovery of cis-regulatory domains that drive epidermal transcription suggests that
C. intestinalis
has arthropod-like Hox patterning in the epidermis.
Nanoscale environments associated with bioweathering of a Mg-Fe-pyroxene
Authors: Benzerara Karim , Yoon Tae Hyun , Menguy Nicolas , Tyliszczak Tolek , Brown Gordon E.
Published: January 2005

Microorganisms are believed to create microenvironments leading to reaction products not predictable from equilibrium thermodynamics and to unique biomineral morphologies. Unambiguous evidence for such environments is, however, rare in natural samples. We have used scanning transmission x-ray microscopy and spectromicroscopy at the sub-40-nm scale, coupled with transmission electron microscopy, to examine bioweathering products on a meteoritic Fe-Mg-orthopyroxene colonized by a filamentous microorganism. Our measurements reveal an amorphous Al-rich layer beneath the microorganism, calcium carbonates of unique morphology intimately associated with polysaccharides adjacent to the microorganism, and regions surrounding the microorganism with different iron oxidation states. Our results confirm the presence of different microenvironments at this microorganism–mineral interface and provide unique nanometer-scale views of microbially controlled pyroxene weathering products.
Mg
2+
as activator of uridine phosphorylation in coordination with other cellular responses to growth factors
Authors: Vidair Charles , Rubin Harry
Published: January 2005

The divalent cation ionophore A23187 facilitates the manipulation of intracellular Mg
2+
without increasing the general permeability of the cell. The uptake of uridine into cells is limited by its rate of intracellular phosphorylation that increases within minutes after the addition of growth factors. In the experiments described here, the rate of uridine uptake in ionophore-treated cells stimulated by either serum or insulin depended on the extracellular and intracellular concentrations of Mg
2+
and was independent of the extracellular Ca
2+
concentration. In very high concentrations of Mg
2+
(50 mM), ionophore-treated cells take up uridine as fast, in the absence of growth factors as in their presence, demonstrating that Mg
2+
can replace the growth factor requirement for the stimulation of uridine uptake. In contrast, thymidine uptake, which also is limited by its rate of intracellular phosphorylation, showed no early response to either growth factors or Mg
2+
concentration, which is consistent with the 10-fold lower Mg
2+
requirement of thymidine kinase compared with uridine kinase. The feedback inhibition of uridine kinase by UTP and CTP in cell-free extracts was alleviated by increased Mg
2+
concentration. The results support the thesis that the increased uptake of uridine in cells treated with growth factors is determined by a membrane-induced increase in intracellular free Mg
2+
. Such increase would also accelerate the rate of translation-initiation and other coordinate responses that, unlike increased uridine uptake, are essential for cell proliferation. The rate of uridine uptake is suggested as a direct indicator of free cytosolic Mg
2+
that drives the shift from quiescence to proliferation.
Targeting gene expression selectively in cancer cells by using the progression-elevated gene-3 promoter
Authors: Su Zhao-Zhong , Sarkar Devanand , Emdad Luni , Duigou Gregory J. , Young Charles S. H. , Ware Joy , Randolph Aaron , Valerie Kristoffer , Fisher Paul B.
Published: January 2005

One impediment to effective cancer-specific gene therapy is the rarity of regulatory sequences targeting gene expression selectively in tumor cells. Although many tissue-specific promoters are recognized, few cancer-selective gene promoters are available. Progression-elevated gene-3 (
PEG-3
) is a rodent gene identified by subtraction hybridization that displays elevated expression as a function of transformation by diversely acting oncogenes, DNA damage, and cancer cell progression. The promoter of
PEG-3
, PEG-Prom, displays robust expression in a broad spectrum of human cancer cell lines with marginal expression in normal cellular counterparts. Whereas GFP expression, when under the control of a CMV promoter, is detected in both normal and cancer cells, when GFP is expressed under the control of the PEG-Prom, cancer-selective expression is evident. Mutational analysis identifies the AP-1 and PEA-3 transcription factors as primary mediators of selective, cancer-specific expression of the PEG-Prom. Synthesis of apoptosis-inducing genes, under the control of the CMV promoter, inhibits the growth of both normal and cancer cells, whereas PEG-Prom-mediated expression of these genes kills only cancer cells and spares normal cells. The efficacy of the PEG-Prom as part of a cancer gene therapeutic regimen is further documented by
in vivo
experiments in which PEG-Prom-controlled expression of an apoptosis-inducing gene completely inhibited prostate cancer xenograft growth in nude mice. These compelling observations indicate that the PEG-Prom, with its cancer-specific expression, provides a means of selectively delivering genes to cancer cells, thereby providing a crucial component in developing effective cancer gene therapies.
Quantitative phosphorylation profiling of the ERK/p90 ribosomal S6 kinase-signaling cassette and its targets, the tuberous sclerosis tumor suppressors
Authors: Ballif Bryan A. , Roux Philippe P. , Gerber Scott A. , MacKeigan Jeffrey P. , Blenis John , Gygi Steven P.
Published: January 2005

