TRANES analysis of the fluorescence of nile red in organized molecular assemblies confirms emission from two species

Time-resolved area normalized emission spectroscopy (TRANES) is a new method for the analysis of fluorescence of dyes in complex chemical and biological systems (A S R Koti, M M G Krishna and N Periasamy, 2001,J. Phys. Chem. 105, 1767). The model-free method extends the power of time-resolved emission spectroscopy (TRES) analysis and removes the ambiguity in the interpretation when the emission spectrum is time-dependent. Observation of an isoemissive point in TRANES analysis of fluorescence is an unambiguous indication for the presence of two emissive species in the sample. The isoemissive point occurs at a wavelength where the ratio of the radiative rates of the two species is equal to the ratio of their total radiative rates. The polarity-sensitive nile red dye shows time-dependent emission spectra in the organized bilayer assemblies of TX micelle and bilayer egg-phosphotidylcholine (egg-PC) membrane. Time-dependent spectra in complex systems support many important models (solvation model and heterogeneity in the ground and/or excited state). TRANES analysis shows that the fluorescence emission of nile red in TX micelle and egg-PC membrane is due to two emissive species solubilized in different sites

Time resolved area normalized emission spectroscopy (TRANES) of DMABN confirms emission from two states

4-N, N-Dimethylaminobenzonitrile (DMABN) is a simple molecule which is extensively studied to understand the excited state kinetics and the origin of time dependent fluorescence in several organic solvents. We use a recently described method, time resolved area normalized emission spectroscopy (TRANES), for the analysis of wavelength dependent fluorescence of DMABN in acetonitrile and 1,4-dioxane. An isoemissive point was observed in the TRANES spectra, which confirms that there are only two emissive species A∗ and B∗:A→A∗⇔B∗

Solvent exchange in excited-state relaxation in mixed solvents

The fluorescence of styrylthiazoloquinoxaline (STQ) in the solvent mixture methanol and dichloromethane (DCM) and 2-octanol have many common characteristics: biexponential fluorescence decay, wavelength-dependent amplitudes, a negative amplitude for the short-lifetime component at long emission wavelengths, and a time-dependent red shift of the emission spectrum. In octanol, the fluorescence lifetime decreases with increasing temperature, whereas the lifetime increases with temperature in the methanol/DCM mixture. The fluorescence characteristics in 2-octanol (η=7.29 cP) are readily explained by the conventional model of excited-state relaxation kinetics by solvent reorientation. This model is not applicable for low-viscosity (η=0.455 cP) solvent mixtures. A model of excited-state relaxation kinetics involving solvent exchange (versus solvent reorientation in pure solvents) in the excited state is proposed for the solvent mixture. The model assumes that the solvent compositions around the solute are different in the ground and excited states and the solvent composition is temperature dependent

Implementation of MPPT Algorithm for Solar Photovoltaic Cell by Comparing Short-circuit Method and Incremental Conductance Method

AbstractThis paper presents simulation of incremental conductance (IncCond) maximum power point tracking (MPPT) algorithm used in solar array power systems with direct control method. The main difference between the proposed system to that of the existing MPPT systems includes the elimination of the proportional–integral control loop and investigation of the effect of simplifying the control circuit. Contributions are made in several aspects of the whole system, including converter design, system simulation and controller programming. The resultant system is capable of tracking MPPs accurately and rapidly without steady-state oscillation, and also, its dynamic performance is satisfactory. The IncCond algorithm is used to track MPPs because it performs precise control under rapidly changing atmospheric conditions. MATLAB and Simulink were employed for simulation studies

NMR studies on truncated sequences of human telomeric DNA: observation of a novel A-tetrad

The structure of the telomeric DNA has been a subject of extensive investigation in recent years due to the realization that it has important functional roles to play in vivo and the observations that truncated telomeric sequences exhibit a great variety of 3D structures in aqueous solutions. In this context, we describe here NMR structural studies on two truncated human telomeric DNA sequences, d-AG3T and d-TAG3T in solutions containing K+ ions. The G3 stretches in both the oligonucleotides were seen to form parallel-stranded quadruplexes. However, the AG3 segment as a whole, had different structural characteristics. The structure of d-AG3T revealed the formation of a novel A-tetrad, which was not seen in d-TAG3T. The A's in the tetrad had syn glycosidic conformation as opposed to the anti conformation of the G's in the G-tetrads. The A-tetrad stacked well over the adjacent G-tetrad and the twist angle at this step was smaller in d-AG3T than in d-TAG3T. These observations are expected to be significant from the point of view of structural diversity and recognition in telomeres

