Nonwoven Carrier Research Articles

Effect of expansive soils on swelling behavior of encapsulated sodium bentonite of geosynthetic clay liner (GCL)

Due to the rapid urbanization of Indian cities, the generation of MSW is exponentially increasing. The confinement of the hazardous emission from a municipal solid waste (MSW) dumpsite is the major responsibility of management and engineers. Landfill gases and leachate generation are the results of chemical and biological activities in municipal solid waste and its decomposition process. The seepage control of leachate is a crucial aspect of MSW management. The flow of leachate to groundwater is one of the major causes of groundwater contamination resulting in human health risks nearby population. Geosynthetic clay liners (GCLs) are the most preferred options to restrict the flow of leachate from dumpsite to groundwater. GCL consists of sodium/ calcium bentonite as an encapsulated material between woven and non-woven carriers. The swelling behavior of sodium bentonite with low hydraulic conductivity makes it suitable to prevent the flow through it. In this study, the swelling nature of sodium bentonite was assessed in combination with expansive soils. The soils were collected from two different regions of Uttar Pradesh as Banda and Mahoba districts. The results showed that the swelling tendency of sodium bentonite can be enhanced by using specific proportions of expansive soils.

Comparison of Different Carriers to Maintain a Stable Partial Nitrification Process for Low-Strength Wastewater Treatment.

Practical application of the partial nitritation–anaerobic ammonium oxidation (anammox) process has attracted increasing attention because of its low operational costs. However, the nitritation process, as a promising way to supply nitrite for anammox, is sensitive to the variations in substrate concentration and dissolved oxygen (DO) concentration. Therefore, a stable supply of nitrite becomes a real bottleneck in partial nitritation–anammox process, limiting their potential for application in mainstream wastewater treatment. In this study, five 18-L sequencing batch reactors were operated in parallel at room temperature (22°C ± 4°C) to explore the nitritation performance with different carrier materials, including sepiolite-nonwoven carrier (R1), zeolite-nonwoven carrier (R2), brucite-nonwoven carrier (R3), polyurethane carrier (R4), and nonwoven carrier (R5). The ammonia oxidation rate (AOR) in R1 reached the highest level of 0.174 g-N L−1 d−1 in phase II, which was 1.4-fold higher than the control reactor (R4). To guarantee a stable supply of nitrite for anammox process, the nitrite accumulation efficiency (NAE) was always higher than 77%, even though the free ammonia (FA) decreases to 0.08 mg-N/L, and the pH decreases to 6.8 ± 0.3. In phase V, the AOR in R1 reached 0.206 g-N L−1 d−1 after the DO content increase from 0.7 ± 0.3 mg/L to 1.7 ± 0.3 mg/L. The NAE in R1 was consistently higher than 68.6%, which was much higher than the other reactor systems (R2: 43.8%, R3: 46.6%, R4: 23.7%, R5: 22.7%). Analysis of 16S rRNA gene sequencing revealed that the relative abundance of Nitrobacter and Nitrospira in R1 was significantly lower than other reactors, indicating that the sepiolite carrier plays an important role in the inhibition of nitrite-oxidizing bacteria. These results indicate that the sepiolite nonwoven composite carrier can effectively improve the nitritation process, which is highly beneficial for the application of partial nitritation–anammox for mainstream wastewater treatment.

Enrichment and characterization of Anammox bacteria in a non-woven membrane reactor

Abstract An upflow column reactor packed with nonwoven fabric carrier was used to enrich anaerobic ammonium oxidation (Anammox) sludge. After 101 days, the reactor Anammox sludge concentration increased from 470 to 3,118 mg·L−1. In the stable operating stage, the average total nitrogen (TN) volume loading rate was 818.3 mg·L−1, and the maximum removal efficiencies of NH4+-N, NO2−-N and TN were 65.9, 81.2 and 63.8%, respectively. Scanning electron microscopy (SEM) showed that the cultivated sludge was dominated by a mix of short rod-shaped and spherical bacteria, which accumulated to the typical cauliflower-like aggregates assumed to be the Anammox culture. Fluorescence in situ hybridization (FISH) analysis using 16S rRNA showed that the dominant population developed in the reactor when hybridized with both PLA46 and Amx820 gene probes. This indicates that the cultivated biomass may comprise Planctomycetes bacteria. The results of real-time quantitative PCR (qPCR) showed that these bacteria formed 45 to 60% of the total bacteria in the Anammox sludge. The study demonstrated successful detection and enrichment of Anammox bacteria in wastewater.

