bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Ferroelectric Slab Waveguide: a Geometry for Microwave Components that Incorporate Ferroelectric Materials
Authors: Crowne Frank J. , Tidrow Steven C. 
Published: June 2019

AbstractA slab geometry, in which ferroelectric is inserted between two “cladding” layers with a microstrip electrode placed on top, is proposed as a way to integrate the properties of ferroelectric materials into microwave components. This structure distributes the propagating microwave fields between the ferroelectric and the cladding, so that the microwave dielectric constant is a weighted average of the dielectric constants of the two materials. It is shown that this geometry drastically reduces dissipation due to dielectric losses in the ferroelectric. In addition, by applying a dc bias to the microstrip line, the dielectric constant of the ferroelectric layer can be varied and with it the microwave properties of the structure.
Rapid Gel Cast Prototyping of Complex Paraelectric (Ba,Sr)TiO3/MgO Composites
Authors: Synowczynski Jennifer , Hirsch Samuel , Gersten Bonnie 
Published: June 2019

AbstractA rapid prototyping process for manufacturing complex three-dimensional RF structures in ceramic systems was developed. The process combines fundamentals from lost wax investment casting and ceramic gelcasting. The first step is to directly deposit a mold made of a low melting point wax using a high precision inkjet rapid prototyper. Then, a gelcasting slurry containing polymeric precursors, a high solids loading of ceramic powders and a free radical initiator is cast into the mold and polymerized to lock in the structure. Finally, the mold is melted and the remaining green part is sintered. Aqueous gelcasting slurries were developed for MgCO3, (Ba,Sr)TiO3, and a composite of (Ba,Sr)TiO3 and MgO. The maximum solids loading attained for each of the powders was 22 V%, 50 V%, and 25 V% respectively. The 50V% gelcast part had a more uniform microstructure, higher sintered density, less open porosity and smaller grain size than parts produced through dry pressing. The microstructural improvements resulted in a high dielectric permittivity.
Honeycomb Films of Biodegradable Polymers for Tissue Engineering
Authors: Nishikawa Takehiro , Arai Keiko , Hayashi Junko , Hara Masahiko , Shimomura Masatsugu 
Published: June 2019

AbstractWe report that microporous films (honeycomb films) can lead various types of cells to tissue formation. The honeycomb films were fabricated by applying a moist air to a spread polymer solution containing biodegradable polymers (poly(L-lactic acid) (PLLA) and poly (ε-caprolactone) (PCL)) and an amphiphilic polymer. Hepatocytes were cultured on a self-supporting honeycomb film of PLLA. The hepatocytes formed a single layer of columnar shape cells with a thickness of 20 μm. The tissue formation of hepatocytes specifically occurred on the honeycomb film of PLLA, not on a flat film of PLLA. Three dimensional tissue structures were formed, when cells were cultured on both sides of the self-supporting honeycomb film. Double layers of hepatocytes were obtained by the method. Striated tissues such as heart and blood vessel could be reconstructed by utilizing a stretched honeycomb film of PCL.
Biologically-Based Self-Assembling Hydrogels
Authors: Seal Brandon L. , Panitch Alyssa 
Published: June 2019

AbstractWe have developed polymers, which borrowing from biology, assemble into networks. The self-assembly regions of fibrinogen were cloned to form a scaffolding that either interacts with fibrin or assembles independently. Peptides consisting of a binding pocket (BP), ligand (L), and/or a Factor XIIIa substrate were synthesized and conjugated to methacroylated dextran or acrylated poly(ethylene glycol). Peptide-conjugated dextran was added to polymerizing fibrin, and the resulting hydrogels were evaluated rheologically. These conjugates significantly affected the mechanical properties of fibrin while the addition of unconjugated dextran did not. The BP and L peptides were conjugated to PEG star polymer. Mixtures of conjugated PEG-BP and PEG-L were found to assemble. This work shows that peptides directing assembly can be designed using motifs found in proteins. The peptides in this study not only alter the mechanical properties of fibrin, but also allow a mechanism for creating a self-assembling network.
Self-Assembly of a Modular Polypeptide based on Blocks of Silk-Mimetic and ElastinMimetic Sequences
Authors: Cazalis Chrystelle S. , Conticello Vincent P. 
Published: June 2019

