Theory of Impedance Loaded Loop Antennas and Nano-Rings from RF to Optical Wavelengths

The analytical theory of perfectly conducting thin-wire closed-loop antennas with multiple loads in the periphery was formally derived in the 1950s and 1960s. In this paper, it is extended to loop antennas and nanorings for use in communications, in the “Internet of things,” and as metamaterials. The new derivation relies on recent work from 2013 that incorporates the surface impedance of metal wires into the standard theory, thus pushing its applicability into the gigahertz, terahertz, and optical regimes. Surface impedance effects cause losses and phase shifts in the current within the loop, which in turn cause wavelength scaling and degradation of signal strength. These effects are modeled using a critical point transition model of permittivity and of the index of refraction. The new results therefore extend standard loop antenna theory so that it now includes characteristics of multiply loaded loops over a very broad spectrum from radio frequencies to the optical region. The new model is verified using modern simulation tools. The examples given here include resistive and capacitive loading

The Physics and Mathematical Theory of Nano-Scaled Ring Resonators and Loop Antennas

This thesis is based on the realisation that no analytical theory of loop antennas and rings exists that is at once applicable to the Radio Frequency (RF), Micro-wave (MW), TeraHertz (THz), Infra-red (IR), and Optical (OR) regions. Nor is there any Electrical Engineering circuit model, rigorously developed from the results of that theory, that generates results which match numerical simulations and experimental work in the literature across all of these regimes. This thesis fills that gap. Maxwell’s equations for perfectly conducting, closed circular loops are presented, and then solved, using standard RF andMWantenna theory. The governing equation is then extended to include real, lossy metals with focus on the noble metals, gold, silver and copper. The solution to the extended equation yields results for rings in the THZ, IR and OR. Next, the governing equation is extended to include a single impedance on the periphery. The solution is studied using a capacitive reactance, in particular. These results are compared to simulations of illuminated rings with a single gap, and a relationship is developed between the width of the gap and its capacitive reactance. Primary results are these: • An analytical set of mathematical functions derived from Maxwell’s equations now exist that give the current distribution on closed and single gapped loops at all frequency regimes from the RF through OR, constructed of any metal for which the index of refraction is known. • A detailed RLC circuit model has been derived from these functions, accurate at all frequency bands, from which the total R, L and C of the loop at any frequency or wavelength, and the R, L and C of any modal resonance, can be calculated. The model yields the functions R(w), L(w), C(w) from which radiation resistance, power loss, radiation efficiency, radar cross-section, and the quality factor (Q) of any resonance can be calculated. • The input impedance of the circuit model representing the loop can be calculated as a function of wavelength for closed loops and single gap loops. • The introduction of a single gap in the periphery of a loop will cause a very high-Q resonance in the sub-wavelength region. This is due to the zero-order mode inductance of the loop resonating with a combination of the gap capacitance and the closed loop capacitance. The Q is on the order of several thousand. • Gap width and capacitance value of the gap are closely related. However, none of the simple models suggested in the literature, such as the flat-plate capacitance model, generates the correct relationship, at least for gaps in rings

Far-Field Radiation Properties of Impedance-Loaded Loop Antennas from RF to Optical Frequencies

Impedance loading of antennas has been of interest for more than half a century due to its ability to fundamentally change an antenna’s operating characteristics. Variable reactive loading can be employed for configurability of the frequency response, polarization and far-field properties of an antenna. Closed-form expressions for the current and input impedance of a thin-wire loop antenna with loads in the periphery were derived in the RF and optical regimes in 1965 and 2017, respectively. Meanwhile, closed-form far-field radiation properties of circular loop antennas in the RF and optical regimes were derived in 1996 and 2017. This paper extends this theory to provide closed-form analytical expressions for the far-field radiation properties of impedance loaded loop antennas valid from the RF to the optical regimes. The expressions are validated by comparison with commercial simulation tools. In addition, a beam steering example is presented as a potential application of the theory

Design and Optimization of Radiation Pattern Reconfigurable Nanoloop Antennas

The loading of antennas greatly expands the design space by making otherwise challenging performance goals more easily realizable. It is demonstrated that the pairing of the analytical theory of loop antennas with a powerful global optimizer can achieve designs that offer significant radiation pattern shaping in both the RF and optical regimes

