Directional flow of solitons with asymmetric potential wells: Soliton diode

We study the flow of bright solitons through two asymmetric potential wells. The scattering of a soliton by certain type of single potential wells, e.g., Gaussian or Rosen-Morse, is distinguished by a critical velocity above which solitons can transmit almost completely and below which solitons can reflect nearly perfectly. For two such wells in series with certain parameter combinations, we find that there is an appreciable velocity range for which solitons can propagate in one direction only. Our study shows that this directional propagation or diode behavior is due to a combined effect of the sharp transition in the transport coefficients at the critical velocity and a slight reduction in the center-of-mass speed of the soliton while it travels across a potential well.Comment: 7 pages, 5 figure

Infected foot ulcers in male and female diabetic patients: a clinico-bioinformative study

<p>Abstract</p> <p>Background</p> <p>The study aimed at (i) characterizing the mode of transmission of <it>bla</it>_CTX-Mand <it>bla</it>_TEM-1among extended-spectrum-β-lactamase (ESBL)-producing <it>Escherichia coli </it>strains isolated from infected diabetic foot ulcers, and (ii) identifying the risk factors for "sex-associated multidrug resistant Gram-negative bacterial (MDRGNB)-infection status" of the ulcers.</p> <p>Methods</p> <p>Seventy-seven diabetic patients having clinically infected foot ulcers were studied in a consecutive series. The <it>E. coli </it>strains isolated from the ulcers were screened for <it>bla</it>_CTX-M, <it>bla</it>_TEM-1, <it>armA</it>, <it>rmtA </it>and <it>rmtB </it>during the 2-year study-period. PCR amplified <it>bla</it>_CTX-Mgenes were cloned and sequenced. Enterobacterial repetitive intergenic consensus (ERIC)-PCR was used for the analysis of genetic relatedness of the ESBL-producers. Risk factors for "sex-associated MDRGNB-infection status" of ulcers were assessed. Modeling was performed using Swiss-Model-Server and verified by Procheck and verify3D programmes. Discovery Studio2.0 (Accelrys) was used to prepare Ramachandran plots. Z-scores were calculated using 'WHAT IF'-package. Docking of cefotaxime with modeled CTX-M-15 enzyme was performed using Hex5.1.</p> <p>Results</p> <p>Among 51 <it>E. coli </it>isolates, 14 (27.5%) ESBL-producers were identified. Only 7 Class1 integrons, 2 <it>bla</it>_CTX-M-15, and 1 <it>bla</it>_TEM-1were detected. Ceftazidime and cefotaxime resistance markers were present on the plasmidic DNA of both the <it>bla</it>_CTX-M-15positive strains and were transmissible through conjugation. The residues Asn132, Glu166, Pro167, Val172, Lys234 and Thr235 of CTX-M-15 were found to make important contacts with cefotaxime in the docked-complex. Multivariate analysis proved 'Glycemic control at discharge' as the single independent risk factor.</p> <p>Conclusions</p> <p>Male diabetic patients with MDRGNB-infected foot ulcers have poor glycemic control and hence they might have higher mortality rates compared to their female counterparts. Plasmid-mediated conjugal transfer, albeit at a low frequency might be the possible mechanism of transfer of <it>bla</it>_CTX-M-15resistance marker in the present setting. Since the docking results proved that the amino acid residues Asn132, Glu166, Pro167, Val172, Lys234 and Thr235 of CTX-M-15 (enzyme) make important contacts with cefotaxime (drug) in the 'enzyme-drug complex', researchers are expected to duly utilize this information for designing more potent and versatile CTX-M-inhibitors.</p