bluuebunny/crossref_metadata_2025 huggingface dataset:
Analyses of structures for a synthetic leather made of polyurethane and microfiber
Authors: Chen Min , Zhou Dong‐Liang , Chen Yong , Zhu Pu‐Xin
Published: October 2006

A gradient extraction method was developed and used for a synthetic leather made of polyurethane (PU) and microfiber polycaprolactam (PA‐6), by which the two components were separated using DMF and formic acid as solvents, respectively. Their chemical structure was confirmed by FTIR spectra, and the result showed that the PU is a kind of polyester polyurethane with phenylene rings in the molecule. The condensed phase structure was analyzed using X‐ray diffraction (XRD). The crystallinity of the PA‐6 is about 65.6%, and for the PU, there was not distinct crystalline character shown in the XRD pattern but a phase separation structure of hard block‐soft block with the hard domains content about 58.7%. SEM images showed that the PA‐6 microfibers transfixing the PU matrix form a net bundle structure, and there are two kinds of porous structures in the synthetic leather, with one type of pore sized 5–80 μm between the components of PU and PA‐6, and the other in PU matrix with a size of 0.1–2 μm. The multipores run through the synthetic leather as three‐dimensional channels, benefit for transportation of air, water, dyes, and so on. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 903–908, 2007
Crosslinked poly(vinyl alcohol) and starch composite films. II. Physicomechanical, thermal properties and swelling studies
Authors: Ramaraj B.
Published: October 2006

Poly(vinyl alcohol) (PVA) was blended with 10, 20, 30, 40, and 50 wt % of starch with and without crosslinking by solution casting process. The solution‐casted films were dried and tested for physicomechanical properties like tensile strength, tensile elongation, tensile modulus, tear and burst strengths, density, and thermal analysis by differential scanning calorimetry (DSC). These PVA/starch films were further characterized for moisture content; solubility resistance in water, 5% acetic acid, 50% ethanol, and sunflower oil; and swelling characteristics in 50% ethanol and sunflower oil. The crosslinked PVA/starch composite films show significant improvement in tensile strength, tensile modulus, tear and burst strengths, and solubility resistance over the uncrosslinked films. Between the crosslinked and uncrosslinked films, the uncrosslinked films have higher tensile elongation, moisture content, moisture absorption, and swelling over the crosslinked films. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 909–916, 2007
Phosphorylcholine end‐capped poly‐ε‐caprolactone: A novel biodegradable material with improved antiadsorption property
Authors: Meng Sheng , Zhong Wei , Chou Laisheng L. , Wang Qihong , Liu Zongjun , Du Qiangguo
Published: October 2006

In this study, the synthesis, characterization, and properties of a novel biodegradable polymer with improved hemocompatibility were introduced. It was synthesized by end‐capping poly‐ε‐caprolactone (PCL) with phosphorylcholine (PC) groups. The polyester backbone provided the mechanical stability and biodegradability, while the PC‐end groups improved its hemocompatibility. The obtained polymer was characterized using 1H NMR, 31P NMR, FTIR, and GPC, its crystallization behavior was studied by DSC. Compared with original PCL, the resulting polymer (PC‐PCL) showed a lower crystallization capability and a faster degradation rate in PBS. The degradation rate of the polymer blends of PCL/PC‐PCL increased with increasing PC‐PCL content. The results of water contact angle measurements revealed a more hydrophilic surface property of PC‐PCL than neat PCL. The hemocompatibility of PC‐PCL was estimated using rabbit platelet‐rich plasma, a better resistance to platelet adhesion and activation was observed. During the human blood plasma contacting process, PC‐PCL showed a prolonged activated partial thromboplastin time over neat PCL. Material–cell interaction was evaluated with human umbilical vein endothelial cell, the result indicated that PC‐PCL may to some extent have an antihyperplasia property, compared with neat PCL. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 989–997, 2007
Wilhelm von Waldeyer‐Hartz (1836–1921): An anatomist who left his mark
Authors: Winkelmann Andreas
Published: October 2006

Wilhelm Waldeyer was anatomist, physiologist, and pathologist during the German Empire (the so‐called Second Reich). His scientific career left many traces still noticeable today. Not only is he commemorated in “his” pharyngeal lymphoid ring and other eponyms, but he also coined an impressive range of successful medical terms, including “chromosome” and “neuron.” Moreover, Waldeyer left truly physical traces by donating parts of his body to his own Institute of Anatomy in Berlin. His scientific production does, however, also include “pseudoscientific” works, notably his questionable research on African brains. Clin. Anat. 20:231–234, 2007. © 2006 Wiley‐Liss, Inc.
Polyurethane elastomer: A new material for the visualization of cadaveric blood vessels
Authors: Meyer Eric P. , Beer Gertrude M. , Lang Axel , Manestar Mirjana , Krucker Thomas , Meier Sonja , Mihic‐Probst Daniela , Groscurth Peter
Published: October 2006

