bluuebunny/crossref_metadata_2025 huggingface dataset:
Peptidomic Analysis of the Central Nervous System of the Protochordate, Ciona intestinalis: Homologs and Prototypes of Vertebrate Peptides and Novel Peptides
Authors: Kawada Tsuyoshi , Ogasawara Michio , Sekiguchi Toshio , Aoyama Masato , Hotta Kohji , Oka Kotaro , Satake Honoo
Published: April 2011

The phylogenetic position of ascidians as the chordate invertebrates closest to vertebrates suggests that they might possess homologs and/or prototypes of vertebrate peptide hormones and neuropeptides as well as ascidian-specific peptides. However, only a small number of peptides have so far been identified in ascidians. In the present study, we have identified various peptides in the ascidian, Ciona intestinalis. Mass spectrometry-based peptidomic analysis detected 33 peptides, including 26 novel peptides, from C. intestinalis. The ascidian peptides are largely classified into three categories: 1) prototypes and homologs of vertebrate peptides, such as galanin/galanin-like peptide, which have never been identified in any invertebrates; 2) peptides partially homologous with vertebrate peptides, including novel neurotesin-like peptides; 3) novel peptides. These results not only provide evidence that C. intestinalis possesses various homologs and prototypes of vertebrate neuropeptides and peptide hormones but also suggest that several of these peptides might have diverged in the ascidian-specific evolutionary lineage. All Ciona peptide genes were expressed in the neural complex, whereas several peptide gene transcripts were also distributed in peripheral tissues, including the ovary. Furthermore, a Ciona neurotensin-like peptide, C. intestinalis neurotensin-like peptide 6, was shown to down-regulate growth of Ciona vitellogenic oocytes. These results suggest that the Ciona peptides act not only as neuropeptides in the neural tissue but also as hormones in nonneuronal tissues and that ascidians, unlike other invertebrates, such as nematodes, insects, and sea urchins, established an evolutionary origin of the peptidergic neuroendocrine, endocrine, and nervous systems of vertebrates with certain specific molecular diversity.
The Pauper's Gift: Postcolonial Theory and the New Democratic Dispensation
Authors: Gandhi Leela
Published: April 2011

This essay considers recent critiques of postcolonial theory and proposes democracy as a theme likely to prove crucial for the future of the field. It argues that a properly postcolonial turn toward democracy demands a new philosophical, political, and ethical valuation of the concept of naïveté.
Provincializing France?
Authors: Mbembe Achille
Published: April 2011

In the rest of the world, the “postcolonial turn” in the social sciences and humanities took place nearly a quarter century ago. Since then, the method or style of critique associated with that movement has influenced myriad political, epistemological, institutional, and disciplinary debates in the United States, the United Kingdom, and regions across the Southern Hemisphere (South America, Australia, New Zealand, the Indian subcontinent, and South Africa). From its inception, postcolonial studies has been interpreted in extremely diverse ways; over time, it has spawned robust waves of polemic and controversy, not to mention the many objections, each contradicting the previous, that continue today. It has also given rise to an abundance of profoundly rich and tremendously divergent intellectual, political, and aesthetic practices — so much so that one might earnestly ask where the unity of “postcolonial studies” lies. But despite this logic of segmentation, one can assert that, at its core, the object of postcolonial critique is best described in terms of the interlacing of histories and the concatenation of distinct worlds. Given that slavery and especially colonization (but also migrations, the ordering of sex and sexuality, and the circulation of forms, imaginaries, goods, ideas, and people) played such decisive roles in this process of human collision and entanglement, it is logical that postcolonial studies has made them the privileged objects of its inquiry.
Designing benefit rules for flexible retirement: Welfare vs. redistribution
Authors: Eső P. , Simonovits A. , Tóth J.
Published: April 2011

With flexible (variable) retirement every individual determines his optimal retirement age, depending on a common benefit-retirement age schedule and his life expectancy. The government maximises the average expected lifetime utilityminusa scalar multiple of the variance of the lifetime pension balances to achieve harmony between the maximisation of welfare and the minimisation of redistribution. Since the government cannot identify types by life expectancy, it must take the individual incentive compatibility constraints into account. Second-best schedules strongly reduce the variances of benefits and of retirement ages of the so-called actuarially fair system, thus achieving higher social welfare and lower redistribution.
Electrical Detection of Oscillations in Micro- and Nano- Cantilevers Using Harmonic Detection of Resonance
Authors: Gaillard J. , Ciocan Razvan , Skove Malcolm J. , Rao Apparao M.
Published: April 2011

Accurate determination of the resonant frequency, phase and quality factor in micro and nano-mechanical oscillators permits the detection of: (i) trace amounts of specific adsorbed molecules which affect the resonant frequency; (ii) pressure variations which affect the mechanical damping of the oscillator; or (iii) the temperature dependence of the elastic properties of the oscillator through a shift in the resonant frequency. To date, electrical detection of oscillations in cantilevered multiwalled carbon nanotubes (MWNTs) has eluded researchers in the field. Electrical detection allows a simple means for measuring the resonance frequency, phase and quality factor of cantilevers built into integrated circuits, or cantilevers whose response can be monitored as a function of any external parameter such as temperature or pressure. To this end, we described a fully electrical (actuation and detection) method termed harmonic detection of resonance (HDR) to measure mechanical oscillations in ambient conditions for two systems: Si-based micro- and MWNT based nano-cantilevers. Furthermore, we demonstrate that the resonant frequency in micro- and nano-cantilevers can be tuned without appreciable change in the quality factor which suggests that HDR is an ideal platform in device design and applications.
Active CPU Cooling System with Piezoelectric Actuated Droplet Generator
Authors: Lu Chun-Fu , Huang Chi-Ming , Yang Jinn-Cherng , Chiang Hung -Liang , Fu Chien-Chung , Cheng Chiang-Ho , Chen Chun-Jung
Published: April 2011

