Bioremediation of chromium(VI) by <Emphasis Type="Italic">Stenotrophomonas maltophilia</Emphasis> isolated from tannery effluent     

N. M. Raman  S. Asokan  N. Shobana Sundari  S. Ramasamy 《International Journal of Environmental Science and Technology》2018,15(1):207-216

Bioremediation of chromates using bacteria primarily involves the removal/reduction of heavy metals in effluent using indigenous micro-organisms such as chromium reducing bacteria as biosorbents for cleaner and healthier environment. In the present study, the removal of hexavalent chromium by micro-organisms isolated from acclimatized tannery effluent was investigated. Biochemical assays and molecular sequencing revealed strain SRS05 to be Stenotrophomonas maltophilia. Resistance to chromium was determined by agar and broth dilution assays followed by determination of minimal inhibitory concentration. Strain SRS05 was able to resist 400 mg/ml of chromium which reflects that the heavy metal could be utilized by the micro-organism for its growth. Results by atomic absorption spectroscopy, Fourier transform infrared spectroscopic analysis and scanning electron microscopy revealed effective biosorption of chromium by S. maltophilia SRS05 with no intracellular changes morphologically indicating the stability of the organism in the presence of chromium. It is therefore recommended that this bacterium can be used widely for remediation of hexavalent chromium although the genetic basis for observations concluded in this study is to be confirmed.  相似文献   

Pulse profile stability of the Crab pulsar     

Chetana Jain  Biswajit Paul 《中国天文和天体物理学报》2011,(10)

We present an X-ray timing analysis of the Crab pulsar, PSR B0531+21, using archival RXTE data. We have investigated the stability of the Crab pulse profile, in soft (2-20 keV) and hard (30-100 keV) X-ray energies, over the last decade of RXTE operation. The analysis includes measurement of the separation between the two pulse peaks and the intensity and widths of the two peaks. We did not find any significant time dependency in the pulse shape. The two peaks have been stable in phase, intensity and width f...  相似文献   

Numerical Simulation of the Response of the Ocean Surface Layer to Precipitation     

Shaowu?BaoEmail author  Sethu?Raman  Lian?Xie 《Pure and Applied Geophysics》2003,160(12):2419-2446

Numerical experiments were conducted to investigate the ocean's response to the precipitation. A squall line observed in TOGA COARE was simulated. The simulation reproduced some of the observed ocean responses to the precipitation, such as the formation of a fresh water layer, surface cooling and the variation of upper layer turbulent mixing. The precipitation-induced fresh layer can cause the vertical turbulent diffusivities to decrease from the surface to a depth of about 11–13 meters within a few hours. After the rainfall, the turbulence increases near the surface of the ocean due to the combined effect of increased shear and wind forcing, but decreases with depth due to the development of a stable layer. The main reason for the turbulence variation is the decrease in the vertical turbulence flux below the surface fresh layer because of increased static stability. Sensitivity experiments reveal that the sea-surface temperature increases faster after rainfall due to the formation of a shallow fresh water layer near the surface.  相似文献   

A Novel Technique for Noise Reduction in InSAR Images   总被引：3，自引：0，他引：3  

Meng  D. Sethu  V. Ambikairajah  E. Ge  L. 《Geoscience and Remote Sensing Letters, IEEE》2007,4(2):226-230

This letter proposes a new technique for noise reduction applied to synthetic aperture radar interferometry. This technique involves a nonlinear filter that separates the interferogram into two components: one containing the smooth (low frequency) part and the other containing the detail (high frequency) part. The smooth part is obtained using a combination of a median filter and a smoothing filter. The detail component is obtained by subtracting the smooth component from the original signal. This detail component is filtered to remove noise and then added to the smooth component to generate the final output. Both simulated and real data are used to evaluate the performance of the proposed technique under different conditions. The experimental results show that the proposed technique outperforms most commonly used interferometric phase filters  相似文献   

Numerical Simulation of Mesoscale Circulations in a Region of Contrasting Soil Types     

Sethu Raman  Aaron Sims  Robb Ellis  Ryan Boyles 《Pure and Applied Geophysics》2005,162(8-9):1689-1714

Mesoscale processes that form due to changes in surface characteristics play a dominant role in the development of the planetary boundary layer structure and the formation of convection. In this study, effects of the Sandhills region of North and South Carolina on mesoscale processes are examined. Climatological analyses indicate increased convective precipitation in this location as compared to the surrounding region. This is believed to be due to enhanced convection induced by horizontal heat flux gradients caused by sharp changes in soil type and hence the heat capacity of the soil. Simulations using a non-hydrostatic mesoscale model (MM5 version 3.3) were made for a non-precipitation case with a 5-km resolution domain centered over the Carolinas from August 15, 2000 to August 18, 2000. The results showed the existence of a mesoscale circulation over the Sandhills region. Differential heating induced by contrasting soil types dividing the Coastal Plain from the central Piedmont causes this circulation. Sea-breeze circulation often combines with the Sandhills circulation to initiate convection in this region. Diurnal variations are handled well by the model indicating that the thermodynamic structure of the atmosphere is well simulated.  相似文献   

Three-dimensional Simulations of the Mean Air Transport During the 1997 Forest Fires in Kalimantan, Indonesia Using a Mesoscale Numerical Model     

