Results Of Resistance Analysis Research Articles

One-Dimensional Study on Hydrate Formation from Migrating Dissolved Gas in Sandy Sediments

Upward migration of gas-dissolved pore fluid is an important mechanism for many naturally occurring hydrate reservoirs. However, there is limited understanding in this scenario of hydrate formation in sediments. In this preliminary work, hydrate formation and accumulation from dissolved gas in sandy sediments along the migration direction of brine was investigated using a visual hydrate simulator. Visual observation was employed to capture the morphology of hydrates in pores through three sapphire tubes. Meanwhile, the resistivity evolution of sediments was detected to characterize hydrate distribution in sediments. It was observed that hydrates initially formed as a thin film or dispersed crystals and then became a turbid colloidal solution. With hydrate growth, the colloidal solution converted to massive solid hydrates. Electrical resistivity experienced a three-stage evolution process corresponding to the three observed hydrate morphologies. The results of resistivity analysis also indicated that the bottom–up direction of hydrate growth was consistent with the flow direction of brine, and two hydrate accumulation centers successively appeared in the sediments. Hydrates preferentially formed and accumulated in certain depths of the sediments, resulting in heterogeneous hydrate distribution. Even under low saturation, the occurrence of heterogeneous hydrates led to the sharp reduction of sediment permeability.

Fouling in microalgal membrane bioreactor containing nitrate-enriched wastewater under different trophic conditions

The present study examined fouling in a microalgal membrane bioreactor under mixotrophic, heterotrophic and photoautotrophic conditions. N-enriched wastewater, containing nitrate source, was used as a nutrient source for cultivation of microalgae. The results confirmed that the membrane fouling rates increased under mixotrophic cultivation through enhanced production of carbohydrates in soluble microbial products (SMPc) and protein in extracellular polymeric substances (EPSp). The transmembrane pressure (TMP) jumping was observed under mixotrophic and photoautotrophic cultivation after 31 and 47 days of operation, respectively, while the TMP of heterotrophic cultivation did not exceed 10 kPa throughout 51 days. The highest EPSp was produced under mixotrophic condition due to high nitrogen removal rate. Also, the results of resistance analysis indicated that cake resistance was the main fouling resistance in all cultivation types and the latter result was confirmed by SEM analysis. In addition, higher protein fraction of cake layer on membrane foulants in comparison to carbohydrates fraction increased the hydrophobicity of membrane's surface in all cultivations (except heterotrophic culture). Compared to mixotrophic and photoautotrophic cultures, hydrophobic properties and cell size of heterotrophic microalgae increased and resulted in low membrane fouling rates.

Initial Finding of CYP9M10 Gene Haplotype in Culex Quinquefasciatus-Permethrin Resistant Isolate from Natural Population of Central Java Province, Indonesia

Introduction: Culex is a mosquito genus which widely distributed in the tropical, subtropical and temperate climates, both in urban and rural areas all over the world. Culex mosquitoes, especially Culex quinquefasciatus, are the main vector of filariasis. Thus, public health prevention is mainly directed to control these species and the chemical control is the most widely used approach. However, unfavourable effects of such control to the C. quinquefasciatus population have been known in the form of resistance and emergence of this resistance to various insecticides has been reported in many countries. Methods: The metabolic resistance in mosquitoes occurs through the expression of P450 gene family. One of the P450 families is CYP9M10 gene. Partial analysis of the CYP9M10 gene sequences C. quinquefasciatus mosquito reveals the differences between susceptible and resistant alleles. This study was started from the bioassay test of C. quinquefasciatus mosquitoes from five filariasis-endemic areas in Central Java and was continued on the molecular analysis of CYP9M10 gene. Results: The results of resistance analysis using bioassay test showed that the C. quinquefasciatus mosquito which has been isolated in Central Java showed high levels of resistance against permethrin 0.75% when mortality rates ranged from 4.8% to 21.6%. Conclusion: On the other hand, the molecular analysis revealed three types of haplotypes. The third haplotype had the highest frequency and it exhibited sequence pattern change in the CYP9M10 gene altering the susceptible strain into a resistant one.