bluuebunny/crossref_metadata_2025 huggingface dataset:
E-Cadherin, CD44 and CD44v6 in Squamous Intraepithelial Lesions and Invasive Carcinomas of the Uterine Cervix: An Immunohistochemical Study
Authors: Faleiro-Rodrigues C. , Lopes C.
Published: December 2004

Objective: To evaluate the immunoexpression pattern of E-cadherin, CD44std and the variant isoform v6 in normal squamous epithelium, low and high squamous intraepithelial lesions (SILs) and invasive squamous cell carcinomas (ISCCs) of the uterine cervix. The purpose was to determine whether any distinctive change in antigenic expression could contribute to the recognition of the earliest commitment to neoplasia and/or the onset of the invasive phenotype. Methods: Immunohistochemistry using the avidin-biotin indirect immunoperoxidase method was used to study the protein expression of epithelial cadherin (E-cadherin), cluster differentiation 44 (CD44), and the isoform v6 (CD44v6) in 124 human cervical samples (5 normal, 39 low-grade, 54 high-grade and 26 ISCCS) in formalin-fixed, paraffin-embedded tissue blocks. Results: Membranous expression of E-cadherin, CD44 and CD44v6 was preserved in normal squamous epithelium and in low-grade squamous intraepithelial lesions. A significant association was observed with the histological grade of the SILs and the immunoreactivity (membranous versus cytoplasmic) pattern of E-cadherin (p < 0.001), CD44std (p = 0.027) and CD44v6 (p < 0.001). A loss of membranous staining and a progressive increase in cytoplasmic staining was observed from low to high grade SILs to ISCCs. Conclusions: Our study demonstrates that during the development of cervical lesions substantial qualitative (subcellular localization-membrane to cytoplasmic) and quantitative alterations (changes in expression) occur in the protein expression of E-cadherin, CD44, and CD44v6 in cervical cancer. The most striking observation was the decrease in membranous immunoreactivity and the progressive increase in cytoplasmic staining of E-cadherin, CD44 and CD44v6, relating to loss of differentiation as a consequence of neoplastic transformation.
Determination of the Aqueous Humor Volume by Three-Dimensional Mapping of the Anterior Chamber
Authors: Behndig Anders , Markström Klas
Published: December 2004

In this study involving 12 patients planned for routine cataract surgery, we used the topography of the anterior chamber depth and the corneal diameter obtained from Orbscan II® data to calculate the aqueous humor volume. Prior to the surgical procedure, a small amount of fluorescein was injected into the anterior chamber and an aqueous humor sample was taken, from which the aqueous humor volume could be calculated by fluorometry. The volumes obtained from Orbscan IIdata were validated by the fluorometric measurements and compared to three theoretical formulas for aqueous humor volume calculation. The aqueous humor volume calculations based on the Orbscan IIdata aligned better to the fluorometric values (R2 = 0.890) than the values obtained by Heim’s formula (R2 = 0.677), Brubaker’s formula (R2 = 0.671), and Schenker’s formula (R2 = 0.585), or the assumption of a constant aqueous humor volume.
Oral Adsorbent Prevents Reduction of Anionic Sites of the Glomerular Basement Membrane in Diabetic Nephropathy
Authors: Okada Kazuyoshi , Matsumoto Koichi , Takahashi Susumu
Published: December 2004

Background: AST-120, an oral adsorbent, inhibits progression of diabetic nephropathy by reducing albuminuria. The purpose of the present study was to explore the mechanism underlying the protective effect of AST-120 against albuminuria. Methods: Twenty-four male Sprague-Dawley rats underwent intravenous injection of streptozotocin and subsequent uninephrectomy. Half of the rats were fed standard rat chow, and the other half were fed rat chow containing AST-120. All rats were killed at week 6 after a clearance study. Results: There were no significant differences in body weight, kidney weight, urinary volume, blood pressure, blood glucose or inulin clearance between the two groups at week 6. However, urinary albumin excretion at week 6 was significantly lower in the AST-120 group than in the control group (p < 0.05). Light microscopic observation showed that the planar area of glomeruli was significantly smaller in the AST-120 group than in the control group (p < 0.01), and the shortest diameter of proximal tubules was less in the AST-120 group than in the control group (p < 0.01). Electron microscopic observation showed a significantly greater number of anionic sites on the lamina rara externa of the glomerular basement membrane in the AST-120 group than in the control group (p < 0.01). Conclusion: We conclude that AST-120 reduces albuminuria by preventing the decrease in the number of anionic sites in the glomerular basement membrane in rats with diabetic nephropathy. In addition, AST-120 inhibits the appearance of glomerular and tubular hypertrophy.
Aggravation of Focal Cerebral Ischemia by Tissue Plasminogen Activator Is Reversed by 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase Inhibitor but Does Not Depend on Endothelial NO Synthase
Authors: Kilic Ertugrul , Kilic Ülkan , Matter Christian M. , Lüscher Thomas F. , Bassetti Claudio L. , Hermann Dirk M.
Published: December 2004

Background and Purpose—

It has repeatedly been reported that the thrombolytic tissue plasminogen activator (tPA) may aggravate ischemic injury after stroke. The underlying mechanisms, however, remain unknown. We hypothesized that tPA induces an inhibition of endothelial NO synthase (eNOS) after focal ischemia that is responsible for ischemic damage and may be restored by 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors.

Methods—

We examined the effects of tPA, administered either alone or in combination with rosuvastatin, on ischemic injury, on eNOS expression, and cell signaling after 90 minutes of intraluminal middle cerebral artery occlusion.

