Active Sinking Particles: Sessile Suspension Feeders significantly alter the Flow and Transport to Sinking Aggregates

Mapping Intimacies ◽

10.1101/2021.08.05.455190 ◽

2021 ◽

Author(s):

Deepak Krishnamurthy ◽

Rachel Pepper ◽

Manu Prakash

Keyword(s):

Cross Sections ◽

Hot Spots ◽

Waste Water Treatment ◽

Critical Role ◽

Scale Free ◽

Flow And Transport ◽

Water Treatment Plants ◽

Sinking Particles ◽

Material Fluxes

Sinking or sedimentation of biological aggregates plays a critical role in carbon sequestration in the ocean and in vertical material fluxes in waste-water treatment plants. In both these contexts, the sinking aggregates are "active", since they are hot-spots of biological life and are densely colonized by microorganisms including bacteria and sessile protists, some of which generate feeding currents. However, the effect of these feeding currents on the sinking rates, trajectories, and mass transfer to these "active sinking particles", has not previously been studied. Here we use a novel scale-free vertical-tracking microscope (a.k.a. Gravity Machine, Krishnamurthy et al. "Scale-free vertical tracking microscopy." Nature Methods (2020)) to follow model sinking aggregates (agar spheres) with attached protists (Vorticella convallaria), sinking over long distances while simultaneously measuring local flows. We find that activity generated by attached Vorticella cause substantial changes to the flow around aggregates in a dynamic manner and reshape mass transport boundary layers. Further, we find that activity-mediated local flows along with sinking significantly changes how aggregates interact with the water-column at larger scales by modifying the encounter and plume cross-sections and by inducing sustained aggregate rotations. In this way our work suggests an important role of biological activity in understanding the growth, degradation, composition and sinking speeds of aggregates with consequences for predicting vertical material fluxes in marine, freshwater and man-made environments.

Download Full-text

Hydrogeological Criteria to Improve the Sponge City Strategy of China

Frontiers in Environmental Science ◽

10.3389/fenvs.2021.700463 ◽

2021 ◽

Vol 9 ◽

Author(s):

Mengxiao Jin ◽

Michele Lancia ◽

Yong Tian ◽

Stefano Viaroli ◽

Charles Andrews ◽

...

Keyword(s):

Urban Areas ◽

Waste Water Treatment ◽

Green Roofs ◽

Rain Gardens ◽

Hydraulic Characteristics ◽

Sponge City ◽

Water Treatment Plants ◽

Direct Infiltration ◽

The Government

China is facing frequent waterlogging and an increasing water scarcity that mirrors the fast urban and economic expansion of the last 4 decades. To mitigate these issues, the government promulgated the “Sponge City” strategy; a concept rooted in practices in western countries aimed at collecting and reusing 65–90% of urban rainfall. The application consists of absorbent infrastructures such as green roofs and rain gardens combined with the pre-existing urban environment. However, due to climate heterogeneities and the different urbanization contexts in China, these goals may seem overly ambitious in many areas of the country. Compact urbanization, together with heavy rainfall concentrated in short events, puts dramatic stresses on these infrastructures. At the same time, overdesigned infrastructures are expensive and may not be practical to retrofit in existing urban areas. In this paper, the role of urban aquifers as natural Sponge City elements are investigated throughout China. The method of implementation is inexpensive and easy to apply, favoring the direct infiltration to the subsoil after the conversion of the urban surfaces from impervious to permeable. Infiltration to urban aquifers alleviates the pressure on sewers, urban streams, as well as waste-water treatment plants. Considering urban aquifers with different hydraulic characteristics, water table dynamics after large infiltration events from rainfall are simulated via numerical analysis. Hydrogeological and geomorphological analyses are carried out to individuate criteria for the mapping of high absorbance areas at the regional and local scales. A Sponge City approach involving the urban aquifers can represent a winning formula for the success of this ambitious but compelling plan.

Download Full-text

Diffraction as a critical element in soft scattering

International Journal of Modern Physics A ◽

10.1142/s0217751x16450202 ◽

2016 ◽

Vol 31 (28n29) ◽

pp. 1645020

Author(s):

Uri Maor ◽

Keyword(s):

Cross Sections ◽

Critical Role ◽

Theoretical Models ◽

Critical Element ◽

Hard Scattering ◽

Fitting Procedures

Gribov’s partonic Pomeron provides the foundations of updated models which incorporate soft and hard scattering, so as to reproduce the recent LHC p-p cross sections. Explicitly, total, elastic, inelastic and diffrative data. Leading models are: GLM (Gotsman, Levin, Maor), KMR (Khoze, Martin, Ryskin), Kaidalov-Poghosyan and Ostapchenco. None of these models in their pre-LHC versions reproduced the TOTEM, ALICE, ATLAS and CMS soft LHC data, needing considerable reconstructions, either in the fitting procedures (GLM), or in the details of the theoretical models. In the following, I shall relate mostly to the GLM model, emphasizing the critical role of the diffractive channels.

