bluuebunny/crossref_metadata_2025 huggingface dataset:
A two‐degree‐of‐freedomℋ︁∞control design method for robust model matching
Authors: Dehghani Arvin , Lanzon Alexander , D. O. Anderson Brian
Published: May 2006

We propose anℋ︁∞controller design method which achieves a closed‐loop transfer function equal or otherwise sensibly close to a desired transfer function, viz. a model reference design. The proposed controller design method inherits the model reference feature of the internal model control design method and incorporates the weighting scheme of theℋ︁∞loop‐shaping. It utilizes Youla–Kucera parameterization in a two‐degree‐of‐freedom scheme to achieve robust model reference and high performance design while ensuring a sensible robust stability margin, and can be readily applied to the generic class of LTI systems (SISO, MIMO, stable, unstable). Copyright © 2006 John Wiley & Sons, Ltd.
Explicit robust model predictive control using recursive closed‐loop prediction
Authors: Chu Danlei , Chen Tongwen , Marquez Horacio J.
Published: May 2006

In this paper, we develop an algorithm to compute robust MPC explicit solutions for constrained MIMO systems with internal uncertainties and external disturbances. Our approach is based on a recursive closed‐loop prediction strategy to realize a finite horizon robust MPC regulator, which has the feature that only one‐step state prediction is sufficient to realize robust MPC with an arbitrary prediction horizon. The paper defines a set of recursive sub‐optimization problems as multiple‐parametric sub‐quadratic programming (mp‐SQP), and shows that the optimal solution to the mp‐SQP problem is piecewise affine functions of states, associated with piece objectives and state critical regions. Asymptotic closed‐loop stability can be guaranteed by a terminal weighting and a terminal feedback gain; also by introducing two tuning variables, the algorithm is capable of adjusting the trade‐off between system performance and robustness. The state admissible set, which is not easily derived from physical vision, is constructed by two methods: a piecewise linear norm of signals, and polyhedral Voronoi sets. Finally, two simulation examples demonstrate that the algorithm is efficient, feasible and flexible, and can be applied to both slow and fast industrial MIMO systems. Copyright © 2006 John Wiley & Sons, Ltd.
Determination of Amylose Content in Different Starches Using Modulated Differential Scanning Calorimetry
Authors: Moorthy Subramoney N. , Andersson Lena , Eliasson Ann‐Charlotte , Santacruz Stalin , Ruales Jenny
Published: May 2006

A simple calorimetric method for determination of amylose content in starch is reported. Starches were heated in the presence of two common surfactants, viz., sodium dodecyl sulphate (SDS) and cetyltrimethylammonium bromide (CTAB), and the enthalpies of melting of the amylose‐surfactant complexes were determined using Modulated Differential Scanning Calorimetry (MDSC). A large number of native starches including cereal, root and pea starches were examined. The results were compared with those obtained by iodimetry and gel permeation chromatography (GPC) for all the starches. There was a good correlation between the values from iodimetry and GPC with those obtained using the surfactants. Both surfactants seemed to work equally well, even for those starches with about 40% amylose content. However, in case of SDS higher standard deviations were usually obtained than for CTAB in the determination of transition enthalpies.
Placental volume in twin and triplet pregnancies measured by three‐dimensional ultrasound at 11 + 0 to 13 + 6 weeks of gestation
Authors: Wegrzyn P. , Fabio C. , Peralta A. , Faro C. , Borenstein M. , Nicolaides K. H.
Published: May 2006

Objective

To compare the placental volume at 11 + 0 to 13 + 6 weeks' gestation between singleton and multiple pregnancies and to examine the possible effect of chorionicity on placental volume.

Methods

The placental volume was measured by three‐dimensional (3D) ultrasound using the Virtual Organ Computer‐aided AnaLysis (VOCAL) technique in 290 consecutive twin and 37 triplet pregnancies at 11 + 0 to 13 + 6 weeks of gestation. For the comparison of twin, triplet and singleton placental volumes each measurement was expressed as a multiple of the median (MoM) for singletons, previously established from the study of 417 normal fetuses at 11 + 0 to 13 + 6 weeks of gestation.

Results

Median twin and triplet placental volumes were 1.66 and 2.28 MoM for singletons, respectively. In twins the placental volumes increased significantly with gestation from a median of 83.6 mL (5th and 95th centiles: 56.0 mL and 124.9 mL) at 11 + 0 weeks to 149.3 mL (5th and 95th centiles: 100.0 mL and 223.1 mL) at 13 + 6 weeks. The median MoM in monochorionic twins was not significantly different from that in dichorionic twins with fused placentas or dichorionic twins with separate placentas. In triplets the placental volumes increased significantly with gestation from a median of 114.9 mL (5th and 95th centiles: 77.6 mL and 170.1 mL) at 11 weeks to 217.9 mL (5th and 95th centiles: 147.2 mL and 322.5 mL) at 13 + 6 weeks. There were no significant differences in total placental volume between monochorionic and dichorionic triplets, monochorionic and trichorionic triplets, or dichorionic and trichorionic triplets.

