Activated drying in hydrophobic nanopores and the line tension of water

We study the slow dynamics of water evaporation out of hydrophobic cavities by using model porous silica materials grafted with octylsilanes. The cylindrical pores are monodisperse, with a radius in the range of 1–2 nm. Liquid water penetrates in the nanopores at high pressure and empties the pores when the pressure is lowered. The drying pressure exhibits a logarithmic growth as a function of the driving rate over more than three decades, showing the thermally activated nucleation of vapor bubbles. We find that the slow dynamics and the critical volume of the vapor nucleus are quantitatively described by the classical theory of capillarity without adjustable parameter. However, classical capillarity utterly overestimates the critical bubble energy. We discuss the possible influence of surface heterogeneities, long-range interactions, and high-curvature effects, and we show that a classical theory can describe vapor nucleation provided that a negative line tension is taken into account. The drying pressure then provides a determination of this line tension with much higher precision than currently available methods. We find consistent values of the order of −30 pN in a variety of hydrophobic materials.     

Effect of Shrinkage Reducing Admixture on Drying Shrinkage of Concrete with Different w/c Ratios

The reduction of the moisture content of concrete during the drying process reduces the concrete’s volume and causes it to shrink. In general, concrete shrinkage is a phenomenon that causes concrete volume to dwindle and can lead to durability problems. There are different types of this phenomenon, among them chemical shrinkage, autogenous shrinkage, drying shrinkage including free shrinkage and restrained shrinkage, and thermal contraction. Shrinkage-reducing admixtures are commercially available in different forms. The present study investigates the effect of liquid propylene glycol ether on mechanical properties and free shrinkage induced by drying at different water-cement (w/c) ratios. Furthermore, the effect of shrinkage-reducing admixtures on the properties of hardened concrete such as compressive and tensile strength, electrical resistivity, modulus of elasticity, free drying shrinkage, water absorption, and depth of water penetration was investigated. The results indicated that shrinkage reducing agents performed better in a low w/c ratio and resulted in up to 50% shrinkage reduction, which was due to the surface reduction of capillary pores. The prediction of free shrinkage due to drying was also performed using an artificial neural network.     

Manufacturing of Open-Cell Aluminium Foams: Comparing the Sponge Replication Technique and Its Combination with the Freezing Method

The manufacturing of aluminium foams with a total porosity of 87% using the sponge replication method and a combination of the sponge replication and freezing technique is presented. Foams with different cell counts were prepared from polyurethane (PU) templates with a pore count per inch (ppi) of 10, 20 and 30; consolidation of the foams was performed in an argon atmosphere at 650 °C. The additional freezing steps resulted in lamellar pores in the foam struts. The formation of lamellar pores increased the specific surface area by a factor of 1.9 compared to foams prepared by the sponge replication method without freezing steps. The formation of additional lamellar pores improved the mechanical properties but reduced the thermal conductivity of the foams. Varying the pore cell sizes of the PU template showed that—compared to foams with dense struts—the highest increase (~7 times) in the specific surface area was observed in foams made from 10 ppi PU templates. The effect of the cell size on the mechanical and thermal properties of aluminium foams was also investigated.     

Incorporation of Powder Particles into an Impeller-Stirred Liquid Bath through Vortex Formation

The present study addresses the incorporation of fine particles into liquids via the creation of a large-scale swirling vortex on the liquid free surface using a rotary impeller positioned along the axis of a cylindrical vessel. Four types of particles are used in the experiments to investigate the incorporation efficiency of the particles into a water bath under different impeller rotation speeds. Additionally, the vortex characteristics are investigated numerically. The results reveal that two factors, namely the particle wettability and turbulent oscillations at the bottom part of vortex surface, play dominant roles in determining the particle incorporation behavior. Hydrophobic particles are incapable of being incorporated into the water bath under any of the conditions examined in the present study. Partly wettable particles are entrained into the water bath, with the efficiency increasing with the impeller rotation speed and particle size. This is because an increase in the impeller rotation speed causes vortex deformation, whereby its bottom part approaches the impeller blades where the turbulent surface oscillations reach maximum amplitudes. Another possible mechanism of particle incorporation is the effect of capillary increases of liquid into the spaces between particles, which accumulate on the bottom surface of the vortex.     

