bluuebunny/crossref_metadata_2025 huggingface dataset:
New Flexible High Gamma Dose Dosimeter Based on Luminescent and Biodegradable Polymer Blend
Authors: Schimitberger T. , Franco M.R. , Lopes F.A. , Curti P.S. , Bianchi R.F. , Faria L.O.
Published: June 2019

In this work we investigate the radio-degradation of MEH-PPV polymer film as a tool for measuring high doses of gamma radiation. In order to produce film samples with thickness in the micron range, we have mixed the photoluminescent poly(2-methoxy-5(2'-ethylhexyloxy)-p-phenylenevinylene) copolymer (MEH-PPV) with a biodegradable poly(butylene adipate-co-terephthalate) copolymers (PBAT). The system was irradiated with a Co-60 source with doses ranging from 1 to 1,000 kGy. Ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectroscopy have been used to investigate the radiation induced changes in the absorption and photon-emission spectra of the irradiated samples. Results indicate that the PL emission intensity varies exponentially with the applied gamma radiation dose for doses ranging from 30 to 500 kGy. The unambiguous relationship betweenPL & Dosetogether with the good flexibility of the copolymer films indicate that MEH-PPV/PBAT blends have great potential for applications in high gamma dose dosimetry.
HR XRD and Emission of InxGa1-xAs/GaAs quantum wells with embedded InAs quantum dots at the variation of InxGa1-xAs composition
Authors: Vega Macotela Leonardo G. , Tamayo Ricardo Cisneros , Polupan Georgiy
Published: June 2019

The high resolution X ray diffraction (HR-XRD) diagrams have been studied in the GaAs /InxGa1-xAs /In0.15Ga0.85As/GaAs quantum wells with embedded InAs quantum dots (QDs) in dependence on the composition of the capping InxGa1-xAs layers. The parameter x in capping InxGa1-xAs layers varied from the range 0.10-0.25. These technological changes have been accompanied by the variation non-monotonously of InAs QD emission. Numerical simulation of HR-XRD results has shown that the level of elastic strains and the composition of quantum layers vary none monotonously in studied QD structures. Simultaneously it was revealed that the process of Ga/In inter diffusion at the InxGa1-xAs/InAs QD interface are characterized by the dependence non monotonous versus parameter x in capping InxGa1-xAs layers. The physical reasons of the mentioned optical and structural effects in studied structures have been discussed.
Size dependent optical properties in ZnO nanosheets
Authors: El Filali Brahim , Díaz Cano Aaron I.
Published: June 2019

Photoluminescence (PL), scanning electronic microscopy (SEM) and Raman scattering have been studied in crystalline ZnO nanosheets with different sizes after the thermal annealing at 400 °C for 2 hours in ambient air. ZnO nanosheets were created by the electrochemical (anodization) method using the variation of the etching durations with obtained ZnO nanosheet sizes from the range 40-360 nm. Earlier it was shown using the X ray diffraction (XRD) method that thermal annealing performed the ZnO oxidation and crystallization with the creation of the wurtzite crystal lattice. Four PL bands are revealed in PL spectra with the PL peaks at 1.60, 2.08, 2.50 and 3.10 eV. Size decreasing of ZnO nanosheets stimulates tremendous changes of ZnO optical parameters. It is shown that decreasing the ZnO nanosheet sizes is accompanied by the intensity increase of a set of Raman peaks and the surface defect related PL bands. The reasons of emission transformation and the nature of optical transitions have been discussed as well.
Photoluminescence Study of ZnO Nanosheets with embedded Cu Nanocrystals.
Authors: Diaz Cano Aaron I. , El Filali Brahim
Published: June 2019

In this work a simple method to produce the ZnO nanosheets (NSs) with inclusions of Cu nanocrystals by means of electrochemical etching without the necessity of any surfactant has been presented. The Raman spectroscopy demonstrates that the amorphous samples of ZnO-Cu present appreciable changes in its vibrational behavior after the thermal treatment at 400°C in ambient atmosphere. The study of Photoluminescence (PL) shows monotonous increasing the bands centered in 3.07, 2.41, 2.03 and 1.57 eV versus etching time in freshly prepared samples. The intensity variation of the PL bands, the changes in vibrational behavior, as well as the impact of the copper content and preparation conditions allow identifying emission inside the visible spectral range related to the surface defects that is interesting for the future possible application this ZnO system in room temperature “white” light-emitting diodes.
Colloidal indium sulfide quantum dots in water: synthesis and optical properties
Authors: Ivanchenko Mariia V. , Rayevska Oleksandra E. , Stroyuk Oleksandr L. , Kuchmiy Stepan Ya.
Published: June 2019

Colloidal β-In2S3 quantum dots stabilized in water by a number of polymers or sodium polyphosphate and mercaptoacetate were synthesized. An increase in the stabilizer content was found to result in a decrease in the average dot size from 20–30 to 5–10 nm and formation of a narrow absorption band centered at 290 nm. The position and spectral width of the band were found to be independent on stabilizer concentration, synthesis temperature and molar In:S ratio. The band was assumed to belong to a molecular cluster smaller than 1 nm which is a precursor for formation of larger regular indium sulfide quantum dots.
Photoluminescence and Structural Properties of CdSe Quantum Dot-Polymer Composite Films
Authors: Borkovska L. , Korsunska N. , Stara T. , Bondarenko V. , Gudymenko O. , Stroyuk O. , Raevska O. , Kryshtab T.
Published: June 2019

