bluuebunny/crossref_metadata_2025 huggingface dataset:
The cholinergic mesopontine tegmentum is a relatively neglected nicotinic master modulator of the dopaminergic system: relevance to drugs of abuse and pathology
Authors: Maskos U
Published: January 2008

The mammalian mesopontine tegmentum (MPT) contains two cholinergic nuclei, the pedunculopontine tegmental nucleus (PPTg) and the laterodorsal tegmental nucleus (LDTg). These provide the cholinergic innervation of, among other brain areas, the dopaminergic A9 and A10 cell groups. Their axons are thus the source of endogenous acetylcholine (ACh) acting on somato‐dendritic acetylcholine receptors in the substantia nigra (SN) and ventral tegmental area (VTA). The anatomy, physiology, functional and pathological implications of these interactions with the nicotinic subtype of acetylcholine receptors (nAChRs) are discussed with a view of the important role of the MPT as a master regulator of nicotinic dopaminergic signalling in the brain, including for nicotine addiction.

British Journal of Pharmacology (2008) 153, S438–S445; doi:10.1038/bjp.2008.5; published online 28 January 2008
Procoagulant signalling mechanisms in lung inflammation and fibrosis: novel opportunities for pharmacological intervention?
Authors: Chambers R C
Published: January 2008

There is compelling evidence that uncontrolled activation of the coagulation cascade following lung injury contributes to the development of lung inflammation and fibrosis in acute lung injury/acute respiratory distress syndrome (ALI/ARDS) and fibrotic lung disease. This article reviews our current understanding of the mechanisms leading to the activation of the coagulation cascade in response to lung injury and the evidence that excessive procoagulant activity is of pathophysiological significance in these disease settings. Current evidence suggests that the tissue factor‐dependent extrinsic pathway is the predominant mechanism by which the coagulation cascade is locally activated in the lungs of patients with ALI/ARDS and pulmonary fibrosis. Whilst, fibrin deposition might contribute to the pathophysiology of ALI/ARDS following systemic insult; current evidence suggests that the cellular effects mediated via activation of proteinase‐activated receptors (PARs) may be of particular importance in influencing inflammatory and fibroproliferative responses in experimental models involving direct injury to the lung. In this regard, studies in PAR1 knockout mice have shown that this receptor plays a major role in orchestrating the interplay between coagulation, inflammation and lung fibrosis. This review will focus on our current understanding of excessive procoagulant signalling in acute and chronic lung injury and will highlight the novel opportunities that this may present for therapeutic intervention.

British Journal of Pharmacology (2008) 153, S367–S378; doi:10.1038/sj.bjp.0707603; published online 28 January 2008
Comparative study on transduction and toxicity of protein transduction domains
Authors: Sugita T , Yoshikawa T , Mukai Y , Yamanada N , Imai S , Nagano K , Yoshida Y , Shibata H , Yoshioka Y , Nakagawa S , Kamada H , Tsunoda S‐i , Tsutsumi Y
Published: January 2008

Background and purpose:

Protein transduction domains (PTDs), such as Tat, antennapedia homeoprotein (Antp), Rev and VP22, have been extensively utilized for intracellular delivery of biologically active macromolecules in vitro and in vivo. There is little known, however, about the relative transduction efficacy, cytotoxicity and internalization mechanism of individual PTDs.

Experimental approach:

We examined the cargo delivery efficacies of four major PTDs (Tat, Antp, Rev and VP22) and evaluated their toxicities and cell internalizing pathways in various cell lines.

Key results:

The relative order of the transduction efficacy of these PTDs conjugated to fluorescein was Rev>Antp>Tat>VP22, independent of cell type (HeLa, HaCaT, A431, Jurkat, MOLT‐4 and HL60 cells). Antp produced significant toxicity in HeLa and Jurkat cells, and Rev produced significant toxicity in Jurkat cells. Flow cytometric analysis demonstrated that the uptake of PTD–fluorescein conjugate was dose‐dependently inhibited by methyl‐β‐cyclodextrin, cytochalasin D and amiloride, indicating that all four PTDs were internalized by the macropinocytotic pathway. Accordingly, in cells co‐treated with ‘Tat‐fused’ endosome‐disruptive HA2 peptides (HA2‐Tat) and independent PTD‐fluorescent protein conjugates, fluorescence spread throughout the cytosol, indicating that all four PTDs were internalized into the same vesicles as Tat.

Conclusions and implications:

These findings suggest that macropinocytosis‐dependent internalization is a crucial step in PTD‐mediated molecular transduction. From the viewpoint of developing effective and safe protein transduction technology, although Tat was the most versatile carrier among the peptides studied, PTDs should be selected based on their individual characteristics.

British Journal of Pharmacology (2008) 153, 1143–1152; doi:10.1038/sj.bjp.0707678; published online 28 January 2008
Effect of CCR5 receptor antagonists on endocytosis of the human CCR5 receptor in CHO‐K1 cells
Authors: Longden J , Cooke E‐L , Hill S J
Published: January 2008

Background and purpose:

The CCR5 chemokine receptor is a member of the G protein‐coupled receptor (GPCR) family that is expressed by macrophages, memory T‐lymphocytes and dendritic cells and is activated by chemotactic proteins (e.g. MIP‐1α [CCL3], MIP‐1β [CCL4] and RANTES [CCL5]). CCR5 is also the principal co‐receptor for macrophage‐tropic strains of human immunodeficiency virus‐1 (HIV‐1) and some chemokines can inhibit HIV‐1 infection by stimulating CCR5 receptor endocytosis. The aim of this study was to evaluate the effect of CCR5 antagonists on CCR5 endocytosis.

