Dispersion and Stratification Dynamics in the Upper Sacramento River Deep Water Ship Channel

Hydrodynamics control the movement of water and material within and among habitats, where time-scales of mixing can exert bottom-up regulatory effects on aquatic ecosystems through their influence on primary production. The San Francisco Estuary (estuary) is a low-productivity ecosystem, which is in part responsible for constraining higher trophic levels, including fishes. Many research and habitat-restoration efforts trying to increase primary production have been conducted, including, as described here, a whole-ecosystem nutrient addition experiment where calcium nitrate was applied in the Sacramento River Deep Water Ship Channel (DWSC) to see if phytoplankton production could be increased and exported out of the DWSC. As an integral part of this experiment, we investigated the physical mechanisms that control mixing, and how these mechanisms affect the strength and duration of thermal stratification, which we revealed as critical for controlling phytoplankton dynamics in the relatively turbid upper DWSC. Analysis of a suite of mixing mechanisms and time-scales show that both tidal currents and wind control mixing rates and stratification dynamics in the DWSC. Longitudinal and vertical dispersion increased during periods of high wind, during which wind speed influenced dispersion more than tidal currents. Thermal stratification developed most days, which slowed vertical mixing but was rapidly broken down by wind-induced mixing. Stratification rarely persisted for longer than 24 hours, limiting phytoplankton production in the study area. The interaction between physical mechanisms that control mixing rates, mediate stratification dynamics, and ultimately limit primary production in the DWSC may be useful in informing habitat restoration elsewhere in the Delta and in other turbid aquatic environments.

Vertical Mixing and Heat Fluxes Conditioned by a Seismically Imaged Oceanic Front

The southwest Atlantic gyre connects several distinct water masses, which means that this oceanic region is characterized by a complex frontal system and enhanced water mass modification. Despite its significance, the distribution and variability of vertical mixing rates have yet to be determined for this system. Specifically, potential conditioning of mixing rates by frontal structures, in this location and elsewhere, is poorly understood. Here, we analyze vertical seismic (i.e., acoustic) sections from a three-dimensional survey that straddles a major front along the northern portion of the Brazil-Falkland Confluence. Hydrographic analyses constrain the structure and properties of water masses. By spectrally analyzing seismic reflectivity, we calculate spatial and temporal distributions of the dissipation rate of turbulent kinetic energy, ε, of diapycnal mixing rate, K, and of vertical diffusive heat flux, FH. We show that estimates of ε, K, and FH are elevated compared to regional and global mean values. Notably, cross-sectional mean estimates vary little over a 6 week period whilst smaller scale thermohaline structures appear to have a spatially localized effect upon ε, K, and FH. In contrast, a mesoscale front modifies ε and K to a depth of 1 km, across a region of O(100) km. This front clearly enhances mixing rates, both adjacent to its surface outcrop and beneath the mixed layer, whilst also locally suppressing ε and K to a depth of 1 km. As a result, estimates of FH increase by a factor of two in the vicinity of the surface outcrop of the front. Our results yield estimates of ε, K and FH that can be attributed to identifiable thermohaline structures and they show that fronts can play a significant role in water mass modification to depths of 1 km.

Diverse thermophilic Bacillus species with multiple biotechnological activities are associated within the Egyptian soil and compost samples

Thermophilic strains of Bacillus can express enzymes of higher thermal stability, which allows carrying out industrial fermentations under higher temperatures. This lowers the contamination potential, accelerates mixing rates and facilitates the recovery of fermentation end products. The present study was thus designed to isolate and characterize thermophilic Bacillus cultures from soil and compost samples. Forty-two thermophilic Bacillus isolates could be identified employing morphological, physiological and the 16S rRNA gene sequencing analyses. The isolates showed a high degree of biological diversity involving 13 Bacillus species and 1 subspecies but were dominated by Bacillus licheniformis. Phylogenetic analysis of B. licheniformis isolates based on the DNA sequencing of gyrA and rpoB genes presented them in two main genetic groups. Isolates of five thermophilic species including B. licheniformis, Bacillus altitudinis, Bacillus paralicheniformis, Bacillus subtilis and Bacillus thermoamylovorans showed multiple activities to degrade all of cellulose, hemicellulose and lignin. Those multifunctional thermophilic Bacillus isolates can be harnessed in the degradation of plant wastes for the production of biofuels and compost.

