Synthesis and Antimicrobial Activity of 2-(Aminoacid ester)-3-(6-methyl-2-pyridyl)-3,4-dihydro-2H-1,3,2 λ5- benzoxazaphosphinin-2-thiones

Synthesis of 2-(aminoacid ester)-3-(6-methyl-2-pyridyl)-3,4-dihydro-2H-1,3,2λ5-benzoxazaphosphinin-2-thiones (3a–j) was accomplished through a two-step process. It involves the prior preparation of 2-chloro-3-(6-methyl-2-pyridyl)-3,4-dihydro-2H-1,3,2λ5-benzoxazaphosphinin-2-thione monochloride (2) and its subsequent reaction with the aminoacid ester hydrochlorides in dry tetrahydrofuran-toluene in the presence of triethylamine at various temperatures. These compounds were characterizedby IR, 1H, 13C, 31P NMR and mass spectral data.Keywords: 2-[(6-methyl-2-pyridyl) amino] methylphenol, 1,3,2-benzoxazaphosphinin-2-thione, antimicrobial activit

Empirical model for mean temperature for Indian zone and estimation of precipitable water vapor from ground based GPS measurements

Estimation of precipitable water (PW) in the atmosphere from ground-based Global Positioning System (GPS) essentially involves modeling the zenith hydrostatic delay (ZHD) in terms of surface Pressure (<I>P<sub>s</sub></I>) and subtracting it from the corresponding values of zenith tropospheric delay (ZTD) to estimate the zenith wet (non-hydrostatic) delay (ZWD). This further involves establishing an appropriate model connecting PW and ZWD, which in its simplest case assumed to be similar to that of ZHD. But when the temperature variations are large, for the accurate estimate of PW the variation of the proportionality constant connecting PW and ZWD is to be accounted. For this a water vapor weighted mean temperature (<I>T<sub>m</sub></I>) has been defined by many investigations, which has to be modeled on a regional basis. For estimating PW over the Indian region from GPS data, a region specific model for <I>T<sub>m</sub></I> in terms of surface temperature (<I>T<sub>s</sub></I>) is developed using the radiosonde measurements from eight India Meteorological Department (IMD) stations spread over the sub-continent within a latitude range of 8.5°–32.6° N. Following a similar procedure <I>T<sub>m</sub></I>-based models are also evolved for each of these stations and the features of these site-specific models are compared with those of the region-specific model. Applicability of the region-specific and site-specific <I>T<sub>m</sub></I>-based models in retrieving PW from GPS data recorded at the IGS sites Bangalore and Hyderabad, is tested by comparing the retrieved values of PW with those estimated from the altitude profile of water vapor measured using radiosonde. The values of ZWD estimated at 00:00 UTC and 12:00 UTC are used to test the validity of the models by estimating the PW using the models and comparing it with those obtained from radiosonde data. The region specific <I>T<sub>m</sub></I>-based model is found to be in par with if not better than a similar site-specific <I>T<sub>m</sub></I>-based model for the near equatorial station, Bangalore. A simple site-specific linear relation without accounting for the temperature effect through <I>T<sub>m</sub></I> is also found to be quite adequate for Bangalore. But for Hyderabad, a station located at slightly higher latitude, the deviation for the linear model is found to be larger than that of the <I>T<sub>m</sub></I>-based model. This indicates that even though a simple linear regression model is quite adequate for the near equatorial stations, where the temperature variations are relatively small, for estimating PW from GPS data at higher latitudes this model is inferior to the <I>T<sub>m</sub></I>-based model

Upper tropospheric humidity from SAPHIR on-board Megha-Tropiques

Upper tropospheric humidity (UTH) has been derived using a ‘brightness temperature (Tb) transformation’ method from the humidity sounder channels of SAPHIR payload on - board Megha - Tropiques (MT). These channels are very close to the water vapour absorption peak at 183.31 GHz. The channel at 183.31 0.2 GHz enables retrieval of humidity up to the hig h est altitude possible wit h the present nadir - looking microwave humidity sounders. Megha - Tropiques satllite has an equatorially inclined orbit, which e n sures frequent spatial and temporal coverage of the global tropical belt. Transformation coeff i cients for the first three channels for all the incidence angles have been derived and are used to convert brightness temperatures to weighted average upper tropospheric humidity having weighting function peaks at different pressure levels. The methodology has been validated by comparing the SAPHIR - derived UTH with that derived from radiosonde observations. Inter - comparison of the derived UTH has been done with layer averaged humidity product from SAPHIR measurements and with UTH product using infrared measurements from Kalpana satellite ( MOSDAC). UTH over the tropical belt for six months has been studied taking the advantage of the humidity product with high spatial and temporal resolution. The transformation coefficients and methodology to identify the cloud - free pixels to derive UTH from the three channels for all the possible incidence angles are presented here, so that the users can directly derive UTH from the brightness temperature data

