Several RF and microwave radiating devices, such as horn antennas, Fabry-Perot cavity antennas, and aperture-fed focusing devices, are excited through rectangular waveguides. The impedance matching ...of the overall system (from the waveguide feed to the radiating aperture) is a task of crucial importance that is often addressed by means of brute-force parameter-sweep full-wave analyses or blind optimization algorithms. In both cases, a significant amount of memory and time resources are required. For this purpose, we propose here a simple, yet effective solution, which only requires a single full-wave simulation and a semi-analytical procedure. The former is used to retrieve the antenna input impedance at the end of the waveguide port excitation. The semi-analytical procedure consists in a transmission-line equivalent circuit that models two waveguide discontinuities (namely two capacitive irises) within the waveguide section, whose position and geometric features are finely tuned to obtain a satisfactory impedance matching around the working frequency. The proposed method is shown to be effective in diverse and attractive application-oriented contexts, from the impedance matching of a Fabry-Perot cavity antenna to that of a wireless near-field link between two aperture-fed focusing devices. A remarkable agreement between full-wave simulations and numerical results is found in all cases. Thanks to its versatility, simplicity, and a rather low demand of computational resources, the proposed approach may become an essential tool for the effective design of waveguide-fed antennas.
Terahertz (THz) radiation is a very appealing band of the electromagnetic spectrum due to its practical applications. In this context, the THz generation and manipulation is an essential part of the ...technological development. The demand of THz antennas is still high because it is already difficult to obtain directive, efficient, planar, low-cost, and easy-to-fabricate THz radiating systems. In this regard, Fabry-Perot cavity leaky-wave antennas are gaining increasing attention at THz, due to their very interesting radiating features: the combination of planar designs with metamaterials and metasurfaces could offer a promising platform for future THz manipulation technologies. In this short review, we focus on different classes of leaky-wave antennas, based on materials with tunable quasi-optical parameters. The possibility of producing directive patterns with particularly good efficiencies, as well as the capability of dynamically reconfiguring their radiating features, are discussed by taking into account the risk of increasing costs and fabrication complexity.
The transmission of antimicrobial resistance bacteria from animals to humans has become an important concern. The extended-spectrum beta-lactamase (ESBL) -AmpC- producing Escherichia coli (ESBL-AmpC ...EC) and quinolones resistant E. coli are of particular interest. The present study aimed to evaluate the load and prevalence of antibiotic-resistant commensal E. coli along the goose production cycle on 2 free-range farms in central Italy. On A farm, oxytetracycline was administered, while the B farm did not use antibiotics during the geese productive cycle. One hundred geese of 1-day-old from the same batch were divided into the two farms. At hatching, the animals showed an average of E. coli loads was 6.83 ± 0.48 log CFU/g, and 0.28 ± 0.28, 0, 5.12 ± 0.54 log CFU/g for E. coli resistant to nalidixic acid (E. colinal), to cefotaxime (E. colicef) and to tetracyclines (E. colitet), respectively. The loads of E. coli, E. colinal, E. colicef and E. colitet on 224 environmental faecal pools were determined at 8 time points. Antimicrobial susceptibility and molecular characterization of E. colicef isolates were performed. The ANOVA was used to assess the difference in bacterial loads between the two farms. We described more than 50% of resistances for tetracyclines in both farms, and sulphonamides and cephazolin in the A farm. The loads of E. coli and E. colinal in faeces were estimated at approximately 6–7 log (CFU/g) and 5–6 log (CFU/g) in the two farms, respectively. The average load of extended-spectrum beta-lactamase Escherichia coli (ESBL EC) in goose faeces varied broadly along the production cycle: in the first weeks, a sharp increase was observed in both farms, while later on A farm, the burden of ESBL EC remained steady until the end of the production cycle and on B farm the load dramatically decreased from 6 wk of age onward. An increase in the proportion of E. colinal was observed on A farm shortly after the antibiotic administration. Our study shows that the dynamics of antibiotic-resistant E. coli in farmed geese are similar to the ones observed in broilers. However, the risk of the emergence of antibiotic-resistant commensal E. coli, might be mitigated by the adoption of good management practices, including prudent use of antibiotics.
Microwave fabrication and design techniques are commonly employed in the terahertz (THz) domain. However, a characterization of commercially available microwave dielectric materials is usually ...lacking at sub-THz and THz frequencies. In this work, we characterized four substrates by Rogers and an Ordyl dry resist between 0.2 and 2 THz, in terms of relative permittivity and loss tangent. The reflectance spectra of the investigated materials were retrieved by means of THz time-domain spectroscopy in reflection mode and post-processed according to a transmission-line model in which the materials’ parameters are fit by means of the Havriliak–Negami variation of the Debye model. The relative permittivity of the investigated materials showed negligible frequency dispersion in the sub-THz and in the THz range. In terms of the loss tangent, the Rogers substrates revealed a more pronounced frequency-dispersive behavior among different materials, as dictated by the Havriliak–Negami model. The Ordyl resist was dispersive in the 0.2–1.2 THz range and presented a nearly constant loss tangent value between 1.2 and 2 THz. These results may represent a reference for the development of innovative components for THz and sub-THz emerging applications.
