Investigating Echo-State Networks Dynamics by Means of Recurrence Analysis

This is the author accepted manuscript. The final version is available from IEEE via the DOI in this record.In this paper, we elaborate over the well-known interpretability issue in echo-state networks (ESNs). The idea is to investigate the dynamics of reservoir neurons with time-series analysis techniques developed in complex systems research. Notably, we analyze time series of neuron activations with recurrence plots (RPs) and recurrence quantification analysis (RQA), which permit to visualize and characterize high-dimensional dynamical systems. We show that this approach is useful in a number of ways. First, the 2-D representation offered by RPs provides a visualization of the high-dimensional reservoir dynamics. Our results suggest that, if the network is stable, reservoir and input generate similar line patterns in the respective RPs. Conversely, as the ESN becomes unstable, the patterns in the RP of the reservoir change. As a second result, we show that an RQA measure, called Lmax, is highly correlated with the well-established maximal local Lyapunov exponent. This suggests that complexity measures based on RP diagonal lines distribution can quantify network stability. Finally, our analysis shows that all RQA measures fluctuate on the proximity of the so-called edge of stability, where an ESN typically achieves maximum computational capability. We leverage on this property to determine the edge of stability and show that our criterion is more accurate than two well-known counterparts, both based on the Jacobian matrix of the reservoir. Therefore, we claim that RPs and RQA-based analyses are valuable tools to design an ESN, given a specific problem

Tetracycline-resistance encoding plasmids from Paenibacillus larvae, the causal agent of American foulbrood disease, isolated from commercial honeys

Paenibacillus larvae, the causal agent of American foulbrood disease in honeybees, acquires tetracycline-resistance via native plasmids carrying known tetracycline-resistance determinants. From three P. larvae tetracycline-resistant strains isolated from honeys, 5-kb-circular plasmids with almost identical sequences, designated pPL373 in strain PL373, pPL374 in strain PL374, and pPL395 in strain PL395, were isolated. These plasmids were highly similar (99%) to small tetracycline-encoding plasmids (pMA67, pBHS24, pBSDMV46A, pDMV2, pSU1, pAST4, and pLS55) that replicate by the rolling circle mechanism. Nucleotide sequences comparisons showed that pPL373, pPL374, and pPL395 mainly differed from the previously reported P. larvae plasmid pMA67 in the oriT region and mob genes. These differences suggest alternative mobilization and/or conjugation capacities. Plasmids pPL373, pPL374, and pPL395 were individually transferred by electroporation and stably maintained in tetracycline-susceptible P. larvae NRRL B-14154, in which they autonomously replicated. The presence of nearly identical plasmids in five different genera of gram-positive bacteria, i.e., Bhargavaea, Bacillus, Lactobacillus, Paenibacillus, and Sporosarcina, inhabiting diverse ecological niches provides further evidence of the genetic transfer of tetracycline resistance among environmental bacteria from soils, food, and marine habitats and from pathogenic bacteria such as P. larvae. [Int Microbiol 2014; 17(1):49-61]Keywords: American foulbrood disease (AFB) · Paenibacillus larvae · tetracycline resistance · plasmids · honeybee

Event-triggered robust control for multi-player nonzero-sum games with input constraints and mismatched uncertainties

In this article, an event-triggered robust control (ETRC) method is investigated for multi-player nonzero-sum games of continuous-time input constrained nonlinear systems with mismatched uncertainties. By constructing an auxiliary system and designing an appropriate value function, the robust control problem of input constrained nonlinear systems is transformed into an optimal regulation problem. Then, a critic neural network (NN) is adopted to approximate the value function of each player for solving the event-triggered coupled Hamilton-Jacobi equation and obtaining control laws. Based on a designed event-triggering condition, control laws are updated when events occur only. Thus, both computational burden and communication bandwidth are reduced. We prove that the weight approximation errors of critic NNs and the closed-loop uncertain multi-player system states are all uniformly ultimately bounded thanks to the Lyapunov's direct method. Finally, two examples are provided to demonstrate the effectiveness of the developed ETRC method

A case of intoxication due to a highly cytotoxic Bacillus cereus strain isolated from cooked chicken

Outbreaks of Bacillus cereus infection/intoxication are not commonly reported because symptoms are often mild, and the disease is self-limiting. However, hypervirulent strains increase health risks. We report a case, which occurred in Argentina, of severe food The studied strain was highly cytotoxic, showed high ability to detach Caco-2 cells and was positive for the hblA, hblB, and hblC genes of the hbl complex, bceT, entS and ces. As it is considered that B. cereus emetic cluster evolved from a panmictic population of diarrhoeal strains, B. cereus MVL2011 could constitute an intermediate strain between diarrhoeal and emetic strains.Prepint aceptado el 14 de agosto de 2014 para su publicación

