Thin Membrane Structures Research Articles

Co-enhancement of permeability and selectivity on mixed matrix catalytic membrane with high loading of porous Co-N-C filler for efficient water purification

The water treatment performance of membrane filtration is usually restricted via the paradox between permeability and selectivity. Herein, the nitrogen doped porous carbon supported Co catalysts (CoNPC), serving as both porous filler and peroxymonosulfate (PMS) activator, were firstly filled into polyvinylidene fluoride (PVDF) matrix to construct a novel mixed matrix catalytic membrane (CoNPC@PVDF) for enhanced water purification. Owing to the robust binding between CoNPC and PVDF, a high loading (50 wt%) and even dispersion of CoNPC were realized in CoNPC@PVDF, and its permeability and selectivity were both improved with the increase of CoNPC content. The optimum CoNPC@PVDF with PMS activation assistance (FCP) exhibited effective phenol removal at short retention time (1.5 s) and high permeability (256.6 L m−2h−1 bar−1). The performance of CoNPC@PVDF FCP was 2.9 and 2.5 times higher than that of filtration alone and PMS activation alone, respectively, and even dramatically outweighed the reported catalytic membranes and heterogeneous catalysts. The outstanding performance of CoNPC@PVDF catalytic membrane was mainly attributed to its thin membrane structure and high filling degree of CoNPC, resulting in ultrahigh mass transfer rate (1.8 × 10−4 m s−1) and more exposed active sites for enhanced PMS activation into radicals (mainly •OH and SO4•−) towards pollutant removal.

Schatzki’s Ring in Asian Group of Patients

Schatzki's lower esophageal rings appear as thin membranous structures which do not contain any muscularis propria; resulting in a constricting ring at the esophagogastric junction, they are mostly asymptomatic. However, patients present with symptoms of dysphagia to solids and liquids and a sense of impaction of food. Diagnosis can be easily overlooked and can be confirmed by endoscopic inspection of the esophagogastric junction. 3 cases of Schatzki ring diagnosed on oesophagal endoscopy and its management are presented.

Wrinkle Prediction of Membrane Structures under Uniform Normal Tensions

Wrinkles always produce to counteract the compressive stress in the thin membrane structures, which has become a popular topic. In this paper, for the inhomogeneous membrane structure with depth-dependent Young’s modulus, a power-law index is introduced. The effect of inhomogeneity on the displacement and stress fields is analyzed. On this foundation, the membrane structures with uniform normal tension loadings are studied to be accorded with practical cases of engineering application. The stress fields are derived by the superposition of the concentrated tension solution based on the Airy stress superposition theory. Compressive stress generally leads to wrinkling, then the wrinkle regions under different tension conditions are predicted accurately. The proposed stress model is simple, and the computation complexity is reduced without using a finite element solution.

Preparation and properties of composite membranes of fully fluorinated nanofibrous electrospun mat impregnated with highly sulfonated polysulfone: Effect of thermal treatment on the mat and the membranes thereof

To prepare highly sulfonated/fully fluorinated nanofibrous composites, sulfonated polysulfone with 70% degree of sulfonation and fully fluorinated poly(aryl ether) are synthesized as components. Nucleophilic aromatic substitution reaction is applied for polymerization. Then, the composite membrane with thickness of 60 μm and 30 wt% electrospun nanofibers is prepared via impregnation of the fully fluorinated mat by a suitable solution of the sulfonated polymer. In the next step, two treated composite samples with thicknesses of 60 and 20 μm containing 20 wt% of treated electrospun nanofibers are also prepared by impregnation. A simple thermal treatment on fully fluorinated mat is used to obtain the latter composites. The thermal crosslinking make the handling of the thin mat possible. Fourier transform infrared spectroscopy, solubility assessment, and gel content measurement are used to confirm thermal crosslinking. The properties of three developed composites are studied to investigate the presence of fluorinated electrospun nanofibers, thermal treatment effectiveness, and nature of the thin membrane structure. The remarkable tensile strength of 87.52 MPa is attained for the thin membrane. Moreover, the conductivity value of 0.146 S/cm at 30 °C with an activation energy of 10.22 kJ/mol in this sample is motivating.