A multitude of various materials are available for the visualization of cadaveric vessels, ranging from natural materials like gelatin and latex to synthetic materials like silicone rubber or acrylates. To achieve a detailed overview of the vascular architecture in microvascular studies in experimental flap surgery, the injected material should have low viscosity to assure perfusion of even the smallest vessels. In addition, the material ideally should have either no or only minimal shrinkage, and should harden within a reasonable time, but retain sufficient elasticity and resistance to withstand tearing off the delicate vessels during subsequent dissection or casting. Because none of the available injection materials adequately combines these attributes, we evaluated the polyurethane elastomer “PU4ii” in latissimus dorsi muscles as a new material for the visualization of cadaveric vessels in comparison with the frequently used silicone rubber. The dissection of vessels injected with PU4ii proved easy largely because of its exceptional hardness. Even if not visible before dissection, the completely perfused vessels were easily palpated in the surrounding fat or muscle tissue of the microsurgical latissimus dorsi model. Despite the significantly higher hardness of PU4ii over silicone rubber (98 Sh‐A vs. 12 Sh‐A), PU4ii proved enough elasticity (20–25 N/mm2 E modulus) and a high tear resistance (64–68 N/mm vs. 15 N/mm) preventing breakage during dissection even within the smallest vessels. In contrast to silicone rubber (and latex or gelatin), the high corrosion resistance and form stability of PU4ii also allowed building of casts for qualitative examination by scanning electron microscopy and quantitative analysis of the vessel density using micro‐computed tomography with accurate 3D representation. In this study we show that PU4ii has physical characteristics that make it a multi‐purpose material that allows at the same breath an excellent gross visualization of the architecture of cadaveric blood vessels as well as a detailed evaluation of casts by modern microscopic and or radiologic tools. Thus, the new polyurethane elastomer PU4ii is in many respects superior to the widely used silicone rubber and can be strongly recommended as a visualization material for a comprehensive evaluation of cadaveric blood vessels in microsurgery. Clin. Anat. 20:448–454, 2007. © 2006 Wiley‐Liss, Inc.
Synthesis, Solution Structure and Immune Recognition of an Epidermal Growth Factor‐Like Domain from Plasmodium falciparum Merozoite Surface Protein‐1
Authors: James Sonya , Moehle Kerstin , Renard Annabelle , Mueller Markus S. , Vogel Denise , Zurbriggen Rinaldo , Pluschke Gerd , Robinson John A.
Published: October 2006

The Plasmodium falciparum merozoite surface protein‐1 19 kDa fragment (MSP‐119) comprises two closely packed EGF‐like domains (EGF=epidermal growth factor), each stabilized by three disulfide bonds. The native conformation of this protein is important for eliciting P. falciparum growth inhibitory antibodies. Here we show that the N‐terminal EGF domain alone can be chemically synthesized and efficiently refolded to a native‐like state, as shown by its solution structure as determined by NMR spectroscopy. In order to study its immunogenicity, the domain was coupled through its N terminus to a phospholipid and incorporated into reconstituted influenza virus‐like particles (virosomes). When used to immunize mice, the peptide‐loaded virosomes elicited potent humoral immune responses that were shown by Western blots and immunofluorescence assays to cross‐react with native MSP‐1 on the surfaces of P. falciparum blood stage parasites. This opens the way for a medicinal chemistry‐oriented approach to the study and optimization of the antigenicity of the protein as a potential malaria vaccine candidate, whilst exploiting the immunopotentiating properties of influenza virosomes as a delivery vehicle.
Switching between Ligand‐to‐Ligand Charge‐Transfer, Intraligand Charge‐Transfer, and Metal‐to‐Ligand Charge‐Transfer Excited States in Platinum(II) Terpyridyl Acetylide Complexes Induced by pH Change and Metal Ions
Authors: Han Xue , Wu Li‐Zhu , Si Gang , Pan Jie , Yang Qing‐Zheng , Zhang Li‐Ping , Tung Chen‐Ho
Published: October 2006

A series of platinum(II) terpyridyl alkynyl complexes, [Pt{4′‐(4‐R1‐C6H4)terpy}(CC‐C6H4‐R2‐4)]ClO4 (terpy = 2,2′:6′,2′′‐terpyridyl; R1 = R2 = N(CH3)2 (1); R1 = N(CH3)2, R2 = N‐[15]monoazacrown‐5 (2); R1 = CH3, R2 = N(CH3)2 (3); R1 = N(CH3)2, R2 = H (4); R1 = CH3, R2 = H (5)), has been synthesized and the photophysical properties of the complexes have been examined through measurement of their UV/Vis absorption spectra, photoluminescence spectra, and transient absorptions. Complex 3 shows a lowest‐energy absorption corresponding to a ligand‐to‐ligand charge‐transfer (LLCT) transition from the acetylide to the terpyridyl ligand, whereas 4 shows an intraligand charge‐transfer (ILCT) transition from the π orbital of the 4′‐phenyl group to the π* orbital of the terpyridyl. Upon protonation of the amino groups in 3 and 4, their lowest‐energy excited states are switched to dπ(Pt)→π*(terpy) metal‐to‐ligand charge‐transfer (MLCT) states. The lowest‐energy absorption for 1 and 2 may be attributed to an LLCT transition from the acetylide to the terpyridyl. Upon addition of an acid to a solution of 1 or 2, the amino group on the acetylide is protonated first, followed by the amino group on the terpyridyl. Thus, the lowest excited state of 1 and 2 can be successively switched from the LLCT state to the ILCT state and then to the MLCT state by controlling the amount of the acid added. Such switches in the excited state are fully reversible upon subsequent addition of a base to the solution. Sequential addition of alkali metal or alkaline earth metal ions and then an acid to a solution of 2 also leads to switching of its lowest excited state from the LLCT state, first to the ILCT state and then to the MLCT state. All of the complexes exhibit a transient absorption of the terpyridyl anion radical, which is present in all of the LLCT, ILCT, and MLCT states. However, the shape of the transient absorption spectrum depends on both the substitution pattern on the terpyridyl moiety and the nature of the excited state.
Ursachen der erhöhten Resistenz von Mikroorganismen in Biofilmen
Authors: Schulte Simone , Flemming Hans‐Curt
Published: October 2006

