Experimental composites using either bisGMA/TEGDMA or UEDMA/ TEGDMA matrices, quartz or barium glass fillers, and 2 different filler silanization methods were evaluated regarding monomer leachability in distilled water. The leached amount was detected and quantified using gas chromatography. The results showed that twice as much TEGDMA is leached from a bisGMA/TEGDMA based composite than from an UEDMA/ TEGDMA based composite, when both contain 50 wt% TEGDMA. The hypothesis suggested that the higher degree of cure of UEDMA/TEGDMA based composites would be reflected in a lower monomer leaching value, and this hypothesis was supported by the findings. Whether such a correlation exists within groups of UEDMA/TEGDMA based matrices having different degrees of cure was not determined and needs to be investigated in future studies. Variables such as filler composition and silane treatment did not affect the leaching values of TEGDMA in water. That finding suggests that future studies should target differences in matrices, and that the need for considering effects of filler composition and silane treatment methods should not receive the same priority. 相似文献
An unsymmetrical diamine monomer 4‐(p‐aminophenoxy)‐3‐trifluoromethyl‐4′‐aminobiphenyl has been synthesized successfully. This monomer leads to the synthesis of different novel poly(ether imide)s when reacted with different dianhydrides like pyromellatic dianhydride (PMDA), benzophenone tetracarboxylic acid dianhydride (BTDA), 2,2‐bis(3,4‐dicarboxyphenyl) hexafluoropropane (6FDA), and oxy diphthalic anhydride (ODA). The poly(ether imide) prepared from this monomer on reaction with 6FDA is soluble in several organic solvents such as N‐methylpyrolidinone (NMP), dimethylformamide (DMF), N,N‐dimethylacetamide (DMAc), tetrahydrofuran (THF), and CHCl3. The poly(ether imide)s prepared from BTDA and ODA are soluble in NMP, DMF, and DMAc but not in THF or CHCl3, whereas the polymer prepared from PMDA is soluble only in NMP. The water uptake value for these poly(ether imide) films is very low (0.2–0.5%), and exhibited low dielectric constants (2.81 at 1 MHz). The polymers exhibited high thermal stability up to 532 °C in air for 5% weight loss, and high glass transition temperatures up to 288 °C. The polymer exhibited high tensile strength up to 135 MPa, modulus 3.2 GPa, and elongation at break up to 25%, depending on the exact polymer structure.
The structure of the poly(ether imide) synthesised from 4‐(p‐aminophenoxy)‐3‐trifluoromethyl‐4′‐aminobiphenyl and 2,2‐bis(3,4‐dicarboxyphenyl) hexafluoropropane. This polymer was soluble in many organic solvents. 相似文献
Incubation of histone H3 with normal citrated plasma resulted in the formation of insoluble aggregates, as determined by turbidity measurements. The precipitate was subjected to sodium dodecyl sulfate polyacrylamide gel electrophoresis, confirming that fibrinogen was a major component. Purified fibrinogen precipitated rapidly as determined with turbidity experiments and experiments with radioiodinated protein. The amount of fibrinogen precipitation was strongly dependent on H3 concentration. Variation of ionic strength (0.2-0.84) and pH (5.3-7.4), however, had little or no effect on the reaction. Fibrinogen subjected to gelatin-Sepharose chromatography or dialysis against 3.3M urea reacted equivalently with H3. Precipitation of 125I-fibrinogen by H3 was strongly favored by increasing temperature (4 degrees-45 degrees C). Precipitation of fibrinogen by protamine was maximized by decreasing the temperature. In addition, formation of insoluble fibrinogen-protamine aggregates was highly dependent on ionic strength and pH, suggesting that different types of protein-interaction are involved in the two studied precipitation reactions. Of the fibrinogen degradation products, only fragment X precipitated significantly when incubated with H3. Radioiodinated fibrin monomer also precipitated when incubated with H3 in solutions of sufficient ionic strength to prevent spontaneous polymerization. The extent of precipitation was equivalent for fibrin monomer and fibrinogen. Fragment D inhibited the precipitation of fibrinogen by H3 or protamine. These studies indicate that the proteins termed "paracoagulants" are not all equivalent and that the hydrophobic domain of H3 plays a critical role in fibrinogen precipitation. 相似文献
A cationic photo-curable cycloaliphatic epoxy resin has been investigated as reactive monomer in blue light crosslinking process. We have demonstrated that camphorquinone is able to abstract labile hydrogen from the epoxy monomer, giving rise to the formation of carbon-centered radicals that are oxidized by the onium salt; a complete epoxy group conversion was reached after 50 s of irradiation. The presence of water up to 1 wt% was tolerated without any important detrimental effect on the kinetics of light-curing. The presence of the inorganic filler up to 65 wt% did not significantly influence the curing process. 相似文献
