AIMS Intracoronary adenosine (ICA) yields similar fractional flow reserve (FFR) results to the "gold standard" of intravenous adenosine (IVA). Whether they have similar prognostic significance is unknown. We therefore sought to study the prognostic value of the route of adenosine administration for the measurement of FFR in deferred coronary lesions in a large, real-world cohort. METHODS AND RESULTS Five hundred and seventy-six patients with 787 lesions in whom PCI was deferred based on FFR >0.75 were studied. The primary outcome was the first major adverse cardiovascular event (MACE; defined as death, myocardial infarction [MI], or target vessel revascularisation [TVR]), and the secondary outcome was a composite of MI and target vessel failure (TVF). FFR was measured with ICA in 426 lesions and IVA in 361 lesions. Median follow-up duration was 3.2 years (interquartile range: 1.7- 4.6). Propensity-matched cohorts of ICA and IVA were well matched for baseline clinical, angiographic and haemodynamic characteristics. In the propensity-matched cohort, MACE occurred in 23.5% of the ICA group and in 22.3% of the IVA group (p=0.29). On multivariate analysis, acute coronary syndrome, FFR and prior MI/revascularisation were independent predictors of MACE and MI/TVF. The route of adenosine administration was not predictive of MACE or MI/TVF. CONCLUSIONS ICA and IVA yield similar FFR values and show comparable long-term prognostic utility in a deferred population. These findings provide confirmation that non-ischaemic FFR using a simpler ICA protocol provides prognostic data similar to the gold standard IVA.

Cardiac resynchronization therapy is known to improve clinical outcomes in patients with heart failure and left ventricular dyssynchrony. However, the optimal positioning of the right ventricular lead is unknown, and there is conflicting data on the acute hemodynamic effects and long-term outcomes. Here, we present a case of a patient who underwent implantation of a dual-chamber pacemaker for complete heart block, but who after three months, still had symptoms consistent with New York Heart Association (NYHA) Class IV heart failure. After optimal medical therapy failed and a left ventricular lead was placed, he still remained symptomatic, so the right ventricular lead was repositioned from the right ventricular outflow tract to the right ventricular apex. Afterwards, the patient's symptoms improved from NYHA Class IV to NYHA Class II, and his left ventricular ejection fraction improved from 20% to 45%.

We hereby report a solution to the problem of reflections from passive lossless refracting metasurfaces that works even at wide deflection angles. The phenomenon of reflections is due to not accounting for the local wave-impedance mismatch at the source and load faces of the metasurface; this cannot be fully mitigated even with an impedance-equalized Huygens' (IEH) metasurface. The solution is demonstrated to be enabled through the correct application of generalized, instead of canonical, scattering parameters. The canonical and IEH approaches are compared to the generalized scattering parameter approach. It is seen that though the approaches are similar at low-to-moderate levels of refraction, at wide-angle refraction only the generalized S-matrix approach is capable of good matching. This is demonstrated via full-wave simulations, for refraction from normal incidence, using an asymmetric structure comprising three cascaded admittance surfaces.

We propose a novel concept for highly-directive low-profile antennas, based on a single localized source embedded in a cavity, covered by an omega-type bianistoropic metasurface (BMS). We show that such metasurfaces, which include subwavelength particles with electric and magnetic polarizabilities, and magnetoelectric coupling, allow control of both the aperture field phase and the BMS reflection coefficient, without requiring active or lossy components. Subsequently, we use this degree of freedom to exclusively excite the highest-order fast lateral mode, guaranteeing optimal aperture illumination efficiency for arbitrarily-large apertures, without incurring edge-taper losses. We verify our semianalytical calculations with full-wave simulations, showing that the proposed antenna can outperform our previously-introduced cavity-excited Huygens' metasurface antenna, offering a simple and efficient design for compact high-gain antennas.

One of the long-standing problems in antenna engineering is the realization of highly directive beams using low-profile devices. In this paper, we provide a solution to this problem by means of Huygens’ metasurfaces (HMSs), based on the equivalence principle. This principle states that a given excitation can be transformed to a desirable aperture field by inducing suitable electric and (equivalent) magnetic surface currents. Building on this concept, we propose and demonstrate cavity-excited HMS antennas, where the single-source-fed cavity is designed to optimize aperture illumination, while the HMS facilitates the current distribution that ensures phase purity of aperture fields. The HMS breaks the coupling between the excitation and radiation spectra typical to standard partially reflecting surfaces, allowing tailoring of the aperture properties to produce a desirable radiation pattern, without incurring edge-taper losses. The proposed low-profile design yields near-unity aperture illumination efficiencies from arbitrarily large apertures, offering new capabilities for microwave, terahertz and optical radiators.

Transmitarrays and transmissive metasurfaces must efficiently couple incident power to the transmitted beam. Inefficiency is manifested in sidelobe levels, reflections, and insertion loss. The Huygens metasurface embodies the Huygens and equivalence principles, suppressing these sidelobe levels and reflections. This is accomplished with a single thin layer of Huygens sources, which contains both an electric and a magnetic response. In this paper, 2-D interfacial refraction is implemented with a scalar Huygens metasurface. The measured total efficiency is on average 71.06% for a 70° range, the maximum being 80.87% at θi=0°. Moreover, it is on average 68.64% over a fractional bandwidth of 8%, the maximum being 80.87% at 10.0 GHz. This demonstrates that the insertion loss, reflection, and sidelobe powers are low in our design. Furthermore, the questions of polarization purity, and the appropriate polarization definition for a scalar Huygens metasurface, are addressed. Our design contains only printed elements, and consists of two bonded boards, instead of many stacked interspaced layers. This simplifies fabrication, and makes it scalable to millimeter-wave frequencies and beyond. The design is also λ/9.3 thick, in contrast to traditional transmitarrays, which require 3-4 λ/4 spaced layers to obtain the same degree of phase control and matching.

