A monolithic and flexible fluoropolymer film microreactor for organic synthesis applications

A photocurable and viscous fluoropolymer with chemical stability is a highly desirable material for fabrication of microchemical devices. Lack of a reliable fabrication method, however, limits actual applications for organic reactions. Herein, we report fabrication of a monolithic and flexible fluoropolymer film microreactor and its use as a new microfluidic platform. The fabrication involves facile soft lithography techniques that enable partial curing of thin laminates, which can be readily bonded by conformal contact without any external forces. We demonstrate fabrication of various functional channels (similar to 300 mu m thick) such as those embedded with either a herringbone micromixer pattern or a droplet generator. Organic reactions under strongly acidic and basic conditions can be carried out in this film microreactor even at elevated temperature with excellent reproducibility. In particular, the transparent film microreactor with good deformability could be wrapped around a light-emitting lamp for close contact with the light source for efficient photochemical reactions with visible light, which demonstrates easy integration with optical components for functional miniaturized systems.open1112Ysciescopu

Cationic Polymers based on Fructose and Galactose Moieties for Nucleic Acids Delivery

Cationic polymers and glycopolymers were synthesised using the RAFT technique. Combining cationic polymers with glycopolymers has great potential in targeted nucleic acid delivery.1,2 However, many obstacles prevent the use of cationic glycopolymers as vectors including low success in nucleic acid delivery and high toxicity of the cationic polymer. This project aims to investigate RAFT synthesis of cationic glycopolymers with galactose or fructose carbohydrates, their binding ability with their specific lectins and with negatively charged nucleic acids. The cationic polymer poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) was synthesised using RAFT polymerisation. The galactose monomer, 2-(2’,3’,4’,6’-tetra-O-acetyl-β-D-galactosyloxy)ethyl methacrylate (AcGalEMA), and the fructose monomer, 1-O-methacryloyl-2,3:4,5-di-O-isopropylidene--D-fructopyranose (1-O-MAiPFru)3, were polymerised with PDMAEMA to form cationic glycopolymers. Chain extension was confirmed using proton nuclear magnetic spectroscopy (NMR) and gel permeation chromatography (GPC). Gel permeation chromatography was also performed to determine the polydispersity index (uniformity) of the polymers. The protected glycopolymer blocks were modified by deacetylation of the galactose block and acid deprotection of the fructose block. Characterisation of the modified cationic glycopolymers was achieved using proton nuclear magnetic spectroscopy for confirmation of deacetylation/deprotection, and dynamic light scattering to determine the sizes of the diblock copolymers. The zeta potential (ionic charge) of the diblock copolymers was recorded. Aggregation assays between the cationic glycopolymers and plant lectins were assessed. The galactose-containing glycopolymers were conjugated with peanut agglutinin lectin and the fructose-containing glycopolymers were conjugated with lectin from Ulex europaeus. The assays were analysed using dynamic light spectroscopy and ultraviolet-visible spectroscopy. Complexation of the cationic glycopolymer with small interfering RNA (siRNA) was accomplished. The size of the resulting polyplex was recorded with dynamic light spectroscopy. The zeta potential was measured and compared to the zeta potential measurement before complexation with siRNA. Results indicated that RAFT polymerisation was successful in producing diblock polymers of controlled weight and uniform size. The cationic glycopolymers were partially successful in deacetylation/deprotection and highly successful in binding to their specific lectins. The cationic glycopolymer complexed with siRNA; however, further research into the appropriate N:P ratio is necessary. In conclusion, RAFT polymerisation is a suitable technique for the synthesis of cationic glycopolymers for use in nucleic acid delivery. The cationic block of the polymer is able to complex with nucleic acids while the glycopolymer block is able to bind to specific lectins. Further research into carbohydrates specific binding and further modifications to increase nucleic acid delivery efficiency would be beneficial

Crystallization and preliminary crystallographic studies of an antimicrobial protein from Pharbitis nil

