bluuebunny/crossref_metadata_2025 huggingface dataset:
First Pass Study of Surface Modified Porous Low-k by Ion Implantation for Zero Thickness Barrier Requirement of Cu/MSQ/Si Stacks in Copper Metallization Scheme
Authors: Nandini Alok , Roy U. , Patel Zubin P. , Bakhru H.
Published: June 2019

Low-κ dielectrics have to meet stringent requirements in material properties in order to be successfully integrated. A particularly difficult challenge for material development is to obtain a combination of low dielectric constant with good thermal and mechanical properties. Incorporation of low dielectric constant materials such as porous silica based materials as a replacement to conventional dielectrics like SiO2 and use of Cu metallization schemes has become a necessity as critical dimensions of devices decrease. This paper is focused on the challenges in developing materials with low dielectric constant but strong thermo mechanical properties.
Thin films of Ultra-Low materials such as porous Methyl Silsesquioxane (MSQ) (κ=2.2) were implanted with argon 1 × 1016 cm-2 dose at energies varying from 20 to 50 keV at room temperature. This work shows that the surface hardness of the porous films can be improved five times as compared to the as-deposited porous films by implanting Ar with 1 × 1016 cm-2 doses at 20 keV, sacrificing only a slight increase (∼9%) in dielectric constant (e.g., from
2.2 to 2.4). The hardness persists after 4500C annealing. In this current work, an ion implantation strategy was pursued to create a SiO2-like surface on MSQ. The effects of implantation parameters on the barrier property and bulk stability of MSQ were then studied. The results reveal one possible route to attain the “zero barrier thickness” requirement for interconnects systems.
Stress Generation in PECVD Silicon Nitride Thin Films for Microelectronics Applications
Authors: Belyansky M. , Klymko N. , Madan A. , Mallikarjunan A. , Li Y. , Chakravarti A. , Deshpande S. , Domenicucci A. , Bedell S. , Adams E. , Coffin J. , Tai L. , Sun S.P. , Widodo J. , Lai C.W
Published: June 2019

Thin SiN films deposited by plasma enhanced chemical vapor deposition (PECVD) have been analyzed by a variety of analytical techniques including Fourier Transform Infrared Spectroscopy (FTIR), X-ray reflectivity (XRR), and Rutherford Backscattering Spectrometry/Hydrogen Forward Scattering (RBS/HFS) to collect data on bonding, density and chemical composition respectively. Both tensile and compressive SiN films have been deposited and analyzed. Mechanisms of stress formation in SiN thin films are discussed. It has been found that amount of bonded hydrogen as detected by FTIR is higher for compressive films compared to tensile SiN films. Amount of bonded hydrogen in a film is correlated well with tensile stress. Effect of deposition temperature and other process parameters on stress have been studied. Exposure of SiN films to elevated temperature after deposition lead to increase in tension and degradation in compressive stress. New approaches to stress generation in thin films like creation of multilayer film structures have been delineated.
Application of Nanoindentation to Characterize Fracture in ILD Films Used in the BEOL.
Authors: Simonyi Eva E. , Liniger E. , Lane M. , Lin Q. , Dimitrakopoulos C. D. , Tyberg C.
Published: June 2019

It is of importance to understand cracking behavior in low dielectric constant, low modulus materials. Nanoindentation method is presented as a tool to estimate the critical film thickness, thickness above which spontaneous cracking could occur, for ILD films used in the BEOL. The critical film thickness was then used to calculate cohesive energies and fracture toughness of the films. Materials were investigated using nanoindentation combined with AFM imaging. The results were compared to data acquired by four point bend methods.
Reduction of Residual Transient Photocurrents in A Si:H Elevated Photodiode Array Based Cmos Image Sensors
Authors: Theil Jeremy A.
Published: June 2019

While a-Si:H based elevated photodiode arrays hold the promise of superior performance and lower cost CMOS-based image sensors relative to those based upon crystalline silicon photodiodes, the one area where a-Si:H based sensor performance has not been as good is in image lag. This problem is only exacerbated by Staebler Wronski Effect induced junction degradation. Image lag is caused by residual charge from photocurrents trapped within the junction once the light source is removed and can be measured for several seconds, even under continuous applied reverse bias. It is seen both in constant and variable bias pixel architectures. However, by carefully controlling a-Si:H junction bias conditions, it is possible to significantly reduce these transient photocurrents. This article will describe how the photocurrent decay time exponent can be reduce by almost an order of magnitude. Finally the physical causes behind image lag in a-Si:H based photodiode arrays will be discussed.
Efficient Focusing with an Ultra-Low Effective-Index Lens Based on Photonic Crystals
Authors: Foca Eugen , Föll Helmut , Daschner Frank , Sergentu Vladimir V. , Carstensen Jürgen , Knöchel Reinhard , Tiginyanu Ion M.
Published: June 2019

This work focuses on photonic crystals (PC) that can be ascribed an effective index of refraction > 1 or even > 0. We investigate the possibility to design optical elements (in this case a lens) based on this type of PC. A new approach for determining the effective refractive index of PCs with unusual index of refraction is used, which is simpler than earlier methods based on analyzing equi-frequency surfaces in k-space. An ultra-low refractive index PC is given a form approximating a concave lens and is proven theoretically and experimentally that it efficiently focuses the electromagnetic radiation in the microwave range. Strong focusing effects are found for both polarizations (TE and TM mode). Intensity gains as large as 35 for TM polarizations and 29 for TE polarizations are found. Measurements are in a good accordance with simulations.
MBE Growth of GaAs on Si through Direct Ge Buffers
Authors: Yu Xiaojun , Kuo Yu-Hsuan , Fu Junxian , Harris James S
Published: June 2019

