LC compensators for power factor correction of nonlinear loads

This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of Brunel University's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. Copyright @ 2004 IEEEA method is presented for finding the optimum fixed LC compensator for power factor correction of nonlinear loads where both source voltage and load current harmonics are present. The LC combination is selected because pure capacitive capacitors alone would not sufficiently correct the power factor. Optimization minimizes the transmission loss, maximizes the power factor, and maximizes the efficiency. The performance of the obtained compensator is discussed by means of numerical examples

Practical considerations regarding power factor for nonlinear loads

This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of Brunel University's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. Copyright @ 2004 IEEEThe choice of LC compensator may be constrained by the availability of manufacturers units. To account for this, the capacitor values are chosen from among standard values and for each value the transmission losses is minimized, or power factor is maximized, or transmission efficiency is maximized. The global minimum or maximum is obtained by scanning all local minims or maxims. The performance of the obtained compensator is discussed by means of numerical examples

Chemistry private tutoring in Malaysia

The unsatisfactory result obtained by Malaysian secondary students in international assessment has caused the Ministry of Education to put much effort into structuring the curriculum. Variety of teaching pedagogies has been suggested but not all the approaches are applicable due to many constraints. It leads students to enroll in extra private tutoring classes after their regular school hours. This research aimed to identify the reason students attend chemistry private tutoring, to explore the teaching pedagogies used in chemistry private tutoring, and to identify the perceptions of students on the pedagogies used in chemistry private tutoring. This is an exploratory qualitative study that is conducted among six tutors and five students in Malaysia. The result was analyzed through thematic analysis. Interestingly, the study has indicated that despite improving their academic result, students attend tuition to enhance their understanding and knowledge of chemistry as they were ably exposed to a variety of teaching methods. A new insight on pedagogies used in private tutoring lessons was determined, such as deductive learning, inquiry-based teaching and contextualization. It is found that student’s learning needs are highly emphasized in tuition classes. Students experience more meaningful learning and obtain interesting learning experiences in tuition

Effect of low-dose oral contraceptives on Lipid profile levels in Sudanese women using oral contraceptive pills

Background: Oral contraceptives provide highly reliable contraceptive protection even though imperfect use is considered, and are widely used worldwide.Objective: This study aimed to assess the effect of low dose combined oral contraceptive pills use on lipid profile levels in Sudanese women, and to find its correlation with age, BMI and duration of using oral contraceptive.Material and Methods: A clinically-based descriptive study was conducted during the period from May to October 2013. Sixty six women using low dose combined oral contraceptive were selected as a test group compared to sixty six apparently healthy non users as a control, attending the family planning center of Omdurman Maternity Hospital in Khartoum state, Sudan. Blood specimens were collected from both groups and serum levels of Total Cholesterol, Triglyceride and High Density Lipoprotein (HDL) were estimated and Low Density Lipoprotein (LDL) was calculated using Friedewaled equation.Results : Results showed a significant increase in the mean serum levels of Total Cholesterol, Triglyceride and HDL in the test group compared with the control group (p <0.05) and insignificant increase in the mean serum levels of LDL in the test group (P = 0.327). HDL levels decreased with age (P value 0.000) while Cholesterol, Triglyceride and LDL levels were not affected. The study also showed significant increase in Cholesterol, Triglyceride and decrease in HDL with duration of oral contraceptive use (P <0.05).The BMI was significantly higher in users than non-users (P 0.025).Conclusion: Combined oral contraceptive pills adversely affect the lipid profile. This may be due to drug responsiveness, as well as increased BMI. There isa correlation between duration of oral contraceptive use and lipid profile among the studied cases.Key words: Contraceptive pill, Low Doses, Serum lipids, Sudanese Women

Tyrosine kinase inhibitors for the therapy of anaplastic thyroid cancer

Anaplastic thyroid cancer (ATC) is often incurable so new therapeutic approaches are needed. Tyrosine kinases inhibitors (such as imanitib, sunitinib or sorafenib) are under evaluation for the treatment of ATC. Other vascular disrupting agents, such as combretastatin A4 phosphate, and antiangiogenic agents, such as aplidin, PTK787/ZK222584 and human VEGF monoclonal antibodies (bevacizumab, cetuximab), have been evaluated. Small-molecule adenosine triphosphate competitive inhibitors directed intracellularly at EGFRs tyrosine kinase, such as erlotinib or gefitinib, are also studied. Furthermore, new molecules have been shown to be active against ATC, such as CLM94 and CLM3. However, more research is needed to finally identify therapies able to control and to cure this disease

