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1.
Stud Hist Philos Sci ; 77: 130-140, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31701877

RESUMO

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.


Assuntos
Conhecimento , Física Nuclear , Tecnologia , Malásia
2.
Life Sci Space Res (Amst) ; 22: 98-124, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31421854

RESUMO

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.


Assuntos
Radiação Cósmica , Modelos Teóricos , Astronautas , Humanos , Física Nuclear , Atividade Solar , Voo Espacial , Astronave , Estados Unidos , United States National Aeronautics and Space Administration
3.
PLoS One ; 14(2): e0211963, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30735548

RESUMO

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.


Assuntos
Fusão Nuclear , Física Nuclear/instrumentação , Pesquisa , Bibliografias como Assunto , Canadá , China , Humanos , Índia , Estudos Interdisciplinares , Japão , Modelos Teóricos , Países Baixos , Energia Renovável , República da Coreia , Suécia
4.
PLoS One ; 13(8): e0200910, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30133443

RESUMO

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.


Assuntos
Hólmio/química , Hólmio/isolamento & purificação , Radioquímica/métodos , Isótopos , Nêutrons , Física Nuclear
5.
Nature ; 557(7704): 171-172, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29740137
8.
Nature ; 548(7665): 34-35, 2017 08 02.
Artigo em Inglês | MEDLINE | ID: mdl-28770844
9.
Ann Sci ; 74(2): 126-148, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28492099

RESUMO

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.


Assuntos
Fenômenos Astronômicos , Astronomia/história , Física Nuclear/história , Astros Celestes , Dinamarca , História do Século XX
11.
Health Phys ; 112(4): 376-383, 2017 04.
Artigo em Inglês | MEDLINE | ID: mdl-28234697

RESUMO

Contributions from men to radiation science are well known, particularly the early contributions from such luminaries as William Roentgen, James Chadwick, Niels Bohr, Robert Oppenheimer, and the like. Although not ignored per se, beyond Marie Curie and Lise Meitner, the contributions of female nuclear scientists are not as widely recognized. This paper provides a concise historical summary of contributions to radiation science from the discovery of radiation through the current status of international leadership within the radiation protection community. Beyond lead scientists and academics, this paper also considers support personnel as well as the role women have played in the advancement of radiation epidemiology.


Assuntos
Física Sanitária/história , Física Nuclear/história , Proteção Radiológica/história , Pesquisa/história , Ciência/história , Mulheres/história , História do Século XIX , História do Século XX , História do Século XXI , Internacionalidade
12.
J Radiol Prot ; 36(3): 456-473, 2016 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-27355162

RESUMO

Measured neutron energy distribution emitted from a thick stopping target of natural carbon at 0°, 30°, 60° and 90° from nuclear reactions caused by 12 MeV amu-1 incident 12C5+ ions were converted to energy differential and total neutron absorbed dose as well as ambient dose equivalent H *(10) using the fluence-to-dose conversion coefficients provided by the ICRP. Theoretical estimates were obtained using the Monte Carlo nuclear reaction model code PACE and a few existing empirical formulations for comparison. Results from the PACE code showed an underestimation of the high-energy part of energy differential dose distributions at forward angles whereas the empirical formulation by Clapier and Zaidins (1983 Nucl. Instrum. Methods 217 489-94) approximated the energy integrated angular distribution of H *(10) satisfactorily. Using the measured data, the neutron doses received by some vital human organs were estimated for anterior-posterior exposure. The estimated energy-averaged quality factors were found to vary for different organs from about 7 to about 13. Emitted neutrons having energies above 20 MeV were found to contribute about 20% of the total dose at 0° while at 90° the contribution was reduced to about 2%.