Biofilme stellen die älteste Form des Lebens auf der Erde dar, in der sie durch Selektion über Milliarden Jahre ein enormes Überlebenspotenzial entwickelt haben. Dazu gehört, dass sie wesentlich widerstandsfähiger gegenüber Bioziden sind als in der planktonischen Form in der Wasserphase. Die Gründe für die Resistenz sind vielfältig. Für die Praxis bedeutet dies, dass es schwierig ist, Biofilme vollständig abzutöten, weil immer damit gerechnet werden muss, dass ein kleiner Teil der Population überlebt. Rasche und generelle Lösungen für Biofilm‐Probleme gibt es nicht – es kommt immer auf die jeweiligen Gegebenheiten des zu schützenden Systems an. Daher sind integrative Ansätze entscheidend, bei denen sowohl das Medium, die Materialien, das Design, der Prozess und die Überwachung ineinander greifen. Dann aber lassen sich Biofilm‐Probleme durchaus unter Kontrolle halten.
Kombination von Mikrofiltration und thermischen Verfahren zur Haltbarkeitsverlängerung von Lebensmitteln
Authors: Kaufmann V. , Kulozik U.
Published: October 2006

Mittels Mikrofiltration lässt sich ein Großteil der im Produkt enthaltenen Mikroorganismen mechanisch abtrennen und damit die Haltbarkeit von Milch verlängern. Um eine möglichst effiziente und selektive Keimretention bei konstantem Flux zu erreichen, sind dabei verschiedene Einflussgrößen (Anlagenkonzeption, Prozessbedingungen) und im Laufe des Filtrationsprozesses auftretende Effekte wie Deckschichtbildung und/oder (Bio)Fouling zu berücksichtigen. Die Kombination von membrantrenntechnischer und thermischer Behandlung ermöglicht eine produktschonende Prozessintensivierung. Neben dem eigentlichen Herstellprozess spielen im Hinblick auf die Qualität und die Stabilität der Milch zudem vor‐ und nachgelagerte Faktoren (Rohmilchbeschaffenheit, Prozesshygiene und Verpackung sowie Lager‐ und Distributionsbedingungen) eine Rolle.
Relationship of presympathetic‐premotor neurons to the serotonergic transmitter system in the rat brainstem
Authors: Kerman Ilan A. , Shabrang Cyrus , Taylor Larry , Akil Huda , Watson Stanley J.
Published: October 2006

Numerous physiological conditions and emotionally motivated behaviors require concomitant activation of somatomotor and sympathetic efferents. Using a virally mediated retrograde transsynaptic tract‐tracing approach, we have previously determined locations of presympathetic‐premotor neurons (PSPMNs) in the rat brainstem. These putative dual‐function neurons send projections to somatomotor and sympathetic targets and likely participate in sympatho‐somatomotor integration. A significant portion of these neurons is found within brainstem areas known to contain serotonergic neurons. Thus, we hypothesized that some of the PSPMNs utilize serotonin as their neurotransmitter. To test this hypothesis we first produced an antibody against TPH2, a brain‐specific isoform of tryptophan hydroxylase (serotonin synthetic enzyme). We identified PSPMNs by using recombinant strains of the pseudorabies virus (PRV) for transsynaptic tract‐tracing. PRV‐152, a strain that expresses enhanced green fluorescent protein, was injected into sympathectomized gastrocnemius muscle, while PRV‐BaBlu, which expresses β‐galactosidase, was injected into the adrenal gland in the same animals. Using immunofluorescent methods we determined whether coinfected neurons expressed TPH2. Our findings demonstrate that TPH2‐positive PSPMNs are present at different rostrocaudal levels of the brainstem. Just over half of them are found at the pontomedullary junction within raphe obscurus, raphe magnus, and gigantocellular nucleus pars alpha. These cells may play a role in mediating responses to acute pain stimuli and/or participate in the central control of exercise. Overactivity of these serotonergic sympatho‐somatomotor circuits may also play a role in the pathophysiology of serotonin syndrome. J. Comp. Neurol. 499:882–896, 2006. © 2006 Wiley‐Liss, Inc.
Distinct expression and localization of serine protease HtrA1 in human endometrium and first‐trimester placenta
Authors: Nie Guiying , Hale Kathryn , Li Ying , Manuelpillai Ursula , Wallace Euan M. , Salamonsen Lois A.
Published: October 2006

Mammalian embryos cannot survive without the placenta. Development of the human placenta requires trophoblast proliferation, differentiation, and invasion as well as highly coordinated modulation of the maternal uterus. HtrA1 is a member of the recently identified mammalian HtrA (high temperature requirement factor A) serine protease family with a high level of expression in the placenta. In this study, we examined whether HtrA1 expression (mRNA and protein) is associated with placental development in the human. HtrA1 is up‐regulated in both endometrial glands and decidual cells during endometrial preparation for embryo implantation and during first‐trimester pregnancy at placentation. HtrA1 expression was also detected in certain trophoblast subtypes during early pregnancy. The villous syncytiotrophoblast and cytotrophoblast showed the strongest expression while the interstitial extravillous trophoblast showed the lowest or no expression of HtrA1. The distinct distribution of HtrA1 at the maternal‐trophoblast interface suggests that HtrA1 may play a role in placental development. Developmental Dynamics 235:3448–3455, 2006. © 2006 Wiley‐Liss, Inc.
New Bis(silyl)cyclopentadienidoniobium and ‐tantalum Complexes:X‐ray Crystal Structures of [NbCp∧Cl4] and [NbCp∧Cl4(CNAr)][Cp∧ = η5‐C5H3(SiClMe2)(SiMe3); Ar = 2,6‐Me2C6H3]
Authors: Gómez Manuel , Gómez‐Sal Pilar , Hernández José Manuel
Published: October 2006