Experimental approach:

The effects of CCR5 agonists and antagonists on receptor internalization in CHO cells, expressing a C‐terminal green fluorescent protein‐tagged human CCR5 receptor (CCR5‐GFP), were quantified using a confocal imaging plate reader.

Key results:

MIP‐1α [CCL3], MIP‐1β [CCL4] and RANTES [CCL5] were all able to stimulate potently the internalization of CCR5‐GFP. This effect was inhibited by the non‐peptide antagonist TAK 779. The CCR5 peptide antagonist met‐RANTES antagonized MIP‐1α‐mediated increases in intracellular free calcium but was also able to stimulate a substantial internalization of the human CCR5‐GFP receptor. However, CHO cells exhibited an aminopeptidase activity that was able to metabolize sufficient met‐RANTES into an agonist metabolite capable of stimulating calcium mobilization via CCR5 receptors in naïve cells.

Conclusions and implications:

These data suggest that there is an endogenous aminopeptidase activity on the surface of CHO cells, that produces a slow internalization of the receptor following a time‐dependent conversion of receptor‐bound met‐RANTES from a CCR5 receptor antagonist into a CCR5 agonist molecule.

British Journal of Pharmacology(2008)153, 1513–1527; doi:10.1038/sj.bjp.0707691; published online 28 January 2008
Investigation of H− production by surface interaction of the plasma generated in “Camembert III” reactor via distributed electron cyclotron resonance at 2.45GHz (abstract)
Authors: Béchu Stéphane , Bès Alexandre , Lemoine Didier , Pelletier Jacques , Bacal Marthe
Published: January 2008

When considering the state-of-the-art on H− ion sources, ions can be produced either by plasma-surface interaction and/or inside the plasma volume. For the production of negative ions by surface ionization, a low work function material is required. For this purpose, cesium has been used in many cases at LBNL, JAEA, KEK, and in other facilities [M. Bacal, Nucl. FusionNUFUAU0029-5515 46, 250 (2006)]. Despite an enhancement in the negative ion production (by a factor of 2.5 in JAEA source), the use of cesium could lead to many drawbacks in the plasma functioning of ITER, for example. An alternative material to cesium could lead to an important improvement for negative ion source.For this purpose, both theoretical and experimental studies must be undertaken. Surface mechanisms have to be taken into account both for creation and loss mechanisms: (i)By recycling the atomic hydrogen into highly vibrationally excited molecular hydrogen via recombinative desorption on specific surfaces (fresh tantalum on surface increases the negative ion density [M. Bacal, A. A. Ivanov, Jr. et al., Rev. Sci. Instrum.RSINAK0034-674810.1063/1.1699456 75, 1699 (2004)] by more than 60%). It has been shown for a rigid substrate model that both the recombination cross section and the degree of vibrational excitation are highly sensitive to the nature of the surface [B. Jackson and D. Lemoine, J. Chem. Phys.JCPSA60021-960610.1063/1.1328041 114, 474 (2001)].(ii)By surface passivation, which could lead to a substantial decrease in H2 (X,v″) wall losses.In order to understand the fundamental mechanisms of surface production and losses, “Camembert III” experimental setup, recently settled in the LPSC laboratory (Grenoble, France) is used. In this experimental structure, hydrogen multidipolar plasma sustained by microwaves (2.45GHz) presents the potential advantage to operate either in a metallic or a conductive chamber. The inner walls could be then frequently coated, by sputtering or chemical vapor deposition techniques, with no opening of the chamber with various materials. First experiments of H− surface production will be performed on target material. Hence, perfectly knowing the target material (in terms of composition and structural and physical properties), H− ion density production near the target surface will be monitored by laser photodetachment [M. Bacal, Rev. Sci. Instrum.RSINAK0034-674810.1063/1.1310362 71, 3981 (2000)]. Even if this diagnostic gives no direct information on high rovibrationally excited level of the H2 molecule, its implementation and use are far less complicated than vuv LIF.
Experimental and theoretical charge density distribution of the colossal magnetoresistive transition metal sulfide FeCr2S4
Authors: Lo Presti Leonardo , Destro Riccardo
Published: January 2008