The result of GaAs growth on Si using a thin Ge buffer layer (about 0.5μm thick) is presented in this paper. A two-step method with a high temperature anneal between two steps is used to grow the Ge buffer layer. Single phase GaAs is grown on Ge by controlling the growth temperature, substrate miscut and the prelayers. No APD defect is observed by the XTEM and the threading dislocation density of GaAs grown using this method is about 5˜10×107cm-2. The PL intensity of GaAs is 10× less on Si substrate than on GaAs substrates.
Novel Strategy for Antifouling Paints with Zero Endocrine Disrupting Chemical (EDC) Elution based on Interpenetrating Polymer Networks (IPNs)
Authors: Naito Masanobu , Nakai Takashi , Kawabe Takuma , Mori Kenji , Furuta Daisuke , Imanishi Yukio , Fujiki Michiya
Published: June 2019

Environmentally friendly organic-inorganic hybrid materials with repellent activity against marine fouling organisms have been developed using interpenetrating polymer networks (IPNs), composed of a three-dimensional silica matrix of tetraethoxysilane (TEOS) and chain-like polymers, such as poly(methylmethacrylate) (PMMA) and poly(vinylacetate) (PVAc). The repellent activity of the IPNs reached a maximum of approximately 90% relative to that of tetrabutyl tin oxide (TBTO). Simple bioassays using blue mussels and algae were used to screen out the adequate proportions of those components.
Fabrication of Coated Polycaprolactone Scaffolds and Their Effects on Murine Embryonic Stem Cells
Authors: Tollon Michael H. , Hamazaki Takashi , Willenberg Bradley J. , Batich Christopher , Terada Naohiro
Published: June 2019

In the past decade, tissue engineering has become a great interest in materials science research. Embryonic stem (ES) cell transplantation has become one of the most researched therapies for restoring tissue and organ function. Many studies have investigated the use of porous biodegradable scaffolds to promote cell adhesion, growth, proliferation, differentiation, and to help steer the course of tissue development. Research has shown that extracellular matrices and the basement membranes affect various cell types and cellular behaviors. However, the effects of these materials on ES cell behavior are currently understudied and poorly understood.

In this study, the synthetic biodegradable polymer polycaprolactone (PCL) was chosen to create an interconnected, fibrous foam structure. A phase separated scaffold method was developed and the product made was coated with various extracellular materials. When the phase separated PCL scaffolds were coated with Matrigel and gelatin solutions, murine ES (mES) cells attached, spread, and differentiated within the scaffolds. There was little growth on the uncoated material. Coating effects on mES cells were analyzed using flow cytometry, reverse-transcriptase polymerase chain reaction and scanning electron microscopy. It was found that coating the scaffold with different extracellular matrices affects mES cell morphology and differentiation. Matrigel coating causes expression of neural proteins and gelatin produces a hepatocyte-like cell.
Functionalized Calcium Phosphate-based Nanoparticles for the Treatment of Osteoporosis
Authors: G Balasundaram , M Sato , TJ Webster
Published: June 2019

In an effort to decrease the number of problems associated with osteoporosis, the long-term goal of the present study is to design calcium phosphate-based nanoparticles that specifically attach to areas of low bone density and once attached, allow for the targeted release of bioactive agents that can quickly increase bone formation. Efforts are focused on nanoparticles of calcium phosphate-based materials since they are similar in size and chemistry to the major inorganic components of bone. As a first step in this research, the objective of the present study was to synthesize nanoparticles of crystalline hydroxyapatite (or HA) and amorphous calcium phosphate. Crystalline HA is stable under physiological fluids and, thus, will release embedded bioactive agents slowly. Alternatively, amorphous calcium phosphate is highly biodegradable and will, thus, release embedded bioactive agents quickly. A further objective of the present study was to functionalize such inorganic biodegradable materials with amino groups which would allow for the subsequent attachment of entities to direct such nanoparticles to osteoporotic bone and increased bone formation once attached. One promising approach to direct the nanoparticles to osteoporotic bone is to attach antibodies to pentosidine on the nanoparticles since pentosidine is present in higher amounts in osteoporotic compared to healthy bone. A promising approach to increase bone growth once nanoparticles attach to osteoporotic bone, is to embed nanoparticles with regions of the bone growth factor: bone morphogenic protein-2 (or BMP-2). Results of this study demonstrated the successful synthesis of both crystalline HA and amorphous calcium phosphate nanoparticles. Furthermore, results showed that these nanoparticles can be functionalized with versatile amino groups. In this manner, this study takes the first steps toward utilizing calcium phosphate based nanoparticles to reverse bone loss associated with osteoporosis.
Nanobiohybrids: Bioinspired Sensors
Authors: Chalkias Nikolaos , Giannelis Emmanuel P.
Published: June 2019

