The Design and Analysis of a Novel Split-H-Shaped Metamaterial for Multi-Band Microwave Applications

This paper presents the design and analysis of a novel split-H-shaped metamaterial unit cell structure that is applicable in a multi-band frequency range and that exhibits negative permeability and permittivity in those frequency bands. In the basic design, the separate split-square resonators are joined by a metal link to form an H-shaped unit structure. Moreover, an analysis and a comparison of the 1 × 1 array and 2 × 2 array structures and the 1 × 1 and 2 × 2 unit cell configurations were performed. All of these configurations demonstrate multi-band operating frequencies (S-band, C-band, X-band and K_u-band) with double-negative characteristics. The equivalent circuit model and measured result for each unit cell are presented to validate the resonant behavior. The commercially available finite-difference time-domain (FDTD)-based simulation software, Computer Simulation Technology (CST) Microwave Studio, was used to obtain the reflection and transmission parameters of each unit cell. This is a novel and promising design in the electromagnetic paradigm for its simplicity, scalability, double-negative characteristics and multi-band operation.     

A Thin C-Band Polarization and Incidence Angle-Insensitive Metamaterial Perfect Absorber

A novel metamaterial absorber design able to operate in the C frequency band is presented, along with an analysis and a method to improve both its bandwidth and its angular stability. Simulation results for a FR4-based design are shown for comparison with existing designs. In addition, a simplified equivalent circuit is provided for a better understanding of the great angular stability and wide bandwidth exhibited by the proposed structure. Moreover, simulations, manufacturing and measurements of a thinner and more flexible metamaterial absorber, keeping the angular stability of the former one, while providing a wide bandwidth, are presented.     

A Near Zero Refractive Index Metamaterial for Electromagnetic Invisibility Cloaking Operation

The paper reveals the design of a unit cell of a metamaterial that shows more than 2 GHz wideband near zero refractive index (NZRI) property in the C-band region of microwave spectra. The two arms of the unit cell were splitted in such a way that forms a near-pi-shape structure on epoxy resin fiber (FR-4) substrate material. The reflection and transmission characteristics of the unit cell were achieved by utilizing finite integration technique based simulation software. Measured results were presented, which complied well with simulated results. The unit cell was then applied to build a single layer rectangular-shaped cloak that operates in the C-band region where a metal cylinder was perfectly hidden electromagnetically by reducing the scattering width below zero. Moreover, the unit cell shows NZRI property there. The experimental result for the cloak operation was presented in terms of S-parameters as well. In addition, the same metamaterial shell was also adopted for designing an eye-shaped and triangular-shaped cloak structure to cloak the same object, and cloaking operation is achieved in the C-band, as well with slightly better cloaking performance. The novel design, NZRI property, and single layer C-band cloaking operation has made the design a promising one in the electromagnetic paradigm.     

A Miniaturized Antenna with Negative Index Metamaterial Based on Modified SRR and CLS Unit Cell for UWB Microwave Imaging Applications

A miniaturized antenna employing a negative index metamaterial with modified split-ring resonator (SRR) and capacitance-loaded strip (CLS) unit cells is presented for Ultra wideband (UWB) microwave imaging applications. Four left-handed (LH) metamaterial (MTM) unit cells are located along one axis of the antenna as the radiating element. Each left-handed metamaterial unit cell combines a modified split-ring resonator (SRR) with a capacitance-loaded strip (CLS) to obtain a design architecture that simultaneously exhibits both negative permittivity and negative permeability, which ensures a stable negative refractive index to improve the antenna performance for microwave imaging. The antenna structure, with dimension of 16 × 21 × 1.6 mm³, is printed on a low dielectric FR4 material with a slotted ground plane and a microstrip feed. The measured reflection coefficient demonstrates that this antenna attains 114.5% bandwidth covering the frequency band of 3.4–12.5 GHz for a voltage standing wave ratio of less than 2 with a maximum gain of 5.16 dBi at 10.15 GHz. There is a stable harmony between the simulated and measured results that indicate improved nearly omni-directional radiation characteristics within the operational frequency band. The stable surface current distribution, negative refractive index characteristic, considerable gain and radiation properties make this proposed negative index metamaterial antenna optimal for UWB microwave imaging applications.     

