bluuebunny/crossref_metadata_2025 huggingface dataset:
Zeolites and Zeotypes as catalysts
Authors: Corma Avelino , Martinez Agustin
Published: May 2005

Microreactors based on zeolitesand related materials are one of the latest developments in the field which started with the use of crystalline aluminosilicates for catalysis in the 1960s. These crystalline materials are highly thermally and hydrothermally stable, the number and strength of their acid sites can be conrolled, they have a high adsorption capacity, and contain channels of molecular dimensions, properties of interest for a number of applications. The history of the field is traced and a number of new applications of these materials is reviewed.
Thermally stable polymers: Novel aromatic polyamides
Authors: de Ahajo Juvier , de la Campa José G. , Lozano Angel E. , Alvarez Julio C.
Published: May 2005

The solubility, processability, thermal behavior, and even the hydrophilicity of thermally stable aromatic polyamides can be influenced profoundly and relatively easily and inexpensively, by the introduction of bulky pendant groups. Here, the influence of various pendant groups anchored in the 5‐position of the isophthaloyl moiety of polyisophthalomides is assesed.
In situ X‐ray diffraction evidence of guest molecule reorientation during an intercalation reaction
Authors: Evans John S. O. , Barlow Stephen , Wong Heng‐Vee , O'Hare Dermot
Published: May 2005

Superconductivity and co‐operative magnetism are just two of the interesting features of materials based on the intercalation of organic or organometallic moieties into lamellar host lattices. In situ energ dispersive X‐ray diffraction is used here to probe the kinetic and mechanistic details of guest reorientation during intercalation (see Figure).

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Three‐dimensional woven glass fabrics
Authors: Alba Juan J. , Miravete Antonio
Published: May 2005

Textile composites are a class of materials in which reinforcement is provided by textile performs. Owing to their unique combination of light weight, flexibility, strength, and toughness these materials have been used in reinforcement in both structural and other applications. New applications i advanced structural composites using 3‐D braiding (see Figure) are reviewed.

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Electroluminescent porous silicon
Authors: Martínez‐Duart José M. , Parkhutik Vitaly P. , Guerrero‐Lemus Ricardo , Moreno José D.
Published: May 2005

Porous silicon layers with controlled structure and well‐defined surface chemical compositio and the deposition of solid contacts to form electroluminescent devices have recently been reported. The growth and characterization of the layers, several models of the morphology, and the formation processes are discussed, and the use of electrically conductive polymers as the contact materials to porous silicon layers presented.
High temperature superconducting materials
Authors: Alario‐Franco Miguel Angel
Published: May 2005

The perovskite structure (see Figure) is the basis of all known high‐temperature superconducting materials. Many of the most successful (ighest Tc) materials are based on mercury and thallium phases but, due to the high toxicity of the component compoudns effort has been invested in the substitution of these elements with silver. Progress is reviewed.

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Dielectrics for Field Effect Technology
Authors: Balk Pieter
Published: May 2005

The availability of stable MOS gate systems and high density storage capacitors is an essential requirement for the development of the field effect storage technology. For standard MOSFET gates this role has been fulfilled by SiO2grown by thermal oxidation of the Si substrate. Improved insight into the properties of the Si/Si02system and perfection of its growth technology will secure its role in Si MOSFET memories for the future. For charge storage application the stability requirements are less demanding. However, here SiO2is not able to provide sufficient capacity. In this case higher dielectric constant materials (Si3N4or Ta2O5) have to take over. Particularly attractive appears the use of ferroelectrics. These dielectric materials not only offer a high dielectric constant, but also the perspective of providing non‐volatile storage in capacitor structures.
Synthesis of AIPO4‐5 aluminumphosphate molecular sieve crystals for membrane applications by microwave heating**
Authors: Girnus Irina , Pohl Marga‐Martina , Richter‐Mendau Jürgen , Schneider Matthias , Noack Manfred , Venzke Dieter , Caro Jürgen
Published: May 2005

Aluminum phosphate molecular sieves with well‐shaped hexagonal column‐like morpholgoy (see Figure) have been produced by applying microwave heating to a gel. The crystals are effective materials for application in one‐dimensional membranes for molecular sieving. As can be seen in the figure, crystals containing a central tubular void can also be produced

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Polar inclusion compounds of perhydrotriphenylene (phtp) and efficient nonlinear optical molecules**
Authors: Hulliger Jürg , König Olaf , Hoss Ralf
Published: May 2005

Host lattices based on piperazines, which can include a large variety of linear “rod‐shaped” π systems, are presented. One example is the inclusion of efficient nonlinear optical molecules (e.g. see Figure, and the cover picture this month) which leads to materials exhibiting attractive electro‐optical properties

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Tunable electroluminescence and photoluminescence in phenylenevinylene‐naphthylenevinylene copolymers**
Authors: Faraggi Enez Z. , Chayet Haim , Cohen Gil , Neumann Ronny , Avny Yain , Davidov Dan
Published: May 2005

Color tuning of the electro‐ and photoluminescence from naphthalenevinylene–PPV–based light‐emitting diodes between yellow‐green and red is reported. Band structure considerations are employed to explain that chemical selectivity and selective band‐gap tuning are observed in some of the copolymers studied but not in others. It is also found that light emission can be tuned by changing the thickness of the copolymer film in the LED.
Nature and dynamics of radicals in polyaramide as studied by pulsed electron nuclear double resonance**
Authors: Sammet Axel , Hubrich Michael , Maresch Günter , Spiess Hans Wolfgang
Published: May 2005

