Diagenetic Alterations and Reservoir Quality Evolution of Lower Cretaceous Fluvial Sandstones: Nubian Formation, Sirt Basin, North-Central Libya

Lower Cretaceous meandering and braided fluvial sandstones of the Nubian Formation form some of the most important subsurface reservoir rocks in the Sirt Basin, north-central Libya. Mineralogical, petrographical and geochemical analyses of sandstone samples from well BB6-59, Sarir oilfield, indicate that the meandering fluvial sandstones are fine- to very fine-grained subarkosic arenites (av. Q91F5L4), and that braided fluvial sandstones are medium- to very coarse-grained quartz arenites (av. Q96F3L1). The reservoir qualities of these sandstones were modified during both eodiagenesis (ca. <70oC; <2 km) and mesodiagenesis (ca. >70oC; >2km). Reservoir quality evolution was controlled primarily by the dissolution and kaolinitization of feldspars, micas and mud intraclasts during eodiagenesis, and by the amount and thicknessof grain-coating clays, chemical compaction and quartz overgrowths during mesodiagenesis. However, dissolution and kaolinitization of feldspars, micas and mud intraclasts resulted in the creation of intercrystalline micro- and mouldic macro-porosity and permeability during eodiagenesis, which were more widespread in braided fluvial than in meandering fluvial sandstones. This was because of the greater depositional porosity and permeability in the braided fluvial sandstones which enhanced percolation of meteoric waters. The development of only limited quartz overgrowths in the braided fluvial sandstones, in which quartz grains are coated by thick illite layers, retained high porosity and permeability (12-23 % and 30- 600 mD). By contrast, meandering fluvial sandstones underwent porosity loss as a result of quartz overgrowth development on quartz grains which lack or have thin and incomplete grain-coating illite (2-15 % and 0-0.1mD). Further loss of porosity in the meandering fluvial sandstones occurred as a result of chemical compaction (pressuredissolution) induced by the occurrence of micas along grains contacts. Otherdiagenetic alterations, such as the growth of pyrite, siderite, dolomite/ankerite and albitization, had little impact on reservoir quality. The albitization of feldspars may have had minor positive influence on reservoir quality throughthe creation of intercrystalline micro-porosity between albite crystals.The results of this study show that diagenetic modifications of the braided and meandering fluvial sandstones in the Nubian Formation, and resulting changes in reservoir quality, are closely linked to depositional porosity and permeability. They are also linked to the thickness of grain-coating infiltrated clays, and to variations in detrital composition, particularly the amounts of mud intraclasts, feldspars and mica grains as well as climatic conditions.

Phase composition, microstructure and microhardness of electroless nickel composite coating co-deposited with SiC on cast aluminium LM24 alloy substrate

Electroless Ni–P (EN) and composite Ni–P–SiC (ENC) coatings were developed on cast aluminium alloy substrate, LM24. The coating phase composition, microstructure and microhardness were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and microhardness tester, respectively, on as-plated and heat-treated specimens. The original microstructure of the Ni–P matrix is not affected by the inclusion of the hard particles SiC. No formation of Ni–Si phase was observed up to 500 °C of heat treatment. The microhardness is increased on incorporation of SiC in Ni–P matrix. The hardening mechanism is the formation of intermetallic phase Ni3P on annealing at elevated temperature.

Electroless nickel composite (Ni-P/SiC) coating - A study on interface and corrosion characteristic

Surface behaviour is of paramount importance as failure and degradation tend to initiate from the surface. Electroless composite coating (NiP/SiC) was developed using SiC as reinforcing particles. As heat treatment plays a vital role in electroless nickel coating owing to the changes in microstructure, phase structure and mechanical properties, an insight at the interface changes in chemistry and micromechanical behaviour was investigated using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) and microindentation techniques. Corrosion performance was analysed using electrochemical impedance spectroscopy (EIS). Absence of zinc and migration of copper at the interface was detected. Brittleness and microcracks was seen long the interface when indenting at load of 500 gf (Vickers). Corrosion performance is weaker than particles free coating. However, a thin blanket of NiP could enhance the resistance to corrosive medium.