Investigation of the Resistivity and Emissivity of a Pellicle Membrane for EUV Lithography.

A pellicle is a thin membrane structure that protects an extreme ultraviolet (EUV) mask from contamination during the exposure process. However, its limited transmittance induces unwanted heating owing to the absorption of EUV photons. The rupture of the EUV pellicle can be avoided by improving its thermal stability, which is achieved by improving the emissivity of the film. However, the emissivity data for thin films are not easily available in the literature, and its value is very sensitive to thickness. Therefore, we investigated the dependence of emissivity on structural parameters, such as thickness, surface roughness, and grain size. We found a correlation between resistivity and emissivity using theoretical and experimental approaches. By changing the grain size of the Ru thin film, the relationship between resistivity and emissivity was experimentally verified and confirmed using the Lorentz–Drude model. Finally, we present a method to develop an EUV pellicle with better thermal stability that can withstand high-power EUV light sources.

Primary breakup of shear‐thickening suspension jet by an annular air jet

AbstractAn experimental investigation is conducted to study the influence of shear‐thickening behavior on the primary breakup process of suspension jets. The primary breakup morphologies of cornstarch–water suspension are observed via a high‐speed camera. The unique hardened breakup mode only occurs when the suspension exhibits discontinuous shear thickening (DST). During hardened breakup mode, the oscillating portion of the suspension jet becomes perpendicular to the air direction and keeps cylindrical instead of deforming into a thin sheet or membrane structure. The suspension jets break off into large pieces rather than tiny droplets. The dimensionless number N is established to describe the relative magnitude of the increment of the viscous force and aerodynamic force during the primary breakup process. The primary breakup regime map of Newtonian fluids and shear‐thickening suspensions is also promoted based on the dimensionless number N and the Weber number We.

Buckling of stretched disks—With comparisons and extensions to auxetics

In this paper, we investigate the instability behavior of thin elastic circular disks subjected to two concentrated edge loads arranged along a diameter. Despite the determination of critical load intensities for disks, made of conventional, linear elastic material, under some specific boundary conditions has been published in the past, we show some new and quite interesting findings. Particularly new are the investigations of tensile buckling of completely free disks as well as the post-buckling behavior of such disks under tension and compression, respectively. Comparisons with already existing results are presented, too. As far as the buckling load is concerned, all results are expressed in terms of a non-dimensional buckling factor.It is well known that the use of auxetic materials provides some potential for improving the behavior of lightweight structures. This fact has motivated us to consider, in which way the variation of the Poisson’s ratio ν influences the stability behavior of the disks both under compression and under tension not just for the so far not investigated completely free stretched disks but also for the already published configurations. The Poisson’s ratio is varied in the full thermodynamically admissible range [−1.0, 0.5] and some quite peculiar results are found and explained, especially for disks made of auxetic materials, i.e. for ν<0. Although the stress fields are independent of the value of ν, the dependency of the critical load intensities is not simply proportional to the dependency of the plate’s bending stiffness on ν, and the buckling modes show significant changes when ν is varied.The buckling factors for disks under tensile loading are by an order of magnitude larger than those for the compressed disks. Of course, also the buckling modes differ completely between compression and tension. Furthermore, the post-buckling behavior is qualitatively and quantitatively significantly different, too.The considerations and the achieved results are interesting for scientists working in the field of structural stability and for engineers in lightweight design of structures. Furthermore, there are applications in the design of sensors and actors as well as of flexible electronics. Since similar thin membrane structures appear in biological tissues, the paper might be interesting also for biologists.

Reducing the crossover of carbonate and liquid products during carbon dioxide electroreduction

Membrane electrode assembly (MEA) electrolyzers can perform stable, high-rate carbon dioxide (CO2) electroreduction for renewable fuels and chemicals, thereby realizing effective carbon utilization to mitigate anthropogenic CO2 emissions. Here, we present a numerical, multiphysics model, computationally intensified 60-fold with a machine learning analysis of computational and experimental data, to address the most urgent systems challenges in CO2 MEA electrolyzers: mitigating carbonate and liquid product crossover to increase CO2 utilization and energy efficiency. We explore the effect of varying the applied potential, CO2 partial pressure, ion-exchange membrane thickness, membrane porosity, and membrane charge on these three metrics. By selectively tuning these physical system parameters, we identify conditions that realize negligible CO2 reactant loss, a 2-fold enhancement in CO2 utilization, and a 2-fold decrease in Nernstian overpotential, corresponding to a multi-carbon, full-cell energy efficiency of 21%. These results may direct future MEA system designs and motivate thin anion-exchange membrane structures.

