Spectral studies of some hydroxy-derivatives of anthraquinones

The u.v., visible, and i.r. spectra of several hydroxy-anthraquinones are discussed and the bands are assigned. These bands are compared with those of anthracene and anthraquinone. The band at 207 nm. is assigned to a n-sigma* transition; the bands at 252, 272, and 326 nm. are assigned by measuring spectra in solvents of various polarities. The stability constant for the 12-dihydroxyanthraquinone-ethanol complex is obtained

Impedance interaction between islanded parallel voltage source inverters and the distribution network

In an islanded microgrid consisting of parallel-connected inverters, the interaction between an inverter’s output impedance (dominated by the inverter’s filter and voltage controller) and the impedance of the distribution network (dominated by the other paralleled inverters’ output impedances and the interconnecting power cables) might lead to instability. This paper studies this phenomenon using root locus analysis. A controller based on the second derivative of the output capacitor voltage is proposed to enhance the stability of the system. Matlab simulation results are presented to confirm the validity of the theoretical analysis and the robustness of the proposed controlle

Hybrid Generators-based AC Microgrid Performance Assessment in Island Mode

Achieving an accurate steady-state averaged active power sharing between parallel inverters in islanded AC microgrids could be realized by a traditional droop control. For identical inverters having the same droop gains, it is assumed that the transient average power responses will be similar, and no circulating current will flow between the units. However, different line impedances could influence the instantaneous power significantly and thus circulating power flows among the inverters particularly during sudden disturbances such as load changes. This power, if absorbed by an inverter, will lead the DC link voltage to rise abruptly and trip the inverter, thus, degrading the performance of the whole microgrid. The problem becomes worse when hybrid generators are serving as unidirectional power source. This paper assesses the performance of hybrid generators within an islanded microgrid against the mismatch in line impedances. Two schemes to stabilize the microgrid are proposed. In addition, a participation factor analysis is developed to select the most effective controller scheme to bound the DC link voltage and minimize the circulating power. Simulation and experimental results are presented to verify the analysis and the capability of the proposed controller

Making a Case for New Directions in English Language Teaching Research at an Omani University: A Critical Qualitative Content Analysis Report

Sultan Qaboos University (SQU) has been the sole English Language Teaching (ELT) research enterprise in the Sultanate of Oman through the Master of Education (M.Ed.) in Curriculum and Methods of Teaching English degree program it launched in the early 1990s. Eighty-two theses have been completed so far about topics pertinent to ELT in the Sultanate of Oman. However, a review of those theses has shown that the discussion of these topics lacks a critical dimension that can advance Omani ELT at the micro and macro levels. This critical qualitative study, therefore, sets out to make a case for new directions in ELT research at the M.Ed. in ELT program at SQU. The discussion should lead to better understanding of the multiple ELT problems in the Sultanate of Oman and have implications for other similar contexts

Aeromonas Pneumonia in a Trauma Patient Requiring Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome: Case Report and Literature Review

Background: Aeromonas species, particularly Aeromonas hydrophila, cause a wide spectrum of diseases in human being such as gastroenteritis; soft tissue infections including necrotizing fasciitis, meningitis, peritonitis, and bacteremia; but pneumonia and respiratory tract infections are uncommon. Methods: Case report and literature review. Results: A 30-year-old victim of a motor vehicle crash sustained pelvic fractures and splenic injury. Delayed splenic rupture caused sudden cardiorespiratory arrest. The patient was resuscitated but suffered septic shock and severe hypoxemia refractory to advanced mechanical ventilatory strategies. Aeromonas hydrophila was isolated as the causative pathogen of severe bilateral pneumonia. Venovenous extracorporeal membrane oxygenation (ECMO) was used temporarily. The patient recovered uneventfully. Conclusion: This is the first case, to our knowledge, of the use of ECMO in a trauma patient with severe fulminant A. hydrophila pneumonia. Clinicians should be aware of the characteristics of this pathogen and associated clinical infections.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90457/1/sur-2E2010-2E037.pd

Mesocosm experiments reveal the impact of mosquito control measures on malaria vector life history and population dynamics

The impact of control measures on mosquito vector fitness and demography is usually estimated from bioassays or indirect variables in the field. Whilst indicative, neither approach is sufficient to quantify the potentially complex response of mosquito populations to combined interventions. Here, large replicated mesocosms were used to measure the population-level response of the malaria vector Anopheles arabiensis to long-lasting insecticidal nets (LLINs) when used in isolation, or combined with insecticidal eave louvers (EL), or treatment of cattle with the endectocide Ivermectin (IM). State-space models (SSM) were fit to these experimental data, revealing that LLIN introduction reduced adult mosquito survival by 91% but allowed population persistence. ELs provided no additional benefit, but IM reduced mosquito fecundity by 59% and nearly eliminated all populations when combined with LLINs. This highlights the value of IM for integrated vector control, and mesocosm population experiments combined with SSM for identifying optimal combinations for vector population elimination

Metallicities of 0.3<z<1.0 Galaxies in the GOODS-North Field

We measure nebular oxygen abundances for 204 emission-line galaxies with redshifts 0.3<z<1.0 in the Great Observatories Origins Deep Survey North (GOODS-N) field using spectra from the Team Keck Redshift Survey (TKRS). We also provide an updated analytic prescription for estimating oxygen abundances using the traditional strong emission line ratio, R_{23}, based on the photoionization models of Kewley & Dopita (2003). We include an analytic formula for very crude metallicity estimates using the [NII]6584/Halpha ratio. Oxygen abundances for GOODS-N galaxies range from 8.2< 12+log(O/H)< 9.1 corresponding to metallicities between 0.3 and 2.5 times the solar value. This sample of galaxies exhibits a correlation between rest-frame blue luminosity and gas-phase metallicity (i.e., an L-Z relation), consistent with L-Z correlations of previously-studied intermediate-redshift samples. The zero point of the L-Z relation evolves with redshift in the sense that galaxies of a given luminosity become more metal poor at higher redshift. Galaxies in luminosity bins -18.5<M_B<-21.5 exhibit a decrease in average oxygen abundance by 0.14\pm0.05 dex from z=0 to z=1. This rate of metal enrichment means that 28\pm0.07% of metals in local galaxies have been synthesized since z=1, in reasonable agreement with the predictions based on published star formation rate densities which show that ~38% of stars in the universe have formed during the same interval. (Abridged)Comment: AASTeX, 49 pages, 16 figures, accepted for publication in The Astrophysical Journa

Evaluation of High Impedance Surfaces for MRI RF Coil Applications ­ Simulations of RF Field and Specific Absorption Rate

This paper investigates the use of High Impedance Surfaces (HIS) to enhance the magnetic near-field within a dielectric phantom stimulated by a surface coil antenna resonating at 63.8 MHz for use in Magnetic Resonance Imaging (MRI) systems. Specifically, the optimization of the space between the surface of the coil and the HIS is presented here. The HIS incorporates interdigitated capacitive elements that produce an electrically small unit cell size. The magnetic field strength is shown to be improved by 42% as compared to a system which uses only an RF shield The associated Specific Absorption Rate (SAR) for the optimum design is simulated and compared to international standards. The work is aimed at 1.5T MRI applications