Reversible protein phosphorylation is an essential cellular regulatory mechanism. Many proteins integrate and are modulated by multiple phosphorylation events derived from complex signaling cues. Simultaneous detection and quantification of temporal changes in all of a protein's phosphorylation sites could provide not only an immediate assessment of a known biochemical activity but also important insights into molecular signaling mechanisms. Here we show the use of stable isotope-based quantitative MS to globally monitor the kinetics of complex, ordered phosphorylation events on protein players in the canonical mitogen-activated protein kinase signaling pathway. In excellent agreement with activity assays and phosphospecific immunoblotting with the same samples, we quantified epidermal growth factor-induced changes in nine phosphorylation sites in the extracellular signal-regulated kinase (ERK)/p90 ribosomal S6 kinase-signaling cassette. Additionally, we monitored 14 previously uncharacterized and six known phosphorylation events after phorbol ester stimulation in the ERK/p90 ribosomal S6 kinase-signaling targets, the tuberous sclerosis complex (TSC) tumor suppressors TSC1 and TSC2. By using quantitative phosphorylation profiling in conjunction with pharmacological kinase inhibitors we uncovered a ERK-independent, protein kinase C-dependent pathway to TSC2 phosphorylation. These results establish quantitative phosphorylation profiling as a means to simultaneously identify, quantify, and delineate the kinetic changes of ordered phosphorylation events on a given protein and defines parameters for the rapid discovery of important
in vivo
phosphoregulatory mechanisms.
Defining the Properties of the Nonhelical Tail Domain in Type II Keratin 5: Insight from a Bullous Disease-causing Mutation
Authors: Gu Li-Hong , Coulombe Pierre A.
Published: January 2005

Inherited mutations in the intermediate filament (IF) proteins keratin 5 (K5) or keratin 14 (K14) cause epidermolysis bullosa simplex (EBS), in which basal layer keratinocytes rupture upon trauma to the epidermis. Most mutations are missense alleles affecting amino acids located in the central α-helical rod domain of K5 and K14. Here, we study the properties of an unusual EBS-causing mutation in which a nucleotide deletion (1649delG) alters the last 41 amino acids and adds 35 residues to the C terminus of K5. Relative to wild type, filaments coassembled in vitro from purified K5-1649delG and K14 proteins are shorter and exhibit weak viscoelastic properties when placed under strain. Loss of the C-terminal 41 residues contributes to these alterations. When transfected in cultured epithelial cells, K5-1649delG incorporates into preexisting keratin IFs and also forms multiple small aggregates that often colocalize with hsp70 in the cytoplasm. Aggregation is purely a function of the K5-1649delG tail domain; in contrast, the cloned 109 residue-long tail domain from wild type K5 is distributed throughout the cytoplasm and colocalizes partly with keratin IFs. These data provide a mechanistic basis for the cell fragility seen in individuals bearing the K5-1649delG allele, and point to the role of the C-terminal 41 residues in determining K5's assembly properties.
Golgi Fragmentation Is Associated with Ceramide-induced Cellular Effects
Authors: Hu Wei , Xu Ruijuan , Zhang Guofeng , Jin Junfei , Szulc Zdzislaw M. , Bielawski Jacek , Hannun Yusuf A. , Obeid Lina M. , Mao Cungui
Published: January 2005