The [bis(silyl)cyclopentadienido]tetrachloroniobium and‐tantalum complexes [MCp∧Cl4] [Cp∧ = η5‐C5H3(SiClMe2)(SiMe3); M = Nb 3, Ta 4] were synthesized by reaction of the pentachlorides MCl5 with C5H3(SiClMe2)(SiMe3)2 (1). Although the Lewis acidity of tetrachloro complexes 3 and 4 is lower than that of the pentahalides, two adducts [M{η5‐C5H3(SiClMe2)(SiMe3)}Cl4(CNAr)] (Ar = 2,6‐Me2C6H3; M = Nb 5, Ta 6) have been isolated by reaction with ArNC. Complexes 3 and 4 react with tert‐butylamine or lithium amides to afford the dichloroimido and amidochloroimido complexes [M{η5‐C5H3(SiClMe2)(SiMe3)}Cl2(NR)] (R = tBu, M = Nb 7, Ta 8; R = Me, M = Nb 9) and [Ta{η5‐C5H3(SiClMe2)(SiMe3)}Cl(NHtBu)(NtBu)] (10), respectively. In addition, 7 and 8 can be prepared by treatment of the pentachlorides with [C5H3(SiMe2NHtBu)(SiMe3)2] (2) by elimination of 1. The tetrachloro compound 3 reacts with four equivalents of tBuNH2 to give the constrained‐geometry derivative [Nb{η5‐C5H3(SiMe2NtBu‐κN)(SiMe3)}Cl(NtBu)] (11), whereas the treatment of toluene solutions of 3 and 4 with H2NCH2CH2NH2 in the presence of triethylamine leads to the trichloro complexes [M{η5‐C5H3(SiMe2NCH2CH2NH2‐κ2N,N)(SiMe3)}Cl3] (M = Nb 12, Ta 13). All the reported complexes were studied by IR and NMR spectroscopy and the molecular structures of complexes 3 and 5 were determined by X‐ray diffraction methods. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Enhanced differentiation and mineralization of human fetal osteoblasts on PDLLA containing Bioglass® composite films in the absence of osteogenic supplements
Authors: Tsigkou O. , Hench L.L. , Boccaccini A.R. , Polak J.M. , Stevens M.M.
Published: October 2006

This study investigates the cellular response of fetal osteoblasts to bioactive resorbable composite films consisting of a poly‐D,L‐lactide (PDLLA) matrix and bioactive glass 45S5 Bioglass® (BG) particles at three different concentrations (0% (PDLLA), 5% (P/BG5), and 40% (P/BG40)). Using scanning electron microscopy (SEM) we observed that cells were less spread and elongated on PDLLA and P/BG5, whereas cells on P/BG40 were elongated but with multiple protrusions spreading over the BG particles. Vinculin immunostaining revealed similar distribution of focal adhesion contacts on all cells independent of substratum, indicating that all materials permitted cell adhesion. However, when differentiation and maturation of fetal osteoblasts was examined, incorporation of 45S5 BG within the PDLLA matrix was found to significantly (p < 0.05) enhance alkaline phosphatase enzymatic activity and osteocalcin protein synthesis compared to tissue culture polystyrene controls and PDLLA alone. Alizarin red staining indicated extracellular matrix mineralization on both P/BG5 and P/BG40, with significantly more bone nodules formed than on PDLLA. Real time RT‐PCR revealed that expression of bone sialoprotein was also affected by the BG containing films compared to controls, whereas expression of Collagen Type I was not influenced. By performing these investigations in the absence of osteogenic factors it appears that the incorporation of BG stimulates osteoblast differentiation and mineralization of the extracellular matrix, demonstrating the osteoinductive capacity of the composite. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
A novel poly(ethylene glycol)–fibrinogen hydrogel for tibial segmental defect repair in a rat model
Authors: Peled Eli , Boss Jochanan , Bejar Jacob , Zinman Chaim , Seliktar Dror
Published: October 2006

The aim of this study is to investigate regeneration in a segmental bone defect using a novel fibrinogen‐based hydrogel material. The use of hydrogels made from poly(ethylene glycol) (PEG) conjugated to fibrinogen for this purpose may be better to conventional fibrin‐based materials as it offers an additional degree of control over the structural characteristics and biodegradation of the material. At the same time, it maintains some of the inherent biofunctionality of the fibrinogen molecule. PEGylated fibrinogen hydrogels with various degrees of proteolytic resistance based on PEG and fibrinogen composition were designed for slow, intermediate, and fast biodegradation. The hydrogels were implanted into 7‐mm segmental rat tibial defects without additional osteoinductive factors with the rationale that the ingrowth matrix will displace the normal fibrin clot while sustaining a similar healing effect for a longer duration. Histological and X‐ray results confirmed that the extent and distribution of newly formed bone in the defect after 5 weeks strongly parallels the biodegradation pattern of the implanted material. When compared to nonunions in animals treated with the fast‐degrading implants and untreated control animals, the rats implanted with the intermediate‐degrading material exhibited osteoneogenesis. This data supports the hypothesis that the perseverance of the PEGylated fibrinogen material can be synchronized with the optimal healing characteristics of a segmental osseous defect and that the consequent sustained release of fibrinogen fragments facilitates the osteogenic response at the injury site. The PEGylated fibrinogen material may, therefore, be a highly efficacious material for promoting the healing of bone defects and especially nonunion fractures. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
A mathematical model for predicting controlled release of bioactive agents from composite fiber structures
Authors: Zilberman Meital , Sofer Moran
Published: October 2006

