bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exciting Erbium-Doped Planar Optical Amplifier Materials
Authors: Polman A. 
Published: April 2011

AbstractErbium-doped planar optical amplifiers can find numerous applications in photonic integrated circuits operating at 1.5 μm. The challenge is to fabricate these devices with high gain, operating at low pump power, and having small overall size. In this paper a review is given of our recent work in the area of Er-doped waveguide materials and amplifiers based on three materials classes: oxide films (A12O3, Y2O3, SiO2), polymers, and silicon.
Single State Absorption Spectra of Novel Nonlinear Optical Materials
Authors: Kirkpatrick Sean M. , Clark Casey , Sutherland Richard L. 
Published: April 2011

AbstractDuring the absorption of a laser pulse of moderate length, the leading edge can experience excited state absorption out of the first singlet state. The measurement of this excited state absorption spectrum can only be accurately probed using short pulse pump-probe techniques. Specifically, we examine the excited state absorption of AF-380 in THF using ultrafast transient white light absorption spectroscopy (TWLA). This material has been the focus of several investigations due to it's purported large two-photon absorption cross-section, the discrepancies between long and short pulse measurements, and it's use in holographic twophoton induced photopolymerization. It is believed that a substantial excited state absorbance can account for the difference in two-photon cross section measurements. It is also possible that this excited state exhibits coherence for time scales that can affect further absorption of longer pump pulses. We examine the transient absorption of this species, as well as polarization and free carrier effects and discuss the possible implications with regards to measurement techniques.
Optical Power Limiters for Nanosecond Pulses: Design of New Dendritic Chromophores with Exceptionally Large Two-Photon Cross-Sections
Authors: Elandaloussi E. H. , Spangler C. , Casstevens M. , Kumar D. , Weibel J. , Burzynski R. , HE G.-S. , Prasad P. 
Published: April 2011

AbstractOver the past five years there has been a renaissance in design studies of chromophores with the possibility of enhanced two-photon absorption (TPA). While two-photon absorption has been described for molecules such as laser dyes in solution for a number of years1, it has only been recently that researchers have attempted detailed structure-property relationships to elucidate how new chromophores with greatly enhanced two-photon cross-sections might be designed. Since the intrinsic cross-sections are related to the Im component of the third order optical nonlinearity, it should come as no surprise that much of the previous work in the literature which focused on structure-property relationships for molecules with enhanced NLO response might be applicable to the design of new TPA chromophores. In this presentation we will review our recent studies in this area, and our rationale for the applicability of dendritic strctures based on photonic-active repeat units for enhancment of two-photon absorption, particularly in the area of optical power limiting applications.
Fourier Transform Techniques for Measuring Absorption of Transient Species Inoptical Limiting Materials
Authors: Han Yanong , Sonnenberg Wendi , Short Kurt W. , Hyfield Amy , Spangler Lee H. 
Published: April 2011

AbstractWe have developed methods of measuring absorption of transient species utilizing both rapid scan and stepped-scan Fourier transform interferometery that allows a combination of broad spectral coverage (10,000 – 15,000 cm-1 per spectrum), good spectral resolution, and the ability to cover temporal ranges from minutes to nanoseconds. A wide range of pump sources are used including continuous, modulated, ns pulsed, and ultrafast lasers. The probe is provided by a broadband, incoherent source providing large spectral information in each experiment. This capability enables investigation of phenomena such as excited state absorption, charge transfer, formation of metastable species, and others. Extension of the technique to the ps realm is underway and will be discussed.
Syntheses and Optical Limiting Characterizations of a Series of Porphyrin-Buckminsterfullerene Dyads
Authors: Ang How-Ghee , Loh Zhi-Heng , Chng Leng-Leng , Lee Yiew-Wang , Yang Guo-Ying , McEwan Kenneth J. , Robertson John M. , Lewis Keith L. 
Published: April 2011