Ceramide has been shown to cause anoikis, a subtype of apoptosis due to inadequate cell adhesion. However, the underlying mechanism is unclear. Herein, we report that D-e-C6-ceramide (D-e-Cer), via generating sphingosine, disrupts the Golgi complex (GC), which is associated with various cellular effects, including anoikis. Treatment of HeLa cells with D-e-Cer caused cell elongation, spreading inhibition, rounding, and detachment before apoptosis (anoikis). In D-e-Cer–treated cells, glycosylation of β1 integrin in the GC was inhibited, thus its associated integrin receptors failed to translocate to the cell surface. Ceramide treatment also inhibited the reorganization of both microtubule and F-actin cytoskeletons, focal adhesions, and filopodia. These cellular effects were preceded by fragmentation of the Golgi complex. In contrast, L-e-C6-ceramide (L-e-Cer), the enantiomer of D-e-Cer, failed to induce these cellular effects. Mass spectrometric analysis revealed that treatment HeLa cells with D-e-Cer but not L-e-Cer caused a >50-fold increase in the levels of sphingosine, a product of hydrolysis of ceramide. Treatment with D-e-sphingosine and its enantiomer, L-e-sphingosine, caused massive perinuclear vacuolization, Golgi fragmentation, and cell rounding. Together, these results suggest that sphingosine generated from hydrolysis of ceramide causes the GC disruption, leading to various cellular effects.
Golgi-to-Late Endosome Trafficking of the Yeast Pheromone Processing Enzyme Ste13p Is Regulated by a Phosphorylation Site in its Cytosolic Domain
Authors: Johnston Holly D. , Foote Christopher , Santeford Andrea , Nothwehr Steven F.
Published: January 2005

This study addressed whether phosphorylation regulates trafficking of yeast membrane proteins that cycle between the trans-Golgi network (TGN) and endosomal system. The TGN membrane proteins A-ALP, a model protein containing the Ste13p cytosolic domain fused to alkaline phosphatase (ALP), and Kex2p were found to be phosphorylated in vivo. Mutation of the S13residue on the cytosolic domain of A-ALP to Ala was found to block trafficking to the prevacuolar compartment (PVC), whereas a S13D mutation generated to mimic phosphorylation accelerated trafficking into the PVC. The S13residue was shown by mass spectrometry to be phosphorylated. The rate of endoplasmic reticulum-to-Golgi transport of newly synthesized A(S13A)-ALP was indistinguishable from wild-type, indicating that the lack of transport of A(S13A)-ALP to the PVC was instead due to differences in Golgi/endosomal trafficking. The A(S13A)-ALP protein exhibited a TGN-like localization similar to that of wild-type A-ALP. Similarly, the S13A mutation in endogenous Ste13p did not reduce the extent of or longevity of its localization to the TGN as shown by α-factor processing assays. These results indicate that S13phosphorylation is required for TGN-to-PVC trafficking of A-ALP and imply that phosphorylation of S13may regulate recognition of A-ALP by vesicular trafficking machinery.
The Mitochondrial Inner Membrane Protein Mitofilin Controls Cristae Morphology
Authors: John George B. , Shang Yonglei , Li Li , Renken Christian , Mannella Carmen A. , Selker Jeanne M.L. , Rangell Linda , Bennett Michael J. , Zha Jiping
Published: January 2005

Mitochondria are complex organelles with a highly dynamic distribution and internal organization. Here, we demonstrate that mitofilin, a previously identified mitochondrial protein of unknown function, controls mitochondrial cristae morphology. Mitofilin is enriched in the narrow space between the inner boundary and the outer membranes, where it forms a homotypic interaction and assembles into a large multimeric protein complex. Down-regulation of mitofilin in HeLa cells by using specific small interfering RNA lead to decreased cellular proliferation and increased apoptosis, suggesting abnormal mitochondrial function. Although gross mitochondrial fission and fusion seemed normal, ultrastructural studies revealed disorganized mitochondrial inner membrane. Inner membranes failed to form tubular or vesicular cristae and showed as closely packed stacks of membrane sheets that fused intermittently, resulting in a complex maze of membranous network. Electron microscopic tomography estimated a substantial increase in inner:outer membrane ratio, whereas no cristae junctions were detected. In addition, mitochondria subsequently exhibited increased reactive oxygen species production and membrane potential. Although metabolic flux increased due to mitofilin deficiency, mitochondrial oxidative phosphorylation was not increased accordingly. We propose that mitofilin is a critical organizer of the mitochondrial cristae morphology and thus indispensable for normal mitochondrial function.
Distinct LIN-10 Domains Are Required for Its Neuronal Function, Its Epithelial Function, and Its Synaptic Localization
Authors: Glodowski Doreen R. , Wright Tricia , Martinowich Keri , Chang Howard Chia-Hao , Beach Douglas , Rongo Christopher
Published: January 2005

