Analysis of groundwater-level response to rainfall and recharge estimates in fractured hard rock aquifers, NW Ireland

Despite fractured hard rock aquifers underlying over 65% of Ireland, knowledge of key processes controlling groundwater recharge in these bedrock systems is inadequately constrained. In this study, we examined 19 groundwater-level hydrographs from two Irish hillslope sites underlain by hard rock aquifers. Water-level time-series in clustered monitoring wells completed at the subsoil, soil/bedrock interface, shallow and deep bedrocks were continuously monitored hourly over two hydrological years. Correlation methods were applied to investigate groundwater-level response to rainfall, as well as its seasonal variations. The results reveal that the direct groundwater recharge to the shallow and deep bedrocks on hillslope is very limited. Water-level variations within these geological units are likely dominated by slow flow rock matrix storage. The rapid responses to rainfall (⩽2 h) with little seasonal variations were observed to the monitoring wells installed at the subsoil and soil/bedrock interface, as well as those in the shallow or deep bedrocks at the base of the hillslope. This suggests that the direct recharge takes place within these units. An automated time-series procedure using the water-table fluctuation method was developed to estimate groundwater recharge from the water-level and rainfall data. Results show the annual recharge rates of 42–197 mm/yr in the subsoil and soil/bedrock interface, which represent 4–19% of the annual rainfall. Statistical analysis of the relationship between the rainfall intensity and water-table rise reveal that the low rainfall intensity group (⩽1 mm/h) has greater impact on the groundwater recharge rate than other groups (>1 mm/h). This study shows that the combination of the time-series analysis and the water-table fluctuation method could be an useful approach to investigate groundwater recharge in fractured hard rock aquifers in Ireland.

Rock slope risk analysis based on non-linear failure criterion

The probability of failure of a rock slope is generally estimated by using the Limit Equilibrium Method (LEM) in conjunction with a reliability analysis. Although the LEM is relatively simple and time efficient, recent studies have indicated that using the LEM may overestimate the factor of safety by 21%, when based on a non-linear failure criterion. Fortunately, the solutions presented by Li et al. (2008, 2009) can provide more accurate evaluations for rock slope stability as the numerical upper and lower bound limit analysis methods (2002a, 2002b, 2005) were employed. The advantages of these methods are used in this study to assess the rock slope probability of failure. The motivation is that with more accurate methods to evaluate the factor of safety, more economic designs can be performed.

Analysis of the efficiency of silicate clay on the control of Xanthomonas axonopodis PV. passiflorae in vitro and in seedlings of yellow passion fruit contaminated

The bacterial spot in yellow passion fruit plants, caused by the bacteria Xanthomonas axonopodis pv. passiflorae, occurs in all producing areas of the country, and is responsible for great economic losses in the culture of passion fruit. This study aimed to test the efficiency of the silicate clay in the inhibition of the bacteria Xanthomonas axonopodis pv. passiflorae in vitro, and in both preventive and curative control of the bacterial spot in seedlings of yellow passion fruit plants. The silicate clay was added to the growth medium at concentrations of. 0.5, 1.0, 1.5 and 2.0%, placed in Petri dishes. After the culture medium was cooler, the bacterial suspension was inoculates (10(7) UFC.mL(-1)) with a handle, and left incubating at 28 degrees C for three days, and then the bacterial growth was evaluated. Subsequently, the product at the same concentrations above was sprayed on seedlings of 'Afruvec' passion fruit, as preventive or curative. The inoculation of the bacteria was made by foliar spraying of bacterial suspension (10(7) ufc.mL(-1)), 24 hours before or after the curative and preventive treatments, respectively. The severity of the disease was measured comparing each four true leaves from bottom up, with a diagrammatic scale. In the concentrations evaluated, the silicate clay inhibited both bacteria in vitro and symptoms of bacterial spot in the curative treatment. In preventive treatment, significant results were obtained using more than 1.0% of clay silicates. Based on these results, the clay silicate can be recommended, the concentration of 1.0-2.0% for the control of bacterial spot of passion fruit plants, in foliar sprays.

