146 research outputs found
Free energy of colloidal particles at the surface of sessile drops
The influence of finite system size on the free energy of a spherical
particle floating at the surface of a sessile droplet is studied both
analytically and numerically. In the special case that the contact angle at the
substrate equals a capillary analogue of the method of images is
applied in order to calculate small deformations of the droplet shape if an
external force is applied to the particle. The type of boundary conditions for
the droplet shape at the substrate determines the sign of the capillary
monopole associated with the image particle. Therefore, the free energy of the
particle, which is proportional to the interaction energy of the original
particle with its image, can be of either sign, too. The analytic solutions,
given by the Green's function of the capillary equation, are constructed such
that the condition of the forces acting on the droplet being balanced and of
the volume constraint are fulfilled. Besides the known phenomena of attraction
of a particle to a free contact line and repulsion from a pinned one, we
observe a local free energy minimum for the particle being located at the drop
apex or at an intermediate angle, respectively. This peculiarity can be traced
back to a non-monotonic behavior of the Green's function, which reflects the
interplay between the deformations of the droplet shape and the volume
constraint.Comment: 24 pages, 19 figure
Математическое моделирование равновесия жидкость-пар в системе продуктов синтеза оксида пропилена в среде метанола
Comparison of literature and calculated data on vapor-liquid equilibrium for systems formed by products of propylene oxide synthesis was carried out. On the basis of models NRTL and UNIQUAC the literature data on vapor-liquid equilibrium for the investigated systems were optimized. The values of model parameters and their deviations were estimated. The corresponding phase diagrams were calculated and plotted.Проведено сравнение литературных и расчетных данных по парожидкостному равновесию для систем, образованных продуктами синтеза оксида пропилена. На основе моделей NRTL и UNIQUAC оптимизированы приведенные в литературе данные о равновесии жидкость-пар для исследуемых систем, оценены значения параметров модели и их погрешности, рассчитаны и построены соответствующие фазовые диаграммы
Direct measurements of the effects of salt and surfactant on interaction forces between colloidal particles at water-oil interfaces
The forces between colloidal particles at a decane-water interface, in the
presence of low concentrations of a monovalent salt (NaCl) and of the
surfactant sodium dodecylsulfate (SDS) in the aqueous subphase, have been
studied using laser tweezers. In the absence of electrolyte and surfactant,
particle interactions exhibit a long-range repulsion, yet the variation of the
interaction for different particle pairs is found to be considerable. Averaging
over several particle pairs was hence found to be necessary to obtain reliable
assessment of the effects of salt and surfactant. It has previously been
suggested that the repulsion is consistent with electrostatic interactions
between a small number of dissociated charges in the oil phase, leading to a
decay with distance to the power -4 and an absence of any effect of electrolyte
concentration. However, the present work demonstrates that increasing the
electrolyte concentration does yield, on average, a reduction of the magnitude
of the interaction force with electrolyte concentration. This implies that
charges on the water side also contribute significantly to the electrostatic
interactions. An increase in the concentration of SDS leads to a similar
decrease of the interaction force. Moreover the repulsion at fixed SDS
concentrations decreases over longer times. Finally, measurements of three-body
interactions provide insight into the anisotropic nature of the interactions.
The unique time-dependent and anisotropic interactions between particles at the
oil-water interface allow tailoring of the aggregation kinetics and structure
of the suspension structure.Comment: Submitted to Langmui
Nanoemulsion stability: experimental evaluation of the flocculation rate from turbidity measurements
The coalescence of liquid drops induces a higher level of complexity compared
to the classical studies about the aggregation of solid spheres. Yet, it is
commonly believed that most findings on solid dispersions are directly
applicable to liquid mixtures. Here, the state of the art in the evaluation of
the flocculation rate of these two systems is reviewed. Special emphasis is
made on the differences between suspensions and emulsions. In the case of
suspensions, the stability ratio is commonly evaluated from the initial slope
of the absorbance as a function of time under diffusive and reactive
conditions. Puertas and de las Nieves (1997) developed a theoretical approach
that allows the determination of the flocculation rate from the variation of
the turbidity of a sample as a function of time. Here, suitable modifications
of the experimental procedure and the referred theoretical approach are
implemented in order to calculate the values of the stability ratio and the
flocculation rate corresponding to a dodecane-in-water nanoemulsion stabilized
with sodium dodecyl sulfate. Four analytical expressions of the turbidity are
tested, basically differing in the optical cross section of the aggregates
formed. The first two models consider the processes of: a) aggregation (as
described by Smoluchowski) and b) the instantaneous coalescence upon
flocculation. The other two models account for the simultaneous occurrence of
flocculation and coalescence. The latter reproduce the temporal variation of
the turbidity in all cases studied (380 \leq [NaCl] \leq 600 mM), providing a
method of appraisal of the flocculation rate in nanoemulsions
COL4A3 is degraded in allergic asthma and degradation predicts response to anti-IgE therapy.