AbstractWe report herein the syntheses and optical limiting characterizations of a series of porphyrin-C60 dyads in which the porphyrin and C60 moieties are held within close proximity of one another by an o-phenylene bridge. The electron-donating ability of the porphyrin moiety in the dyads is systematically varied through chemical modification. This allows us to control the ease of electron transfer from the porphyrin to the C60 moiety in these dyads. Optical limiting measurements at 532 nm using 3-ns pulses show that the limiting performances of the dyads are poorer relative to their model compounds. This could be due to an ultra-short lifetime for the charge-separated species or a depopulation of the triplet states by photoinduced electron transfer. The optical limiting performances of the free-base porphyrin-C60 dyads are also related to the electron- donating abilities of the meso substituents of the porphyrin moieties. 12PorphyC60 displays better limiting performance at 532 nm (with 3-ns and 15-ns pulses) compared to Val12PorphyC60. This trend has been rationalized in terms of the relative energies of the first excited singlet and triplet states of the fullerene moiety and the charge-separated state of the dyads.
Design and Synthesis of a 33-Layer Narrow Bandpass Filter with Graded Refractive Index Profiles
Authors: Wang X. , Masumoto H. , Chen L. , Hirai T. , Someno Y. 
Published: April 2011

AbstractA novel bandp ass filter consisting of graded refractive index profiles and a three-cavity stack was designed. It exhibits good optical characteristics, i.e., high transmittance (>99%) at the designated wavelength of 1550±25 nm and high reflectance (>99%) in wavelength regions of 1400±50 nm and 1780±100 nm. This designed 33-layer TiO2-SiO2 film with graded refractive index profiles was prepared by helicon plasma sputtering. The measured transmittance spectrum exhibited good agreement with the designed spectrum. The microstructure of this multilay er film was investigated using electron microscopy.
An Omnidirectional Reflector and Microcavity Resonatorvia the Sol-Gel Method
Authors: Chen Kevin M. , Sparks Andrew W. , Luan Hsin-Chiao , Lim Desmond R. , Wada Kazumi , Kimerling Lionel C. 
Published: April 2011

AbstractThin films of sol-gel SiO2 and TiO2 were used to fabricate two types of onedimensional photonic crystals: an omnidirectional reflector and microcavity resonator. The reflector consisted of six SiO2/TiO2 bilayers, designed with a stopband in the near infrared. Reflectance measurements over an incident angle range of 0–80° showed an omnidirectional band of 70 nm, which agrees with theoretical predictions for this materials system. The microcavity resonator consisted of a TiO2 Fabry-Perot cavity sandwiched between two SiO2/TiO2 mirrors of three bilayers each. We have fabricated a microcavity with resonance at λcavity = 1500nm and achieved a quality factor of Q=35. We measured a modulation in the cavity resonance frequency with a change of defect layer thickness and incident angle of light. This work demonstrates the feasibility of fabricating photonic crystals via the sol-gel method.
Carbonate Apatite-Bearing Pure Titanium Implant
Authors: Teraoka K. , Nonami T. , Taoda H. , Naganuma K. , Yokogawa Y. , Doi Y. , Kameyama T. 
Published: April 2011

AbstractNew bone formation around implants is one of preferable conditions for the successful implantation. In this study, formable carbonate apatite ceramics were prepared and implanted in cavities (φ 400 μm, depth 400 μm) on the surface of pure titanium implant (ASTMB348-GR2) to enhance new bone formation around the titanium implant.
Ceramic Thin Films on Organic Self-Assembled Monolayers: Synthesis and the Mechanism of Formation
Authors: Sampathkumaran U. , Supothina S. , Wang R. , De Guire M. R. 
Published: April 2011

AbstractIn recent years, several research groups have pursued biomimetic or bio-inspired techniques for the synthesis of ceramic thin films from aqueous solutions at low temperatures. The substrates range from inorganic materials (metals, glass, single-crystal silicon) without special surface preparation, to functionalized organic surfaces such as self-assembled organic monolayers (SAMs). Our results on the deposition of tin (IV) oxide (SnO2, cassiterite) and hydroxyapatite (Ca10(PO4)6(OH)2) thin films on SAMs will be reviewed. The former system forms films via assembly of nano-scale particles on the substrate, while the latter system appears to form films via heterogeneous nucleation. In both cases, the role of the substrate in film formation is discussed.
Morphology of Mesoporous Silica Grown on Organic Surfaces: Effects of Surface Functional Groups and Microstructures
Authors: Hozumi Atsushi , Yokogawa Yoshiyuki , Kameyama Tetsuya , Hiraku Katsumasa , Sugimura Hiroyuki , Takai Osamu , Okido Masazumi 
Published: April 2011

