THz antennas design,developments, challenges,and applications: A review

Terahertz (0.1–10 THz) wireless communication will be the future technology to reach a top-notch data rate. THz is one of the most promising candidates for 6G systems because it provides enormous bandwidth, up to 100 GHz, and a massive data rate of up to 1 Tbps. THz antennas, antenna arrays, and MIMO antenna arrays in 6G are hot research topics for implementing 6G wireless communication systems. The 6G aims to continue to enhance the features of the 5G as it is capable of achieving the maximum high-speed data rate, excellent reliable communication, massive connectivity, and very low latency connectivity. The 6G requirements need high-gain antenna arrays and MIMO antenna arrays to combat the effect of atmospheric losses in high frequencies. An in-depth discussion of the planar THz antennas that have been extensively used in THz applications like imaging, sensing, and Internet-of-Things (IoT) has been conducted. The study of the THz antennas, antenna arrays, and MIMO antennas on different conducting materials such as copper and graphene, which are designed on different dielectric substrates such as polyimide, quartz, liquid crystalline polymer, and polytetrafluoroethylene, has been carried out in detail. Metamaterial, photoconductive, plasmonic antennas, and THz beamforming are significant parts of THz communications. This paper also provides antennas and antenna arrays based on them.     

Postoperative radiation for cervical cancer with pathologic risk factors

PURPOSE: To examine the efficacy of postoperative radiation therapy for early-stage cervical cancer with pathologic risk factors. METHODS AND MATERIALS: We reviewed the charts of 83 patients who received postoperative radiation therapy at our facility from March 1980 to November 1993 for early stage cervix cancer with positive surgical margins, positive pelvic or periaortic lymph nodes, lymphovascular space invasion, deep invasion, or for disease discovered incidently at simple hysterectomy. Twenty-eight patients received low dose rate (LDR) intracavitary radiation with or without external beam pelvic irradiation and 55 patients received external beam pelvic irradiation with high dose rate (HDR) intracavitary implants. Of these 83 patients, 66 were evaluable--20 LDR and 46 HDR patients. All patients received 45-50 Gy external beam irradiation and 20 Gy LDR equivalent intracavitary irradiation prescribed to 0.5 cm below the mucosa. Ninety percent of the LDR group and 92% of the HDR group completed treatment within < 56 days. Treatment-related toxicities were scored according to the GOG toxicity scale. Mean and median follow-up times were 101 months and 111 months (3-172 months) for the LDR group and 42 and 40 months (3-98 months) for the HDR group. RESULTS: The 5-year disease-free survival was 89% for the LDR group and 72% for the HDR group. Local control was observed in 90% (18 out of 20) of the LDR patients and 89% (41 out of 46) of the HDR patients for an overall local control rate of 89.5%. Two of 20 LDR patients (10%) experienced recurrence (two pelvic with distant metastasis). Nine of 46 HDR patients (22%) had recurrence of disease (three pelvic, four distant metastasis, and two pelvic with distant metastasis). In the HDR group, 6 out of 16 (38%) with positive lymph nodes died of disease whereas, 27 out of 30 (90%) of the patients with negative lymph nodes remain free of disease. Three of 20 (15%) LDR patients and 4 out of 46 (9%) HDR patients experienced Grade 2 or 3 late treatment- related complications. No patient in either group had Grade 4 or 5 complications. Pathologic risk factors were analyzed. Lymph node positivity and lymphovascular space invasion were found to be significant (p = 0.01 and p = 0.02). Positive margins, deep invasion, and age were not significant. CONCLUSION: Our results demonstrate the efficacy of postoperative irradiation for cervical cancer with pathologic risk factors. Overall, the local control rate was 89.5% The HDR results demonstrate that this method can be delivered safely and effectively.     

Interfacial viscoelastic properties of adsorbed surfactant and polymeric films at fluid interfaces

The viscous and elastic properties of fluid interfaces play an important role in the stability of foams and emulsions as well as in the selection of surfactants for tertiary oil recovery. These properties were determined for aqueous solutions of surfactant, polymer, and polymer plus surfactant systems using a deep channel surface viscometer. The surface rheology of the adsorbed film was represented in terms of the two-parameter Maxwell model. Depending on the system investigated, the films were found to be either viscoelastic, purely viscous, neither viscous nor elastic, or rigid.     

Film Flip and Transfer Process to Enhance Light Harvesting in Ultrathin Absorber Films on Specular Back‐Reflectors

Optical interference is used to enhance light–matter interaction and harvest broadband light in ultrathin semiconductor absorber films on specular back‐reflectors. However, the high‐temperature processing in oxygen atmosphere required for oxide absorbers often degrades metallic back‐reflectors and their specular reflectance. In order to overcome this problem, a newly developed film flip and transfer process is presented that enables high‐temperature processing without degradation of the metallic back‐reflector and without the need of passivation interlayers. The film flip and transfer process improves the performance of photoanodes for photoelectrochemical water splitting comprising ultrathin (<20 nm) hematite (α‐Fe₂O₃) films on silver–gold alloy (90 at% Ag–10 at% Au) back‐reflectors. Specular back‐reflectors are obtained with high reflectance below hematite films, which is necessary for maximizing the productive light absorption in the hematite film and minimizing nonproductive absorption in the back‐reflector. Furthermore, the film flip and transfer process opens up a new route to attach thin film stacks onto a wide range of substrates including flexible or temperature sensitive materials.     