Performance Evaluation of a Carbon Nanotube Sensor for Fatigue Crack Monitoring of Metal Structures.

This article describes research that investigated the ability of a carbon nanotube (CNT) sensor to detect and monitor fatigue crack initiation and propagation in metal structures. The sensor consists of a nonwoven carrier fabric with a thin film of CNT that is bonded to the surface of a structure using an epoxy adhesive. The carrier fabric enables the sensor to be easily applied over large areas with complex geometries. Furthermore, the distributed nature of the sensor improves the probability of detecting crack initiation and enables monitoring of crack propagation over time. Piezoresistivity of the sensor enables strains to be monitored in real time and the sensor, which is designed to fragment as fatigue cracks propagate, directly measures crack growth through permanent changes in resistance. The following laboratory tests were conducted to evaluate the performance of the sensor: (1) continuous crack propagation monitoring, (2) potential false positive evaluation under near-threshold crack propagation conditions, and (3) crack re-initiation detection at a crack-stop hole, which is a commonly used technique to arrest fatigue cracks. Real-time sensor measurements and post-mortem fractography show that a distinguishable resistance change of the sensor occurs due to fatigue crack propagation that can be quantitatively related to crack length. The sensor does not show false positive responses when the crack does not propagate, which is a drawback of many other fatigue sensors. The sensor is also shown to be remarkably sensitive to detecting crack re-initiation.

Curcumin-loaded electrospun nonwoven as a colorimetric indicator for volatile amines

Colorimetric indicators are useful in intelligent food packaging applications. As a natural food colorant, curcumin is a promising colorimetric indicator for the detection of alkaline compounds produced during food spoilage. In this study, curcumin-loaded electrospun nonwovens were developed for the detection of amines, which are principal spoilage volatiles of fish and aquatic products. The spin dope solution for electrospinning was prepared by dispersing curcumin (0.32% w/w) in 14% (w/w) polyvinylpyrrolidone (PVP) or 9% (w/w) ethylcellulose (EC)/0.2% (w/w) poly(ethylene oxide) (PEO) solution in anhydrous ethanol. Curcumin-loaded nonwovens were obtained by free surface electrospinning and subsequently characterized for amine detection. When exposed to amine volatiles, the nonwoven indicators exhibited striking yellow-to-orange/red color transition, along with a reduction in curcumin's fluorescence intensity. Both EC/PEO- and PVP-based nonwovens were capable of discriminating six different volatile amines (trimethylamine, ammonia, dimethylamine, triethylamine, piperidine and hydrazine) at 0.2 mmol level. Comparing the two nonwoven carriers, EC/PEO resulted in smaller fiber diameter (1.06 μm) and higher curcumin loading efficiency (91%) than those derived from PVP (83% loading efficiency and 1.52 μm diameter). The limit of detection (LOD) and limit of quantitation (LOQ) of using EC/PEO-based fiber for amine detection were lower than PVP-based fiber, except for TMA.

Preliminary performance and biofilm characteristics of ANAMMOX process in an improved FBR with mixture of honeycomb-like and non-woven carriers

Preliminary performance and biofilm characteristics of ANAMMOX process in an improved FBR with mixture of honeycomb-like and non-woven carriers

Performance of Anammox process and low-oxygen adaptability of Anammox biofilms in a FBR with small ring non-woven carriers

Performance of Anammox process and low-oxygen adaptation of the cultivated Anammox biofilms were investigated in a lab-scale fixed-bed reactor filled with small ring non-woven carriers. (NH4)2SO4 and NaNO2 provided NH4+-N and NO2−-N in the synthetic wastewater. Anammox reaction occurred on day 17. After 67 days operation, start-up of Anammox was achieved with a total nitrogen loading rate (NLR) of 5.78×10−2kgNm−3d−1 and nitrogen removing rate (NRR) of 4.64×10−2kgNm−3d−1 on day 131. Under the strict anaerobic condition, the max total NLR and NRR reached 4.35×10−1kgNm−3d−1 and 3.83×10−1kgNm−3d−1. Subsequently, a stepwise oxygen adaptation strategy was applied by increasing influent dissolved oxygen (DO) to 8mgL−1 with each increment of 2mgL−1. The Anammox biofilms manifested a satisfactory oxygen adaptability. The reactor performance was only slightly affected as the average total NLR and NRR decreased by 7.08% and 4.39% respectively. Fluorescent in situ hybridization analysis further confirmed that, after low-oxygen adaptation, Anammox bacteria occupied 70.2% of the total bacteria and aerobic ammonium oxidizers moderately increased to 8.5%, which could alleviate the impact of influent DO on the reactor performance. Utilization of the low-oxygen adaptability of Anammox biofilms can markedly reduce energy and material consumption of Anammox operation.