BACKGROUND: Asthma is a heterogeneous syndrome substantiating the urgent requirement for endotype-specific biomarkers. Dysbalance of fibrosis and fibrolysis in asthmatic lung tissue leads to reduced levels of the inflammation-protective collagen 4 (COL4A3). OBJECTIVE: To delineate the degradation of COL4A3 in allergic airway inflammation and evaluate the resultant product as a biomarker for anti-IgE therapy response. METHODS: The serological COL4A3 degradation marker C4Ma3 (Nordic Bioscience, Denmark) and serum cytokines were measured in the ALLIANCE cohort (paediatric cases/controls: n=134/n=35; adult cases/controls: n=149/n=31). Exacerbation of allergic airway disease in mice was induced by sensitising to ovalbumin (OVA), challenge with OVA aerosol and instillation of poly(cytidylic-inosinic). Fulacimstat (chymase inhibitor; Bayer) was used to determine the role of mast cell chymase in COL4A3 degradation. Patients with cystic fibrosis (n=14) and cystic fibrosis with allergic bronchopulmonary aspergillosis (ABPA; n=9) as well as patients with severe allergic uncontrolled asthma (n=19) were tested for COL4A3 degradation. Omalizumab (anti-IgE) treatment was assessed using the Asthma Control Test. RESULTS: Serum levels of C4Ma3 were increased in asthma in adults and children alike and linked to a more severe, exacerbating allergic asthma phenotype. In an experimental asthma mouse model, C4Ma3 was dependent on mast cell chymase. Serum C4Ma3 was significantly elevated in cystic fibrosis plus ABPA and at baseline predicted the success of the anti-IgE therapy in allergic, uncontrolled asthmatics (diagnostic OR 31.5). CONCLUSION: C4Ma3 levels depend on lung mast cell chymase and are increased in a severe, exacerbating allergic asthma phenotype. C4Ma3 may serve as a novel biomarker to predict anti-IgE therapy response
Preconceptional smoking alters spermatozoal miRNAs of murine fathers and affects offspring’s body weight
Background
Active smoking has been reported among 7% of teenagers worldwide, with ages ranging from 13 to 15 years. An epidemiological study suggested that preconceptional paternal smoking is associated with adolescent obesity in boys. We developed a murine adolescent smoking model before conception to investigate the paternal molecular causes of changes in offspring’s phenotype.
Method
Male and female C57BL/6J mice were exposed to increasing doses of mainstream cigarette smoke (CS) from onset of puberty for 6 weeks and mated with room air (RA) controls.
Results
Thirteen miRNAs were upregulated and 32 downregulated in the spermatozoa of CS-exposed fathers, while there were no significant differences in the count and morphological integrity of spermatozoa, as well as the proliferation of spermatogonia between CS- and RA-exposed fathers. Offspring from preconceptional CS-exposed mothers had lower body weights (p = 0.007). Moreover, data from offspring from CS-exposed fathers suggested a potential increase in body weight (p = 0.062).
Conclusion
We showed that preconceptional paternal CS exposure regulates spermatozoal miRNAs, and possibly influences the body weight of F1 progeny in early life. The regulated miRNAs may modulate transmittable epigenetic changes to offspring, thus influence the development of respiratory- and metabolic-related diseases such as obesity, a mechanism that warrants further studies for elaborate explanations
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