California Nano Systems Institute

Westwood, CA, United States

California Nano Systems Institute

Westwood, CA, United States
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Dadras J.,University of California at Los Angeles | Jimenez-Izal E.,University of California at Los Angeles | Alexandrova A.N.,University of California at Los Angeles | Alexandrova A.N.,California Nano Systems Institute
ACS Catalysis | Year: 2015

Immobilized Pt clusters are interesting catalysts for dehydrogenation of alkanes. However, surface-deposited Pt clusters deactivate rapidly via sintering and coke deposition. The results reported here suggest that adding boron to oxide-supported Pt clusters could be a magic bullet against both means of deactivation. The model systems studied herein are pure and B-doped Pt clusters deposited on MgO(100). The nonstoichiometric boride cluster obtained via such alloying is found to anchor to the support via a covalent B-O bond, and the cluster-surface binding is much stronger than in the case of pure Pt clusters. Additionally, B introduces covalency to the intracluster bonding, leading to structural distortion and stabilization. The energy required to dissociate a Pt atom from a boride cluster is significantly larger than that of pure Pt clusters. These energetic arguments lead to the proposal that sintering via both Ostwald ripening and particle coalescence would be discouraged relative to pure Pt clusters. Finally, it is shown that the affinity to C also drops dramatically for borated clusters, discouraging coking and increasing the selectivity of potential cluster catalysts. © 2015 American Chemical Society.

Saotome T.,University of California at Los Angeles | Kim H.,University of California at Los Angeles | Wang Z.,University of California at Los Angeles | Lashmore D.,Nanocomp Technologies Inc. | Hahn H.T.,California Nano Systems Institute
Bulletin of Materials Science | Year: 2011

Vacuum filtration process to fabricate a transparent conducting carbon nanotube (CNT) film is reported. A CNT mat, which is a fibrous sheet of long multi-walled carbon nanotubes (MWNT), was prepared and dispersed in oleum by solution-sonication. The suspension was then vacuum filtered to obtain a thin MWNT layer with improved dispersion. Sheet resistance of the obtained MWNT layer was increased despite the improved dispersion. SEM micrographs and energy dispersive spectroscopy results indicated that the increase of the sheet resistance could be attributed to degradation and oxidation of the MWNT bundles. Though the chemical approach in this study did not improve the electrical property of the CNT mat, a mechanical approach proposed in our recent work was deemed suitable to enhance optical and electrical properties of the CNT mat. © Indian Academy of Sciences.

Tanoue R.,Kumamoto University | Higuchi R.,Kumamoto University | Ikebe K.,Kumamoto University | Uemura S.,Kumamoto University | And 9 more authors.
Journal of Nanoscience and Nanotechnology | Year: 2014

Two-dimensional-conjugated metal-porphyrin covalent organic frameworks were produced in aqueous solution on an iodine-modified Au(111) surface by "on-site" azomethine coupling of FeIII- 5,10,15,20-tetrakis(4- aminophenyl)porphyrin (FeTAPP) with terephthal dicarboxaldehyde and investigated in detail using in-situ scanning tunneling microscopy. Mixed covalent organic porphyrin frameworks consisting of FeTAPP and metal-free TAPP (H2TAPP) were prepared through simultaneous adsorption in a mixed solution as well as partial replacement of FeTAPP by H2TAPP in an as-prepared metal-porphyrin framework. In the mixed framework, the relative distribution of FeTAPP to H2TAPP was not random and revealed a preference for homo-connection rather than heteroconnection. The construction of substrate-supported,-conjugated covalent frameworks from multiple building blocks, including metal centers, will be of significant utility in the design of functional molecular nanoarchitectures Copyright © 2014 American Scientific Publishers All rights reserved.

Arora A.,Arizona State University | Sant G.,University of California at Los Angeles | Sant G.,California Nano Systems Institute | Neithalath N.,Arizona State University
Construction and Building Materials | Year: 2016

The influence of high volume cement replacement using a combination of slag and limestone, on the hydration, reaction products and pore structure, and strength of cementitious systems is reported in this paper. Total replacement levels vary from 20% to 50% by volume. Slag is blended with: (i) Portland-limestone cement (PLC) that contains limestone interground with cement, or (ii) OPC and limestone of four different sizes in such a way that the resulting particle size distribution of the composite matches that of the corresponding PLC-based mixture. The hydration response of cement and cement-slag mixtures are found to be modified in the presence of limestone. It is observed from calorimetric and thermogravimetric analysis that a favorable slag-limestone synergy exists, that enables high volume replacement of cement without concomitant loss in properties. The early-age compressive strengths are beneficially impacted by the presence of limestone whereas the clinker factor does not play a significant role in later-age strengths in both the blended and interground systems. The study paves the way for development of multiple-material binders containing higher levels of cement replacement that demonstrate early and later age properties that are comparable to or better than that of traditional straight cement systems. © 2015 Elsevier Ltd. All rights reserved.

