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  • 1
    Publication Date: 2014-11-05
    Description: The pollen morphology of Nepenthes khasiana (the pitcher plant) from India, was investigated using both light microscopy and scanning electron microscopy. This was to investigate fine details that may contribute to the taxonomic characterisation of species, as well as to utilise the knowledge of its morphology in order to correlate it with Bornean Nepenthes species. The size of the tetrad is the defining feature. The pollen grain is non-aperturate, the sexine is spinuliferous and thicker than the nexine. The study indicates that the species is similar in shape, aperture and ornamentation, and can be discriminated by the size of the tetrad, the length of the spines and the exine thickness. The size of the tetrad (30.7 μ m) is closer to two Bornean species such as N. rafflesiana and N. mirabilis (30.5 and 31.0 μ m respectively). These observations will be helpful in morphotaxonomy for accurate identification. This will help in finding these taxa from modern and sub-surface soils in order to study the present status of pollen preservation and decipher the palaeovegetation and past climate of the region.
    Print ISSN: 0191-6122
    Electronic ISSN: 1558-9188
    Topics: Geosciences
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  • 2
    Publication Date: 2015-06-26
    Description: The Eastern Himalayan foothills constitute an important part of the Indo-Burma hotspot due to their richness in biodiversity and representative nature for the region. This contribution enhances the data bank on the variation in rich floral diversity from northeast India. Here, we present the first palynological report for the region on palaeovegetation and past climate variations as reflected in the Subankhata swamp of Assam. This is an attempt to show the affinity of the vegetation records of this swamp with Indo-Burma flora based on the remarkable similarity in the trend of vegetation changes over a time period of about 27,000 yrs. The studied palynoassemblage reflects six different vegetational and climatic phases (S-I to S-VI) since the Late Pleistocene. The first phase (S-I) comprises compact organic clay with a little silt. During this phase, a vast lowland savanna forest existed in a cool and dry climate regime similar to what was observed during the Ice Age. Later, during the S-II phase, the forest initially continued with little alteration in tree taxa under a relatively less cool and dry climate. Thereafter, the establishment of forest occurred under the influence of moderate monsoons that led to the onset of a warm and humid climate during the S-III phase which mainly comprises organic clay with silt. During the span of the S-IV phase, vegetation consisting of Dipterocarpaceae, Mesua ferrea , Elaeocarpus and Syzygium are found, indicating warm and humid climatic conditions with high rainfall. The clearance of forest by humans has also been noted in this period. Subsequently, during the S-V zone, the beginning of a gradual decline in arboreals suggests an acceleration in forest clearance, possibly due to human activities as the climate turned warm and less humid. Entering the S-VI zone (probably Late Holocene), a drastic decline occurred in major tree elements, implying relatively dry climatic conditions indicating weakened monsoonal activity. The trend in our findings shows a clear affinity of these variations in the region with the whole Indo-Burma range since the Late Pleistocene.
    Print ISSN: 0191-6122
    Electronic ISSN: 1558-9188
    Topics: Geosciences
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  • 3
    Publication Date: 2017-01-13
    Description: Nitrogen is cycled throughout ecosystems by a suite of biogeochemical processes. The high complexity of the nitrogen cycle resides in an intricate interplay between reversible biochemical pathways alternatively and specifically activated in response to diverse environmental cues. Despite aggressive research, how the fundamental nitrogen biochemical processes are assembled and maintained in fluctuating soil redox conditions remains elusive. Here, we address this question using a kinetic modelling approach coupled with dynamical systems theory and microbial genomics. We show that alternative biochemical pathways play a key role in keeping nitrogen conversion and conservation properties invariant in fluctuating environments. Our results indicate that the biochemical network holds inherent adaptive capacity to stabilize ammonium and nitrate availability, and that the bistability in the formation of ammonium is linked to the transient upregulation of the amo-hao mediated nitrification pathway. The bistability is maintained by a pair of complementary subsystems acting as either source or sink type systems in response to soil redox fluctuations. It is further shown how elevated anthropogenic pressure has the potential to break down the stability of the system, altering substantially ammonium and nitrate availability in the soil, with dramatic effects on biodiversity.
    Keywords: biocomplexity, ecology, environmental science
    Electronic ISSN: 2054-5703
    Topics: Natural Sciences in General
    Published by Royal Society
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  • 4
    Publication Date: 2014-10-30
    Description: Author(s): V. Häfner, J. Schindler, N. Weik, T. Mayer, S. Balakrishnan, R. Narayanan, S. Bera, and F. Evers The density of states ϱ(E) of graphene is investigated numerically and within the self-consistent T-matrix approximation in the presence of vacancies within the tight binding model. The focus is on compensated disorder, where the concentration of vacancies nA and nB in both sublattices is the same. ... [Phys. Rev. Lett. 113, 186802] Published Wed Oct 29, 2014
    Keywords: Condensed Matter: Electronic Properties, etc.