A mathematical model for predicting bioactive agent release profiles from core/shell fiber structures was developed and studied. These new composite fibers, which combine good mechanical properties with desired protein release profiles, are designed for use in tissue regeneration and other biomedical applications. These fibers are composed of an inner dense polymeric core surrounded by a porous bioresorbable shell, which encapsulates the bioactive agent molecules. The model is based on Fick's second law of diffusion, and on two major assumptions: (a) first‐order degradation kinetics of the porous shell, and (b) a nonconstant diffusion coefficient for the bioactive agent, which increases with time because of degradation of the host polymer. Three factors are evaluated and included in this model: a porosity factor, a tortuosity factor, and a polymer concentration factor. Our study indicates that the model correlates well with in vitro release results, exhibiting a mean error of less than 2.2% for most studied cases. In this study, the model was used for predicting protein release profiles from fibers with shells of various initial molecular weights and for predicting the release of proteins with various molecular weights. This new model exhibits a potential for simulating fibrous systems for a wide variety of biomedical applications. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Preparation of nano‐tentacle polypyrrole with pseudo‐molecular template for ATP incorporation
Authors: Xiao Yinghong , Che Jianfei , Li Chang Ming , Sun Chang Q. , Chua Yek T. , Lee Vee S. , Luong John H.T.
Published: October 2006

Polypyrrole was electrochemically synthesized onto a gold electrode in the presence of sodiump‐toluenesulfonate (TSNa) as the key dopant. Under the optimal synthesis condition, the surface morphology of PPy/TSNa was tailored and exhibited a nano‐tentacle structure. The resulting rough and fuzzy morphology greatly enhanced the apparent surface area as well as the polymer film conductivity. Adenosine triphosphate (ATP) was then incorporated in the structure by subsequent ion exchanging. This procedure could be envisaged as pseudo‐molecular templating to eliminate several shortcomings associated with physical templating. Fourier transform infrared (FTIR) and ultraviolet‐visible (UV‐vis) spectroscopy were conducted to investigate the incorporation of ATP. The pronounced rough surface of PPy/TSNa provided a higher density of active sites for ATP binding. The resulting PPy/ATP film exhibited a high charged capacity and lower impedance compared to the bare gold electrode. ATP remained stable in the PPy film; however, a negative bias to the electrode stimulated the conducting polymer to release ATP. This concept could serve as a mechanism for drug delivery and biosensing applications. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2006
Transfer of apatite coating from porogens to scaffolds: Uniform apatite coating within porous poly(DL‐lactic‐co‐glycolic acid) scaffold in vitro
Authors: Li Jiashen , Beaussart Audrey , Chen Yun , Mak Arthur F.T.
Published: October 2006

Strategies to bone tissue engineering have focused on the use of synthetic or natural degradable materials as scaffolds for cell transplantation to guide bone regeneration. Biocompatibility, biodegradability, biomechanical integrity, and osteoconductivity are important requirements for the scaffold materials. This study explored a new approach of apatite coating to enhance the osteoconductivity of a synthetic degradable poly(DL‐lactic‐co‐glycolic acid) (PLGA) scaffold. The new approach was developed to ensure a relatively uniform apatite coating on the interior pore surfaces deep inside a scaffold, even for a relatively thick scaffold with small pores. Apatite was first coated on the surface of paraffin spheres of the desirable sizes. The paraffin spheres were then molded to form a foam. PLGA/pyridine solution was cast into the interspaces among the paraffin spheres. After the paraffin spheres were dissolved and removed by cyclohexane, PLGA scaffold with controlled pore size, good interconnectivity and high porosity was obtained with apatite left on the pore surface uniformly throughout the whole scaffold. The scaffold and apatite coating were characterized using thermogravimetry analysis, scanning electron microscopy, energy dispersive X‐ray spectroscopy, and X‐ray diffractometry. © 2006 Wiley Periodicals, Inc. J Biomed Mater Res, 2007
Small complete caps inPG(N,q),qeven
Authors: Giulietti Massimo
Published: October 2006

A new family of small complete caps inPG(N,q),qeven, is constructed. Apart from small values of eitherNorq, it provides an improvement on the currently known upper bounds on the size of the smallest complete cap inPG(N,q): forNeven, the leading term$q^{{N}\over{2}}$is replaced by$\alpha q^{{N}\over{2}}$with$\alpha \le {{1}\over{2}}$, forNodd the leading term$3q^{{N-1}\over{2}}$is replaced by$\beta q^{{N-1}\over{2}}$with$\beta \le {{5}\over{2}}$. © 2006 Wiley Periodicals, Inc. J Combin Designs 15: 420–436, 2007
There is no 2‐(22, 8, 4) block design
Authors: Bilous Richard , Lam Clement W. H. , Thiel Larry H. , Li (Ben) P. C. , van Rees G. H. John , Radziszowski Stanisław P. , Holzmann Wolfgang H. , Kharaghani Hadi
Published: October 2006

In this article, we show that a 2‐(22,8,4) design does not exist. This result was obtained by a computer search. © 2006 Wiley Periodicals, Inc. J Combin Designs 15: 262–267, 2007
High‐performance four‐node shell element with piezoelectric coupling for the analysis of smart laminated structures
Authors: Zemčík Robert , Rolfes Raimund , Rose Michael , Teßmer Jan
Published: October 2006

A new four‐node bilinear shell element with full piezoelectric coupling is presented. It can be used for the analysis of light‐weight smart structures (adaptive structures), i.e. laminated composite structures with piezoelectric patches attached to its surface or embedded within the laminated layers. The piezoelectric patches can be both passive (sensors) or active (actuators). The element has been successfully integrated into ANSYS 7.1 and thus can take full advantage of all capabilities of this commercial package, e.g. the connection to electric circuit elements, so far within the scope of linear problems.