Thermal stability of the luminescent properties of CdSe and CdSe/ZnS quantum dots (QDs) in polymer films of gelatin and polyvinyl alcohol (PVA) is studied. Thermal annealing of the films at the air ambience at 100 °C is found to result in two effects in the photoluminescence (PL) spectra: (i) an enhancement of the PL intensity and (ii) a red spectral shift of the PL bands. The first effect is observed in both QDs-gelatin and QDs-PVA composites, while the second one - in the QDs-gelatin only. The passivation of CdSe QDs with ZnS shell reduces the effects. The enhancement of the PL intensity is supposed to be due to the decrease of nonradiative defect density. The red shift is explained by dissociation of coordination bonds between surface Cd atoms and amino-groups of gelatin. This dissociation decreases the PL intensity too. This effect competes with the effect of PL enhancement and is supposed to be responsible for non-monotonous dependence of the PL intensity versus annealing time in the QDs-gelatin composite.
Spatial resonances of the Cherenkov emission in dispersive metamaterials
Authors: Burlak Gennadiy , Martinez-Sanchez Erika
Published: June 2019

We systematically study the Cherenkov optical emission by a nonrelativistic modulated source crossing 3D dispersive metamaterial. It is found that the interference of the field produced by the modulated source with the periodic plasmonic-polariton excitations leads to the specific interaction in the frequency range where the dispersive refractive index of a metamaterial is negative. Such resonance considerably modifies the spatial structure of the Cherenkov fieldand the reversed Cherenkov emission. In our study parameters of metamaterial and modulated source are fixed while the frequency spectrum of the plasmonic excitations is formed due to the fields interplay in the frequency domain.
Plasmon-polariton signature in the transmission and reflection spectra of one-dimensional metamaterial heterostructures
Authors: Reyes-Gómez E. , Cavalcanti S. B. , Oliveira L. E.
Published: June 2019

The transmission and reflection properties of a meta-stack composed of a periodic AB arrangement of an air(A)/metamaterial(B) bilayer is presented, with the multi layered system embedded between two semi-infinite layers of the A material. For oblique incidence, a finite projection along the growth direction of the electric or magnetic field of the incident wave associated with the TM or TE modes, respectively, leads to a coupling of the photon modes with the bulk electric or magnetic metamaterial plasmons, in each layer of the meta-stack. This field-matter coupling gives rise to plasmon-polariton modes and signatures of electric or magnetic longitudinal bulk-plasmon polariton modes in the transmission, as well as in the reflection properties of the meta-stack, by means of a plasmon-polariton gap. Such features survive even in the case of a single bilayer and experimental observation should be, therefore, easily achieved.
Polarization Control of Optically Pumped Terahertz Lasers
Authors: Slavcheva Gabriela , Kavokin Alexey V.
Published: June 2019

Two-photon pumping of excited exciton states in semiconductor quantum wells is a tool for realization of ultra-compact terahertz (THz) lasers based on stimulated optical transition between excited 2p and ground 1s exciton state. We show that the probability of two-photon absorption by a 2p-exciton is strongly dependent on the polarization of both photons. Variation of the threshold power for THz lasing by a factor of 5 is predicted by switching from linear to circular pumping. We calculate the polarization dependence of the THz emission and identify photon polarization configurations for achieving maximum THz photon generation quantum efficiency.
Glass-Oxide Nanocomposites as Effective Thermal Insulation Materials
Authors: Hao Qing , Li Minqing , Coleman Garrett Joseph , Li Qiang , Lucas Pierre
Published: June 2019

With extremely disordered atomic structures, a glass possesses a thermal conductivitykthat approaches the theoretical minimum of its composition, known as the Einstein’s limit.1Depending on the material composition and the extent of disorder, the thermal conductivity of some glasses can be down to 0.1-0.3 W/m∙K at room temperature,2,3representing some of the lowestkvalues among existing solids. Such a lowkcan be further reduced by the interfacial phonon scattering within a nanocomposite that can be used for thermal insulation applications. In this work, nanocomposites hot pressed from the mixture of glass nanopowder (GeSe4or Ge20Te70Se10) and commercial SiO2nanoparticles, or pure glass nanopowder, are investigated for the potentialkreduction. It is found that adding SiO2nanoparticles will instead increasekif the measuredkvalues for usually porous nanocomposites are converted into those for the corresponding solid (kSolid) with Eucken’s formula. In contrast, pure glass nano-samples always showkSoliddata significantly reduced from that for the starting glass. For a pure GeSe4nano-sample,kSolidwould beat the Einstein’s limit for its composition.
Optically Active Nanoparticle Coated Polystyrene Spheres
Authors: Kinkead Brandy , Ali Abdiwali A. , Boyer John-C. , Gates Byron D.
Published: June 2019

Nanoparticles (NPs) with either plasmonic or upconverting properties have been selectively coated onto the surfaces of polystyrene (PS) spheres, imparting their optical properties to the PS colloids. These NP coated PS spheres have many potential applications, such as in medicine as drug-delivery systems or diagnostic tools. To prepare the NP coated PS spheres, gold or core-shell NaYF4Tm0.5Yb30/NaYF4NPs were synthesized and separately combined with amino-functionalized PS spheres. The mechanism by which the NPs adhered to the PS spheres is attributed to interactions of the NP and a polyvinylpyrrolidone additive with the surfaces of the PS spheres. Two-photon fluorescence microscopy and SERS analysis demonstrate the potential applications of these NP coated PS spheres.
Size Controlled Synthesis of Silicon Nanocrystals within Inverse Micelles
Authors: Linehan Keith , Doyle Hugh
Published: June 2019

