bluuebunny/crossref_metadata_2025 huggingface dataset:
Regional econometric income forecast accuracy
Authors: Fullerton Thomas M. , Tinajero Roberto , Waldman Lawrence
Published: August 2005

Econometric prediction accuracy for personal income forecasts is examined for a region of the United States. Previously published regional structural equation model (RSEM) forecasts exist ex ante for the state of New Mexico and its three largest metropolitan statistical areas: Albuquerque, Las Cruces and Santa Fe. Quarterly data between 1983 and 2000 are utilized at the state level. For Albuquerque, annual data from 1983 through 1999 are used. For Las Cruces and Santa Fe, annual data from 1990 through 1999 are employed. Univariate time series, vector autoregressions and random walks are used as the comparison criteria against structural equation simulations. Results indicate that ex ante RSEM forecasts achieved higher accuracy than those simulations associated with univariate ARIMA and random walk benchmarks for the state of New Mexico. The track records of the structural econometric models for Albuquerque, Las Cruces and Santa Fe are less impressive. In some cases, VAR benchmarks prove more reliable than RSEM income forecasts. In other cases, the RSEM forecasts are less accurate than random walk alternatives. Copyright © 2005 John Wiley & Sons, Ltd.
Sediment infiltration traps: their use to monitor salmonid spawning habitat in headwater tributaries of the Cascapédia River, Québec
Authors: Zimmermann André E. , Lapointe Michel
Published: August 2005

Sediment infiltration can clog salmon nests and reduce egg survival. As a countermeasure, environmental managers often deploy infiltration traps to monitor sediment infiltration. Traps provide a repeatable means of measuring infiltration and enable comparisons to be made between sites. Results from infiltration rates measured with traps have also been used to estimate infilling rates into salmon nests. Application of these data is questionable, as the composition of the bed and the amount of fine sediment within the bed is known to affect infiltration rates. Thus, infiltration rates measured with infiltration traps may differ from the infiltration rates occurring in redd and riffle gravels.

To examine how relationships between sediment infiltration rates varied between four watersheds, we continuously monitored suspended sediment transport, shear stress and infiltration rates at four sites over 5 months. We also compared infiltration rates measured with infiltration traps with changes in the hydraulic conductivity and subsurface grain size distribution of adjacent artificially constructed salmon nests and natural riffle gravels.

Among the four watersheds, clear differences in sediment infiltration rates were observed. The differences correlated with the subsurface silt content but no strong relationship existed between land‐use or basin physiography/geology. Despite observing an average of 30 kg m−2 of sediment finer than 2 mm being deposited in the infiltration traps during the study, no change in redd or riffle substrate was observed. If the deposition rates measured with the traps reflect the processes in redds, enough sediment would have been deposited to inhibit egg emergence. However, no reduction in egg survival to the eyed stage was observed. In summary, our results show that infiltration traps with clean gravels can be used to detect intersite differences in sediment transport regimes. Extrapolations of sediment infiltration rates measured with such collectors to estimate infiltration rates in redds or riffles is, however, flawed. Copyright © 2005 John Wiley & Sons, Ltd.
Analysis of the epidermal growth factor receptor specific transcriptome: Effect of receptor expression level and an activating mutation
Authors: Pedersen Mikkel W. , Pedersen Nina , Damstrup Lars , Villingshøj Mette , Sønder Søren U. , Rieneck Klaus , Bovin Lone F. , Spang‐Thomsen Mogens , Poulsen Hans S.
Published: August 2005

Overexpression or expression of activating mutations of the epidermal growth factor receptor (EGFR) is common in cancer and correlates with neoplastic progression. The present study employed Affymetrix® oligonucleotide arrays to profile genes induced by ligand‐activated EGFR with the receptor either moderately expressed or overexpressed at an in‐itself transforming level. These changes were compared to those induced by the naturally occurring constitutively active variant EGFRvIII. This study provides novel insight on the activities and mechanisms of EGFRvIII and EGFR mediated transformation, as genes encoding proteins with functions in promoting cell proliferation, invasion, antiapoptosis, and angiogenesis featured prominently in the EGFRvIII‐ and EGFR‐expressing cells. Surprisingly, it was found that ligand‐activated EGFR induced the expression of a large group of genes known to be inducible by interferons. Expression of this module was absent in the EGFRvIII‐expressing cell line and the parental cell line. Treatment with the specific EGFR inhibitor AG1478 indicated that the regulations were primary, receptor‐mediated events. Furthermore, activation of this module correlated with activation of STAT1 and STAT3. The results thus demonstrate that ligand‐activated EGFR at different expression levels results in different kinetics of signaling and induction of gene expression. In addition, the constitutively active variant EGFRvIII seems to activate only a subset of signal pathways and induce a subset of genes as compared to the ligand‐activated EGFR. © 2005 Wiley‐Liss, Inc.
Statins in nephrotic syndrome: A new weapon against tissue injury
Authors: Buemi Michele , Nostro Lorena , Crascì Eleonora , Barillà Antonio , Cosentini Vincenzo , Aloisi Carmela , Sofi Tito , Campo Susanna , Frisina Nicola
Published: August 2005

