LYOCELL AND COTTON FIBERS AS REINFORCEMENTS FOR A THERMOSET POLYMER

Cellulose fibers obtained from the textile industry (lyocell) were investigated as a potential reinforcement for thermoset phenolic matrices, to improve their mechanical properties. Textile cotton fibers were also considered. The fibers were characterized in terms of their chemical composition and analyzed using TGA, SEM, and X-ray. The thermoset (non-reinforced) and composites (phenolic matrices reinforced with randomly dispersed fibers) were characterized using TG, DSC, SEM, DMTA, the Izod impact strength test, and water absorption capacity analysis. The composites that were reinforced with lyocell fibers exhibited impact strengths of nearly 240 Jm(-1), whereas those reinforced with cotton fibers exhibited impact strengths of up to 773 Jm(-1). In addition to the aspect ratio, the higher crystallinity of cotton fibers compared to lyocell likely plays a role in the impact strength of the composite reinforced by the fibers. The SEM images showed that the porosity of the textile fibers allowed good bulk diffusion of the phenolic resin, which, in turn, led to both good adhesion of fiber to matrix and fewer microvoids at the interface.

Soil properties in a sugarcane plantation after the application of treated sewage effluent and phosphogypsum in Brazil

In a field experiment performed in Lins County (Sao Paulo State, Brazil), treated sewage effluent (TSE) irrigation increased sugarcane yield but caused an excessive increase in the exchangeable sodium percentage (ESP) and clay dispersion after 16 months due to an intense irrigation regime (2500 mm/16 months) with sodium rich effluents. After two additional complete cycles with lower TSE irrigation rates (1200 mm year(-1)), 1700 kg ha(-1) of phosphogypsum was added to a section of the irrigated plots to evaluate its residence time and its implications on Na+ dynamics and other soil properties. Undisturbed soil cores were taken 2 years after phosphogypsum application to verify soil physical properties up to 0.2 m depth, and disturbed soil samples were taken every year up to 1 m depth for chemical analyses. After 5 years of consecutive TSE irrigation (2005-2010), soil acidity (pH approximate to 5) and basic cations (Ca approximate to 12, Mg approximate to 6 and K approximate to 2 mmol(c) kg(-1)) were maintained in adequate conditions for plant development without the necessity of liming, while acidity was increased (pH approximate to 4.5) and Ca (approximate to 9 mmol(c) kg(-1)), and the Mg (approximate to 4.5 mmol(c) kg(-1)) concentration decreased in the rainfed without phosphogypsum treatment. An increase in water retention capacity at -30 (from 0.14 to 0.17 m(3) m(-3)) and -1500 kPa (from 0.08 to 0.12 m(3) m(-3)) potentials was also observed in all TSE irrigated treatments. The plots with a phosphogypsum treatment showed average increases of 2 mmol(c) kg(-1) of Ca2+ and 7 mg kg(-1) of S-SO42- in all soil profiles and an average reduction of 2 mmol(c) kg(-1) of Na+ up to 0.4 m from 2008 to 2009. However, the extent of the chemical effects was greater after the first year compared to the second year. The high concentration of Na+ found in previous studies performed in the same area returned to low concentrations after continued TSE irrigation at lower rates, even without the phosphogypsum application. An unusual phosphorus migration was observed to the 0.4-0.8 m soil layer as a result of TSE irrigation, most likely due to a high pH and a Na carbonate-dominated TSE. (C) 2012 Elsevier B.V. All rights reserved.

Mechanical Performance of Cylindrical and Dual-Core Pedicle Screws After Repeated Insertion

Study Design. Ex vivo study of the mechanical performance of cylindrical and dual-core pedicle screws after insertion, removal, and reinsertion in the same hole. Objective. To evaluate the effect of repeated use of same screw hole on the insertion torque and the retentive strength of the cylindrical and dual-core screws. Summary of Background Data. Insertion and removal of pedicle screws is sometimes necessary during surgical procedure to assess the integrity of the pilot-hole wall. However, this maneuver may compromise the implant-holding capacity. Methods. Sixty thoracolombar vertebrae (T13-L5), harvested from 10 healthy calves, were used to insert 2 different designs of pedicle screws: cylindrical (5.0-mm outer diameter) and dual-core screws (5.2-mm outer diameter). Three experimental groups were created on the basis of the number of insertions of the screws and 2 subgroups were established according to the core pedicle screw design (dual-core and cylindrical). The insertion torque was measured during initial insertion, second insertion, and third insertion. Pullout screw tests were performed using a universal testing machine to evaluate the pullout strength after initial insertion, second insertion, and third insertion. Results. Significant reductions of 38% in mean insertion torque and 30% in mean pullout strength of dual-core screw were observed between the initial insertion and the third insertion. The cylindrical screw observed significant reductions of 52.5% in mean insertion torque and 42.3% in mean pullout strength between the initial insertion and the third insertion. A reduction of mean insertion torque and pullout strength between the first insertion and the second insertion but without significance was also observed for both types of screws. Conclusion. Insertions and reinsertion of either cylindrical or dual-core pedicle screws have compromised insertion torque and pullout strength of the implants as measured by mechanical tests.