Critical geometric boundary for the design of wrinkling-free thin film samples in the elastic regime of a uniaxial tensile test

Wrinkling has been observed frequently in the mechanical testing of thin films or membrane structures, which may cause adverse effects on the accuracy of stress and strain measurements. To overcome this problem, a dogbone geometry design is proposed and investigated to eliminate the occurrence of wrinkling when the thin film sample is stretched in a uniaxial tensile test. A numerical experiment is carried out using finite element code to parametrically study the influence of the geometry on the wrinkling phenomenon. Based on numerical experiments, it is found that even though the material property is linear, the geometric nonlinearity occurring in the pre-buckling stage makes the critical buckling load obtained from post-buckling analysis more consistent and reliable than that predicted by eigenvalue buckling analysis. Non-dimensional geometric parameters are used to select the geometry that can prevent the wrinkling in the elastic regime of the uniaxial tensile test. A critical geometric boundary (CGB) is proposed to evaluate the parametric range of the dogbone geometry to prevent the wrinkling. It is found that the CGBs can be achieved by two modes, which are ‘wrinkling delay’ for the relatively thicker geometries and ‘wrinkling elimination’ for the relatively thinner geometries. Finally, a function of CGB is determined for the design of wrinkling-free thin film samples in uniaxial tensile tests without reducing the accuracy of stress and strain measurements in a uniaxial tensile test.

Studies on the thermal optical properties and solar heat gain of thin membrane structure industrial building

In recent years, the construction of enclosed material yard projects has becoming an urgent requirement to improve ecological environment and living environment quality. Thin membrane structures have been widely used in industrial building, especially for storage building roofs. Due to the thermal-optical properties of translucent thin fabric material, such as the absorption and transmittance of solar radiation, the indoor thermal environment is seriously disturbed. Moreover, membrane building structures are usually irregular. Compared with conventional buildings material, the translucent thin fabric material particularly responsive to changes in external environment conditions. As a result, the solar radiation heat gain calculation of membrane buildings is complicated. It is worth exploring measures to tackle this problem. Therefore, in order to solve the problem that the relevant thermal-optical parameter is difficult to obtain. The 13 thin membrane samples were tested and the thermal optical characteristic parameters were analyzed in this paper. A practical enclosed membrane structure building was selected as the research object. In addition, a solar radiation heat transfer model was established. The indoor solar heat gain under the action of solar radiation heat was calculated and the effect of different light transmittance and absorptance on the indoor radiation heat gain was studied. It can provide reference for heat gain calculation and ventilation design of membrane structure storage buildings.

Basic Consideration for Facial Aging: Analyses of the Superficial Musculoaponeurotic System Based on Anatomy.

The superficial musculoaponeurotic system (SMAS) is an important structure to understand for face-lift surgeries. However, the detailed distribution and imaging findings of the SMAS have not been established yet. The aim of this study was to establish the accurate distribution and computed tomography (CT) imaging findings of the SMAS based on cadaveric studies. This study was designed in a 3-step procedure. First, 7 cadaver faces were utilized to understand the distribution and histology of the SMAS. Second, the SMAS findings from the cadaveric studies were compared with the CT images. Third, CT images were enrolled for the SMAS interpretation. In 7 cadaveric studies, the SMAS was observed as a subcutaneous fibro-membranous structure extending from the galea aponeurotica to the platysma muscle and laterally connected to the parotid fascia. On the medial side, it also connects with major and minor zygomatic muscles. The SMAS consisted of muscular fibers, collagen fibers, and elastic fibers histologically. Eighteen CT images (all females; age range, 21-82 years) showed the thin linear structures corresponding to the fibro-membranous structures in the cadaveric studies. CT density of the SMAS was similar with that of the muscle, and the SMAS was recognizable in all 18 subjects. The SMAS is a definite anatomical structure that can be demonstrated as a thin membranous structure on CT. This clinical application could be applicable to the development the cosmetic surgical procedures.