Ink jet technology is applied to the industry application of CPU cooling in this study. The PZT actuated micro-cooling device which generating the micro-scale liquid droplet is used in the CPU cooling of desktop and laptop PCs. It consists the advantages of long lifetime of operation, simple and easily manufactured of the structure with PZT actuator. Since the high latent heat transfer rate, 2260 J/g, of water droplet for the liquid-vapor phase change cooling system, it removes heat from the CPU surface effectively for over 100 W. In order to design an efficient cooling device, it is important to study the PZT material property varies after the laser cutting process and the dimensional effects of PZT actuator on the nozzle plate vibration mode. The frequency and amplitude of the voltage used to energize the PZT transducer are also important parameters that should be properly controlled in order to achieve the optimal liquid breakup conditions. It also reveals the low noise and power consumption in the CPU cooling system with some appropriate operational conditions.
Electronic Structure of VO2 near Phase Transition by Tunneling Spectroscopy
Authors: Kim Changman , Oikawa Yasushi , Tamura Takashi , Shin Jae-Soo , Ozaki Hajime
Published: April 2011

Tunneling spectroscopy was carried out on W doped VO2 single crystal in the temperature region across the phase transition. Double pseudo gap structures were observed across the Fermi level at temperatures below the phase transition. When the temperature was increased across the phase transition, the outer gap structure disappeared and the inner gap structure of about 0.36 eV became sharp. A precursor of phase transition to low temperature phase was observed in the tunneling density of states near the Fermi level, when the temperature approached 0.2 K to the threshold of transition in the electrical resistivity.
Porous methylsiloxane gel thick film for millimeter-wave antenna substrate prepared by gap filling method
Authors: Tanaka Takeharu , Kawakami Nobuyuki , Hirano Takayuki , Fukumoto Yoshito , Suzuki Tetsuo , Kanamori Kazuyoshi , Nakanishi Kazuki
Published: April 2011

A novel process to fabricate a thick silica gel film on an aluminum substrate, named the “gap filling method”, has been developed. The process is based on a sol-gel method accompanied by phase separation in a submillimeter thick space defined by two facing substrates. Dielectric thick film integrated on a metal ground plate is successfully formed by using a SiO2 coated aluminum substrate and a cap plate covered with an amorphous carbon thin film, which control the hydrophilicity and the hydrophobicity of the plates, respectively. A thin continuous layer of less than 0.5 μm thick is formed at the interface between the porous film and the cap plate, which gives the film a smooth surface preferable for patterning metal circuits of an antenna. The observed dielectric constants (εr) at 60 GHz measured by the Fabry-Perot resonator method are in the range between 1.4 and 1.6. Methyl groups homogeneously distributed in the siloxane network give a hydrophobic siloxane gel film, thus the obtained films have enough environmental stability. These results show that the gap filling method is applicable to the preparation of the porous thick film that is needed for antenna applications.
Effect of High-Energy-Electron Irradiation on Nonisothermal Crystallization Kinetics in P(VDF-TrFE) 65/35 mol% Copolymers
Authors: Li Zhi-Min , Cheng Z.-Y.
Published: April 2011

The effect of the high-energy-electron irradiation on the crystallization process in poly(vinylidene fluoride-trifluoroethyelene) [(P(VDF-TrFE)] 65/35 mol% copolymers was studied by nonisothermal crystallization using the differential scanning calorimetry (DSC) technique. The experimental data are analyzed using modified Avrami, Ozawa, and combined Avrami-Ozawa methods. It is found that the crystals grow in three dimensions in the irradiated samples. It is found that the irradiation results in a lower crystallization temperature and a lower crystallization activation energy. It is also found that the irradiated samples have a lower crystallization temperature than the unirradiated samples. All these results indicate that the crystals grown in the irradiated samples have a smaller surface energy, which corresponds to a thicker interfacial layer.
Emeraldine Base Thin Film Carbon Dioxide Sensor
Authors: Irimia-Vladu Mihai , Fergus Jeffrey W.
Published: April 2011

A thin film of emeraldine base polyaniline in NMP was cast on an interdigitated electrode and its conductivity investigated by impedance spectroscopy. The thin film responded to carbonic acid solutions of various pHs lower than 5. In general, an emeraldine base (EB) to emeraldine salt (ES) transformation occurs by protonation when the pH is less than 4. In the present case, the stages that occur prior to the onset of changes in total conductivity are detected by impedance spectroscopy. The sensor output was stable and reversible over a period of 3 months of testing.
Emerging Magnetism Arising from Self Damage in α- and δ-Pu
Authors: McCall Scott , Fluss Micheal J , Chung Brandon W , Chapline George F , Jackson Damon D , McElfresh Micheal W
Published: April 2011