The total charge density distribution ρ(r) of the colossal magnetoresistive transition metal sulfide FeCr2S4 was evaluated through a multipole formalism from a set of structure factors obtained both experimentally, by means of single crystal high-quality x-ray diffraction data collected at T=23K, and theoretically, with an extended-basis unrestricted Hartree-Fock periodic calculation on the experimental geometry. A full topological analysis, followed by the calculation of local energy density values and net atomic charges, was performed using the quantum theory of atoms in molecules. The experimental and theoretical results were compared. Good agreement was found for the topological properties of the system, as well as for the atomic net charges and the nature of the chemical bonds. An analysis of the electron density ρ(r), its Laplacian ∇2[ρ(r)], and the total energy density H(r) at the bond critical points was employed to classify all the interactions that resulted as predominantly closed shell (ionic) in nature. The topological indicators of the bonded interactions for Fe are distinct from those for Cr. The Fe–S bond distances were found to be 0.145Å shorter than the ideal values computed on the basis of Shannon’s crystal radii, much shorter than the Cr–S distances with respect to their ideal Shannon lengths. Concomitantly, ρ(r) and ∣H(r)∣ at the bond critical points are greater for Fe–S interactions, indicating that the local concentration of charge density in the internuclear region is larger for the tetrahedrally coordinated iron than for the octahedrally coordinated chromium. The isosurface in the real space for ∇2[ρ(r)]=0 was plotted for both iron and chromium, pointing out the local zones of valence shell charge concentration and relating them to the partial d-orbital occupancy of the two transition metal atoms.
On the angular dependence of the optical polarization anisotropy in ladder-type polymers
Authors: Vaughan Helen L. , Monkman Andrew P. , Pålsson Lars-Olof , Nehls Benjamin S. , Farrell Tony , Scherf Ullrich
Published: January 2008

Two ladder-type polymers have been examined using polarized optical absorption and fluorescence spectroscopy in solution and solid state. The fluorescence anisotropy excitation spectra of ladder-type methyl-substituted poly(para-phenylene) and poly(naphthylene-phenylene) follow their absorption profiles, contrary to the typical behavior in other conjugated polymers, which show excitation wavelength dependent anisotropy until the onset of the typical red edge effect. Using Raman microscopy and linear dichroism of aligned stretched polyethylene films containing the ladder polymer, it has been found that the orientation of the absorption transition dipole moment is dependent on the conjugation length. The transition dipole of the shorter conjugation lengths of the distribution is localized approximately 7° off axis, and that of the longer conjugation lengths is delocalized along the chain.
Quasihomogeneous nucleation of amyloid beta yields numerical bounds for the critical radius, the surface tension, and the free energy barrier for nucleus formation
Authors: Garai K. , Sahoo B. , Sengupta P. , Maiti S.
Published: January 2008

Amyloid aggregates are believed to grow through a nucleation mediated pathway, but important aggregation parameters, such as the nucleation radius, the surface tension of the aggregate, and the free energy barrier toward aggregation, have remained difficult to measure. Homogeneous nucleation theory, if applicable, can directly relate these parameters to measurable quantities. We employ fluorescence correlation spectroscopy to measure the particle size distribution in an aggregating solution of Alzheimer’s amyloid beta molecule (Aβ1–40) and analyze the data from a homogeneous nucleation theory perspective. We observe a reproducible saturation concentration and a critical dependence of various aspects of the aggregation process on this saturation concentration, which supports the applicability of the nucleation theory to Aβ aggregation. The measured size distributions show a valley between two peaks ranging from 5to50nm, which defines a boundary for the value of the nucleation radius. By carefully controlling the conditions to inhibit heterogeneous nucleation, we can hold off nucleation in a 25 times supersaturated solution for at least up to 3h at room temperature. This quasi-homogeneous kinetics implies that at room temperature, the surface energy of the Aβ∕water interface is ⩾4.8mJ∕m2, the free energy barrier to nucleation (at 25 times supersaturation) is ⩾1.93×10−19J, and the number of monomers in the nucleus is ⩾29.
Exchange narrowing of the J band of molecular dye aggregates
Authors: Walczak P. B. , Eisfeld A. , Briggs J. S.
Published: January 2008

The exchange narrowing of the J band of certain dye monomers upon aggregation in solution has been known since the 1930s. Here, we analyze the theoretical explanations put forward to account for these narrow absorption bands. Although the theories range from models of identical monomers interacting with vibrations to the opposite of rigid monomers with statistically distributed electronic site energies, all approaches exhibit exchange narrowing. However, we show that the origins of the narrowing are different. A unified theory incorporating the two approaches is presented in which features of both narrowing mechanisms are evident.
Phenomenological model of anomalously high photovoltages generated in obliquely deposited semiconductor films
Authors: Singh S. N. , Kumar Dinesh
Published: January 2008

Photovoltage in obliquely deposited films of semiconductors is found to be much higher in magnitude than the corresponding band gap of the semiconductor. Also, the magnitude of the photovoltage depends on the angle of deposition, the separation between the electrodes, the wavelength of the incident light, the intensity of the illumination and temperature, but this behavior is not understood well. In this work a phenomenological model of the generation of photovoltage along the horizontal plane of the obliquely deposited films on transparent substrates is presented for the first time. The model is based on the presence of obliquely grown grains separated by parallel grain boundaries and the existence of grain boundary potential barriers across the grain boundaries. In the case of semiconductor films with a high absorption coefficient for short wavelengths in the visible range, there occurs a relatively large photogeneration of carriers on the front side of the grain boundaries rather than on the back side, and this gives rise to a net photocurrent and a photovoltage across each grain boundary. The horizontal components of this photovoltage get added up due to a large number of grain boundaries lying between the electrodes on the front surface and produce a large photovoltage due to the series combination. An expression has been derived based on this model which shows that for low intensities of illumination the horizontal component V¯och of the photovoltage increases linearly with electrode separation, resistivity of the film, and the incident light intensity. It depends on the angle of deposition and under certain conditions it is expected to be maximum when the angle of deposition is 45°. The analysis can be applied to study the effect of increase in intensity or decrease in temperature on V¯och. It also shows that the photovoltage across the thickness of the obliquely deposited film V¯ocv is minimum for normal deposition and increases with the increase in the angle of oblique deposition.
Magnetostriction of Tb0.1Ho0.9−xPrx(Fe0.9B0.1)2 (x=–0.4) compounds
Authors: Hari Babu V. , Subrahmanyam A. , Markandeyulu G.
Published: January 2008

