Pellegri L.,National Institute of Nuclear Physics, Italy |
Pellegri L.,University of Milan |
Bracco A.,National Institute of Nuclear Physics, Italy |
Bracco A.,University of Milan |
And 89 more authors.
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2014
The γ decay from the high-lying states of 124Sn was measured using the inelastic scattering of 17O at 340 MeV. The emitted γ rays were detected with high resolution with the AGATA demonstrator array and the scattered ions were detected in two segmented δE-E silicon telescopes. The angular distribution was measured both for the γ rays and the scattered 17O ions. An accumulation of E1 strength below the particle threshold was found and compared with previous data obtained with (γ, γ') and (α, α'γ) reactions. The present results of elastic scattering, and excitation of E2 and E1 states were analysed using the DWBA approach. From this comprehensive description the isoscalar component of the 1- excited states was extracted. The obtained values are based on the comparison of the data with DWBA calculations including a form factor deduced using a microscopic transition density. © 2014 The Authors.
News Article | November 30, 2016
Everything is pointing towards success in unravelling the mysteries inherent in every human language, which for nearly 100 years have been an object of intrigue for mathematicians and linguists working on studies into statistics of literature. New analysis of the frequencies of word occurrence in the most famous works of literature, undertaken at the Institute of Nuclear Physics of the Polish Academy of Sciences in Krakow, have shown that our languages are structurally more complex and more exhaustive than they ever before seemed. It's been said that 80% of a person's success is achieved from only 20% of their efforts. That famous ratio holds up over a surprising number of domains. For example, it is apparent that in every language, whether spoken or written, that 80% of all statements are made up of merely 20% of the most common words. One possible reason is that when we talk to each other we want to convey as much content as possible with the least effort (among other factors). This phenomenon of dependency was one of the earliest of the series of power laws to be discovered, and is known as Zipf's law. It has turned out that it is not as trivial as it might seem at first glance. Scientists from the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Krakow have established that certain puzzling features of Zipf's law, for decades a source of intrigue for those involved in the statistical analysis of literary texts, are a consequence of neglecting one of the basic components of language. "A year ago, with the help of detailed multiscale analysis we showed that the length of sentences in literature -- that is, the distance between the sentence-ending punctuation -- shows a very complex dependency of a multifractal nature, especially evident in the works of the genre known as stream of consciousness. It was an intriguing result that prompted us to look with greater attention to the role of other punctuation marks, especially in the context of Zipf's law. The results have provided us with a new way to look at not only the role of punctuation among languages, but even within the same language," says Prof. Stanislaw Drozdz (IFJ PAN, Cracow University of Technology). Charts showing Zipf's law for literary texts are created with the use of an uncomplicated procedure. Each word is counted per how often it occurs in the text. Those which occur most often are assigned to rank 1, the next are placed in rank 2, etc. (in richer texts the ranks can even exceed ten thousand, and exotic words usually appear far above rank 1,000). Zipf's law states that the probability of a word is inversely proportional to its rank: the larger the rank, the lower the probability. Graphs showing the relationship are (on a logarithmic scale) on a straight line. Ever since the American linguist George Zipf popularized his law, it never ceases to amaze. How can something as complex as a structure created using language be described by such a straightforward law? There were more puzzles. Quite early on it was noticed that the graphs relating to the frequency of words for ranks closer to unity curve slightly downward from a straight line. That deviation particularly intrigued Benoit Mandelbrot, the great French mathematician of Polish origin, who worked on this issue for many years. He even suggested his own amendment to Zipf's original law, to better map deviation (it is worth mentioning at this point, that his work on Zipf's law, among other interests, helped guide him toward the concept of fractals). In this latest study, the physicists at IFJ PAN analyzed texts written in six Indo-European languages, two of each belonging to these groups: Germanic (English and German), Romance (French and Italian) and Slavic (Polish and Russian). The selected literary works come from the archives of Project Gutenberg , and each is at least five thousand sentences long. For each of the languages at least five different texts were chosen, and merged to form one text totaling about a million words. All words unrelated to the transmitted content were removed, such as 'chapter', 'part' and 'epilogue', and for all language-specific abbreviations like 'Mr.' and 'Dr.' the dots were removed and they were treated