Realization of high capacity transmission in fiber optic communication systems using Absolute Polar Duty Cycle Division Multiplexing (AP-DCDM) technique.

An electrical multiplexing technique, namely Absolute Polar Duty Cycle Division Multiplexing (AP-DCDM) is reported for high-speed optical fiber communication systems. It is demonstrated that 40 Gb/s (4 × 10 Gb/s) AP-DCDM system shows a clear advantage over conventional 40 Gb/s RZ-OOK with 50% duty cycle in terms of dispersion tolerance and spectral efficiency. At 40 Gb/s its tolerance to chromatic dispersion (CD) is 124 ps/nm and 194 ps/nm for the worst and the best user, respectively. These values are higher than that of 40 Gb/s RZ-OOK, which is around 100 ps/nm. The spectral efficiency, receiver sensitivity and OSNR for different number of channels are discussed. Comparison against other modulation formats namely duobinary, Non-Return-to-Zero (NRZ)-OOK and RZ-Differential Quadrature Phase-Shift Keying (RZ-DQPSK) at 40 Gb/s are made. It is shown that AP-DCDM has the best receiver sensitivity (−32 dBm) and better CD tolerance (±200 ps/nm) than NRZ-OOK and RZ-DQPSK. In reference to duobinary, AP-DCDM has better receiver sensitivity but worse dispersion tolerance

Absolute Polar Duty Cycle Division Multiplexing (APDCDM); technique for wireless communications

A new multiplexing and demultiplexing technique for wireless communications which is called Absolute Polar Duty Cycle Division Multiplexing (APDCDM) is presented in this paper. APDCDM can become an alternative multiplexing technique in wireless communications. The new technique allows for better error detection, correction, clock recovery and more efficient use of time slots as well as spectrum. The principle of the APDCDM technique has been discussed in this paper based on theoretical analysis as well as simulation studies. The performance comparison is made against time division multiplexing technique (TDM). The simulation has been set for wireless transmission, based on free space propagation model with adaptive white Gaussian noise (AWGN); QAM is used as modulation scheme to evaluate this technique against data rate and number of users. The simulation result correspond with the theoretical study show that APDCDM has better performance than TDM for supporting higher number of multiplexing users and bit rate

Analysis of return-to-zero-on-off-keying over absolute polar duty cycle division multiplexing in dispersive transmission medium

We propose and investigate a technique to reduce the spectral width as well as increase the tolerance to chromatic dispersion (CD) using improved return-to-zero (RZ) on-off-keying (OOK) over absolute polar duty cycle division multiplexing (AP-DCDM) technique. The proposed channel multiplexing and demultiplexing are performed electrically using only one modulator for n number of users, which is very economical. It is demonstrated that the spectral width occupied by 30 Gb/s RZ-OOK without AP-DCDM measured at -20 dB from the peak power is around 105 GHz whereas, this value can be reduced to around 64 GHz for 30 Gb/s RZ-OOK over AP-DCDM. This amount of saving in the spectral width is a significant achievement, which leads to better tolerance to CD. Its tolerance to CD is in the range of plusmn109 and plusmn155 ps/nm, for the worst and the best users, respectively. These values are higher than that of 30 Gb/s conventional RZ-OOK, which is around plusmn86.5 ps/nm. At 120 Gb/s RZ-OOK over AP-DCDM (the worst user) has pre-amplified receiver sensitivity and optical signal to noise ratio (OSNR) of -22.5 dBm and 28.57 dB, respectively

Unstable os odontoideum contributing to cervical myelopathy and obstructive sleep apnea

Background: Sleep apnea is characterized by repetitive cessation of breathing during sleep. It may be attributed to obstructive, central, or mixed pathologies close to the upper airway resulting in a decreased diameter of the oropharyngeal tract. Case Description: A 36-year-old male with progressive cervicomedullary myelopathy/quadriparesis exhibited obstructive sleep apnea (OSA) attributed to an anteriorly displaced os odontoideum (OO). Atlantoaxial screw-rod stabilization resulted in improvement of both neurological function and OSA. Conclusion: A symptomatic unstable OO may contribute to suboccipital pain, progressive quadriparesis, vertebrobasilar insufficiency, and OSA. Appropriate operative intervention utilizing atlantoaxial screw-rod stabilization may help to resolve these deficits. © 2019 Published by Scientific Scholar on behalf of Surgical Neurology Internationa

The use of pulse-compression thermography for detecting defects in paintings

Interest in the conservation of paintings grows year by year. Their periodic inspection is essential for their conservation over the time. Thermographic non-destructive inspection is one technique useful for paintings, but it is essential to be able to detect buried defects while minimising the level of thermal stimulus. This paper describes a pulse-compression infrared thermography technique whereby defect detection is optimized while minimising the rise in temperature. To accomplish this task, LED lamps driven by a coded waveform based on a linear frequency modulated chirp signal have been used on paintings on both a wooden panel and a canvas layer. These specimens contained artificially fabricated defects. Although the physical condition of each painting was different, the experimental results show that the proposed signal processing procedure is able to detect defects using a low temperature contrast

Indirect co-culture of testicular cells with bone marrow mesenchymal stem cells leads to male germ cell-specific gene expressions

