New frequency reconfigurable antennas for wide frequency range tuning

Frequency reconfigurable antennas are becoming a compelling solution for the increasing demand of higher antenna capabilities, since they can operate at tunable narrow frequency bands while rejecting the undesirable signals from other bands. The aim of this project is to develop new designs for frequency reconfigurable antennas that can work across a wide frequency range (from 1 GHz up to 6 GHz) while maintaining stable radiation pattern and polarisation as required by the industry sponsors. A Vivaldi antenna is considered as the basis for a frequency reconfigurable design as it maintains the radiation characteristics in its operating band. Dual-band, tri-band and quad-band switched reconfigurable designs are proposed and analysed. These antennas are electronically-tuned using RF switches which adjust the impedance to reconfigure the operating band of the antenna. A prototype is tested in an anechoic chamber obtaining good performance. However, as the switches lead to several challenges, such as the effect of bias lines and the excessive insertion losses, a new approach is taken. State-of-the-art technologies are studied and fluid antennas are introduced. Current developments show that liquid antennas can have radiation efficiencies up to 90 % and conductivities close to copper, which makes them a good candidate to fulfil the requirements of this project. A hybrid Vivaldi antenna with an ionised water switch is proposed and a prototype tested. By introducing ionised water into a specific point of the feed line the operating frequency of the antenna is adjusted. The replacement of RF switches for electronically-controlled fluids brings high flexibility, suppression of the bias lines impact, dynamic adjustment and continuous frequency tuning compared to conventional antenna systems

Comparison between a novel liquid switch and a GaAs MMIC switch for reconfiguring the operating frequency of a Vivaldi antenna

This article proposes a novel liquid switch to reconfigure the operating frequency of a frequency-independent antenna. A Vivaldi antenna using a low-cost GaAs MMIC RF switch is used as a landmark to compare the measured results. Two prototypes are measured in an anechoic chamber and the results have been compared. The antennas operate in two modes: low-band mode at 3 GHz with 11 dBi of gain and high-band mode operating at 4.5 GHz with a measured gain of 10.8 dBi. The reconfigurable Vivaldi antenna proposed here presents high isolation between operating bands, a minimum of 12 dB, while maintaining high gain and stable radiation pattern which is suitable for cognitive radio applications

Low-Cost 3D-Printed Coupling-Fed Frequency Agile Fluidic Monopole Antenna System

A low-cost 3D-printed frequency agile fluidic monopole antenna system is demonstrated to respond to the increasing demand for reconfigurable antennas, which can operate in a dynamic environment, in this paper. Antennas that can be reconfigured for different operating frequencies, polarizations, or radiation patterns are attracting attention. Traditional reconfigurable antennas using a metallic radiating element with electronic switches are limited by their pre-defined physical geometries. As conductive fluid, either liquid metal or ionized fluid has no defined shape, so it is possible to create the desired shape of a fluidic antenna to support different wireless environments. The fabrication of the leakage-free containers for fluidic antennas needs special consideration, and stereo-lithography-based 3D-printing technology is a possible option to support the fabrication. Moreover, researchers will have higher design freedom and accuracy to create new container shapes for fluidic antennas. The fluidic monopole antenna proposed is coupling-fed by a ring geometry for separating the electrical and mechanical structures; such an approach enables individual optimization and minimizes mutual disturbances in the system. A parametric study of the proposed coupling-feed geometry and the experimental verification of the antenna prototypes have been performed. Reasonable frequency agility from 3.2 to 5 GHz has been demonstrated, and the peak efficiency is about 80%. A maximum gain of 3.8 dBi is obtained. The radiation patterns of the antenna are stable across the operating bandwidth. The proposed antenna could be useful for the applications in the recent 5G mid-bands operations

Low-cost distributed acoustic sensor network for real-time urban sound monitoring

Continuous exposure to urban noise has been found to be one of the major threats to citizens’ health. In this regard, several organizations are devoting huge efforts to designing new in-field systems to identify the acoustic sources of these threats to protect those citizens at risk. Typically, these prototype systems are composed of expensive components that limit their large-scale deployment and thus reduce the scope of their measurements. This paper aims to present a highly scalable low-cost distributed infrastructure that features a ubiquitous acoustic sensor network to monitor urban sounds. It takes advantage of (1) low-cost microphones deployed in a redundant topology to improve their individual performance when identifying the sound source, (2) a deep-learning algorithm for sound recognition, (3) a distributed data-processing middleware to reach consensus on the sound identification, and (4) a custom planar antenna with an almost isotropic radiation pattern for the proper node communication. This enables practitioners to acoustically populate urban spaces and provide a reliable view of noises occurring in real time. The city of Barcelona (Spain) and the UrbanSound8K dataset have been selected to analytically validate the proposed approach. Results obtained in laboratory tests endorse the feasibility of this proposal