The structural and magnetic properties of Tb0.1Ho0.9−xPrx(Fe0.9B0.1)2 (x=0, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, and 0.4) compounds are investigated. The compounds with 0⩽x⩽0.25 are found to stabilize in single cubic Laves phase structures. Small quantities of the (Tb,Ho,Pr)2Fe14B phase and rare-earth phases for x⩾0.3 and also the (Tb,Ho,Pr)(Fe,B)3 phase for x⩾0.35 are observed along with the Laves phase. The saturation magnetization and Curie temperature are found to decrease with Pr content. However, the magnetostriction (at 10kOe) is found to increase with Pr content. The x=0.15 compound is found to exhibit a possible anisotropy compensation between the (Tb∕Ho) and Pr sublattices. The easy magnetization direction (EMD) is found to rotate toward ⟨113⟩ as the Pr content increases, up to x=0.25, and for x⩾0.35 there is a tendency for the EMD to shift toward ⟨111⟩.
Proteresis in Co:CoO core-shell nanoclusters
Authors: Wei X.-H. , Skomski R. , Sun Z.-G. , Sellmyer D. J.
Published: January 2008

The magnetism of ultrasmall Co:CoO core-shell nanoclusters is investigated. The structures, produced by cluster-beam deposition, have Co core sizes ranging from 1to7nm and a CoO shell thickness of about 3nm. Hysteresis loops as well as zero-field-cooled and field-cooled magnetization curves have been measured and a striking feature of the nanostructures is the existence of proteretic (clockwise) rather than hysteretic loops in the core-size range from 3to4nm. The proteretic behavior and its particle-size dependence reflect a subtle interplay between various anisotropies and exchange interactions in the Co and CoO phases and at the Co–CoO interface.
Magnetoresistive behavior in hole doped La1−xPbxMn0.8Ru0.2O3 (0.2⩽x⩽0.4) epitaxial thin films
Authors: Sundar Manoharan S. , Singh Brajendra , Chandra Vimlesh , Zimmer A. , Lim S.-H. , Salamanca-Riba L. G.
Published: January 2008

Epitaxially grown thin films of La1−xPbxMn0.8Ru0.2O3 (0.2⩽x⩽0.4) on LAO (001) substrate using pulsed electron deposition technique shows a systematic decrease in metal to insulator transition from 300to250K when hole concentration varies from 40% to 20%. However, an increase in magnetoresistance ratio by ∼5%–15% is observed for Ru substituted films at the respective Curie temperatures when compared to the parent La0.6Pb0.4MnO3 film. Transport and magnetoresistive properties show that Ru substitution maintains a considerable hole carrier density even for La0.8Pb0.2Mn0.8Ru0.2O3 (8282) composition to stabilize the double exchange interactions.
Spin waves in exchange-biased NiFe∕IrMn circular nanorings
Authors: Tacchi S. , Madami M. , Gubbiotti G. , Carlotti G. , Jung W. , Ross C. A.
Published: January 2008

We present the experimental investigation of the static and dynamical properties of NiFe(20nm)∕IrMn(5nm) rings. Magneto-optic Kerr effect measurements show that the IrMn introduces a sizable exchange-bias field HEB≈80Oe, which shifts the hysteresis loop along the excange-bias direction. Measured loops were satisfactorily reproduced using a micromagnetic calculation which includes the presence of HEB. Measurement of high frequency normal modes, by Brillouin light scattering, shows that the presence of the IrMn layer causes an overall up-shift of the spin wave frequency, in qualitative agreement with pervious studies of other exchange-biased systems. Moreover, the frequency asymmetry of the spin wave frequency upon reversing the external field is quantitatively consistent with the presence of the exchange-bias field measured by the Kerr effect.
Magnetic and microwave properties of basal-plane oriented BaFe11In1O19 ferrite thick films processed by screen printing
Authors: Chinnasamy C. N. , Sakai T. , Sivasubramanian S. , Yang Aria F. , Vittoria C. , Harris V. G.
Published: January 2008

In-doped BaFe11In1O19 particles were prepared by a modified ceramic reaction using In2O3, BaCo3, and Fe2O3 followed by mechanical dispersion. X-ray diffraction analysis confirmed the formation of pure BaFe11In1O19 phase and scanning electron micrographs showed platelet particles of about 1μm in diameter. This powder was subsequently screen printed on alumina substrate using a suitable binder and oriented under a dc magnetic field of 15kOe. The screen printed films were annealed at different durations to produce dense and thick ferrite materials. The hysteresis loops for the as-prepared and annealed screen printed, in-plane oriented films show a hysteresis squareness ratio (Mr∕Ms) of 0.93, saturation magnetic moment of 4000G, and coercivity of 634Oe. The ferrimagnetic resonance measurements showed a linewidth (ΔH) of ∼860Oe. The g (Lande spectroscopic splitting factor) value deduced from the relation between resonant frequencies versus resonance field for the screen printed films was found to be 1.91.
Sample path properties of fractional Riesz–Bessel field of variable order
Authors: Lim S. C. , Teo L. P.
Published: January 2008

