Investigation of soil salinity to distinguish boundary line between saline and agricultural lands in Bonab Plain, southeast Urmia Lake, Iran

Gradual drying of Urmia Lake has left vast saline areas all around it, increasing the risk of salinization of agricultural lands next to the Lake. The current research was aimed to predict soil salinity and distinguish the boundary line between saline and agricultural lands by taking in to account the spatial variability of soil salinity in Bonab Plain, Iran. To do so, soil samples were taken from depth 0-25 cm in 78 points with spatial intervals of 500 m and were analyzed for their electrical  conductivity in saturated paste extractions. Data analysis showed that soil salinity mean wasn’t stationary and was varying among dataset. Therefore to build up a  variogram, the spatial components of the mean trend were computed and subtracted from laboratory measured ECe values, which resulted in residuals. The  semivariogram function was then calculated and modelled based on the residuals. Cross-validation results showed that kriging method along with modified  semi-variogram, resulted in better predictions of soil salinity with ME and MSE equal to 0.12 and 0.3. Setting 4 dSm-1 as the limit between saline and non-saline soils in kriging algorithms resulted in a sharp boundary line between saline and non-saline lands in the study area. The presence of highly saline soils next to the agricultural lands in the area can increase the risk of secondary salinization of the Bonab Plain which is one of the important agricultural production centers in the area. Therefore, careful monitoring of lands near salinity boundary in the area should be of high priority.Key Words: Bonab Plain, Kriging, variogram, soil salinity, spatial prediction, Urmia Lake

Repetitive acoustic streaming patterns in sinusoidal shaped microchannels

Geometry of the fluid container plays a key role in the shape of acoustic streaming patterns. Inadvertent vortices can be troublesome in some cases, but if treated properly, the problem turns into a very useful parameter in acoustic tweezing or micromixing applications. In this paper, the effects of sinusoidal boundaries of a microchannel on acoustic streaming patterns are studied. Results show that while top and bottom sinusoidal walls are vertically actuated at the resonance frequency of basic hypothetical rectangular microchannel, some repetitive acoustic streaming patterns are recognized in classifiable cases. Such patterns can never be produced in rectangular geometry with flat boundaries. Relations between geometrical parameters and emerging acoustic streaming patterns lead us to propose formulas in order to predict more cases. Such results and formulations were not trivial at a glance

How predictable is development of resistance after β-lactam therapy in Enterobacter cloacae infection?

Certain non-fastidious Gram-negative bacilli, notably Enterobacter cloacae, although classified as susceptible by usual in-vitro susceptibility testing, often become resistant in patients treated with newer β-lactam antibiotics. Here various in-vitro tests were carried out together with an animal model allowing the quantification of resistance that emerges after short term therapy. Mice were challenged (102 cfu plus talcum) intraperitoneally with one each of four strains of Ent. cloacae. Two hours later, a single β-lactam dose was administered subcutaneously. The following day, the peritoneal bacterial population was analysed by using antibiotic-containing gradient plates. Development of resistance after therapy varied according to the compound considered. Imipenem (50 mg/kg) produced no resistance, and piperacillin (200 mg/kg) only a few, while resistance occurred frequently after therapy with aztreonam (50 mg/kg), ceftazidime (50 mg/kg), cefotaxime (50 mg/kg) and cefpirome (50 mg/kg). MICs increased by at least 16-fold when resistance developed. No simple correlations were found between these in-vivo results and initial MICs, killing kinetics, frequency of resistant variants within the bacterial populations before therapy, initial MIC of these variants or antibiotic concentrations assayed in peritoneal fluid 60 min after dosing. The most reliable predictive in-vitro test appeared to be the determination of resistance emerging in broth containing at least 16 times the MIC of the antibiotic tested. Such a test is unlikely to be used on a routine basis. When a β-lactam compound seems appropriate for treating an Enterobacter infection, it may be advisable to avoid drugs that are prone prone to produce resistance in experimental or clinical infections, whatever the results of conventional in-vitro susceptibility test

Multiscale statistical quantum transport in porous media and random alloys with vacancies

We have developed a multi-scale self-consistent method to study the charge conductivity of a porous system or a metallic matrix alloyed by randomly distributed nonmetallic grains and vacancies by incorporating Schr\"{o}dinger's equation and Poisson's equation. To account for the random distribution of the nonmetallic grains and clusters within the alloy system, we have used an uncorrelated white-noise Monte-Carlo sampling to generate numerous random alloys and statistically evaluate the charge conductance. We have performed a parametric study and investigated various electrical aspects of random porous and alloy systems as a function of the inherent parameters and density of the random grains. Our results find that the charge conductance within the low-voltage regime shows a highly nonlinear behavior against voltage variations in stark contrast to the high-voltage regime where the charge conductance is constant. The former finding is a direct consequence of the quantum scattering processes. The results reveal the threshold to the experimentally observable quantities, e.g., voltage difference, so that the charge current is activated for values larger than the threshold. The numerical study determines the threshold of one quantity as a function of the remaining quantities. Our method and results can serve to guide future experiments in designing circuital elements, involving this type of random alloy system.Comment: 10 pages, 8 figure