Conclusions

Placental volume in multiple pregnancies does not depend on chorionicity, and the rate of placental growth between 11 and 13 + 6 weeks is not significantly different between singletons, twins and triplets. Moreover, for a given gestational age the placental volume corresponding to each fetus in twins and triplets is 83% and 76%, respectively, of the placental volume in singletons. Copyright © 2006 ISUOG. Published by John Wiley & Sons, Ltd.
Effect of calcium carbonate particle size on PVC foam
Authors: Azimipour Bahar , Marchand Frederic
Published: May 2006

Calcium carbonate is the predominant filler used in polyvinyl chloride compounding. Selection of fillers, as in the case with other compounding ingredients, involves consideration of available types and their effects on processing, product properties, and economics. In this article the effect of the particle size of CaCO3 on the properties of PVC foam is investigated. The study analyzes the correlation between fusion time, extrusion torque, and foam density as well as foam cell structure with the filler particle size. J. VINYL. ADDIT. TECHNOL. 12:55–57, 2006. © 2006 Society of Plastics Engineers.
Continuous process for melt intercalation of PP–clay nanocomposites with aid of power ultrasound
Authors: Lapshin Sergey , Isayev A.I.
Published: May 2006

A continuous ultrasound‐assisted process using a single screw extruder with an ultrasonic attachment was developed to prepare PP/clay nanocomposites of varying clay concentrations. The feed rate that controlled the residence time of the polymer in the ultrasonic treatment zone was varied. Die pressure and power consumption were measured. Rheological properties, morphology, and mechanical properties of the untreated and ultrasonically treated nanocomposites were studied. An intercalation of polymer molecules into clay galleries and a partial exfoliation, which occur at short residence times (of the order of seconds), were observed as evident from measurements by X‐ray diffraction and transmission electron microscopy. The obtained results indicate a possibility of the rapid intercalation and partial exfoliation of PP/clay nanocomposites without the matrix being chemically modified. J. VINYL. ADDIT. TECHNOL. 12:78–82, 2006. © 2006 Society of Plastics Engineers.
Authenticated encryption protocol with perfect forward secrecy for mobile communication
Authors: Lu Rongxing , Cao Zhenfu , Dong Xiaolei
Published: May 2006

Secure and authenticated message transmission is one of the major aims of mobile communication security research. To achieve this goal, a typical methodology in mobile communication is a mobile device and its server first establish a session key, then use the session key to encrypt all subsequent messages. However, establish such an authenticated session key itself is a hard work, and only use the session key to encrypt subsequent messages also cannot provide nonrepudiation. Therefore, there is a desire to seek an alternative method. In this paper, we would like to propose a new authenticated encryption protocol for mobile communication. The proposed protocol, compared with other authenticated encryption protocols, will simultaneously achieve confidentiality, integrity, authentication, nonrepudiation, and perfect forward secrecy. Copyright © 2006 John Wiley & Sons, Ltd.
Secure cell relay routing protocol for sensor networks
Authors: Du Xiaojiang , Xiao Yang , Chen Hsiao‐Hwa , Wu Qishi
Published: May 2006

Past researches on sensor network routing have been focused on efficiency and effectiveness of data dissemination. Few of them consider security issues during the design time of routing protocols. Security is very important for many sensor network applications. Studies and experiences have shown that considering security during design time is the best way to provide security for sensor network routing. In this paper, we propose an efficient key management scheme and a novel secure routing protocol—Secure cell relay (SCR) for sensor networks. We also present an effective key setup scheme for sensor nodes deployed in the later stage. We analyze the security of SCR under various attacks and show that SCR is very effective in defending against several sophisticated attacks, including selective forwarding, sinkhole, wormhole, Sybil, hello flooding, and clone attacks. SCR is an energy‐efficient routing protocol with acceptable security overhead. Our simulations demonstrate that with all the security primitives, SCR still has lower energy consumption and higher delivery ratio than a popular routing protocol—directed diffusion. Copyright © 2006 John Wiley & Sons, Ltd.
Autonomous cytoplasmic linear plasmid pPac1‐1 of Pichia acaciae: molecular structure and expression studies
Authors: Jeske Stefanie , Meinhardt Friedhelm
Published: May 2006

The genome organization of the linear DNA‐element pPac1‐1 from Pichia acaciae was determined. It turned out to be the smallest autonomous cytoplasmic yeast plasmid known so far, consisting of only 12 646 bp, carrying the shortest terminal inverted repeats yet found (138 bp). As for other cytoplasmic linear yeast plasmids, it is characterized by a strikingly high A + T content (75.35%). Ten putative genes (open reading frames, ORFs) reside on the element, leaving only 2.9% of the sequence outside a coding region. Highest similarities of the predicted proteins were obtained for proteins encoded by the three hitherto known autonomous cytoplasmic linear yeast plasmids. Amino acid sequences correspond to predicted polypeptides encoded by ORFs 2–11 of the linear plasmids pGKL2 of Kluyveromyces lactis, pSKL of Saccharomyces kluyveri and pPE1B of Pichia etchellsii. As for the latter, ORF1 existing on the two other plasmids is lacking on pPac1‐1. Consistent with cytoplasmic localization, a cytoplasmic promoter termed upstream conserved sequence (UCS) is located in front of each reading frame. RT‐PCR transcript analyses for ORFs 8, 9 and 11 proved expression of such genes but functions could not be attributed. The genome organization of pPac1‐1 and other autonomous linear elements was found to be almost congruent, irrespective of the accompanying smaller elements, which may or may not encode their own element‐specific DNA polymerases. The sequence of pPac1‐1 has been submitted to the EMBL database, Accession No. AM 180622. Copyright © 2006 John Wiley & Sons, Ltd.
A 5‐hydroxymethyl furfural reducing enzyme encoded by the Saccharomyces cerevisiae ADH6 gene conveys HMF tolerance
Authors: Petersson Anneli , Almeida João R. M. , Modig Tobias , Karhumaa Kaisa , Hahn‐Hägerdal Bärbel , Gorwa‐Grauslund Marie F. , Lidén Gunnar
Published: May 2006