Nanohybrid artificial membranes made by intercalation of amphiphilic molecules into the galleries of a layered host, exhibit characteristics similar to biological membranes and they can be used as sensors. Different responses have been observed even for molecules that have similar features for example, saccharin and its sodium salt suggesting that the nanohybrid might be useful in developing an electronic nose. The dynamic range of the saccharin sensor is 20 - 300μM. In this paper we present our results on sensor fabrication and testing and discuss possible sensing mechanisms. In addition, we describe our work on immobilizing in the nanohybrid membranes Glucose Oxidase, Horseradish Peroxidase and Gramicidin and evaluating their performance.
Interfacial Adhesion of Pure-Silica-Zeolite Low-k Thin Films
Authors: Hu Lili , Wang Junlan , Li Zijian , Li Shuang , Yan Yushan
Published: June 2019

Nanoporous zeolite thin films are promising candidates as future low dielectric constant (low-k) materials. During the integration process with other semiconductor materials, the residual stresses resulting from the synthesis processes may cause fracture or delamination of the thin films. In order to achieve high quality low-k zeolite thin films, the evaluation of the adhesion performance is important. In this paper, laser spallation technique is utilized to investigate the interfacial adhesion of zeolite thin film-Si substrate interfaces prepared using three different processes. The experimental results demonstrate that the nature of the deposition method has a great effect on the resulted interfacial adhesion of the film-substrate interfaces. This is the first time that the interfacial strength of zeolite thin films-Si substrates is quantitatively evaluated. The results have great significance in the future applications of low-k zeolite thin film materials.
Experimental and Theoretical Investigations of the Magnetic Phases of Epitaxially Grown EuSe at Low Fields and Temperatures
Authors: Rumpf K. , Granitzer P. , Krenn H.
Published: June 2019

Due to its metamagnetic behaviour the magnetic phases of EuSe are more complicated than for the other Eu-chalcogenides, e.g. EuTe. At very low temperatures (below 2K) there occurs an additional antiferromagnetic phase. This behaviour cannot be solely explained by exchange interaction of nearest neighbors and next nearest neighbors but requires more information about the NNSSNN, NSNS and NNSNNS spin arrangements. Because the nearest and next nearest neighbour exchange constants are nearly cancelled out, higher order interaction becomes important and the biquadratic exchange has also to be taken into account. Our measurements were carried out on an epitaxial grown 2.5 micrometers EuSe film on BaF2. Three regions predicted in the phase diagram of a EuSe bulk crystal are of special interest. For low temperatures (below 1.8K) and low magnetic fields (below 0.05T) a NSNS antiferromagnetic (type II) phase occurs. For higher temperatures from 1.8K to 4.6K and B = 0.1T to 2.5T a NNSNNS ferrimagnetic order exists whereas for lower magnetic fields a further antiferromagnetic (type I) NNSSNNSS-phase is formed above a temperature of 3.6-3.7K. The experimental data show that bilinear mean field calculations taking into account only nearest (JNN) and next nearest exchange (JNNN) interaction fail on this system. Therefore biquadratic exchange (K) has to be included. We present a 12x12 matrix MFA-formalism to extract the proper exchange parameters, which deviate slightly from the bilinear MFA-approach: JNN = 0.165 K, JNNN = -0.1209 K. The biquadratic exchange constant is taken as K = -0.0458 K. We prove this theoretical implication by testing Arrott plots for a varying slope. We made a fit to the experimental data even beyond MFA by taking the corresponding critical exponents of the Heisenberg model.
Imaging And Spectroscopy Of Nanostructures Through Aberration-Corrected Stem
Authors: Pennycook S. J. , Chisholm M. F. , Lupini A. R. , Borisevich A. , Sohlberg K. , Mcbride J. R. , Rosenthal S. J. , Kumar D. , Franceschetti A. , Rashkeev S. , Wang S. , Pantelides S. T.
Published: June 2019

The aberration-corrected STEM allows nanostructures to be investigated with greater resolution and sensitivity than ever before. Single atom sensitivity is achieved both in imaging and also for spectroscopy, for atoms on surfaces or within the bulk. Nanocrystal size, shape, surface termination, 3D structure and the presence of any defects can be seen with unprecedented ease. The improved sensitivity provides improved input for theory, allowing new insights into nanostructure properties and the origin of their unique functionality. Furthermore, the larger aperture available with aberration-corrected STEM improves the depth resolution dramatically. Nanometer depth resolution can be achieved by simply taking a focal series of images, which may then be reconstructed into a 3D rendering of the material in the same manner as with confocal optical microscopy but maintaining sensitivity to individual atoms.
Controlled Synthesis and Characterization of Co-Au Core-shell Nanoparticles
Authors: Bao Yuping , Calderon Hector , Krishnan Kannan M.
Published: June 2019

Co-Au Core-shell nanoparticles are synthesized by slowly reducing an organo-gold compound on pre-made cobalt seeds with a weak reducer at mild condition. For the first time, these coreshell nanoparticles are generated in non-polar solvent in a controlled manner. The formation theory of core-shell structure, especially the seed size effect, is addressed as well. These coreshell structures are confirmed with a wide range of transmission electron microscopy (TEM) methods, which includes routine TEM images, high resolution TEM, and z-contrast imaging.
Size Effect Study of the L10Phase Transformation in FePt Nanoparticles
Authors: Ding Yi , Majetich Sara A.
Published: June 2019