Alkyl-terminated Si nanocrystals (NCs) are synthesized at room temperature by hydride reduction of SiCl4 within inverse micelles. Highly monodisperse Si NCs (2 – 6 nm) are produced by variation of the cationic quaternary ammonium salts used to form the inverse micelles. Transmission electron microscopy imaging confirms the NCs are highly crystalline, while FTIR spectra confirm that the NCs are passivated by covalent attachment of alkanes, with minimal surface oxidation. The photoluminescence intensity of the Si NCs exhibits an inverse relationship with the mean NC diameter, with a quantum yield of 12 % recorded for 2 nm NCs.
Colloidal Synthesis of Luminescent Quantum Dots in Macadamia Oil
Authors: Li Menglu , Chan Weng Leong , Gardner Hannah C.
Published: June 2019

Semiconductor nanocrystals or quantum dots are becoming increasingly popular in research fields as wide ranging as cancer therapies, solar energy and disease detection. Colloidal synthesis provides a low-cost method of producing high quality quantum dots with narrow size distributions. The controllable nature of colloidal synthesis allows researchers to design the size, shape and surface functionalization of the resulting particles.

Here we investigate a simple low temperature method to produce CdSe quantum dots. The quantum dots were grown in solution by dissolving the CdO precursor in a mixture of macadamia oil, and oleic acid. Elemental Se was heated separately before the two mixtures were combined under an inert atmosphere. The injection temperature, reaction temperature and oleic acid concentration were all varied.

Optical absorption and photoluminescence spectroscopies showed the size of the quantum dots increased with time, temperature and oleic acid concentration. Dynamic light scattering has shown the hydrodynamic particle size to range from 7 to 22nm and the samples for up to 6 months.
Degradation of Transparent Conductive Oxides, and the Beneficial Role of Interfacial Layers
Authors: Lemire Heather M. , Peterson Kelly A. , Breslau Mona S. , Singer Kenneth D. , Martin Ina T. , French Roger H.
Published: June 2019

The lifetime performance and reliability of photovoltaic (PV) modules are critical factors in their successful deployment. Interfaces in thin film PV, such as that between the transparent conductive oxide (TCO) electrode and the absorber layer, are frequently an avenue for degradation; this degradation is promoted by exposure to environmental stressors such as irradiance, heat and humidity. Understanding and suppressing TCO degradation is critical to improving stability and extending the lifetime. Commercially available indium tin oxide (ITO), fluorine doped tin oxide (FTO) and aluminum doped zinc oxide (AZO) were exposed to damp heat (DH), ASTM G154 cycle 4, and modified ASTM G154 for up to 1000 hours. The TCOs’ electrical and optical properties and surface energies were determined before and after each exposure and their relative degradation classified. Data demonstrate that AZO degraded most rapidly of all the TCOs, whereas ITO and FTO degraded at lower to non-quantifiable rates. One approach to suppress degradation could be to use interfacial layers (IFLs), including organofunctional silane layers, to modify the TCO. We modified the TCO surfaces using a variety of organofunctional silanes, and determined a range of surface energies could be obtained without affecting the electrical and optical properties of the TCO. Degradation studies of TCOs with a silane layer were also conducted. We found that an inhomogeneous silane layer was able to delay the resistivity increase for ITO in DH.
Effects of Vapor Grown Carbon Fiber Substitution for Conductive Carbon in Anode Systems for LiB Applications
Authors: Kambe Yu , Fernandes Alberto J. , Archer Lynden A.
Published: June 2019

Isotropic and anisotropic conductive carbon particles, carbon black (CB) and vapor grown carbon fiber (VGCF), were incorporated into a Lithium Titanate (LTO) battery anode material composition, and their effect on conductivity and electrochemical properties investigated. Nanocomposite electrodes comprised of LTO, polyvinyldine floride (PVDF) and as little as 5 wt% VGCF are reported to manifest more than one order of magnitude enhancement in conductivity over their CB counterparts. VGCF-based anodes are also found to exhibit more stable voltage discharge profiles and as much as 20% improvement in capacity retention during extended electrochemical cycling at charge/discharge rates as high as 2.625 A/g (15 C). Remarkably, we find that the benefits of VGCF relative to CB conductivity aids diminish at higher particle loadings and that a LTO anode formulation containing 5 wt% CB | 5 wt% VGCF yields optimal capacity retention. At 5C, this composite system outperformed both the 10 wt% VGCF and 10 wt% CB electrode systems by delivering 20% higher capacity during extended charge/discharge cycling. We explain this finding in terms of two synergetic effects: enhanced electrode conductivity facilitated by incorporation of a percolated network of anisotropic VGCF particles; and shorter transport distances between the insulative LTO and high surface area CB.
Translating Research Into the Classroom: The NIST Summer Institute for Middle School Science Teachers
Authors: Satterfield Mary B. , Ratcliffe Toby , Heller-Zeisler Susan
Published: June 2019

The National Institute of Standards and Technology (NIST) has developed a dynamic and on-going educational outreach program designed to support middle school science teachers and increase their understanding of the science they teach with applications to the real world and connections to the latest NIST research. In the NIST Summer Institute for Middle School Science Teachers, science topics are taken from NIST research pertinent to the middle school curriculum, and the research is translated for use in the classroom. During the two-week summer program teachers from around the country are given the opportunity to focus on NIST research as it relates to the middle school classroom by participating in a combination of hands-on activities, lectures, tours, and visits with scientists and engineers in their laboratories. The NIST Summer Institute is designed to increase teacher understanding of the subjects they teach, provide inquiry activities for the classroom, rekindle teachers’ enthusiasm for science, provide increased understanding of how scientific research is performed, create a learning community of teachers and scientists, and provide role models for the teachers. Teachers finish the NIST Summer Institute with a wealth of knowledge about core topics in introductory biology, chemistry, physics, and materials to integrate these topics into their existing curriculum.

