Superconducting Quantum Point contacts and Maxwell Potential

The quantization of the current in a superconducting quantum point contact is reviewed and the critical current is discussed at different temperatures depending on the carrier concentration as well by suggesting a constant potential in the semiconductor and then a Maxwell potential. When the Fermi wave length is comparable with the constriction width we showed that the critical current has a step-like variation as a function of the constriction width and the carrier concentration.Comment: 13 pages, 8 figures, some figures are clarified; scheduled to appear in an issue in MPLB Vo.21, (2007

Synergetic effect of aged garlic extract and methotrexate on rheumatoid arthritis induced by collagen in male albino rats

33-38Aged garlic extract (AGE) exhibit anti-inflammatory effect in many diseases, and methotrexate (MTX) as rheumatoid arthritis (RA) treatment drug shows adverse hepatotoxicity effect. Therefore, in this study, we evaluated the antioxidant and anti-inflammatory effects of AGE treatment alone or with MTX in collagen-induced arthritis (CIA) rats to diminish the hepatotoxicity. The study used eight groups of rats as one control non treated group and seven treated groups with CIA, AGE (200 mg/kg/PO), MTX (1.5 mg/kg/2 days/subcutaneous), CIA-AGE, CIA-MTX, AGE-MTX and CIA-MTX-AGE. All treatments started from day 21 after the symptoms of arthritis appeared to day 50. The CIA-AGE and CIA-MTX-AGE groups showed significantly decreased serum liver function markers ASAT, ALAT and ALP enzymes activities. In line with the significantly increased antioxidants, total glutathione and SOD and CAT enzymes activities and decreased MDA levels as compared to CIA and CIA-MTX treated groups' values. In addition, the CIA-AGE and CIA-MTX-AGE groups recorded significant decrease in the measured cytokines (CRP and TNF) and interleukins (IL-17, IL-6, and IL-1) values as compared to the corresponding values in CIA and CIA-MTX groups. Results suggested the safety of AGE for achieving a better control in treatment of RA with the conventional drug MTX to diminish its hepatotoxicity

Biochemical and histological study on the effect of levetiracetam on the liver and kidney of pregnant albino rats

Background: Levetiracetam is a broad-spectrum antiseizure agent and one of the most commonly prescribed drugs for epilepsy. The aim of this work was to assess the effect of levetiracetam at its therapeutic range on the liver and kidney of pregnant albino rats. Materials and methods: Forty pregnant rats were divided equally into two groups (I–II), Rats in the group I were gavaged 1.5 mL/day distilled water in two divided doses throughout pregnancy. Rats in the group II were gavaged 1.5 mL/day distilled water (containing 36 mg levetiracetam) in two divided doses throughout pregnancy. At the end of the experiment, blood samples were taken and the sera were separated and used for biochemical analysis. The kidneys and livers of both groups were excised and used for light and electron microscopic examination. Results: Treatment with levetiracetam induced undesirable histopathological changes in the liver and kidney of pregnant albino rats. These changes were in the form of distortion of the hepatic architecture, dilatation of the central and the portal veins, widening of the Bowman’s spaces, thickening and disruption of the glomerular basement membrane, fusion and effacement of secondary foot processes, cytoplasmic vacuolation, and swollen mitochondria with loss of their cristae. Such changes were confirmed by alteration of certain biochemical parameters related to the liver and kidney functions. Conclusions: Levetiracetam induced deleterious effects on the liver and kidney of pregnant albino rats. Further investigations are recommended to clarify the mechanism of levetiracetam toxicity

Design, synthesis and potential anti-proliferative activity of some novel 4-aminoquinoline derivatives

Novel nineteen compounds based on a 4-aminoquinoline scaffold were designed and synthesized as potential anti-proliferative agents. The new compounds were N-substituted at the 4-position by aryl or heteroaryl 1-9, quinolin-3-yl 10, 2-methylquinolin-3-yl 11, thiazol-2-yl 12, and dapsone moieties 13, 14 and 18. Bis-compounds 15, 16 and 19 were also synthesized to assess their biological activity. All the newly synthesized comounds were tested for in vitro antiproliferative activity against the MCF-7 breast cancer cell line. Seventeen of the novel compounds showed higher activity than the reference drug doxorubicin. The corresponding 7-(trifluoromethyl)-N-(3,4,5-trimethoxyphenyl)quinolin-4-amine 1, N-(7-(trifluoromethyl)quinolin-4-yl)quinolin-3-amine (10), 2-methyl-N-(7-trifluorome-thyl)quinolin-4-yl)quinolin-3-amine (11) and N-(4-(4-aminophenylsulf-onyl)phenyl)-7-chloroquinolin-4-amine (13) were almost twice to thrice as potent as doxorubicin

