3D QUANTITATIVE SEISMIC STRATIGRAPHY OF JURASSIC CARBONATE STRATA ON THE ARABIAN PLATFORM

Quantitative seismic stratigraphy of a 3D seismic volume of the Arabian platform provides critical information on the heterogeneity of reservoir quality of a productive Jurassic carbonate grainstone. The Vail method of sequence stratigraphy allowed the delineation of thirteen sequence boundaries from the Permian to the Cenozoic. Integrating the Galloway petrophysical methods of sequence stratigraphy from well constraints, four third-order cycles of HST, RST, TST, and LST parasequence sets are identified. As these are regionally correlated on the seismic they appear to be allocyclically controlled. The 3D porosity prediction via neural network application successfully predicted the continuity of HST high porosities, suggesting the porosities were caused by fresh-water vadose/phreatic diagenesis of these Hothouse mineralogies during sea level falls of the ensuing RST’s. Unfortunately, while discernible in the wells, these parasequence sets are below seismic resolution for interpretation. The LST’s have good mudstone deposition with accompanying enriched organic matter content for potential self-sourcing of the overlying HST’s. The TST’s which followed, much like the RST’s, are below seismic resolution for mapping. Combined with post-depositional structural, this parasequence porosity centralization in these stacked cycles of carbonates provides an ideal assemblage of reservoir criticals for hydrocarbon accumulation and suggests quantitative seismic stratigraphy is a powerful tool for Arabian platform Jurassic carbonate exploration and exploitation

What Is the Metabolic Amplification of Insulin Secretion and Is It (Still) Relevant?

The pancreatic beta-cell transduces the availability of nutrients into the secretion of insulin. While this process is extensively modified by hormones and neurotransmitters, it is the availability of nutrients, above all glucose, which sets the process of insulin synthesis and secretion in motion. The central role of the mitochondria in this process was identified decades ago, but how changes in mitochondrial activity are coupled to the exocytosis of insulin granules is still incompletely understood. The identification of ATP-sensitive K+-channels provided the link between the level of adenine nucleotides and the electrical activity of the beta cell, but the depolarization-induced Ca2+-influx into the beta cells, although necessary for stimulated secretion, is not sufficient to generate the secretion pattern as produced by glucose and other nutrient secretagogues. The metabolic amplification of insulin secretion is thus the sequence of events that enables the secretory response to a nutrient secretagogue to exceed the secretory response to a purely depolarizing stimulus and is thus of prime importance. Since the cataplerotic export of mitochondrial metabolites is involved in this signaling, an orienting overview on the topic of nutrient secretagogues beyond glucose is included. Their judicious use may help to define better the nature of the signals and their mechanism of action

Cage-defining Ring: A Molecular Sieve Structural Indicator for Light Olefin Product Distribution from the Methanol-to-Olefins Reaction

The methanol-to-olefins (MTO) process produces high-value-added light olefins from nonpetroleum sources. Acidic zeotypes containing cages bounded by 8-ring (small-pore) windows can effectively catalyze the MTO reaction, since their cages can accommodate the necessary aromatic intermediates that produce the light olefin products that escape. While progress on the mechanisms of the MTO reaction continues, zeotype structure–reaction property relationships have yet to be elucidated. Here, we report MTO reaction results from various small-pore, cage-containing silicoaluminophosphate/metalloaluminophosphates (SAPO/MAPOs) and zeolites under the same reaction conditions. The MTO behaviors of microporous materials having the following topologies are investigated: LEV, ERI, CHA, AFX, SFW, AEI, DDR, RTH, ITE, SAV, LTA, RHO, KFI, and UFI. The previous observation that light olefin product distributions from a series of small-pore, cage-containing zeolites can be classified into four structural categories is further supported by the results shown here from zeolite structures not investigated in the previous study and SAPO and MAPO materials with isostructural frameworks to all the zeolites. Additionally, these data reveal that light olefin product distributions are very similar over a given topology independent of framework composition. To develop a structure–property relationship between the framework topology and the MTO light olefin product distribution, the concept of the cage-defining ring size is introduced. The cage-defining ring size is defined as the minimum number of tetrahedral atoms of the ring encircling the center of the framework cages in the molecular sieve topology. It is shown that the cage-defining ring size correlates with MTO light olefin product distribution

Evaluation of appendicitis risk prediction models in adults with suspected appendicitis