Chain scission is one of the factors which leads to the failure of high‐performance materials based on main‐chain liquid crystalline polymers. Stable radical species are formed wich can be studied using the ENDOR technique, thus throwing some light on the degradation mechanism, dynamics and kinetics in a range of commercial polymers
Preparation of a flexible polyaniline‐pvc composite
Authors: Conn Costa , Booth Norman , Unsworth Joe
Published: May 2005

An inexpensive, highly conducting polymer‐thermoplastic composite material is reported which is both flexible and possesse a low percolation threshold. The method used to prepare the PANI‐PVC material “see Figure” allows control of the flexibility of the product through the use of commercially available plasticizers

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Luminescence and anti‐aggregative properties of polyoxyethylene‐substituted phthalocyanine complexes
Authors: Simon Jacques , Vacus Joël
Published: May 2005

A water‐soluble phthalocyanine derivative with 16 poly‐oxyethylene side chains which effectively prevent aggregation is reported. The first demonstration of luminescence in a water‐soluble, non‐ionic phthalocyanine in aqueous solution is discussed an important results from the development of effective manomeric dyes for use in phototherapy.
Semi‐interpenetrating polymer networks with temperature‐dependent light transmission—a new smart material for solar technology
Authors: Wilson Helen Rose , Cantow Hans‐Joachim , Eck Wolfgang
Published: May 2005

The protection of solar energy collecting technology against overheating can be achieved using the co‐polymer reported here. In the form of a semi‐interpenetrating polymer network, te co‐polymer demixes when the temperature rises above a certain value “which can be tuned between 30 and 150°C by adjusting the ratio of the repeat units of the components”. In the phase‐separated state the light transmission of the material is reduced significantly by backward light scattering.
Liquid crystals based on 2‐ fluoropyrimidine and ‐pyridine: synthesis, dielectric anisotropy and phase behavior*
Authors: Bremer Matthias
Published: May 2005

Polar liquid crystals with strongly positive dielectric anisotropies are of continuing interest to the display industry because theyhelp to lower both the operating voltage and the total power consumption of LCDs in portable devices. Fluorinated heterocyclic materials “Figure, right, MG = mesogenic group” are shown here to exhibit impoved mesophase properties and higher dielectric and optical anisotropies than commonly used materials used in the purely fluorine substituted moietie

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Wavelength dependance in laser floating zone processing. A case study with bi‐SR‐CA‐CU‐O superconductors*
Authors: de la Fuente German F. , Carlos Diez Juan , Angurel Luis A. , Peña JoséI. , Sotelo Andre , Navarro Rafael
Published: May 2005

Laser floating zone processing methods are particularly suitable for studying crystal growth and the development of texture from the melt in many materials used n electrooptics, for example. A system is descrbed that allows different laser wavelengths to be used, and first results on BSCCO superconducting fibers processed using different lasers are presented. The Figure compares textures produced using Nd:YAG and CO2 lasers

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Push‐pull substituted polythiophenes: towards charge confinement in molecular quantum wells
Authors: Demanze Frederic , Yassar Abderrahim , Garnier Francis
Published: May 2005

Poly(bithiophene) dervatives unsymmetrically substituted with strong electron‐donating groups and strong electron‐withdrawing groups (e.g. see Fig.) have been synthesized. The substituents induce electronic push–pull effects along the conjugated chain which could be exploited in the design of organic‐based multiple quantum well structures

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A polysiloxane‐based photorefractive polymer with high optical gain and diffraction efficiency*
Authors: Zobel O. , Eckl M. , Strohriegl P. , Eckl Martin , Strohriegl Peter , Haarer Dietrich
Published: May 2005

Photorefractive polymers have gret potential in applications such as all‐optical switching and optical communication. Here, new charge‐transporting polymers are presented based on a polysiloxane backbone with pendant carbazole groups, which provide both transport and room‐temperature poling properties without the need for additional plasticizing components. A quantitative evaluation of the phase behavior of holographic gratings based on the new materials is also presented.
Design of a solvatochromic polymer‐based fiber optics chemical sensor for polar solvent detection*
Authors: Fichou Denis , Hubert Christine , Garnier Francis
Published: May 2005

An optical sensor for organic solvents with a detection limit of 10−2 v/v‐% for methanol in mixed hydrocarbons is presented. The system, a fiber optic chemical sensor based on Reichardt's dye covalently bound to an insoluble Merrifield peptide resin (see Fig.), is shown to have a response time of ca. 1 minute

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Effective synthesis of HgBa2Ca2CU308+y, the highest Tc superconductor*
Authors: Peacock Graeme B. , Ganzeson Ian , Zhou Wuzhong , Edwards Peter P. , Slaski Marcin , Zhou Wuzhong , Cooper John R.
Published: May 2005

The preparation of the superconductor Hg‐1223 (see this month's title picture) with 60‐70% phase purity by a simplified route is reported. The material is produced in a single step from air‐stable mono‐oxides and exhibits a sharp superconducting transition, possibly due to the lack of observable defects (see Fig.)