Radiogenic heat production of Late Archaean Bundelkhand granite and some Proterozoic gneisses and granitoids of Central India

Abundances of heat-producing elements, K, U and Th, in some of the granites and gneisses of the Bundelkhand and Bastar terrains have been estimated by in situ gamma-ray spectrometry. The Bundelkhand granite is an I-type, calc-alkaline granite complex made up of porphyritic, coarse-to-medium grained and fine-grained granites. It carries macro enclaves of ~ 3.5 Ga-old tonalitic gneisses. These gneisses have a low heat production of 1.4 μWm-3. The mean heat production of the dominant porphyritic and mediumto- coarse grained Bundelkhand granite is 5.5 μWm-3. The heat production of the Proterozoic Jabalpur granite intruding the Mahakhosal greenstone belt is 3.4 μWm-3. The Tirodi gneisses resulting from migmatization of psammopelites of the Sausar Group, are characterized by a mean heat production of 3.8 μWm-3. The cataclastic biotite gneisses of the Tattapani geothermal area are the highest heat-producing rocks encountered in the Bundelkhand terrain with a mean heat production of 7.4 μWm-3. The tonalitic Amgaon gneisses of the Bastar terrain are characterized by a heat production of 0.7 μWm-3, which is about half of the mean heat production of the tonalitic gneisses occurring as inclusions in the Bundelkhand granite. Mean heat production of the Proterozoic Amgaon and Dongargarh granites are 2.5 and 2.9 μWm-3, respectively. Preliminary heat production data presented here show that the gneisses and granitoids of the Bundelkhand and Bastar terrains may have distinct heat production ranges, with the rocks of the Bundelkhand terrain being more heat-producing

On the Security of an Efficient Group Key Agreement Scheme for MANETs

Yang et al. have proposed an efficient group key agreement scheme for Mobile Adhoc Networks. The scheme is efficient as only one bilinear computation is required for group members to obtain the session key. The scheme is analyzed for security without random oracle model. However, we prove that their scheme is not secure. In particular, we show that any passive adversary (or non-group member) can compute the session key without having access to the individual secret keys of the group members. Hence, Yang et al. scheme cannot be used for secure group communication. We also show that, the scheme cannot be used for secure group communication unless there exists a central entity, and hence cannot be used for secure communication in mobile adhoc networks

A Rare Case of Situs Inversus with Mesocardia

A ten year old male child having congenital heart disease admitted with recurrent history of respiratory infection. ECHO cardioraphy showed Mesocardia, congenitally corrected TGA, bidirectional VSD and severe pulmonary valve stenosis.On sonographic evaluation showed intra-abdominal mirror imaging of all the solid organs and vessels which was suggestive of a rare presentation of Sinus inverses with Mesocardia. Corrective surgery as pulmonary valve balloon dilation or valvuloplasty and vestricular septal repair has to be done to the child for better morbidity and reducing the mortality risk. This anomaly complicates the diagnosis and management of acute abdominal conditions like appendicitis, diverticulitis and biliary coli

Salinity Tolerance of Forage Range Legumes during Germination and Early Seedling Growth

Salinity is one of the rising problems causing tremendous yield losses in many regions of the world especially in arid and semiarid regions. In India, about 5.95M ha areas were affected by salinity. Five states viz. Haryana, Punjab, Rajasthan, Gujarat and Andhra Pradesh accounts for 48% of the total salt affected soils of the country. Establishment of seedlings at early growth stages of crop plants as one of the most important determinants of high yield is severely affected by soil salinity. Increasing salinity levels significantly decreased germination parameters, shoot and root length, shoot and root fresh and dry weights of some forage sorghum cultivars (Kandil et al., 2012). Therefore, in the present investigation three forage range legumes namely centro, clitoria and siratro were tested for their relative salt tolerance to increasing levels of salinity in those combinations of salts which nearly exist in the natural salt affected soils