Solid Mat Research Articles

Symbiotic relationship between filamentous algae (Halomicronema sp.) and extracellular polymeric substance-producing algae (Chlamydomonas sp.) through biomimetic simulation of natural algal mats.

To lower the cost of biomass harvesting, the growth of natural biofilm is considered to be an optimal alternative to microalgae aggregation. This study investigated algal mats that naturally agglomerate into a lump and float on water surfaces. Halomicronema sp., a filamentous cyanobacterium with high cell aggregation and adhesion to substrates, and Chlamydomonas sp., which grows rapidly and produces high extracellular polymeric substances (EPS) in certain environments, are the main microalgae that make up selected mats through next-generation sequencing analysis. These two species play a major role in the formation of solid mats, and showed a symbiotic relationship as the medium and nutritional source, particularly owing to the large amount of EPS formed by the reaction between EPS and calcium ions through zeta potential and Fourier-transform infrared spectroscopy analysis. This led to the formation of an ecological biomimetic algal mat (BAM) that mimics the natural algal mat system, and this is a way to reduce costs in the biomass production process as there is no separate treatment process for harvesting.

Bending strength and stiffness of three-ply bolt-laminated mixed oak and hardwood industrial mats

Crane mats provide safe, stable, and flat work surfaces for heavy equipment and provide environmental protection. In this manuscript, two types of three-ply mats from two geographic regions were evaluated for stiffness and strength. Mats were sourced from the Southern USA and Midwestern USA in both solid configurations where the boards in all plies are touching and waffle configurations where gaps of approximately 1.8 inches were left between boards. Both types were mechanically fastened with regularly scheduled 3/8th inch diameter carriage bolts. The mats consisted of 1.5-inch-thick mixed oak and hardwood lumber oriented in a similar manner to plywood to form 4.5-inch-thick panels, each of which is 8 ft x 14 ft. Mats were prepped for testing by being ripped into strips 24 ± 4 inches wide. In this manner, 28 test specimens were developed from 7 parent mats. Mats were subjected to three-point bending tests. In both types of mats, the Southern-sourced specimens were statistically stronger and stiffer than those from the Midwest. Modulus of rupture (MOR) results showed that solid mats from the South were stiffer compared to waffle configurations produced in either location. The regression analysis indicated that modulus of elasticity could potentially estimate MOR.

Photocatalytic Activity of Cellulose Acetate Nanoceria/Pt Hybrid Mats Driven by Visible Light Irradiation.

A photocatalytic system for the degradation of aqueous organic pollutants under visible light irradiation is obtained by an innovative approach based on ceria/platinum (Pt) hybrid nanoclusters on cellulose acetate fibrous membranes. The catalytic materials are fabricated by supersonic beam deposition of Pt nanoclusters directly on the surface of electrospun cellulose acetate fibrous mats, pre-loaded with a cerium salt precursor that is transformed into ceria nanoparticles directly in the solid mats by a simple thermal treatment. The presence of Pt enhances the oxygen vacancies on the surface of the formed ceria nanoparticles and reduces their band gap, resulting in a significant improvement of the photocatalytic performance of the composite mats under visible light irradiation. Upon the appropriate pretreatment and visible light irradiation, we prove that the most efficient mats, with both ceria nanoparticles and Pt nanoclusters, present a degradation efficiency of methylene blue of 70% and a photodegradation rate improved by about five times compared to the ceria loaded samples, without Pt. The present results bring a significant improvement of the photocatalytic performance of polymeric nanocomposite fibrous systems under visible light irradiation, for efficient wastewater treatment applications.

Embedded Ceria Nanoparticles in Crosslinked PVA Electrospun Nanofibers as Optical Sensors for Radicals.

This work presents a new nanocomposite of cerium oxide (ceria) nanoparticles embedded in electrospun PVA nanofibers for optical sensing of radicals in solutions. Our ceria nanoparticles are synthesized to have O-vacancies which are the receptors for the radicals extracted from peroxide in water solution. Ceria nanoparticles are embedded insitu in PVA solution and then formed as nanofibers using an electrospinning technique. The formed nanocomposite emits visible fluorescent emissions under 430 nm excitation, due to the active ceria nanoparticles with fluorescent Ce3+ ionization states. When the formed nanocomposite is in contact with peroxide solution, the fluorescence emission intensity peak has been found to be reduced with increasing concentration of peroxide or the corresponding radicals through a fluorescence quenching mechanism. The fluorescence intensity peak is found to be reduced to more than 30% of its original value at a peroxide weight concentration up to 27%. This work could be helpful in further applications of radicals sensing using a solid mat through biomedical and environmental monitoring applications.