The fermentation of lignocellulose hydrolysates by Saccharomyces cerevisiae for fuel ethanol production is inhibited by 5‐hydroxymethyl furfural (HMF), a furan derivative which is formed during the hydrolysis of lignocellulosic materials. The inhibition can be avoided if the yeast strain used in the fermentation has the ability to reduce HMF to 5‐hydroxymethylfurfuryl alcohol. To enable the identification of enzyme(s) responsible for HMF conversion in S. cerevisiae, microarray analyses of two strains with different abilities to convert HMF were performed. Based on the expression data, a subset of 15 reductase genes was chosen to be further examined using an overexpression strain collection. Three candidate genes were cloned from two different strains, TMB3000 and the laboratory strain CEN.PK 113‐5D, and overexpressed using a strong promoter in the strain CEN.PK 113‐5D. Strains overexpressing ADH6 had increased HMF conversion activity in cell‐free crude extracts with both NADPH and NADH as co‐factors. In vitro activities were recorded of 8 mU/mg with NADH as co‐factor and as high as 1200 mU/mg for the NADPH‐coupled reduction. Yeast strains overexpressing ADH6 also had a substantially higher in vivo conversion rate of HMF in both aerobic and anaerobic cultures, showing that the overexpression indeed conveyed the desired increased reduction capacity. Copyright © 2006 John Wiley & Sons, Ltd.
Depositional environment and OSL chronology of the Homeb silt deposits, Kuiseb River, Namibia
Authors: Srivastava Pradeep , Brook George A. , Marais Eugene , Morthekai P. , Singhvi Ashok K.
Published: May 2006

Previous studies suggest that the Homeb silts of the Kuiseb valley, Namibia (i) accumulated in a dune-dammed lake, (ii) are end-point deposits, (iii) represent an aggrading river bed, and (iv) are slackwater deposits. Thus, they have been used alternatively as evidence of past drier conditions or past wetter conditions. Lithostratigraphic analysis of two sediment sequences at Homeb indicates sedimentation by aggradation of the Kuiseb River triggered by a transition from an arid to humid climate. OSL ages for the sequences were obtained by the SAR protocol on aliquots of 9.6-mm and 4.0-mm diameter and on single grains. Four-millimeter aliquot minimum ages closely approximate the single-grain minimum ages and are younger than 9.6-mm aliquot minimum and central ages. Based on these results, the small-aliquot (4-mm) approach appears to provide ages comparable to those obtained by the more laborious and time-consuming single-grain method. Minimum ages indicate rapid deposition of the Homeb Silts in at least two episodes centered at ∼15 ka and ∼6 ka during climate transitions from arid to humid. Flash floods eroded the valley fills during slightly more arid conditions.
Some notes on teaching myself Russian
Authors: Blaisdell Bob
Published: May 2006

A teacher of EFL takes up RFL, and all on his own.
Local meaning in the English of West Africa
Authors: Anchimbe Eric
Published: May 2006

THIS ARTICLE addresses differences in meaning that are current in English as it is used along the West African coast. It is not uncommon for an ESL teacher to be confronted with such questions as, ‘Is that what “stranger” means?’ or such responses as, ‘Sir, I do not have a “belly”!’ However, in this context, a sound knowledge (or simply an awareness) of new meanings attached to old words may save some embarrassment. This paper proposes that, for the sound and successful teaching of English as a second language in West Africa, teachers should acquaint themselves with such usages.
Twenty years on
Authors: McArthur Tom
Published: May 2006

In 1986, I was interviewed by a long-standing colleague and friend, Arnold Pitt, for the British journal The Esperanto Teacher. As editor of that periodical he referred to the journal I had recently begun to edit, English Today, as ‘the other ET’. His interview questions began with English worldwide, and ended with his key concern, Esperanto as a (or the) world’s auxiliary language. I have always had a strong fellow feeling for ‘Esperantism’. Many artificial languages have been ‘manufactured’ for commendable philanthropic reasons, but only Esperanto has had any kind of impact on the world, and, to my mind, it is admirable in its cosmopolitanism. That said, however, my views on the pre-eminence for good and/or ill of English and, sadly, the limited prospects of Esperanto have not changed in the twenty years since that interview. The interview is therefore reprinted here with some further reflections [in square brackets]. Comments are welcomed.
Der Mozart-Effekt - Eine wissenschaftliche Legende?
Authors: Jansen-Osmann Petra
Published: May 2006

Zusammenfassung. Diese Arbeit bietet einen Überblick über die zentralen Studien zum Einfluss von Musik auf die kognitive Leistungsfähigkeit. Unter dem “Mozart-Effekt“ wird die Annahme verstanden, dass die visuell-räumliche Leistungsfähigkeit durch zuvor gehörte Musik, insbesondere Musik von Mozart, verbessert werden kann. Die dargelegten Studien machen deutlich, dass dieser Einfluss wenig mit dem Hören der Mozart-Musik zu tun hat, sondern vielmehr ein Erregungs- bzw. ein Stimmungseffekt ist und darüber hinaus von der Art der experimentellen Versuchsanordnung und der untersuchten Versuchspersonengruppe abhängig ist. Die Analyse der Studien zur Bedeutung des überdauernden praktischen Musizierens weisen insgesamt einen schwachen Zusammenhang zur Verbesserung der allgemeinen Intelligenz auf. Am Ende des Artikels wird die Frage diskutiert, inwiefern neueste Erkenntnisse aus den Neurowissenschaften und der kognitiven Psychologie es erlauben, sich dem Thema der Bedeutung von Musik auf die kognitive Leistungsfähigkeit unter einem anderen Blickwinkel zu nähern. Die Bedeutung dieses Ansatzes für die Musiktherapie wird umrissen.
Die langfristige Wirksamkeit eines Elterntrainings zur universellen Prävention kindlicher Verhaltensstörungen:
Authors: Heinrichs Nina , Hahlweg Kurt , Bertram Heike , Kuschel Annett , Naumann Sebastian , Harstick Sylvia
Published: May 2006

