![]() The radiotoxicity of α particles is virtually independent of the phase in the cell cycle, oxygenation, and the dose rate. Linear energy transfer of α particles emitted by 227Th and its daughter 223Ra is within the range of the optimum relative biological effectiveness. Published reports indicate that 227Th has limited myelotoxicity, can be stably chelated to its carriers and, as it decays at targeted sites, 227Th produces 223Ra that is subsequently incorporated into the areas of increased osteoblastic activity, that is, osseous metastatic lesions. 227Th-labeled molecular probes based on ligands to OST-associated receptors such as IGF-1R (insulin-like growth factor receptor 1), HER2 (human epidermal growth factor receptor 2), and PSMA (prostate-specific membrane antigen) are expected to detect and treat osseous and nonosseous sites of multifocal OST. The use of aggressive therapies in an attempt to eradicate these cells can have long-term negative consequences in these vulnerable patient populations. Moreover, multifocal OST contains tumor-initiating cells that are resistant to chemotherapy. ![]() Subjects with metastatic disease or whose disease relapses after the initial therapy have a poor prognosis. This is called Rutherford’s atom model.Osteosarcoma (OST) is the most common bone tumor in children and adolescents with a second peak of incidence in elderly adults usually diagnosed as secondary tumors in Paget's disease or irradiated bone. So it can safely be said that electrons inside the atoms of the gold foil being so light do not appreciably affect the motion of incident alpha particles and can never scatter the alpha particles to such a large angle of 180′ or to any other large angles.īy analyzing the deflection of the alpha particles and the results obtained, Rutherford put forward a model of an atom. It is to be mentioned that alpha particles are about 7000 times heavier than electrons and they strike the gold foil with tremendous speed. Besides, those alpha particles which approach directly the nucleus will encounter intense electric field and according to the Coulomb’s inverse square law these particles will be repelled by maximum force and will be scattered in the backward direction making an angle of 180°. Again, those alpha particles which tome very close to the nucleus will be repelled by the positive charge of the nucleus and will be deflected from their initial paths. So, most of the alpha particle go straight through the empty space of the atom. The probability of coming closer to the nucleus of the positively charged alpha particles is less while going through the gold foil. Electrons are distributed randomly around the nucleus. the matter.Įxplanation of the results of the experiment: According to Rutherford all the positive charges and the mass of the atom are concentrated at the center of the atom. So, the credit of discovery of nucleus goes to Rutherford Nucleus is the heart or source of energy of the atoms i.e. Scientist Rutherford named it as the nucleus. From this experiment, Rutherford reached the conclusion that total positive charges and mass of the atom were concentrated at the center of a very small space. Later on in 1913, complete agreement of Rutherford’s proposal was found with the experimental results of Geiger and Marsden. Some particles even scattered in the backward direction making 180° angle.įrom this experiment, Lord Rutherford first proposed that scattering of α-particles through large angles is only possible if all the positive charges and the mass of the atom are concentrated at the center covering only a very small space around it. In this experiment, they noticed that some alpha particles went straight through the foil and some particles were scattered making small angles and some went making the angle more than 90°. This experiment is known as the famous Rutherford’s alpha deflection experiment. In 1909, scientists Geiger and Marsden, at the suggestion of Ernest Rutherford, performed a deflection experiment of alpha-particles having an energy of 7.68 MeV emitted from the radioactive polonium, on a 6 x l0 -7 m thick gold foil. ![]() Each atom contained the same number of positive and negative charges. Within this positively charged matter, negatively charged electrons were randomly distributed. Throughout the nineteenth century, scientists had the idea that each atom was composed of positive charges and these charges were distributed all over the atom. ![]()
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