As a consequence of the unusual nature of plutonium's electronic structure, point- and extended-defects are expected to, and do exhibit extraordinary properties. Low temperature magnetic susceptibility measurements on Pu and fcc-Pu(Ga) show that the magnetic susceptibility increases as a function of time, yet upon annealing the specimen returns to its initial magnetic susceptibility. This excess magnetic susceptibility (EMS) arises from the alpha-decay and U recoil damage cascades which produce vacancy and interstitials as point and extended defects. The temperature of the first annealing stage defines a temperature (<35K) below which we are able to characterize the time and temperature evolution of the accumulating damage cascades as being a saturation function. The temperature dependence of the EMS is well described by a time independent, Curie-Weiss curve arising from a volumetric region surrounding each U damage cascade. This saturation picture also leads directly to a determination of the microscopic volume of the specimen that is affected by the frozen-in damage cascade. For our measurements in δ-Pu we calculate a diameter of the magnetically affected volume of ∼250Å per damage cascade. This should be compared with an estimated volume that encloses the damage cascade itself (determined from molecular dynamics) of ∼100 Å. Hence, the ratio of these volumes is ∼8. The observed anomalous magnetic behavior is likely a consequence of the highly correlated nature of the electrons. Similarities with defects in hole-doped superconductors suggest a general phenomenon in strongly correlated electron systems, of which Pu may be a particularly unusual or special example.
Burst Martensitic Transformations in a Pu-Ga Alloy
Authors: Blobaum Kerri J.M. , Mitchell J. N. , Krenn C. R. , Wall M. A. , Massalski T. B. , Schwartz A. J.
Published: April 2011

Martensitic transformations can occur via two modes: thermoelastic and burst. In thermoelastic martensites, deformation can be accommodated elastically and transformations occur smoothly with changes in temperature or stress. Burst martensitic transformations require both elastic and plastic deformation to accommodate strain; individual martensite particles form at the speed of sound, and the overall accumulation of martensite may increase in discrete, incremental steps. Here, we examine a unique martensitic transformation and reversion in a Pu-2.0 at% Ga alloy and show evidence that they proceed via the burst mode. Upon cooling from ambient conditions, the metastable delta phase partially transforms martensitically to the alpha-prime phase with a volume contraction of 20%. This large volume change suggests a burst transformation. Furthermore, using differential scanning calorimetry (DSC), we observed that the alpha-prime to delta reversion proceeds in discrete increments, which appear as sharp peaks in DSC data. The DSC data is compared to similar results obtained using dilatometry and resistometry. This incremental progression is believed to be the result of autocatalytic cascades of many alpha-prime particles reverting nearly-simultaneously to the delta phase. Finite-element modeling suggests that residual stresses in the regions of reverted alpha-prime particles may catalyze (or retard) additional transformation. These stresses could initiate cascades of alpha-prime particles that revert nearly-simultaneously. The cascades are likely quenched by stress and/or temperature changes resulting from the transformation itself. During the forward delta to alpha-prime transformation, burst events are not observed with the above techniques. The transformation, however, is still expected to proceed via the burst martensite mode because of the large volume changes required. Because alpha-prime must be nucleated in the delta matrix before it can grow as an individual burst, the transformation may not occur cooperatively. These individual bursts may be too small to be resolved by the above techniques, and the signal observed corresponds to a cumulative total of all the events.
The Radiation Induced Chemistry of the Uranyl Cation in Carbonate –Bicarbonate Solutions as Followed by NMR Spectroscopy
Authors: McNamara Bruce Kevin , Snow Lanee A. , Soderquist Chuck Z. , Sinkov Sergei , Cho Herman M. , Friese Judah I.
Published: April 2011

Hydrogen peroxide formed by radiolysis of carbonate –bicarbonate media was followed by 13C NMR using dissolved [233UO2(13CO3)3]4- as the alpha source (Dα=12.1 Gy/hr). It is shown that the speciation of the peroxide carbonates (or other species) that are formed in the pH region 5.9 and 11.6 by titration with hydrogen peroxide are common to those formed by hydrogen peroxide generated by radiolysis. Radiolytic generation of hydrogen peroxide was followed by observing the formation of a uranyl peroxide carbonate complex. Complex formation was observed to accelerate for about 1200 hours and to terminate between 1×10-4 and 5×10-4 M. It is assumed that either a steady state H2O2 production rate was established in solution or that some limiting feature of the experiment was responsible for slowing the yield of product.
Oxidation of uranium nanoparticles produced via pulsed laser ablation
Authors: Trelenberg Tom , Glade Stephen C , Tobin James G , Felter Thomas E , Hamza Alex V
Published: April 2011

An experimental apparatus designed for the synthesis, via pulsed laser deposition, and analysis of metallic nanoparticles and thin films of plutonium and other actinides was tested on depleted uranium samples. Five nanosecond pulses from a Nd:YAG laser produced films of ∼1600 Å thickness that were deposited showing an angular distribution typical of thermal ablation. The films remained contiguous for many months in vacuum but blistered due to induced tensile stresses several days after exposure to air. The films were allowed to oxidize from the residual water vapor within the chamber (2×10-10 Torr base pressure). The oxidation was monitored by in-situ analysis techniques including x-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS), and scanning tunneling microscopy (STM) and followed Langmuir kinetics.
Combinatorial approach to exploration of a novel fluid oxide flux stable in vacuum for material processing
Authors: Matsumoto Yuji , Koinuma Hideomi , Tsuruta Hirohiko , Takahashi Ryota
Published: April 2011