Soil compressibility and least limiting water range of a constructed soil under cover crops after coal mining in Southern Brazil

The use of cover crops affects the support capacity of soil and least limiting water range to crop growth. The objective of this study was to quantify preconsolidation pressure (sigma(p)), compression index (CI) and least limiting water range (LLWR) of a reclaimed coal mining soil under different cover crops, in Candiota, RS, Brazil. In the experiment, with randomized blocks design and four replicates, the following cover crops (treatments) were evaluated: Hemarthria altissima (Poir.) Stapf & C.E. Hubbard, treatment 1 (T1), Paspalum notatum Flugge, treatment 4 (T4), Cynodon dactilon (L) Pers., treatment 5 (T5), control Brachiaria brizantha (Hochst.) Stapf, treatment 7 (T7) and without cover crop treatment 8 (reference treatment, T8). Soil compression and least limiting water range were evaluated with undisturbed samples at a depth of 0.00-0.05 m. In order to evaluate parameters of soil compressibility, the soil samples were saturated with water and subjected to -10 kPa matric potential and then submitted to a uniaxial compression test under the following pressures: 25, 50, 100, 200, 400, 800 and 1600 kPa. Cover crops decreased the preconsolidation pressure of constructed soils after coal mining and the greatest soil reclamation was obtained with the H. altissima cover crop, where the lowest degree of soil compactness and soil load capacity were observed. Soils cultivated under H. altissima or B. brizantha presented the highest least limiting water range and these two cover crops generated similar soil critical bulk density obtained by least limiting water range and soil load support capacity. (C) 2012 Elsevier B.V. All rights reserved.

Both the dorsal hippocampus and the dorsolateral striatum are needed for rat navigation in the Morris water maze

The multiple memory systems theory proposes that the hippocampus and the dorsolateral striatum are the core structures of the spatial/relational and stimulus-response (S-R) memory systems, respectively. This theory is supported by double dissociation studies showing that the spatial and cue (S-R) versions of the Morris water maze are impaired by lesions in the dorsal hippocarnpus and dorsal striatum, respectively. In the present study we further investigated whether adult male Wistar rats bearing double and bilateral electrolytic lesions in the dorsal hippocampus and dorsolateral striatum were as impaired as rats bearing single lesions in just one of these structures in learning both versions of the water maze. Such a prediction, based on the multiple memory systems theory, was not confirmed. Compared to the controls, the animals with double lesions exhibited no improvement at all in the spatial version and learned the cued version very slowly. These results suggest that, instead of independent systems competing for holding control over navigational behaviour, the hippocampus and dorsal striatum both play critical roles in navigation based on spatial or cue-based strategies. (C) 2011 Elsevier B.V. All rights reserved.

Gender Effect on Oral Volume Capacity

Studies have shown anatomical and functional differences between men and women with respect to the mouth, pharynx, upper esophageal sphincter, and esophagus. The aim of this investigation was to analyze the influence of gender, body mass index (BMI), age, and orofacial anthropometric measurements on the intraoral maximum volume capacity for liquid. The investigation included asymptomatic subjects, 56 females and 44 males, aged 19-53 years. The volunteers sucked water through a straw up to the maximum tolerated oral volume, which was greater in men (71.2 +/- A 15.0 ml) than in women (55.4 +/- A 13.4 ml). Age, BMI, height, and number of teeth had no influence on the intraoral tolerated volume. Anthropometric orofacial measurements were greater in men than in women. In individuals with height between 1.66 and 1.89 m, anthropometric orofacial measurements were greater in men than in women, and the tolerated intraoral volume was greater in men than in women. There was a positive correlation between orofacial measurements and intraoral maximum volume. In conclusion, men have the capacity to place a larger volume of water inside their mouth than women. This observation is associated with higher anthropometric orofacial measures, but not with age, number of teeth, height, or BMI.