Comparative in vivo study of commercially pure Ti implants with surfaces modified by laser with and without silicate deposition: Biomechanical and scanning electron microscopy analysis

The purpose of this study was to evaluate commercially pure titanium implant surfaces modified by laser beam (LS) and LS associated with sodium silicate (SS) deposition, and compare them with machined surface (MS) and dual acid-etching surfaces (AS) modified. Topographic characterization was performed by scanning electron microscopy-X-ray energy dispersive spectroscopy (SEM-EDX), and by mean roughness measurement before surgery. Thirty rabbits received 60 implants in their right and left tibias. One implant of each surface in each tibia. The implants were removed by reverse torque for vivo biomechanical analysis at 30, 60, and 90 days postoperative. In addition, the surface of the implants removed at 30 days postoperative was analyzed by SEM-EDX. The topographic characterization showed differences between the analyzed surfaces, and the mean roughness values of LS and SS were statistically higher than AS and MS. At 30 days, values removal torque LS and SS groups showed a statistically significant difference (p < 0.05) when compared with MS and AS. At 60 days, groups LS and SS showed statistically significant difference (p < 0.05) when compared with MS. At 90 days, only group SS presented statistically higher (p < 0.05) in comparison with MS. The authors can conclude that physical chemistry properties and topographical of LS and SS implants increases bone-implant interaction and provides higher degree of osseointegration when compared with MS and AS. © 2012 Wiley Periodicals, Inc.

Analysis of implants with laser irradiated surface and silicate deposition

Objectives: the purpose of this study was to evaluate the surfaces of commercially pure titanium (cpTi) implants surface modified by laser beam (LS), by laser beam associated with sodium silicate deposition (SS) and compare them with surfaces modified by dual-acid etched (AS) and with machined surface (MS). Methods: thirty rabbits received two implants each (one for each tibia). After 30, 60 and 90 days postoperative, the implants were removed by reverse torque for biomechanical analysis and surfaces were analyzed by scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS). Results: the mean values of reverse torque at 30, 60 and 90 days postoperative were respectively 24.60, 43.60 e 60.40 N.cm to MS, 43.00, 68.20 e 63.80 N.cm to AS group, 59.80, 76.60 e 78.00 N.cm to LS group and 63.00, 75.40 e 76.60 N.cm to SS group. At 30 days, LS and SS groups showed statistically significant difference (p<0.05) compared to the other groups. At 60 days, LS and SS groups showed statistically significant difference (p<0.05) when compared to MS. Conclusions: it was concluded that SL and SS implants' biomechanical and topographical properties increased bone-implant interaction when compared to the AS and MS implants.

Analysis of the color alteration and radiopacity promoted by bismuth oxide in calcium silicate cement

The aim of the study was to determine if the increase in radiopacity provided by bismuth oxide is related to the color alteration of calcium silicate-based cement. Calcium silicate cement (CSC) was mixed with 0%, 15%, 20%, 30% and 50% of bismuth oxide (BO), determined by weight. Mineral trioxide aggregate (MTA) was the control group. The radiopacity test was performed according to ISO 6876/2001. The color was evaluated using the CIE system. The assessments were performed after 24 hours, 7 and 30 days of setting time, using a spectrophotometer to obtain the ΔE, Δa, Δb and ΔL values. The statistical analyses were performed using the Kruskal-Wallis/Dunn and ANOVA/ Tukey tests (p < 0.05). The cements in which bismuth oxide was added showed radiopacity corresponding to the ISO recommendations ( > 3 mm equivalent of Al). The MTA group was statistically similar to the CSC / 30% BO group (p > 0.05). In regard to color, the increase of bismuth oxide resulted in a decrease in the ΔE value of the calcium silicate cement. The CSC group presented statistically higher ΔE values than the CSC / 50% BO group (p < 0.05). The comparison between 24 hours and 7 days showed higher ΔE for the MTA group, with statistical differences for the CSC / 15% BO and CSC / 50% BO groups (p < 0.05). After 30 days, CSC showed statistically higher ΔE values than CSC / 30% BO and CSC / 50% BO (p < 0.05). In conclusion, the increase in radiopacity provided by bismuth oxide has no relation to the color alteration of calcium silicate-based cements.