asphaltene precipitation and deposition is a serious problem in many iranian fields. the deposited asphaltene results in partial or total blockage of the wellbore and wellstring reducing or completely seizing oil production. this paper studies the asphaltene problem and mitigation methods in wellstring systematically. it presents new approach based on the combination of thermodynamic modeling o...

the suitability of three vapor deposition techniques for pore size modification was evaluated using polycarbonate track etched membranes as model supports. a feature scale model was employed to predict the pore geometry after modification and the resulting pure water flux. physical vapor deposition (pvd) and pulsed plasma-enhanced chemical vapor deposition (pecvd), naturally, form asymmetric na...

Plants are exposed to a wide range of potential pathogens, which derive from diverse phyla. Therefore, plants have developed successful defense mechanisms during co-evolution with different pathogens. Besides many specialized defense mechanisms, the plant cell wall represents a first line of defense. It is actively reinforced through the deposition of cell wall appositions, so-called papillae, ...

To gain insight into the homeostatic mechanisms regulating airway ion/water fluxes and mucociliary transport, the canine tracheobronchial airway fluid was perturbed by deposition of hypo- and hyperosmotic aerosols for >1 h. Tracheal ciliary beat frequency (CBF) was measured by using heterodyne laser light scattering. Tracheal mucus velocity (TMV) and bronchial mucociliary clearance (BMC) were m...

A growing body of experimental evidence suggests that the deposition behavior of microbial particles (e.g., bacteria and viruses) is inconsistent with the classical colloid filtration theory (CFT). Well-controlled laboratory-scale column deposition experiments were conducted with uniform model particles and collectors to obtain insight into the mechanisms that give rise to the diverging deposit...

An analytical model is used .to describe the behavior of inhaled particulate matter in the human respiratory tract. Three different geometries, symmetric and asymmetric, are utilized to simulate the tracheobronchial (TB) tree. The suitability of each geometry for representing the human is evaluated by comparing calculated aerosol deposition probabilities with experimental data from inhalation e...

A 43-year-old woman with rheumatoid arthritis (RA), renal amyloidosis and crescentic glomerulonephritis had severe abdominal pain, melena and progressive renal failure. Autopsy findings revealed vasculitis of small and middle size of vessels and there was a deposition of amyloid in the small intestines. Although there were no findings of vasculitis in the kidney, amyloid deposition was noticed ...

BACKGROUND Sub-epithelial extracellular matrix deposition is a feature of asthmatic airway remodelling associated with severity of disease, decline in lung function and airway hyperresponsiveness. The composition of, and mechanisms leading to, this increase in subepithelial matrix, and its importance in the pathogenesis of asthma are unclear. This is partly due to limitations of the current mod...

Random surface roughness very often can occur during the growth or etching of films under non-equilibrium conditions. Several competing mechanisms such as noise, surface diffusion, and shadowing all play a role in the evolution of surface roughness. However, recent results obtained in many growth and etching processes exhibit an unusual tendency: the morphology is very rough where it is expecte...

Chemical vapor deposition (CVD) is a process that solid formed on substrate by the chemical reaction in phase. Employing this technology, wide range of materials, including ceramic nanocomposite coatings, dielectrics, and single crystalline silicon can be coated variety substrates. Among factors influencing design CVD system are dimensions or geometry substrate, temperature, composition type pr...