The nephrotic syndrome is characterized by metabolic disorders leading to an increase in circulating lipoproteins levels. Hypertriglyceridemia and hypercholesterolemia in this case may depend on a reduction in triglyceride‐rich lipoproteins catabolism and on an increase in hepatic synthesis of Apo B‐containing lipoproteins. These alterations are the starting point of a self‐maintaining mechanism, which can accelerate the progression of chronic renal failure. Indeed, hyperlipidemia can affect renal function, increase proteinuria and speed glomerulosclerosis, thus determining a higher risk of progression to dialysis. 3‐hydroxy‐3‐methylglutaryl‐coenzyme A (HMG‐CoA) reductase is the rate‐limiting enzyme in cholesterol synthesis from mevalonate and its inhibitors, or statins, can therefore interfere with the above‐mentioned consequences of hyperlipidemia. Statins are already well known for their effectiveness on primary cardiovascular prevention, which cannot be explained only through their hypolipemic effect. As far as kidney diseases are concerned, statin therapy has been shown to prevent creatinine clearance decline and to slow renal function loss, particularly in case of proteinuria, and its favorable effect may depend only partially on the attenuation of hyperlipidemia. Statins may therefore confer tissue protection through lipid‐independent mechanisms, which can be triggered by other mediators, such as angiotensin receptor blockers. Possible pathways for the protective action of statins, other than any hypocholesterolemic effect, are: cellular apoptosis/proliferation balance, inflammatory cytokines production, and signal transduction regulation. Statins also play a role in the regulation of the inflammatory and immune response, coagulation process, bone turnover, neovascularization, vascular tone, and arterial pressure. In this study, we would like to provide scientific evidences for the pleiotropic effects of statins, which could be the starting point for the development of new therapeutical strategies in different clinical areas. © 2005 Wiley Periodicals, Inc.
New polymer syntheses: XV. Synthesis and characterization of new polyketoamine polymers containing ether or thioether linkages in the main chain
Authors: Abbady MA , Aly KI , Mahgoub SA , Hussein MA
Published: August 2005

An interesting new class of linear polyketoamine polymers containing ether or thioether linkages in the main chain has been synthesized by solution polycondensation of 4,4′‐bis(chloroacetyl)diphenyl ether (I), 4,4′‐bis(chloroacetyl)diphenyl sulfide (II) and 4,4′‐bis(chloroacetyl)diphenyl sulfone (III) with various aliphatic and aromatic diamines. The model compounds IV, V and VI were synthesized from the monomers I, II and III with aniline in dry benzene and their structures were confirmed by elemental and spectral analyses. The resulting polymers were characterized by elemental and spectral analyses, as well as by solubility and viscometry measurements. The thermal properties were evaluated by TGA and DSC and correlated to their structural units. X‐ray analysis showed that the polymers had some degree of crystallinity in the region 2θ = 5° to 60°. The UV‐visible spectra of some selected polymers were measured in dimethylsulfoxide (DMSO) solution and showed absorption bands in the range 260–475 nm, due to n–π* and π–π* transition. In addition, the morphological properties of selected examples were tested by SEM, and the electrical properties of these polymers were measured. Copyright © 2005 Society of Chemical Industry
Synthesis and monomer reactivity ratios of ethyl α‐acetoxyacrylate and acrylic acid copolymers
Authors: Loubat Cédric , Batt‐Coutrot Delphine , Guyot Bernard , Robin Jean‐Jacques , Boutevin Bernard
Published: August 2005

The synthesis of ethyl α‐acetoxyacrylate (EAA) and the study of its radical polymerization is described. We report the monomer reactivity ratios for copolymers of EAA and acrylic acid (AA) using three different methods: the Jaacks, the Macret and the Fineman–Ross methods. Copolymers were obtained by free radical polymerization initiated by 2,2′‐azobisisobutyronitrile in acetonitrile solutions and were analyzed by NMR and HPLC. The HPLC analysis was used to determine the molar fractions of EAA and AA in the copolymers. The reactivity ratios were estimated to be close to 1 for each monomer. Thus, copolymers of poly(acrylic acid) bearing some biodegradable units of EAA in the chain were subsequently prepared. The study of the hydrolysis of these units shows that only basic conditions were efficient to lead to hydrolyzed monomer units. Copyright © 2005 Society of Chemical Industry
Book Reviews: Chemical Genomics. By Ferenc Darvas, Andras Guttmann, Gyorgy Dorman (Eds.)
Authors: Cagney Gerard
Published: August 2005

No abstracts.
Book Reviews: Genomics, Proteomics, and Clinical Bacteriology: Methods and Reviews. By Neil Woodford, Alan P. Johnson (Eds.)
Authors: Cash Phillip
Published: August 2005

No abstracts.
Alternating copolymerization of carbon dioxide and epoxide catalyzed by an aluminum Schiff base–ammonium salt system
Authors: Sugimoto Hiroshi , Ohtsuka Hiroaki , Inoue Shohei
Published: August 2005

