Low Permeability Coefficient Research Articles

Mechanical, rheological, and carbon dioxide barrier properties of polyvinylidene fluoride/TiO2composites for flexible riser applications

AbstractNanoparticles can act as a barrier to gas penetration in the polymer matrix. However, the agglomeration of nanoparticles has a negative effect on the comprehensive properties of nanocomposites. We envisioned surface modification of 25 nm TiO2nanoparticles with KH550 to enable better dispersion in the polyvinylidene fluoride (PVDF) matrix and prepared PVDF/TiO2composites by the melt blending method. The effects of adding modified nanoparticles into the matrix on the thermodynamic, mechanical, rheological, and gas barrier properties were studied. We find that the dispersion of TiO2in the matrix significantly improved after modification, as observed in the SEM images. As a result, the mechanical properties of composites decreased with an increase in the content of nanoparticles, and PVDF/N‐TiO2composites showed better mechanical and CO2barrier properties. The permeability coefficient of PVDF/0.5% N‐TiO2has the lowest permeability coefficient, which is 18.30% lower than primary PVDF. At a high shear rate, the viscosity of PVDF/N‐TiO2with 0.5% and 1.0% content decreased, and the viscosity of 1.5% ratio was higher than that of primary PVDF. PVDF/0.5% N‐TiO2has the best comprehensive performance and also possesses the advantages of simple preparation, low cost, and ease of industrial production.

A Conductive Molecular Semiconductor Composite with Over 160 °C Glass Transition Temperature for Heat‐Resistant Perovskite Solar Cells

AbstractUnder long‐term thermal stress, the decomposition of organic‐inorganic hybrid perovskite is a big challenge to realize stable and efficient perovskite solar cells (PSCs). Thereby, it is of pivotal importance to engineer an organic hole transport layer, which is featured not only by an excellent hole conduction but also by a high glass transition temperature. Here, a solution‐processible molecular semiconductor (T5H‐EP‐BMCA) is reported. The air‐doped composite of T5H‐EP‐BMCA presents a hole density of 6.5 × 1017 cm–3, a space‐charge‐limited current hole mobility of 5.1 × 10–4 cm2 V–1 s–1, and a direct‐current electrical conductivity of 30.6 µS cm–1. Moreover, the conductive composite owns a high glass transition temperature of 165 °C, a heat‐resistant morphology, and low gas permeability coefficients. These joint attributes allow for the fabrication of 21.0%‐efficiency, 85 °C‐durable PSC by controlling the thermal decomposition of perovskite.

Porous stones in permeability measurement: drawbacks and solution

Porous stones are commonly used in geotechnical laboratory testing to provide solid support at the two ends of the tested specimen. Although porous stones can have several advantages, they can induce a hydraulic impedance that might alter the flowrate results. Numerous suggestions and recommendations were issued to avoid some of the problems encountered when using porous stones, such as clogging and stones' low permeability coefficient ( Kp). However, it is proven in this technical note that the existence of a soil–porous stones interaction prevents the elimination of porous stones' influence, leading to unreliable permeability results. A practical solution based on manufacturing unique porous stones (MS) is suggested in an attempt to eliminate such an influence. The porous stones' influence is highlighted by running excess pore pressure dissipation tests under triaxial conditions with calibrated beads. The results show a soil–porous stones interaction and a flowrate increase up to 700% due to MS. This interaction is addressed through permeability measurements of three soil types in a flexible-wall permeameter using standard porous stones (SS) and the newly manufactured stones (MS). At least one order of magnitude of difference in the soil permeability measurement and a decrease in the dissipation test time are observed with MS. This technical note also validates the limitation of the superposition approach for correcting the soil's permeability ( Ksoil). It is shown that porous stones can induce a signature directly related to the soil type and applied pressure.