In this paper we consider fractional Riesz–Bessel field of variable order, which is also known as multifractional Riesz–Bessel field. Sample path properties of this random field such as local regularity, locally self-similar property, Hausdorff dimension of the graph, and long∕short range dependent property are studied. The relationship between the multifractional Riesz–Bessel field and the multifractional Brownian field is also established.
Interfacial resistance and spin flip effects on the magnetoresistance of a current perpendicular to plane spin valve
Authors: Chung N. L. , Jalil Mansoor B. A. , Tan S. G. , Bala Kumar S.
Published: January 2008

We extend the semiclassical drift diffusion theory of current-perpendicular-to-plane magnetoresistance (MR) to include the realistic effects of spin flip (spin memory loss) at the interfaces and derive the resultant spin transport across a pseudo-spin-valve device. The calculated MR results are compatible with recent experiments, which showed significant effects of interfacial spin flip in metallic multilayers. We present a detailed analysis on the combined effects of interfacial spin flip and interfacial spin-asymmetric scattering on MR, as well as the MR dependence on spin asymmetry of interfacial scattering. Our analysis shows that by optimizing the interfacial resistances, one can mitigate the MR suppressive effects of interfacial spin flip in practical devices.
Three-dimensional features of the turbulent flow through a planar sudden expansion
Authors: Casarsa L. , Giannattasio P.
Published: January 2008

An experimental investigation of the turbulent flow downstream of a planar sudden expansion has been performed by means of a 2D particle image velocimetry (PIV) technique. Flow fields at the Reynolds number of 104 have been measured in several mutually perpendicular planes of a channel having an expansion ratio of 3 and an aspect ratio of 10. As usual for large expansion ratios, the separated flow exhibits a strong asymmetry about the expansion axis and, consequently, very different reattachment lengths on the two side walls of the channel. The mean flow turns out to be substantially symmetric about the midspan plane and strong three-dimensional effects are observed in wide portions of the separation bubbles adjacent to the upper and lower walls. The reattachment lengths exhibit significant spanwise variations that are particularly pronounced in the longer reattachment line. Measurements performed in a single flow plane at Re=4⋅104 show that the influence of the Reynolds number on the mean flow is not completely negligible in the considered variation range. Based on a careful analysis of the PIV data, a model of the three-dimensional mean flow structure in the separation bubbles has been conjectured and it is provided in the paper. The present investigation contributes to clarifying the controversial three-dimensional character of the turbulent flow in a planar sudden expansion and provides accurate and detailed reference data for numerical simulations.
Writer flux closure, transition degradation mechanism, and frequency dependent side track erasure in perpendicular recording
Authors: Fernandez-de-Castro Juan , Xue Jianhua , Lu Pu-Ling , Zhou Yuming
Published: January 2008

In this second part of the work, the MAGPAR micromagnetic/finite element model was reused to investigate the physics of the write and erase processes in perpendicular recording. The damping constant needed in the Landav–Lifshitz–Gilbert equation was found by applying the Klaassen nonlinear eddy current damped model and set to be 0.1. Previous work highlighted the fact that domains were formed in the soft magnetic underlayer (SUL) under the writer pole in regions where the field opposes the SUL magnetization direction. The domains participate in flux closure and help a more linear response out of the return pole that enhanced fields with an overshoot and opposite polarity relative to the main pole field. These return pole fields could cause adjacent track erasure and MAGPAR was used to study the physics behind it. Particular attention was given to the analysis of frequency or time dependent effects caused by flux delays from the slow moving SUL domains (between the main and return poles). In contrast, fast writing near the main pole was the result of nonlinear flux driven by efficient writers and large currents with overshoot. The writer and SUL used in this work caused a 550ps delay. The delay was analyzed over a range of frequencies between 50 and 1000MHz (i.e., linear densities). The numerical and experimental results showed that this delay played an important role in the erasure process. The strength and location of the return pole erasure fields were affected by the current frequency (i.e., the delay). In particular, the erasure level was substantially reduced at the middle frequencies due to the time match between the current pulses and the domain propagation that influenced flux closure. Return pole field strength increased again at higher frequencies.
The α-particle excited scintillation response of the liquid phase epitaxy grown LuAG:Ce thin films
Authors: Prusa P. , Cechak T. , Mares J. A. , Nikl M. , Beitlerova A. , Solovieva N. , Zorenko Yu. V. , Gorbenko V. I. , Tous J. , Blazek K.
Published: January 2008

Liquid phase epitaxy grown Lu3Al5O12:Ce (LuAG:Ce) 20μm thick films and plate cut from the bulk Czochralski-grown LuAG:Ce crystal were prepared for comparison of photoelectron yield (PhY) and PhY dependence on shaping time (0.5–10μs). Am241 (α particles) was used for excitation. At the 0.5μs shaping time, the best film shows comparable PhY with the bulk sample. PhY of bulk material increases noticeably more with shaping time than that of the films. Energy resolution of films is better. Influence of Pb2+ contamination in the films (from the flux) and antisite LuAl defect in bulk material is discussed.
Enhanced localized fluorescence in plasmonic nanoantennae
Authors: Bakker Reuben M. , Yuan Hsiao-Kuan , Liu Zhengtong , Drachev Vladimir P. , Kildishev Alexander V. , Shalaev Vladimir M. , Pedersen Rasmus H. , Gresillon Samuel , Boltasseva Alexandra
Published: January 2008

