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Synthesis of Cs-ABW nanozeolite in organotemplate-free system
No full textCesium-aluminosilicate zeolite nanocrystals with ABW framework structure are synthesized free of organic template using hydrothermal approach. The crystallization process of Cs-ABW zeolite nanocrystals by varying the initial gel molar composition, heating temperature and crystallization time was studied. More detailed investigations of the formation of Cs-ABW nanozeolite using a reactive clear precursor hydrogel (4SiO2:1Al2O3:16Cs2O:160H2O) were then carried out. Fully crystalline Cs-ABW nanozeolites were obtained within 120 min at 180 °C and 22 bar, which is considerably faster and safer in comparison to the currently available method involving treatment at 695 °C, 1000 bar and 46 h. The Cs-ABW nanocrystals have grain shape morphology with a mean size of 32 nm and they do not agglomerate for long durations. The nanosized Cs-ABW zeolite has high alumina content (Si/Al ratio = 1.04). These nanocrystals can be prepared in high solid yield (ca. 82%) thus offering a promising route for large-scale production of highly basic zeolite nanoparticles
Evolutionary and biogeographic history of the black fly Simulium wayani (Diptera: Simuliidae) on the island of Timor
No full textA recently described species of black fly, Simulium wayani Takaoka and Chen, from the island of Timor was chromosomally mapped to provide insights into its evolutionary and biogeographic history. The morphologically based species status of S. wayani is supported by a suite of fixed chromosomal rearrangements and unique sex chromosomes derived primarily from a large pool of polymorphisms in the S. ornatipes complex in Australia. The banding patterns of its polytene chromosomes indicate that S. wayani is closely related to a pair of homosequential cryptic species (S. norfolkense Dumbleton and S. ornatipes cytoform A2) in the S. ornatipes Skuse complex on mainland Australia; all three species uniquely share the same amplified band in their chromosomal complement. The low level of polymorphism and heterozygosity in S. wayani, relative to Australian populations of the S. ornatipes complex, suggests few colonization events from the larger land mass. © 2019 Elsevier B.V
The level of awareness and production of English lexical stress among English language teacher trainees in Malaysia
No full textThe realisation of lexical stress among Malaysian speakers of English is likely to be different from other varieties of English. In spite of this, there is a preference for a native pronunciation model in the teaching of English in Malaysia. In relation to this issue, this paper focuses on lexical stress among a group of Teaching of English as a Second Language teacher trainees. The objectives of this paper are to assess the overall level of awareness of lexical stress among them, to examine their production of lexical stress, and to determine the link between their level of awareness and production. The method used to elicit data for the first objective was a Lexical Stress Awareness Test (LSAT), completed by 104 teacher trainees. Data for the second objective were obtained by recording the trainees reading sentences containing test words. The findings from the LSAT indicate that most of the trainees have an intermediate level of awareness of English lexical stress. They were generally unable to describe the characteristics of a stressed syllable. In addition, the findings from the acoustic analysis of the recordings suggest that they did not have a systematic pattern of stressing syllables with the main correlate of stress being vowel lengthening. In contrast, most of them chose 'higher pitch' as the characteristic of a stressed syllable. Hence, there is an inconsistency between their awareness and production of lexical stress in English. We discuss the implications of these findings in relation to the teaching of pronunciation in the classroom and the effect of lexical stress placement on intelligibility. Our general conclusion is that more attention needs to be given in teacher education to how lexical stress is used in English, and also to the characteristics of stress in the Malaysian variety of English. © 2018, IJAL
Prediction of Suspended Sediment Load Using Data-Driven Models