Assuntos
Carbono/química , Nêutrons , Doses de Radiação , Radiometria/métodos , Ciclotrons , Íons Pesados , Humanos , Modelos Teóricos , Método de Monte Carlo , Física Nuclear , Espalhamento de Radiação
13.
Phys Rev Lett ; 116(14): 141801, 2016 04 08.
Artigo em Inglês | MEDLINE | ID: mdl-27104698

RESUMO

We investigate the decays of the excited (bq[over ¯]) mesons as probes of the short-distance structure of the weak ΔB=1 transitions. These states are unstable under the electromagnetic or strong interactions, although their widths are typically suppressed by phase space. Compared to the pseudoscalar B meson, the purely leptonic decays of the vector B^{*} are not chirally suppressed and are sensitive to different combinations of the underlying weak effective operators. An interesting example is B_{s}^{*}→ℓ^{+}ℓ^{-}, which has a rate that can be accurately predicted in the standard model. The branching fraction is B∼10^{-11}, irrespective of the lepton flavor and where the main uncertainty stems from the unmeasured and theoretically not well known B_{s}^{*} width. We discuss the prospects for producing this decay mode at the LHC and explore the possibility of measuring the B_{s}^{*}→ℓℓ amplitude, instead, through scattering experiments at the B_{s}^{*} resonance peak.


Assuntos
Mésons , Modelos Teóricos , Física Nuclear
14.
Phys Rev Lett ; 116(14): 141802, 2016 04 08.
Artigo em Inglês | MEDLINE | ID: mdl-27104699

RESUMO

We show that by adding a single new scalar particle to the standard model, a TeV-scale leptoquark with the quantum numbers of a right-handed down quark, one can explain in a natural way three of the most striking anomalies of particle physics: the violation of lepton universality in B[over ¯]→K[over ¯]ℓ^{+}ℓ^{-} decays, the enhanced B[over ¯]→D^{(*)}τν[over ¯] decay rates, and the anomalous magnetic moment of the muon. Constraints from other precision measurements in the flavor sector can be satisfied without fine-tuning. Our model predicts enhanced B[over ¯]→K[over ¯]^{(*)}νν[over ¯] decay rates and a new-physics contribution to B_{s}-B[over ¯]_{s} mixing close to the current central fit value.


Assuntos
Partículas Elementares , Modelos Teóricos , Física Nuclear/métodos
16.
Phys Rev Lett ; 115(21): 212002, 2015 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-26636847

RESUMO

We present lattice QCD results on the neutron tensor charges including, for the first time, a simultaneous extrapolation in the lattice spacing, volume, and light quark masses to the physical point in the continuum limit. We find that the "disconnected" contribution is smaller than the statistical error in the "connected" contribution. Our estimates in the modified minimal subtraction scheme at 2 GeV, including all systematics, are g_{T}^{d-u}=1.020(76), g_{T}^{d}=0.774(66), g_{T}^{u}=-0.233(28), and g_{T}^{s}=0.008(9). The flavor diagonal charges determine the size of the neutron electric dipole moment (EDM) induced by quark EDMs that are generated in many new scenarios of CP violation beyond the standard model. We use our results to derive model-independent bounds on the EDMs of light quarks and update the EDM phenomenology in split supersymmetry with gaugino mass unification, finding a stringent upper bound of d_{n}<4×10^{-28} e cm for the neutron EDM in this scenario.


Assuntos
Modelos Teóricos , Nêutrons , Partículas Elementares , Física Nuclear , Termodinâmica
17.
Phys Rev Lett ; 115(15): 152002, 2015 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-26550717

RESUMO

The rare decay B→πℓ^{+}ℓ^{-} arises from b→d flavor-changing neutral currents and could be sensitive to physics beyond the standard model. Here, we present the first ab initio QCD calculation of the B→π tensor form factor f_{T}. Together with the vector and scalar form factors f_{+} and f_{0} from our companion work [J. A. Bailey et al., Phys. Rev. D 92, 014024 (2015)], these parametrize the hadronic contribution to B→π semileptonic decays in any extension of the standard model. We obtain the total branching ratio BR(B^{+}→π^{+}µ^{+}µ^{-})=20.4(2.1)×10^{-9} in the standard model, which is the most precise theoretical determination to date, and agrees with the recent measurement from the LHCb experiment [R. Aaij et al., J. High Energy Phys. 12 (2012) 125].