Objective: Non-obstructive azoospermia is mostly irreversible. Efforts to cure this type of infertility have led to the application of stem cells in the reproduction field. In the present study, testicular cell-mediated differentiation of male germ-like cells from bone marrow-derived mesenchymal stem cells (BM-MSCs) in an in vitro indirect co-culture system is investigated. Materials and Methods: In this experimental study, mouse BM-MSCs were isolated and cultured up to passage three. Identification of the cells was evaluated using specific surface markers by flow-cytometry technique. Four experimental groups were investigated: control, treatment with retinoic acid (RA), indirect co-culture with testicular cells, and combination of RA and indirect co-culture with testicular cells. Finally, following differentiation, the quantitative expression of germ cell-specific markers including Dazl, Piwil2 and Stra8 were evaluated by real-time polymerase chain reaction (PCR). Results: Molecular analysis revealed a significant increase in Dazl expression in the indirect co-culture with testicular cells group in comparison to the control group. Quantitative expression level of Piwil2 was not significantly changed in comparison to the control group. Stra8 expression was significantly higher in RA group in comparison to other groups. Conclusion: Indirect co-culture of BM-MSCs in the presence of testicular cells leads to expression of male germ cell-specific gene, Dazl, in the induced cells. Combination of co-culture with testicular cells and RA did not show any positive effect on the specific gene expressions. © 2019 Royan Institute (ACECR). All rights reserved

Nonordered dendritic mesoporous silica nanoparticles as promising platforms for advanced methods of diagnosis and therapies

Dendritic mesoporous silica nanoparticles (DMSNs) are a new generation of porous materials that have gained great attention compared to other mesoporous silicas due to attractive properties, including straightforward synthesis methods, modular surface chemistry, high surface area, tunable pore size, chemical inertness, particle size distribution, excellent biocompatibility, biodegradability, and high pore volume compared with conventional mesoporous materials. The last years have witnessed a blooming growth of the extensive utilization of DMSNs as an efficient platform in a broad spectrum of biomedical and industrial applications, such as catalysis, energy harvesting, biosensing, drug/gene delivery, imaging, theranostics, and tissue engineering. DMSNs are considered great candidates for nanomedicine applications due to their ease of surface functionalization for targeted and controlled therapeutic delivery, high therapeutic loading capacity, minimizing adverse effects, and enhancing biocompatibility. In this review, we will extensively detail state-of-the-art studies on recent advances in synthesis methods, structure, properties, and applications of DMSNs in the biomedical field with an emphasis on the different delivery routes, cargos, and targeting approaches and a wide range of therapeutic, diagnostic, tissue engineering, vaccination applications and challenges and future implications of DMSNs as cuttingedge technology in medicine

Smart and biomimetic 3D and 4D printed composite hydrogels: opportunities for different biomedical applications

In recent years, smart/stimuli-responsive hydrogels have drawn tremendous attention for their varied applications, mainly in the biomedical field. These hydrogels are derived from different natural and synthetic polymers but are also composite with various organic and nano-organic fillers. The basic functions of smart hydrogels rely on their ability to change behavior; functions include mechanical, swelling, shaping, hydrophilicity, and bioactivity in response to external stimuli such as temperature, pH, magnetic field, electromagnetic radiation, and biological molecules. Depending on the final applications, smart hydrogels can be processed in different geometries and modalities to meet the complicated situations in biological media, namely, injectable hydrogels (following the sol-gel transition), colloidal nano and microgels, and three dimensional (3D) printed gel constructs. In recent decades smart hydrogels have opened a new horizon for scientists to fabricate biomimetic customized biomaterials for tissue engineering, cancer therapy, wound dressing, soft robotic actuators, and controlled release of bioactive substances/drugs. Remarkably, 4D bioprinting, a newly emerged technology/concept, aims to rationally design 3D patterned biological matrices from synthesized hydrogel-based inks with the ability to change structure under stimuli. This technology has enlarged the applicability of engineered smart hydrogels and hydrogel composites in biomedical fields. This paper aims to review stimuli-responsive hydrogels according to the kinds of external changes and t recent applications in biomedical and 4D bioprinting

Absolute polar duty cycle division multiplexing over wavelength division multiplexing system

The performance of absolute polar duty cycle division multiplexing (AP-DCDM) over wavelength division multiplexing (WDM) system is presented based on the simulation results. The AP-DCDM signal has narrower bandwidth than conventional time division multiplexing (TDM) signal, which makes its implementation in WDM system advantageous. In this paper, characteristics of AP-DCDM and TDM signals in WDM system are compared at the speed of 40 Gbit/s per channel, for the minimum allowed channel spacing and the chromatic dispersion tolerance. The results clearly show that AP-DCDM performs significantly better than TDM. By using AP-DCDM, 1.28 Tbit/s (32 × 40 Gbit/s) was successfully transmitted over 320 km standard single mode fiber. Spectral efficiency of 0.64 b/s/Hz was achieved by using 10 Gbit/s transmitters and receivers without polarization multiplexing

Performance analysis on transmission of multilevel optical pulses using absolute polar duty cycle division multiplexing

In order to explore the potential of optical multilevel signaling for high speed optical fiber networks, an absolute polar duty cycle division multiplexing (AP-DCDM) is demonstrated. Three users, each with the data rate of 10 Gb/s were successfully multiplexed and transmitted over a single WDM channel, which can offer a possible transmission rate of 30 Gb/s per WDM channel. The performance of AP-DCDM technique is examined, with comparison to 30 Gb/s Time Division Multiplexing (TDM). Back-to-back receiver sensitivity of -29.2 dBm with OSNR of 22.5 dB was achieved for the worst user, together with the chromatic dispersion tolerance ranging from 207 ps/nm to 276 ps/nm. A comparison with conventional TDM technique shows a clear advantage of the proposed AP-DCDM technique