Effect of imperfect flat earth on the vertically polarized radiation of a cylindrical reflector antenna

Cataloged from PDF version of article.The radiation of a circular cylindrical reflector antenna in the presence of imperfect flat earth is treated in an accurate manner. The boundary value problem is formulated in terms of a full-wave integral equation converted to the dual-series equations and then regularized by using analytical inversion of the static part. The resulting Fredholm second-kind matrix equation is solved numerically with guaranteed accuracy. The feed directivity is included in the analysis by using the complex source-point method. Various antenna features, which include the overall directivity, efficiency, gain, and radiated and absorbed power fractions have been calculated and compared with the free-space antenna characteristics. They show some phenomena not predicted by approximate techniques

Characterisation and modelling of water wicking and evaporation in capillary porous media for passive and energy-efficient applications

Passive devices based on water wicking and evaporation offer a robust, cheap, off-grid, energy-efficient and sustainable alternative to a wide variety of applications, ranging from personal thermal management to water treatment, from filtration to sustainable cooling technologies. Among the available, highly-engineered materials currently employed for these purposes, polyethylene-based fabrics offer a promising alternative thanks to the precise control of their fabrication parameters, their light-weight, thermal and mechanical properties, chemical stability and sustainability. As such, both woven and non-woven fabrics are commonly used in capillary-fed devices, and their wicking properties have been extensively modelled relying on analytical equations. However, a comprehensive and flexible modelling framework able to investigate and couple all the heat and mass transfer phenomena regulating the water dynamics in complex 2-D and 3-D porous components is currently missing. This work presents a comprehensive theoretical model aimed to investigate the wetting and drying performance of hydrophilic porous materials depending on their structural properties and on the external environmental conditions. The model is first validated against experiments (R2=0.99 for the wicking model; errors lower than 14% and 1% for the evaporation and radiative models, respectively), then employed in three application cases: the characterisation of the capillary properties of a novel textile; the assessment of the thermal performance of a known material for personal thermal management when used in different conditions; the model-assisted design of a porous hydrophilic component of passive devices for water desalination. The obtained results showed a deep interconnection between the different heat and mass transfer mechanisms, the porous structure and external working conditions. Thus, modelling their non-linear behaviour plays a crucial role in determining the optimal material characteristics to maximise the performance of porous materials for passive devices for the energy and water sector

Electrically tunable near-field radiative heat transfer via ferroelectric materials

We explore ways to actively control near-field radiative heat transfer between two surfaces that relies on electrical tuning of phonon modes of ferroelectric materials. Ferroelectrics are widely used for tunable electrical devices, such as capacitors and memory devices; however, their tunable properties have not yet been examined for heat transfer applications. We show via simulations that radiative heat transfer between two ferroelectric materials can be enhanced by over two orders of magnitude over the blackbody limit in the near field, and can be tuned as much as 16.5% by modulating the coupling between surface phonon polariton modes at the two surfaces via varying external electric fields. We then discuss how to maximize the modulation contrast for tunable thermal devices using the studied mechanism.United States. Dept. of Energy. Office of Basic Energy Sciences (DE-FG02-02ER45977

Иммуноглобулины в неврологической практике: обзор литературы

Today intravenous immunoglobulins are used increasingly in the management of patients with neurological conditions. The efficacy and safety of intravenous immunoglobulins treatment in chronic inflammatory demyelinating polyradiculoneuropathy, Guillain–Barre syndrome and multifocal motor neuropathy have been established in randomized controlled trials and declared in systematic reviews. There are discussions about the dose, timing, duration and necessity of repeated infusions in these disorders. The intravenous immunoglobulins treatment is an option in myasthenia gravis crisis and exacerbations the disease, stiff-person syndrome, a second-line therapy in dermatomyositis and some patients with polymyositis. The use of intravenous immunoglobulins in patients with multiple sclerosis, inclusion body myositis, resistant epilepsy is not finally proved. The review discussed the data of immunoglobulins efficacy in neurological disorders based on informative studies with an emphasis on the main criteria for choosing a drug for effective high-dose intravenous immunotherapy. Сегодня высокодозная терапия иммуноглобулинами человека получает все большее распространение в лечении болезней нервной системы. Эффективность и безопасность использования иммуноглобулинов доказана в рандомизированных контролируемых исследованиях у пациентов с хронической воспалительной демиелинизирующей полинейропатией, синдромом Гийена–Барре, мультифокальной моторной нейропатией, что отражено в систематических обзорах. Обсуждаются вопросы о дозах, интервалах и продолжительности лечения и необходимости повторных инфузий при этих состояниях. Использование высокодозной терапии иммуноглобулинами является опцией при миастенических кризах и обострениях миастении гравис, синдроме ригидного человека, а также терапией 2-й линии при дерматомиозите и в некоторых случаях при полимиозите. Применение иммуноглобулинов при рассеянном склерозе, миозите с включениями, резистентной эпилепсии остается не до конца обоснованной. В обзоре обсуждается эффективность высокодозной терапии иммуноглобулинами в неврологии на основании информативных исследований, с учетом основных критериев выбора препарата для адекватной внутривенной иммунотерапии