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Polaron migration in doped polysilanes: am i calculations on the radical cation Si17(CH3)36+
Authors: Clark Timothy , Gröppel Mwzfioed , Roth Wolfgang
Published: May 2005

The conductivity of bulk polysilanes is reported to occur via the migration of holes. Since there is considerable σ delocalization along the backbone of polysilanes these materials can be considered as a one‐dimensitonal molecular wire, the backbone being the wire and the alkyl side groups acting as the insulator, Here, quantum mechanical calculations on the polysilane model compound Si17(CH3)36 aimed at elucidation of the electronic properties related to electrical conductance are presented.
Novel ceramic particle synthesis for optical applications: Dispersion polymerized preceramic polymers as size templates for fine ceramic powders
Authors: Beecroft Laura L. , Ober Christopher K.
Published: May 2005

A shape template for small ceramic particles (see figure) is provided by the dispersion polymerization of preceramic polymers. The particle size can be closely controlled through adjusting the reaction conditions, allowing the design of materials for applications as diverse as optical composite materials, catalyst supports, and particulate reinforcement

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Self‐organized phases combined with IDC devices‐switchable materials for solvent vapor detection
Authors: Dickert Franz L. , Keppler Monika
Published: May 2005

A new concept for analyte detection based on the combination of interdigitated capacitor technology with supramolecular structures (see this month's cover picture) is presented. Analyte molecules disturb the hydrogen bonds between pyridone units, and it is this structure‐breaking effect (see figure) which is the basis of the sensor detection

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Bioactive silicon structure fabrication through nanoetching techniques
Authors: Canham Leigh T.
Published: May 2005

A microporous film of silicon is shown to induce hydroxyapatite growth both on itself and on neighboring areas of bulk silicon (e.g. see figure). This indicates that silicon could be developed as an active biomaterial, which has encouraging implications for the use of VLSI technology in, for example, invasive sensing and biosensing and other electronic prosthetic devices

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Polymer Layered Silicate Nanocomposites
Authors: Giannelis Emmanuel P.
Published: May 2005

Polymer nanocomposites with layered silicates as the inorganic phase (reinforcement) are discussed. The materials design and synthesis rely on the ability of layered silicates to intercalate in the galleries between their layers a wide range of monomers and polymers. Special emphasis is placed on a new, versatile and environmentally benign synthesis approach by polymer melt intercalation. In contrast to in‐situ polymerization and solution intercalation, melt intercalation involves mixing the layered silicate with the polymer and heating the mixture above the softening point of the polymer. Compatibility with various polymers is accomplished by derivatizing the silicates with alkyl ammonium cations via an ion exchange reaction. By fine‐tuning the surface characteristics nanodispersion (i. e. intercalation or delamination) can be accomplished. The resulting polymer layered silicate (PLS) nanocomposites exhibit properties dramatically different from their more conventional counterparts. For example, PLS nanocomposites can attain a particular degree of stiffness, strength and barrier properties with far less inorganic content than comparable glass‐ or mineral reinforced polymers and, therefore, they are far lighter in weight. In addition, PLS nanocomposites exhibit significant increase in thermal stability as well as self‐extinguishing characteristics. The combination of improved properties, convenient processing and low cost has already led to a few commercial applications with more currently under development.
A novel thermoset polymer optical fiber
Authors: Flipsen Theo A. C. , Steendam Rob , Pennings Albert J. , Hadziioannou Georges
Published: May 2005

Polymer optical fibers are being investigated with a view to overcoming some of the disadvantages of glass optical fibers in communications applications. Dense cross‐linked polymers, such as the polyisocyanurate discussed here (see figure), have been found to be superior in some respects to the thermoplastic polymers used today. Details are given of the fabrication of a polyisocyanurate network using a rare‐earth complex as a catalyst.

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Regularly interstratified layered silicate heterostructures: Precursors to pillared rectorite‐like intercalates
Authors: Ijdo Wouter L. , Lee Ton , Pinnavaia Thomas J.
Published: May 2005

A fundamental advance in the intercalation chemistry of claysis the formation for the first time of smectite clay heterostructures with regularly stratified organic and inorganic exchange cations, e.g. the fluorohectorite heterostructure with gallery cations Na⊕ and C16H33PBushown in the figure. Their transformation into rectorite‐like alumina pillared analogues is also demonstrated.

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Fast Li⊕ Conducting Ceramic Electrolytes
Authors: Adachi Gin‐ya , Imanaka Nobuhito , Aono Hiromichi
Published: May 2005

The all‐solid, lithium rechargeable battery, which if available would find many applications, is one reason for carrying out research into Li⊕‐conducting solids. Fast Li⊕‐conducting ceramic electrolytes are reviewed with regard to their electrical properties and crystal structure. Both non‐oxide based ceramics and oxide materials are considered, and possibilities for further developments—e.g., the preparation of the electrolyte by thin film techniques—are pointed out.
Fabrication of arrays of channel waveguides by self‐assembly using patterned organic monolayers as templates
Authors: Kim Enoch , Whitesides George M. , Lee Larry K. , Smith Stephen P. , Prentiss Mara
Published: May 2005

Complex arrays of channel waveguides can be easily fabricated by the new approach reported here, which is based on microcontact printing and self‐assembly of solid, three‐dimensional polymeric structures from liquid precursors. It shows that structures produced by the procedure described act as multi‐mode optical waveguides, and suggestions are made for improvements following on from this demonstration of principle. Waveguides are important in communications, photonic sensors, and optical devices.
Decoration of carbon nanotubes
Authors: Ebbesen Thomas W. , Hiura Hidefumi , Bisher Margaret E. , Treacy Michael M. J. , Shreeve‐Keyer Julie L. , Haushalter Robert C.
Published: May 2005

Applications of carbon nanotubes, a unique material, are limited by the relative inertness of the carbon surface. A general method of overcoming this is proposed in which the surface is preoxidized, producing various groups on the surface. These surface groups then act as nucleation points. For example, in the electroless plating reaction the surface of the nanotubes becomes decorated with silver particles (see figure).

