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The major sudden stratospheric warming (SSW) events of 2003–04 and 2005–06 are considered to investigate changes in equatorial convection due to circulation changes associated with the SSW events. It is observed that the SSW events are accompanied by a considerable decrease in Outgoing Longwave Radiation (OLR), a proxy for tropical convection, over equatorial latitudes (15°N–15°S) in the Indonesian sector (90°E–150°E). However, unlike noted by earlier observations, the zonal mean OLR does not show any notable relationship with the SSW events. It can be explained from the latitude–longitude map of potential vorticity (PV) at 100 hPa, which shows a tongue of high PV emanating from high latitudes towards equator and converges in the longitude band of 90°E–150°E on the day of peak warming at 1 hPa in the case of 2003–04 and 10 hPa in the case of 2005–06. The latitude-height map of Eliassen–Palm (EP) vector and its divergence show convergence of EP flux in the upper troposphere at latitudes even lower than 20°N on these days. Further, vertical winds computed from the convergence of momentum flux are upward indicating convective activity at low-latitudes and downward at mid-latitudes. 相似文献
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A preliminary study was undertaken to determine the optimal conditions for the biodegradation of a crude oil. Among 57 oil‐degrading bacterial cultures isolated from oil‐contaminated soil samples, Bacillus sp. IOS1‐7, Corynebacterium sp. BPS2‐6, Pseudomonas sp. HPS2‐5, and Pseudomonas sp. BPS1‐8 were selected for the study based on the efficiency of crude oil utilization. Along with the selected individual strains, a mixed bacterial consortium prepared using the above strains was also used for degradation studies. The mixed bacterial consortium showed more growth and degradation than did individual strains. At 1% crude oil concentration, the mixed bacterial consortium degraded a maximum of 77% of the crude oil. This was followed by 69% by Pseudomonas sp. BPS1‐8, 64% by Bacillus sp. IOS1‐7, 45% by Pseudomonas sp. HPS2‐5, and 41% by Corynebacterium sp. BPS2‐6. The percentage of degradation by the mixed bacterial consortium decreased from 77 to 45% as the concentration of crude oil was increased from 1 to 12%. Temperature of 35°C and pH 7 were found to be optimum for maximum degradation. 相似文献
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S. Sridharan P. Vishnu Prasanth Y. Bhavani Kumar Geetha Ramkumar S. Sathishkumar K. Raghunath 《Journal of Atmospheric and Solar》2009,71(5):575-582
Resonance lidar observations of sodium density in the upper mesosphere region over Gadanki (13.5°N, 79.2°E) rarely show complex structures with rapid enhancements of sodium density, completely different from normal sporadic sodium structures. The hourly averaged meteor radar zonal winds over Trivandrum (8.5°N, 76.5°E) show an eastward shear with altitude during the nights, when these events are formed. As suggested by Kane et al. [2001. Joint observations of sodium enhancements and field-aligned ionospheric irregularities. Geophysical Research Letters 28, 1375–1378], our observations show that the complex structures may be formed due to Kelvin–Helmholtz instability, which can occur in the region of strong wind shear. 相似文献
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Palanivel Sathishkumar Kannan Balan Thayumanavan Palvannan Seralathan Kamala‐Kannan Byung‐Taek Oh Susana Rodríguez‐Couto 《洁净——土壤、空气、水》2013,41(7):665-672
Laccase from the white‐rot fungus Pleurotus florida, produced under solid‐state fermentation conditions, was used for the decolorization of reactive dye Remazol Brilliant Blue R (RBBR). RBBR was decolorized up to 46% by P. florida laccase alone in 10 min. In the presence of N‐hydroxybenzotriazole (HBT), the rate of decolorization was enhanced 1.56‐fold. Central composite design of response surface methodology with four variables namely, dye, enzyme, redox mediator concentrations, and time at five levels was applied to optimize the RBBR decolorization. The predicted optimum level of variables for maximum RBBR decolorization (87%) was found to be 52.90 mg L?1 (RBBR), 1.87 U mL?1 (laccase), 0.85 mM (HBT), and 7.17 min (time), respectively. The validation results showed that the experimental value of RBBR decolorization (82%) was close to the predicted one. The disappearance of C–N and C–X groups, and a small shift in N–H groups in Fourier‐transform infra red (FTIR) spectroscopy confirms the degradation of RBBR chromophore by laccase enzyme. The phytotoxicity of RBBR was considerably reduced after the treatment with laccase. RBBR decolorization kinetics; Km and Vmax were calculated to be 145.82 mg L?1 and 24.86 mg L?1 min, respectively. 相似文献
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Arthur Raj Binupriya Muthuswamy Sathishkumar Chang Sub Ku Sool Il Yun 《洁净——土壤、空气、水》2010,38(8):775-780
Bacillus subtilis and its extracellular polysaccharide (EPS) were used in free form as well as immobilized form as biosorbent for the removal of an anionic dye Procion Red MX 5B. Low pH was favourable for biosorption. Immobilization resulted in reduced biosorption of the dye. The presence of functional groups responsible for the high adsorption capacity in free cells (FC) and EPS was confirmed by FTIR analysis. High Qmax and b values were noted in the case of FC and free EPS in contrast to immobilized cells and EPS. The kinetics data showed that the adsorption system followed pseudo‐first‐order reaction at low dye concentration. Desorption of the dye was found to be 100% in 1 N NaOH. In the case of immobilized biomass and EPS the alginate was found to be unstable under high alkaline conditions of NaOH. 相似文献
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Arthur Raj Binupriya Muthuswamy Sathishkumar Dhamodaran Kavitha Krishnaswamy Swaminathan Sei‐Eok Yun Sung‐Phil Mun 《洁净——土壤、空气、水》2007,35(2):143-150