Patients with Crohn's disease have longer post-operative in-hospital stay than patients with colon cancer but no difference in complications' rate

BACKGROUNDRight hemicolectomy or ileocecal resection are used to treat benign conditions like Crohn's disease (CD) and malignant ones like colon cancer (CC).AIMTo investigate differences in pre- and peri-operative factors and their impact on post-operative outcome in patients with CC and CD.METHODSThis is a sub-group analysis of the European Society of Coloproctology's prospective, multi-centre snapshot audit. Adult patients with CC and CD undergoing right hemicolectomy or ileocecal resection were included. Primary outcome measure was 30-d post-operative complications. Secondary outcome measures were post-operative length of stay (LOS) at and readmission.RESULTSThree hundred and seventy-five patients with CD and 2,515 patients with CC were included. Patients with CD were younger (median = 37 years for CD and 71 years for CC (P < 0.01), had lower American Society of Anesthesiology score (ASA) grade (P < 0.01) and less comorbidity (P < 0.01), but were more likely to be current smokers (P < 0.01). Patients with CD were more frequently operated on by colorectal surgeons (P < 0.01) and frequently underwent ileocecal resection (P < 0.01) with higher rate of de-functioning/primary stoma construction (P < 0.01). Thirty-day post-operative mortality occurred exclusively in the CC group (66/2515, 2.3%). In multivariate analyses, the risk of post-operative complications was similar in the two groups (OR 0.80, 95%CI: 0.54-1.17; P = 0.25). Patients with CD had a significantly longer LOS (Geometric mean 0.87, 95%CI: 0.79-0.95; P < 0.01). There was no difference in re-admission rates. The audit did not collect data on post-operative enhanced recovery protocols that are implemented in the different participating centers.CONCLUSIONPatients with CD were younger, with lower ASA grade, less comorbidity, operated on by experienced surgeons and underwent less radical resection but had a longer LOS than patients with CC although complication's rate was not different between the two groups

Predictors for anastomotic leak, postoperative complications, and mortality after right colectomy for cancer: Results from an international snapshot audit

Background: A right hemicolectomy is among the most commonly performed operations for colon cancer, but modern high-quality, multination data addressing the morbidity and mortality rates are lacking. Objective: This study reports the morbidity and mortality rates for right-sided colon cancer and identifies predictors for unfavorable short-term outcome after right hemicolectomy. Design: This was a snapshot observational prospective study. Setting: The study was conducted as a multicenter international study. Patients: The 2015 European Society of Coloproctology snapshot study was a prospective multicenter international series that included all patients undergoing elective or emergency right hemicolectomy or ileocecal resection over a 2-month period in early 2015. This is a subanalysis of the colon cancer cohort of patients. Main Outcome Measures: Predictors for anastomotic leak and 30-day postoperative morbidity and mortality were assessed using multivariable mixed-effect logistic regression models after variables selection with the Lasso method. Results: Of the 2515 included patients, an anastomosis was performed in 97.2% (n = 2444), handsewn in 38.5% (n = 940) and stapled in 61.5% (n = 1504) cases. The overall anastomotic leak rate was 7.4% (180/2444), 30-day morbidity was 38.0% (n = 956), and mortality was 2.6% (n = 66). Patients with anastomotic leak had a significantly increased mortality rate (10.6% vs 1.6% no-leak patients; p 65 0.001). At multivariable analysis the following variables were associated with anastomotic leak: longer duration of surgery (OR = 1.007 per min; p = 0.0037), open approach (OR = 1.9; p = 0.0037), and stapled anastomosis (OR = 1.5; p = 0.041). Limitations: This is an observational study, and therefore selection bias could be present. For this reason, a multivariable logistic regression model was performed, trying to correct possible confounding factors. Conclusions: Anastomotic leak after oncologic right hemicolectomy is a frequent complication, and it is associated with increased mortality. The key contributing surgical factors for anastomotic leak were anastomotic technique, surgical approach, and duration of surgery

The impact of stapling technique and surgeon specialism on anastomotic failure after right?sided colorectal resection: an international multicentre, prospective audit