Characterisation of phase composition, microstructure and microhardness of electroless nickel composite coating co-deposited with SiC on casting aluminium LM24 alloy substrate

Electroless Ni-P (EN) and composite Ni-P-SiC (ENC) coatings were developed on cast aluminium alloy, LM24. The coating phase composition, microstructure and microhardness were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and microhardness tester, respectively, on as-plated and heat-treated specimens. The original microstructure of the Ni-P matrix is not affected by the inclusion of the hard particles SiC. No formation of Ni-Si phase was observed upto 500°C of heat treatment. The microhardness is increased on incorporation of SiC in Ni-P matrix. The hardening mechanism is the formation of intermetallic phase Ni3P on annealing at elevated temperature. Overall, the composite coating (ENC) was found to be superior as compared to particles free (EN) coating in both as-deposited and heat-treated conditions.

Micro-scale abrasion behaviour of electroless Ni-P-SiC coating on aluminium alloy

Electroless nickel (EN) and electroless nickel composite (ENC) coatings were deposited on aluminium alloy substrate, LM24. The micro abrasion test was conducted to study the wear behaviour of the coatings with the effect of SiC concentration. Microhardness of the coatings was tested also. The wear scars were analysed using optical microscope and scanning electron microscope (SEM). The wear resistance was found to be improved in composite coating that has higher microhardness as compared to particles free and the bare aluminium substrate. In as-deposited condition for the composite coating, the wear volume increases on increase in SiC percentage in the coating but is found to be minimum for lower SiC percentage. The increase in hardness on heat treatment at 400°C is due to the hardening or grain coarsening with the formation Ni3P.

Oxidation-induced Cu coating on steel surface

Copper is accumulated in recycled steels and is difficult to be removed during steelmaking processes when steel scrap is used as steel sources. Meanwhile, copper characteristic properties are of importance both to human beings and to animals and plants. In this paper, integrated copper coating was observed on the surface of copper-containing steels when the steels were heated at around 1150°C. However, the copper was separately scattered after heating at 1000°C. The forming mechanisms of copper coating will be discussed in detail. By choosing proper descaling reagent, self-generated oxidation-induced copper coating appeared on the steel surface. The method proposed in this work is environmentally friendly for nontoxic chemicals being used. In addition, this provides a new concept for producing protective composite by oxidizing from the substrate directly and there is no binding problem.

Oxidation-induced Cu coating on steel surface

Copper is accumulated in recycled steels and is difficult to be removed during steelmaking processes when steel scrap is used as steel sources. Meanwhile, copper characteristics are of importance both to human beings and to animals and plants. In this paper, integrated copper coating was observed on the surface of copper-containing steels when the steels were heated at around 1150°C. However, the copper was separately scattered in and under the surface rust after heating at 1000°C. The forming mechanisms of copper coating are discussed in detail. By choosing a proper descaling reagent, self-generated oxidation-induced copper coating appeared on the steel surface. The method proposed in this work is environmentally friendly for nontoxic chemicals being used. In addition, this provides a new concept for producing protective composite by oxidizing from the substrate directly and there is no bonding problem.

Data on carotid intima-media thickness and lipoprotein subclasses in type 1 diabetes from the Diabetes Control and Complications Trial and the Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC)

Type 1 diabetes (T1DM) is associated with increased risk of macrovascular complications. We examined longitudinal associations of serum conventional lipids and nuclear magnetic resonance (NMR)-determined lipoprotein subclasses with carotid intima-media thickness (IMT) in adults with T1DM (n=455) enrolled in the Diabetes Control and Complications Trial (DCCT). Data on serum lipids and lipoproteins were collected at DCCT baseline (1983-89) and were correlated with common and internal carotid IMT determined by ultrasonography during the observational follow-up of the DCCT, the Epidemiology of Diabetes Interventions and Complications (EDIC) study, at EDIC 'Year 1' (199-1996) and EDIC 'Year 6' (1998-2000). This article contains data on the associations of DCCT baseline lipoprotein profiles (NMR-based VLDL & chylomicrons, IDL/LDL and HDL subclasses and 'conventional' total, LDL-, HDL-, non-HDL-cholesterol and triglycerides) with carotid IMT at EDIC Years 1 and 6, stratified by gender. The data are supplemental to our original research article describing detailed associations of DCCT baseline lipids and lipoprotein profiles with EDIC Year 12 carotid IMT (Basu et al. in press) [1].