Batch biosorption experiments were carried out for the removal of Congo red from aqueous solution using native and pretreated mycelial pellets/biomass of Trametes versicolor. The effect of process parameters such as contact time, dye concentration, and pH on the extent of Congo red biosorption has been investigated. Higher dye concentrations resulted in lower biosorption. Increases in biomass dosage led to increases in the levels of biosorption. Biosorption kinetics and equilibrium data are essential basic requirements to develop an effective and accurate design model for the removal of the dye. A kinetic study showed that the biosorption of the dye on fungal biomass was a gradual process. Pseudo‐first‐order, pseudo‐second‐order, and Bangham's model were used to fit the experimental data. The results of the kinetic studies showed that the second‐order kinetic model fitted well for the present experimental data. Equilibrium isotherms were analyzed by Langmuir, Freundlich, Dubnin‐Radushkevich, and Temkin isotherms. The biosorption equilibrium data obeyed the Langmuir and Temkin isotherms well. Acidic pH was favorable for the biosorption of the dye. Studies on the pH effect and desorption show that chemisorption seems to play a major role in the biosorption process. Among the native and pretreated biomass studied, autoclaved biomass showed a better biosorption capacity. 相似文献
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Bharti Jayanti Prabha Mishra Pratishtha moorthy Usha Sathishkumar V. E. Cho Yongyun Samui Pijush 《Geotechnical and Geological Engineering》2021,39(5):3741-3752
Slopes in geotechnical and mining engineering are the most crucial geo-structure. Predicting or forecasting the stability or instability of the slope and then classifying the slope accordingly helps in mitigating the risks and enhancing the design by maximizing the safety. Computing techniques have overpowered the analytical and statistical models used for predicting the stability of the slopes. To reduce the uncertainties and ambiguity of the previously used models, lately, researchers have come up with the novel techniques for Slope Stability Classification (SSC) which are Random Forest, Gradient Boosting Machine, Extreme Gradient Boosting, Boosted Trees and Classification and Regression Trees. These computational algorithms are employed in this research paper and the slope details are taken from a literature i.e. 221 input datasets are used and slopes are classified accordingly using the mentioned models. The relation between the inputs such as height (H), slope angle (β), cohesion (c), pore water pressure ratio (ru), unit weight (γ), angle of internal friction (φ) and slope stability (output) is established and slopes are categorized according to their failure and stability. Performance analysis is done thereafter to analyses and compare different models and let the readers and researchers know that which model sufficed and fitted best to the study.
相似文献8.
S. Sridharan K. Raghunath S. Sathishkumar D. Nath 《Journal of Atmospheric and Solar》2010,72(14-15):1139-1146
Rayleigh lidar observations at Gadanki (13.5°N, 79.2°E) show an enhancement of the nightly mean temperature by 10–15 K at altitudes 70–80 km and of gravity wave potential energy at 60–70 km during the 2009 major stratospheric warming event. An enhanced quasi-16-day wave activity is observed at 50–70 km in the wavelet spectrum of TIMED–SABER temperatures, possibly due to the absence of a critical level in the low-latitude stratosphere because of less westward winds caused by this warming event. The observed low-latitude mesospheric warming could be due to wave breaking, as waves are damped at 80 km. 相似文献
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The zonally averaged UK Meteorological Office (UKMO) zonal mean temperature and zonal winds for the latitudes 8.75°N and 60°N are used to investigate the low-latitude dynamical response to the high latitude sudden stratospheric warming (SSW) events that occurred during winter of the years 1998–1999, 2003–2004 and 2005–2006. The UKMO zonal mean zonal winds at 60°N show a short-term reversal to westward winds in the entire upper stratosphere and lower mesosphere and the low-latitude winds (8.75°N) show enhanced eastward flow in the upper stratosphere and strong westward flow in the lower mesosphere during the major SSW events at high latitudes. The mesosphere and lower thermosphere (MLT) zonal winds acquired by medium frequency (MF) radar at Tirunelveli (8.7°N, 77.8°E) show a change of wind direction from eastward to westward several days before the onset of SSW events and these winds decelerate and weak positive (eastward) winds prevail during the SSW events. The time variation of zonal winds over Tirunelveli is nearly similar to the one reported from high latitudes, except that the latter shows intense eastward winds during the SSW events. Besides, the comparison of daily mean meridional winds over Tirunelveli with those over Collm (52°N, 15°E) show that large equatorial winds are observed over Tirunelveli during the 2005–2006 event and over Collm during the 1998–1999 events. The variable response of MLT dynamics to different SSW events may be explained by the variability of gravity waves. 相似文献
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G.J. Bhagavathiammal S. Sathishkumar S. Sridharan Manohar Lal S. Gurubaran K.U. Nair 《Journal of Atmospheric and Solar》2010,72(16):1204-1211
Spectral analysis of Tirunelveli (8.7°N, 77.8°E) MF radar winds for the year 2007 indicate the presence of long-period Kelvin waves with periods ～23 and ～16 days in the low-latitude mesosphere during Indian summer monsoon months. The dominant presence of these slow-phase speed waves at mesospheric altitudes motivated us to investigate their origin and vertical propagation characteristics. Space-time Fourier analysis of NCEP winds and OLR show the presence of these periodicities with zonal wavenumber 1 indicating that tropical convection is the potential source for these waves and westward phase of stratospheric QBO winds might have favoured these waves to reach the mesosphere. 相似文献
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