bluuebunny/crossref_metadata_2025_split huggingface dataset:
Efficient Upconverting Nanophosphors for Imaging and Photodynamic Therapy
Authors: Yust Brian G. , Kumar Gangadharan Ajith , Mimun Lawrence C. , Sardar Dhiraj K. 
Published: November 2012

ABSTRACTErbium-Ytterbium codoped nanophosphor systems are explored for high efficiency upconversion. The NIR to visible upconversion from 1550 nm and 980 nm excitation are of particular interest to us for biomedical applications such as imaging, sensing, and photodynamic therapy. Variations in synthesis method and rare earth concentration are carried out in sodium, potassium, and transition metal based phosphor materials. The spectroscopic properties of the material dry and in biologically appropriate solution are taken. After bioconjugation, these particles will be used in a mouse model to demonstrate that cancer imaging with a near-infrared excitation source is possible.
Rare Earth Based Upconverting Materials for Solar Cell Application
Authors: Pokhrel Madhab , Kumar G. A. , Sardar Dhiraj K. 
Published: November 2012

ABSTRACTBasic spectroscopic studies of Yb and Er-doped M2O2S (M= Gd, La,Y) phosphor was reported with particular attention to its upconversion properties under 1550 nm excitation. Since the absorption spectra of Co2+overlaps with Er3+(4I13/2→4I15/2) at near infrared (NIR) region, we are proposing the concept of an efficiency enhancement of infrared upconverting phosphors as an energy converting material that could potentially improve the efficiency of Si solar cells in bifacial configuration. Different concentrations of Er3+/Co2+ phosphors were synthesized by solid state flux fusion method. The phosphor powders were well crystallized in a hexagonal shape with an average size 4 mm. Preliminary upconversion analysis of singly Er3+ and doubly Co2+/Er3+ doped Y2O2S under 980 and 1550 nm excitation indicates that the composition has to be optimized to understand the role of Co2+ in the system.
Nanometer Resolution XANES Imaging of Individual PC-RAM Devices
Authors: Richter Jan H. , Krbal Milos , Kolobov Alexander V. , Fons Paul , Wang Xiaomin , Mitrofanov Kirill V. , Simpson Robert E. , Tominaga Junji , Osawa Hitoshi , Suzuki Motohiro 
Published: November 2012

ABSTRACTWe introduce a technique to permit x-ray absorption spectroscopy studies focusing on individual phase-change (Ge2Sb2Te5) memory cells in fully integrated PC-RAM structures. Devices were investigated employing an x-ray nanobeam of only about 300 nm diameter, which could be fully contained within the spatial extent of the active area within a single device cell and enabled us to investigate individual devices without interference from non-switching material surrounding the area of interest. By monitoring the fluorescence signals of tungsten and germanium at a photon energy corresponding to the Ge K-edge absorption edge white line position, we were successful in producing 2D area maps of the active cell region, which clearly show the imbedded tungsten heater element and the switched region of the phase change material. Additionally, position dependent changes in the phase change material could be traced by taking an array of XANES spectra at the Ge K-edge on and in the vicinity of individual devices.
Nonlinear Two-Photon Photocurrent Spectroscopy of CdS Nanosheets
Authors: Kumar Parveen , Wade Aaron , Smith Leigh Morris , Jackson Howard E , Yarrison-Rice Jan M , Choi Young-Jin , Park Jae-Gwan 
Published: November 2012

AbstractWe study the photocurrent from photoexcited charged carriers excited with lasers of energy both above and below the energy gap in CdS nanostructures. We observe non-linear photocurrents in CdS nanosheet devices in the metal-semiconductor-metal configuration with Schottky contacts for sub-band gap excitations. Analysis of two-photon absorption dominated photocurrents reveals a nonlinear coefficient of β = 2 cm/GW for these nanosheet devices, which is comparable to those of bulk CdS. We demonstrate the use of the photocurrent polarization measurements to determine the orientation of atoms in the nanosheet.
Fabrication and antimicrobial effects of silver nanoparticle-poly(N-isopropylacrylamide)-poly(ferrocenylsilane) hydrogel composites
Authors: Sui Xiaofeng , Feng Xueling , Di Luca Andrea , van Blitterswijk Clemens A. , Moroni Lorenzo , Hempenius Mark A. , Vancso G. Julius 
Published: November 2012

