bluuebunny/crossref_metadata_2025 huggingface dataset:
The Pax gene eyegone facilitates repression of eye development in Tribolium
Authors: ZarinKamar Nazanin , Yang Xiaoyun , Bao Riyue , Friedrich Frank , Beutel Rolf , Friedrich Markus
Published: April 2011

Background

The Pax transcription factor gene eyegone (eyg) participates in many developmental processes in Drosophila, including the Notch signaling activated postembryonic growth of the eye primordium, global development of the adult head and the development of the antenna. In contrast to other Pax genes, the functional conservation of eyg in species other than Drosophila has not yet been explored.

Results

We investigated the role of eyg during the postembryonic development of the red flour beetle Tribolium castaneum. Our results indicate conserved roles in antennal but not in eye development. Besides segmentation defects in the antenna, Tribolium eyg knockdown animals were characterized by eye enlargement due to the formation of surplus ommatidia at the central anterior edge of the compound eye. This effect resulted from the failure of the developing gena to locally repress retinal differentiation, which underlies the formation of the characteristic anterior notch in the Tribolium eye. Neither varying the induction time point of eyg knockdown nor knocking down components of the Janus kinase/Signal Transducer and Activators of Transcription signaling pathway in combination with eyg reduced eye size like in Drosophila.

Conclusions

Taken together, expression and knockdown data suggest that Tribolium eyg serves as a competence factor that facilitates the repression of retinal differentiation in response to an unknown signal produced in the developing gena. At the comparative level, our findings reveal diverged roles of eyg associated with the evolution of different modes of postembryonic head development in endopterygote insects as well as diversified head morphologies in darkling beetles.
Pyothorax in a cat managed by intrathoracic debridement and postoperative ventilatory support
Authors: Doyle Ronan S. , Bellenger Christopher R. , Campoy Luis , McAllister Hester
Published: April 2011

A domestic-longhair cat presented due to lethargy, dyspnoea and hypersalivation. Radiographic examination revealed a bilateral pleural effusion, which was diagnosed as pyothorax based on cytological examination. Ultrasonographic examination revealed extensive loculations within the thoracic cavity. Exploratory sternotomy, under general anaesthesia, allowed the removal of approximately 100 ml of purulent fluid and debridement of a partially walled-off abscess and necrotic material from the pleural cavity. Postoperative positive-pressure ventilation was required due to severe respiratory depression. Intensive postoperative care, including intensive continuous monitoring, thoracostomy tube drainage and lavage of the pleural cavity and oesophagostomy tube feeding, was performed. Complete resolution of clinical signs had occurred by 15 days postoperatively. Clinical or radiographic abnormalities were not detected at a follow-up examination one year after surgery.
Identification and characterization of alkaline serine protease from goat skin surface metagenome
Authors: Pushpam Paul Lavanya , Rajesh Thangamani , Gunasekaran Paramasamy
Published: April 2011

Metagenomic DNA isolated from goat skin surface was used to construct plasmid DNA library in Escherichia coli DH10B. Recombinant clones were screened for functional protease activity on skim milk agar plates. Upon screening 70,000 clones, a clone carrying recombinant plasmid pSP1 exhibited protease activity. In vitro transposon mutagenesis and sequencing of the insert DNA in this clone revealed an ORF of 1890 bp encoding a protein with 630 amino acids which showed significant sequence homology to the peptidase S8 and S53 subtilisin kexin sedolisin of Shewanella sp. This ORF was cloned in pET30b and expressed in E. coli BL21 (DE3). Although the cloned Alkaline Serine protease (AS-protease) was overexpressed, it was inactive as a result of forming inclusion bodies. After solubilisation, the protease was purified using Ni-NTA chromatography and then refolded properly to retain protease activity. The purified AS-protease with a molecular mass of ~63 kDa required a divalent cation (Co2+ or Mn2+) for its improved activity. The pH and temperature optima for this protease were 10.5 and 42°C respectively.
Postcolonial Studies: A Political Invention of Tradition?
Authors: Bayart Jean-François
Published: April 2011

It is misguided to imagine that French researchers and French universities are unaware of postcolonial studies. In reality, forms close to this school of thought emerged very early in the French university context, but they were obliged to take other academic traditions into account. The contribution of postcolonial studies to an understanding of the historicity of societies that were colonized by their metropoles, and of the colonial legacies left behind, thus appears limited from the point of view of a historical sociology of politics inspired by Marx and Weber.
Racial France, or the Melancholic Alterity of Postcolonial Studies
Authors: Khanna Ranjana
Published: April 2011

The essay responds to attacks and defenses of postcolonial studies by Jean-François Bayart, Achille Mbembe, and Ann Laura Stoler, drawing attention to the limited understanding of difference and subjectivity in all essays.
Oxidative cleavage of non-phenolic β-O-4 lignin model dimers by an extracellular aromatic peroxygenase
Authors: Kinne Matthias , Poraj-Kobielska Marzena , Ullrich René , Nousiainen Paula , Sipilä Jussi , Scheibner Katrin , Hammel Kenneth E. , Hofrichter Martin
Published: April 2011

