The microtubule associated protein (MAP) tau forms a new class of triple-stranded left-hand helical fibrous protein polymer

1992 ◽  
Vol 50 (1) ◽  
pp. 540-541
Author(s):  
G. C. Ruben ◽  
K. Iqbal ◽  
I. Grundke-Iqbal ◽  
H. Wisniewski ◽  
T. L. Ciardelli ◽  
...  
Keyword(s):  
Axial Ratio ◽  
Normal Structure ◽  
Paired Helical Filaments ◽  
Left Hand ◽  
New Class ◽  
Protein Polymer ◽  
Fibrous Protein ◽  
Protein Map ◽  
Neurotransmitter Transport ◽  
Alzheimer Neurofibrillary Tangles

In neurons, the microtubule associated protein, tau, is found in the axons. Tau stabilizes the microtubules required for neurotransmitter transport to the axonal terminal. Since tau has been found in both Alzheimer neurofibrillary tangles (NFT) and in paired helical filaments (PHF), the study of tau's normal structure had to preceed TEM studies of NFT and PHF. The structure of tau was first studied by ultracentrifugation. This work suggested that it was a rod shaped molecule with an axial ratio of 20:1. More recently, paraciystals of phosphorylated and nonphosphoiylated tau have been reported. Phosphorylated tau was 90-95 nm in length and 3-6 nm in diameter where as nonphosphorylated tau was 69-75 nm in length. A shorter length of 30 nm was reported for undamaged tau indicating that it is an extremely flexible molecule. Tau was also studied in relation to microtubules, and its length was found to be 56.1±14.1 nm.

Intraneuronal Neurofibrillary Tangles Isolated from Alzheimer’ Disease Affected Brains Visualized by Vertical Platinum-Carbon Replication for TEM

1997 ◽  
Vol 3 (S2) ◽  
pp. 47-48
Author(s):  
G.C. Ruben
Keyword(s):  
Alzheimer Disease ◽  
Axonal Transport ◽  
Nerve Cell ◽  
Neurofibrillary Tangles ◽  
High Frequency ◽  
Molecular Level ◽  
Paired Helical Filaments ◽  
Left Hand ◽  
Protein Map ◽  
Amorphous Structures

Neurofibrillary tangles (NFT) occur with high frequency in brains of patients with Alzheimer' disease (AD). The frequency of NFT directly correlates with the degree of dementia. Extra cellular plaque core amyloid also occurs in high frequently in AD brains when few intraneuronal NFT are present, these individuals are not demented.The microtubule associated protein (MAP) tau is recognized as the principal constituent in paired helical filaments (PHF) and NFT. NFT contain PHF, amorphous structures containing tau, and a triple-stranded left-hand helical ˜2.1 nm filament similar to tau polymer which has been identified in isolated tangles. Tau is located in nerve cell axons and associates with and stabilizes the microtubules required for axonal transport. Sequestration of tau into tangles and its removal from microtubules not only compromises axonal transport but cripples synaptic communication between nerve cells.NFT were isolated in the absence of detergent so these gel-like structures (Fig. 1) could be studied at the molecular level.

Bilayer split-ring chiral metamaterial based reconfigurable antenna for polarization conversion

Frequenz ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Preet Kaur ◽  
Pravin R. Prajapati
Keyword(s):  
Low Cost ◽  
Axial Ratio ◽  
Center Frequency ◽  
Impedance Bandwidth ◽  
Split Ring ◽  
Circularly Polarized ◽  
Left Hand ◽  
Rectangular Patch ◽  
Mode 2 ◽  
Chiral Metamaterial

Abstract A bilayer split-ring chiral metamaterial converts the linearly polarized wave, into a nearly perfect left or right-handed circularly polarized wave. The proposed antenna is intended to operate at center frequency of 5.80 GHz with switchable polarization capability. The polarization re-configurability is achieved by electronically switching of two PIN-diode pairs, which are embedded into bilayer split-ring Chiral Metamaterial. The optimized length of rectangular patch is 16 mm and width is 12.1 mm. Two types of radiation characteristics offered by the proposed antenna; left hand circularly polarized in mode 1 and right hand circularly polarized in mode 2. Measured results show that its impedance bandwidth is 155 MHz from 5.70 to 5.855 GHz for both mode 1 and mode 2. The measured axial-ratio bandwidth is 100 MHz from 5.75 to 5.85 GHz for mode 1 and 110 MHz from 5.73 to 5.84 GHz for mode 2. Antenna has LHCP gain of 2.52 dBi and RHCP gain of −23 dBi in mode 1. RHCP gain of 2 dBi and polarization purity of about −20 dBi is obtained in mode 2. The proposed antenna has simple structure, low cost and it has potential application in field of wireless communication (i.e., WiMax, WLAN etc.).

scholarly journals Wideband Circular Polarized Dielectric Resonator Antenna Array for Millimeter-Wave Applications

