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1.
Eur J Clin Nutr ; 2024 May 04.
Artigo em Inglês | MEDLINE | ID: mdl-38704428

RESUMO

BACKGROUND: Olive oil consumption has been reportedly associated with lower mortality rates, mostly from cardiovascular diseases, but its potential impact on cancer death remains controversial. Moreover, biological mechanisms possibly linking olive oil consumption to mortality outcomes remain unexplored. METHODS: We longitudinally analysed data on 22,892 men and women from the Moli-sani Study in Italy (follow-up 13.1 y), to examine the association of olive oil consumption with mortality. Dietary data were collected at baseline (2005-2010) through a 188-item FFQ, and olive oil consumption was standardised to a 10 g tablespoon (tbsp) size. Diet quality was assessed through a Mediterranean diet score. Multivariable-adjusted Cox proportional hazard models, also including diet quality, were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs). The potential mediating role of inflammatory, metabolic, cardiovascular and renal biomarkers on the association between olive oil intake and mortality was evaluated on the basis of change-in-estimate and associated p values. RESULTS: Multivariable HRs for all-cause, cancer, cardiovascular and other cause mortality associated with high (>3 tbsp/d) versus low (≤1.5 tbsp/d) olive oil consumption were 0.80 (0.69-0.94), 0.77 (0.59-0.99), 0.75 (0.58-0.97) and 0.97 (0.73-1.29), respectively. Taken together, the investigated biomarkers attenuated the association of olive oil consumption with all-cause and cancer mortality by 21.2% and 13.7%, respectively. CONCLUSIONS: Higher olive oil consumption was associated with lower cancer, cardiovascular and all-cause mortality rates, independent of overall diet quality. Known risk factors for chronic diseases only in part mediated such associations suggesting that other biological pathways are potentially involved in this relationship.

2.
Front Oncol ; 13: 1276253, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-38146510

RESUMO

Introduction: Central nervous system (CNS) tumors are severe health conditions with increasing incidence in the last years. Different biological, environmental and clinical factors are thought to have an important role in their epidemiology, which however remains unclear. Objective: The aim of this pilot study was to identify CNS tumor patients' subtypes based on this information and to test associations with tumor malignancy. Methods: 90 patients with suspected diagnosis of CNS tumor were recruited by the Neurosurgery Unit of IRCCS Neuromed. Patients underwent anamnestic and clinical assessment, to ascertain known or suspected risk factors including lifestyle, socioeconomic, clinical and psychometric characteristics. We applied a hierarchical clustering analysis to these exposures to identify potential groups of patients with a similar risk pattern and tested whether these clusters associated with brain tumor malignancy. Results: Out of 67 patients with a confirmed CNS tumor diagnosis, we identified 28 non-malignant and 39 malignant tumor cases. These subtypes showed significant differences in terms of gender (with men more frequently presenting a diagnosis of cancer; p = 6.0 ×10-3) and yearly household income (with non-malignant tumor patients more frequently earning ≥25k Euros/year; p = 3.4×10-3). Cluster analysis revealed the presence of two clusters of patients: one (N=41) with more professionally active, educated, wealthier and healthier patients, and the other one with mostly retired and less healthy men, with a higher frequency of smokers, personal history of cardiovascular disease and cancer familiarity, a mostly sedentary lifestyle and generally lower income, education and cognitive performance. The former cluster showed a protective association with the malignancy of the disease, with a 74 (14-93) % reduction in the prevalent risk of CNS malignant tumors, compared to the other cluster (p=0.026). Discussion: These preliminary data suggest that patients' profiling through unsupervised machine learning approaches may somehow help predicting the risk of being affected by a malignant form. If confirmed by further analyses in larger independent cohorts, these findings may be useful to create potential intelligent ranking systems for treatment priority, overcoming the lack of histopathological information and molecular diagnosis of the tumor, which are typically not available until the time of surgery.

