Planar Loop Research Articles

Micro-coil detection of nuclear magnetic resonance for nanofluidic samples

We have developed a novel dc SQUID system with a micro-coil input circuit to act as a local probe of quantum matter and nanosystems. The planar niobium micro-coil pickup loop is located remotely from the SQUID, coupled through a superconducting twisted pair. A high degree of coupling between the coil and the region of interest of similar dimensions (up to ∼ 100 microns) can be achieved. We report nuclear magnetic resonance (NMR) measurements to characterise the sensitivity of these coils to 3He in the gas phase at 4.2 K in a 30 mT magnetic field.

Ultra wideband loop antenna on contact with human body tissues

Human body tissues have a strong effect on the antenna operation in wireless body area networks (WBANs). In this study, the authors present the deep investigations of the effect of body tissue thicknesses on the performance of an ultra wideband (UWB) loop antenna by simulations when the antenna is operated on contact with tissues. The planar UWB loop antenna is designed for the examinations, which is targeted to be used in UWB WBAN applications. The effect of tissue thicknesses on the antenna performance is analysed and characterised in the terms of reflection coefficient S 11 , gain and total antenna efficiency, group delay, radiation patterns and specific absorption rate by simulations. A parametric layered human body tissue model with the frequency-dependent behaviour is exploited in the investigations. Further, the reflection coefficient of the presented antenna is measured in the different locations of the author's body. The main aim of these investigations is to demonstrate how the thickness of outermost body tissues affects the antenna performance.

Manifestation of Constrained Dynamics in a Low-Pressure Spark

Some features of neutron emission from dense plasma focus suggest that the participating deuterons have energy in the range of 105 eV and have a directionality of toroidal motion. Theoretical models of these devices assume that the plasma evolves through a purely irrotational flow and thus fail to predict such solenoidal flow on the scale of the plasma dimensions. Predictions of a relaxation theory are consistent with experimental data [S K H Auluck, Physics of Plasmas,18, 032508 (2011)], but the assumptions upon which it is based are not compatible with known features of these devices. There is thus no satisfactory theoretical construct which provides the necessity for solenoidal flow in these devices. This paper proposes such theoretical construct, namely, the principle of constrained dynamics, and describes an experiment which provides support for this idea. The experiment consisted of low inductance, self-breaking spark discharge in helium at a pressure ~100 hPa between two pointed electrodes separated by 30-50 mm distance kept inside a vacuum chamber mounted on a low inductance high voltage capacitor. The current derivative signal showed reproducible sharp dips at all the extrema of the damped sinusoidal discharge. A planar diamagnetic loop centered with and perpendicular to the discharge axis consistently showed a signal representing rate of change of axial magnetic flux. A qualitative explanation of observed phenomena is obtained using a simple model using the proposed principle.

A Broadband Dual-Polarized Omnidirectional Antenna for Base Stations

A broadband vertically/horizontally dual-polarized omnidirectional antenna is proposed for mobile communications. The dual-polarized antenna is a combination of a modified low-profile monopole for vertical polarization (VP) and a circular planar loop for horizontal polarization (HP). The modified low-profile monopole is a circular folded patch shorted by four tubes while the circular loop consists of four half-wavelength arc dipoles. The dual-polarized omnidirectional antenna achieves a bandwidth of ~ 25% (1.7-2.2 GHz) with an isolation of around 40 dB. The gain variations in the horizontal plane are less than 2.5 dB for VP and 1.5 dB for HP. An eight-element dual-polarized antenna array is developed for base station applications. The antenna gains of the array for both VP and HP are ~ 8 dBi with a difference of less than 1 dB. The beamwidths in the vertical plane are 9±1 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> for VP and 9±1.5 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">°</sup> for HP. The cross-polarization levels in the horizontal plane for both VP and HP are lower than -20 dB.

Dielectric-Loaded Compact WLAN/WCDMA Antenna With Shorted Loop and Monopole Elements

A compact, planar, dielectric-loaded, and multiple-band antenna for 2.45/5-GHz WLAN and 2.1-GHz wideband code-division multiple access (WCDMA) applications is presented in this letter. The antenna has a planar loop element with a shorting pin and a planar monopole element that are printed on the same substrate and driven by a microstrip line. The loop and monopole elements are covered by a thin FR4 layer on top to achieve good impedance matching at both bands. Analysis of the antenna has been realized using extensive 3-D full-wave electromagnetic simulations. Antenna measurements have also been presented, and it is shown that measurements and simulations are in good agreement.