铁离子螯合剂去铁胺对巨噬细胞、泡沫细胞细胞外基质金属蛋白酶诱导因子表达的影响

目的:观察铁负荷过低对巨噬细胞、泡沫细胞细胞外基质金属蛋白酶诱导因子(EMMPRIN)表达的影响。方法: 体外诱导THP-1单核细胞转化为巨噬细胞、泡沫细胞。实验细胞分为3组:对照组（正常巨噬细胞、泡沫细胞）、铁离子螯合剂去铁胺(DFO)刺激组、柠檬酸铁和DFO共刺激组。应用RT-PCR和Western blot测定巨噬细胞、泡沫细胞中EMMPRIN基因和蛋白的表达。用Western blot测定MMP-9蛋白的表达。用明胶酶谱法测定MMP-9的活性。结果: DFO刺激组中EMMPRIN基因及蛋白的水平、MMP-9蛋白表达的水平及活性均明显高于对照组（P<0.05,P<0.01）。柠檬酸铁逆转了DFO对EMMPRIN表达的上调作用。结论: 铁负荷过低可增加巨噬细胞及泡沫细胞中炎症因子的表达及活性,可能会促进心血管事件的发生。     

Conductive Polymer Porous Film with Tunable Wettability and Adhesion

A conductive polymer porous film with tunable wettability and adhesion was fabricated by the chloroform solution of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyricacid-methyl-ester (PCBM) via the freeze drying method. The porous film could be obtained from the solution of 0.8 wt%, whose pore diameters ranged from 50 nm to 500 nm. The hydrophobic porous surface with a water contact angle (CA) of 144.7° could be transferred into a hydrophilic surface with CA of 25° by applying a voltage. The water adhesive force on the porous film increased with the increase of the external voltage. The electro-controllable wettability and adhesion of the porous film have potential application in manipulating liquid collection and transportation.     

Electroosmotic enhancement of the binding of a neutral molecule to a transmembrane pore

The flux of solvent water coupled to the transit of ions through protein pores is considerable. The effect of this electroosmotic solvent flow on the binding of a neutral molecule [beta-cyclodextrin (betaCD)] to sites within the staphylococcal alpha-hemolysin pore was investigated. Mutant alpha-hemolysin pores were used to which betaCD can bind from either entrance and through which the direction of water flow can be controlled by choosing the charge selectivity of the pore and the polarity of the applied potential. The Kd values for betaCD for individual mutant pores varied by >100-fold with the applied potential over a range of -120 to +120 mV. In all cases, the signs of the changes in binding free energy and the influence of potential on the association and dissociation rate constants for betaCD were consistent with an electroosmotic effect.     

Volume Deformation of Steam-Cured Concrete with Slag during and after Steam Curing

In order to better predict the development of shrinkage deformation of steam-cured concrete mixed with slag, a deformation-temperature-humidity integrated model test, a hydration heat test, and an elastic modulus test were performed. The effects of the steam-curing process and the content of slag on shrinkage deformation, hydration degree and elastic modulus of concrete were studied. The results indicate that during the steam-curing process, the concrete has an “expansion-shrinkage” pattern. After the steam curing, the deformation of concrete is dominated by drying shrinkage. After the addition of slag, the shrinkage deformation of steam-cured concrete is increased. The autogenous shrinkage increases by 0.5–12%, and the total shrinkage increases by 1.5–8% at 60 days. At the same time, slag reduces the hydration degree of steam-cured concrete and modulus of elasticity. A prediction model for the hydration degree of steam-cured concrete is established, which can be used to calculate the degree of hydration at any curing age. Based on the capillary tension generated by the capillary pores in concrete, an integrated model of autogenous shrinkage and total shrinkage is established with the relative humidity directly related to the water loss in the concrete as the driving parameter. Whether the shrinkage deformation is caused by hydration reaction or the external environment, this model can better predict the shrinkage deformation of steam-cured concrete.     