Sollier E.,University of California at Los Angeles | Sollier E.,Vortex Biosciences Inc. | Go D.E.,University of California at Los Angeles | Che J.,University of California at Los Angeles | And 18 more authors.
Lab on a Chip - Miniaturisation for Chemistry and Biology | Year: 2014

A blood-based, low cost alternative to radiation intensive CT and PET imaging is critically needed for cancer prognosis and management of its treatment. "Liquid biopsies" of circulating tumor cells (CTCs) from a relatively non-invasive blood draw are particularly ideal, as they can be repeated regularly to provide up to date molecular information about the cancer, which would also open up key opportunities for personalized therapies. Beyond solely diagnostic applications, CTCs are also a subject of interest for drug development and cancer research. In this paper, we adapt a technology previously introduced, combining the use of micro-scale vortices and inertial focusing, specifically for the high-purity extraction of CTCs from blood samples. First, we systematically varied parameters including channel dimensions and flow rates to arrive at an optimal device for maximum trapping efficiency and purity. Second, we validated the final device for capture of cancer cell lines in blood, considering several factors, including the effect of blood dilution, red blood cell lysis and cell deformability, while demonstrating cell viability and independence on EpCAM expression. Finally, as a proof-of-concept, CTCs were successfully extracted and enumerated from the blood of patients with breast (N = 4, 25-51 CTCs per 7.5 mL) and lung cancer (N = 8, 23-317 CTCs per 7.5 mL). Importantly, samples were highly pure with limited leukocyte contamination (purity 57-94%). This Vortex approach offers significant advantages over existing technologies, especially in terms of processing time (20 min for 7.5 mL of whole blood), sample concentration (collecting cells in a small volume down to 300 μL), applicability to various cancer types, cell integrity and purity. We anticipate that its simplicity will aid widespread adoption by clinicians and biologists who desire to not only enumerate CTCs, but also uncover new CTC biology, such as unique gene mutations, vesicle secretion and roles in metastatic processes. This journal is © 2014 The Royal Society of Chemistry.

Kranz W.T.,University of Oxford | Gelimson A.,University of Oxford | Zhao K.,Tianjin University | Zhao K.,California Nano Systems Institute | And 2 more authors.
Physical Review Letters | Year: 2016

Like ants, some microorganisms are known to leave trails on surfaces to communicate. We explore how trail-mediated self-interaction could affect the behavior of individual microorganisms when diffusive spreading of the trail is negligible on the time scale of the microorganism using a simple phenomenological model for an actively moving particle and a finite-width trail. The effective dynamics of each microorganism takes on the form of a stochastic integral equation with the trail interaction appearing in the form of short-term memory. For a moderate coupling strength below an emergent critical value, the dynamics exhibits effective diffusion in both orientation and position after a phase of superdiffusive reorientation. We report experimental verification of a seemingly counterintuitive perpendicular alignment mechanism that emerges from the model. © 2016 American Physical Society.

Maier B.,University of Cologne | Wong G.C.L.,California Nano Systems Institute
Trends in Microbiology | Year: 2015

The bacterial type IV pilus (T4P) is a versatile molecular machine with a broad range of functions. Recent advances revealed that the molecular components and the biophysical properties of the machine are well conserved among phylogenetically distant bacterial species. However, its functions are diverse, and include adhesion, motility, and horizontal gene transfer. This review focusses on the role of T4P in surface motility and bacterial interactions. Different species have evolved distinct mechanisms for intracellular coordination of multiple pili and of pili with other motility machines, ranging from physical coordination to biochemical clocks. Coordinated behavior between multiple bacteria on a surface is achieved by active manipulation of surfaces and modulation of pilus-pilus interactions. An emerging picture is that the T4P actively senses and responds to environmental conditions. © 2015 Elsevier Ltd.

Arora A.,Arizona State University | Vance K.,Arizona State University | Sant G.,University of California at Los Angeles | Sant G.,California Nano Systems Institute | Neithalath N.,Arizona State University
Construction and Building Materials | Year: 2016

This paper compares the performance of commercial interground Portland-limestone cements (PLC) to those of blended limestone systems. Limestone of four different median sizes is mixed with ordinary portland cement (OPC) to create blends in an attempt to match the particle size distribution of the PLCs. The interground systems are found to outperform the blended systems, plausibly because of the difference in size distributions of the clinker and limestone fractions between the PLCs and the blended systems. A novel methodology to extract the particle size distributions of the components in the interground systems is reported. This method, applicable for several types of multi-component powder systems, considers Rosin-Rammler size distributions for the ground clinker and limestone, and optimizes the parameters of the distribution to obtain a composite distribution of the same fineness as the interground system. The model is verified using a cement hydration and microstructure model. © 2016 Elsevier Ltd. All rights reserved.

Bouchard L.-S.,California Nano Systems Institute | Acosta V.M.,University of California at Berkeley | Bauch E.,University of California at Berkeley | Budker D.,University of California at Berkeley
New Journal of Physics | Year: 2011

We examine the possibility of probing superconductivity effects in metal nanoclusters via diamond magnetometry. Metal nanoclusters have been proposed as constitutive elements of high-Tc superconducting nanostructured materials. Magnetometry based on the detection of spin-selective fluorescence of nitrogen-vacancy (NV) centers in diamond is capable of nanoscale spatial resolution and can be used as a tool for investigating the properties of single or multiple clusters interacting among each other or with a surface.We have carried out sensitivity estimates and experiments to understand how these magnetometers could be used in such a situation. We detected the flux exclusion effect in a superconductor by monitoring the magnetic resonance spectrum of a large ensemble of NV centers in diamond. Our results show that phase transitions can be ascertained in a bulk superconductor with this technique. We also discovered temperature-dependent behavior of the zero-field splitting parameter D and conclude that the general implementation of such measurements may require compensation schemes. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

PubMed | Tianjin University, University of Oxford and California Nano Systems Institute
Type: Journal Article | Journal: Physical review letters | Year: 2016

Guided movement in response to slowly diffusing polymeric trails provides a unique mechanism for self-organization of some microorganisms. To elucidate how this signaling route leads to microcolony formation, we experimentally probe the trajectory and orientation of Pseudomonas aeruginosa that propel themselves on a surface using type IV pili motility appendages, which preferentially attach to deposited exopolysaccharides. We construct a stochastic model by analyzing single-bacterium trajectories and show that the resulting theoretical prediction for the many-body behavior of the bacteria is in quantitative agreement with our experimental characterization of how cells explore the surface via a power-law strategy.

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