Controllable Internal Mixing in Coalescing Droplets Induced by The Solutal Marangoni Convection of Surfactants with Distinct Headgroup Architectures

Through several complementary experiments, an investigation of the bulk and interfacial flows that emerged during the coalescence of two water-in-oil droplets with asymmetric compositional properties was performed. By adding surfactant to one of the coalescing droplets and leaving the other surfactant-free, a strong interfacial tension gradient (i.e., solutal Marangoni) driving energy between the merging droplets generated pronounced internal mixing. The contributions of two distinct types of surfactant, anionic ammonium lauryl sulfate (ALS) and cationic cetyltrimethylammonium bromide (CTAB) on the rate of coalescence bridge expansion and on the generation of opposing flows during coalescence were investigated. All coalescence experiments supported the power law relation between the radius of the expanding connective liquid bridge and time, rb ∝ t1/2. However, the presence of surfactant decreased the magnitude of the prefactor in this relationship due to induced interfacial solutal Marangoni convection. Experiments showed that packing efficiency, diffusivity, and bulk concentration of the selected surfactant are vital in solutal Marangoni convection and thus the degree and timescale of internal mixing between merging droplets, which has yet to be adequately discussed within the literature. Denser interfacial packing efficiency and lower diffusivity of CTAB produced stronger opposing bulk and interfacial flow as well as greater bulk mixing. A discussion of how optimized surfactant selection and solutal Marangoni convection can be used for passively inducing convective mixing between coalescing drops in microfluidic channels when viscosity modulation is not feasible is provided

RP-LC and HPTLC Methods for the Determination of Olmesartan Medoxomil and Hydrochlorothiazide in Combined Tablet Dosage Forms

Two new, rapid, precise, accurate and specific chromatographic methods were described for the simultaneous determination of olmesartan medoxomil and hydrochlorothiazide in combined tablet dosage forms. The first method was based on reversed phase liquid chromatography using an Eurosphere 100 RP C18 column (250 × 4.6 mm ID, 5 μm). The mobile phase was methanol–0.05% o-phosphoric acid (60:40 v/v) at a flow rate of 1.0 mL min−1. Commercially available tablets and laboratory mixtures containing both drugs were assayed and detected using a UV detector at 270 nm. The second method involved silica gel 60 F254 high performance thin layer chromatography and densitometric detection at 254 nm using acetonitrile–ethyl acetate–glacial acid (7:3:0.4 v/v/v) as the mobile phase. Calibration curves ranged between 200–600 and 125–375 ng spot−1 for olmesartan and hydrochlorothiazide, respectively

An integrated bioinformatics approach to improve two-color microarray quality-control: impact on biological conclusions

Omics technology used for large-scale measurements of gene expression is rapidly evolving. This work pointed out the need of an extensive bioinformatics analyses for array quality assessment before and after gene expression clustering and pathway analysis. A study focused on the effect of red wine polyphenols on rat colon mucosa was used to test the impact of quality control and normalisation steps on the biological conclusions. The integration of data visualization, pathway analysis and clustering revealed an artifact problem that was solved with an adapted normalisation. We propose a possible point to point standard analysis procedure, based on a combination of clustering and data visualization for the analysis of microarray data

Interfacial effects on droplet dynamics in poiseuille flow

Many properties of emulsions arise from interfacial rheology, but a theoretical understanding of the effect of interfacial viscosities on droplet dynamics is lacking. Here we report such a theory, relating to isolated spherical drops in a Poiseuille flow. Stokes flow is assumed in the bulk phases, and a jump in hydrodynamic stress at the interface is balanced by Marangoni and surface viscous forces according to the Boussinesq–Scriven constitutive law. Our model employs a linear equation of state for the surfactant. Our analysis predicts slip, cross-stream migration and droplet-circulation velocities. These results and the corresponding interfacial parameters are separable: e.g., cross-stream migration occurs only if gradients in surfactant concentration are present; slip velocity depends on viscosity contrast and dilatational properties, but not on shear Boussinesq number. This separability allows a new and advantageous means to measure surface viscous and elastic forces directly from the drop interface

Limitation of Microbial Processes at Saturation-Level Salinities in a Microbial Mat Covering a Coastal Salt Flat

