22,337 research outputs found
Thermal and mechanical properties of syndiotactic polystyrene/organoclay nanocomposites with different microstructures
No full textThe fabrication of syndiotactic polystyrene (sPS)/organoclay nanocomposite was conducted via a stepwise mixing process with poly(styrene-co-vinyloxazolin) (OPS), that is, melt intercalation of OPS into organoclay followed by blending with sPS. The microstructure of nanocomposite mainly depended on the arrangement type of the organic modifier in clay gallery. When organoclays that have a lateral bilayer arrangement were used, an exfoliated structure was obtained, whereas an intercalated structure was obtained when organoclay with a paraffinic monolayer arrangement were used. The thermal and mechanical properties of sPS nanocomposites were investigated in relation to their microstructures. From the thermograms of nonisothermal crystallization and melting, nanocomposites exhibited an enhanced overall crystallization rate but had less reduced crystallinity than a matrix polymer. Clay layers dispersed in a matrix polymer may serve as a nucleating agent and hinder the crystal growth of polymer chains. As a comparison of the two nanocomposites with different microstructures, because of the high degree of dispersion of its clay layer the exfoliated nanocomposite exhibited a faster crystallization rate and a lower degree of crystallinity than the intercalated one. Nanocomposites exhibited higher mechanical properties, such as strength and stiffness, than the matrix polymer as observed in the dynamic mechanical analysis and tensile tests. Exfoliated nanocomposites showed more enhanced mechanical properties than intercalated ones because of the uniformly dispersed clay layers. (C) 2004 Wiley Periodicals, Inc
Preparation and characterization of syndiotactic polystyrene/ethylene‐propylene copolymer blends
No full textThe reactive compatibilization of syndiotactic polystyrene (sPS)/oxazolinestyrene copolymer (RPS)/maleic anhydride grafted ethylene-propylene copolymer (EPR-MA) blends is investigated in this study. First, the miscibility of sPS/RPS blends is examined by thermal analysis. The cold crystallization peak (T-cc) moved toward higher temperature with increased PRS, and, concerning enthalpy relaxation behaviors, only a single enthalpy relation peak was found in all aged samples. These results indicate that the sPS/RPS blend is miscible along the various compositions and RPS can be used in the reactive compatibilization of sPS/RPS/EPR-MA blends. The reactive compatibilized sPS/RPS/EPR-MA blends showed finer morphology than sPS/EPR-MA physical blends and higher storage modulus (G') and complex viscosity (eta*) when RPS contents were increased. Moreover, the impact strength of sPS/RPS/EPR-MA increased significantly compared to sPS/EPR-MA blend, and SEM micrographs after impact testing show that the sPS/RPS/EPR-MA blend has better adhesion between the sPS matrix and the dispersed EPR-MA phase. (C) 2002 Wiley Periodicals, Inc
Comparison of Choi criteria and Response Evaluation Criteria in Solid Tumors (RECIST) for intrahepatic cholangiocarcinoma treated with glass-microspheres Yttrium-90 selective internal radiation therapy (SIRT)
No full textInternational audienceObjective: To compare Choi criteria with Response Evaluation Criteria in Solid Tumors (RECIST) for the prediction of overall survival (OS) in patients treated with glass-microspheres, Yttrium-90 selective internal radiation therapy (SIRT) for intrahepatic cholangiocarcinoma (ICC). Methods: Between 2010 and 2014, 45 adult patients with locally advanced ICC treated with SIRT were retrospectively analyzed. Computed tomography scans performed before and after treatment were analyzed using both RECIST 1.1 and Choi criteria. Response was correlated with survival. Results: Patients who achieved an objective response according to Choi had a longer OS than non responders (median OS 19.9 months [95% CI, 1.1-38.7 months] vs. 7.5 months if stable disease [uncountable CI] and 3 months if progressive disease [95% CI, 0-6.2 months], log-rank test: p = 0.003) whereas there was no significant survival difference according to the RECIST response (p = 0.339). Among the 39 RECIST non-responding patients, those identified as responders by Choi (n = 31) had significantly better OS than Choi non-responders (median OS 19.9 months (95% CI, 5.1-34.7 months) and 5.4 months (95% CI, 0-11.6 months), p = 0.005). Conclusions: Choi criteria appear more appropriate than RECIST to identify responders with long survival among patients who received SIRT for ICC. (C) 2016 Elsevier Ireland Ltd. All rights reserved
Evaluating radiological response in pancreatic neuroendocrine tumours treated with sunitinib: comparison of Choi versus RECIST criteria (CRIPNET_ GETNE1504 study)
No full text[Background] The purpose of our study was to analyse the usefulness of Choi criteria versus RECIST in patients with pancreatic neuroendocrine tumours (PanNETs) treated with sunitinib.
[Method] A multicentre, prospective study was conducted in 10 Spanish centres. Computed tomographies, at least every 6 months, were centrally evaluated until tumour progression.