The element is a continuum‐based degenerated solid shell element based on the Reissner–Mindlin theory of plates. It uses the modification of the enhanced assumed strain (EAS) theory for the in‐plane strains together with the discrete shear gap method for the transverse shear strains, hence it is free of both membrane locking and shear‐locking in bending. It has six mechanical degrees of freedom at each node without difficulties in the drilling rotations, and up to six voltage degrees of freedom. A special logic has been implemented so as to allow for a natural description of the electric interconnections between the piezoelectric layers.

The element passes the structural patch tests from the standard set of tests proposed by MacNeal and Harder (Finite Element Anal. Design 1985; 1:3–20) including warped geometry problems. The piezoelectric behaviour was verified by comparing it with analytical solutions for plannar and curved geometry. A further validation was made by comparison with experimental measurements of harmonic response of actuated beam having both active and passive piezoelectric patches. A good agreement of the results was achieved. It can be concluded that the combination of the theories used makes this element robust and reliable. Copyright © 2006 John Wiley & Sons, Ltd.
Fabrication of freestanding GaN microstructures using AlN sacrificial layers
Authors: Zaus E. , Hermann M. , Stutzmann M. , Eickhoff M.
Published: October 2006

The fabrication of freestanding GaN microstructures using AlN sacrificial layers (SLs) is reported. GaN layers were grown by plasma assisted molecular beam epitaxy (PAMBE) on polycrystalline AlN sacrificial layers that have been deposited at 600 °C. Isotropic wet chemical etching of the AlN film released GaN microbridges and – cantilevers. The stress gradient and the compressive stress in the GaN‐film was extracted by analysis of the relation between beam geometry and displacement. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cover Picture: Structural Relaxation in Charged Metal Surfaces and Cluster Ions (Small 12/2006)
Authors: Weigend Florian , Evers Ferdinand , Weissmüller Jörg
Published: October 2006

The cover picture shows the contour plot of the difference between the total electronic densities of the dianionic and neutral states of the Au309 cluster, as predicted by density functional theory calculations. The excess charge of the dianion is located almost entirely outside of the outermost atom core positions. Investigations of such species can help the understanding of processes at charged surfaces and interfaces, for example, the forces and atomic relaxation at the interface of a metal electrode and an electrolyte. For more information, please read the Full Paper “Structural Relaxation in Charged Metal Surfaces and Cluster Ions” by J. Weissmüller and co‐workers on page 1497 ff.
Extending the START framework: Computation of optimal capability development portfolios using a decision theory approach
Authors: Elfes A. , Weisbin C. R. , Manvi R. , Adumitroaie V. , Lincoln W. P. , Shelton K.
Published: October 2006

Space program managers and decision‐makers must make strategic investment decisions regarding R&D on technologies, capabilities, missions, and programs, while under a variety of constraints. These constraints include limited budgets, infrastructure, and time restrictions, as well as programmatic and institutional priorities. Acquiring, analyzing, and synthesizing the large amount of information required for a rational decision poses an enormous challenge. To address these challenges, the authors have developed analytical methodologies and computational systems to support strategic decision‐makers within NASA: the START (STrategic Assessment of Risk and Technology) approach, a methodology allowing the quantitative assessment of technologies, capabilities, missions, scenarios and programs in support of human decision‐makers. Supporting the START methodology, new analytical formulations were added, addressing additional decision issues intrinsic to space programs. These include: (1) a utility‐based assessment of capabilities and technologies; (2) modeling dependencies between capabilities and/or between capabilities and programmatic goals; (3) modeling the impact of partial versus complete funding; (4) compute temporally optimal portfolios for staging funding over time; and (5) provide a robustness assessment of the analysis results. We also assess the results, and present sensitivity analysis procedures for validating the START results. We present two case studies; a study conducted for NASA's Aeronautics Research Mission Directorate (ARMD), and an analysis for NASA's Exploration Systems Mission Directorate (ESMD). We conclude with the next steps in the evolution of the START methodology. © 2006 Wiley Periodicals, Inc.*Syst Eng 9:331–357, 2006
Factors affecting egg predation in Black‐tailed Gulls
Authors: Kazama Kentaro
Published: October 2006

In colonial seabirds, nesting density, egg‐laying date and nest microhabitat affect the probability of eggs being taken by avian predators. Jungle Crows (Corvus macrorhynchos) are dominant predators of eggs of Black‐tailed Gulls (Larus crassirostris). Factors affecting the probability of gulls allowing the crows to attack their nests or depredate their eggs and the probability of eggs being taken were studied by direct observation and egg census, respectively. The effect of vegetation heights, position in the colony, egg‐laying date and neighbour nests on the probability of eggs being taken were examined at multiple spatial scales. Gull nests were depredated more easily by larger groups of crows. Nests in peripheral areas (<4 m from the edge of the colony) were also depredated more easily by the crows walking on the ground. Although the nests where eggs were laid early in the season were depredated more frequently, such nests highly synchronised in egg laying within a <2‐m radius were less likely to be depredated than less‐synchronised nests. The nests in tall vegetation were less likely to be depredated though those having neighbour nests in tall vegetation were not. The number of neighbour nests did not affect the probability of eggs being taken. Antipredation effects of nesting microhabitats vary with spatial scales at which the crows search and attack the nests of gulls.
Rise and fall of Kantu: A historical study of an ancient Tibeto-Burmese speaking group
Authors: Ping He
Published: October 2006

