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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 397-403 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Smoke visualization studies have been made on the flow fields of wall bounded vortices generated by puffing air through an orifice. The characteristics of wall bounded vortices produced by three orifices constructed by placing a dividing plate perpendicular to a circular orifice plate have been investigated. The three orifices were a full circular opening, a three-quarter circular opening, and a semicircular opening. It was found that the vorticity concentrated in the wall shear layer of the three-quarter and semicircular orifices was due to the separation of the boundary layer on the dividing plate and its interaction with the arch shaped vortex generated at the perimeter of the orifice. An interesting observation is that the wall bounded vortex from the semicircular orifice moved in a stable manner, whereas, the vortex ring produced by the circular orifice with the dividing plate at the bottom of the orifice was extremely unstable.
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 14 (2002), S. 143-149 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: For a vortex ring at Re=1600, it was found that two types of azimuthal flow (axial flow) exist inside the vortex tube. The axial flow appears when the amplitude of a wavy deformation of the vortex ring becomes appreciable. The axial flow starts to grow before the wave-breaking and its speed increases gradually. In order to investigate the relation between the deformation of the vortex core and the axial flow, the flow field was examined experimentally using smoke visualization and the smoke wire technique simultaneously. Axial flow velocities are estimated from flow visualization images. © 2002 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 1280-1282 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A wall vortex was found, which was induced by, and moved together with, a confined vortex pair, near the parallel plates between which the confined vortex pair was traveling. The generation of the wall vortex can be attributed to the boundary layer separation that was caused by the characteristic flow field of the vortex pair itself.
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of organic chemistry 40 (1975), S. 1351-1353 
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
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  • 5
    ISSN: 1573-904X
    Keywords: mepitiostane ; intrinsic lymphatic partition rate ; intestinal lymphatics ; portal absorption ; epitiostanol ; oleic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Mepitiostane (MP), epitiostanol (EP), and oleic acid were administered to the jejunal loop of mesenteric vein- and thoracic duct-cannulated rats, and the intrinsic lymphatic partition rate (ILPR) of the absorbed compounds was directly determined. When 14C-EP was administered to the jejunal loop, recovery of unchanged EP in the mesenteric blood and the lymph was 7.9 and 0.03% of the administered dose, respectively. In contrast, following administration of 14C-MP, recovery of unchanged MP in the mesenteric blood and the lymph was 1.2 and 15.0%, respectively. Thus, following passage through the mucosal cell, 99.6% of the unchanged EP was partitioned into the blood and 0.4% into the lymph, while for unchanged MP, 7.6% was partitioned into the blood and 92.4% into the lymph. When 14C-oleic acid was administered to the jejunal loop, most of the penetrating oleic acid was incorporated into triglycerides in epithelial cells and transferred exclusively into the lymph. However, of the unchanged oleic acid, only 37.6% was partitioned into the lymph and 62.4% into the blood. The ILPR was 92.4% for MP, 0.4% for EP, and 37.6% for oleic acid. We conclude that the ILPR values indicate the true lymphotropic property of the compounds.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Pharmaceutical research 9 (1992), S. 1617-1621 
    ISSN: 1573-904X
    Keywords: mepitiostane ; epitiostanol ; intrinsic lymphatic partition rate ; lipophilicity ; chylomicron
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Substitution of the steroid epitiostanol (EP) at position 17 with methoxycyclopentane yields the extremely lipophilic mepitiostane (MP) with preferential partitioning into the lymph. Most of the MP in the lymph was associated with the core lipids of chylomicrons and very low-density lipoproteins (VLDL), as was also the case for EP. However, the dialysis velocity of EP and MP from lymph to plasma differed greatly; EP, but not MP, was transferred from the lymph to the plasma. This difference was attributed to differences in their unbound fraction in the lymph. Lymphatic transfer and the logP value of several tested steroids correlated well. Therefore, the oral EP prodrug, MP, partitioned into the lymph because of its superlipophilicity and resultant retention in the core lipids of chylomicrons and VLDL.
