bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nanoporous Polymeric Periodic Structures Fabricated by Emulsion-assisted Holographic Patterning
Authors: Hsiao Vincent K.S , Chang Wei-Ting 
Published: August 2010

AbstractWe report a new technique of creating a nanoporous polymeric nanostructure by photo-patterning emulsions generated from a formamide (polar phase) and an acrylate-monomer (nonpolar phase). Formamide is a highly polar solvent that forms well dispersed, non-aqueous emulsion droplets within the monomer-containing nonpolar phase before holographic patterning. Photochemically initiated polymerization of the nonpolar phase (acrylate monomer) forces the formation of ordered formamide emulsions defined by the holographic interference. Evaporation of the formamide from the ordered structure yields a periodic structure with high optical reflectivity and a wide reflection bandwidth. The average size and the size distribution of formamide droplets in the photopolymer fluid must be controlled to fabricate a periodic structure with high reflectivity. Furthermore, we found that the addition of sodium dioctyl sulfosuccinate (AOT) surfactant helps to stabilize the formamide emulsion which further facilitates the formation of the ordered nanopores with uniform size.
Collinear Generation of Ultrashort UV and XUV Pulses for Pump/probe Spectroscopy
Authors: Bothschafter Elisabeth , Schiffrin Agustin , Krausz Ferenc , Ernstorfer Ralph , Kienberger Reinhard 
Published: August 2010

AbstractThe collinear generation of sub-4 fs ultraviolet (UV) and attosecond extreme ultraviolet (XUV) pulses via subsequent third-harmonic and high harmonic generation in noble gases is demonstrated. The ultrashort coherent light bursts are produced by focusing a sub-1.5 cycle near-infrared/visible (NIR) laser pulse in two subsequent quasi-static noble gas targets. With this simple approach, inherently synchronized UV pulsed radiation with a photon energy of ˜5 eV and a pulse energy of ˜1 μJ, and XUV pulses with a cut-off photon energy of more than 120 eV and up to ˜107 XUV photons can be generated. This source represents a novel tool for future UV pump/XUV probe experiments with unprecedented time-resolution.
Ultrafast Mid-Infrared Intra-Excitonic Response of Individualized Single-Walled Carbon Nanotubes
Authors: Wang Jigang , Graham Matt W. , Ma Yingzhong , Fleming Graham R. , Kaindl Robert A 
Published: August 2010

AbstractWe present femtosecond mid-infrared (mid-IR) studies of the broadband low-energy response of individualized (6,5) and (7,5) single-walled carbon nanotubes. Strong photoinduced absorption is observed in these semiconducting tubes around 200 meV photon energy. The transition energy and broadly sloping spectral shape are characteristic of quasi 1D intra-excitonic transitions between different relative-momentum states. Our result yields a value of the intra-excitonic absorption cross section of σ∥MIR≈4×10-5.
Ultrafast Dynamics of Highly Excited Dirac Fermions in Few-Layer Graphene: Evidence for Three-Particle Auger Scattering
Authors: Li T , Luo L , Hupalo M. , Tringides M C , Wang Jigang 
Published: August 2010

AbstractWe present femtosecond differential reflectivity studies of few-layer graphene from weak to strong excitation regime. Temporal profiles of the differential reflectivity exhibit strong non-exponential decay. A nonlinear, cubic root dependence of their peak amplitudes on the pump fluence is clearly observed under relatively high intensity excitation, which indicates three-particle decay of transient carrier population via Auger scattering. Our results identify the critical role of such three-particle scattering in the initial electronic relaxation in photo-excited graphene with increasing phase-space filling of the correlated Dirac Fermions.
The Role of Friction in the Mechanics of Non-bonded Random Fiber Networks
Authors: Subramanian Gopinath , Picu R. Catalin 
Published: August 2010

AbstractThe mechanics of systems of non-cross-linked fiber networks is studied in this work using a computational model inspired from the bead-spring models of polymeric melts. The fibers have random orientation and distribution in space, interact via stiff repulsive potentials and are characterized by their axial and bending stiffness. Fiber-fiber Coulombian friction is considered. The system is subjected to isostatic compression (strain control) and various statistical measures are evaluated. As the system is compacted, a critical density is reached at which stiffness develops. At this stage there is in average one fiber-fiber contact per fiber and the fiber free segment length has a uniform probability distribution function. Upon further compaction, the number of contacts per fiber increases and the segment length distribution becomes exponential. The respective cross-over densities depend on the fiber length and the friction coefficient. Significant hysteresis is observed upon loading-unloading in the total energy and the number of contacts per fiber. It is also observed that the distribution of contact energies in the range of densities where the system forms a topological network is a power law.
Biosensor Capture Kinetics Model of Nanocube-Augmented Carbon Nanotube Networks
Authors: Claussen Jonathan , Porterfield David Marshall , Fisher Timothy 
Published: August 2010