Zusammenfassung. Theoretischer Hintergrund: Die Bedeutung universeller Prävention und der Stand der Präventionsforschung werden dargestellt. Fragestellung: Ziel der vorliegenden Studie ist die Überprüfung der Wirksamkeit des Triple P-Gruppenprogramms als universelle Präventionsmaßnahme aus Sicht von Müttern und Vätern. Methode: Zur Rekrutierung wurden alle städtischen Kindertagesstätten in Braunschweig angesprochen. Familien wurden gemäß ihrer Kindertagesstättenzugehörigkeit zufällig der Durchführung eines Präventionsprogramms (Elterntraining) oder einer Kontrollgruppe zugewiesen. Die langfristige Wirksamkeit wurde mit einer multimethodalen diagnostischen Batterie an N = 219 Zwei-Eltern-Familien überprüft. Ergebnisse: Aus Sicht der Mütter zeigten sich signifikante Verbesserungen ihres Erziehungsverhaltens sowie deutliche Reduktionen des kindlichen Problemverhaltens. Darüber hinaus verringerte sich ihre psychische Belastung und ihre partnerschaftliche Zufriedenheit stieg an. Bei den Vätern zeigte sich eine Verbesserung ihres Erziehungsverhaltens. Schlussfolgerungen: Die Ergebnisse unterstützen die Wirksamkeit des Triple P-Gruppenprogramms als universelle Maßnahme zur Prävention kindlicher Verhaltensprobleme. Möglichkeiten der Dissemination werden diskutiert.
Factorial Structure of Three Procrastination Scales with a Spanish Adult Population
Authors: Díaz-Morales Juan Francisco , Ferrari Joseph R. , Díaz Karem , Argumedo Doris
Published: May 2006

The present study explored the factorial structure of three well-known procrastination measures: the General Procrastination Scale (GP; Lay, 1986 ), the Adult Inventory of Procrastination (AIP; McCown & Johnson, 1989 ), and the Decisional Procrastination Scale (DP; Mann, 1982 ) with 502 Spanish adults between 25 and 67 years old. The principal component analysis indicated a one-factor structure for GP and DP, and two factor components for AIP. The internal consistency of the three scales was satisfactory. Results suggested that the Spanish versions of the three procrastination scales were effective and reliable. Finally, a principal component analysis with the three scales indicated a four-factor model of procrastination, namely: dilatory behaviors, indecision, lack of punctuality, and lack of planning.
Copy‐number control of the Escherichia coli chromosome: a plasmidologist's view
Authors: Nordström Kurt , Dasgupta Santanu
Published: May 2006

The homeostatic system that sets the copy number, and corrects over‐replication and under‐replication, seems to be different for chromosomes and plasmids in bacteria. Whereas plasmid replication is random in time, chromosome replication is tightly coordinated with the cell cycle such that all origins are initiated synchronously at the same cell mass per origin once per cell cycle. In this review, we propose that despite their apparent differences, the copy‐number control of the Escherichia coli chromosome is similar to that of plasmids. The basic mechanism that is shared by both systems is negative‐feedback control of the availability of a protein or RNA positive initiator. Superimposed on this basic mechanism are at least three systems that secure the synchronous initiation of multiple origins; however, these mechanisms are not essential for maintaining the copy number.
T‐cell antigen‐receptor stoichiometry: pre‐clustering for sensitivity
Authors: Alarcón Balbino , Swamy Mahima , van Santen Hisse M , Schamel Wolfgang W A
Published: May 2006

The T‐cell antigen receptor (TCR˙CD3) is a multi‐subunit complex that is responsible for triggering an adaptive immune response. It shows high specificity and sensitivity, while having a low affinity for the ligand. Furthermore, T cells respond to antigen over a wide concentration range. The stoichiometry and architecture of TCR˙CD3 in the membrane have been under intense scrutiny because they might be the key to explaining its paradoxical properties. This review highlights new evidence that TCR˙CD3 is found on intact unstimulated T cells in a monovalent form (one ligand‐binding site per receptor) as well as in several distinct multivalent forms. This is in contrast to the TCR˙CD3 stoichiometries determined by several biochemical means; however, these data can be explained by the effects of different detergents on the integrity of the receptor. Here, we discuss a model in which the multivalent receptors are important for the detection of low concentrations of ligand and therefore confer sensitivity, whereas the co‐expressed monovalent TCR˙CD3s allow a wide dynamic range.
High resolution spectroscopy and potential determination of the (3)Π1 state of NaCs
Authors: Docenko O. , Tamanis M. , Zaharova J. , Ferber R. , Pashov A. , Knöckel H. , Tiemann E.
Published: May 2006

