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The axial compressive experiments were carried out on 21 welded composite T-shaped concrete-filled steel tubular columns, and 395 finite element models were established for parameter calculation. The calculating formula of axial compressive bearing capacity of welded composite T-shaped concrete-filled steel tubular columns is established. The results show that three typical failure modes were found: middle buckling, end local buckling, and integral bending. When the slenderness ratio λ exceeds the elastic instability limit λp, the axial stress of steel is lower than yield strength fy, and the axial stress of core concrete is lower than axial compressive strength fc. Increasing the thickness of steel has a more obvious effect on increasing the axial compressive bearing capacity of specimen. The theoretical calculating formula can effectively predict the axial compressive bearing capacity, and the theoretical calculation is partial to safety. The average ratio of axial compressive bearing capacity of the theoretical calculation to the experimental is 0.909, and the standard deviation is 0.075. The average ratio of axial compressive bearing capacity of the finite element calculation to the experimental is 0.957, and the standard deviation is 0.045. The average ratio of axial compressive bearing capacity of the theoretical calculation to the finite element calculation is 0.951, and the standard deviation is 0.039.

Rationale and objectives: To develop and partially characterize a new class of potential blood pool magnetic resonance (MR) contrast agents.Methods: Various copolymeric chelates of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) were prepared with differing molecular weights of polyethylene glycol (PEG) or polypropylene glycol (PPG) as linkers between the monomeric chelate units. Gadolinium content of the polymeric chelates was determined by atomic absorption spectra. Relaxivity of the polymeric chelates was measured at 1.5 Tesla and compared with Gadolinium-DTPA. MR angiography (MRA) was performed in rabbits comparing Gd-DTPA with Gd-copolymers.Results: The gadolinium content of the copolymeric chelates ranged from 2.95 to 22.2% on weight basis. The molecular weight of the PEG linkers in the copolymers ranged from about 150 to about 3400. Ther1 (1/T1, mM−1 s−1) for Gd-DTPA=4.1. Ther1 values for the different Gd-containing polymers ranged from 3.8 to 5.8, with the lowestr1 for the polymer prepared with the lowest-molecular-weight complex. The higher-molecular-weight complexes resulted in moderately higher relaxivity. MRA with Gd-copolymers, in rabbits, showed markedly greater vascular enhancement relative to an equivalent dose of Gd-DTPA. Vascular enhancement was much more sustained with the copolymeric agent and confined to vascular space; i.e. no appreciable background tissue enhancement—a reflection of distribution into extravascular fluid space—was observed.Conclusions: Relative to Gd-DTPA monomers, PEG-containing Gd-DTPA polymeric complexes provided moderate increases in relaxivity but markedly greater efficacy during in vivo MRA. In vitro relaxivity studies of Gd-copolymers showed only an approximately 50% increase inr1 relaxivity compared with Gd-DTPA. The PEG-containing complex's lack of rigidity may have diminished the effect of spin diffusion on relaxation, thereby accounting for this modest increase. The greater efficacy of Gd-copolymers during in vivo MRA may reflect compartmentalization within the vascular space and possibly enhanced relaxation of the macromolecular copolymers in the blood. Gd-copolymers are promising agents that merit additional study.

Liposomes are spheres composed of relatively non-toxic and biodegradable lipids which are useful for entrapping a variety of drugs, decreasing drug toxicity and targeting. For a number of years we have evaluated the use of liposomes as MR contrast agents. We have prepared and tested contrast agents entrapped within the internal aqueous space of liposomes as well as liposomes incorporating lipophilic contrast agents in the lipid bilayer. When chelates such as Gd-DTPA are entrapped within the internal aqueous space of lipid vesicles, delivery is primarily to the Kupffer cells and clearance is slow. Manganese ions entrapped within lipid vesicles cause more enhancement per micromole of paramagnetic ion than gadolinium. Lipophilic derivatives of manganese EDTA chelates when incorporated into liposomes confer the greatest hepatic enhancement per micromole of metal ion and have favorable clearance kinetics. An apparently hepatocyte specific liposomal MR contrast agent has been prepared based upon a lipop...

The in vitro biooxidation of 4-hydroxy-2,2,6,6-tetramethylpiperidine (TEMP), 4-hydroxy-2,2,4,4-tetramethyl-1,3-oxazolidine (TEMO) and diphenylamine (DPA) by hog liver microsomes to their respective nitroxide free radicals, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), 2,2,4,4-tetramethyl-1,3-oxazolidine-1-oxyl (TEMOO), and diphenylnitroxide (DPNO) has been investigated. For extending the life span of the liver microsomes, a calcium alginate immobilization procedure was used. The biooxidation rates of the above amines to their respective nitroxide metabolites were measured by means of oxygen uptake at 37 degrees C and pH 7.4. N-octylamine was found to be an activator in the biooxidation of the amines. The formation of the nitroxide radicals was identified by E.S.R. spectroscopy.