The alternating copolymerization of carbon dioxide (CO2) and cyclohexene oxide (CHO) with an aluminum Schiff base complex in conjunction with an appropriate additive as a novel initiator is demonstrated. A typical example is the copolymerization of CO2 and CHO with the (Salophen)AlMe (1a)–tetraethylammonium acetate (Et4NOAc) system. When a mixture of the 1a–Et4NOAc system and CHO was pressurized by CO2 (50 atm) at 80 °C in CH2Cl2, the copolymerization of CO2 and CHO took place smoothly and produced a high polymer yield in 24 h. From the IR and NMR spectra, the product was characterized to be a copolymer of CO2 and CHO with an almost perfect alternating structure. The matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analysis indicated that an unfavorable reaction between Et4NOAc and CH2Cl2 and a possible chain‐transfer reaction with concomitant water occurred, and this resulted in the bimodal distribution of the obtained copolymer. With carefully predried reagents and apparatus, the alternating copolymerization in toluene gave a copolymer with a unimodal and narrower molecular weight distribution. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4172–4186, 2005
Pediocin‐like antimicrobial peptides (class IIa bacteriocins) and their immunity proteins: biosynthesis, structure, and mode of action
Authors: Fimland Gunnar , Johnsen Line , Dalhus Bjørn , Nissen‐Meyer Jon
Published: August 2005

Pediocin‐like antimicrobial peptides (AMPs) form a group of lactic acid bacteria produced, cationic membrane‐permeabilizing peptides with 37 to 48 residues. Upon exposure to membrane‐mimicking entities, their hydrophilic, cationic, and highly conserved N‐terminal region forms a three‐stranded antiparallel β‐sheet supported by a conserved disulfide bridge. This N‐terminal β‐sheet region is followed by a central amphiphilic α‐helix and this in most (if not all) of these peptides is followed by a rather extended C‐terminal tail that folds back onto the central α‐helix, thereby creating a hairpin‐like structure in the C‐terminal half. There is a flexible hinge between the β‐sheet N‐terminal region and the hairpin C‐terminal region and one thus obtains two domains that may move relative to each other. The cationic N‐terminal β‐sheet domain mediates binding of the pediocin‐like AMPs to the target‐cell surface through electrostatic interactions, while the more hydrophobic and amphiphilic C‐terminal hairpin domain penetrates into the hydrophobic part of the target‐cell membrane, thereby mediating leakage through the membrane. The hinge provides the structural flexibility that enables the C‐terminal hairpin domain to dip into the hydrophobic part of the membrane. Despite extensive sequence similarities, these AMPs differ markedly in their target‐cell specificity, and results obtained with hybrid AMPs indicate that the membrane‐penetrating hairpin‐like C‐terminal domain is the major specificity determinant.

Bacteria that produce pediocin‐like AMPs also produce a 11‐kDa cognate immunity protein that protects the producer. The immunity proteins are well‐structured, 4‐helix bundle cytosolic proteins. They show a high degree of specificity in that they largely recognize and confer immunity only to their cognate AMP and in some cases to a few AMPs that are closely related to their cognate AMP. The C‐terminal half of the immunity proteins contains a domain that is involved in specific recognition of the C‐terminal membrane‐penetrating specificity‐determining hairpin domain of the cognate AMP. Copyright © 2005 European Peptide Society and John Wiley & Sons, Ltd.
Exact solutions for spherically confined hydrogen‐like atoms
Authors: Burrows B. L. , Cohen M.
Published: August 2005

We present exact analytical solutions for the much‐studied problem of a hydrogen‐like atom confined in a spherical box of radiusR.These solutions, which are obtained for all states and allR, are expressed directly in terms of the KummerM‐functions whose analytical and numerical properties are well known, and may be calculated using standard computing packages. The solutions are illustrated by precise calculations that yield accurate energiesEfor any given radiusR,or forRwhenEis known. In the special case whereE= 0, it is shown that the solution may be expressed in terms of Bessel functions. Finally, the physical assumptions made in applying this model to describe atomic confinement are discussed critically. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
Characterization of carbofuran photodegradation by‐products by liquid chromatography/hybrid quadrupole time‐of‐flight mass spectrometry
Authors: Detomaso Antonia , Mascolo Giuseppe , Lopez Antonio
Published: August 2005

The original article to which this Erratum refers was published in Rapid Commun. Mass Spectrom. 2005; 19: 2193–2202.
Plasmatechnik – meist unsichtbar, aber unverzichtbar für die Zukunft. Plasma Technology ‐ mostly invisible, but important for the future
Authors: Reichel Karin
Published: August 2005

Die Plasmatechnik ist eine bedeutende Querschnittstechnologie mit einer enormen Anwendungsvielfalt und einem großen Zukunftspotenzial. Dies ist das Ergebnis der Evaluierung des Förderschwerpunktes Plasmatechnik des Bundesministeriums für Bildung und Forschung (BMBF), die im Jahr 2004 abgeschlossen wurde. Der Beitrag gibt einen Überblick über die wesentlichen Aussagen der Evaluierung und die relevanten Anwendungs‐ und Forschungsthemen.
2002 FIFA World Cup and Its Effects on the Reconciliation between Japan and the Republic of Korea
Authors: SAKAEDANI AKIKO
Published: August 2005

Japan and the Republic of Korea have been going through a painful process of reconciliation since World War II. But with the momentum created by the FIFA World Cup and the high popularity of Korean pop culture in Japan, the trend shifted and the two countries seem to be enjoying a more amicable relationship. This paper aspires to understand when and how the steps toward reconciliation were taken between the two countries. The overarching research questions are: what steps were taken, and what channels of communication contributed to or hindered the process of reconciliation? Section 1 first lays the historical context of the dispute, and Section 2 assesses the diplomatic steps taken toward reconciliation by applying Assefa's reconciliation model, which leads to an analysis of discrepancy between the governments and the civil societies. Section 3 considers the impact of the FIFA World Cup in 2002, when momentum for friendship was reinforced by the various exchange activities at civil society level, as well as the Korean pop culture. The in-depth interview adds insights and public opinion polls clarify the perceived status of reconciliation. Section 4 concludes by returning to the more generalized issue of how communication between the two nation states has changed with the information technology, which is key to understanding the dynamism of the lingering reconciliation process.
‘Malice to None, Goodwill to All?’: The Legitimacy of Commonwealth Enforcement
Authors: CHAU CHI-KAN LAWRENCE
Published: August 2005