Results—

In wild-type mice, tPA delivered immediately after ischemia significantly increased infarct volume 24 hours after reperfusion. Coadministration of rosuvastatin completely reversed the tPA-induced brain damage. Western blots of ischemic brain lysates showed that tPA markedly diminished eNOS levels, increased extracellular regulated kinase (ERK)-2, and decreased MAP kinase/p38 activity. Cotreatment with rosuvastatin prevented the decrease in eNOS, reduced ERK-1/-2 and normalized p38 levels. To elucidate the role of eNOS in tPA-induced ischemic injury, we also evaluated tPA effects in eNOS knockout mice. In eNOS knockout animals, tPA again significantly increased infarct size after transient focal ischemia.

Conclusions—

In a mouse model of focal cerebral ischemia, tPA induces eNOS inhibition, ERK-2 activation, and p38 inhibition, possibly as part of a more complex signaling response exacerbating brain injury. 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibition reverses the effects of tPA by a mechanism independent of eNOS.
Soluble Oligo‐ and Polyphenylenes
Authors: Tour James M.
Published: December 2004

Soluble main chain phenylene polymers and oligomers are much less well studied than their intractable relative poly(p‐Phenylene). This review considers the synthesis and properties of poly(o‐phenylene)s, poly(m‐phenylene)s, and substituted polyphenylenes with alkyle‐, aryl‐, carbonyle‐, nitro‐, halo‐, fused aromatic, and ladder containing substituents, together with related compounds. The figure shows a planar polyphenylene derivative that can be obtained as a flexible free‐standing film.

magnified image
Fluorescence and excited‐state structure of conjugated polymers
Authors: Soos Zoltán G. , Galvão Douglas S. , Etemad Shahab
Published: December 2004

The electronic structure of conjugated polymers can be understood to a certain extent by applying the Pariser‐Parr‐Pople model for interacting π‐electrons in conjugated molecules. In this review, particular emphasis is laid on spectroscopic and theoretical studies of conjugated polymers in which different types are compared. The electroluminescence behavior is of special interest. The nature of the lowest singlet excitation is found to determine whether, in general, the flourescence is stron or weak.
Nonplanar bis(1,3‐dithiole) donors affording novel cation radical salts
Authors: Yamashita Yoshiro , Ono Katsuhiko , Tanaka Shoji , Imaeda Kenichi , Inokuchi Hiroo
Published: December 2004

A nonplanar molecule that forms stable ion radical salts is reported, demonstrating that planar molecules are not a prerequisite for the preparation of organic conductors. The results of cyclic voltammetry and X‐ray structural analysis are presented for stable single crystals of the cation radical salt of the dibenzo derivative of 4,9‐bis(1,3,‐dithio‐2‐ylidene)‐4,9‐dihydronaphtho[2,3‐c][1,2,5]thiadiazole. This is the first stable cation radical salt to have been succesfully obtained from a nonplanar molecule.
BiSrCaCuO High‐Tc Superconductors
Authors: Majewski Peter
Published: December 2004

High‐Tc superconductivity in the Bi‐Sr‐Ca‐Cu Osystem was discovered six years ago. Since then the superconducting compounds have been indentified and their structures, crystal chemistry, phase equilibria, and properties investigated extensively. Recent results of studies of the crystal chemistry and phase equilibria of these challenging materials are presented and discussed. Possible areas for future work, where knowledge is lacking or measurements are contradictory, are pointed out.
Green Electroluminescence in Poly‐(3‐cyclohexylthiophene) light‐emitting diodes
Authors: Berggren Magnus , Gustafsson Göran , Inganäs Olle , Andersson Mats R. , Wennerström Olof , Hjertberg Thomas
Published: December 2004

Electoluminescent devices based on polythiophene‐system this films have been demonstrated that together span the entire visible range, steric hindrance being used to vary the bandgap between compunds. Poly‐(3‐cyclohexylthiophene), see Figures, exhibits green electoluminescence. Possible interpretations of this observation are proposed.

magnified image
Novel Ultrahard Materials
Authors: Riedel Ralf
Published: December 2004

Superhard materials are needed to replace diamond in applications at high temperatures, where diamond is unstable. Novel carbon‐ and boron‐based materials are described whose discovery or postulation has greatly stimulated research in this area. The use of calculations to predict the properties of new materials is illustrated for B‐C3N4, which was synthesized only after its structure (see Figure) had been calculated.

magnified image
Localized incorporation of lanthanum carbide crystals in carbon nanotubes
Authors: Ata Masafumi , Kijima Yasunori , Hudson Andrew J. , Imoto Hiroshi , Matsuzawa Nobuyuki , Takahashi Noboru
Published: December 2004

Carbon nanotubes containing lanthanum carbide suggest that lanthanum may show catalytic activity for the formation of nanotubes. Images of the graphitic structures growing on the surface of silver‐colored deposits such as the SEM image of a straight carbon nanotube shown in the Figure, are presented.

magnified image
Microfabrication by microcontact printing of self‐assembled monolayers
Authors: Wilbur James L. , Kumar Amit , Kim Enoch , Whitesides George M.
Published: December 2004

Microcontact printing, is described. It offers extreme experimental simplicity and flexibility, relying on the ability of self‐assembled monolayers (SAMs) of longchain alkanethiolates on gold and other metals to act as nanometer resists. The Figure is an electron micrograph of a silicon microstructure resulting from chemical etching of a patterned SAM.