The extracellular aromatic peroxygenase of the agaric fungusAgrocybe aegeritacatalyzed the H2O2-dependent cleavage of non-phenolic arylglycerol-β-aryl ethers (β-O-4 ethers). For instance 1-(3,4-dimethoxyphenyl)-2-(2-methoxy-phenoxy)propane-1,3-diol, a recalcitrant dimeric lignin model compound that represents the major non-phenolic substructure in lignin, was selectivelyO-demethylated at thepara-methoxy group to give formaldehyde and 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)propane-1,3-diol. The phenol moiety of the latter compound was then enzymatically oxidized into phenoxy radicals and a quinoid cation, which initiated the autocatalytic cleavage of the dimer and the formation of monomers such as 2-methoxy-1,4-benzoquinone and phenoxyl-substituted propionic acid. The introduction of18O from H218O2and H218O at different positions into the pro-ducts provided information about the routes of ether cleavage. Studies with a14C-labeled lignin model dimer showed that more than 70% of the intermediates formed were further coupled to form polymers with molecular masses above 10 kDa. The results indicate that fungal aromatic peroxygenases may be involved in the bioconversion of methoxylated plant ingredients originating from lignin or other sources.
Effect of diets with different inclusion levels of distillers dried grain with solubles combined with lysine and methionine supplementation on the lipid peroxidation and glutathione status of chickens
Authors: Heincinger Mónika , Balogh Krisztián , Fébel Hedvig , Erdélyi Márta , Mézes Miklós
Published: April 2011

To study the possible effects of different inclusion levels of distillers dried grain with solubles (DDGS) on the lipid peroxidation and glutathione redox status of chickens, 200 three-week-old Ross 308 cockerels were assigned to four treatment groups of 50 birds each. The groups were fed a control and three experimental, isocaloric and isonitrogenous grower diets containing 15, 20 and 25% DDGS, respectively, combined with lysine (Lys) and methionine (Met) supplementation until 6 weeks of age. It was found that DDGS inclusion increased the ether extract content of the diets which resulted in higher reduced glutathione (GSH) content and elevated glutathione peroxidase activity (GSHPx) in the liver. However, DDGS addition with Lys and Met supplementation did not influence the malondialdehyde content of the blood and the liver. The oleic acid proportion of the diet showed a close positive correlation with GSH content of the liver. A smaller ratio of methionine and cysteine in the diet with DDGS resulted in significantly higher liver GSH content. GSHPx activity increased parallel with the elevated GSH content of the liver homogenate, suggesting that the enzyme is activated by the actual supply of its co-substrate. In conclusion, the results show that DDGS, even at a high inclusion level combined with Lys and Met supplementation, has no initiative effect on lipid peroxidation in the blood and liver of broiler chickens.
Effect of recombinant interleukin-10 on some haematological and biochemical parameters in a rat endotoxaemic model
Authors: Çöl Ramazan , Durgun Zafer
Published: April 2011

Recombinant interleukin-10 (rIL10) has been found to suppress the synthesis of tumour necrosis factor (TNF), interleukin-1 (IL-1), interleukin-6 (IL-6) and tissue factor and to improve survival from experimental sepsis. The aim of this study was to evaluate the protective effect of rIL-10 on lipopolysaccharide-(LPS-) induced haematological and biochemical disturbances in rats. In the present study, 40 rats were used and divided equally into four groups. Group 1 (control group, C) was treated with 0.9% saline. Group 2: LPS was injected intravenously (1.6 mg/100 g), Group 3 received rIL10 treatment (125 μg/kg) 2 min before 0.9% saline injection, Group 4 received rIL10 treatment 2 min before endotoxin treatment. When compared with the controls, platelet count, leukocyte count (with a marked neutrophilia and lymphopenia) and fibrinogen were decreased, while activated partial thromboplastin time (APTT) and prothrombin time (PT) were prolonged in the endotoxaemic rats. In addition, LPS caused statistically significant increases in plasma aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities as well as creatinine, cholesterol and triglyceride concentrations, while it caused a statistically significant decrease in glucose, total protein and albumin levels as compared to the control group. On the other hand, rIL10 significantly suppressed disturbances in the haematological and biochemical parameters associated with endotoxaemia. As a result, rIL10 may be efficacious in preventing haematological disorders, tissue damage and changes in lipid, protein and carbohydrate metabolism in endotoxaemia.
Improvement of Aircraft Aerodynamic Performance Using Piezoelectric Actuators
Authors: Min Li , Wei-min Chen , Wei Li
Published: April 2011

To flight vehicle designer, the ability to adapt air vehicle aerodynamic shape so as to increase the optimum flight envelope is highly desirable. In this work, by distributing piezoelectric actuators on the top and bottom surfaces of a rectangular wing, the improvement of aerodynamic performance of flight vehicle is studied. The approach of the Fictitious Control Surface (FCS) is evaluated at a group of dynamic pressure and wing stiffness, through examining four aspects including the improvement of rolling power, the increase of lift, the decrease of the induced drag and the decrease of the bending moment at root of wing. Then an experimental model of high-speed wind tunnel is designed in order to validate the results of theoretical analysis. The ground tests and wind tunnel tests demonstrate that the lift and rolling moment can be increased by using the favorable aeroelastic effect. And quantificationally the experimental results agree well with the analytical results.
The Optimal Design and Analysis of Piezoelectric Cantilever Beams for Power Generation Devices
Authors: Shen Dongna , Ajitsaria Jyoti , Choe Song-Yul , Kim Dong-Joo
Published: April 2011

With the rapid development of wireless remote sensor systems, battery is becoming the limiting factor in the lifetime of the device and miniaturization. As a way to eliminate battery in the system, the conversion of ambient vibration energy has been addressed. The piezoelectric cantilever beam with a proof mass was exploited for energy conversion since it can generate large strain and power density. The design of cantilever beams was optimized through numerical analysis and FEM simulation at higher acceleration condition. The investigated parameters influencing the output energy of piezoelectric bimorph cantilevers include dimensions of cantilever beam and proof mass. The resonant frequency and robustness of cantilever structure were also considered for enhancing power conversion efficiency and implementing devices at high acceleration condition. The power density generated by the optimized piezoelectric device was high enough (> 1200 μW/cm3) to operate microsensor systems. However, high stress near clamping area of cantilever beam could lead to the fracture at high acceleration condition.
Shape Memory at Nanometer Scales
Authors: Frick Carl Pieter , Lang Travis W. , Spark Kevin , Gall Ken
Published: April 2011

