bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization, Imaging and Degradation Studies of Quantum Dots in Aquatic Organisms
Authors: Ringwood Amy H , Khambhammettu Sireesha , Santiago Patricia , Bealer Emily , Stogner Michelle , Collins John , Gonsalves Kenneth E 
Published: April 2011

AbstractThere are numerous potential environmental risks of engineered nanoparticles that are not yet well-characterized or understood. Nanoparticles may be introduced into aquatic environments during production processes and also as a result of release following their use in electronic and biological applications. The objectives of these studies were to characterize the behavior of quantum dots (QD) in water, and the accumulation of and toxicity to potential biological receptors in aquatic ecosystems. There are natural differences in environmental factors that may affect the degradation rates of QD’s as well as their toxicity, including temperature, salinity, and pH conditions. To assess the responses under different pH conditions, nonfunctionalized QD’s composed of a Cd/Se core surrounded by a ZnS shell (Evident Technologies) were added to distilled water, at pHs of 4, 6, and 8, and the changes in fluorescent emission spectra over time were determined. Likewise, to determine the effects of salinity on degradation rates, QD’s were added to 0.22 filtered seawater samples of different salinities (10, 20, and 30‰). The accumulation and potential toxicity of QD’s were evaluated using hepatopancreas cells of oysters, Crassostrea virginica.Fluorescent spectroscopy studies with water and cell samples indicated some degradation in low pH and high salinity waters, but did not indicate that there was increased degradation of QD’s accumulated in cells. Fluorescent confocal microscopy verified that QD’s were accumulated into the hepatopancreas cells. Transmission electron microscopy (TEM) studies verified cellular accumulation, and also indicated some limited degradation of the QD’s by the cells over the short time periods (e.g. hours) used in these preliminary studies. Using a lysosomal destabilization assay, there was some evidence of toxicity to hepatopancreatic cells. These kinds of basic studies are essential for characterizing potential cellular toxicity and addressing the potential impacts of nanoengineered particles on aquatic organisms and basic cellular responses.
Self-assembled Ordered Energetic Composites of CuO Nanorods and Nanowells and Al Nanoparticles with High Burn Rates
Authors: Subramanium Senthil , Hasan Shameem , Bhattacharya Shantanu , Gao Yuanfang , Apperson Steve , Hossain Maruf , Shende Rajesh , Gangopadhyay Shubhra , Redner Paul , Kapoor Deepak , Nicolich Steven 
Published: April 2011

AbstractCurrent approaches of mixing fuel and oxidizer nanoparticles or adding fuel nanoparticles to oxidizer gel lead to an overall reduced interfacial area of contact between them and thus, limit their burn rates severely. We have developed an approach of self-assembling fuel nanoparticles around an oxidizer matrix using a monofunctional polymer, poly(4)-vinyl pyridine (P4VP). The polymer has been used to accomplish binding of fuel and oxidizer in a molecularly engineered manner. We use composite of Al-nanoparticles and CuO nanorods for executing this self-assembly. TEM images of this composite confirms the self-assembly of Al-nanoparticles around the oxidizer nanorods. The burn rate of self-assembled composite has been found significantly higher than that of the composite prepared by simple mixing.
Energetic Decomposition of High-Nitrogen Metal Complexes and the Formation of Low-Density Nano-Structured Metal Monoliths
Authors: Tappan Bryce C , Huynh My Hang , Hiskey Michael A. , Chavez David E. , Luther Erik P. , Mang Joseph T. , Son Steven F. 
Published: April 2011

AbstractMetal complexes of the energetic high-nitrogen ligand, bistetrazole amine (BTA) were ignited in inert environments and their decomposition characteristics were determined. These molecules were found to have the unique properties of a comparatively slow burning rate with very little pressure dependency, unlike most energetic, metal-containing molecules which tend to detonate, rather than burn steadily. This process resulted in unprecedented ultra-low-density, nano-structured, transition metal monoliths, useful as a self-propagating combustion synthesis technique. The resulting nanostructured metal monolithic foams formed in the post flame-front dynamic assembly have remarkably low densities down to 0.011 g cm-3 and extremely high surface areas as high as 270 m2 g-1. In this work we discuss primary the production of iron monoliths, however have produced monolithic nano-porous metal foams via this method with cobalt, copper and silver metals as well. We expect to be able to apply this to many other metals and to be able to tailor the resulting structure significantly.
Reactive Al-Li Powders Prepared by Mechanical Alloying
Authors: Zhu Xiaoying , Schoenitz Mirko , Hoffmann Vern K. , Dreizin Edward L. 
Published: April 2011