AbstractAu-coated Pd (Au/Pd) nanocubes (˜250 nm in width) connected via a network of single-walled carbon nanotubes (SWCNTs) have been employed as an electrochemical biosensor. As previously reported, these in situ Au/Pd nanocube SWCNT networks are capable of ultrasensitive amperometric sensing of glucose, with a sensitivity, detection limit, and linear sensing range greater than similar CNT-based glucose biosensors. The 3D mass diffusion of glucose molecules to the Au/Pd nanocube surfaces, forced convection environment of the testing vial, and Brownian motion of the Au/Pd nanocubes are all likely factors contributing to the strong electrochemical performance of the Au/Pd-SWCNT biosensor. In an effort to elucidate the effects of these contributing factors, this work demonstrates an analytical biosensor capture kinetics model that analyzes the analyte-biosensor mass transfer by molecular diffusion and convection due to both the fluid motion within the test vial and the Brownian motion of the Au/Pd nanocubes themselves.The biosensor capture kinetics model incorporates a quasi steady-state integrated incident flux equation to model mass diffusion of biomolecules to the surface of a 1D planar, 2D nanowire, and 3D nanosphere surface in Cartesian, cylindrical, and spherical coordinates respectively. A Burgers vortex model is introduced to analyze the biosensor diffusion boundary layer within a test vial that experiences fluid downwelling and upwelling within the vial center and boundaries due to the rotation of a magnetic stir bar. Finally the convection-diffusion equation simplified by Stokes flow is utilized to model the diffusion boundary layer of the Au/Pd nanocubes experiencing Brownian motion.Several key conclusions can be interfered from this model. First, a biosensor experiencing 3D mass diffusion will exhibit a greater analyte concentration flux of at least one order of magnitude greater than a biosensor experiencing 2D diffusion and 1D mass diffusion in quiescent and convective fluid environments. Additionally, mass transfer by convection increases the concentration flux to the biosensor by inhibiting the continued advancement of the analyte depletion layer around the biosensor. Furthermore, the Brownian motion model of the Au/Pd nanocubes is shown to improve the mass transfer to the biosensor surface, portraying a substantial increase in amperometric current signal output as compared to a similar electrochemical-based biosensor with stationary Au/Pd nanocubes. In summary, the results of the biosensor capture kinetics model corroborate the high sensitivities and low detection limits previously observed experimentally by Au/Pd nanocube-SWCNT biosensors.
Exploiting Phosphate Dependent DNA Immobilization on HfO2, ZrO2and AlGaN for Integrated Biosensors
Authors: Fahrenkopf Nicholas M , Jindal Vibhu , Tripathi Neeraj , Oktyabrsky Serge , Shahedipour-Sandvik Fatemeh , Tokranova Natalya , Bergkvist Magnus , Cady Nathaniel C 
Published: August 2010

AbstractA significant challenge for high throughput nucleic acid analysis and sequencing is to increase both throughput and sensitivity. Electrical detection methods are advantageous since they can be easily scaled to high density arrays, are highly sensitive, and do not require bulky optical equipment for readout. A focus of most nucleic acid based sensors is the detection of sequence-specific hybridization events between complementary strands of DNA or RNA. These hybridization events can be detected electrically, due to the intrinsic negative charge associated with the phosphate-rich nucleic acid backbone. Field effect transistors (FETs) and high electron mobility transistors (HEMTs) are ideal devices for detecting such hybridization events, due to their high sensitivity to changes in electrical field strength. A key concern for the construction of DNA-based FET and HEMT biosensors is the immobilization of probe oligonucleotides on the active region of the sensor. In previous work, our group has shown that single stranded DNA can be directly immobilized onto semiconductor materials without the need for complex surface chemistry or crosslinking strategies. In the present work, we have shown that the immobilization of single stranded DNA onto these materials is influenced by the terminal phosphate group of the DNA molecule, independent of backbone phosphates. This agrees with previous studies in which phosphates and phosphonates exhibited strong attachment to a variety of metal oxides. We have also shown that surface-immobilized DNA is available for hybridization and that hybridization is sequence specific. Phosphate-dependent immobilization was demonstrated for HfO2, AlGaN, and ZrO2surfaces using optical detection of DNA-DNA hybridization, as well as x-ray photoelectron spectroscopy (XPS) analysis of DNA-modified surfaces.
Optimized in situ DNA synthesis on patterned glass
Authors: Saaem Ishtiaq , Ma Kuosheng , Tian Jingdong 
Published: August 2010