The (3)Π1 state of the NaCs molecule was studied by high resolution Fourier-transform spectroscopy. The (3)Π1→XΣ+1 laser induced fluorescence was excited by an Ar+ ion laser or by a single-mode frequency-doubled cw Nd:YAG laser. The presence of argon buffer gas yielded rich rotational relaxation spectra allowing to enlarge the data set for the (3)Π1 state term values, as well as to observe Λ splittings in a wide range of vibrational (v′) and rotational (J′) quantum numbers. The data field includes about 820 energy levels of (3)Π1 NaCs in the range from v′=0 to 37 and from J′=3 to 190, which corresponds to ca. 95% of the potential well depth. Direct fit of the potential energy curve to the level energies is realized using the inverted perturbation approach method; a set of Dunham coefficients is also presented.
A theoretical anharmonic study of the infrared absorption spectra of FHF−, FDF−, OHF−, and ODF− anions
Authors: Elghobashi Nadia , González Leticia
Published: May 2006

Anharmonic vibrational frequencies, equilibrium bond lengths, rotational constants, and vibrational absorption spectra have been calculated for the triatomic anions, FHF− and OHF−, and the heavier isotopomers FDF− and ODF−. The triatomic anions are assumed to maintain a collinear configuration throughout all calculations, so only the symmetric (ν1) and asymmetric (ν3) stretching modes are considered. The two-dimensional permanent dipole surfaces and potential energy surfaces are then constructed along bond coordinates, using high-level ab initio methods. Fundamental and combination bands are obtained from the vibrational eigenfunctions, resulting in anharmonic frequencies, which can be compared with the available theoretical and experimental data. The agreement is very good, especially for the pure symmetric modes, while the asymmetric ones show larger discrepancies, presumably due to the neglected coupling between stretching and bending modes. Strong inverse anharmonicity is found in the level spacing of the asymmetric modes, for both FHF− and OHF− anions. The calculated mixed modes (nν1+mν3, n, m=0–3) also agree reasonably with the few available experimental data, supporting our model. Based on the vibrational eigenfunctions, isotope effects are also rationalized. Infrared absorption spectra are calculated from the dipole autocorrelation function for FHF− and FDF−, and for OHF− and ODF−. Peak locations and relative intensities are assigned in terms of the fundamental and mixed transitions.
Correlation energy extrapolation by intrinsic scaling. V. Electronic energy, atomization energy, and enthalpy of formation of water
Authors: Bytautas Laimutis , Ruedenberg Klaus
Published: May 2006

The method of correlation energy extrapolation by intrinsic scaling, recently introduced to obtain accurate molecular electronic energies, is used to calculate the total nonrelativistic electronic ground state energy of the water molecule. Accurate approximations to the full configuration interaction energies are determined for Dunning’s [J. Chem. Phys. 90, 1007 (1989)] correlation-consistent double-, triple- and quadruple-zeta basis sets and then extrapolated to the complete basis set limit. The approach yields the total nonrelativistic energy −76.4390±0.0004hartree, which compares very well with the value of −76.4389hartree derived from experiment. The energy of atomization is recovered within 0.1mh. The enthalpy of formation, which is obtained in conjunction with our previous calculation of the dissociation energy of the oxygen molecule, is recovered within 0.05mh.
High-performance organic red-light-emitting devices based on a greenish-yellow-light-emitting host and long-wavelength emitting dopant
Authors: Chew Siewling , Wang Pengfei , Hong Zirou , Tao Silu , Tang Jianxin , Lee Chun Sing , Wong Ning Bew , Kwong Hoilun , Lee Shuit-Tong
Published: May 2006

We demonstrated an organic red-light-emitting device (ORLED) using a host, 5,6-bis-[4-(naphthalene-1-yl-phenyl-amino)-phenyl]-pyrazine-2,3-dicarbonitrile (BNPPDC), and a dopant, 2,3-bis[[[(2-hydroxy-4-diethylamino)phenyl] (methylene)] amino]-2-butanedinitrile (BDPMB). The device achieved a brightness of 9730cd∕m2 at a 11V, a power efficiency of 2.35lm∕W, a current efficiency of 3.36cd∕A at 4.5V, and a low turn-on voltage of 3.0V, with nearly saturated red emission. The device is superior or equal to the best fluorescent ORLEDs reported. BNPPDC generally induced a significant blueshift in dopant emission, thus it may serve as a host for dopants emitting at long wavelengths in ORLEDs with improved performance.
Combinatorics of n-point functions via Hopf algebra in quantum field theory
Authors: Mestre Ângela , Oeckl Robert
Published: May 2006

We use a coproduct on the time-ordered algebra of field operators to derive simple relations between complete, connected and 1-particle irreducible n-point functions. Compared to traditional functional methods our approach is much more intrinsic and leads to efficient algorithms suitable for concrete computations. It may also be used to efficiently perform tree level computations.
Gravitation theory in a fractal space-time
Authors: Agop M. , Gottlieb I.
Published: May 2006

Assimilating the physical space-time with a fractal, a general theory is built. For a fractal dimension D=2, the virtual geodesics of this space-time implies a generalized Schrödinger type equation. Subsequently, a geometric formulation of the gravitation theory on a fractal space-time is given. Then, a connection is introduced on a tangent bundle, the connection coefficients, the Riemann curvature tensor and the Einstein field equation are calculated. It results, by means of a dilation operator, the equivalence of this model with quantum Einstein gravity.
Room-temperature operation of λ≈7.5μm surface-plasmon quantum cascade lasers
Authors: Bahriz M. , Moreau V. , Palomo J. , Colombelli R. , Austin D. A. , Cockburn J. W. , Wilson L. R. , Krysa A. B. , Roberts J. S.
Published: May 2006