AbstractMechanically alloyed powders with the composition Al0.7Li0.3 are synthesized. Materials milled for different times are studied using electron microscopy, x-ray diffraction, and thermal analysis. A solid solution of Li in Al (α-phase) is formed with as much as 10 at % of dissolved Li. The LiAl intermetallic δ-phase is readily produced by mechanical alloying but disappears after extended milling times. The final product of milling for 102 hours consists of an x-ray amorphous phase. Mechanically alloyed powders heated in inert environment exhibit several weak exothermic reactions between 420 and 700 K, and two endothermic reactions, around 810 and 870 K. All the observed relaxation processes become less pronounced and eventually become undetectable as the milling time increases and an amorphous material is produced. Ignition experiments performed for the powders coated on an electrically heated filament showed that the powders ignited in the vicinity of 1250 K. An experimental setup for studying combustion of reactive mechanically alloyed powders is developed and initial experimental results are described.
Overview of Nanoscale Energetic Materials Research at Los Alamos
Authors: Son Steven F. , Foley Timothy , Sanders V. Eric , Novak Alan , Tasker Douglas , Asay Blaine W. 
Published: April 2011

AbstractMetastable Intermolecular Composite (MIC) materials are comprised of a mixture of oxidizer and fuel with particle sizes in the nanometer range. Characterizing their ignition and combustion is an ongoing effort at Los Alamos. In this paper we will present some recent studies at Los Alamos aimed at developing a better understanding of ignition and combustion of MIC materials. Ignition by impact has been studied using a laboratory gas gun using nano-aluminum (Al) and nano-tantalum (Ta) as the reducing agent and bismuth (III) oxide (Bi2O3) as the oxidant. As expected from the chemical potential, the Al containing composites gave higher peak pressures. It was found, for the Al/Bi2O3 system, that impact velocity under observed conditions plays no role in the pressure output until approximately 100 m/s, below which speed, impact energy is insufficient to ignite the reaction. This makes the experiment more useful in evaluating the reactive performance. Replacing the atmosphere on impact with an inert gas reduced both the amount of light produced and the realized peak pressure. The combustion of low-density MIC powders has also been studied. To better understand the reaction mechanisms of burning MIC materials, dynamic electrical conductivity measurements have been performed on a MIC material for the first time. Simultaneous optical measurements of the wave front position have shown that the reaction and conduction fronts are coincident within 160 μm.
Density of RDX Crystals Grown During High Acceleration in an Ultracentrifuge
Authors: Lanzerotti Mary Y. D. , Squillace Richard Z. , Gandzelko Alexander , Sharma Jagadish 
Published: April 2011

AbstractRDX (cyclotrimethylene-trinitramine) crystals were grown during high acceleration (high g) in an ultracentrifuge. These crystals are found to have a density ∼0.6% greater than 1 g crystals and to have a greatly reduced defect content. The high g crystals should therefore have significantly reduced shock sensitivity as compared to commercial grade RDX. When a RDX saturated acetone solution is accelerated at 200,000 g, the RDX solute molecules move individually through the acetone solvent molecules to form a RDX crystal because the density of the RDX (Theoretical Maximum Density 1.806 g/cc) solute is more dense than the acetone (0.79 g/cc)solvent. Crystal growth is controlled by the g-force. Crystal defects including voids and solution inclusions caused by temperature variation or evaporation at 1 g are minimized and the RDX crystal density increases. A nitrogen pycnometer was used to measure the density of the RDX crystals grown at 1 g and at 200,000 g. The density of the RDX crystals grown at 200,000 g (1.7980±0.0003 g/cc) is found to be greater than the density of RDX crystals grown at 1 g (1.7881±0.0003 g/cc) by 0.0099 g/cc. The density of the high g crystal is 99.6% of the Theoretical Maximum Density of RDX.
A New Approach for Industrial-Scale Production of Carbon Single-Walled Nanotubes
Authors: Harutyunyan A. R. , Mora E. , Tokune T. 
Published: April 2011

