Modal analysis of wave propagation in dispersive media

Surveys on wave propagation in dispersive media have been limited since the pioneering work of Sommerfeld [Ann. Phys. 349, 177 (1914)] by the presence of branches in the integral expression of the wave function. In this article, a method is proposed to eliminate these critical branches and hence to establish a modal expansion of the time-dependent wave function. The different components of the transient waves are physically interpreted as the contributions of distinct sets of modes and characterized accordingly. Then, the modal expansion is used to derive a modified analytical expression of the Sommerfeld precursor improving significantly the description of the amplitude and the oscillating period up to the arrival of the Brillouin precursor. The proposed method and results apply to all waves governed by the Helmholtz equations.Comment: 10 pages, 9 figure

Broadband suppression of backscattering at optical frequencies using low permittivity dielectric spheres

The exact suppression of backscattering from rotationally symmetric objects requires dual symmetric materials where ${\epsilon_r} = {\mu_r}$. This prevents their design at many frequency bands, including the optical one, because magnetic materials are not available. Electromagnetically small non-magnetic spheres of large permittivity offer an alternative. They can be tailored to exhibit balanced electric and magnetic dipole polarizabilities, which result in approximate zero backscattering. In this case, the effect is inherently narrowband. Here, we put forward a different alternative that allows broadband functionality: Electromagnetically large spheres made from low permittivity materials. The effect occurs in a parameter regime that approaches the trivial ${\epsilon_r} \to {\mu_r} =1$ case, where approximate duality is met in a weakly wavelength dependence fashion. Despite the low permittivity, the overall scattering response of the spheres is still significant. Radiation patterns from these spheres are shown to be highly directive across an octave spanning band. The effect is analytically and numerically shown using the Mie coefficients.Comment: 6 Figure

Importance of GLUT Transporters in Disease Diagnosis and Treatment

Facilitative sugar transporters (GLUTs) are the primary method of sugar uptake in all mammalian cells. There are 14 different types of those transmembrane proteins, but they transport only a handful of substrates, mainly glucose and fructose. This overlap and redundancy contradict the natural tendency of cells to conserve energy and resources, and has led researchers to hypothesize that different GLUTs partake in more metabolic roles than just sugar transport into cells. Understanding those roles will lead to better therapeutics for a wide variety of diseases and disorders. In this review we highlight recent discoveries of the role GLUTs play in different diseases and disease treatments

A comparison of methods used to measure the in vitro antimicrobial susceptibilities of Mycoplasma species of animal origin

Antimicrobials are commonly used to treat mycoplasmosis in animals. In spite of this and the fact that antimicrobial resistance has been recorded for this group of bacteria there are no universally accepted in vitro means of testing for this resistance, nor is resistance testing for mycoplasmas a routine in most veterinary laboratories. So prior to testing for resistance to a number of mycoplasmas isolated from animals in South Africa it was necessary to compare different tests including broth and agar microdilution tests to find out which one would perform best. Using the field strains M. bovis, M. crocodyli, M. felis, M. gallisepticum and M. synoviae, and the reference strains M. gallisepticum 56USDA, M. gallisepticum VaxSafe MG vaccine strain, M. mycoides T1/44 vaccine strain, and M. mycoides Ygoat (11706) broth- and agar-microdilution minimum inhibitory concentration (MIC)tests were performed using either modified Hayflicks or Mycoplasma synoviae media. Two different metabolism indicator systems were compared in the broth microdilution test (BrMIC) namely sugar fermentation (glucose or pyruvate) with phenol red (SFS) and evidence of reduction with resazurin (AlamurBlue®). It was also tested whether amoxicillin and clavulanic acid (ACA) could be used in the tests to reduce problems associated with contamination. Statistical analyses of the tests (repeatability and linear association) indicated that the BrMIC with SFS was the most reproducible method (pooled standard deviation = 0.14). The antimicrobial ACA was found to not to affect the MIC values (R2= 0.976 to 0.996). Furthermore one hundred forty two field strains including 93 M. bovis, 5 M. synoviae, 21 M. gallisepticum, 13 M. bovirhinis, 8 M. crocodyli and 6 M. felis were tested using the BrMIC+SFS with ACA method. Generally the mycoplasmas originating from poultry were resistant to commonly used antimicrobials and had higher MIC50 and MIC90 values than isolates originating from cattle, crocodiles and cats. It was found that most of the mycoplasmas were susceptible to doxycycline (tetracycline) and enrofloxacin with the exception of M. gallisepticum where 17.9% of strains were resistant to both. Resistance to tiamulin (100%) and tylosin (20 to 64%) was high for the poultry mycoplasmas. Most field isolates tested were resistant to erythromycin, nalidixic acid, florfenicol, norfloxacin, neomycin, sulphamethoxazole, trimethoprim and sulphamethoxazole/ trimethoprim combination, mostly resistant to norfloxacin and florfenicol. It is concluded that BrMIC+SFS with ACA method is a reproducible method that reduces any problems with bacterial contamination. As observed with the poultry strains, it is quite clear that antimicrobial resistance is developing to commonly used antimicrobials such as tylosin, the related pleuromutilins, fluoroquinolones and tetracyclines. In species where antimicrobial therapy is applied routinely such as poultry and possibly feedlot cattle, it is recommended that MIC testing is done prior to any therapeutic interventions.Dissertation (MSc)--University of Pretoria, 2010.Veterinary Tropical Diseasesunrestricte