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Stabilization of amorphous calcium carbonate by specialized macromolecules in biological and synthetic precipitates
Authors: Aizenberg Joanna , Addadi Lia , Weiner Stephen , Lambert Gretchen
Published: May 2005

Composite structures in which amorphous and crystalline phases coexist are formed by some organisms. The spicules of the sponge Clathrina are shown to be composed of a crystalline calcitic core and an outer layer of amorphous CaCO3 (see figure). The latter material, normally a highly unstable mineral, is stabilized in vitro by macromolecules extracted from the outer sponge spicule layer. The combination of crystalline and stabilized amorphous phases may have important implications for materials applications.

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Evidence for n‐type conduction in a perylene tetracarboxylic diimide derivative
Authors: Horowitz Gilles , Kouki Fayçal , Spearman Peter , Fichou Denis , Nogues Claude , Pan Xavier , Garnier Francis
Published: May 2005

n‐Type—electron transporting—conduction is demonstrated for Schottky diodes and field effect transistors based on N,N′‐diphenyl‐3,4,9,10‐perylenetetracarboxylic‐dimide. The role of the electron‐injecting electrode is discussed, as are the potential improvements in performance offered by devices combining a p‐type semiconducting layer with an n‐type, electron transporting organic compound.
Transition Metal Based Ionic Mesogens
Authors: Neve Francesco
Published: May 2005

Can ionic liquid crystalline metal complexes match the structural variety of electrically neutral molecular and macromolecular related species? Recent progress made in structural design aimed at the formation of ionic materials with anisotropic physical properties—such as the cyclometallated ionic mesogen shown in the figure—is reviewed.

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Layered and pillared metal(IV) phosphates and phosphonates
Authors: Alberti Giulio , Casciola Mario , Costantino Umberto , Vivani Riccardo
Published: May 2005

Proton conductors, catalysts, and solar energy storage materials are some of the potential uses of various crystalline acid salts of tetravalent metals. Results obtained on a large number of metal(IV) phosphates and phosphonates are reviewed, the α‐ and β‐structured layered metal(IV) phosphates and the organic derivatives of zirconium phosphates being emphasized. Methods of preparation and the structures determined—especially layered and pillared—are described.
Optical characterization of amorphous dielectric films
Authors: Sassella Adele
Published: May 2005

Dielectric thin films find technological applications in microelectronics and optoelectronics, for example, which makes it important to be able to characterize their electrical and optical properties easily. Two techniques available for the optical characterization—transmittance measurements and spectroscopic ellipsometry—are considered here and examples presented for the characterization of silicon oxide, nitride, and oxynitride films in the IR and UV‐vis regions by these methods.
Transport properties of refractory and ceramic superconducting materials
Authors: Vaglio Ruggero , Fontana Fabrizio , Iavarone Maria
Published: May 2005

The transport properties of high‐Tc ceramic superconductors and refractory materials are of particular interest in view of potential future applications. After recently developing a technique to deposit thin films of ceramic superconductors and refractory materials, researchers in Naples have investigated their fundamental physical properties using various types of experiments, focusing on the transport properties. Recent results are reviewed.
The CNRS and materials science policy in France
Authors: Beck Gérard
Published: May 2005

An interdisciplinary program for materials science in France was established by the CNRS—the body responsible for basic scientific research—in 1982. The unity and coherence of materials science policy and the need to break down the barriers between traditional subjects were emphasized in 1994, when DIMAT, the interdepartmental delegation for materials science, was set up. Gérard Beck, who heads DIMAT, describes its aims, how it works, and its relationship with the CNRS.
Regeneration, derivatization and utilization of cellulose in ultrathin films
Authors: Wegner Gerhard , Buchholz Vera , Ödberg Lars , Stemme Sara
Published: May 2005

Cellulose films obtained from TISC Langmuir–Blodgett films provide a model system for adsorption studies of dyes and polyelectrolytes. The conversion of multilayers of trimethylsilylcellulose (TMSC), a “hairy‐rod” molecule with short hydrophobic TMS side groups, into ultrathin cellulose films, the derivatization of these films with succinic anhydride, and the use of regenerated and modified cellulose films for adsorption studies are reported with the aim of finding ways of changing the chemical properties of cellulose films.
Second harmonic generation in ferroelectric liquid crystal mixtures
Authors: Ortega Josu , Folcia César Luis , Etxebarría Jesús , Artal M. Carmen , Ros M. Blanca , Serrano José Luis
Published: May 2005

The concentration dependence of the second harmonic generation efficiency has been analyzed in binary mixtures containing a ferroelectric liquid crystal material (W313) with high spontaneous polarization and an achiral host. It has been found that the effective nonlinear coefficient is not, in general, proportional to the mixture mole fraction, although it is linearly correlated to the spontaneous polarization. Far from the transition to the chiral smectic C phase, both quantities display te same temperature dependence.
Nanocrystal gold molecules
Authors: Whetten Robert L. , Khoury Joseph T. , Alvarez Marcos M. , Murthy Srihari , Vezmar Igor , Wang Z. L. , Stephens Peter W. , Cleveland Charles L. , Luedtke W. D. , Landman Uzi
Published: May 2005

Gold nanocrystals passivated by self‐assembled monolayers of straightchain alkylhiolate molecules have been obtained as highly purified molecular materials of high intrinsic stability. Evidence is presented for a predicted discrete sequence of energetically optimal fcc structures of a truncated octahedral morphological motif (see cover). The nanocrystal materials have a propensity to form extended superlattics, such as that in the Figure.

