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- Bikkina, Srinivas, et al.
(författare)
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Atmospheric deposition of phosphorus to the Northern Indian Ocean
- 2015
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Ingår i: Current Science. - 0011-3891. ; 108:7, s. 1300-1305
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Tidskriftsartikel (refereegranskat)abstract
- Air- sea deposition of phosphorus is an important external source of this macronutrient for ocean primary productivity. Although global budgets have shown that atmospheric input of phosphorus is comparable to its riverine supply, studies on regional scale are rather limited. The present article summarizes sources and atmospheric pathway of phosphorus to the ocean surface as a case study of the Northern Indian Ocean. Water-soluble aerosol phosphorus (PInorg) concentrations are significantly high over the Bay of Bengal (BoB) compared to those over the Arabian Sea (ARS). Relative increase in the supply of aerosol-P over BoB is attributed to acid-processing of mineral dust during long-range atmospheric transport in addition to its supply from anthropogenic sources. Our estimate of P-deposition to the Northern Indian Ocean (similar to 1.2 Gmol-P year-1) is comparable to its atmospheric deposition in other oceanic regions such as the North Atlantic and is also consistent with the model-based projections for the Northern Indian Ocean. These results highlight the importance of atmospheric source in influencing the biogeochemical cycle of phosphorus in the Northern Indian Ocean.
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- Björn, Lars Olof, et al.
(författare)
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Detectability of life and photosynthesis on exoplanets.
- 2009
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Ingår i: Current Science. - 0011-3891. ; 96:9, s. 1171-1175
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- ‘Is there life on exoplanets?’. We refer to exoplanets as planets in other solar systems than our own. This often asked question can be further refined by asking ‘is there life on exoplanets which is so extensive that it may impact on its atmosphere, its biosphere and its optical properties?’. And if such a life exists, at astronomical distances from us, can we detect it with instruments on Earth-based or Earth-orbiting observatories? Will then, in that case, our advanced knowledge of present-day and early-day photosynthesis on Earth help us select appropriate biosignatures that may signal its presence? Here we elaborate further on these themes, based on the most recent literature, and from the point of view of photosynthesis. We also provide our considered views. Although search for chlorophyll is considered desirable, we conclude that our best bet is to look for and analyse photosynthesis-related gases, namely O2, CO2 and H2O vapour. We shall keep in mind that the evolutionary tree of life on our planet has its roots in autotrophy, and of the various forms of autotrophy, only oxygenic
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- Björn, Lars Olof, et al.
(författare)
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The evolution of photosynthesis and chloroplasts
- 2009
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Ingår i: Current Science. - 0011-3891. ; 96:11, s. 1466-1474
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Forskningsöversikt (refereegranskat)abstract
- This review focuses on what has been learned about the evolution of photosynthesis in the past five years, and omits evolution of CO2 assimilation. Oxygenic photosynthesis (using both photosystems I and II) has evolved from anoxygenic photosynthesis. The latter occurs in different variants, using either a type 1 photosystem resembling photosystem I, or a type 2 photosystem resembling photosystem II. Opinions differ as to how two types of photosystem came to be combined in the same organism, whether by gene transfer between bacteria, by fusion of bacteria, or as a result of gene duplication and evolution within one kind of bacterium. There are also different opinions about when oxygenic photosynthesis arose, in conjunction with the Great Oxygenation Event, 2.3 billion years before the present, or more than a billion years before that. Cyanobacteria were the first organisms to carry out oxygenic photosynthesis. Some of them gave rise to chloroplasts, while others continued to evolve as independent organisms, and the review outlines both lines of evolution. At the end we consider the evolution of photosynthesis in relation to the evolution of our planet.
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- Choubey, Sandhya
(författare)
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Neutrino oscillations
- 2017
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Ingår i: Current Science. - : Indian National Science Academy. - 0011-3891. ; 112:7, s. 1381-1384
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Tidskriftsartikel (refereegranskat)abstract
- Neutrinos are massless as proposed in the Standard Model of particle physics. However, neutrino experiments in the last few decades have revealed that neutrinos flavour oscillate, a scenario possible only if they have mass and mixing. Existence of neutrino mass was the first conclusive evidence of physics beyond the Standard Model, and explaining the smallness of the neutrino masses and peculiar mixing angles still remains a challenge for model-builders proposing beyond Standard Model scenarios. We give a brief introduction to the phenomenon of neutrino oscillations and showcase some recent work where we look for physics beyond the three-generation neutrino oscillation paradigm and its impact on future experiments.
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| 7. |
- Choudhary, P., et al.
(författare)
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Comparison of bulk organic matter characteristics in sediments of three Kumaun Himalayan lakes
- 2009
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Ingår i: Current Science. - 0011-3891. ; 97:4, s. 572-575
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Tidskriftsartikel (refereegranskat)abstract
- Three lakes (Nainital, Sattal and Naukuchiatal) in the Kumaun Himalayan region were investigated for total organic carbon (TOC%) and nitrogen (N%), their atomic ratios (C/N) and isotopic composition (delta C-13 and delta N-15) in their sediments. These geochemical proxies measured in 35-45 cm long cores indicate that organic matter preserved in the lake sediments is primarily derived from algal matter. Increase in TOC in all the three lakes suggests increased productivity. The sediments are anoxic in all the three lakes and show low N%. Shift in delta C-13 isotopic composition indicates influence of sewage input into the lakes. Likewise, increase in delta N-15 in surface sediments suggests nitrogen fixation by cyanobacteria.
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| 9. |
- Erlandsson, Ragnar, et al.
(författare)
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Progress in scanning probe microscopy : High resolution force microscopy and spectroscopy
- 2000
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Ingår i: Current Science. - 0011-3891. ; 78:12, s. 1445-1457
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Tidskriftsartikel (refereegranskat)abstract
- During the last few years the Atomic Force Microscope (AFM) has become capable of routinely obtaining atomic resolution when operated with a vibrating cantilever (ac-mode). Local measurement of the tip-sample force (force spectroscopy) is a powerful tool for investigations of contact phenomena at the atomic scale that are important in fields like friction, tribology, atom manipulation and chemical bond formation. This paper reviews several aspects of the AFM technique such as tip-surface forces, force sensors, operation modes and contrast effects. A study of the Si(111)7 x 7 reconstruction is presented as an example of high resolution AFM imaging.
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- Grek, G.R., et al.
(författare)
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Experimental study of a Λ-structure development and its transformation into the turbulent spot
- 2000
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Ingår i: Current Science. - 0011-3891. ; 79:6, s. 781-789
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the results of experimental research on the characteristics of Λ-structures, their development, and the mechanism of their transformation into turbulent spots. It has been shown that an isolated Λ-structure can damp as well as increase downstream and transform into a turbulent spot. The structure of the associated disturbances consists of two counter-rotating vortices (the "legs" of disturbance) closed by a "head" at the leading edge. The difference between the two types is that the Λ-structure that damps is a kind of a hairpin vortex which does not cross the upper boundary layer edge; the "head" of the increasing Λ-structure crosses the upper boundary layer edge and the disturbance attains the form of the Greek letter Λ. It has been proposed that the increasing Λ-structure is connected with the development of secondary high frequency disturbances on the "legs" of the structure. The reason for this is probably the local transverse velocity gradient ∂u / ∂z on the "legs" of the Λ-structure, which creates conditions for the development of secondary disturbances in it. It has also been shown that the frequency of the secondary disturbance decreases because of the continuous extension of a localized disturbance under its downstream propagation. Secondary high frequency breakdown of structures is also observed when there is periodical generation.
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