bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical and thermo‐responsive characterisation of surfaces formed by plasma polymerisation of N‐isopropyl acrylamide
Authors: Bullett Nial A. , Talib Rosnita A. , Short Robert D. , McArthur Sally L. , Shard Alexander G.
Published: May 2006

Plasma polymerisation of N ‐isopropyl acrylamide (NIPAAm) presents an exciting route for the production of thermally responsive coatings on a wide variety of substrates for applications in tissue culture and microfluidics. One issue associated with the polymerisation of NIPAAm via plasma polymerisation is the limited volatility of the monomer and the subsequent requirement for monomer and reactor heating to create and maintain the vapour. It is already well established that power is critical in the balance between polymer functionality and coating stability in plasma polymers. However, little is known of how reactor and substrate temperatures may be used to influence the physico‐chemical characteristics of polymers produced from such low‐volatility monomers. In this paper, we examine the effects of a range of plasma deposition parameters on the functionality and stability of plasma‐polymerised NIPAAm surfaces. X‐ray photoelectron spectroscopy (XPS), near‐edge X‐ray absorption fine structure spectroscopy (NEXAFS), ellipsometry and contact angle goniometry have been used to examine coating chemistry, stability in aqueous environments, deposition rates and thermo‐responsive behaviour. Our results indicate that plasma polymerisation at low powers and low temperatures enhances the ability of plasma‐polymerised NIPAAm to display a wettability phase transition, but also contributes to instability of the coating to dissolution or delamination in water. Our spectroscopic measurements confirm that retention of the monomer structure is facilitated by low power and temperature deposition and reveal that conversion of the amide groups to amine and nitrile groups occurs during the polymerisation process, particularly at high discharge powers. Copyright © 2006 John Wiley & Sons, Ltd.
Characterization of surface energetic heterogeneity of pure and poly (acrylic acid)‐adsorbed carbon nanotubes by deconvoluting the nitrogen adsorption isotherm
Authors: Juqing Cui , Haitao Shan , Baixing Hu , Jian Shen
Published: May 2006

The surface energetic heterogeneity of pure and poly (acrylic acid) (PAA)‐adsorbed carbon nanotubes (CNTs) were studied by a nitrogen probe adsorption technique in a wide range of pressures. The adsorption energy distributions (AEDs) were calculated from the low‐pressure data of isotherms by deconvoluting the low‐pressure experimental nitrogen adsorption isotherms. The surface of pure CNTs is heterogeneous as its AED presents four peaks at 42, 52, 57 and 78 K. It is observed that the AED of CNTs can be evidently modified by PAA adsorption. While the PAA adsorption amount increases, the high‐energy peaks at 52, 57 and 78 K gradually weaken and diminish at last, whereas the low ones such as at 42 K strengthen and new peaks arise at 27 and 32 K. It is proposed that PAA molecules prefer interacting with and screening the higher energetic sites to the lower ones. It will facilitate the understanding of the polymer adsorption on energetic heterogeneity surfaces. Copyright © 2006 John Wiley & Sons, Ltd.
Monte Carlo model of the temperature rise at a GaAs surface under an electron beam
Authors: Nouiri A. , Chaguetmi S. , Belabed N.
Published: May 2006

Scanning electron microscopy (SEM) has frequently been used to study semiconductor materials. It offers the possibility of obtaining reliable qualitative and quantitative information on relevant local material parameters. The temperature rise due to electron‐beam bombardment can influence some semiconductor parameters, which then will influence the SEM information. In this work we propose a model calculation based on the Monte Carlo (MC) method to calculate the temperature rise due to electron‐beam heating. The results show that the temperature rise increases with increasing numbers of electrons (electron‐beam current), and the inverse behavior is observed with respect to the electron energy (electron‐beam voltage). The decrease in temperature rise with depth is also obtained. Copyright © 2006 John Wiley & Sons, Ltd.
Is Routine Preoperative Ultrasonographic Mapping for Arteriovenous Fistula Creation Necessary in Patients with Favorable Physical Examination Findings? Results of a Randomized Controlled Trial
Authors: Nursal Tarik Z. , Oguzkurt Levent , Tercan Fahri , Torer Nurkan , Noyan Turgut , Karakayali Hamdi , Haberal Mehmet
Published: May 2006

Introduction

Preoperative ultrasonographic mapping (PUSM) is widely used for arteriovenous fistula creation in end‐stage renal disease patients, and some authors even advocate that it be used routinely. To date, however, there are no prospective randomized data to support this suggestion.

Methods

This prospective, randomized, controlled study compared PUSM and physical examination in relation to short‐term outcome after AVF creation. Data sets from 70 hemodialysis patients who were deemed eligible for AVF surgery—according to specific physical examination (PE) criteria for vessel anatomy—were analyzed. The patients were randomly divided into two groups. In the PE group, no other investigation was performed, and the patient underwent AVF creation. The other patients (M group) underwent PUSM, and the AVF was created according to the mapping results. Early AVF success was defined as clinical detection of thrill (immediately and on postoperative day 1). Ultrasonographic parameters were recorded on the first postoperative day and at 1 and 6 months postoperatively. The need for intervention and intervention‐free AVF survival and cumulative AVF survival were also noted.