ABSTRACTNovel hydrogels composed of thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) and redox-responsive poly(ferrocenylsilane) (PFS) macromolecules were formed by photopolymerization. PFS chains bearing acrylate side groups were copolymerized with NIPAM and N,N’-methylenebisacrylamide in tetrahydrofuran in a predetermined ratio under ultraviolet light-emitting diode (UV-LED) irradiation at a wavelength of 365 nm, in the presence of a photoinitiator. Crosslinking occurred smoothly, providing homogeneous hydrogels. The equilibrium swelling ratio, rheology and morphology of these hybrid PNIPAM-PFS-based hydrogels were investigated. In-situ fabrication of silver nanoparticles inside the hydrogel network via reduction of silver nitrate by the PFS chains led to hydrogel composites. These composites showed strong antimicrobial activity while maintaining a high biocompatibility with cells.
Phosphors as Sensors for Radiation-Induced Displacement Damage
Authors: Gollub S. L. , Harl R. R. , Weeden-Wright S. L. , Rogers B. R. , Walker D. G. 
Published: November 2012

AbstractThe radiation-induced displacement damage in yttrium borate (YBO3) is studied under X-ray, proton, and alpha irradiation. The photoluminescence (PL) was tested before and after irradiation to determine whether damage occurred and whether it could be queried by examining the PL spectrum. Two different dopants (cerium and europium) were used to activate the phosphor because each provides not only a different spectral signature but also a different mechanism for altering the spectrum between the pre- and post-PL measurements. X-rays, being primarily ionizing radiation, did not show any significant change between the pre and post measurements. We expected protons and alphas to damage the crystal structure, evidence of which could be seen in the change in the spectra before and after irradiation. However, we found no change under alpha exposure (3.6 × 1010 particles/cm2) and a significant change after proton exposure (5 × 1015 particles/cm2). While the material appears to be sensitive to protons, we cannot rule out its sensitivity to alphas because the alpha fluence may be too low to show an effect. This result provides strong indication that our materials are being damaged by particle radiation and that the radiation effects can be quantified.
Matrices of inkjet printed OFETs for the realization of artificial robotic skin
Authors: Loi Alberto , Basiricò Laura , Cosseddu Piero , Lai Stefano , Maiolino Perla , Baglini Emanuele , Denei Simone , Mastrogiovanni Fulvio , Cannata Giorgio , Palomba Chiara , Barbaro Massimo , Bonfiglio Annalisa 
Published: November 2012

ABSTRACTIn this paper we introduce a novel, flexible, system for mechanical deformation detection. The core of the system is based on an Organic Thin Film Transistor (OTFT) which has been assembled on a flexible PET substrate and patterned by means of inkjet printing. OTFT-based mechanical sensors were fabricated employing two different organic semiconductors, namely a small molecule (pentacene) deposited by thermal evaporation and its solution-processable derivative 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-pentacene) deposited by drop casting. It will be shown that the surface deformation induced by an external mechanical stimulus gives rise in both cases to a marked, reproducible and reversible (within a certain rage of surface deformation) variation of the device output current. Starting from these results, more complex structures such as arrays and matrices of OTFT-based mechanical sensors have been fabricated by means of inkjet printing. Thanks to the flexibility of the introduced structure, we will show that the presented system can be transferred on different surfaces (hard and soft) and employed for a wide range of applications. In particular, we have designed and fabricated a fully functional system based on a matrix of 64 elements that can be employed for detecting mechanical stimuli over larger areas, and will demonstrate that such a system can be successfully employed for tactile transduction in the realization of artificial “robot skins”.
High Speed Surface Modification in Fine-Pitch Package Substrate Manufacturing Process with High Density 60 Hz Nonequilibrium Atmospheric Pressure Plasma
Authors: Iwata Yoshiyuki , Sakamoto Hajime , Takeda Keigo , Hori Masaru 
Published: November 2012