Nickel-titanium (NiTi) shape memory alloys undergo relatively large recoverable inelastic deformations via a stress-induced martensitic phase transformation. The nanoindentation experimental results presented in this study are the first to show evidence of discrete forward and reverse stress-induced thermoelastic martensitic transformations in nanometer scaled volumes of material. Shape recovery due to indentation, followed by subsequent heating, is demonstrated for indents depths in the sub 10 nm range via atomic force microscopy. It is also shown that the local material structure can be utilized to modify transformation behavior at nanometer scales, yielding insight into the nature of stress-induced martensitic phase transformations at small scales and providing opportunity for the design of nanometer sized NiTi actuators.
Characterization of Calcium Phosphate Films Prepared by RF Magnetron Sputtering
Authors: Narushima Takayuki , Ueda Kyosuke , Goto Takashi , Katsube Tomoyuki , Kawamura Hiroshi , Ouchi Chiaki , Iguchi Yasutaka
Published: April 2011

Calcium phosphate films were prepared on commercially pure titanium (CP-Ti) substrates by RF magnetron sputtering using β-tricalcium phosphate targets. XRD and FTIR analyses showed that the films consisted of amorphous calcium phosphate and oxyapatite phases. The (002) preferred orientation of the oxyapatite phase was observed depending on the oxygen gas concentration in the sputtering gas. The surface reactions of the calcium phosphate films were investigated in Hanks' solution and PBS(-). Apatite crystallites were detected on the films after immersion for 7 days. An active surface reaction was observed on the amorphous calcium phosphate films during immersion in PBS(-). The CP-Ti plates coated with the calcium phosphate films were placed on the mandible of male Japanese white rabbits. These results suggest that the calcium phosphate coating improves the biocompatibility of titanium implants with bone.
Transformation of Helically Structured Nanofibers into Linearly Oriented Nanofibers
Authors: Kim Seon Jeong , Park S. J. , Yoon S. K. , Kim M. S. , Gu B. K. , Kim I. Y. , Kim S. I. , Kim S. J.
Published: April 2011

Helical structures have been fabricated from a solution of poly(2-acrylamido-2-methyl-1-propane sulfonic acid) (PAMPS) in water and ethanol by the whipping instability of a jet in a conventional electrospinning system. The simple modification of the electrospinning system involved introducing two parallel subelectrodes, which enabled the transformation of helical nanofibers into linearly oriented nanofibers due to the tensional forces caused by the modified electric field. This means that the tensional forces caused by the modified electric field had an important effect on linearizing the helical structures. Therefore, a technique using modified electric fields can play a significant role as an intermediary between helical structures and one-dimensional linear structures.
Studies of Bi4−xGdxTi3O12 Bifunctional Material
Authors: Tomar Maharaj S. , Melgarejo Ricardo E. , Singhal Rahúl , Angelats Luis M. , Katiyar Ram S.
Published: April 2011

Gadolinium-substituted Bi4Ti3O12 (i.e. Bi4−xGdxTi3O12) were synthesized by sol-gel process for different compositions, and thin films were deposited on Pt (Pt/TiO2/SiO2/Si) substrate by spin coating. Post annealed films at 700° C were investigated for their structural properties using x-ray diffraction and Raman spectroscopy indicating solid solution for compositions: x = 0.00, 0.46, 0.56, and 0.85 where Bi ion is replaced by Gd-ion. Sol-gel derived Pt/Bi4−xGdxTi3O12 film/Pt capacitor structure was tested for dielectric, ferroelectric, and leakage current responses. Films showed ferroelectricity with polarization, Pr = 22 µC/cm2 for composition: x = 0.46. Magnetic response of the powder sample for composition: x = 0.85 was tested using SQUID, which showed superparamagnetic at room temperature and magnetic at 5 K with magnetic coercivity (Hc) = 29 Oe and very small remanance (σr) = 5.4 × 10−4 emu/g.
Self Assembly in Biologically Synthesized Electrospun Electroactive Polymers
Authors: Bishop A. , Gouma P.
Published: April 2011

The processing parameters of polyaniline (PANI) dictate the desired morphology and overall structural stability of the deposited polymer for biological and chemical sensor applications. Electrospun composites of leucoemeraldine based PANI (LEB-PANI) has exhibited effective separation of aggregates inherent in LEB-PANI powder as a result of charge separation induced on the composite matrix during electrospinning. However it appears the encapsulation of biological (enzyme-Urease E.C.3.5.1.5) in the electrospun matrix intensifies the self assembly process. An investigation of the changes in morphology as an effect of electrospinning and enzyme immobilization is discussed.
Influence of Crystallization Condition on Structure of P(VDF-CTFE) Copolymers
Authors: Yang Xin , Li Zhimin , Odum LeVar , Cheng Z.-Y.
Published: April 2011

The influence of the crystallization condition - temperature and time - on the structure of poly (vinylidene fluoride chlorotrifluoroethylene), P(VDF-CTFE), was studied using DSC and XRD. The DSC results of all studied polymers show three peaks. One peak, which is associated with crystallization temperature, represents the appearance of unstable phase in the polymers. Both XRD and DSC data indicate the coexistence of different phases in the polymers, which may be the reason for the high electrostrictive performance obtained in the polymers.
Bulk and Interface Charging Mechanisms in Organic Semiconductor-Gate Dielectric Bilayers
Authors: Katz Howard E. , Huang Cheng , West James
Published: April 2011

