The Role of Inhibitors' Molecular Structure on Asphaltene Deposition in Reservoir Conditions

Abstract

Due to the lack of research on the effects of inhibitors on asphaltene flocculation in reservoir conditions, operational application of inhibitors in the petroleum industry has not been clearly investigated. In previous studies, molecular structures and the effectiveness of prevalent inhibitors were investigated and other parameters such as cost and environmental issues were also considered.

The proposed inhibitor was tested over a wide variety of Iranian asphaltenic crude oils and optimized quantities of the inhibitor were studied in detail. Moreover, qualitative and quantitative effects of the proposed inhibitor were tested on crude oils in atmospheric conditions and the effect of the proposed inhibitor on asphaltene flocculation and deposition at reservoir conditions was investigated. The amounts of change in onset pressure point due to injection of the inhibitor were measured at reservoir conditions. The proposed inhibitor is in good agreement with reservoir conditions.     

Cone location and correction of keratoconus with rigid gas-permeable contact lenses

Purpose

To evaluate the influence of cone location and corneal cylinder on RGP corrected visual acuities and residual astigmatism in patients with keratoconus.

Methods

In this prospective study, 156 eyes from 134 patients were enrolled. Complete ophthalmologic examination including manifest refraction, Best spectacle visual acuity (BSCVA), slit-lamp biomicroscopy was performed and corneal topography analysis was done. According to the cone location on the topographic map, the patients were divided into central and paracentral cone groups. Trial RGP lenses were selected based on the flat Sim K readings and a ‘three-point touch’ fitting approach was used. Over contact lens refraction was performed, residual astigmatism (RA) was measured and best-corrected RGP visual acuities (RGPVA) were recorded.

Results

The mean age (±SD) was 22.1 ± 5.3 years. 76 eyes (48.6%) had central and 80 eyes (51.4%) had paracentral cone. Prior to RGP lenses fitting mean (±SD) subjective refraction spherical equivalent (SRSE), subjective refraction astigmatism (SRAST) and BSCVA (logMAR) were −5.04 ± 2.27 D, −3.51 ± 1.68 D and 0.34 ± 0.14, respectively. There were statistically significant differences between central and paracentral cone groups in mean values of SRSE, SRAST, flat meridian (Sim K1), steep meridian (Sim K2), mean K and corneal cylinder (p-values < 0.05). Comparison of BSCVA to RGPVA shows that vision has improved 0.3 logMAR by RGP lenses (p < 0.0001). Mean (±SD) RA was −0.72 ± 0.39 D. There were no statistically significant differences between RGPVAs and RAs of central and paracentral cone groups (p = 0.22) and (p = 0.42), respectively. Pearson's correlation analysis shows that there is a statistically significant relationship between corneal cylinder and BSCVA and RGPVA, However, the relationship between corneal cylinder and residual astigmatism was not significant.

Conclusions

Cone location has no effect on the RGP corrected visual acuities and residual astigmatism in patients with keratoconus. Corneal cylinder and Sim K values influence RGP-corrected visual acuities but do not influence residual astigmatism.     

α‐Amylase immobilization on functionalized nano CaCO3 by covalent attachment

In this study, α‐amylase was immobilized on glutaraldehyde activated silanized calcium carbonate nanoparticles by a using covalent binding method. The surface modified nano calcium carbonate (CaCO₃) were characterized using FTIR and SEM. Immobilization yield was found as 199.43 mg/g of calcium carbonate nanoparticles. The maximum activity was observed at pH 6.5. The immobilized enzyme had a higher activity at elevated temperature (50–90°C) than the free one. Reuse studies demonstrated that the immobilized enzyme could reuse 25 times while retaining 18.2% of its activity. Free enzyme lost its activity completely within 15 days. V_max values for the free and immobilized enzymes were calculated as 10 and 0.35 mg/mL/min, respectively.     

