Thin Mat Research Articles

Fabrication of nanofibrous mat surrounded hydrogel scaffold as an encapsulation device for encapsulating pancreas β cells

The main barriers to cells or organ transplantation such as pancreatic β-cells are the need for lifelong immune suppression and the shortage of donors. It may be overcome via cell encapsulation and transplantation techniques. Hydrogels provide a suitable ECM-like microenvironment for cells to adhere, survive, and function, while weakly performing as an immune barrier. In this study, we aimed to macro-encapsulate islet cells in a dual encapsulation device with collagen hydrogel and PCL nanofiber to provide an immune-isolated environment for cells to function more efficiently, where immune cells are not allowed to enter but oxygen, insulin, and nutrients can pass through. PCL thin mats with the pores diameter of 500 nm were synthesized by electrospinning and characterized by scanning electron microscope, porosity measurement, tensile strength test, and contact angle measurement. Collagen hydrogel was fabricated by extracting collagen fibers from rat tail tendons and solving them in acetic acid. β-cells (CRI-D2 cell line) encapsulated after neutralizing collagen solution (pH ≈ 7.4). Cell-collagen gel complex was poured into the nanofibrous mat packets to fabricate the whole device. Histology evaluation, cell viability, and cell function tests were done in 10 days. Live/dead assay of Cri-D2 cells encapsulated within the device showed that cells have diffuse distribution at the core of the hydrogel and the device. Also, cluster formation was seen and shows these cells can live in groups. To identify cells’ function within the device in these 10 days samples’ supernatant insulin level was measured by chemiluminescent immunoassay. It just showed a positive result for existing insulin within the medium. Based on our results, this device presents adequate features to be a good immune-isolation device for cell transplanting.

Magnetic spinel manganese ferrite nanocrystal carbon nanotube thin mats with improved electromagnetic shielding performance

Magnetic spinel manganese ferrite nanocrystal carbon nanotube thin mats with improved electromagnetic shielding performance

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.

Study of the Optical Properties of Electrospun PAN/GO Nanocomposites

Polymer nanocomposites with unique optical properties are currently one of the materials most desired by the industry. An effective method of producing this type of materials is the method of electrospinning from a solution or melted polymers, which allows to obtain a nanocomposite in the form of a mat composed of nanofibers. This paper describes the process of producing nanofibers from polyacrylonitrile (PAN) and composite thin nanofiber mats from PAN with the addition of graphene oxide (GO) particles using the electrospinning method. In addition, the aim of the work was to investigate the influence of process parameters and filler on the morphology and optical properties of the nanomaterial. By changing the configuration of the distance between the nozzle and the collector (10 and 20 cm) and keeping the remaining parameters of the electrospinning process constant, two PAN polymer samples and two PAN/GO composite samples were manufactured. The analysis of the chemical composition and morphology of the obtained materials was performed using X-ray microanalysis (EDX) and scanning electron microscopy (SEM), respectively. In order to examine the chemical structure of the polymer and composite nanofibers, Fourier-Transform Infrared Spectroscopy (FTIR) was used. The analysis of the optical properties and the energy band gap of the prepared nanofibers was determined by spectral analysis using a UV–Vis spectrophotometer. The research showed a significant influence of the filler on the morphology.

Enhancement on vacuum foam mat quality parameters of papaya powder by using chemical preservatives