Fabrication of a Low Density Carbon Fiber Foam and Its Characterization as a Strain Gauge.

Samples of carbon nano-fiber foam (CFF), essentially a 3D solid mat of intertwined nanofibers of pure carbon, were grown using the Constrained Formation of Fibrous Nanostructures (CoFFiN) process in a steel mold at 550 °C from a palladium particle catalysts exposed to fuel rich mixtures of ethylene and oxygen. The resulting material was studied using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDX), Surface area analysis (BET), and Thermogravimetric Analysis (TGA). Transient and dynamic mechanical tests clearly demonstrated that the material is viscoelastic. Concomitant mechanical and electrical testing of samples revealed the material to have electrical properties appropriate for application as the sensing element of a strain gauge. The sample resistance versus strain values stabilize after a few compression cycles to show a perfectly linear relationship. Study of microstructure, mechanical and electrical properties of the low density samples confirm the uniqueness of the material: It is formed entirely of independent fibers of diverse diameters that interlock forming a tridimensional body that can be grown into different shapes and sizes at moderate temperatures. It regains its shape after loads are removed, is light weight, presents viscoelastic behavior, thermal stability up to 550 °C, hydrophobicity, and is electrically conductive.

Rhabdomyosarcoma of the clitoris

Hematol Oncol Stem Cell Ther 1(2) April 2008 hemoncstem.edmgr.com 133 Soft tissue sarcomas are the sixth most common malignancy in childhood and rhabdomyosarcot mas constitute about 50% of soft tissue sarcot mas. This tumor accounts for 10% to 15% of solid mat lignant tumors and 6% of all malignancies in children under 15 years of age. In the United States, the malet totfemale ratio is 1.5:1, and the tumor is twice as comt mon in whites as in AfricantAmericans. Approximately 250 new cases are diagnosed every year.1 Rhabdomyosarcoma is a malignant tumor of strit ated muscle but, because of its mesenchymal origin, can originate in tissue that does not normally contain striated muscle (for example, the ureter). There is a bit modal distribution of rhabdomyosarcoma with peaks between 2 and 4 years of age and 12 and 16 years of age. Nearly 80% of rhabdomyosarcoma is diagnosed by the age of 14 years. The most common primary sites for rhabdomyosarcomas include the head and neck, the genitourinary tract, and extremities. However, primary sites with a favorable prognosis include the orbit and nonparameningeal, head and neck, paratestis, the vat gina, and the biliary tract.2,3

The colonial ascidian Didemnum sp. A: Current distribution, basic biology and potential threat to marine communities of the northeast and west coasts of North America

Didemnum sp. A is a colonial ascidian with rapidly expanding populations on the east and west coasts of North America. The origin of Didemum sp. A is unknown. Populations were first observed on the northeast coast of the U.S. in the late 1980s and on the west coast during the 1990s. It is currently undergoing a massive population explosion and is now a dominant member of many subtidal communities on both coasts. To determine Didemnum sp. A's current distribution, we conducted surveys from Maine to Virginia on the east coast and from British Columbia to southern California on the west coast of the U.S. between 1998 and 2005. In nearshore locations Didemnum sp. A currently ranges from Eastport, Maine to Shinnecock Bay, New York on the east coast. On the west coast it has been recorded from Humboldt Bay to Port San Luis in California, several sites in Puget Sound, Washington, including a heavily fouled mussel culture facility, and several sites in southwestern British Columbia on and adjacent to oyster and mussel farms. The species also occurs at deeper subtidal sites (up to 81 m) off New England, including Georges, Stellwagen and Tillies Banks. On Georges Bank numerous sites within a 230 km 2 area are 50–90% covered by Didemnum sp. A; large colonies cement the pebble gravel into nearly solid mats that may smother infaunal organisms. These observations suggest that Didemnum sp. A has the potential to alter marine communities and affect economically important activities such as fishing and aquaculture.