New preformed catheter and method for retrograde left atrial or complete left heart catheterization

Employing a new catheter and technique complete retrograde left heart catheterization was accomplished in 96 of 100 consecutive patients. These 96 patients included 37 with ischemic heart disease, 13 of 17 with isolated aortic valve deformities, 11 with isolated rheumatic mitral valve deformities, 10 with combined rheumatic aortic and mitral valve deformities, and 25 with other problems. The only failures were in 4 (of 27) patients with aortic valve deformities. No untoward complications occurred. The retrograde catheterization fluoroscopy time was usually less than 2 minutes. The shortest time was 44 seconds, the longest, 6 minutes and 2 seconds. These data indicate that this new catheterization method achieves safe, reliable (when the aortic valve is not deformed), simple, and rapid complete left heart catheterization. They further indicate it may be useful in assessing patients with mitral stenosis, pulmonary hypertension, hypertrophic obstructive cardiomyopathy, and left-to-right shunt problems.     

A New Approach for Potential Combined Chelation Therapy Using Mono- and Bis-Hydroxypyridinones

Iron (Fe) overload diseases, such as β-thalassemia (thal) major and hemochromatosis, have been treated for several decades by chelating therapy with desferrioxamine (DFO). However, drawbacks associated with that drug led to the development of new chelating drugs. The 3-hydroxy-4-pyridinones emerged as highly effective Fe chelators, and deferiprone (L1) has been approved as a Fe chelating drug. The most recent strategy for Fe overload problems is based on the replacement of monotherapies by a combination therapy with both chelators. Following a similar chelating strategy, we present herein the results of animal tests with a combination of two different hydroxypyridinone-based chelators. Both are of the 3-hydroxy-4-pyridinone (HP) type, but with one and two HP chelating units, and extra functional groups to account for differentiation in their physicochemical and biological properties, namely chelating efficacy and bioavailability. Animal studies have shown that the simultaneous administration of this pair of HP chelators, under appropriate proportion, to metal-loaded mice, could speed up metal excretion. This may be rationalized by adjuvant and eventual synergistic effects, due to complementary accessibility of each chelator to different cellular compartments.     

A New Era in Iron Chelation Therapy: The Design of Optimal,Individually Adjusted Iron Chelation Therapies for the Complete Removal of Iron Overload in Thalassemia and other Chronically Transfused Patients

A new era in iron chelation therapy began with the successful removal of excess iron load and the maintenance of normal iron stores in thalassemia patients using the International Committee on Chelation (ICOC) protocols. This achievement was based on two phases, firstly the introduction of deferiprone (L1) (80–100 mg/kg/day) and deferoxamine (DFO) (40–60 mg/kg at least 3 days per week) combination therapy, which appears to progressively remove all excess storage iron and thereafter by the introduction of L1 monotherapy that can maintain physiological range levels of serum ferritin, cardiac and liver magnetic resonance imaging (MRI) T2*. This new development is likely to change current practices and set a new gold standard in the treatment of transfusional iron loaded patients leading to an increased survival and the change of thalassemia from a fatal to a chronic disease. A major aspect of the improved therapies is the ability of L1 to mobilize and remove excess cardiac iron and reduce congestive cardiac failure, which is the main cause of death in thalassemia patients. Further, new developments include the use of alternating sequential chelation therapies and selected dose protocols with L1, DFO and deferasirox (DFRA) for overcoming toxicity and efficacy complications observed in some patients treated with monotherapies or combination therapies. The selection and adjustment of dose protocols is crucial for providing optimum chelation therapy for each individual patient.