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On void fraction and the nature of porous solids
Authors: Garcés Juan M.
Published: May 2005

A new unified model of nanoporous materials, based on a relationship between void fraction and structure, is introduced. The reduction of the complex pore system to a single void and the dense framework components t a single dense shell is shown to help in revealing the system of organization determining the structures of materials such as zeolites, clay minerals, layered compounds, and bioinorganic solids. Examples are given that demonstrate the use of the model as a predictive tool and provide insights into previously unsolved problems.
Non‐carbon nanotubes
Authors: Zettl Alex
Published: May 2005

Nanotube formation is not limited to carbon, and in fact seems to be a general feature of layered materials. The classes of new nanotubes that have been synthesized, e.g., boron‐nitride‐containing compounds and transition‐metal dichalcogenides, are briefly reviewed. Theoretical predictions, such as the type II BC2N nanocoil, the smallest possible solenoid, point to enticing research and application opportunities, for example miniature transformers and magnetic storage or on‐nanotube devices (pn junctions, etc.).
Molecular recognition by self‐assembled monolayers detected with surface plasmon resonance
Authors: Huisman Bart‐Hendrik , Kooyman Rob P. H. , van Veggel Frank C. J. M. , Reinhoudt David N.
Published: May 2005

Self‐assembled monolayers containing cavitand recognition sites have been used for the first time as an interface for vapor detection using surface plasmon resonance (SPR). Fast response times (t90% < 1 s) and high sensitivity for tetrachloroethylene over other chlorinated hydrocarbons were measured with a monolayer of the resorcin[4]arene cavitand adsorbate shown in the Figure.

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New twin liquid crystalline diazole derivatives
Authors: Sato Moriyuki , Ujiie Seiji
Published: May 2005

Twin liquid crystalline diazole derivatives are expected to have a higher potential for liquid crystal (LC) formation than the corresponding non‐twin derivatives. The preparation of twin 1,3,4‐thiadiazole and 1,3,4‐oxadiazole derivatives is described and the investigation of their LC properties reported. A characteristic nematic schlieren texture of one of the oxadiazoles is shown in the Figure.

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Surface modification and patterning of conjugated polymers with near‐field optical microscopy
Authors: Wei P. K. , Hsu J. H. , Hsieh B. R. , Fann W. S.
Published: May 2005

Near‐field scanning optical microscopy (NSOM) has been used to write and read images on a conjugated polymer film—such as that in the Figure–with a resolution of ∼ 0.1 μm, clearly breaking the diffraction limit. It is demonstrated that photo‐oxidation processes produce the contrast and that NSOM has the potential to control the photochemistry of a conjugated polymer at the nanometer scale.

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Electroactive films with a polyrotaxane organic backbone
Authors: Kern Jean‐Marc , Sauvage Jean‐Pierre , Bidan Gérard , Billon Martial , Divisia‐Blohorn Bernadette
Published: May 2005

Polyrotaxane‐like structures consisting of macrocycles trapped to form a polymeric network (see Figure) have been synthesized using a pre‐assembling principle. The synthesis and electrochemical characterization of thin films are described. In addition to the classical properties of organic conducting polymers, the assemblies exhibit very specific properties arising from the coordinating macrocycles sliding between the nodes of the network.

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Efficient blue light emitting devices based on rigid‐rod polyelectrolytes
Authors: Cimrová Vera , Schmidt Wolfgang , Rulkens Rudy , Schulze Margit , Meyer Wolfgang , Neher Dieter
Published: May 2005

Blue light emitting devices based on a rigid‐rod polyelectrolyte–sulfonated poly(p‐phenylene), see Figure–that has both luminescent and ionic moieties have been prepared and their properties investigated. It is reported that the devices exhibited a low onset voltage (3.3 V), the external quantum efficiencies reached 0.8%, and the size of the counter ion had a pronounced influence on the electrical characteristics.