3.
Nutrients ; 15(18)2023 Sep 14.
Artigo em Inglês | MEDLINE | ID: mdl-37764762

RESUMO

Besides the Mediterranean diet, there is a paucity of studies examining plant-based diets in relation to cancer outcomes in Mediterranean populations. We analyzed 22,081 apparently cancer-free participants (mean age 55 ± 12 year) from the Moli-sani study (enrollment period 2005-2010; Italy). A general pro-vegetarian food pattern was computed by assigning positive or negative scores to plant- or animal-derived foods, respectively from a 188-item FFQ. A priori healthful or unhealthful pro-vegetarian food patterns distinguished between healthy plant foods (e.g., fruits, vegetables) and less-healthy plant foods (e.g., fruit juices, refined grains). Cancer incidence was defined as the earliest diagnosis of cancer from hospital discharge records over a median follow-up of 12.9 years. In multivariable-adjusted analyses, a general pro-vegetarian food pattern was associated with a lower rate of cancer incidence (HR = 0.85; 95%CI 0.75-0.97 for Q5 vs. Q1); no association was observed between the healthful or unhealthful pro-vegetarian food patterns and overall cancer incidence. A healthful pro-vegetarian pattern, however, was inversely associated with digestive cancer (HR = 0.76; 95%CI 0.58-0.99 for Q5 vs. Q1), while the unhealthful pro-vegetarian pattern was directly linked to respiratory cancer (HR = 1.68; 95%CI 1.06-2.68 for Q5 vs. Q1). Our findings in a Mediterranean population support the hypothesis that some, but not all pro-vegetarian diets, might prevent some cancers.


Assuntos
Dieta Mediterrânea , Neoplasias , Animais , Humanos , Adulto , Pessoa de Meia-Idade , Idoso , Vegetarianos , Itália/epidemiologia , Dieta Vegetariana , Ração Animal , Neoplasias/epidemiologia
4.
Blood ; 141(19): 2316-2329, 2023 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-36790505

RESUMO

Adeno-associated virus (AAV) vectors have been successfully exploited in gene therapy applications for the treatment of several genetic disorders. AAV is considered an episomal vector, but it has been shown to integrate within the host cell genome after the generation of double-strand DNA breaks or nicks. Although AAV integration raises some safety concerns, it can also provide therapeutic benefit; the direct intrathymic injection of an AAV harboring a therapeutic transgene results in integration in T-cell progenitors and long-term T-cell immunity. To assess the mechanisms of AAV integration, we retrieved and analyzed hundreds of AAV integration sites from lymph node-derived mature T cells and compared these with liver and brain tissue from treated mice. Notably, we found that although AAV integrations in the liver and brain were distributed across the entire mouse genome, >90% of the integrations in T cells were clustered within the T-cell receptor α, ß, and γ genes. More precisely, the insertion mapped to DNA breaks created by the enzymatic activity of recombination activating genes (RAGs) during variable, diversity, and joining recombination. Our data indicate that RAG activity during T-cell receptor maturation induces a site-specific integration of AAV genomes and opens new therapeutic avenues for achieving long-term AAV-mediated gene transfer in dividing cells.


Assuntos
Terapia Genética , Vetores Genéticos , Camundongos , Animais , Vetores Genéticos/genética , Transgenes , Plasmídeos , Terapia Genética/métodos , Receptores de Antígenos de Linfócitos T/genética , Dependovirus/genética , Integração Viral
5.
Clin Nutr ; 42(2): 93-101, 2023 02.
Artigo em Inglês | MEDLINE | ID: mdl-36521255

RESUMO

BACKGROUND: The relationship between diet and central nervous system (CNS) tumours was almost exclusively focused on food composition. We evaluated the relationship of different degrees of food processing with risk of CNS tumours. METHODS: The study sample included 44 CNS tumours cases (20 non-malignant and 24 malignant) recruited from the Neurosurgery Department at the IRCCS Neuromed (Italy), and 88 controls matched 1:2 for sex and age± 10 years, identified from the Moli-sani Study. Dietary intake was assessed using a 188-item FFQ. Food items were grouped according to the NOVA classification on the basis of processing as: (1) unprocessed/minimally processed foods; (2) processed culinary ingredients; (3) processed foods; and (4) ultra-processed food (UPF). Conditional logistic regression models were used to estimate odds ratio (OR) and 95% confidence intervals (95%CI) of dietary contributions from each NOVA group (as weight ratio on the total food eaten) and adjusting for potential confounders. RESULTS: In a multivariable conditional to match logistic regression analysis also controlled for overall diet quality, 1% increment in UPF intake was associated with higher odds of all CNS tumours (OR = 1.06; 1.01-1.13), particularly of malignant CNS tumours (OR = 1.11; 1.02-1.22), while no association with non-malignant CNS tumours was found (OR = 1.06; 0.99-1.15). In contrast, only processed food was inversely associated with risk of both CNS tumours overall (OR = 0.94; 0.90-0.98) and of malignant CNS tumours (OR = 0.90; 0.83-0.96). CONCLUSION: Increasing UPF intake was associated with higher risk of CNS tumours, especially malignant ones, independently of the overall diet quality, while only processed food (but not UPF) was inversely related to the risk of this disease.