ABSTRACTThis study examined surface modification of solder resist and dry film resist using 60 Hz nonequilibrium atmospheric pressure plasma with O2/N2 mixing gas. Results show that the plasma discharge condition at O2/N2 mixing ratio of 0.1% was the best for surface modification for both materials, and the surfaces were modified sufficiently at 0.45 m/min package substrate transportation speed. From the plasma diagnostics by Vacuum Ultraviolet Absorption Spectroscopy (VUVAS) and Optical Emission Spectroscopy (OES), it was found that the behaviors of the oxygen radical density and NO-γ emission intensity correlate strongly with surface modification. The extremely high oxygen radical density around 4.7 × 1013 cm-3 was obtained at O2/N2 mixing ratio of 0.1%. The electron density was 2.5 × 1015 cm-3 that is two digits more than that of the conventional atmospheric pressure plasma such as Dielectric Barrier Discharge (DBD). The solder resist surface with the plasma treatment was analyzed by X-ray Photoelectron Spectroscopy (XPS), and it was clarified that material surface was modified by hydrophilic group generation owing polymer chain oxidation with oxygen radical.
Role of Enthalpy and Relative Electric Permittivity in Electric Field Induced Nucleation
Authors: Kohary K. , Vazquez-Diosdado J. , Ashwin P. , Wright C. D. 
Published: November 2012

ABSTRACTEmerging phase-change electrical memory technologies rely on the fast amorphous to crystalline transition, which is usually characterized by an ‘S-shape’ current-voltage curve. We investigate the possibility that electric field induced nucleation may play a dominant role in defining this characteristic electrical switching behavior. We derive quantitative crystallization maps to study the kinetics of the amorphous to crystalline transition in the presence of electric field contribution to the free energy and we investigate how the prediction of the electric field induced nucleation model is affected by material properties such as enthalpy and relative electric permittivity.
Graphene Electromechanical Actuation; Origins, Optimization and Applications
Authors: Rogers Geoffrey W. , Liu Jefferson Z. 
Published: November 2012

ABSTRACTGraphene-based materials have emerged as exceptional candidates for the development of novel, high performance actuators. Developing such an actuation material requires an in depth knowledge of the physics of operation and, therefrom, how to best optimize its performance. We investigate the electromechanical actuation of pristine monolayer graphene to elucidate the origin of this material’s exceptional electromechanical actuation performance. It is shown that the electrostatic double-layer (EDL) effect is dominant compared to the quantum-mechanical (QM) effect upon charging and electrolyte immersion. Seeking to optimize the QM actuation performance, we preliminarily investigate graphene oxide (GO) as a potential graphene-based actuation material, and find that it exhibits both unique and high performance responses. Having demonstrated huge stresses (~100 GPa) and high strains (~0.4%), graphene-based materials are uniquely positioned to address future industrial actuation challenges.
Modified Polylactide Microfiber Scaffolds for Tissue Engineering
Authors: Vera-Graziano R. , Maciel-Cerda A. , Moreno-Rondon E.V. , Ospina A. , Gomez-Pachon E.Y. 
Published: November 2012

ABSTRACTPhysical properties of porous membranes made of biocompatible and biodegradable polymers have been studied. The membranes are intended to be used as scaffolds for the regeneration of soft and hard tissues. Polylactides, polycaprolactone and some of their derivates are biocompatible as well as biodegradable materials, and are used for the preparation of nanofibers and nanoporous membranes. These membranes also have comparative advantages as cellular scaffolds for tissue engineering since they can be prepared to mimic the morphology of the extra cellular matrix.Chemical, physical, and biological properties of microfibers and scaffolds of polylactic acid (PLLA), as well as PLLA modified with hydroxyapatite nanoparticles and collagen (Col) are reported in this paper. The microfibers and the scaffolds were prepared by electrospinning. Morphology, diameter and porosity of the scaffold were determined by scanning electron microscopy and an image analyzer program. The microfibers are semicrystalline showing a shell of crystalline nanofibrils. The diameter of the fibers varied between 100 and 800 nm and the porous area of the membrane is between 60 and 80%. The mechanical properties of the microfibers and scaffolds were evaluated by microtensile tests and their behavior was simulated by using an original multiscale asymptotic homogenization model. Cultures of mesenchymal stem cells were used to evaluate their biological activity. Cell adhesion was observed in the modified PLLA scaffolds with grafted hydroxyapatite.
Biocompatibility of Polyurethane Urea Elastomers for Cardiac Tissue Engineering
Authors: Paredes-Puerto A. , Dashti D. , Yeghiazarians Y. , Healy K.E. , Hernández-Sánchez F. 
Published: November 2012