AbstractSpider dragline silk fiber displays a unique and technologically significant combination of high tensile and compressive strength. The structural origin of these properties arises from the alternating sequence of crystalline alanine-rich domains and amorphous glycine-rich domains, which undergo microscopic phase separation in the silk fiber. We previously reported the synthesis and the self-assembly of a novel polypeptide 1, which emulates the modular structure of crystalline and amorphous elastomeric domains in dragline silk proteins. The sequence of this polypeptide comprises an alternating arrangement of a self-complementary, amphiphilic silk-mimetic oligopeptide (Ala-Glu-Ala-Glu-Ala-Lys-Ala-Lys) and environmentally-responsive elastin-mimetic segment (Val-Pro-Gly-Val-Gly). We report herein the synthesis and the self-assembly of an analogous polypeptide (2) with an higher content of elastin mimetic pentapeptides. A synthetic gene encoding four repeats of the alternating sequence was expressed in E. coli strain BL21(DE3) as a C-terminal fusion to a decahistidine leader sequence to afford a polypeptide with a molar mass of approximately 39 kDa. The regularly alternating pattern of elastin-mimetic and silk-mimetic blocks within the protein allowed the copolymer to spontaneously self-assemble upon heating above the phase transition of the elastin-mimetic block. The self-assembly process was studied using a combination of CD and solid-state NMR spectroscopy, which suggested that the alanine-rich domains undergo a conformational rearrangement from α-helix to β-sheet. This rearrangement coincides with the macromolecular phase transition of the elastin-mimetic domains, which resulted in irreversible aggregation of the polypeptide above the Tt of the elastin-mimetic domains.
Helical, Disordered, and What that Means: Structural Characterization of a New Series of Methyl 1-Thiaoligo(ethylene Oxide) Self-Assembled Monolayers
Authors: Vanderah David J. , Arsenault Jennifer , La Hongly , Silin Vitalii , Meuse Curtis W. , Gates Richard S. 
Published: June 2019

AbstractSelf-assembled monolayers (SAMs) of a series of linear thiols containing a 1-thiaoligo(ethylene oxide) [TOEO] moiety, i.e., HS(CH2CH2O)xCH3, where x = 3 - 6, were prepared on polycrystalline gold (Au) and characterized by reflection absorption infrared spectroscopy (RAIRS) and spectroscopic ellipsometry (SE). For x = 5 and 6, the RAIRS data show that the TOEO segment, oriented normal to the substrate, adopts the highly ordered 7/2 helical structure of the folded-chain crystal polymorph of poly(ethylene oxide). For x = 3 and 4, the RAIRS and SE data indicate disordered, “amorphous” SAMs with essentially no evidence of the helical conformation in the TOEO segment. These data suggest that, for SAMs with TOEO segments, a minimum of five ethylene oxide units is required to adopt a helical conformation.
Selectivity of Polypeptide Binding to Nanoscale Substrates
Authors: Lustig Steven R. , Jagota Anand 
Published: June 2019

AbstractWe present new computational methodology for designing polymers, such as polypeptides and polyelectrolytes, which can selectively recognize nanostructured substrates. The methodology applies to polymers which might be used to: control placement and assembly for electronic devices, template structure during materials synthesis, as well as add new biological and chemical functionality to surfaces. Optimization of the polymer configurational sequence permits enhancement of both binding energy on and binding selectivity between one or more atomistic surfaces. A novel Continuous Rotational Isomeric State (CRIS) method permits continuous backbone torsion sampling and is seen to be critical in binding optimization problems where chain flexibility is important. We illustrate selective polypeptide binding between either analytic, uniformly charged surfaces or atomistic GaAs(100), GaAs(110) and GaAs(111) surfaces. Computational results compare very favorably with prior experimental phage display observations [S.R. Whaley et al., Nature, 405, 665 (2000)] for GaAs substrates. Further investigation indicates that chain flexibility is important to exhibit selective binding between surfaces of similar charge density. Such chains begin with sequences which repel the surfaces, continue with sequences that attract the surface and end with sequences that neither attract nor repel strongly.
Developing Bio-Stable and Biodegradable Composites for Tissue Replacement and Tissue Regeneration
Authors: Wang Min 
Published: June 2019