Physical Properties and Durability of Lime-Cement Mortars Prepared with Water Containing Micro-Nano Bubbles of Various Gases

The paper presents the experimental studies on the effect of the water containing micro-nano bubbles of various gases on the physico-mechanical properties of lime-cement mortars. In total, 7 types of mortars were prepared: with water containing the micro-nano bubbles of O₂, O₃ or CO₂ as 50% or 100% substitute of ordinary mixing water (tap water) and the reference mortar prepared using tap water. In order to determine the influence of water with micro-nano bubbles of gases, the consistency of fresh mortar and the physical properties of hardened mortar, i.e., specific and apparent density, total porosity, water absorption by weight and capillary absorption, were established. The mechanical strength of the considered mortars was studied as well by conducting the tests for flexural and compressive strengths following 14, 28 and 56 days. Reduced workability and capillary absorption were observed in the modified mortars within the range of 0.9–8.5%. The mortars indicated an increase in the flexural strength after 28 days ranging from 3.4% to 23.5% and improved compressive strength in 1.2–31%, in comparison to the reference mortar. The conducted studies indicated increased flexural and compressive strengths along with the share of micro-nano bubbles of gases in the mixing water.     

Anomalous front broadening during spontaneous imbibition in a matrix with elongated pores

During spontaneous imbibition, a wetting liquid is drawn into a porous medium by capillary forces. In systems with comparable pore length and diameter, such as paper and sand, the front of the propagating liquid forms a continuous interface. Sections of this interface advance in a highly correlated manner due to an effective surface tension, which restricts front broadening. Here we investigate water imbibition in a nanoporous glass (Vycor) in which the pores are much longer than they are wide. In this case, no continuous liquid-vapor interface with coalesced menisci can form. Anomalously fast imbibition front roughening is experimentally observed by neutron imaging. We propose a theoretical pore-network model, whose structural details are adapted to the microscopic pore structure of Vycor glass and show that it displays the same large-scale roughening characteristics as observed in the experiment. The model predicts that menisci movements are uncorrelated, indicating that despite the connectivity of the network the smoothening effect of surface tension on the imbibition front roughening is negligible. These results suggest a new universality class of imbibition behavior, which is expected to occur in any matrix with elongated, interconnected pores of random radii.     

Open-Cellular Alumina Foams with Hierarchical Strut Porosity by Ice Templating: A Thickening Agent Study

Alumina replica foams were manufactured by the Schwartzwalder sponge replication technique and were provided with an additional strut porosity by a freeze-drying/ice-templating step prior to thermal processing. A variety of thickeners in combination with different alumina solid loads in the dispersion used for polyurethane foam template coating were studied. An additional strut porosity as generated by freeze-drying was found to be in the order of ~20%, and the spacings between the strut pores generated by ice-templating were in the range between 20 µm and 32 µm. In spite of the lamellar strut pore structure and a total porosity exceeding 90%, the compressive strength was found to be up to 1.3 MPa. Combining the replica process with freeze-drying proves to be a suitable method to enhance foams with respect to their surface area accessible for active coatings while preserving the advantageous flow properties of the cellular structure. A two-to-threefold object surface-to-object volume ratio of 55 to 77 mm⁻¹ was achieved for samples with 30 vol% solid load compared to 26 mm⁻¹ for non-freeze-dried samples. The freeze-drying technique allows the control of the proportion and properties of the introduced pores in an uncomplicated and predictable way by adjusting the process parameters. Nevertheless, the present article demonstrates that a suitable thickener in the dispersion used for the Schwartzwalder process is inevitable to obtain ceramic foams with sufficient mechanical strength due to the necessarily increased water content of the ceramic dispersion used for foam manufacturing.     