Since the first reports of charge storage in the gate dielectrics of organic semiconductors, several groups have proposed charge-storing dielectrics that become polarized through varied mechanisms, and have offered various explanations for observed charge storage phenomena. These groups were concerned either with nonvolatile memories as an application, or with controlling hysteresis in conventional OFETs. This manuscript describes measurements of surface charging and OFET threshold voltage shift for a case where charge is clearly stored in the dielectric. The magnitude and stability of the charge storage depend on the hydrophobicity of the dielectric and the charge deposition process. We focus on SiO2 as the dielectric and use a thiophene oligomer or hexadecafluoro-copper phthalocyanineas semiconductor. In one case, the phthalocyanine was inverted from electron- to hole-carrying, enabling a complementary device to be made from a single semiconductor.
Mechanisms of Long-Term Uranium Transport under Oxidizing Conditions
Authors: Murakami Takashi
Published: April 2011

Understandings of U transport at the Earth’s surface are quite important especially for the disposal of radioactive waste and the remediation of contaminated ground water. We examined long-term U transport in and around the Koongarra U deposit, Australia, which has been subjected to weathering for the past 2 million years. The formation of saléeite [Mg(UO2)2(PO4)2·10H2O] occurred at the rim of apatite [Ca5(PO4)3(F,OH)], where the ground waters had about 200 - 400 ppb U (∼10-7 mol·l-1) and were undersaturated with respect to saléeite. The laboratory experiments using apatite and U-containing solutions and Rutherford backscattering spectrometry of the apatite surface have suggested that a leached layer of about 100 nm thick is formed on dissolving apatite, saléeite is precipitated only in the leached layer by local saturation, and saléeite precipitated is added to the interface between the leached layer and solution. At lower U concentrations (∼10-8 mol·l-1), U occurred as nanocrystals (20-100 nm in size) of uranyl phosphates such as metatorbernite [Cu(UO2)2(PO4)2·8H2O], scattered between and attached firmly to nanocrystals (2-50 nm in size) of goethite and hematite. A possible mechanism is that U, P, and Mg or Cu adsorbed onto ferrihydrite form nanocrystals of uranyl phosphates during crystallization of goethite and hematite from ferrihydrite. The above two mechanisms significantly lower the U concentration in the ground water that flows into the Koongarra creek, 200 m downstream from the ore deposit, where the U concentration is ∼10-10 mol·l-1. We conclude that the two mechanisms of uranyl-phosphate mineralization control the long-term U transport at Koongarra.
Theoretical Studies of Hydrogen and Water Adsorption on Actinide Oxide Surfaces
Authors: Hay P. Jeffrey
Published: April 2011

The adsorption of H2O on UO2 and PuO2 surfaces is studied using density functional theoretical approaches. Periodic slab models are employed to represent the oxide surface in which five layers of the oxide are explicitly treated. For both oxides the dihydroxyl form corresponding to dissociated H2O is more stable than the molecularly adsorbed H2O on the (111) and (110) surfaces. Adsorption of H2 on PuO2 and Pu2O3 is also investigated where stable forms corresponding to dissociated H atoms are found.
Relationships between the crystal chemistry and magetic properties of Np5+ sulfates
Authors: Forbes Tori Z. , Burns Peter C. , Soderholm L. , Skanthakumar S.
Published: April 2011

Np5+ sulfate compounds were synthesized using hydrothermal methods and their structures were determined using single crystal X-ray diffraction. Several compounds were found to contain cation-cation interactions between the Np polyhedra. Magnetic susceptibility measurements of two Np5+ sulfate compounds containing cation-cation interactions exhibit ferromagnetic ordering. The presence of the cation-cation interactions may provide a superexchange pathway through which magnetic interactions can be enhanced.
Evaluation of Electric Potential at Metal-Insulator Interface Using Electron Spectroscopy and Kelvin Probe Techniques
Authors: Yoshitake Michiko
Published: April 2011

The potential of applying photoelectron spectroscopic and Kelvin probe methods for the interface potential evaluation of materials prepared by combinatorial processes is demonstrated. The physical basis for the evaluation of the interface potential by photoelectron spectroscopy is given. Then, the imaging capability of photoelectron spectroscopy is demonstrated using a two-dimensionally patterned specimen. Finally, the examples of interface potential evaluation with photoelectron spectroscopy and Kelvin probe are presented. Through the evaluation of interface potential with this method, it is possible to deduce the energy level diagram across the interface between two materials with different electron properties.
Cathodic Arc Plasma Combinatorial Material Synthesis for Composition Search of New Amorphous Alloy
Authors: Hata Seiichi , Yamauchi Ryusuke , Sakurai Junpei , Shimokohbe Akira
Published: April 2011

Combinatorial arc plasma deposition (CAPD) method was used to search for new compositions of thin film amorphous alloys. A cathodic arc plasma gun (APG) was adopted as the deposition source for CAPD. The CAPD setup has three APGs radiating out from the center of a substrate. The APGs shoot pulse-like plasma shots one by one at a specific time interval. The plasma from each APG cathode is guided onto a specific area on a substrate by a magnetic field. Each such area overlaps the adjacent ones. Thus, a compositionally-graded thin film is deposited in the overlap area because of mixing of each deposited thin film from each APG that has a thickness grade. The deposited thin film is separated into 1,089 samples (the size of each is 1×1 mm2) using a grid on the substrate. The samples together are referred to as the thin film library. To demonstrate the capability of CAPD, two thin film libraries were deposited in this study. One is a thin film library of a PdCuSi alloy system, and the other is a MoZrPd system. The compositions and crystallinity of the samples were evaluated on the substrate using EDS and IP-XRD respectively. Analysis of the samples showed a graded composition, and some of the samples were shown to be amorphous in both libraries.
High Throughput Screening of Marine Coatings using Biological Assays
Authors: Stafslien Shane , Chisholm Bret , Christianson David , Daniels Justin , Swain Geoffrey
Published: April 2011