AbstractIn the methods reported for continuous synthesis of carbon single-walled nanotubes (SWNTs), the typical production rates are less than 1 g h-1, after purification. Here we report the development of a new technique with higher production rates, up to 6 g h-1, and a scaling capability up to 220 g h-1. SWNTs are produced by vertical floating technique and continuous injection of pre-prepared supported catalyst powder.
Shear Initiated Reactions in Energetic and Reactive Materials
Authors: Meuken Denise , Martines Pacheco Maria , Verbeek Ries , Bouma Richard , Katgerman L 
Published: April 2011

AbstractDeformation of energetic materials may cause undesired reactions and therefore hazardous situations. The deformation of an energetic material and in particular shear deformation is studied in this paper. Understanding of the phenomena leading to shear initiation is not only necessary to explain for example the response of munitions to intrusions or large deformations imposed in storage and transportation accidents. A fundamental understanding of shear initiation also provides the opportunity to initiate energetic materials in a different and controlled manner, and possibly with a tailored reaction rate of the material. Several small and large scale experiments have been performed in which a shear deformation is imposed onto high explosives as well as thermite based reactive materials. Experiments are numerically simulated in order to correlate small and large scale experiments and understand the initiation mechanisms.
Hydration Effects on the Viscoelastic Properties of Collagen
Authors: Ntim M , Bembey Amanpreet , Ferguson Virginia , Bushby Andrew 
Published: April 2011

AbstractThe manner in which liquid interacts with collagen is unclear, with changes in hydration presenting ambiguity. At present, elastic modulus values for collagen quoted range from MPa to GPa. Dynamic mechanical analysis (DMA) of collagen in isolation provides an insight into the mechanical changes due to altered hydration states.Changes in the viscoelastic properties of collagen were examined as the material was systematically dehydrated in a series of water:solvent mixes to examine effects of dehydration. The effect of solvents with varying polarity was also examined. Tails from 11-week old wild type mice were used. Mouse tail is a tissue with a well-defined, hierarchical organization of type I collagen. The viscoelastic response of collagen was measured using dynamic mechanical analysis (DMA) in fiber extension mode over the frequency range of 1Hz to 10Hz. Samples were sequentially dehydrated in a series of solvent concentrations: 70% ethanol to 100% ethanol to 100% acetone and 70% ethanol to 70% methanol to 100% methanol for at least 1h. Selectively removing and then replacing water from collagen samples provides insight into the role of water in the ultrastructure of the tissue from the corresponding changes in the experimentally determined elastic modulus and viscous energy.
Chemical Structuring and Materials Design in the Shells of Modern Brachiopods
Authors: Griesshaber Erika , Job Reinhart , Kelm Klemens , Angelika Sehrbrock , Neuser R. D. , Mader Werner , Schmahl Wolfgang W. 
Published: April 2011

AbstractCompositional and structural variations at various scale levels have been investigated in the shells of the modern brachiopod Megerlia truncata combining transmission electron microscopy (TEM), cathodoluminescence (CL), laser-ablation-inductively-coupled-mass-spectrometric (LA-ICP-MS) and micro-Raman spectroscopical (µRS) analyses. Our results show that these shells can be addressed as hierarchially structured, multi-scaled organic/inorganic fibre composites. A significant chemical as well as a mechanical inhomogeneity is observable within the shells. This occurs on various scale levels ranging from less then one to a few houndred microns. In concert to systematic variations in micro- and nanohardness the µRS and CL analyses reveal a systematic distribution and incorporation of organic material within the shells, which is negligible within the nanocrystalline primary layer but is present in a significant amount in the innermost part of the secondary layer, next to the organic tissue of the animal. Mechanical performance (hardness and fracture toughness) of this biomaterial is mainly determined by textural features, an extreme variation of crystallite size and a purpose oriented interlikage of organic and inorganic components.
Constitutive Modeling of the Stress-Stretch Behavior of Biological Membranes Containing Folded Domains
Authors: Arslan Melis , Boyce Mary C. , Qi Hang J. , Ortiz Christine 
Published: April 2011

