Influence of number and position of porcelain specimens in the furnace on flexural strength and translucency

The aim of this study was to investigate the influence of the quantity and positioning of feldspathic ceramic specimens inside the furnace on their flexural strength and translucency. The tested hypotheses were that the arrangement of specimens in the furnance would not influence 1) the translucency or 2) the biaxial strength of the porcelain. Methods: Ninety porcelain specimens were made (1.2 mm thickness and 13.5 mm diameter) and assigned into two main groups (n=15): G1 group - 15 firing cycles containing only one specimen each, always at the center of the refractory; and G5 group - 15 firing cycles containing five specimen each, where one specimen was at the center of the refractory and four specimens positioned equidistantly on the periphery. The translucency test was performed using a spectrophotometer, followed by the flexural strength test, according to ISO 6872:2015. T-student test was performed for both the mechanical and optical obtained data. Results: The flexural strength of the porcelain was not affected by the positioning (center x periphery) of the specimens inside the furnace (p =0.08), but the translucency was affected (periphery > center; p =0.009). Regarding to the number of feldspathic ceramic specimens, the biaxial flexural strength was affected (p =0.025), as well as the translucency (p <0.05). Conclusion: A higher quantity of feldspathic ceramic specimens for each firing cycle decreased its biaxial flexural strength and translucency. Also, specimens positioned at the center of the refractory became less translucent than those positioned at the periphery.

Effect of sulfonated block copolymer on the equilibrium and thermal properties of sulfonated fluoroblock copolymer blend membrane / Efecto del copolímero en bloque sulfonado sobre las propiedades térmicas y de equilibrio de una membrana sulfonada mezclada con un fluoropolímero en bloque

Polymeric membrane technologies demand the synthesis of new polymers to enhance their equilibrium, thermal, and transport properties. Therefore, the focus of this investigation was the evaluation of the equilibrium and thermal properties of a sulfonated fluoroblock copolymer blend membrane composed of sulfonated poly(styre-ne-isobutylene-styrene) (SIBS SO3H) and a novel sulfonated fluoroblock copolymer composed of poly(4-fluo-rostyrene) (P4FS), poly(styrene) (PS) and poly(isobutylene) (PIB). The fluoroblock copolymer was synthesized using Atom Transfer Radical Polymerization (ATRP) and cationic polymerization. First, the molecular weight and the thermal stability of the block copolymer were determined using Gel Permeation Chromatography (GPC) and Thermogravimetric Analysis (TGA). Second, the chemical composition was monitored utilizing Fourier Transform Infrared spectroscopy (FTIR) and Nuclear Magnetic Resonance (NMR) spectroscopy. The molecular weight of P4FS-b-PS was Mn ~ 36,100; this value increased 8% after the cationic polymerization. The equilibrium properties of the membrane were evaluated using the water uptake and Ion-Exchange Capacity. The degradation behavior and the thermal transitions were determined using TGA and Differential Scanning Calorimetry (DSC), respectively. This newly membrane exhibited water uptake higher than 608% related to the improvement of 36% in the ion-exchange capacity and the increment of 25.31% and 25.24% in the energy required to produce the thermal transitions induced by the addition of the sulfonated fluoroblock copolymer.

