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ABSTRACT:A poly(amic acid) was prepared by the reaction of 3,3Ј-dihydroxybenzidine and pyromellitic dianhydride in N,N-dimethylacetamide. Hexadecylamine was used as an organophilic alkylamine in organoclay. Cast films were obtained from blend solutions of the precursor polymer and the organoclay. The cast film was heat treated at different temperatures to create polyimide (PI) hybrid films. We set out to clarify the intercalation of PI chains to hexadecylamine-montmorillonite (C 16 -MMT) and to improve thermal and tensile properties and the gas barrier. It was found that the addition of only a small amount of organoclay was enough to improve both the thermal and the mechanical properties of PIs. Maximum enhancement in the ultimate tensile strength for PI hybrids was observed for the blends containing 4% C 16 -MMT. The initial modulus monotonically increased with further increases in C 16 -MMT content. Water vapor permeability was decreased with increasing clay loading from 1 to 8 wt %.

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Poly(ethylene terephthalate-co-ethylene naphthalate) (PETN)/organoclay was synthesized with the solution intercalation method. Hexadecylamine was used as an organophilic alkylamine in organoclay. Our aim was to clarify the intercalation of PETN chains to hexadecylamine-montmorillonite (C 16 -MMT) and to improve both the thermal stability and tensile property. We found that the addition of only a small amount of organoclay was enough to improve the thermal stabilities and mechanical properties of PETN/C 16 -MMT hybrid films. Maximum enhancement in both the ultimate tensile strength and initial modulus for the hybrids was observed in blends containing 4 wt % C 16 -MMT. Below a 4 wt % clay loading, the clay particles could be highly dispersed in the polymer matrix without a large agglomeration of particles. However, an agglomerated structure did form in the polymer matrix at a 6 wt % clay content.

Background To determine whether a minimal stimulation (MS) or high-dose stimulation (HDS) protocol is a better option for patients classified as poor ovarian responders (POR) in terms of reproductive and pregnancy outcomes. Materials and methods A database search for evaluation of the study outcome by using meta-analysis method was carried out. The primary outcome was the clinical pregnancy (CP) rate for each of two groups, namely, the MS and HDS groups. The secondary outcomes were the gonadotropin dose used, duration of stimulation, cancellation rate, number of oocytes retrieved, number of fertilized oocytes, number of embryos transferred and live birth rates. Results Across five databases, 4670 potential studies for further screening were selected. But ultimately only six studies, three RCTs and three retrospective or case control studies were selected that meet the Bologna criteria for POR. In all there were 624 cycles. Our meta-analysis indicated that the CP rates, cycle cancellation rates, durations of stimulation, numbers of oocytes fertilized and numbers of embryos transferred were not statistically significant. Clearly, the number of oocytes retrieved in the MS group was significantly lower than in the HDS group, while the HDS group consumed significantly higher doses of gonadotropins than the MS group. The live birth rates were significantly higher in the MS group than in the HDS group. Conclusion MS should be the first-line protocol for managing POR because the live birth rate is significantly higher, even with fewer oocytes retrieved.

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