This review is addressed to the phase inversion process, which is not only a common, low-energy route to make stable emulsions for a variety of industrial products spanning from food to ...pharmaceuticals, but can also be an undesired effect in some applications, such as crude oil transportation in pipelines. Two main ways to induce phase inversion are described in the literature, i.e., phase inversion composition (PIC or catastrophic) and phase inversion temperature (PIT or transitional). In the former, starting from one phase (oil or water) with surfactants, the other phase is more or less gradually added until it reverts to the continuous phase. In PIT, phase inversion is driven by a temperature change without varying system composition. Given its industrial relevance and scientific challenge, phase inversion has been the subject of a number of papers in the literature, including extensive reviews. Due to the variety of applications and the complexity of the problem, most of the publications have been focused either on the phase behavior or the interfacial properties or the mixing process of the two phases. Although all these aspects are quite important in studying phase inversion and much progress has been done on this topic, a comprehensive picture is still lacking. In particular, the general mechanisms governing the inversion phenomenon have not been completely elucidated and quantitative predictions of the phase inversion point are limited to specific systems and experimental conditions. Here, we review the different approaches on phase inversion and highlight some related applications, including future and emerging perspectives.
Possible phase inversion emulsification pathways showed in phase diagram A) and emulsification map B). C) Evidence of multiple emulsion formation prior to phase inversion. D) Example of clathrate hydrate formation.
A) Colloids and Surfaces A, Volume399, pages 25–34, 2012
B) Colloids and Surfaces A, Volume 288, pages 151–157 Issue 1–3, 2006
C) Advanced Materials Volume 25 (2013) pages 2844–2848, 2013
D) Chemical Engineering Science, Volume 63, pages 4570–4579, 2008 Display omitted
•Phase inversion is an important industrial process to make stable emulsions.•Phase inversion can be driven by composition or temperature changes.•Phase behavior or interfacial properties or mixing of the phases has been studied.•A comprehensive picture of phase inversion is still lacking.•Here, we review the different approaches and highlight some related applications.
Stable oil/water emulsions are usually obtained by using mixtures of different surfactants. Such systems display synergistic interface stabilizing effects, which have not been fully elucidated yet. ...Moreover, in many applications surfactants are added at concentrations well above their critical micellar concentration (CMC), and this regime has not been thoroughly explored in the literature as well. Here, we investigate oil/water emulsions through oil/water interfacial tension using two common non-ionic surfactants, Tween 80 and Span 20, in the concentration range C (0.3–1 wt%) well above their respective CMCs. Mesoscale molecular simulations coupled interfacial tensiometry experiments to characterise these interfaces at a molecular level. Interfacial tension γ was measured by a pendant drop technique. Coarse-grained calculations provided a microscopic view of the interface at the molecular level ( i.e. surfactant arrangement, interface thickness), and were employed to extend the study to those surfactant concentrations where experiments could hardly provide reliable data, if any. We found a significant synergistic effect between Tween 80 and Span 20, with low molecular weight Span molecules occupying free spaces between the much larger, bulky Tween compounds. The surfactant intermolecular interactions could be associated to a striking decrease of interfacial tension in going from pure surfactants to a mixture at the same total weight concentration. Furthermore, the interface was found to exhibit a spatial inhomogeneity with a “patch-like” organisation, reminiscent of microphase separation. Our results show that the proposed, combined experimental/ in silico approach provides relevant insights for several industrial applications, such as emulsion stability and oil spill remediation.
Organic electrochemical transistors (OECTs) are powerful amplifying transducers of chemical signals allowing us to measure ionic transport between an electrolyte solution and an organic semiconductor ...film with nanosensing capabilities and low cost of fabrication. Here, we report how OECTs can also be exploited to detect microstructural features of complex soft materials, such as oil/water emulsions. To this purpose, the response of OECTs is investigated for samples obtained at different stages of a nano-emulsification process carried out by gradually adding water to a mixture of oil and two non-ionic surfactants. Our results demonstrate that, above a critical water volume fraction, OECTs are able to work as depletion-mode transistors displaying specific features in terms of the final current modulation capability and the transient time response. In particular, the kinetics of the device current upon the application of step-like probing gate voltages is successfully modelled by using a double exponential law with characteristic time constants. We relate the OECT behavior to the clustering and percolation of water droplets as detected by confocal laser scanning microscopy (CLSM) and rheometrical measurements. Our results lay the foundation for the quantitative application of OECTs to identify the phase behaviour and microstructure in complex soft materials, a relevant issue in industrial processing and material characterization.