We explored a new fluid flux stabilized even in the vacuum condition at high temperature by combinatorial pulsed laser deposition (PLD) approach. A small amount of CuO doped in BiOx was found to effectively stabilize BiOx even in 6 Torr O2 at 800°C. The application of this novel Bi-Cu-O flux to the vacuum process lead to the successful fabrication of a single crystal Bi4Ti3O12 film and the establishment of a more reliable process for preparation of an atomically flat LaAlO3(001) substrate.
A Calculation Method of Deposition Profiles in Chemical Vapor Deposition Reactors Using Genetic Algorithms for The Automatic Modeling System of Reaction Mechanisms
Authors: Takahashi Takahiro , Ema Yoshinori
Published: April 2011

Fast and accurate calculation of the predicted results of Chemical Vapor Depositions (CVD) is very helpful to the high-throughput optimization of the CVD processes. In addition, robustness of the calculation process is important for automation of the optimization process. Therefore, we have developed a novel calculation method, by which robust and accurate calculations along with reduced computing cost were achieved, to reproduce deposition profiles in a macroscopic cavity (macrocavity). Boundary value problems for estimating diffusion-reaction equations by iterations of numerical integrations were changed into problems of finding the linear combinations consisted of a few functions. The coefficients of the linear combinations were optimized by Genetic Algorithms (GA). We could demonstrate the validity of the proposed method using various examples of the reaction mechanisms and conditions.
Analysis of the Structural Specificity of ZrO2Nanoparticles in Pillared Clays by Modeling of the Condensation Process in ZrOCl2*8H2O Solutions
Authors: Mezentseva Natalya , Sadykov Vladislav Aleksandrovich , Avdeev Vasilii Ivanovich , Kuznetsov Vladimir L'vovich
Published: April 2011

A combination of quantum-chemical approaches including DFT, semiempirical PM3 and molecular mechanics (force field MM+) methods has been applied for analysis of the structure of polynuclear hydroxocomplexes of Zr in diluted solutions of its oxochloride as precursors of zirconia nanoparticles in zirconia-pillared clays. Relative stability of complexes differing by their size and shape has been estimated.
Adsorption of atomic and molecular oxygen on the SrTiO3(001) surfaces: Computer simulations by means of hybrid density functional calculations and ab initio thermodynamics
Authors: Piskunov Sergei , Zhukovskii Yuri F. , Kotomin Eugene A. , Heifets Eugene , Ellis Donald E.
Published: April 2011

Ab initio calculations based on density functional theory (DFT) have been used to study the energetics, fully relaxed structure, charge redistribution, and electronic density of states of adsorbed atomic and molecular oxygen on defectless unreconstructed SrO- and TiO2-terminated SrTiO3(001) surfaces. Exchange-correlation functional applied within DFT contains a “hybrid” of the non-local Hartree–Fock exchange, DFT exchange, and generalized gradient approximation correlation functionals. The calculations are performed on periodically repeated systems (two-dimensional slabs) large enough for the adsorbed species to be treated as isolated. We find substantial binding energies of up to 1.8 eV for atomic oxygen adsorption over surface oxygen and of over 2.0 eV at bridge (position between two adjacent surface atoms) sites of both SrO- and TiO2-terminated surface. A range of different adsorption sites and orientations for molecular oxygen have been studied but practically in no case does the adsorption energy exceed 0.1 eV. The stability diagram of surface structures in contact with a gaseous oxygen environment is calculated by means of atomistic thermodynamics. Adsorption of the reactants is found to depend significantly on temperature and partial pressures in the gas phase.
Combinatorial Compounding
Authors: Adams Nico , Moneke Martin , Guelmues Serguel Acikalin , Chenouf Dalil , Rehahn Matthias , Schubert Ulrich S
Published: April 2011

The need for fast and low-cost processes for compound development is obvious when “bespoke” products are required in small quantities. In a typical development workflow, many experiments are needed for the systematic study of the effects of additives and their potential synergistic interactions. This is usually accomplished using the one-variable-at-a-time variational principle. However, if the complexity of the formulation is high, the number of experiments that needs to be conducted soon becomes prohibitive. Therefore, new, but potentially more effective additives are not easily introduced. To address this problem, the plastics processing industry is turning to the notion of combinatorics, which has been shown to accelerate R&D times both in the pharmaceutical industry as well as in other areas of materials science such as catalysis and polymer chemistry.

The contribution discusses the development of a combinatorial compounding line, consisting of a production-size twin screw extruder with four gravimetric feeding units for the addition of additives. Furthermore, the development of fast on-line and in-line analytics for compound characterization is discussed.
pH-dependent Gelation of Gastric Mucin
Authors: Bansil Rama , Celli Jonathan , Chasan Benard , Erramilli Shyamsundar , Hong Zhenning , Afdhal Nezam H. , Bhaskar K.Ramakrishnan , Turner Bradley S
Published: April 2011

We discuss the mechanism by which gastric mucin forms a gel at low pH, which serves to protect the stomach from being damaged by the acidic gastric juice that it secretes. Frequency dependence of viscoelastic moduli of pig gastric mucin gels obtained by microscopic dynamic light scattering is presented. Atomic Force Microscopy provides direct visual evidence to indicate that mucin broken into its subunits does not gel at low pH.
Microparticles of Alginate Calcium Gel Modified by Chitosan for Pulsative Delivery Of Rifampicine
Authors: Batyrbekov Erkesh O , Iskakov Rinat , Kombarova Karlygash , Tleumukhambetova Aliya , Zhubanov Bulat
Published: April 2011