AbstractThe mechanical behavior of the red blood cell membrane is governed by the lipid bilayer which resists changes in surface area and the underlying spectrin network which resists changes in shape. The spectrin network can be modeled as an idealized triangulated network. Each spectrin chain consists of folded domains along the length of the chain which can unfold during stretching of the chain. A domain will completely unfold under the application of a chain force of20to35 pNdepending on the rate of imposed chain stretch. During macroscopic stretch of a network, individual chains within the network will experience different levels of chain stretch since the network chains will collectively stretch and rotate to accommodate the imposed stretch. Hence, the stretch on any individual chain will depend on the magnitude and state of macroscopic strain. A microstructurally informed continuum level constitutive model is developed which tracks individual chain deformation behavior as a function of macroscopic strain and also determines the overall macroscopic network stress-strain behavior. Using the introduced continuum approach and statistical mechanics based models of individual chain force-extension behavior, the stress-stretch behavior of the membrane under uniaxial tension is simulated at large stretches and the behavior of the constituent chains is monitored. Domain unfolding occurs within constituent chains during network deformation and the effects of this domain unfolding on the overall macroscopic stress-strain behavior of the network subject to deformation at different strain rates is revealed.
Self-assembled PS-PMMA nanodot array pattern arranged in a parallelogram guide
Authors: Kimura Kaori , Sakurai Masatoshi 
Published: April 2011

AbstractMask patterns for XY-type magnetic patterned media using phase separation of polystyrene-polymethylmethacrylate (PS-PMMA) block copolymer were fabricated. Parallelogram guides molded by the nanoimprint lithography controlled the PS-PMMA self-assembling pattern that formed in the guide area. 45nm-pitch defect-free PS-PMMA dot patterns were obtained within a 1μm × 1μm area by optimizing the PS-PMMA film thickness.
Fabrication of Hollow Silica Aerogel Spheres for Direct Drive Inertial Confinement Fusion (ICF) Experiments
Authors: Paguio Reny Richard , Nikroo Abbas , Hund Jared F , Frederick Christopher A. , Jaquez Javier , Takagi Masa , Thi Mary 
Published: April 2011

AbstractHollow foam spheres are needed for laser fusion experiments on the OMEGA laser facility at the University of Rochester as part of the demonstration of the feasibility of inertial confinement fusion. Previously polymer based foam and aerogel shells have been produced using resorcinol-formaldehyde (R/F) and divinylbenzene (DVB). In this paper we discuss the development of silica aerogel (SAG) shells. SAG may have the increased robustness, which is important in processing these laser targets. SAG shells were fabricated by the microencapsulation method using a triple orifice droplet generator. This technique allows for precise control of the shell diameter and wall thickness. Reduction of the aerogel gelation time is crucial to fabrication of intact shells with high yield. In addition, the proper choice of the components of the different phases of the microencapsulation process is essential for fabrication of intact SAG shells with proper sphericity and wall uniformity. The density of shells fabricated is approximately 100 mg/cc and the diameter ranges from 700–2000 μm, with a wall thickness of 50–200 μm. Development of a full density permeation barrier for retention of the fusion fuel will also be discussed.
Layer-by-Layer Thin Films of Carbon Nanotubes
Authors: Palumbo Marco , Lee Kye Ung , Ahn Byung Tae , Suri Anil , Coleman Karl , Zeze Dagou , Wood David , Petty Michael C 
Published: April 2011

AbstractLayer-by-layer films incorporating single-wall carbon nanotubes (SWNTs) with anionic or cationic coatings have been prepared. The process of self-assembly was monitored using the quartz microbalance technique, while the morphology of the resulting thin layers was studied with atomic force microscopy. A variety of different architectures have been built up. The dc conductivities of the thin films, in-plane and out-of-plane, were measured at room temperature and contrasted with reference architectures. The results show clearly that the incorporation of SWNTs into the multilayers resulted in electrically conductive thin films.
Optical Thin Films with Very Low Refractive Index and Their Application in Photonics Devices
Authors: Xi Jingqun , Kim Jong Kyu , Ye Dexian , Juneja Jasbir S. , Lu T.-M. , Lin Shawn-Yu , Schubert E. F. 
Published: April 2011

