41 research outputs found
ULTRA-WIDEBAND MICROSTRIP ANTENNA ENHANCED PERFORMANCE USING METAMATERIAL
Antenna engineering is very important in the development of communication systems and the requirements for low profile antennas that cover a wide spectrum of frequencies increase the number of researches in this field. Accordingly, scientists have focused on UWB microstrip antennas that cover the range from 3.1 GHz to 10.6 GHz but others concentrate on enhancing its performance using a special type of materials called metamaterials.
The main objective of this work is to enhance frequency bandwidth, antenna gain, and radiation pattern for the UWB circular microstrip antenna by employing the Split Ring Resonator (SRR) technique, which is one type of metamaterial.
Circular and square split-ring resonators are investigated as an enhancement method after studying their characteristics. Multiple techniques are also applied to these two structures prior to being implemented at the antennaâs backside including different SRR schematics such as the SRR position with respect to the ground, inner and outer ring rotation, positive and negative rotation angle, number of SRR units, SRR size, SRR design, in addition to using the complementary SRR. Furthermore, two techniques are combined together in some designs to observe how the antennaâs performance will be affected. The proposed techniques rely on the variation in capacitance and inductance which will affect the resonant frequency of the SRR unit cell. Then some SRR Schematics were implemented in the proposed circular antenna design to test the functionality within WiFi frequencies 2.4 GHz and 5 GHz. The enhancement can be summarized in increasing antenna bandwidth and transmitting or rejecting specific frequency bands. The results of the study reveal an enhancement in circular antenna performance. UWB circular antenna with elliptical rings has a frequency bandwidth between 3.5 GHz to 9 GHz and a maximum gain of around 5 dB; during the enhancement process using the previously mentioned techniques, the frequency bandwidth increased to cover the range from 2.2 GHz to 9.8 GHz along with some bands rejection. It was noted that some rejected bands have shifted to higher frequencies when applying inner or outer ring rotation. To emphasize this, WiFi frequencies 2.4 GHz and 5GHz are inspected by using the suitable size of S-SRR to decide which frequency to reject or transmit depending on the communication applications.
The outcomes of this work should assist in designing antennas with SRR depending on required communication applications and operating frequencies
Scorpion peptides: Potential use for new drug development
Several peptides contained in scorpion fluids showed diverse array of biological activities with high specificities to their targeted sites. Many investigations outlined their potent effects against microbes and showed their potential to modulate various biological mechanisms that are involved in immune, nervous, cardiovascular, and neoplastic diseases. Because of their important structural and functional diversity, it is projected that scorpion-derived peptides could be used to develop new specific drugs. This review summarizes relevant findings improving their use as valuable tools for new drugs development
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A review of lunar communications and antennas: assessing performance in the context of propagation and radiation
YesOver the previous two decades, a notable array of space exploration missions have been initiated with the primary aim of facilitating the return of both humans and robots from Earth to the moon. The significance of these endeavors cannot be emphasized enough as numerous entities, both public and private, from across the globe have invested substantial resources into this pursuit. Researchers have committed their efforts to addressing the challenges linked to lunar communication. Even with all of these efforts, only a few of the many suggested designs for communication and antennas on the moon have been evaluated and compared. These designs have also not been shared with the scientific community. To bridge this gap in the existing body of knowledge, this paper conducts a thorough review of lunar surface communication and the diverse antenna designs employed in lunar communication systems. This paper provides a summary of the findings presented in lunar surface communication research while also outlining the assorted challenges that impact lunar communication. Apart from various antenna designs reported in this field, based on their intended usage, two additional classifications are introduced: (a) mission-based antennas-utilized in actual lunar missions-and (b) research-based antennas-employed solely for research purposes. Given the critical need to comprehend and predict lunar conditions and antenna behaviors within those conditions, this review holds immense significance. Its relevance is particularly pronounced in light of the numerous upcoming lunar missions that have been announced.This work is part of the âPerformance Evaluation of Lunar Rashid Rover Communication Systemâ research project, supported by the University of Dubai
Twist-2 Controls Myeloid Lineage Development and Function