Designing an Adversarial Model Against Reactive and Proactive Routing Protocols in MANETS: A Comparative Performance Study

Mobile ad-hoc networks are self-organized infrastructure less networks that consists of mobile nodes, which are capable of maintaining and forming the network by themselves. Recently, researchers are designed several routing protocols on these networks. However, these routing protocols are more vulnerable to attacks from the intruders, which can easily paralyze the operation of the network due to its inherited characteristics of MANETS. One such type of attack is wormhole attack. Because of its severity, the wormhole attack has attracted a great deal of attention in the research community. This paper compares reactive and proactive routing protocols in adversarial environment. Specifically, wormhole attack is applied to these routing protocols to evaluate its performance through simulation. Comprehensively the results shows the comparative performance of these protocols against wormhole attack is hard to detect and easy to implement

MT-MADRAS brightness temperature analysis for terrain characterization and land surface microwave emissivity estimation

This article reports the potential of the ‘MADRAS’ payload on-board the Megha-Tropiques satellite for land surface studies. The analysis has been divided into two parts as application of MADRAS data for studying the land surface properties and estimation of microwave emissivity directly from MADRAS brightness temperature (TB) data by applying an in-house developed Microwave Radiative Transfer Computation Code. The derived emissivity is further used to characterize the microwave emissivity of different land surface classes. The polarization difference (PD) parameters, the difference between horizontal (H-) and vertical (V-) polarization of TBs at 18 and 36 GHz clearly discern surface features of different surface classes such as deserts, arid/semi-arid an d vegetated regions. Land surface microwave emissivity for MADRAS channels is derived on a global basis. These are inter-compared with the emissivity derived from the operational TRMM Microwave Imager and are in reasonably good agreement. The analysis based on emissivity shows spectral variation for different surface classes

Synthesis and Antimicrobial Activity of 3-[(4-Substituted) (2-oxo-1,3-oxazolidin-3-yl) phosphoryl]- 1,3-oxazolidin-2-ones

3-[(4-Substituted) (2-oxo-1,3-oxazolidin-3-yl)-phosphoryl]-1,3-oxazolidin-2-ones (4a–j) were synthesized through a two-step process. Bis-(2-oxo-1,3-oxazolidin-3-yl)-phosphonic chloride (2) prepared by the reaction of two moles of oxazolidin-2-one (1) with phosphorus oxychloride in dry tetrahydrofuran in the presence of triethylamine and treatment with various heterocyclic aromatic and aliphatic amines under the same experimental conditions afforded the title compounds (4a–j). They were characterized by elemental analysis, IR,NMR(1H, 13Cand 31P) and mass spectroscopy. Their antimicrobial activities were also evaluated.Keywords: 3-[(4-Substituted) (2-oxo-1,3-oxazolidin-3-yl)-phosphoryl]-1,3-oxazolidin-2-ones, oxazolidin-2-one, bis-(2-oxo-1,3-oxazolidin-3-yl)-phosphonic chloride, antimicrobial activity, spectral studie

Tropical convective cloud characterization using ground-based microwave radiometric observations

Characterization of the microphysical and thermodynamical properties of convective events over the tropical coastal station Thiruvananthapuram (TVM) has been carried out based on multiyear microwave radiometer profiler observations. The analyses have been extended to develop a methodology to identify convective events, which is based on the radiometric brightness temperature (Tb) difference threshold, at 30 and 22.23 GHz channels, and the results are compared with reflectivity and rainfall intensity deduced from concurrent and collocated disdrometer measurements. Eighty-four of such convections were identified using the aforementioned methodology over the station during 2010-2013, i.e., both for pre- and post-Indian summer monsoon months, and further evaluated by computing their stability indexes. The occurrence of convective systems peaks in the afternoon and early-morning hours with genesis, respectively, over the land and the sea