The Effect of Cementitious Materials on the Engineering Properties and Pore Structure of Concrete with Recycled Fine Aggregate

With the rapid development of urbanization, the construction industry consumes a lot of cement and produces a large amount of construction waste. To overcome this situation, the rational use of recycled aggregate produced from waste concrete is one of solutions. In some countries, the building industry has approved the use of recycled coarse aggregates in concrete, with some limits. However, practically all existing standards and regulations prohibit the use of recycled fine aggregate (RFA) in concrete. Therefore, study on improving the performance of RFA concrete is vital. In this study, the effects of fly ash and GGBS on concrete with RFA were investigated. Compressive strength, pore structure, drying shrinkage and accelerated carbonation were tested. The correlation between the pore structure and properties of concrete was analyzed. The results show that adding fly ash and GGBS to RFA concrete increased its compressive strength, modified pore structure, reduced drying shrinkage, and even achieved higher compressive strength and lower drying shrinkage than normal concrete. The compressive strength was mainly affected by the capillary pores, and the carbonation was mainly affected by the gel pores.     

Impact of Chitosan on Water Stability and Wettability of Soils

Chitosan has become increasingly applied in agriculture worldwide, thus entering the soil environment. We hypothesized that chitosan should affect the water stability of soil. Since this problem has not been studied to date, we examined, for the first time, the influence of chitosan on the water stability and wettability of soil aggregates. The aggregates were prepared from four soils with various properties amended with different amounts of two kinds of powdered chitosan, and subjected to 1 and/or 10 wetting–drying cycles. The water stability was measured by monitoring air bubbling after aggregate immersion in water, and the wettability was measured by a water drop penetration test. The biopolymer with a lower molecular mass, lower viscosity, and higher degree of deacetylation was more effective in increasing the water stability of the soil than the biopolymer with a higher molecular mass, higher viscosity, and lower deacetylation degree. After a single wetting-drying cycle, the water stability of the soil aggregates containing chitosan with a higher molecular mass was generally lower than that of the soil; after ten wetting–drying cycles, the water stability increased 1.5 to 20 times depending on the soil. The addition of low-molecular-mass chitosan after a single wetting-drying cycle caused the water stability to become one to two hundred times higher than that of the soil. A trial to find out which soil properties (pH, C and N content, bulk density, porosity, and particle size distribution) are responsible for the effectiveness of chitosan action was not successful, and this will be the objective of further studies.     

白介素-1对单核细胞向泡沫细胞分化过程中ACAT-1蛋白表达和活性的影响

目的探讨白介素-1（IL-1）对单核细胞向泡沫细胞分化过程中脂酰辅酶A-胆固醇酰基转移酶-1（ACAT-1）蛋白表达和活性的影响。方法200nmol／L佛波酯（PMA）诱导THP-1单核细胞48h使其转化为巨噬细胞,流式细胞术检测CDl4的表达;巨噬细胞与80mg／L氧化型低密度脂蛋白（Ox-LDL）共孵育24h,使之向泡沫细胞分化,油红O染色观察细胞质内脂质沉积;Westernblot检测各组细胞（单核细胞组、巨噬细胞组、泡沫细胞组、泡沫细胞＋IL-1组、泡沫细胞＋IL-1／Anti-ILl组）ACAT-l的蛋白表达,液相闪烁计数法检测ACAT-1的酶活性。结果单核细胞株THP-1与200nM的PMA共孵育48h后,分化为巨噬细胞,CDld阳性表达率为85．7％;巨噬细胞与Ox-LDL共孵育24h后,油红O染色胞浆内可见大量吞噬的脂质小滴。与单核细胞组相比,巨噬细胞组、泡沫细胞组和泡沫细胞＋IL-1组ACAT-1蛋白表达上调,活性升高（P〈0．05）,泡沫细胞＋IL-1／Anti-ILl组蛋白表达上调及活性升高不明显（P〉0．05）。结论IL-1对单核细胞向泡沫细胞分化过程中ACAT-1蛋白表达及酶活性有上调作用,IL-1单克隆抗体可以拮抗这种效应。     

