Particle straining in vuggy porous media

Formation damage is the loss of inherent permeability of porous media and is of vital importance in petroleum engineering. One important mechanism of formation damage is particulate straining, where suspended solid particles jam the flow pathways and reduce its flow capability. Most studies of particulate transport have been performed in porous media of uniform pore size, such as sandstones and sandpacks. Carbonates often contain large openings, called vugs, which can affect the flow and transport properties (particle straining) of the porous medium. In this study, particle straining experiments are performed on multiple configurations of synthetic vuggy media. A novel method is introduced to generate synthetic vuggy glass bead cores: glass beads, with dissolvable inclusions, are sintered in the presence of air in a muffle furnace and later dissolved with a core flood. Smaller-sized glass beads are injected at multiple flow rate and injection concentrations and changes in porosity, permeability, vug size, and particle effluent volume are monitored using continuous pressure measurements and computed tomography scanning. The results are combined with quasi-2D streamline simulations to understand the particle deposition patterns in these vuggy media. Furthermore, spontaneous imbibition experiments are conducted on multiple configurations of these synthetic vuggy media and capillary rise is measured. Rudimentary vug-pore flow models are generated, and solved for spontaneous imbibition using a computational fluid dynamics solver, to better explain the behavior observed in the experiments. The results can be summarized as follows: (i) particles penetrate and deposit at a deeper depth when a vug is present; (ii) the particles deposit on the vug-matrix boundary and result in a smaller and smoother vug; (iii) the maximum change in the vug is observed at the bottom of the vug; and (iv) more particle deposition occurs in the matrix around the vug. The high permeability vugs cause flow convergence, which increases the particle-particle and particle-matrix interaction, and results in an increased number of particles dropping out of the flow stream. Each vug has a sphere of influence within which it will affect the particle flow pathway; if the sphere of influence of two vugs overlap, the particle will be affected by both the vugs, with the dominance depending on the separation between the particle and the vug. The results suggest that for the vug conditions studied, the vugs in series focus the flow and increase the depth of particle deposition and the total volume of particles deposited in the core. The vugs in parallel acts independently as separate vugs, with their separation greater than their individual sphere of influence, and do not dictate the deposition of injected particles. In future, this study can be carried forward by conducting experiments inside a CT machine, to enable time-lapse particle deposition maps, on proxy vuggy media or real rocks. Coupled with real-time porosity, permeability, and possibly resistivity measurements, new near-wellbore interpretative models can be envisioned for improved formation evaluation of vuggy carbonatesPetroleum and Geosystems Engineerin

Enzymes used in detergents: Lipases

Microbial lipases are an important group of biotechnologically valuable enzymes, because of the versatility of their applied properties and ease of mass production. Lipases of microbial origin are widely diversified in their enzymatic properties and substrate specificity, which make them very attractive for industrial applications. This review describes the applications of microbial lipases in detergents. Enzymes can reduce the environmental load of detergent products as the chemicals used in conventional detergents are reduced; they are biodegradable, non-toxic and leave no harmful residues. Besides lipases, other enzymes are widely used in household cleaning products, in laundering, medical, agriculture, etc. This article also reviews the use of enzymes, especially lipases as detergents and different types of lipase containing detergents available in the market.Key words: Detergents, enzymes, lipases