Nuclear magnetic resonance-determined lipoprotein subclasses and carotid intima-media thickness in type 1 diabetes

BACKGROUND: Dyslipidemia has been linked to vascular complications of Type 1 diabetes (T1DM). We investigated the prospective associations of nuclear magnetic resonance-determined lipoprotein subclass profiles (NMR-LSP) and conventional lipid profiles with carotid intima-media thickness (IMT) in T1DM.

METHODS: NMR-LSP and conventional lipids were measured in a subset of Diabetes Control and Complications Trial (DCCT) participants (n = 455) at study entry ('baseline', 1983-89), and were related to carotid IMT determined by ultrasonography during the observational follow-up of the DCCT, the Epidemiology of Diabetes Interventions and Complications (EDIC) study, at EDIC Year 12 (2004-2006). Associations were defined using multiple linear regression stratified by gender, and following adjustment for HbA1c, diabetes duration, body mass index, albuminuria, DCCT randomization group, smoking status, statin use, and ultrasound devices.

RESULTS: In men, significant positive associations were observed between some baseline NMR-subclasses of LDL (total IDL/LDL and large LDL) and common and/or internal carotid IMT, and between conventional total- and LDL-cholesterol and non-HDL-cholesterol and common carotid IMT, at EDIC Year 12; these persisted in adjusted analyses (p < 0.05). Large LDL particles and conventional triglycerides were positively associated with common carotid IMT changes over 12 years (p < 0.05). Inverse associations of mean HDL diameter and large HDL concentrations, and positive associations of small LDL with common and/or internal carotid IMT (all p < 0.05) were found, but did not persist in adjusted analyses. No significant associations were observed in women.

CONCLUSION: NMR-LSP-derived LDL particles, in addition to conventional lipid profiles, may help in identifying men with T1DM at highest risk for vascular disease.

Central corneal thickness and corneal hysteresis associated with glaucoma damage.

PURPOSE:

We sought to measure the impact of central corneal thickness (CCT), a possible risk factor for glaucoma damage, and corneal hysteresis, a proposed measure of corneal resistance to deformation, on various indicators of glaucoma damage.

DESIGN:

Observational study.

METHODS:

Adult patients of the Wilmer Glaucoma Service underwent measurement of hysteresis on the Reichert Ocular Response Analyzer and measurement of CCT by ultrasonic pachymetry. Two glaucoma specialists (H.A.Q., N.G.C.) reviewed the chart to determine highest known intraocular pressure (IOP), target IOP, diagnosis, years with glaucoma, cup-to-disk ratio (CDR), mean defect (MD), pattern standard deviation (PSD), glaucoma hemifield test (GHT), and presence or absence of visual field progression.

RESULTS:

Among 230 subjects, the mean age was 65 +/- 14 years, 127 (55%) were female, 161 (70%) were white, and 194 (85%) had a diagnosis of primary open-angle glaucoma (POAG) or suspected POAG. In multivariate generalized estimating equation models, lower corneal hysteresis value (P = .03), but not CCT, was associated with visual field progression. When axial length was included in the model, hysteresis was not a significant risk factor (P = .09). A thinner CCT (P = .02), but not hysteresis, was associated with a higher CDR at the most recent examination. Neither CCT nor hysteresis was associated with MD, PSD, or GHT "outside normal limits."

CONCLUSIONS:

Thinner CCT was associated with the state of glaucoma damage as indicated by CDR. Axial length and corneal hysteresis were associated with progressive field worsening.

Intraocular pressure, central corneal thickness, and glaucoma in chinese adults: the liwan eye study.