A novel approach is presented to reduce the beam squinting of radiating structures with emphasis on leaky-wave antennas (LWAs). This is achieved by taking advantage of the interesting frequency-dependent variation of the generalized law of refraction in metasurfaces, in combination with the beam-squinting characteristics of LWAs dictated by their dispersion diagram. An X-band coplanar waveguide leaky-wave antenna (CPW-LWA) and a Huygens metasurface are fabricated and experimental results verify that the proposed concept can reduce the beam squinting of the LWA by 50% over a 10% bandwidth at angles around broadside. The proposed method is shown to be an excellent approach to build simple, low-profile, and lowcost communication systems composed of LWAs with low beam-squinting characteristics over a reasonably wide frequency range.

Two recently suggested 2D structures for control of electromagnetic beams are presented; the magnetic near-field antenna array and the Huygens metasurface. Opportunities and challenges in the context of medical applications are discussed.

This paper presents a novel thin metasurface for microwave refraction. The metasurface is based on the new concept of establishing orthogonal electric and magnetic currents (Huygens sources) on a surface thus physically implementing the equivalence principle. Such thin Huygens Metasurfaces can be used for refraction, focusing and general beam shaping. Here we discuss the design procedure and experimental validation of such a metasurface for 1D refraction. In contrast to previous work, the proposed metasurface does not require stacked layers, but it comprises collocated electric and magnetic dipoles printed on a single panel. This can be represented in one layer of lattice cells, and its behavior described using transmission-line theory. This makes it electrically thin and readily scalable to millimeter-wave frequencies and beyond.

The systematic design of unit cells for a Huygens metasurface, a particular class of metasurface, is presented here. The design of these unit cells uses transmission-line theory. This is validated through application to 1D refraction and Gaussian-to-Gaussian beam focusing. The 1D refraction is further validated experimentally. These applications demonstrate the practical utility of these Huygens metasurfaces. The Huygens metasurfaces presented here are printed on two bonded boards instead of many stacked, interspaced layers. This simplifies fabrication and enables the scaling down of the metasurfaces to shorter wavelengths. These two bonded boards implement a single, collocated layer of electric and magnetic dipoles. The electric and magnetic dipoles are synthesized using sub-wavelength arrays of printed elements. These printed elements can be manufactured using standard PCB fabrication techniques, and are capable of synthesizing the full range of impedances required. Furthermore, in contrast to frequency-selective surfaces (FSSs) and traditional transmitarrays, which are on the order of a wavelength thick, these designs are only λ/10 thick while incurring minimum reflections losses.

Freezing of commonly used parenteral products to increase pharmaceutical stability for cost-saving purposes is a common practice in patient care. However, frozen meropenem, a model drug, in saline has a shelf life of less than a month due to the low glass transition temperature (Tg'): below -40 degrees C When meropenem is formulated with the 2-hydroxypropyl-beta-cyclodextrin (HPBC) the shelf life ( >= 90% potency) is extrapolated to be greater than one year at -25 degrees C based on data for storage at 6 months. The mechanisms that may explain meropenem-HPBC formulation frozen stability include vitrification and/or formation of an inclusion complex. Although NMR data indicated complexation of meropenem by HPBC in a ratio of 0.6:1, inclusion was unlikely to be the mechanism as stability was not extended to the thawed solutions. Therefore, vitrification is concluded to be the stabilization mechanism. The Tg', for meropenem-HPBC (13.3%) formulation at pH 7.9 was -17.75 degrees C which was similar to that of a meropenem solution formulated with a known vitrifying agent, Dextran 40. This higher Tg' for HPBC was unexpected based on trends predicted by the Fox-Flory equation. Trial formulations containing either Dextran 1, Dextran 40, hydroxyethyl starch, or sulfobutyl-beta-cyclodextrin heptasodium (Captisol (R)) were also unable to stabilize meropenem as the Tg' values were below the frozen storage temperature. Upon 6-month storage, potency losses were -3.0% and -7.7% for meropenem frozen premix formulated in 13.3% HPBC (pH 7.9) at -25 and -20 degrees C storage, respectively; versus -31.2% and -60.8% for controls. Frozen premixes with high ionic strength (containing NaCl or Captisol (R)) and/or at pH 7.3 were also found to be unstable. (C) 2014 Elsevier B.V. All rights reserved.

Recent years have seen continued growth in the area of biologics with a majority of pharmaceutical companies developing a pipeline in next‐generation biologic products. Most biologics are administered via injectable routes of administration and often require frequent injections. Hence, delivery devices that can reduce discomfort associated with injectable delivery (both to the caregiver and the patient) are of interest as part of lifecycle management of biologic products. This chapter attempts to discuss some key features of these delivery devices for biologics (both conventional and novel) that are important for consideration in product development.