Results

The PE and M groups showed similar rates of early AVF success: immediate thrill, PE 24/35 (68.6%) vs. M 26/33 (78.8%), P = 0.340; postoperative day 1, PE 20/34 (58.8%) vs. M 24/32 (75%), P = 0.164. The groups’ results for ultrasonographic parameters of AVF function were also similar on postoperative day 1 and at 1 month after surgery. The groups had similar intervention‐free AVF survival (P = 0.770) and cumulative AVF survival as well (P = 0.916). After an average follow‐up of 217.7 ± 239.7 days, the two groups also had similar proportions of patent AVFs: 23/35 (65.7%) vs. 23/35 (65.7%) for PE vs. M, respectively; P = 1.0).

Conclusions

The results indicate that PUSM offers no advantage over PE with regard to AVF function in patients with favorable forearm anatomy. The authors do not advocate routine use of PUSM in patients with favorable PE findings scheduled for forearm AVF creation.
Effect of Antibiotic Heterogeneity on the Development of Infections with Antibiotic‐resistant Gram‐negative Organisms in a Non‐intensive Care Unit Surgical Ward
Authors: Takesue Yoshio , Ohge Hiroki , Sakashita Mitsuru , Sudo Takeshi , Murakami Yoshiaki , Uemura Kenichiro , Sueda Taijiro
Published: May 2006

Background

Heterogeneous antibiotic use has been suggested to limit the emergence of resistance, but determining the optimal strategy is difficult.

Methods

We developed a new strategy, termed “periodic antibiotic monitoring and supervision” (PAMS) program in a non‐ICU surgical ward. The 2‐year prospective study was divided into a 1‐year observation period and a 1‐year PAMS period. The use of four major classes of antibiotics in empirical therapy for Gram‐negative rod (GNR) infections was supervised. During the PAMS program, recommended, restricted, and off‐supervised classes of antibiotics were changed every 3 months according to the usage pattern of the antibiotics in the preceding term.

Results

Cefepime (45.5%) and imipenem/cilastatin (39.4%) were the most common antibiotics of choice during the observation period. The use of these antibiotics decreased significantly during the PAMS period, and that of fluoroquinolones and extended‐spectrum penicillin/beta‐lactamase inhibitor increased (4.8% vs. 21.4% and 2.4% vs. 21.4%, P < 0.01 respectively). Outcome analysis demonstrated a tendency toward reduction in the incidence of resistant GNR infections (P = 0.079) and that of Pseudomonas aeruginosa (P = 0.053). The incidence of resistant Gram‐positive core infections did not decrease. Analysis of antibiotic susceptibility to GNR revealed no significant beneficial results for any antibiotics.

Conclusions

As significant changes were not observed, the PAMS program is not generally applicable and heterogeneous antibiotic use as a way of reducing infections with resistant GNR in non‐ICU surgical wards was not established.
Purification of the skeletal muscle protein Endopin 1B and characterization of the genes encoding Endopin 1A and 1B isoforms
Authors: Herrera-Mendez Carlos H. , Brémaud Laure , Coulis Gerald , Pélissier Patrick , Sentandreu Miguel A. , Aubry Laurent , Delourme Didier , Chambon Christophe , Maftah Abderrahman , Leveziel Hubert , Ouali Ahmed
Published: May 2006

In the present work, a new endopin‐like serpin designed mEndopin 1B was purified from bovine muscle. Biochemical characterizations (amino acid sequencing and Maldi‐Tof mass spectrometry peptide mapping) demonstrated that the purified protein is different from the previously described Endopin 1, renamed mEndopin 1A. The genes and cDNA of both endopins were characterized. The cDNA sequence of mEndopin 1B encodes a predicted protein of 411 amino‐acids with a molecular mass of 43 808 Da. The mEndopin 1B gene comprised four coding exons and an additional 5′ untranslated exon. The reactive site sequence of mEndopin 1B is somewhat different from that of mEndopin 1A. Nevertheless, both serpins have a similar peptidase inhibitory pattern against examined proteases (elastase, trypsin, plasmin and chymotrypsin). The high expression of both mEndopin 1A and 1B in bovine serum and tissues and their high efficiency to inhibit elastase (k
ass
∼ 106
− 107
M−1
s−1) suggested that these serpins might play a major role in inflammatory processes.
In vitro inhibition of transthyretin aggregate‐induced cytotoxicity by full and peptide derived forms of the soluble receptor for advanced glycation end products (RAGE)
Authors: Monteiro Filipe Almeida , Cardoso Isabel , Sousa Mónica Mendes , Saraiva Maria João
Published: May 2006

Familial amyloidotic polyneuropathy is a neurodegenerative disorder characterized by systemic extracellular deposition of transthyretin (TTR) amyloid fibrils. The latter have been proposed to trigger neurodegeneration through engagement of the receptor for advanced glycation end products (RAGE). Here we show that TTR interaction with RAGE is conserved across mouse and human species and is not dependent on RAGE glycosylation. Moreover, strand D of TTR structure seems important for the TTR–RAGE interaction as well as a motif in RAGE (residues 102–118) located within the V‐domain; this motif suppressed TTR aggregate‐induced cytotoxicity in cell culture.
“ Confiance ” en régime démocratique et en régime totalitaire
Authors: Ogien Albert
Published: May 2006

This article discusses the thesis according to which a necessary link exists between a culture of trust and the emergence of a democratic regime. After analyzing the ordinary uses of the word trust, it differentiates three conceptions of “civic trust”: culturalist, rational-instrumental and moral. Then, by comparing the features of both a democratic and a totalitarian regime, it refutes the idea of a constitutive relation between trust and democracy. It then concludes that one cannot claim that a population lacks the ability to establish a democracy because it possesses certain cultural traits.
Finite element exterior calculus, homological techniques, and applications
Authors: Arnold Douglas N. , Falk Richard S. , Winther Ragnar
Published: May 2006