magnified image
Charged guest recognition by redox responsive ligand systems
Authors: Beer Paul D.
Published: December 2004

Redox responsive macrocyclic ligands can be used for the recognition of charged guest molecules and so are of importance for potential new molecular sensory devices. Systems are reported that enable the electrochemical recognition of various cations and anions. Tripodal cobalticinium and ferrocene ionophores electrochemically recognize H2PO4⊖ in the presence of excess HSO4⊖ and Cl⊖ anions.
Polarized electroluminescence from an oriented substituted polythiophene in a light emitting diode
Authors: Dyreklev Peter , Berggren Magnus , Inganäs Olle , Andersson Mats R. , Wennerström Olof , Hjertberg Thomas
Published: December 2004

Polarized light sources based on stretch‐oriented conjugated polymers are reported. The devices, based on poly 3(4‐octylphenyl)‐2,2′‐bithiophene, show an external quantum efficiency of 0.1% and are produced using a very simple method which may be easily extended to other polymers. The fabrication of the devices is described and factors such as the emission and spectral differences parallel and prependicular to the stretching direction discussed.
Molecular assemblies of functionalized polydiacetylenes
Authors: Spevak Wayne , Nagy Jon O. , Charych Deborah H.
Published: December 2004

Thin films and liposomes composed of polydiacetylenes with biologically active head groups have potential applications in cell adhesion, therapeutics, and biological sensing due to the specific interactions between the functionalized head groups and, for example, virus particles. The synthesis and the applications of these assemblies are discussed.
Opening and purification of carbon nanotubes in high yields
Authors: Hiura Hidefumi , Ebbesen Thomas W. , Tanigaki Katsumi
Published: December 2004

Gram‐quantities of pure carbon nanotubes (see Figure) can be produced using a new method reported here. The nanotubes, which can be thought of as cylindrical graphitic microcrystals, are opened and purified by treating them with a mixtue of sulfuric acid and potassium permanganate. The opening of the nanotubes on a large scale is also of interest in terms of filling the tubes with interesting guest molecules.

magnified image
Novel access to polyboro‐ and polyalumosilazanes suitable as precursors for ternary nitride ceramics
Authors: Löffelholz Josua , Jansen Martin
Published: December 2004

Polymeric precursors for high‐performance niride ceramics have been attracting increasing attention as they offer access to fine‐grained materials with excellent homogeneity. A new method for the synthesis of polymeric precursors to Si/B/N and Si/Al/N ceramics which starts from easily available compounds and avoids the need for oligomeric intermediates is reported. The compositions of the ceramic powders as well as the properties of the polymers can be tailored on a molecular scale.
Electrochemistry using plasma
Authors: Ogumi Zempachi , Uchimoto Yoshiharu , Takehara Zen‐ichiro
Published: December 2004

A glow‐discharge plasma, because of the presence of ions and electrons and because of its potentially high conductivity, can be seen as a conductive fluid which could be used in an electrochemical system. Electrochemistry using such a plasma (see Figure) has bee demonstrated and here its basis and applications, for example in thin film deposition, are discussed.

magnified image
Mosaic tiling in molecular dimensions
Authors: Ferguson Gregory S. , Kleinfeld Elaine R.
Published: December 2004

A strategy for the stepwise formation of organic/inorganic multilayered films is presented. Structurally ordered, alternating stacks of a cationic organic polymer and anionic sheets of an inorganic mineral are produced with lattice spacings as low as 1.5 nm, architectures which have a great potential in the design of, for example, optical elements and sensors. The method allows the close control of the deposited thickness of the layers and a applicable to a wide variety of materials.
Silicon wafer bonding via designed monolayers**
Authors: Gösele Ulrich , Steinnkirchner Johann , Martini Torsten , Reiche Manfred , Kästner Gerhard
Published: December 2004

Silicon wafer bonding is a technology which allows two silicon wafers to stick together without any glue (e.g. see Fig.). The technique is used in the areas of microelectronics, micromechanics, and power electronics. Hydrolyzed tetramethoxysilane is used in he new bonding process presented here, providing a low‐temperature method of wafer bonding compatible with the presence of microelectronics aluminum metallization

magnified image

.
Octahedral, liquid‐crystalline complexes of 1,4‐diazabutadienes with rhenium(I)**
Authors: Morrone Stefania , Harrison Gayle , Bruce Duncan W.
Published: December 2004

Mesomorphic tansition metal complexes have been shown in the past to exhibit technically interesting properties, including a igh birefringence, high linear and nonlinear polarizability, and igh linear dichroism. Here, a general approach to the design and synthesis of metal‐containing liquid crystals based on high coordination number centers is presented. Diazautadienes are used as the ligands for the generation of the complexes and it is thought that they will find wide applicability in he design of new metallomesogens.
The first radical salt of the polyoxometalate cluster [P2W18O62]6⊖ with bis(ethylenedithio)tetrathiafulvalene (ET): ET11[P2W18O62] · 3H2O
Authors: Coronado Eugenio , Galán‐Mascarós José Ramón , Giménez‐Saiz Carlos , Gómez‐Garcĺa Carlos J. , Laukhin Vladimir N.
Published: December 2004

