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David R. Smith

Bio: David R. Smith is an academic researcher from Duke University. The author has contributed to research in topics: Metamaterial & Antenna (radio). The author has an hindex of 110, co-authored 881 publications receiving 91683 citations. Previous affiliations of David R. Smith include Brunel University London & Princeton University.


Papers
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Journal ArticleDOI
TL;DR: In this article, the authors present experimental measurements of three and four-wave mixing phenomena in an artificially structured nonlinear magnetic metacrystal at microwave frequencies, and the sum frequency generation signal for the varactor-loaded split-ring resonator (VLSRR) metamaterial agrees quantitatively with that predicted using an analytical effective medium model describing the VLSRR medium.
Abstract: We present experimental measurements of three- and four-wave mixing phenomena in an artificially structured nonlinear magnetic metacrystal at microwave frequencies. The sum frequency generation signal for the varactor-loaded split-ring resonator (VLSRR) metamaterial agrees quantitatively with that predicted using an analytical effective medium model describing the VLSRR medium. A resonant enhancement of the nonlinear response is observed near the metamaterial resonance.

40 citations

Journal ArticleDOI
20 Dec 2018
TL;DR: In this paper, the authors investigate the coherence of a phaseless imaging system based on metasurface apertures, which can generate a multitude of distinct speckle fields at a single frequency by modulating the electrical properties of complementary metamaterial elements patterned into the surface of a waveguide.
Abstract: Phase information and spatially coherent illumination have usually been considered indispensable components of most microwave imaging systems. Dynamic metasurface apertures (DMAs)—with their ability to generate spatially incoherent illumination—have recently supplanted these assumptions in favor of simplified imaging hardware. In light of this development, we investigate the coherence of a phaseless imaging system based on metasurface apertures. In doing so, we propose and experimentally demonstrate coherent and incoherent computational microwave ghost imaging using DMAs. These apertures can generate a multitude of distinct speckle fields at a single frequency by modulating the electrical properties of radiating complementary metamaterial elements patterned into the surface of a waveguide. We show that a pair of dynamic apertures, one acting as transmit and the other as receive, can achieve two-dimensional, phaseless, coherent imaging. Further, by averaging the intensity measurements obtained in this manner over a random set or ensemble of receive aperture distributions, we demonstrate that an incoherent imaging system can be achieved in which single-port ensemble averaging by the electrically large DMA plays the role of spatial averaging in a bucket detector. We investigate the effects of these different imaging schemes on the resulting reconstructions and provide experimental demonstrations.

40 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a new method for computing the electromagnetic properties of a finite photonic band gap (PBG) structure, which is based on the Green tensor technique in the frequency domain.
Abstract: The electromagnetic (EM) properties of infinitely periodic dielectric and metallic systems have been studied extensively in the context of photonic band gap (PBG) structures [1,2], where powerful numerical methods exist that take advantage of the periodicity. Any physical realization of a PBG structure, however, is finite, and thus will have electromagnetic properties and phenomena distinct from an infinite structure. Such phenomena may include surface modes, sensitivity to boundary termination, or band-edge resonances [3 ‐ 5]. The objective of this Letter is twofold. First, we present a new method of computing the EM properties of a finite PBG structure. Second, we use this approach to study an array of finite-height dielectric cylinders on a substrate, illuminated with an evanescent field. This geometry was chosen to demonstrate the versatility of the scattering method, since it is a nontrivial three-dimensional finite system with open boundary conditions. Furthermore, this configuration is accessible experimentally, requiring only a single PBG layer which could readily be fabricated by lithographic methods. Accurate numerical methods previously reported for calculating the properties of finite PBG structures include modal method [6], finite difference time domain [7], transfer matrix [8,9], and repeated supercell [10]. Our method uses a scattering solution to obtain the EM modes and modes density associated with an arbitrary finite PBG region. The scattering solution is based on the Green’s tensor technique in the frequency domain. Let us consider a scattering system «sr; vd embedded in an infinite homogeneous background «Bsvd like the finite sn 3 md lattice of infinite cylinders shown in Fig. 1(a). We assume harmonic fields with the usual expf2ivtg dependence. When the system is illuminated by an incident field E 0 sr; vd, the total electric field Esr; vd is a solution of the Fredholm equation of the second kind, Esr; vd › E 0 sr; vd

39 citations

Journal ArticleDOI
TL;DR: Adenosine should be recognized as a potentially dangerous intervention in patients with atrial flutter and if it is used for diagnostic purposes, resuscitative equipment should be readily available.