Simple Algorithms for the Calculation of the Intensity of the Magnetic Field of Current Loops and Thin-Wall Air Coils of a General Shape Using Magnetic Dipoles

This paper describes the method by which it is possible to construct simple algorithms for the calculation of the axial and transverse components of the intensity of the magnetic field of current loops and thin-wall air coils (solenoids). These are planar loops and tightly wound coils with a cross section of an arbitrary shape and parallel walls in an axial direction. Computational algorithms show the same formal structure for every shape of coil; the shape of the coils is defined by the special shape function. The method is based on the superposition of the magnetic field of the equivalent magnetic dipoles. Utilization of this method can be observed, for example, in the calculation of the magnetic field of a cylindrical current loop and a thin cylindrical coil, for which the resulting relations are compared with a familiar method of calculation, on which solving equations for the vector potential is based. The method of calculation described can also be equally effectively used for coils of a noncircular shape. In this study, for the purpose of illustration, simple algorithms are created for the calculation of the magnetic field of a rectangular coil and the calculated values of the magnetic field are compared with the actual measurements.

Wheel-Shaped Icosanuclear Homo- and Heterometallic Complexes of NiII, CoII, and CuII Ions Supported by Unsymmetrical Aminoalcohol Ligands

Reactions of M(OAc)2·4H2O (M = Ni, Co) with 3-[benzyl(2-hydroxyethyl)amino]-1-propanol (H2L) in the presence of pyridine or triethylamine afforded novel homometallic icosanuclear wheel-shaped complexes [M20L4(HL)4(OAc)28] (M = Ni (1), Co (2)), which consist of a central M(II)12 single-stranded, nearly planar loop with four peripheral [M2(HL)(OAc)2] fragments attached in an S4 symmetrical fashion. The complexes can alternatively be recognized as saddle-shaped wheel structures, in which four tetranuclear units of [M4L(HL)(OAc)7](2-) are connected by four M(2+) ions (M5). The tetranuclear unit itself can be derived from an ideal C2 symmetrical [M4(HL)2(μ-η(2)-OAc)4(μ-η(1),η(1)-OAc)2(η(1),η(1)-OAc)](-) structure through deprotonation of the HL(-) ligand, and is composed of two plane-shared M3O4 incomplete cubanes in which the M2 and M3 atoms are involved in the central fused plane and the M1 and M4 atoms are disposed at the apex sites. Mixed-metal icosanuclear complexes [NixM20-xL4(HL)4(OAc)28] (3, M = Co, x = 9.5) and [Ni12M8L4(HL)4(OAc)28] (4, M = Cu) were also synthesized by using equimolar amounts of Ni(II) and M(II) ions, and were shown to have similar structures to 1 and 2. X-ray crystallographic and fluorescent analyses revealed that complex 3 contains nonstoichiometric amounts of Ni(2+) and Co(2+) ions in the ratio of 9.5:10.5 and that these are disordered at every metal site. In striking contrast, complex 4 has a stoichiometric formula of Ni12Cu8, which was confirmed by the Jahn-Teller elongation of Cu(2+) ions, and consequently, the M2 and M5 positions are occupied exclusively by the Cu(2+) ions. The temperature-dependent direct current (dc) magnetic susceptibility data showed the presence of ferromagnetic exchange interactions in the Ni homometallic (1) and NiCu bimetallic (4) complexes, while the Co homometallic (2) and NiCo bimetallic (3) complexes exhibited antiferromagnetic interactions due to spin-orbit coupling effects of the octahedral Co(II) ions. The present results demonstrate that the unsymmetrical aminoalcohol ligand H2L is quite effective in organizing the homo- and heterometallic icosanuclear wheel-shaped metal arrangements.

RECONSTRUCTING CCTV, BEIJING

Abstract. This paper deals with the reconstruction of a building, starting from a point cloud. The shape of this building is a non-stellar concave and multi-connected structure, composed of sowns and chains. A sown is the representation of a horizontal plane formed by dense points. A chain is a planar loop modeled by rare points. CCTV structure is defined only by the three orthogonal Cartesian coordinates. The reconstruction uses a sequence of procedures and the desired output is a consistent 3D model. The first procedure is devoted to attributing points to their voxel and to estimating the three values needed afterwards. The second procedure is devoted to analyzing clusters vertically and horizontally, to preliminarily distinguishing chains from sowns and to generating relational matching. The third procedure is devoted to building closed loops between all chains and all their projections on sowns. The fourth procedure is devoted to connecting points with triangles. The fifth procedure, still being implemented, is devoted to interpolating triangles with triangular splines.