The NIST Summer Institute has spawned additional related outreach activities, including “Science Afternoons at NIST,” in which teachers are invited back to NIST during the school year for events in which the focus is on a single topic such as designing buildings to resist earthquakes, infrared energy, and nanomagnetism. Based on continued requests from participants in the NIST Summer Institute, an additional program, the NIST Research Experience for Teachers program, was begun in 2011 with teachers performing research at NIST under the guidance of NIST scientists and engineers, and designing ways to take their research experience back into the classroom to share with their students. This proceeding will give examples of topics covered and activities developed in past Summer Institutes, as well as ways similar Institutes are being implemented at other locations. While not a teaching institution but a research institute focused on meeting the measurement science needs of the nation, NIST has a wealth of resources for the education community. The NIST Summer Institute for Middle School Science Teachers is one way of sharing these resources and building partnerships between middle school science teachers and their students and NIST scientists and engineers.
HERE AND NOW
Authors: Gordon Robert , Thir Shawn
Published: June 2019

Hitachi High Technologies is On the Frontlines of Science Education Outreach Programs. Hitachi High-Technologies Corporation (Hitachi High-Tech), a global leader in the electron microscope industry, is working to inspire a new generation of achievement in science education. In loaning out its tabletop microscopes Hitachi High-Tech is tackling the problem of waning interest in science education, which is becoming a global issue throughout all industrialized nations. Hitachi High-Tech aims to become the global leader in providing high-tech solutions, and its support for science extends beyond Japan to North America, South America, and Europe.
MATERIALS, DESIGN, AND INNOVATION IN NONMAJORS SCIENCE EDUCATION
Authors: Puthoff Jonathan B. , Bentley Anne K. , Autumn Kellar , DePaula Julio
Published: June 2019

In-depth materials science course offerings are crucial for training the next generation of researchers in many pure and applied fields. However, translating discoveries from the laboratory into domestic and industrial settings requires contributions from professionals outside of these strictly technical areas. Providing non-major students instruction in core scientific ideas and illustrating the myriad pathways by which these ideas become innovative technologies should be an additional goal of science and engineering programs. “Technologies of the Future” (ToF) is a novel course for non-science/engineering majors in which students participate in team-based laboratory and design projects with modern materials systems. After learning about a phenomenon or physical principle in class, students are given the opportunity to explore it in lab and are tasked with the design of a novel device that incorporates it. Example laboratory topics include superhydrophobic surfaces and dye-sensitized solar cells. In the design phase, instructors act as “consultants”, lending their expertise to students unfamiliar with engineering analysis or ancillary physical concepts. Summative activities are designed to leverage the diverse talents of the interdisciplinary teams of students. The course concepts and activities are designed to prepare students for both a modern workplace that requires innovative thinking and a modern world in which emerging technologies offer solutions to pressing environmental and social problems.
Hot Exciton Dissociation at Organic Interfaces
Authors: Grancini G. , Fazzi D. , Maiuri M. , Petrozza A. , Egelhaaf H-J. , Brida D. , Cerullo G. , Lanzani G.
Published: June 2019

Interface physics is at the heart of organic photovoltaics (OPV). Here we reveal for the first time the actual charge generation mechanism in a low-band-gap polymer: fullerene blend as prototypical system for efficient OPV. We demonstrate that the photogenerated excitons dissociate into bound interfacial charge transfer states (CTS) and free charges in 20-50 fs, with a branching ratio that depends on the excess energy. Providing an excess energy, high energy singlet polymer states are excited, giving a direct hot electron transfer into the interfacial hot CTS* before internal energy dissipation occurs. This process ultimately leads to a higher fraction of free charges. Thanks to strong electronic coupling between high-energy-states and hot CTS, we demonstrate the opening of additional paths for charge generation that would otherwise be quenched by internal conversion to the lowest-lying states. Our results provide a new framework to understand charge generation in OPV system, suggesting that hot dissociation is a strategic option to enhance the photovoltaic conversion.
Carbon Nano-Onion Ultracapacitor Model
Authors: Parigi Fabio , Gachovska Tanya , Gao Yang , Zhou Yunshen , Hudgins Jerry L. , Lu Yongfeng
Published: June 2019

This paper describes a novel ultracapacitor made from carbon nano-onions. Characterization of the material was performed including measurement of the impedance spectra and cyclic voltammetry. A new ultracapacitor model composed of an LRC circuit and a constant phase element was developed along with a parameter extraction procedure. The model was validated using experimental data and simulation.
Improving the Efficiency of Organic Photovoltaic Devices through Interface Engineering
Authors: Liu Feilong , Crone Brian K. , Ruden Paul , Smith Darryl L.
Published: June 2019