AbstractThrough organized surfactant templating, mesoporous silica (MPS) was prepared on two different types of substrates with a hydrophilic or hydrophobic surface. In this study, a Si substrate covered with photochemically-grown surface oxide was served as the hydrophilic surface. The hydrophobic surfaces were prepared by forming an organosilane self-assembled monolayer (SAM) on Si substrates through chemical vapor deposition. Octadecyltrimetoxysilane or (heptadecafluoro-1,1,2,2-tetrahydro-decyl) trimethoxysilane was used as a precursor. The morphologies of the deposited MPS on these surfaces were found to be quite different. The MPS formed on the hydrophilic Si substrate consisted of small disk-like features of 2∼5 μm in diameter, while those on the hydrophobic SAM surfaces were continuous thin films. These morphological differences of the deposited MPS were ascribable to the differences in the supramolecular template structure formed on each of the surfaces. Furthermore, in order to study microstructure effects on the MPS growth, a micropatterned SAM/Si, on which hydrophobic regions were spaced alternately with hydrophilic regions at a 5 μm-wide interval, was employed as a sample substrate. On this substrate, MPS was preferentially grown on the hydrophobic regions while the hydrophilic regions remained almost undeposited. The spatial control of surfactant-assembling using the micropatterned SAM surface was successfully accomplished.
Involvement of Cellular Membranes and their Lipids in Nucleation of Stone Forming Crystals
Authors: Khan S. R. , Fasano J. M. , Backov R. , Talham D. R. 
Published: April 2011

AbstractMore than 80% of human kidney stones consist of calcium oxalate and/or calcium phosphate. Human urine is generally metastable with respect to these salts and their nucleation is heterogeneous. Based on: 1. ultrastructural and immunohistochemical studies of stones in which cellular degradation products and lipids were commonly seen in association with calcific crystals and 2. in vivo studies of nephrolithiasis in rat models where calcium oxalate (CaOx) and calcium phosphate (CaP) crystals almost always formed and seen in association with cell membranes, we proposed that membranes and their lipids are involved in crystallization of these salts. To test our hypothesis we isolated organic matrix of kidney stones, its lipid contents and membrane vesicles from epithelial cells of rat kidney and incubated them in metastable solution of CaOx. Both membrane vesicles and matrix from the stones supported crystallization of CaOx and crystals formed in association with the membranes. Lipids of the stone matrix appeared better nucleators than whole matrix. Urine spends only minutes within the kidneys thus any nucleation which can lead to stone formation has to occur rapidly. In studies described here, we demonstrate that under specific circumstances relevant to conditions in the kidney, membrane vesicle- supported CaOx crystallization can occur within seconds, demonstrating the possibility of such events happening in the kidneys. We also studied CaOx monohydrate (COM) precipitation at Langmuir monolayers of dipalmitoylphosphatidylglecerol (DPPG), dipalmitoylphosphatidylcholine (DPPC), dipalmitoylphosphatidylserine (DPPS) showed precipitation to be heterogeneous and selective with a majority of crystals orienting with the 101 face of COM facing the monolayer. Our results show that membrane lipids can initiate nucleation of calcium oxalate crystals in solutions similar to those present in the kidneys. In addition these crystals form within the time urine spends inside the renal tubules demonstrating for the first time the likelihood of occurrence of such a phenomenon in the kidneys during stone formation.
Osteointegration of Calcium Phosphate Ceramics in Humans And Animals
Authors: Frayssinet Patrick , Schwartz Claude , Mathona Didier , Rouquet Nicole 
Published: April 2011