Aim There is little evidence to support choice of technique and configuration for stapled anastomoses after right hemicolectomy and ileocaecal resection. This study aimed to determine the relationship between stapling technique and anastomotic failure. Method Any unit performing gastrointestinal surgery was invited to contribute data on consecutive adult patients undergoing right hemicolectomy or ileocolic resection to this prospective, observational, international, multicentre study. Patients undergoing stapled, side?to?side ileocolic anastomoses were identified and multilevel, multivariable logistic regression analyses were performed to explore factors associated with anastomotic leak. Results One thousand three hundred and forty?seven patients were included from 200 centres in 32 countries. The overall anastomotic leak rate was 8.3%. Upon multivariate analysis there was no difference in leak rate with use of a cutting stapler for apical closure compared with a noncutting stapler (8.4% vs 8.0%, OR 0.91, 95% CI 0.54–1.53, P = 0.72). Oversewing of the apical staple line, whether in the cutting group (7.9% vs 9.7%, OR 0.87, 95% CI 0.52–1.46, P = 0.60) or noncutting group (8.9% vs 5.7%, OR 1.40, 95% CI 0.46–4.23, P = 0.55) also conferred no benefit in terms of reducing leak rates. Surgeons reporting to be general surgeons had a significantly higher leak rate than those reporting to be colorectal surgeons (12.1% vs 7.3%, OR 1.65, 95% CI 1.04–2.64, P = 0.04). Conclusion This study did not identify any difference in anastomotic leak rates according to the type of stapling device used to close the apical aspect. In addition, oversewing of the anastomotic staple lines appears to confer no benefit in terms of reducing leak rates. Although general surgeons operated on patients with more high?risk characteristics than colorectal surgeons, a higher leak rate for general surgeons which remained after risk adjustment needs further exploration

Relationship between method of anastomosis and anastomotic failure after right hemicolectomy and ileo-caecal resection: an international snapshot audit

Aim: The anastomosis technique used following right-sided colonic resection is widely variable and may affect patient outcome. This study aimed to assess the association between leak and anastomosis technique (stapled vs handsewn). Method: This was a prospective, multicentre, international audit including patients undergoing elective or emergency right hemicolectomy or ileo-caecal resection operations over a 2-month period in early 2015. The primary outcome measure was the presence of anastomotic leak within 30\ua0days of surgery, determined using a prespecified definition. Mixed effects logistic regression models were used to assess the association between leak and anastomosis method, adjusting for patient, disease and operative cofactors, with centre included as a random-effect variable. Results: This study included 3208 patients, of whom 78.4% (n\ua0=\ua02515) underwent surgery for malignancy and 11.7% (n\ua0=\ua0375) underwent surgery for Crohn's disease. An anastomosis was performed in 94.8% (n\ua0=\ua03041) of patients, which was handsewn in 38.9% (n\ua0=\ua01183) and stapled in 61.1% (n\ua0=\ua01858). Patients undergoing handsewn anastomosis were more likely to be emergency admissions (20.5% handsewn vs 12.9% stapled) and to undergo open surgery (54.7% handsewn vs 36.6% stapled). The overall anastomotic leak rate was 8.1% (245/3041), which was similar following handsewn (7.4%) and stapled (8.5%) techniques (P\ua0=\ua00.3). After adjustment for cofactors, the odds of a leak were higher for stapled anastomosis (adjusted OR\ua0=\ua01.43; 95% CI: 1.04\u20131.95; P\ua0=\ua00.03). Conclusion: Despite being used in lower-risk patients, stapled anastomosis was associated with an increased anastomotic leak rate in this observational study. Further research is needed to define patient groups in whom a stapled anastomosis is safe

The relationship between method of anastomosis and anastomotic failure after right hemicolectomy and ileo-caecal resection: an international snapshot audit.

BACKGROUND: Anastomosis technique following right sided colonic resection is widely variable and may affect patient outcomes. This study aimed to assess the association between leak and anastomosis technique (stapled versus handsewn) METHODS: This was a prospective, multicentre, international audit including patients undergoing elective or emergency right hemicolectomy or ileo-caecal resection operations over a two-month period in early 2015. The primary outcome measure was the presence of anastomotic leak within 30 days of surgery, using a pre-specified definition. Mixed effects logistic regression models were used to assess the association between leak and anastomosis method, adjusting for patient, disease and operative cofactors, with centre included as a random effect variable. RESULTS: This study included 3208 patients, of whom 78.4% (n=2515) underwent surgery for malignancy and 11.7% (n=375) for Crohn's disease. An anastomosis was performed in 94.8% (n=3041) of patients, which was handsewn in 38.9% (n=1183) and stapled in 61.1% (n=1858) cases. Patients undergoing handsewn anastomosis were more likely to be emergency admissions (20.5% handsewn versus 12.9% stapled) and to undergo open surgery (54.7% versus 36.6%). The overall anastomotic leak rate was 8.1% (245/3041), which was similar following handsewn (7.4%) and stapled (8.5%) techniques (p=0.3). After adjustment for cofactors, the odds of a leak were higher for stapled anastomosis (adjusted odds ratio 1.43, 95% confidence interval 1.04-1.95, p=0.03). DISCUSSION: Despite being used in lower risk patients, stapled anastomosis was associated with an increased anastomotic leak rate in this observational study. Further research is needed to define patient groups in whom a stapled anastomosis is safe. This article is protected by copyright. All rights reserve