Compact quad-band reconfigurable antenna for mobile phone applications

A compact reconfigurable antenna for quad-band (GSM/DCS/PCS/ WCDMA) mobile phone applications is proposed and experimentally investigated. By independently controlling the on/off states of a pin diode placed on a radiating element, the proposed antenna can be operated in the planar inverted-F antenna (PIFA) and loop modes, respectively. The measured results show that the 6 dB reflection coefficient bandwidths of the proposed antenna are 8.7% (880-960 MHz) and 14.3% (1950-2250 MHz) in the PIFA mode and 21.5% (1620- 2010 MHz) in the loop mode. By electrically selecting between the two modes, a variety of communication systems can be conveniently served through only one antenna.

A MNG-TL Loop Antenna Array With Horizontally Polarized Omnidirectional Patterns

A horizontally polarized omnidirectional planar loop antenna that employs an artificial mu-negative transmission line (MNG-TL) is proposed. The MNG-TL is designed using periodically loaded parallel-plate lines. The reactive loading is inspired by the zeroth-order resonator (ZOR), which has a propagation constant of zero. Due to the unique property of an infinite wavelength, the MNG-TL loop antenna presented in this paper allows current along the loop to remain in phase so that a horizontal polarized omnidirectional pattern is generated. A series-fed array, which is composed of four MNG-TL loop antennas and operates at 2.4 GHz band, is designed, fabrication, and measured. The MNG-TL loop antenna array offers a horizontally polarized omnidirectional radiation pattern with enhanced gain of 6.5 ~ 7.9 dBi and measured radiation efficiency exceeding 85% for covering bands. The concept extends the degrees of design freedom for horizontally polarized omnidirectional antenna array.

An Electrically Small Planar Loop Antenna with High Efficiency for Mobile Terminal Applications

An electrically small loop antenna with complete planar configuration is proposed. The radiator is directly connected with a 50-Ohm coaxial line when it is coupled-fed by a tiny feeding loop. The interdigital capacitor loaded loop has a size of only 0.116λ 0, where λ 0 is its operating wavelength, and the measured results show that it can have good radiation efficiency and gain. As the loop is placed coplanar with the ground plane, it has higher radiation efficiency and the impedance bandwidth is nearly doubled compared to its vertical counterpart. Other characteristics of such an electrically small loop like the reduced current on the ground plane, the tunable operating frequency, and potential pattern diversity for MIMO applications implies its promising use in mobile terminal applications. The working mechanism of the antenna is illustrated, with the help of an equivalent circuit and some key parameter study is also given.

The three-loop form factor in $ \mathcal{N} = {4} $ super Yang-Mills

In this paper we study the Sudakov form factor in N=4 super Yang-Mills theory to the three-loop order. The latter is expressed in terms of planar and non-planar loop integrals. We show that it is possible to choose a representation in which each loop integral has uniform transcendentality. We verify analytically the expected exponentiation of the infrared divergences with the correct values of the three-loop cusp and collinear anomalous dimensions in dimensional regularisation. We find that the form factor in N=4 super Yang-Mills can be related to the leading transcendentality part of the quark and gluon form factors in QCD. We also study the ultraviolet properties of the form factor in D>4 dimensions, and find unexpected cancellations, resulting in an improved ultraviolet behaviour.

Dressed Wilson loops as dual condensates in response to magnetic and electric fields

We introduce dressed Wilson loops as a novel confinement observable. It consists of closed planar loops of arbitrary geometry but fixed area, and its expectation values decay with the latter. The construction of dressed Wilson loops is based on chiral condensates in response to magnetic and electric fields, thus linking different physical concepts. We present results for generalized condensates and dressed Wilson loops on dynamical lattice configurations and confirm the agreement with conventional Wilson loops in the limit of large probe mass. We comment on the renormalization of dressed Wilson loops.

Planar loop tag antenna with bandwidth enhancement for UHF RFID system

A novel planar loop tag antenna mounted on the plastic pallets for ultra-high frequency (UHF) radio frequency identification (RFID) system is proposed. By insetting the U-shaped slot and a pair of rectangular parasitic strips into the proposed loop tag antenna, the resonant mode close to ultra-high frequency (UHF) 900-MHz band is excited to enhance the operating bandwidth. The obtained impedance bandwidth across the operating band can reach about 174 MHz (18.8%) for UHF band. Also, with bidirectional pattern, the measured reading distance is about 2.0 m as the proposed loop tag antenna mounted on the plastic pallets. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2711–2713, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26361

Compact Dual-Band and Ultrawideband Loop Antennas

Compact planar loop antennas fed by coplanar striplines (CPS) are presented for dual-band and ultrawideband (UWB) operations. The dual-band antenna consists of two resonant radiating parts, namely a strip loop and a slot loop. Based on the dual-band design, a wideband operation can be achieved. Two prototype antennas operating at the 2.4/5 GHz wireless LAN bands with dimensions of 45 × 15 × 0.813 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> and for the lower UWB band (3.1-4.8 GHz) with dimensions of 34 × 13.5 × 0.813 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> were fabricated on a RO4003 substrate. The measured input reflection loss is lower than 15 dB for the dual-band antenna and 10 dB for the UWB antenna. Both of the antennas show accept able gain and dipole-like radiation patterns over the operating frequency bands.

