Fates of a Nonwetting Slug in Tapered Microcapillaries under Gravity and Zero Gravity Conditions: Dynamics, Asymptotic Equilibrium Analysis, and Computational Fluid Dynamics Verifications.

It has been determined experimentally and numerically that a nonwetting slug in a tapered capillary tube, under the sole action of capillary force, self-propels itself toward the wider end of the tube until an equilibrium state is reached. The aim of this work is to highlight the state of the slug at equilibrium in terms of configuration and location. Furthermore, it turns out that gravity adds richness to this phenomenon, and more fates become possible. A modified Bond number is developed that determines the relative importance of gravity and capillarity for this system. According to the magnitude of the Bond number, three more fates are possible. Therefore, in a tapered capillary tube held vertically upward with its wider end at the top, in the absence of gravity or under microgravity conditions, the nonwetting slug moves upward toward the wider end of the tube until it reaches equilibrium with the two menisci part of a single sphere. The location of the slug at equilibrium in this case represents the farthest fate among the other fates. When gravity exists yet capillarity dominates, the slug still moves upward toward the wider end. However, in this case, the two menisci become parts of two different spheres of different curvatures. For this scenario, the slug climbs upward but reaches a lower level compared to the previous scenario. On the other hand, when gravity dominates, the slug experiences a net downward pull toward the narrower end of the tube and starts to move in the direction of gravity until capillary force establishes a balance, then it stops. When gravity sufficiently dominates, it pulls the slug downward until it completely drains off the tube. A computational fluid dynamics (CFD) analysis is conducted in order to build a framework for verification exercises. Excellent agreements between the results of the developed model and the CFD analysis are obtained. A fate map and a scheme are developed to identify these four fates based on two Bond numbers; namely, the initial Bond number and that associated with the slug when it is at the exit.

The Effect of the Oleophobicity Deterioration of a Membrane Surface on Its Rejection Capacity: A Computational Fluid Dynamics Study.

In this work, the effects of the deteriorating affinity-related properties of membranes due to leaching and erosion on their rejection capacity were studied via computational fluid dynamics (CFD). The function of affinity-enhancing agents is to modify the wettability state of the surface of a membrane for dispersed droplets. The wettability conditions can be identified by the contact angle a droplet makes with the surface of the membrane upon pinning. For the filtration of fluid emulsions, it is generally required that the surface of the membrane is nonwetting for the dispersed droplets such that the interfaces that are formed at the pore openings provide the membrane with a criterion for the rejection of dispersals. Since materials that make up the membrane do not necessarily possess the required affinity, it is customary to change it by adding affinity-enhancing agents to the base material forming the membrane. The bonding and stability of these materials can be compromised during the lifespan of a membrane due to leaching and erosion (in crossflow filtration), leading to a deterioration of the rejection capacity of the membrane. In order to investigate how a decrease in the contact angle can lead to the permeation of droplets that would otherwise get rejected, a CFD study was conducted. In the CFD study, a droplet was released in a crossflow field that involved a pore opening and the contact angle was considered to decrease with time as a consequence of the leaching of affinity-enhancing agents. The CFD analysis revealed that the decrease in the contact angle resulted in the droplet spreading over the surface more. Furthermore, the interface that was formed at the entrance of the pore opening flattened as the contact angle decreased, leading the interface to advance more inside the pore. The droplet continued to pass over the pore opening until the contact angle reached a certain value, at which point, the droplet became pinned at the pore opening.

First insights into the molecular basis association between promoter polymorphisms of the IL1B gene and Helicobacter pylori infection in the Sudanese population: computational approach.

BACKGROUND: Helicobacter pylori (H. pylori) infects nearly half of the world's population with a variation in incidence among different geographic regions. Genetic variants in the promoter regions of the IL1B gene can affect cytokine expression and creates a condition of hypoacidity which favors the survival and colonization of H. pylori. Therefore, the aim of this study was to characterize the polymorphic sites in the 5'- region [-687_ + 297] of IL1B in H. pylori infection using in silico tools. RESULTS: A total of five nucleotide variations were detected in the 5'-regulatory region [-687_ + 297] of IL1B which led to the addition or alteration of transcription factor binding sites (TFBSs) or composite regulatory elements (CEs). Genotyping of IL1B - 31 C > T revealed a significant association between -31 T and susceptibility to H. pylori infection in the studied population (P = 0.0363). Comparative analysis showed conservation rates of IL1B upstream [-368_ + 10] region above 70% in chimpanzee, rhesus monkey, a domesticated dog, cow and rat. CONCLUSIONS: In H. pylori-infected patients, three detected SNPs (- 338, - 155 and - 31) located in the IL1B promoter were predicted to alter TFBSs and CE, which might affect the gene expression. These in silico predictions provide insight for further experimental in vitro and in vivo studies of the regulation of IL1B expression and its relationship to H. pylori infection. However, the recognition of regulatory motifs by computer algorithms is fundamental for understanding gene expression patterns.