Sensors ◽  
2021 ◽  
Vol 21 (11) ◽  
pp. 3614
Author(s):  
Arun Kesavan ◽  
Mu’ath Al-Hassan ◽  
Ismail Ben Mabrouk ◽  
Tayeb A. Denidni
Keyword(s):  
Antenna Array ◽  
Millimeter Wave ◽  
Axial Ratio ◽  
Unit Element ◽  
Dielectric Resonator Antenna ◽  
Gain Bandwidth ◽  
Left Hand ◽  
Wide Resonance ◽  
Element Array ◽  
Peak Gain

A novel circular polarized dielectric antenna array (DRA) for millimeter-wave applications at 30 GHz is presented in this paper. The unit element array is a flower-shaped DRA fed with a cross slot. To obtain circular polarization, a sequential network combined with the cross slots is used to feed the 2×2 array. The prototype of the proposed antenna array is fabricated and measured to obtain a wide resonance bandwidth from 27 GHz to 38 GHz frequency band. Furthermore, this left-hand polarized antenna array has achieved a peak gain of 9.5 dBi with 3-dB axial ratio at 30 GHz. The proposed DRA array with wideband resonance and gain bandwidth has the potential to be used for millimeter-wave wireless communications at the 30 GHz band.

Development and Miniaturized of Circularly Polarization Diversity at Cavity Backed SIW Antenna for X-Band Application

Frequenz ◽  
2019 ◽  
Vol 73 (9-10) ◽  
pp. 317-320
Author(s):  
Saeid Karamzadeh ◽  
Vahid Rafiei ◽  
Hasan Saygin
Keyword(s):  
Schottky Diodes ◽  
Axial Ratio ◽  
Impedance Bandwidth ◽  
Polarization Diversity ◽  
Circularly Polarized ◽  
Left Hand ◽  
Low Profile ◽  
X Band ◽  
Coaxial Feed ◽  
Good Agreement

Abstract In this work circularly polarization diversity has been achieved by utilizing two Schottky diodes on low profile cavity-backed substrate integrated waveguide (CBSIW). In comparison with other studies in the literature, the size of antenna has been reduced to 0.54λg × 0.76λg by helping a 50-Ohm coaxial feed line. The impedance bandwidth, axial ratio bandwidth and antenna gain are improved to 10.02 %, 5.2 % and 7.68dBi, respectively. In addition, the proposed antenna can generate either a left-hand circularly polarized (LHCP) or a right-hand circularly polarized (RHCP) radiation. The developed antenna was fabricated and tested and the achieved results were in good agreement with the simulated one.

scholarly journals Dual Circularly Polarized Omnidirectional Antenna with Slot Array on Coaxial Cylinder

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Bin Zhou ◽  
Junping Geng ◽  
Zhe Li ◽  
Wenzhi Wang ◽  
Xianling Liang ◽  
...  
Keyword(s):  
Return Loss ◽  
Axial Ratio ◽  
Coaxial Cylinder ◽  
Circularly Polarized ◽  
Left Hand ◽  
Omnidirectional Antenna ◽  
Right Hand ◽  
Two Sides

A dual circularly polarized (CP) omnidirectional antenna based on slot array in coaxial cylinder structure is presented in this paper. It is constructed by perpendicular slot pairs around and along the axis of the coaxial cylinder to realize the omnidirectional CP property, and two ports are assigned in its two sides as left hand circularly polarized (LHCP) port and right hand circularly polarized (RHCP) port, respectively. The proposed antenna achieves a bandwidth of 16.4% ranging from 5.05 to 5.95 GHz with an isolation higher than 15 dB between the two CP ports, and the return loss (RL) is higher than 10 dB within the bandwidth in both of the two ports. From the measured results, the average axial ratio (AR) of the proposed antenna in omnidirectional plane is lower than 1.5 dB.

scholarly journals Dual Circularly Polarized Planar Four-Port MIMO Antenna with Wide Axial-Ratio Bandwidth

Sensors ◽  
2020 ◽  
Vol 20 (19) ◽  
pp. 5610
Author(s):  
Sachin Kumar ◽  
Gwan Hui Lee ◽  
Dong Hwi Kim ◽  
Hyun Chul Choi ◽  
Kang Wook Kim
Keyword(s):  
Circular Polarization ◽  
Multiple Input Multiple Output ◽  
Vector Current ◽  
Axial Ratio ◽  
Impedance Bandwidth ◽  
Circularly Polarized ◽  
Mimo Antenna ◽  
Left Hand ◽  
Input Multiple Output ◽  
Polarization Mechanism

