Influence of Array Configuration on MIMO Channel Capacity

The use of multiple antennas at each side of the radio link has demonstrated an increase in terms of data bit rate and spectral efficiency [1]. Due to this, different techniques such as spatial multiplexing and space-frequency-time techniques are being applied to MIMO (Multiple-Input Multiple-Output) systems. In order to obtain MIMO performances, most of the research studies have evaluated Uniform Linear Arrays (ULAs) for simulations and measurements. However, other considerations can be taken into account with the similar space used for the transmitter or receiver antenna array using different physical configurations. In this work, several antenna array configurations in the transmitter and the receiver have been studied and compared, in terms of MIMO channel capacity, showing that for a limited space, the linear array could be replaced for a rectangular or circular one with similar performances

Transcriptome changes in response to temperature in the fish pathogen Photobacterium damselae subsp. damselae: Clues to understand the emergence of disease outbreaks at increased seawater temperatures

The marine bacterium Photobacterium damselae subsp. damselae (Pdd) is a generalist and facultative pathogen that causes disease in a wide range of marine animals including fish species of importance in aquaculture. Disease outbreaks in fish farms have been correlated with an increased water temperature during summer months. In this study, we have used RNA sequencing to analyze the transcriptome of Pdd RM-71 cultured at two different temperatures, which simulated temperature conditions experienced during free swimming lifestyle at mid latitudes in winter months (15˚C) and during outbreaks in aquaculture in warm summer months (25˚C). The enhanced bacterial growth of Pdd observed at 25˚C in comparison to 15˚C suggests that an elevated seawater temperature contributes to the build-up of a sufficient bacterial population to cause disease. In comparison to growth at 15˚C, growth at 25˚C resulted in the upregulation of genes involved in DNA synthesis, nutrient uptake, chemotaxis, flagellar motility, secretion systems and antimicrobial resistance. Plasmid-encoded virulence factors, which include a putative adhesin/invasin OmpU, a transferrin receptor and a serum resistance protein, were also upregulated. Transcription factor RpoS, genes involved in cold shock response, modulation of cell envelope and amino acid metabolism, as well as genes of yet unknown function were downregulated at 25˚C. Notably, the gene encoding damselysin cytotoxin (Dly) was among the most highly transcribed genes at the two assayed temperatures, at levels comparable to the most highly expressed housekeeping genes. This study contributes to our understanding of the regulatory networks and biology of a generalist marine bacterial pathogen, and provides evidence that temperature regulates multiple physiological and virulence-related functions in PddThis work has been supported by grant AGL2016-79738-R (AEI/FEDER, EU) from the State Agency for Research (AEI) of Spain, and co-funded by the FEDER Programme from the European Union, to CRO. The support of Xunta de Galicia (Spain) with grant GRC-2014/007 to CRO and XMM is also acknowledged. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Funders websites: http://www.ciencia.gob.es/, http://www.edu.xunta.gal/portal/S

Exposure of the Opportunistic Marine Pathogen Photobacterium damselae subsp. damselae to Human Body Temperature Is a Stressful Condition That Shapes the Transcriptome, Viability, Cell Morphology, and Virulence