The study of organic donor‐inorganic cluster hybrids has been extended to polyoxometalates with higher nuclearities and different shapes using the heteropolyanion [P2W18O62]6⊖ combined with bis(ethylenedithio)tetrathiafulvalene. The resulting hybrid material is unique in several respects: the new radical salt has an unprecedented stoichiometry and β‐type packing; it is the first well‐characterized radical salt of a polymetalate to exhibit metallic behavior. Further possibilities for investigation are briefly outlined.
Rapid switching solid state electrochromic devices based on complementary conducting polymer films
Authors: Sapp Shawn A. , Sotzing Gregory A. , Reddinger Jerry L. , Reynolds John R.
Published: December 2004

New electrochromic materials (ECMs) must exhibit rapid response times, long‐term stability, and a large difference in percentage transmittance between the bleached and colored states. The design, fabrication, and characterization of fast, solid‐state, dual conducting polymer EC devices that utilize PEDOT (see Figure) as the cathodically coloring material are described, following background information on ECMs.

magnified image
λ‐Type BETS salts containing a mixed halide gallium anion, GaXx Y4−x⊖ [X, Y = F, Cl, Br; BETS = Bis(ethylenedithio)tetraselenafulvalene]
Authors: Tanaka Hisashi , Kobayashi Akiko , Saito Taro , Kawano Koichi , Naito Toshio , Kobayashi F. Hayao
Published: December 2004

A new series of organic superconductors is reported: λ‐type salts of bis(ethylenedithio)tetraselenafulvalene (BETS) with mixed halide gallium anions. Their preparation and properties are described, with particular emphasis on the electrical resistivity. A strong correlation is observed between the superconducting transition temperature Tc and the unit cell volume, which should enable the superconducting transition to be investigated systematically and facilitate the design of new organic superconductors with enhanced Tc.
The mobility of charge carriers in all four phases of the columnar discotic material hexakis(hexylthio)triphenylene: Combined TOF and PR‐TRMC results
Authors: van de Craats Anick M. , Warman John M. , de Haas Matthijs P. , Adam Dieter , Simmerer Jürgen , Haarer Dietrich , Schuhmacher Peter
Published: December 2004

Peripherally alkyl‐substituted aromatic molecules are of interest because they are predicted to promote the rapid vectorial conduction of electronic charge. It is shown—using the example of HHTT, see Figure—that the results obtained by flash‐photolysis time‐of‐flight conductivity and pulse‐radiolysis time‐resolved microwave conductivity measurements are complementary, allowing the charge‐carrier mobility to be determined in all four phases of HHTT.

magnified image
Molecular orbital energy level engineering in organic transistors
Authors: Dodabalapur Ananth , Katz Howard E. , Torsi Luisa
Published: December 2004

The application of heterostructure concepts to organic field effects transistors (FETs) is briefly reviewed. In particular, the physics of operation of α‐sexithiophene‐ and C60‐based FETs—which can act as p‐ or n‐channel transistors depending on the sign and magnitude of the gate bias—and of isotype heterostructure FETs is outlined. In the latter, both active materials, e.g., an aromatic diamine and α‐sexithiophene, transport the same (majority) carrier type.
Laser action in poly (m‐phenylenevinylene‐co‐2,5‐dioctoxy‐p‐phenylenevinylene)
Authors: Holzer Wolfgang , Penzkofer Alfons , Gong Sung‐Huan , Bleyer Andreas , Bradley Donal D. C.
Published: December 2004

The lasing action of a new conjugated copolymer in tetrahydrofuran (THF), xylene, toluene, and chloroform is reported. The title copolymer differs from many of the other conjugated copolymers that have been studied in that it includes meta‐linked phenylene rings in its backbone (see Figure). The results presented—e.g., lasing threshold energy of 25 μJ, spectral halfwidth of 8 nm in THF, an expected wide tuning range—hold promise for the realization of solid state polymer lasers.

magnified image
Gold particle generation by spray pyrolysis
Authors: Majumdar Diptarka , Kodas Toivo T. , Glicksman Howard D.
Published: December 2004

Phase‐pure, micrometer‐sized, spherical gold particles(see Figure) have been generated for the first time by spray pyrolysis of gold nitrate at temperatures well below the melting point of gold. The effects of reaction atmosphere, temperature, and residence time on the morphology of the final product are described. The resulting gold powder is shown to be suitable for a variety of microelectronics applications.

magnified image
Columnar discotics for light emitting diodes
Authors: Wendorff Joachim H. , Christ Thomas , Glüsen Birgit , Greiner Andreas , Kettner Andreas , Sander Roland , Stümpflen Volker , Tsukruk Vladimir V.
Published: December 2004

The suitability fo columnar discotics for applications in light emitting diodes (LEDs) has been investigated following the demonstration of their unusually large charge carrier mobilities. Results of X‐ray diffraction, computer simulations, and electroluminescence measurements are presented and discussed for discotic systems such as that shown in the Figure. Their use in LEDs is expected to the advantageous.

magnified image
Thermally induced colloid formation of au on a polysilane film pre‐exposed to UV light and its application to novel optical recording media
Authors: Nagayama Norio , Itagaki Kazuhiro , Yokoyama Masaaki
Published: December 2004

A novel write‐once optical recording medium is one application of a phenomenon reported here: when a thin layer of gold on PMPS—a typical polysilane—is pre‐exposed to UV radiation before being heated, a gold colloid is formed in the PMPS in those areas which were exposed to the radiation. The accompanying reduction in reflectance due to the gold‐to‐magenta color change can be used as an optical memory that is compatible with the current CD reading system. Details of the observation and follow‐up studies are reported.
Polarized electroluminescence from an oriented poly (3‐alkylthiophene) langmuir–blodgett structure
Authors: Bolognesi Alberto , Bajo Giuseppe , Paloheimo Jari , Östergärd Toni , Stubb Henrik
Published: December 2004

