RESUMEN
Prof. P. Venkataramaiah (P.V.), born on July 08, 1937, has been active in research for the past five decades in several areas of Nuclear Physics and Environmental Sciences. He has visited several Universities and research institutes in various countries such as Japan, Hong Kong, Singapore, France, the UK, Canada and the USA. Apart from research work he has also held many administrative positions and made revolutionary improvements in the education sector of India. Even after retirement, Prof. P.V. has actively involved himself inspiring and encouraging the younger generation at secondary level. As an honour for his untiring dedication even in his eighties, his colleagues and students have written articles about his contributions to research and education. This include contributions from Prof. P.V. himself along with Prof. K.S. Mallesh, Prof. N. Nagaiah, Prof. S.A. Bari, Prof. M. Venkateshwaralu, Shri. M. Vasudev, Dr K. Nagaraja, Mrs. Sreemathi Hariprasad and Dr N. Bhagyalakshmi.
Asunto(s)
Física Nuclear , India , Historia del Siglo XX , Historia del Siglo XXI , Humanos , Investigación , Física/educación , Física/historiaRESUMEN
We consider the longitudinal quadrupole relaxation rate enhancement (QRE) of a 1H nucleus due to the time fluctuations of the local dipolar magnetic field created by a close quadrupole 14N nucleus, the electric-field gradient (EFG) Hamiltonian of which changes with time because of vibrations/distortions of its chemical environment. The QRE is analytically expressed as a linear combination of the cosine Fourier transforms of the three quantum time auto-correlation functions GAA(t) of the 14N spin components along the principal axes A = X, Y, and Z of the mean (time-averaged) EFG Hamiltonian. Denoting the three transition frequencies between the energy levels of this mean Hamiltonian by νA, the functions GAA(t) oscillate at frequencies νA + sA/(2π) with mono-exponential decays of relaxation times τA, where the frequency dynamic shifts sA and the relaxation times τA are closed expressions of the magnitude of the fluctuations of the instantaneous EFG Hamiltonian about its mean and of the characteristic fluctuation time. Thus, the theoretical QRE is the sum of three Lorentzian peaks centered at νA + sA/(2π) with full widths at half maxima 1/(πτA). The predicted peak widths are nearly equal. The predicted dynamic shifts of the peaks are much smaller than their widths and amazingly keep proportional to the transition frequencies νA for reasonably fast EFG fluctuations. The theory is further improved by correcting the transition frequencies by the 14N Zeeman effects of second order. It is successfully applied to reinterpret the QRE pattern measured by Broche, Ashcroft, and Lurie [Magn. Reson. Med. 68, 358 (2012)] in normal cartilage.
Asunto(s)
Electricidad , Física Nuclear , Cartílago/químicaRESUMEN
Artificial Intelligence (AI) techniques have been implemented in the field of Medical Imaging for more than forty years. Medical Physicists, Clinicians and Computer Scientists have been collaborating since the beginning to realize software solutions to enhance the informative content of medical images, including AI-based support systems for image interpretation. Despite the recent massive progress in this field due to the current emphasis on Radiomics, Machine Learning and Deep Learning, there are still some barriers to overcome before these tools are fully integrated into the clinical workflows to finally enable a precision medicine approach to patients' care. Nowadays, as Medical Imaging has entered the Big Data era, innovative solutions to efficiently deal with huge amounts of data and to exploit large and distributed computing resources are urgently needed. In the framework of a collaboration agreement between the Italian Association of Medical Physicists (AIFM) and the National Institute for Nuclear Physics (INFN), we propose a model of an intensive computing infrastructure, especially suited for training AI models, equipped with secure storage systems, compliant with data protection regulation, which will accelerate the development and extensive validation of AI-based solutions in the Medical Imaging field of research. This solution can be developed and made operational by Physicists and Computer Scientists working on complementary fields of research in Physics, such as High Energy Physics and Medical Physics, who have all the necessary skills to tailor the AI-technology to the needs of the Medical Imaging community and to shorten the pathway towards the clinical applicability of AI-based decision support systems.