Inhibition of TIMP1 enhances angiogenesis in vivo and cell migration in vitro

Neovascular invasion into a 3-dimensional matrix is controlled, in part, by matrix metalloproteinases (MMPs) and their inhibitors, tissue inhibitors of metalloproteinases (TIMPs). We tested the hypothesis that increasing MMP activity, via a specific blocking antibody to TIMP1, would enhance fibrovascular invasion into a PVA sponge. In vivo, inhibition of TIMP1 doubled the amount of angiogenic invasion (percentage area of invasion 33.5 +/- 3.5 vs 16.9 +/- 9.5, P = 0.003). The blocking antibody to TIMP1 did not increase the proportion of cells that were proliferating in the sponge implants, underscoring the importance of migration. In vitro, human microvascular endothelial cells (hmEC) and dermal fibroblasts treated with the antibody did not secrete greater amounts of collagenase but migrated significantly farther on collagen I (increase in distance migrated 26.6 +/- 9.4%, P = 0.003). Human dermal microvascular endothelial cells exposed to the TIMP1 blocking antibody exhibited a significant change in cell shape to a more elongated morphology. In conclusion, inhibition of TIMP1 increased angiogenesis into a PVA sponge in vivo and enhanced the migration of dermal hmEC and fibroblasts on collagen I in vitro. We propose that blocking TIMP1 improves angiogenesis by increasing cell motility during fibrovascular invasion.     

Gravity filtration as a quantitative viscometric technique

Gravity filtration tests of human blood have been carried out using a clear cylindrical tube standing vertically on a single filter element consisting of a glass capillary array with cylindrical pores 50 μm in diameter and 2 mm in length. Flow rates are controlled by means of a Parafilm template cut out to permit flow only through the desired number of pores. This experimental setup produces minimum wall shear stresses of the order of 1 dyne/cm² and offers a simple procedure which yields experimental data of column height vs time with extremely small scatter. Because of the very uniform cylindrical pores in the glass array, these data lend themselves to the analysis of Metzner and Reed for very general non-Newtonian fluids. Mathematical expressions are, therefore, derived for apparent viscosity as a function of strain rate in terms of the experimental measurements of column height vs time. The experimental data are closely matched by the Casson equation (r² = 0.998) with a yield stress of about 0.02 dyne/cm² for normal human blood at 35% hematocrit. Agreement with rotary viscometer data for the same sample is good when the correction of Barbee and Cokelet is used to determine the hematocrit in each pore of the capillary array. It appears that gravitational viscometry using glass capillary arrays offers a simple, inexpensive test with results for blood which are comparable to those of rotary viscometers under more realistic flow conditions.     

Production and Characterization of a New Bacterial Cellulose/Poly(Vinyl Alcohol) Nanocomposite

Bacterial cellulose (BC) is characterized for its high water holding capacity, high crystallinity, an ultrafine fiber network and high tensile strength. This work demonstrates the production of a new interpenetrated polymer network nanocomposite obtained through the incorporation of poly(vinyl alcohol) (PVA) on the BC matrix and evaluates the effect of oven drying on the morphological, mechanical and mass transfer properties of the composite membranes. Both the addition of PVA and oven drying induce the appearance of larger pores (circa 1–3 µm in average diameter) in dried BC/PVA membranes. Both types of treatments also affect the permeability of the composite, as assessed by the diffusion coefficients of polyethylene glycol (PEG) molecules (900, 8,000, 35,000 and 100,000 Da) across the membranes. Finally, the Young’s modulus of dry pristine BC decreases following PVA incorporation, resulting in a change from 3.5 GPa to 1 GPa and a five-fold loss in tensile strength.     