On the basis of Chinese records and previous academic achievements in and outside China, the author makes a deeper study on the history of Kantu. As an ancient Tibeto-Burmese speaking group, Kantu was likely to have developed from the Qiongdu (Kontu) of Xinan yi (ancient ethnic groups in southwestern China). During the 12th–13th centuries, the Kantu group resided in an extensive area expanding from the border area between present Sichuan and Yunnan provinces of China to Burma. In the late 13th century, the Yuan troops occupied the area of Kantu. Since then, there have been no more record about Kantu in Chinese annals, and they were likely merged into the groups of “Luoluo” (Lolo). In Burma, most of the Kantu people had been merged into the local peoples, with only a few remaining in remote mountain forests of northern Burma and still keeping their own name and customs. Thus, these people are just the living sources for our studies on ancient Kantu.
Silicic magmas of Protector Shoal, South Sandwich arc: indicators of generation of primitive continental crust in an island arc
Authors: LEAT P. T. , LARTER R. D. , MILLAR I. L.
Published: October 2006

Protector Shoal, the northernmost and most silicic volcano of the South Sandwich arc, erupted dacite–rhyolite pumice in 1962. We report geochemical data for a new suite of samples dredged from the volcano. Geochemically, the dredge and 1962 samples form four distinct magma groups that cannot have been related to each other, and are unlikely to have been related to a single basaltic parent, by fractional crystallization. Instead, the silicic rocks are more likely to have been generated by partial melting of basaltic lower crust within the arc. Trace element and Sr–Nd isotope data indicate that the silicic volcanics have compositions that are more similar to the volcanic arc than the oceanic basement formed at a back-arc spreading centre, and volcanic arc basalts are considered to be the likely source for the silicic magmas. The South Sandwich Islands are one of several intra-oceanic arcs (Tonga–Kermadec, Izu–Bonin) that have: (1) significant amounts of compositionally bimodal mafic–silicic volcanic products and (2) 6.0–6.5 km s−1P-wave velocity layers in their mid-crusts that have been imaged by wide-angle seismic surveys and interpreted as intermediate-silicic plutons. Geochemical and volume considerations indicate that both the silicic volcanics and plutonic layers were generated by partial melting of basaltic arc crust, representing an early stage in the fractionation of oceanic basalt to form continental crust.
Adam Smith and the Theme of Corruption
Authors: Hill Lisa
Published: October 2006

This paper seeks to locate Adam Smith's thought within corruption debates and traditions. The discussion commences by outlining the material and intellectual context within which Smith wrote, after which it disputes claims that Smith may be readily aligned with either a classical or proto-Marxist “corruption and decline” tradition. The remainder of the paper is devoted to exploring in detail how he approached the topic. It is argued that he does not fit easily into any of the recognizable corruption frameworks but that he forges one all his own, borne of his anxieties about the activities of the English state in a rapidly expanding economy and his desire to develop the new science of political economy.
Reading for the Plot? Philip Roth’s The Plot Against America
Authors: Sokoloff Naomi
Published: October 2006

In his study Reading for the Plot, Peter Brooks defines plot as that which “makes us read forward, seeking in the unfolding of narrative a line of intention and a portent of design that hold the promise of progress toward meaning.” Plot proves to be a rich and multifaceted concept to explore in reading Philip Roth’s novel The Plot against America (2004), in which counterfactual histories, personal plotlines, a cluster of subplots, and the reader’s awareness of metanarrative (“masterplot”) all contribute to the complex shaping of the text.
On a wave‐induced turbulence and a wave‐mixed upper ocean layer
Authors: Babanin A. V.
Published: October 2006

A concept of wave‐amplitude‐based Reynolds number is suggested which is hypothesised to indicate a transition from laminarity to turbulence for the wave‐induced motion. If the hypothesis is correct, the wave‐induced motion can be turbulent and the depth of upper ocean mixing due to such wave‐generated turbulence can be predicted based on knowledge of the wave climate. Estimates of the critical wave Reynolds number provide an approximate value of Recr = 3000. This number was tested on mechanically‐generated laboratory waves and was confirmed. Once this number is used for ocean conditions when mixing due to heating and cooling is less important than that due to the waves, quantitative and qualitative characteristics of the ocean's Mixed Layer Depth (MLD) are shown to be predicted with a satisfactory degree of agreement with observations. Testing the hypothesis against other known results in turbulence generation and wave attenuation is also conducted.
Solar dimming and CO2 effects on soil moisture trends
Authors: Robock Alan , Li Haibin
Published: October 2006

Summer soil moisture increased significantly from 1958 to the mid 1990s in Ukraine and Russia. This trend cannot be explained by changes in precipitation and temperature alone. To investigate the possible contribution from solar dimming and upward CO2 trends, we conducted experiments with a sophisticated land surface model. We demonstrate, by imposing a downward trend in incoming shortwave radiation forcing to mimic the observed dimming, that the observed soil moisture pattern can be well reproduced. On the other hand, the effects of upward CO2 trends were relatively small for the study period. Our results suggest tropospheric air pollution plays an important role in land water storage at the regional scale, and needs to be addressed accurately to study the effects of global warming on water resources.
Field imaging spectroscopy: A new methodology to assist the description, interpretation, and archiving of paleoseismological information from faulted exposures
Authors: Ragona Daniel , Minster Bernard , Rockwell Thomas , Jussila Jouni
Published: October 2006