as separate words. Also deleted were annotations and footnotes, page numbers, and punctuation marks of a more typographical nature: quotation marks and parentheses. "The eventual punctuation marks considered for analysis were commas, colons, and semicolons, and those which end sentences: periods, exclamation marks, question marks, and ellipses," specifies Prof. Jaroslaw Kwapien (IFJ PAN), one of the co-authors of the scientific paper published in the renowned journal Information Sciences. Among the studied works of literature are: 1984 by George Orwell, Moby Dick by Herman Melville, Ulysses by James Joyce, Gulliver's Travels by Jonathan Swift, Gone with the Wind by Margaret Mitchell, Thus Spake Zarathustra by Friedrich Nietzsche, The Trial by Franz Kafka, The Magic Mountain by Thomas Mann, Madame Bovary by Gustave Flaubert, The Phantom of the Opera by Gaston Leroux, Foucault's Pendulum by Umberto Eco, Giacinta by Luigi Capuana, The Spring to Come by Stefan Zeromski, The Promised Land by Wladyslaw Reymont, The Doll by Boleslaw Prus, Anna Karenina and War and Peace by Leo Tolstoy, and The Brothers Karamazov by Fyodor Dostoevsky. Including punctuation marks led a to highly significant result: the downward bend seen on the original Zipf's graph for ranks close to unity practically disappears. The 'new words' (the punctuation marks) fall into place almost exactly so that together with the 'real words' the rank-frequency distribution now fits into the straight line for all ranks, thus extending the original form of Zipf's law to all the scales. Mandelbrot's amendment turned out to be generally redundant. "When we begin to treat punctuation marks like they are words they start occupying ranks closer to unity and with frequency relative to the ordinary words, so that the original Zipf departure from the straight line for small ranks basically disappears. Thus, upon considering punctuation, our language emerges as a more consistent composition! That's why it seems well-founded to say that punctuation is just as important to a language as its words, and language without it is basically incomplete," says Prof. Drozdz. New graphs reveal several novel and significant features. For example, considering punctuation in Slavic languages the thus generalized Zipf rank-frequency distribution falls almost perfectly along one line for all ranks. Some trace of the original Zipf's deviation remains for Romance and Germanic languages, and this is especially apparent with the English language. "What if while analyzing non-Slavic languages we didn't consider their additional specific features?" wonders Prof. Drozdz, being mindful of other interesting interpretations: "Might it also be that the cause of incomplete reduction of curvature is rooted in the language itself? For instance, in English there might be a source of easily discernable tendencies of authors to limit the number of punctuation marks. If this last cause holds true, it might be worth asking the question: can we be sure that excessive reduction of punctuation is a beneficial action that doesn't harm the integrity of the language?" The latest discovery from the IFJ PAN could potentially have implications beyond linguistic research. Zipfian deviation for ranks closer to unity is being observed in many areas and has diverse origins, which are often not fully understood. In the graphs prepared based on literary works the deviation disappears after accounting for the common factor, but so far this has been considered negligible. Perhaps in other cases it could also be eliminated by including elements which have thus far been deprived of a greater role. The Henryk Niewodniczanski Institute of Nuclear Physics (IFJ PAN) is currently the largest research institute of the Polish Academy of Sciences. The broad range of studies and activities of IFJ PAN includes basic and applied research, ranging from particle physics and astrophysics, through hadron physics, high-, medium-, and low-energy nuclear physics, condensed matter physics (including materials engineering), to various applications of methods of nuclear physics in interdisciplinary research, covering medical physics, dosimetry, radiation and environmental biology, environmental protection, and other related disciplines. The average yearly yield of the IFJ PAN encompasses more than 450 scientific papers in the Journal Citation Reports published by the Thomson Reuters. The part of the Institute is the Cyclotron Centre Bronowice (CCB) which is an infrastructure, unique in Central Europe, to serve as a clinical and research centre in the area of medical and nuclear physics. IFJ PAN is a member of the Marian Smoluchowski Krakow Research Consortium: "Matter-Energy-Future" which possesses the status of a Leading National Research Centre (KNOW) in physics for the years 2012-2017. The Institute is of A+ Category (leading level in Poland) in the field of sciences and engineering. Prof. Stanislaw Drozdz The Institute of Nuclear Physics of the Polish Academy of Sciences tel. 48-12-6628220 email: email@example.com "In narrative texts punctuation marks obey the same statistics as words"; A. Kulig, J. Kwapien, T. Stanisz, S. Drozdz; Information Sciences 375 (2017) 98-113; DOI: http://dx. The website of the Institute of Nuclear Physics of the Polish Academy of Sciences. Press releases of the Institute of Nuclear Physics of the Polish Academy of Sciences.