La tecnología de membranas poliméricas requiere de la síntesis de nuevos polímeros que mejoren sus propiedades de equilibrio, térmicas y de transporte. Esta investigación tuvo como objetivo determinar las pro-piedades de equilibrio y térmicas de una membrana compuesta de poli(estireno-isobutileno-estireno) sulfonado (SIBS SO3H) y un fluoropolímero en bloque sulfonado compuesto de poli(4-fluorostireno) (P4FS), poli(estireno) (PS) y poli(isobutileno) (PIB). El fluoropolímero en bloque se sintetizó utilizando la técnica de polimerización radical por transferencia atómica (ATRP por sus siglas en inglés) y polimerización catiónica. El peso molecular y la estabilidad térmica del fluoropolímero en bloque fueron determinadas por medio de Cromatografía de Permeación en Gel (GPC) y un análisis termogravimétrico (TGA). La composición química se monitorizó utilizando espectroscopía infrarroja por transformada de Fourier (FTIR) y espectroscopía de Resonancia Magnética Nuclear (RMN). El peso molecular de P4FS-b-PS fue Mn ~ 36,100; este valor aumentó un 8% después de la polimerización catiónica. Las propiedades de equilibrio de la membrana fueron evaluadas por medio de la absorción de agua y la capacidad de intercambio iónico. El comportamiento de degradación y las transiciones térmicas se determinaron utilizando TGA y Calorimetría Diferencial de Barrido (DSC). Esta nueva membrana exhibió una absorción de agua mayor del 608% relacionada con la mejora del 36% en la capacidad de intercambio iónico y el incremento en 25.31% y 25.24% en la energía requerida para producir las transiciones termales inducidas por la adición del fluoropolímero sulfonado en bloque.

Influence of third cemetery location on the quality of domestic and groundwater resources in Benin City, Nigeria

ABSTRACT: The present study investigates impact of burial practices on water quality in Benin City, Nigeria by collecting groundwater samples from boreholes located by the peripheral area of Third Cemetery in Benin City and a reference site approximately 4 km away using standard methods. With the exception of SO4, CaCO3, Fe and DO, the concentrations of other parameters were higher in water samples obtained from the peripheral area of Third Cemetery than that from the reference site. Principal component analysis (PCA) revealed that pH, Fe, and CaCO3 were differentiating parameters related to reference site, similar condition was attributed to SO4 and Mg for site 2 and Pb, Mn, Cu, Ni, Zn and DO for sites 1 & 3. Cluster analysis (CA) placed the reference site as outlier to other sites. Higher concentrations of Cl, NO3, Na, K and BOD5 in samples obtained by cemetery peripheral when compared to reference site and positive correlations among these parameters are indications of impacts of decomposing activities in cemetery upon water quality in underlying aquifer. Limiting water quality index (WQI) computation to pH, EC, Cl, NO3, SO4, Na and BOD5 showed that quality of groundwater obtained from cemetery peripheral is not good for domestic uses

Qualitative assessment of some available water resources in Efon-Alaaye, Ekiti State Nigeria

ABSTRACT: As water is a major life sustainer, hence its portability is of great importance in performing that role well. In this study, various water samples were collected within Efon-Alaaye for both physicochemical and bacteriological tests. A total of nine (9) water samples were taken for analysis with six (6) from various surface sources and three (3) from groundwater sources in the study area. The mean turbidity value, temperature, total dissolved solids (TDS) concentration, hardness and EC are 2.92 NTU, 23°C, 447.8 mg/l, 48.1 mg/l and 138.4 µS/cm respectively. Manganese has mean value of 0.27 mg/l. The concentration of both copper and zinc ranges from 0.07 ­ 0.13 mg/l and 0.16 ­ 0.55 mg/l with an average value of 0.04 mg/l and 0.28 mg/l respectively. Water samples collected were also analyzed for total coliform bacteria and ranged from 1 to 4.6/100 ml with an average value of 3.29 colony/100 ml. On the basis of findings, the physico-chemical analysis reveals that some of the water samples were above the WHO standards for parameters like turbidity and TDS while the bacteriological test reveals that seven (7) of the water samples considered met the WHO requirement of portability while the other two samples contain faecal contaminant as E.coli was discovered, though at reasonable rate

Water sorption and solubility of bulk-fill composites polymerized with a third generation LED LCU