Immunological profile in a family with nephrogenic diabetes insipidus with a novel 11 kb deletion in AVPR2 and ARHGAP4 genes

<p>Abstract</p> <p>Background</p> <p>Congenital nephrogenic diabetes insipidus (NDI) is characterised by an inability to concentrate urine despite normal or elevated plasma levels of the antidiuretic hormone arginine vasopressin. We report a Japanese extended family with NDI caused by an 11.2-kb deletion that includes the entire <it>AVPR2 </it>locus and approximately half of the <it>Rho GTPase-activating protein 4 </it>(<it>ARHGAP4</it>) locus. ARHGAP4 belongs to the RhoGAP family, Rho GTPases are critical regulators of many cellular activities, such as motility and proliferation which enhances intrinsic GTPase activity.</p> <p>ARHGAP4 is expressed at high levels in hematopoietic cells, and it has been reported that an NDI patient lacking <it>AVPR2 </it>and all of <it>ARHGAP4 </it>showed immunodeficiency characterised by a marked reduction in the number of circulating CD3+ cells and almost complete absence of CD8+ cells.</p> <p>Methods</p> <p>PCR and sequencing were performed to identify the deleted region in the Japanese NDI patients. Immunological profiles of the NDI patients were analysed by flow cytometry. We also investigated the gene expression profiles of peripheral blood mononuclear cells (PBMC) from NDI patients and healthy controls in microarray technique.</p> <p>Results</p> <p>We evaluated subjects (one child and two adults) with 11.2-kb deletion that includes the entire <it>AVPR2 </it>locus and approximately half of the <it>ARHGAP4</it>. Hematologic tests showed a reduction of CD4+ cells in one adult patient, a reduction in CD8+ cells in the paediatric patient, and a slight reduction in the serum IgG levels in the adult patients, but none of them showed susceptibility to infection. Gene expression profiling of PBMC lacking <it>ARHGAP4 </it>revealed that expression of RhoGAP family genes was not influenced greatly by the lack of <it>ARHGAP4</it>.</p> <p>Conclusion</p> <p>These results suggest that loss of <it>ARHGAP4 </it>expression is not compensated for by other family members. ARHGAP4 may play some role in lymphocyte differentiation but partial loss of <it>ARHGAP4 </it>does not result in clinical immunodeficiency.</p

Core components for effective infection prevention and control programmes: new WHO evidence-based recommendations

Abstract Health care-associated infections (HAI) are a major public health problem with a significant impact on morbidity, mortality and quality of life. They represent also an important economic burden to health systems worldwide. However, a large proportion of HAI are preventable through effective infection prevention and control (IPC) measures. Improvements in IPC at the national and facility level are critical for the successful containment of antimicrobial resistance and the prevention of HAI, including outbreaks of highly transmissible diseases through high quality care within the context of universal health coverage. Given the limited availability of IPC evidence-based guidance and standards, the World Health Organization (WHO) decided to prioritize the development of global recommendations on the core components of effective IPC programmes both at the national and acute health care facility level, based on systematic literature reviews and expert consensus. The aim of the guideline development process was to identify the evidence and evaluate its quality, consider patient values and preferences, resource implications, and the feasibility and acceptability of the recommendations. As a result, 11 recommendations and three good practice statements are presented here, including a summary of the supporting evidence, and form the substance of a new WHO IPC guideline

The pathogenesis of low pathogenicity H7 avian influenza viruses in chickens, ducks and turkeys

