RESUMO
Polymer-based magnetoelectrics are identified as a newly emerging area of research due to their profound potential applications centered on spintronic technology. In line with this, we have developed a novel, flexible nickel ferrite (NiFe2O4)-PVDF-TrFE (NF-PVDF-TrFE) polymer based magnetoelectric film, with excellent magnetoelectric coupling at room temperature. Nanocomposite films were prepared by the solution cast method, in which the nickel ferrite nanoparticles with different weight percentages (2, 4, 8 and 16%) were incorporated in the electroactive PVDF-TrFE polymer matrix. The ferroelectric ß-crystalline phase of PVDF-TrFE was confirmed by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and Raman studies. Dielectric and thermal properties of the composite films were found to be substantially improved with the addition of magnetic nanoparticles. Ferroelectric and magnetic characteristics of the composite films were also considerably improved with an increase in NiFe2O4 concentration. A magnetic saturation (Ms) of 4.81 emu g-1 and a ferroelectric maximum polarization of 18.9 µC cm-2 were shown by the composite film at room temperature for 16 wt% loading of NF nanoparticles. Besides these functionalities, ac and dc magnetoelectric coupling coefficients of 69 mV cm-1 Oe-1 and 90 mV cm-1 Oe-1 were obtained for 16NF-PVDF-TrFE along with excellent mechanical stability. These flexible and self-standing magnetoelectric composite films with enhanced magnetoelectric coupling coefficients at room temperature could be suitable candidates for the development of ultramodern information storage devices, memory devices, signal processing devices etc.
RESUMO
CONTEXT: Chronic pancreatitis is common in India. However, its risk factors are not clear. There is sparse data on the current prevalence of tropical pancreatitis in India. OBJECTIVE: To undertake a prospective nationwide study of the risk factors and clinical profile of chronic pancreatitis. SETTING: Thirty-two major centers from different regions of India contributed data on 1,086 patients to a common online website (www.ipans.org). MAIN OUTCOME MEASURES: Risk factors, clinical features complications and treatment of chronic pancreatitis. RESULTS: Of the 1,086 subjects, complete data on risk factors were available for 1,033 subjects. Idiopathic pancreatitis was the most common form of pancreatitis (n=622; 60.2%) and alcoholic chronic pancreatitis accounted for about a third of the cases (n=400; 38.7%); the rest (n=11; 1.1%) had rare risk factors. Smoking and cassava intake were documented in 292 (28.3%) and 189 (18.3%) subjects, respectively. Using well-defined criteria, only 39 (3.8%)cases could be labeled as 'tropical pancreatitis'. Pain occurred in 971 patients (94.0%). Four hundred and eighteen (40.5%) subjects had diabetes mellitus. Of alcohol consumers, alcoholism and female gender were independent risk factors for diabetes in subjects with chronic pancreatitis (OR=1.48, P=0.003; and OR=1.75, P<0.001, respectively). The most common complications were pseudocysts (15.8%) and biliary obstruction (8.2%). Pancreatic cancer occurred in 42 subjects (4.1%). Ultrasound detected calculi in 69.7%, ductal dilatation in 63.4% and atrophy in 27.3%. The majority of patients were on medical therapy (n=849; 82.2%); endotherapy and surgery accounted for the rest. About 50% percent of the patients with diabetes required insulin (198/418). CONCLUSIONS: In this first nationwide prospective survey of chronic pancreatitis in India, idiopathic pancreatitis was the most common form, followed by alcoholic pancreatitis. The classical form of tropical chronic pancreatitis is becoming less common.