ABSTRACT
In Iran, which is at high risk of the Wild Poliovirus (WPV) and Vaccine-Derived Poliovirus (VDPV) importation due to its neighborhood with two polio endemic countries, Pakistan and Afghanistan, Environmental Surveillance (ES) was established in November 2017. Sistan-Balouchestan province was chosen for the ES due to its vicinity with Pakistan and Afghanistan. Five sewage collection sites in 4 cities (Zahedan, Zabol, Chabahar and Konarak) were selected in the high-risk areas. Since the establishment of ES in November 2017 till the end of 2023, 364 sewage specimens were collected and analyzed. The ES detected polioviruses which have the highest significance for polio eradication program, that is, Wild Poliovirus type 1 (WPV1) and Poliovirus type 2 (PV2). In April and May 2019, three of 364 (0.8%) sewage specimens from Konarak were positive for imported WPV1. According to phylogenetic analysis, they were highly related to WPV1 circulating in Karachi (Sindh province) in Pakistan. PV2 was also detected in 5.7% (21/364) of the sewage specimens, most of which proved to be imported from the neighboring countries. Of 21 isolated PV2s, 7 were VDPV2, of which 5 proved to be imported from the neighboring countries as there was VDPV2 circulating in Pakistan at the time of sampling, and 2 were ambiguous VDPVs (aVDPV) with unknown source. According to the findings of this study, as long as WPV1 and VDPV2 outbreaks are detected in Iran's neighboring countries, there is a definite need for continuation and expansion of the environmental surveillance.
ABSTRACT
In this paper, a combined three-dimensional (3D) optical-electrical simulation of non-pb and flexible four-terminal (4T) all perovskite tandem solar cell (APTSC) is presented. In this structure, polyethylene terephthalate (PET) is used as substrates, while the top sub cell has a [Formula: see text] absorber layer and the bottom sub cell has a [Formula: see text] absorber layer. This structure is used as a reference in this paper and the optical and electrical properties of it are investigated using the finite element method (FEM). It is shown that this structure has a total power conversion efficiency (PCE) of [Formula: see text]. Then, the elimination of the buffer layer and the addition of antireflection layer (ARL) strategies, as well as the use of periodic nano-texture patterns, are used to increase the reference structure's total PCE. A free-buffer layer tandem device is presented to minimize the parasitic absorption. While the total PCE is improved by [Formula: see text] in this case, one of the fabrication steps is also eliminated. A plasma-polymer-fluorocarbon (PPFC) coating layer is suggested as ARL on the substrates of both sub cells to reduce reflection loss. With optimized these layers thickness, total PCE is increased by [Formula: see text]. Because the PPFC layer is hydrophobic, the top surface of two sub cells in this structure has self-cleaning characteristic. As a result, this device offers long-term moisture resistance. Finally, the best structure in terms of the maximum total PCE is presented by increasing optical path-length utilizing nano-photonic and nano-plasmonic structures. The final structure is offered as a 4T tandem solar cell (TSC) that is environmentally friendly, extremely flexible, and has self-cleaning capability, with a total PCE of [Formula: see text], which is greater than the total PCE of the reference structure by [Formula: see text].
ABSTRACT
A microring flower-like architecture is introduced to obtain optical logic gates that can be reconfigured. The proposed design can operate as a time-division multiplexer, a half adder/subtractor, and an optical single bit comparator circuit. The optical pump pulses modulate the microring resonators in this arrangement. Green lasers with a resonant wavelength of 532 nm are used to generate the optical pump pulses. To theoretically analyze the structure, the signal flow graph approach is applied. The proposed structure's performance is investigated by calculating certain figures of merit for the resulting output data streams. Outputs of the presented combinational logic gates are optimized by designing the most proper geometry of flower-like structure and simultaneously by opting for the best input port to drop port's optical path. It is demonstrated that proper distinguishing between 0 and 1 levels occurs in the output. The compact structure proposed is simple, expandable, and reconfigurable. The proposed structure can be used as a key component in high-speed optical networks, according to simulation results.
ABSTRACT
In this paper, a simulation and general analysis of nonlinear microring resonators (MRRs) as all-optical switches are discussed in a flower-like structure. These MRRs are modulated through an optical pump beam, which receives temporal shift of MRRs' resonance wavelengths. These shifts are a result of the refractive index changing due to carrier injection. A green laser is used as the optical pump to shift the resonant wavelength of each MRR. This proposed structure can operate as all-optical logic gates. Of those innovations are reconfigurable structure to achieve various gates, integrating capability, and a high extinction ratio between zero and one logical levels. This configuration would be useful to design optical integrated circuits.
ABSTRACT
Background. This study aimed to evaluate the effect of different pouring times and spacer thicknesses on the three-dimensional accuracy of casts made of 3D-printed custom trays. Methods. A partial edentulous maxillary model was scanned for fabricating custom acrylic trays. Twenty custom trays were created using a CAD/CAM system and divided into two groups in terms of their spacer thicknesses (2 mm and 4 mm). All the trays were designed with 2-mm thickness, multiple retentive holes measuring 2 mm in diameter, and three interior seating stops (two on the edentulous ridge and one on the incisal edge of the central incisors). Impressions were made using monophasic polyvinyl siloxane and poured in two different times (one hour and 24 hours after removal) with type IV dental stone. All the casts were scanned to measure three distances (inter-buccal cusps, inter-palatal cusps, and inter-fossa distances) between the two first premolars. The data were analyzed with two-way ANOVA and Bonferroni test at a significance level of 0.05. Results. There was no significant difference between the 3D accuracy of casts made using two different spacer thicknesses poured at 1-hour and 24-hour intervals. However, there was a difference between casts made after 1 hour and 24 hours when using custom trays with 2 mm of spacer thickness in terms of inter-buccal distance. Conclusion. There was no significant difference between the accuracy of casts made using custom trays with either 2 or 4 mm of spacer thickness, which were poured 1 hour or 24 hours after tray removal.