α-Amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA)-type glutamate receptors (AMPARs) mediate excitatory neurotransmission at neuronal synapses, and their regulated localization plays a role in synaptic plasticity. In Caenorhabditis elegans, the PDZ and PTB domain-containing protein LIN-10 is required both for the synaptic localization of the AMPAR subunit GLR-1 and for vulval fate induction in epithelia. Here, we examine the role that different LIN-10 domains play in GLR-1 localization. We find that an amino-terminal region of LIN-10 directs LIN-10 protein localization to the Golgi and to synaptic clusters. In addition, mutations in the carboxyl-terminal PDZ domains prevent LIN-10 from regulating GLR-1 localization in neurons but do not prevent LIN-10 from functioning in the vulval epithelia. A mutation in the amino terminus prevents the protein from functioning in the vulval epithelia but does not prevent it from functioning to regulate GLR-1 localization in neurons. Finally, we show that human Mint2 can substitute for LIN-10 to facilitate GLR-1 localization in neurons and that the Mint2 amino terminus is critical for this function. Together, our data suggest that LIN-10 uses distinct modular domains for its functions in neurons and epithelial cells and that during evolution its vertebrate ortholog Mint2 has retained the ability to direct AMPAR localization in neurons.
Cyclical Regulation of the Exocyst and Cell Polarity Determinants for Polarized Cell Growth
Authors: Zajac Allison , Sun Xiaoli , Zhang Jian , Guo Wei
Published: January 2005

Polarized exocytosis is important for morphogenesis and cell growth. The exocyst is a multiprotein complex implicated in tethering secretory vesicles at specific sites of the plasma membrane for exocytosis. In the budding yeast, the exocyst is localized to sites of bud emergence or the tips of small daughter cells, where it mediates secretion and cell surface expansion. To understand how exocytosis is spatially controlled, we systematically analyzed the localization of Sec15p, a member of the exocyst complex and downstream effector of the rab protein Sec4p, in various mutants. We found that the polarized localization of Sec15p relies on functional upstream membrane traffic, activated rab protein Sec4p, and its guanine exchange factor Sec2p. The initial targeting of both Sec4p and Sec15p to the bud tip depends on polarized actin cable. However, different recycling mechanisms for rab and Sec15p may account for the different kinetics of polarization for these two proteins. We also found that Sec3p and Sec15p, though both members of the exocyst complex, rely on distinctive targeting mechanisms for their localization. The assembly of the exocyst may integrate various cellular signals to ensure that exocytosis is tightly controlled. Key regulators of cell polarity such as Cdc42p are important for the recruitment of the exocyst to the budding site. Conversely, we found that the proper localization of these cell polarity regulators themselves also requires a functional exocytosis pathway. We further report that Bem1p, a protein essential for the recruitment of signaling molecules for the establishment of cell polarity, interacts with the exocyst complex. We propose that a cyclical regulatory network contributes to the establishment and maintenance of polarized cell growth in yeast.
Organelle-specific Control of Intracellular Transport: Distinctly Targeted Isoforms of the Regulator Klar
Authors: Guo Yi , Jangi Sushrut , Welte Michael A.
Published: January 2005