Polarized electroluminescence (EL) from an oriented poly(3‐alkylthiophene) structure is reported, which is a first step towards the fabrication of an organic light‐emitting diode (LED) that emits polarized light. A multilayer structure is described that includes a Langmuir‐Blodgett film of poly(3‐decylmethoxythiophene), PDMT, in which the polyenic backbones are oriented along the dipping direction. The optical properties–absorption, EL, photoluminescence–and the I–V curve for an ITO/PDMT/Al device are presented.
Dipolar NLO‐phores with large off‐diagonal components of the second‐order polarizability tensor
Authors: Wolff J. Jens , Längle Daniela , Hillenbrand Daniela , Wortmann Rüdiger , Matschiner Ralf , Glania Christoph , Kramer Peter
Published: December 2004

A new class of nonlinear optical chromophores (NLO‐phores) with large off‐diagonal components of the second‐order polarization and remarkable transparency properties have been investigated. The synthesis and NLO characterization of a series of C2n symmetry benzene derivatives, such as that shown in the Figure, are described. The results of UV‐vis, EFISH, hyper‐Rayleigh scattering, etc., measurements are compared.

magnified image
Multicoloured chromophore for white‐light‐emitting diodes
Authors: Christ Thomas , Greiner Andreas , Sander Roland , Stümpflen Volker , Wendorff Joachim H.
Published: December 2004

Light‐emitting diodes that emit white light require active materials that are able to emit throughout the entire visible spectrum. A simple approach is reported here, based on hist‐guest systems in which the guest is a single chromophore and the host a polymer blend. It is demonstrated that the emission of the chromophore may depend strongly on the choice of the matrix polymer. The absorption, photoluminescence, and electroluminescence spectra of the chromophore PSA in matrices of polynorbornene, Durel (a polyarylate), polyvinylpyridine, and blends are presented.
Electrodeposited quantum dots: Coherent nanocrystalline cdse on oriented polycrystalline au films
Authors: Golan Yuva , Alperson Boaz , Hutchison John L. , Hodes Gary , Rubinstein Israel
Published: December 2004

The formation of highly coherent nanocrystalline semiconductor films on polycrystalline metal substrates has important practical and theoretical implications. Electron diffraction patterns reveal that quantum dots (QDs) of CdSe grown on a gold film on a mica substrate are coherent over several micrometers in the lateral directions (see Figure), while in the case of a glass substrate there is a complete loss of epitaxy for QD layers not in direct contact with the gold. Fig.

magnified image
Liquid crystalline macrocycles: Novel glass‐forming nematic materials that can undergo charge transfer induced phase transitions
Authors: Neumann Bernhard , Joachimi Detlev , Tschierske Carsten
Published: December 2004

Macrocyclic liquid crystals incorporating two different rigid cores are reported for the first time. The synthesis of polyethercyclophanes such as that shown in the Figure is described, together with their phase behavior as investigated by differential scanning calorimetry and polarizing microscopy. The synthesis of macrocycles that combine non‐identical building blocks is describe in order to obtain materials with tailor‐made properties.

magnified image
Blue and green light emission from new soluble alternating copolymers
Authors: Cho Hyun Nam , Kim Dong Young , Kim Young Chul , Lee Jun Young , Kim Chung Yup
Published: December 2004

Visible‐light‐emitting alternating copolymers consisting of two different repeat units have been investigated. The synthesis and optical characterization of PDHFPPV (top in Figure) and PDHEMPV (bottom in Figure) are described. It is shown that these soluble copolymers can be used as the active layer in light‐emitting diodes, just like the corresponding homopolymers.

magnified image
Electrodeposition of quantum‐confined metal/semiconductor nanocomposites
Authors: Switzer Jay A. , Hung Chen‐Jen , Bohannan Eric W. , Shumsky Mark G. , Golden Teresa D. , Van Aken David C.
Published: December 2004

Electrodepositiona s an approach to quantum confinement is the idea behind the work on nanocomposite films of Cu and Cu2O reported here. The phase of the film electrodeposited from an alkaline aqueous solution of copper(II) lactate depends on the cathodic current density used, varying from pure Cu2O (a p‐type semiconductor) to 98 mol‐% Cu, the color of the film changing correspondingly; the electrode potential oscilates spontaneously at fixed current density. It is shown that the Cu2O crystallites exhibit the optical properties of quantum dots.
Concerted transport of electrons and protons across conducting polymer membranes
Authors: Matsumura Michio , Ohno Teruhisa
Published: December 2004

The efficient conversion of light energy into chemical energy is essential if solar energy is to be utilized successfully. The mechanisms of photosynthesis in green plants are used as guiding principles to propose different types of electron and proton transporting systems, for example, a chemical system based on polyaniline film, an electrochemical system using doped polypyrrole film, and the photochemical system shown in the Figure. Fig.

magnified image
Phasmids and Polycatenar Mesogens
Authors: Nguyen Huu‐Tinh , Destrade Christian , Malthécte Jacques
Published: December 2004

Polycatenar mesogens have a shape intermediate between classical rod‐like and disc‐like liquid crystals which allows practically all the mesomorphic symmetrics to be obtained with the same molecular core by varying the temperature or the number and position of grafted chains (see Figure: R = H(CH2)nO). The synthesis, mesomorphic properties, and structures of polycatenar mesogens are reviewed, with emphasis on the structure–properties relationship.