A combinatorial workflow for developing organic surface coatings has been developed. The workflow is uniquely designed to prepare and evaluate marine coatings that prevent biofouling on the hulls of ships. A critical component of the workflow is the high throughput screening of settlement and ease of removal of marine organisms from coating surfaces. Methods have been developed to directly and indirectly quantify marine bacterial biofilm growth and retention. Correlations have been developed between these high throughput bioassays and results from ocean testing.
Lessons from Simulation Regarding the Control of Synthetic Self-Assembly
Authors: Douglas Jack F. , Van Workum Kevin
Published: April 2011

We investigate the role of particle potential symmetry on self-assembly by Monte Carlo simulation with the particular view towards synthetically creating structures of prescribed form and function. First, we establish a general tendency for the rotational potential symmetries of the particles to be locally preserved upon self-assembly. Specifically, we find that a dipolar particle potential, having a continuous rotational symmetry about the dipolar axis, gives rise to chain formation, while particles with multipolar potentials (e.g., square quadrupole) having discrete rotational symmetries led to the self-assembly of random surface polymers preserving the rotational symmetries of the particles within these sheet structures. Surprisingly, these changes in self-assembly geometry with the particle potential symmetry are also accompanied by significant changes in the thermodynamic character and in the kinetics of the self-assembly process. Linear chain growth involves a continuous chain growth process in which the chains break and reform readily, while the growth of the two-dimensional polymers only occurs after an ‘initiation’ or ‘nucleation’ time that fluctuates from run to run. We show that the introduction of artificial seeds provides an effective method for controlling the structure and growth kinetics of sheet-like polymers. The significance of these distinct modes of polymerization on the functional character of self-assembly growth is illustrated by constructing an artificial centrosome structure derived from particles having continuous and discrete rotational potential symmetries.
Fluorescence Correlation Spectroscopy Study of TAMRA Diffusion in Poly(vinyl-alcohol) and Ficoll70 Solutions
Authors: Michelman-Ribeiro Ariel , Horkay Ferenc , Nossal Ralph , Boukari Hacene
Published: April 2011

We compare fluorescence correlation spectroscopy (FCS) measurements of the fluorescent nanoparticle, TAMRA, diffusing in non-fluorescent -hence invisible- poly(vinyl-alcohol) (PVA) or Ficoll70 solutions as a function of the polymer concentration, c. We determine changes of the translational diffusion coefficient of TAMRA and fit the data with the universal scaling law (D ∼ exp[−α(c/c*)ν], to extract information about solvent quality. For PVA, we find ν = 0.74, suggesting that water in this case acts as a good solvent, whereas ν = 1.02 in Ficoll70 solutions, indicating theta-like behavior.
Characterizations of Multiphase Biogenic Polymer Blends from Poly(L-lactide) and Poly(methyl methacrylate)
Authors: Le Kim-Phuong Nguyen , Lehman Richard Long , VanNess Kenneth , Idol James D
Published: April 2011

Melt processing of binary immiscible polymer systems has been a focus of our group as an economical and scalable route to achieve synergistic or superior mechanical properties at and around the co-continuous region without the need of compatibilization. System of poly(L-lactide) (PLLA) and poly(methyl methacrylate) (PMMA) was selected to target bio-related applications, including bone fillers and scaffolds, where the biodegradability of PLLA will enable the integration of native tissue into the material over time. Tunable properties such as morphology, interconnectivity, resorbability and interfacial bonding control the long-term integrity of the new material and influence the interaction and integration of new tissue. Binary blends of PLLA and PMMA has been prepared and characterized over a large range of compositions in which regions of co-continuity are of special interest. Such regions exhibit a well interconnected structure that ensures controlled release of resorbable PLLA. Modulated differential scanning calorimetry (MDSC) detected a broad and unexpected transition between 70 °C and 100 °C. The magnitude of this transition is greatest within co-continuous regions, suggesting the presence of a complex or other derivative of the two primary phases. This complex appears to provide a degree of compatibilization between the phases, thus inducing mechanical property synergism which has been confirmed by flexural and nano-indentation analyses.
Synthesis and luminescence properties of novel ZnO nanostructures: micro and nanospheres, polyhedral cages, tetra-pods, needles, tipped nanorods, nanowires and other “microphone–shaped” structures
Authors: Khan Aurangzeb , Jadwisienczak Wojciech M , Kordesch Martin E
Published: April 2011

Novel ZnO nanostructures such as hollow nanospheres, nano-cages, nanoneedles, tetra-pods, nanowires, aligned nanorods and nanotubes are synthesized via thermal evaporation of ZnO and graphite powder mixtures in reduced oxygen atmosphere in the presence of argon and nitrogen flows. The ZnO nanostructures, especially nanospheres, have a unique shape and are hollow inside with walls densely decorated with aligned nanowires. Photoluminescence of synthesized ZnO structures measured at 300 K exhibits a strong near band edge peak at ∼380 nm and deep level green band centered at ∼550 nm. Fabricated ZnO structures can be studied for various applications in optoelectronics and sensors.
Synthesis of ZnO Nanowires by Pulsed Laser Deposition in Furnace
Authors: Jeon Kyung Ah , Son Hyo Jeong , Kim Jong Hoon , Yoo K. H. , Lee Sang Yeol
Published: April 2011

