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Date: 20-12-2018
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Date: 6-1-2019
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Date: 20-12-2018
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Helium has eight known isotopes but only two are stable: 3He and 4He. 3He is found in only very small quantities compared to 4He. It is produced in trace amounts by the beta decay of tritium. This form is found in abundance in stars, as a product of nuclear fusion. Extraplanetary materials have trace amounts of 3He from solar winds. 4He is produced by the alpha decay of heavier radioactive elements on Earth. It is an unusually stable isotope because its nucleons are arranged in complete shells.
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لخفض ضغط الدم.. دراسة تحدد "تمارين مهمة"
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طال انتظارها.. ميزة جديدة من "واتساب" تعزز الخصوصية
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مشاتل الكفيل تزيّن مجمّع أبي الفضل العبّاس (عليه السلام) بالورد استعدادًا لحفل التخرج المركزي
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