magnified image
Synthesis of nanometer‐scale silver crystallites via a room‐temperature electrostatic spraying process
Authors: Hull Peter J. , Hutchison John L. , Salata Oleg V. , Dobson Peter J.
Published: December 2004

Thin films of silver nanoparticles have been prepared by a room temperature electrospraying technique—the apparatus is shown schematically in the Figure. The characterization of the particles by optical absorption spectroscopy and high‐resolution transmission electron microscopy is described. The behavior is compared with theory and a tentative mechanism proposed for the reduction of the silver.

magnified image
Three‐dimensional hexagonal close‐packed superlattice of passivated Ag nanocrystals
Authors: Harfenist Steven A. , Wang Zhong L. , Whetten Robert L. , Vezmar Igor , Alvarez Marcos M.
Published: December 2004

Superlattices of self‐assembled Ag nanocrystals have been prepared and the structure analyzed using a combination of techniques. It is shown that the supercrystals are hexagonally close‐packed, attributed to a high proportion of icosahedral and decahedral particles. The Figure (a TEM image of the Ag supercrystals) illustrates that the crystals formed are predominantly triangular in morphology and can be as large as 3–5 μm.

magnified image
Purification and size‐selection of carbon nanotubes
Authors: Bonard Jean‐Marc , Stora Thierry , Salvetat Jean‐Paul , Maier Frédéric , Stöckli Thömas , Duschl Claus , Forró László , de Heer Walt A. , Châtelain André
Published: December 2004

A non‐destructive method for purifying carbon nanotubes produced by are discharge is described. The nanotubes, in the form of a kinetically stable colloidal dispersion in a water–surfactant solution, are separated from the nanoparticles by filtration. The Figure shows that purified nanotubes after two filtration steps. Through controlled flocculation, nanotube size election is also possible.

magnified image
Solid‐state Carbon Nitrides
Authors: Badding John V.
Published: December 2004

Whether crystalline or amorphous sp3‐bonded carbon nitrides containing substantial amounts of nitrogen can be synthesized remains an open question. Various deposition techniques and high pressure syntheses to 40 GPa have not been successful thus far. The use of appropriately designed molecular or solid‐state precursors and low enough synthesis temperatures to insure kinetic control of reaction products appears to be a promising direction for future efforts. In addition, synthesis at higher pressures, which can effect larger shifts in free energies of reaction should be pursued. The importance of careful characterization to obtain structural (by means of electron or X‐ray diffraction), compositional (by means of EELS, EDX, or RBS), and, especially, bonding (by means of EELS) information on single‐phase material cannot be overemphasized. Because few examples are known of covalently bonded networks containing carbon, synthesis of a sp3‐bonded carbon nitride would be a spectacular achievement.
Micromolding and photopolymerization
Authors: Hanemann Thomas , Ruprecht Robert , Haußelt Jürgen H.
Published: December 2004

Micromolding techniques for the fabrication of polymer microstructures are discussed with reference to the features important for commercial success. Particular emphasis is placed on a recently developed photo‐polymerization reaction injection molding (RIM) technique. The progress made to date on the molding of microstructures using this technique is detailed and compared with thermally initiated RIM. The goal is to fabricate structures with lateral dimensions in the micrometer range, structural details in the submicrometer range, and high aspect ratios.
An alternative synthetic route to soluble polyetherimide derivatives with high second‐order optical nonlinearity
Authors: Lee Kwang‐Sup , Moon Ki‐Jeong , Woo Han Young , Shim Hong‐Ku
Published: December 2004

Processible polytherimide‐based polymers that display nonlinear optical (NLO) activityare reported to have been synthesized by the Mitsunobu reaction, in which the polyimide structure is synthesized directly in a single step from a diimide and a diol, without a high‐temperature thermal imidization step. The resulting polymers, with pendant‐incorporated tricyanovinyl azobenzene chromophores, showed very large second‐order NLO activity with good temporal and thermal stability—in one case no decay of the signal was observed up to 125°C.
Photorefractive materials for holographic interferometry
Authors: Schloter Stefan , Haarer Dietrich
Published: December 2004

The photorefractive properties of polymersfor holographic interferometry are currently often better than those of their inorganic counterparts. The theory of the photorefractive effect is briefly outlined before the relevant experimental techniques and chemical approaches are reviewed. Applications are mentioned, for example the possibility of visualizing vibrations as a fringe pattern (see Figure).

magnified image
Imaging polymers with supercritical carbon dioxide
Authors: Ober Christopher K. , Gabor Allen H. , Gallagher‐Wetmore Paula , Allen Robert D.
Published: December 2004

In lithographic techniques for forming nanostructures in surface and polymer thin films, the selectivity of the solvent becomes increasingly important as the target dimensions decrease. Polymer‐based developers. The Figure shows the SC CO2–developed image of a copolymer of pentafluoroproyl methacrylate and tert‐butyl methacrylate.

magnified image
Insoluble Poly [2‐(2′‐ethylhexyloxy)‐5‐methoxy‐1,4‐phenylenevinylene] for Use in Multilayer Light‐Emitting Diodes
Authors: Burn Paul L. , Grice Alan W. , Tajbakhsh Ali , Bradley Donal D. C. , Thomas Andrew C.
Published: December 2004