ABSTRACTCardiac disease is the main cause of death in men and women in México and the U.S.A. When heart muscle suffers an injury, i.e. cardiac infarction, the tissue dies and is replaced by a fibrotic scar that does not allow for normal organ function. To alleviate scar tissue, the objective of this work was to investigate and synthesize polyurethane ureas from polycaprolactone diol, methylene bis(4-cyclohexilisocyanate), and butanediamine with different hard segment contents, characterize them, and prove their biocompatibility by seeding SCA-1+/CD45-cardiac progenitor cells obtained from mice cardiospheres. Ultimately, this work aims to explore how polyurethane urea elastomers can aid in therapeutic cardiac tissue regeneration.
Photoluminescence transformation of core/shell CdSe/ZnS quantum dots at the conjugation to biomolecules
Authors: Torchynska T. V. , Ballardo Rodríguez I. Ch. , Shcherbyna Ye. 
Published: November 2012

AbstractThe paper presents the results of PL spectrum analysis of CdSe/ZnS QDs covered by PEG polymer with and without bioconjugation to bio-molecules .– the Osteopontin antibodies. Commercial CdSe/ZnS QDs used in the study are characterized by the color emission with the maximum at 640 nm (1.96 eV) at 300K. It is shown that PL spectra of nonconjugated QDs can be presented as a superposition of PL bands related to exciton emission in the CdSe core (1.96 eV) and some high energy PL bands (in the spectral range 2.37 .– 3.00 eV). The comparative study of PL spectrum at high (300K) and low (10K) temperatures has testified that high energy PL bands deal with electronhole emission via interface states at the CdSe/ZnS/polymer interfaces.It is revealed that the QD bioconjugation to the anti Osteopontin antibody is accompanied by the change dramatically in PL spectra. Main features of PL spectrum transformstions deal with decreasing the PL intensity of interface related PL bands and the rise of intensity of CdSe core related PL bands. The explanation of mentioned effects has been proposed on the base of re-charging of interface related states at the bioconjugation process.
Stress Analysis of Molars Restored with Full Cast Metal Crowns
Authors: Porojan S. , Sandu L. , Topală F. , Babeş V. 
Published: November 2012

ABSTRACTThe incomplete fit of full cast crown restorations remains a critical problem for dentists, leading many researchers to study this problem. Marginal and internal accuracy of fit is valued as one of the most important criteria for the clinical quality and success of complete crowns. The geometry of tooth preparation has been the subject of many debates without clear evidence that one type of tooth preparation or method of fabrication provides consistently superior marginal fit. The objective of this study was to evaluate, by finite element analysis, the influence of different marginal geometries (shoulderless, chamfer, shoulder) on the stress distribution in teeth prepared for cast metal crowns.A 3D model of a molar was created: intact teeth, unrestored teeth different marginal geometries: shoulderless, with chamfer, with shoulder preparations; the same tooth restored full cast metal crowns. These were exported in Ansys finite element analysis software for structural simulations.The values of the maximal equivalent stress were higher for the shoulder preparations, but distributed under the preparation line. Regarding the stress distribution for the other two preparation designs, the largest area is present for the chamfer preparation, followed by the shoulderless preparation.Within the limitations of the present study, the shoulder preparation is the recommended preparation design from biomechanical point of view. It is followed by the shoulderless preparation. Chamfer margins are less favorable only from this point of view. In light of these results, consideration should be given to the designs from prophylactic and biological points of view, with emphasis on conserving tooth structure and preventing preparation trauma.
Auger Recombination of Biexcitons and Charged Excitons in CdSe/CdS core/shell Nanocrystals
Authors: Marceddu Marco , Saba Michele , Quochi Francesco , Lai Adriano , Huang Jing , Talapin Dmitri V. , Mura Andrea , Bongiovanni Giovanni 
Published: November 2012

ABSTRACTCdSe/CdS colloidal nanocrystals are light-emitting nanoparticles with remarkable optical properties such as suppressed fluorescence blinking and enhanced emission from multiexciton states. These properties have been attributed to the suppression of non-radiative Auger recombination. In this work we employ ultrafast spectroscopy techniques to identify optical signatures of neutral and charged excitonic and multiexcitonic states.
“Design of Poly(ethylene glycol)-Polycaprolactone Diblock Micelles with RGD Targeting Ligands and Embedded Iron Oxide Nanoparticles for Thermally-activated Release”
Authors: Brazel Christopher S. , Bennett James B. , Glover Amanda L. , Nikles Jacqueline A. , Everts Maaike , Glasgow Joel N. , Nikles David E. 
Published: November 2012