Geometrically nonlinear isogeometric analysis of a partly wrinkled membrane structure

An isogeometric membrane element based on the non-uniform rational basis spline (NURBS) model is presented that accounts for membrane wrinkling based on tension-field theory. First, the element is validated by means of a benchmark problem involving a partly wrinkled membrane. It is then applied to the large deformation of a thin membrane structure using a two-stage procedure that combines dynamic relaxation and Newton–Raphson iteration. A simple technique is introduced that takes advantage of the geometrical symmetry of an isogeometric analysis model by using a “one-sided” open knot vector to treat the continuity of the membrane surface with respect to the symmetry plane. Because NURBS has many suitable features for representing complex geometries, it enriches the function space of the membrane element. Consequently, the characteristic mechanical responses of membranes, such as deep folding, are captured appropriately by the present isogeometric membrane element. In addition, a numerical example demonstrates that the convergence rate of the isogeometric membrane analysis with respect to refinement of the discretization is much better when tension-field theory is introduced in the analysis.

Far-infrared properties of cyclic olefin copolymer.

Cyclic olefin copolymer (COC) is an amorphous thermoplastic with desirable dielectric and mechanical characteristics for optical applications. In particular, its low refractive index, overall mechanical strength, and absence of strong absorption features make it a promising substrate material for far-infrared applications, which include frequency-selective surfaces, scattering filters, and windows. The dielectric properties of selected COC formulations are surveyed from $ \approx 10 - 700\,\, {{\rm cm}^{ - 1}} $≈10-700cm-1 ($ 1000 - 14\,\, \unicode{x00B5} {\rm m} $1000-14µm), and representative usage as a thin film membrane structure in optical filters is presented.

A Report on Prenatal Diagnosis of a Rare Case of Fetal Acrania and Omphalocele by Doppler Examination

A congenital anomaly, fetal acrania (exencephaly) is, in which the fetal brain is not surrounded completely or partially by the skull bones. It is suggested that there is lacking of mesenchymal migration in the fourth week of embryological age. The first-trimester diagnosis must be made with restraint because the fetal cranium is not fully calcified before 10-11 weeks; therefore, if only midsagittal views of the fetus are obtained, misdiagnosis may occur. Another anomaly, omphalocele, a ventral defect of the umbilical ring resulting in herniation of the abdominal viscera, is one of the most common congenital abdominal wall defects seen in the newborn. Omphalocele is associated with trisomy [18]. The defect occurs in 1 in 6000 to 1 in 10,000 live births. The anencephaly sequence begins with acrania, which affecting the central nervous system with an incidence of ~1:1000 pregnancies. In our case a female 28 years old visited our ultrasound clinic for anomaly scan. The gestational age was 18 weeks 4 days. On ultrasound examination the presentation of fetus was cephalic and longitudinal lie. The sonographic scan revealed fully developed fetal brain having no calvarium. The brain was covered by a thin membranous structure. Compression of fetal brain by transducer was observed due to absence of cranium. The scan revealed the brain floating in the amniotic fluid over the base of skull. Facial structures were normal. Normal and well-coordinated movements were noted in in the fetal body parts. There was symmetry in Fetal nose and naso-labial folds and were well appreciated. It was also noted that spinal canal showed normal morphology with normal Cervical, thoracic and lumbar spines. The fetal abdomen showed a central mass protruding out from anterior abdominal wall. The mass is covered by a membrane and contains small intestines and liver. There was direct insertion of the umbilical cord into the midline of omphalocele. After taking consent form from the patient and her family, an elective prostaglandin abortion was performed. After delivery placenta was completely removed. Brain was covered by a membrane. There was a mass protruding through anterior abdominal wall and multiple abdominal viscera’s were protruding out through the midline gap in the anterior abdominal wall. This breach was centrally located equivalent to umbilicus connection. About 1-2mm thick was covering the protruding organs.