The aim of this work is the development of controlled delivery system immobilized by antimicrobial drug rifampicine on the basis of microparticles of alginate calcium gel, modified by natural polymer chitosan. Modified microparticles were obtained by syringed dropwise a solution of rifampicine in solution of sodium alginate was into a mixed solution of chitosan in calcium chloride. The obtained modified alginate microparticles were contained immobilized rifampicine and a surface layer of chitosan. Effects of chithosan concentration and exposure duration on the thickness of polymer coating were determined. For the determination of surface thickness a red congo dye has been used able to form a complex with chitosan. It has been established that with an increase in the concentration of a polymer from 0,3 up to 1,5 mass % the thickness of the modified layer increases from 5 up to 60 mcm, and an increase of the time of gel exposition in a 2,5% solution of chitosan from 30 min to 24 h results in an increase in thickness of a layer from 5 up to 20 mcm respectively. When studying an influence of pH of the medium upon an interaction of alginate and chitosan it was been observed a formation of a polyelectrolyte complex between a chitosan polycation and an alginate polyanion stabilized by ionic bonds. The release of rifampicine from the modified alginate gel particles into a physiological solution with different thickness of a chitosan coating were studied. It was shown that the characteristic maximums on the curve of release observe after 10, 30, 90 and 120 min for the samples without the coating and with the coating thickness of 55, 100 and 150 mcm respectively. The data obtained shown a possibility of the regulation of the rate of rifampicine relase from the modified alginate particles by way of alternation of thickness of the chitosan coating.
Segmented Polyurethane/Collagen Blends for Biomedical Application
Authors: Batyrbekov Erkesh O , Iskakov Rinat , Esenalina Gulsharat , Kurashev Aman , Kim Maria , Zhubanov Bulat
Published: April 2011

In the present study the preparation of biomedical devices and some biomedical application of implantable devices based on segmented polyurethane (SPU)/collagen blends have been described. SPU with different content of hard and soft segments were synthesised by a two-step polymerization using a number of polyethylene and propylene glycols and tolylene diisocyanate.

The successful biomedical application of SPU/collagen blends as biomaterials at some fields of medicine has been shown. These blends were used for the fabrication of artificial esophageal prostheses for treatment of injures and diseases of esophagus such as chemical burns, cicatrical structures, total stenosis in children when standard technique of surgical bypass of the nonfunctioning esophagus can not be used. The SPU/collagen blends containing anticancer agents were used for treatment of sarcoma of the orbit. It was established that the anticancer effect against Rhabdomiosarcoma of implanted blends prolongs 17-20 days and the toxic effects decrease due to reduce a total therapeutic dose from 2,0 mg/kg to 1,4 mg/kg.

Microparticles of SPU with diameter 200-500 microns were prepared with water-toluene interface emulsion polycondensation of toluene-2,4-diisocyanate and poly(ethylene glycol) of various molecular weight 400-2000. The current procedure allows to develop a series of microcapsulated drug delivery forms for respiratory therapeutic use. A method of exterior nose correction using a biocompatible SPU/collagen blend has been developed. The successful application of polyurethane films for reconstruction of the bridge and septum of nose in 15 patients was described.
Compositionally Modified Hydroxyapatite Nanocrystals for Polymer/Ceramic Scaffold Applications
Authors: Stanishevsky Andrei , Chinoda Peserai , Chowdhury Shafiul , Thomas Vinoy , Catledge Aaron , Dean Derrick
Published: April 2011

The polymer/bioceramic composite materials attract much attention for the development of bioresorbable implants and tissue engineering scaffolds. Hydroxyapatite (HA) is the most commonly used bioceramic material due to its similarity to the major mineral component of the hard tissue. We synthesized carbonated and Mg-substituted HA nanocrystals with various concentrations of CO32− and Mg2+ ions by chemical precipitation in the range of the process temperatures from 25 °C to 100 °C.

The HA nanocrystals were mixed with several polymeric materials (PCL, PLA, PVA, collagen) to fabricate bulk and nanofiber polymer/HA nanoparticle composites with the HA loading up to 80 % by weight. The HA nanocrystals and polymer/HA composites were characterized by X-ray diffraction, FT-IR spectroscopy, scanning electron and atomic force microscopy. Mechanical properties of the composites were investigated using nanoindentation technique.
Biomimetic Recognitive Polymer Networks for Ocular Delivery of Anti-Histamines
Authors: Venkatesh Siddarth , Sizemore Stephen P , Byrne Mark E.
Published: April 2011

Enhanced drug partitioning in hydrogels can be achieved by configurational biomimetic imprinting (CBIP) techniques which involve the formation of pre-polymerization complexes between template molecules and functional monomers with specific chemical structures designed to interact with the template via non-covalent chemistry. This new class of recognitive intelligent materials is designed by incorporating motifs with structural and molecular homology to biological receptors and has a strong potential to impact the administration of a number of ocular therapies.

This work addresses the unmet need for the controlled release of histamine antagonists such as ketotifen fumarate on the surface of the eye to treat allergic conjunctivitis. Mast cell and eosinophil degranulation occurs due to the IL-4 driven TH2 cell response to allergens and the subsequent IgE secretion. This prompts the release of inflammatory mediators such as histamine, which binds to the H1-receptors. Pharmacological downregulation is possible by the local delivery of H1-antihistamines, resulting in decreased vascular permeability, bronchodilation, and exudation of effector cells.