A Novel, Microcarrier-Based in Vitro Assay for Rapid and Reliable Quantification of Three-Dimensional Cell Migration and Angiogenesis

Angiogenesis in situ occurs within the interstitial extracellular matrix. The complexity of currently used three-dimensional in vitro angiogenesis systems makes it difficult to quantify cellular growth and neovessel formation. To overcome this problem we were interested to develop an angiogenesis system which allows rapid and reliable quantification of three-dimensional neovessel formation in vitro. Endothelial cells were seeded on gelatine coated microcarriers (MCs). Cell-coated MCs were suspended in a solution of fibrinogen which was then induced to polymerize by addition of thrombin. By this way, MCs were entrapped in a three-dimensional fibrin matrix. Within a few hours, endothelial cells began to leave their supporting microcarriers and to migrate into the fibrin gel. Without addition of stimulators of angiogenesis, endothelial cells showed incoherent migration into the matrix. In contrast, in response to fibronectin, basic fibroblast growth factor (bFGF), or vascular endothelial growth factor (VEGF), respectively, endothelial cells assembled to form multicellular capillary-like structures occasionally exceeding 1000 μm in length. Each MC gave rise to a limited number of capillaries. A single culture dish contained hundreds of MCs, ensuring that a sufficient number of random samples was present for a reliable statistical evaluation. The angiogenic response could be easily quantified by determination of the average number of capillary-like formations per MC (cap/MC). The capillary count for macrovascular endothelial cells from the bovine pulmonary artery was 0.14 cap/MC when no angiogenic stimulators were contained within the fibrin gel. Addition of 200 μg/ml fibronectin increased capillary formation to 0.63 cap/MC (P < 0.0001) at Day 6. Already after 3 days, addition of bFGF (30 ng/ml) yielded a capillary count of 1.05 and addition of VEGF (100 ng/ml) resulted in 0.91 cap/MC. In contrast, addition of hyaluronic acid stimulated migration of dispersed endothelial cells into the fibrin matrix without leading to significant capillary formation (0.09 cap/MC). Hydrocortisone alone or in combination with heparin led to a significant inhibition of bFGF-stimulated angiogenesis. We thus have developed a convenient angiogenesis in vitro system which allows reliable quantification of capillary formation in a three-dimensional environment. Based on this assay we conclude that apart from proliferation and migration of endothelial cells, angiogenesis additionally requires the assembly of cells to form multicellular capillaries. This process is strongly induced by the extracellular matrix protein fibronectin. Hyaluronic acid, on the other hand, promotes migration but not capillary formation (assembly).     

Characterization of Open-Cell Sponges via Magnetic Resonance and X-ray Tomography

The applications of polymeric sponges are varied, ranging from cleaning and filtration to medical applications. The specific properties of polymeric foams, such as pore size and connectivity, are dependent on their constituent materials and production methods. Nuclear magnetic resonance imaging (MRI) and X-ray micro-computed tomography (µCT) offer complementary information about the structure and properties of porous media. In this study, we employed MRI, in combination with µCT, to characterize the structure of polymeric open-cell foam, and to determine how it changes upon compression, µCT was used to identify the morphology of the pores within sponge plugs, extracted from polyurethane open-cell sponges. MRI T₂ relaxation maps and bulk T₂ relaxation times measurements were performed for 7° dH water contained within the same polyurethane foams used for µCT. Magnetic resonance and µCT measurements were conducted on both uncompressed and 60% compressed sponge plugs. Compression was achieved using a graduated sample holder with plunger. A relationship between the average T₂ relaxation time and maximum opening was observed, where smaller maximum openings were found to have a shorter T₂ relaxation times. It was also found that upon compression, the average maximum opening of pores decreased. Average pore size ranges of 375–632 ± 1 µm, for uncompressed plugs, and 301–473 ± 1 µm, for compressed plugs, were observed. By determining maximum opening values and T₂ relaxation times, it was observed that the pore structure varies between sponges within the same production batch, as well as even with a single sponge.