Cytotoxic xanthones isolated from calophyllum depressinervosum and calophyllum buxifolium with antioxidant and cytotoxic activities

The stem bark of Calophyllum depressinervosum and Calophyllum buxifolium were extracted and examined for their antioxidant activities, together with cytotoxicity towards human cancer cells. The methanol extract of C. depressinervosum exhibited good DPPH and NO scavenging effects. The strongest BCB inhibition and FIC effects were shown by dichloromethane and ethyl acetate extracts of both species. Overall, DPPH, FRAP and FIC assays showed strong correlation with TPC. For cytotoxicity, hexane extract of C. depressinervosum possessed the strongest anti-proliferative activities towards SNU-1 cells while the hexane extract of C. buxifolium showed the strongest activity towards LS-174T and K562 cells with the IC values ranging from 7 to 17 μg/mL. The purification of plant extracts afforded eight xanthones, ananixanthone (1), caloxanthone B (2), caloxanthone I (3), caloxanthone J (4) xanthochymone B (5), thwaitesixanthone (6), 1,3,5,6-tetrahydroxyxanthone (7) and dombakinaxanthone (8). All the xanthones, except 1 were reported for the first time from both Calophyllum species. The xanthones were examined for their cytotoxic effect against K562 leukemic cells. Compounds 1 and 2 showed strong cytotoxicity with the IC values of 2.96 and 1.23 μg/mL, respectively. The molecular binding interaction of 2 was further investigated by performing molecular docking study with promising protein receptor Src kinase

A Framework of MRI Fat Suppressed Imaging Fusion System for Femur Abnormality Analysis

AbstractShort T1 Inversion Recovery (STIR) is a fat suppressed technique commonly used in Magnetic Resonance Imaging (MRI) to suppress fat signals from tissues. The technique is to improve visual inspection during diagnosis. Suspected fluids will appear bright in STIR to identify the abnormality. Due to hardware limitation, tissue contrast and signal-to-noise ratio are reduced. We propose a framework of image fusion system which mimics the MRI machine to produce a fused ‘STIR’ image. The resultant fused ‘STIR’ image has high similarity index (0.989971), small mean square error (0.1092), high peak signal-to-noise ratio (106.9173) and good Pearson correlation coefficient (0.696)

rac-[3-Hydroxy-6,9-dimethyl-6-(4-methylpent-3-en-1-yl)-6a,7,8,9,10,10a-hexahydro-6H-1,9-epoxybenzo[c]chromen-4-yl](phenyl)methanone

The title compound congestiflorone, C28H32O4, which was isolated from the stem bark of Mesua congestiflora, consists of a benzophenone skeleton with two attached pyran rings to which a cyclo­hexane ring and a C6 side chain are bonded. The benzene ring is significantly distorted from planarity (r.m.s. deviation = 0.0007 Å) due to the constraints imposed by junctions with the two pyran rings. The cyclo­hexane ring is in a chair conformation, one pyran ring is in a boat conformation, while the other is a distorted chair. The phenyl and benzene rings make a dihedral angle of 55.85 (9)°. An intra­molecular O—H⋯O hydrogen bond is observed. In the crystal, mol­ecules are linked via C—H⋯O inter­actions

Caloxanthone C: a pyran­oxanthone from the stem bark of Calophyllum soulattri

The title compound [systematic name: 5,10-di­hy­droxy-2,2-di­methyl-12-(2-methyl­but-3-en-2-yl)­pyrano[3,2-b]xanthen-6(2H)-one], C23H22O5, isolated from the stem bark of Calophyllum soulattri, consists of four six-membered rings and a 2-methyl­but-3-en-2-yl side chain. The tricyclic xanthone ring system is almost planar [maximum deviation = 0.093 (2) Å], whereas the pyran­oid ring is in a distorted boat conformation. The 2-methyl­but-3-en-2-yl side chain is in a synperiplanar conformation. There are two intra­molecular O—H⋯O hydrogen bonds. In the crystal, mol­ecules are linked by C—H⋯O inter­actions, forming a zigzag chain propagating in [010]