Pairs of gold elliptical nanoparticles form antennae, resonant in the visible. A dye, embedded in a dielectric host, coats the antennae; its emission excites plasmon resonances in the antennae and is enhanced. Far-field excitation of the dye-nanoantenna system shows a wavelength-dependent increase in fluorescence that reaches 100 times enhancement. Near-field excitation shows enhanced fluorescence from a single nanoantenna localized in a subwavelength area of ∼0.15μm2. The polarization of enhanced emission is along the main antenna axis. These observed experimental results are important for increasing light extraction from emitters localized around antennae and for potential development of a subwavelength sized laser.
Effect of diamagnetic Ca, Sr, Pb, and Ba substitution on the crystal structure and multiferroic properties of the BiFeO3 perovskite
Authors: Khomchenko V. A. , Kiselev D. A. , Vieira J. M. , Jian Li , Kholkin A. L. , Lopes A. M. L. , Pogorelov Y. G. , Araujo J. P. , Maglione M.
Published: January 2008

In this work, we studied the effect of heterovalent Ca, Sr, Pb, and Ba substitution on the crystal structure, dielectric, local ferroelectric, and magnetic properties of the BiFeO3 multiferroic perovskite. Ceramic solid solutions with the general formula Bi0.7A0.3FeO3 (A is a doping element) were prepared and characterized by x-ray diffraction, dielectric, piezoresponse force microscopy (PFM), and magnetic measurements. It is shown that the crystal structure of the compounds is described within the space group R3c, permitting the spontaneous polarization, whose existence was confirmed by the PFM data. Magnetic properties of the solid solutions are determined by the ionic radius of the substituting element. Experimental results suggest that the increase in the radius of the A-site ion leads to the effective suppression of the spiral spin structure of BiFeO3, resulting in the appearance of net magnetization.
Nanoampere charge pump by single-electron ratchet using silicon nanowire metal-oxide-semiconductor field-effect transistor
Authors: Fujiwara Akira , Nishiguchi Katsuhiko , Ono Yukinori
Published: January 2008

Nanoampere single-electron pumping is presented at 20K using a single-electron ratchet comprising silicon nanowire metal-oxide-semiconductor field-effect transistors. The ratchet features an asymmetric potential with a pocket that captures single electrons from the source and ejects them to the drain. Directional single-electron transfer is achieved by applying one ac signal with the frequency up to 2.3GHz. We find anomalous shapes of current steps which can be ascribed to nonadiabatic electron capture.
Effects of atmospheric turbulence on remote optimal control experiments
Authors: Extermann J. , Béjot P. , Bonacina L. , Billaud P. , Kasparian J. , Wolf J.-P.
Published: January 2008

Distortions of ultrashort laser pulses propagating through turbulence are investigated both experimentally and numerically. As expected, a strong correlation is found between temporal distortions and local intensity on the speckle pattern. We suggest that the localization of distortions in low-intensity regions may favor remote control strategies based on nonlinear interactions with respect to those based on linear schemes.
Tunable pure spin currents in a triple-quantum-dot ring
Authors: Gong Weijiang , Zheng Yisong , Lü Tianquan
Published: January 2008

Electronic transport through a triple-quantum-dot ring with three terminals is theoretically studied. By introducing local Rashba spin-orbit interaction on an individual quantum dot, we calculate the charge and spin currents in one lead. We find that a pure spin current without an accompanying charge current appears even at zero magnetic field case. The polarization direction of the spin current can be inverted by altering the bias voltage. In addition, by tuning the magnetic field strength, the charge and spin currents reach their respective peaks alternately.
Fabrication of graded index waveguides in azo polymers using a direct writing technique
Authors: Karimi–Alavijeh Hamidreza , Parsanasab Gholam-Mohammad , Baghban Mohammad-Amin , Sarailou Edris , Gharavi Alireza , Javadpour Sirus , Shkunov Vladimir
Published: January 2008

Fast direct writing of waveguides on polymers using low power continuous-wave lasers has been investigated. Using the cis-trans property of a functionalized sulfonated azo chromophores, we have fabricated graded index waveguides with low loss, which is due to graded index sidewalls. Fabrication is done by exposing the polymer film to a 532nm wavelength laser beam focused to about 5μm spot at the film. Losses were calculated to be 0.48±0.04dB∕cm at 830nm wavelength with no surface deformation. This technique enables us to fabricate integrated optical circuits including directional couplers, dividers, filters, switches, etc., as they are currently investigated in our laboratory.
Identifying Systematic Land-Cover Transitions Using Remote Sensing and GIS: The Fate of Forests inside and outside Protected Areas of Southwestern Ghana
Authors: Alo Clement Aga , Pontius Robert Gilmore
Published: January 2008