AbstractBone is the substantial unit of human skeletal system, which supports the body and its movement. At the ultra-structure level, the bone matrix is a composite material consisting of bone mineral particles, which are mainly substituted, calcium-deficient hydroxyapatite, and collagen, which is a natural polymer. Bone serves as the template for developing bone replacement materials. Research on biomaterials analogous to bone was started in the early 1980s by incorporating bioactive particles into biocompatible polymers so as to produce bone substitutes. Over the last two decades, a variety of bioactive polymer matrix composites have been developed for tissue substitution and tissue regeneration. The bioactive phases in these composites are normally one of the calcium phosphates, especially synthetic hydroxyapatite (HA, Ca10(PO4)6(OH)2) which closely resembles bone apatite and exhibits osteoconductivity. If enhanced bioactivity is required, bioceramics having higher bioactivity such as Bioglass® and A-W glass-ceramic can be used as the bioactive phase in the composites. For tissue replacement, bio-stable polymers such as polyethylene (PE) and polysulfone (PSU) are used as the matrix polymer. For tissue regeneration, natural, biodegradable polymers such as polyhydroxybutyrate (PHB) and chitin are used as matrices. Furthermore, mechanical as well as biological performance of a particular composite can be controlled by varying the amount of the bioactive phase in the composite, thus meeting specific clinical requirements. For bioactive ceramic-polymer composites, major influencing factors such as shape, size and size distribution of bioactive particles, mechanical properties and volume percentage of the bioactive phase, properties of the matrix polymer, distribution of bioactive particles in the matrix and the particle-matrix interfacial state should be controlled in order to obtain materials of desirable properties. Various techniques are used to evaluate the composites.
The Investigation on Preparation & Physicochemical Process of Nanosized Hydroxyapatite Powder
Authors: Song Yunjing , Wen Shulin , Li Musen 
Published: June 2019

AbstractThe investigations of the preparation and physicochemical process of the HA nanostructured powder with high performance have been performed at present study. The HA preparation starts from the ethanol solution of calcium nitrate tetra-hydrate and phosphorous pentoxide as raw materials. The characterization of the effects of reacting temperatures on preparation, the crystalline degrees (some amorphous HA formed at certain condition) of the reacting products are carried out in the meanwhile. The physicochemical processes and the conditions for different reactions stages of the HA preparation have been traced and characterized by the TG-DTA (thermogravimetric and differential thermal analysis), the FTIR (Fourier-transformed infrared spectroscopy) and other methods. The investigations of the chemical reactions for the HA preparation show that the synthesis of HA is completely finished at the temperature of 500°for hours. The grain sizes and shapes of the HA reacting products are observed and characterized by the TEM and the XRD. The results show that the mean diameters of these product grains are as fine as 30-40nm at the temperature of 500°C. The XRD pattern of the present HA powders sintered at 500°C for 2h coincided very well with the JCPDS standards showing its superior purity and therefore, with really high performance for later applications.
Magnetic Material Arrangement In Apis MelliferaAbdomens
Authors: Esquivel Darci M. S. , Wajnberg Eliane , Cernicchiaro Geraldo R. , Acosta-Avalos Daniel , Garcia B.E. 
Published: June 2019