Rift Valley fever is a vector-borne zoonotic disease caused by the Rift Valley fever virus (Phlebovirus genus) listed among the eight pathogens included in the Bluepoint list by the WHO. The ...transmission is mainly vehicled by
and
mosquito species. Symptoms of the disease are varied and non-specific, making clinical diagnosis often challenging, especially in the early stages. Due to the difficulty in distinguishing Rift Valley fever from other viral hemorrhagic fevers, as well as many other diseases that cause fever, an early diagnosis of the infection is important to limit its spread and to provide appropriate care to patients. To date, there is no validated point-of-care diagnostic tool. The virus can only be detected in the blood for a brief period, suggesting that molecular methods alone are not sufficient for case determination. For this, it is preferable to combine both molecular and serological tests. The wide distribution of competent vectors in non-endemic areas, together with global climate change, elicit the spread of RVFV to continents other than Africa, making surveillance activities vital to prevent or to limit the impact of human outbreaks and for a rapid identification of positive cases, making diagnosis a key factor for this achievement.
Porcine noroviruses and sapoviruses have been sporadically reported in European countries, and more rarely in Italy. In this study, stools samples were collected from both asymptomatic and diarrheic ...pigs from northern Italy and were screened for caliciviruses by RT-PCR. Sapoviruses were detected frequently and were genetically related to both the GIII reference strain and the newly described porcine sapovirus genogroups. Porcine norovirus was detected in one asymptomatic pig (0.5 %) and was genotyped as GII.11. This is the first detection of porcine norovirus in Italy.
Equine influenza (EI) is a highly contagious viral disease of equids characterized by pyrexia and respiratory signs. Like other influenza A viruses, antigenic drift or shift could lead to a ...vaccine-induced immunity breakdown if vaccine strains are not updated. The aim of this study was to genetically characterize EIV strains circulating in Italy, detected in PCR-positive samples collected from suspected cases, especially in the absence of formal active surveillance.
Between February and April 2019, blood samples and nasal swabs collected from each of the 20 symptomatic horses from North and Central Italy were submitted to the National Reference Centre for Equine Diseases in Italy to confirm preliminary analysis performed by other laboratories.
None of the sera analysed using haemagglutination inhibition and single radial haemolysis presented a predominant serological reactivity pattern for any antigen employed. All nasal swabs were positive with IAV RRT-PCR. Only one strain, isolated in an embryonated chicken egg from a sample collected from a horse of a stable located in Brescia, Lombardy, was identified as H3N8 Florida lineage clade 1 (FC1). In the constructed phylogenetic trees, this strain is located within the FC1, together with the virus isolated in France in 2018 (MK501761).
This study reports the first detection of H3N8 FC1 in Italy, highlighting the importance of monitoring circulating EIV strains to verify the vaccine composition appropriateness for maximum efficacy.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Abstract
PdCoO
2
layered delafossite is the most conductive compound among metallic oxides, with a room-temperature resistivity of nearly
$$2\,\mu \Omega \,{{{\rm{cm}}}$$
2
μ
Ω
cm
, corresponding to ...a mean free path of about 600 Å. These values represent a record considering that the charge density of PdCoO
2
is three times lower than copper. Although its notable electronic transport properties, PdCoO
2
collective charge density modes (i.e. surface plasmons) have never been investigated, at least to our knowledge. In this paper, we study surface plasmons in high-quality PdCoO
2
thin films, patterned in the form of micro-ribbon arrays. By changing their width
W
and period 2
W
, we select suitable values of the plasmon wavevector
q
, experimentally sampling the surface plasmon dispersion in the mid-infrared electromagnetic region. Near the ribbon edge, we observe a strong field enhancement due to the plasmon confinement, indicating PdCoO
2
as a promising infrared plasmonic material.
The emergence of
as the main agent of antibiotic-associated diarrhoea has raised concerns about its potential zoonotic role in different animal species. The use of antimicrobials is a major risk ...factor for
infection. Here, we provide data on
infection in dairy and beef calves in Umbria, a region in central Italy. This cross-sectional study focuses on prevalence, risk factors, ribotypes, toxinotypes and antimicrobial resistance profiles of circulating ribotypes. A prevalence of 19.8% (CI95%, 12-27.6%) positive farms was estimated, and the prescription of penicillins on the farms was associated with
detection (OR = 5.58). Eleven different ribotypes were found, including the ST11 sublineages RT-126 and -078, which are also commonly reported in humans. Thirteen isolates out of 17 showed resistance to at least one of clindamycin, moxifloxacin, linezolid and vancomycin. Among them, multiple-drug resistance was observed in two isolates, belonging to RT-126. Furthermore, RT-126 isolates were positive for tetracycline resistance determinants, confirming that tetracycline resistance is widespread among ST11 isolates from cattle. The administration of penicillins increased the risk of
in calves: this, together with the recovery of multi-resistant strains, strongly suggests the need for minimising antibiotic misuse on cattle farms.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Among the causes of bee colony death, viruses are among the number of pathogens that can contribute to the ill health of a colony. This study focuses on two of the several honeybee viruses, Slow Bee ...Paralysis Virus-1 (SBPV-1) and Deformed Wing Virus B (DWV-B), both belonging to the Iflavirus genus. To date, there is limited information available on the presence of these viruses in Italy. For this research project (IZS LT 04/19 RC), funded by the Ministry of Health, the presence and positivity of several honeybee viruses were evaluated in Italy using molecular methods. Convenience sampling was used, and these samples were analyzed for the two viruses and/or other main honeybee viruses, using specific PCR protocols and Sanger sequencing when necessary. A statistical analysis was conducted to study the independence between the viruses. Our data demonstrate for the first time the presence of SBPV-1 in Italian territory with a rather low number in most of the regions investigated, except for Emilia-Romagna and Lazio where it was detected more frequently, while DWV-B was detected at a higher level in all the regions investigated.
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