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Amorphous silica molecular sieving membranes by sol‐gel processing
Authors: Cao Guozhong , Lu Yunfeng , Delattre Laurent , Brinker C. Jeffrey , López Gabriel P.
Published: May 2005

Microporous ceramics and ceramic membranes have many potential applications, for example, in the chemical, environmental, energy conversion, and automotive industries. An organic template approach using sol‐gel processing is described by which microporous amorphous silica is synthesized. It is shown that the very narrow pore size distribution is comparable to that of the zeolite ZSM‐5 and that the membranes have ideal gas separation factors at least two orders of magnitude larger than those expected for a Knudsen diffusion separation mechanism.
Self‐assembly of an acentric co‐crystal of a highly hyperpolarizable merocyanine dye with optimized alignment for nonlinear optics
Authors: Bosshard Christian , Wong Man Shing , Pan Feng , Günter Peter , Gramlich Volker
Published: May 2005

Non‐centrosymmetric arrangement of the chromophores is a prerequisite for non‐vanishing macroscopic second‐order nonlinear optical responses. It is shown that an acentric packing of a highly polarizable merocyanine dye, with optimized orientation for frequency conversions, can be induced by hydrogen‐bond‐directed self‐assembly with appropriate phenolic derivatives. The highly polar co‐crystal is demonstrated to have potential for both second‐ and third‐order nonlinear optics applications owing to its large nonlinear response and favorable crystal properties.
A schottky barrier junction based on nanometer‐scale interpenetrating GaP/Gold networks
Authors: Vanmaekelbergh Daniel , Koster Alfred , Marín Francisco Iranzo
Published: May 2005

An interpenetrating GaP and gold nanometer‐scale network system has been formed by electrochemical deposition of the metal on a nanoporous n‐type semiconductor GaP network. The electrical characteristics of the system–in particular capacitance and current–voltage measurements–indicate that a semiconductor/metal Schottky barrier junction with a huge internal contact area is produced, which could find applications in solid‐state electronic devices.
Nanometer‐size Cu clusters formed by reversible deintercalation on layered chalcogenides with scanning probe techniques
Authors: Jaegermann Wolfram , Jiang Lei , Iyoda Tomakazu , Tomm Yvonnne , Pettenkofer Christian , Hashimoto Kazuhito , Fujishima Akira
Published: May 2005

Modification of surfaces by scanning probe techniques is the key to future nanotechnologies. In the novel approach described here, the reversible deintercalation of Cu from (0001) surfaces of 1T TaSe2 by means of the atomic force microscope can produce large Cu clusters, such as that in the Figure, that can be reintercalated. A mechanism is proposed for the intercalation and tip‐induced deintercalation.

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Growth of silicalite films on pre‐assembled layers of nanoscale seed crystals on piezoelectric chemical sensors
Authors: Bein Thomas , Mo Shangyi , Mintova Svetlana , Valtchev Valentin , Schoeman Brian , Sterte Johan
Published: May 2005

Zeolite‐modified quartz crystal microbalances are demonstrated to have excellent characteristics as chemical sensors. The Figure illustrates the synthetic strategy used to form the zeolite film on the electrode: the gold electrode (left) is covered with a partially crosslinked surface of siloxy groups, to which a cationic polymer is attached. The colloidal silicalite‐1 crystals (blocks) act as seeds for the growth of an oriented silicalite layer.

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Thermally responsive rigid polymer monoliths
Authors: Peters Eric C. , Svec Frantisek , Fréchet Jean M. J.
Published: May 2005

A composite that changes its permeability with temperature–leading to the possibilites of a thermal gate, thermal valve, or thermal cotnrol of hydrophobicity/hydrophilicity–is reported. A method is described to modify the internal pore surface of rigid polymer moonoliths by grafting‐on PNIPAAm, a temperature‐responsive polymer. Isocratic hydrrophobic interaction chromatography of proteins is presented, which is a novel separation technique based on the changes in surface polarity (and thus adsorption) accompanying the temperature‐induced phase transition of the grafted PNIPAAm.
Self‐Propagating High Temperature Synthesis of Hexagonal Ferrites MFe12O19 (M = Sr, Ba)
Authors: Parkin Ivan P. , Elwin Gareth , Barquin Luis Fernández , Bui Quang T. , Pankhurst Quentin A. , Komarov Alexei V. , Morozov Yuri G.
Published: May 2005

Hexagonal ferrites, materials widely used for permanent bard magnets, are currently commercially synthesized by multistep ceramic methods. Alternative routes are also multistep as well as being time‐consuming and expensive. Teh self‐propagating, high‐temperature synthesis (SHS) presented here is convenient, quick, inexpensive, and single‐step and it enables a range of ferrites, SrxBayFe12O19 (x + y equals; 1), to be prepared. The principles of SHS are briefly explained before the characterization of the reaction products, including their magnetic properties, is described.
Effect of surface fractality on the permeability of transparent gas barrier coatings
Authors: Garcfa‐Ayuso Gema , Salvarezza Roberto , Martinez‐Duart Jos Ea M. , Sánchez Olga , Vázquez Luis
Published: May 2005

The permeability of inorganic barrier coatings on polymers is important in applications in the flexible packaging industry, for exmaple. Relationships are reported between the film surface nanostructure, in particular the film pore surface fractality, and the permeability of water and oxygen molecules through different SiO2–Al2O3 films. Following a brief out‐line of the various contributions to transport of gases through a porous solid, it is shown that water undergoes surface‐mediated permeation, the permeability thus varying with the surface fractal dimension D, while oxygen does not.
Euroscience: Linking science and society
Authors: Praderie Françoise
Published: May 2005

An Association for the Advancement of Science for Europe? In March this year at a meeting in Strasbourg, France, attended by about 150 people, Euroscience, a Europe‐wide association open to all those interested in science and technology—and particularly their role in society—came into being. Dr. Praderie, General Secretary of Euroscience, outlines the objectives and aims of the association, current and proposed activities, and longer term prospects. An invitation to join is extended to all readers.
Effect of the anion on the level and aging of the conducting state of electropolymerized 3‐methylthiophene thin films
Authors: Fuvre Catherine , Abello Louis , Delubouglise Didier
Published: May 2005