The relation between particle size and anisotropy in the fcc to L10phase transformation in FePt nanoparticles is described. After annealing to partially sinter the particles, the volume distribution was found by transmission electron microscopy, and related to the magnetic switching field distribution. With the assumption that larger particles have higher switching fields, we find a consistent size threshold,d*, of about 12 nm for high anisotropy, independent of the annealing conditions. Our analysis shows that the phase transformation is limited by the lack of nucleation sites in small particles rather than by the chemical inhomogeneity.
Manipulation of Non-Magnetic Materials in Ferrofluid Containing Media
Authors: Halverson Derek , Yellen Ben , Friedman Gary
Published: June 2019

A novel method is proposed whereby non-magnetic objects can be moved along a surface at the microscale and nanoscale. It uses a negative magnetophoretic force, explained in the caption for figure one, on the non-magnetic objects which results from stabilized 10nm diameter iron oxide particles (ferrofluid) being attracted to regions of field maxima around magnetic islands on a surface, which pushes the non-magnetic objects to regions of field minima. By varying an external magnetic field we can control where these minima are and thus control how objects will position themselves with static fields and by using rotating time varying fields we can control how they move across the surface. This method does not require the objects to be initially in contact with the surface, as they will be pulled down to the surface from solution. While this paper deals with beads, any arbitrarily shaped object should be manipuable using this method. Additionally, while we address non-magnetic objects in this work similar methods could easily manipulate objects that are magnetic.
Synthesis of Well-aligned ZnO Nanowires Using Simple Physical Vapor Deposition without Catalysts or Additives
Authors: Wang Lisheng , Zhang Xiaozhong , Zhao Songqing , Zhou Guoyuan , Zhou Yueliang , Qi Junjie
Published: June 2019

Well-aligned ZnO nanowires were synthesized by simple physical vapor deposition using c-oriented ZnO thin films as substrate without catalysts or additives. The synthesized ZnO nanowires have two typical average diameters: 60 nm in majority and 120 nm in minority. They are about 4ím in length and well aligned along the normal direction of the substrate. Most of the synthesized ZnO nanowires are single crystalline in a hexagonal structure and grow along the [001] direction. The c-oriented ZnO thin films control the growth direction. Photoluminescence spectrum was measured showing a single strong ultraviolet emission (380 nm). Such result indicates that the ZnO nanowire arrays can be applied to excellent optoelectronic devices.
Shadow Nanosphere Lithography: Simulation and Experiment
Authors: Giersig Michael
Published: June 2019

The creation of two dimensional large-areas of nanoparticles of different morphology and ordering is still a not fully solved problem. The presented paper shows new outstanding methods based on nanosphere lithography for controlling the mask morphology to improve fabrication of nanoscales perfectly ordered over some cm2 dots, rods and rings. An annealed mask with 30nm aperatures was used for the fabrication of ferromagnetic iron nanorings. These nanosystems are expected to find various unique applications. Our method permitted fabrication of nanostructured materials with unique morphology and properties. This field is expected to open new venues in science and technology.
Mechanical Properties of Amorphous Al85Ni10La5 Alloy by Indentations
Authors: Zhang Zhihui , Ajdelsztajn Leonardo , Zhou Yizhang , Lavernia Enrique J.
Published: June 2019

Indentation techniques have been carried out to study the mechanical behavior of amorphous Al85Ni10La5 alloy powders produced by inert gas atomization. The present work reveals that this amorphous alloy undergoes a three-stage crystallization process in the temperature range of 250°C ~ 390°C, with a glass transition temperature of approximately 259°C. In this study, the influence of devitrification on mechanical response was investigated via indentation of the Al85Ni10La5 alloy powders annealed at various temperatures, for instance, at temperatures well below or close to glass transition (235°C, 245°C, 250°C), and well above glass transition (283°C). Moreover, the microstructure evolution and the formation of nanoscale crystallites were studied using TEM and XRD. The influence of devitrification on the indentation response was characterized, paying particular attention to shear band formation and variations in hardness. The hardening behavior was analyzed on the basis of a rule-of-mixtures approach by treating the partially crystallized alloy as a nanocomposite.
Thermal Plasma Chemical Vapor Deposition of Superhard Nanostructured Si-C-N Coatings
Authors: Wagner Nicole J. , Cordill Megan J. , Zajickova Lenka , Gerberich William W. , Heberlein Joachim V. R.
Published: June 2019

A triple torch plasma reactor was used to synthesize Si—C—N composite films via the thermal plasma chemical vapor deposition process. The argon-nitrogen plasma provided atomic nitrogen to carbon- and silicon-based reactants, which were injected through a central injection probe and ring configuration. Films were deposited with variations of the total nitrogen flow through the torches (1.5-4.5slm), reactant mixture (silicon tetrachloride and acetylene or hexamethyldisilazane) and substrate material (silicon and molybdenum). Micro X-ray diffraction was used to determine that both α-Si3N4 and β-Si3N4 were dominant in most of the depositions. Composites of silicon nitride and silicon carbide were synthesized on molybdenum. The bonding of amorphous phases was investigated using Fourier transform infrared spectroscopy, which indicated the presence of N—H, CHx and CΞ in various films. Indentation tests on the polished film cross-sections determined that large variations in hardness and elastic modulus existed for minor changes in film composition. Correlations between indentation results and scanning electron and optical microscope images showed that the mechanical properties greatly depend on the film morphology; the denser, smoother, and more crystalline films tended to display enhanced mechanical properties.
Investigation of the deformation behavior in nanoindented metal/nitride multilayers by coupling FIB-TEM and AFM observations
Authors: Abadias G. , Tromas C. , Tse Y.Y. , Michel A.
Published: June 2019