Finite element exterior calculus is an approach to the design and understanding of finite element discretizations for a wide variety of systems of partial differential equations. This approach brings to bear tools from differential geometry, algebraic topology, and homological algebra to develop discretizations which are compatible with the geometric, topological, and algebraic structures which underlie well-posedness of the PDE problem being solved. In the finite element exterior calculus, many finite element spaces are revealed as spaces of piecewise polynomial differential forms. These connect to each other in discrete subcomplexes of elliptic differential complexes, and are also related to the continuous elliptic complex through projections which commute with the complex differential. Applications are made to the finite element discretization of a variety of problems, including the Hodge Laplacian, Maxwell’s equations, the equations of elasticity, and elliptic eigenvalue problems, and also to preconditioners.
The ‘three pillars of stagnation’: challenges for air transport reform
Authors: FINDLAY CHRISTOPHER , ROUND DAVID K.
Published: May 2006

Various aspects of trade and investment in air transport services are regulated by a series of bilateral agreements in which rights of market access are exchanged. Industry commentators have identified this system and the associated national ownership rules as well as the prevailing attitude of competition authorities (on merger policy and on airport pricing) as the most important factors limiting adjustment in the international air transport industry. These ‘pillars of stagnation’ are examined here. Features of the bilateral agreements in aviation that are similar to those of other preferential trading agreements are noted and linked to the slow pace of policy reform in this industry. The three ‘pillars’ are not independent, and effective liberalization of trade and investment in air transport services depends on complementary regulatory reform. Options are presented on ways in which these changes might be designed and introduced, and in what sequence that might be done. Air transport services are currently excluded from the WTO's General Agreement on Trade in Services (GATS), and an important enquiry is how multilateral commitments recorded in the GATS might support reform.
Amplitude and frequency of temperature extremes over the North Atlantic region
Authors: Nogaj M. , Yiou P. , Parey S. , Malek F. , Naveau P.
Published: May 2006

Recent studies on extreme events have focused on the potential change of their intensity during the 20th century, but their frequency evolution has often been overlooked although its socio‐economic impact is equally important. This paper focuses on extreme events of high and low temperatures and their amplitude and frequency changes over the last 60 years in the North Atlantic (NA) region. We analyze the temporal evolution of the amplitude and frequency of extreme events through the parameters of an extreme value distribution applied to NCEP reanalysis for the winter and summer seasons. We examine the relation of the statistics of extremes with greenhouse gas forcing and an atmospheric circulation index and obtain a spatial distribution of the trends of those extreme parameters. We find that the frequency of warm extremes increases over most of the NA while their magnitude does not vary as systematically. Apart from the Labrador Sea and parts of Scandinavia, the features of winter cold extremes exhibit decreasing or no trends.
Mathematical space‐time model of a sky wave radio field
Authors: Barabashov B. G. , Anishin M. M. , Pelevin O. Y.
Published: May 2006

The three‐dimensional mathematical field model of HF sky waves reflected by a spatially nonuniform nonstationary magnetoactive ionosphere is described. The model is based on the structural physical approach, which leads to complete understanding of the field structure in space and time associated with specific geomagnetic conditions.
Geodetic constraints on the Bhuj 2001 earthquake and surface deformation in the Kachchh Rift Basin
Authors: Wallace K. , Bilham R. , Blume F. , Gaur V. K. , Gahalaut V.
Published: May 2006

GPS measurement of historic survey points in the region of the Mw 7.6 Bhuj earthquake of 26 January 2001 reveal a rupture area 25 km × 15 km, with the top of the rupture located at least 9 km beneath the surface. The geodetic data also reveal north‐south convergence of ∼18 mm/yr across the Rann of Kachchh since 1856. Convergence and the occurrence of south‐dipping reverse earthquakes on the northern edge of the Kachchh mainland suggest that the region is one of incipient or ongoing tectonic uplift. The small rupture of the Bhuj earthquake indicates that other earthquakes are likely to occur in the region, although few clues exist to indicate the progression of future ruptures.
Excitatory P2‐receptors at sympathetic axon terminals: role in temperature control of cutaneous blood flow
Authors: von Kügelgen Ivar
Published: May 2006

The mechanisms underlying the reduction in cutaneous blood flow in response to cooling are only partially understood. A study published in this issue of theBritish Journal of Pharmacologynow provides evidence for the involvement of excitatory P2‐receptors located at sympathetic axon terminals in the cooling‐induced vasoconstriction in the skin. Cooling appears to cause the release of adenine nucleotides followed by the activation of excitatory presynaptic P2‐receptors at noradrenergic axon terminals. Activation of these excitatory P2‐receptors induces the release of noradrenaline, which subsequently causes constriction of blood vessels in the skin by action on smooth muscleα1‐ andα2‐adrenoceptors. The commentary discusses the implication of the results and remaining questions.

British Journal of Pharmacology(2006)148, 561–562. doi:10.1038/sj.bjp.0706767
Pharmacological regulation of insulin secretion in MIN6 cells through the fatty acid receptor GPR40: identification of agonist and antagonist small molecules
Authors: Briscoe Celia P , Peat Andrew J , McKeown Stephen C , Corbett David F , Goetz Aaron S , Littleton Thomas R , McCoy David C , Kenakin Terry P , Andrews John L , Ammala Carina , Fornwald James A , Ignar Diane M , Jenkinson Stephen
Published: May 2006

Long chain fatty acids have recently been identified as agonists for the G protein‐coupled receptors GPR40 and GPR120. Here, we present the first description of GW9508, a small‐molecule agonist of the fatty acid receptors GPR40 and GPR120. In addition, we also describe the pharmacology of GW1100, a selective GPR40 antagonist. These molecules were used to further investigate the role of GPR40 in glucose‐stimulated insulin secretion in the MIN6 mouse pancreatic β‐cell line.

