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1.
P. Kanmani K. Kumaresan J. Aravind S. Karthikeyan R. Balan 《International Journal of Environmental Science and Technology》2016,13(6):1541-1552
Polyhydroxyalkanoates (PHAs) are an important class of biodegradable polymers synthesized by a few bacteria under nutrient-limiting conditions. In this study, the lipase-catalysed degradation of PHA synthesized by Enterobacter sp. was monitored. For this, the lipase-encoding gene from Bacillus subtilis DI2 was PCR-amplified, cloned into a T vector system and sequenced. It was expressed in Escherichia coli DH5α cells, the recombinant enzyme was purified 24.25-fold, and its molecular weight was determined to be around 28 kDa. When PHA biodegradation studies were carried out with this enzyme, gel permeation chromatography showed 21.3 and 28.3 % molecular weight decrease and weight loss, respectively. Further, scanning electron micrographs revealed alterations in polymer surface morphology. Changes in molecular vibrations were noticed in the FTIR spectra. When the chemical shifts in NMR spectra were studied, a steep reduction in area under the peak at 1.57 ppm was observed. In the heating range of 30–930 °C employed during thermogravimetry analysis, the degraded sample showed a total of 45.82 % weight loss, as against 18.89 % for the native sample. The melting temperature (T m) of the polymer was also brought down from 126.22 to 118.18 °C, as inferred from differential scanning calorimetry. Lipase-catalysed chain scission reactions could thus be used to generate low molecular weight functional biopolymers with wide-ranging pharmaceutical applications, such as in sustained drug release. 相似文献
2.
P. Maharaja R. Boopathy S. Karthikeyan M. Mahesh A. S. Komal V. K. Gupta G. Sekaran 《International Journal of Environmental Science and Technology》2016,13(9):2143-2152
Reverse osmosis (RO) concentrate generated from tannery was treated by advanced electrochemical oxidation using graphite electrodes. Catechol was selected as model organic pollutant in the RO concentrate. The influence of applied current density, catechol concentration, pH, temperature and inner electrode space of electrodes was investigated in electrochemical oxidation system. The optimized conditions were found to be current density (j), 100 mA/cm2; electrolysis time (t eco), 60 min; pH, 7.0; and temperature, 25 °C at an inner electrode space, 2 cm. The average mass transport coefficient for the removal of catechol as COD was found to be 3.0 × 10?5 m/s at optimum conditions. Faradic efficiency and specific energy consumption were also calculated for the applied current density. Further, the treatment of catechol was confirmed through Fourier transform infrared spectroscopy. Theoretical evaluation of current density suggested that the removal of catechol was controlled when supplied at above limiting applied current densities and mass transport controlled at lower of limiting current densities. 相似文献
3.
Spatial and temporal variability of temperature,precipitation, and streamflow in upper Sang‐kan basin,China 
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下载免费PDF全文 Temporal streamflow variability in an inland hydrologic station and temporal trends and frequency changes at three weather stations in a semiarid river basin located in Loess Plateau, China, were detected by using linear regression, Mann–Kendall analysis, and wavelet transform methods. Double cumulative curve and ordered clustering were used to identify the hydrological periods of upper Sang‐kan (USK) basin between 1957 and 2012. The results indicate that (1) precipitation in the USK basin over the study period did not show any trend, while the temperature showed a significant increase; (2) streamflow flowing out of the USK basin indicated a significant decrease; (3) two distinct hydrological periods – the ‘natural period’ from 1957 to 1984 and the ‘human impact period’ from 1985 to 2012 – were present; and (4) the contributions of climate change and human activities to reduce the streamflow were 36.9% and 63.1% respectively. The results indicate that human activities may be contributing to a decrease in streamflow in the USK basin. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
4.
Determination of liquefaction susceptibility of soil: a least square support vector machine approach
This article adopts least square support vector machine (LSSVM) for determination of liquefactions susceptibility of soil based on standard penetration test data. Two models (Models I and II) have been developed. For Model I, input variables are cyclic stress ratio and standard penetration test value (N). Model II employs peak ground acceleration and N as input variables. The developed LSSVM models (Models I and II) give equations for determination of liquefaction susceptibility of soil. The performances of Models I and II are the same. The developed LSSVM gives probabilistic output. The results of LSSVM have been compared with the artificial neural network model. This article shows that N and the peak ground acceleration are sufficient input parameters for determination of liquefaction susceptibility of soil. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
5.
B. Karthikeyan V. Raja N. Rajamanickam S. P. Bagare 《Astrophysics and Space Science》2006,306(4):231-234
For molecular identification in astrophysical sources, an astrophysicist needs some spectroscopic parameters such as dissociation
energy, vibrational or rotational temperature of the source, band or line wavelengths, transition probability parameters,
etc. The Franck-Condon(FC) factors are proportional to the transition probabilities. In this study, the FC factors and r-centroids for the vibronic (vibration-electronic) transitions C
1 Σ + → X
1 Σ + of aluminium hydride (AlH), b
3 Σ ( −) → a
3 Π, C
1 Σ + → A
1 Π & C
′1 Δ → Δ 1 Π of boron hydride (BH) have been evaluated and the results are presented in tables which include band origin/head wavelengths.
The physical & astrophysical significances of our evaluated FC factors & r-centroids have been discussed and the possible presence of AlH in sunspot umbral spectra is also predicted.