Mixing rates for potentials of non-summable variations

Mixing rates, relaxation rates, and decay of correlations for dynamics defined by potentials with summable variations are well understood, but little is known for non-summable variations. This paper exhibits upper bounds for these quantities for dynamics defined by potentials with square-summable variations. We obtain these bounds as corollaries of a new block coupling inequality between pairs of dynamics starting with different histories. As applications of our results, we prove a new weak invariance principle and a Hoeffding-type inequality.

Energetics and mixing of stratified, rotating flow over abyssal hills

One of the proposed mechanisms for energy loss in the ocean is through dissipation of internal waves, in particular above rough topography where internal lee waves are generated. Rates of dissipation and diapycnal mixing are often estimated using linear theory and a constant value for mixing efficiency. However, previous oceanographic measurements found that non-linear dynamics may be important close to topography. In order to investigate the role of non-linear interactions, we conduct idealized 3D numerical simulations of steady flow over 1D topography and vary the topographic height, which correlates to the degree of flow non-linearity. We analyze spatial distribution of energy transfer rates between internal waves and the non-geostrophic portion of time-mean flow, and of dissipation and diapycnal mixing rates. In our simulations with taller, more non-linear topographies, energy transfer rates are similar to previously unexplained oceanographic observations near topography: internal waves gain energy from time-mean flow through horizontal straining and lose energy through vertical shearing. In the tall topography simulations, buoyancy fluxes also play a significant role, consistent with observations but contrary to linear wave theory, suggesting that quasigeostrophy-based approximations and linear theory may not hold in some regions above rough topography. Both dissipation and mixing rates increase with topographic height, but their vertical distributions differ between topographic regimes. As such, vertical profile of mixing efficiency is different for linear and non-linear topographic regimes, which may need to be incorporated into parameterizations of small-scale processes in models and estimates of ocean energy loss.

Water-in-Oil Nano-Emulsions Prepared by Spontaneous Emulsification: New Insights on the Formulation Process

Nano-emulsions consist of stable suspensions of nano-scaled droplets that have huge loading capacities and are formulated with safe compounds. For these reasons, a large number of studies have described the potential uses of nano-emulsions, focusing on various aspects such as formulation processes, loading capabilities, and surface modifications. These studies typically concern direct nano-emulsions (i.e., oil-in-water), whereas studies on reverse nano-emulsions (i.e., water-in-oil) remain anecdotal. However, reverse nano-emulsion technology is very promising (e.g., as an alternative to liposome technology) for the development of drug delivery systems that encapsulate hydrophilic compounds within double droplets. The spontaneous emulsification process has the added advantages of optimization of the energetic yield, potential for industrial scale-up, improved loading capabilities, and preservation of fragile compounds targeted for encapsulation. In this study, we propose a detailed investigation of the processes and formulation parameters involved in the spontaneous nano-emulsification that produces water-in-oil nano-emulsions. The following details were addressed: (i) the order of mixing of the different compounds (method A and method B), (ii) mixing rates, (iii) amount of surfactants, (iv) type and mixture of surfactants, (v) amount of dispersed phase, and (vi) influence of the nature of the oil. The results emphasized the effects of the formulation parameters (e.g., the volume fraction of the dispersed phase, nature or concentration of surfactant, or nature of the oil) on the nature and properties of the nano-emulsions formed.

Impact of Hijlan Creek springs on water quality of the Euphrates River and the Hydrochemical characterization of the contamination plumes

This work aims to present the hydrochemical mechanisms describing the system of the Euphrates River before and after mixing with groundwater from the springs of Hijlan (western Iraq). Continuously, the data generated from these springs' water have been adapted to provide an updated assessment for future water therapeutic purposes. Physicochemical characteristics of water in the mixing plume of Hijlan Creek and the Euphrates indicate the multi Hydrochemical plumes as revealed by the spatial variation of important parameters related to the ecological parameters including K+, Na+, Ca+ 2, Mg+ 2, HCO3−, SO4 − 2, Cl−, NO3−, PO4 − 3, Pb, Zn, Cd, Fe, Mn, Temp, DO, BOD5, H2S, Turbidity, EC, pH, and TDS. The re-aeration (k2) and de-oxygenation rate (k1) coefficients, as well as the self-purification factor (f) of the mixing plume, are 0.51 sec− 1, 2.03 sec− 1, and 0.25, respectively. The Cl− concentration in the confluence zone changes, due to the chloride content mixing rates of 7.1% and 92.9% for Euphrates and Hijlan creek water, respectively, with water discharge of 316,224 m3/day and chloride load discharge of 420 tons/day. The assessment of the water quality indicates unsuitability for aquaculture purposes. However, the water can be used for therapeutic purposes and to cure multiple diseases.