PURPOSE: To describe the distribution of central corneal thickness (CCT), intraocular pressure (IOP), and their determinants and association with glaucoma in Chinese adults.DESIGN: Population-based cross-sectional study.METHODS: Chinese adults aged 50 years and older were identified using cluster random sampling in Liwan District, Guangzhou. CCT (both optical [OCCT] and ultrasound [UCCT]), intraocular pressure (by Tonopen, IOP), refractive error (by autorefractor, RE), radius of corneal curvature (RCC), axial length (AL), and body mass index (BMI) were measured, and history of hypertension and diabetes (DM) was collected by questionnaire. Right eye data were analyzed.RESULTS: The mean values of OCCT, UCCT, and IOP were 512 ± 29.0 μm, 542 ± 31.4 μm, and 15.2 ± 3.1 mm Hg, respectively. In multiple regression models, CCT declined with age (P < .001) and increased with greater RCC (P < .001) and DM (P = .037). IOP was positively associated with greater CCT (P < .001), BMI (P < .001), and hypertension (P < .001). All 25 persons with open-angle glaucoma had IOP <21 mm Hg. CCT did not differ significantly between persons with and without open- or closed-angle glaucoma. Among 65 persons with ocular hypertension (IOP >97.5th percentile), CCT (555 ± 29 μm) was significantly (P = .01) higher than for normal persons.CONCLUSIONS: The distributions of CCT and IOP in this study are similar to that for other Chinese populations, though IOP was lower than for European populations, possibly due to lower BMI and blood pressure. Glaucoma with IOP <21 mm Hg is common in this population. We found no association between glaucoma and CCT, though power (0.3) for this analysis was low.

Contribution of genetic and environmental effects on lens thickness: the Guangzhou Twin Eye study.

PURPOSE:

This study investigated the heritability of lens thickness (LT) and relative lens thickness (LT/axial length, rLT) measured by Lenstar among Chinese children and adolescents in the Guangzhou Twin Eye study.

METHODS:

Twins aged 8 to 22 years were enrolled from the Guangzhou Twin Registry. A series of LT and axial length (AL) measurements using the Lenstar were taken for each twin. Zygosity was confirmed by genotyping in all same-sex twin pairs. Heritability was assessed by structural variance component genetic modeling, after adjustment for age and sex with the Mx program.

RESULTS:

Seven hundred sixty-eight twin pairs (482 monozygotic [MZ] and 286 dizygotic [DZ] twins) were available for data analysis. The mean (standard deviation) LT and rLT were 3.45 (0.18) mm and 0.142 (0.01), respectively. The intraclass correlation coefficients (ICCs) for LT were 0.90 for the MZ and 0.39 for the DZ twins; and those for rLT were 0.90 for the MZ and 0.40 for the DZ twins, respectively. The best-fitting model yielded 89.5% (95% CI: 87.8%-91.0%) of additive genetic effects and 10.5% (95% CI: 9.0%-12.2%) of unique environmental effects for LT, and 89.3% (95% CI: 89.2%-89.3%) of additive genetic effects and 10.7% (95% CI: 10.7%-11.4%) of unique environmental effects for rLT.

CONCLUSIONS:

This study confirms that the LT in young healthy subjects may be mainly affected by additive genetic factors. High heritability remains even when the data are corrected for the influence of AL with the use of rLT.

Effects of Poly (ε-caprolactone) Coating on the Properties of Three-Dimensional Printed Porous Structures

Powder-based inkjet three-dimensional printing (3DP) to fabricate pre-designed 3D structures has drawn increasing attention. However there are intrinsic limitations associated with 3DP technology due to the weak bonding within the printed structure, which significantly compromises its mechanical integrity. In this study, calcium sulphate ceramic structures demonstrating a porous architecture were manufactured using 3DP technology and subsequently post-processed with a poly (ε-caprolactone) (PCL) coating. PCL concentration, immersion time, and number of coating layers were the principal parameters investigated and improvement in compressive properties was the measure of success. Interparticle spacing within the 3DP structures were successfully filled with PCL material. Consequently the compressive properties, wettability, morphology, and in vitro resorption behaviour of 3DP components were significantly augmented. The average compressive strength, Young’s modulus, and toughness increased 217%, 250%, and 315%, following PCL coating. Addition of a PCL surface coating provided long-term structural support to the host ceramic material, extending the resorption period from less than 7 days to a minimum of 56 days. This study has demonstrated that application of a PCL coating onto a ceramic 3DP structure was a highly effective approach to addressing some of the limitations of 3DP manufacturing and allows this advanced technology to be potentially used in a wider range of applications.