A broadband compact-sized planar four-port multiple-input–multiple-output (MIMO) antenna with polarization diversity is presented. The proposed dual circularly polarized (CP) MIMO antenna consists of four G-shaped monopole elements, two of which are left-hand CP and the other two are right-hand CP. A vertical line strip in the G-shaped radiating element acts in balancing the vertical and horizontal electric field components to obtain 90° phase difference between them for circular polarization. Also, an I-shaped strip is incorporated between the ground planes of the G-shaped antenna elements to obtain equal voltage level in the proposed MIMO configuration. The dual circular polarization mechanism of the proposed MIMO/diversity antenna is analysed from the vector current distributions. The impedance bandwidth (S11 ≤ –10 dB) of the MIMO antenna is 105.9% (4–13 GHz) and the 3 dB axial ratio bandwidth (ARBW) is 67.7% (4.2–8.5 GHz), which is suitable for C-band applications. The overall size of the MIMO antenna is 70 × 68 × 1.6 mm3, and the minimum isolation between the resonating elements is 18 dB. The envelope correlation coefficient is less than 0.25, and the peak gain within the resonating band is 6.4 dBi.

scholarly journals Proximal quasi-normal structure in convex metric spaces

2014 ◽  
Vol 22 (3) ◽  
pp. 45-58
Author(s):  
Moosa Gabeleh
Keyword(s):  
Metric Spaces ◽  
Nonexpansive Mappings ◽  
Normal Structure ◽  
Best Proximity Points ◽  
New Class ◽  
Convex Metric Spaces

Abstract We consider, in the setting of convex metric spaces, a new class of Kannan type cyclic orbital contractions, and study the existence of its best proximity points. The same problem is then discussed for relatively Kannan nonexpansive mappings, by using the concept of proximal quasi-normal structure. In this way, we extend the main results in Abkar and Gabeleh [A. Abkar and M. Gabeleh, J. Nonlin. Convex Anal. 14 (2013), 653-659].

scholarly journals LHCP four patches stack triangular truncated antenna using corporate feed microstrip-line for CP-SAR sensor

2021 ◽  
Vol 11 (5) ◽  
pp. 4125
Author(s):  
Muhammad Fauzan Edy Purnomo ◽  
Vita Kusumasari ◽  
Rudy Yuwono ◽  
Rahmadwati Rahmadwati ◽  
Rakhmad Romadhoni ◽  
...  
Keyword(s):  
Circular Polarization ◽  
Microstrip Antenna ◽  
Microstrip Line ◽  
Axial Ratio ◽  
Synthetic Aperture ◽  
Impedance Bandwidth ◽  
Target Frequency ◽  
Left Hand ◽  
S Parameter ◽  
Aerial Vehicle

<span>In this paper, we acquire the configuration of the left-hand circular polarization (LHCP) array four patches stack triangular truncated microstrip antenna. This construction use the basic corporate feed microstrip-line with modified lossless T-junction power divider on radiating patch for circularly polarized-synthetic aperture radar (CP-SAR) sensor embedded on unmanned aerial vehicle (UAV) with compact, small, and simple configuration. The design of circular polarization (CP) is realized by truncating the whole three tips and adjusting the parameters of antenna at the target frequency, <em>f </em>= 5.2 GHz. The results of characteristic performance and <em>S</em>-parameter for the LHCP array four patches stack antenna at the target frequency show successively about 9.74 dBic of gain, 2.89 dB of axial ratio (<em>Ar</em>), and </span><span>-</span><span>10.91 dB of S-parameter. Moreover, the impedance bandwidth and the 3 dB-<em>Ar</em> bandwidth of this antenna are around 410 MHz (7.89%) and 100 MHz (1.92%), respectively.</span>

A CPW-fed reconfigurable patch antenna with circular polarization diversity

2014 ◽  
Vol 7 (6) ◽  
pp. 753-758 ◽  
Author(s):  
Ch. Sulakshana ◽  
L. Anjaneyulu
Keyword(s):  
Circular Polarization ◽  
Patch Antenna ◽  
Return Loss ◽  
Coplanar Waveguide ◽  
Axial Ratio ◽  
Polarization Diversity ◽  
Left Hand ◽  
Switching Condition ◽  
Parametric Studies ◽  
Made In

This paper presents a simple and compact coplanar waveguide (CPW)-fed circular-shaped reconfigurable patch antenna with a switchable circular polarization (CP) sense. The circular patch is cut at the ends vertically and switches are introduced to connect the patch ends. By controlling the ON/OFF status of the two switches, the polarization of the antenna can be switched between two states: left-hand circular polarization and right-hand circular polarization. The patch is designed on a very thin RT Duroid substrate of dielectric constant (εr) of 2.2 and thickness of 0.254 mm. The overall antenna dimensions are 35 × 30 mm. The antenna is designed and simulated using finite-element method -based EM simulator, HFSS. For each switching condition the return loss curve, radiation pattern are obtained. Axial ratio curves for polarization diversity cases are also plotted. Parametric studies have been made in order to get optimized values for certain antenna dimensions such as thickness, CPW ground to feed gap, etc.

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