Assuntos
Neoplasias Encefálicas , Neoplasias do Sistema Nervoso Central , Dieta Mediterrânea , Humanos , Fast Foods , Manipulação de Alimentos , Dieta/efeitos adversos , Neoplasias do Sistema Nervoso Central/epidemiologia , Estudos de Casos e Controles , Neoplasias Encefálicas/epidemiologia , Ingestão de Energia
6.
Nutrients ; 14(24)2022 Dec 08.
Artigo em Inglês | MEDLINE | ID: mdl-36558388

RESUMO

Polyphenols are naturally occurring compounds endowed with antioxidant and anti-inflammatory properties. We sought to examine the association of dietary polyphenols with the risk of severe lumbar spinal stenosis (LSS), a condition possibly characterized by a high inflammatory component. A case-control study included 156 patients with LSS and indication to surgery and 312 controls, matched (1:2) for sex, age (±6 months), and physical activity. The polyphenol intake was calculated by matching food consumption data from a 188-item food frequency questionnaire with the Phenol-Explorer database regarding the polyphenol content of each reported food. In a multivariable-adjusted logistic regression analysis including lifestyles, sociodemographic factors, and the Mediterranean Diet Score, a 1-standard deviation (SD) increase in dietary polyphenols intake was associated with lower odds of LSS (Odds ratio [OR] = 0.65; 95% CI: 0.47-0.89). Analyses of different polyphenol classes showed that a per 1-SD in the consumption of flavonoids and stilbenes was related to lower LSS risk (OR = 0.57; 95% CI: 0.42-0.78; OR = 0.40; 95% CI: 0.27-0.61, respectively). Further adjustment for the total dietary antioxidant capacity did not modify the strength of these associations. A diet rich in polyphenols is independently associated with a lower risk of severe LSS, possibly through mechanisms that include the anti-inflammatory potential of these bioactive compounds.


Assuntos
Dieta Mediterrânea , Estenose Espinal , Humanos , Lactente , Polifenóis , Antioxidantes , Estudos de Casos e Controles , Dieta , Ingestão de Alimentos
7.
Cell Stem Cell ; 29(10): 1428-1444.e9, 2022 10 06.
Artigo em Inglês | MEDLINE | ID: mdl-36206730

RESUMO

Long-range gene editing by homology-directed repair (HDR) in hematopoietic stem/progenitor cells (HSPCs) often relies on viral transduction with recombinant adeno-associated viral vector (AAV) for template delivery. Here, we uncover unexpected load and prolonged persistence of AAV genomes and their fragments, which trigger sustained p53-mediated DNA damage response (DDR) upon recruiting the MRE11-RAD50-NBS1 (MRN) complex on the AAV inverted terminal repeats (ITRs). Accrual of viral DNA in cell-cycle-arrested HSPCs led to its frequent integration, predominantly in the form of transcriptionally competent ITRs, at nuclease on- and off-target sites. Optimized delivery of integrase-defective lentiviral vector (IDLV) induced lower DNA load and less persistent DDR, improving clonogenic capacity and editing efficiency in long-term repopulating HSPCs. Because insertions of viral DNA fragments are less frequent with IDLV, its choice for template delivery mitigates the adverse impact and genotoxic burden of HDR editing and should facilitate its clinical translation in HSPC gene therapy.


