Obstructing mass

The excretory products of the kidneys and the excretory glands may be eliminated directly through a specific canal into an environment in direct contact with the outside—such as the skin, the mouth, the salivary gland, the intestine, or the pancreatic duct—or they may be collected into reservoirs, such as the gallbladder and the urinary bladder, before they are drained to the outside. Under normal conditions all excretory products remain in solution. Damage to the epithelium of the excretory canals or the reservoirs or changes in the composition of the secretions (because of abnormal intake or metabolic alterations) may lead to the precipitation of the metabolites in solution, causing obstructive masses called stones to be formed. 

The indications for CTC closely follow the indications for conventional optical colonoscopy with few exceptions. These indications include screening asymptomatic high- and average-risk patient populations, pre-operative assessment of the colon proximal to an obstructing mass, evaluation of patients with change in bowel habits, surveillance of patients post colorectal cancer surgery, and incomplete or failed colonoscopy. Patients with bleeding diathesis, contraindications to sedation, and frail and elderly patients may also be better suited for CTC than conventional colonoscopy. 

Double contrast barium enema remains in the algorithm for work-up of colorectal cancer in evaluation of the proximal bowel in cases of an obstructing mass. This examination is not preferred, as the proximal colon often does not drain all of the barium by the time of surgery. Patients are also at increased risk for post-operative morbidity if a reactive peritonitis develops secondary to barium contamination intr a- operatively. 

The incidence of synchronous neoplasia in the colon has been described at a rate of 1.5-9%. Adenomas harboring in the colon in patients with colon cancer have been reported at an incidence of 27-55%. Fenlon et al. compared CTC to pre-operative double contrast barium enema in the evaluation of patients with an obstructing carcinoma (Fenlon et al. 1999a). CTC identified all ofthe cancers including 2 synchronous cancers proximal to the obstructing mass that were missed by barium enema (Fenlon et al. 1999a). In addition, CTC demonstrated 16 of 18 polyps in the proximal colon. 

Characteristic features of intraductal peripheral CCA at CT include segmental or lobar dilatation of the intrahepatic bile ducts with higher attenuation than that of bile. An obstructing mass is occasionally seen as a spontaneously hypodense lesion relative to the liver parenchyma, when it is larger than 1 cm. On contrast-enhanced CT, it appears as an enhancing soft-tissue intraductal mass (Yoon et al. 2000). Because the intraductal-growing tumour does not penetrate the bile duct wall, its outer margin is relatively clear on CT. The tumour may not be depicted when it is small and isodense to the adjacent hepatic parenchyma or when the complex orientation of the dilated bile ducts obscures the presence of the mass. 

Figure 635 Extreme-case design-maximum channel width current collector along boundary and otherwise open. This design has the least obstructed mass transfer but the worst electrical contact and would suffer severe DM tenting.

On the basis of an extended experimental program described in Section 4.1.3, Harris and Wickens (1989) concluded that overpressure effects produced by vapor cloud explosions are largely determined by the combustion which develops only in the congested/obstructed areas in the cloud. For natural gas, these conclusions were used to develop an improved TNT-equivalency method for the prediction of vapor cloud explosion blast. This approach is no longer based on the entire mass of flammable material released, but on the mass of material that can be contained in stoichiometric proportions in any severely congested region of the cloud. 

The reason for this can be seen as follows. In a perfect crystal with the ions held fixed, a positive hole would move about like a free particle with a mass m depending on the nature of the crystal. In an applied electric field, the hole would be uniformly accelerated, and a mobility could not be defined. The existence of a mobility in a real crystal derives from the fact that the uniform acceleration is continually disturbed by deviations from a perfect lattice structure. Among such deviations, the thermal motions of the ions, and in particular, the longitudinal polarisation vibrations, are most important in obstructing the uniform acceleration of the hole. Since the amplitude of the lattice vibrations increases with temperature, we see how the mobility of a... 

Cell BR, Cote CG, Marin JM et al (2004) The body-mass index, airflow obstruction, dyspnea, and exercise capacity index in chronic obstructive pulmonary disease. New Engl J Med 350 1005-1012... 