We explore theoretically the effect of incorporating a thin tunnel barrier between the electron and hole transport layers of organic heterostructure photovoltaic devices. The device efficiency can be improved significantly by controlling the rates of microscopic processes associated with exciton dissociation and recombination at the interface between the electron and hole transport layers. The effects of different parameters are examined, and conclusions for organic photovoltaic device design are discussed.
Processing of pristine single and multiwalled carbon nanotubes as different stacking layers in bulk heterojunction solar cells
Authors: Khan M. Alam , Matsumura Michio , Manasreh Omar
Published: June 2019

A study on the individualization of commercially purchased SWCNT and MWCNT were made in an N-N dimethyl tetraformamide solvent by a combination of ultrasonication and centrifugation, and processing of these individualized CNTs are applied as a stacking layer in bulk-heterojunction (BHJ) solar cells. The wt% (mg) of pristine CNTs loading was optimized in respect to volume of solvent (ml). Then as prepared BHJ devices were modified by spin casting at 4000 rpm/30s of these pristine individualized CNTs by incorporating a stacking layer (∼30 nm) for efficiency evaluation. Comparisons of the devices made with known functionalized CNTs (acid treated) and found that stacking of pristine individualized CNTs between the PEDOT:PSS and active (P3HT:PCBM) layer demonstrate a significantly enhanced efficiency of 2.1% (JSC of 9 mA/cm2, VOC of 0.6, FF of 39) from the normal BHJ of 1.2% (JSC of 5.3 mA/cm2, VOC of 0.62, FF of 33). However, SWCNT with acid treated when applied in BHJ shows degrading efficiency (0.51%) which can be attributed to the degradation of corrugated tubular side walls leading to potential loss of opt-oelectric properties. The enhanced efficiency of devices with pristine individualize CNTs can be conjectured due to better opto-electrical properties and undamaged tubes. The microstructures of the heterojunction active layer were examined by using UV-Vis spectra, IV curve and EQE techniques.
Hydrothermal Synthesis and Characterization of ThO2, UxTh1-xO2, and UOx
Authors: Castilow Jacob , Zens Timothy W , Mann J. Matthew , Kolis Joseph W. , McMillen Colin D. , Petrosky James
Published: June 2019

Hydrothermal synthesis of ThO2, UxTh1-xO2, and UOxat temperatures between 670°C and 700°C has been demonstrated. Synthesis at these temperatures is 50-80°C below prior growth studies and represents a new lower bound of successful growth. ThO2single crystals of dimensions 6.49mm x 4.89mm x 3.89 mm and weighing 0.633g have been synthesized at average growth rates near 0.125mm/week. Single crystal UxTh1-xO2crystals with mole fractions up to x≈0.30 have also been grown. The largest alloyed crystal with mole fraction x≈0.23 has dimensions of 2.97mm x 3.23mm x ∼3mm and recorded average growth rates near 0.2mm/week. Four structures were solved from X-ray diffraction data and their crystallographic data reported here. Rocking curve analysis determined a dislocation density of 1.2×109cm-2.
Enhanced Attachment and Proliferation of Fibroblasts on Anodized 316L Stainless Steel with Nano-pit Arrays
Authors: Ni Siyu , Sun Linlin , Ercan Batur , Liu Luting , Ziemer Katherine , Webster Thomas J.
Published: June 2019

The aim of this study was to prepare various sized nano-pits on 316 L stainless steel and examine their effects on the attachment and proliferation of fibroblasts. In this study, 316L stainless steel with tunable pit sizes (0, 25, 50, and 60 nm) were fabricated by an anodization procedure in an ethylene glycol electrolyte solution containing 5 vol.% perchloric acid. The surface morphology of 316L stainless steel were characterized by scanning electron microscopy (SEM). The nano-pit arrays on all the 316L stainless steel samples were in a regular arrangement. The surface properties of the 316L stainless steel nano-pit surface showed improved wettability properties as compared to the untreated 316L stainless steel. The nano-pit surfaces with 50 nm and 60 nm diameter were rougher at the nanoscale than other samples. The attachment and proliferation of fibroblasts were investigated for up to 3 days in culture using MTT assays. Compared to unanodized (that is, nano-smooth) and smooth surfaces, 50 and 60 nm diameter nano-pit surfaces dramatically enhanced the initial fibroblast attachment and growth up to 3 days in culture. The results reported in this study showed that the 50 and 60 nm nano-pit surfaces promoted fibroblast adhesion and proliferation by increasing the surface roughness and adsorption of fibronectin. Such nano-pit surfaces can be designed to support fibroblast growth and be important for improving the use of 316L stainless steel for various implant applications (such as for improved skin healing for amputee devices or for percutaneous implants).
Bone Microenvironment Tissue Surrogates Engineered for Reporting of Metastasized Breast Cancer Osteolytic Activity
Authors: Dumas Jerald E. , Parks Akia N. , Platt Manu O.
Published: June 2019

