Fresh groundwater lenses in the Arabian Peninsula: formative, stability and management assessments, The

2019 Fall.Includes bibliographical references.The formation of fresh groundwater lenses (FGLs) overlying denser, saline or brackish groundwater is a fascinating hydrologic phenomenon that creates groundwater supplies of great potential value for humans and ecosystems in several formation settings, such as coastal areas, atoll islands, riverine floodplains, and subterranean oases in arid regions. In particular, FGLs in subterranean oases are a critical source of freshwater supply in arid regions, due to a general lack of perennial rivers and lakes. These FGLs are in danger of salinization due to natural events and anthropogenic stresses. Although extensive research has been conducted on FGLs in general, the FGLs in subterranean oases in arid regions have received less attention. Key knowledge gaps include the quantity and frequency of natural recharge to these FGLs; reliable estimates of environmental aquifer dispersivity at the scale of subterranean FGLs; the timing of lens development; and the impact of anthropogenic activities on lens dynamics. This dissertation focuses on the FGLs of subterranean oases in the Arabian Peninsula (AP), using the Rawdatain FGL in Kuwait as a case study. Among the FGLs in the AP, the Rawdatain FGL in Kuwait is perhaps a unique candidate because of its size and the availability of extensive subsurface data for the pre-development period. The main objectives of this study are as follows: (1) estimate long-term average annual recharge for the Rawdatain FGL and investigate the timing of lens depletion due to climate change; (2) provide a realistic range of longitudinal (αL), horizontal transverse (αh), and vertical transverse (αv) dispersivity values for the aquifer; and (3) assess the impacts of historical and future anthropogenic activities and evaluate artificial recharge alternatives for lens recovery storage (LSR). In this study, a 3D density-dependent groundwater flow and solute transport model using the SEAWAT modeling code is developed using the following pre-development period calibration targets: (1) groundwater head, (2) spatially-variable total dissolved solids (TDS) groundwater concentration, (3-5) three groundwater volume targets, (6-8) three vertical thickness targets of stored groundwater of three different water quality TDS ranges (0−700, 700−1000, and 1000−2000 mg/L), and (9) geometrical shape features of the lens along cross-sections. In addition, groundwater age data of the Rawdatain FGL was used as an independent factor to constrain the dispersivity and recharge rate during the simulated period of lens development. Moreover, a sensitivity analysis was performed to explore the effects of the hydraulic conductivity, boundary conditions, and vertical transverse dispersivity on lens geometry. Based on a comparison of twelve annual recharge amount scenarios using a constant recharge mechanism (CRM) (R1 to R12: 0.2 to 5.0 million m³/year) with data targets, the R5 (0.5 million m³/year) recharge scenario is selected to represent the long-term average annual recharge. These results demonstrated that the annual natural replenishment of the Rawdatain FGL is minimal compared with its size. A macro-scale stability assessment shows that a 50% reduction in annual recharge within a 100-year time frame would reduce the lens volumes by 21%, 17% and 9% for the three water quality categories. A multi-criteria score-based method was performed to rank the best performance of 28 dispersivity sets (D1 to D28: 1 to 500 m) among all of the targets with an equal weight, on a scale of 0 to 300 x 106 m3. The results illustrated that the D16 dispersivity set (αL = 50 m: αh = 5 m: αv = 0.1 m) represents the best large-scale environmental dispersivity values for the Rawdatain FGL and can be used for analyzing the natural mixing between the ambient brackish water and fresh water. A new baseline model for the predevelopment period using a pulse recharge mechanism (PRM) was established to assess the recharge frequency along with the longitudinal dispersivity. The results revealed that the 50 m longitudinal dispersivity set and one pulse recharge every two years had the best performance, and they were selected to simulate the effects of the infrequent rainfall events and anthropogenic impacts simultaneously. During the groundwater abstraction from 1963 to 2018, the reduction in the stored volumes was 28%, 17% and 12% for the three quality categories. The future pumping scenarios (2019-2100) suggested that the 0.16×106 m3/year is a suitable alternative for long-term use, 0.5×106 m³/year)is an appropriate option for short-term use, and extraction scenarios greater than 1.0×106 m³/year will cause a remarkable degeneration of the Rawdatain FGL. Artificial recharge scenarios (2019-2028) imply that a successful LSR for the Rawdatain FGL depends on selecting appropriate well locations and amounts of injected water. For instance, the I2 alternative could achieve a 100% storage recovery within 7.5, 8 and 9 years for the three water quality categories. This study provides a first attempt to model the formation of a FGL, assess the historical anthropogenic stresses, and evaluate future management scenarios in subterranean oases in arid regions. Implementing multiple data targets and water age is a unique process of calibration that was helpful in eliminating several non-unique calibration parameters and in decreasing the uncertainty of the calibrated parameters. The methodology presented herein provides a general approach that can be extrapolated to other FGLs with similar climatic and environmental circumstances. The outputs of this dissertation enhance the understanding of the formation, stability, and management of these lenses and will be very valuable to water managers for establishing appropriate water supply plans for these valuable water reserves, leading to preferable future water security in the AP