[Results] One hundred and seven patients were included. Median progression-free survival (PFS) by RECIST and Choi were 11.42 (95% confidence interval [CI], 9.7–15.9) and 15.8 months (95% CI, 13.9–25.7). PFS by Choi (Kendall’s τ = 0.72) exhibited greater correlation with overall survival (OS) than PFS by RECIST (Kendall’s τ = 0.43). RECIST incorrectly estimated prognosis in 49.6%. Partial response rate increased from 12.8% to 47.4% with Choi criteria. Twenty-four percent of patients with progressive disease according to Choi had stable disease as per RECIST, overestimating treatment effect. Choi criteria predicted PFS/OS. Changes in attenuation occurred early and accounted for 21% of the variations in tumour volume. Attenuation and tumour growth rate (TGR) were associated with improved survival.
[Conclusion] Choi criteria were able to capture sunitinib’s activity in a clinically significant manner better than RECIST; their implementation in standard clinical practice shall be strongly considered in PanNET patients treated with this drug
RECIST and CHOI criteria in the evaluation of tumor response in patients with metastatic colorectal cancer treated with regorafenib, a prospective multicenter study
No full textInternational audienceBackground: To evaluate the objective response rate (ORR) at 2 months of treatment with regorafenib according to RECIST 1.1, Choi, and modified Choi (mChoi) criteria in patients with metastatic colorectal cancer (mCRC).Methods: Baseline and 2-month contrast-enhanced computed-tomography (CECT) scans of 55 patients with mCRC, prospectively enrolled in phase II TEXCAN trial, were centrally assessed. The primary endpoint was 2-month ORR by RECIST 1.1, Choi, and mChoi criteria. Final outcome was overall survival (OS).Results: Of 55 patients included in this study (Intention-to-treat [ITT1] population), 35 had CECT at 2 months (ITT2 population). According to RECIST 1.1 criteria, 20 (57%) patients were SD and 15 were PD (43%) in the ITT2 population. According to Choi criteria, 18 (51%) patients were responders and 17 (48%) were non-responders. Median OS was 5.3 months (95% CI 3.7-8.6) in the ITT1 population and 8.9 months (95% CI 5.1-12.6) in the ITT2 population. In the ITT2 population, median OS was 16 months (95% CI 6.6-17.5) in SD patients (n = 20) and 4.6 months (95% CI 3.3-5.8) in PD patients (n = 15), according to RECIST 1.1 criteria (HR = 6.48). Median OS was 7.9 months (95% CI 4.2-17.5) in responders (n = 18) and 9.9 months (95% CI 3.7-NA) in non-responders (n = 17) according to Choi criteria (HR = 1.06). All patients except one were classified as non-responders with mChoi criteria.Conclusion: At 2 months, unlike RECIST 1.1, Choi and mChoi criteria could not identify mCRC patients with regorafenib survival benefit
Synthesis and material properties of syndiotactic polystyrene/organophilic clay nanocomposites
No full textSyndiotactic polystyrene (sPS)/organophilic clay nanocomposites were fabricated by direct-melt intercalation method. To overcome the thermal instability of organophilic clay at high-melt processing temperatures of sPS, an organophilic clay modified by alkyl phosphonium was adopted, which is known to be thermally stable. By using the newly synthesized clay, we could fabricate sPS intercalated nanocomposites. The microstructures of nanocomposites were confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The crystallization rate of nanocomposites investigated by differential scanning calorimetry (DSC) does not increase despite the presence of clay, which may be due to the physical hindrance of organic modifiers in the clay dispersion. Nanocomposites exhibited enhanced mechanical properties such as strength and stiffness relative to the virgin polymer. In addition, thermal stability was confirmed to be improved by thermogravimetric analysis (TGA). (C) 2004 Wiley Periodicals, Inc
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Predictors of Stunting, Wasting and Underweight among Tanzanian Children Born to HIV-Infected Women.
No full textChildren born to human immunodeficiency virus (HIV)-infected women are susceptible to undernutrition, but modifiable risk factors and the time course of the development of undernutrition have not been well characterized. The objective of this study was to identify maternal, socioeconomic and child characteristics that are associated with stunting, wasting and underweight among Tanzanian children born to HIV-infected mothers, followed from 6 weeks of age for 24 months. Maternal and socioeconomic characteristics were recorded during pregnancy, data pertaining to the infant's birth were collected immediately after delivery, morbidity histories and anthropometric measurements were performed monthly. Multivariate Cox proportional hazards methods were used to assess the association between potential predictors and the time to first episode of stunting, wasting and underweight. A total of 2387 infants (54.0% male) were enrolled and followed for a median duration of 21.2 months. The respective prevalence of prematurity (<37 weeks) and low birth weight (<2500 g) was 15.2% and 7.0%; 11.3% of infants were HIV-positive at 6 weeks. Median time to first episode of stunting, wasting and underweight was 8.7, 7.2 and 7.0 months, respectively. Low maternal education, few household possessions, low infant birth weight, child HIV infection and male sex were all independent predictors of stunting, wasting and underweight. In addition, preterm infants were more likely to become wasted and underweight, whereas those with a low Apgar score at birth were more likely to become stunted. Interventions to improve maternal education and nutritional status, reduce mother-to-child transmission of HIV, and increase birth weight may lower the risk of undernutrition among children born to HIV-infected women
ENHANCED FLUORIMETRIC DETERMINATION OF EUROPIUM(III) WITH THENOYLTRIFLUOROACETONE AND 4,7-DIPHENYL-1,10-PHENANTHROLINE BY GADOLINIUM(III)
No full textChemistry, AnalyticalSCI(E)37ARTICLE81499-15132
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