Breast cancer metastasis to bone continues to be a major clinical problem, and patient-to-patient variability in rates of disease progression and metastasis complicate treatment even further. This may be due to differences in the cancer cells, the osteoclasts, or the pre-metastatic niche, but all of these contribute to proteolytic remodeling necessary for osteolytic lesion establishment, primarily through secretion of cathepsin K, the most powerful human collagenase. There is debate about the relative contributions of breast cancer cells and osteoclasts and synergism between the two in altering the biochemical and biomechanical properties of the colonized bone, as these are difficult to parse with animal models. To quantify the relative contributions of breast cancer cells and osteoclasts in bone resorption, we have been developing engineered bone microenvironment tissue surrogates by adapting a poly(ester urethane) urea system embedded with microbone particles. Here, we report their use with MDA-MB-231 breast cancer cells and RAW264.7 derived osteoclasts, to provide temporal, multiscale reporters of bone resorption that can be measured non-destructively: 1) collagen degradation measured by C-terminal collagen fragment release, 2) mineral dissolution by measuring calcium released with the calcium arsenazo assay, and also show their beneficial effects in upregulating cathepsin K expression compared to tissue culture polystyrene controls. These more natural derived bone surrogates may be useful tools in mimicking bone metastatic niche and determining differences between proteolytic activity of different patients’ tumor and bone resident cells in a controlled manner.
Electrochemical Performance of Cu Nanoparticle/Carbonized Wood Electrode for Supercapacitor Application
Authors: Teng Shiang , Tiwari Ashutosh
Published: June 2019

The electrochemical effects of embedding Cu nanoparticles in carbonized wood supercapacitor electrodes have been investigated. The nanoparticles were embedded using a solution method. Subsequent X-ray diffraction (XRD) and scanning electron microscopy (SEM) results showed that the Cu nanoparticles were anchored uniformly on the surface and deep within the pores of the electrode. Cyclic voltammetry measurements showed that the electrode has typical pseudocapacitive behavior, with two pairs of redox reaction peaks. The charge-discharge cycling also indicated that the redox charge transformation was a reversible process. An ultra-high specific capacitance of 888 F/g and an energy density of 123 Wh/kg were observed for the Cu loaded electrodes, as compared to the pure carbonized wood electrodes, which had a specific capacitance of 282 F/g and an energy density of 39 Wh/kg. Furthermore, both the carbonized wood and Cu loaded electrodes exhibited excellent long cycle abilities with at least 95% of the specific capacitance retained after 2000 cycles. These remarkable results demonstrate the potential for using Cu nanoparticle loaded carbonized wood as a high performance and environmentally friendly supercapacitor electrode material.
Influence of deposition chamber pressure and substrate temperature on the properties of fluorescent blue and phosphorescent red OLED deposited by OVPD
Authors: van Gemmern Philipp , Zimmermann Christoph , Niyamakom Phenwisa , Wuttig Matthias , Brand Sabine , Schwab Holger , Becker Heinrich , Fortte Rocco , Heuken Michael , Kalisch Holger , Jansen Rolf H.
Published: June 2019

Organic light-emitting diodes (OLED) offer the potential to replace conventional light sources such as incandescent bulbs and fluorescent tubes. The question which thin-film technology is most favorable to produce OLED on an industrial scale is still unanswered. The most established technology for the deposition of small-molecule organic layers is vacuum thermal evaporation. A comparably novel technology is organic vapor phase deposition (OVPD), which offers some unique features in terms of adjustable process parameters such as deposition chamber pressure (P) and substrate temperature (TS). The impact of these parameters on the morphology of organic single layers as well as on the performance of OLED is mostly unknown. In this work, phosphorescent red OLED were produced with different TS and a strong influence on the device efficiency was found. Atomic force microscopy measurements were conducted to investigate the morphology of the hole injection and hole transport layers of the devices deposited at different TS. In addition to this, the influence of TS and P on the performance of fluorescent blue OLED and the morphology of organic single layers was tested. By varying TS and P for the emission layer only, current efficiencies in the range from 4.3 to 6.8 cd/A were found despite the fact that all devices had the same structure. Atomic force microscopy measurements conducted on organic single layers which were deposited at the same process conditions showed rms values ranging from 1.4 to 57 nm.
Microstructure and Fracture At the Cement Paste-Aggregate Interface
Authors: Struble L.
Published: June 2019

The mechanical behavior of concrete is thought to be affected by the microstructure of the paste-aggregate interface, which differs in several respects from the microstructure of bulk paste. General aspects of interfacial microstructure, which appear to be fairly well understood, are reviewed. Recent microstructural studies using backscattered electron imaging show that there is a zone along the interface (approximately 50 μm wide) within which there are generally few large unhydrated clinker grains, many large voids (greater than 5 μm), a generally porous microstructure, many hollow-shell hydration grains, and in some cases little calcium hydroxide. The tendency for cracks to develop or grow along the paste-aggregate interface is discussed in relation to specific features of the interfacial microstructure.
Effect of Fiber-Matrix Bond Strength on the Crack Resistance of Synthetic Fiber Reinforced Cementitious Composites
Authors: Li Victor C. , Wang Youjiang , Backer Stanley
Published: June 2019

Fiber matrix bond characteristics can be changed by treatments of the fiber surface. The effect of such treatments on the fiber reinforced concrete (FRC) tension-softening behavior and crack resistance is studied in this paper. Various R-curve behaviors are predicted based on a simple double cantilevered beam (DCB) model using the experimentally derived tensionsoftening curves. The result suggests that fiber surface treatments can substantially alter the composite fracture resistance as measured by the R-curve.
Silica Fume Effects on the Pull-Out Behavior of Randomly Oriented Steel Fibers from Concrete
Authors: Soroushian Parviz , Bayasi Ziadz
Published: June 2019

Silica fume is known to improve the pore system of cementitious pastes and their adhesion capacity to fibers and other mix inclusions. This study has been mainly concerned with the effect of silica fume on the pull-out strength of randomly oriented steel fibers from concrete. Silica fume effects on the fresh mix workability and the overall flexural and compressive behavior of steel fiber reinforced and plain concretes were also assessed. The only variable in different fibrous and plain mixes was the fraction of portland cement substituted with silica fume. This fraction ranged from 0% to 20%.