Basic helix-loop-helix (bHLH) transcription factors play critical roles in lymphoid and erythroid development; however, little is known about their role in myeloid lineage development. In this study, we identify the bHLH transcription factor Twist-2 as a key negative regulator of myeloid lineage development, as manifested by marked increases in mature myeloid populations of macrophages, neutrophils, and basophils in Twist-2âdeficient mice. Mechanistic studies demonstrate that Twist-2 inhibits the proliferation as well as differentiation of granulocyte macrophage progenitors (GMP) by interacting with and inhibiting the transcription factors Runx1 and C/EBPα. Moreover, Twist-2 was found to have a contrasting effect on cytokine production: inhibiting the production of proinflammatory cytokines such as interleukin-12 (IL-12) and interferon-Îł (IFNÎł) while promoting the regulatory cytokine IL-10 by myeloid cells. The data from further analyses suggest that Twist-2 activates the transcription factor c-Maf, leading to IL-10 expression. In addition, Twist-2 was found to be essential for endotoxin tolerance. Thus, this study reveals the critical role of Twist-2 in regulating the development of myeloid lineages, as well as the function and inflammatory responses of mature myeloid cells
A Genome-Wide Association Study Identifies Susceptibility Variants for Type 2 Diabetes in Han Chinese
To investigate the underlying mechanisms of T2D pathogenesis, we looked for diabetes susceptibility genes that increase the risk of type 2 diabetes (T2D) in a Han Chinese population. A two-stage genome-wide association (GWA) study was conducted, in which 995 patients and 894 controls were genotyped using the Illumina HumanHap550-Duo BeadChip for the first genome scan stage. This was further replicated in 1,803 patients and 1,473 controls in stage 2. We found two loci not previously associated with diabetes susceptibility in and around the genes protein tyrosine phosphatase receptor type D (PTPRD) (Pâ=â8.54Ă10â10; odds ratio [OR]â=â1.57; 95% confidence interval [CI]â=â1.36â1.82), and serine racemase (SRR) (Pâ=â3.06Ă10â9; ORâ=â1.28; 95% CIâ=â1.18â1.39). We also confirmed that variants in KCNQ1 were associated with T2D risk, with the strongest signal at rs2237895 (Pâ=â9.65Ă10â10; ORâ=â1.29, 95% CIâ=â1.19â1.40). By identifying two novel genetic susceptibility loci in a Han Chinese population and confirming the involvement of KCNQ1, which was previously reported to be associated with T2D in Japanese and European descent populations, our results may lead to a better understanding of differences in the molecular pathogenesis of T2D among various populations
Embryotoxicity following repetitive maternal exposure to scorpion venom
Although it is a frequent accident in a few countries, scorpion envenomation during pregnancy remains scarcely studied. In the present study, the effects of repetitive maternal exposure to Buthus occitanus tunetanus venom are investigated and its possible embryotoxic consequences on rats. Primigravid rats received a daily intraperitoneal dose of 1 mL/kg of saline solution or 300 ”g/kg of crude scorpion venom, from the 7th to the 13th day of gestation. On the 21st day, the animals were deeply anesthetized using diethyl-ether. Then, blood was collected for chemical parameter analysis. Following euthanasia, morphometric measurements were carried out. The results showed a significant increase in maternal heart and lung absolute weights following venom treatment. However, the mean placental weight per rat was significantly diminished. Furthermore, blood urea concentration was higher in exposed rats (6.97 ± 0.62 mmol/L) than in those receiving saline solution (4.94 ± 0.90 mmol/L). Many organs of venom-treated rat fetuses (brain, liver, kidney and spleen) were smaller than those of controls. On the contrary, fetal lungs were significantly heavier in fetuses exposed to venom (3.2 ± 0.4 g) than in the others (3.0 ± 0.2 g). Subcutaneous blood clots, microphthalmia and total body and tail shortening were also observed in venom-treated fetuses. It is concluded that scorpion envenomation during pregnancy potentially causes intrauterine fetal alterations and growth impairment
Ătude de lâallergie croisĂ©e entre les diffĂ©rents inhibiteurs de la pompe Ă protons
Bien que des réactions allergiques aux inhibiteurs de la pompe à protons (IPP) aient été
décrites par certains auteurs, la présence de réactions croisées entre les différentes
molĂ©cules est un sujet de discussion. Le but de notre travail est dâanalyser tous les cas
de réactions cutanées allergiques aux IPP notifiés au service régional de
pharmacovigilance de Sfax durant une pĂ©riode de 12 ans allant du mois dâaoĂ»t 2000 au mois
de juillet 2012 et dâĂ©valuer la possibilitĂ© de rĂ©actions croisĂ©es entre les diffĂ©rentes
molĂ©cules de cette classe. Une enquĂȘte de pharmacovigilance a Ă©tĂ© rĂ©alisĂ©e pour chaque cas
selon la méthode française d'imputabilité. Nous avons convoqué ensuite, tous les patients
qui ont développé une réaction allergique à un IPP avec une imputabilité plausible ou
vraisemblable. Un patch-test Ă toute les molĂ©cules a Ă©tĂ© rĂ©alisĂ© afin dâĂ©tudier la
possibilitĂ© dâallergie croisĂ©e entre les IPP. Trente-sept patients ont dĂ©veloppĂ© des
réactions cutanées aux IPP durant une période de 12 ans, avec un total de 1 172
toxidermies, soit 3 % du total des toxidermies rapportées au centre de pharmacovigilance
de Sfax. La toxidermie la plus frĂ©quemment observĂ©e Ă©tait lâĂ©ruption maculo-papuleuse (19
cas soit 51 %), suivie de lâurticaire dans 9 cas (24 %). LâomĂ©prazole Ă©tait lâIPP le plus
incriminé (dans 31 cas soit 83,78 %). La prise ultérieure du lansoprazole a été faite chez
5 patients ayant dĂ©veloppĂ© une allergie Ă lâomĂ©prazole et sâest dĂ©roulĂ©e sans incidents.
Les patch-tests ont Ă©tĂ© rĂ©alisĂ©s chez 6 patients ayant dĂ©veloppĂ© une rĂ©action cutanĂ©e Ă
lâomĂ©prazole. La lecture de ces tests Ă 72 h a Ă©tĂ© positive Ă lâomĂ©prazole dans tout les
cas, et négatifs au lansoprazole dans 5 cas. Dans un tiers des cas, le lansoprazole a été
une bonne alternative en cas dâallergie Ă lâomĂ©prazole, Ă lâĂ©somĂ©prazole ou au
pantoprazole. Dans 1 cas, nous avons contre-indiqué tous les IPP. Dans les autres cas, une
surveillance sâimposera lors de lâutilisation ultĂ©rieure du lansoprazole