<p>Abstract</p> <p>Background</p> <p>Avian influenza (AI) viruses infect numerous avian species, and low pathogenicity (LP) AI viruses of the H7 subtype are typically reported to produce mild or subclinical infections in both wild aquatic birds and domestic poultry. However relatively little work has been done to compare LPAI viruses from different avian species for their ability to cause disease in domestic poultry under the same conditions. In this study twelve H7 LPAI virus isolates from North America were each evaluated for their comparative pathogenesis in chickens, ducks, and turkeys.</p> <p>Results</p> <p>All 12 isolates were able to infect all three species at a dose of 10⁶50% egg infectious doses based on seroconversion, although not all animals seroconverted with each isolate-species combination. The severity of disease varied among isolate and species combinations, but there was a consistent trend for clinical disease to be most severe in turkeys where all 12 isolates induced disease, and mortality was observed in turkeys exposed to 9 of the 12 viruses. Turkeys also shed virus by the oral and cloacal routes at significantly higher titers than either ducks or chickens at numerous time points. Only 3 isolates induced observable clinical disease in ducks and only 6 isolates induced disease in chickens, which was generally very mild and did not result in mortality. Full genome sequence was completed for all 12 isolates and some isolates did have features consistent with adaptation to poultry (e.g. NA stalk deletions), however none of these features correlated with disease severity.</p> <p>Conclusions</p> <p>The data suggests that turkeys may be more susceptible to clinical disease from the H7 LPAI viruses included in this study than either chickens or ducks. However the severity of disease and degree of virus shed was not clearly correlated with any isolate or group of isolates, but relied on specific species and isolate combinations.</p

Rheo-PIV of a shear-banding wormlike micellar solution under large amplitude oscillatory shear

We explore the behavior of a wormlike micellar solution under both steady and large amplitude oscillatory shear (LAOS) in a cone–plate geometry through simultaneous bulk rheometry and localized velocimetric measurements. First, particle image velocimetry is used to show that the shear-banded profiles observed in steady shear are in qualitative agreement with previous results for flow in the cone–plate geometry. Then under LAOS, we observe the onset of shear-banded flow in the fluid as it is progressively deformed into the non-linear regime—this onset closely coincides with the appearance of higher harmonics in the periodic stress signal measured by the rheometer. These harmonics are quantified using the higher-order elastic and viscous Chebyshev coefficients e [subscript n] and v [subscript n] , which are shown to grow as the banding behavior becomes more pronounced. The high resolution of the velocimetric imaging system enables spatiotemporal variations in the structure of the banded flow to be observed in great detail. Specifically, we observe that at large strain amplitudes (γ [subscript 0] ≥ 1), the fluid exhibits a three-banded velocity profile with a high shear rate band located in-between two lower shear rate bands adjacent to each wall. This band persists over the full cycle of the oscillation, resulting in no phase lag being observed between the appearance of the band and the driving strain amplitude. In addition to the kinematic measurements of shear banding, the methods used to prevent wall slip and edge irregularities are discussed in detail, and these methods are shown to have a measurable effect on the stability boundaries of the shear-banded flow.Spain. Ministerio de Educación y Ciencia (MEC) (Project FIS2010-21924-C02-02

Allelic Origin of Protease-Sensitive and Protease-Resistant Prion Protein Isoforms in Gerstmann-Sträussler-Scheinker Disease with the P102L Mutation

Gerstmann-Sträussler-Scheinker (GSS) disease is a dominantly inherited prion disease associated with point mutations in the Prion Protein gene. The most frequent mutation associated with GSS involves a proline-to-leucine substitution at residue 102 of the prion protein, and is characterized by marked variability at clinical, pathological and molecular levels. Previous investigations of GSS P102L have shown that disease-associated pathological prion protein, or PrPSc, consists of two main conformers, which under exogenous proteolysis generates a core fragment of 21 kDa and an internal fragment of 8 kDa. Both conformers are detected in subjects with spongiform degeneration, whereas only the 8 kDa fragment is recovered in cases lacking spongiosis. Several studies have reported an exclusive derivation of protease-resistant PrPSc isoforms from the mutated allele; however, more recently, the propagation of protease-resistant wild-type PrPSc has been described. Here we analyze the molecular and pathological phenotype of six GSS P102L cases characterized by the presence of 21 and 8 kDa PrP fragments and two subjects with only the 8 kDa PrP fragment. Using sensitive protein separation techniques and Western blots with antibodies differentially recognizing wild-type and mutant PrP we observed a range of PrPSc allelic conformers, either resistant or sensitive to protease treatment in all investigated subjects. Additionally, tissue deposition of protease-sensitive wild-type PrPSc molecules was seen by conventional PrP immunohistochemistry and paraffin-embedded tissue blot. Our findings enlarge the spectrum of conformational allelic PrPSc quasispecies propagating in GSS P102L thus providing a molecular support to the spectrum of disease phenotypes, and, in addition, impact the diagnostic role of PrP immunohistochemistry in prion diseases