We report the pulsed, room-temperature operation of λ≈7.5μm quantum cascade lasers (QCLs) in which the optical mode is a surface-plasmon polariton excitation. Previously reported devices based on this concept operate at cryogenic temperatures only. The use of a silver-based electrical contact with reduced optical losses at the QCL emission wavelength allows a reduction of the laser threshold current by a factor of 2 relative to samples with a gold-based contact layer. As a consequence, the devices exhibit room-temperature operation with threshold current densities ∼6.3kA∕cm2. These devices could be used as all-electrical surface-plasmon generators at midinfrared wavelengths.
High Q-factor colloidal nanocrystal-based vertical microcavity by hot embossing technology
Authors: Martiradonna Luigi , Carbone Luigi , De Giorgi Milena , Manna Liberato , Gigli Giuseppe , Cingolani Roberto , De Vittorio Massimo
Published: May 2006

We report on the fabrication and optical characterization of vertical hybrid microcavities in which a layer of colloidal nanocrystals dispersed in an organic matrix is embedded between two inorganic mirrors. The devices are fabricated by a technique based on the unconventional use of the hot embossing technology, which allows a very fine control of the cavity length. The technique exploits a λ-thick microstructured dielectric top mirror pressed onto the bottom one, previously coated with the active layer, to sandwich the cavity and precisely control its thickness. Room-temperature photoluminescence measurements show a Q factor as high as 146 for our devices.
Analytical solution of space charge limited current for spherical and cylindrical objects
Authors: Oksuz L.
Published: May 2006

Analytical solutions for space charge limited currents in collisionless, electron-free sheaths are given for Cartesian, spherical, and cylindrical geometries. Constant current and current density are assumed. Until now, the problem of space charge limited current has not been solved either directly, in terms of series expansions, or numerically, for spherical and cylindrical objects. Analytical results show that the geometry of the system is important for determining the space charge limited current, sheath thickness, and sheath potential profile. This solution method can be used to solve similar nonlinear differential equations.
Terahertz detection schemes based on sequential multiphoton absorption
Authors: Castellano Fabrizio , Iotti Rita C. , Rossi Fausto
Published: May 2006

We present modeling and simulation of prototypical multi-bound-state quantum-well infrared photodetectors and show that such a detection design may overcome the problems arising when the operation frequency is pushed down into the far infrared spectral region. In particular, after a simplified analysis on a parabolic-potential design, we propose a fully three-dimensional model based on a finite-difference solution of the Boltzmann transport equation for realistic potential profiles. The performances of the proposed simulated devices are encouraging and support the idea that such design strategy may face the well-known dark current problem.
Reinterpreting Central Place Networks Using Ideas from Fractals and Self-Organized Criticality
Authors: Chen Yanguang , Zhou Yixing
Published: May 2006

The basic rules of central place networks are abstracted and formulated as three geometric series scaling laws, which can be transformed into several power laws associated with fractal structure. The scaling laws might be the Rosetta Stone to understand the complexity of human geographical systems because they take the form of Horton and Strahler's laws in geomorphology and Gutenberg and Richter's laws in seismology indicative of fractals and self-organized criticality (SOC). An empirical analysis is conducted with the use of data from southern Germany, given by Christaller. The fractal dimensions, Df, of four systems are calculated as follows: Df is 1.733 for Munich, 1.685 for Nuremberg, 1.837 for Stuttgart, and 1.481 for Frankfurt. SOC theory is employed to interpret the fractality of central places, and the power laws are seen as signatures of feasible optimality, thus yielding further support to the suggestion that optimality of the system as a whole explains the dynamic origin of fractal forms in nature.
Mammalian cell survival and processing in supercritical CO
2
Authors: Ginty Patrick J. , Howard Daniel , Rose Felicity R. A. J. , Whitaker Martin J. , Barry John J. A. , Tighe Patrick , Mutch Stacey R. , Serhatkulu Gulay , Oreffo Richard O. C. , Howdle Steven M. , Shakesheff Kevin M.
Published: May 2006

We demonstrate that mammalian cells can survive for 5 min within high-pressure CO
2
.
Cell survival was investigated by exposing a range of mammalian cell types to supercritical CO
2
(scCO
2
) (35°C, 74 bar; 1 bar = 100 kPa) for increasing exposure and depressurization times. The myoblastic C2C12 cell line, 3T3 fibroblasts, chondrocytes, and hepatocytes all displayed appreciable but varying metabolic activity with exposure times up to 1 min. With depressurization times of 4 min, cell population metabolic activity was ≥70% of the control population. Based on survival data, we developed a single-step scCO
2
technique for the rapid production of biodegradable poly(
dl
-lactic acid) scaffolds containing mammalian cells. By using optimum cell-survival conditions, scCO
2
was used to process poly(
dl
-lactic acid) containing a cell suspension, and, upon pressure release, a polymer sponge containing viable mammalian cells was formed. Cell functionality was demonstrated by retention of an osteogenic response to bone morphogenetic protein-2 in C2C12 cells. A gene microarray analysis showed no statistically significant changes in gene expression across 4,418 genes by a single-class
t
test. A significance analysis of microarrays revealed only eight genes that were down-regulated based on a δ value of 1.0125 and a false detection rate of 0.
On the Pleistocene extinctions of Alaskan mammoths and horses
Authors: Solow Andrew R. , Roberts David L. , Robbirt Karen M.
Published: May 2006

The fossil record has been used to shed light on the late Pleistocene megafaunal extinctions in North America and elsewhere. It is therefore important to account for variability due to the incompleteness of the fossil record and error in dating fossil remains. Here, a joint confidence region for the extinction times of horses and mammoths in Alaska is constructed. The results suggest that a prior claim that the extinction of horses preceded the arrival of humans cannot be made with confidence.
Inadequate histone deacetylation during oocyte meiosis causes aneuploidy and embryo death in mice
Authors: Akiyama Tomohiko , Nagata Masao , Aoki Fugaku
Published: May 2006