AbstractCalcium phosphate ceramics are bioactive, osteoconductive materials used as guides for bone regeneration. We were able to carry out a histological study of ceramics implanted in large mammals and humans. An identical sequence of events apparently occurred at the contact of the ceramics. The osteoblasts differentiated preferentially in close proximity to the ceramic surface in animals. The early stage lasted longer in humans and was characterized by the presence of a monolayer of multinucleated cells containing TRAP+ (tartrate resistant acid phosphatase activity) granules at the surface of the ceramic. The loose connective tissue invading the pores contained almost exclusively fibroblast-like cells with TRAP+ nucleus. Differentiation of the osteogenic cells around the ceramic is diffuse in humans and not always related to the material surface. Ceramics become embedded in immature bone both in humans and animals. The immature bone and the ceramics are then remodeled and progressively replaced by layered bone. The degradation of the ceramic occurs preferentially at the grain boundaries and the grains released are phagocytosed by the macrophages when below a critical size and degraded in the low pH compartments of the cell. In conclusion: the integration of calcium phosphate ceramics is comparable in animals and man. Although in the cases studied the ceramics were unable to induce osteogenic differentiation, they did favor the differentiation of pre-determined osteogenic cells.
Bioactive Hydroxyapatite-Polysulfone Composite for Tissue Replacement
Authors: Chua B , Wang M 
Published: April 2011

AbstractA new composite material consisting of hydroxyapatite (HA) and polysulfone (PSU) was produced and evaluated for potential medical applications. The HA/PSU composite containing up to 40vol% of particulate HA was manufactured via a standardised procedure which included drying, compounding, and injection or compression moulding. Defect-free composite samples (bars, discs and dumbbell specimens) could be obtained by injection moulding. Thick composite plates suitable for making fatigue specimens were compression moulded. Both compounded materials and moulded parts were assessed using various techniques. It was found that HA particles were well dispersed in the PSU matrix. Thermogravimetric analysis verified the amount of HA in the composite. Density close to the theoretical value could be achieved for the composite, indicating a void-free structure. Differential scanning calorimetry results indicated that the glass transition temperature of the polymer matrix was not significantly affected by the incorporation of HA. Rheological analysis revealed that PSU and the composite exhibited pseudoplastic flow behaviour at processing temperatures. It was shown that the hardness and modulus of the composite were increased with an increase in HA volume percentage.
Preparation of Hydroxyapatite/Collagen Composites Using Biomimetic Process and their Biocompatibility
Authors: Kikuchi Masanori , Tanaka Junzo , ltoh Soichiro , lchinose Shizuko , Koyama Yoshihisa , Takakuda Kazuo , Nagaoka Katsuyoshi , Tanaka Shigeo 
Published: April 2011

AbstractNanocomposites of hydroxyapatite (HAp) and collagen (Col) were prepared by a biomimetic coprecipitation method under controlled pH and temperature. Transmission electron micrographs showed that the c-axis of HAp nanocrystals aligned along collagen by a self- rganization mechanism; a very similar alignment to bone's structure was found in the sample prepared at nearbiological conditions, i.e. pH8–9 and 40'C, which consisted of fibers with length of 20μm. From the material scientific point of view, therefore, osteoblasts may control the chemical condition in a small area around the cells to pH 8–9 as well as supply raw materials of bone, hydroxyapaite and collagen, at the initial state of osteogenesis. The biocompatibility of the composites was examined by animal tests using beagles. The composites were absorbed and new bone was formed as rapidly as a bone remodeling process. The HAp/Col composites prepared by biomimetic process were expected to be applicable as filler materials changing to new bone instead of autograft.
Fabrication and Characterization of Calcium Phosphate / Porous Silicon / Silicon Structures Doped with Platinum Antitumor Compounds
Authors: Coffer Jeffery L. , Li Xin , John John St. , Pinizzotto Russell F. , Chen Yandong , Newey Jon , Canham Leigh T. 
Published: April 2011

AbstractA process has been developed which permits the encapsulation of an established class of platinum anticancer drugs such as cis-Platin (cis-diammine-dichloroplatinum (II)) within synthetic biocompatible calcium phosphate films that are electrochemically-grown on porous Si/Si substrates. These platinum complex-doped hydroxyapatite / porous Si / Si materials have been characterized by scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (XEDS), and secondary ion mass spectrometry (SIMS). Upon immersion of these structures into aqueous media, the desired platinum species can be released into the surrounding environment. This study also focuses on the influence of initial platinum concentration for a given complex in the deposition process on the rate and resultant amount of platinum complex that can be delivered to the surroundings in vitro. Both inductively-coupled plasma (ICP) spectroscopy and uv-visible absorption spectrometry have been employed to monitor the release of the encapsulated drug from the calcium phosphate layers.
Atomic Displacement Parameters of Carbonate Apatites from Powder Neutron Diffraction Data
Authors: Leventouri Th. , Moghaddam H. Y. , Papanearchou N. , Bunaciu C. E. , Levinson R. L. , Martinez O. 
Published: April 2011