Asunto(s)
Inteligencia Artificial , Nube Computacional , Humanos , Italia , Física Nuclear , Medicina de PrecisiónRESUMEN
Some concepts in nuclear radiation physics are abstract and intellectually demanding. In the present paper, an "MCHP platform" (MCHP was an acronym for Monte Carlo simulations + Human Phantoms) was proposed to provide assistance to the students through visualization. The platform involved Monte Carlo simulations of interactions between ionizing radiations and the Oak Ridge National Laboratory (ORNL) adult male human phantom. As an example to demonstrate the benefits of the proposed MCHP platform, the present paper investigated the variation of the absorbed photon dose per photon from a 137Cs source in three selected organs, namely, brain, spine and thyroid of an adult male for concrete and lead shields with varying thicknesses. The results were interesting but not readily comprehensible without direct visualization. Graphical visualization snapshots as well as video clips of real time interactions between the photons and the human phantom were presented for the involved cases, and the results were explained with the help of such snapshots and video clips. It is envisaged that, if the platform is found useful and effective by the readers, the readers can also propose examples to be gradually added onto this platform in future, with the ultimate goal of enhancing students' understanding and learning the concepts in an undergraduate nuclear radiation physics course or a related course.
Asunto(s)
Método de Montecarlo , Física Nuclear/educación , Protección Radiológica/métodos , Encéfalo/efectos de la radiación , Radioisótopos de Cesio/química , Cuerpo Humano , Humanos , Fotones , Protección Radiológica/instrumentación , Radiación Ionizante , Radiometría , EstudiantesRESUMEN
The American Board of Radiology offers certification in three specialties of medical physics: Therapeutic Medical Physics, Diagnostic Medical Physics, and Nuclear Medical Physics. Of these specialties, medical nuclear physics has the fewest active diplomates, only a few hundred. The diagnostic medical physics specialty certification incudes a variety of modalities (ultrasound, radiography, computed tomography, and magnetic resonance imaging) yet does not address nuclear medicine imaging or therapy. This separation dates to the beginning of the ABR certification process for medical physicists in 1947; originally there were three certificates available: X-ray and Radium Physics, Medical Nuclear Physics and, as combination of these two, Radiological Physics. Over the span of 75 years since the Medical Nuclear Physics certification was created, much has changed in the scope and proliferation of the nuclear medicine endeavor and the question arises as to the need for change in the preparation process for medical physicists in the field. I offer thanks to our contributors and note that they are writing in the classic style of a debate, the opinions that they argue may or may not reflect their personal views.
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Internado y Residencia , Medicina Nuclear , Certificación , Física Sanitaria , Humanos , Física Nuclear , Radiografía , Estados UnidosRESUMEN
The history concerning an experimental verification of the standard model of particle physics is reviewed with special emphasis on results from experiments using the highest-energy particle colliders, namely, PETRA, LEP and LHC. This article covers physics subjects from discovering the gluon and precise measurements at LEP, to discovering the Higgs boson. It also covers some searches for physics beyond the standard model, particularly supersymmetry, as well as recent developments of some particle detectors that were used in those experiments.