Open string Regge trajectory and its field theory limit

We study the properties of the leading Regge trajectory in open string theory including the open string planar one-loop corrections. With SU(N) Chan-Paton factors, the sum over planar open string multi-loop diagrams describes the 't Hooft limit N\to\infty. Our motivation is to improve the understanding of open string theory at finite \alpha' as a model of gauge theories. SU(N) gauge theories in D space-time dimensions are described by requiring open strings to end on a stack of N Dp-branes of space-time dimension D=p+1. The large N leading trajectory \alpha(t)=1+\alpha' t+\Sigma(t) can be extracted, through order g^2, from the s\to-\infty limit, at fixed t, of the four open string tree and planar loop diagrams. We analyze the t\to0 behavior with the result that \Sigma(t)\sim-Cg^2(-\alpha' t)^{(D-4)/2}/(D-4). This result precisely tracks the 1-loop Reggeized gluon of gauge theory in D>4 space-time dimensions. In particular, for D\to4 it reproduces the known infrared divergences of gauge theory in 4 dimensions with a Regge trajectory behaving as -\ln(-\alpha^\prime t). We also study \Sigma(t) in the limit t\to-\infty and show that, when D<8, it behaves as \alpha^\prime t/(\ln(-\alpha^\prime t))^{\gamma}, where \gamma>0 depends on D and the number of massless scalars. Thus, as long as 4<D<8, the 1-loop correction stays small relative to the tree trajectory for the whole range -\infty<t<0. Finally we present the results of numerical calculations of \Sigma(t) for all negative t.

Formula omitted] affine quiver matrix model

We introduce A n ( 1 ) ( n = 1 , 2 , … ) affine quiver matrix model by simply adopting the extended Cartan matrices as incidence matrices and study its finite N Schwinger–Dyson equations as well as their planar limit. In the case of n = 1 , we extend our analysis to derive the cubic planar loop equation for one-parameter family of models labelled by α: α = 1 and α = 2 correspond to the non-affine A 2 case and the affine A 1 ( 1 ) case respectively. In the case of n = 2 , we derive three sets of constraint equations for the resolvents which are quadratic, cubic and quartic respectively.

Modeling DNA-Bending in the Nucleosome: Role of AA Periodicity

This paper uses atomistic molecular mechanics within the framework of the JUMNA model to study the bending properties of DNA segments, with emphasis on understanding the role of the 10 bp periodicity associated with AA repeats that has been found to dominate in nucleosomal DNA. The calculations impose a bending potential on 18 bp segments that is consistent with nucleosome structures (i.e., radius of curvature of 4.1 nm), and then determine the energies of the minimum energy structures for different values of the rotational register (a measure of the direction of bending of the DNA) subject to forces derived from the Amber force field (parm99bsc0). The results show that sequences that contain the 10 bp repeats but are otherwise random have a narrow distribution of rotational register values that minimize the energy such that it is possible to combine several minimized structures to give the 147 bp nearly planar loop structure of the nucleosome. The rotational register values that lead to minimum bending energy with 10 bp AA repeats have a narrower minor groove, which points toward the histone interior at the positions of the AA repeats, which is a result that matches the experiments. The calculations also show that these sequences have a relatively flat potential energy landscape for bending to a 4.1 nm radius of curvature. Random sequences that do not have the 10 bp AA repeats have less stable bent structures, and a flat rotational register distribution, such that low energy nearly planar loops are less likely.

Non-linear waves in heterogeneous elastic rods via homogenization

We consider the propagation of a planar loop on a heterogeneous elastic rod with a periodic microstructure consisting of two alternating homogeneous regions with different material properties. The analysis is carried out using a second-order homogenization theory based on a multiple scale asymptotic expansion.

Simple loop integrals and amplitudes in $ \mathcal{N} = 4 $ SYM

We use momentum twistors to evaluate planar loop integrals. Infrared divergences are regulated by the recently proposed AdS-inspired mass regulator. We show that two-loop amplitudes in N=4 super Yang-Mills can be expanded in terms of basis integrals having twistor numerators. We argue that these integrals are considerably simpler compared to the ones conventionally used. Our case in point is the two-loop six-point MHV amplitude. We present analytical results for the remainder function in a kinematical limit, and find agreement with a recent Wilson loop computation. We also provide two-loop evidence that the logarithm of MHV amplitudes can be written in terms of simple twistor space integrals.