Photobacterium damselae subsp. damselae (Pdd), an important pathogen for marine animals, is also an opportunistic human pathogen that can cause fatal necrotizing fasciitis. The regulatory changes triggered by the temperature shift experienced by this marine pathogen upon entering the human body, are completely unknown. Here we report an RNA-seq approach combined with phenotypical assays to study the response of Pdd to cultivation at 37°C in comparison to 25°C. We found that cultivation of a Pdd highly virulent strain for fish and mice, RM-71, at 37°C, initially enhanced bacterial growth in comparison to 25°C as evidenced by the increase in optical density. However, cells were found to undergo a progressive loss of viability after 6 h cultivation at 37°C, and no viable cells could be detected from 30 h cultures at 37°C. In contrast, at 25°C, viable cell counts achieved the highest values at 30 h cultivation. Cells grown at 25°C showed normal rod morphology by scanning electron microscopy analysis whereas cells grown at 37°C exhibited chain-like structures and aberrant long shapes suggesting a defect in daughter cell separation and in septum formation. Cells grown at 37°C also exhibited reduced tolerance to benzylpenicillin. Using a RNA-seq approach we discovered that growth at 37°C triggered a heat-shock response, whereas genes involved in motility and virulence were repressed including iron acquisition systems, the type two secretion system, and damselysin toxin, a major virulence factor of Pdd. Human isolates did not exhibit advantage growing at 37°C compared to fish isolates, and comparative genomics did not reveal gene markers specific of human isolates, suggesting that any Pdd genotype existing in the marine environment might potentially cause disease in humans. Altogether, these data indicate that the potential of Pdd to cause disease in humans is an accidental condition rather than a selected trait, and that human body temperature constitutes a stressful condition for Pdd. This study provides the first transcriptome profile of Pdd exposed at human body temperature, and unveils a number of candidate molecular targets for prevention and control of human infections caused by this pathogenThis work was supported by the Agencia Estatal de Investigación (AEI) of Spain co-funded by the FEDER Programme from the European Union (grant no. AGL2016-79738-R) and by Xunta de Galicia (Spain) (grant no. ED431C 2018/18). XM thanks Xunta de Galicia for a predoctoral fellowshipS

A highly unstable and elusive plasmid that encodes the type III secretion system is necessary for full virulence in the marine fish pathogen photobacterium damselae subsp. piscicida

The marine bacterium Photobacterium damselae subsp. piscicida (Pdp) causes photobacteriosis in fish and important financial losses in aquaculture, but knowledge of its virulence factors is still scarce. We here demonstrate that an unstable plasmid (pPHDPT3) that encodes a type III secretion system (T3SS) is highly prevalent in Pdp strains from different geographical origins and fish host species. We found that pPHDPT3 undergoes curing upon in vitro cultivation, and this instability constitutes a generalized feature of pPHDPT3-like plasmids in Pdp strains. pPHDPT3 markers were detected in tissues of naturally-infected moribund fish and in the Pdp colonies grown directly from the fish tissues but were undetectable in a fraction of the colonies produced upon the first passage of the primeval colonies on agar plates. Notably, cured strains exhibited a marked reduction in virulence for fish, demonstrating that pPHDPT3 is a major virulence factor of Pdp. The attempts to stabilize pPHDPT3 by insertion of antibiotic resistance markers by allelic exchange caused an even greater reduction in virulence. We hypothesize that the existence of a high pressure to shed pPHDPT3 plasmid in vitro caused the selection of clones with off-target mutations and gene rearrangements during the process of genetic modification. Collectively, these results show that pPHDPT3 constitutes a novel, hitherto unreported virulence factor of Pdp that shows a high instability in vitro and warn that the picture of Pdp virulence genes has been historically underestimated, since the loss of the T3SS and other plasmid-borne genes may have occurred systematically in laboratories for decadesS

La construcción del pensamiento político y la tradición en Colombia es más que un cuento: propuesta didáctica para el fortalecimiento de la comprensión lectora de cuentos cortos latinoamericanos

La presente investigación tiene como objetivo principal, la presentación de una secuencia didáctica que responda a las necesidades actuales de la educación Colombiana, para ello se propone esta unidad, como estrategia pedagógica para el fortalecimiento de la comprensión lectora en los estudiantes de grado noveno de básica secundaria de la institución educativa INEM Felipe Pérez. Para el desarrollo de lo anterior, se exponen una serie de actividades que respondan y cumplan a cabalidad con las exigencias educativas que los estudiantes demandan a diario, tendiendo siempre a la formación de mentes críticas, con capacidad de reflexión y cuestionamiento de su realidad y a la trasformación de espacios que permitan la interacción del estudiante con su entorno social, es así como desde las perspectivas teóricas propuestas desde Camps, Pérez Abril y Rincón Bonilla, se trabaja el concepto de secuencia didáctica, en Cortés Y Bautista el texto narrativo y por último, como forma de reconocimiento cultural y nacional se rescata la literatura latinoamericana con el cuento “Espuma y Nada Más” de Hernando Téllez. Del mismo modo esta investigación ha tenido sus cimientos desde las disposiciones expuestas en los lineamientos curriculares de lengua castellana, el PNLE, ley general de educación, DBA y demás orientaciones brindadas por parte del MEN