Errors in meiotic chromosome segregation are the leading cause of spontaneous abortions and birth defects. Almost all such aneuploidy derives from meiotic errors in females, with increasing maternal age representing a major risk factor. It was recently reported that histones are globally deacetylated in mammalian oocytes during meiosis but not mitosis. In the present study, inhibition of meiotic histone deacetylation was found to induce aneuploidy in fertilized mouse oocytes, which resulted in embryonic death
in utero
at an early stage of development. In addition, a histone remained acetylated in the oocytes of older (10-month-old) female mice, suggesting that the function for histone deacetylation is decreased in the oocytes of such mice. Thus, histone deacetylation may be involved in the fair distribution of chromosomes during meiotic division. The high incidence of aneuploidy in the embryos of older females may be due to inadequate meiotic histone deacetylation.
Bioportfolio: Lifelong persistence of variant and prototypic erythrovirus DNA genomes in human tissue
Authors: Norja Päivi , Hokynar Kati , Aaltonen Leena-Maija , Chen Renwei , Ranki Annamari , Partio Esa K. , Kiviluoto Olli , Davidkin Irja , Leivo Tomi , Eis-Hübinger Anna Maria , Schneider Beate , Fischer Hans-Peter , Tolba René , Vapalahti Olli , Vaheri Antti , Söderlund-Venermo Maria , Hedman Klaus
Published: May 2006

Human erythrovirus is a minute, single-stranded DNA virus causing many diseases, including erythema infectiosum, arthropathy, and fetal death. After primary infection, the viral genomes persist in solid tissues. Besides the prototype, virus type 1, two major variants (virus types 2 and 3) have been identified recently, the clinical significance and epidemiology of which are mostly unknown. We examined 523 samples of skin, synovium, tonsil, or liver (birth year range, 1913–2000), and 1,640 sera, by qualitative and quantitative molecular assays for the DNA of human erythroviruses. Virus types 1 and 2 were found in 132 (25%) and 58 (11%) tissues, respectively. DNA of virus type 1 was found in all age groups, whereas that of type 2 was strictly confined to those subjects born before 1973 (
P
< 0.001). Correspondingly, the sera from the past two decades contained DNA of type 1 but not type 2 or 3. Our data suggest strongly that the newly identified human erythrovirus type 2 as well as the prototype 1 circulated in Northern and Central Europe in equal frequency, more than half a century ago, whereafter type 2 disappeared from circulation. Type 3 never attained wide occurrence in this area during the past ≥70 years. The erythrovirus DNA persistence in human tissues is lifelong and represents a source of information about our past, the
Bioportfolio
, which, at the individual level, provides a registry of one’s infectious encounters, and at the population level, a database for epidemiological and phylogenetic analyses.
Groucho/transducin-like Enhancer-of-split (TLE)-dependent and -independent transcriptional regulation by Runx3
Authors: Yarmus Merav , Woolf Eilon , Bernstein Yael , Fainaru Ofer , Negreanu Varda , Levanon Ditsa , Groner Yoram
Published: May 2006

Regulation of gene expression by tissue-specific transcription factors involves both turning on and turning off transcription of target genes. Runx3, a runt-domain transcription factor, regulates cell-intrinsic functions by activating and repressing gene expression in sensory neurons, dendritic cells (DC), and T cells. To investigate the mechanism of Runx3-mediated repression in an
in vivo
context, we generated mice expressing a mutant Runx3 lacking the C-terminal VWRPY, a motif required for Runx3 interaction with the corepressor Groucho/transducin-like Enhancer-of-split (TLE). In contrast with Runx3
−/−
mice, which displayed ataxia due to the death of dorsal root ganglia TrkC neurons, Runx3
VWRPY−/−
mice were not ataxic and had intact dorsal root ganglia neurons, indicating that ability of Runx3 to tether Groucho/TLE is not essential for neurogenesis. In the DC compartment, the mutant protein Runx3
VWRPY−
promoted normally developed skin Langerhans cells but failed to restrain DC spontaneous maturation, indicating that this latter process involves Runx3-mediated repression through recruitment of Groucho/TLE. Moreover, in CD8
+
thymocytes, Runx3
VWRPY−
up-regulated α
E
/CD103-like WT Runx3, whereas unlike wild type, it failed to repress α
E
/CD103 in CD8
+
splenocytes. Thus, in CD8-lineage T cells, Runx3 regulates α
E
/CD103 in opposing regulatory modes and recruits Groucho/TLE to facilitate the transition from activation to repression. Runx3
VWRPY−
also failed to mediate the epigenetic silencing of
CD4
gene in CD8
+
T cells, but normally regulated other pan-CD8
+
T cell genes. These data provide evidence for the requirement of Groucho/TLE for Runx3-mediated epigenetic silencing of
CD4
and pertain to the mechanism through which other Runx3-regulated genes are epigenetically silenced.
Effect of light on germination of seeds of Cactaceae from the Chihuahuan Desert, Mexico
Authors: Flores Joel , Jurado Enrique , Arredondo Alberto
Published: May 2006

