Phytoplankton characterization in a tropical tidal river impacted by a megacity: the case of the Saigon River (Southern Vietnam).

The spatiotemporal variation of phytoplankton and their relationship with environmental variables were analyzed in the Saigon River-a tropical river in Southern Vietnam. Two longitudinal profiles were conducted during dry and rainy season at 18 sampling sites covering more than 60 km long in the river. Besides, a bi-weekly monitoring conducted in the upstream, urban area (Ho Chi Minh City-HCMC), and downstream of Saigon River was organized from December 2016 to November 2017.

Sedimentological and geochemical data in bed sediments from a tropical river-estuary system impacted by a developing megacity, Ho Chi Minh City - Vietnam.

Sedimentological and geochemical data were obtained for bed sediments from a tropical estuary environment in Vietnam in October 2014, January 2016, and November 2016. The data include grain-size distribution, percentage of clay, silt and sand, percentage of organic matter, concentration of total particulate phosphorus (TPP), concentration of particulate inorganic phosphorus (PIP), concentration of particulate organic phosphorus (POP), percentage of total nitrogen (TN), percentage of total carbon (TC), trace metals concentrations (V, Cr, Co, Ni, Cu, Zn, As, Mo, Cd, Pb) and major elements (Al, Fe, Mn). Geochemical indexes (Enrichment factor EF and Geo-accumulation Index I-geo) and sediment quality guideline (mean Effect Range Median quotients) were calculated.

Nutrient dynamics and eutrophication assessment in the tropical river system of Saigon - Dongnai (southern Vietnam).

Saigon-Dongnai Rivers in Southern Vietnam is a complex lowland hydrological network of tributaries that is strongly influenced by the tidal cycles. The increasing economic, industrial and domestic developments in and around Ho Chi Minh City (HCMC) have led to serious impacts on water quality due to lack of appropriate wastewaters treatment. Drinking water production is impacted and the large aquaculture production areas may also be affected.

Multi-MHz micro-electro-mechanical sensors for atomic force microscopy.

Silicon ring-shaped micro-electro-mechanical resonators have been fabricated and used as probes for dynamic atomic force microscopy (AFM) experiments. They offer resotnance frequency above 10MHz, which is notably greater than that of usual cantilevers and quartz-based AFM probes. On-chip electrical actuation and readout of the tip oscillation are obtained by means of built-in capacitive transducers.

Signal replication in a DNA nanostructure.

Logic circuits based on DNA strand displacement reaction are the basic building blocks of future nanorobotic systems. The circuits tethered to DNA origami platforms present several advantages over solution-phase versions where couplings are always diffusion-limited. Here we consider a possible implementation of one of the basic operations needed in the design of these circuits, namely, signal replication.

G-Quadruplexes Light up Localized DNA Circuits.

DNA circuits tethered to nanoplatforms can perform cascade reactions for signal amplification. One DNA single strand activates a strand-displacement cascade generating numerous outputs, and therefore amplifying the signal. These localized circuits present, however, an important limitation: the spontaneous activation of the cascade reaction.

Shape and Effective Spring Constant of Liquid Interfaces Probed at the Nanometer Scale: Finite Size Effects.

We investigate the shape and mechanical properties of liquid interfaces down to nanometer scale by atomic force microscopy (AFM) and scanning electron microscopy (SEM) combined with in situ micromanipulation techniques. In both cases, the interface is probed with a cylindrical nanofiber with radius R of the order of 25-100 nm. The effective spring constant of the nanomeniscus oscillated around its equilibrium position is determined by static and frequency-modulation (FM) AFM modes.

Connecting localized DNA strand displacement reactions.

Logic circuits based on DNA strand displacement reactions have been shown to be versatile enough to compute the square root of four-bit numbers. The implementation of these circuits as a set of bulk reactions faces difficulties which include leaky reactions and intrinsically slow, diffusion-limited reaction rates. In this paper, we consider simple examples of these circuits when they are attached to platforms (DNA origamis).

Guided assembly of tetramolecular G-quadruplexes.

Nucleic acids are finding applications in nanotechnology as nanomaterials, mechanical devices, templates, and biosensors. G-quadruplex DNA, formed by π-π stacking of guanine (G) quartets, is an attractive alternative to regular B-DNA because of the kinetic and thermodynamic stability of quadruplexes. However, they suffer from a fatal flaw: the rules of recognition, i.

Cooperativity in the annealing of DNA origamis.

DNA based nanostructures built on a long single stranded DNA scaffold, known as DNA origamis, offer the possibility to organize various molecules at the nanometer scale in one pot experiments. The folding of the scaffold is guaranteed by the presence of short, single stranded DNA sequences (staples), that hold together separate regions of the scaffold. In this paper, we modelize the annealing-melting properties of these DNA constructions.

Modeling the mechanical properties of DNA nanostructures.

We discuss generalizations of a previously published coarse-grained description [Mergell et al., Phys. Rev.

Measured dose rate constant from oncology patients administered 18F for positron emission tomography.