ZnO nanowires (NWs) were fabricated on Au coated sapphire (0001) substrates by using a pulsed laser deposition (PLD) system in vacuum furnace with a Q-switched Nd:YAG laser. ZnO NWs have various size and shape with a substrate position inside a furnace, and their morphologic construction is reproducible. Scanning electron microscopy (SEM) images indicate that the diameters of ZnO NWs ranged from 100 to 150 nm and the average length was greater than 3 μm. Room-temperature photoluminescence spectra of the NWs show the near band-edge emissions and the deep-level green light emissions. The formation mechanism of the NWs is discussed.
Nitrogen and Fluorine Roles in Visible-Light-Driven Anion-Doped TiO2 Photocatalysis
Authors: Di Li , Ohashi Naoki , Hishita Shunichi , Kolodiazhnyi Taras , Haneda Hajime
Published: April 2011

This paper describes the synthesis of N-doped, F-doped, and N-F-codoped TiO2 powders (NTO, FTO, NFTO) by spray pyrolysis (SP). An overall comparative study was carried out on these anion-doped powders in order to elucidate the roles of N and F played in visible-light (Vis)-driven photocatalysis. The comparisons in their characteristics were based on the analysis of UV-Vis, PL, NH3-TPD and ESR spectra. As the results, N-doping into TiO2 resulted in both the improvement of Vis absorption and the creation of surface oxygen vacancies (OVs). F-doping produced several beneficial effects including the creation of surface OVs, the enhancement of surface acidity and the increase of Ti3+ ions. The photocatalytic tests indicated that the NFTO demonstrated the highest Vis activity for decomposition of both acetaldehyde and trichloroethylene. This high activity was ascribed to a synergetic consequence of doped N and F.
EXAFS Study on Nanosized PtRu Catalyst for Direct Methanol Fuel Cell
Authors: Nitani Hiroaki , Ono Takahiro , Honda Yusuke , Koizumi Akiko , Nakagawa Takashi , Yamamoto Takao A. , Daimon Hideo , Kurobe Yukiko
Published: April 2011

Nano-sized PtRu catalysts supported on carbon nanoparticles were synthesized by a polyol process. The PtRu catalyst prepared at pH=3 indicated higher catalysis for methanol oxidation than one prepared at pH=5.5. The samples were analyzed by techniques of the extended X-ray absorption fine structure (EXAFS), transmission electron microscope (TEM), X-ray diffraction (XRD) and X-ray fluorescence (XRF). Their results showed that the pH of the precursor solution during the polyol process affected the substructure of the PtRu nanoparticles. The correlation of the substructure with the catalytic activity was studied.
Atomistic Simulations of Nanoporous Anodic Aluminum Oxide
Authors: Adiga Shashishekar P. , Zapol Peter , Curtiss Larry A
Published: April 2011

Nanoporous membranes based on anodized aluminum oxide are prepared with atomic level control of pore dimensions and pore wall compositions by atomic layer deposition and are under investigation for use in catalysis. Simulation and modeling help to understand reactivity in confined geometry and to develop rational design of these new materials. In this context, we present results of molecular dynamics simulations of amorphous aluminum oxide surfaces. The surface structure is discussed in terms of density profiles, bond angle distributions and coordination numbers of surface atoms.
Piezoelectric Properties of Lead Zirconate Titanate Films Prepared by Arc Discharged Reactive Ion-Plating Method
Authors: Akamatsu Masahiro , Yasuda Yoshiaki , Tani Masanao , Iijima Takashi
Published: April 2011

This study is about new plasma deposition method fabricating piezoelectric films applied for actuators in MEMS devices.
Extrinsic Contributions to Piezoresponse Force Microscopy
Authors: Peter Frank , Reichenberg Bernd , Rüdiger Andreas , Waser Rainer , Szot Krzysztof
Published: April 2011

Piezoresponse force microscopy (PFM) is the method of choice to investigate piezoactivity on a nanometer scale. A careful distinction between intrinsic and extrinsic effects are mandatory, especially when measuring ferroelectric nanostructures. We focus on two omnipresent extrinsic contributions with a substantial impact: firstly adsorbates on the surface of perovsike materials and secondly the dependence of the lateral piezoresponse on the topography. A thorough understanding of these extrinsic contributions is essential in order to avoid ambiguities in the analysis of PFM measurements.
Real Information Recording in Ferroelectric Data Storage Medium with Memory Density of 1 Tbit/inch2
Authors: Tanaka Kenkou , Hiranaga Yoshiomi , Cho Yasuo
Published: April 2011

In this study, a new method to achieve real information recording with a density of 1 Tbit/inch2 in ferroelectric data storage systems is proposed. In this system, data bits were written in the form of the polarization direction of nano domains. Local domain switching was carried out by applying a voltage pulse. A series of test writes revealed that the bit size varied according to the polarization direction of the bits in the immediate environment. Therefore, in order to keep the bit size constant (at 25.6 nm), the pulse amplitude required to create each individual bit was calculated as a function of the polarities of the surrounding data bits. As a result, real information storage at a density of 1 Tbit/inch2 was successfully achieved, with a low bit error rate of 1.8 × 10-2.
Surface Potential Investigation on Nano Domain Formation in Lithium Tantalate Single Crystal
Authors: Katoh Mirai , Cho Yasuo
Published: April 2011