The workability of plain and fibrous mixes were obtained by slump and inverted slump cone tests, respectively. In both the flexure and compression tests on fiber concrete, the complete load-deformation relationship was obtained. The pull-out strength of randomly oriented fibers was assessed through analysis of the flexural test data.

All aspects of the fresh and hardened steel fiber reinforced concrete performance considered in this study, especially the pull-out strength of randomly oriented fibers from concrete, were observed to improve with the increase in silica fume-cementitious ratio up to a certain limit, after which the trends in silica fume effects were reversed.
The Effect of Blast Furnace Slag on the Microstructure of the Cement Paste/Steel Interface
Authors: Onabolu O. A. , Pratt P. L.
Published: June 2019

The microstructures of steel reinforced ordinary Portland cement mortar samples, and those containing 40% and 70% slag as cement replacement, have been studied by electron optical techniques, after exposure to stagnant sea-water at 23°C for 320 days. Fracture surfaces along the interface with steel were examined using secondary electron imaging in the SEM. This revealed differences between the OPC and slag specimens as regards the morphology of the phases and the amounts of calcium hydroxide present. The microstructure at the interface with steel was studied by means of back scattered electron imaging combined with quantitative image analysis. Chloride concentrations at sections around the interface were determined by means of an EDXA facility linked to the SEM. Even after 320 days immersion in sea-water, there was some calcium hydroxide present in the interfacial zone.
Adhesion Between Concrete and Treated or Untreated Flat Metal Surfaces
Authors: Montgomery D. G. , Samarin A.
Published: June 2019

Modern construction techniques for floor and slab systems often make use of the composite action developed between steel and concrete. Knowledge of the magnitude of adhesive force, other than mechanical bond, is necessary in the design of permanent steel formwork, which ultimately becomes an integral part of the load bearing reinforced concrete structure. To investigate the extent of adhesion at the interface between concrete and flat metal surfaces, different treatments of the metal surfaces were considered. Results are presented for six types of treated and untreated metal plates when tested in a pull-off mode with conventional concrete. The mode and the type of failures were investigated, and those parameters, which are considered to be significant in the study of this phenomenon, evaluated
Bubble Characteristics as they Pertain to Compressive Strength and Freeze-Thaw Durability
Authors: Gutmann Paul F.
Published: June 2019

There are numerous chemical agents to achieve the specified air entrainment system. Generally, these are organic chemicals which are broadly classified as soaps and detergents. One of the best known chemical agents of this type is known in the art as Vinsol resin, manufactured by Hercules, Inc., which is a wood resin salt and is the standard against which other air-entraining agents are tested under ASTM C-233.
Changing the Interface Cementitious Materials/Aqueous Solution For Performing Electroosmosis
Authors: Kuin A. J. , Stein H. N.
Published: June 2019

Removal of excess water from cement/sand/water mixes can be effected by electroosmosis with an efficiency of several hundred g per Watt sec, if an additive is applied which increases the absolute value of the zeta potential.
The Influence of the Matrix-Aggregate Bond on the Strength and Brittleness of Concrete
Authors: Keru Wu , Jianhua Zhou
Published: June 2019

In this paper, the influence of the matrix-aggregate bond on the strength and brittleness of concrete is studied. Six different matrixaggregate interfaces are used to evaluate the interfacial bond capability. The results obtained on the strength and brittleness index of concrete show that strengthening and toughening of concrete can be obtained simultaneously, if the interfacial bonds are changes so that they conform to a rational distribution according to aggregate size. These results are discussed in terms of the energy dissipation and crack propagation during failure of concrete.
The Effect of Ca(OH)2-Treated Ceramic Microspheres on the Mechanical Properties of High-Temperature Lightweight Cement Compos
Authors: Sugama Toshifumi
Published: June 2019

The compressive strength and water permeability of high-temperature lightweight cementing materials containing sillimanite-based hollow microspheres as a filler can be improved by treating the surfaces of the microspheres with a Ca(OH)2-saturated solution at temperatures up to 200°C. The precipitation of an epitaxial layer formed by an interaction between a hot calcium hydroxide solution and the surface of the sphere plays an essential role in developing favorable bonding characteristics at the interfaces and in promoting the hydration of the cement matrix. The properties of the composites include a slurry density of <1.2 g/cc at 25°C, a 300°C-24 hour compressive strength of >1015 psi (7.0 MPa), a water permeability of <10-4 Darcy, and a bulk density of <1.0 g/cc. It was observed that tobermoritetruscottite transformation and anorthite formation during autoclave exposure for 180 days in brine at 300°C results in slight strength reductions and increased water permeability.
The Microstructure of Cement Aggregate Interfaces
Authors: Zhang X. , Groves G. W. , Rodger S. A.
Published: June 2019

Mortar bars of tricalcium silicate or ordinary portland cement with small aggregate particles have been sectioned and examined in the transmission electron microscope (TEM). The presence of calcium silicate hydrate (CSH) gel at the interface is seen by TEM in many cases in intimate contact with the aggregate. In some cases calcium hydroxide (CH) is observed near the interface but is seldom in contact with the aggregate. Microanalysis in the TEM shows that in the case of reactive silica aggregate a gel of relatively low Ca:Si ratio is found at the interface. Aggregates of different degrees of reactivity and mortars of different ages are compared. It is suggested that interface fractures may occur beyond the coating of CSH rather than at the true interface in the case of the type of particles we have studied.
Improvement of Compressive Strength in Ordered Polymer Films and Fibers by Sol-Gel Glass Processing
Authors: Kovar Robert F. , Haghighat R. Ross , Lusignea Richard W.
Published: June 2019