Treatment options for seasonal and perennial allergic conjunctivitis primarily consist of oral antihistamines (which provide only partial and delayed relief with potential systemic side effects) and topical treatments. Since ocular bioavailability of topical drugs is very poor (typically less than 7% is absorbed by the eye), a high dosage is needed which prohibits contact lens use. Controlling and tailoring the release of anti-histamines via novel recognitive contact lenses with significantly enhanced partitioning can solve these problems with increased bioavailability, less irritation to ocular tissue, and reduced ocular and systemic side effects. Controlled release by conventional soft contact lenses typically does not work due to a lack of sufficient drug loading.

Inspired by Nature, we have successfully synthesized and characterized recognitive networks for H1 antihistamines by choosing monomers on the basis of the non-covalent interactions found in histamine docking sites. This leads to significantly enhanced drug loading and tailorable controlled release of a therapeutically viable dosage of drug.
Modifying the Properties of Collagen Scaffolds with Microfluidics
Authors: Shreiber David I , Sundararaghavan Harini G , Song Minjung , Munikoti Vikram , Uhrich Kathryn E
Published: April 2011

It is now well accepted that the mechanical properties and cell adhesion profile of 2D and 3D extracellular matrix molecules combine to dictate cellular fate processes, such as differentiation, migration, proliferation, and apoptosis, through a process generally known as 'mechanotransduction', or the conversion of mechanical signals into a cellular response. The stiffness and adhesion density combine to affect the force balance that exists between an adherent cell and the surrounding substrate. We have established BioMEMS, microfluidic technology to alter the mechanical properties and cell adhesion profile of collagen scaffolds. Using soft lithography, we fabricate elastomeric networks that serve as conduits for the controlled mixing of type I collagen solutions. Our technology enables us to generate reproducible, controlled homogeneous and inhomogeneous microenvironments for 3D cell culture, assays of cell behavior in 3D, and the development of bioartificial tissue equivalents for regenerative and reparative therapies. The adhesivity of collagen is modulated by covalently grafting peptides (such as RGD) or proteins (such as albumin) to soluble collagen molecules with 1- ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC), a hetero-bifunctional coupling agent. EDC activates the carboxylic group of collagen and forms an amine bond with the grafting molecule. The grafted collagen self-assembles into a fibrillar gel at physiological temperature and pH with no measurable changes in rheological properties compared to controls. A solution of peptide-grafted collagen is then mixed in microfluidic networks with unaltered collagen to form controlled gradients or other patterns of the two solutions, which immobilize upon self-assembly. Separately or in the same network, the mechanical properties of the collagen gel can be altered regionally by the microfluidic delivery a solution of a cell-tolerated crosslinking agent. We use genipin, which has the unique property of generating crosslinks that autofluoresce. The intensity of the fluorescence correlates with the degree of crosslinking (and thus the mechanical properties) enabling us to monitor and measure changes in mechanical properties dynamically and non-invasively. Lastly, though it requires constant delivery or recirculation, the same networks can be used to impose gradients of soluble factors, such as growth factors and cytokines. Thus, we have developed a platform to examine the response of cells to simultaneous chemotactic, haptotactic, and durotactic gradients in a 3D environment. We are employing this technology to examine the response of neural cells to gradients of biomaterial properties to optimize cues for spinal cord regeneration.
Ultrafast Orientational Dynamics of Nanoconfined Benzene
Authors: Zhu Xiang , Farrer Richard , Fourkas John
Published: April 2011

Optical Kerr effect spectroscopy has been used to study the orientational dynamics of benzene and benzene-d6 confined in nanoporous sol-gel glasses. Orientational diffusion was found to be inhibited considerably in confinement due to the strong wetting of benzene on silica. The orientational dynamics of benzene-d6 were found to be affected less than those of benzene, which is in agreement with the somewhat larger contact angle of benzene-d6 on silica. Comparison of our results to Raman data for confined benzene-d6 suggests that this liquid is considerably more organized at the pore surfaces than in the bulk.
Non-lithographic Nanofabrication Using Porous Alumina Membranes
Authors: Ram K. Bhargavan , Tian L. , Wu Z , Menon Latika
Published: April 2011

We describe a fabrication method to prepare highly ordered Si nanopore arrays. A nanoporous alumina template of thickness ∼1μm is prepared by means of anodization of an aluminum film. The template has a highly ordered hexagonal array of pores of diameter ∼50nm. The template is detached from the aluminum layer and placed on a Si substrate. The nanoporous pattern is transferred onto silicon substrate by means of a dry plasma etch process. This produces an array of nanopores in silicon with a diameter of ∼50nm and depth of ∼300nm. We have used such an array to prepare Fe nanopillars inside the pores by means of thermal evaporation. Magnetization versus applied magnetic field measurements for the Fe nanoarrays, demonstrate large perpendicular anisotropy typical of high aspect ratio magnetic nanopillars. The value of coercivity is about 500Oe in the perpendicular direction and 40Oe in the parallel direction.
Nanoscale characterization of Pd/TiO2 catalysts and Ag/TiO2 catalysts by electron holography
Authors: Ichikawa Satoshi , Akita Tomoki , Okazaki Kazuyuki , Tanaka Koji , Kohyama Masanori
Published: April 2011