Effect of screening and management of diabetes during pregnancy on stillbirths

Background:Diabetes during pregnancy is associated with significant risk of complications to the mother, fetus and newborn. We reviewed the potential impact of early detection and control of diabetes mellitus during pregnancy on stillbirths for possible inclusion in the Lives Saved Tool (LiST). Methods: A systematic literature search up to July 2010 was done to identify all published randomized controlled trials and observational studies. A standardized data abstraction sheet was employed and data were abstracted by two independent authors. Meta-analyses were performed with different sub-group analyses. The analyses were graded according to the CHERG rules using the adapted GRADE criteria and recommendations made after assessing the overall quality of the studies included in the meta-analyses. Results: A total of 70 studies were selected for data extraction including fourteen intervention studies and fifty six observational studies. No randomized controlled trials were identified evaluating early detection of diabetes mellitus in pregnancy versus standard screening (glucose challenge test between 24(th) to 28(th) week of gestation) in pregnancy. Intensive management of gestational diabetes (including specialized dietary advice, increased monitoring and tailored dietary therapy) during pregnancy (3 studies: 3791 participants) versus conventional management (dietary advice and insulin as required) was associated with a non-significant reduction in the risk of stillbirths (RR 0.20, 95% CI: 0.03-1.10) (\u27moderate\u27 quality evidence). Optimal control of serum blood glucose versus sub-optimal control was associated with a significant reduction in the risk of perinatal mortality (2 studies, 5286 participants: RR=0.40, 95% CI 0.25-0.63), but not stillbirths (3 studies, 2469 participants: RR=0.51, 95% CI 0.14-1.88). Preconception care of diabetes (information about need for optimization of glycemic control before pregnancy, assessment of diabetes complications, review of dietary habits, intensification of capillary blood glucose self-monitoring and optimization of insulin therapy) versus none (3 studies: 910 participants) was associated with a reduction in perinatal mortality (RR=0.29, 95% CI 0.14 -0.60). Using the Delphi process for estimating effect size of optimal diabetes recognition and management yielded a median effect size of 10% reduction in stillbirths. Conclusion: Diabetes, especially pre-gestational diabetes with its attendant vascular complications, is a significant risk factor for stillbirth and perinatal death. Our review highlights the fact that very few studies of adequate quality are available that can provide estimates of the effect of screening for aid management of diabetes in pregnancy on stillbirth risk. Using the Delphi process we recommend a conservative 10% reduction in the risk of stillbirths, as a point estimate for inclusion in the LiST

Psychrotrophic bacteria isolated from -20°C freezer

Three psychrotrophic bacteria, morpho-physiologically, identified as Bacillus subtilis MRLBA7, Bacillus licheniformis MRLBA8 and Bacillus megaterium MRLBA9 were isolated from -20°C freezer of the Microbiology Research Laboratory (MRL), Quaid-i-Azam University, Islamabad, Pakistan. These strains were able to grow aerobically at 6°C but not at 40°C except MRLBA8 that could grow at 48°C. None of the isolates showed inhibition of growth in the presence of glycerol. Isolate MRLBA7, bearing central spore, grew in the presence of 30% glycerol at 0°C after 48 h of incubation and showed maximum growth without glycerol at 25°C after 24 h. Isolate MRLBA8 showed growth in the presence of 50% glycerol at 4°C after 72 h of incubation and maximum growth was observed at 20°C in the absence ofglycerol. Isolate MRLBA9 showed growth at 6°C in the presence of 40% glycerol after 48 h of incubation and maximum growth was observed at 25°C in the absence of glycerol. Isolates were susceptible to antibiotics except Bacillus subtilis MRLBA7 that exhibited antibiotic resistance against penicillin and fosphomycin, Bacillus licheniformis MRLBA8 against aztreonam and fosphomycin, and Bacillus megaterium MRLBA9 against vancomycin and penicillin. The growth profile and biochemical characteristics of all the isolates were rather similar to that of mesophilic counterparts except adaptation to low temperature. These strains could be used as model microbial strains for characterization of food contaminants in freezers, to understand the mechanism of antibiotic resistanceinduced at low temperature and as a source of psychrotrophic enzymes

A Review on Synthesis of Silicon Nanowires by Laser Ablation

Silicon (Si) is the most widely used semiconductor since many decades. Due to the developments in the synthesis and manufacturing technology new semiconductor materials have been introduced in semiconductor industry. Along with the newly developed semiconductors, Si is still considered the most reliable and durable semiconductor. The synthesis techniques of the Si have also been affected by the technological revolution and different Si based materials engineered at the nano-scale have been synthesized. Silicon nanowires (SiNWs) are one of the newly developed semiconductors of Si. SiNWs have interesting features due to their high aspect ratio and small size. The chemical, mechanical and electrical properties of SiNWs have opened new ways for the research in this field. Especially the charge carrying abilities and quantum confinement effects have gathered much attention of the scientific community. Different efforts have been made to synthesize SiNWs over the course of few years. Synthesis of SiNWs by laser ablation is one of the methods widely used due to its simplicity and good control over the parameters of the process. Different modifications have been made in this synthesis process by different researchers. The variations in laser ablation synthesis process and its outputs have been analyzed in this review paper. And effect of different parameters on the properties of SiNWs has been discussed. Keywords: Laser ablation, Nanowires, Supersaturation, Vapor liquid solid mechanism, Lithography, Catalys