The surface potential distribution following polarization reversal by scanning probe microscopy is examined in order to determine the mechanism of anti-parallel polarization reversal and ring-shaped domain formation in single-crystal lithium tantalate. Lithium vacancy lattice defects are identified as charge-trapping sites, with the resultant surface potential distribution governing the formation of ring-shaped nano-domains. The behavior of this charge injection is shown to be dependent on atmospheric humidity.
Effect of Radiation in Solid during SiC Sublimation Growth
Authors: Nishizawa Shin-ichi , Nakashima Shin-ichi , Kato Tomohisa
Published: April 2011

The effect of infrared absorption on SiC sublimation growth was numerically investigated. At first, absorption coefficient was estimated as function of doping concentration. Then temperature distribution inside a crucible was numerically analyzed with taking account of absorption in growing crystal. It was pointed out that temperature distribution in a growing crystal strongly depends on absorption coefficient, i.e. doping concentration. As increasing the absorption coefficient, the growth front temperature and temperature gradient inside a growing crystal increase. It might cause large thermal stress and affect the grown crystal quality. This agrees well with growth features in experiment. The growth condition should be determined with taking account of absorption coefficient, i.e. doping concentration.
Crystal face and C/Si ratio Dependence of Phosphorus Doping by SiC Epitaxial Growth
Authors: Tawara Takeshi , Ueki Yuko , Nakamura Shunichi , Gotoh Masahide , Yonezawa Yoshiyuki , Nishiura Masaharu
Published: April 2011

The dependence of phosphorus doping on crystal face and C/Si ratio in the epitaxial growth of 4H-SiC using phosphine were investigated. Phosphorus incorporation was highest on off-axis (000-1) and lowest on off-axis (0001). Phosphorus incorporation on (11-20) came between that on off-axis (0001) and (000-1). With increasing C/Si ratio from 0.5 to 2.5, phosphorus incorporation increased on (11-20) and off-axis (000-1). Phosphorus incorporation on off-axis (0001) showed unclear C/Si ratio dependence. On (000-1), the highest phosphorus concentration of 2 × 1018cm-3 was obtained by an increasing PH3 flow rate. The roughness, growth rate, and surface morphology of the high phosphorus doped epilayer were investigated.
Process-Induced Deformations and Stacking Faults in 4H-SiC
Authors: Okojie Robert S , Huang Xianrong , Dudley Michael , Zhang Ming , Pirouz Pirouz
Published: April 2011

We used Film Stress Measurement (FSM), Transmission Electron Microscopy (TEM), and High-Resolution X-ray Diffraction (HRXRD) techniques to obtain further knowledge with respect to the deformation, warpage, and stacking faults (SF's) that are induced in n-type 4H-SiC wafers and epilayers when subjected to mechanical polishing and high temperature (1150 oC) processing.
Development of a high-growth rate 3C-SiC on Si CVD process
Authors: Reyes M. , Shishkin Y. , Harvey S. , Saddow S. E.
Published: April 2011

Growth rates from 10 to 38 μm/h were achieved for heteroepitaxial 3C-SiC on Si (100) substrates by using the propane-silane-hydrogen gas chemistry with HCl as a growth additive. A low-pressure horizontal hot-wall CVD reactor was employed to perform the deposition. The growth rate dependences on silane mole fraction, the process pressure and the growth time were determined experimentally. The growth rate dependence on silane mole fraction was found to follow a linear relationship. The 3C-SiC films were characterized by Normaski Optical Microscopy, Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, Atomic Force Microscopy and X-ray Diffraction. The X-ray rocking curve taken on the (002) diffraction plane displayed a FWHM of 360 arcsec which indicates that the films are monocrystalline.
Laser Endotaxy and PIN Diode Fabrication of Silicon Carbide
Authors: Tian Zhaoxu , Quick Nathaniel R , Kar Aravinda
Published: April 2011

A laser solid phase diffusion technique has been utilized to fabricate endolayers in n-type 6H-SiC substrates by carbon incorporation. X-ray energy dispersive spectrometry (XEDS) analysis showed that the thickness of endolayer is about 100 nm. High resolution transmission electron microscopy (HREM) images indicate that the laser endotaxy process maintains the crystalline integrity of the substrate without any amorphization. The resistivity of the endolayer was 1.1 ¡Á105 •cm and 9.4 ¡Á104 •cm after annealing at 1000C for 10 min. These resistivities provide device isolation for many applications. The silicon carbide endolayer was doped with aluminum using a laser doping technique to create p-region on the top surface of the endolayer in order to fabricate PIN diodes.
Impact of EBAS annealing on sheet resistance reduction for Al-implanted 4H-SiC(0001)
Authors: Shibagaki Masami , Egami Akihiro , Kumagai Akira , Numajiri Kenji , Watanabe Fumio , Haga Shigetaka , Miura Kuniaki , Miyagawa Shingo , Kudoh Naohiro , Suzuki Tomoyuki , Satoh Masataka
Published: April 2011

In this paper, we demonstrate that high temperature and short time EBAS annealing is effective to obtain low sheet resistance without surface roughening in heavily Al-implanted 4H-SiC (0001) samples (Al concentration: 1.0 × 1021 /cm3, thickness: 0.3 microns, total dose: 2.6 × 1016 /cm2). The sheet resistance and rms surface roughness of the sample annealed at 1800 °C for 0.5 min is estimated to be 4.8k ohm/sq. and 0.82 nm, respectively. Also, we discuss the advantage of EBAS annealing for the suppression of surface roughening during annealing.
Ti/AlNi/W Ohmic Contacts to P-Type SiC
Authors: Tsao Bang-Hung , Lawson Jacob , Scofield James
Published: April 2011