In the early 1990s, the Commonwealth reformed its political structure to allow interference in domestic affairs of member states. This article examines whether such an institutional transformation has helped the organization to fulfil its purpose to work in the common interests of member countries and of their people. The article demonstrates that, while, as a consequence of post-Cold War globalization, concerns about the Commonwealth's political credibility and public perception have relaxed Commonwealth leaders' reluctance to accept legally binding norms of the organization, strong resistance to Commonwealth interference in internal affairs exists among developing member states. It is argued that, because the new Commonwealth political structure lacks legitimacy and is contrary to the real interests of the majority of members, institutionalizing the Commonwealth has not contributed to the formation of a collective identity among Commonwealth members and to the resolution of the problem of inequality within and without the organization.
W. V. QUINE AND THE ORIGINS OF ANALYTIC PHILOSOPHY IN THE UNITED STATES
Authors: ISAAC JOEL
Published: August 2005

W. V. Quine is widely regarded as one of the most important and influential philosophers of the twentieth century. Quine wrote and lectured on logic, philosophy of language, and epistemology throughout his long career, and was one of the American figures who did most to establish the analytic tradition of philosophy in the United States. Until recently, the historical development of both Quine's philosophy and the analytic tradition of which it is a part remained unexamined by historians and philosophers alike. In the last decade or so, however, analytic philosophers have begun to assess the history of their enterprise, and Quine's place within it. Building on this welcome development with the tools of intellectual history, this essay examines Quine's philosophical apprenticeship in the late 1920s and 1930s.

The basic tenets of Quine's mature thought set in early in his studies. Most notably, he displayed in his student writings a commitment to science as the primary theory of the world within which philosophical inquiry should take place. Yet he found the uncertain direction of interwar American philosophy uncongenial to his views. During a year of postdoctoral research in Europe, Quine encountered the work of analytic philosophers and logicians such as Rudolf Carnap and Alfred Tarski. Their scientific program for philosophy captivated Quine, who returned to Harvard a champion of their work. For the rest of the 1930s, Quine was an indefatigable advocate of the analytic tradition; he brought news of European logic and scientific philosophy to American universities. His purpose in doing so was to move American philosophy towards science and away from what he saw as its metaphysical entanglements. The reception and transformation of analytic philosophy in the United States is shown to have involved a complex dynamic between foreign and domestic conceptions of philosophy.
A unified methodological framework for the simulation of nonisothermal ensembles
Authors: Escobedo Fernando A.
Published: August 2005

A general framework is developed for the simulation of nonisothermal statistical-mechanical ensembles. This framework is intended to synthesize the formulation of advanced Monte Carlo simulation methods such as multihistogram reweighting, replica-exchange methods, and expanded ensemble techniques so that they can be applied to different nonisothermal ensembles. Using Lennard-Jones systems as test cases, novel implementations of these methods are demonstrated with different ensembles including the microcanonical, isobaric-isoenthalpic, and isobaric-semigrand ensembles. In particular, it is shown that the use of multiensemble methods allows the efficient simulation of microcanonical density of states, entropies, vapor-liquid and solid–liquid equilibrium for pure component systems, and fluid-phase coexistence for binary mixtures. In these applications, comparisons are also presented that highlight the advantages of the proposed multiensemble implementations over alternative methods used before.
Nonorthogonal density-matrix perturbation theory
Authors: Niklasson Anders M. N. , Weber Valéry , Challacombe Matt
Published: August 2005

Recursive density-matrix perturbation theory [A.M.N. Niklasson and M. Challacombe, Phys. Rev. Lett. 92, 193001 (2004)] provides an efficient framework for the linear scaling computation of materials response properties [V. Weber, A.M.N. Niklasson, and M. Challacombe, Phys. Rev. Lett. 92, 193002 (2004)]. In this article, we generalize the density-matrix perturbation theory to include properties computed with a perturbation-dependent nonorthogonal basis. Such properties include analytic derivatives of the energy with respect to nuclear displacement, as well as magnetic response computed with a field-dependent basis. The theory is developed in the context of linear scaling purification methods, which are briefly reviewed.
Quantum channels and representation theory
Authors: Ritter William Gordon
Published: August 2005

In the study of d-dimensional quantum channels (d⩾2), an assumption which includes many interesting examples, and which has a natural physical interpretation, is that the corresponding Kraus operators form a representation of a Lie algebra. Physically, this is a symmetry algebra for the interaction Hamiltonian. This paper begins a systematic study of channels defined by representations; the famous Werner-Holevo channel is one element of this infinite class. We show that the channel derived from the defining representation of su(n) is a depolarizing channel for all n, but for most other representations this is not the case. Since the standard Bloch sphere only exists for the qubit representation of su(2), we develop a consistent generalization of Bloch’s technique. By representing the density matrix as a polynomial in Lie algebra generators, we determine a class of positive semidefinite matrices which represent quantum states for various channels defined by finite-dimensional representations of semisimple Lie algebras. We also give a general method for finding positive semidefinite matrices using Lie algebraic trace identities. This includes an analysis of channels based on the exceptional Lie algebra g2 and the Clifford algebra.
Mutual information and correlation measures in atomic systems
Authors: Sagar Robin P. , Guevara Nicolais L.
Published: August 2005

