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Zhao F.,Alliance Technology Group | Medard M.,Massachusetts Institute of Technology | Ozdaglar A.,Massachusetts Institute of Technology | Lun D.,Rutgers University
IEEE Transactions on Information Theory | Year: 2014

The problem of establishing minimum-cost multicast connections in coded networks can be viewed as an optimization problem, and decentralized algorithms were proposed by Lun to compute the optimal subgraph using the dual subgradient method. However, the convergence rate problem for these algorithms remains open. There are limited results in the literature, which bound the amount of infeasibility of the primal solution recovered after each iterations or the convergence rate. However, due to the special structure of the network coding problem, we have an algorithm that generates a feasible solution after each iterations. In addition, the convergence rate of the primal problem is $O(1/n)$ to a neighborhood of the optimal solution. We also propose heuristics to further improve our algorithm and demonstrate through simulations that the distributed algorithm converges to the optimal subgraph quickly and is robust against network topology changes. © 1963-2012 IEEE.

Zheng D.,Alliance Technology Group
American journal of respiratory cell and molecular biology | Year: 2014

Transformation-related protein 63-expressing (p63(+)) basal cells are confined to the trachea in the mouse lung. However, after influenza virus infection or bleomycin treatment, patches of p63(+) cells were observed in the damaged lung parenchyma. To address whether the newly induced p63(+) cells are derived from the p63(+) basal cells, we performed lineage tracing. In a keratin 5 promoter-driven CreER system, although preexisting p63(+) basal cells were labeled by enhanced green fluorescent protein (EGFP) after tamoxifen treatment, none or only a small fraction (∼ 15%) of the p63(+) patches was labeled by EGFP after bleomycin treatment or influenza virus infection, respectively. In contrast, > 60% of p63(+) patches contained EGFP(+) cells in Scgb1a1-CreER transgenic system where club cells are labeled. Many p63(+) cells were found in bronchiole-like lumen structures with columnar cells at the lumen side. The columnar cells were positive for club cell marker Cyp2f2 and could be traced to the newly induced p63(+) cells. These results suggest that most of the newly induced p63(+) cells in the damaged parenchyma are likely derived from club cells rather than from p63(+) basal cells and that newly induced p63(+) cells may be involved in the regeneration of bronchioles.

Guo C.X.,National University of Singapore | Huang S.,Alliance Technology Group | Lu X.,National University of Singapore
Green Chemistry | Year: 2014

A green and one-step solventless thermolysis approach is developed for large-scale production of ultra-small magnetic ferrite nanocrystals with size down to 3.5 nm. By simply heating a mixed solid powder containing metal acetylacetonate and sodium citrate, a series of metal ferrite nanocrystals including Fe3O4, MnFe2O4, NiFe 2O4 and CoFe2O4 are prepared. The nanocrystals exhibit both high hydrophilicity and good biocompatibility with uniform sizes that can be controlled by varying the ratio of metal acetylacetonate to sodium citrate, a green agent that is widely used as a food additive, a buffering regulator and an anticoagulant in blood transfusions. Thanks to the high hydrophilicity, the nanocrystals are demonstrated to be efficient draw solutes for protein enrichment with retained conformational structure based on an osmotically driven process. The green and one-step solventless thermolysis approach with advantages of minimal use of organic solvents and simplicity may be extended to fabrication of other ultra-small and hydrophilic nanoparticles with biocompatibility for a variety of applications. © the Partner Organisations 2014.

Zeiger A.S.,Massachusetts Institute of Technology | Zeiger A.S.,Alliance Technology Group | Hinton B.,University of Minnesota | Van Vliet K.J.,Massachusetts Institute of Technology
Acta Biomaterialia | Year: 2013

There is wide anecdotal recognition that biological cell viability and behavior can vary significantly as a function of the source of commercial tissue culture polystyrene (TCPS) culture vessels to which those cells adhere. However, this marked material dependency is typically resolved by selecting and then consistently using the same manufacturer's product-following protocol-rather than by investigating the material properties that may be responsible for such experimental variation. Here, we quantified several physical properties of TCPS surfaces obtained from a wide range of commercial sources and processing steps, through the use of atomic force microscopy (AFM)-based imaging and analysis, goniometry and protein adsorption quantification. We identify qualitative differences in surface features, as well as quantitative differences in surface roughness and wettability that cannot be attributed solely to differences in surface chemistry. We also find significant differences in cell morphology and proliferation among cells cultured on different TCPS surfaces, and resolve a correlation between nanoscale surface roughness and cell proliferation rate for both cell types considered. Interestingly, AFM images of living adherent cells on these nanotextured surfaces demonstrate direct interactions between cellular protrusions and topographically distinct features. These results illustrate and quantify the significant differences in material surface properties among these ubiquitous materials, allowing us to better understand why the dish can make a difference in biological experiments. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Pan H.M.,National University of Singapore | Beyer S.,Alliance Technology Group | Beyer S.,1 CREATE Way and 04 13 14 Enterprise Wing | Zhu Q.,National University of Singapore | Trau D.,National University of Singapore
Advanced Functional Materials | Year: 2013

The unique inwards interweaving morphology of polyamines and polyacids within agarose hydrogels that leads to the formation of striated shells with different porosities within the spherical scaffold is reported. Microcompartments with sophisticated structures are commonly used in drug delivery, tissue engineering, and other biomedical applications. However, a method capable of producing well-defined, multiporous shells within a single compartment is still lacking. By the alternating deposition of polyallylamine (PA) and polystyrenesulfonic acid (PSS) in 1-butanol, at equal mass ratios, multiple levels of porosity are generated within an agarose microsphere. Each level of porosity is represented by a well-defined, concentric shell of interweaving PA and PSS layers. The number, thickness, and porosity of the striated shells can be easily controlled by varying the number of PA/PSS bilayers and the polymer concentration, respectively. The feasibility of utilizing this morphology for the assembly of a multi-shell porous spherical scaffold is validated by trapping different molecular weight dextrans within different regions of porosity. The unique interaction of polyacids and polyamines in hydrogels represents a facile and inexpensive approach to the development of intricate scaffold architectures. The inwards interweaving of polyamine and polyacid layers within an agarose matrix leads to the creation of well-defined, spherical multi-shells with different porosities. The higher the density of interweaving layers, the lower the porosity. The number and thickness of different levels of porosity are easily tuned by varying the number of polymer depositions and polymer concentration, respectively. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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