Vacuum foam-mat drying is a technique that involves whipping a liquid concentration with an appropriate foaming agent into a stable foam that is then dehydrated into a thin mat of foam at a low temperature. The effect of variables on responses was determined using response surface methodology (RSM). The moisture content of raw papaya pulp was 856.023 % (db.). The total soluble solid (TSS) was tested by hand refractrometer i.e. 12.8 o Brix. Parameters such as whipping time (10 minute) , papaya pulp thickness (4 mm) and vacuum oven pressure (25 inch Hg), pH value 5.56 and TSS(10 o Brix) remain constant throughout the work. The drying time, drying rate and moisture ratio varies from 60 minutes to 840 minutes, 0.001-1.279 and 0.01-4.402 respectively. The drying duration, drying rate, and moisture ratio range from 60 to 840 minutes, respectively, 0.001-1.279 and 0.01-4.402. In experiment number 2, the ingredients, temperature (70 oC), maltodextrin 0.30 (w/w), glycerol monostearate 2.0 percent, and tricalcium phosphate 2.0 percent of dried papaya powder were combined to achieve a minimum drying time of 660 minutes. Experiments also revealed that increasing the amount of tricalcium phosphate (2%) and glycerol monostearate 2.0 percent in the materials reduced drying time, which helped to lower the moisture content of the papaya powder. As the drying time increases, the moisture ratio for all samples decreases in a nonlinear manner. The moisture ratio of each sample declined rapidly while the drying period was very short, but the rate of decrement of moisture ratio became quite slow as the drying time increased. The solubility of papaya powder is found to be as low as 69.08 percent in experiment number 24 and as high as 96.45 percent in experiment number 20. Ascorbic acid is found in the range of 88.43 to 115.75 (mg/100g) in experiment numbers 28 and 1, while beta carotene is found in the range of 10-51 (g/100g) experiment numbers 24 and 12. L* (Lightness) is varied from 53.1 to 82.79 experiment numbers 14 and 10, chromatic component a* (from green to red) is varied from 27.25 to 105.92 experiment numbers 3 and 17, and chromatic component b* (from blue to yellow) is varied from -15.92 experiment number 3 to 73.67 experiment number 10 during colour value estimation. It is reported that solubility increases with increase in maltodextrin at 5% level of significance. The interaction between maltodextrin and glycerol monostearate are significant at P

Unobtrusive vital signs and activity monitoring based on dual mode fiber

A solid unobtrusive fiber-optic sensor based on modal interference in dual mode fiber (DMF) embedded in a thin mat is proposed and investigated theoretically and experimentally, realizing real-time vital signs and activity monitoring. The whole sensing setup only consists of one laser diode, one section of DMF, one photo-detector and few standard single mode fibers (SMFs). The DMF fiber is sandwiched into the SMFs using core-offset splicing, i.e., SMF-DMF-SMF structure. The optimal value of the core offset is numerically simulated and experimentally validated. It has to be noted that all the fibers used in the experiment are with 900-μm protection jacket, which can effectively avoid fiber breaking. The proposed sensor is both investigated in different postures and different subjects. And the results of vital signs monitoring performance show great consistency compared with commercial monitors. Besides, the activity monitoring is also addressed with one-second discrimination resolution, identifying three basic states, i.e., on bed, body movement and off bed. It is easy to fabricate and shows great potential in future non-invasive vital signs and activity monitoring applications.

Surface sensitization of TiO2 nanorod mats by electrodeposition of ZIF-67 for water photo-oxidation

Results reported in this research paper are related to the photo-oxidation of water into molecular oxygen, using n-type photoelectrodes operated with the support of an external electric bias. These photoanodes are made of 1 cm2 rectangular glass substrates, surface-covered by thin films of conductive fluorine-doped tin oxide (FTO). Thin mats of titanium dioxide nanorods (TDNRs) have been deposited over the FTO surfaces. The TDNRs have then been sensitized by surface deposition of cobalt dodecahedral Zeolitic Imidazolate Framework (ZIF-67) metal organic framwork (MOF). ZIF-67 has been deposited using a two-step process: (i) deposition of cobalt hydroxide by chronoamperometry; (ii) in-situ transformation of cobalt hydroxide into ZIF-67 by chemical reaction with a solution of 2-methylimidazol. The amount of ZIF-67 has been adjusted by monitoring the duration of the electro-reduction step. The photoanodes have been characterized by scanning electron microscopy, X-ray diffraction spectroscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and UV–Vis absorption spectroscopy. The photoelectrochemical responses of the different photoanodes have been measured under chopped illumination conditions. Dark currents as high as 100–150 μA/cm2 and photocurrents of only 10–15 μA/cm2 have been measured on fresh samples with large MOF contents, at an operating potential of +1.0 V vs. saturated calomel electrode, 25 °C, under UV–Vis irradiation. No dark current and photocurrents close to 40 μA/cm2 have been measured on samples with low MOF contents. The dynamics of charge transfer leading to the formation of molecular oxygen has been analyzed by photoelectrochemical impedance spectroscopy to understand the interplay between the OER electroactivity and photoelectroactivity. It is shown that large MOF contents induce two contradictory effects: the first one (faster charge transfer kinetics) is desirable while the second one (faster charge recombination kinetics) is not desirable. Only limited MOF contents are beneficial to maximize the photocurrent density.