Prevention Technology of Coal Spontaneous Combustion Induced by Gas Drainage in Deep Coal Seam Mining

Due to high gas content and a low permeability coefficient in deep coal seam mining, the spontaneous combustion of coal around the wellbore can easily occur, leading to difficulties in extracting gas during the mining process. To determine the dangerous area around the borehole and conduct advanced prevention and control measures are the keys to preventing spontaneous combustion in boreholes. However, the dangerous area around the borehole is not clear, the sealing parameters lack scientific basis, and the key prevention and control measures are not clear, which have caused great harm to coal mines. This study took the 24,130 working face of Pingdingshan No. 10 Mine as an example, using numerical simulation, theoretical analysis, and field tests to classify the risks of studying the surrounding area of the wellbore. The dangerous area variations under different lengths of shotcrete in the roadway were analyzed, the optimal plugging parameters were studied, and the current “two plugs and one injection” plugging device was optimized. Based on the oxygen concentration and air leakage rate, a method was proposed to divide the dangerous area of fissure coal spontaneous combustion around the borehole induced by gas extraction. The dangerous area of spontaneous combustion around the borehole was defined as having an oxygen concentration larger than 7% and an air leakage rate less than 0.004 m/s. The comprehensive control measures of the grouting length at 2–4 m, hole-sealing parameter at 20-13 (hole-sealing depth 20 m, hole-sealing length 13 m) and the “two plugs, one injection and one row” device were determined.

Ultra-high temperature oxidation resistance of a novel (Mo, Hf, W, Ti)Si2 ceramic coating with Nb interlayer on Ta substrate

In order to solve the challenge of recyclability of tantalum substrates in high temperature oxidation environments, a novel MoSi2-WSi2-HfSi2-TiSi2 composite ceramic coating containing an Nb interlayer was prepared on the surface of tantalum substrate by a three-step method. The mix ceramic silicide coating exhibited superior performance and effective protection for 10.2 h at 1800 °C, possibly due to the formation of an outer SiO2-HfO2-HfSiO4 composite oxide film with low oxygen permeability, moderate viscosity and thermal expansion coefficient, as well as good self-healing ability. Furthermore, the coating successfully passed 537 thermal cycles from room temperature to 1800 °C. The presence of Nb interlayer significantly mitigated the thermal mismatch between the ceramic coating and the tantalum substrate, and the bidirectional diffusion of Nb element during the high temperature oxidation and thermal shock process further reduced the tendency of the coating to crack.

Study on the Influence and Law of Waterproof System Design Factors on the Typical Stress of Bridge Deck Pavement

To improve the structural design rationality of cement concrete bridge deck pavement systems and reduce diseases such as interlayer displacement and rutting in the early stage of bridge deck use, this paper studies the influence and law of the coupling effect of various factors of the waterproof system on the typical stress of bridge deck pavement and determines the best structure combination for the bridge deck pavement structure. A finite element model was established by using commercial software to simulate the mechanical response of different types of waterproof bonding layer, waterproof leveling layer, and impervious structure layer under different parameters. The simulation results show that when the thickness of the pavement layer was 8 cm, the maximum shear stress of the pavement layer occurred in the middle of the wearing course and the junction between layers. When the pavement layers were continuous, the maximum strain of the waterproof bonding layer with the “rubber asphalt + protective plate” structure in the transverse and longitudinal directions was the largest. When the waterproof leveling layer was cement concrete, the structure bore a large amount of stress and easily produced cracks, resulting in water damage. High-density water-based asphalt concrete with a low permeability coefficient can reduce the interlayer shear stress and effectively ensure the interlayer bonding effect. On this basis, the following bridge deck pavement structure was proposed: waterproof system + multifunctional waterproof layer + load-bearing structure layer + surface functional layer.

Functionalised graphene oxide-bromobutyl rubber composites with segregated structure for enhanced gas barrier properties

ABSTRACT Graphene-based elastomer composites with a segregated structure were prepared by electrostatic self-assembly. The morphology and microstructures of the composites were characterised by scanning electron microscope (SEM) and transmission electrical microscope (TEM). The segregated network leads to a low gas permeability coefficient for BIIR composites. With the incorporation as low as 0.4 wt-% GTA-GO, the helium permeability coefficient decreased about 63% when compared with that of neat BIIR. The tensile strength and percentage elongation increased with an increase in the GTA-GO content. This is attributed to the complete exfoliation, uniform dispersion and the segregated structure of GTA-GO in the BIIR matrix. These results demonstrate that such electrostatic self-assembly method between latex and sheet-fillers is an effective strategy to design and produce polymeric nanocomposites with good gas barrier properties. The results will effectively promote the application of barrier polymer in the production of protective clothing, gas storage devices and coatings.