News Article | February 22, 2017
Cracow, 22 February 2017 The world around us is mainly constructed of baryons, particles composed of three quarks. Why are there no antibaryons, since just after the Big Bang, matter and antimatter came into being in exactly the same amounts? A lot points to the fact that after many decades of research, physicists are closer to the answer to this question. In the Large Hadron Collider beauty (LHCb) experiment the first trace of the differences between baryons and antibaryons has just been encountered. In data collected during the first phase of operation of the Large Hadron Collider the LHCb collaboration team has discovered an interesting asymmetry. The most recent analysis of decays of the beauty baryon Lambda b, a particle six times more massive than a proton, suggests that it decays a little differently than its antimatter counterpart. If this result is confirmed, it will be possible to talk about having observed the first difference between antibaryons and baryons, i.e. the family of particles which to a greater degree make up our everyday world. Certain differences between matter and antimatter have already been observed previously. In 1964, it was noticed that kaons - that is, K mesons, particles made up of a strange quark and an up or down antiquark - sometimes decay somewhat differently than antikaons (the Nobel Prize was awarded for this discovery in 1980). In turn, in recent years there have been reports of the discovery of slightly clearer differences in the decays of antimesons and B mesons of various types (the B meson consists of a beauty quark and an up, down, strange or charm quark). Mesons are quark-antiquark pairs with short lifetimes, appearing today in the Universe in small quantities, and on Earth, produced mainly in high-energy collisions in particle accelerators. Meanwhile the matter of which the macroscopic structures of our world are composed is made up of leptons (these include electrons) and to a greater degree baryons - clusters of three quarks (the proton is a baryon containing two up quarks and one down, as is the neutron which is composed of two down quarks and one up). The most recent analysis of data from the LHCb collaboration, published in the journal Nature Physics and concerning the decays of Lambda b particles composed of down, up and beauty quarks, is thus the first indication of the possible differences between baryonic matter and its antimatter reflection. "We cannot yet talk about a discovery. Nevertheless, we are dealing with something that seems to be an increasingly promising observational clue, taken from the data from the first stage of operation of the LHC accelerator. We will, however, have to wait for the final confirmation - or denial... - of the current result another dozen or so months until the official end of the analysis of data from the second run," stresses Prof. Marcin Kucharczyk from the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Cracow, one of the participants of the LHCb collaboration. Modern particle physics and cosmological models suggest that antimatter came into being in exactly the same amounts as matter. This fact is linked with spectacular consequences: When a particle encounters its antiparticle, there is a great likelihood of mutual annihilation, i.e. a process in which both particles completely transform into energy. This mechanism is extremely efficient. The amount of energy generated by the annihilation of a kilogram of antimatter with a good approximation corresponds to the amount of energy that would be released as a result of burning the annual petrol production of all the refineries in Poland. If in the contemporary Universe there were planets, stars or galaxies made of antimatter, they should emit large amounts of radiation with very characteristic energies. This would arise due to the inevitable interactions with matter of the opposite type, leading to annihilation. Meanwhile, astronomers only observe annihilation radiation here and there and in residual amounts, well explained by physical phenomena which are also today responsible for the formation of small amounts of antimatter. Thus the fundamentally important question arises: since originally matter and antimatter filled the Universe in exactly equal amounts, why have they not completely disappeared? Why has a small portion of matter managed to survive the era of annihilation? In the living world great extinctions leading to the extinction of species last for tens and hundreds of thousands of years. Meanwhile, everything points to the fact that antimatter annihilated by matter disappeared from our universe fractions of a second after the Big Bang. For every few billion particles of matter just one particle survived the giant cataclysm. If a similar scale of destruction touched the human species, within seconds the Earth's population would be down to one live individual. The question of why only he survived would certainly be most apt. "In modern physics, it is assumed that the existence of matter should be due to some minor differences between the properties of particles and antiparticles. In equations, to convert a particle into an antiparticle, you have to change the sign of the corresponding quantum characteristics - in the case of electrons or the quarks making up protons or neutrons it is the electrical charge - and change the character of the spatial coordinates, i.e. form a mirror image. The combination of these two operations is called CP symmetry, that is, charge and parity symmetry. Thus, attempts to detect differences between matter and antimatter boil down to tracking events in which CP symmetry is not preserved," explains Prof. Kucharczyk. Looking for signs of CP violation, the LHCb collaboration researchers chose from a huge number of collisions and the products of their decays approx. 