Unger E, Shen D, Fritz T, Kulik B, Lund P, Wu G-L, Yel-lowhair D, Ramaswami R, Matsunaga T. Gas-filled lipid bilayers as ultrasound contrast agents. Invest Radiol 1994;29: S134–S136.

Our group has developed technology for stabilizing microbubbles with phospholipid coatings (Aerosomes®‐ImaRx Pharmaceutical Corp.). The first agent (MRX‐115) is based upon lipid‐coated microspheres filled with perfluoropropane gas and is in phase III clinical trials (October, 1997) for radiology and cardiology applications. Myocardial perfusion studies show the potential for the agent to detect ischemia in patients with myocardial infarcts. Targeting ligands have been covalently bound to lipids and incorporated into the stabilizing shells on the microbubbles. The first targeted agent planned for clinical trials is MRX‐408 (perfluorobutane gas, linear hexapeptide‐RGD analog). In vitro studies show enhanced visualization of thrombi, and in vivo studies in dogs with arterial and venous thrombi show selective enhancement, even in animals injected with heparin. In vitro studies have been performed to test sonothrombolysis comparing MRX‐115 to MRX‐408 with and without urokinase. The targeted contrast agent MRX‐408 increases the rate of clot dissolution with ultrasound. Targeted, tissue‐specific agents are feasible for ultrasound. A thrombus‐specific ultrasound contrast agent has the potential to improve clot characterization and detection as well as clot lysis.

Transfection experiments were performed in vitro in cell culture and in vivo in fish and mice using cationic liposomes with several different reporter genes. The effect of continuous‐wave 1‐MHz ultrasound on cell viability, cell permeability, and gene expression was assessed. RT‐PCR was used to monitor gene expression of cell repair genes in insonated cells. Acoustically active halocarbon‐containing liposomes were prepared for gene delivery. Ultrasound increased cell permeability and gene expression following liposomal transfection. RT‐PCR showed upregulation of repair of a number of cell repair genes after ultrasound exposure. The acoustically active gene delivery vehicles provided highly efficient transfection both with and without ultrasound in vitro and in vivo. Following IV administration of halocarbon‐containing liposomes/gene complexes, preferential gene expression was observed in the insonated tissue. Ultrasound has potentially useful applications for targeting and enhancing gene therapy.

Novel complexes of paramagnetic ions and compounds bearing long acyl chains have been synthesized as magnetic resonance imaging contrast agents. These novel liposoluble contrast agents may be administered alone, or with lipids, suspending agents or other additives. The lipids may be in the form of liposomes, micelles or lipid emulsions. The contrast agents of the invention have particular use in magnetic resonance imaging of the liver, blood pool and reticuloendothelial system.

Mechanisms are proposed for the formation of M+, [M + 2H]+ and [M + 3H]+ ions in the fast atom bombardment (FAB) mass spectra of 4-(2,2,6,6-tetramethyl-1-oxyl)-piperidol and its carboxylates. Free radical quenching induced by the fast atom beam has been observed. The effects of temperature on the radical quenching and of acid on the FAB mass spectra are discussed. The experiment showed that the volatile liquid samples with vapour pressures higher than that for glycerol produced M+ even-electron molecular ions, and the FAB mass spectra were similar to the corresponding electron ionization mass spectra. For the solid samples, it was found that the free radicals were quenched during the FAB process so that the mononitroxide and dinitroxide compounds produced [M + 2H]+ and [M + 3H]+ ions, respectively. Further experiments showed that the intensities and stabilities of [M + 2H]+ and [M + 3H]+ ions could be improved by addition of acids.

(4) Two new spin labeled metal complexes; cobalt(II) bis(2,2,6,6-tetramethyl-1-oxyl-4-piperidyl p-salicylaldiminobenzoate) (3), copper(II) bis(2,2,6,6-tetramethyl-1-oxyl-4-piperidyl-p-salicylaldiminobenzoate) were prepared. The synthesis of amino derivatives of nitroxide compounds were improved by a simplified synthetic route. The XPS spectra of 3 and 4 were determined. The observed N Is, Cu 2p and Co 2p spectra of spin labeled metal complex are discussed.

Synthese du compose du titre et d'acides furanne- et thiopheneacryliques-3 et -propioniques-3; activite biologique