AbstractThis paper describes studies of patterned arrays on glass surfaces and their use as spatially separated reactors for in situ synthesis of DNA using an inkjet synthesizer. Photolithographic methods were employed to fabricate arrays composed of homogenous circular features containing a hydroxyl-terminated silane coupled to the surface of the glass via a siloxane bond. Features are embedded within a background matrix composed of a fluorosilane attached to the glass. Due to the differential wettability of the two silanes, whereby the hydroxyl-terminated silane and fluorosilane are hydrophilic and hydrophobic respectively because of their head groups, the patterned circular features are able to constrain liquid within a defined site. The silanization result was analyzed using X-ray photoelectron spectroscopy (XPS) to optimize silanization time and solvent. Synthesis was then performed using a custom-built inkjet system using phosphoramidite chemistry. Base-by-base analysis using fluorescent labeling showed consistent coupling efficiency on synthesis of a 50-mer homopolymer.
The Combination of Drug or Gene Delivery System Responding to Cellular Signals (D-RECS) and Sonoporation System for Effective and Safe Gene Delivery
Authors: Tsuchiya Akira , Mori Takeshi , Naritomi Yuki , Kang Jeong-Hun , Asai Daisuke , Niidome Takuro , Endo Yoko , Suzuki Ryo , Negishi Yoichi , Maruyama Kazuo , Katayama Yoshiki 
Published: August 2010

AbstractWe have developed new gene expression-regulating polymer that can activate transgene expression in response to target intracellular signals. Here, we tried applying sonoporation system to this gene regulation system to enhance the gene expression efficacy. Sonoporation is the method for effective gene transfection in vitro and in vivo. Therefore, the method might enhance the transfection efficiency in our polymer and realize an efficient and safe gene delivery system. Results suggested that the combination of our polymer and sonoporation could improve the gene expression compared to the system using only our polymer that transfers genes into cells via endocytosis. It also kept the ability of the gene regulation responding to cellular signals.
Effects of Magnetic Nanoparticles on Magnetic Resonance and Spin Relaxation in Systems of Different Viscosity
Authors: Noginova Natalia , Andreyev Aleksandr , Noginova Julia , Hall Joseph C , Ramesh Vani , Atsarkin Vadim A 
Published: August 2010

AbstractNuclear Magnetic Resonance (NMR) technique is a convenient method to monitor magnetic nanoparticles in different biomedical applications and observe changes induced by the particles. To better understand the specifics of the magnetic resonance and spin relaxation in the systems with magnetic nanoparticles, the NMR spectra and magnetization dynamics of the host protons are studied in the model systems of different viscosity and some biological systems in the presence of magnetic nanoparticles. The results confirmed that nanoparticles affect the proton relaxation kinetics of liquid solutions, changing the relaxation time (T1) significantly, whereas in systems of high viscosity the relaxation times are unchanged. The kinetics in intermediate systems is multi-exponential. A complicated picture is observed in biological systems, demonstrating contributions of liquid-like and solid-like behavior.
Novel Gelation System For Fabricating 3-D Structures via Ink Jet Printing
Authors: Saunders Rachel E. , Liem Kwan P , Mart Robert J , Webb Simon J , Derby Brian 
Published: August 2010

AbstractDrop-on-demand inkjet printing is a fabrication technique that is capable of depositing materials layer-by-layer to form complex 3-dimensional (3-D) constructs. Here we present a new single drop delivery method in which both the matrix and cross-linker are present but separated through the use of vesicle packaging. Changing the printing parameters has little effect on the integrity of the calcium(II)-loaded vesicles, with calcium(II) released selectively by warming after printing. Alginate solutions containing calcium(II)-loaded vesicles were successfully printed and the printed layers were shown to gel on demand at 37 °C. The printed alginate layers were evaluated with regards to their potential to provide 3-D structures for cell culture.
Impedance Spectroscopy and Structural Studies on Silver Doped Hydroxyapatite
Authors: Singh Brajendra , Kumar Samayendra , Basu Bikramjit , Gupta Rajeev 
Published: August 2010