GW9508 and linoleic acid both stimulated intracellular Ca2+ mobilization in human embryonic kidney (HEK)293 cells expressing GPR40 (pEC50 values of 7.32±0.03 and 5.65±0.06, respectively) or GPR120 (pEC50 values of 5.46±0.09 and 5.89±0.04, respectively), but not in the parent HEK‐293 cell line.

GW1100 dose dependently inhibited GPR40‐mediated Ca2+ elevations stimulated by GW9508 and linoleic acid (pIC50 values of 5.99±0.03 and 5.99±0.06, respectively). GW1100 had no effect on the GPR120‐mediated stimulation of intracellular Ca2+ release produced by either GW9508 or linoleic acid.

GW9508 dose dependently potentiated glucose‐stimulated insulin secretion in MIN6 cells, but not in primary rat or mouse islets. Furthermore, GW9508 was able to potentiate the KCl‐mediated increase in insulin secretion in MIN6 cells. The effects of GW9508 on insulin secretion were reversed by GW1100, while linoleic acid‐stimulated insulin secretion was partially attenuated by GW1100.

These results add further evidence to a link between GPR40 and the ability of fatty acids to acutely potentiate insulin secretion and demonstrate that small‐molecule GPR40 agonists are glucose‐sensitive insulin secretagogues.

British Journal of Pharmacology (2006) 148, 619–628. doi:10.1038/sj.bjp.0706770
Relevance of tumour necrosis factor‐α for the inflammatory and nociceptive responses evoked by carrageenan in the mouse paw
Authors: Rocha Ana C C , Fernandes Elizabeth S , Quintão Nara L M , Campos Maria M , Calixto João B
Published: May 2006

The present study evaluated the participation of tumour necrosis factor‐α (TNF‐α) in the inflammatory and nociceptive responses evoked by carrageenan in the mouse paw.

The intraplantar injection of carrageenan (300 μg paw−1) induced a marked and biphasic paw oedema formation (peaks at 6 and 72 h), which was accompanied by a long‐lasting mechanical allodynia (that remained elevated for up to 72 h) and a significant increase of myeloperoxidase (MPO) activity (peak at 6 h) in both Swiss and C57/BL6 mice.

The paw oedema, the elevation of MPO activity and to a lesser extent the mechanical allodynia elicited by carrageenan were found to be significantly reduced in TNF‐α p55 receptor knockout mice.

Of interest, the systemic administration of an anti‐TNF‐α antibody produced a significant inhibition of paw oedema, mechanical allodynia and MPO activity. A noteworthy decrease in inflammatory and nociceptive responses caused by carrageenan was also observed when mice were previously treated with the preferential inhibitor of TNF‐α synthesis, thalidomide.

The present results clearly indicate that the proinflammatory cytokine TNF‐α plays a critical role in the oedema formation, as well as in the mechanical allodynia and the neutrophil migration, following carrageenan administration into the mouse paw. Intraplantar injection of carrageenan in mice could constitute a useful model for assessment of the in vivo effects of potential inhibitors of TNF‐α‐related pathways.

British Journal of Pharmacology (2006) 148, 688–695. doi:10.1038/sj.bjp.0706775
Energy deposition of MeV electrons in compressed targets of fast-ignition inertial confinement fusion
Authors: Li C. K. , Petrasso R. D.
Published: May 2006

Energy deposition of MeV electrons in dense plasmas, important for fast ignition in inertial confinement fusion, is modeled analytically. It is shown that classical stopping and scattering dominate electron transport and energy deposition when the electrons reach the dense plasmas in the cores of compressed targets, while “anomalous” stopping associated with self-generated fields and micro-instabilities (suggested by previous simulations) might initially play an important role in the lower-density plasmas outside the dense core. For MeV electrons in precompressed deuterium-tritium fast-ignition targets, the initial penetration results in approximately uniform energy deposition but the latter stages of penetration involve mutual couplings of energy loss, straggling, and blooming that lead to enhanced, nonuniform energy deposition. This model can be used for quantitatively assessing ignition requirements for fast ignition.
Forming cryogenic targets for direct-drive experiments
Authors: Harding D. R. , Meyerhofer D. D. , Loucks S. J. , Lund L. D. , Janezic R. , Elasky L. M. , Hinterman T. H. , Edgell D. H. , Seka W. , Wittman M. D. , Gram R. Q. , Jacobs-Perkins D. , Early R. , Duffy T. , Bonino M. J.
Published: May 2006