PACS: 33 · 70 · Ca 相似文献
6.
Seasonal variations in groundwater upwelling zones in a Danish lowland stream analyzed using Distributed Temperature Sensing (DTS) 下载免费PDF全文
下载免费PDF全文 The distribution of groundwater inflows in a stream reach plays a major role in controlling the stream temperature, a vital component shaping the riverine ecosystem. In this study, the Distributed Temperature Sensing (DTS) system was installed in a small Danish lowland stream, Elverdamsåen, to assess the seasonal dynamics of groundwater inflow zones using high spatial (1 m) and temporal (3 minutes) resolution of water temperature measurements. Four simple criteria consisting of 30 min average temperature at 16:00, mean and standard deviation of diurnal temperatures, and the day–night temperature difference were applied to three DTS datasets representing stream temperature responses to the variable meteorological and hydrological conditions prevailing in summer, winter and spring. The standard deviation criterion was useful to identify groundwater discharge zones in summer and spring conditions, while the mean temperature criterion was better for the winter conditions. In total, 20 interactions were identified from the DTS datasets representing summer, 16 in winter and 19 in spring, albeit with only two interactions contributing in all three seasons. Higher baseflow to streamflow ratio, antecedent precipitation and presence of fractured clayey till in the stream reach were deemed as the vital factors causing apparent seasonal variation in the locations of upwelling zones, prompting use of DTS not only in preconceived scenarios of large diurnal temperature change but rather a long‐term deployment covering variable meteorological and hydrological scenarios. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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8.
N. Rajamanickam G. Karthikeyan S. Jagathesan K. Saravanakumar K. Kannan R. Anandraj T. Sankaralingam 《Astrophysics and Space Science》1995,225(2):271-274
The Franck-Condon (FC) factors (transition probabilities) andr-centroids have been evaluated by the reliable numerical integration procedure for the bands of the A6+ X
6+ system of astrophysical molecule CrH, using a suitable potential. The dissociation energyD
0
0
= 2.3 eV for the electronic ground state of CrH has been estimated by fitting the Hulburt-Hirschfelder function to the experimental potential energy curve, using the correlation coefficient. 相似文献
9.
A search has been carried out for the presence of rotational lines of two bands of the (0, 0) and (1, 1) A 1Π?–?X 1Σ+ system of the AlH molecule in the high resolution Fourier Transform Spectra of sunspots observed at the National Solar Observatory at Kitt Peak. Though the presence of the AlH molecule in sunspots was confirmed by Wallace, Hinkle, and Livingston (An Atlas of Sunspot Umbral Spectra in the Visible from 15?000 to 25?000 cm?1 (3920 to 6664 Å), Tech. Rep. 00-001, National Solar Observatory, Tucson, AZ, 2000), there is no report on the rotational temperature in the literature by identifying AlH molecular lines. The results obtained in this new search using a suitable identification technique are compared with the results reported by Wallace, Hinkle, and Livingston (2000). In view of the fact that the rotational temperatures of the molecules could be used to test photospheric and sunspot models, the effective rotational temperature for the (0, 0) band of the A?–?X system of AlH molecule is estimated by measuring the equivalent widths of well resolved spectral lines and its value justifies the existence of the AlH molecule in sunspots. 相似文献
10.
Using radiometric fingerprinting and phosphorus to elucidate sediment transport dynamics in an agricultural watershed 下载免费PDF全文
下载免费PDF全文 The major goals of this study were to determine stream bed sediment erosion/deposition rates, sediment age, percent ‘new’ sediment, and suspended sediment origin during two storm events of contrasting magnitudes (11.9 mm over 5 h and 58.9 mm over 39 h) using fallout radionuclides (excess lead 210 – 210Pbxs and beryllium 7 – 7Be) and link the nature and type of sediment source contributions to potential phosphorus (P) off‐site transport. The study was conducted in cropland‐dominated and mixed land use subwatersheds in the non‐glaciated Pleasant Valley watershed (50 km2) in South Central Wisconsin. Fine sediment deposition and erosion rates on stream beds varied from 0.76 to 119.29 mg cm?2 day?1 (at sites near the watershed outlet) and 1.72 to 7.72 mg cm?2 day?1 (at sites in the headwaters), respectively, during the two storm events. The suspended sediment age ranged from 123 ± 12 to 234 ± 33 days during the smaller storm event; however, older sediment was more prevalent (p = 0.037) in the streams during the larger event with suspended sediment age ranging from 226 ± 9 to 322 ± 114 days. During the small and large storm event, percent new sediment in suspended sediment ranged from 5.3 ± 2.1 to 21.0 ± 2.9% and 5.3 ± 2.7 to 6.7 ± 5.7%, respectively. In the cropland‐dominated subwatershed, upland soils were the major source of suspended sediment, whereas in the mixed land use subwatershed, both uplands and stream banks had relatively similar contributions to suspended sediment. In‐stream (suspended and bed) sediment P levels ranged from 703 ± 193 to 963 ± 84 mg kg?1 during the two storm events. The P concentrations in suspended and bed sediment were reflective of the dominant sediment source (upland or stream bank or mixed). Overall, sediment transport dynamics showed significant variability between subwatersheds of different land use characteristics during two contrasting storm events. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献