Improved AlNi-based ohmic contacts to p-type 4H-SiC have been achieved using low energy ion (Al+) implantation, the addition of a thin Ti layer, and a novel two-step implant activation anneal process. Resistivities sometimes as low as 5×10−5 Ω-cm2 were reached by doping the surface region of lightly p-doped 4H-SiC epilayers via low energy Al+ implantation. Acceptor activation was achieved by annealing the samples with a 1400+1700°C two-step sequence in an Ar atmosphere, which also yielded improved surface morphology when implanted samples were capped with photo resist during the anneals. In this study, Ti/AlNi/W contacts on implanted layers were compared to Ti/AlNi/Au contacts. Even though the resistivities are higher than those of the Ti/AlNi/W system, the reduced anneal temperature, 650°C for Ti/AlNi/Au compared to 950°C for Ti/AlNi/W implies that Ti/AlNi/Au is a promising stacking configuration. Furthermore, the effects of a longer 30 minute anneal time at 600 − 700°C, in atmospheric pressure Ar ambients was observed. Namely, the 2 minute annealing cycle used for the Ti/AlNi/W study resulted in higher anneal temperatures before ohmic characteristics were seen. This same anneal time was not sufficient for the Ti/AlNi/Au samples, whereas increasing the cycle time to 30 minutes resulted in ohmic behavior at a much lower temperature. Increasing the anneal time however, had little or no impact on reducing the required anneal temperature of the Ti/AlNi/W.
Alternative Magnesium Calcium Oxide Gate Dielectric for Silicon Carbide MOS Application
Authors: Stodilka Danielle , Gerger A. P. , Hlad M. , Kumar P. , Gila B. P. , Singh R. , Abernathy C. R. , Pearton S. J. , Ren F.
Published: April 2011

Films of MgO and MgCaO ternaries were grown at low temperature as dielectrics on 6H-SiC by gas-source MBE. MgO grown at 300 and 400°C revealed crystallites textured toward the (111) orientation on SiC (0001). A solid-solution Mg.75Ca.25O ternary was grown having a minimal lattice mismatch and low root mean square (RMS) roughness of 0.5 nm. SiC pretreatments in UV-ozone reduced carbon contaminants on the surface of SiC, but resulted in the increase of fixed oxide charge in the oxide/SiC interface. Electrical breakdown fields >3.5 MV cm-1 and low density of interface states on the order of 1011 cm-2eV-1 were achieved for a Mg.75Ca.25O ternary grown at 300°C. These oxides are presented for the first time as low temperature alternatives to SiO2 gate dielectrics for SiC MOS applications.
Nanofabrication of Vertically Aligned Carbon Nanofibers for Contact Characterization
Authors: Ominami Yusuke , Ngo Quoc , Suzuki Makoto , Mcilwrath Kevin , Jarausch Konrad , Cassell Alan M , Li Jun , Yang Cary Y
Published: April 2011

Recent studies in nanostructural characterization for on-chip interconnect applications using carbon nanofibers (CNFs) are presented. In this paper, we propose a novel technique, for the purpose of characterizing interfacial structures of vertically aligned CNFs for cross-sectional imaging with scanning transmission electron microscopy (STEM). In this technique, vertically aligned CNFs are selectively grown, by plasma-enhanced chemical vapor deposition (PECVD), on a substrate comprising a narrow strip (width ~100nm) fabricated by focused ion beam (FIB). Using high-resolution STEM, we show that CNFs with diameters ranging from 10 -100 nm exhibit very similar graphitic layer morphologies at the base contact interface.
Poly-L-Lysine Mediated Fractal Titania Structures
Authors: Sowards Laura A. , Singh Kristi M. , Drummy Lawrence F. , Kasten Linda S. , Tomczak Melanie M. , Naik Rajesh R.
Published: April 2011

We demonstrate here the use of Poly-L-lysine to mediate the mineralization of fractal titania structures.
Time Resolved Dynamics of Femtosecond Laser Ablation of Si (100) with Thin Thermal Oxide Layers (20 - 1200 nm)
Authors: McDonald Joel Patrick , Mistry Vanita R. , Nees John A. , Yalisove Steven M.
Published: April 2011

Femtosecond (fs = 10−15 sec.) laser ablation of Si(100) with thermally grown oxide films was studied with pump/probe imaging techniques in order to determine the role of film thickness on ablation dynamics. Two different imaging geometries were used in this study. Front view images were formed with the reflection of a delayed probe pulse from the area of a sample irradiated with a pump pulse. By changing the delay between the pump and probe pulses, images were obtained showing the evolution of the surface as a function of time (0 – 12 ns after the arrival of the pump pulse). The side view imaging technique, also known as shadowographic imaging, an image was formed of a delayed probe pulse which passed through the ablation plume produced by a pump pulse parallel to the sample surface. Both laser induced shock wave propagation and material removal were observed to change with increased thermal oxide thickness.
Surface Modification of Glassy Polymeric Carbon by Glow Discharge
Authors: Abidzina Volha , Tereshko I. , Elkin I. , Zimmerman R.L. , Muntele I. , Muntele C. , Minamisawa R.A. , Chhay B. , Ila D.
Published: April 2011

We have studied the effects of low energy ion beam produced by glow discharge on glassy polymeric carbon (GPC) produced at pyrolysis temperature ranging from 200C to 1000C. The pristine and irradiated GPC were studied using FTIR, Raman Spectrometry indicating changes at the surface of the GPC samples.