Tunneling nanotube-mediated intercellular vesicle and protein transfer in the stroma-provided imatinib resistance in chronic myeloid leukemia cells

Intercellular communication within the bone marrow niche significantly promotes leukemogenesis and provides protection of leukemic cells from therapy. Secreted factors, intercellular transfer of mitochondria and the receptor–ligand interactions have been shown as mediators of this protection. Here we report that tunneling nanotubes (TNTs)—long, thin membranous structures, which have been identified as a novel mode of intercellular cross-talk—are formed in the presence of stroma and mediate transfer of cellular vesicles from stroma to leukemic cells. Importantly, transmission of vesicles via TNTs from stromal cells increases resistance of leukemic cells to the tyrosine kinase inhibitor, imatinib. Using correlative light-electron microscopy and electron tomography we show that stromal TNTs contain vesicles, provide membrane continuity with the cell bodies and can be open-ended. Moreover, trans-SILAC studies to reveal the non-autonomous proteome showed that specific sets of proteins are transferred together with cellular vesicles from stromal to leukemic cells, with a potential role in survival and adaptation. Altogether, our findings provide evidence for the biological role of the TNT-mediated vesicle exchange between stromal and leukemic cells, implicating the direct vesicle and protein transfer in the stroma-provided protection of leukemic cells.

Neural and vascular architecture of the septum pellucidum: an anatomical study and considerations for safe endoscopic septum pellucidotomy.

The septum pellucidum is a bilateral thin membranous structure representing the border between the frontal horns of the lateral ventricles. Its most examined components are the septal veins due to their surgical importance during endoscopic septum pellucidotomy (ESP), which is a well-accepted method for surgical treatment of unilateral hydrocephalus. It is widely accepted that the septum pellucidum contains nerve fibers as well, but interestingly, no anatomical study has been addressed to its neural components before. The aim of the present study was to identify these elements as well as their relations to the septal veins and to define major landmarks within the ventricular system for neurosurgical use. Nine formalin-fixed human cadaveric brains (18 septa pellucida) were involved in this study. A central block containing both septa pellucida was removed and frozen at -30°C for 2 weeks in 7 cases. The fibers of the septum pellucidum and the adjacent areas including the venous elements were dissected under magnification by using homemade wooden spatulas and microsurgical instruments. In 2 cases a histological technique was used to validate the findings of the dissections. The blocks were sliced, embedded in paraffin, cut in 7-µm-thick slices, and then stained as follows: 1) with H & E, 2) with Luxol fast blue combined with cresyl violet, and 3) with Luxol fast blue combined with Sirius red. The septum pellucidum and the subjacent septum verum form the medial wall of the frontal horn of the lateral ventricle. Both structures contain nerve fibers that were organized in 3 groups: 1) the precommissural fibers of the fornix; 2) the inferior fascicle; and 3) the superior fascicle of the septum pellucidum. The area directly rostral to the postcommissural column of the fornix consisted of macroscopically identifiable gray matter corresponding to the septal nuclei. The histological examinations validated the findings of the authors' fiber dissections. The nerve elements of the septum pellucidum as well as the subjacent septum verum were identified with fiber dissection and verified with histology for the first time. The septal nuclei located just anterior to the fornix and the precommissural fibers of the fornix should be preserved during ESP. Considering the venous anatomy as well as the neural architecture of the septum pellucidum, the fenestration should ideally be placed above the superior edge of the fornix and preferably dorsal to the interventricular foramen.

High-Performance Polybenzimidazole Membranes for Helium Extraction from Natural Gas.

Increasing helium use in research and production processes necessitates separation techniques to secure sufficient supply of this noble gas. Energy-efficient helium production from natural gas is still a big challenge. Membrane gas separation technology could play an important role. Herein, a novel poly(p-phenylene benzobisimidazole) (PBDI) polymeric membrane for helium extraction from natural gas with low He abundance is reported. The membranes were fabricated by a facile interfacial polymerization at room temperature. The thin and defect-free membrane structure was manipulated by the confined polymerization of monomers diffusing through the interface between two immiscible liquids. Both He/CH4 selectivity and He permeance are competitive over those of other commercial perfluoropolymers. Even at low He content of 1%, separation performance of the PBDI membrane transcended the current upper bound. The unprecedented selectivity (>1000) together with the excellent stability (∼360 h) endows PBDI membranes with a great potential for energy-efficient industrial recovery and production of this precious He resources from reservoirs with low abundance.