Epitaxial TiN/Cu bilayers and multilayers with periods L between 5 and 50 nm have been grown by ultrahigh vacuum ion beam sputtering on Si and MgO(001) substrates at room temperature. The deformation modes induced by a Berkovich nanoindent have been imaged using Focused Ion Beam – Transmission Electron Microscopy (FIB-TEM) and Atomic Force Microscopy (AFM). The observations suggest that the mechanical response of the multilayers is essentially governed by an extensive plastic flow inside the Cu layers, which is confined by a bending of the more rigid TiN layers. This specific deformation behavior, with no contribution of the interfaces as a barrier for dislocation motion could explain the absence of significant hardness enhancement in this system.
Optimum Integrated Heterodyne Photoreceiver for Coherent Lidar Applications
Authors: Amzajerdian Farzin , Pierrottet Diego , Singh Upendra , Kavaya Michael
Published: June 2019

Many coherent lidar applications, particularly airborne and space-based applications, impose stringent power and size constraints while requiring high levels of sensitivity. For this reason, optimization of the lidar heterodyne photoreceiver is one of the critical steps in ensuring full utilization of limited resources to achieve the required sensitivity. The analysis of 2-micron heterodyne receivers shows that substantial improvement of the order of 3 dB can be obtained by proper optimization of the receiver key control parameters and elimination of its parasitic capacitances by integrating the detector, its bias circuit, and the preamplifier on a single substrate. This paper describes analytical steps for defining optimum heterodyne receiver design parameters and development of experimental devices operating at 2-micron wavelength.
Measurement of Stress-strain Curves of PECVD Silicon Oxide Thin Films by Means of Nanoindentation
Authors: Cao Zhiqiang , Zhang Xin
Published: June 2019

In this paper, we explore the use of nanoindentation techniques as a method of measuring equivalent stress-strain curves of the PECVD SiOx thin films. Three indenter tips with different geometries were adopted in our experiments, enabling us to probe different regimes of plastic deformation in the PECVD SiOx thin films. A shear transformation zone (STZ) based amorphous plasticity theory is applied to depict the underlying plastic deformation mechanism.
Wear Resistance and Mechanical Properties of Polymeric Fibers Filled with Inorganic Fillers
Authors: Irisawa Toshihira , Shioya Masatoshi , Kobayashi Haruki , Kaneko Junichi
Published: June 2019

The wear resistance and the mechanical properties of polymer matrix composite fibers filled with inorganic fillers have been investigated in order to find out the way to increase the wear resistance of the fibers without losing tensile modulus and strength. Nylon 6 and poly(ethylene terephthalate) have been used as the matrix polymer and aluminum borate whisker and carbon nanotube have been used as the fillers. The wear resistance of the fibers has been evaluated by observing the fiber cross section after the side of the fiber was worn using a rotating drum covered with abrasive paper. The wear resistance of the nylon 6 and PET fibers was increased by the addition of these fillers without the loss of tensile modulus and strength. The effects of the addition of the fillers on the wear resistance have been compared with the effects of stretching and heat treatment of the fibers.
Helically Perforated Thin Films -- Dependence of Mechanical Properties on Microstructure
Authors: Fernando Sumudu P. , Elias Anastasia L. , Brett Michael J.
Published: June 2019

The effects of several microstructural parameters on the mechanical behaviour of a helically perforated thin film structure, or inverse microspring, were investigated using a finite element model[1]. The parameters investigated were the helical pitch angle, the cross-section radius, and the coil spacing. The elastic modulus was found to depend most strongly on the helical pitch angle (changing by a factor of 1.3 as the pitch angle went from 35° to 70°). Variations in the coil radius and the film thickness had a minor effect on the modulus. It was also found that using a finite size model (as opposed to an infinite model using periodic boundary conditions) produced better conditioned results. A preliminary confirmation of the model's validity was performed by comparison to nanoindentation results of a nickel helically perforated thin film.
Multipolar Expansion Methods for Coarse Grained Force Fields [PowerPoint Submission]
Authors: Chao Sheng D.
Published: June 2019

Current large scale atomistic simulations remain too computationally demanding to be generally applicable to industrial and bioengineering materials. It is desirable to develop multiscale modeling algorithms to perform efficient and informative mesoscopic simulations. Here we present a multipolar expansion method to construct coarse grained force fields (CGFF) for polymer nanostructures and nanocomposites. This model can effectively capture the stereochemical response to anisotropic long-range interactions and can be systematically improved upon adding higher order terms. The coarse-graining procedure forms the basis to perform a hierarchy of multiscale simulations starting with the quantum chemistry calculations to coarse grained molecular dynamics, hopefully toward continuum modeling. We have applied this procedure to molecular clusters such as alkane, benzene, and fullerene. For liquid alkane, molecular dynamics simulations using the CGFF can reproduce the pair distribution functions using atomistic force fields. Molecular mechanics simulations using the CGFF can well reproduce the energetics of benzene clusters from quantum chemistry electronic structure calculations. Subtle anisotropy in the interaction potentials of the fullerene dimer using the Brenner force field can also be well represented by the model. It is promising this procedure can be standardized and further extended.
Effect of Surface Roughness on Remelting and Stresses During Splat Solidification [PowerPoint Submission]
Authors: Ye Guosheng , Khare Rajesh , Wroblewski Donald , Gevelber Michael , Basu Soumendra
Published: June 2019