A Self-Healing Nanofiber-Based Self-Responsive Time-Temperature Indicator for Securing a Cold-Supply Chain.

Perishable foods at undesired temperatures can generate foodborne illnesses that present significant societal costs. To certify refrigeration succession in a food-supply chain, a flexible, easy-to-interpret, damage-tolerant, and sensitive time-temperature indicator (TTI) that uses a self-healing nanofiber mat is devised. This mat is opaque when refrigerated due to nanofiber-induced light scattering, but becomes irreversibly transparent at room temperature through self-healing-induced interfibrillar fusion leading to the appearance of a warning sign. The mat monitors both freezer (-20 °C) and chiller (2 °C) successions and its timer is tunable over the 0.5-22.5 h range through control of the polymer composition and film thickness. The thin mat itself serves as both a temperature sensor and display; it does not require modularization, accurately measures localized or gradient heat, and functions even after crushing, cutting, and when weight-loaded in a manner that existing TTIs cannot. It also contains no drainable chemicals and is attachable to various shapes because it operates through an intrinsic physical response.

Effect of fiberglass form on the tensile and bending characteristic of epoxy composite material

This search focuses on the tensile and bending characteristics of a composite material that reinforced by various forms of fiberglass. Two fiber forms are considered; the first is bi-directional of (0°–90°) fiber direction, the second is random. The fiber thickness of bi-directional form has been investigated by considering thick and thin mats. The composite has been developed by hand lay-up process with a fiber weight ratio of 10%. Three samples of the developed composited have been compared with a base case sample (pure matrix of epoxy resin). Also, a microscopic vision has been captured on the fracture zone of tensile specimens. The results reveal that the random-form composite had maximum tensile strength and transverse stiffness, also, the thin-fiber composite showed maximum ductility.

Nitrogen Mineralization in Mississippi River Deltaic Plain Freshwater Floating Marshes

ABSTRACTThe mineralization of soil organic nitrogen in two floating marshes types in Louisiana, USA with different vegetation and mat thickness (and biomass) was measured by incubating peat soil in situ in polyethylene bottles at depths of 10 and 25 cm. The size of the extractable inorganic N (NH4+ – N) pool was related to mat thickness and soil bulk density. The N mineralization rates were twice as great at the thick mat site (1.5 mg N/kg soil/day) compared to the thin mat floating marsh (0.71 mg N/kg soil/day). The amount mineralized on a volume basis to 30 cm depth were 22 mg N/m2/day for the thick mat marsh and 6 mg N/m2/day for the thin mat marsh. The nitrogen mineralization rates observed in this study reflect plant biomass differences between the thick mat and thin mat marshes, with the former exhibiting approximately 7-fold greater biomass. These low overall mineralization rates suggest that nitrogen entering these freshwater floating marshes from Mississippi River water percolating through the root zone, would result in increased plant productivity-increasing marsh stability and also providing a natural mechanism contributing to the processing and removal of dissolved inorganic nitrogen in river water entering these wetlands.