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Partículas Elementales , Modelos Teóricos , Interpretación Estadística de Datos , Historia del Siglo XX , Historia del Siglo XXI , Método de Montecarlo , Física Nuclear , Aceleradores de PartículasAsunto(s)
Física Nuclear/tendencias , Radiometría/tendencias , Radioterapia/tendencias , Programas Informáticos , Simulación por Computador , Francia , Humanos , Investigación Interdisciplinaria , Cooperación Internacional , Metales , Método de Montecarlo , Nanotecnología/tendencias , Física Nuclear/organización & administraciónRESUMEN
This essay considers the development of the nuclear science programme in Malaysia from a transnational perspective by examining the interactions between state agents and other external nuclear-knowledge/technology related actors and agents. Going beyond the model of knowledge diffusion that brings together concerns articulated in Harris's (2011) geographies of long distance knowledge and Reinhardt's (2011) role of the expert in knowledge transfer, the proposed three-phase model of knowledge transfer theorises the pathways undertaken by a late-blooming participant of modern science and technology as the latter moves from epistemic dependency to increasing independence despite the hurdles encountered, and the underdevelopment of many areas of its technoscientific economy. The model considers tensions stemming from the pressures of expediency for meeting national developmental goals on the one side, and the call to support the objectives of basic science on the other. The three phases of the model are epistemic transition, epistemic transplantation and localisation, and epistemic generation (ETTLG). As additional support for the proposed model, three arguments are proffered as deeper explanations of the epistemic goal by using Malaysia as a case study: knowledge transfer for political legitimization, knowledge transfer for countering agnotology, and knowledge transfer for social engineering and science diplomacy.
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Conocimiento , Física Nuclear , Tecnología , MalasiaRESUMEN
The space radiation environment is a complex mixture of particle types and energies originating from sources inside and outside of the galaxy. These environments may be modified by the heliospheric and geomagnetic conditions as well as planetary bodies and vehicle or habitat mass shielding. In low Earth orbit (LEO), the geomagnetic field deflects a portion of the galactic cosmic rays (GCR) and all but the most intense solar particle events (SPE). There are also dynamic belts of trapped electrons and protons with low to medium energy and intense particle count rates. In deep space, the GCR exposure is more severe than in LEO and varies inversely with solar activity. Unpredictable solar storms also present an acute risk to astronauts if adequate shielding is not provided. Near planetary surfaces such as the Earth, moon or Mars, secondary particles are produced when the ambient deep space radiation environment interacts with these surfaces and/or atmospheres. These secondary particles further complicate the local radiation environment and modify the associated health risks. Characterizing the radiation fields in this vast array of scenarios and environments is a challenging task and is currently accomplished with a combination of computational models and dosimetry. The computational tools include models for the ambient space radiation environment, mass shielding geometry, and atomic and nuclear interaction parameters. These models are then coupled to a radiation transport code to describe the radiation field at the location of interest within a vehicle or habitat. Many new advances in these models have been made in the last decade, and the present review article focuses on the progress and contributions made by workers and collaborators at NASA Langley Research Center in the same time frame. Although great progress has been made, and models continue to improve, significant gaps remain and are discussed in the context of planned future missions. Of particular interest is the juxtaposition of various review committee findings regarding the accuracy and gaps of combined space radiation environment, physics, and transport models with the progress achieved over the past decade. While current models are now fully capable of characterizing radiation environments in the broad range of forecasted mission scenarios, it should be remembered that uncertainties still remain and need to be addressed.
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Radiación Cósmica , Modelos Teóricos , Astronautas , Humanos , Física Nuclear , Actividad Solar , Vuelo Espacial , Nave Espacial , Estados Unidos , United States National Aeronautics and Space AdministrationRESUMEN
Dissolution dynamic nuclear polarization (d-DNP) is a versatile method to enhance nuclear magnetic resonance (NMR) spectroscopy. It boosts signal intensities by four to five orders of magnitude thereby providing the potential to improve and enable a plethora of applications ranging from the real-time monitoring of chemical or biological processes to metabolomics and in-cell investigations. This perspectives article highlights possible avenues for developments and applications of d-DNP in biochemical and physicochemical studies. It outlines how chemists, biologists and physicists with various fields of interest can transform and employ d-DNP as a powerful characterization method for their research.