Catalytic properties of noble metal catalysts are often caused by their nanostructures and the interaction between nano particles and oxides supports. We examine the mean inner potential of Pd particles in Pd/TiO2 catalyst and Ag particles in Ag/TiO2 catalysts using electron holography and HRTEM. And we compare the results of the Pd/TiO2 and Ag/TiO2 systems with our previous results of the Au/TiO2 and Pt/TiO2 systems. In the case of the Pd/TiO2 catalysts, when the size of Pd particle is smaller than 5nm, the mean inner potential of Pd changes to be higher than the calculated value of the mean inner potential which is thought to be higher than the experimental values of bulk Pd by 3-5V. The mean inner potential of Pd becomes to increase gradually as the size of the Pd particle decreases. The rate of the increment in the mean inner potential of Pd is lower than that of Au/TiO2 catalysts and Pt/TiO2 catalysts. On the other hand, in the case of Ag/TiO2 catalysts, the mean inner potential of Ag does not increase though the size of the Ag particle decreases to under 2nm.
A superlattice approach to the synthesis of ferroelectric Strontium Bismuth Tantalate thin films using liquid-injection-MOCVD
Authors: Potter Richard , Awad Ahmed , Chalker Paul R. , Wang Peng , Jones Anthony C. , Noakes Timothy C.Q. , Bailey Paul
Published: April 2011

The synthesis of SrBi2Ta2O9 (SBT) thin films has been investigated using a superlattice approach. Thin films were deposited on silicon by independent injection of each source to produce Bi2O3/SrTa2O6 superlattices. The effects of post-deposition annealing have been investigated using high-resolution TEM and medium energy ion scattering (MEIS) to depth profile the superlattices. X-ray diffraction has also been used to characterize the conversion of the superlattices from distinct layers of Bi2O3 and SrTa2O6 into a polycrystalline layer of strontium bismuth tantalate.
Growth of Ferroelectric PbZrxTi1-xO3 (PZT) Thin Films by Liquid-Delivery Metalorganic Chemical Vapor Deposition
Authors: Matichyn Serhiy , Lisker Marco , Burte Edmund P.
Published: April 2011

In this study lead zirkonat titanate (PZT) thin films were deposited using direct liquid injection metal organic chemical vapor deposition (DLI-MOCVD).

The chemical states and the stoichiometry of PZT-films were characterized using X-ray photoelectron spectroscopy (XPS). The crystal structure of the films was investigated by X-ray diffraction (XRD).

The surface composition of the films was Pb : Zr : Ti = 1.05 : 0.52 : 0.48, which indicates that the deposited films had a stoichiometric PZT composition. 130 nm thick PZT films deposited on Ir showed <110> preferred orientation.

The main role for formation of the perovsktive PZT films plays the content of the lead in the deposited films. Lead deficiency causes the formation of the pyrochlore phase with poor electrical properties. In films with a significant excess of lead a second PbO phase appeared that can be observed even with naked eyes. Negligible excess of lead can be reduced by post-deposition annealing at 500-600 °C.

The Ir/PZT/Ir capacitor showed large values of the remanent polarisation of about 60μC/cm2 at an applied voltage of 3 V. So high value of the remanent polarisation can be induced by structural stress in the films. After ten switch impulses the values of the remanent polarisation have significantly decreased. This is probably due to a relaxation of crystal cells.
Ba substituted Pb(ZrxTi1-x)O3 thin films grown by MOCVD
Authors: Puchalla Jochen , Hoffmann-Eifert Susanne , Cattaneo Lorena , Carella Sergio , Waser Rainer
Published: April 2011

High quality Pb(Zr,Ti)O3 [PZT] and (Pb1-xBax)(ZryTi1-y)O3 (x ≤ 0.15, 0.25 ≤ y ≤ 0.50) [PBZT] thin films were grown on Pt (111) and Ir (111) coated silicon substrates by means of a pulsed liquid injection metal organic chemical vapor deposition (MOCVD) technique. The precursor solutions of Pb(DPM)2, Ba(DPM)2, Zr(IBPM)4, and Ti(OiPr)2(DPM)2 dissolved in butylacetate were separately injected into an AIX-200 reactor using a TriJet™ vaporizer. Stoichiometric films (0.98 ≤ A/B ≤ 1.06) with thickness between 80 nm and 150 nm were deposited at a susceptor temperature of 615 °C to 660 °C. Pure PZT films grown on platinum coated substrates show a randomly oriented perovskite structure accompanied with formation of a PbPtx alloy at the PZT/Pt interface. On the Ir(111) coated substrates the pure PZT films also exhibit a random orientation possibly due to oxidation of the Ir surface layer during the deposition process. Ferroelectric properties of Pr = 35 µC/cm2 and Ec = 90 kV/cm were obtained for a PZT (30/70) film of 150 nm thickness grown on Ir/Si. In contrast, PBZT films with a Ba content of about 5 to 15% show lower tendency for formation of a PbPtx interfacial layer, and a preferred (111) texture was observed for PBZT films grown on the Ir (111) substrates under optimized process conditions. Tetragonal and rhombohedral PBZT films with 15% Ba and a Zr-content of about 0.35 and 0.50, respectively, show an orientation dependence of the ferroelectric properties in the way that Ec is highest for <111> textured films in comparison to Ec determined for <110> textured films. The remanent polarization of 85 nm thick tetragonal PBZT films changes from 17 µC/cm2 for <111> orientation to 13.5 µC/cm2 for <110> texture. The relative permittivity changes in the same way from 600 to 540, respectively. The rhombohedral films exhibit a nearly independent Pr value of about 11 µC/cm2 while the switching field changes from 75 kV/cm for an <111> textured film to 46 kV/cm for an (110) textured one. The relative permittivity values of both films are 890 and 715 for the (110) and the (111) textured films, respectively. The trends observed for the textured PBZT films grown on Si substrates reflect the behaviour reported for epitaxial films [2]
Optical, Electrical and Lifetime Characterization of In-Grown Stacking Faults in 4H-SiC
Authors: Caldwell Joshua David , Klein Paul B , Glembocki Orest J , Stahlbush Robert E , Liu Kendrick X , Hobart Karl D , Kub Fritz
Published: April 2011