Effect of compaction parameters on preform permeability and mechanical properties of unidirectional flax fiber composites

This paper presents the effect of compaction parameters on the permeability to resin, tensile and flexural performances of unidirectional (UD) composites made of UD flax-mat reinforcements. In these reinforcements the UD fiber yarns are held together by a thin mat layer of short flax fibers. Reinforcements were compacted in dry or wet conditions at ambient or high temperature prior to permeability testing and composites molding with the resin transfer molding (RTM) process. A micrographic analysis of the morphology and structure of the laminates prior to and after tensile testing was also performed. It is found that hot and wet compaction do not change the permeability. Moreover, after molding with compacted reinforcements, the tensile strength increases while the tensile modulus is not affected. It also leads to a substantial increase in the flexural properties (strength and modulus). This means the chosen compaction parameters are appropriate for preforming this type of reinforcement.

Successional Changes in the Microbial Community of the Alkaline Lake Khilganta during the Dry Season

Microbial processes in a shallow, saline, alkaline Lake Khilganta (Southern Siberia) were studied during the dry season. During the drought, a crust was formed on the lake surface, where low rates of production processes were observed, with predominance of anoxygenic photosynthesis at 2.3 mg C/(dm3 day). The rates of microbial processes increased after short-term rains. During this period, a thin cyanobacterial mat was formed on the bottom, in which filamentous cyanbacteria Geitlerinema spp. predominated and the rate of oxygenic photosynthesis was up to 18 mg C/(dm3 day). Subsequent water evaporation and salinity increase resulted in altered community types and their activity. Red spots emerged on the mat surface, where anoxygenic prototrophic members of the genus Ectothiorhodospira predominated. Anoxygenic photosynthesis became the main production process in microbial mats, with the rate of 60 mg C/(dm3 day). At salinity increase to 200 g/L, the water remained in small depressions on the bottom, where extremophilic green algae Dunaliella sp. predominated, and the rate of oxygenic photosynthesis was 0.877 mg C/(dm3 day). These changes in the type and activity of microbial communities is an example of succession of microbial communities in Southern Siberia saline lakes during drought.

Performance In Square Stepping Exercise Is Associated With Working Memory

Square-Stepping Exercise (SSE) program improves cognitive function as well as lower-extremity functional fitness in the elderly. However, it is unclear which aspects of cognitive function are closely associated with performance in SSE. Given that SSE comprises stepping exercise while remembering step pattern, we hypothesized that working memory plays a key role in performance in SSE. PURPOSE: The purpose of the present study was to test the hypothesis that performance in SSE is associated with working memory. METHODS: Sixteen elderly people (10 males and 6 females, age: 72.9 ± 6.3 years, body mass index: 22.1 ± 3.2 kg/m2) participated in the study. The participants performed a combination of spatial delayed response (SDR) and Go/No-Go (GNG) tasks and SSE. SDR task requires working memory. GNG task requires response inhibition and interference control. The SDR task was graded into three levels of difficulty. Cognitive performance was assessed by reaction time (RT) and accuracy. In SSE, the participants performed multiple directional step patterns on a thin mat partitioned into squares. SSE was graded into five levels of difficulty depending on step pattern. Time to complete SSE was used to assess performance. One-way repeated measures analysis of variance was used for each variable. Pearson correlation analysis was performed to determine the correlation. Data were expressed as mean ± standard deviation. The significance level was set at p < 0.05. RESULTS: RT in the SDR task increased with task difficulty (main effect: p < 0.001, level 1: 1.4 ± 0.2 sec, level 2: 1.8 ± 0.3 sec, level 3: 2.2 ± 0.4 sec), while accuracy was not altered. Time to complete SSE also increased with task difficulty (main effect: P < 0.001, level 1: 5.4 ± 0.7 sec, level 2: 8.6 ± 1.4 sec, level 3: 16.7 ± 1.7 sec, level 4: 18.0 ± 3.4 sec). Only eight participants completed SSE at level 5 (26.6 ± 3.4 sec). RT in the SDR task at level 2 was associated with time to complete SSE at level 2 (r = 0.54, p = 0.03). Performance in the GNG task was not associated with time to complete SSE. CONCLUSION: The moderate correlation suggests that performance in SSE is associated with working memory. Exercise intervention with square stepping may be particularly effective to improve working memory.