We use remote sensing and GIS to map changes in land cover and to identify systematic land-cover transitions in Southwestern Ghana. Landsat Thematic Mapper satellite imagery of 1990 and 2000 is used to create two land-cover classifications, and the two maps are then compared to produce transition matrices both for protected and for unprotected areas. These matrices are analyzed according to their various components to identify systematic landscape transitions based on deviations between the transitions observed and the transitions expected owing to random processes of change. The results show that closed forest regions inside the protected area transition systematically to bare ground or bush fire, but closed forest outside the protected area transitions systematically to open cultivated woodland. These results are consistent with the hypothesis that logging is the main cause of the loss of closed forest inside the protected areas whereas farming is the main cause of the loss of closed forest outside the protected areas. The research highlights the need for the implementation of this methodological approach to landscape change. Identification of strong signals of forest transformation is particularly important in the light of efforts by policy makers to curb deforestation in Ghana.
Landscape Metrics and Visual Topology in the Analysis of Landscape Preference
Authors: Sang Neil , Miller David , Ode Åsa
Published: January 2008

Recognition of the value of landscapes, environmentally, economically, and to quality of life—and, importantly, the embedding of these concepts in legislation such as the European Landscape Convention—has led to the need for an ‘objective’ assessment of these values and the potential impact of changes to them. But studies relating preference information to metric analysis of planimetric viewsheds have so far provided only limited explanation of preference. It has been suggested that this is due to the effect of perspective on the visual topology of the view generating different metrics in perspective from those on the flat map. The completion of the Pan European Study under the EU Framework 5 Visulands project provided a large sample of preference responses to a limited number of computer-generated simple landscape scenarios. As such this is an ideal opportunity to test the significance of perspective on metric correlation with preference. This paper considers the degree to which metrics are altered by a panoramic or viewshed analysis, and the significance of this for any correlation with the preference scores. The implications for the role of the respective media in planning are considered, including that of 3D visualisation as a means for eliciting opinion on landscape preference.
Gender and the Use of Business Advice: Evidence from Firms in the Scottish Service Sector
Authors: Robson Paul J A , Jack Sarah L , Freel Mark S
Published: January 2008

Within the UK the levels of female entrepreneurship are considerably lower than in many of its peer countries. As part of a strategy to remedy this apparent shortfall, and to improve the environment for existing female-owned businesses, the UK Department of Trade and Industry (DTI) launched a ‘Strategic Framework for Women's Enterprise’ in 2003. A central rationale for the development of this strategy is a belief in the inadequacies of current business-advice provision and limited access to informal and formal business networks, mentors, and business support for women. However, there appears to be little evidence, either in this paper or in the body of previous research, to support the view that, within the UK, government agencies need to shape business support to reflect the gender of the business user. Drawing upon a sample of 650 small service sector firms in Scotland, we report the findings of a detailed postal questionnaire concerned with exploring usage and satisfaction of a range of formal and informal sources of business advice amongst male and female business owners. Bivariate analysis shows that amongst formal sources women are more likely to use friends and relatives, the Small Business Gateway, and chambers of commerce but are less likely to use suppliers and consultants. However, multivariate analysis suggests that, within the service sector, neither use of external advice nor impact of advice—either formal or informal—is greatly influenced by gender. Rather, it was the characteristics of service sector firms, most notably the number of employees and exporting activity, that explained the use of external advice. Therefore, a nongendered view of business support by the DTI appears more appropriate within the service sector. Nevertheless, the data do indicate more frequent use of informal family-network contacts amongst women business owners.
Performance Measurement in Planning—Towards a Holistic View
Authors: Carmona Matthew , Sieh Louie
Published: January 2008

The UK's House of Commons Public Services Committee has described the state of performance measurement across the public sector as being data rich and information poor. This reflects the fact that the performance of most public services is extremely complex to measure, and as a result, performance measurement is often limited to those aspects that can easily and expediently be measured. Examining this conundrum, and in particular the processes, impact, and future of performance measurement in planning, provided the basis for research reported in this paper. The research drew from and relates to a profound and complex discussion about how the quality of the planning process per se can be reliably and usefully measured. The paper begins by summarising the results of a wide-ranging literature review in the form of a series of conceptual dilemmas. The objectives and methods of the research are then established, before the key research tool—the analytical framework—is presented. Space does not permit a full examination of the empirical phases of the research, although the results from this work is summarised before the research objectives are once again revisited. These lead, finally, to a suggested new model for measuring performance in planning.
Loss of ATRX leads to chromosome cohesion and congression defects
Authors: Ritchie Kieran , Seah Claudia , Moulin Jana , Isaac Christian , Dick Frederick , Bérubé Nathalie G.
Published: January 2008

αThalassemia/mental retardation X linked (ATRX) is a switch/sucrose nonfermenting-type ATPase localized at pericentromeric heterochromatin in mouse and human cells. Human ATRX mutations give rise to mental retardation syndromes characterized by developmental delay, facial dysmorphisms, cognitive deficits, and microcephaly and the loss of ATRX in the mouse brain leads to reduced cortical size. We find that ATRX is required for normal mitotic progression in human cultured cells and in neuroprogenitors. Using live cell imaging, we show that the transition from prometaphase to metaphase is prolonged in ATRX-depleted cells and is accompanied by defective sister chromatid cohesion and congression at the metaphase plate. We also demonstrate that loss of ATRX in the embryonic mouse brain induces mitotic defects in neuroprogenitors in vivo with evidence of abnormal chromosome congression and segregation. These findings reveal that ATRX contributes to chromosome dynamics during mitosis and provide a possible cellular explanation for reduced cortical size and abnormal brain development associated with ATRX deficiency.
Cell adaptive response to extracellular matrix density is controlled by ICAP-1–dependent β1-integrin affinity
Authors: Millon-Frémillon Angélique , Bouvard Daniel , Grichine Alexei , Manet-Dupé Sandra , Block Marc R. , Albiges-Rizo Corinne
Published: January 2008