Assuntos
DNA Viral , Proteína Supressora de Tumor p53 , Sistemas CRISPR-Cas , Dano ao DNA , Edição de Genes , Células-Tronco Hematopoéticas , Humanos , Integrases , Proteína Supressora de Tumor p53/genética
8.
Front Cardiovasc Med ; 9: 997013, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36158799

RESUMO

Hyperglycaemia at the time of myocardial infarction has an adverse effect on prognosis irrespective of a prior diagnosis of diabetes, suggesting glucose is the damaging factor. In ex vivo models of ischaemia, we demonstrated that deleterious effects of acutely elevated glucose are PKCα/ß-dependent, and providing PKCα/ß are inhibited, elevated glucose confers cardioprotection. Short pre-treatments with high glucose were used to investigate time-dependent glucose cardiotoxicity, with PKCα/ß inhibition investigated as a potential mechanism to reverse the toxicity. Freshly isolated non-diabetic rat cardiomyocytes were exposed to elevated glucose to investigate the time-dependence toxic effects. High glucose challenge for >7.5 min was cardiotoxic, proarrhythmic and lead to contractile failure, whilst cardiomyocytes exposed to metabolic inhibition following 5-min high glucose, displayed a time-dependent protection lasting ∼15 min. This protection was further enhanced with PKCα/ß inhibition. Cardioprotection was measured as a delay in contractile failure and KATP channel activation, improved contractile and Ca2+ transient recovery and increased cell survival. Finally, the effects of pre-ischaemic treatment with high glucose in a whole-heart coronary ligation protocol, where protection was evident with PKCα/ß inhibition. Selective PKCα/ß inhibition enhances protection suggesting glycaemic control with PKC inhibition as a potential cardioprotective therapeutics in myocardial infarction and elective cardiac surgery.

9.
Eur J Clin Nutr ; 76(12): 1697-1704, 2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-35906332

RESUMO

BACKGROUND/OBJECTIVES: Unsaturated fats, fibre-rich foods and polyphenols are distinctive features of a traditional Mediterranean diet and have pleiotropic properties possibly contributing to reduce the long-term risk of non-communicable diseases and mortality associated with this diet. We aimed to evaluate whether changes over time in dietary fats, fibre and polyphenols consumption are associated with modifications in cardiovascular disease (CVD) risk factors. METHODS: The analytic sample consists of a sub-cohort of 2023 men and women enrolled in the Moli-sani Study (n = 24,325). Dietary and health data were obtained both at baseline (2005-2010) and at re-examination (2017-2020). The exposures were changes in dietary fats, fibre and polyphenols consumption measured after 12.7 years (median), and the outcome was change in a composite score including 13 modifiable CVD risk factors (e.g., blood lipids, C-reactive protein), measured both at enrolment and after the 12.7 years period. RESULTS: In multivariable-adjusted analysis including lifestyles, sociodemographic and clinical factors, an incremental intake of the ratio of monounsaturated to saturated fats or of fibre was associated with a reduction in the composite score of CVD risk factors (ß = -0.086; 95%CI -0.150, -0.021 and ß = -0.051; 95%CI -0.091, -0.012, respectively). Change in polyphenol intake was not associated with a substantial variation in the CVD risk score (p = 0.15). CONCLUSIONS: An incremental consumption over time of monounsaturated versus saturated fats and of fibre was associated with an improvement in modifiable CVD risk factors as reflected by a composite score.


Assuntos
Doenças Cardiovasculares , Dieta Mediterrânea , Masculino , Feminino , Humanos , Estudos Prospectivos , Doenças Cardiovasculares/etiologia , Doenças Cardiovasculares/prevenção & controle , Fibras na Dieta , Gorduras na Dieta/efeitos adversos , Ácidos Graxos , Polifenóis , Fatores de Risco
10.
Clin Nutr ; 41(5): 1025-1033, 2022 05.
Artigo em Inglês | MEDLINE | ID: mdl-35390726

RESUMO

BACKGROUND & AIMS: Biological age (BA) is the hypothetical underlying age of an organism and has been proposed as a more powerful predictor of health than chronological age (CA). The difference between BA and CA (Δage) reflects the rate of biological aging, with lower values indicating slowed-down aging. We sought to compare the relationship of four a priori-defined dietary patterns, including a traditional Mediterranean diet (MD) and three non-Mediterranean diets, with biological aging (Δage) among Italian adults. We also examined distinctive nutritional traits of these diets as potential mediators of such associations. METHODS: Cross-sectional analysis on a sub-cohort of 4510 subjects (aged ≥35 y; 52.0% women) from the Moli-sani Study (enrolment, 2005-2010). Food intake was recorded by a 188-item semi-quantitative food-frequency questionnaire. A Mediterranean diet score (MDS) was used as exposure and compared with non-Mediterranean dietary patterns, i.e. DASH (Dietary Approaches to Stop Hypertension), Palaeolithic and the Nordic diets. A Deep Neural Network based on 36 blood biomarkers was used to compute BA and the resulting Δage (BA-CA), which was tested as outcome in multivariable linear regressions adjusted for clinical factors, lifestyles and sociodemographic factors. RESULTS: In a multivariable-adjusted model, 1 standard deviation increase in the MDS was inversely associated with Δage (ß = -0.23; 95%CI -0.40, -0.07), and similar findings were observed with the DASH diet (ß = -0.17; 95%CI -0.33, -0.01). High dietary polyphenol content explained 29.8% (p = 0.04) and 65.8% (p = 0.02) of these associations, respectively, while other nutritional factors analysed (e.g. dietary fibre) were unlikely to be on the pathway. No significant associations were found with either the Palaeolithic or the Nordic diets. CONCLUSIONS: Increasing adherence to either the traditional MD or the DASH diet was associated with delayed biological aging, possibly through their high polyphenol content.


