82 research outputs found
Strongly interacting bosons in a disordered optical lattice
Disorder, prevalent in nature, is intimately involved in such spectacular
effects as the fractional quantum Hall effect and vortex pinning in type-II
superconductors. Understanding the role of disorder is therefore of fundamental
interest to materials research and condensed matter physics. Universal
behavior, such as Anderson localization, in disordered non-interacting systems
is well understood. But, the effects of disorder combined with strong
interactions remains an outstanding challenge to theory. Here, we
experimentally probe a paradigm for disordered, strongly-correlated bosonic
systems-the disordered Bose-Hubbard (DBH) model-using a Bose-Einstein
condensate (BEC) of ultra-cold atoms trapped in a completely characterized
disordered optical lattice. We determine that disorder suppresses condensate
fraction for superfluid (SF) or coexisting SF and Mott insulator (MI) phases by
independently varying the disorder strength and the ratio of tunneling to
interaction energy. In the future, these results can constrain theories of the
DBH model and be extended to study disorder for strongly-correlated fermionic
particles.Comment: 15 pages, 4 figures updated to correct errors in referencing previous
wor
Nitrogen driven niche differentiation in bacterioplankton communities of northeast coastal Bay of Bengal
The Bay of Bengal receives nitrogen inputs from multiple sources and the potential role of nitrogenmetabolizing
microbial communities in the surface water is not well understood. The nitrogen budget
estimate shows a deficit of 4.7±2.4 TgNyr-1, suggesting a significant role of dissolved organic
nitrogen remineralization in fuelling ecosystem processes. Unravelling the process of remineralization
leading to increasing concentrations of dissolved inorganic nitrogen (DIN) in coastal ecosystems such
as in mangroves require a better understanding of the composition of functional resident
bacterioplankton communities. Bacterioplankton communities were elucidated from eight stations
along different estuaries spanning west to east of northeast coastal Bay of Bengal to understand the
influence of DIN on shaping these communities. The eight stations were differentiated into ‘low’ and
‘high’ DIN stations based on DIN concentration, with five stations with High DIN concentration
(>45 μM) and three stations with Low DIN concentration (<40μM). The V3–V4 region of 16S rRNA
was amplified and sequenced to elucidate resident bacterioplankton community structure from
environmental DNA. Proteobacteria, Bacteroidetes, and Firmicutes were the dominant bacterioplankton
phyla across all stations. Nitrogen-fixing groups such as Nitrospirae, Lentisphaerae,
Chloroflexi, and Planctomycetes make up about1%of the bacterioplankton communities.
Abundances of Spirochaetes and Tenericutes showed a positive correlation with DIN. Pseudomonadales,
Alteromonadales, and Desulfovibrionales were found to distinctly vary in abundance between
Low and High DIN stations. Predicted metagenomic profiles from taxonomically derived community
structures indicated bacterial nitrate-nitrite reductase to be negatively correlated with prevalent DIN
concentration in High DIN stations but positively correlated in Low DIN stations. This trend was also
consistent for genes encoding for nitrate/nitrite response regulators and transporter proteins. This
indicates the need to delineate functional bacterioplankton community structures to better understand their role in influencing rates and fluxes of nitrogen within mangroves
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