AbstractWe report the structural transformation and the transport studies of Silver doped hydroxyapatites Ca10-xAgx(PO4)6(OH)2 (0.0 ≤ x ≤ 1.5). A dramatic increase in the conductivity by two orders of magnitude for hydroxyapatite in presence of silver ions is recorded using impedance spectroscopy measurements in the temperature range of 450°C to 650°C. The characteristic surface plasmon resonance effect is used to explore the presence of silver nano-particles, and Ag+ ions in hydroxyapatite using optical absorption measurements. The activation energy has been found to be 0.07 eV in silver doped composition in comparison to 0.39 eV for the parent hydroxyapatite. The sintering temperature dependence and compositional variation on the structural transformations from hydroxyapatite into tricalcium phosphate phases have been explored using Raman Spectroscopy and X-ray diffraction techniques.
Pulsed-DC Electrospray for Biopolymer Particle Production
Authors: Lim Cho-Hui , Schierbeek Kiersten R , Mullins Michael E 
Published: August 2010

AbstractPLLA microparticles were successfully fabricated via pulsed-DC electrospray. In this study, we investigated the effect of the pulsed voltage characteristics (e.g. pulse frequency, pulse amplitude and pulse width) on the particle’s size. We found that pulse frequency, pulse amplitude, pulse width, and the combinations of these factors had a statistically significant effect on the particle’s size. The process conditions to obtain smaller particles with uniform shape and size are a low pulse frequency, high pulse amplitude, and long pulse width (or a high duty cycle).
3D-printing of Urethane-based Photoelastomers for Vascular Tissue Regeneration
Authors: Baudis Stefan , Pulka Thomas , Steyrer Bernhard , Wilhelm Harald , Weigel Guenter , Bergmeister Helga , Stampfl Juergen , Liska Robert 
Published: August 2010

AbstractThe mechanical properties of materials designated for vascular tissue replacement are of crucial importance. The elastic modulus, the tensile strength as well as the suture tear resistance have to be adjusted. Our approach is to use photopolymers for artificial vascular grafts. Via the layer-by-layer photopolymerization of suitable resin formulations as performed in additive manufacturing (AM) very complex structures are realizable. Hence AM offer the possibility to create cellular structures within the artificial grafts that might favor the ingrowth of new tissue. Commercially available urethane acrylates (UA) were chosen as base monomers since urethane groups are known to have good cell-adhesion behavior and poly-UAs show adequate mechanical performance. The mechanical properties of the photoelastomers can be tailored by addition of reactive diluents (e.g. 2-hydroxyethyl acrylate, HEA) and thiols (e.g. 3,6 dioxa-1,8-octane-dithiol) as chain transfer agents to comply with the mechanical properties of natural blood vessels. To examine the suture tear resistance a new testing method has been developed. Finally, a formulation containing 30 wt% UA and 70 wt% HEA complies with the mechanical properties of natural blood vessels, shows good biocompatibility in in-vitro tests and was successfully 3D-printed with digital light processing AM.
Fabrication of Highly Conductive Pedot Nanofibers
Authors: Laforgue Alexis , Robitaille Lucie 
Published: August 2010

AbstractPoly(3,4-ethylenedioxythiophene) (PEDOT) nanofibers were obtained by the combination of electrospinning and vapour-phase polymerization. The fibers had diameters around 350 ± 60 nm, and were soldered at every intersection, ensuring superior dimensional stability of the mats. The nanofiber mats demonstrated very high conductivity (60 ± 10 S/cm, the highest value reported so far for polymer nanofibers) as well as very interesting electrochemical properties, due to the porous and nanostructured nature of the electrospun mats. The mats were incorporated into all-solid flexible supercapacitors that showed interesting performances for applications where flexible and lightweight energy storage devices are required.
Ion Exchange Functional Nanofibers
Authors: Patra Prabir K , Sengupta Sukalyan 
Published: August 2010

