1,741 research outputs found

    Whale origins as a poster child for macroevolution

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    Deccan volcanism, the KT mass extinction and dinosaurs

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    Recent advances in Deccan volcanic studies indicate three volcanic phases with the phase-1 at 67.5 Ma followed by a 2 m.y. period of quiescence. Phase-2 marks the main Deccan volcanic eruptions in Chron 29r near the end of the Maastrichtian and accounts for ~80% of the entire 3500 m thick Deccan lava pile. At least four of the world's longest lava flows spanning 1000 km across India and out into the Gulf of Bengal mark phase-2. The final phase-3 was smaller, coincided with the early Danian Chron 29n and also witnessed several of the longest lava flows. The KT boundary and mass extinction was first discovered based on planktic foraminifera from shallow marine intertrappean sediments exposed in Rajahmundry quarries between the longest lava flows of the main volcanic phase-2 and smaller phase-3. At this locality early Danian (zone P1a) planktic foraminiferal assemblages directly overlie the top of phase-2 eruptions and indicate that the masse extinction coincided with the end of this volcanic phase. Planktic foraminiferal assemblages also mark the KT boundary in intertrappean sediments at Jhilmili, Chhindwara, where freshwater to estuarine conditions prevailed during the early Danian and indicate the presence of a marine seaway across India at KT time. Dinosaur bones, nesting sites with complete eggs and abundant eggshells are known from central India surrounding the hypothesized seaway through the Narmada-Tapti rift zone. A Maastrichtian age is generally assigned to these dinosaur remains. Age control may now be improved based on marine microfossils from sequences deposited in the seaway and correlating these strata to nearby terrestrial sequences with dinosaur remains

    Standardized method to extract phenolic compounds from Lagerstroemia speciosa L. (Jarul) for enhanced antioxidant activity

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    Phenolic compounds contribute to the antioxidant property of plants and the efficient extraction of plant phenolics could enhance its antioxidant potential. Lagerstroemia speciosa (L.) Pers. has been investigated for its pharmacological activities, but comparing its antioxidant activities of phenolics derived from its various parts has a key role in developing natural antioxidants. This study was conducted to standardize the extraction of phenolics from leaves, pods and branches of L. speciosa plant, followed by determination of antioxidant activities of their solvent fractions. Phenolic compounds were extracted from the leaves, pods and branches under different parameters such as temperature, pH, type of solvent and volume of the solvent. The extracted phenolic compounds were subjected to solvent fractions and antioxidant assays were performed. Among the various extraction methods tested, the best method was 50% ethanol +1% HCl, refluxing temperature, 100 ml of solvent and 1 hour extraction time. The best solvent fractions were determined as NaHCO3 + ethyl acetate for pods and ethyl acetate alone for leaves and branches with extracted phenolics content of 150.2 mg/g, 136.2 mg/g and 82.9 mg/g, respectively. The chloroform fraction was best among the fractions with maximum ascorbic acid equivalent (ASE) in all the parts of L. speciosa tested. Ferrous ion chelating capacity indicated that butanol fraction had the highest chelation and the same was recorded in ferric ion chelating assay with an EC50 value of 28.2. Hydroxyl radical scavenging activity of the fractions indicated that NaHCO3 + EtOAc fraction of pods had potential activity. Thus, the phenolic compounds from L. speciosa are excellent sources for future investigation on potent natural antioxidant compounds

    Interface driven magnetoelectric effects in granular CrO2

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    Antiferromagnetic and magnetoelectric Cr2O3-surfaces strongly affect the electronic properties in half metallic CrO2. We show the presence of a Cr2O3 surface layer on CrO3 grains by high-resolution transmission electron microscopy. The effect of these surface layers is demonstrated by measurements of the temperature variation of the magnetoelectric susceptibility. A major observation is a sign change at about 100 K followed by a monotonic rise as a function of temperature. These electric field induced moments in CrO3 are correlated with the magnetoelectric susceptibility of pure Cr2O3. This study indicates that it is important to take into account the magnetoelectric character of thin surface layers of Cr2O3 in granular CrO2 for better understanding the transport mechanism in this system. The observation of a finite magnetoelectric susceptibility near room temperature may find utility in device applications.Comment: Figure 1 with strongly reduced resolutio

    A new miocene sirenian from Kutch, India

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    We report a new Miocene sirenian from District Kutch, State of Gujarat, India: Domingia sodhae gen. et sp. nov. The new species is a dugongine dugongid with flattened tusk-like upper incisors. Like some other Miocene dugongids, Domningia is large and has complex, bilophodont molars and three-rooted premolars, which are strongly worn. The rostrum is downturned significantly, similar to modern dugongs, and indicative of a specialized feeding mode. Phylogenetically, it is closely related to Dioplotherium, Rytiodus, Corystosiren, and Bharatisiren. Among these, Domningia is most similar to Bharatisiren indica and Dioplotherium manigaulti, in that all three taxa retain multi-rooted premolars. Similar to Bharatisiren, the nasal process of the premaxilla is long. Bharatisiren and Domningia are part of a late Oligocene and early Miocene radiation of dugongines in South Asia

    Vertebrate fauna from Panandhro lignite field (Lower Eocene), District Kachchh, western India

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    Physicochemical and antibacterial activities of Apis honey types derived from Coorg, Karnataka, India

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    Natural honey has various ingredients in it that contribute to its incredible properties. The aim of this investigation was to evaluate the physicochemical and antibacterial activity of various Apis honey from Coorg, Karnataka. Four samples of Apis honey viz., A. florea, A.  mellifera, A. cerana and A.  dorsata were collected from various regions of Coorg, Karnataka. The honey samples' physicochemical properties and antibacterial activities against Streptococcus sp., Staphylococcus aureus, Bacillus subtilis and Enterococcus sp were determined in vitro. The moisture and ash content varied from 13.6 - 17.2% and 0.32 – 0.49%, respectively. Hydroxy methyl furfurals) content of A. dorsata honey samples was highest with 9.2±0.5 mg/Kg and least was recorded with 6.8±0.4 mg/Kg for A. florae honey. The reducing sugar content of A. florea honey sample was highest with 87.5±3.2 (%) and the peroxide levels were in the range of 10.2 – 14.9 µg/g/h at 20°C. The antibacterial assay revealed that S. aureus, Enterococcus sp and Streptococcus sp were most susceptible against the honey varieties tested and minimum inhibitory concentration (MIC) values between 25-6.5 (%v/v) were determined. In conclusion, honey varieties from Coorg could be used in specific antibacterial prophylaxis as the activity depends on the honey bee species, their metabolism and floral sources in specific geographical regions

    The origin and early evolution of whales: macroevolution documented on the Indian Subcontinent

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    The origin of whales (order Cetacea) from a four-footed land animal is one of the best understood examples of macroevolutionary change. This evolutionary transition has been substantially elucidated by fossil finds from the Indian subcontinent in the past decade and a half. Here, we review the first steps of whale evolution, i.e. the transition from a land mammal to obligate marine predators, documented by the Eocene cetacean families of the Indian subcontinent: Pakicetidae, Ambulocetidae, Remingtonocetidae, Protocetidae, and Basilosauridae, as well as their artiodactyl sister group, the Raoellidae. We also discuss the influence that the excellent fossil record has on the study of the evolution of organ systems, in particular the locomotor and hearing systems
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