ABSTRACT
In this paper, we numerically analyze nonlinear asymmetric switching using a semiconductor optical amplifier (SOA) phase-shifter-based Mach-Zehnder interferometer (MZI), for the first time, to the best of our knowledge. The self-phase modulation (SPM) effect and nonlinear phase shift in each MZI arm are investigated for different input pulse intensities and linear gains in both picosecond and femtosecond regimes. The input light signal is split unequally over the two arms, where SOAs are placed and act as nonlinear phase shifters in each arm. The finite difference beam propagation method is used to solve the modified nonlinear Schrodinger equation to analyze the wave propagation. In this work, the main nonlinear effects in SOA, such as group velocity dispersion, Kerr effect, two-photon absorption, carrier heating, and spectral hole burning, are considered. Furthermore, the effect of SPM on distortion of the pulse shape and its spectrum, which can be used for pulse shaping in a picosecond-switching scheme, is studied. We depicted red and blue shifts that each pulse experiences in the process of switching in picosecond and femtosecond regimes, respectively. Based on the results for sub-picosecond input pulses, by controlling the bias current level in the MZI arms, the pulse distortion due to nonlinear effects of SOAs can be decreased at the switch output port, and symmetric pulse can be obtained. Switching with higher speed is possible in bulk SOAs in the femtosecond regime using asymmetric MZI-switching structure.
ABSTRACT
In this paper, a theoretical model for a quantum dot semiconductor optical amplifier (QDSOA) is proposed. The dynamics of carriers in ground, excited, and continuum states and wetting layer are considered in this model. The effects of the second excited state (ES2) inclusion are investigated for the first time, to the best of our knowledge, in the proposed QDSOA model. Moreover, the inhomogeneous broadening effect due to size distribution of dots, and the homogeneous broadening effect of a single dot in the gain spectrum by grouping of dots based on their optical resonant frequency, are included in the model. Furthermore, grouping of photon modes is considered in the model. It is shown that improvement of QDSOA performance is possible by considering ES2 in rate equations. Gain saturation in different injection currents is obtained for various square-shaped pulse train bit-rates. It is shown that carriers' relaxation time plays an important role in signal amplification and processing of QDSOA. The results illustrate that QDSOA can be used for high bit-rate signal processing devices (up to 450 Gbps) with negligible wave distortion and fast gain recovery.
ABSTRACT
INTRODUCTION: To assessment of the efficacy and safety of transurethral cystolithotripsy of large bladder stones by holmium laser in the outpatient setting. METHODS: In a prospective study, 48 consecutive adult patients with large bladder stones, were enrolled for transurethral cystolithotripsy. Patients older than 18 years, with bladder stones larger than 2 cm were enrolled. Urethral stricture, active urinary infection, and any anesthetic contraindications for operation, were the exclusion criteria. Demographic characteristics of patients, outcomes and complications related to operation and post operation period, were recorded. RESULTS: Patients mean age was 46 ± 7.3 years. Male to female ratio was 45/3. Mean body mass index of patients was 28.5 ± 3.5. Mean stone size was 3.7 ± 1.6 cm. Mean operation time was 43.5 ± 15.5 minutes. Nearly complete stone clearance (98.5%) was achieved in all patients. Mean hospital stay was 6.5 ± 1.3 hours. No major complications were seen. Mean visual analog pain score (VAS) was 4.2 ± 2.1 and 1.4 ± 0.6, during and 1 hour after operation, respectively. During follow up of 22.4 ± 12.5 months, recurrence of bladder stone was not seen. No case of urethral stricture was detected. CONCLUSION: Transurethral holmium laser lithotripsy is an effective and safe alternative in selected patients with large bladder stones. This procedure can be easily performed in the outpatient setting.
ABSTRACT
INTRODUCTION: To compare outcomes of retrograde intrarenal surgery (RIRS) with extracorporeal shock wave lithotripsy (ESWL) as treatment of choice. METHODS: A total number of 46 patients with renal pelvic stones 10-20 mm and body mass index (BMI) >30 randomized in two groups underwent RIRS and ESWL from 2011 to 2014 and followed for 3 months. RESULTS: The patients mean ± SD age was 36.1 ± 13.1 years in ESWL and 33.2 ± 11.4 years in RIRS groups (P = .1) with comparable BMI in both groups (36.2 vs 38.1). In ESWL and RIRS groups, the operation time was 72.2 ± 21 vs 66.5 ± 19 minutes (P = .061), respectively. Stone free rate (SFR) at 3 months was 68% in ESWL group vs 90.4% in RIRS group (P = .019). The complication rate was 20% in ESWL group vs 14.2% in RIRS group (P = .211) but all of them were minor and managed conservatively. CONCLUSION: According to our study, RIRS procedure in comparison with ESWL is a safe and successful option of treatment for renal pelvis stone of 10-20 mm in obese people.