Histological study of the thin membranous structure made of dense connective tissue around the esophagus in the upper mediastinum

The structure of the fascia in upper mediastinum has already been reported from gross anatomical viewpoints by Sarrazin. But it is necessary to understand meticulous anatomy for thoracoscopic or mediastinoscopic surgery. So herein, we investigate histologically the thin membranous structure made of dense connective tissues. Semi-sequential transverse sections of the mediastinum were obtained from three cadavers. Hematoxylin and eosin staining, Elastica van Gieson staining, and Masson trichrome staining were performed to identify the presence and location of the thin membranous structure made of dense connective tissues. The "visceral sheath" and "vascular sheath," as previously described by Sarrazin, were observed histologically. These two thin membranous structures do not surround the esophagus and trachea cylindrically. In addition, the "visceral sheath" on the right side of the upper mediastinum was unclear in comparison to the left side. The "visceral sheath" (on the left side) gradually became unclear, and seemed to almost disappear; the esophagus was found to be very close to the thoracic duct on the caudal side of the bifurcation of the trachea. Although the left recurrent nerve was located inside the "visceral sheath" in all cadavers, the left recurrent nerve lymph nodes were located inside the "visceral sheath" in cadaver 1 and between the "visceral sheath" and "vascular sheath" in cadaver 3. The "visceral sheath" around the esophagus in the upper mediastinum was histologically demonstrated; however, the findings were not constant.

Intracellular origin and ultrastructure of platelet‐derived microparticles

Background Platelet-derived microparticles comprise the major population of circulating blood microparticles that play an important role in hemostasis and thrombosis. Despite numerous studies on the (patho)physiological roles of platelet-derived microparticles, mechanisms of their formation and structural details remain largely unknown. Objectives Here we studied the formation, ultrastructure and composition of platelet-derived microparticles from isolated human platelets, either quiescent or stimulated with one of the following activators: arachidonic acid, ADP, collagen, thrombin or calcium ionophore A23187. Methods Using flow cytometry, transmission and scanning electron microscopy, we analyzed the intracellular origin, structural diversity and size distributions of the subcellular particles released from platelets. Results The structure, dimensions and intracellular origin of microparticles depend on the cell-activating stimulus. The main structural groups include a vesicle surrounded by one thin membrane or multivesicular structures. Thrombin, unlike other stimuli, induced formation of microparticles not only from the platelet plasma membrane and cytoplasm but also from intracellular structures. A fraction of these vesicular particles having an intracellular origin contained organelles, such as mitochondria, glycogen granules and vacuoles. The size of platelet-derived microparticles depended on the nature of the cell-activating stimulus. Conclusion The results obtained provide a structural basis for the qualitative differences of various platelet activators, for specific physiological and pathological effects of microparticles, and for development of advanced assays.

Wrinkle-free design of thin membrane structures using stress-based topology optimization

Thin membrane structures would experience wrinkling due to local buckling deformation when compressive stresses are induced in some regions. Using the stress criterion for membranes in wrinkled and taut states, this paper proposed a new stress-based topology optimization methodology to seek the optimal wrinkle-free design of macro-scale thin membrane structures under stretching. Based on the continuum model and linearly elastic assumption in the taut state, the optimization problem is defined as to maximize the structural stiffness under membrane area and principal stress constraints. In order to make the problem computationally tractable, the stress constraints are reformulated into equivalent ones and relaxed by a cosine-type relaxation scheme. The reformulated optimization problem is solved by a standard gradient-based algorithm with the adjoint-variable sensitivity analysis. Several examples with post-bulking simulations and experimental tests are given to demonstrate the effectiveness of the proposed optimization model for eliminating stress-related wrinkles in the novel design of thin membrane structures.