Emerging Designs of Aggregation-Induced Emission Agents for Enhanced Phototherapy Applications

Emerging Designs of Aggregation-Induced Emission Agents for Enhanced Phototherapy Applications

Development of a Mosquito Repellent Formulation Based on Nanostructured Lipid Carriers.

Arboviral diseases are a threat to global public health systems, with recent data suggesting that around 40% of the world’s population is at risk of contracting arboviruses. The use of mosquito repellents is an appropriate strategy to avoid humans coming into contact with vectors transmitting these viruses. However, the cost associated with daily applications of repellents can make their use unfeasible for the low-income populations that most need protection. Therefore, the development of effective formulations offers a way to expand access to this means of individual protection. Consequently, research efforts have focused on formulations with smaller quantities of active agents and sustained release technology, aiming to reduce re-applications, toxicity, and cost. The present study investigates the development of nanostructured lipid carriers (NLCs) loaded with a mixture of the compounds icaridin (synthetic) and geraniol (natural), incorporated in cellulose hydrogel. The NLCs were prepared by the emulsion/solvent evaporation method and were submitted to physicochemical characterization as a function of time (at 0, 15, 30, and 60 days). The prepared system presented an average particle size of 252 ± 5 nm, with encapsulation efficiency of 99% for both of the active compounds. The stability profile revealed that the change of particle size was not significant (p > 0.05), indicating high stability of the system. Rheological characterization of the gels containing NLCs showed that all formulations presented pseudoplastic and thixotropic behavior, providing satisfactory spreadability and long shelf life. Morphological analysis using atomic force microscopy (AFM) revealed the presence of spherical nanoparticles (252 ± 5 nm) in the cellulose gel matrix. Permeation assays showed low fluxes of the active agents through a Strat-M® membrane, with low permeability coefficients, indicating that the repellents would be retained on the surface to which they are applied, rather than permeating the tissue. These findings open perspectives for the use of hybrid formulations consisting of gels containing nanoparticles that incorporate repellents effective against arthropod-borne virus. These systems could potentially provide improvements considering the issues of effectiveness, toxicity, and safety.

Preparation of functionalized MXene-stitched-graphene oxide/poly (ethylene-co-acrylic acid) nanocomposite with enhanced hydrogen gas barrier properties

The storage of H2 is one of the critical issues to be resolved to expand H2-based energy. Herein, MXene was employed in combination with GO for the first time for H2 gas barrier coating on nylon 6 substrate (commonly used in storage tanks). A facile two-step method was acquired to covalently bond MXene and GO through 3-aminopropyl triethoxysilane (APTES) by employing carbodiimide reaction. The MXene-GO hybrid nanofiller (f-MXene-GO) exhibited a higher gallery gap between the nanosheets than that of the pristine MXene and GO. Besides, GO was also partially reduced by the amine functional groups of APTES. To the best of our knowledge, the stitching of MXene and GO using APTES has not yet been discussed in the literature. When f-MXene-GO was dispersed in poly (ethylene-co-acrylic acid) (EAA), a significant improvement in the mechanical properties was observed. An increase in the gallery gap between the MXene layers in f-MXene-GO/EAA nanocomposite as compared to MXene/EAA suggested the effectiveness of APTES grafting to enhance the interaction with EAA. MXene/EAA exhibited a higher H2 gas barrier and mechanical properties than GO/EAA, whereas the adhesion of MXene/EAA to the nylon 6 substrate was weak. f-MXene-GO/EAA exhibited a judicious combination of both barrier and adhesion properties. The 10 wt% f-MXene-GO/EAA coated layer showed a very low H2 permeability coefficient (0.03 cc.mm.m−2.d−1.atm−1) and a significant 89% reduction in the H2 gas transmission rate with respect to nylon 6.