Background Appendicitis is the most common general surgical emergency worldwide, but its diagnosis remains challenging. The aim of this study was to determine whether existing risk prediction models can reliably identify patients presenting to hospital in the UK with acute right iliac fossa (RIF) pain who are at low risk of appendicitis. Methods A systematic search was completed to identify all existing appendicitis risk prediction models. Models were validated using UK data from an international prospective cohort study that captured consecutive patients aged 16–45 years presenting to hospital with acute RIF in March to June 2017. The main outcome was best achievable model specificity (proportion of patients who did not have appendicitis correctly classified as low risk) whilst maintaining a failure rate below 5 per cent (proportion of patients identified as low risk who actually had appendicitis). Results Some 5345 patients across 154 UK hospitals were identified, of which two‐thirds (3613 of 5345, 67·6 per cent) were women. Women were more than twice as likely to undergo surgery with removal of a histologically normal appendix (272 of 964, 28·2 per cent) than men (120 of 993, 12·1 per cent) (relative risk 2·33, 95 per cent c.i. 1·92 to 2·84; P < 0·001). Of 15 validated risk prediction models, the Adult Appendicitis Score performed best (cut‐off score 8 or less, specificity 63·1 per cent, failure rate 3·7 per cent). The Appendicitis Inflammatory Response Score performed best for men (cut‐off score 2 or less, specificity 24·7 per cent, failure rate 2·4 per cent). Conclusion Women in the UK had a disproportionate risk of admission without surgical intervention and had high rates of normal appendicectomy. Risk prediction models to support shared decision‐making by identifying adults in the UK at low risk of appendicitis were identified

Comparing the Outcomes of Tubularized Incised Plate Urethroplasty and Dorsal Inlay Graft Urethroplasty in Children with Hypospadias: A Systematic Review and Meta-Analysis

Background: Due to their simplicity and excellent outcomes, the tubularized incised plate urethroplasty (TIPU) and the dorsal inlay graft urethroplasty (DIGU) are two of the most commonly used techniques for hypospadias repair in children. However, there is a lack of consensus on which technique offers more favourable results and less added morbidity to the patient. Aims: This study aimed to systematically compare the reported outcomes of the TIPU and DIGU techniques in an effort to determine the procedure of choice in children undergoing primary hypospadias repair. Design: A systematic review and meta-analysis of randomized and observational studies. Methods: An electronic database search was conducted up to May 2018. Sources included Medline, Embase, Cochrane library, CINAHL, Web of Science, and Google Scholar as well as trial registries and grey literature sources. Studies were selected if they compared the operative complications of TIPU and DIGU in children. Secondary outcomes included standardized cosmetic scores and urinary flow studies. A metaanalysis of reported complications was performed using a random-effects model. Results: Two randomized, two prospective, and two retrospective studies met the inclusion criteria. TIPU and DIGU were performed in 350 and 267 patients respectively. Pooled analysis did not demonstrate a significant difference regarding post-operative urethrocutaneous fistula, meatal/urethral stenosis, wound dehiscence, or total complications. Subgroup analysis according to hypospadias severity did not alter initial findings. Sensitivity analysis with exclusion of retrospective studies demonstrated a significant increase in post-operative meatal/urethral stenosis and total complications after TIPU. Statistical analysis of secondary outcomes was not feasible due to insufficient data. Most studies were of low methodological quality with a high risk of bias. Conclusions: There is no strong evidence to suggest that either technique offers more favourable outcomes. Until more robust randomized trials exist, decisions regarding the appropriate repair should be based on the surgeon’s experience and outcomes.</p

Electrospun Nanofiber Metal Oxides for Reactive Sorption and Catalysis

Electrospun metal oxides is a new class of materials that have demonstrated auspicious potential and have been used in a wide range of applications. In this work, various smooth, continuous, and defect-controlled metal-polymer nanofibers were synthesized via electrospinning with diameters ranging from approximately 50 to 600 nm, and subsequently thermally treated to decompose the polymer (PVP or PEO) and form highly porous, fibrous metal (Cu-, Ni-, Mg-, and Ca-) oxide nanostructures. In the first part of this thesis, parameters that influence the electrospinning process were systematically investigated for PVP-Cu(NO3)2 systems. Both solution properties (polymer/metal concentration, polymer molecular weight, and solvent identity) and processing conditions (applied voltage, tip-of-needle to collector distance, extrusion rate, and humidity) were varied to probe the effect of these electrospinning factors on fiber quality prior to thermal treatment. The data collected demonstrated that factors that do not directly and strongly influence viscosity, conductivity and solvent evaporation (e.g., applied voltage, extrusion rate, and tip-of-needle to collecting plate distance) do not have substantial effects on fiber diameter and morphology. Subsequent thermal treatment of the electrospun nanofibers and choice of metal, however, were found to markedly impact the morphology of the formed fiber oxides (e.g., string-like structures or segmented particles). In the second part of this thesis, electrospun fiber metal oxide materials were tested in two main applications (high temperature CO2 removal and low-temperature H2S removal) and their performance was compared to materials prepared via traditional synthesis routes (e.g., sol-gel, co-precipitation, hydrothermal treatment, etc.) In the first application, CaO-based materials were tested as potential sorbents in sorption enhanced steam methane reforming (SE-SMR) to capture CO2 and shift the reaction towards producing more hydrogen. The electrospun CaO-nanofibers, when reacted with CO2, achieved complete conversion to CaCO3 and had an initial CO2 sorption capacity of 0.79gCO2/gsorbent at 873 K and 923 K (highest of all materials tested), as the macro-porosity imparted by the electrospinning process improved the CO2 diffusion through the CaCO3 product layers. Furthermore, when these electrospun sorbents were added to a commercial catalyst and tested in SE-SMR conditions, they had three to four times longer breakthrough times than CaO sorbents derived from natural sources (e.g., CaO-marble). To further improve the stability of CaO-based sorbents, chemical doping of Ca-supports with Mg, Al, Y, La, Zn, Er, Ga, Li, Nd, In, and Co was combined with electrospinning to yield mixed oxide materials with high sorption capacities (~0.4-0.7 gCO2/gsorbent) and improved durability (up to 17 cycles). It was demonstrated that metals that have high Tammann temperatures were effective at reducing sintering and CaO particle agglomeration by acting as spacers, thus, retaining the sorbent’s initial sorption capacity upon repeated cycling.In the second application, CuO nanofibers with varying diameters (~70-650 nm) were prepared from two polymers (PEO and PVP) and reacted with H2S at ambient conditions to form CuS. The results from this study demonstrated that the sulfur removal capacity of CuO materials, whether prepared via electrospinning, hydrothermal treatment, sol-gel or co-precipitation, was strongly dependent on crystallite size (a linear relationship was established between CuO removal capacity and crystallite size and held true for all CuO materials with crystallites between 5-26 nm) and CuO purity (i.e., presence of residual carbon on the surface of the oxide). Indeed, properties such as surface area, pore volume and morphology (e.g., flowerlike, fiber-like, belt-like, etc.) were found to have an insignificant impact on removal capacity. This work offers fundamental insights into the design of multifunctional and highly porous metal oxide nanofibers for sorptive and catalytic applications

