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Numerical Investigation on Aerodynamic Drag and Noise of Pantographs with Modified Structures
(2022-01-01)
Yao, Y.
;
Sun, Z.
;
Li, G.
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Prapamonthon, P.
;
Cheng, G.
It is well known that the pantograph, which works as a complex component of high-speed trains, is an important source of aerodynamic drag and aerodynamic noise of a high-speed train (HST) that can affect HST performance, comfort for passengers, and quietness of nearby communities. Thus, comprehensive studies on aerodynamic characteristics including aerodynamic drag and aerodynamic noise obtained by the pantograph need to be conducted. This work presents the aerodynamic characteristics including aerodynamic resistance and aerodynamic noise generated by the prototype pantograph of a high-speed train running at a speed of 300 km/h using numerical techniques of improved delayed detached-eddy simulation (IDDES) and acoustic finite element method (FEM). Then, the structure of the original pantograph is modified by wrapping the insulators, and the base frame, so that aerodynamic resistance and aerodynamic noise may be reduced as expected. Numerical results obtained from the pantograph without modification, with two modifications to the original design i.e. the base frame, and the insulators, are discussed. Compared to the original pantograph, the two modifications of the pantograph at the base frame and the support insulators are conducive to reducing the aerodynamic drag of the pantograph. However, the results also show that the modified insulator may not achieve considerable success in noise reduction. Only the modified base frame shows that noise is reduced significantly. Therefore, this suggests that the pantograph with base frame modification is a better choice for resistance and noise reduction.
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Molecular characterization of amikacin, kanamycin and capreomycin resistance in M/XDR-TB strains isolated in Thailand
(2014-06-22)
Sowajassatakul, Angkanang
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Prammananan, Therdsak
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Chaiprasert, Angkana
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Phunpruch, Saranya
Background: The emergence of multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB) makes the treatment and control of tuberculosis difficult. Rapid detection of drug-resistant strains is important for the successful treatment of drug-resistant tuberculosis; however, not all resistance mechanisms to the injectable second-line drugs such as amikacin (AK), kanamycin (KM), and capreomycin (CAP) are well understood. This study aims to validate the mechanisms associated with AK, KM, and CAP resistance in M. tuberculosis clinical strains isolated in Thailand. Results: A total of 15,124 M. tuberculosis clinical strains were isolated from 23,693 smear-positive sputum samples sent from 288 hospitals in 46 of 77 provinces of Thailand. Phenotypic analysis identified 1,294 strains as MDR-TB and second-line drugs susceptibility was performed in all MDR-TB strains and revealed 58 XDR-TB strains. Twenty-nine KM-resistant strains (26 XDR-TB and 3 MDR-TB) could be retrieved and their genes associated with AK, KM, and CAP resistance were investigated compared with 27 KM-susceptible strains. Mutation of the rrs (A1401G) was found in 21 out of 29 KM-resistant strains whereas mutations of eis either at C-14 T or at G-37 T were found in 5 strains. Three remaining KM-resistant strains did not contain any known mutations. Capreomycin resistance was determined in 28 of 29 KM-resistant strains. Analysis of tlyA revealed that the A33G mutation was found in all CAP-resistant strains and also in susceptible strains. In contrast, the recently identified tlyA mutation T539G and the novel Ins49GC were found in two and one CAP-resistant strains, respectively. In addition, our finding demonstrated the insertion of cytosine at position 581 of the tap, a putative drug efflux encoding gene, in both KM-resistant and KM-susceptible strains. Conclusions: Our finding demonstrated that the majority of KM resistance mechanism in Thai M. tuberculosis clinical strains was rrs mutation at A1401G. Mutations of the eis promoter region either at C-14 T or G-37 T was found in 5 of 29 strains whereas three strains did not contain any known mutations. For CAP resistance, 3 of 28 CAP-resistant strains contained either T539G or Ins49GC mutations at tlyA that might be associated with the resistant phenotype. © 2014 Sowajassatakul et al.; licensee BioMed Central Ltd.