Permeability Characteristics of Poorly Graded Sand Conditioned with Foam in Different Conditioning States

Abstract Investigating the permeability characteristics of sand-foam mixtures in different conditioning states is important not only in earth pressure balance (EPB) shield tunneling and standstill but also for posttunneling soil handling. Slump and permeability tests were carried out on poorly graded sand that was conditioned with different foam injection ratios (FIRs) and water contents. According to the slump values and the apparent states of the conditioned sand in the slump tests, the sand conditioning was classified into five cases: insufficient, suitable without any water or foam bleeding, suitable but with water bleeding, excessive with likely foam bleeding, and excessive with water bleeding. With suitable conditioning, the permeability in the conditioned sand generally exhibited three consecutive stages during the tests: the stable stage, fast growth stage and slow growth stage. An increasing FIR and water content enhanced the antipermeability effect (the ability of preventing water from flowing in porous medium), but a considerable increase in water content (≥10 %) weakened the antipermeability effect. Finally, a simplified model was proposed to explain the rheology. The foam significantly reduced the total energy required for the sand particles to flow. In addition, the permeability characteristics of the conditioned sand found in the tests were explained. The low initial permeability coefficient and its duration depended on the ability of the water to penetrate the plugging structures formed by the foam.

Investigation of gamma shielding and liquid permeability properties of kaolin for liquid radioactive waste management

Gamma radiation shielding and liquid permeability coefficient of baked and unbaked kaolin powder were experimentally and theoretically investigated. A NaI(Tl) detector was used to measure attenuation properties of the samples. The experimental values for the linear coefficient were validated by theoretical values using WinXCOM software. The results established that unbaked kaolin with density 2.65 g/cm3 yielded highest mass attenuation coefficients of 0.0736 cm2/g, 0.0561 cm2/g and 0.0527 cm2/g for 661.7, 1173.2 and 1332.5 keV respectively and liquid permeability coefficient of 2.33 x 10 -12 m/s. The study concludes that compacted unbaked kaolin be considered a valid alternative for radiation shielding due to its low liquid permeability coefficient for liquid radioactive waste management.

Maltoheptaose-Presenting Nanoscale Glycoliposomes for the Delivery of Rifampicin to E. coli.

Liposomes, a nanoscale drug delivery system, are well known for their ability to improve pharmacokinetics and reduce drug toxicity. In this work, maltoheptaose (G7)-presenting glycoliposomes were synthesized and evaluated in the delivery of the antibiotic rifampicin. Two types of liposomes were prepared: nonfluid liposomes from l-α-phosphatidylcholine (PC) and cholesterol, and fluid liposomes from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and 1,2-dimyristoyl-sn-glycero-3-phospho-(1'-rac-glycerol). G7-derivatized glycolipid, G7-DPPE (DPPE: 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine), was incorporated into the liposomes at 21 and 14 μmol/mg to form nanoparticles of 75 ± 12 and 146 ± 14 nm for the nonfluid and fluid G7-glycoliposomes, respectively. The multivalent G7-glycoliposomes were characterized by lectin binding with concanavalin A (Con A). The dissociation constant K d between Con A and the nonfluid or fluid G7-glycoliposomes was 0.93 or 0.51 μM, which represented ~900- or 1600-fold stronger affinity than the binding between Con A and G7. The G7-glycoliposomes were loaded with rifampicin at 6.6 and 16 wt % encapsulation for the nonfluid and fluid G7-glycoliposomes, respectively. Introducing a carbohydrate in the liposomes slowed down the release of rifampicin, with the G7-glycoliposomes having the slowest release rate and the lowest permeability coefficient among the liposome formulations. The fluid G7-glycoliposomes lowered the minimal inhibitory concentration (MIC) of rifampicin against E. coli ORN208 by about 3 times, whereas liposomes without G7 or Man (d-mannose)-glycoliposomes showed no improvement in MIC. The rifampicin-loaded fluid G7-glycoliposomes demonstrated the best sustained antibacterial activity against E. coli, with up to 2 log reduction in the colony forming units at 4 × MIC after 24 h. Fluorescence resonance energy transfer and confocal fluorescence microscopy revealed stronger interactions of the bacterium with the fluid G7-glycoliposomes than other liposome formulations.

