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  • 1
    Publication Date: 2017-05-23
    Description: Extracellular polymeric substances (EPS) are ubiquitous on tidal flats but their impact on sediment erosion has not been fully understood. Laboratory-controlled sediment beds were incubated with Bacillus subtilis for 5, 10, 16 and 22 days before the erosion experiments, to study the temporal and spatial variations in sediment stability caused by the bacterial secreted EPS. We found the bio-sedimentary systems showed different erosional behaviour related to biofilm maturity and EPS distribution. In the first stage (5 days), the bio-sedimentary bed was more easily eroded than the clean sediment. With increasing growth period, bound EPS became more widely distributed over the vertical profile resulting in bed stabilisation. After 22 days, the bound EPS was highly concentrated within a surface biofilm, but a relatively high content also extended to a depth of 5 mm and then decayed sharply with depth. The biofilm increased the critical shear stress of the bed and furthermore, it enabled the bed to withstand threshold conditions for an increased period of time as the biofilm degraded before eroding. After the loss of biofilm protection, the high EPS content in the sub-layers continued to stabilise the sediment (hindered erosion) by binding individual grains, as visualized by electron microscopy. Consequently, the bed strength did not immediately revert to the abiotic condition but progressively adjusted, reflecting the depth profile of the EPS. Our experiments highlight the need to treat the EPS-sediment conditioning as a bed-age associated and depth-dependent variable that should be included in the next generation of sediment transport models.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
    Publication Date: 2009-03-28
    Description: Similarities in the behavior of diverse animal species that form large groups have motivated attempts to establish general principles governing animal group behavior. It has been difficult, however, to make quantitative measurements of the temporal and spatial behavior of extensive animal groups in the wild, such as bird flocks, fish shoals, and locust swarms. By quantifying the formation processes of vast oceanic fish shoals during spawning, we show that (i) a rapid transition from disordered to highly synchronized behavior occurs as population density reaches a critical value; (ii) organized group migration occurs after this transition; and (iii) small sets of leaders significantly influence the actions of much larger groups. Each of these findings confirms general theoretical predictions believed to apply in nature irrespective of animal species.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Makris, Nicholas C -- Ratilal, Purnima -- Jagannathan, Srinivasan -- Gong, Zheng -- Andrews, Mark -- Bertsatos, Ioannis -- Godo, Olav Rune -- Nero, Redwood W -- Jech, J Michael -- New York, N.Y. -- Science. 2009 Mar 27;323(5922):1734-7. doi: 10.1126/science.1169441.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA. makris@mit.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19325116" target="_blank"〉PubMed〈/a〉
    Keywords: Animal Migration ; Animals ; Atlantic Ocean ; *Behavior, Animal ; Ecosystem ; Fishes/*physiology ; Population Density ; Reproduction ; Spatial Behavior ; *Swimming ; Time Factors
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2010-10-23
    Description: Appropriate preferences for light or dark conditions can be crucial for an animal's survival. Innate light preferences are not static in some animals, including the fruit fly Drosophila melanogaster, which prefers darkness in the feeding larval stage but prefers light in adulthood. To elucidate the neural circuit underlying light preference, we examined the neurons involved in larval phototactic behavior by regulating neuronal functions. Modulating activity of two pairs of isomorphic neurons in the central brain switched the larval light preference between photophobic and photophilic. These neurons were found to be immediately downstream of pdf-expressing lateral neurons, which are innervated by larval photoreceptors. Our results revealed a neural mechanism that could enable the adjustment of animals' response strategies to environmental stimuli according to biological needs.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gong, Zhefeng -- Liu, Jiangqu -- Guo, Chao -- Zhou, Yanqiong -- Teng, Yan -- Liu, Li -- New York, N.Y. -- Science. 2010 Oct 22;330(6003):499-502. doi: 10.1126/science.1195993.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, People's Republic of China. zfgong@moon.ibp.ac.cn〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20966250" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Behavior, Animal/*radiation effects ; Brain/cytology/physiology ; Drosophila melanogaster/cytology/growth & development/*radiation effects ; Green Fluorescent Proteins ; Larva/physiology/radiation effects ; *Light ; Neural Pathways ; Neurons/*physiology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2012-06-16
    Description: Active DNA demethylation is an important part of epigenetic regulation in plants and animals. How active DNA demethylation is regulated and its relationship with histone modification patterns are unclear. Here, we report the discovery of IDM1, a regulator of DNA demethylation in Arabidopsis. IDM1 is required for preventing DNA hypermethylation of highly homologous multicopy genes and other repetitive sequences that are normally targeted for active DNA demethylation by Repressor of Silencing 1 and related 5-methylcytosine DNA glycosylases. IDM1 binds methylated DNA at chromatin sites lacking histone H3K4 di- or trimethylation and acetylates H3 to create a chromatin environment permissible for 5-methylcytosine DNA glycosylases to function. Our study reveals how some genes are indicated by multiple epigenetic marks for active DNA demethylation and protection from silencing.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3575687/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3575687/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Qian, Weiqiang -- Miki, Daisuke -- Zhang, Heng -- Liu, Yunhua -- Zhang, Xi -- Tang, Kai -- Kan, Yunchao -- La, Honggui -- Li, Xiaojie -- Li, Shaofang -- Zhu, Xiaohong -- Shi, Xiaobing -- Zhang, Kangling -- Pontes, Olga -- Chen, Xuemei -- Liu, Renyi -- Gong, Zhizhong -- Zhu, Jian-Kang -- R01 GM059138/GM/NIGMS NIH HHS/ -- R01 GM070795/GM/NIGMS NIH HHS/ -- R01GM059138/GM/NIGMS NIH HHS/ -- R01GM070795/GM/NIGMS NIH HHS/ -- New York, N.Y. -- Science. 2012 Jun 15;336(6087):1445-8. doi: 10.1126/science.1219416.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Shanghai Center for Plant Stress Biology and Shanghai Institute of Plant Physiology and Ecology, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, China.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22700931" target="_blank"〉PubMed〈/a〉