Offset planar MIMO antenna for omnidirectional radiation patterns

An offset quad element multi‐band planar MIMO antenna with omnidirectional radiation patterns is proposed for nonline of site (NLOS) communication on low‐cost FR‐4 dielectric substrate for 4G and future technologies. A 1 × 2 power divider arm results in dual beam and enhances diversity parameters and omnidirectional radiation patterns. Moreover, the MIMO antenna limits the proximity/coupling effects using a T‐shaped isolator and achieves more than 12.4 dB of isolation between the radiating ports. The proposed design covers WLAN/WiMAX bands with gain and radiation efficiency of more than 2.6 dBi and 71%, respectively, in 2:1 VSWR bands of bandwidths 16.39% (2.24‐2.64 GHz) and 7.88% (3.41‐3.69 GHz). The ?10 dB impedance bandwidth is more than 280 MHz in each band. An ECC level of ≤ 0.01 has been achieved in the whole band.     

The Impact of Silicon on Photosynthetic and Biochemical Responses of Sugarcane under Different Soil Moisture Levels

Silicon - Increasing drought stress is one of the most limiting factors for agricultural crop productivity across the world. Silicon (Si) has been known to augment plant protection against drought...     

Plasma membrane lipids of bovine adrenal chromaffin cells

The lipid composition of plasma membranes isolated from bovine adrenal chromaffin cells has been determined. Choline and ethanolamine phosphatides were predominant; the level of lyso compounds was very low. The amount of cholesterol and the cholesterol/phospholipid molar ratio was low compared to those of the other subcellular fractions of chromaffin cells. A complex pattern of neutral glycolipids was observed in contrast to that of gangliosides.     

Postoperative apnea in former preterm infants after inguinal herniorrhaphy. A combined analysis

BACKGROUND: Controversy exists as to the risk for postoperative apnea in former preterm infants. The conclusions of published studies are limited by the small number of patients. METHODS: The original data from eight prospective studies were subject to a combined analysis. Only patients having inguinal herniorrhaphy under general anesthesia were included; patients receiving caffeine, regional anesthesia, or undergoing other surgical procedures were excluded. A uniform definition for apnea was used for all patients. Eleven risk factors were examined: gestational age, postconceptual age, birth weight, history of respiratory distress syndrome, bronchopulmonary dysplasia, neonatal apnea, necrotizing enterocolitis, ongoing apnea, anemia, and use of opioids or nondepolarizing muscle relaxants. RESULTS: Two hundred fifty-five of 384 patients from eight studies at four institutions fulfilled study criteria. There was significant variation in apnea rates and the location of apnea (recovery room and postrecovery room) between institutions (P < 0.001). There was considerable variation in the duration and type of monitoring, definitions of apnea, and availability of historical information. The incidence of detected apnea was greater when continuous recording devices were used compared to standard impedance pneumography with alarms or nursing observations. Despite these limitations, it was determined that: (1) apnea was strongly and inversely related to both gestational age (P = 0.0005) and postconceptual age (P < 0.0001); (2) an associated risk factor was continuing apnea at home; (3) small-for-gestational-age infants seemed to be somewhat protected from apnea compared to appropriate- and large-for-gestational-age infants; (4) anemia was a significant risk factor, particularly for patients > 43 weeks' postconceptual age; (5) a relationship to apnea with history of necrotizing enterocolitis, neonatal apnea, respiratory distress syndrome, bronchopulmonary dysplasia, or operative use of opioids and/or muscle relaxants could not be demonstrated. CONCLUSIONS: The analysis suggests that, if it is assumed that the statistical models used are equally valid over the full range of ages considered and that the average rate of apnea reported across the studies analyzed is accurate and representative of actual rates in all institutions, the probability of apnea in nonanemic infants free of recovery-room apnea is not less than 5%, with 95% statistical confidence until postconceptual age was 48 weeks with gestational age 35 weeks. This risk is not less than 1%, with 95% statistical confidence, for that same subset of infants, until postconceptual age was 56 weeks with gestational age 32 weeks or postconceptual age was 54 weeks and gestational age 35 weeks. Older infants with apnea in the recovery room or anemia also should be admitted and monitored. The data do not allow prediction with confidence up to what age this precaution should continue to be taken for infants with anemia. The data were insufficient to allow recommendations regarding how long infants should be observed in recovery. There is additional uncertainty in the results due to the dramatically different rates of detected apnea in different institutions, which appear to be related to the use of different monitoring devices. Given the limitations of this combined analysis, each physician and institution must decide what is an acceptable risk for postoperative apnea.     

UWB antenna and MIMO antennas with bandwidth,band‐notched,and isolation properties for high‐speed data rate wireless communication: A review

The prospective of ultrawide band (UWB) technology is enormous due to its remarkable advantages such as the capability of providing high‐speed data rates at short transmission distances with low power dissipation. The swift growth in wireless communication systems has made UWB an exceptional technology to replace the conventional wireless technologies in today's use. UWB bandwidth (3.1‐10.6 GHz) covers most of the communication applications. High frequency of operation with high level of miniaturization has enhanced the interest in designing high performance antennas. There is a growing demand for small and low cost UWB antennas that are able to provide satisfactory performance in both time and frequency domains. The trend in recent wireless systems, including UWB based systems, are to build small, low‐profile integrated circuits so as to be compatible with portable wireless devices. Transformation of UWB in MIMO achieved high data rate and solved the problem of multipath propagation. The main reason for writing this review is to investigate various UWB methods and band rejection approaches on a single platform. Some of the isolation enhancement approaches are also included in article due to the requirement in MIMO antennas.