In the Chihuahuan Desert, there are many cacti species considered to be at risk due to illegal extraction, land-use change and overgrazing. To reduce their illegal extraction,ex situplant propagation has been suggested. However, the literature regarding seed germination biology of these species is scarce. We investigated the effect of light on germination percentages and germination rate (t50) in seeds of 28 cactus species from the Chihuahuan Desert. Seeds were incubated at a 14-h daily photoperiod (light) and in continuous darkness at 25°C for 30 d, after which seeds failing to germinate in darkness were transferred to light for 30 d. Only 11 of the species had non-dormant seeds, germinating ≥70% in the light; thus an evaluation of the effect of light versus darkness on germination was confined to them. All species were positively photoblastic, and all of them had seeds weighing <1 mg. Ten species did not germinate in darkness, and one species had only 7% germination. From these 11 species, 8 did not germinate to a significantly higher percentage when the same set of seeds was transferred from dark to light, suggesting that darkness had triggered secondary dormancy (skotodormancy). To our knowledge, these results are the first to show that darkness triggers secondary dormancy in cacti. Implications of having a light requirement for germination and having small seeds to accumulate a persistent soil seed bank are discussed. These results contribute to understanding the germination biology of cactus species at risk, and could enhance the propagation of large numbers of cultivated individuals outside their habitats, promotingex situconservation.
The dispersal of traditionally managed hay meadow plants via farmyard manure application
Authors: Edwards A.R. , Younger A.
Published: May 2006

The dispersal of plants within botanically rich grassland is an important area of study if such swards are to be maintained. The application of farmyard manure provides a possible mechanism by which seeds contained within hay can be returned/introduced to grasslands. In this study, hay, dung and manure samples taken from farms with botanically rich meadows contained very limited quantities of seeds of desirable species. Digestion by cattle, and storage within a manure heap for 6 months or longer, further reduced seed germination. Samples were characterized by an abundance of the grass,Poa trivialis, with few forbs present. Confirmation of the negative effect of the digestive processes of cattle on seed viability was achieved using anin vitrolaboratory experiment. However, this experiment did show that the perennial herbs,Filipendula ulmariaandSanguisorba officinalis, were able to survive digestion at least as well asP. trivialis. The burial of known quantities of seeds in a manure heap also showed these perennial herbs to be at least as resistant to damage asP. trivialis. The results demonstrate that, given appropriate timing of the hay cut, seeds of species with high conservation value could become incorporated into manure for subsequent dispersal. However, manure dispersal would appear to be of limited value for many species desirable from a conservation viewpoint.
Goitrous congenital hypothyroidism in a twin pregnancy causing respiratory obstruction at birth: Implications for management
Authors: Reynolds Ben Christopher , Simpson Judith Helen , Macara Lena , Bruce Watt Andrew James , Kubba Haytham , Donaldson Malcolm David Cairns , Pohlen Joachim
Published: May 2006

We report a twin pregnancy complicated by fetal goitrous hypothyroidism secondary to dyshormonogenesis caused by thyroglobulin deficiency. Antenatal treatment with intra‐amniotic thyroxine was considered but not performed, given the late gestational age at diagnosis and the multiple nature of the pregnancy. Both twins developed airway obstruction at delivery, requiring intubation and ventilation. We review the literature and describe the practical issues relating to the antenatal assessment and perinatal management of fetal goitre.
The activity status of cofilin is directly related to invasion, intravasation, and metastasis of mammary tumors
Authors: Wang Weigang , Mouneimne Ghassan , Sidani Mazen , Wyckoff Jeffrey , Chen Xiaoming , Makris Anastasia , Goswami Sumanta , Bresnick Anne R. , Condeelis John S.
Published: May 2006

Understanding the mechanisms controlling cancer cell invasion and metastasis constitutes a fundamental step in setting new strategies for diagnosis, prognosis, and therapy of metastatic cancers. LIM kinase1 (LIMK1) is a member of a novel class of serine–threonine protein kinases. Cofilin, a LIMK1 substrate, is essential for the regulation of actin polymerization and depolymerization during cell migration. Previous studies have made opposite conclusions as to the role of LIMK1 in tumor cell motility and metastasis, claiming either an increase or decrease in cell motility and metastasis as a result of LIMK1 over expression (Zebda, N., O. Bernard, M. Bailly, S. Welti, D.S. Lawrence, and J.S. Condeelis. 2000. J. Cell Biol. 151:1119–1128; Davila, M., A.R. Frost, W.E. Grizzle, and R. Chakrabarti. 2003. J. Biol. Chem. 278:36868–36875; Yoshioka, K., V. Foletta, O. Bernard, and K. Itoh. 2003. Proc. Natl. Acad. Sci. USA. 100:7247–7252; Nishita, M., C. Tomizawa, M. Yamamoto, Y. Horita, K. Ohashi, and K. Mizuno. 2005. J. Cell Biol. 171:349–359). We resolve this paradox by showing that the effects of LIMK1 expression on migration, intravasation, and metastasis of cancer cells can be most simply explained by its regulation of the output of the cofilin pathway. LIMK1-mediated decreases or increases in the activity of the cofilin pathway are shown to cause proportional decreases or increases in motility, intravasation, and metastasis of tumor cells.
The Importance of Two-Step Tuberculin Skin Testing for Newly Employed Healthcare Workers
Authors: Frenzel Elizabeth C. , Thomas Georgia A. , Hanna Hend A.
Published: May 2006

At the time of hire, 4059 of 6522 healthcare workers required a 2-step tuberculin skin test; 114 workers (2.8%) demonstrated a boosted reaction after the second step. Boosted reactions were significantly associated with male sex and older age. A verbal history of previous tuberculin skin test results was not a reliable indicator of baseline tuberculin skin test status at the time of hire.