Hypersaline microbial mats are dense microbial ecosystems capable of performing complete element cycling and are considered analogs of early Earth and hypothetical extraterrestrial ecosystems. We studied the functionality and limits of key biogeochemical processes, such as photosynthesis, aerobic respiration, and sulfur cycling, in salt crust-covered microbial mats from a tidal flat at the coast of Oman. We measured light, oxygen, and sulfide microprofiles as well as sulfate reduction rates at salt saturation and in flood conditions and determined fine-scale stratification of pigments, biomass, and microbial taxa in the resident microbial community. The salt crust did not protect the mats against irradiation or evaporation. Although some oxygen production was measurable at salinities of <= 30% (wt/vol) in situ, at saturation-level salinity (40%), oxygenic photosynthesis was completely inhibited and only resumed 2 days after reducing the porewater salinity to 12%. Aerobic respiration and active sulfur cycling occurred at low rates under salt saturation and increased strongly upon salinity reduction. Apart from high relative abundances of Chloroflexi, photoheterotrophic Alphaproteobacteria, Bacteroidetes, and Archaea, the mat contained a distinct layer harboring filamentous Cyanobacteria, which is unusual for such high salinities. Our results show that the diverse microbial community inhabiting this salt flat mat ultimately depends on periodic salt dilution to be selfsustaining and is rather adapted to merely survive salt saturation than to thrive under the salt crust. IMPORTANCE Due to their abilities to survive intense radiation and low water availability, hypersaline microbial mats are often suggested to be analogs of potential extraterrestrial life. However, even the limitations imposed on microbial processes by saturation-level salinity found on Earth have rarely been studied in situ. While abundance and diversity of microbial life in salt-saturated environments are well documented, most of our knowledge on process limitations stems from culture-based studies, few in situ studies, and theoretical calculations. In particular, oxygenic photosynthesis has barely been explored beyond 5 M NaCl (28% wt/vol). By applying a variety of biogeochemical and molecular methods, we show that despite abundance of photoautotrophic microorganisms, oxygenic photosynthesis is inhibited in salt-crust-covered microbial mats at saturation salinities, while rates of other energy generation processes are decreased several-fold. Hence, the complete element cycling required for self-sustaining microbial communities only occurs at lower salt concentrations

Критерии энергоаудита сельскохозяйственных предприятий: новые подходы и оценки (по промежуточным результатам российско-финляндского проекта)

Currently implemented project “Russian-Finnish Bioeconomy Competence Сentre – BioCom” within South-East Finland – Russia Cross-Border Cooperation Programme 2014-2020 aims to integrate the BioEconomy principles and approaches into the agricultural sector of the neighbouring border areas of Russia and Finland. The energy efficiency of farming and sustainable use of energy resources is one of the fundamentals of the bio-economy concept. The energy audit is the first step in identifying opportunities to reduce the energy inputs on the farms.(Research purpose) To discover the new approaches to the energy auditing of agricultural enterprises and new assessment indicators following the project experience.(Materials and methods) Four farms were selected for the energy inspection – two farms located in the Leningrad Region, Russia, and two farms located in the South Savo Region, Finland. In Russia the standard energy auditing, measurement, and calculation procedure was applied. The systems of electrical power supply, heat supply, water supply, sewage, and building envelopes on the farms were examined and estimated.(Results and discussion) Following the outcomes of the energy audits in the project framework and the previous relevant experience, the basic energy-saving and efficiency improvement measures were established. Three new approaches to the energy auditing of agricultural enterprises were suggested – energy and environmental assessment of applied technologies and equipment; consideration of the application of renewable energy-generating sources; consideration of the conversion of vehicles to biogas.(Conclusions) The study outcomes proved the energy audits to play an important role in improving the energy efficiency of agricultural production provided they are mandatory, take into account the energy environmental assessment criteria, consider the application of renewable energy-generating sources and the conversion of vehicles to biogas.Реализуемый в настоящее время проект «Российско-финляндский центр компетенции в области биоэкономики – BioCom» в рамках Программы приграничного сотрудничества Юго-Восточной Финляндии и России на 2014-2020 годы направлен на интеграцию принципов и подходов биоэкономики в сельскохозяйственный сектор соседних приграничных районов России и Финляндии. Подтвердили, что энергоэффективность сельского хозяйства и устойчивое использование энергоресурсов составляют одну из основ концепции биоэкономики. Показали необходимость проведения энергоаудита при определении возможностей для снижения энергозатрат в сельском хозяйстве.(Цель исследования) Выявить новые подходы к энергоаудиту сельхозпредприятий и показатели оценки на основе опыта реализации проекта.(Материалы и методы) Для энергетического обследования выбрали четыре хозяйства – два в Ленинградской области, Россия, и два в регионе Южное Саво, Финляндия. В России применяли стандартную процедуру энергоаудита, измерений и расчетов. Обследовали и оценили системы электро-, тепло-, водоснабжения, канализации и ограждающих конструкций.(Результаты и обсуждение). По результатам энергетических аудитов в рамках проекта и предыдущего соответствующего опыта установили основные меры по энергосбережению и повышению энергоэффективности. Предложили три новых подхода к энергоаудиту сельскохозяйственных предприятий: энергоэкологическую оценку применяемых технологий и оборудования; рассмотрение вопроса об использовании возобновляемых источников энергии; изучение возможности перевода транспорта на биогаз.(Выводы) Подтвердили необходимость энергоаудита в целях повышения энергоэффективности сельскохозяйственного производства. Показали, что энергетические обследования должны учитывать критерии энергоэкологической оценки, возможность применения возобновляемых источников энергии и перевода транспортных средств на биогаз