Molecular Phylogenetic Analysis of 16S rRNA Sequences Identified Two Lineages of Helicobacter pylori Strains Detected from Different Regions in Sudan Suggestive of Differential Evolution.

BACKGROUND: Helicobacter pylori (H. pylori) is ubiquitous among humans and one of the best-studied examples of an intimate association between bacteria and humans. Phylogeny and Phylogeography of H. pylori strains are known to mirror human migration patterns and reflect significant demographic events in human prehistory. In this study, we analyzed the molecular evolution of H. pylori strains detected from different tribes and regions of Sudan using 16S rRNA gene and the phylogenetic approach. Materials and methods. A total of 75 gastric biopsies were taken from patients who had been referred for endoscopy from different regions of Sudan. The DNA extraction was performed by using the guanidine chloride method. Two sets of primers (universal and specific for H. pylori) were used to amplify the 16S ribosomal gene. Sanger sequencing was applied, and the resulted sequences were matched with the sequences of the National Center for Biotechnology Information (NCBI) nucleotide database. The evolutionary aspects were analyzed using MEGA7 software. RESULTS: Molecular detection of H. pylori has shown that 28 (37.33%) of the patients were positive for H. pylori and no significant differences were found in sociodemographic characteristics, endoscopy series, and H. pylori infection. Nucleotide variations were observed at five nucleotide positions (positions 219, 305, 578, 741, and 763-764), and one insertion mutation (750_InsC_751) was present in sixty-seven percent (7/12) of our strains. These six mutations were detected in regions of the 16S rRNA not closely associated with either tetracycline or tRNA binding sites; 66.67% of them were located in the central domain of 16S rRNA. The phylogenetic analysis of 16S rRNA sequences identified two lineages of H. pylori strains detected from different regions in Sudan. The presence of Sudanese H. pylori strains resembling Hungarian H. pylori strains could reflect the migration of Hungarian people to Sudan or vice versa. CONCLUSION: This finding emphasizes the significance of studying the phylogeny of H. pylori strains as a discriminatory tool to mirror human migration patterns. In addition, the 16S rRNA gene amplification method was found useful for bacterial identification and phylogeny.

Numerical investigation of nanoparticles transport in anisotropic porous media.

In this work the problem related to the transport of nanoparticles in anisotropic porous media is investigated numerically using the multipoint flux approximation. Anisotropy of porous media properties is an essential feature that exists almost everywhere in subsurface formations. In anisotropic media, the flux and the pressure gradient vectors are no longer collinear and therefore interesting patterns emerge. The transport of nanoparticles in subsurface formations is affected by several complex processes including surface charges, heterogeneity of nanoparticles and soil grain collectors, interfacial dynamics of double-layer and many others. We use the framework of the theory of filtration in this investigation. Processes like particles deposition, entrapment, as well as detachment are accounted for. From the numerical methods point of view, traditional two-point flux finite difference approximation cannot handle anisotropy of media properties. Therefore, in this work we use the multipoint flux approximation (MPFA). In this technique, the flux components are affected by more neighboring points as opposed to the mere two points that are usually used in traditional finite volume methods. We also use the experimenting pressure field approach which automatically constructs the global system of equations by solving multitude of local problems. This approach facilitates to a large extent the construction of the global system. A set of numerical examples is considered involving two-dimensional rectangular domain. A source of nanoparticles is inserted in the middle of the anisotropic layer. We investigate the effects of both anisotropy angle and anisotropy ratio on the transport of nanoparticles in saturated porous media. It is found that the concentration plume and porosity contours follow closely the principal direction of anisotropy of permeability of the central domain.

The underlying aetiologies of coma in febrile Sudanese children.

BACKGROUND: Cerebral malaria, acute bacterial meningitis and viral encephalitis are the main causes of fever and altered consciousness in the tropics. In areas where reliable laboratory testing is unavailable, over diagnosis and misdiagnosis of these conditions is likely. In malaria endemic countries non-malarial contributors to coma may be overlooked, overburdening available resources. The aim of this study is to evaluate the underlying causes of altered mental state in children presenting with fever and coma to tertiary medical facilities in Sudan. METHODS: Children over one month of age admitted to the emergency departments of three main hospitals in Khartoum with fever and coma were investigated for cerebral malaria, acute bacterial meningitis and Herpes simplex encephalitis during April to November 2011. RESULTS: One hundred and four children presenting with fever and coma were evaluated. Cerebral malaria was clinically suspected in 38 patients and 5 were confirmed. Acute bacterial meningitis was suspected in 63 patients and confirmed in 15. Herpes encephalitis was confirmed in only one case. There were five cases of mixed infection and the remainder were unknown. CONCLUSION: The clinical diagnoses of cerebral malaria, acute bacterial meningitis and viral encephalitis are unreliable. Further studies to evaluate the underlying causes of coma in febrile Sudanese children are warranted.