Abstract The aim of this study was to compare the degree of water sorption and solubility in bulk-fills after curing with a polywave light source. A total of 120 disc-shaped specimens (8 mm diameter; 4 mm depth) were prepared from three regular bulk-fill materials (X-tra Fil, Tetric N-Ceram Bulk Fill, SonicFill), and a control material (Filtek Z250), cured in 3 different modes (standard: 1000 mW/cm2-20 s; high power: 1400 mW/cm2-12 s; xtra power: 3200 mW/cm2-6 s) using a third generation light-emitting diode light curing unit. Water sorption and solubility levels of the specimens were measured according to the ISO 4049:2009 specification after storing in distilled water for 30 days. Data were analyzed using two-way ANOVA and Tukey's post-hoc test (p < 0.05). The Z250 sample exposed to high power presented a higher sorption compared to the X-tra Fil and SonicFill samples. In xtra power mode, the values of Z250 and SonicFill were similar to each other and higher compared to those of X-tra Fil. Only SonicFill exhibited significantly different sorption values depending on the curing mode, the highest of which was achieved when using the xtra power mode. The highest solubility values were obtained for SonicFill. No statistically significant differences were found among other groups. No significant correlation was detected between water sorption and solubility. The traditional composite group exhibited a higher water sorption values than the bulk-fills. The reduction in polymerization time significantly increased the sorption of SonicFill. SonicFill showed the highest water solubility value among the composites tested.

In vitro response of date palm (Phoenix dactylifera L) to K/Na ratio under saline conditions

BACKGROUND: Salinity is a serious factor limiting the productivity of agricultural plants. One of the potential problems for plants growing under saline conditions is the inability to up take enough K+. The addition of K+ may considerably improve the salt tolerance of plants grown under salinity. It is assumed that increasing the K+ supply at the root zone can ameliorate the reduction in growth imposed by high salinity. The present study aims to determine whether an increase in the K/Na ratio in the external media would enhance the growth of date palm seedlings under in vitro saline conditions. METHODS: Date palm plants were grown at four concentrations of Na + K/Cl (mol/m³) with three different K/Na ratios. The 12 salt treatments were added to modified MS medium. The modified MS medium was further supplemented with sucrose at 30 g/l. RESULTS: Growth decreased substantially with increasing salinity. Growth expressed as shoot and root weight, enhanced significantly with certain K/Na ratios, and higher weight was maintained in the presence of equal K and Na. It is the leaf length, leaf thickness and root thickness that had significant contribution on total dry weight. Na+ contents in leaf and root increased significantly increased with increasing salinity but substantial decreases in Na+ contents were observed in the leaf and root with certain K/Na ratios. This could be attributed to the presence of a high K+ concentration in the media. The internal Na+ concentration was higher in the roots in all treatments, which might indicate a mechanism excluding Na+ from the leaves and its retention in the roots. K/Na ratios up to one significantly increased the leaf and root K+ concentration, and it was most pronounced in leaves. The K+ contents in leaf and root was not proportional to the K+ increase in the media, showing a high affinity for K+ uptake at lower external K+ concentrations, but this mechanism continues to operate even with high external Na+ concentrations. CONCLUSION: Increasing K/Na ratios in the growing media of date plam significantly reduced the absorption of Na+ less than 200 mM and also balance ions compartmentalization.

Seed germination of Agave species as influenced by substrate water potential

BACKGROUND: Plants of Agave spp. perform Crassulacean acid metabolism (CAM) and are highly drought-tolerant, but little is known concerning seed germination under low water availability. The aim of this study was to assess the effect of substrate water potential (ΨW) on seed germination and contrast hydrotime parameters of seven valuable and commercially-important Agave species from different geographical distributions and climatic regions of Mexico. Our hypothesis was that seed germination of Agave species is not affected by low water availability independently of seed biomass and the climate of their distribution area. RESULTS: Seed germination (at 25°C and in the dark) between 85 and 100% for all species occurred within 80 - 180 h at -0.03 MPa and 250 - 430 h at -1.0 MPa. Seed germination at -1.5 MPa declined to less than 50% (p < 0.05) for A. asperrima and A. cupreata but did not change significantly for A. americana var. marginata, A. lechuguilla and A. striata, although they showed the lowest mean base water potential (-2.01 to -2.64 MPa). Seed germination of 40% Agave species, from arid and semi-arid climates in this study, was not affected by the lower ΨW. CONCLUSION: Germination of seeds of Agave species is moderately affected by low water availability, is partially dependent of their ecological distribution, and is independent of seed mass.