On the ecology of Azolla filiculoidesLam. in Damietta district, Egypt

Azolla filiculoides Lam. is a tiny aquatic fern growing as free floating mats covering the stagnant water of the irrigation and drainage canals of Damietta district, Egypt. Ecological characteristics and distribution of the fern were investigated and results were discussed. Vegetation analysis of Azolla indicate that the most common associated species with Azolla are: Phragmites australis [presence (P) = 93.3%], Echinochloa stagnina (P = 70%), Eichhornia crassipes (P = 57%), Pluchea dioscoridis (P = 56.7%), Persicaria salicifolia (P = 26.7%), Phylla nodiflora (P = 13.3%) and Ludwigia stolonifera (P = 10%). Submerged species, e.g. Ceratophyllum spp. and Potamogeton spp. are completely absent in the stands dominated with solid mats of Azolla. This could be explained by that these mats prevent light penetration and oxygen which are required to submerged plants which in turn are decayed. The pH of the water where Azolla was recorded ranged from 7.1 to 9.0 (mean = 7.8), total dissolved salts ranged from 280 to 2600 mg/l (mean = 880 mg/l). The total phosphorus showed the range from 0.01 to 0.82 mg/l (mean = 0.22 mg/l). The ammonia-N is relatively high, varying from 2 to 18 mg/l (mean = 7.0 mg/l), however, the nitrate-N varied from 2.1 to 54.1 mg/l with a mean value of 20.5 mg/l. The fresh biomass of Azolla ranged from 114 to 4280 g/m 2 in irrigation canals and from 506 to 2760 g/m 2 in drainage canals. The dry biomass varied from 16 to 23 g/m 2 in irrigation canals. The range from 26 to 320 g/m 2 was obtained for drainage canals.

Nutrient partitioning in a clay-based surface flow wetland

A constructed, clay-based, surface flow wetland located in Byron Bay, New South Wales, Australia, was studied to determine the relative importance of living plant tissue, plant litter, sediment, and the water column as nutrient stores. The nitrogen, phosphorus and carbon contents of each nutrient compartment were determined throughout the wetland. The nitrogen and phosphorus content of the plants was higher at the inlet end of the wetland and declined with distance away from it. Nutrient levels in the sediment and water column did not vary significantly with distance through the wetland. Phosphorus concentrations in the sediments were high, but plants were shown to be responsible for the majority of nutrient accumulation from this system. The plants had failed to penetrate the clay substrate and a solid mat of adventitious roots had developed in the overlying water. In essence the plants, mainly grasses, were growing hydroponically.

Nutrient partitioning in a clay-based surface flow wetland

A constructed, clay-based, surface flow wetland located in Byron Bay, New South Wales, Australia, was studied to determine the relative importance of living plant tissue, plant litter, sediment, and the water column as nutrient stores. The nitrogen, phosphorus and carbon contents of each nutrient compartment were determined throughout the wetland. The nitrogen and phosphorus content of the plants was higher at the inlet end of the wetland and declined with distance away from it Nutrient levels in the sediment and water column did not vary significantly with distance through the wetland. Phosphorus concentrations in the sediments were high, but plants were shown to be responsible for the majority of nutrient accumulation from this system. The plants had failed to penetrate the clay substrate and a solid mat of adventitious roots had developed in the overlying water. In essence the plants, mainly grasses, were growing hydroponically.

Resource Allocation and Demography of Sexual and Apomictic Antennaria Parlinii

Survivorship and allocation to seed and ramets of sexual and apomictic Antennaria parlinii were studied to determine whether these forms differed in colonizing and competitive ability. Apomictic plants produced more seeds per inflorescence, but their mean mass per seed was lower compared to sexual plants. However, because sexual seedling survivorship was higher than that of apomictic seedlings, the estimated numbers of offspring recruited, when male seedlings were included, were not different. Thus the primary difference in colonizing ability between sexuals and apomicts appears to be in the potential for dispersal provided by the greater number of lighter seeds produced by apomictic plants. The pattern of allocation to ramet production, one indication of potential competitive ability, was different among males, females, and apomicts. In general, both mean length of a stolon and total stolon length per plant were lower in apomicts than in males and females. Apomicts also had the highest frequency of ramet mortality, while males had the lowest. This pattern of ramet production in sexuals results in a growth form of a solid mat of long—lived, wandering stolons. Males consistently had the lowest mortality and also the highest total allocation to ramet production. Although all of an apomict's offspring bear the costs of maternity, the sons of a sexual female do not. Therefore, sexuality may be advantageous in competitive environments because of the higher adult survivorship and increased opportunity for future reproduction in those offspring that can reproduce as males.

The mechanical and structural response of skin to irradiation

Fracture of the fibrous networks of normal and irradiated rat dermis have been studied using the SEM. The implications of these observations are discussed with regard to the mechanical behaviour of the tissue in the living animal. It is shown that after radiation the normal fibrous structure of collagen is replaced by a solid mat which is ill adapted to support stress, so that rupture at low stress levels is inevitable.