O. Roswintiarti  S. Raman 《Pure and Applied Geophysics》2003,160(1-2):429-438

— This paper describes the meteorological processes responsible for the mean transport of air pollutants during the ENSO-related forest fires in Kalimantan, Indonesia from 00 UTC 21 September to 00 UTC 25 September, 1997. The Fifth Generation of the Pennsylvania State University-National Center for Atmospheric Research (PSU-NCAR) Mesoscale Model (MM5) is used to simulate three-dimensional winds at 6-hourly intervals. A nonhydrostatic version of the model is run using two nested grids with horizontal resolutions of 45 km and 15 km. From the simulated wind fields, the backward and forward trajectories of the air parcel are investigated using the Vis5D model.¶The results indicate that the large-scale subsidence over Indonesia, the southwest monsoon low-level flows (2–8 m s^?1), and the shallow planetary boundary layer height (400–800 m) play a key role in the transport of air pollutants from Kalimantan to Malaysia, Singapore and Brunei.  相似文献   

Effect of three different boundary-layer parameterisations in a regional atmospheric model on the simulation of summer monsoon circulation     

K. V. J. Potty  U. C. Mohanty  S. Raman 《Boundary-Layer Meteorology》1997,84(3):363-381

Bulk, first-order and turbulent kinetic energy (TKE) closure schemes are used to parameterise the boundary-layer physics in a high resolution, limited area model. The model was used to simulate the summer monsoon circulations over India. The domain selected included the monsoon trough over northern India, a region of mesoscale convection. A monsoon depression was present at the time of the simulation. The results indicate that the TKE closure scheme combined with the Monin–Obukhov surface-layer similarity relation provided the best 48-hour simulation of the circulation and the rainfall associated with the monsoon depression.  相似文献   

The Role of Radiative Transfer in Maintaining the Indian Summer Monsoon Circulation     

M. J. Leach  S. Raman  U. C. Mohanty  R. V. Madala 《Pure and Applied Geophysics》1997,149(3):601-622

—The radiative-convective feedback and land-sea thermal forcing play significant roles in maintenance of the summer monsoon circulation over the Indian sub-continent. In this study, the role of radiative transfer in maintaining the monsoon circulation is examined with numerical sensitivity experiments. For this purpose, a sixteen layer primitive equation limited area model is used to perform numerical simulations with and without atmospheric radiative transfer processes parameterized in the model. The initial values and boundary conditions for the numerical integrations of the model are derived from operational analyses of the ECMWF, UK. The results show that the radiative transfer is essential in maintaining the intensity of the low level Somali Jet as well as the upper level Tropical Easterly Jet (TEJ) over the Indian sub-continent and adjoining seas. The meridional circulation over the region is also well simulated. As a result, enough moisture transports from the warm equatorial region to simulate more realistic orographic precipitation in the windward side of the mountains along the West coast of India. Without radiative transfer processes in the model atmosphere the simulated monsoon circulation weakens, moisture transport decreases and the precipitation lessens.  相似文献   

Numerical simulation of a mesolow over a Gulf Stream filament     

Sethu Raman  Neeraja C. Reddy 《Pure and Applied Geophysics》1996,147(4):789-819

A three-dimensional mesoscale numerical model is used to investigate mesoscale circulation over a Gulf Stream filament. Two numerical experiments are performed with different initial uniform ambient wind speeds (U=0.1 m s^–1, 3.5 m s^–1 and 7 m s^–1) for a typical winter day. It is found that for both low and moderate winds, a closed mesoscale circulation forms over the Gulf Stream filament. When the Gulf Stream filament was removed, the model did not predict a mesoscale circulation. The modeled circulation over the filament is in agreement with the observations, suggesting that the atmospheric circulations over the filaments may be an important mechanism in the U.S. East Coast cyclogenesis.  相似文献   

The Summertime Great Plains Low Level Jet And The Effect of Its Origin On Moisture Transport     

Yihua Wu  Sethu Raman 《Boundary-Layer Meteorology》1998,88(3):445-466

Radiosonde data from six stations in Kansas and Oklahoma for the period of June 16–24, 1993 indicate that a low-level jet (LLJ) occurred almost every day except on the 20th. Major characteristics of these LLJs are documented in this paper. The maximum wind speed (the jet speed) varied from 13 to 32 m s^-1 and heights ranged from 167 to 910 m. All the jets were southerly except the one on June 19 which changed its direction dramatically from a southerly to a northerly direction in about three hours although its intensity did not change appreciably. Thermal stability of the boundary layer during these LLJ occurrences ranged from near-neutral to highly stable. All the low-level jets exhibited significant diurnal variations. Analyses show that relatively weak large-scale forcing existed for the LLJs on June 21 and June 22, while strong forcing was present on other days. Analyses also show that moisture transport by the LLJ from the Gulf of Mexico to the Great Plains depends on the location of the LLJ origin. In the two weeks of June 13–19 and 20–26, 1993, powerful storms swept through the central United States, accompanied by tornadoes, strong wind, large hail and heavy rainfall. The analyses indicate that these weather events could be a result of the interactions of the LLJs with synoptic-scale flow.  相似文献