More than 100 spherical deuterium ice layers have been formed to make cryogenic targets for direct-drive ICF implosion experiments on OMEGA. These ice layers have an inner surface roughness that ranges from 1.3to6μm root-mean-square (rms), with the best layers having a value less than 2μm rms. These surface roughness values are averaged two-dimensional roughness measurements that cover the entire surface and includes all of the Fourier cosine modes. The ice thickness variation within the layer is predominately in the low spectral modes (mode 5 and lower) and is caused by the support used to hold the target. Changing the design of this support to minimize the thermal effect is constrained by the necessity of having a dynamically stable target for the implosion. We have demonstrated that it is possible to form crystalline ice layers that are facet-free and transparent by slowing the solidification rate of the liquid. Faster freezing rates form layers comprised of polycrystalline ice with a greater roughness (1to2μm greater). Cooling an ice layer 0.5K below the triple point temperature does not affect the roughness of the layer. Cooling the layer a further 1K to achieve the desired internal gas pressure sometimes induces additional ice roughness; this roughness is manifest over low- to mid-spectral modes. Removing the thermal shrouds from around the target causes the ice to melt and the internal gas pressure to increase. Using the behavior of a cryogenic deuterium target as a reference, calculations of the response of the more interesting National Ignition Facility-scale deuterium and tritium targets show that exposing the target for 0.8s to ambient radiation will cause ∼10% of the ice to melt and partially slump whereas the gas pressure will increase by 15%.
Phase behavior of the lattice restricted primitive model with nearest neighbor exclusion
Authors: Diehl Alexandre , Panagiotopoulos Athanassios Z.
Published: May 2006

The global phase behavior of the lattice restricted primitive model with nearest neighbor exclusion has been studied by grand canonical Monte Carlo simulations. The phase diagram is dominated by a fluid (or charge-disordered solid) to charge-ordered solid transition that terminates at the maximum density ρmax*=2 and reduced temperature T*≈0.29. At that point, there is a first-order phase transition between two phases of the same density, one charge-ordered, and the other charge-disordered. The liquid-vapor transition for the model is metastable, lying entirely within the fluid-solid phase envelope.
Elucidating the hard/soft acid/base principle: A perspective based on half-reactions
Authors: Ayers Paul W. , Parr Robert G. , Pearson Ralph G.
Published: May 2006

A comprehensive analysis is presented for the acid-base double-exchange reaction as well as the associated acid-displacement and base-displacement “half-reactions” with the goal of elucidating the meaning of the hard/soft acid/base (HSAB) principle and the conditions for its validity. When electron-transfer effects are important and other effects are negligible, the HSAB principle is driven by the surpassing stability of the soft acid/soft base product. When electrostatic effects dominate the reactivity, the HSAB principle is driven by the surpassing stability of the hard acid/hard base product. Because electron-transfer effects favor soft/soft interactions, while electrostatic effects favor hard/hard interactions, acid-base exchange reactions may be used to determine whether a reagent’s reactivity is dominated by electron-transfer or by electrostatic effects. Because electron-transfer and electrostatic considerations separately favor the HSAB principle whenever the electronic chemical potentials of the acids and bases involved in the reaction are similar, our analysis provides strong support for the HSAB principle. The electronic chemical potential measures the intrinsic strength of acids and bases.
Experimental and theoretical investigation of the dispersed fluorescence spectroscopy of HC4S
Authors: Reilly N. J. , Cupitt G. C. , Kable S. H. , Schmidt T. W.
Published: May 2006

A high-resolution single vibronic level emission study from the ÃΠ3∕22 state of the HC4S radical is reported. Ground state density functional theory frequencies have been used to assign ground state vibronic levels involving three stretching modes ν2, ν3, and ν5 in the region of 0–3250cm−1, while the frequency of ν4 remains speculative. Tentative assignments are given for the complicated structures arising from Renner-Teller and spin-orbit interactions within the bending energy levels. From analysis of the dispersed emission spectra, Fermi resonances involving pairs of bands have been identified in the ÃΠ3∕22←X̃Π3∕22 laser induced fluorescence spectrum.
Charge trapping and dielectric relaxation in connection with breakdown of high-k gate dielectric stacks
Authors: Luo Wen , Yuan Tao , Kuo Yue , Lu Jiang , Yan Jiong , Kuo Way
Published: May 2006

Charge trapping/detrapping and dielectric polarization/relaxation of high-k dielectrics have been investigated. Relaxation behaviors of TiN∕SiO2∕p-Si and TiN∕Zr-doped HfOx∕SiO2∕p-Si capacitors were studied with a ramp-relax method. The latter shows a relaxation current, which signifies the high-k dielectric integrity and disappears at breakdown, while the former does not. The breakdown sequences of TiN∕Zr-doped HfOx∕SiO2∕p-Si and Al∕Hf-doped TaOx∕silicate∕p-Si were identified with relaxation current. For the former, the breakdown initiated at the interfacial SiO2 layer; for the latter, the breakdown starts from the Hf-doped TaOx layer. The breakdown sequence is explained with the material properties and thicknesses of individual layers.
Structural, electrical, and optical properties of p-type ZnO thin films with Ag dopant
Authors: Kang Hong Seong , Ahn Byung Du , Kim Jong Hoon , Kim Gun Hee , Lim Sung Hoon , Chang Hyun Woo , Lee Sang Yeol
Published: May 2006

p -type ZnO films have been fabricated on a (0001) Al2O3 substrate, using Ag2O as a silver dopant by pulsed laser deposition. The structural property of those films is systematically characterized by observing the shift of (0002) peak to investigate the substitution of Ag+ for Zn+. Narrow deposition temperature for Ag-doped p-type ZnO films has been obtained in the range of 200–250°C with the hole concentration of 4.9×1016–6.0×1017cm−3. A neutral acceptor bound exciton has been clearly observed by photoluminescence emitted at 3.317eV in Ag-doped p-type ZnO thin films.
Reduced buckling in one dimension versus two dimensions of a compressively strained film on a compliant substrate
Authors: Peterson R. L. , Hobart K. D. , Kub F. J. , Yin H. , Sturm J. C.
Published: May 2006