An Overview of Physical,Microbiological and Immune Barriers of Oral Mucosa

The oral mucosa, which is the lining tissue of the oral cavity, is a gateway to the body and it offers first-line protection against potential pathogens, exogenous chemicals, airborne allergens, etc. by means of its physical and microbiological-immune barrier functions. For this reason, oral mucosa is considered as a mirror to the health of the individual as well as a guard or early warning system. It is organized in two main components: a physical barrier, which consists of stratified epithelial cells and cell–cell junctions, and a microbiological-immune barrier that keeps the internal environment in a condition of homeostasis. Different factors, including microorganism, saliva, proteins and immune components, have been considered to play a critical role in disruption of oral epithelial barrier. Altered mucosal structure and barrier functions results in oral pathologies as well as systemic diseases. About 700 kinds of microorganisms exist in the human mouth, constituting the oral microbiota, which plays a significant role on the induction, training and function of the host immune system. The immune system maintains the symbiotic relationship of the host with this microbiota. Crosstalk between the oral microbiota and immune system includes various interactions in homeostasis and disease. In this review, after reviewing briefly the physical barriers of oral mucosa, the fundamentals of oral microbiome and oral mucosal immunity in regard to their barrier properties will be addressed. Furthermore, their importance in development of new diagnostic, prophylactic and therapeutic strategies for certain diseases as well as in the application for personalized medicine will be discussed.     

Selection Separation Method for Hydrogen and Light Hydrocarbons Gases from Waste-Gas Streams of a Petroleum Refinery

Abstract

The four main processes for hydrogen upgrading in refineries include pressure swing adsorption, selective permeation using polymer membranes, cryogenic separation, and dephlegmation. Each of these processes is based on a different separation principle and, consequently, the process characteristics differ significantly. Selection of an appropriate hydrogen and light gas separation process depends not only on economics but on other project considerations such as process flexibility, reliability, and ease of future expansion. A review of the separation process characteristics and equipment is provided in this article, followed by discussions of other project considerations. General and application-specific selection guidelines are then presented, along with process integrations that take advantage of the complementary characteristics of the four processes. Due to the worldwide depletion of petroleum reservoirs and the growing use of hydrotreating in petroleum refineries, much attention has been given to light hydrocarbons and hydrogen recovery from refinery waste streams.     

Effect of Aging Time and Temperature on Mechanical Properties and Microstructural Evolution of 2205 Ferritic-Austenitic Stainless Steel

Duplex stainless steels(DSS)with ferritic–austenitic microstructures offer good combination of resistance to pitting corrosion and high strength that are not concomitantly attainable using conventional single phase austenitic or ferritic stainless steels.The DSS used in this investigation was 2205 alloy having a stable mi-crostructure consisting of about 45%ferrite and 55%austenite at ambient temperature.In order to investigate aging behavior of this steel and the influences on mechanical properties,differe...     

Challenges of adaptive control-past, permanent and future

This paper reviews three different types of challenges to adaptive control. The first group comprises challenges met in the subject’s development. They include difficulties associated with the MIT rule, bursting, the Rohr’s counterexample and unplanned instability in iterative identification and control. An understanding of these phenomena and mitigating strategies are now available. The second group comprises difficulties that are intrinsic to virtually any adaptive control algorithm, and that have frequently been overlooked. For example, if a plant is unknown, and a control objective is set, the objective may in practical terms be unachievable, and any adaptive control algorithm needs to deal with that possibility. The third group comprises some issues to which researchers are currently devoting significant attention, including multiple model adaptive control and model-free design.     

Synthesis and characterisation of a selective adsorbent based on the molecularly imprinted polymer for the removal of cloxacillin antibiotic residue from milk

In recent decades, environmental pollution has been a subject of growing concern. This is partly due to the overuse of antibiotics, the consequent drug resistance and the discharge of drugs into the environment. The aim of this study was to synthesise molecularly imprinted polymer (MIP) particles via a noncovalent procedure for the removal of cloxacillin from milk. Accordingly, the effects of operational parameters such as pH, contact time and MIP dosage were studied. The performance of MIP particles in removing cloxacillin from livestock milk samples proved that these adsorbents can effectively help to reduce drug contamination from dairy sources.