An antimicrobial protein from seeds of Pharbitis nil (Pn-AMP) which shows an antifungal activity towards several agriculturally important plant pathogens has been crystallized in the presence of equimolar N-acetylglucosamine with sodium citrate as precipitant. The crystal belongs to the hexagonal space group P6(1)22 (or P6(5)22), with unit-cell parameters a = b = 29.33 (5), c = 133.44 (12) Angstrom. Native data were collected using a crystal at 100 K to a resolution of 1.78 Angstrom.open2

Dynamical mass generation in quantum field theory : some methods with application to the Gross-Neveu model and Yang-Mills theory

We introduce some techniques to investigate dynamical mass generation. The Gross-Neveu model (GN) is used as a toy model, because the GN mass gap is exactly known, making it possible to check reliability of the various methods. Very accurate results are obtained. Also application to SU(N) Yang-Mills (YM) is discussed.Comment: 8 LaTeX2e pages, uses Kluwer class file crckbked.cls. Kluwer package included. To appear in: Proceedings of the NATO Advanced Research Workshop on "Confinement, Topology, and other Non-Perturbative Aspects of QCD", Stara Lesna, Slovakia, 21-27 jan 200

Porohyperelastic anatomical models for hydrocephalus and idiopathic intracranial hypertension

This is the accepted manuscript of a paper published in the Journal of Neurosurgery, Published online February 6, 2015; DOI: 10.3171/2014.12.JNS14516.OBJECT Brain deformation can be seen in hydrocephalus and idiopathic intracranial hypertension (IIH) via medical images. The phenomenology of local effects, brain shift, and raised intracranial pressure and herniation are textbook concepts. However, there are still uncertainties regarding the specific processes that occur when brain tissue is subject to the mechanical stress of different temporal and spatial profiles of the 2 neurological disorders. Moreover, recent studies suggest that IIH and hydrocephalus may be diseases with opposite pathogenesis. Nevertheless, the similarities and differences between the 2 subjects have not been thoroughly investigated. METHODS An anatomical porohyperelastic finite element model was used to assess the brain tissue responses associated with hydrocephalus and IIH. The same set of boundary conditions, with the exception of brain loading for development of the transmantle pressure gradient, was applied for the 2 models. The distribution of stress and strain during tissue distortion is described by the mechanical parameters. RESULTS The results of both the hydrocephalus and IIH models correlated with pathological characteristics. For the hydrocephalus model, periventricular edema was associated with the presence of positive volumetric strain and void ratio in the lateral ventricle horns. By contrast, the IIH model revealed edema across the cerebral mantle, including the centrum semiovale, with a positive void ratio and volumetric strain. CONCLUSIONS The model simulates all the clinical features in correlation with the MR images obtained in patients with hydrocephalus and IIH, thus providing support for the role of the transmantle pressure gradient and capillary CSF absorption in CSF-related brain deformation. The finite element methods can be used for a better understanding of the pathophysiological mechanisms of neurological disorders associated with parenchymal volumetric fluctuation.Dr. M. Czosnyka is a consultant for J&J (Codman), and has received payment for lectures from Integra Lifescience. This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRFK) funded by the Ministry of Science, ICT, & Future Planning (2013R1A1A1004827); and the International Research & Development Program of the NRFK funded by the Ministry of Education, Science, and Technology of Korea (Grant No. 2014K1A3A1A21001366)

Room temperature plasmon laser by total internal reflection

Plasmon lasers create and sustain intense and coherent optical fields below light's diffraction limit with the unique ability to drastically enhance light-matter interactions bringing fundamentally new capabilities to bio-sensing, data storage, photolithography and optical communications. However, these important applications require room temperature operation, which remains a major hurdle. Here, we report a room temperature semiconductor plasmon laser with both strong cavity feedback and optical confinement to 1/20th of the wavelength. The strong feedback arises from total internal reflection of surface plasmons, while the confinement enhances the spontaneous emission rate by up to 20 times.Comment: 8 Page, 2 Figure