The unique character of the triffimide anion has been revealed in a study of how the doping anion affects the properties of conducting polymer thin films using poly(3‐methylthiophene) doped with triflimide ((CF3SO2)2N⊖), perchlorate (CIO⊖). Variations in film morphology, conductivity, and the time dependence of the conductivity are described. Particularly noticeable are the differences in surface de‐doping, which lasts of up the one month in the trifflimide‐doped films.
Transparent flexible organic light‐emitting devices
Authors: Gu Gong , Shen Zilan , Burrows Paul E. , Forrest S. R.
Published: May 2005

Ultra‐lightweight, portable, roll‐up, full‐color flat panel displays move into the realm of the possible with the demonstration of transparent, flexible organic light‐emitting devices (T‐FOLEDs). The emission properties of the T‐FOLEDs and the effect of flexing are reported. The Figure shows a T‐FOLED after repeated bending—cracks appear when a 7 mm radius of curvature is reached.

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Silver nanocluster formation in silica coatings by the sol‐gel route
Authors: Armelao Lidia , Bertoncello Renzo , De Dominicis Mattia
Published: May 2005

The sol‐gel synthesis of silver‐nanocluster‐doped silica coatings is described, which leads to samples containing only silver cations. Subsequent thermal treatments cause these to evolve into metal silver particles with spherical shape, narrow size distribution, and homogeneous dispersion. It is shown that the size, distribution, and stability of the silver clusters can be controlled by the choice of precursor compounds and subsequent thermal treatments. A hypothesis is put forward to explain the cluster formation and observed heat‐dependent color change.
Stability of molded polydimethylsiloxane microstructures
Authors: Delamarche Emmanuel , Schmid Heinz , Michel Bruno , Biebuyck Hans
Published: May 2005

How stable are the features in elastomeric stamps—as used in microcontact printing (μCP) and micromolding in capillaries (MIMIC)—during their formation and subsequent application? Their stability is examined with respect to aspect ration and forces during handling. In the Figure, lines in the structure (gold on silicon), produced using an elastomeric stamp, can be seen to have merged into larger ensembles.

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MyoD and myogenin are coexpressed in regenerating skeletal muscle of the mouse
Authors: Füchtbauer Ernst‐Martin , Westphal Heiner
Published: May 2005

The differential expression of genes triggering myogenesis might cause or reflect differences among myoblasts. Little is known about the presence of MyoD1 and myogenin during the process of regeneration. We therefore examined the expression of MyoD1 and myogenin in muscle regeneration after grafting. Immunostaining of regenerating skeletal muscle of the mouse revealed the presence of both MyoD1 and myogenin. In mononucleated cells the proteins were not detected until shortly before fusion into myotubes. They persisted in the nuclei of regenerated muscle fibers for at least 2 weeks. MyoD1 and myogenin were not detected in nonregenerating control muscle.
Expression of testis‐specific histone genes during the development of rat spermatogenic cells in vitro
Authors: Smith Frank F. , Tres Laura L. , Kierszenbaum Abraham L.
Published: May 2005

We have used two radiolabeled oligonucleotide probes (TH2B and H1t), Northern blotting, two‐dimensional gel electrophoresis, and autoradiography to study the temporal expression of TH2B and H1t testis‐specific histone genes during the development of rat spermatogenic cells in vitro. These studies were carried out to determine whether meiotic prophase spermatocytes, known to synthesize in vivo TH2B and H1t histones among other histones, are capable of expressing these testis‐specific genes in vitro during an extended period of time. We have found abundant TH2B and H1t mRNA steady state levels as well as newly‐synthesized TH2B and H1t histones after 5 days of coculture. Northern blots reprobed with H1t‐specific oligonucleotide showed that H1t mRNA remained prominent when TH2B mRNA started to decline after 8–12 days of coculture. Phase‐contrast and transmission electron microscopy studies carried out throughout the course of the experiments demonstrated that the number of viable spermatogonia and meiotic prophase spermatocytes was relatively constant during 12 days of coculture. Spermatocytes, in a clone‐like arrangement, remained attached to Sertoli cell surfaces and displayed subcellular features consistent with those observed in the intact seminiferous epithelium. Spermatogonia formed long, branching chains of interconnected cells. Results of this study indicate that spermatogenic cells in coculture with Sertoli cells express testis‐specific histone genes for an extended period of time. Testis‐specific histone gene expression in vitro should facilitate further studies for understanding the role of these histones in chromatin structure, transcription, and genetic recombination during male meiotic prophase.
Deciduous dental morphology and the biological affinities of a late Chalcolithic skeletal series from western India
Authors: Lukacs John R. , Walimbe Subhash R.
Published: May 2005

Morphological variations of the dental crown and roots provide valuable data for determining the genetic affinities and evolutionary adaptedness of prehistoric human skeletal populations. This paper documents morphological variations of a sample of deciduous teeth from the late Chalcolithic farming village of Inamgaon (1600–700 B.C.) in western India.

Hanihara's (1963) grading system of deciduous dental traits was employed in assessing the degree of expression of shovel‐shape of incisors, cusp number of upper and lower first molars, hypocone variation, Carabelli's trait, cusp number of lower second molars and the protostylid. Turner's (1970) classification was used to determine presence and size of accessory cusps: entoconulid (C‐6) and metaconulid (C‐7).