Sol-gel glass processing of poly (benzobisthiazole) (PBZT) films increased the compressive strength of PBZT/PEEK film laminates by more than four times, with the potential for further improvement indicated. This was accomplished by infiltrating sol-gel glass precursor reagents into microfibrillar regions of PBZT film, forming PBZT/sol--gel glass microcomposites that combined the high compressive strength of glass with the exceptional strength and toughness of PBZT ordered polymer. The presence of glass within PBZl/sol-gel microcomposite films inhibited the buckling of microfibrils during film compression, greatly increasing the resistance of the films to compressive failure. The use of sol-gel glass compositions that fuse at temperatures within thermal stability limits of PBZT (600 C) should further improve PBZI film compressive strength.

Preliminary experiments involving sol-gel processing of PBZT fibers did not show improvements in fiber compressive strength. Microscopic analysis of treated fibers indicated that fiber abrasion and kinking had occurred during batch processing steps.

The results of our continuing efforts to achieve 100 Ksi compressive strength in PBZT films and fibers will be discussed.
Viscosity, Structural Relaxation and Defect Annihilation Kinetics of Amorphous Si
Authors: Witvrouw Ann , Spaepen Frans
Published: June 2019

Substrate curvature measurements were used to monitor viscous flow in ion beam sputtered amorphous Si for temperatures ranging from 150 to 400 °C. The viscosity increases linearly with time, characteristic of a bimolecular defect annihilation process. This is consistent with the defects governing viscous flow being dangling bonds. The isoconfigurational activation enthalpy for the viscosity is 1.8 ±.3 eV.
Electron Cyclotron Resonance Hydrogen Plasma Induced Defects in Thermally Grown and Spuiter Deposited SiO2
Authors: Hallett W. L. , Ditizio R. A. , Fonash S. J.
Published: June 2019

In this study we show that upon exposure to electron cyclotron resonance hydrogen plasmas, both thermally grown and sputter deposited oxides are degraded, resulting in large shifts of flat band voltage, and increases in fixed charge and interface state density.
Study of the Orientation of Y1Ba2cu/3O7−x Thin Films In-Situ Prepared by Reactive Coevaporation With RF Activated Oxygen-Ozone Plasma.
Authors: Nagata M. , Nojima H. , Shintaku H. , Koba M.
Published: June 2019

Superconducting films of Y1Ba2Cu3O7−x have been prepared in-situ onto SrTiO3 (100) substrates by reactive coevaporation with rf activated oxygenozone plasma. Crystal quality and orientation of the films were evaluated as a function of substrate temperature(Ts). The films evaporated at Ta between 680°C, and 690°C had an a,b-axis orientation perpendicular to the substrate. The zero resistance temperature(Tc) of the film evaporated at Ts, of 690°C was 80K. The films evaporated at Ta above 700°C had c-axis orientation. The Ts of the film evaporated at a Ts, of 710°C was 90K.
Preparation of Optically Smooth Surfaces of High TcSuperconducting Films
Authors: kim J. H. , Kapitulnik A. , Harris J. S. , Char K. , Bozovic I. , Lee W. Y.
Published: June 2019

We report optical studies of predominantly c-axis oriented high-Tc superconducting films before and after ion milling. A significant increase in midinfrared reflectivity resulted from ion milling of a few thousand Å Features associated with α-axis texture vanished after ion milling, resulting in pure c-axis films. This suggests that α-axis grains reside mostly near the surface in post-annealed high-Tc superconducting films. Therefore, even after annealing (for the purpose of raising Tc), highly oriented c-axis films can be retained by ion milling. This may be important for device applications where optically smooth surfaces and interfaces are to be routinely prepared.
Persistent Photoconductivity And Thermal Recovery Kinetics Of Low Energy Ar + Bombarded GaAs
Authors: Vaseashta A. , Burton L. C.
Published: June 2019

Kinetics of persistent photoconductivity, photoquenching, and thermal and optical recovery observed in low energy Ar+ bombarded on (100) GaAs surfaces have been investigated. Rate and transport equations for these processes were derived and simulated employing transport parameters, trap locations and densities determined by deep level transient spectroscopy. Excellent correlation was obtained between the results of preliminary simulation and the experimentally observed values. The exponential decay of persistent photoconductivity response curve was determined to be due to metastable electron traps with longer lifetime and is consistent with an earlier proposed model.
Evidence of Oscillating Oxide Growth Mechanism during Oxygen Plasma Oxidation of Silicon
Authors: Nguyen Son , Nguyen Tue , Dobuzinsky D. , Gleason R. , Gibson M.
Published: June 2019

Evidence of an oscillating thin-film oxide growth reaction was observed on silicon surfaces during low RF power (13.6 MHz, < I W/cm2) plasma oxidation. Ex-situ ellipsometric, X-ray photoelectron (XPS) and Fourier-transform infrared (FTIR) spectroscopic measurements show that the oscillating growth layer is silicon-rich oxide and its oscillating thickness is very sensitive to both surface preparation and plasma oxidation conditions. A simple low-energy oxygen ion-assisted plasma oxidation and sputtering mechanism is proposed to clarify and to account for the observed oscillating oxide growth reaction.