    Keywords: Acetylation ; Arabidopsis/*genetics/*metabolism ; Arabidopsis Proteins/chemistry/genetics/*metabolism ; Chromatin/metabolism ; DNA Glycosylases/metabolism ; *DNA Methylation ; DNA, Plant/*metabolism ; Gene Silencing ; Genes, Plant ; Histone Acetyltransferases/chemistry/genetics/*metabolism ; Histones/metabolism ; Methylation ; Mutation ; Nuclear Proteins/genetics/metabolism ; Protein Structure, Tertiary ; Transgenes
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 2017-11-18
    Description: Biofilms, consisting of microorganisms and their secreted extracellular polymeric substances (EPS), serve as “ecosystem engineers” stabilizing sedimentary environments. Natural sediment bed provides an excellent substratum for biofilm growth. The porous structure and rich nutrients allow the EPS matrix to spread deeper into the bed. A series of laboratory-controlled experiments were conducted to investigate sediment colonization of Bacillus subtilis and the penetration of EPS into the sediment bed with incubation time. In addition to EPS accumulation on the bed surface, EPS also penetrated downwards. However, EPS distribution developed strong vertical heterogeneity with a much higher content in the surface layer than in the bottom layer. Scanning Electron Microscope (SEM) images of vertical layers also displayed different micro-morphological properties of sediment-EPS matrix. In addition, colloidal and bound EPS exhibited distinctive distribution patterns. After the full incubation, the bio-sedimentary beds were eroded to test the variation of bed stability induced by biological effects. This research provides an important reference for the prediction of sediment transport, and hence deepens the understanding of the biologically mediated sediment system and broadens the scope of the burgeoning research field of “biomorphodynamics”.
    Print ISSN: 0148-0227
    Topics: Biology , Geosciences
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 6
    Publication Date: 2019
    Description: Abstract We develop a process‐based model to simulate the geomorphodynamic evolution of tidal channels, considering hydrodynamics, flow‐induced bank erosion, gravity‐induced bank collapse, and sediment dynamics. A stress‐deformation analysis and the Mohr‐Coulomb criterion, calibrated through previous laboratory experiments, are included in a model simulating bank collapse. Results show that collapsed bank soil plays a primary role in the dynamics of bank retreat. For bank collapse with small bank height, tensile failure in the middle of the bank (stage I), tensile failure on the bank top (stage II) and sectional cracking from bank top to the toe (stage III) are present sequentially before bank collapse occurs. A significant linear relation is observed between bank height and the contribution of bank collapse to bank retreat. Contrary to flow‐induced bank erosion, bank collapse prevents further widening since the collapsed bank soil protects the bank from direct bank erosion. The bank profile is linear or slightly convex and the planimetric shape of tidal channels (gradually decreasing in width landward) is similar when approaching equilibrium, regardless of the consideration of bank erosion and collapse. Moreover, the simulated width‐to‐depth ratio in all runs is comparable with observations from the Venice Lagoon. This indicates that the equilibrium configuration of tidal channels depends on hydrodynamic conditions and sediment properties, while bank erosion and collapse greatly affect the transient behaviour (before equilibrium) of the tidal channels. Overall, this contribution highlights the importance of collapsed bank soil in investigating tidal channel morphodynamics using a combined perspective of geotechnics and soil mechanics.
    Print ISSN: 0043-1397
    Electronic ISSN: 1944-7973
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
    Publication Date: 2017-08-26
    Description: Although statistical mechanics describes thermal equilibrium states, these states may or may not emerge dynamically for a subsystem of an isolated quantum many-body system. For instance, quantum systems that are near-integrable usually fail to thermalize in an experimentally realistic time scale, and instead relax to quasi-stationary prethermal states that can be described by statistical mechanics, when approximately conserved quantities are included in a generalized Gibbs ensemble (GGE). We experimentally study the relaxation dynamics of a chain of up to 22 spins evolving under a long-range transverse-field Ising Hamiltonian following a sudden quench. For sufficiently long-range interactions, the system relaxes to a new type of prethermal state that retains a strong memory of the initial conditions. However, the prethermal state in this case cannot be described by a standard GGE; it rather arises from an emergent double-well potential felt by the spin excitations. This result shows that prethermalization occurs in a broader context than previously thought, and reveals new challenges for a generic understanding of the thermalization of quantum systems, particularly in the presence of long-range interactions.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 8
    Publication Date: 2018-08-18
    Description: Leveraging the quantum information-processing ability of superconducting circuits and long-distance distribution ability of optical photons promises the realization of complex and large-scale quantum networks. In such a scheme, a coherent and efficient quantum transducer between superconducting and photonic circuits is critical. However, this quantum transducer is still challenging because the use of intermediate excitations in current schemes introduces extra noise and limits bandwidth. We realize direct and coherent transduction between superconducting and photonic circuits based on the triple-resonance electro-optic principle, with integrated devices incorporating both superconducting and optical cavities on the same chip. Electromagnetically induced transparency is observed, indicating the coherent interaction between microwave and optical photons. Internal conversion efficiency of 25.9 ± 0.3% has been achieved, with 2.05 ± 0.04% total efficiency. Superconducting cavity electro-optics offers broad transduction bandwidth and high scalability and represents a significant step toward integrated hybrid quantum circuits and distributed quantum computation.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 9
    Publication Date: 2006-01-01
    Print ISSN: 0361-5995
    Electronic ISSN: 1435-0661
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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  • 10
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