Constructing robust chain entanglement network, well-defined nanosized crystals and highly aligned graphene oxide nanosheets: Towards strong, ductile and high barrier Poly(lactic acid) nanocomposite films for green packaging

It is a great challenge to develop a feasible strategy for reconciling barrier performance and mechanical ductility of environmentally friendly poly(lactic acid) (PLA) in the application of packaging industry. In the current study, the combination of manipulating the amorphous chain entanglement network of PLA and constructing “dual barrier walls” of highly aligned GONSs and well-defined PLA crystals simultaneously enhanced barrier properties and ductility of PLA nanocomposite films via “biaxial stretching-constrained annealing” method. The intense extensional field during biaxial stretching induced highly aligned GONSs as the first barrier wall and regulated the amorphous chain entanglement network. Constrained annealing promoted the growth and perfection of PLA crystals as the second effective barrier wall and strengthened amorphous chain entanglement network to some extent. More interestingly, GONSs were first verified as contributors to stabilize the enhanced amorphous chain entanglement network of PLA and benefited for the mechanical ductility of PLA nanocomposite films. As a result, this synergetic structure manifested excellent comprehensive ability in ameliorating the intrinsic drawbacks of brittle and poor barrier PLA films, exhibiting low oxygen permeability coefficient of 0.712 × 10−14 cm3 cm cm−2 s−1 Pa−1, excellent ductility with elongation at break of 147.8%, high yield strength of 83.1 MPa and good dimensional stability with deformation ratio of as low as 3%. The as-prepared PLA nanocomposite films with excellent comprehensive properties hold great potential prospects in the application of packaging industry. The methodology proposed here opens up a new avenue to fabricate environmentally friendly PLA films for promoting the sustainable development of packaging industry.

MORPHOMETRIC CHARACTERIZATION OF BANHO AND CAÚRA BEACHES IN THE MUNICIPALITY OF SÃO JOSÉ DE RIBAMAR, SÃO LUÍS ISLAND, STATE OF MARANHÃO, BRAZIL

The aim of the present study was to perform a morphodynamic and sedimentary characterization of Banho Beach and Caúra Beach, which are located in the municipality of São José de Ribamar, state of Maranhão, Brazil (2°33'25"S - 2°33'52"S and 44°02'21"W - 44°03'13"W). Morphodynamic and geological studies were performed on both beaches in campaigns carried out in the dry season (October 2016). Sediment samples were collected along the beach profiles at both beaches for the determination of grain classification and permeability. The direction of the coastal drift current was determined using a red organic fluorescent tracer at Banho Beach. The results showed a greater width of sediments on Banho Beach, with a 624-meter foreshore, whilst Caúra Beach had a width of 105 m, with the advance of the tide at several points, as well as a trough system, sand bar and cliffs. Regarding granulometry, medium-coarse sand was found at Banho Beach and fine sand predominated at Caúra Beach. The sediment permeability test showed an inverse relation to particle size. In the foreshore region, Banho Beach had a lower permeability coefficient (k) and a higher textural class (medium sand), whereas Caúra Beach had a higher coefficient (k) and lower textural class (fine sand). Mean granulometry at Banho Beach was predominantly in the range of 1.48 to 1.79 ɸ, which is classified a medium-coarse sand, whereas the sand at Caúra Beach was classified as fine (2.31 ɸ). The coastal drift experiment at Banho Beach revealed flow parallel to the coastline at a speed of 0.10 ms-1. A B S T R A C TThe aim of the present study was to perform a morphodynamic and sedimentary characterization of Banho Beach and Caúra Beach, which are located in the municipality of São José de Ribamar, state of Maranhão, Brazil (2°33'25"S - 2°33'52"S and 44°02'21"W - 44°03'13"W). Morphodynamic and geological studies were performed on both beaches in campaigns carried out in the dry season (October 2016). Sediment samples were collected along the beach profiles at both beaches for the determination of grain classification and permeability. The direction of the coastal drift current was determined using a red organic fluorescent tracer at Banho Beach. The results showed a greater width of sediments on Banho Beach, with a 624-meter foreshore, whilst Caúra Beach had a width of 105 m, with the advance of the tide at several points, as well as a trough system, sand bar and cliffs. Regarding granulometry, medium-coarse sand was found at Banho Beach and fine sand predominated at Caúra Beach. The sediment permeability test showed an inverse relation to particle size. In the foreshore region, Banho Beach had a lower permeability coefficient (k) and a higher textural class (medium sand), whereas Caúra Beach had a higher coefficient (k) and lower textural class (fine sand). Mean granulometry at Banho Beach was predominantly in the range of 1.48 to 1.79 ɸ, which is classified a medium-coarse sand, whereas the sand at Caúra Beach was classified as fine (2.31 ɸ). The coastal drift experiment at Banho Beach revealed flow parallel to the coastline at a speed of 0.10 ms-1.Keywords: beach profile; granulometry, sediments; coastal drift.