The aim of this study was to investigate the effects of Cactus (Opuntia spp) levels in total mixed ration silages based on Cactus and Gliricidia (Gliricidia sepium (Jacq.) Steud) on the fermentation ...profile, microbial populations, aerobic stability and taxonomic diversity. The completely randomized design was used in a 4 × 4 factorial design with four replications, being four rations with different levels of Cactus (15, 30, 45, 60% based on the dry matter) and four opening periods (0, 15, 30 and 60 days of fermentation). An interaction effect (P < 0.050) was observed among the diets and opening times for mould and yeast populations. An interaction effect for the levels of acetic acid was observed, where the diets 15, 30, 45 and 60% showed higher values at 60 days (0.44, 0.41, 0.35 and 0.40 g/kg DM, respectively). A significant difference was observed for the richness and diversity index (Chao1 and Shannon). The most abundant bacterial phyla were Proteobacteria and Firmicutes and the genera Lactobacillus and Weissella. Cactus can be added in total mixed ration silages up to the level of 60% in a way that it positively affects the qualitative indicators of the silages, modulating the taxonomic communities and allowing the predominance of important groups for preservation of the ensiled mass.
The objective of this study was to evaluate the fermentative characteristics and chemical composition of cochineal nopal cactus silage additives with urea or Lactobacillus buchneri (LB), as well as ...the association of both additives in four storage times (7, 15, 60 and 120 days) and during aerobic stability, with evaluations at 0, 48 and 96 h. Four silages were used: no additive, addition of 2% urea, addition of LB and addition of 2% urea and LB. The study was divided into two experiments: the first experiment evaluated the silages at different storage times, and the second experiment evaluated the silages during the aerobic stability test. In both experiments, the experimental design was completely randomized in a factorial scheme (4 × 4 and 4 × 3) with three replicates per treatment. After the ensiling process, lactic acid bacteria predominated in all treatments. The concentration of lactic acid increased significantly from 60 days of ensiling. The concentration of acetic acid varied significantly between the storage times only for the silages treated with urea and LB alone. The silage treated with urea maintained a constant pH value up to 120 days of storage. During the 96 h aerobic stability test, no breaking in the stability of silages was observed. The exclusive or associated use of urea and LB promotes improvement in the fermentative characteristics of cochineal nopal cactus silage, without major alterations in the chemical composition or interfering with the aerobic stability of the silages.
Summary
Aims
We prospectively enrolled 207 patients (121 were 75 or older and 86 younger than 75) who were admitted to three Respiratory Monitoring Units. The primary outcomes were intubation and ...mortality rates; the secondary outcomes were changes in arterial blood gases analysis, non‐invasive ventilation (NIV) duration and length of hospital stay.
Results
Hospital mortality was similar in the two groups, as were intubation rates. The proportion who died in the very old patient group was 19.8% (24/121) vs. 10.4% (9/86) in the younger group. Intubation rate was 10.7% (13/121) in the very old patient group and 11.6% (10/86) in the younger group. The presence of comorbidities, the severity of illness (SAPS II), the level of consciousness, NIV failure (intubation), absolute value of pH prior to NIV, as well as the changes in pH and paCO2 and PaO2/FiO2 after 2 h of NIV, were the variables associated with higher mortality. Very old patients had significantly higher NIV duration than younger patients (69.0 ± 47.0 vs. 57.0 ± 27.0 h) (p ≤ 0.03) and hospital stays (11.6 ± 3.8 vs. 8.4 ± 1.4) (p ≤ 0.02).
Conclusions
The use of NIV in very old patients was effective in many cases. Endotracheal intubation after NIV failure was not efficacious in either group.
In this work, a flexible and efficient flow microreactor has been developed for the synthesis of an aromatic amine
via
a Buchwald-Hartwig reaction, a key bond-forming reaction in the synthesis of a ...wide range of naturally-occurring and pharmaceutically active targets. The microreactor, coupled with a highly active palladium N-heterocyclic carbene (NHC) catalyst, enabled the full conversion of the reagents within twenty minutes, even at very low catalyst concentrations. In addition to the classical two-feed design, a novel, more flexible four-feed flow system was developed with a configuration optimised to avoid clogging, which is one of the main problems in microreactors and in continuous flow reactive systems in general. We report the effect of flow rate, temperature and catalyst loading on conversion degree. In particular, a slight increase in temperature allowed faster conversion even at low catalyst loadings, likely due to the highly efficient heat transfer provided by the confined microreactor geometry.
A four-feed continuous flow microreactor is exploited for the synthesis of an aromatic amine
via
a Buchwald-Hartwig reaction, a key bond-forming reaction in the synthesis of a wide range of naturally-occurring and pharmaceutically active targets.
The objective of this study was to evaluate the chemical composition and in situ degradability of elephant grass silage dry matter with increasing levels of sugarcane bagasse. A completely randomized ...design was adopted with five treatments: 0, 5, 10, 15, and 20% inclusion of sugarcane bagasse on an as-fed matter basis, with five replications, totalling 25 experimental units. The increasing proportion of sugarcane bagasse analysed was favourable only in increasing the concentration of dry matter and fibre of silages and in maintaining a considerable crude protein content. In the in situ degradation assay, the addition of sugarcane bagasse in silage decreased the ruminal degradability of dry matter, and as the passage rates increased, the effective degradability decreased. In the in vitro gas production assay, the total production of gases was decreased with the inclusion of sugarcane bagasse, as did the degradability of organic matter and neutral detergent fibre. The recommendation for the inclusion of sugarcane bagasse should be analysed according to the desired objective, emphasizing that values higher than 5% can greatly compromise the final nutritive value of elephant grass silage
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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