In order to understand the microstructural evolution in plasma sprayed coatings, the solidification process was modeled using a 2-D FEM model based on enthalpy formation. Studies of the surface of the coatings showed surface roughnesses across multiple length scales. The model was used to examine the effects of the substrate and splat temperatures and the surface roughness features on the onset of remelting of the underlying surface on which the splat solidifies. The surface roughness was found to promote remelting, indicating that it was an important parameter that determines splat solidification. The temperatures of the splat and substrate were consolidated into one non-dimensional parameter that captured the onset of remelting with a non-dimensional remelting point.

A fully coupled thermo-mechanical finite element model was also run for a single splat case, to provide more insight stress buildup during solidification. An important result was that the relative size of the surface roughness features, as compared to the splat thickness, is very important. Very large wavelengths compared to splat thickness lead to smaller stresses, since the solidification and the interface are essentially 1-D. Very small wavelengths compared to splat thickness also leads to reduced stresses, since the solidification front quickly becomes 1-D. Only roughness features on the scale of splat thickness are important in providing locations of maximum stress concentration, which are locations of microcrack formation.
Modeling of Atomistic Processes in Semiconductors: from Defect Signatures to a Hierarchy of Annealing Mechanisms
Authors: Bockstedte Michel
Published: June 2019

The modeling of atomistic processes in semiconductors based on the density functional theory is outlined. The role of intrinsic defects in the self and dopant diffusion, as well as in the dopant activation is investigated for the case of silicon carbide. A hierarchy of annealing mechanisms for vacancies and interstitials is proposed. The identification of the microscopic origin of experimental defect centers by calculated defect signatures establishes a link between theoretical modeling and experiments.
Computation of Temperature-Pressure Phase Diagrams of High-Pressure Nitrides
Authors: Kroll Peter
Published: June 2019

We propose an explicit scheme to include the fugacity of nitrogen in computations of phase diagrams of nitride compounds at high-temperature/high-pressure conditions. The assessment is based on available thermochemical data and two kind of extrapolating functions to provide upper and lower boundary for the fugacity coefficient as a funtion of p and T. The procedure is applied to investigate the synthesis of novel nitrides of tantalum, tungsten, and platinum. The combination of first-principle and thermochemical calculations let us predict the synthesis of a new high-pressure phase of Ta3N5 at about 27 GPa. Synthesis of WN2 becomes feasible at about 45 GPa. We furthermore explain why the synthesis of the noble metal subnitride, PtN2, occurs at about 40 GPa, and why PtN is not accessible in high-pressure experiments.
Does Osmium Carbide Exist? Ab initio Investigation
Authors: Zemzemi M. , Hebbache M. , Zivkovic D. , Stuparevic L
Published: June 2019

Transition metals of the platinum group (Os, Ir, Pt, Ru, Re, Rh) do not form carbides and nitrides at ambient pressure. Osmium carbide seems to have been synthesized at zero pressure by Kempter and Nadler forty six years ago. According to the authors, OsC crystallizes in WC-type structure and has a hardness equal to 2000 kg mm-2. Up to date, no other experimental confirmation is available. We studied the electronic and mechanical properties of this hypothetical carbide using an approach based on the density-functional theory. We found that the work of the above mentioned authors is sound. The calculated lattice parameters are in good agreement with that given by those authors and a rough estimate also showed that the hardness given by them is reasonable. However, we found that the hexagonal structure of osmium carbide is electronically and mechanically unstable.
High-Pressure Studies of the Rotor-Stator Compound C60-Cubane
Authors: Sundqvist Bertil , Iwasiewicz-Wabnig Agnieszka , Kovats Eva , Pekker Sandor
Published: June 2019

Insertion of cubane (C8H8) into the octahedral voids of the C60 lattice leads to the formation of an interesting rotor-stator compound which can be converted into a C60 co-polymer by heating. We have treated a number of C60·C8H8 samples for up to 3 h each in the range 380-875 K under pressures up to 2 GPa. The resulting materials were investigated by Raman spectroscopy and X-ray diffraction. Depending on treatment conditions, at least five different structural phases can be found. In addition to the four structural phases observed at atmospheric pressure and different temperatures we find that a new polymeric state is created at pressures above 1 GPa, and we tentatively identify its structure as pseudo-orthorhombic. The cubic-orthorhombic phase transition line is found to have a slope of 295 K GPa-1, much larger than the slope of the fcc-sc line in pure C60.
Some characterizations of inner product spaces based on angle
Authors: NABAVİ SALES S.m.s.
Published: June 2019

A problem in functional analysis that  arises naturally is about finding necessary and sufficient conditions for a normed space to be an inner product space. By answering this question, mathematicians try to understand the inner product and normed spaces features. In this note, we have discussed this issue and we prove some results concerned with it. We introduce a notion of angle between two vectors in a normed space, denoted by $A_\theta(.,.)$ where $\theta\neq{k\pi\over2}$. We also speak about a notion of orthogonality concerning it, we call it $\theta$-orthogonality.
Análisis químico proximal y metabolitos secundarios en frutos de Washingtonia robusta (Arecaceae): relevancia para la alimentación de la vida silvestre y humana
Authors: Armenta-Méndez Lucila , Ortega-Nieblas María Magdalena , Gallo-Reynoso Juan Pablo , Gardea Alfonso A. , Wilder Benjamin , González-Aguilar Gustavo , Preciado-Saldaña Alejandra M.
Published: June 2019