AbstractHoneybees are the most studied insects in the magnetic orientation research field. Experiments on the magnetic remanence of honeybees have shown the presence of magnetite nanoparticles, aligned transversely to the body axis on the anterodorsal abdomen horizontal plane. These results support the hypothesis of ferromagnetic sensors for the magnetoreception mechanism. An Electron Paramagnetic Resonance (EPR) study identified isolated magnetite nanoparticles and aggregates of these particles with a low temperature transition (52 K – 91 K). Hysteresis curves of Apis mellifera abdomens organized parallel and perpendicular to the applied magnetic field were obtained from 5K to 310K. At low temperatures, the hysteresis curves indicate a preferential orientation of the magnetic easy axis parallel to the body axis. The saturation (Js) and remanent (Jr) magnetizations, coercive field (Hc) and initial susceptibility (Ψ) were obtained. Results were interpreted based on the presence of magnetite nanoparticles with 50 K and 120 K mean blocking temperatures.
Thermal Properties of Mineralized and Non Mineralized Type I Collagen in Bone
Authors: Lozano L. F. , Peña-Rico M. A. , Jang-Cho H. , Heredia A. , Villarreal E. , Ocotlán-Flores J. , Gomez-Cortes A. L. , Aranda-Manteca F. J. , Orozco E. , Bucio L. 
Published: June 2019

AbstractThe research about the structural stability of bone, as a composite material, compromises a complete understanding of the interaction between the mineral and organic phases. The thermal stability of human bone and type I collagen extracted from human bone by different methods was studied in order to understand the interactions between the mineral and organic phases when is affected by a degradation/combustion process. The experimental techniques employed were calorimetry and infrared spectroscopy (FTIR) techniques. The extracted type I collagens result to have a bigger thermal stability with a Tmax at 500 and 530 Celsius degrees compared with the collagen present in bone with Tmax at 350 Celsius degrees. The enthalpy value for the complete degradation/combustion process were similar for all the samples, being 8.4 +- 0.11 kJ/g for recent bones diminishing with the antiquity, while for extracted collagens were 8.9 +- 0.07 and 7.9 +-1.01 kJ/g. These findings demonstrate that the stability loss of type I collagen is due to its interactions with the mineral phase, namely carbonate hydroxyapatite. This cause a change in the molecular properties of the collagen during mineralization, specifically in its cross-links and other chemical interactions, which have a global effect over the fibers elasticity, but gaining tensile strength in bone as a whole tissue. We are applying this characterization to analyze the diagenetic process of bones with archaeological interest in order to identify how the environmental factors affect the molecular structure of type I collagen. In bone samples that proceed from an specific region with the same environmental conditions, the enthalpy value per unit mass was found to diminish exponentially with respect to the bone antiquity.
Self-Assembly of Hydrogels From Elastin-Mimetic Block Copolymers
Authors: Wright Elizabeth R. , McMillan R. Andrew , Cooper Alan , Apkarian Robert P. , Conticello Vincent P. 
Published: June 2019

AbstractTriblock copolymers have traditionally been synthesized with conventional organic components. However, triblock copolymers could be synthesized by the incorporation of two incompatible protein-based polymers. The polypeptides would differ in their hydrophobicity and confer unique physiochemical properties to the resultant materials. One protein-based polymer, based on a sequence of native elastin, that has been utilized in the synthesis of biomaterials is poly (Valine-Proline-Glycine-ValineGlycine) or poly(VPGVG) [1]. This polypeptide has been shown to have an inverse temperature transition that can be adjusted by non-conservative amino acid substitutions in the fourth position [2]. By combining polypeptide blocks with different inverse temperature transition values due to hydrophobicity differences, we expect to produce amphiphilic polypeptides capable of self-assembly into hydrogels. Our research examines the design, synthesis and characterization of elastin-mimetic block copolymers as functional biomaterials. The methods that are used for the characterization include variable temperature 1D and 2D High-Resolution-NMR, cryo-High Resolutions Scanning Electron Microscopy and Differential Scanning Calorimetry.
Antimicrobial Coatings Obtained in an Atmospheric Pressure Dielectric Barrier Glow Discharge
Authors: Paulussen Sabine , Vangeneugden Dirk , Goossens Olivier , Dekempeneer Erik 
Published: June 2019