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
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  • 5
    Publication Date: 2016-02-19
    Description: Integration of the reverse-transcribed viral DNA into the host genome is an essential step in the life cycle of retroviruses. Retrovirus integrase catalyses insertions of both ends of the linear viral DNA into a host chromosome. Integrase from HIV-1 and closely related retroviruses share the three-domain organization, consisting of a catalytic core domain flanked by amino- and carboxy-terminal domains essential for the concerted integration reaction. Although structures of the tetrameric integrase-DNA complexes have been reported for integrase from prototype foamy virus featuring an additional DNA-binding domain and longer interdomain linkers, the architecture of a canonical three-domain integrase bound to DNA remained elusive. Here we report a crystal structure of the three-domain integrase from Rous sarcoma virus in complex with viral and target DNAs. The structure shows an octameric assembly of integrase, in which a pair of integrase dimers engage viral DNA ends for catalysis while another pair of non-catalytic integrase dimers bridge between the two viral DNA molecules and help capture target DNA. The individual domains of the eight integrase molecules play varying roles to hold the complex together, making an extensive network of protein-DNA and protein-protein contacts that show both conserved and distinct features compared with those observed for prototype foamy virus integrase. Our work highlights the diversity of retrovirus intasome assembly and provides insights into the mechanisms of integration by HIV-1 and related retroviruses.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Yin, Zhiqi -- Shi, Ke -- Banerjee, Surajit -- Pandey, Krishan K -- Bera, Sibes -- Grandgenett, Duane P -- Aihara, Hideki -- AI087098/AI/NIAID NIH HHS/ -- AI100682/AI/NIAID NIH HHS/ -- GM109770/GM/NIGMS NIH HHS/ -- P41 GM103403/GM/NIGMS NIH HHS/ -- England -- Nature. 2016 Feb 18;530(7590):362-6. doi: 10.1038/nature16950.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA. ; Institute for Molecular Virology, University of Minnesota, Minneapolis, Minnesota 55455, USA. ; Masonic Cancer Center, University of Minnesota, Minneapolis, Minnesota 55455, USA. ; Northeastern Collaborative Access Team, Cornell University, Advanced Photon Source, Lemont, Illinois 60439, USA. ; Institute for Molecular Virology, St. Louis University Health Sciences Center, St. Louis, Missouri 63104, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26887497" target="_blank"〉PubMed〈/a〉
    Keywords: Catalytic Domain ; Crystallography, X-Ray ; DNA, Viral/*chemistry/metabolism ; HIV-1/enzymology/metabolism ; Integrases/*chemistry/metabolism ; Models, Molecular ; Protein Binding ; Protein Multimerization ; Rous sarcoma virus/*chemistry/*enzymology/genetics/metabolism ; Spumavirus/enzymology ; Virus Integration
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 6
    Publication Date: 2013-08-27
    Description: Author(s): S. Bera, J. Maloney, L. B. Lurio, N. Mulders, Z. G. Cheng, M. H. W. Chan, C. A. Burns, and Z. Zhang Transmission x-ray diffraction experiments have been carried out on solid helium grown in porous Vycor glass. Measurements were made at temperatures near 0.7 K and at pressures up to 162 bars. The crystalline phases of solid helium in Vycor are found to differ significantly from the bulk. At pressur... [Phys. Rev. B 88, 054512] Published Mon Aug 26, 2013
    Keywords: Superfluidity and superconductivity
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
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  • 7
    Publication Date: 2019
    Electronic ISSN: 2045-2322
    Topics: Natural Sciences in General
    Published by Springer Nature
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  • 8
    Publication Date: 2015-03-01
    Description: The Epoch of Reionization (EoR) 21-cm signal is expected to become increasingly non-Gaussian as reionization proceeds. We have used seminumerical simulations to study how this affects the error predictions for the EoR 21-cm power spectrum. We expect ${\rm SNR}=\sqrt{N_k}$ for a Gaussian random field where N k is the number of Fourier modes in each k bin. We find that non-Gaussianity is important at high SNR where it imposes an upper limit [SNR] l . For a fixed volume V , it is not possible to achieve SNR 〉 [SNR] l even if N k is increased. The value of [SNR] l falls as reionization proceeds, dropping from ~500 at $\bar{x}_{{\rm H\,{\small {i}}}}= 0.8{\rm -}0.9$ to ~10 at $\bar{x}_{{\rm H\,{\small {i}}}}= 0.15$ for a [150.08 Mpc] 3 simulation. We show that it is possible to interpret [SNR] l in terms of the trispectrum, and we expect $[{\rm SNR}]_l \propto \sqrt{V}$ if the volume is increased. For SNR 〈〈 [SNR] l we find ${\rm SNR}= \sqrt{N_k}/A$ with A  ~ 0.95–1.75, roughly consistent with the Gaussian prediction. We present a fitting formula for the SNR as a function of N k , with two parameters A and [SNR] l that have to be determined using simulations. Our results are relevant for predicting the sensitivity of different instruments to measure the EoR 21-cm power spectrum, which till date have been largely based on the Gaussian assumption.
    Print ISSN: 1745-3925
    Electronic ISSN: 1745-3933
    Topics: Physics
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  • 9
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Photochemistry and Photobiology A: Chemistry 60 (1991), S. 101-110 
    ISSN: 1010-6030
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Photochemistry and Photobiology A: Chemistry 49 (1989), S. 121-130 
    ISSN: 1010-6030
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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