Microtubule-based transport in cells is powered by a small set of distinct motors, yet timing and destination of transport can be controlled in a cargo-specific manner. The mechanistic basis for this specificity is not understood. To address this question, we analyzed the Drosophila Klarsicht (Klar) protein that regulates distinct microtubule-based transport processes. We find that localization of Klar to its cargoes is crucial for Klar function. Using mutations, we identify functionally important regions of Klar that confer distinct cargo specificity. In ovaries, Klar is present on the nuclear envelope, a localization that requires the C-terminal KASH domain. In early embryos, Klar is attached to lipid droplets, a localization mediated by a novel C-terminal domain encoded by an alternatively spliced exon. In cultured cells, these two domains are sufficient for targeting to the correct intracellular location. Our analysis disentangles Klar's modular organization: we propose that a core region integral to motor regulation is attached to variable domains so that the cell can target regulators with overlapping, yet distinct functions to specific cargoes. Such isoform variation may be a general strategy for adapting a common regulatory mechanism to specifically control motion and positioning of multiple organelles.
Human Splicing Factor SF3a, but Not SF1, Is Essential for Pre-mRNA Splicing In Vivo
Authors: Tanackovic Goranka , Krämer Angela
Published: January 2005

The three subunits of human splicing factor SF3a are essential for the formation of the functional 17S U2 snRNP and prespliceosome assembly in vitro. RNAi-mediated depletion indicates that each subunit is essential for viability of human cells. Knockdown of single subunits results in a general block in splicing strongly suggesting that SF3a is a constitutive splicing factor in vivo. In contrast, splicing of several endogenous and reporter pre-mRNAs is not affected after knockdown of SF1, which functions at the onset of spliceosome assembly in vitro and is essential for cell viability. Thus, SF1 may only be required for the splicing of a subset of pre-mRNAs. We also observe a reorganization of U2 snRNP components in SF3a-depleted cells, where U2 snRNA and U2-B″ are significantly reduced in nuclear speckles and the nucleoplasm, but still present in Cajal bodies. Together with the observation that the 17S U2 snRNP cannot be detected in extracts from SF3a-depleted cells, our results provide further evidence for a function of Cajal bodies in U2 snRNP biogenesis.
Differential role of inhibition in habituation of two independent afferent pathways to a common motor output
Authors: Bristol Adam S. , Carew Thomas J.
Published: January 2005

Many studies of the neural mechanisms of learning have focused on
habituation, a simple form of learning in which a response decrements with
repeated stimulation. In the siphon-elicited siphon withdrawal reflex (S-SWR)
of the marine mollusk Aplysia, the prevailing view is that
homosynaptic depression of primary sensory afferents underlies short-term
habituation. Here we examined whether this mechanism is also utilized in
habituation of the tail-elicited siphon withdrawal reflex (T-SWR), which is
triggered by an independent, polysynaptic afferent pathway that converges onto
the same siphon motor neurons (MNs). By using semi-intact preparations in
which tail and/or siphon input to siphon MNs could be measured, we found that
repeated tail stimuli administered in the presence of a reversible conduction
block of the nerves downstream of the tail sensory neurons (SNs) completely
abolished the induction of habituation. Subsequent retraining revealed no
evidence of savings, indicating that the tail SNs and their immediate
interneuronal targets are not the locus of plasticity underlying T-SWR
habituation. The networks closely associated with the siphon MNs are modulated
by cholinergic inhibition. We next examined the effects of network
disinhibition on S-SWR and T-SWR habituation using an Ach receptor antagonist
d-tubocurarine. We found that the resulting network disinhibition disrupted
T-SWR, but not S-SWR, habituation. Indeed, repeated tail stimulation in the
presence of d-tubocurarine resulted in an initial enhancement in responding.
Lastly, we tested whether habituation of T-SWR generalized to S-SWR and found
that it did not. Collectively, these data indicate that (1) unlike S-SWR,
habituation of T-SWR does not involve homosynaptic depression of SNs; and (2)
the sensitivity of T-SWR habituation to network disinhibition is consistent
with an interneuronal plasticity mechanism that is unique to the T-SWR
circuit, since it does not alter S-SWR.
Intact visual discrimination of complex and feature-ambiguous stimuli in the absence of perirhinal cortex
Authors: Levy Daniel A. , Shrager Yael , Squire Larry R.
Published: January 2005