The synthesis and characterization of a series of green‐, blue‐, and red‐fluorescent exo‐oxanorbornene acid and imide monomers carrying nitrobenzofurazan, coumarin, and rhodamin B, respectively, as fluorophores are presented. These monomers carry oxanorbornene as polymerizable unit, and are readily copolymerized with bioactive functional oxanorbornene monomers by ring‐opening metathesis polymerization, as demonstrated by gel permeation chromatography and NMR spectroscopy. Due to the ease of synthesis of these monomers, and their cost‐effectiveness compared many to other fluorescent probes, they are useful for biomaterial applications. 相似文献
Summary Enhanced activation of the clotting system has been recently implicated in the pathogenesis of vascular complications in
patients with diabetes mellitus. Abnormalities of the anticoagulant system may constitute a potential trigger factor for the
haemostatic activation observed in diabetic subjects. The current study aimed to evaluate anticoagulant activity in diabetic
patients by assessing the plasma levels of activated protein C-protein C inhibitor complex; and by measuring the anticoagulant
response to exogenous thrombomodulin. This study comprised 61 patients (34 men, 27 women) with non-insulin-dependent diabetes
mellitus (NIDDM) of whom 22 showed microalbuminuria and 39 normoalbuminuria. Data obtained in 31 non-obese and non-diabetic
subjects were available for comparison. The plasma levels of fibrinogen (p < 0.02), prothrombin fragment 1 + 2 (p < 0.05), fibrin monomer (p < 0.0001), protein C antigen (p < 0.005), total protein S antigen (p < 0.02), soluble thrombomodulin (p < 0.005) and soluble E-selectin (p < 0.005) were significantly higher in diabetic patients than in healthy subjects. The plasma level of activated protein C-protein
C inhibitor complex (7.4 ± 3.8 vs 3.0 ± 0.4 pmol/l) was significantly higher (p < 0.0001) and the anticoagulant response to exogenous thrombomodulin (23.4 ± 2.6 vs 35.3 ± 3.0 ng/ml) was markedly lower
(p = 0.005) in all diabetic patients than in healthy subjects. Cases with microalbuminuria presented low plasma levels of activated
protein C-protein C inhibitor complex (5.5 ± 0.6 vs 8.6 ± 0.7 pmol/l, p < 0.05) and significantly decreased values of the anticoagulant response to exogenous thrombomodulin (16.5 ± 2.9 vs 23.4
± 2.6 %, p = 0.03) as compared to those with normoalbuminuria. The present study suggests that the hyper-coagulable state in NIDDM is
associated with an increased activation of protein C but with a poor plasma reactivity to the anticoagulant effect of thrombomodulin.
[Diabetologia (1996) 39: 1455–1461]
Received: 27 February 1996 and in revised form: 3 June 1996 相似文献
New insights are provided into the atom transfer radical polymerizations of styrene with 1,6‐bismaleimidohexane, tri‐ethylene glycol dimethacrylate (tri‐EGDMA), and divinyl benzene (DVB) as branching agents. Gas chromatography, proton nuclear magnetic resonance spectroscopy, and triple detection size exclusion chromatography are used to analyze the polymerizations and the polymers. The polymerizations and molecular weights of polymers differ because of the different levels of intramolecular cyclization and initiator efficiencies (IEs) among the three polymerization systems. High IE increases polymerization rate and restrains gelation, thereby facilitating preparation of branched polymers with high molecular weights. Polymers in the tri‐EGDMA system exhibit the lowest molecular weight and the broadest polydispersity because of some evident primary chain residues, whereas polymers in the DVB system show the highest molecular weight because of the low amount of the primary chain residues and high IE. The absence of branching monomer units in the primary chain residue of all these polymerizations is confirmed.
The free radical copolymerization of 2-thienylmethyl 4-vinylbenzyl ether (TMVBE) with 2-oxo-2-(2-thienylmethoxy)ethyl-2-methylacrylate (TMOEM) has been carried out in 1,4-dioxane at 65?°C?±?1 and were analyzed by Fourier transform infrared, 1H NMR, and 13C NMR spectroscopy. 1H NMR analysis was used to determine the molar fractions of TMVBE and TMOEM in the copolymers. The monomer reactivity ratios were calculated according to the general copolymerization equation using Kelen–Tüdõs and Finemann–Ross linearization methods. The reactivity ratios indicated a tendency toward alternation copolymerization. The thermal behaviors of copolymers with various compositions were investigated by differential scanning calorimetry and thermogravimetric analysis. Also, the apparent thermal decomposition activation energies were calculated by the Ozawa and Kissinger methods with a Shimadzu TGA 60 thermogravimetric analysis thermobalance. All the products showed moderate activity against different strains of bacteria and fungi. 相似文献