Download Full-text

Gold Nanorod Assemblies: The Roles of Hot-Spot Positioning and Anisotropy in Plasmon Coupling and SERS

Nanomaterials ◽

10.3390/nano10050942 ◽

2020 ◽

Vol 10 (5) ◽

pp. 942 ◽

Cited By ~ 2

Author(s):

Priyanka Dey ◽

Verena Baumann ◽

Jessica Rodríguez-Fernández

Keyword(s):

Hot Spots ◽

Hot Spot ◽

Critical Role ◽

Gold Nanorod ◽

Plasmon Coupling ◽

Surface Enhanced ◽

Sybr Gold ◽

Surface Enhanced Raman ◽

Enhanced Raman Scattering

Plasmon-coupled colloidal nanoassemblies with carefully sculpted “hot-spots” and intense surface-enhanced Raman scattering (SERS) are in high demand as photostable and sensitive plasmonic nano-, bio-, and chemosensors. When maximizing SERS signals, it is particularly challenging to control the hot-spot density, precisely position the hot-spots to intensify the plasmon coupling, and introduce the SERS molecule in those intense hot-spots. Here, we investigated the importance of these factors in nanoassemblies made of a gold nanorod (AuNR) core and spherical nanoparticle (AuNP) satellites with ssDNA oligomer linkers. Hot-spot positioning at the NR tips was made possible by selectively burying the ssDNA in the lateral facets via controlled Ag overgrowth while retaining their hybridization and assembly potential at the tips. This strategy, with slight alterations, allowed us to form nanoassemblies that only contained satellites at the NR tips, i.e., directional anisotropic nanoassemblies; or satellites randomly positioned around the NR, i.e., nondirectional nanoassemblies. Directional nanoassemblies featured strong plasmon coupling as compared to nondirectional ones, as a result of strategically placing the hot-spots at the most intense electric field position of the AuNR, i.e., retaining the inherent plasmon anisotropy. Furthermore, as the dsDNA was located in these anisotropic hot-spots, this allowed for the tag-free detection down to ~10 dsDNA and a dramatic SERS enhancement of ~1.6 × 108 for the SERS tag SYBR gold, which specifically intercalates into the dsDNA. This dramatic SERS performance was made possible by manipulating the anisotropy of the nanoassemblies, which allowed us to emphasize the critical role of hot-spot positioning and SERS molecule positioning in nanoassemblies.

Download Full-text

Oxygen K near edge structures studied with multiple scattering calculations

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100104583 ◽

1988 ◽

Vol 46 ◽

pp. 504-505

Author(s):

Xudong Weng ◽

Peter Rez

Keyword(s):

Cross Section ◽

Cross Sections ◽

Partial Cross Section ◽

Energy Window ◽

Edge Structure ◽

Fine Structures ◽

Hydrogenic Model ◽

Electron Energy Loss ◽

Quantitative Chemical

In electron energy loss spectroscopy, quantitative chemical microanalysis is performed by comparison of the intensity under a specific inner shell edge with the corresponding partial cross section. There are two commonly used models for calculations of atomic partial cross sections, the hydrogenic model and the Hartree-Slater model. Partial cross sections could also be measured from standards of known compositions. These partial cross sections are complicated by variations in the edge shapes, such as the near edge structure (ELNES) and extended fine structures (ELEXFS). The role of these solid state effects in the partial cross sections, and the transferability of the partial cross sections from material to material, has yet to be fully explored. In this work, we consider the oxygen K edge in several oxides as oxygen is present in many materials. Since the energy window of interest is in the range of 20-100 eV, we limit ourselves to the near edge structures.

Download Full-text

The Role of the SLP in Autism Spectrum Disorder Screening and Assessment

Perspectives on Language Learning and Education ◽

10.1044/lle15.2.50 ◽

2008 ◽

Vol 15 (2) ◽

pp. 50-59 ◽

Cited By ~ 1

Author(s):

Amy Philofsky

Keyword(s):

Language Development ◽

Critical Role ◽

Children With Autism ◽

Autism Spectrum ◽

Children With Asd ◽

Prevalence Estimates ◽

Notable Increase ◽

Screening Assessment ◽

Critical Components

AbstractRecent prevalence estimates for autism have been alarming as a function of the notable increase. Speech-language pathologists play a critical role in screening, assessment and intervention for children with autism. This article reviews signs that may be indicative of autism at different stages of language development, and discusses the importance of several psychometric properties—sensitivity and specificity—in utilizing screening measures for children with autism. Critical components of assessment for children with autism are reviewed. This article concludes with examples of intervention targets for children with ASD at various levels of language development.

Download Full-text