Processing and Characterization of a Novel Distributed Strain Sensor Using Carbon Nanotube-Based Nonwoven Composites.

This paper describes the development of an innovative carbon nanotube-based non-woven composite sensor that can be tailored for strain sensing properties and potentially offers a reliable and cost-effective sensing option for structural health monitoring (SHM). This novel strain sensor is fabricated using a readily scalable process of coating Carbon nanotubes (CNT) onto a nonwoven carrier fabric to form an electrically-isotropic conductive network. Epoxy is then infused into the CNT-modified fabric to form a free-standing nanocomposite strain sensor. By measuring the changes in the electrical properties of the sensing composite the deformation can be measured in real-time. The sensors are repeatable and linear up to 0.4% strain. Highest elastic strain gage factors of 1.9 and 4.0 have been achieved in the longitudinal and transverse direction, respectively. Although the longitudinal gage factor of the newly formed nanocomposite sensor is close to some metallic foil strain gages, the proposed sensing methodology offers spatial coverage, manufacturing customizability, distributed sensing capability as well as transverse sensitivity.

Performance of three GCLs used for covering gold mine tailings for 4 years under field and laboratory exposure conditions

ABSTRACT: The performance of geosynthetic clay liners (GCLs) above arsenic-rich gold mine tailings was investigated by the construction of a test cover comprised of three GCL products placed above the tailings at an abandoned gold mine in Nova Scotia, Canada. In parallel research, the performance of the three commercially available GCLs was assessed based on a series of laboratory column experiments. Of the three needle-punched GCLs tested, one has untreated Wyoming bentonite and a woven carrier geotextile; the second has a polymer-enhanced Wyoming bentonite and a scrim-reinforced nonwoven carrier geotextile, and the third has a polymer-enhanced Wyoming bentonite and woven carrier geotextile coated by a thin polypropylene geofilm. After 4 years of exposure in the field and laboratory, the bentonite structure of all exhumed GCLs appeared to be well hydrated with no visible cracks provided that the cover soil thickness was ≥ 0.7 m. The GCL with untreated bentonite exhibited the highest reduction in the exchangeable sodium percentage (ESP; decreased to 1–3% in field and 4–29% in laboratory) and swell index (decreased to 7–12 ml/2 g in both field and laboratory tests). Despite this reduction in the swelling capacity, the maximum measured hydraulic conductivity (k) for this GCL was 1 × 10−10 m/s, which is still considered low. The GCLs with polymer-enhanced bentonite experienced less cation exchange (ESP = 10–27% in the field and 17–53% in the laboratory) than the GCL with untreated bentonite. The k values of the GCL with polymer-enhanced bentonite and non-coated carrier geotextile (3.6 × 10−11 to 7.9 × 10−11 m/s in the field and 1.6 × 10−11 to 6.7 × 10−11 m/s in the laboratory) were lower than those measured for the GCL with untreated bentonite. The lowest measured k values (3.6 × 10−12 to 9.4 × 10−12 m/s) were for the GCL with polymer-enhanced bentonite and geofilm coating the carrier geotextile. All three GCLs prevented the migration of arsenic to the overlying cover soil, even when the GCL was resting directly above the tailings without a foundation layer.

Removal of nitrogen from secondary effluent of a petrochemical industrial park by a hybrid biofilm-carrier reactor with one-stage ANAMMOX.