No full textEstimation of suspended sediments carried by natural rivers is essential for projects related to water resource planning and management. This study proposes a dynamic evolving neural fuzzy inference system (DENFIS) as an alternative tool to estimate the suspended sediment load based on previous values of streamflow and sediment. Several input scenarios of daily streamflow and suspended sediment load measured at two locations of China-Guangyuan and Beibei-were tried to assess the ability of this new method and its results were compared with those of the other two common methods, adaptive neural fuzzy inference system with fuzzy c-means clustering (ANFIS-FCM) and multivariate adaptive regression splines (MARS) based on three commonly utilized statistical indices, root mean square error (RMSE), mean absolute error (MAE), and Nash-Sutcliffe efficiency (NSE). The data period covers 01/04/2007-12/31/2015 for the both stations. A comparison of the methods indicated that the DENFIS-based models improved the accuracy of the ANFIS-FCM and MARS-based models with respect to RMSE by 33% (32%) and 31% (36%) for the Guangyuan (Beibei) station, respectively. The NSE accuracy for ANFIS-FCM and MARS-based models were increased by 4% (36%) and 15% (19%) using DENFIS for the Guangyuan (Beibei) station, respectively. It was found that the suspended sediment load can be accurately estimated by DENFIS-based models using only previous streamflow data. © 2019 by the authors
Surface plasmonic effect of nanoparticle-like silver nanostructure on the high responsivity of visible/infrared silver-based heterojunction photodetector
No full textThe fabrication of a silver (Ag) based photodetector on a silicon dioxide/p-silicon (SiO2/p-Si) substrate using direct current (DC) magnetron sputtering is demonstrated. The proposed method deposits a nanoparticle-like Ag thin film that favours the photoconduction mechanism under light illumination at 468 nm and laser illumination at 660 and 980 nm. The thin film is characterized using scanning electron microscope (SEM), energy dispersive x-ray (EDX), x-ray diffraction (XRD), Raman scattering, photoluminescence (PL) and ultraviolet–visible (UV–VIS) analysis. Current–voltage (I–V) analysis and the calculated rectifying ratio (RR) suggests the establishment of good Schottky contacts for incident light/laser at 468, 660 and 980 nm, with good responsivity towards light and laser illumination in the forward and reverse DC bias regions. The responsivity increases as the wavelength decreases from 980 nm → 660 nm → 468 nm, with the highest responsivity of 213.7 mAW−1 at 468 nm indicating better photoconduction at low light powers. © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group
Tungsten-disulphide-based heterojunction photodetector
No full textTwo-dimensional (2D) materials have realized significant new applications in photonics, electronics, and optoelectronics. Among these materials is tungsten disulphide (WS2), which is a 2D material that shows excellent optoelectronic properties, tunable/sizable bandgap in the visible range, and good absorption. A polycrystalline WS2 thin film is successfully deposited on a substrate using radio frequency magnetron sputtering at room temperature. The x-ray diffraction pattern reveals two hexagonal structured peaks along the (100) and (110) planes. Energy-dispersive x-ray spectroscopy reveals a non-stoichiometric WS2 film with 1.25 ratio of S/W for a 156.3 nm thick film, while Raman shifts are observed at the E1 2g and A1g phonon modes located at 350.70 cm−1 and 415.60 cm−1, respectively. A sandwiched heterojunction photodetector device is successfully fabricated and illuminated within the violet range at 441 nm and 10 V of bias voltage. The maximum photocurrent values are calculated as 0.95 μA, while the responsivity is observed at 169.3 mA W−1 and detectivity 1.48 × 108 Jones at illuminated power of 0.6124 μm. These results highlight the adaptability of the present technique for large-scale applications as well as the flexibility to promote development of advanced optoelectronic devices. © 2019 Optical Society of America
Mode-locked thulium-fluoride fibre laser with an adjustable pulse width using a nonlinear optical loop mirror
No full textA mode-locked thulium-fluoride fibre laser with a tunable pulse width using a nonlinear optical loop mirror (NOLM) for operation in the S-band region is proposed and demonstrated. Stable dissipative soliton resonance (DSR) mode-locked pulses are obtained at a threshold pump power of 186.8 mW and maintain stability until a maximum pump power of 249.7 mW. Pulse width modulation of between 70.8 ns and 120.3 ns is obtained over the operating pump power range, with a fundamental frequency at 97.4 kHz. A maximum output power of 0.99 mW and a pulse energy of 10.21 nJ are obtained. The output pulse has a signal-to-noise ratio of 69 dB at the maximum pump power, indicating a highly stable output. The variable pulse width will find significant applications as modulated light sources for various optical and optoelectronic systems. © 2019 Kvantovaya Elektronika and Turpion Lt
