Scalability of Optical Networks: Crosstalk Limitations

Optical networks represent a promising solution for the future high capacity and flexible transport network. This paper presents a model for the performance evaluation of optical networks with respect to linear crosstalk and accumulated spontaneous emission noise. The proposed model is intended for the evaluation of the crosstalk requirements on the devices needed to support an optical network with a certain number of nodes and with a given level of bit-error rate.     

Chemical Modeling of Acid-Base Properties of Soluble Biopolymers Derived from Municipal Waste Treatment Materials

This work reports a study of the proton-binding capacity of biopolymers obtained from different materials supplied by a municipal biowaste treatment plant located in Northern Italy. One material was the anaerobic fermentation digestate of the urban wastes organic humid fraction. The others were the compost of home and public gardening residues and the compost of the mix of the above residues, digestate and sewage sludge. These materials were hydrolyzed under alkaline conditions to yield the biopolymers by saponification. The biopolymers were characterized by ¹³C NMR spectroscopy, elemental analysis and potentiometric titration. The titration data were elaborated to attain chemical models for interpretation of the proton-binding capacity of the biopolymers obtaining the acidic sites concentrations and their protonation constants. The results obtained with the models and by NMR spectroscopy were elaborated together in order to better characterize the nature of the macromolecules. The chemical nature of the biopolymers was found dependent upon the nature of the sourcing materials.     

Intermittent pneumatic compression in patients with ESRD. A systematic review

Introduction: Patients with end‐stage renal disease (ESRD) experience frequent hemodialysis (HD) complications. Intradialytic hypotension (IDH) is a common complication presenting in approximately between 20 and 50% of HD sessions. Available interventions such as volume replacement or vasoactive medications are associated with significant side effects. Intermittent pneumatic compression (IPC) has been proposed as a feasible intervention for the prevention of IDH, treatment of peripheral arterial disease and venous ulcers. These devices apply intermittent pressure to the legs improving arterial blood flow, mobilization of pooled blood with an increase in venous return increasing the effective circulatory volume. Our goal was to identify the published clinical evidence on whether IPC has a circulatory benefit and is it well‐tolerated among patients receiving HD. Methods: We conducted a systematic review to identify studies assessing the efficacy and safety of IPC in patients with ESRD. Our primary outcome was IDH. Secondary outcomes such as HD comfort, ultrafiltration volume, and physical activity were collected. No restrictions where used and we included all observational and interventional studies. Two reviewers performed screening and study quality assessment. Findings: We included seven studies. Out of the seven studies, five addressed IDH, and the rest were included for secondary outcomes such as physical capacity and HD comfort. In one randomized crossover trial comparing exercise against IPC, 21 patients were randomized to 3 different arms (no intervention, cycling, IPC) a decrease in the rates of IDH with IPC was described (43%, 38%, and 24% respectively P = 0.014). The smaller studies corroborated these results. All studies where at high risk of bias. Discussion: IPC might offer significant benefits for patients undergoing HD not limited to prevention of IDH but also improvement of hemodialysis comfort and physical capacity. However, our results should be interpreted in the context of its limitations.     

Energy efficiency analysis for flexible-grid OFDM-based optical networks

As the Internet traffic grows, the energy efficiency gains more attention as a design factor for the planning and operation of telecommunication networks. This paper is devoted to the study of energy efficiency in optical transport networks, comparing the performance of an innovative flexible-grid network based on Orthogonal Frequency Division Multiplexing (OFDM) with that of conventional fixed-grid Wavelength Division Multiplexing (WDM) networks with a Single Line Rate (SLR) and with a Mixed Line Rate (MLR) operation. The power consumption values of the network elements are introduced. Energy-aware heuristic algorithms are proposed for the resource allocation both in static (offline) and dynamic (online) scenarios with time-varying demands for the Elastic-bandwidth OFDM-based network and the WDM networks (with SLR and MLR). The energy efficiency performance of the two network technologies under different traffic load conditions have been demonstrated for different network sizes through simulations based on the proposed algorithms. The results in energy efficiency and network blocking highlight the benefits of the bandwidth elasticity and the flexibility of selecting different modulation formats offered by OFDM networks.     

Regenerative all-optical wavelength multicast for next generation WDM network and system applications

We experimentally demonstrate regenerative all-optical wavelength multicast by simultaneous multi-wavelength conversion of 10 Gb/s non-return-to-zero signals to four ITU 100 GHz spaced channels with a receiver sensitivity improvement of 1.84 dB and less than 0.14 dB difference among all the multicast channels, using a single commercial monolithically integrated SOA-MZI. The multicast device also exhibited about 22 dB optical signal-to-noise ratio enhancement for all the converted channels compared to the original signal channel without wavelength conversion. Our experiment for the first time revealed the regeneration properties of a SOA-MZI device for WDM wavelength multicast purposes, and proved the excellent performance of a simple scheme for various future network and system applications, such as all-optical wavelength routing and grid networking.     