A laboratory study was undertaken to explore the capability of one-stage ANAMMOX in a hybrid biofilm-carrier reactor (HBCR) fed with petrochemical wastewater. Under favorable operating conditions in continuous-flow operations (at the dissolved oxygen level of 0.5-1.0 mg L(-1)), the average total nitrogen (TN) removal efficiency reached 62-67% and approximately 90% of TN can be removed by ANAMMOX. In batch operations of the hybrid biofilm-carrier reactor (without adding carbon substrate), the specific TN removal rate of the reactor in which both Kaldnes and nonwoven carriers were kept was two-fold higher than that of the reactor in which only nonwoven carriers were kept. This indicated that the microbial activity of thinner biofilms (Kaldnes carriers) was remarkably higher than that of thicker biofilms (nonwoven carriers). Finally, based on the 16S rRNA clone library, a cluster of ANAMMOX Candidatus Kuenenia stuttgartiensis was identified.

Start-up of the anammox process from the conventional activated sludge in a hybrid bioreactor

The anaerobic ammonium oxidation (anammox) process was successfully started up from conventional activated sludge using a hybrid bioreactor within 2 months. The average removal efficiencies of ammonia and nitrite were both over 80%, and the maximum total nitrogen removal rate of 1.85 kg N/(m3·day) was obtained on day 362 with the initial sludge concentration of 0.7 g mixed liquor suspended solids (MLSS)/L. Scanning electron microscope (SEM) observation of the granular sludge in the hybrid reactor clearly showed a high degree of compactness and cell sphericity, and the cell size was quite uniform. Transmission electron microscope photos showed that cells were round or oval, the cellular diameter was 0.6-1.0 μm, and the percentage of the anammoxosome compartment was 51%–85% of the whole cell volume. Fluorescence in situ hybridization analysis (FISH) indicated that anammox bacteria became the dominant population in the community (accounting for more than 51% of total bacteria on day 250). Seven planctomycete 16S rRNA gene sequences were present in the 16S rRNA gene clone library generated from the biomass and affiliated to Candidatus Kuenenia stuttgartiensis and Candidatus Brocadia sp., a new anammox species. In addition, the average effluent suspended solid (MLSS) concentrations of outlets I (above the non-woven carrier) and II (below the non-woven carrier) were 0.0009 and 0.0035 g/L, respectively. This showed that the non-woven carrier could catch the biomass effectively, which increased biomass and improved the nitrogen removal rate in the reactor.

Anisotropy and directional shrinkage of geosynthetic clay liners

ABSTRACT: Results are reported from laboratory experiments to examine the potential shrinkage of two different geosynthetic clay liners (GCLs) when subject to repeated wetting and drying cycles. One GCL had a scrim-reinforced nonwoven carrier geotextile (denoted as GCL2) and the other had a nonwoven carrier geotextile (GCL4). Tests were conducted with both restrained and unrestrained GCL specimens of the same size as well as restrained specimens with different specimen sizes and length-to-width aspect ratios. For unrestrained specimens, there was no apparent difference between shrinkage in the transverse and longitudinal directions for GCL2, whereas GCL4 tended to shrink more in the longitudinal direction. There was only a small difference between restrained and unrestrained tests, with the restrained specimens giving a maximum strain about 1.1 times higher than the unrestrained for GCL4. There was no clear effect of the specimen size on the measured shrinkage. For restrained specimens, shrinkage increased with increasing aspect ratio up to an aspect ratio of approximately 5. The dry mass per unit area of the product was found not to affect shrinkage when the mass per unit area was evenly distributed. However, specimens with an uneven bentonite distribution (typically those with a low mass per unit area) can have areas of little to no bentonite content, and these specimens experienced much higher shrinkage than other specimens. A high degree of variability between specimens for apparently similar test conditions was observed. Even more noteworthy is the fact that the maximum shrinkage observed in these tests (14.4%) was well below the maximum of 23% observed by previous investigators using the same methodology and nominally the same product. This shows the difference that can occur between different rolls of nominally the same product.