Cell migration is an integrated process requiring the continuous coordinated assembly and disassembly of adhesion structures. How cells orchestrate adhesion turnover is only partially understood. We provide evidence for a novel mechanistic insight into focal adhesion (FA) dynamics by demonstrating that integrin cytoplasmic domain–associated protein 1 (ICAP-1) slows down FA assembly. Live cell imaging, which was performed in both Icap-1–deficient mouse embryonic fibroblasts and cells expressing active β1 integrin, shows that the integrin high affinity state favored by talin is antagonistically controlled by ICAP-1. This affinity switch results in modulation in the speed of FA assembly and, consequently, of cell spreading and migration. Unexpectedly, the ICAP-1–dependent decrease in integrin affinity allows cell sensing of matrix surface density, suggesting that integrin conformational changes are important in mechanotransduction. Our results clarify the function of ICAP-1 in cell adhesion and highlight the central role it plays in the cell's integrated response to the extracellular microenvironment.
The small GTPase Rab2 functions in the removal of apoptotic cells in Caenorhabditis elegans
Authors: Mangahas Paolo M. , Yu Xiaomeng , Miller Kenneth G. , Zhou Zheng
Published: January 2008

We identify here a novel class of loss-of-function alleles of uncoordinated locomotion(unc)-108, which encodes the Caenorhabditis elegans homologue of the mammalian small guanosine triphosphatase Rab2. Like the previously isolated dominant-negative mutants, unc-108 loss-of-function mutant animals are defective in locomotion. In addition, they display unique defects in the removal of apoptotic cells, revealing a previously uncharacterized function for Rab2. unc-108 acts in neurons and engulfing cells to control locomotion and cell corpse removal, respectively, indicating that unc-108 has distinct functions in different cell types. Using time-lapse microscopy, we find that unc-108 promotes the degradation of engulfed cell corpses. It is required for the efficient recruitment and fusion of lysosomes to phagosomes and the acidification of the phagosomal lumen. In engulfing cells, UNC-108 is enriched on the surface of phagosomes. We propose that UNC-108 acts on phagosomal surfaces to promote phagosome maturation and suggest that mammalian Rab2 may have a similar function in the degradation of apoptotic cells.
Cell biology of stem cells: an enigma of asymmetry and self-renewal
Authors: Lin Haifan
Published: January 2008

Stem cells present a vast, new terrain of cell biology. A central question in stem cell research is how stem cells achieve asymmetric divisions to replicate themselves while producing differentiated daughter cells. This hallmark of stem cells is manifested either strictly during each mitosis or loosely among several divisions. Current research has revealed the crucial roles of niche signaling, intrinsic cell polarity, subcellular localization mechanism, asymmetric centrosomes and spindles, as well as cell cycle regulators in establishing self-renewing asymmetry during stem cell division. Much of this progress has benefited from studies in model stem cell systems such as Drosophila melanogaster neuroblasts and germline stem cells and mammalian skin stem cells. Further investigations of these questions in diverse types of stem cells will significantly advance our knowledge of cell biology and allow us to effectively harness stem cells for therapeutic applications.
Intrinsic Electrostatic Potential in the BK Channel Pore: Role in Determining Single Channel Conductance and Block
Authors: Carvacho Ingrid , Gonzalez Wendy , Torres Yolima P. , Brauchi Sebastian , Alvarez Osvaldo , Gonzalez-Nilo Fernando D. , Latorre Ramon
Published: January 2008

The internal vestibule of large-conductance Ca2+ voltage-activated K+ (BK) channels contains a ring of eight negative charges not present in K+ channels of lower conductance (Glu386 and Glu389 in hSlo) that modulates channel conductance through an electrostatic mechanism (Brelidze, T.I., X. Niu, and K.L. Magleby. 2003. Proc. Natl. Acad. Sci. USA. 100:9017–9022). In BK channels there are also two acidic amino acid residues in an extracellular loop (Asp326 and Glu329 in hSlo). To determine the electrostatic influence of these charges on channel conductance, we expressed wild-type BK channels and mutants E386N/E389N, D326N, E329Q, and D326N/E329Q channels on Xenopus laevis oocytes, and measured the expressed currents under patch clamp. Contribution of E329 to the conductance is negligible and single channel conductance of D326N/E329Q channels measured at 0 mV in symmetrical 110 mM K+ was 18% lower than the control. Current–voltage curves displayed weak outward rectification for D326N and the double mutant. The conductance differences between the mutants and wild-type BK were caused by an electrostatic effect since they were enhanced at low K+ (30 mM) and vanished at high K+ (1 M K+). We determine the electrostatic potential change, Δφ, caused by the charge neutralization using TEA+ block for the extracellular charges and Ba2+ for intracellular charges. We measured 13 ± 2 mV for Δφ at the TEA+ site when turning off the extracellular charges, and 17 ± 2 mV for the Δφ at the Ba2+ site when the intracellular charges were turned off. To understand the electrostatic effect of charge neutralizations, we determined Δφ using a BK channel molecular model embedded in a lipid bilayer and solving the Poisson-Boltzmann equation. The model explains the experimental results adequately and, in particular, gives an economical explanation to the differential effect on the conductance of the neutralization of charges D326 and E329.