Study of the interfacial magnetism in NiO/NiFe system

The interfacial magnetism of NiO/NiFe bilayers with different NiFe layer thicknesses, produced by DC and RF magnetron sputtering, has been studied by magnetometry and X-ray magnetic circular dichroism (XMCD). In magnetic hysteresis loops, the exchange bias field was found to be inversely proportional to the NiFe layer thickness. The fit using the Meiklejohn and Bean model gives a coupling energy at the NiO/NiFe interface of approximately 0.027 mJ/m². The analysis of the XMCD spectra of Fe and Ni, using the sum rules, shows a reduction of the effective spin magnetic moments in bilayers with NiFe thickness less than 4 nm. This reduction is attributed to hybridization of ferromagnetic and antiferromagnetic atoms d orbitals near the interface and/or formation of antiferromagnetic alloys due to atomic diffusion at the interfaces.     

Prevalence of Salmonella on retail broiler chicken meat carcasses in Colombia

A cross-sectional study was performed to estimate the prevalence of Salmonella on retail market chicken carcasses in Colombia. A total of 1,003 broiler chicken carcasses from 23 departments (one city per department) were collected via a stratified sampling method. Carcass rinses were tested for the presence of Salmonella by conventional culture methods. Salmonella strains were isolated from 27 % of the carcasses sampled. Logistic regression analysis was used to determine potential risk factors for Salmonella contamination associated with the chicken production system (conventional versus free-range), storage condition (chilled versus frozen), retail store type (supermarket, independent, and wet market), poultry company (integrated company versus nonintegrated company), and socioeconomic stratum. Chickens from a nonintegrated poultry company were associated with a significantly (P < 0.05) greater risk of Salmonella contamination (odds ratio, 2.0) than were chickens from an integrated company. Chilled chickens had a significantly (P < 0.05) higher risk of Salmonella contamination (odds ratio, 4.3) than did frozen chicken carcasses.     

Prevalence, risk factors, and antimicrobial resistance profiles of Salmonella from commercial broiler farms in two important poultry-producing regions of Colombia

Salmonella is one of the most common foodborne pathogens associated with diarrheal disease in humans. Food animals, especially poultry, are important direct and indirect sources of human salmonellosis, and antimicrobial resistance is an emerging problem of public health concern. The use of antimicrobials benefits producers but contributes to the emergence of antimicrobial resistant bacteria. As a step toward implementing the Colombian Integrated Program for Antimicrobial Resistance Surveillance, this study was conducted to establish the prevalence, distribution of serovars, antimicrobial resistance profiles, and risk factors for Salmonella on poultry farms in the two largest states of poultry production in Colombia. Salmonella was isolated from 41% of farms and 65% of the 315 chicken houses sampled. Salmonella Paratyphi B variant Java was the most prevalent serovar (76%), followed by Salmonella Heidelberg (23%). All Salmonella isolates were resistant to 2 to 15 of the antimicrobial drugs tested in this study. For Salmonella Paratyphi B variant Java, 34 drug resistance patterns were present. The predominant resistance pattern was ciprofloxacin, nitrofurantoin, tetracycline, trimethoprim-sulfamethoxazole, ceftiofur, streptomycin, enrofloxacin, and nalidixic acid; this pattern was detected in 15% of isolates. The resistance pattern of tetracycline, ceftiofur, and nalidixic acid was found in over 40% of the isolates of Salmonella Heidelberg. Of the biosecurity practices considered, two factors were significantly associated with reduction in Salmonella: cleaning of fixed equipment and composting of dead birds on the farm. Findings from the present study provide scientific evidence to inform implementation of official policies that support new biosecurity legislation in an effort to decrease the prevalence of Salmonella on Colombian poultry farms.     

Recognition of spectral amplitude codes by frequency swept coherent detection for flexible optical label switching

We propose a new method of recognizing spectral amplitude codes by using optical coherent detection with a frequency swept local light source oscillator. Our proposed method offer a substantial simplification in terms of required components to built optical label processing units with enhanced flexibility to accommodate for wavelength tuneability and a large number of labels. We present a performance analysis, comparison with conventional spectral codes recognition methods, based on computer simulation results. We consider a payload bit rate of 40 Gb/s.