Q-switched erbium-doped fiber laser using silver nanoparticles deposited onto side-polished D-shaped fiber by electron beam deposition method
No full textA stable Q-switched erbium-doped fiber laser (EDFL) is demonstrated using silver nanoparticles (AgNPs) as a passive saturable absorber. A prefabricated D-shaped silica fiber is coated with AgNPs using electron beam deposition method. Four different sizes of D-shaped fiber, which were controlled by observing the loss during the polishing process are used in this study. All four samples with losses of 1.2 dB, 2 dB, 3 dB and 3.5 dB were able to produce Q-switched pulse in 1.5-µm region, with an ability to lase at a threshold of 35.2 mW. Maximum repetition rate was recorded at 66.74 kHz for the D-shaped fiber configured with 3 dB loss, while the narrowest pulse width was obtained at 6.17 µs for 2 dB loss. All samples were also producing pulses at the maximum applicable pump power of 65.7 mW, and output power recorded at that power level are between 5.86 mW and 7.36 mW. © 2019 Elsevier Inc
Evaluation of 222Rn and 226Ra concentrations in cement and limestone of Sheikh Buddin Hill, Pezu, Pakistan using different techniques
No full textLucky Cement Factory, Pezu is using limestone of Sheikh Buddin Hills as a raw material in cement. Workers of the factory have direct and general public have indirect exposure to radiological hazard due to natural radionuclides present in limestone. To address the radiological hazards, limestone, mixed (limestone+clay) and cement samples were evaluate for concentrations of 222Rn and 226Ra using CR-39, RAD7 and HPGe detectors. Maximum mean values of 222Rn using CR-39 and RAD7 detectors were found 1447 ± 198 and 1416 ± 74 Bq.m−3 in cement samples and minimum were found in 536 ± 122 and 525 ± 45 Bq.m−3 limestone samples, respectively. Maximum mean value of radon exhalation rate of 12.28 ± 1.68 Bq.m−2 h−1 in cement samples was found below the world average value of 57.6 Bq.m−2 h−1. Maximum mean values of 226Ra measured by CR-39 and HPGe detectors were found 24.25 ± 3.35 and 23.6 ± 0.70 Bq.kg−1 in cement samples and minimum were found in 8.98 ± 2.02 and 9.19 ± 0.40 Bq.kg−1 limestone samples, respectively. A positive correlations (R2 = 0.9714) using CR-39 and RAD7 detectors and (R2 = 0.9573) using CR-39 and HPGe detectors were obtained for the concentrations of 222Rn and 226Ra, respectively. Maximum mean value of annual effective dose of 347.78 ± 47.58 µSv.y−1 in cement samples was found below the world average value of 1100 µSv.y−1. © 2019, © 2019 Informa UK Limited, trading as Taylor & Francis Group
Longitudinal associations of active renal disease with irreversible organ damage accrual in systemic lupus erythematosus
No full textObjective: To examine longitudinal associations of active lupus nephritis with organ damage accrual in patients with systemic lupus erythematosus (SLE). Methods: This study was performed using data from a large multinational prospective cohort. Active lupus nephritis at any visit was defined by the presence of urinary casts, proteinuria, haematuria or pyuria, as indicated by the cut-offs in the SLE Disease Activity Index (SLEDAI)-2K, collected at each visit. Organ damage accrual was defined as a change of SLICC-ACR Damage Index (SDI) score >0 units between baseline and final annual visits. Renal damage accrual was defined if there was new damage recorded in renal SDI domains (estimated glomerular filtration rate 3.5 g per 24 h/end-stage kidney disease). Time-dependent hazard regression analyses were used to examine the associations between active lupus nephritis and damage accrual. Results: Patients (N = 1735) were studied during 12,717 visits for a median (inter-quartile range) follow-up period of 795 (532, 1087) days. Forty per cent of patients had evidence of active lupus nephritis at least once during the study period, and active lupus nephritis was observed in 3030 (24%) visits. Forty-eight per cent of patients had organ damage at baseline and 14% accrued organ damage. Patients with active lupus nephritis were 52% more likely to accrue any organ damage compared with those without active lupus nephritis (adjusted hazard ratio = 1.52 (95% confidence interval (CI): 1.16, 1.97), p < 0.02). Active lupus nephritis was strongly associated with damage accrual in renal but not in non-renal organ domains (hazard ratios = 13.0 (95% CI: 6.58, 25.5) p < 0.001 and 0.96 (95% CI: 0.69, 1.32) p = 0.8, respectively). There was no effect of ethnicity on renal damage accrual, but Asian ethnicity was significantly associated with reduced non-renal damage accrual. Conclusion: Active lupus nephritis measured using the SLEDAI-2K domain cut-offs is associated with renal, but not non-renal, damage accrual in SLE. © The Author(s) 2019