Long-term clinical outcomes of percutaneous coronary intervention in saphenous vein grafts in a low to middle-income country

Background: Revascularization of saphenous vein grafts (SVGs) is challenging and debated for the last few decades. The percutaneous revascularization of SVGs was reported to have poorer long-term outcomes than native coronary artery revascularization.Purpose: We aim to study the peri-procedural complications and long-term outcomes of the percutaneous revascularization of SVGs in a low-middle-income country.Methods: In this retrospective study, we included 110 patients who underwent percutaneous revascularization from January 2011 to March 2020 and followed them retrospectively for long-term outcomes and major adverse cardiovascular events.Results: The mean age was 71 ±9, and 81% were male. The most common reason for the presentation was non-ST segment elevation myocardial infarction (NSTEMI) (46%). The mean follow-up period of the study was 48±27 months. The most common comorbidity was hypertension (86%). A drug-eluting stent (80%) was placed in most of the patients, followed by a bare-metal stent (BMS) (14%) and percutaneous balloon angioplasty (POBA) (6%). We did not find any significant difference in major adverse cardiac events (MACE) (P=0.48), target vessel revascularization (TVR) (p=0.69), and target lesion revascularization (TLR) (p=0.54) with drug-eluting stent (DES) as compared to either BMS or POBA. The mean period from coronary artery bypass grafting (CABG) to SVG percutaneous coronary intervention (PCI) was 15± 5.5 years. Multivariate Cox regression analysis showed that an acute coronary syndrome (ACS) event, stroke, and female sex were independently associated with MACE.Conclusion: The long-term outcomes of SVG PCI are not affected by the types of stents. Female gender, ACS, and stroke are the independent predictors of MACE after SVG PCI, and statin therapy has a positive impact on the long-term outcomes of SVG PCI

Prolonged activated partial thromboplastin time secondary to factor XII deficiency in two surgical patients

Factor XII (FXII) plays a pivotal role in hemostasis, inflammation and complement system. Its deficiency is usually an incidental finding in an otherwise asymptomatic patient who is identified during his/her routine preoperative blood work. This study aimed in evaluating the clinical course of the surgical patients having FXII deficiency. Information regarding demographics, laboratory tests and management of patients was obtained through medical chart and in-house integrated laboratory management system whereas the medical literature was searched through PubMed®. During the study period, two patients were consulted for FXII deficiency prior to the various surgical procedures. Both patients had uneventful surgeries without any thrombotic events while hemorrhage observed in one patient was secondary to obstetric complications. With the limited evidence today, it is concluded that patients having FXII deficiency are not at increased risk of bleeding, thrombosis or infections during surgery, but a personalized approach is needed for planning an appropriate perioperative management

Forensic Analysis of Tor Browser on Windows 10 and Android 10 Operating Systems

Smartphones and Internet have become prevalent in our society with various applications in businesses, education, healthcare, gaming, and research. One of the major issues with the Internet today is its lack of security since an eavesdropper can potentially intercept the communication. This has contributed towards an increased number of cyber-crime incidents, resulting in an increase in users’ consciousness about the security and privacy of their communication . One example is the shift towards using private browsers such as Tor. Tor is a well-recognized and widely used privacy browser based on The Onion Router network that provisions anonymity over the insecure Internet. This functionality of Tor has been a major hurdle in cybercrime investigations due to the complex nature of its anonymity. This paper investigates artifacts from the Tor privacy browser on the latest Windows 10 and Android 10 devices to determine potential areas where evidence can be found. We examine the registry, storage, and memory of Windows 10 devices and the memory, storage, logs, and Zram of Android 10 devices for three possible scenarios i.e. before, during, and after use of the Tor browser. Our results do not support the claims made by the Tor Project regarding user privacy and anonymity. We find that it is possible to retrieve significant details about a user’s browsing activities while the Tor browser is in use as well as after it is closed (on both operating systems). This paper also provides an investigative methodology for the acquisition and analysis of Tor browser artifacts from different areas of the targeted operating systems. Therefore, it can serve as a base to expand research in the forensic analysis of other privacy browsers and improve the efficiency of cybercrime investigations efficiency