THE PHYSICAL SCALE OF THE FAR-INFRARED EMISSION IN THE MOST LUMINOUS SUBMILLIMETER GALAXIES

We present high-resolution submillimeter interferometric imaging of two of the brightest high-redshift submillimeter galaxies known: GN 20 and AzTEC1 at 0.8\u27\u27 and 0.3\u27\u27 resolution, respectively. Our data—the highest resolution submillimeter imaging of high-redshift sources accomplished to date—were collected in three different array configurations: compact, extended, and very extended. We derive angular sizes of 0.6\u27\u27 and 1.0\u27\u27 for GN 20 and 0.3\u27\u27 and 0.4\u27\u27 for AzTEC1 from modeling their visibility functions as a Gaussian and an elliptical disk, respectively. Because both sources are B-band dropouts, they likely lie within a relatively narrow redshift window around z ~ 4, which indicates their angular extent corresponds to physical scales of 4-8 and 1.5-3 kpc, respectively, for the starburst region. By way of a series of simple assumptions, we find preliminary evidence that these hyperluminous starbursts—with star formation rates \u3e1000 M yr−1—are radiating at or close to their Eddington limit. Should future high-resolution observations indicate that these two objects are typical of a population of high-redshift Eddington-limited starbursts, this could have important consequences for models of star formation and feedback in extreme environments

CO(1-0) in z gtrsim 4 Quasar Host Galaxies: No Evidence for Extended Molecular Gas Reservoirs

We present 12CO(J = 1 → 0) observations of the high-redshift quasi-stellar objects (QSOs) BR 1202-0725 (z = 4.69), PSS J2322+1944 (z = 4.12), and APM 08279+5255 (z = 3.91) using the NRAO Green Bank Telescope (GBT) and the MPIfR Effelsberg 100 m telescope. We detect, for the first time, the CO ground-level transition in BR 1202-0725. For PSS J2322+1944 and APM 08279+5255, our observations result in line fluxes that are consistent with previous NRAO Very Large Array (VLA) observations, but they reveal the full line profiles. We report a typical lensing-corrected velocity-integrated intrinsic 12CO(J = 1 → 0) line luminosity of L = 5 × 1010 K km s-1 pc2 and a typical total H2 mass of M(H2) = 4 × 1010 M for the sources in our sample. The CO/FIR luminosity ratios of these high-z sources follow the same trend as seen for low-z galaxies, leading to a combined solution of log LFIR = (1.39 ± 0.05) log LCO - 1.76. It has previously been suggested that the molecular gas reservoirs in some quasar host galaxies may exhibit luminous, extended 12 CO(J = 1 → 0) components that are not observed in the higher J CO transitions. Using the line profiles and the total intensities of our observations and large velocity gradient (LVG) models based on previous results for higher J CO transitions, we derive that emission from all CO transitions is described well by a single gas component in which all molecular gas is concentrated in a compact nuclear region. Thus, our observations and models show no indication of a luminous extended, low surface brightness molecular gas component in any of the high-redshift QSOs in our sample. If such extended components exist, their contribution to the overall luminosity is limited to at most 30%

Theories for influencer identification in complex networks

In social and biological systems, the structural heterogeneity of interaction networks gives rise to the emergence of a small set of influential nodes, or influencers, in a series of dynamical processes. Although much smaller than the entire network, these influencers were observed to be able to shape the collective dynamics of large populations in different contexts. As such, the successful identification of influencers should have profound implications in various real-world spreading dynamics such as viral marketing, epidemic outbreaks and cascading failure. In this chapter, we first summarize the centrality-based approach in finding single influencers in complex networks, and then discuss the more complicated problem of locating multiple influencers from a collective point of view. Progress rooted in collective influence theory, belief-propagation and computer science will be presented. Finally, we present some applications of influencer identification in diverse real-world systems, including online social platforms, scientific publication, brain networks and socioeconomic systems.Comment: 24 pages, 6 figure