Mutual information is introduced as an electron correlation measure and examined for isoelectronic series and neutral atoms. We show that it possesses the required characteristics of a correlation measure and is superior to the behavior of the radial correlation coefficient in the neon series. A local mutual information, and related local quantities, are used to examine the local contributions to Fermi correlation, and to demonstrate and to interpret the intimate relationship between correlation and localization.
Dual-topology/dual-coordinate free-energy simulation using QM/MM force field
Authors: Hu Hao , Yang Weitao
Published: August 2005

We have developed a dual-topology/dual-coordinate free-energy simulation method for use with a QM/MM force field. By combining two parallel processes into one alchemical process, we are able to compute the double free-energy difference (ΔΔF) within a single simulation, which eliminates half of the expensive quantum-mechanical simulation in general. The method has been tested in computing the solvation free-energy differences of several molecular pairs and shows close agreement with experimental results.
Investigation of bismuth-based perovskite system: (1−x)Bi(Ni2∕3Nb1∕3)O3–xPbTiO3
Authors: Zhang Shujun , Stringer Craig , Xia Ru , Choi Soon-Mok , Randall Clive A. , Shrout Thomas R.
Published: August 2005

The dielectric and piezoelectric properties for bismuth-based perovskite system (1−x)Bi(Ni2∕3Nb1∕3)O3–xPbTiO3 (BNN–PT100x) with x=0.6–0.95 were investigated. High-density polycrystalline ceramics were fabricated using a conventional solid-state reaction method. Morphotropic phase boundary (MPB) at x=0.625–0.65 composition was observed by x-ray-diffraction measurements, separating rhombohedral and tetragonal phases. Analogous to Pb(ZrTi)O3 ceramic, enhanced dielectric and piezoelectric activities were associated with the composition near the MPB. The dielectric constant (K33T) and piezoelectric coefficient (d33) for BNN–PT65 composition were found to be 1100 and 140pC∕N, respectively, with a Curie temperature (Tc) around 273 °C. The addition of manganese (Mn) resulted in lowering the dielectric loss and increasing the mechanical quality factor Q when compared with the pure counterpart. The coercive field was found to increase to 30.7kV∕cm when BNN-PT65 was modified with magnesium (Mg). These results demonstrate the BNN–PT system to be a competitive piezoelectric material with a reduced lead content.
Planar degenerate substrate for micro- and nanopatterned nematic liquid-crystal cells
Authors: Syed Ishtiaque M. , Carbone Giovanni , Rosenblatt Charles , Wen Bing
Published: August 2005

A micro- or nanopatterned planar-aligned cell ordinarily requires a pair of mirror-image patterned substrates that must be aligned in register to ⪡1μm. As an alternative we examine the director orientation profile of a nematic liquid crystal in a cell composed of one substrate whose easy axis is patterned on micrometer length scales λ and a second substrate treated for planar degenerate alignment using polymethyl methacrylate. For cell thickness <λ, the experimentally measured director profile in the bulk corresponds approximately to that imposed at the micropatterned substrate. The results are compared with theoretical calculations. This method provides an excellent alternative to the use of a pair of substrates aligned in close register.
An experimental and numerical investigation of drag reduction in a turbulent boundary layer using a rigid rodlike polymer
Authors: Paschkewitz J. S. , Dimitropoulos Costas D. , Hou Y. X. , Somandepalli V. S. R. , Mungal M. G. , Shaqfeh Eric S. G. , Moin Parviz
Published: August 2005

The drag reduction in a zero pressure gradient (ZPG) turbulent boundary layer (TBL) using a rigid rodlike polymer was experimentally and numerically investigated. Using injection of the rigid polysaccharide scleroglucan, drag reductions of approximately 10–15 % were observed, with three distinct drag reduction regimes: a non-Newtonian flow region near the injector, followed by a region of nearly constant drag reduction, and finally a region of negligible drag reduction. Decreasing the effective rotary Peclét number reduced the drag reduction effectiveness. Increasing the concentration did not improve the drag reduction, but instead shifted the spatial development of the drag reduction further downstream. A complementary direct numerical simulation of the ZPG TBL using the rigid rod constitutive equation was performed at a matching inlet Reynolds number. The simulation assumed a homogeneous concentration distribution and used estimated effective parameters for the rodlike additive. Spatial evolution of the fiber stresses is rapid and develops asynchronously with the flow structure. The simulated turbulence statistics and experimental measurements at a position 23 boundary layer thicknesses downstream compare favorably, with the primary differences due to the concentration distribution assumed in the simulation.
On approximately symmetric informationally complete positive operator-valued measures and related systems of quantum states
Authors: Klappenecker Andreas , Rötteler Martin , Shparlinski Igor E. , Winterhof Arne
Published: August 2005