Both soluble and insoluble conjugated polymers have advantages and disadvantages for the construction of light‐emitting diodes (LEDs). A route is reported fo the formation of optical quality films of insoluble (I) MEHPV, a poly(phenylenevinylene) derivative whose soluble form is widely used in single‐layer devices. The incorporation of 1‐MEHPPV into a multilayer device is described, in which the electron‐transport/holeblocking layer was deposited on top of the 1‐MEHPPV layer from a solvent in which the standard soluble MEHPPV should dissolve.
Impurity survey analysis of CdxHgi−xTe by laser scan mass spectrometry
Authors: Grainger F. , Gale I. G. , Capper P. , Maxey C. D. , Mackett P. , O'Keefe E. , Gosney J.
Published: December 2004

A laser scan mass spectrometry (LSMS) technique has been applied to the analysis of epitaxial layers and bulk CdxHg1−xTe (CMT) materials. The samples are raster scanned under a focused Q‐switched Nd–YAG laser beam which ionises all elements with approximately unit sensitivity. The ions are extracted into a high‐resolution mass spectrometer and interpretation of the mass spectra gives a complete impurity survey of the material with detection limits down to 1 part in 109 (3 × 1013 cm−1) in bulk materials and 5 parts in 109 in epitaxial layers. Surface impurities are effectively removed in the first scan and subsequent scans over the same area give a true measurement of the impurities present in the material. Successive erosion of the sample surface gives impurity depth profiles with the thickness of material eroded in each scan variable between 1 and 4 μm. Results are given for impurities found in bulk CMT grown by standard Bridgman and ACRT (accelerated crucible rotation technique) processes and in epitaxial CMT produced by liquid phase epitaxy (LPE), metal organic vapour phase epitaxy (MOVPE) and molecular beam epitaxy (MBE). Bulk material is shown to be purer in general than epitaxial material. Semiquentitative depth profiles of dopants in CMT, such as iodine, arsenic and phosphorus, can also be obtained and comparative LSMS and secondary ion mass spectrometry (SIMS) depth profiles showing good agreement are given for arsenic in an MOVPE layer.
Deposition, annealing and characterisation of high‐dielectric‐constant metal oxide films
Authors: Treichel H. , Mitwalsky A. , Tempel G. , Zorn G. , Bohling D. A. , Coyle K. R. , Felker B. S. , George M. , Kern W. , Lane A. P. , Sandler N. P.
Published: December 2004

Flims of metal oxides, such as Ta2O5, Nb2O5, Al2O3, HfO2, ZrO2 and TiO2 have been fabricated by use of different precursor materials, deposition techniques and annealing techniques. Several analytical methods were applied to study the layers. New data of fundamental properties of these metal oxides are reported and related to practical features that are of importance in device design and manufacturing of advanced, highly integrated devices. This overview may facilitate the choice of an optimal combination of precursor material, deposition technique and corresponding annealing procedure for a specific application of these metal oxide films in microelectronics.
Capillary physiology and drug delivery in central nervous system lymphomas
Authors: Warnke Peter C. , Timmer Jens , Ostertag Christoph B. , Kopitzki Klaus
Published: December 2004

To evaluate whether the chemosensitivity of primary central nervous system lymphomas to water‐soluble drugs could result from improved drug delivery, we quantitatively assessed pharmacokinetic factors in seven patients. The capillary permeability surface product was found to be significantly increased in central nervous system lymphomas compared with glioblastoma multiforme, medulloblastomas, and metastases. Tumoral blood flow was significantly greater than in normal white matter. Our results suggest favorable pharmacokinetics to water‐ and lipid‐soluble drugs in primary central nervous system lymphomas. Ann Neurol 2005;57:136–139
Conformational aspects of polypeptides. XVII. Synthesis of oligomers and co‐oligomers derived from L‐alanine and L‐glutamic acid
Authors: Goodman Murray , Langsam Michael
Published: December 2004

A series of oligomers was synthesized of the form:

Where Z is the benzyloxycarbonyl group and n = 2, 3, 5, 10. We encountered difficulty in dissolving the decamer in any solvent except strong organic acids. We therefore prepared co‐oligomers of the type:

equation image

where (a) w = x = y = 1; (b) w = 0, x = y = 3; and (c) w = x = y = 3. A series of model compounds composed of glycine L‐alamine and γ‐methyl‐L‐glutamate were also prepared. We converted manyof the benzyloxycarbonyl oligopeptides into their corresponding acetyl derivatives. Some of these peptides were synthesized by mixed anhydride and active ester techniques while others were prepared via azide coupling techniques using the tert‐butoxycarbonylhydrazide blocking group. All reactions proceeded with retention of configuration.
Some water‐insoluble papain derivatives
Authors: Silman Israel H. , Albu‐Weissenberg Martin , Katchalski Ephraim
Published: December 2004

A description is given of the preparation and properties of four water‐insoluble papain derivatives by three different techniques: (a) covalent binding to a water‐insoluble diazoimitn salt derived from a copolymer of p‐aminophenylalanine and leucine; (b) binding to insoluble preparations of collagen via bisdiazobenzidine‐2,2′‐disulfonic acid; (c) in‐solubilization by crosslinking the enzyme itself with bisdiazobenzidine. By all three methods it, was possible to obtain stable water‐insoluble papain derivatives retaining much of the activity of the native enzyme on low and high molecular weight substrates.
Optical rotatory dispersion studies of poly‐O‐acetyl‐γ‐hydroxy‐L‐proline forms I and II
Authors: Fasman Gerald D.
Published: December 2004

