The Effect of Sand and Dust Storms (SDSs) and Rain on the Performance of Cellular Networks in the Millimeter Wave Band

Future cellular systems are expected to use millimeter-wave (mm-Wave) frequency bands in addition to the existing microwave bands under 6 GHz. Severe weather conditions, including sand and dust storms (SDSs) and heavy rainfalls, challenge reliable communications over wireless links at those higher frequencies. In such conditions, besides frequency-dependent path-loss, radio signals experience additional attenuation. The SDS attenuation is related to visibility, receiver distance to the storm origin point, soil type, frequency, temperature and humidity. On the other hand, the rainfall attenuation is affected by rainfall rate, polarization, carrier frequency, temperature and raindrop size distribution. Leveraging on experimental measurements carried out in previous works, a novel unified mathematical framework is introduced in this paper to include SDS/rainfall-dependent attenuation in the performance evaluation of terrestrial wireless cellular networks in terms of coverage probability, bit error rate (BER) and achievable rate in the mm-Wave band. Extensive numerical results are presented to show the effects of the different SDS/rainfall parameters on performance, showing that the degradation due to SDS is generally higher than that due to rain and may cause a reduction of even six orders of magnitude in the average achievable bit rate when the frequency increases from 28 to 38 GHz

Photonic Crystal Chemical/Biochemical Sensors

In this chapter, the definitions of the photonic crystals (PhCs) are presented and the photonic crystal-based sensors are described. The structures of some photonic crystal biosensors that can detect chemical or biochemical molecules are also investigated. Sensing mechanism in the most photonic crystal sensors is based on the refractive index (RI) change mechanism. By binding the chemical or biochemical molecules to active sensing surface, the refractive index will be changed. So, the resonant wavelength or the intensity of the transmission spectrum is changed. This process can be used as a way to measure the concentration of the molecules. To simulate the optical wave behavior in the structure and evaluating the ability of biosensing, the two-dimensional finite-difference time-domain (2D-FDTD) and plane-wave expansion (PWE) methods are used. The sensors that are presented in this chapter are mostly based on photonic crystal resonators. Some structures based on micro-/nano-resonators, structures based on LX resonators, and structures based on ring resonator are investigated. Important parameters on sensing applications for these structures are also calculated

The Effect of Low-Level Laser Therapy on the Acceleration of Orthodontic Tooth Movement

In clinical practice, Low-Level Laser Therapy (LLLT) is widely used. The main aim of this review is to assess the effectiveness of LLLT on accelerating tooth movement in human subjects. The PRISMA checklist was utilized as a guideline to carry out this systematic review. The electronic databases were searched from Google Scholar (2014-2018) and PubMed, and comprehensive research on this topic was also manually conducted. Therefore, 76 Randomized Clinical Trials (RCT) or Controlled Clinical Trials (CCT) articles were selected. After screening studies, consequently, ten trials met the inclusion criteria. Eight out of ten studies showed LLLT has a significant impact on the acceleration of orthodontic tooth movement, and there was no statistically significant difference in the rate of tooth movement between the laser group and the control group in the two remaining studies. Furthermore, five out of ten articles showed that LLLT has no adverse effects. Although we have some degree of understanding from a cellular point of view to low-level laser therapy effects, we still do not know whether this cellular level changes have any effect on clinical acceleration of the orthodontic tooth movement. The results are inconclusive and cannot be generalized to the public community; therefore, well-structured studies are required

The therapeutic effects of chamomilla tincture mouthwash on oral aphthae: a randomized clinical trial

Introduction: Recurrent aphthous stomatitis (RAS) is a common clinical condition producing painful ulcerations in the oral cavity. However, there has been no optimal therapeutic approach. Topical and systemic steroids commonly prescribed for the condition have local and systemic side-effects. Recently, there is growing tendency toward herbal medication in the modern society. The objective of this study was to assess the efficacy of a chamomilla mouth rinse on reducing the signs and symptoms of aphthous lesions in comparison with a placebo mouth rinse. Material and Methods: A randomized, triple-blind, placebo-controlled trial was performed on 36 patients, from cases diagnosed with RAS, attending the Department of Oral Medicine, Mashhad University of Medical Sciences. They were randomly divided into two groups: the intervention group(A), receiving chamomilla mouth rinse, and the control group (B) receiving a placebo rinse. The ability of the solution to control the pain and burning sensation and the number and size of the ulcers were evaluated. Results: The number of ulcers in the 3 rd visit (four days after treatment) showed a significant difference between the groups ( P <0.001). The pain and burning sensation (VAS) was reduced significantly in the test group in the 2 nd ( p =0.001),3 rd and 4 th visit ( P <0.001). Conclusions: Chamomilla mouth rinse was effective in the treatment of RAS, controlling the pain and burning sensation without producing any adverse side effects and can be advised as an alternative RAS treatment