AbstractWe have synthesized a series of ion exchange functionalized fibers (IXF) from polystyrene (PS) and polyacrylonitrile (PAN). To obtain strong-acid cation exchange fibers, polystyrene was sulfonated using specific sulfonation protocols. Micron sized fibers (average diameter of 100m) were then produced from the functionalized polystyrene using a single-screw extruder equipped with a 30 hole spinneret with orifice diameter of 0.5 mm with a precise screw speed of 5 rpm, pump speed of 15 rpm, and with a feed rate of 2.4 cc/min. The extruder zone temperature was kept at 250 – 270 °C. Fiber was drawn at 120 degree with a draw ratio of 2. Electrospinning of functionalized polystyrene was also carried out to produce ultrafine functionalized fibers of 100 nm in average diameter. We have also electrospun polystyrene and polyisoprene blended nanofibers to increase the strength of the resulting blend nanofibers compared to pure PS nanofibers. To synthesize weak-acid cation exchange fibers polyacrylonitrile (PAN) was electrospun and the nanofibers obtained were alkaline hydrolyzed with 2 N NaOH for 20 minutes at room temperature to convert nitrile bonds to carboxylate. Cation exchange capacity (CEC) of the microfibers and nanofibers was determined. Sulfonated PS microfibers show high CEC of 4.0 meq/gm compared to that of nanofibers with 2.5 meq/gm. CEC of blended nanofibers of PS and polyisoprene was 2.0 meq/gm. In case of PAN fibers, nanosized electrospun fibers were found to show a CEC of 1.5 meq/gm. Weak-base anion exchange fiber synthesis was undertaken using appropriate protocol and its CEC was measured. For all IXF synthesized, fiber diameter was measured using SEM, degree of functionalization was qualitatively determined using FTIR and ion exchange capacity was computed after mass balance on a binary exchange system after equilibrium.
Chiral CdTe Quantum Dots
Authors: Moloney Mícheál P , Gallagher Shane A , Gun'ko Yurii K 
Published: August 2010

AbstractQuantum dots (QDs) are fluorescent semiconductor (e.g. II-VI) nanocrystals, which have a strong characteristic spectral emission. This emission is tunable to a desired energy by selecting variable particle size, size distribution and composition of the nanocrystals. QDs have recently attracted enormous interest due to their unique photophysical properties and range of potential applications in photonics and biochemistry.The main aim of our work is develop new materials based chiral quantum dots (QDs) and establish fundamental principles influencing the structure and properties of chiral QDs. Here we report the quantum efficiency control in cysteine capped CdTe quantum dots (QDs) by varying ratios of enantiomeric stabilizers. We also demonstrate that the circular dichroism (CD) of CdTe QDs can be introduced by utilizing the mixture of penicilamine and cysteine stabilizers of the same chirality. This approach results in QDs with the enhanced CD activity, but causes a decrease in the quantum yield and widening of the emission due to the presence of chiral defects at the nanoparticle surface. We believe that these new QDs could find important applications as fluorescent assays and sensors (or probes) in asymmetric synthesis, catalysis, enantioseparation, biochemical analysis and medical diagnostics.
From R&D to Large-Area Modules at Oerlikon Solar
Authors: Meier Johannes , Benagli Stefano , Bailat Julien , Borello Daniel , Steinhauser Jerome , Hötzel Jochen , Castens Lucie , Orhan Jean-Baptiste , Djeridane Yassine , Vallat-Sauvain Evelyne , Kroll Ulrich 
Published: August 2010

AbstractAmorphous silicon single-junction p-i-n and Micromorph tandem solar cells are deposited in KAI-M reactors on in-house developed LPCVD ZnO front TCO's. An a-Si:H p-i-n cell with a stabilized efficiency of 10.09 % on 1 cm2 has been independently confirmed by NREL. An alternative ZnO/a-Si:H cell process with an intrinsic absorber of only 180 nm has reached 10.06 % NREL confirmed stabilized efficiencies as well. Up-scaling of such thin cells to 10x10 cm2 mini-modules has led to an aperture module efficiency of stabilized 9.20 ± 0.19 % as well independently confirmed by ESTI of JRC Ispra.Micromorph tandem cells with stabilized efficiencies of 11.0% have been achieved on as-grown LPCVD ZnO front TCO at bottom cell thickness of just 1.3 μm in combination with the in-house developed AR concept. Applying an advanced LPCVD ZnO front TCO stabilized tandem cells of 10.6 % have been realized at a bottom cell thickness of only 0.8 μm. Implementing in-situ intermediate reflectors in Micromorph tandems on LPCVD ZnO reached in a stabilized cell efficiency of 11.3% with a bottom cell thickness of 1.6 μm.