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  • 7
    ISSN: 1573-904X
    Keywords: mepitiostane ; superlipophilicity ; lymph–blood partition ratio ; dynamic partitioning model ; chylomicron
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The partition of mepitiostane, testosterone, and some structurally related compounds between lymph and blood in rat jejunum (lymph–blood partition ratio; LBPR) was determined, and the quantitative relationship between LBPR and lipophilicity was examined. When the ΔR m values (hydrophobic parameter derived from the mobility) relative to testosterone were 〈0.2, their logLBPRs remained approximately constant in the range of −2 to −3. When the ΔR m values of the compounds were 〉0.2, a linear correlation (r = 0.986, n = 8) was observed between these values and the logLBPRs. The LBPR, but not the extent of lymphatic absorption, of lipophilic molecules was determined strictly by the superlipophilicity, and for high partitioning into the lymph (〉50% of the absorbed amount), the ΔR m value had to be 〉0.50 (5.65 as the logP value). The relationship between LBPR and superlipophilicity could be explained on the basis of the theoretical equations derived from absorption kinetics based on a dynamic partitioning model.
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  • 8
    ISSN: 1573-904X
    Keywords: moxalactam ; epimerization ; frozen solution ; ice ; activation energy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The epimerization rate constants of R- and S-epimers of moxalactam (LMOX) in a frozen aqueous solution decreased as the temperature decreased. The reaction proceeded in the unfrozen region remaining in the frozen solution, without being affected by the ice. The reaction stopped completely below the collapse temperature of the LMOX aqueous solution. The ratio of R- and S-epimers at equilibrium, which was equal to the ratio of the epimerization rate constant, increased as the temperature decreased. This change in the ratio at equilibrium could be ascribed to the difference in the activation energy between the two epimers.
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  • 9
    ISSN: 1573-904X
    Keywords: ceftibuten ; proton-coupled uphill transport ; rat intestinal brush-border membrane vesicles ; stereoselective transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The transport characteristics of ceftibuten in rat intestinal brush-border membrane vesicles were investigated by a rapid filtration technique. Ceftibuten uptake was markedly stimulated by an inwardly directed H+ gradient (pH 7.5 inside, pH 5.5 outside) in comparison with that in the absence of a H+ gradient. The uptake at 30 sec was four times greater than that observed at equilibrium (overshoot phenomenon), while the H+ gradient-stimulated uptake of ceftibuten was markedly reduced in the presence of FCCP, a protonophore. These results suggested H+-coupled uphill transport of ceftibuten. In contrast, an inwardly directed Na+ gradient had no effect on ceftibuten uptake. The valinomycin-induced K+ diffusion potential (inside positive) significantly stimulated the ceftibuten uptake, suggesting net transfer of the negative charge. In contrast to the cis-isomer ceftibuten, the trans isomer of ceftibuten is not readily absorbed from the intestine, and its uptake was found not to be affected by a H+ gradient. Since the lipophilicity of the trans isomer is similar to that of ceftibuten, the uptake process appears to be stereoselective. The initial uptake of ceftibuten and its analogue cefaclor was concentration dependent under a H+ gradient. The apparent K m value was 0.2 mM for ceftibuten and 3.0 mM for cefaclor.
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  • 10
    ISSN: 1573-904X
    Keywords: ceftibuten ; transport ; brush-border membrane ; oligopeptide ; amino β-lactam ; oral cephem
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ceftibuten undergoes H+-coupled uphill transport across rat small intestinal brush-border membrane vesicles. The effects of amino acids, peptides, folate, and β-lactams on the uptake of ceftibuten were examined. Uptake of ceftibuten was competitively inhibited by dipeptides or tripeptides. A counter-transport effect on ceftibuten uptake was observed in the vesicle preloaded with these peptides, and the transport was temporarily against a concentration gradient (overshooting). On the other hand, ceftibuten uptake was not changed by amino acids and a tetrapeptide. Therefore, ceftibuten is predominantly transported via the oligopeptide transport system in the brush-border membranes. The relationship of ceftibuten transport to folate and other oral antibiotics was also investigated. Cyclacillin, cephradine, and cefadroxil exhibited both inhibitory and countertransport effects, but folate, cefaclor, and cephalexin showed only a slight inhibitory effect. As the transport of cefaclor showed no uphill uptake in the presence of a H+ gradient and its H+ stimulated uptake was small, a H+ gradient-independent carrier-mediated system seems to participate in its transport. These findings suggest that two different carrier-mediated transport systems, H+ gradient dependent and independent, may exist for oral cephems.
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