Ab Externo Imaging of Human Episcleral Vessels Using Fiberoptic Confocal Laser Endomicroscopy

Purpose: There is a growing interest in targeting minimally invasive surgery devices to the aqueous outflow system to optimize treatment outcomes. However, methods to visualize functioning, large-caliber aqueous and episcleral veins in-vivo are lacking. This pilot study establishes an ex-vivo system to evaluate the use of a confocal laser microendoscope to noninvasively image episcleral vessels and quantify regional flow variation along the limbal circumference. Methods: A fiber-optic confocal laser endomicroscopy (CLE) system with lateral and axial resolution of 3.5 μm and 15 μm, respectively, was used on three porcine and four human eyes. Diluted fluorescein (0.04%) was injected into eyes kept under constant infusion. The microprobe was applied to the sclera 1 mm behind the limbus to acquire real-time video. Image acquisition was performed at 15-degree intervals along the limbal circumference to quantify regional flow variation in human eyes. Results: Vascular structures were visualized in whole human eyes without processing. Schlemm’s canal was visualized only after a scleral flap was created. Fluorescent signal intensity and vessel diameter variation were observed along the limbal circumference, with the inferior quadrant having a statistically higher fluorescein signal compared to the other quadrants in human eyes (P < 0.05). Conclusion: This study demonstrates for the first time that the fiber-optic CLE platform can visualize the episcleral vasculature with high resolution ex-vivo with minimal tissue manipulation. Intravascular signal intensities and vessel diameters were acquired in real-time; such information can help select target areas for minimally invasive glaucoma surgery (MIGS) to achieve greater intraocular pressure reduction

