Backscattering suppression in supersonic 1D polariton condensates

We investigate the effects of disorder on the propagation of one-dimensional polariton condensates in semiconductor microcavities. We observe a strong suppression of the backscattering produced by the imperfections of the structure when increasing the condensate density. This suppression occurs in the supersonic regime and is simultaneous to the onset of parametric instabilities which enable the "hopping" of the condensate through the disorder. Our results evidence a new mechanism for the frictionless flow of polaritons at high speeds.Comment: 5 pages, 3 figure

Realization of an all optical exciton-polariton router

We report on the experimental realization of an all optical router for exciton-polaritons. This device is based on the design proposed by H. Flayac and I.G. Savenko [APL 103, 201105 (2013)], in which a zero-dimensional island is connected through tunnel barriers to two periodically modulated wires of different periods. Selective transmission of polaritons injected in the island, into either of the two wires, is achieved by tuning the energy of the island state across the band structure of the modulated wires. We show such polariton routing using an optical control beam which blueshifts the island quantum states thanks to polariton-exciton interactions. Operation of the device is demonstrated both under cw and pulsed operation.Comment: 12 pages, 3 figure

Giant phase modulation in a Mach-Zehnder exciton-polariton interferometer

We report on a new mechanism of giant phase modulation. The phenomenon arises when a dispersed photonic mode (slow light) strongly couples to an excitonic resonance. In such a case, even a small amount of optically injected carriers creates a potential barrier for the propagating exciton-polariton which provokes a considerable phase shift. We evidence this effect by fabricating an exciton-polariton Mach-Zehnder interferometer, modulating the output intensity by constructive or destructive interferences controlled by optical pumping of a micrometric size area. The figure of merit for a {\pi} phase shift, defined by the control power times length of the modulated region, is found at least one order of magnitude smaller than slow light photonic crystal waveguides.Comment: 18 pages, 6 figure

Talbot effect for exciton-polaritons

We demonstrate, experimentally and theoretically, a Talbot effect for hybrid light-matter waves - exciton-polariton condensate formed in a semiconductor microcavity with embedded quantum wells. The characteristic `Talbot carpet' is produced by loading the exciton-polariton condensate into a microstructured one-dimensional periodic array of mesa traps, which creates an array of sources for coherent polariton ow in the plane of the quantum wells. The spatial distribution of the Talbot fringes outside the mesas mimics the near- field diffraction of a monochromatic wave on a periodic amplitude and phase grating with the grating period comparable to the wavelength. Despite the lossy nature of the polariton system, the Talbot pattern persists for distances exceeding the size of the mesas by an order of magnitude. Thus, our experiment demonstrates efficient shaping of two-dimensional ow of coherent exciton-polaritons by a one-dimensional "flat lens".PostprintPeer reviewe

Domain structure of the Moloney murine leukemia virus reverse transcriptase: mutational analysis and separate expression of the DNA polymerase and RNase H activities

The reverse transcriptase of Moloney murine leukemia virus, like that of all retroviruses, exhibits a DNA polymerase activity capable of synthesis on RNA or DNA templates and an RNase H activity with specificity for RNA in the form of an RNA.DNA hybrid. We have generated a library of linker insertion mutants of the Moloney murine leukemia virus enzyme expressed in bacteria and assayed these mutants for both enzymatic activities. Those mutations affecting the DNA polymerase activity were clustered in the 5'-proximal two-thirds of the gene, and those affecting RNase H were in the remaining 3' one-third. Based on these maps, plasmids were made that expressed each one of the domains separately; assays of the proteins encoded by these plasmids showed that each domain exhibited only the expected activity

Observations in using parallel and sequential evolutionary algorithms for automatic software testing

Computers & Operations Research, 35 (10),2007, pp.3161-3183In this paper we analyze the application of parallel and sequential evolutionary algorithms (EAs) to the automatic test data generation problem. The problem consists of automatically creating a set of input data to test a program. This is a fundamental step in software development and a time consuming task in existing software companies. Canonical sequential EAs have been used in the past for this task. We explore here the use of parallel EAs. Evidence of greater efficiency, larger diversity maintenance, additional availability of memory/CPU, and multi-solution capabilities of the parallel approach, reinforce the importance of the advances in research with these algorithms. We describe in this work how canonical genetic algorithms (GAs) and evolutionary strategies (ESs) can help in software testing, and what the advantages are (if any) of using decentralized populations in these techniques. In addition, we study the influence of some parameters of the proposed test data generator in the results. For the experiments we use a large benchmark composed of twelve programs that includes fundamental algorithms in computer science.Ministry of Education and Science and FEDER under Contract TIN2005-08818-C04-01 (the OPLINK Project). Francisco Chicano was supported by a Grant (BOJA 68/2003) from the Junta de Andalucía (Spain)

Metabolism within the tumor microenvironment and its implication on cancer progression: an ongoing therapeutic target

Since reprogramming energy metabolism is considered a new hallmark of cancer, tumor metabolism is again in the spotlight of cancer research. Many studies have been carried out and many possible therapies have been developed in the last years. However, tumor cells are not alone. A series of extracellular components and stromal cells, such as endothelial cells, cancer-associated fibroblasts, tumor-associated macrophages and tumor-infiltrating T cells, surround tumor cells in the so-called tumor microenvironment. Metabolic features of these cells are being studied in deep in order to find relationships between metabolism within the tumor microenvironment and tumor progression. Moreover, it cannot be forgotten that tumor growth is able to modulate host metabolism and homeostasis, so that tumor microenvironment is not the whole story. Importantly, the metabolic switch in cancer is just a consequence of the flexibility and adaptability of metabolism and should not be surprising. Treatments of cancer patients with combined therapies including anti-tumor agents with those targeting stromal cell metabolism, anti-angiogenic drugs and/or immunotherapy are being developed as promising therapeutics.Mª Carmen Ocaña is recipient of a predoctoral FPU grant from the Spanish Ministry of Education, Culture and Sport. Supported by grants BIO2014-56092-R (MINECO and FEDER), P12-CTS-1507 (Andalusian Government and FEDER) and funds from group BIO-267 (Andalusian Government). The "CIBER de Enfermedades Raras" is an initiative from the ISCIII (Spain). The funders had no role in the study design, data collection and analysis, decision to publish or preparation of the manuscript

Expression of enzymatically active reverse transcriptase in Escherichia coli

Reverse transcriptase of murine retroviruses is a monomeric protein of approximately 80,000 daltons, which is encoded by the central portion of the viral pol gene. To prepare large quantities of the enzyme, we have constructed gene fusions between the trpE gene and portions of the pol gene of Moloney murine leukemia virus. The inserted pol gene sequences include the entire coding region for the mature enzyme and various amounts of additional coding sequences. Many of these constructs express high levels of reverse transcriptase activity even though the NH2 and COOH termini of the protein product only approximate the correct termini of the authentic protein