Three-dimensional nonwoven scaffolds from a novel biodegradable poly(ester amide) for tissue engineering applications

Biodegradable polyesters are established biomaterials in medicine due to their chemical characteristics and options for material processing. A main problem, however, is the release of acid degradation products during biodegradation with severe local pH-drops and inflammatory reactions. Polyesteramides, in contrast, show a less prominent pH-drop during degradation. In this study, we developed a simple, reproducible synthesis of the poly(ester amide) (PEA) type C starting from epsilon-caprolactame, 1,4-butanediol, and adipic acid in a one-batch two-step reaction and conducted the manufacturing of PEA-derived 3D textile scaffolds applicable for tissue engineering purposes. The thermal and mechanical properties of PEA-type C were analysed and the structural conformity of different batches was confirmed by NMR spectroscopy and size exclusion chromatography. The polymer was formed into nonwovens by textile manufacturing. Cytotoxicity tests and X-ray photoelectron spectroscopy (XPS) were used to analyze the effect of scaffold extraction before cell seeding. The manufactured carriers were seeded with human preadipocytes and examined for cellular proliferation and differentiation. The production of PEA type C successfully occurred via simultaneous ring-opening polymerization of epsilon-caprolactame and polycondensation with 1,4-butanediol and adipic acid at 250 degrees C under high-vacuum. Soxhlet extraction allowed optimal cleaning of nonwoven scaffolds. Extracted PEA-derived matrices were capable of allowing good adherence, proliferation, and differentiation of preadipocytes. These results are encouraging and guidance towards an optimally prepared nonwoven carrier applicable for clinical use.

Effect of GCL and subgrade type on internal erosion in GCLs under high gradients

GCLs incorporating different combinations and types of carrier geotextile and resting on three different subgrades are examined using a fixed-ring hydraulic conductivity apparatus. The results demonstrate that for GCLs with a conventional woven or nonwoven carrier geotextile and resting on a gravel or geonet, high hydraulic gradients can cause internal erosion within the GCL that can result in an increase in hydraulic conductivity of at least one order of magnitude. The method of GCL construction is shown to be important and GCLs with a scrim-reinforced nonwoven geotextile carrier layer performed better than those with a single light-weight (woven or nonwoven) geotextile carrier. The tests on GCLs with the scrim-reinforced geotextile carrier layer indicated that hydraulic gradients of up to 7000 (equivalent to about 70 m of water head) could be sustained without measurable internal erosion for the cases examined. When the GCLs were resting on a sand subgrade, all GCLs performed adequately (i.e. no evidence of internal erosion) in these tests with applied water heads of up to about 70 m.

Characterization of the Microbial Community in an Anaerobic Ammonium-Oxidizing Biofilm Cultured on a Nonwoven Biomass Carrier.

The enrichment and characterization of anaerobic ammonium-oxidizing biofilm cultures are ongoing in our laboratories. Biomass, with a predominately red color, demonstrating simultaneous removal of ammonium and nitrite under autotrophic and anoxic conditions, which is characteristic of anaerobic ammonium-oxidizing planctomycetes, was enriched and maintained for an extended period on a polyester nonwoven carrier. To investigate the bacterial composition of the mature biofilm community, 16S rDNA sequences were amplified by PCR and comparative analyses using DNA databases were conducted. Only one sequence had a notable similarity (92.2%) to that of the first discovered anaerobic ammonium-oxidizing planctomycete and lesser, yet significant, similarities to the 16S rDNA sequences of other recently reported anaerobic ammonium-oxidizing strains. The newly discovered strain (designated KSU-1) reported here was dominant among detectable members of the biofilm community. By fluorescence imaging, KSU-1 was shown to form spherical clusters wrapped in a thin layer of Zoogloea sp. Possible interactions and interdependencies of these two species are discussed with regard to the putative unculturability of the anaerobic ammonium-oxidizing planctomycetes.

Characterization of the microbial community in an anaerobic ammonium-oxidizing biofilm cultured on a nonwoven biomass carrier

The enrichment and characterization of anaerobic ammonium-oxidizing biofilm cultures are ongoing in our laboratories. Biomass, with a predominately red color, demonstrating simultaneous removal of ammonium and nitrite under autotrophic and anoxic conditions, which is characteristic of anaerobic ammonium-oxidizing planctomycetes, was enriched and maintained for an extended period on a polyester nonwoven carrier. To investigate the bacterial composition of the mature biofilm community, 16S rDNA sequences were amplified by PCR and comparative analyses using DNA databases were conducted. Only one sequence had a notable similarity (92.2%) to that of the first discovered anaerobic ammonium-oxidizing planctomycete and lesser, yet significant, similarities to the 16S rDNA sequences of other recently reported anaerobic ammonium-oxidizing strains. The newly discovered strain (designated KSU-1) reported here was dominant among detectable members of the biofilm community. By fluorescence imaging, KSU-1 was shown to form spherical clusters wrapped in a thin layer of Zoogloea sp. Possible interactions and interdependencies of these two species are discussed with regard to the putative unculturability of the anaerobic ammonium-oxidizing planctomycetes.