Assuntos
Dieta Mediterrânea , Adulto , Envelhecimento , Estudos de Coortes , Estudos Transversais , Dieta , Feminino , Humanos , Masculino , Polifenóis
11.
Nutrients ; 13(7)2021 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-34202377

RESUMO

Mushroom cell walls are rich in ß-glucans, long or short-chain polymers of glucose subunits with ß-1,3 and ß-1,6 linkages, that are responsible for the linear and branching structures, respectively. ß-glucans from cereals, at variance, have no 1,6 linkages nor branching structures. Both immunomodulatory and anti-inflammatory effects of mushrooms have been described using purified ß-glucans or fungi extracts on cellular and experimental models; their potential clinical use has been tested in different conditions, such as recurrent infections of the respiratory tract or complications of major surgery. Another promising application of ß-glucans is on cancer, as adjuvant of conventional chemotherapy. ß-glucans may protect the cardiovascular system, ameliorating glucose, lipid metabolism, and blood pressure: these activities, observed for oat and barley ß-glucans, require confirmation in human studies with mushroom ß-glucans. On the other hand, mushrooms may also protect the cardiovascular system via a number of other components, such as bioactive phenolic compounds, vitamins, and mineral elements. The growing knowledge on the mechanism(s) and health benefits of mushrooms is encouraging the development of a potential clinical use of ß-glucans, and also to further document their role in preserving health and prevent disease in the context of healthy lifestyles.


Assuntos
Agaricales/química , Plantas Comestíveis/química , Substâncias Protetoras/farmacologia , beta-Glucanas/farmacologia , Humanos
12.
Nutrients ; 13(5)2021 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-34067821

RESUMO

Biological aging, or the discrepancy between biological and chronological age of a subject (Δage), has been associated with a polyphenol-rich Mediterranean diet and represents a new, robust indicator of cardiovascular disease risk. We aimed to disentangle the relationship of dietary polyphenols and total antioxidant capacity with Δage in a cohort of Italians. A cross-sectional analysis was performed on a sub-cohort of 4592 subjects (aged ≥ 35 y; 51.8% women) from the Moli-sani Study (2005-2010). Food intake was recorded by a 188-item food-frequency questionnaire. The polyphenol antioxidant content (PAC)-score was constructed to assess the total dietary content of polyphenols. Total antioxidant capacity was measured in foods by these assays: trolox equivalent antioxidant capacity (TEAC), total radical-trapping antioxidant parameter (TRAP) and ferric reducing-antioxidant power (FRAP). A deep neural network, based on 36 circulating biomarkers, was used to compute biological age and the resulting Δage, which was tested as outcome in multivariable-adjusted linear regressions. Δage was inversely associated with the PAC-score (ß = -0.31; 95%CI -0.39, -0.24) but not with total antioxidant capacity of the diet. A diet rich in polyphenols, by positively contributing to deceleration of the biological aging process, may exert beneficial effects on the long-term risk of cardiovascular disease and possibly of bone health.