Compliant substrates are useful for manipulating the strain state of thin films. However the compliant layer may permit undesirable roughening (buckling) of a compressively strained film. In this work, we quantitatively compare two-dimensional and one-dimensional buckling in thin silicon-germanium films under biaxial and uniaxial compressive stresses, respectively. For the same strain level, films with one-dimensional stress and thus one-dimensional buckling exhibit slower buckling and lower final steady state buckling amplitude, which makes them technologically advantageous compared to biaxially strained films, which exhibit two-dimensional buckling. The results are explained through modeling.
Investigations of the characteristics of strain-free oxidation on InAlAs epilayer lattice matched to indium phosphide
Authors: Perumal Premchander , Kim Jong Min , Lee Yong Tak , Kim Sang Sub
Published: May 2006

High resolution x-ray diffraction and transmission electron microscopy (TEM) were used to study the strain behavior in InAlAs oxides grown on In0.52Al0.48As epilayer lattice matched to InP (100) substrates by wet thermal oxidation technique. The relaxed strain morphology has been observed between the InAlAs oxides and lattice matched InAlAs epilayer to InP substrates with the optimization of process temperature, rate of oxidation, and time. Almost strain-free InAlAs oxide layer with high crystallographic quality was obtained on InAlAs epilayer, which is similar to that of lattice matched InAlAs epilayer grown on InP substrate.
Terahertz imaging with a direct detector based on superconducting tunnel junctions
Authors: Ariyoshi S. , Otani C. , Dobroiu A. , Sato H. , Kawase K. , Shimizu H. M. , Taino T. , Matsuo H.
Published: May 2006

We demonstrated terahertz imaging using a direct detector based on niobium superconducting tunnel junctions (STJs). The detector is composed of linearly distributed junctions placed on a superconducting microstrip line and is integrated on two wings of a log-periodic antenna. We succeeded nondestructive imaging for an integrated-circuit card and dry material using the detector around its sensitivity peak (∼0.66THz). The dynamic range was measured to be higher than 4×107 (76dB). Thus, the STJ detector is applicable to high-sensitivity and high-speed terahertz imaging for various nondestructive inspection applications.
Radio-frequency point-contact electrometer
Authors: Qin Hua , Williams David A.
Published: May 2006

We fabricate and characterize a radio-frequency semiconductor point-contact (rf-PC) electrometer analogous to radio-frequency single-electron transistors (rf-SETs) [see Schoelkopf et al., Science 280, 1238 (1998)]. The point contact is formed by surface Schottky gates in a two-dimensional electron gas in an AlGaAs∕GaAs heterostructure. In the present setup, the PC is operating as a simple voltage-controlled resistor rather than a quantum point contact and demonstrates a charge sensitivity of about 2×10−1e∕Hz at a bandwidth of 30kHz without the use of a cryogenic rf preamplifier. Since the impedance of a typical point-contact device is much lower than the impedance of the typical SET, a semiconductor-based rf-PC, equipped with practical cryogenic rf preamplifiers, could realize an ultrafast and ultrasensitive electrometer.
Lifetime study of N impurity states in GaAs1−xNx (x=0.1%) under hydrostatic pressure
Authors: Wang W. J. , Yang X. D. , Ma B. S. , Sun Z. , Su F. H. , Ding K. , Xu Z. Y. , Li G. H. , Zhang Y. , Mascarenhas A. , Xin H. P. , Tu C. W.
Published: May 2006

The lifetimes of a series of N-related photoluminescence lines (A2–A6) in GaAs1−xNx (x=0.1%) were studied under hydrostatic pressures at ∼30K. The lifetimes of A5 and A6 were found to increase rapidly with increasing pressure: from 2.1ns at 0GPa to more than 20ns at 0.92GPa for A5 and from 3.2ns at 0.63GPa to 10.8ns at 0.92GPa for A6. The lifetime is found to be closely correlated with the binding energy of the N impurity states, which is shown either in the pressure dependence for a given emission line or in the lifetime variation from A2 to A6.
Room-temperature, high-power, and continuous-wave operation of distributed-feedback quantum-cascade lasers at λ∼9.6μm
Authors: Darvish S. R. , Slivken S. , Evans A. , Yu J. S. , Razeghi M.
Published: May 2006

High-power continuous-wave (cw) operation of distributed-feedback quantum-cascade lasers is reported. Continuous-wave output powers of 100mW at 25°C and 20mW at 50°C are obtained. The device exhibits a cw threshold current density of 1.34kA∕cm2, a maximum cw wall-plug efficiency of 1% at 25°C, and a characteristic temperature of ∼190K in pulsed mode. Single-mode emission near 9.6μm with a side-mode suppression ratio of ⩾30dB and a tuning range of 2.89cm−1 from 15to50°C is obtained.
Juvenile tree growth and demography in response to feral water buffalo in savannas of northern Australia: an experimental field study in Kakadu National Park
Authors: Werner P. A. , Cowie I. D. , Cusack J. S.
Published: May 2006