The perirhinal cortex is known to be important for memory, but there has
recently been interest in the possibility that it might also be involved in
visual perceptual functions. In four experiments, we assessed visual
discrimination ability and visual discrimination learning in severely amnesic
patients with large medial temporal lobe lesions that included complete
lesions of perirhinal cortex. Experiment 1 tested complex visual object
perception. Experiments 2a and 2b tested in two different ways the ability to
discriminate between feature-ambiguous images, which was reported to be
impaired in monkeys with perirhinal lesions. Experiment 3 involved images that
were successfully discriminated in Experiment 2a and asked patients to learn
across 20 trials which of the images had been designated as
“correct.” Patients performed as well as controls in Experiments
1, 2a, and 2b, but one of the patients had difficulty in Experiment 3 when the
task required remembering from trial to trial which image was
“correct.” These findings indicate that perirhinal cortex is not
needed for visual perception across a wide range of visual perceptual
tasks.
E‐recruitment service providers review
Authors: Yoon Kin Tong David , Sivanand C.N
Published: January 2005

Purpose

Aims to review e‐recruiters' web site platform features and tools that are designed to facilitate job seekers' job applications. Also intends to elucidate the financial performance of two international and two Malaysian e‐recruiters.

Design/methodology/approach

Discusses and compares three international (Monster.com, CareerBuilder.com, and HotJobs.com) and three Malaysian (JobStreet.com, JobLinkAsia.com, and JobDB.com) e‐recruiters' backgrounds and initiatives. Presents the e‐recruiters' and online platforms, their current practices and overall strategies and financial performances.

Findings

Observes that the e‐recruiters' revenues are growing rapidly while profits are still elusive.

Originality/value

Presents an overview of e‐recruitment service providers, both international and malaysian.
The impact of supply chain relationship dynamics on manufacturing performance
Authors: Fynes Brian , Voss Chris , de Búrca Seán
Published: January 2005

Purpose

The purpose of this paper is to investigate how the dynamics of supply chain (SC) relationships impact on manufacturing performance.

Design/methodology/approach

A conceptual framework was developed incorporating dimensions of SC relationship dynamics and manufacturing performance. Structural equation modelling was used to test the model with data collected using a postal questionnaire from 200 suppliers in the electronics sector in the Republic of Ireland.

Findings

There was mixed support for the impact of SC relationship dynamics on manufacturing performance. Hypotheses in respect of cost and quality were supported but those in respect of flexibility and delivery were not.

Research limitations/implications

Using single informants and focal customers in research design.

Practical implications

The process of forming and developing SC relationships can be complex and requires firms to be competent in areas such as negotiation skills, conflict management, anticipating problems/finding solutions in advance and joint problem solving. The selection of such managers should be driven by the need to find individuals who possess supply chain management skills and relational competencies.

Originality/value

The nature of the relationship between measures of manufacturing performance has been addressed by two dominant theories: the cumulative or “sandcone” theory and the “trade‐off” theory. Findings provide only partial support for this theory with respect to quality and cost. In contrast, the model is more aligned with the Skinner's (1969) “trade‐off” theory.
Logistics‐production, logistics‐marketing and external integration
Authors: Gimenez Cristina , Ventura Eva
Published: January 2005

Purpose

This paper examines the logistics‐production and logistics‐marketing interfaces and their relation with the external integration. The study also investigates the causal impact of these internal and external relationships on the company's logistical performance.

Design/methodology/approach

An empirical study was conducted in the Spanish FMCG sector and the theoretical model was subjected to analysis using SEM.

Findings

The generic results derived from this study are: Internal and external integration influence each other. Integration in the logistics‐marketing interface does not lead to reductions in costs, stock‐outs and lead‐times, while the integration achieved in the logistics‐production interface does improve these performance measures, if there is no external integration. The external collaboration among supply chain members does always contribute to improving firms’ logistical performance.

Research/limitations/implications

The study has some limitations: other important members of the grocery supply chain (such as retailers, TPL, etc.) have not been considered and the effect of inter‐firm co‐ordination has only been analyzed from the perspective of the provider (as most studies do). Further research on the logistics‐marketing impact on performance should be carried out and other important supply chain members should be considered.

Practical implications

The study contributes to the existing literature by showing that the impact on performance of internal integration depends on the functional areas that are being integrated and the level of external integration.

Originality/value

It is believed that this paper will be insightful to researchers and managers in the SCM field. For researchers, this paper has provided new lines of research. And, for managers, this paper has shown that there is a positive relationship between firms’ logistical performance and SCM.