ABSTRACTA thermally-activated micelle consisting of a crystallizable poly(caprolactone), PCL, core and a poly(ethylene glycol), PEG, corona was developed to contain magnetic nanoparticles and anti-cancer agent doxorubicin as well as display a targeting RGD peptide. This system has the potential to target cancer cells, deliver combination hyperthermia and chemotherapy, and offer magnetic resonance imaging contrast. The micelles self-assemble in aqueous solutions and form a crystalline core with a melting transition ranging from 40 to 50 °C, depending on the length of the PCL blocks, with dynamic light scattering showing micelle sizes typically ranging from 20 to 100 nm, depending on block lengths and added drug or nanoparticles. The micelles become unstable as they are heated above their melting point, creating a thermally-activated drug release mechanism. By adding magnetite (Fe3O4) nanoparticles into the PCL core, the micelles can be heated using an externally applied AC magnetic field to induce hyperthermia in combination with the thermally-activated drug release. The polymers and magnetic nanoparticles (MNPs) were synthesized and characterized in our laboratories. The melting transitions of the PCL micelle cores were investigated using microcalorimetry. The heating of nanoparticles and magnetomicelles was conducted using a custom-built hyperthermia coil capable of generating fields of several hundred Oersteds at frequencies ranging from 50 to 450 kHz. Heating of MNPs was maximized at high field intensities. RGD peptides were attached to the PEG corona using maleimide chemistry, and the ability of the RGD-derivatized micelles to target integrin-expressing cells was investigated using fluorescent dye PKH26 to identify the localization of micelles in cultured human kidney (293) cells in vitro. The crystallizable (and meltable) cores in these micelles were designed to overcome drug leakage common in liposome systems and release the drug on demand after a period of time for localization to integrin receptors.
Composite nanosilver structures suitable for plasmonic biosensors
Authors: Sotiriou Georgios A. , Blattmann Christoph O. , Pratsinis Sotiris E. 
Published: November 2012

ABSTRACTSilver (Ag) nanoparticles dispersed in an amorphous silica (SiO2) matrix or coated by a SiO2 layer were synthesized by flame spray pyrolysis (FSP). The coated nanoparticles were produced by using a modified enclosed FSP setup, in which the SiO2 precursor was injected through a ring above the FSP nozzle at various burner-ring-distances (BRDs), after the core Ag nanoparticles had been formed. The produced nanoparticles were characterized by XRD, BET, TEM and UV/vis analysis. The Ag particle size was possible to be controlled by tuning the FSP parameters. For the SiO2 coated nanoparticles, larger Ag core sizes were obtained for higher BRDs. All the produced nanoparticles exhibited the characteristic plasmon resonance frequency of Ag nanoparticles.
Surface Engineered Porous Silicon-based Nanostructures for Cancer Therapy
Authors: Tzur-Balter Adi , Massad-Ivanir Naama , Segal Ester 
Published: November 2012

ABSTRACTIn this work, nanostructured porous silicon (PSi) hosts, synthesized by electrochemical etching of Si, are designed to carry and release the anti cancer drug, mitoxantrone dihydrochloride (MTX). We study the effect of surface chemistry of the Si scaffold on its properties as a drug carrier. The freshly-etched PSi is modified by surface alkylation using thermal hydrosilylation with 1-dodecene. Fourier-transform infrared spectroscopy and nitrogen adsorption-desorption measurements are employed to characterize the PSi carriers after chemical modification. Both, drug loading efficiency and release kinetics are found to be significantly affected by surface chemistry of the PSi.In vitrocytotoxicity studies on human breast carcinoma (MDA-MB-231) cells show that the MTX released from the PSi hosts maintains its cytotoxic functionality.
Young’s Modulus of Cortical and P19 Derived Neurons Measured by Atomic Force Microscopy
Authors: Spedden Elise , White James D. , Kaplan David , Staii Cristian 
Published: November 2012

ABSTRACTIn this paper we use the Atomic Force Microscope to measure the Young’s modulus for two types of neuronal cell bodies: cortical neurons obtained from rat embryos and neurons derived from P19 mouse embryonic carcinoma stem cells. The neurons are plated on different substrates coated with two types of protein growth factors, poly-D-lysine and laminin. We report on the Young’s modulus of each type of neuron as well as the variation of modulus between cells plated on different protein substrates. We compare these results to various individual cell and bulk tissue measurements reported in literature. We additionally report on an observed change in the Young’s modulus of cortical neurons when subjected to a short-term reduction in ambient temperature.