We address the problem of constructing positive operator-valued measures (POVMs) in finite dimension n consisting of n2 operators of rank one which have an inner product close to uniform. This is motivated by the related question of constructing symmetric informationally complete POVMs (SIC-POVMs) for which the inner products are perfectly uniform. However, SIC-POVMs are notoriously hard to construct and, despite some success of constructing them numerically, there is no analytic construction known. We present two constructions of approximate versions of SIC-POVMs, where a small deviation from uniformity of the inner products is allowed. The first construction is based on selecting vectors from a maximal collection of mutually unbiased bases and works whenever the dimension of the system is a prime power. The second construction is based on perturbing the matrix elements of a subset of mutually unbiased bases. Moreover, we construct vector systems in Cn which are almost orthogonal and which might turn out to be useful for quantum computation. Our constructions are based on results of analytic number theory.
On Holmboe’s instability for smooth shear and density profiles
Authors: Alexakis Alexandros
Published: August 2005

The linear stability of a stratified shear flow for smooth density profiles is studied. This work focuses on the nature of the stability boundaries of flows in which both Kelvin–Helmholtz and Holmboe instabilities are present. For a fixed Richardson number the unstable modes are confined to finite bands between a smallest and a largest marginally unstable wavenumber. The results in this paper indicate that the stability boundary for small wavenumbers is comprised of neutral modes with phase velocity equal to the maximum/minimum wind velocity whereas the other stability boundary, for large wavenumbers, is comprised of singular neutral modes with phase velocity in the range of the velocity shear. We show how these stability boundaries can be evaluated without solving for the growth rate over the entire parameter space as was previously done. The results indicate further that there is a new instability domain that has not been previously noted in the literature. The unstable modes, in this new instability domain, appear for larger values of the Richardson number and are related to the higher harmonics of the internal gravity wave spectrum.
Photonic crystal with diamondlike structure fabricated by holographic lithography
Authors: Zhong Y. C. , Zhu S. A. , Su H. M. , Wang H. Z. , Chen J. M. , Zeng Z. H. , Chen Y. L.
Published: August 2005

In this letter, we report a diamondlike structure. Our theoretical analysis reveals that a large complete band gap exists between the second and third bands with only a very low refractive index is needed (n⩾2.05) to open the complete band gap for this inverse structure. Large-scale and high-quality three-dimensional structures with this diamondlike symmetry are fabricated by a holographic lithography method using four laser beams incident from the same half-space. The beam geometry is similar to that for the face-centered cubic (fcc) structure except that the central beam is circularly polarized and the polarizations of the three outer beams must be optimized, which is critical to construct this diamondlike interference pattern.
The role of Al on Ohmic contact formation on n-type GaN and AlGaN∕GaN
Authors: Van Daele B. , Van Tendeloo G. , Ruythooren W. , Derluyn J. , Leys M. R. , Germain M.
Published: August 2005

A standard metallization scheme for the formation of Ohmic contacts on n-type GaN does exist. It has the following multilayer structure: Ti∕Al∕metal∕Au. Ti is known to extract N out of the GaN. This leaves a high density of N vacancies (donors) near the interface pinning the Fermi level. The created tunnel junction is responsible for an Ohmic contact behavior. Au is deposited as the final metal layer to exclude oxidation of the contact and the metal should limit the diffusion of Au into the layers below and vice versa. Al in the metallization scheme is known to improve the contact resistance, but the reason why has not been reported yet. We studied Ti and Ti∕Al contacts on GaN and AlGaN∕GaN as a function of annealing temperature by transmission electron microscopy. The role of Al in the metal multilayer, and of Al in the AlGaN on the Ohmic contact formation, has been determined. The latter result indicates that the standard metallization scheme for GaN cannot be simply transferred to AlGaN∕GaN structures.
Effect of barrier thickness on electromigration reliability of Cu/porous low k interconnects
Authors: Pyun Jung Woo , Lu Xia , Chung Jayhoon , Yoon Sean , Ho Paul S. , Henis Neil , Neuman Kyle , Smith Larry , Pfeifer Klaus
Published: August 2005

The effects of Ta barrier thickness on electromigration reliability of dual-damascene Cu/porous methylsilsesquioxane interconnects were investigated. With decreasing Ta barrier thicknesses, the threshold product of current density and line length (jL)c was found to be reduced due to less structural confinement from thinner barriers. The effect can be accounted for by the effective modulus of the structure except for the 75-Å Ta barrier where the (jL)c product is reduced more than expected, probably due to the presence of defects in the barrier. Results from the early failure test structures revealed a bimodal failure distribution for samples with the 75-Å and l00-Å barriers. Focused ion beam microprobe and transmission electron microscopy observations revealed that the weak-mode early failure was caused by Cu outdiffusion through structural defects in the thin Ta barrier.
Electric field controlled polarization grating based on a hybrid structure “photosensitive polymer-liquid crystal”
Authors: Blinov L. M. , Cipparrone G. , Mazzulla A. , Provenzano C. , Palto S. P. , Barnik M. I. , Arbuzov A. V. , Umanskii B. A.
Published: August 2005

An investigation was carried out on a hybrid structure consisting of a photosensitive polymer in contact with a nematic liquid crystal (NLC) layer. Before assembling the structure, holographic gratings of different periods were recorded in the photopolymer by two laser beams with opposite circular polarization. Such gratings are known for their unique asymmetric diffraction in case of elliptically polarized light and can be used in optical polarization devices. Due to a spatial modulation of the direction of the local optical axis, the photopolymer modulates the anchoring conditions for NLC in a similar way. As a result, a new grating is induced in NLC with the enhanced diffraction efficiency (in a particular experiment it was four orders of magnitude higher than that of the photopolymer). The NLC grating also shows the characteristic asymmetric diffraction for the reconstructing beams of opposite circular polarizations. The diffraction efficiency is easily controlled by an external electric field.
Surface relief grating formation on a single crystal of 4-(dimethylamino)azobenzene
Authors: Nakano Hideyuki , Tanino Takahiro , Shirota Yasuhiko
Published: August 2005