Another contributing mechanism is the direct cooling of hot propellant surface by contact with the injected fluid. The fluid should cause the decomposing surface to reduce its pyrolysis rate to a point where combustion cannot be sustained. In addition, the presence of water on the surface would obstruct heat transfer from the gas-phase reaction zones to the solid surface, thus augmenting the cooling of the surface. Proponents of these two approaches have correlated the injection data on the basis of mass of fluid required per unit area of surface, but theoretical justifications for the use of this particular correlating parameter have not been presented. 

A similar classification scheme is used to gauge the severity of active CD.2 Patients with mild to moderate CD are typically ambulatory and have no evidence of dehydration, systemic toxicity, loss of body weight, or abdominal tenderness, mass, or obstruction. Moderate to severe disease is considered in patients who fail to respond to treatment for mild to moderate disease, or those with fever, weight loss, abdominal pain or tenderness, vomiting, intestinal obstruction, or significant anemia. Severe to fulminant CD is classified as the presence of persistent symptoms or evidence of systemic toxicity despite outpatient corticosteroid treatment, or presence of cachexia, rebound tenderness, intestinal obstruction, or abscess. 

Most patients with severe to fulminant CD require hospitalization for appropriate treatment. Patients should be assessed for possible surgical intervention if abdominal distention, masses, abscess, or obstruction are present. Intravenous daily doses of corticosteroids equivalent to prednisone 40 to 60 mg are recommended as initial therapy to rapidly suppress severe inflammation. 

As for the other obstruction meters, when the continuity equation is used to eliminate the upstream velocity from Eq. (10-11), the resulting expression for the mass flow rate through the orifice is... 

Adenopathy can be localized or generalized. Involved nodes are painless, rubbery, and discrete and are usually located in the cervical and supraclavicular regions. Mesenteric or GI involvement can cause nausea, vomiting, obstruction, abdominal pain, palpable abdominal mass, or GI bleeding. Bone marrow involvement can cause symptoms related to anemia, neutropenia, or thrombocytopenia. 

Merkel, D., et al., Proteomic study of human bronchoalveolar lavage fluids from smokers with chronic obstructive pulmonary disease by combining surface-enhanced laser desorp-tion/ionization-mass spectrometry profiling with mass spectrometric protein identification, Proteomics. 5, 11, 2972, 2005. 

Release momentum. For jet releases, the amount of air entrained in an unobstructed jet is proportional to the jet velocity. Depending on the orientation of the jet relative to nearby obstructions, the momentum of a jet can be dissipated without significant air entrainment. The degree of initial air entrainment can be an important determinant of the hazard extent, particularly for flammable hazards. It would be (possibly overly) conservative to assume the source momentum is dissipated without air dilution. Explosive releases are high-momentum, instantaneous releases. For explosive releases, a rough first approximation is to assume that the mass of contaminant in the explosion is mixed with 10 times that mass of air. 

There are two different mechanisms behind ordinary causes of constipation, functional and outlet obstructions. Functional constipation is caused by the slower movement of the colon, peristalsis, which comes with old age, often in combination with less physical activity and less intake of fibre containing food. Outlet obstruction is a result of incapacity to empty the rectum from faeces often due to too large masses of stool blocking the anus. It can also be caused by anal stricture from haemorrhoids or scar tissue caused by fissures. 

Figure 17.8 shows the probe, which consists of a 1-millimeter diameter t3rpe K thermocouple centered between two 1-millimeter diameter pressure taps. Each of the pressure tubes was bent 90° and sheared at the bend. To obtain a measurement, the tube is rotated until the pressure difference between the two taps is maximized. This is the position at which one tube is directed into the oncoming flow and the other is parallel to it. The approach flow thus observes an approximately 1-millimeter thick planar obstruction. The pressure difference and temperature are then recorded. The pressure difference is related to the approach velocity, and the angle determines the tangential and axial velocity components in this case. The local mass flux is then determined from the axial velocity component and the temperature (necessary to compute the flow density), and... 

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