AbstractWe present a comparison between detailed structural parameters of a low temperature synthetic carbonate hydroxyapatite, a hydroxyapatite, and a natural carbonate fluorapatite from Rietveld refinements of neutron powder diffraction data. The observed modifications in the crystallographic parameters of the synthetic carbonate apatite are consistent with the carbonate substitution on the mirror plane of the tetrahedral site as in the case of the natural carbonate apatite.
Nano-Mechanical Properties Across Dentin-Enamel Junction of Adult Human Incisors
Authors: Fong H. , Sarikaya M. , White S. N , Snead M. L. 
Published: April 2011

AbstractThe structure and mechanical properties of the dentin-enamel junction (DEJ) in human teeth play a critical role in transferring stress from hard enamel to soft dentin efficiently in order to preserve the longevity of this functionally gradient biocomposite. In this investigation, nano-hardness and elastic modulus of incisor teeth were studied across the dentin-enamel junction. It was found that, over a length scale of between 15 to 25 μm, there were decreasing trends in the values of both hardness and elastic modulus across the DEJ zone profiling from enamel to dentin. Images obtained, using atomic force and scanning electron microscopy techniques, from polished surfaces of cross-sectioned teeth samples showed an interpenetrating microstructure of enamel and dentin at the DEJ zone. These results suggest that the nano-mechanical property profiles across the DEJ were due to a continuous variation in the relative amount of enamel and dentin. These characteristics of the DEJ zone could be significant for describing the structural and mechanical coupling of the two structures. By increasing the interfacial contact area across the two mineralized tissues, stresses are dissipated into the softer dentin, thus reducing interfacial stress concentrations at the DEJ. This promotes effective load transfer from the hard enamel to soft dentin.
Tem Observance and Analysis of the (000l), l=2n+l, Forbidden Reflections in Synthetic and Biological Hydroxyapatites
Authors: Reyes-Gasga J. , Reyes-Reyes M. , García-García R. 
Published: April 2011

AbstractThe systematic appearance of (000l), l=2n+1, forbidden reflections in the electron diffraction patterns of hydroxyapatite, both synthetic and natural (human tooth enamel), is discussed. Structural disorder, double diffraction, and modulated structures and are discussed as possible causes. Structural disorder and modulated structure could be responsible for the rupture of the reported symmetry, in which oxygen and hydrogen perform an important role.
Lattice Distortions and Domain Structure in Epitaxial Manganite Thin Films
Authors: Suzuki Y. , Wu Yan , Rüdiger U. , Yu J. , Kent A.D. , Nath T.K. , Eom C.B. 
Published: April 2011

AbstractLattice distortions, be they in the form of chemical and hydrostatic pressure in bulk or lattice mismatch between film and substrate, have significant effects on the transport as well as the magnetic properties of colossal magnetoresistance (CMR) materials. We summarize here our results on tensilely and compressively strained La0.7Sr0.3MnO3 (LSMO) thin films that indicate the important role of lattice distortions due to the lattice mismatch between the film and substrate. The strain due to lattice distortions can be used to tune the magnetic domain structure, magnetization, magnetic anisotropy and magnetotransport of LSMO thin films.
Strain-Induced Magnetic Properties of Pr0.67Sr0.33MnO3 Thin Films
Authors: Wu X. W. , Rzchowski M. S. , Wang H. S. , Li Qi 
Published: April 2011

AbstractWe report the temperature dependence of the magnetic anisotropy in both compressive and tensile strained films of Pr0.67Sr0.33MnO3 (PSMO). Compressive strain induced by growth on LaAlO3 (LAO) substrates results in a spontaneous out-of-plane magnetization, while tensile strain (grown on SrTiO3) results in in-plane magnetization. The coefficient of linear proportionality between the magnetic anisotropy energy and the tetragonal strain for both compressive and tensile strained PSMO films is larger than that found previously in strained La0.67Ca0.33MnO3 films. From the data, we estimate a 20 unit cell magnetic domain wall width for PSMO / LAO. Scattering from such a narrow domain wall could produce a potentially significant contribution to the resistivity.