Surface relief grating (SRG) formation on an organic single crystal by irradiation with two coherent laser beams has been demonstrated by using 4-(dimethylamino)azobenzene (DAAB). It was found that the SRG formation was greatly depending upon both the coordination of the crystal and the polarization of the writing beams. The dependence of the polarization of writing beams on the SRG formation using the single crystal was found to be quite different from that reported for amorphous polymers and photochromic amorphous molecular materials, suggesting that the mechanism of the SRG formation on the organic crystal is somewhat different from that on amorphous materials.
Imaging of the intracellular topography of copper with a fluorescent sensor and by synchrotron x-ray fluorescence microscopy
Authors: Yang Liuchun , McRae Reagan , Henary Maged M. , Patel Raxit , Lai Barry , Vogt Stefan , Fahrni Christoph J.
Published: August 2005

Copper is an essential micronutrient that plays a central role for a broad range of biological processes. Although there is compelling evidence that the intracellular milieu does not contain any free copper ions, the rapid kinetics of copper uptake and release suggests the presence of a labile intracellular copper pool. To elucidate the subcellular localization of this pool, we have synthesized and characterized a membrane-permeable, copper-selective fluorescent sensor (CTAP-1). Upon addition of Cu(I), the sensor exhibits a 4.6-fold emission enhancement and reaches a quantum yield of 14%. The sensor exhibits excellent selectivity toward Cu(I), and its emission response is not compromised by the presence of millimolar concentrations of Ca(II) or Mg(II) ions. Variable temperature dynamic NMR studies revealed a rapid Cu(I) self-exchange equilibrium with a low activation barrier of Δ
G
‡
= 44 kJ·mol
–1
and
k
obs
∼ 10
5
s
–1
at room temperature. Mouse fibroblast cells (3T3) incubated with the sensor produced a copper-dependent perinuclear staining pattern, which colocalizes with the subcellular locations of mitochondria and the Golgi apparatus. To evaluate and confirm the sensor's copper-selectivity, we determined the subcellular topography of copper by synchrotron-based x-ray fluorescence microscopy. Furthermore, microprobe x-ray absorption measurements at various subcellular locations showed a near-edge feature that is characteristic for low-coordinate monovalent copper but does not resemble the published spectra for metallothionein or glutathione. The presented data provide a coherent picture with strong evidence for a kinetically labile copper pool, which is predominantly localized in the mitochondria and the Golgi apparatus.
Catalytic asymmetric alkynylation of α-imino ester: A versatile approach to optically active unnatural α-amino acid derivatives
Authors: Ji Jian-Xin , Wu Jing , Chan Albert S. C.
Published: August 2005

The catalytic asymmetric introduction of alkynyl functionality to α-amino acid derivatives was realized by the direct addition of terminal alkynes to α-imino ester in the presence of chiral Cu(I) complex under mild reaction conditions. Owing to the rich chemistry to which alkyne can be subjected, the present system provides a remarkably versatile tool for the construction of optically active α-amino acid derivatives. Good yields and enantiomeric excess values were achieved with an array of terminal alkynes and challenging, biologically active, unnatural α-amino acid derivatives could be conveniently obtained.
Petrographic evidence shows that pottery exchange between the Olmec and their neighbors was two-way
Authors: Stoltman James B. , Marcus Joyce , Flannery Kent V. , Burton James H. , Moyle Robert G.
Published: August 2005

Petrographic thin sections of pottery from five Formative Mexican archaeological sites show that exchanges of vessels between highland and lowland chiefly centers were reciprocal, or two-way. These analyses contradict recent claims that the Gulf Coast was the sole source of pottery carved with iconographic motifs. Those claims were based on neutron activation, which, by relying on chemical elements rather than actual minerals, has important limitations in its ability to identify nonlocal pottery from within large data sets. Petrography shows that the ceramics in question (and hence their carved motifs) have multiple origins and were widely traded.
Dynamic formation of RecA filaments at DNA double strand break repair centers in live cells
Authors: Kidane Dawit , Graumann Peter L.
Published: August 2005

We show that RecN protein is recruited to a defined DNA double strand break (DSB) in Bacillus subtilis cells at an early time point during repair. Because RecO and RecF are successively recruited to DSBs, it is now clear that dynamic DSB repair centers (RCs) exist in prokaryotes. RecA protein was also recruited to RCs and formed highly dynamic filamentous structures, which we term threads, across the nucleoids. Formation of RecA threads commenced ∼30 min after the induction of DSBs, after RecN recruitment to RCs, and disassembled after 2 h. Time-lapse microscopy showed that the threads rapidly changed in length, shape, and orientation within minutes and can extend at 1.02 μm/min. The formation of RecA threads was abolished in recJ addAB mutant cells but not in each of the single mutants, suggesting that RecA filaments can be initiated via two pathways. Contrary to proteins forming RCs, DNA polymerase I did not form foci but was present throughout the nucleoids (even after induction of DSBs or after UV irradiation), suggesting that it continuously scans the chromosome for DNA lesions.
Maternal embryonic leucine zipper kinase (MELK) regulates multipotent neural progenitor proliferation
Authors: Nakano Ichiro , Paucar Andres A. , Bajpai Ruchi , Dougherty Joseph D. , Zewail Amani , Kelly Theresa K. , Kim Kevin J. , Ou Jing , Groszer Matthias , Imura Tetsuya , Freije William A. , Nelson Stanley F. , Sofroniew Michael V. , Wu Hong , Liu Xin , Terskikh Alexey V. , Geschwind Daniel H. , Kornblum Harley I.
Published: August 2005