Effects of sub-lethal exposure of lead acetate on histopathology of gills, liver, kidney and muscle and its accumulation in these organs of Clarias gariepinus

The aim of this work was to study the effects of sub-lethal exposure of lead acetate on the histopathology of the gills, liver, kidney and muscle and its accumulation in these organs of Clarias gariepinus. Results showed that lead accumulation in the tissues of C. gariepinus was dependent on the exposure period and lead concentration. Gills and liver were the predominant storage tissue and the order of accumulation in tissues was gill > liver > kidney > muscle. Some structural changes were observed in different organs, especially in the gills of the fishes exposed to lead acetate. Epithelial hypertrophy and epithelial lifting were apparent in the gills of exposed fishes. The degeneration of cytoplasm and secondary lamellae was also observed. Necrosis of hepatocytes was apparent. Glomerular expansion and gaps between the muscular bundles were found in the fishes exposed to lead acetate.

Cigarette smoking among medical students in The National Ribat University, Sudan.

The problem of smoking among medical students is common worldwide, but the pattern and extent of the problem varies from place to place. Data from Sudanese medical students is limited. The aims of study was to know the extent of the problem of smoking among medical students, its routes and how it can be reduced. All students in the first and fifth year in the Faculty of Medicine, The National Ribat University were asked to fill a questionnaire regarding their knowledge and practice of smoking and when they started smoking. The questionnaire inquired about the role of their peers and the staff to help them stop smoking. Two hundred and forty (96%) of the first year students and 174 (94 %) of the fifth year students responded by filling the questionnaires. Around 10 % of all students smoke. Although non-smokers knew much about the problems of smoking, many of the smokers did not. The main influence on students to start smoking was from parents, siblings and friends. Eighty per cent of the smokers are willing to give up smoking and they tried many times. The study showed that little effort was made by the University Staff to help students stop smoking. Most students started smoking in the high secondary schools. There is a need for family community and institutional campaign to contain the problem of smoking.

Ultrasound guidance during embryo transfer: a prospective, single-operator, randomized, controlled trial.

OBJECTIVE: To determine whether the implementation of ultrasound (US) guidance will improve the clinical outcomes of ET compared with the standard clinical touch method of embryo catheter placement. DESIGN: Prospective, single-operator, randomized, controlled trial. SETTING: Saudi Center for Assisted Reproduction. PATIENT(S): Three hundred seventy-three women. INTERVENTION(S): Transcervical, intrauterine ET with or without US guidance. MAIN OUTCOME MEASURE(S): Primary outcomes were the live-birth/ongoing pregnancy and clinical pregnancy rates per randomized woman. Secondary outcomes were the incidences of difficult transfers, blood and/or mucus on the catheter tip, spontaneous miscarriages, and ectopic pregnancies. RESULT(S): Demographics and cycle characteristics were not different between the two groups. The live-birth/ongoing pregnancy rate was significantly higher in the US ET group (68 of 183, 40.98%) than in the clinical touch ET group (50 of 190, 28.42%) (odds ratio = 1.66, 95% confidence interval 1.07-2.57). In addition, there was a significantly higher number of clinical pregnancies in the US ET group (75 of 183, 40.98%) than in the clinical touch ET group (54 of 190, 28.42%) (odds ratio = 1.75, 95% confidence interval 1.14-2.69). Secondary outcomes were not significantly different between the two groups. CONCLUSION(S): Ultrasound-guided ET significantly increases ongoing pregnancy/live-birth and clinical pregnancy rates compared with the clinical touch method.

Removal of cervical mucus prior to embryo transfer improves pregnancy rates in women undergoing assisted reproduction.

The removal of cervical mucus during embryo transfer has been postulated to increase the pregnancy and implantation rates by not interfering with embryo implantation. Even so, this is a time-consuming procedure that may increase the incidence of difficult transfers by removing the naturally lubricant mucus. In addition, any cervical manipulations at the time of embryo transfer may cause unwarranted uterine contractions. In this prospective, controlled study, 286 women undergoing embryo transfer between January and May 2006 were divided into two groups according to whether the cervical mucus was scheduled to be aspirated (group A) or not (group B). The two groups were similar with regards to the demographics, cause of infertility, characteristics of ovarian stimulation and embryos transferred. Even so, the clinical pregnancy rate was significantly higher in group (A) than group (B) (OR = 2.18, 95% CI = 1.32-3.58), although there were easier transfers in group (B) than group (A) (OR = 3.00, 95% CI = 1.05-8.55). This demonstrates that even though embryo transfers were easier to perform when the cervical mucus was left in place, aspiration resulted in an increased chance of clinical pregnancy.