UiO-66-NH2 functionalized cellulose nanofibers embedded in sulfonated polysulfone as proton exchange membrane

Metal–organic frameworks (MOFs) exhibit high proton conductivity, thermal stability, and offer immense flexibility in terms of tailoring their size. Owing to their unique characteristics, they are desirable candidates for proton conductors. Nevertheless, constructing ordered MOF proton channels in proton exchange membranes (PEMs) remains a formidable challenge. Herein, blend nanofibers of cellulose and UiO-66-NH2 (Cell–UiO-66-NH2) obtained via the electrospinning process were embedded in a sulfonated polysulfone matrix to obtain high-performance composite PEMs with an orderly arrangement of UiO-66-NH2. Comprehensive characterization and membrane performance tests reveal that composite membrane with 5 wt% (nominal) UiO-66-NH2 have revealed high proton conductivity of 0.196 S cm−1 at 80 °C and 100% relative humidity. Meantime, the composite membrane exhibits a low methanol permeability coefficient (~5.5 × 10−7 cm2 s−1). Moreover, the composite membrane exhibits a low swelling ratio (17.3%) even at 80 °C. The Cell–UiO-66-NH2 nanofibers exhibit strong potential for use as a proton-conducting nanofiller in fuel-cell PEMs.

Deformation characteristics, mechanisms, and influencing factors of hydrodynamic pressure landslides in the Three Gorges Reservoir: a case study and model test study

Hydrodynamic Pressure landslides are the most typical landslides affected by the water level in the Three Gorges Reservoir. These types of landslides are large and cause severe deformation. Therefore, they may significantly affect the safe operation of the Three Gorges Reservoir once losing stability. Taking the Shuping landslide in the Three Gorges Reservoir as a typical case, this study explored the deformation characteristics and influencing factors of the Hydrodynamic Pressure landslide using monitoring data of its surface deformation, 17 years of GPS displacement data, automatic displacement metre of surface cracks, and groundwater level. To determine the deformation mechanism of the Hydrodynamic Pressure landslide, the model of Hydrodynamic Pressure landslide was designed and carried out to simulate the fluctuation of reservoir water level. The results showed that the hydrodynamic pressure landslides deformation was mainly affected by the overall deformation of the front edge of the landslide, and the amount of deformation was relatively large. The back part of the landslide mainly encountered tensile deformation. The Hydrodynamic Pressure landslides are a typical retrogressive deformation. The deformation of Hydrodynamic Pressure landslide was affected by the periodic change in the reservoir water level and the overall deformation trend is increasing. The intrinsic factor influencing the deformation of the hydrodynamic pressure landslide is the low permeability coefficient of the sliding mass, and the extrinsic factor is the drawdown of the reservoir water level. When the reservoir water table drawdown occurred, there was a noticeable water level difference with the underground water level in the landslide mass and generated hydrodynamic pressure. The Hydrodynamic Pressure landslide model results showed that the pore-water pressure, effective stress, and groundwater level in the landslide were consistent with the reservoir water level but with noticeable hysteresis. The key hydrodynamic factor for the deformation of this type of landslide was the hydrodynamic pressure towards the outside of the slope, formed when the reservoir water level dropped. Moreover, it was found that the faster reservoir water-level drawdown rates led to an increased influence on the stability of the landslide.

Characterization of edible film based on grape juice and cross-linked maize starch and its effects on the storage quality of chicken breast fillets