Incidencia de loque americana en mieles

La loque americana de las abejas, ocasionada por la bacteria esporulada Paenibacillus larvae subsp. larvae, es la enfermedad más grave que afecta a las larvas de las abejas melíferas. Las esporas bacterianas permanecen viables en miel manteniendo su capacidad infectiva durante tiempo prolongado y de esa forma diseminan la enfermedad aún desde colmenas asintomáticas. Para determinar la incidencia de la enfermedad, se realizó un monitoreo de la distribución de esporas de P. l. larvae en mieles de distintos partidos de la Prov. de Bs. As., con un tamaño muestral de 394 (95% de certeza) durante 3 años de muestreo: 1999-2000-2001. Del total, se obtuvieron 219 muestras positivas (55,4% de incidencia). Se optimizó la técnica de aislamiento logrando disminuir el límite de detección de esporas viables. Las poblaciones del patógeno se caracterizaron mediante rep-PCR empleando primers BOX, REP y ERIC; mediante pruebas bioquímicas y fisiológicas y por susceptibilidad/resistencia al bacteriófago PPL1c

First report of leaf spot disease of maize caused by Pantoea ananatis in Argentina

From 2007 to 2008, an uncharacterized disease of maize (Zea mays L.) was observed in commercial fields of Laguna Blanca, Formosa, Argentina and from different fields of Santa Fe and Catamarca provinces of Argentina. Symptoms included light-colored necrotic streaks on leaves and tan or white irregular blotches that sometimes were surrounded by reddish purple-to-dark brown margins. Severity of symptoms varied greatly from one field to another. Abundant bacterial streaming was observed from lesions when examined at ×150. Gram-negative, facultatively anaerobic bacteria were consistently isolated from lesions. These formed light yellow-to-orange, glistening, convex colonies on yeast dextrose calcium carbonate agar incubated at 30°C. Ten isolates from ten different symptomatic plants were selected for further study. All isolates were motile, induced a hypersensitive response in tobacco plants, and were oxidase negative. Colonies developed at 37°C. Physiological and biochemical characterization with the API 20E test strips and database (bioMerieux, Buenos Aires, Argentina) showed that the strains belonged to the genus Pantoea. All strains were positive for β-galactosidase, utilized citrate and tartrate, and produced acid from d-glucose, d-mannitol, d-melibiose, l-arabinose, sucrose, meso-inositol, glycerol, d-sorbitol, and amygdalin. All were negative for arginine dihydrolase, lysine decarboxylase, ornithine decarboxylase, tryptophane deaminase, H2S production, urease, and reduction of nitrate to nitrite. Variable results were obtained for indole, gelatinase, and l-rhamnose. Their identity was confirmed by sequencing the 16S rRNA gene strain F327 (GenBank Accession No. GU068363). A BlastN search of GenBank revealed 99% nt identity with strains LMG 20103 (AF364847.1), LMG 20105 (AF364845.1), and LMG 2665 (FJ611815.1) of Pantoea ananatis. Pathogenicity was verified on Z. mays (EM 6079 HX, Dow Morgan) by injection-infiltration of bacterial suspensions at 105 CFU/ml. Controls were infiltrated with sterile distilled water. Plants were kept at 26 ± 3°C in a greenhouse. Symptoms were first detected 15 to 17 days after inoculation and then lesions expanded to resemble natural infections within 30 days. Bacteria were reisolated and the original and reisolated strains were compared by using repetitive sequence-based (rep)-PCR with ERIC primers (1) and fingerprints of the reisolated strains were identical to those of the original strains, thereby fulfilling Koch's postulates. No lesions were observed on controls. Known strains of P. stewartii from the United States (SW2, DC400, DC441, and DC283) were also tested for comparison. On the basis of sequencing data, pathogenicity, and physiological tests, the pathogen was identified as P. ananatis (4). To our knowledge, this is the first report of P. ananatis causing a disease of maize in Argentina, although a similar disease has been reported in Brazil (2) and Mexico (3)

First report of Pseudomonas mediterranea causing tomato pith necrosis in Argentina

During the summers of 2007 and 2008 fruiting tomato plants (Solanum lycopersicum cv. Orco) from commercial greenhouses near La Plata, Argentina (35 ºS 57 ºW) showed abundant adventitious root production, apical chlorosis of leaves and a brown discoloration of the stem pith (Fig. 1). These symptoms were similar to those reported by López et al. (1994) and Catara et al. (2002) on tomatoes affected by Pseudomonas corrugata or Pseudomonas mediterranea. Bacteria consistently isolated from stem lesions formed cream-coloured, glistening, convex colonies on sucrose peptone agar (SPA) and were non-fluorescent on King’s medium B (KMB). Four isolates were selected for further study. All were aerobic, Gram-negative rods with PHB inclusions. In LOPAT tests, all induced a hypersensitive response in tobacco plants, were oxidase positive, did not cause soft rot of potato tubers, and were negative for levan and arginine dihydrolase. Colonies developed at 28ºC and 37ºC but not at 41ºC. Additional characterisation was achieved by API 20 NE tests strips (Biomerieux®, Argentina). Reference strains 536.7 (Spain), 592.4 (Spain) and CFBP 10906 (France) of P. mediterranea and strain NCPPB 2445 of P. corrugata were included in all tests for comparison. Further identity was confirmed by PCR, using species-specific primers PC5/1-PC5/2 for P. mediterranea and primers PC1/1-PC1/2 for P. corrugata (Catara et al., 2002). All the strains were identified by the amplification of a 600 bp DNA fragment characteristic of Pseudomonas mediterranea (Fig. 2; Catara et al., 2002). The isolates of P. mediterranea were also differentiated from those of P. corrugata by PCR/RFLP analysis of 16S rDNA gene by using endonuclease AluI (Fig. 3). Pathogenicity was verified on four-week-old tomato plants (cv. Presto) by injecting bacterial suspensions at 107 cfu/ml or sterile distilled water for controls, after which the plants were kept for 72 h in a humid chamber before incubation at 25°C. After 45 days inoculated plants showed necrotic pith symptoms similar to those observed on field-grown plants, whereas no lesions were observed on controls. Pith necrosis caused by P. corrugata and P. viridiflava has been previously reported in Argentina (Alippi et al., 1993 Alippi et al, 2003). This is the first report of a disease caused by P. mediterranea on greenhouse-grown tomatoes in Argentina and South America