AbstractThe refractive index contrast in dielectric multilayer structures, optical resonators and photonic crystals is an important figure of merit, which creates a strong demand for high quality thin films with a very low refractive index. SiO2 nano-rod layers with low refractive indices n = 1.08, the lowest ever reported in thin-film materials, is grown by oblique-angle e-beam deposition of SiO2 with vapor incident angle 85 degree. Scanning electron micrographs reveal a highly porous columnar structure of the low-refractive-index (low-n) film. The gap between the SiO2 nano-rods is ≤50 nm, i.e. much smaller than the wavelength of visible light, and thus sufficiently small to make scattering very small. Optical micrographs of the low-n film deposited on a Si substrate reveal a uniform specular film with no apparent scattering. The unprecedented low index of the SiO2 nano-rod layer is confirmed by both ellipsometry measurements and thin film interference measurements. A single-pair distributed Bragg reflector (DBR) employing the SiO2 nano-rod layer is demonstrated to have enhanced reflectivity, showing the great potential of low-n films for applications in photonic structures and devices.
Colloidal Silver Nanoparticle Induced Photoluminescence Quench on the Surface Functionalized Planar Si
Authors: Tay Li-Lin , Rowell Nelson , Boukherroub Rabah 
Published: April 2011

AbstractThe photoluminescence (PL) intensity of undecylenic acid surface functionalized planar Si (001) was investigated in the presence of colloidal Ag nanoparticles. The acid passivated Si surface has a weak PL at 1125 nm. Upon exposure to a Ag nanoparticle sol, the PL quenched exponentially with a characteristic decay time of ∼ 18 minutes. It is known that the metal mediated charge-transfer process provides a pathway for energy decay and leads to a quenching of luminescence in light emitting material. An in-situ study of the surface passivated Si revealed that the Ag nanoparticle was likely to have come into contact or was sited close enough to the semiconductor surface through adsorption to cause effective PL quenching.
Nanofluidic capillaries produced via femtosecond laser induced delamination of thin thermal oxide films from Si(100) substrates
Authors: McDonald Joel Patrick , Mistry Vanita R. , Ray Katherine E. , Yalisove Steven M. 
Published: April 2011

AbstractHighly selective and repeatable delamination of thermal oxide films from Si(100) substrates has been performed using single and multiple femtosecond laser pulses forming bubbles or blisters. By overlapping the bubbles laterally, tubes or capillaries can be formed with a range of volumes suitable for nanofluidics. By scanning the sample through the laser using an automated translation stage, patterns of tubes with arbitrary complexity can be formed, while the scan velocity can easily control the volume of the tubes. The production time for capillaries in this fashion is considerably less than with other lithographic techniques, while the proximity of the tubes to the underlying silicon substrate yields the possibility for integrated devices. The mechanism responsible for the delamination will be discussed and the optimal laser and sample translation conditions will be presented which provide the most uniform tubes. Atomic force microscopy and optical microscopy of capillaries with a range of volumes will be presented.
Supramolecular Chemistry at the Liquid/Solid Interface
Authors: De Feyter Steven , Uji-i Hiroshi , Miura Atsushi , Mamdouh Wael , Zhang Jian , van Esch Jan , Feringa Ben , Schenning A. P. H. J. , Meijer E. W. , Wuerthner Frank , De Schryver Frans 
Published: April 2011

AbstractThe liquid/solid interface provides an ideal environment to investigate self-assembly phenomena and scanning tunneling microscopy (STM) is the preferred methodology to probe the structure and the properties of physisorbed monolayers on the nanoscale. Physisorbed monolayers are of relevance in areas such as lubrication, patterning of surfaces on the nanoscale, and thin film based organic electronic devices, to name a few. It's important to gain insight in the factors which control the ordering of molecules at the liquid/solid interface in view of the targeted properties. STM provides detailed insight into the importance of molecule-substrate (epitaxy) and molecule-molecule interactions to direct the ordering of both achiral and chiral molecules on the atomically flat surface. The electronic properties of the self-assembled physisorbed molecules can be probed by taking advantage of the operation principle of STM, revealing spatially resolved intramolecular differences within these physisorbed molecules.
Unconventional Approaches for Advanced Nanotechnology: Functional Patterning and Microfluidic Synthesis
Authors: Choi Kyung , Shea Kenneth , Rogers John 
Published: April 2011

AbstractSince chemists and materials scientists have been seeking for unconventional routes to synthesize and fabricate novel patterns for applied nanotechnology, we introduced useful functional polymers, which can be patternable on a variety of substrates to fabricate devices with specific functions. We introduce new silicon elastomeric polymers as a stamp material for high fidelity in nano-scale soft lithography. We also fabricated elastic photopatterns by synthesizing photocurable PDMS prepolymers. Photopatternable polymers with specific molecular recognition functions were also employed to fabricate functional patterns with specific functions for our diverse applications.