Purpose: Patient exposure rate measurements verify published patient dose rate data and characterize dose rates near 2-18-fluorodeoxyglucose ((18)F-FDG) patients. A specific dose rate constant based on patient exposure rate measurements is a convenient quantity that can be applied to the desired distance, injection activity, and time postinjection to obtain an accurate calculation of cumulative external radiation dose. This study reports exposure rates measured at various locations near positron emission tomography (PET) (18)F-FDG patients prior to PET scanning.

Direct visualization of transient thermal response of a DNA origami.

The DNA origami approach enables the construction of complex objects from DNA strands. A fundamental understanding of the kinetics and thermodynamics of DNA origami assembly is extremely important for building large DNA structures with multifunctionality. Here both experimental and theoretical studies of DNA origami melting were carried out in order to reveal the reversible association/disassociation process.

Folding of small origamis.

A model that preserves the known thermodynamic properties of double stranded DNA is introduced to study the formation of more complex DNA constructions, such as small origamis or Holliday junctions. We show that the thermodynamic behaviour of these complex DNA constructions is not only given by their sequence but also by their topology.

Investigation of the carbon nanotube AFM tip contacts: free sliding versus pinned contact.

Mechanical response of carbon nanotube atomic force microscope probes are investigated using a thermal noise forcing. Thermal noise spectra are able to investigate mechanical behaviors that cannot be studied using classical atomic force microscope modes. Experimental results show that the carbon nanotube contacts can be classified in two categories: the free sliding and pinned cases.

Competition of elastic and adhesive properties of carbon nanotubes anchored to atomic force microscopy tips.

In this paper we address the mechanical properties of carbon nanotubes anchored to atomic force microscopy (AFM) tips in a detailed analysis of experimental results and exhaustive description of a simple model. We show that volume elastic and surface adhesive forces both contribute to the dynamical AFM experimental signals. Their respective weights depend on the nanotube properties and on an experimental parameter: the oscillation amplitude.

Wetting an oscillating nanoneedle to image an air-liquid interface at the nanometer scale: dynamical behavior of a nanomeniscus.

The dynamical behavior of a nanomeniscus is investigated with a oscillating nanoneedle recording information on the change of the shape and viscous contribution. At the air-glycerol interface, the dynamical properties exhibit a nonlinear behavior making the nanomeniscus evolution similar to a first-order phase transition. Also shown is the capability to record height images of the liquid interface with resolutions at nanometer scale.

Enzymatic activity of immobilized yeast phosphoglycerate kinase.

This work reports the first evidence that recombinant yeast phosphoglycerate kinase (PGK) is still significantly active when immobilized on glass and muscovite mica. Using previous work to improve the sensitivity of the existing setup, Tapping Mode atomic force microscopy (AFM) was used in a liquid environment to determine the surface enzyme coverage of derivatized mica and glass slides. When associated to spectrophotometric measurements, the AFM data allows assessing the catalytic constant of surface enzymes and comparing it to bulk values.

Oscillatory dissipation of a simple confined liquid.

We present a sensitive measurement of the dissipation and the effective viscosity of a simple confined liquid (octamethylcyclotetrasiloxane) using an atomic force microscope. The experimental data show that the damping and the effective viscosity increase and present oscillations as the gap between the cantilever tip and the surface is diminished. To our knowledge, the damping and the viscosity modulation are reported here with such good accuracy for the first time.

Study of two grafting methods for obtaining a 3-aminopropyltriethoxysilane monolayer on silica surface.

In order to establish a 3-aminopropyltriethoxysilane (APTES) grafting procedure with limited number of APTESs noncovalently linked to the silica surface, two different methods of grafting (in acid-aqueous solution and in anhydrous solution) were compared. The grafted surface state was investigated by atomic force microscopy (AFM). The stability of the grafting was checked at different temperatures by AFM.

Liquid mechanical behavior of mixed monolayers of amino and alkyl silanes by atomic force microscopy.

The adsorption of mixed terminally aminated organosilyl compounds with long-chain n-alkyltrichlorosilanes on silica substrates has been studied by FTIR and AFM to deposit and study DNA. By optimization of deposition conditions, the mixed monolayers were found to be well organized and homogeneous. The amino group was protected to obtain a reproducible grafting and then deprotected after the film formation.

Heterogeneous cell mechanical properties: an atomic force microscopy study.

Atomic force microscopy (AFM) is a non-invasive microscopy to explore living biological systems like cells in liquid environment. Thus AFM is an appropriate tool to investigate surface chemical modification and its influence on biological systems. In particular, control over biomaterial surface chemistry can result in a regulated cell response.

Characterization of dynamic cellular adhesion of osteoblasts using atomic force microscopy.

Background: Atomic force microscopy (AFM) can be used to visualize the cell morphology in an aqueous environment and in real time. It also allows the investigation of mechanical properties such as cell compliance as a function of cell attachment. This study characterized and evaluated osteoblast adhesion by AFM.

DNA properties investigated by dynamic force microscopy.

In this work, we show that by varying the experimental conditions, the driving amplitude, a dynamic force microscope allows DNA properties to be selectively imaged. The substrate on which the DNA is fixed is a silica surface grafted with silane molecules terminated with amine groups. Use of small oscillation amplitudes favors the attractive interaction between the tip and the sample, while the use of large amplitudes renders the contribution of the attractive interaction negligible.