Free field representation of Toda field theories

We study the following problem: can a classical $sl_n$ Toda field theory be represented by means of free bosonic oscillators through a Drinfeld--Sokolov construction? We answer affirmatively in the case of a cylindrical space--time and for real hyperbolic solutions of the Toda field equations. We establish in fact a one--to--one correspondence between such solutions and the space of free left and right bosonic oscillators with coincident zero modes. We discuss the same problem for real singular solutions with non hyperbolic monodromy.Comment: 29 pages, Latex, SISSA-ISAS 210/92/E

Vertex Operator Representation of the Soliton Tau Functions in the An(1)A_n^{(1)} Toda Models by Dressing Transformations

We study the relation between the group-algebraic approach and the dressing symmetry one to the soliton solutions of the $A_n^{(1)}$ Toda field theory in 1+1 dimensions. Originally solitons in the affine Toda models has been found by Olive, Turok and Underwood. Single solitons are created by exponentials of elements which ad-diagonalize the principal Heisenberg subalgebra. Alternatively Babelon and Bernard exploited the dressing symmetry to reproduce the known expressions for the fundamental tau functions in the sine-Gordon model. In this paper we show the equivalence between these two methods to construct solitons in the $A_n^{(n)}$ Toda models.Comment: 35 pages, LaTe

Has the internet fostered inclusive innovation in the developing world?

Based on 50,013 firm observations covering 117 developing and emerging countries, this paper shows knowledge spillover effects from industries' use of the internet boosted the average firm's productivity and innovation performance. We document that industries' "digitization" had heterogeneous impacts: results from quantile regressions indicate that the most productive firms benefited much more than others. Wider Internet adoption rates were also of larger benefit to single-plant establishments, non-exporters and firms in remote locations, particularly to the most productive among these firms. Overall, we document that the internet can play an important role to support inclusive innovation, conditional on firms' "absorptive" capacities

An(1)A_n^{(1)} Toda solitons and the dressing symmetry

We present an elementary derivation of the soliton-like solutions in the $A_n^{(1)}$ Toda models which is alternative to the previously used Hirota method. The solutions of the underlying linear problem corresponding to the N-solitons are calculated. This enables us to obtain explicit expression for the element which by dressing group action, produces a generic soliton solution. In the particular example of monosolitons we suggest a relation to the vertex operator formalism, previously used by Olive, Turok and Underwood. Our results can also be considered as generalization of the approach to the sine-Gordon solitons, proposed by Babelon and Bernard.Comment: 26 pages, Latex file, amssym.def needed, no figures; one new reference adde

Recast layers on high speed steel surface after electrical discharge treatment in electrolyte

In this work are discussed some experimental data about the obtaining of recast layers on the surface of high speed tool steel after electrical discharge treatment in electrolyte. The electrical discharge treatment of steel surface in electrolyte produces a recast layer with specific combination of structure characteristics in result of nonequilibrium phase transformations. The modification goes by a high energy thermal process in electrical discharges on a very small area on the metallic surface involving melting, alloying and high speed cooling in the electrolyte. Obtained recast layers have a different structure in comparison with the metal matrix and are with higher hardness, wear- and corrosion resistance

Rapid and direct magnetization of GFP-reporter yeast for micro-screening systems

Saccharomyces cerevisiae containing fluorescent markers are ideal candidates for applications in microfluidic screening systems as fluorescence signal is emitted without the need of additional reagents. Here we develop a method for magnetic functionalisation of such cells which allows their handling and immobilization in micro-screening devices. After exposure of the magnetized GFP-reporter yeast (GreenScreen™) to a genotoxic compound, the fluorescence emission was detected using fluorescent spectrometer and an Epi-fluorescent microscope. Results demonstrate that GFP production and fluorescence emission is not altered by their magnetic functionalization, indicating its potential employment on biosensors, bioreactors and micro-screening studies. © 2009 Elsevier B.V

Bioimprint Mediated Label-Free Isolation of Pancreatic Tumor Cells from a Healthy Peripheral Blood Cell Population

New techniques are required for earlier diagnosis and response to treatment of pancreatic cancer. Here, a label-free approach is reported in which circulating pancreatic tumor cells are isolated from healthy peripheral blood cells via cell bioimprinting technology. The method involves pre-fabrication of pancreatic cell layers and sequential casting of cell surfaces with a series of custom-made resins to produce negative cell imprints. The imprint is functionalized with a combination of polymers to engineer weak attraction to the cells which is further amplified by the increased area of contact with the matching cells. A flow-through bioimprint chip is designed and tested for selectivity toward two pancreatic tumor cell lines, ASPC-1 and Mia-PaCa-2. Healthy human peripheral blood mononuclear cells (PBMCs) are spiked with pancreatic tumor cells at various concentrations. Bioimprints are designed for preferential retention of the matching pancreatic tumor cells and with respect to PBMCs. Tumor bioimprints are capable of capturing and concentrating pancreatic tumor cells from a mixed cell population with increased retention observed with the number of seedings. ASPC-1 bioimprints preferentially retain both types of pancreatic tumor cells. This technology could be relevant for the collection and interrogation of liquid biopsies, early detection, and relapse monitoring of pancreatic cancer patients

A direct technique for preparation of magnetically functionalised living yeast cells

A direct technique for preparation of magnetically functionalised yeast cells by using polyelectrolyte mediated deposition of magnetite nanoparticles is reported. We demonstrate that the cells preserve their viability after the magnetite deposition and show that the magnetic nanoparticles form a multilayered coating on the outer side of the yeast cell's wall. We applied our technique to produce magnetically functionalised yeast cells expressing green fluorescent protein (GFP) under the control of RAD54-GFP reporter and demonstrated that their fluorescence emission is not influenced by the presence of magnetite-polyelectrolyte composite coating. We show that the individual cells can be successfully manipulated by an external magnetic field which can be used for their deposition, holding and subsequent removal from microfluidic devices for genotoxicity and cytotoxicity biosensor applications. Our technique for direct magnetization of cells can find many other biotech applications including biosensors, bioreactors and bioseparation. © 2011 The Royal Society of Chemistry

Microfluidic device for the rapid coating of magnetic cells with polyelectrolytes

We demonstrate a rapid method of coating a layer of polymer onto magnetically modified yeast cells, so-called cyborg cells, in continuous flow within a microfluidic chamber. Laminar flow streams of polyelectrolyte and washing buffers were generated across the chamber, and the magnetic cells were deflected sequentially through the co-flowing streams via an external magnet, allowing polyelectrolyte deposition onto the cells immediately followed by the washing step, all in less than 90 s. This simple deposition technique shows promise for the functionalization of such cyborg cells for applications including bioelectronics, bioanalysis, and toxicity screening, while the addition of more reagent streams would enable the fabrication of multilayered capsules. © 2013 Elsevier B.V

Directed assembly of yeast cells into living yeastosomes by microbubble templating

We report the fabrication of yeastosomes - novel multicellular assemblies, which consist of a spherical monolayer of living yeast cells held together by colloid interactions. Our method is based on templating of microbubbles with cells coated with cationic polyelectrolyte and the layer-by-layer technique. We show the mechanism of formation of yeastosomes which involves a gradual dissolution of the air-cores and their infusion with water. We demonstrate that the cells remain viable in the yeastosome structures. Yeastosomes and similar structures may find applications in the development of novel symbiotic bio-structures, artificial multicellular organisms and in tissue engineering. The unusual structure of these multicellular assemblies resembles the primitive forms of multicellular species, like Volvox, and other algae and could be regarded as one possible stage of the evolutionary development of multicellularity. © 2010 The Royal Society of Chemistry