Comparative evaluation of the Inamgaon deciduous dental data is hampered by the absence of data for dental features of living and prehistoric South Asian populations. Many of the traits observed in the Inamgaon series exhibit a frequency of occurrence intermediate between figures characteristic of the “Mongoloid” dental complex and the “Caucasoid” dental complex.
Cytophysiological studies on isolated pancreatic islets in vitro
Authors: Slavin Bernard G. , Beigelman Paul M. , Bessman Samuel P.
Published: May 2005

Single, isolated pancreatic islets of mice and rats were incubated for varying time intervals (0.5‐60) minutes with high (300 mg%) and low (50 mg%) levels of glucose. The structural integrity of islets decreased progressively with time regardless of glucose concentration. Degeneration of islets was greatest after 60 minutes of incubation. The total amount of insulin released from cytologically intact mouse islets incubated with high glucose levels was always greater than that with low glucose except following 30 seconds of incubation when no difference was observed. Peaks of insulin secretion noted after 2 and 15 minutes of incubation were correlated with light microscopic and fine structural changes indicative of active secretion in β‐cells, i.e., degranulation, granule margination. At 5 and 30 minutes of incubation many β‐cells contained enlarged Golgi zones and abundant profiles of swollen rough endoplasmic reticulum containing pale, amorphous granular material presumably indicating insulin synthesis. Emphasis is placed on the desirability of correlating physiological and biochemical studies of isolated pancreatic islets with cytologic examination.
Morphology and histochemistry of the mandibular gland of the australian brush‐tail possum Trichosurus vulpecula (Marsupialia)
Authors: Blood Louise A. , Kennerson Alan R. , Van Lennep Ernest W.
Published: May 2005

A histological, ultrastructural and histochemical study of the mandibular gland of the Australian possum Trichosurus vulpecula revealed essentially similar features as those described earlier for the mandibular gland of the taxonomically relatively unrelated American opossum Didelphis. The secretory endpieces consist of a branched tubular part, composed of serous cells whose secretion granules contain neutral glycoproteins, and terminal acini, consisting of seromucous cells containing small amounts of sialomucins. Relatively short intercalated ducts lead to striated ducts of variable ultrastructural appearance. The striated ducts run in bundles in the center of each sublobule of the gland. The possible functional significance of the abundance and variability in ultrastructure of the striated ducts is discussed.
The anionic charge barrier in the renal corpuscle of the pronephros in the lamprey, Petromyzon marinus L.
Authors: Ellis L. C. , Youson J. H.
Published: May 2005

The charge barrier within the renal corpuscle of the pronephric kidney of the lamprey, Petromyzon marinus, was investigated at two life cycle intervals using cationized ferritin and polythyleneimine. In the larval renal corpuscle the endothelium of the glomerular capillaries and the laminae rarae externa and interna of the glomerular basement membrane show regularly‐spaced deposits of the tracers. The lamina densa remains unstained. Concmitant with a loss of major processes of the visceral epithelial podocytes and development of an extensive mesangial matrix in late adult life are alterations in the distribution of the anionic sites. The lamina rara interna is no longer a distinct entity and the mesangium contains irregularly‐distributed anionic sites surrounding electron‐dense deposits. The results indicate that the distribution of the anionic sites during adult life most likely affects the ability of the renal corpuscle to act as an efficient filtration device. This charge distribution is consistent with that seen during some renal pathologies of higher vertebrates.
Application of stereological analysis of cell volume to isolated myocytes in culture with and without adrenergic innervation
Authors: Atkins Dianne L. , Rosenthal Jane K. , Krumm Penny A. , Marvin William J.
Published: May 2005

A three‐dimensional analysis to evaluate structural changes in cultured cardiac myocytes following adrenergic innervation was performed using stereological techniques formerly limited to cells in tissue and organs. Cell volumes were calculated for two groups of cells at 96 hours in culture: isolated myocytes and myocytes innervated with adrenergic neurons. Relative and absolute volumes of the nucleus, cytoplasm, and cell were quantified by systematically sampling sections throughout the cell and by point count sampling techniques. Volumetric estimates were similarly determined for the mitochondria, sarcomeres, and other cellular components in the cytoplasm. Data were analyzed with ANOVA and randomized block design to control for variation among the cultures. Adrenergic innervation produced a 44% increase in cell volume, X±SEM, (3,344±196 μm3 to 4,816±400 μm3, P = 0.007). The absolute volume of mitochondria significantly increased after innervation (521±42 μm3 to 744 ± 54 μm3, P<0.01). Absolute sarcomere volume did not change significantly (750 ± 92 μm3 to 642 ± 1061 μm3, P = 0.14). Other cellular components, defined as all cytoplasmic components except mitochondria and sarcomeres, significantly increased with innervation (1,739 ± 166 μm3 to 3,097 ± 338 μm3, P = 0.02). The relative volume of the nucleus and the cytoplasm in the cell remained unchanged following innervation. However, the relative volume of mitochondria decreased by 6%, the percent of the cytoplasm occupied by the sarcomeres decreased by 44%, and the volume occupied by the other cellular components increased by 22%. These findings support the use of stereological analysis as a means to quantify cell volumes of cultured myocytes. Significant increases in cell size, as well as changes in intracellular composition, accompany in vitro adrenergic innervation in the developing cardiac myocyte.