AbstractThis paper addresses the development of plasma polymer coatings that should prevent bacteria from adhering to medical devices, implants, textile fibers, packaging materials, etc. The two main parameters affecting bacterial colonization onto surfaces are the surface energy and the surface roughness. Both parameters can be adjusted by the deposition of a thin plasma polymer coating in an atmospheric pressure dielectric barrier glow discharge. According to SEM, FTIR, SPM, XPS and contact angle measurements, smooth, hydrophilic plasma polymer coatings were obtained under specific plasma conditions starting from 2-hydroxyethyl methacrylate (HEMA) and ethyl diazoacetate (EDA).
Calcium Carbonate Reinforced Natural Polymer Composite For Bone Grafts
Authors: Kalita Samar J. , Bose Susmita , Hosick Howard L. , Martinez Steve A. , Bandyopadhyay Amit 
Published: June 2019

AbstractChallenges in tissue engineering have always-motivated scientists and engineers to develop new biomaterials that can restore the structural features and physiological functions of natural tissues. A novel ceramic-polymer composite was processed with bio-active ceramics dispersed in a natural bio-active polymer for bone graft applications. A commercially available caster bean extract polymer (CBP) was used. It is a natural polymer extracted from the oily caster beans of the dicotyledonous class. During processing of these composites, in situ random interconnected porosity was generated similar to natural bone. Hg-porosimetry results of these composites show that most of the pores are between 50 to 150 microns. Compression tests were performed on cylindrical samples to determine the mechanical properties. Average compression modulus was calculated as 173 MPa, while the average failure strength was 6.7 MPa. Cytotoxicity and cell proliferation studies were conducted with modified human osteoblast cell-line (OPC-1) to show that these composites are biocompatible. Composites showed good cell attachment with a continuous increase in cell growth for at least up to two weeks.
Synthesis and Characterization of Electrostatical Self-Assembly CdSe/Polymer Nanocomposite Films
Authors: Zhang Liangmin , Zhang Fajian , Claus R. O. 
Published: June 2019

AbstractUsing a novel electrostatic self-assembly (ESA) method to incorporate CdSe quantum dots into polymer we have successfully synthesized ultrathin films. This method allows the molecular-level thickness control and layer-by-layer formation of multilayer thin and thick films using alternative anionic and cationic molecular solution dipping. From ellipsometric measurements, we obtained that the thickness of per bilayer is around 3.7 nm. UV-vis absorption spectra versus the number of bilayers have also been obtained using an Hitachi 2001 spectrometer. The size of CdSe quantum dots has been measured using transmission electron microscopy before the CdSe quantum dots are incorporated and confirmed using atomic force microscopy after the formation of the film, respectively. Both measurements indicate that the diameter of the CdSe quantum dots is 2-3 nm. Xray photoelectron spectroscopy indicates that the concentration of the CdSe quantum dots in the film is 2.14%.
Spectral Analysis of Frictional Forces in ILD CMP
Authors: Philipossian Ara , Rosales-Yeomans Daniel , Charns Leslie , Rogers Chris , Doy Toshiroh , Kinoshita Masaharu 
Published: June 2019

AbstractSpectral analysis of real-time friction data obtained during ILD CMP is used to elucidate the tribology of the process in terms of stick-slip phenomena. Fourier transform analysis is employed to quantify the total amount of mechanical interaction in the pad-slurry-wafer interface as a function of various IC-1000 pad surface textures, PL-4217 fumed silica concentrations, relative pad-wafer velocities and applied wafer pressures. A new parameter termed the ‘Interfacial Interaction Index’ (γ) is defined and determined empirically by integrating the amplitude of the force spectra over a wide range of frequencies. Values of γ extracted from individual force spectra are in qualitative agreement with the tribological information obtained in previous studies using Stribeck curve analysis. This new method is remarkable since it has the potential to eliminate having to perform a multitude of experiments needed for constructing and interpreting Stribeck curves. For a given tribological mechanism, analysis of the spectra for various types of pad textures indicates significant differences between the K-Grooved pad and other types of pads. A qualitative model relating the observed spectra to pad storage modulus is presented as a potential explanation for the above observation.