Primary torsion of the greater omentum: An overlooked cause of acute abdomen

Background/purpose Primary torsion of the greater omentum is an uncommon cause of acute abdomen in children. It was estimated to be found in 0.1% of cases operated for acute appendicitis and is almost impossible to be diagnosed preoperatively. Surgical excision of the infarcted omentum is the treatment of choice. In this study, we aimed to highlight the importance of suspecting primary omental torsion when operating upon a child presenting with a picture of acute appendicitis with normal appearing appendix intraoperatively.Patients and methods Through the period from June 2009 to May 2016, medical records of patients who had definite diagnosis of primary omental torsion were retrospectively reviewed. Clinical presentations, laboratory findings, imaging studies results, intraoperative findings, and histopathological findings were reviewed.Results During the specified time period, out of 1344 patients operated upon for acute appendicitis in our department, only four patients proved to have primary torsion of the greater omentum. All the patients were obese with clinical picture mimicking acute appendicitis. The postoperative histopathological examination showed normal appendix and ischemic necrosis of the resected omental segment.Conclusion Inspection of the greater omentum is essential when finding a normal appearing appendix in any case operated for suspicion of acute appendicitis. Keywords: acute abdomen, appendix, greater omentum, omental torsio

Comparative Study of Sensorless Control Methods of PMSM Drives

Recently, permanent magnet synchronous motors (PMSMs) are increasingly used in high performance variable speed drives of many industrial applications. This is because the PMSM has many features, like high efficiency, compactness, high torque to inertia ratio, rapid dynamic response, simple modeling and control, and maintenance-free operation. In most applications, the presence of such a position sensor presents several disadvantages, such as reduced reliability, susceptibility to noise, additional cost and weight and increased complexity of the drive system. For these reasons, the development of alternative indirect methods for speed and position control becomes an important research topic. Many advantages of sensorless control such as reduced hardware complexity, low cost, reduced size, cable elimination, increased noise immunity, increased reliability and decreased maintenance. The key problem in sensorless vector control of ac drives is the accurate dynamic estimation of the stator flux vector over a wide speed range using only terminal variables (currents and voltages). The difficulty comprises state estimation at very low speeds where the fundamental excitation is low and the observer performance tends to be poor. The reasons are the observer sensitivity to model parameter variations, unmodeled nonlinearities and disturbances, limited accuracy of acquisition signals, drifts, and dc offsets. Poor speed estimation at low speed is attributed to data acquisition errors, voltage distortion due the PWM inverter and stator resistance drop which degrading the performance of sensorless drive. Moreover, the noises of system and measurements are considered other main problems. This paper presents a comprehensive study of the different methods of speed and position estimations for sensorless PMSM drives. A deep insight of the advantages and disadvantages of each method is investigated. Furthermore, the difficulties faced sensorless PMSM drives at low speeds as well as the reasons are highly demonstrated. Keywords: permanent magnet, synchronous motor, sensorless control, speed estimation, position estimation, parameter adaptation

Optimizing Information Freshness in Wireless Networks: A Stochastic Geometry Approach

Optimization of information freshness in wireless networks has usually been performed based on queueing analysis that captures only the temporal traffic dynamics associated with the transmitters and receivers. However, the effect of interference, which is mainly dominated by the interferers' geographic locations, is not well understood. In this paper, we leverage a spatiotemporal model, which allows one to characterize the age of information (AoI) from a joint queueing-geometry perspective, for the design of a decentralized scheduling policy that exploits local observation to make transmission decisions that minimize the AoI. To quantify the performance, we also derive accurate and tractable expressions for the peak AoI. Numerical results reveal that: i) the packet arrival rate directly affects the service process due to queueing interactions, ii) the proposed scheme can adapt to traffic variations and largely reduce the peak AoI, and iii) the proposed scheme scales well as the network grows in size. This is done by adaptively adjusting the radio access probability at each transmitter to the change of the ambient environment.Comment: arXiv admin note: substantial text overlap with arXiv:1907.0967