Maternal embryonic leucine zipper kinase (MELK) was previously identified in a screen for genes enriched in neural progenitors. Here, we demonstrate expression of MELK by progenitors in developing and adult brain and that MELK serves as a marker for self-renewing multipotent neural progenitors (MNPs) in cultures derived from the developing forebrain and in transgenic mice. Overexpression of MELK enhances (whereas knockdown diminishes) the ability to generate neurospheres from MNPs, indicating a function in self-renewal. MELK down-regulation disrupts the production of neurogenic MNP from glial fibrillary acidic protein (GFAP)–positive progenitors in vitro. MELK expression in MNP is cell cycle regulated and inhibition of MELK expression down-regulates the expression of B-myb, which is shown to also mediate MNP proliferation. These findings indicate that MELK is necessary for proliferation of embryonic and postnatal MNP and suggest that it regulates the transition from GFAP-expressing progenitors to rapid amplifying progenitors in the postnatal brain.
The limited role of NH2-terminal c-Jun phosphorylation in neuronal apoptosis
Authors: Besirli Cagri G. , Wagner Erwin F. , Johnson Eugene M.
Published: August 2005

c-Jun is induced in many neuronal death paradigms. A critical step in c-Jun regulation involves phosphorylation of Ser63/Ser73 located in the NH2-terminal transactivation domain. To determine the importance of this phosphorylation for neuronal apoptosis, we analyzed the sympathetic neurons of mice carrying a mutant c-Jun gene that lacks Ser63/Ser73 phosphorylation sites (jun aa). Trophic factor–deprivation or DNA damage–induced death was significantly delayed in jun aa/aa neurons. Neuronal c-Jun induction was only partially inhibited, demonstrating that phosphorylation of Ser63/73 is not required for c-Jun activation. The inductions of proapoptotic BH3-only proteins, Bim and PUMA/Bbc3, were delayed during neuronal apoptosis in mutant neurons. These results demonstrate that NH2-terminal c-Jun phosphorylation is important, but not necessary, for the induction of proapoptotic genes and neuronal apoptosis. Thus, additional JNK substrates may be critical for neuronal death. As potential mediators, we identified additional nuclear MLK/JNK substrates, including Nup214 subunit of the nuclear pore complex.
Asymmetric cortical and nuclear localizations of WRM-1/β-catenin during asymmetric cell division in C. elegans
Authors: Takeshita Hisako , Sawa Hitoshi
Published: August 2005

β-Catenin can promote adhesion at the cell cortex and mediate Wnt signaling in the nucleus. We show that, in Caenorhabditis elegans, both WRM-1/β-catenin and LIT-1 kinase localize to the anterior cell cortex during asymmetric cell division but to the nucleus of the posterior daughter afterward. Both the cortical and nuclear localizations are regulated by Wnts and are apparently coupled. We also found that the daughters show different nuclear export rates for LIT-1. Our results indicate that Wnt signals release cortical WRM-1 from the posterior cortex to generate cortical asymmetry that may control WRM-1 asymmetric nuclear localization by regulating cell polarity.
Gaining weight: the Keystone Symposium on PPAR and LXR
Authors: Lehrke Michael , Pascual Gabriel , Glass Christopher K. , Lazar Mitchell A.
Published: August 2005

The nuclear receptor superfamily consists of 48 mammalian transcription factors that regulate nearly all aspects of development, inflammation, and metabolism. Two subclasses, the Peroxisome Proliferator-Activated Receptors (PPARs) and Liver X Receptors (LXRs), are lipid-sensing receptors that have critical roles in lipid and glucose metabolism. The parallel epidemics of obesity and diabetes shine a spotlight on the potential for therapeutic manipulation of PPARs and LXRs to combat these diseases. In recognition of this, a recent Keystone Symposium was devoted to these metabolic receptors. Here, we summarize some of the major highlights and future projections discussed at the meeting.
Variant histone H3.3 is deposited at sites of nucleosomal displacement throughout transcribed genes while active histone modifications show a promoter-proximal bias
Authors: Wirbelauer Christiane , Bell Oliver , Schübeler Dirk
Published: August 2005

Deposition of variant histones provides a mechanism to reset and to potentially specify chromatin states. We determined the distribution of H3 and its variant H3.3 relative to chromatin structure and elongating polymerase. H3.3 is enriched throughout active genes similar to polymerase, yet its distribution is very distinct from that of several euchromatic histone modifications, which are highly biased toward the 5′ part of active genes. Upon gene induction we observe displacement of both H3 and H3.3 followed by selective deposition of H3.3. These results support a model in which H3.3 deposition compensates for transcription-coupled nucleosomal displacement yet does not predetermine tail modifications.