Here we present optical beam induced current, electroluminescence, time resolved photoluminescence and current-voltage measurements on several 4H-SiC PiN diodes containing in-grown stacking faults (IGSFs). These defects were observed to act as either current shorts, creating a direct electrical contact between the p+ and n+ layers, or as a current barrier. Carrier lifetime measurements verify that the change in behavior is indeed associated with changes in the conductivity of the material in the vicinity of the defect and not due to local changes in the carrier lifetime. The IGSFs discussed here appear to differ from those previously discussed in the literature and may constitute a new, multi-layered IGSF.
Deep Levels in 4H Silicon Carbide Epilayers Induced by Neutron-Irradiation up to 1016 n/cm2
Authors: Cavallini Anna , Castaldini Antonio , Nava Filippo , Errani Paolo , Cindro Vladimir
Published: April 2011

We investigated the electronic levels of defects introduced in 4H-SiC α-particle detectors by irradiation with 1 MeV neutrons up to a fluence equal to 8x1015 n/cm2. As well, we investigated their effect on the detector radiation hardness. This study was carried out by deep level transient spectroscopy (DLTS) and photo-induced current transient spectroscopy (PICTS). As the irradiation level approaches fluences in the order of 1015 n/cm2, the material behaves as highly resistive due to a very great compensation effect but the diodes are still able to detect with a acceptably good charge collection efficiency (CCE) equal to 80%. By further increasing fluence, CCE decreases reaching the value of ≈ 20% at fluence of 8x1015 n/cm2.

The dominant peaks in the PICTS spectra occur in the temperature range [400, 700] K. Enthalpy, capture cross-section and order of magnitude of the density of such deep levels were calculated. In the above said temperature range the deep levels associated to the radiation induced defects play the key role in the degradation of the CCE. Two deep levels at Et = 1.18 eV and Et = 1.50 eV are likely to be responsible of such dramatic decrease of the charge collection efficiency. These levels were reasonably associated to an elementary defect involving a carbon vacancy and to a defect complex involving a carbon and a silicon vacancy, respectively.
Surface morphology and structure of hydrogen etched 3C-SiC(001) on Si(001)
Authors: Coletti Camilla , Hetzel Martin , Virojanadara Chariya , Starke Ulrich , Saddow Stephen E.
Published: April 2011

The surface of 3C-SiC(001) single-crystal epilayers grown on Si(001) substrates is well known to be inhomogeneous and defective. Therefore, the control and understanding at the atomic scale of 3C-SiC surfaces is a key issue. We study the effect of hydrogen etching at different temperatures on the morphology of 3C-SiC(001) surfaces by using Nomarksi optical microscopy, atomic force microscopy (AFM) and scanning electron microscopy (SEM). As-grown 3C-SiC(001) samples have been hydrogen etched in a horizontal hot-wall chemical vapor deposition (CVD) reactor at atmospheric pressure for different times and temperatures. Flat, high-quality surfaces presenting defined atomic terraces were observed within the 3C-SiC grain boundaries after etching at 1200°C for 30 minutes. Higher etching temperatures resulted in surfaces with step bunching and enlarged surface defects. Samples etched under the best conditions have been studied using low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES).
Homoepitaxial growth on 4H-SiC Substrates by Chemical Vapor Deposition
Authors: Hallin Christer , Khlebnikov Igor , Khlebnikov Yuri , Muzykov Peter , Berkman Elif , Sharma Monica , Stratiy George , Silan Murat , Basceri Cem , Balkas Cengiz
Published: April 2011

Low dislocation density and even micropipe free substrates open up a great opportunity to produce high quality epitaxial layers. The epi-layer will become more sensitive to the epitaxial process itself and less dependent on varying substrate quality. Results presented here indicate a strong dependence of the epitaxial layers' growth mode and surface roughness on the substrates' dislocations and domain structure. Thick epitaxial layers grown on near on-axis wafers, both C-face and Si-face, show very similar growth behaviors as for physical vapor transport (PVT) grown crystals. The mix between step-flow and dislocation driven growth on near on-axis C-face chemical vapor deposition (CVD) grown epi-layers (30 μm thick) is resulting in a as smooth, and measured surface roughness is as low, as for growth on 8o off-axis substrates.

Surface roughness, Ra, measured on a 50 μm thick epitaxial layer, grown on a low EPD (1E+4 cm-2) 8o off-axis micropipe free substrate, was as low as 1.0 nm (2.98x2.32 mm area).
Nanopatterning of Si/SiGe Two-dimensional Hole Gases by PFOTS-aided AFM Lithography of Carrier Supply Layer
Authors: Yao Kun , Sturm James C
Published: April 2011

The nanopatterning of Si/SiGe layers by PFOTS (perfluorooctyl trichlorosilane) -aided AFM (atomic force microscopy) lithography is demonstrated. We use self-assembled PFOTS monolayers as a resist for AFM exposure and then transfer patterns in to underlying SiGe layers by a two-step selective wet etching. Linewidths well under 100nm can be achieved with improved uniformity and repeatability compared to AFM lithography without PFOTS. This lithography technique was used to pattern the carrier supply layer in Si/SiGe 2-D hole gases to localize holes for epitaxially passivated quantum dot applications.