Dave Didn't Have To Die: On Health Care For Homeless Patients.

A writer watches a homeless man's health decline because of a lack of care.

Analysis of optical properties of TiO2 nanoparticles and PAN/TiO2 composite nanofibers

ABSTRACTThe aim of the study was the production of thin composite nanofibrous mats PAN/TiO2 nanoparticles using the electrospinning method from solution of PAN/TiO2/DMF. TiO2 nanoparticles were obtained using sol-gel method. To prepare sol mixture, organic alkoxides precursor of titanium isopropoxide and water solution were used. Calcination of TiO-gel and following milling were carried out to obtain nanoparticles of TiO2 rutile phase. In order to analyze the structure of the obtained particles, we used X-ray diffraction analysis (XRD) and energy dispersive spectrometer (EDS). Analysis of the morphology and chemical composition of the resulting composite nanofibers were carried out using a scanning electron microscope (SEM) with EDS. The analysis of the optical properties and the energy band structure prepared nanoparticles and thin composite nanofibrous mats were determined by spectral analysis of the absorbance as a function of the energy of radiation obtained using a UV–Vis spectrophotometer.

Janus‐Faced, Dual‐Conductive/Chemically Active Battery Separator Membranes

Battery separators are supposed to be electrical insulators to prevent internal short‐circuit failure between electrodes as well as having porous channels to allow ion transport. Here, as a multifunctional membrane strategy to dispel this stereotypical belief about battery separators, a new class of Janus‐faced, dual (ion/electron)‐conductive/chemically active battery separators (denoted as “Janus separators”) based on a heterolayered nanofiber mat architecture is demonstrated. The Janus separator, which is fabricated through in‐series, concurrent electrospraying/electrospinning processes, consists of an ion‐conductive/metal ion‐chelating support layer (a mat of densely packed, thiol‐functionalized silica particles spatially besieged by polyvinylpyrrolidone/polyacrylonitrile nanofibers) and a dual‐conductive top layer (a thin mat of polyetherimide nanofibers wrapped with multi‐walled carbon nanotubes). The support layer acts as a chemical trap that can capture heavy metal ions dissolved in liquid electrolytes and the top layer serves as an upper current collector for cathodes to boost the redox reaction kinetics. Notably, the unusual porous microstructure of the top layer is theoretically elucidated using molecular dynamics simulation. Benefiting from such material/structural uniqueness, the Janus separator enables significant improvements in fast‐rate charge/discharge reactions (even for high‐mass loading cathodes) and in the high‐temperature cycling performance, which lie far beyond those achievable with conventional polyethylene separators.

Abiotically-formed, primary dolomite in the mid-Eocene lacustrine succession at Gebel El-Goza El-Hamra, NE Egypt: An approach to the role of smectitic clays

This study discusses the role of smectitic clays in the formation of an abiotic (physio-chemical) primary dolomite within an evaporative alkaline-saline marginal lake system, in the absence of carbonate precursor and microbes. The present work has been achieved in terms of textural, mineralogical, and geochemical characteristics of dolostones in the Mid-Eocene (Bartonian) lacustrine succession cropping out at Gebel El-Goza El-Hamra (Shabrawet area, NE Egypt). This lacustrine succession is 15–16m thick, and made up of alternating horizontal beds of dolostone, marlstone and mudrock that show some pedogenic and subaerial exposure features. The dolostones are composed mainly of dolomite (60–90%), smectite (20–30%) and quartz grains (5–10%). The dolomite comprises fine-crystalline rhombs to micro-spherical crystals with no obvious relics of microbial activity and/or carbonate precursor. It is, ordered, nearly stoichiometric (with 46–50% mole of MgCO3) and has δ18O and δ13C values ranging from +0.44 to +2.96 VPDB ‰, and 0.93 to −8.95 VPDB ‰, respectively. The smectite occurs as thin mats that are commonly intergrown and associated with dolomite. Mineralogical, textural and stable isotopic results of the dolomite indicated that the dolomite was formed as an abiotic primary precipitate in alkaline saline lacustrine systems. In this respect, the gel-like highly viscous smectitic medium plus progressive CO2 degassing, elevated evaporation, low sedimentation rate, low sulphates level and alkaline soil solution lowered the kinetic barriers of dolomite precipitation from solution and promoted the incorporation of Mg2+ in the structure of dolomite. Consequently, the presence of smectitic clays in evaporative saline lakes is significant for dolomite formation because they can generate a gel-like highly viscous medium and provide Mg2+ that can facilitate the physcio-chemical precipitation of primary dolomite from solution at ambient temperatures. However, more work is needed to better characterize the role of clays during dolomite formation in alkaline lacustrine environments at ambient temperatures.