Limit overturning moment chuck

Limited memory capacity is one of the major constraints in Delay Tolerant Wireless Sensor Networks. Efficient management of the memory is critical to the performance of the network. This paper proposes a novel buffer management algorithm, SmartGap, a Quality of Information (QoI) targeted buffer management algorithm. That is, in a wireless sensor network that continuously measures a parameter which changes over time, such as temperature, the value of a single packet is governed by an estimation of its contribution to the recreation of the original signal. Attractive features of SmartGap include a low computational complexity and a simplified reconstruction of the original signal. An analysis and simulations in which the performance of SmartGap is compared with the performance of several commonly used buffer management algorithms in wireless sensor networks are provided in the paper. The simulations suggest that SmartGap indeed provides significantly improved QoI compared the other evaluated algorithms.QC 20150605</p

First report of Pectobacterium carotovorum subsp. carotovorum on Spathiphyllum wallisii in Argentina

Peace lily (Spathiphyllum wallisii Regel) is a popular ornamental potted plant in Argentina. During May of 2008 (austral autumn), necrotic lesions of unknown etiology were observed on S. wallisii in a nursery in Pontevedra (34°45′6″S, 58°42′42″W). Plants first showed water-soaked areas starting from the leaf tips. Infected tissue became irregular, brown, dark-to-black lesions on leaves ~12 to 14 mm in diameter surrounded by yellowish haloes. Disease incidence approached 30%. Abundant bacterial streaming was observed from lesions when examined at ×100. Bacteria isolated from lesions formed white-to-cream, glistening, convex colonies on yeast dextrose calcium carbonate agar. Three bacterial strains isolated from different symptomatic plants were selected for comparative analysis with Pectobacterium carotovorum subsp. carotovorum type strain ATCC 15713. All were facultatively, anaerobic, gram-negative rods, pectolytic on crystal violet pectate agar, nonfluorescent on King's medium B, and elicited a hypersensitive response in tobacco plants. All strains were oxidase and arginine dihydrolase negative, fermented glucose, did not hydrolyze starch, did not produce lecithinase, indole or the blue pigment indigoidine, reduced nitrates, hydrolyzed gelatin and esculin, able to rot onion slices, caused soft rot of potato tubers, resistant to erythromycin, and grew at 37°C. Acid was produced from cellobiose, D-glucose, D-melibiose, D-mannitol, D-mannose, Lrhamnose, D-sucrose, and L-arabinose but not from inositol and D-sorbitol. Bacteria utilized N-acetyl-glucosamine and citrate but not tartrate, benzoate, or propionate. Their identity was confirmed by 16S rRNA gene sequencing of strain F402Pcc (GenBank Accession No. FJ717337) showing a 99% homology with that of strain ATCC 3326 (FJ 5958691). Pathogenicity was verified on S. wallisii, Dieffenbachia picta, Aglaonema commutatum, and Anthurium andraeanum within the Araceae family by spraying two plants per strain tested with bacterial suspensions (108 CFU/ml) in sterile distilled water with and without wounding the leaves with sterile needles. Controls were sprayed with sterile distilled water. After 48 h in a humidity chamber, inoculated plants and controls were maintained at 25 ± 3°C in a greenhouse. Water-soaked areas developed from 24 to 48 h after inoculation and became necrotic within 4 to 5 days. Lesions expanded to resemble natural infection in S. wallisii within 20 days, while in the rest of the hosts tested, lesions were smaller and remained brown surrounded by yellowish haloes. All strains were reisolated from each host tested. The original and all reisolated strains were compared by enterobacterial repetitive intergeneric consensus-PCR (4) confirming that DNA fingerprints of the reisolated strains were identical to those of the original strains. No lesions were observed on controls. The pathogen was identified as P. carotovorum subsp. carotovorum based on biochemical, physiological, pathogenicity tests, and 16S rRNA sequencing (1–3).To our knowledge, this is the first report of this pathogen on S. wallisii in Argentina although it has been reported as causing tomato pith necrosis (1) and soft rot of vegetables after harvest (3)