Assuntos
Envelhecimento/fisiologia , Antioxidantes/análise , Doenças Cardiovasculares/etiologia , Ingestão de Alimentos/fisiologia , Polifenóis/análise , Adulto , Envelhecimento/sangue , Biomarcadores/sangue , Fenômenos Cronobiológicos , Estudos de Coortes , Estudos Transversais , Dieta/efeitos adversos , Inquéritos sobre Dietas , Dieta Mediterrânea/estatística & dados numéricos , Feminino , Fatores de Risco de Doenças Cardíacas , Humanos , Itália , Modelos Lineares , Masculino , Redes Neurais de Computação , Medição de Risco
14.
Int J Food Sci Nutr ; 72(8): 1105-1117, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33823720

RESUMO

We investigated the effect of confinement during the COVID-19 pandemic on the consumption of foods characterising the Mediterranean dietary pattern (MDP) and its major correlates in two Italian population-based cohorts comprising 3161 subjects (mean age 57.7 ± 15.4 y). At population level, 38.8% of participants reported an improvement of diet quality during the first nationwide lockdown. Healthful dietary changes were associated with older age (ß = 0.41; 95% confidence interval [CI] 0.08, 0.73 for 56-65 vs. 18-39 y), greater wealth (ß = 0.45; 0.01, 0.89 for >40,000 ≤ 60,000 vs. ≤ 10,000 EUR/y), increased physical activity (ß = 0.52; 0.22, 0.81) and reduced body weight (ß = 0.36; 0.11, 0.62). Switching to healthy eating was also related to increased consumption of organic (ß = 1.24; 0.88, 1.60) and locally-grown food (ß = 0.74; 0.51, 0.96). The first Italian lockdown led, in a substantial part of the population, to higher intake of foods characterising a MDP; this was also accompanied by healthier lifestyle and more sustainable food choices.


Assuntos
COVID-19 , Dieta Mediterrânea , Comportamento Alimentar , Estilo de Vida , Pandemias , Distanciamento Físico , Adulto , Fatores Etários , Idoso , Peso Corporal , Estudos de Coortes , Controle de Doenças Transmissíveis , Dieta Saudável , Exercício Físico , Alimentos Orgânicos , Humanos , Itália , Masculino , Pessoa de Meia-Idade , SARS-CoV-2 , Classe Social
15.
J Cell Physiol ; 234(5): 6067-6076, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30246374

RESUMO

Histone deacetylase 8 (HDAC8) is a class 1 histone deacetylase and a member of the cohesin complex. HDAC8 is expressed in smooth muscles, but its expression in skeletal muscle has not been described. We have shown for the first time that HDAC8 is expressed in human and zebrafish skeletal muscles. Using RD/12 and RD/18 rhabdomyosarcoma cells with low and high differentiation potency, respectively, we highlighted a specific correlation with HDAC8 expression and an advanced stage of muscle differentiation. We inhibited HDAC8 activity through a specific PCI-34051 inhibitor in murine C2C12 myoblasts and zebrafish embryos, and we observed skeletal muscles differentiation impairment. We also found a positive regulation of the canonical Wnt signaling by HDAC8 that might explain muscle differentiation defects. These findings suggest a novel mechanism through which HDAC8 expression, in a specific time window of skeletal muscle development, positively regulates canonical Wnt pathway that is necessary for muscle differentiation.


Assuntos
Histona Desacetilases/metabolismo , Desenvolvimento Muscular/fisiologia , Músculo Esquelético/metabolismo , Proteínas Repressoras/metabolismo , Via de Sinalização Wnt/fisiologia , Animais , Diferenciação Celular/fisiologia , Humanos , Camundongos , Músculo Esquelético/citologia , Mioblastos/metabolismo , Peixe-Zebra
16.
Polymers (Basel) ; 10(2)2018 Feb 08.
Artigo em Inglês | MEDLINE | ID: mdl-30966198

RESUMO

The development of a highly oriented fiber morphology by effect of tensile deformation of stereodefective isotactic polypropylene (iPP) samples, starting from the unoriented γ form, is studied by following the transformation in real time during stretching through wide angle X-ray scattering (WAXS) measurements. In the stretching process, after yielding, the initial γ form transforms into the mesomorphic form of iPP through mechanical melting and re-crystallization. The analysis of the scattering invariant measured in the WAXS region highlights that the size of the mesomorphic domains included in the well oriented fiber morphology obtained at high deformations increases through a process which involves the coalescence of the small fragments formed by effect of tensile stress during lamellar destruction with the domain of higher dimensions.

17.
J Am Chem Soc ; 127(9): 2850-1, 2005 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-15740110

RESUMO

Crystals of alternating isotactic ethylene-cyclopentene copolymer include conformational disorder of cyclopentene rings and packing disorder of chains.

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