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Identification of blast-resistant varieties from Landrace, improved and wild species of rice
(2013-07-18)
Salih, Abdu
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Sreewongchai, Tanee
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Sripichitt, Prapa
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Parinthawong, Nonglak
An experiment was conducted to identify rice varieties resistant to blast disease. Samples of 311 genetically diversified varieties/accessions comprised of landrace (263), improved (43) and wild (5) rice varieties/accessions were provided by the National Rice Gene Bank of Thailand. The screening for blast at the seedling stage was done using 29 diversified blast isolates. The blast isolates were collected from seven provinces (Phitsanulok, Ubon Ratchathani, Khon Kean, Chiang Rai, Nong Khai, Chaiyaphum and Udon Thani) of Thailand. The results indicated a total of 35 varieties/accessions (25 landrace, 9 improved and 1 wild) were resistant to all tested blast isolates. The 25 resistant landrace varieties were collections from Northern (10), Northeastern (9) and Southern (6) Thailand. Moreover four of the resistant landrace varieties (GS23107, GS19769, GS20874 and GS23774) were highly resistant with no symptom of the disease. From this study, it can be suggested that the resistant landraces from the Southern, Northern and Northeastern regions could be used as sources of resistant varieties in designing future breeding programs aimed at developing disease-resistant genotypes.
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A role for 16S rRNA dimethyltransferase (ksgA) in intrinsic clarithromycin resistance in Mycobacterium tuberculosis
(2013-06-01)
Phunpruch, Saranya
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Warit, Saradee
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Suksamran, Rungaroon
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Billamas, Pamaree
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Jaitrong, Sarinya
The emergence of extensively drug-resistant tuberculosis (XDR-TB) makes the control of tuberculosis (TB) difficult. As a result, there is an urgent need to develop new anti-TB drugs. Alternatively, drugs that have already been used in humans as anti-infectives and later found to have antitubercular activity might be useful as anti-TB drugs, particularly against drug-resistant TB. Clarithromycin (CLR), a 14-membered macrolide and protein synthesis inhibitor, has potent activity against most mycobacterial infections, except Mycobacterium tuberculosis. Mycobacterium tuberculosis is naturally resistant to CLR [minimum inhibitory concentration (MIC) of 8-16 μg/mL] owing to the presence of inducible erm methylase (ErmMT). With a view to gaining further insight into the mechanisms of innate CLR resistance in M. tuberculosis, CLR-susceptible M. tuberculosis H37Rv mutants were generated by transposon mutagenesis. One mutant, designated as Tn-196, was further investigated and it was found that ksgA (Rv1010) was inactivated by the transposon. The ksgA gene encodes a 16S rRNA adenine dimethyltransferase that methylates A1518 and A1519 (Escherichia coli numbering) of 16S rRNA and plays an important role in ribosome biogenesis. Complementation of the Tn-196 mutant with a wild-type ksgA gene restored the resistant phenotype (MIC of 8-16 μg/mL), corroborating the association of ksgA with intrinsic CLR resistance in M. tuberculosis. © 2013 Elsevier B.V. and the International Society of Chemotherapy.
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Effects of track width and stripe height ratio on the characteristics of CPP-GMR and TMR heads
(2011-08-12)
Kamwan, S.
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Pijitrojana, W.
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Sa-Ngiamsak, C.
Hard disk drive industry has been facing strong competition from other data storage devices. The primary reader technology based on the Giant magnetoresistance (GMR) and Tunneling magnetoresistance (TMR). TMR head reaches the limit at the 2Tb/in<sup>2</sup> recording density, because of its high impedance affected on the bit rate of the signal. Overcoming the previous limit, CPP-GMR reader using all metallic materials and in current perpendicular to the plane (CPP) geometry has to be employed for areal density <2Tb/in <sup>2</sup>. In this study we focus on physical dimension designs of CPP-GMR head. CPP-GMR still shows the potential gaps of resistance to narrow down the reader size, in terms of static signal to noise ratio (SNR), CPP-GMR shows maximum static SNR at bit aspect ratio (BAR) ∼0.6, which suggests that the key physical dimension track width and stripe height ratio should be optimized to achieve static SNR of CPP-GMR sensor. By the way we need to consider more about other design parameters, for examples magnetic materials, Resistance area (RA) and alternative metal spacers. © 2011 IEEE.

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