Antecedentes: Los frutos de Washingtonia robusta son un alimento para aves, pequeños y medianos mamíferos y humanos. Sin embargo, se desconocen los datos cuantificados de su contribución nutricional. Este es el primer informe sobre sus componentes fitoquímicos en la pulpa de su fruta y semillas.Preguntas: ¿Los compuestos de la pulpa favorecen su consumo y contribuyen con nutrientes para la vida silvestre, así como para el consumo humano? ¿El contenido de las semillas favorece las interacciones ecológicas para la germinación y el desarrollo vegetal?Especie en estudio: Washingtonia robusta H. Wendl . Sitio de estudio y fechas: Sierra El Aguaje, Sonora, México, febrero-abril 2016 Métodos: Análisis químico proximal y de metabolitos secundarios a partir de extractos crudos , pruebas fitoquímicas de coloración y cromatografía líquida de ultra resolución; actividad antioxidante por DPPH.Resultados: La semilla contiene 73 % azúcares, 7.4 % proteína, 8.4 % humedad, 4.3 % cenizas, 8.7 % grasa, 0.2 % calcio y glucósidos cianogénicos 0.8 ?g/g. Los componentes de la pulpa incluyen: 71 % azúcares, 10.8 % proteína, 1.6 % humedad, 5.5 % cenizas, 9.4 % grasa, 1.5 % calcio y 0.2 ?g/g de glucósidos cianogénicos. Los alcaloides, taninos y saponinas son más abundantes en las semillas que en la pulpa, lo mismo ocurre con fenoles y flavonoides. El ensayo DPPH expresado en equivalentes Trolox indicó la capacidad antioxidante.Conclusiones: Los frutos de W. robusta son una fuente de azúcares y antioxidantes naturales para el consumo por la fauna y los humanos. Los metabolitos secundarios presentes en la semilla son disuasorios a patógenos, y pueden ser benéficos para la germinación y el desarrollo de la plántula .
Ruptura de la latencia física y germinación de semillas de Chiranthodendron pentadactylon (Malvaceae)
Authors: Apodaca-Martínez Maribel , Cetina Alcalá Victor Manuel , Jasso-Mata Jesús , López-López Miguel Ángel , González-Rosas Héctor , Uscanga-Mortera Ebandro , García-Esteva Antonio
Published: June 2019

Antecedentes: Los problemas para propagar C. pentadactylon por semilla se deben a su poca disponibilidad, bajo porcentaje de germinación, plagas y periodo juvenil mayor a 25 años.Hipótesis: Existe variación morfofisiológica de la semilla entre árboles y los tratamientos pregerminativos incrementan el porcentaje y la velocidad de germinación en semillas con seis meses de almacenamiento a temperatura ambiente . Especie en estudio: Chiranthodendron pentadactylon Larreat.Sitio de estudio y fechas: Colegio de Postgraduados, Campus Montecillo, Estado de México, Méx. Junio, 2016.Métodos: Se determinó el contenido de humedad, la viabilidad y el efecto de tratamientos pregerminativos en el porcentaje y velocidad de germinación de las semillas . Se utilizó un diseño de bloques al azar. Los bloques al azar con los tratamientos: 1 (escarificación mecánica + estratificación en frío a 5 °C durante 5 días), 2 (escarificación mecánica + imbibición durante 12 h), 3 (escarificación mecánica + corte en la base de la semilla) y 4 (testigo). Los tratamientos se aleatorizaron dentro de cada bloque.Resultados: El contenido de humedad fue menor a 10 % y la viabilidad de 100 %. Se encontraron diferencias significativas en la germinación entre tratamientos. La prueba de Tukey (? = 0.05) mostró diferencias entre los tratamientos pregerminativos 1, 2 y 3 con respecto al T4. La velocidad de germinación registró el mayor valor en el tratamiento 3.Conclusiones: Con los tratamientos 1, 2 o 3 se obtuvo más de 77 % germinación. El tratamiento 3 mostró mayor velocidad de germinación, lo que resulta importante en la producción de plántulas.
Hemiparasitic interaction between Castilleja tenuiflora (Orobanchaceae) and Baccharis conferta (Asteraceae): haustorium anatomy and C- and N-fluxes
Authors: Montes-Hernández Edith , Sandoval-Zapotitla Estela , Bermúdez-Torres Kalina , Trejo-Espino José Luis , Trejo-Tapia Gabriela
Published: June 2019