A Novel Ultra-Wideband Frequency Planar Notch-filter Antenna.

Many research works have emerged for ultra-wideband (UWB) systems. One important issue is the antenna design to cover all frequency bands (3.1–10.6 GHz). In most applications, a reduced compact antenna is needed but with several requirements. In this paper, a novel triangle–semicircular planar monopole UWB antenna is presented with a notch filter to avoid the undesirable interferences in ISM (Industrial, Scientific and Medical) band at 5.3 GHz

Secreted citrate serves as iron carrier for the marine pathogen photobacterium damselae subsp damselae

Photobacterium damselae subsp damselae (Pdd) is a Vibrionaceae that has a wide pathogenic potential against many marine animals and also against humans. Some strains of this bacterium acquire iron through the siderophore vibrioferrin. However, there are virulent strains that do not produce vibrioferrin, but they still give a strong positive reaction in the CAS test for siderophore production. In an in silico search on the genome sequences of this type of strains we could not find any ORF which could be related to a siderophore system. To identify genes that could encode a siderophore-mediated iron acquisition system we used a mini-Tn10 transposon random mutagenesis approach. From more than 1,400 mutants examined, we could isolate a mutant (BP53) that showed a strong CAS reaction independently of the iron levels of the medium. In this mutant the transposon was inserted into the idh gene, which encodes an isocitrate dehydrogenase that participates in the tricarboxylic acid cycle. The mutant did not show any growth impairment in rich or minimal media, but it accumulated a noticeable amount of citrate (around 7 mM) in the culture medium, irrespective of the iron levels. The parental strain accumulated citrate, but in an iron-regulated fashion, being citrate levels 5–6 times higher under iron restricted conditions. In addition, a null mutant deficient in citrate synthase showed an impairment for growth at high concentrations of iron chelators, and showed almost no reaction in the CAS test. Chemical analysis by liquid chromatography of the iron-restricted culture supernatants resulted in a CAS-positive fraction with biological activity as siderophore. HPLC purification of that fraction yielded a pure compound which was identified as citrate from its MS and NMR spectral data. Although the production of another citrate-based compound with siderophore activity cannot be ruled out, our results suggest that Pdd secretes endogenous citrate and use it for iron scavenging from the cell environmentThis work was supported by grants AGL2012-39274-C02-01/02 and AGL2015-63740-C2-1/2-R (AEI/FEDER, EU) from the State Agency for Research (AEI) of Spain, and co-funded by the FEDER Programme from the European Union. The support of Xunta de Galicia (Spain) with grant GRC-2014/007 is also acknowledgedS

A 2x2 MIMO DVB-T2 System: Design, New Channel Estimation Scheme and Measurements With Polarization Diversity

The increasing interest in MIMO (Multiple-Input Multiple-Output) systems has given rise to a prolific research activity in recent years. Both theoretical and practical issues have been studied. However, so far few MIMO testbeds or prototypes have been built for DVB-T or future standards. In this paper, a novel 2 × 2 MIMO testbed specifically designed for evaluating the performances of a DVB-T2 MIMO system is presented. The description of signal processing is detailed including a new scheme to estimate the MIMO channel matrix. Finally, measurement results with different polarization schemes are presented for typical scenarios, obtaining higher capacity in LoS situations using polarization diversity