Microbial examination of drinking water supply systems of Elobeid city, Sudan

The present investigation was carried out to evaluate the microbial parameters of Elobeid drinking water supply systems, which comprise of Bara underground water system and the surface rainwater harvesting (RWH) system, during the period from July 2010–June 2011. Four samples from Bara and nine from RWH were collected. The microbial parameters were determined using different microbial techniques. The results showed that the mean total viable bacterial (TVC) and spore-forming bacteria counts in the RWH system were ranged as 80.26-1030.11 and 82.8-3479.8 cfu/ml, respectively and 4.67-110.5 and 0.83- 292.5 cfu/ml, respectively in Bara. Moreover, high counts of coliforms, faecal coliforms; faecal Streptococci, Salmonella, Staphylococci, Clostridia and Cyanobacteria were recorded in the RWH system, particularly during the rainy months (June–September), which not in agreement with international or local standards for drinking water. The predominant bacteria in the two water supply systems were Bacillus (6 species) Proteus mirabilis, Pseudomonas aeruginosa, Pseudomonas maltophilia, Enterobacter gergoviae, Enterobacter alvi, Proteus vulgaris, E. coli, Salmonella choleraesuis, Staphylococcus aureus, Streptococcus faecium and Streptococcus faecalis, in addition to many Cyanobacterial genera: Lyngbya, Microcystis, Oscillatoria, Synechocystis, Anabaena, Leptolyngbya, Dermocarpa, Aphanizomenon, Schizothrix and Phormidium. The presence of those harmful bacteria in water before and after treatment in the RWH system indicated that water treatment measures adopted by the North Kordofan State Water Corporation (coagulation, sand filtration and disinfection by chlorination) do not guarantee acceptable levels of water disinfection. To alleviate these problems, blending of the two water systems and subsequent treatments to reduce microbial load were suggested as recommended point of view. Published by the International journal of Microbiology and Mycology (IJMM

Effects of symmetry-breaking on electromagnetic backscattering

International audienceAbstract Systems with a discrete rotational symmetry $$2\pi /n$$ 2 π / n where $$n\ge 3$$ n ≥ 3 that also have electromagnetic duality symmetry exhibit zero backscattering. The impact of breaking one of the two symmetries on the emerging backscattering has not yet been systematically studied. Here, we investigate the effect that perturbatively breaking each of the two symmetries has on the backscattering off individual objects and 2D arrays. We find that the backscattering off electromagnetically-small prisms increases with the parameters that determine the symmetry breaking, and that the increase of the backscattering due to the progressive breaking of one of the symmetries can be related to the other symmetry. Further exploration of the interplay between the two symmetries reveals that, in systems lacking enough rotational symmetry, the backscattering can be almost-entirely suppressed for a given linear polarization by deliberately breaking the duality symmetry. This duality breaking can be interpreted as an effective increase of the electromagnetic degree of rotational symmetry for that linear polarization

BALANITES KERNEL OIL FOR THE TREATMENT OF DERMATOPHYTES: A CLINICAL TRIAL

In a previous in vitro study, we have shown that the kernel oil of fruits of the tree Balanites aegyptiaca referred to as Balanites kernel oil ((BKO) is active against dermatophytes (i.e. superficial mycosis, ringworms, tineas (T. captitis, T. cercinata and T. pedis). We report here our clinical trials with BKO. Trials were performed on patients presenting at Wad Medani Dermatology Teaching Hospital as well as primary school children in Elsoreeba Town (5 km south of Wad Medani). Not all patients followed treatment till completely cured. Patients treated with BKO (half of the total) achieved complete cure in 3-5 weeks, on average, while those treated with the standard antifungal drug Miconazole (half of the total patients) did the same in the longer period of 3-8 weeks. Photographs showing progress of response to BKO treatments are included. BKO has great potential for development as a commercial drug for the treatment of dermatophytes