In-vitro activity of newer quinolones against aerobic bacteria

Nalidixic and five newer 4-quinolones, ciprofloxacin, enoxacin, norfloxacin, ofloxacin and pefloxacin were tested against 576 recent clinical aerobic bacterial isolates. The 4-quinolones were regularly active (MIC90 < 4 mg/1) against the following bacteria: Staphylococcus aureus, S. epidermidis, S. saprophyticus, different Enterobacteriaceae, Haemophilus influenzae, Campylobacter jejuni, Pseudomonas aeruginosa, Agrobacter spp., Aeromonas spp., Plesiomonas spp., Neisseria meningitidis. Other bacteria were usually intermediately susceptible or resistant: different streptococci, Listeria monocytogenes, Nocardia asteroides, P. maltophilia, Achromobacter xylosoxydans and Alcaligenes denitrificans. Ciprofloxacin was the most potent compound, followed by ofloxacin and pefloxacin, norfloxacin and enoxacin being less active. All the 4-quinolones were much more active than nalidixic acid. The MBC/MIC ratios of the 4-quinolones were between 1 and 2 with a majority of strains, and between 2 and 3 with Streptococcus agalactiae, Str. faecalis and L. monocytogenes. A two- to eight-fold increase of MIC was observed by increasing the inoculum 10,000-fold with most of the strains tested. Susceptible bacterial population of Klebsiella pneumoniae, Enterobacter cloacae, Serratia marcescens and P. aeruginosa contained more clones resistant to nalidixic acid (104 to 108 at four times the MIC) than to 4-quinolones (105 to 109 at four times the MIC). Supplementing the media with MgSO4 produced smaller inhibition zone diameters with a disc diffusion method than those obtained with non-supplemented agar, with all quinolone or strains. Less regular effect, or no effect was obtained after supplementation with ZnSO4 or Ca(NO3)

Geomorphic surfaces of eastern lake Urmia Playa and their influence on dust storms

Lake Urmia is one of the most important salt lakes in the world and the largest in Iran. At present, because of the recession of Lake Urmia and deposition of lacustrine sediments on the lake bed, a large part of the surrounding areas has become flat with several playa surfaces. So far, there have been very few studies related to Lake Urmia playa and its geomorphology. Therefore, the aim of this research was to field study of playa surfaces of Lake Urmia in its eastern part and also to identify areas susceptible to wind erosion. In this study, different playa surfaces from the northeast to the south of the lake were identified and mapped using satellite imagery. Then, boundaries of the mapped surfaces were checked during field observations. Moreover, physical soil properties, such as texture, bulk density, saturation percentage, resistancy, particle size distribution and soil aggregate stability, were determined. Next, the correlation of the studied properties with each surface resistance to wind erosion was investigated, and finally the geomorphic surfaces of Urmia Playa and their resistance to wind erosion were mapped using ARCGIS software. Based on the results, the study area included agricultural lands, shrub-grass zones, sand and gravel zones, mud-clay salt flats, sand-salt crusts, puffy grounds, delta-fans and wet zones. Results showed that approximately 25% of the surfaces had high resistance to wind erosion and they are therefore stable surfaces with no potential for generating dust in the future. About 35% of the surfaces were strongly susceptible to wind erosion, highly prone to generate saline dusts and sand storms. These areas were located in the east and southeast of the lake. Also, 40% of playa surfaces had moderate resistance to wind erosion. These areas can become very sensitive to wind erosion if ground water depth or the roughness of the surface changes. In conclusion, sandy-salt surfaces in the east and southeast of the lake are the most susceptible to wind erosion with high potential for generating dust, sand, and salt storms, which can affect agricultural lands and human health in the near future.Keywords: dust, erosion, geomorphology, Inceptisols, playa, Lake Urmi

Emergence of resistance after therapy with antibiotics used alone or combined in a marine model

A murine model of peritonitis allowing detection and quantification of in-vivo acquired resistance during short term therapy has been used in order to evaluate the capacity of antimicrobial combinations to limit emergence of resistance, as compared to individual components of the regimens. Mice were challenged intraperitoneally with 108 cfu of bacteria. Two hours later, a single antibiotic dose was injected subcutaneously: amikacin (15 mg/kg), ceftriaxone (50 mg/kg), pefloxacin (25 mg/kg), amikacin + ceftriaxone, amikacin + pefloxacin or ceftriaxone + pefloxacin. Escherichia coli and Staphylococcus aureus never became resistant. Single drug therapy yielded resistant mutants in Enterobacter cloacae, Serratia marcescens, Klebsiella pneumoniae and Pseudomonas aeruginosa as follows: 74% of ceftriaxone-treated animals, 57% of pefloxacin treated animals and 27% of amikacin treated animals. All the tested combinations reduced the frequency of in-vivo acquired resistance produced by single drugs, and no combination selected resistance when the separate agents of the combination did not. Combining antimicrobial agents limits the risk of emergence of resistance during antibiotic therap