Influence of Different Biodegradable Carriers on the in Vivo Behavior of Human Adipose Precursor Cells

The correction of soft-tissue defects presents a challenge in plastic and reconstructive surgery. The implantation of isolated and culture-expanded adipose precursor cells is a solution to this problem because these cells differentiate into adipocytes when implanted in vivo. Appropriate scaffolds are needed in soft-tissue engineering to allow the differentiation of precursor cells. The optimal carrier needs to be defined. In this study, human preadipocytes were isolated and cultured. Three different carrier materials were seeded with 106 preadipocytes each and implanted in 42 nude mice. Sponges and nonwoven carriers based on hyaluronic acid modified by esterification (HYAFF 11) were compared with collagen sponges. Scaffolds without cells served as negative controls in the same animal. After 3 and 8 weeks, the grafts were explanted. Macroscopic appearance, weight, thickness, microscopy, immunohistochemistry, and TEM (scaffold structure, cellularity, penetration depth of the seeded cells, vascularization) were assessed and evaluated for differences in scaffold-cell interactions.Preadipocytes differentiated earlier in vitro when attached to HYAFF 11 scaffolds than to other carrier materials. Macroscopically, all preadipocyte constructs were yellowish and well vascularized, and the controls were white and avascular. Vessel formation was more pronounced around mature adipocytes. Microscopically, HYAFF 11 constructs showed a higher cell density than collagen constructs. The pores of the sponges contained more differentiated adipocytes than the nonwoven carriers, whereas the undifferentiated preadipocytes were more numerous in the nonwoven material. Penetration of adipose precursor cells was deeper and more homogeneous in HYAFF 11 scaffolds. Electron microscopy demonstrated well-differentiated adipocytes and large amounts of extracellular matrix in HYAFF 11 sponges.HYAFF 11 sponges supported the expansion and differentiation of the adipose precursor cells. This carrier is superior to the nonwoven carrier with regard to adipocyte differentiation and superior to the collagen sponge with regard to cellularity. This is a promising method for the reconstruction of soft-tissue defects. Modifications of the scaffold (larger pore size and coating with adipogenic factors) will be examined in further experiments.

Tensile Properties and Plane-Stress Fracture Toughness of Thin Film Aerospace Adhesives

Tensile and Mode I plane-stress fracture toughness tests were performed at room temperature on three film-type aerospace adhesives, two epoxies and one polyimide. Specimens were cut from cured sheets. Tensile modulus, strength, failure strain, and fracture toughness values were obtained for supported versions of the epoxy films which contained a non-woven carrier (“scrim”) cloth and for the polyimide which contained a woven carrier cloth. The same tensile and fracture properties were obtained for unsupported versions of the epoxies and for the supported polyimide subjected to thermal cycling or isothermal exposure. The polyimide adhesive displayed a higher tensile strength and fracture toughness than the epoxy adhesives. Isothermal exposure for 5,000 hours to a hot/wet (71°C [160°F], > 90% relative humidity [rh]) environment was the most detrimental condition for all of the adhesives. The presence of a scrim cloth reduced many of the tensile and fracture properties of the epoxy adhesives.

Effect of Growth Factors and Defined Medium on Primary Hepatocyte Culture on Polyester Carriers with Varying Surface Treatment

The growth and function of primary rat hepatocytes was characterized on commercial, electrostatically treated nonwoven polyester carriers (Fibra-Cel) designed for use in a packed-bed bioreactor. Such carriers are attractive in that they allow three-dimensional cellular interactions and afford shear protection. To initiate investigations of the potential of these carriers for hepatocyte support, novel hepatocyte media were evaluated along with a variety of carrier surface treatments in static cell culture. Different serum-free chemically defined media with recombinant growth factors known to be complete mitogens for hepatocytes were contrasted. Carrier treatments included unmodified surfaces contrasted with carriers coated with type I collagen or HepG2-derived extracellular matrix. Hepatocytes were also co-cultured with nonparenchymal cells. Cellular mitochondrial metabolism of 3-(4,5-dimethylthiozol- 2-yellow)-2,5 diphenyl tetrazolium bromide (MTT) was used to ascertain continued viability. Cell prolifera...