Modification by wheat germ agglutinin delays the ocular elimination of liposome / 药学学报

The purpose of this study is to explore the feasibility of wheat germ agglutinin (WGA) modified liposome as a vehicle for ophthalmic administration. Liposome loaded with 5-carboxyfluorescein (FAM) was prepared by lipid film hydration method. WGA was thiolated and then conjugated to the surface of the liposome via polyethylene glycol linker to constitute the WGA-modified and FAM-loaded liposome (WGA-LS/FAM). The amount of thiol groups on each WGA molecule was determined, and the bioactivity of WGA was estimated after it was modified to the surface of liposome. The physical and chemical features of the WGA-modified liposome were characterized and the ocular bioadhesive performance was evaluated in rats. The result showed that each thiolated WGA molecule was conjugated with 1.32 thiol groups. WGA-LS/FAM had a mean size of (97.40 +/- 1.39) nm, with a polydispersity index of 0.23 +/- 0.01. The entrapment efficacy of FAM was about (2.95 +/- 0.21)%, and only 4% of FAM leaked out of the liposome in 24 h. Erythrocyte agglutination test indicated that after modification WGA preserved the binding activity to glycoprotein. The in vivo ocular elimination of WGA-LS/FAM fitted first-order kinetics, and the elimination rate was significantly slower than that of the unmodified liposome, demonstrating WGA-modified liposome is bioadhesive and suitable for ophthalmic administration.

Resposta do feijão-caupi à doses e formas de aplicação de fósforo em Latossolo Amarelo do Estado de Roraima / Response of cowpea (Vigna unguiculata (L. ) Walp. ) to phosphorus fertilization levels and application forms in Yellow Latosol of Roraima State/Brazil

A adubação fosfatada e as formas de aplicação de fertilizantes fosfatados são fatores importantes no manejo das culturas. O objetivo do presente trabalho foi avaliar os efeitos de doses de fósforo e formas de aplicação de fertilizante fosfatado na cultura do feijão-caupi (Vigna unguiculata (L.) Walp) em solo de cerrado do Estado de Roraima. O experimento foi realizado em condições de campo, em Latossolo Amarelo distrocoeso, no Campus do Cauamé da Universidade Federal de Roraima. O delineamento experimental foi o de parcelas subdivididas, com as parcelas principais organizadas em blocos casualizados, com três repetições. As parcelas foram constituídas pelas formas de aplicação do fertilizante fosfatado: a) Lanço - L; b) Sulco simples - SS e c) Sulco duplo - SD. As subparcelas corresponderam às doses da adubação fosfatada: 0; 0,5; 1,0; 1,5 e 2,0 vezes a dose recomendada para adubação de manutenção do feijão-caupi. Houve efeito das doses de fósforo sobre o crescimento e absorção de fósforo pelas plantas. O maior crescimento, produção de vagem por planta, de grãos e absorção de fósforo ocorreu com a aplicação do fertilizante fosfatado aplicado em sulcos duplos.

Phosphorus fertilization and ways of phosphate fertilizers application are important factors considering crop management. This study aimed at assessing the effect of phosphorus rates and phosphate fertilizers application forms on growth and phosphorus uptake of cowpea plants cropped on cerrado soil in the State of Roraima, Brazil. An experiment took place under field conditions, on a Yellow Latosol, at Cauamé Campus of Roraima's Federal University, located in the municipality of Boa Vista/RR. The experimental design was split-plot, in a completely randomized blocks, with three replicates. The plots consisted of the following phosphoric fertilizers application forms: a) broadcasting; b) single furrow and c) double furrow. Sub-plots corresponded to phosphorus doses: 0, 0,5; 1,0; 1,5, and 2,0 times the recommended dose for cowpea maintenance fertilization (60 kg ha-1 of P2O5). There was a significant effect of P rates over plant growth and plant uptake. Application of fertilizer in double furrows promoted higher plant growth, grain yield, and plant phosphorous uptake.