Functionalized Nanocellulose-Integrated Heterolayered Nanomats toward Smart Battery Separators.

Alternative materials obtained from natural resources have recently garnered considerable attention as an innovative solution to bring unprecedented advances in various energy storage systems. Here, we present a new class of heterolayered nanomat-based hierarchical/asymmetric porous membrane with synergistically coupled chemical activity as a nanocellulose-mediated green material strategy to develop smart battery separator membranes far beyond their current state-of-the-art counterparts. This membrane consists of a terpyridine (TPY)-functionalized cellulose nanofibril (CNF) nanoporous thin mat as the top layer and an electrospun polyvinylpyrrolidone (PVP)/polyacrylonitrile (PAN) macroporous thick mat as the support layer. The hierarchical/asymmetric porous structure of the heterolayered nanomat is rationally designed with consideration of the trade-off between leakage current and ion transport rate. The TPY (to chelate Mn(2+) ions) and PVP (to capture hydrofluoric acid)-mediated chemical functionalities bring a synergistic coupling in suppressing Mn(2+)-induced adverse effects, eventually enabling a substantial improvement in the high-temperature cycling performance of cells.

Development of flexible materials based on plasticized electrospun PLA–PHB blends: Structural, thermal, mechanical and disintegration properties

In this work flexible PLA–PHB electrospun materials were developed by means of electrospinning technique. The processing parameters to obtain PLA–PHB electrospun fibers in different proportions (100:0; 75:25; 50:50, 25:75 and 0:100) were conditioned. A complete morphological, structural, thermal and mechanical characterization of the developed materials was conducted. The addition of PHB to PLA matrix, reduced considerably the formation of beads. PHB acts as nucleating agent for PLA in PLA–PHB blends. FTIR and Raman studies have showed interactions between PLA–PHB, mainly at proportion 75:25. The influence of the presence of plasticizer was also studied to obtain information on the possibility to use these thin mats as flexible films. Thus, PLA and PLA75–PHB25 electrospun mats were further plasticized with acetyl tri-n-butyl citrate (ATBC), which provoked an increase in elongation at break, achieving the ductility required for flexible films. The ternary system, PLA75–PHB25/ATBC, showed improved thermal stability due to the good interaction among three components. Disintegrability tests under composting conditions confirmed the biodegradable character of all electrospun mat formulations. Also, it was found that PHB slowed down the disintegration, while ATBC speeded it up.

A three-dimensional model of fine particle retention during percolation through a fiber mat

Fine particles are usually retained in fiber mats by sieving. To date, no theory has combined fiber and mat characteristics into a predictive retention model. A multilayer analytical retention model developed during this study predicts retention within a thick fiber mat by modeling retention as particles pass through a series of very thin fiber mats. A suspension of 5-75 μm toner particles was percolated through rayon fiber mats. The model’s prediction approached the experimental data only when the ratio of particle diameter to fiber diameter increased toward 2.0, the upper limit within the rayon fiber mat data set. Retention was also experimentally determined on the macroscale with simulated fiber mats, through which 4-20 mm beads were dropped. The particle diameter was at least 2.2 times the fiber diameter for all of the macroscale experimental data, explaining the much better fit of the data from those experiments to the model’s predictions.