Tree populations in the wooded savannas of northern Australia lack a well developed seed bank, but instead rely on a persistent ground layer of suppressed juvenile plants <1 m of indeterminate ages. The feral Asian water buffalo has been implicated as a factor in inhibiting the movement of juvenile trees to sapling stage. In a 6-year field study in Kakadu National Park, 656 juvenile plants were monitored for growth and survival, and in exploring the effects of buffalo, clipping surrounding vegetation and ambient fire. Buffalo were removed from one half of the sites across an environmental gradient in a landscape-scale experiment. Juvenile trees grew more slowly but fewer became dormant where buffalo were absent. Experimental clipping of surrounding vegetation produced significantly increased height at the buffalo-absent sites, but not at the buffalo-present sites, demonstrating that the positive effect of buffalo on growth was indirect, by reducing the competitive regime for juvenile trees. Within 3 years of removal of buffalo, ground-level green biomass increased 2–10 times and litter 1.3–2 times over a topographic gradient. Mortality of juvenile trees was not significantly different between buffalo-present and buffalo-absent sites when plots remained unburnt. By contrast, at buffalo-absent sites, three times more juveniles died after late dry-season fires than at unburnt sites, but there was no difference among buffalo-present sites. Overall, the total juvenile tree bank decreased by 7% where buffalo grazed and by 18% where buffalo had been removed. The study demonstrated a major mechanism(s) responsible for recorded changes in vegetation patterns of these savannas, whereby buffalo initiate a cascade of effects by changing ground-level biomass, which change competitive relationships and fuel loads, which then have an impact on tree growth and demography. The results are discussed with respect to dynamics of the juvenile tree bank and implications for long-term sustainability of these wooded savannas.
Instantaneous photosynthetic responses to temperature of deciduous and evergreen Nothofagus species
Authors: Kohout M. , Read J.
Published: May 2006

Deciduous species of Nothofagus tend to replace evergreen Nothofagus at the highest altitudes. We investigated whether deciduous Nothofagus species have higher maximum rates of net photosynthesis (Pmax) and specific leaf area (SLA) than evergreen species and whether there is an increasing photosynthetic advantage (e.g. higher Pmax) in deciduous species relative to evergreen species with increasing altitude that might explain their replacement of evergreen species. Net photosynthesis was investigated in (1) five deciduous and five evergreen species of Nothofagus grown in a common environment and (2) two co-occurring species, N. gunnii (Hook.f.) Oerst. (deciduous) and N. cunninghamii (Hook.) Oerst. (evergreen), across a range of altitudes in Tasmania. In the first experiment, the maximum rate of net photosynthesis per leaf mass (Pmax, mass) and SLA were higher in deciduous species, whereas the maximum rate of net photosynthesis per leaf area (Pmax, area) did not differ between leaf habits. However, in the field-based study, both mass- and area-based Pmax were higher in N. gunnii than N. cunninghamii across all sites. The high Pmax, mass of deciduous species may provide a competitive advantage at higher altitudes by maximising carbon gain during the growing season. However, in the study of sympatric populations of N. gunnii and N. cunninghamii there was no evidence of increasing photosynthetic advantage of the deciduous N. gunnii with increasing altitude.
Floral biology and late-acting self-incompatibility in Jacaranda racemosa (Bignoniaceae)
Authors: Bittencourt Nelson S. , Semir João
Published: May 2006

Breeding-system studies have been conducted with 38 of the approximately800 species of Bignoniaceae, and self-incompatibility was found in 31 of these. In species for which the site of self-incompatibility barrier was studied, self-pollinated flowers consistently failed to develop into fruits, even though pollen tubes grew down to the ovary and penetrated most of the ovules. In this study, we have investigated the floral biology and the breeding system in Jacaranda racemosa Chamisso, with hand-pollination experiments and the histology of post-pollination events. Flower anthesis lasted 1–3 days, and although the frequency of flower visitation was extremely low, natural pollination seemed to be effected mainly by medium-sized bees. Because the conspicuous staminodium favours eventual pollination by small bees, a possible role of the staminodium in the increase of potential pollinators is suggested. Hand-pollinations indicated that J. racemosa is a self-sterile species. Histological analysis of post-pollination events indicated the occurrence of a kind of late-acting self-incompatibility in which the processes of ovule penetration, fertilisation and endosperm initiation were slower in selfed than in crossed pistils. Until the time of self-pollinated pistil abscission, no signs of endosperm malfunction or proembryo development were observed in selfed pistils. Therefore, inbreeding depression is an unlikely explanation for self-sterility in J. racemosa.
Arbuscular mycorrhizas and ectomycorrhizas on Eucalyptus grandis (Myrtaceae) trees and seedlings in native forests of tropical north-eastern Australia
Authors: Adams Felicity , Reddell Paul , Webb Michael J. , Shipton Warren A.
Published: May 2006

Eucalypts have been shown to form both arbuscular mycorrhizas (AM) and ectomycorrhizas (ECM) in glasshouse experiments. Little is known, however, about the relative dominance of these two mycorrhiza types on individual eucalypt species across their natural range. This study examined mycorrhizal colonisation levels of Eucalyptus grandis Hill ex Maiden roots at 29 sites representing a broad range of wet sclerophyll forest types in the wet tropics of north-eastern Australia. Adult E. grandis trees sampled in situ were invariably heavily ectomycorrhizal, with 76–100% fine root length colonised (% RLC). There were comparatively low levels of AM, with typically less than 10% RLC. Seedling E. grandis grown in intact soil cores from the field sites under glasshouse conditions had lower total levels of mycorrhiza formation compared with adult trees, with more variable ECM formation (10–95% RLC) and more extensive AM formation (10–40% RLC). There were no apparent trends in mycorrhiza formation across different soil parent material, rainfall or vegetation categories used. The current research suggests that arbuscular mycorrhizas are more prominent on seedlings, whereas ectomycorrhizas predominate in adult trees of E. grandis. Possible reasons for these differences and a comparison with other studies of eucalypt mycorrhizas under natural conditions are presented.
Impacts of tree invasion on floristic composition of subtropical grasslands on the Bunya Mountains, Australia
Authors: Butler Don William , Fairfax Russell James , Fensham Roderick John
Published: May 2006