Poly‐O‐acetyl‐hydroxy‐L‐proline, forms I and II have been studied by optical rotatory dispersion (ORD) and ultraviolet spectrophotometry in solution and in the solid state. Cotton effects of opposite sign, but not mirror images, were observed in the 250 mμ region for the two forms (Form I, peak 278 mμ; crossover, 254 mμ; trough, 244 mμ: Form II, trough 270 mμ; crossover, 248 mμ; peak, 238 mμ). Thus, the Cotton effects for a right‐handed and left‐handed helix have been shown to be opposite for the proline type helices I and II. The ORD of films of form I was found to have a positive Cotton effect further into the ultraviolet region with peak at 218 mμ. Absorption spectra showed a shift of 8 mμ in the absorption peak in the 200 mμ region for the two forms (form. I, 211 mμ; form II, 203 mμ). A shoulder was demonstrated in the film absorption spectra in the 250 mμ region where the Cotton effects are found. The mixing of the n, π* and π, π* states of the amide chromophore and n, π* state of the ester chromophore was suggested as being responsible for the Cotton effects in the 250 mμ region.
pH‐Induced conformational changes of DNA
Authors: Costantino L. , Vitagliano V.
Published: December 2004

The electrophoretic mobility of calf thymus DNA has been measured in aqueous buffered solutions as a function of pH. In the pH range 3.7–3.0, two electrophoretic species appear. The faster one migrates with the mobility of native DNA, the slower one migrates with a mobility close to that of thermally denatured DNA. The ratio of the two species varies with pH. Decreasing the pH increase the relative amount of the slower‐moving component. These results may be interpreted by assuming that the DNA used in these experiments has a broad heterogeneity of base composition and that the conformational stability with respect to pH increases with increasing G + C content.
Conformational transition of poly(L‐glutamic acid) in aqueous solution
Authors: Barone G. , Crescenzi V. , Quadrifoglio F.
Published: December 2004

Further direct evidences are given that a clear correlation exists between potentiometric and spectroscopic measurements in monitoring the poly(L‐glutamic, acid) helix+ coil transtition. Specific Li+ ion poly (L‐glUtamic acid) interactions have been observed, suresting that Li+ ions may exert a distinct destabilizing action on the helical conformation of the polyelectrolyte.
Infrared absorption spectrum of keratin. I. Spectra of α‐, β‐, and supercontracted keratin
Authors: Bendit E. G.
Published: December 2004

A number of basic features of the infrared spectrum of keratin have been confirmed and some new features have been found. In the 3‐μ region, the amide A frequency of helical material in α‐keratin at 3286 cm.−1 is close to the expected value, but that of the crystalline phase in α‐keratin, near 3270 cm.−1, is lower than had previously been reported. The noncrystalline phase absorbs in the vicinity of 3300 cm.−1 or above, and this causes the low‐intensity component of the amide A band in both α‐ and β‐keratin to occur at higher frequencies than those of the high‐intensity component. In the 6‐μ region, the amide II frequency of noncrystalline material is below 1525 cm.−1. Keratin denatured in lithium bromide, after washing out the reagent, appears to have a considerable helix content, possibly as much as that of the original protein. Hydration causes significant spectral changes. In the 6‐mu; region, the frequency of the amide I band of crystalline material is lowered, while that of the amide II band is increased, both by a few wavenumbers; the amide II frequency of noncrystaline material is also increased by a few wavenumbers. In the 3‐μ region, no significant change is observed in the amide A frequency of crystalline material, while the frequency of the noncrystaline material is reduced. These spectral changes are interpreted in terms of a weak association of water with main‐chain carbonyl groups in the crystalline phase, while in the noncrystaline phase it is thought likely that water molecules form hydrogen‐bond bridges between polypetide chains. The absorption coefficient of the amide A band and the integrated absorption intensities of the amide A, I, and II bands do not vary appreciably in the three forms of keratin investigated.
Mathematics of band centrifugation: Concentration‐independent sedimentation and diffusion in shallow density gradients
Authors: Rubin Merry M. , Katchalsky Aharon
Published: December 2004

Integral expressions for concentration as a function of time and distance are derived from the continuity equation for centrifugation in a sector‐shaped cell for a macro‐molecular solute initially contained in a finite upper layer and a solute of low molecular weight in the supporting liquid. Computer patterns based on the sedimentation and diffusion coefficients of sucrose and of spherical and randomly coiled model solutes illustrate: (1) the time course of redistribution of both banded and supporting solutes from initial uniform concentrations; (2) the influence of the initial concentration, width, and solute concentration of the upper band; and (3) the effect of restricted diffusion at the meniscus on subsequent band shape. A Gaussian, approximation to band shape is derived and graphically tested. Rapid methods, not requiring computers, are out lined for the estimation of sedimentation and diffusion coefficients, where their concentration dependence is negligible, by band centrifugtion. The theoretical resolution of mixtures attainable by this technique is compared with moving‐boundary centrifugation, with the use of both integral (interferotmetric or absorption) and derivative (schlieren) optics.
Solvent effects in N‐carboxyanhydride (NCA) polymerization initiated by strong base type initiators
Authors: Cosani A. , D'este G. , Peggion E. , Scoefone E.
Published: December 2004

The γ‐benzyl‐L‐glutamate N‐carboxyanhydride (NCA) polymerization initialed by diisopropylamine was studied in dimethylformamide (DMF)‐dioxane mixtures of different compositions. It was found that the shape of the conversion versus time plots and the molecular weights of the polymers depend on the solvent composition. Auto‐catalysis is present only when dioxane predominates in the solvent mixtures. Moreover, the molecular weight of the final polymer depends strongly on the precipitation conditions when the polymerization is carried out in DMF.