39 citations

Journal ArticleDOI
12 Aug 2011-Sensors
TL;DR: The recently developed technique of transformation optics is applied to a lesser-known refractive Luneburg lens and the design with a metamaterial composed of a semi-crystalline distribution of holes drilled in a dielectric is implemented.
Abstract: The Luneburg lens is a powerful imaging device, exhibiting aberration free focusing for parallel rays incident from any direction. However, its advantages are offset by a focal surface that is spherical and thus difficult to integrate with standard planar detector and emitter arrays. Using the recently developed technique of transformation optics, it is possible to transform the curved focal surface to a flat plane while maintaining the perfect focusing behavior of the Luneburg over a wide field of view. Here we apply these techniques to a lesser-known refractive Luneburg lens and implement the design with a metamaterial composed of a semi-crystalline distribution of holes drilled in a dielectric. In addition, we investigate the aberrations introduced by various approximations made in the implementation of the lens. The resulting design approach has improved mechanical strength with small aberrations and is ideally suited to implementation at infrared and visible wavelengths.

39 citations


Cited by
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Journal ArticleDOI

[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1(PfPMP1)与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员,通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

18,940 citations

Journal ArticleDOI
TL;DR: A review of gold nanoparticles can be found in this article, where the most stable metal nanoparticles, called gold colloids (AuNPs), have been used for catalysis and biology applications.
Abstract: Although gold is the subject of one of the most ancient themes of investigation in science, its renaissance now leads to an exponentially increasing number of publications, especially in the context of emerging nanoscience and nanotechnology with nanoparticles and self-assembled monolayers (SAMs). We will limit the present review to gold nanoparticles (AuNPs), also called gold colloids. AuNPs are the most stable metal nanoparticles, and they present fascinating aspects such as their assembly of multiple types involving materials science, the behavior of the individual particles, size-related electronic, magnetic and optical properties (quantum size effect), and their applications to catalysis and biology. Their promises are in these fields as well as in the bottom-up approach of nanotechnology, and they will be key materials and building block in the 21st century. Whereas the extraction of gold started in the 5th millennium B.C. near Varna (Bulgaria) and reached 10 tons per year in Egypt around 1200-1300 B.C. when the marvelous statue of Touthankamon was constructed, it is probable that “soluble” gold appeared around the 5th or 4th century B.C. in Egypt and China. In antiquity, materials were used in an ecological sense for both aesthetic and curative purposes. Colloidal gold was used to make ruby glass 293 Chem. Rev. 2004, 104, 293−346

11,752 citations

Journal ArticleDOI
14 Aug 2003-Nature
TL;DR: By altering the structure of a metal's surface, the properties of surface plasmons—in particular their interaction with light—can be tailored, which could lead to miniaturized photonic circuits with length scales that are much smaller than those currently achieved.
Abstract: Surface plasmons are waves that propagate along the surface of a conductor. By altering the structure of a metal's surface, the properties of surface plasmons--in particular their interaction with light--can be tailored, which offers the potential for developing new types of photonic device. This could lead to miniaturized photonic circuits with length scales that are much smaller than those currently achieved. Surface plasmons are being explored for their potential in subwavelength optics, data storage, light generation, microscopy and bio-photonics.

10,689 citations

Journal ArticleDOI
01 Apr 1988-Nature
TL;DR: In this paper, a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) is presented.
Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

9,929 citations