Enhancing the Ethylene and Propylene Selectivities in the Methanol-to-Olefins Reaction by Exploiting the Intricate Relationship between Framework Topology and Acidity

This thesis describes and presents results from several related projects within the theme of molecular sieve synthesis and catalysis. The early part of the thesis focuses on understanding the link between cage size/dimension and acidity (i.e., acid site density and strength) in the methanol-to-olefins (MTO) reaction. This relationship between cage size and acidity, once identified and investigated, is exploited in the latter parts of the thesis to rationally design materials that are able to steer the light olefins product distribution toward either more ethylene or propylene in a significant improvement over SAPO-34 (CHA), the commercial catalyst. In Chapters 2, 44 zeolites and silicoaluminophosphates (SAPOs) belonging to five frameworks (AEI, CHE, LEV, SWY, and ERI) with a wide range of Si/Al=4-31 and Si/(Al+P)=0.04-0.3, are synthesized and characterized using a myriad of techniques. Their MTO behavior is then systematically investigated to rationalize the effect of cage dimensions on the olefins product distribution as a function of acid site density and strength. The results from this study show that changes in acid site density and strength play a secondary role to the dominating influence of cage architecture on product distribution in AEI- and CHA-type molecular sieves. Decreasing the cage size, in going from AEI and CHA to LEV, SWY, and ERI, however, results in substantial changes in the ethylene-to-propylene ratio (E/P) as a function of acidity. These changes are attributed to differences in the identity and concentration of the hydrocarbon-pool (HP) species that form, particularly in early stages of the reaction. In Chapters 3 and 4, ERI-type molecular sieves (e.g., SSZ-98, UZM-12, ERI-type zeolites, and SAPO-17) are thoroughly investigated as promising methanol-to-ethylene materials due to their narrow cage size. Specifically, numerous ERI-type molecular sieves are synthesized using several organic structure-directing agents (OSDAs) with varied Si/Al or Si/T-atoms ratios. The list of ERI-related materials synthesized and tested in MTO included a new disordered SAPO, denoted as CIT-16P, which upon thermal treatment in air transforms to SAPO-17 (ERI). The reaction results show that decreasing the Si/Al (or increasing the Si/T) ratio, irrespective of other material properties, improves the E/P of ERI-type molecular sieves (E/P=1.1-1.9) over CHA-type molecular sieves (E/P=0.82-0.85) in MTO. Dissolution-extraction experiments reveal that the rapid formation of cyclic intermediates and the shift in their composition toward less-methylated methylbenzenes and methylnaphthalenes are found to be key to enhancing the ethylene selectivity in ERI-type molecular sieves. In Chapter 5, several SAT-type molecular sieves are investigated as promising methanol-to-propylene catalysts. This effort entails the synthesis of CIT-17, an SAT SAPO-type molecular sieve, which is isostructural to STA-2 (MgAPO-SAT). Following the successful synthesis of CIT-17, the MTO behavior of several SAT-type molecular sieves (MgAPO, CoAPO, and SAPO) are investigated in MTO. The combination of low acidity of CIT-17 and unique structural features of the narrow SAT-cage lead to a catalytic pathway and mechanism that predominantly favors propylene (propylene-to-ethylene ratios (P/E) of 2-4.2; propylene selectivity of 40-50%). Indeed, CIT-17 achieves one of the highest P/E ratio values reported for this class of materials.</p