The role of the ultrasound examination of the brachial plexus in thoracic outlet syndrome

Introduction. Difficulties in determining the compression of the neurovascular bundle with the thoracic outlet syndrome raises the question of finding an accessible and reproducible method for the neuroimaging of the brachial plexus and surrounding tissues.Purpose of the study – to develop an ultrasound diagnostic algorithm using a stress test to determine the level and cause of brachial plexus compression in comparison with the results of a clinical assessment.Materials and methods. 111 patients with verified compression of the brachial plexus at the level of the interstitial (65.7 %) and bone-clavicular space (21.6 %), as well as the tendon of the pectoralis minor muscle (12.6 %) were examined. The study protocol including the Adson ultrasound stress test, the assessment of the lower trunk in the interstitial space, and the test with ultrasound evaluation of the axillary artery at the level of the tendon of the pectoralis minor muscle with passive abduction of the arm back and up was used.Conclusion. An ultrasound study of the brachial plexus demonstrated informativeness in assessing the level and possible cause of compression, which opens up the possibility of using the method in routine neurological practice

Sustainable polyethylene fabrics with engineered moisture transport for passive cooling

Polyethylene (PE) has emerged recently as a promising polymer for incorporation in wearable textiles owing to its high infrared transparency and tuneable visible opacity, which allows the human body to cool via thermal radiation, potentially saving energy on building refrigeration. Here, we show that single-material PE fabrics may offer a sustainable, high-performance alternative to conventional textiles, extending beyond radiative cooling. PE fabrics exhibit ultra-light weight, low material cost and recyclability. Industrial materials sustainability (Higg) index calculations predict a low environmental footprint for PE fabrics in the production phase. We engineered PE fibres, yarns and fabrics to achieve efficient water wicking and fast-drying performance which, combined with their excellent stain resistance, offer promise in reducing energy and water consumption as well as the environmental footprint of PE textiles in their use phase. Unlike previously explored nanoporous PE materials, the high-performance PE fabrics in this study are made from fibres melt spun and woven on standard equipment used by the textile industry worldwide and do not require any chemical coatings. We further demonstrate that these PE fibres can be dry coloured during fabrication, resulting in dramatic water savings without masking the PE molecular fingerprints scanned during the automated recycling process

Multifrequency broadband tapered plasmonic nanoantennas

We suggest a novel multifrequency broadband plasmonic Yagi-Uda-type nanoantenna equipped with an array of tapered directors. Each director can be used for the excitation of the antenna by nanoemitters matched spectrally with the director resonant frequency and placed in the director near-field region. Multifrequency op- eration of nanoantennas provides tremendous opportunities for broadband emission enhancement, spectroscopy and sensing. By the principle of reciprocity, the same tapered nanoantenna architecture can be used both as a transmitter and/or as a receiver, thus being useful for creating a broadband wireless communication system

Photonic molecules and spectral engineering

This chapter reviews the fundamental optical properties and applications of pho-tonic molecules (PMs) - photonic structures formed by electromagnetic coupling of two or more optical microcavities (photonic atoms). Controllable interaction between light and matter in photonic atoms can be further modified and en-hanced by the manipulation of their mutual coupling. Mechanical and optical tunability of PMs not only adds new functionalities to microcavity-based optical components but also paves the way for their use as testbeds for the exploration of novel physical regimes in atomic physics and quantum optics. Theoretical studies carried on for over a decade yielded novel PM designs that make possible lowering thresholds of semiconductor microlasers, producing directional light emission, achieving optically-induced transparency, and enhancing sensitivity of microcavity-based bio-, stress- and rotation-sensors. Recent advances in material science and nano-fabrication techniques make possible the realization of optimally-tuned PMs for cavity quantum electrodynamic experiments, classical and quantum information processing, and sensing.Comment: A review book chapter: 29 pages, 19 figure