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Aumento de la Imagen , Resonancia Magnética Nuclear Biomolecular/métodos , Bioquímica/instrumentación , Química Física/instrumentación , Diseño de Equipo , Física Nuclear/instrumentaciónRESUMEN
In the era of big science, countries allocate big research and development budgets to large scientific facilities that boost collaboration and research capability. A nuclear fusion device called the "tokamak" is a source of great interest for many countries because it ideally generates sustainable energy expected to solve the energy crisis in the future. Here, to explore the scientific effects of tokamaks, we map a country's research capability in nuclear fusion research with normalized revealed comparative advantage on five topical clusters-material, plasma, device, diagnostics, and simulation-detected through a dynamic topic model. Our approach captures not only the growth of China, India, and the Republic of Korea but also the decline of Canada, Japan, Sweden, and the Netherlands. Time points of their rise and fall are related to tokamak operation, highlighting the importance of large facilities in big science. The gravity model points out that two countries collaborate less in device, diagnostics, and plasma research if they have comparative advantages in different topics. This relation is a unique feature of nuclear fusion compared to other science fields. Our results can be used and extended when building national policies for big science.
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Fusión Nuclear , Física Nuclear/instrumentación , Investigación , Bibliografías como Asunto , Canadá , China , Humanos , India , Estudios Interdisciplinarios , Japón , Modelos Teóricos , Países Bajos , Energía Renovable , República de Corea , SueciaRESUMEN
This paper describes the production and chemical separation of the 163Ho isotope that will be used in several nuclear physics experiments aiming at measuring the neutrino mass as well as the neutron cross section of the 163Ho isotope. For this purpose, several batches of enriched 162Er have been irradiated at the Institut Laue-Langevin high flux reactor to finally produce 6 mg or 100 MBq of the desired 163Ho isotope. A portion of the Er/Ho mixture is then subjected to a sophisticated chemical separation involving ion exchange chromatography to isolate the Ho product from the Er target material. Before irradiation, a thorough analysis of the impurity content was performed and its implication on the produced nuclide inventory will be discussed.
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Holmio/química , Holmio/aislamiento & purificación , Radioquímica/métodos , Isótopos , Neutrones , Física NuclearAsunto(s)
Biofisica/historia , Carcinoma de Células Transicionales/historia , Neoplasias Inducidas por Radiación/historia , Física Nuclear/historia , Armas Nucleares/historia , Teleterapia por Radioisótopo/historia , Neoplasias de la Vejiga Urinaria/historia , Carcinoma de Células Transicionales/radioterapia , Carcinoma de Células Transicionales/cirugía , Radioisótopos de Cobalto/uso terapéutico , Terapia Combinada , Cistostomía , Historia del Siglo XX , Humanos , Hungría , Neoplasias Inducidas por Radiación/radioterapia , Neoplasias Inducidas por Radiación/cirugía , Teleterapia por Radioisótopo/métodos , Inducción de Remisión , Estados Unidos , Neoplasias de la Vejiga Urinaria/radioterapia , Neoplasias de la Vejiga Urinaria/cirugía , Segunda Guerra MundialRESUMEN
Faced with various anomalies related to nuclear physics in particular, in 1929 Niels Bohr suggested that energy might not be conserved in the atomic nucleus and the processes involving it. By this radical proposal he hoped not only to get rid of the anomalies but also saw a possibility to explain a puzzle in astrophysics, namely the energy generated by stars. Bohr repeated his suggestion of stellar energy arising ex nihilo on several occasions but without ever going into detail. In fact, it is not very clear what he meant or how seriously he took the stellar energy hypothesis. This paper relates Bohr's comments to the period's attempts to find a mechanism for stellar energy and also to the role played by astrophysics at the Copenhagen institute. Moreover, it looks at how Bohr's hypothesis was received not only by physicists but also by astronomers. In this regard the disciplinary status of astrophysics and its contemporary relation to the new quantum mechanics is of relevance. It turns out that, with very few exceptions, the hypothesis was met with silence by astronomers and astrophysicists concerned with the problem of stellar energy production. And yet, for a brief period of time it did have an impact on how physicists thought about the interior of the stars.