Background: Castilleja tenuiflora is a hemiparasite of Baccharis conferta . The haustorium is the characteristic structure of hemiparasitic plants and its anatomy varies depending several factors such as host species, position on the root and environment.Question: What is the structure and anatomy of haustoria builded in field interaction? Based on C, N and chlorophyll contents, is C. tenuiflora a facultative hemiparasite of B. conferta ?Species studied: Castilleja tenuiflora Benth. and Baccharis conferta Kunth.Study site and dates: Plant materials were collected in the Iztaccihuatl-Popocatepetl National Park (N 19° 0.5´ 9.6'', W 98° 40´ 24.2'', 3,480 m.a.s.l.), State of Mexico, Mexico, in December 2013.Methods: Individuals of B. conferta and C. tenuiflora growing independently or in hemiparasite interactions were collected and samples were processed for anatomical and histochemical characterization, determination of C, N and chlorophyll.Results: Haustoria were globular and located mainly in the lateral roots of B. conferta . Anatomy of haustorium shows the characteristic structures: exophyte and endophyte. Haustorial tissues storage starch, tannins and essential oils while in the B. conferta roots also calcium oxalate crystals were found. C levels were significantly influenced by hemiparasitic interaction. This is the first study that characterizes a hemiparasitic interaction in the field and specifically between C. tenuiflora and B. conferta .Conclusions: Haustoria builded in interaction with B. conferta show the characteristic structure and anatomy. Hemiparasitic relationship represents for C. tenuiflora a source of C and other compounds such as essential oils.
Carbon footprint of the University of Cape Town
Authors: Letete Thapelo C.M. , Mungwe Nothando Wandile , Guma Mondli , Marquard Andrew
Published: June 2019

Since signing the Talloires Declaration in 1990, the University of Cape Town (UCT) has been striving to set an example of environmental responsibility by establishing environmentally sound policies and practices, and by developing curricula and research initiatives to support an environmentally sustainable future. One of the most recent efforts in this quest was the release of a Green Campus Action Plan for the University of Cape Town by the Properties and Services Department in 2008. While the Plan proposed a number of carbon emission mitigation interventions for the University, it also stressed the need to conduct a detailed and comprehensive carbon footprint analysis for the whole University. The aim of this analysis was to determine the carbon footprint of UCT, not only to give a tangible number with which the University’s carbon sustainability level can be compared with other academic institutions, but also to provide the much needed baseline against which future mitigation efforts on the university campus can be measured. UCT’s carbon footprint for the year 2007 was found to be about 83 400 tons CO2-eq, with campus energy consumption, Transportation and Goods and Services contributing about 81%, 18% and 1% the footprint respectively. Electricity consumption alone contributes about 80% of all the emissions associated with university activities. UCT’s per-capita emissions for 2007 amount to about 4.0 tons CO2-eq emissions per student. For comparison only, South Africa’s 2007 per capita emissions were estimated at 10.4 tons CO2-eq. In terms of energy consumption only, UCT’s footprint is about 3.2 tons CO2-eq per student, higher than the National University of Lesotho’s value of 0.1 and much lower than Massachusetts Institute of Technology’s value of 33.1.
Analysis of distributed energy resources for domestic electricity users
Authors: Raji Atanda , Kahn Mohamed Tariq
Published: June 2019

After over a century with utilization of the benefits of economics of scale, power systems planning and development gets bigger and transmission grids have needed to transmit wide bringing the concept of onsite or close-to-load generation back. The turnaround strategy is prompted by market liberalization, transmission expansion constraints, related technology advancements, environmental pollution, health hazards, fossil fuel depletion, and climate change concerns. In the last decade, many countries have started the process of liberalisation of the electric systems, opening access to transmission and distribution grids.Technical feasibility analysis of a hybrid energy system for two types of geographical regions in South Africa using Homer is performed in this paper. Wind-PV hybrid systems are modelled as a micro-power system using Homer. The simulation results analyses conducted for a typical middle income earner electricity load profile for both a coaster and inlander domestic users of electricity showed that Wind-PV hybrid system is technically feasible and economical.
Economic growth and electricity consumption: Auto regressive distributed lag analysis
Authors: Bildirici Melike E. , Bakirtas Tahsin , Kayikci Fazıl
Published: June 2019

Knowledge of the direction of causality between electricity consumption and economic growth is of primary importance if appropriate energy policies and energy conservation measures are to be devised. This study estimates the causality relationship between electricity consumption and economic growth in per capita and aggregate levels. The study uses the price and income elasticities of total electricity demand and industrial demand by using the auto regressive distributed lag (ARDL) method for some developed and developing countries, including the US, UK, Canada, Japan, China, India, Brazil, Italy, France, Turkey and South Africa. There is evidence to support the growth hypothesis for the US, China, Canada and Brazil. There is evidence to support the conservation hypothesis for India, Turkey, South Africa, Japan, UK, France and Italy.
Projecting the external health costs of a coal-fired power plant: The case of Kusile
Authors: Riekert Johannes W. , Koch Steven F.
Published: June 2019

We examine an important subset of the expected health costs associated with the commissioning of Kusile, a new coal-fired electricity generation plant in South Africa. The subset of health impacts focuses on sulphur dioxides, nitrous oxides and large particulate matter (greater than 10 mm). The analysis makes use of the Impact Pathway Approach combined with the data transfer methodology. The plant, which is expected to contribute 4 800 MW of additional electricity to the South African grid is found to have modest health impacts, partly due to the limited additional pollutant emissions expected at the plant. Specifically, additional localised external health costs are found to be in the region of 0.09c/kWh to 6.08c/kWh. Limitations of the analysis are also examined.
Table of Contents
Authors: Editors KJM
Published: June 2019

table of contents
Table of Contents
Authors: Staff Editorial
Published: June 2019

table of contents