We present a new methodology to acquire, interpret, and store stratigraphic and structural information from paleoseismic exposures. For this study we employed portable hyperspectral cameras to acquire field‐based visible near‐infrared (VNIR) and short‐wave infrared (SWIR) high spatial/spectral resolution images. We first analyzed 400 small sediments cores using a hand‐held, single‐pixel spectrometer (VNIR‐SWIR) to determine the feasibility of the method and to assess its potential problems. We then acquired high‐spatial resolution (submillimeter) spectral data of a large sample (60 × 60 cm) and four cores (7.5 × 60 cm) of faulted sediments from a paleoseismic excavation using portable push broom AISA hyperspectral scanner. These data, which contain 244 (VNIR) and 245 (SWIR) narrow contiguous spectral bands between 400 and 1000 and 960 to 2403 nm, respectively, were processed to obtain the reflectance spectra at each pixel. In this study we are focusing on the analysis of the short‐wave infrared data sets (SWIR). The SWIR data were transformed into relative reflectance and geometrically corrected and processed with well‐known imaging processing algorithms. Selected spectra were then used to create false color composite images that best display the faulted stratigraphy. We compared the hyperspectral images to those recorded by a digital camera as well as directly to the field sample and show that the reflectance properties of the materials in the SWIR region cannot only enhance the visualization of the sedimentary layers and other features that are not obvious to the human eye but can also make visible many detailed features that were not visible in the digital photography. This new data collection and interpretation methodology, herein termed field imaging spectroscopy, makes available, for the first time, a tool to quantitatively analyze paleoseismic and stratigraphic information. In addition, hyperspectral data sets in the visible short‐wave infrared spectral range provide a better alternative for data storage. The reflectance spectra at each pixel of the images provide unbiased compositional information that can be processed in a variety of ways to assist with the interpretation of stratigraphy and structure at a site.
The case for regulating indispensable amino acid metabolism: the branched-chain α-keto acid dehydrogenase kinase-knockout mouse
Authors: Hutson Susan M.
Published: October 2006

BCAAs (branched-chain amino acids) are indispensable (essential) amino acids that are required for body protein synthesis. Indispensable amino acids cannot be synthesized by the body and must be acquired from the diet. The BCAA leucine provides hormone-like signals to tissues such as skeletal muscle, indicating overall nutrient sufficiency. BCAA metabolism provides an important transport system to move nitrogen throughout the body for the synthesis of dispensable (non-essential) amino acids, including the neurotransmitter glutamate in the central nervous system. BCAA metabolism is tightly regulated to maintain levels high enough to support these important functions, but at the same time excesses are prevented via stimulation of irreversible disposal pathways. It is well known from inborn errors of BCAA metabolism that dysregulation of the BCAA catabolic pathways that leads to excess BCAAs and their α-keto acid metabolites results in neural dysfunction. In this issue of Biochemical Journal, Joshi and colleagues have disrupted the murine BDK (branched-chain α-keto acid dehydrogenase kinase) gene. This enzyme serves as the brake on BCAA catabolism. The impaired growth and neurological abnormalities observed in this animal show conclusively the importance of tight regulation of indispensable amino acid metabolism.
Formation of Ohmic contacts: A breakdown mechanism in metal-insulator-metal structures
Authors: Hickmott T. W.
Published: October 2006

The occurrence of low currents in metal-insulator-metal (MIM) structures when high fields are present depends on the presence of a large energy barrier to charge injection at both metal-insulator interfaces. Formation of an Ohmic contact at either metal-insulator interface results in the easy injection of charge carriers into the insulator. The temperature dependence of current-voltage (I-V) characteristics of an Al–Al2O3–Au diode with 23nm of anodically formed Al2O3, after nondestructive dielectric breakdown, is reported. An Ohmic contact forms after initial breakdown as shown by the occurrence of space-charge limited currents, I∝V2, with an effective barrier height of 0.01–0.02eV that is independent of bias. Further breakdown of the MIM sample results in the forming of voltage-controlled negative resistance (VCNR) in the I-V characteristic and the observation of electroluminescence. Elimination of the VCNR conduction regime results in I-V characteristics of a form I∝Vn, where n is temperature dependent and varies between 3.2 and 2.25 as the diode temperature increases from 100to300K. The effective barrier height decreases with bias. All three conduction regimes depend on the presence of an Ohmic contact at both metal-insulator interfaces. The Ohmic contact results from the interaction of the metal electrodes with an impurity band in the insulator.
Ablation of crystalline oxides by infrared femtosecond laser pulses
Authors: Watanabe Fumiya , Cahill David G. , Gundrum Bryan , Averback R. S.
Published: October 2006

We use focused laser pulses with duration of 180fs and wavelength of 800nm to study the interactions of high power near-infrared light with the surfaces of single-crystal transparent oxides (sapphire, LaAlO3, SrTiO3, yttria-stabilized ZrO2, and MgO); the morphologies of the ablation craters are studied by atomic force microscopy and scanning electron microscopy. With the exception of LaAlO3, the high temperature annealing of these oxide crystals produces atomically flat starting surfaces that enable studies of the morphology of ablation craters with subnanometer precision. The threshold fluence for ablation is determined directly from atomic-force microscopy images and increases approximately linearly with the band gap of the oxide. For all oxides except sapphire, the depth of the ablation crater increases approximately as the square root of the difference between the peak laser fluence and the threshold fluence for ablation. Sapphire shows unique behavior: (i) at laser fluences within 1J∕cm2 of the threshold for ablation, the depth of the ablation crater increases gradually instead of abruptly with laser fluence, and (ii) the rms roughness of the ablation crater shows a pronounced minimum of <0.2nm at a laser fluence of 1J∕cm2 above the threshold.