Assuntos
Partículas Elementares , Modelos Teóricos , Física Nuclear , Prótons
18.
Nuklearmedizin ; 54(6): N50-4, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26478117

RESUMO

The history of the early identification of elements and their designation to the Mendeleev Table of the Elements was an important chapter in German science in which Ida (1896-1978) and Walter (1893-1960) Noddack played an important role in the first identification of rhenium (element 75, 1925) and technetium (element 43, 1933). In 1934 Ida Noddack was also the first to predict fission of uranium into smaller atoms. Although the Noddacks did not for some time later receive the recognition for the first identification of technetium-99m, their efforts have appropriately more recently been recognized. The discoveries of these early pioneers are even more astounding in light of the limited technologies and resources which were available during this period. The Noddack discoveries of elements 43 and 75 are related to the subsequent use of rhenium-188 (beta/gamma emitter) and technetium-99m (gamma emitter) in nuclear medicine. In particular, the theranostic relationship between these two generator-derived radioisotopes has been demonstrated and offers new opportunities in the current era of personalized medicine.


Assuntos
Medicina Nuclear/história , Física Nuclear/história , Compostos Radiofarmacêuticos/história , Rênio/história , Tecnécio/história , Nanomedicina Teranóstica/história , Alemanha , História do Século XX , Fissão Nuclear
19.
J Radiol Prot ; 35(3): 649-58, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26270745

RESUMO

The quest for new sensing phenomena continues because detecting, discriminating, identifying, measuring and monitoring nuclear materials and their radiation from greater range, at lower concentrations, and in a more timely fashion brings greater safety, security and efficiency. The potential phenomena are diverse, and those that have been realised can be found in disparate fields of science, engineering and medicine, which makes the full range difficult to realise and record. The framework presented here offers a means to systematically and comprehensively explore nuclear sensing phenomena. The approach is based on the fundamental concepts of matter and energy, where the sequence starts with the original nuclear material and its emissions, and progressively considers signatures arising from secondary effects and the emissions from associated materials and the environment. Concepts of operations such as active and passive interrogation, and networked sensing are considered. In this operational light, unpacking nuclear signatures forces a fresh look at the sensing concept. It also exposes how some phenomena that exist in established technology may be considered novel based on how they could be exploited rather than what they fundamentally are. This article selects phenomena purely to illustrate the framework and how it can be best used to foster creativity in the quest for novel phenomena rather than exhaustively listing, categorising or comparing any practical aspects of candidate phenomena.


Assuntos
Monitoramento de Radiação/métodos , Proteção Radiológica/métodos , Gestão da Segurança/métodos , Algoritmos , Humanos , Física Nuclear , Liberação Nociva de Radioativos , Radioatividade , Tecnologia de Sensoriamento Remoto/métodos
20.
Clin Calcium ; 25(6): 871-6, 2015 Jun.
Artigo em Japonês | MEDLINE | ID: mdl-26017864

RESUMO

The "two photon absorption" phenomenon had been predicted by the American Physicist, Maria Ghöppert-Mayer in 1931. Denk and Webb group had proved it in 1990 and the first product had been launched in the market in 1996. But ever since the product became available, the number of users are not increased. Moreover, the system had been too difficult to use and the system sometimes stay not working in labs. But recently, the new easier-to-use products are released and the ultra short pulse IR laser became stable. And its applications are extending from neuro-science to oncology or immunology fields. Due to these reasons, the shipment of multi-photon microscope in Japan in 2013 is approximately 40 units which is 3 times bigger than in 2010. In this paper, I would like to discuss the principles of two-photon microscopy and some of the new technologies for the higher signal capture efficiency.


Assuntos
Microscopia de Fluorescência por Excitação Multifotônica , Imagem Molecular/métodos , Animais , Aumento da Imagem/instrumentação , Aumento da Imagem/métodos , Japão/epidemiologia , Microscopia de Fluorescência por Excitação Multifotônica/instrumentação , Microscopia de Fluorescência por Excitação Multifotônica/métodos , Microscopia de Fluorescência por Excitação Multifotônica/estatística & dados numéricos , Microscopia de Fluorescência por Excitação Multifotônica/tendências , Imagem Molecular/instrumentação , Física Nuclear , Fótons
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