The effect of ongoing forest invasion on floristic composition of subtropical montane grasslands was considered by examining vascular plant species frequencies across 13 adjoining areas of grassland, invaded grassland (eucalypt forest <50 years old) and eucalypt forest (>50 years old) on the Bunya Mountains in subtropical eastern Australia. Tree invasion of grasslands over the last 50 years has had substantial facilitative or antagonistic net impacts on populations of many plant species. Increases in species frequency, indicating net facilitation, generally appear to occur earlier in forest development than do decreases in frequency, indicative of net antagonism. Although more than 20% of the flora showed substantial association with either grassland or forest, the dominant ground-stratum species in each habitat were quite similar and very few grassland species were not recorded in grassy forests. Forb species composition appears to change more rapidly after tree invasion than grass species composition. Relatively few forbs preferred forest to grassland, whereas shrubs, trees or lianes were substantially more frequent in forests. Replacement of grasslands by grassy forests would reduce landscape diversity and impact on other values in the Bunya Mountains. However, this study suggests that most, if not all, vascular plants that currently occur on the grasslands will persist in the area provided the grassy character of the eucalypt forests is maintained.
Serial coalescent simulations suggest a weak genealogical relationship between Etruscans and modern Tuscans
Authors: Belle Elise M. S. , Ramakrishnan Uma , Mountain Joanna L. , Barbujani Guido
Published: May 2006

The Etruscans, the only preclassical European population that has been genetically characterized so far, share only two haplotypes with their modern geographic counterparts, the Tuscans, who, nonetheless, appear to be their closest relatives. We modeled 10 demographic scenarios spanning the last 2,500 years and tested by serial coalescent simulation whether any are consistent with the patterns of genetic diversity observed within and between the Etruscan and the modern Tuscan populations. Models in which the Etruscans are the direct ancestors of modern Tuscans appear compatible with the observed data only when they also include a very high mutation rate and an ancient founder effect. A better fit was obtained when the ancient and the modern samples were extracted from two independently evolving populations, connected by little migration. Simulated and observed parameters were also similar for a scenario in which the ancient samples came from a subset, e.g., a social elite, genetically differentiated from the bulk of the Etruscan population. In principle, these results may be biased by factors such as gross and systematic errors in the ancient DNA sequences and failure to sample suitable modern individuals. If neither proves to be the case, this study strongly suggests that either the mitochondrial mutation rate is much higher than currently believed or the Etruscans left very few modern mitochondrial descendants.
Failing to deactivate: Resting functional abnormalities in autism
Authors: Kennedy Daniel P. , Redcay Elizabeth , Courchesne Eric
Published: May 2006

Several regions of the brain (including medial prefrontal cortex, rostral anterior cingulate, posterior cingulate, and precuneus) are known to have high metabolic activity during rest, which is suppressed during cognitively demanding tasks. With functional magnetic resonance imaging (fMRI), this suppression of activity is observed as “deactivations,” which are thought to be indicative of an interruption of the mental activity that persists during rest. Thus, measuring deactivation provides a means by which rest-associated functional activity can be quantitatively examined. Applying this approach to autism, we found that the autism group failed to demonstrate this deactivation effect. Furthermore, there was a strong correlation between a clinical measure of social impairment and functional activity within the ventral medial prefrontal cortex. We speculate that the lack of deactivation in the autism group is indicative of abnormal internally directed processes at rest, which may be an important contribution to the social and emotional deficits of autism.
Factor B of the alternative complement pathway regulates development of airway hyperresponsiveness and inflammation
Authors: Taube Christian , Thurman Joshua M. , Takeda Katsuyuki , Joetham Anthony , Miyahara Nobuaki , Carroll Michael C. , Dakhama Azzeddine , Giclas Patricia C. , Holers V. Michael , Gelfand Erwin W.
Published: May 2006

Exposure to inhaled allergens leads to increases in airway hyperresponsiveness (AHR) and inflammation, associated with increased levels of biologically active fragments derived from the complement C3 and C5 family of proteins. Further, complement activation during allergen challenge in sensitized animals is necessary for the development of AHR and airway inflammation. To define the complement pathway involved, we studied mice deficient in complement factor 4 (C4−/−), a critical component of the classical pathway, or factor B (fB−/−), an essential protein in the alternative complement pathway. WT,C4−/−, andfB−/− mice were sensitized to ovalbumin and subsequently exposed to nebulized ovalbumin (1% in saline) on 3 consecutive days. After allergen sensitization and challenge,fB−/− mice demonstrated significantly lower airway responsiveness to methacholine and less airway inflammation. In contrast,C4−/− mice showed no reduction in AHR and airway inflammation compared with WT mice. Tissue inflammation, goblet cell hyperplasia, and IL-4, IL-5, and IL-13 levels in BAL fluid were significantly reduced infB−/− mice compared withC4−/− and WT mice. The development of AHR and airway inflammation in sensitizedfB−/− mice could be restored after intranasal administration of purified factor B before the airway challenge. In addition, administration of a neutralizing anti-factor B mAb to sensitized mice before airway challenge reduced the development of AHR and airway inflammation. These results demonstrate that in sensitized hosts complement activation through the alternative pathway after allergen exposure is critical to the development of AHR and airway inflammation.