Optimal Currency-Peg for an Oil-Exporting Country: The Case of Saudi Arabia

Economic

Preparation of nano-structured catalysts

gold catalysts have been found to be effective for many oxidation reactions and it is known that the performance of these catalysts depends strongly on the particle size of Au nanoparticles. However, other factors have strong influence on the catalytic activity such as the preparation methods, choice of support, the structure and morphology of supports. The effect of support morphology and structure on the activity of Au catalysts was investigated using two hydrothermally prepared supports, CeO2 and MnO2. Ceria foams as a support for nano-clusters of gold were synthesised hydrothermally at 160 °C by the reaction of L-Asparagine and CeCl3.7H2O at different crystallisation times. The effect of the reaction time on the morphology of prepared CeO2 was investigated. The morphology varied remarkably and it was found to change from spherical particles to foam and eventually to a collapsed foam as the crystallisation time increased. Gold catalysts were prepared by sol-immobilisation, supported on the foam ceria and examined for solvent free oxidation of benzyl alcohol using molecular O2 as an oxidant and the effect of the support was compared with commercial ceria. Au/CeO2 foam catalysts were more active than the Au/commercialCeO2 although the Au nanoparticles were larger in ceria foam supports. This was due to the greater lability of surface oxygen in the foam support compared with commercial CeO2 materials. The Au/CeO2 foam catalyst was found to be reusable over three experiments. The effect of catalyst loading, oxygen pressure and reaction time-online were also studied. It was found that there was no mass transfer limitation when the mass of catalyst varied from 5 to 40 mg under the reaction conditions. The conversion of benzyl alcohol decreased as the oxygen pressure decreased which shows that oxygen was involved in the oxidation process. For time-online study, the conversion increased as the reaction time increased with slightly increase. MnO2 supports were synthesised by reacting MnSO4.H2O with (NH4)2S2O8 hydrothermally at 160 °C. Two different phases and morphologies of MnO2 were formed and as the reaction time increased the morphology changed from microspheres to nanowires and the MnO2 phase changed from α- to β-. Gold was deposited on all prepared MnO2 materials and the catalysts were examined for solvent free benzyl alcohol and CO oxidation. The influence of the preparation method on the catalytic activity was studied and sol-immobilisation was found to be the best for benzyl alcohol VII oxidation whereas the deposition-precipitation was found to be the best for CO oxidation. Impregnation method exhibited poor activity for both reactions. The effect of the morphology and phase on the catalyst activity for both reactions was researched and Au/α-MnO2 microspheres catalysts were best for benzyl alcohol oxidation while Au/β- MnO2 nanowires catalysts exhibited better performance for CO oxidation due to their smaller Au nanoparticles and easier surface reduction. The catalysts reusability, timeonline and the effect of catalyst loading were also studied of an Au/MnO2 microsphere catalyst for benzyl alcohol oxidation reaction. Vanadium phosphate catalysts have been extensively studied for the selective oxidation of butane to maleic anhydride. The catalytic activity of vanadium phosphates is greatly dependant on the preparation method of the catalyst precursor VOHPO4·0.5H2O. Poly (acrylic acid-co-maleic acid) copolymer, PAAMA, was employed as a structure directing agent in the preparation of VOHPO4.0.5H2O via two routes. The effect of PAAMA concentration on the structure morphology of VOHPO4·0.5H2O was studied in both preparation routes. As the concentration of PAAMA increased the morphology changed from rosette like for the standard precursors to rosette-like agglomerates with isolated rhomboidal platelets and eventually to isolated rhomboidal platelets at highest concentration of PAAMA. The XRD confirmed that all precursors were VOHPO4·0.5H2O but as the concentration of PAAMA increased the (001) reflection increased and the (220) reflection decreased. When these precursors were tested for butane selective oxidation, the standard precursors that contain rosettes VPO0 and VPD0 activated to the active phase ((VO)2P2O7) over typically observed time (> 100 h). While the precursors that had rosette-like agglomerates with isolated rhomboidal platelets and a relative intensity ratio of the (001)/(220) reflections of around 1.4, VPO5 and VPD15, activated much faster, less than 20 h with a comparable conversion and selectivity. The isolated rhomboidal platelets precursors which had a high relative intensity ratio of the (001)/(220) reflections, VPO15, VPO25 and VPD25, displayed very poor activity because the thin platelets were rapidly oxidised to αII-VOPO4 phase as confirmed by the XRD and Laser Raman Spectroscopy

Prostaglandin-Induced Cystoid Macular Edema Following Routine Cataract Extraction

To our knowledge, we are reporting the first case of a 59-year-old man who developed recurrent CME with three separate trials of three different prostaglandin class drugs following uncomplicated phacoemulsification with intraocular lens implantation. Despite multiple reports of individual prostaglandin (PG) analogues being suggested as the cause of CME, there are no recommendations regarding withholding these medications in the perioperative period. Our patient first developed CME OD 4-months post uncomplicated cataract extraction. XALATAN (Latanoprost) had been restarted after surgery and discontinued at onset of CME. While off XALATAN (Latanoprost), the patient's CME resolved, but his IOP rose. The patient was started on LUMIGAN (Bimatoprost) to control the IOP, but within weeks his CME recurred. The patient's CME was again treated and his IOP remained acceptable, but then progressively increased. TRAVATAN (Travoprost) was attempted, but he presented with a third round of CME. Definitive conclusions about causal relationships cannot be made without well-designed, prospective clinical trials addressing this issue