Grape juice, maize starch cross-linked with sodium trimetaphosphate and glycerol were used to prepare edible film. The effects of grape juice:water volume ratio (10:90–50:50), cross-linked maize starch (3–5%, w/v), and glycerol (0.5–1.0%, w/v) concentration on the solubility, color, phenolic content, and barrier properties of edible films was examined with response surface methodology. Optimized film with low solubility (0.53 g soluble solid g−1 total solid), yellowness index (8.71), oxygen and water permeability coefficients (8.48 cm3μm m−2d−1kPa−1; 1.33 gmm m−2h−1kPa−1, respectively), and high phenolic content (43.34 mg GAE 100 g−1 dm) was found to be 16.15:83.85 of grape juice:water ratio, 3.61% of starch and 0.5% of glycerol. The best formula that meets defined quality constraints for edible film was used for the preservation of physicochemical and microbiological properties of chicken breast fillets. The amount of thiobarbituric acid-reactive substance in the coated chicken fillets decreased from 1.98 to 0.91 mg MDA kg−1 as a result of reduction of oxygen permeability and availability. Total aerobic mesophilic, psychrophilic, and Enterobacteriaceae counts decreased by 1.58, 0.94, and 0.85 log, respectively. These results clearly proved that coating chicken fillets with grape juice-based edible film affected positively lipid oxidation and microbial growth during cold storage.

A comparative study on methods for determining the hydraulic properties of a clay shale

SUMMARY A comprehensive characterization of clay shale behavior requires quantifying both geomechanical and hydromechanical characteristics. This paper presents a comparative laboratory study of different methods to determine the water permeability of saturated Opalinus Clay: (i) pore pressure oscillation, (ii) pressure pulse decay and (iii) pore pressure equilibration. Based on a comprehensive data set obtained on one sample under well-defined temperature and isostatic effective stress conditions, we discuss the sensitivity of permeability and storativity on the experimental boundary conditions (oscillation frequency, pore pressure amplitudes and effective stress). The results show that permeability coefficients obtained by all three methods differ less than 15 per cent at a constant effective stress of 24 MPa (kmean = 6.6E-21 to 7.5E-21 m2). The pore pressure transmission technique tends towards lower permeability coefficients, whereas the pulse decay and pressure oscillation techniques result in slightly higher values. The discrepancies are considered minor and experimental times of the techniques are similar in the range of 1–2 d for this sample. We found that permeability coefficients determined by the pore pressure oscillation technique increase with higher frequencies, that is oscillation periods shorter than 2 hr. No dependence is found for the applied pressure amplitudes (5, 10 and 25 per cent of the mean pore pressure). By means of experimental handling and data density, the pore pressure oscillation technique appears to be the most efficient. Data can be recorded continuously over a user-defined period of time and yield information on both, permeability and storativity. Furthermore, effective stress conditions can be held constant during the test and pressure equilibration prior to testing is not necessary. Electron microscopic imaging of ion-beam polished surfaces before and after testing suggests that testing at effective stresses higher than in situ did not lead to pore significant collapse or other irreversible damage in the samples. The study also shows that unloading during the experiment did not result in a permeability increase, which is associated to the persistent closure of microcracks at effective stresses between 24 and 6 MPa.

Influences of different calcium sources on the early age cracks of self-healing cementitious mortar

Self-healing schematic diagram of mortar cracks. • Studied the changes of Ca 2+ concentration and calcification rate in alkali solution. • Early age cracks of mortar could be well repaired by microorganisms. • The maximum average healing depth of early age cracks could reach 4.0 mm. • The self-healing mechanism of mortar cracks was discussed. • Calcium lactate was more suitable as an external calcium source than calcium nitrate. Microbial induced calcium carbonate precipitation (MICP) has become an efficient and environmentally friendly technology for repair of cracks in cement-based materials. In this research, the alkali-tolerant microbial spores was prepared by spray drying, and two kinds of microbial self-healing agents were used to study the mineralization reaction in alkaline environment, then they were used in the self-healing of the early age cracks with a width of 0.2−0.3 mm. The self-healing efficiency of cracks was characterized by the area repair ratio, permeability coefficient and healing depth. Meanwhile, the morphologies and polymorphs of precipitates were analyzed by SEM equipped with an EDS and XRD. The results indicated that the calcification rate using calcium lactate as calcium source was higher than that of calcium nitrate, and had good self-healing efficiency on mortar cracks. However, compared with the specimens adding N-Ca and spores, the specimens adding L-Ca and spores had lower permeability coefficient and deeper healing depth, their average healing depth was 1.9 mm and 4.0 mm, respectively. In addition, the precipitates generated were most at the crack surface, with the increase of the crack depth, the precipitates gradually decreased. XRD analysis showed that the precipitates at the crack mouth were calcite. Finally, the reasons for the different healing depth of the microbial self-healing agents were analyzed and the self-healing mechanism was discussed.