6,000 cases in which Lambda b particles decayed to a proton and three pi mesons (pions), and approx. 1,000 cases with a decay path leading to a proton, a pion and two kaons. Detailed analysis revealed that the angles at which the products of decays diverge are sometimes somewhat different for Lambda b baryons than for their antimatter partners. The result is confirmed with a statistical significance of 3.3 standard deviations (sigma), which corresponds to a probability of approx. 99% that it is not a random fluctuation. In particle physics it is assumed, however, that one can talk of a discovery only with a statistical significance of over 5 sigma, that is, when the probability of a random fluctuation is less than one to more than three million. The Henryk Niewodniczanski Institute of Nuclear Physics (IFJ PAN) is currently the largest research institute of the Polish Academy of Sciences. The broad range of studies and activities of IFJ PAN includes basic and applied research, ranging from particle physics and astrophysics, through hadron physics, high-, medium-, and low-energy nuclear physics, condensed matter physics (including materials engineering), to various applications of methods of nuclear physics in interdisciplinary research, covering medical physics, dosimetry, radiation and environmental biology, environmental protection, and other related disciplines. The average yearly yield of the IFJ PAN encompasses more than 500 scientific papers in the Journal Citation Reports published by the Thomson Reuters. The part of the Institute is the Cyclotron Centre Bronowice (CCB) which is an infrastructure, unique in Central Europe, to serve as a clinical and research centre in the area of medical and nuclear physics. IFJ PAN is a member of the Marian Smoluchowski Krakow Research Consortium: "Matter-Energy-Future" which possesses the status of a Leading National Research Centre (KNOW) in physics for the years 2012-2017. The Institute is of A+ Category (leading level in Poland) in the field of sciences and engineering. Prof. Marcin Kucharczyk The Institute of Nuclear Physics of the Polish Academy of Sciences tel. +48 12 6628050 email: firstname.lastname@example.org http://www. The website of the Institute of Nuclear Physics of the Polish Academy of Sciences. http://press. Press releases of the Institute of Nuclear Physics of the Polish Academy of Sciences. IFJ170222b_fot01s.jpg HR: http://press. The first trace of differences between matter and "common", baryonic antimatter has just been encountered in decays of the beauty baryon Lambda b. Pictured above: LHCb Collaboration in front of LHCb detector. (Source: CERN, The LHCb Collaboration)
News Article | November 27, 2015
Abstract: Iron oxides occur in nature in many forms, often significantly different from each other in terms of structure and physical properties. However, a new variety of iron oxide, recently created and tested by scientists in Cracow, surprised both physicists and engineers, as it revealed features previously unobserved in any other material. The new form of iron oxide (FeO) is a metallic crystal with virtually no defects, a unique conglomerate of electrical and magnetic characteristics, and atoms that vibrate as if the number of dimensions has been reduced. This remarkable material has been prepared, modelled and tested by physicists at the Leading National Research Centre (KNOW) in Cracow, Poland, which includes, among others, the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN), the Institute of Catalysis and Surface Chemistry of the PAS (IKiFP PAN) and the Faculty of Physics and Applied Computer Science of the University of Science and Technology (WFiIS AGH). A group at IFJ PAN was responsible for computer simulations of material. The team from IKiFP PAN and WFiIS AGH, who initiated the research, carried out experiments determining the formation of new iron oxide layers and its properties. Physicists at the European Synchrotron Radiation Facility (ESRF) in Grenoble, the University of the Sorbonne in Paris, and the Pedagogical University of Cracow also participated in the work. "We've been working with modelling materials, including varieties of iron oxide, for years. Our models, constructed on the basis of the fundamental principles of quantum mechanics and statistical physics, have allowed us to determine the positions of atoms in the crystal lattice and to predict the electric, magnetic and thermodynamic properties of materials," explains Dr. Przemyslaw Piekarz, head of Computational Materials Science at IFJ PAN. The theorists in Cracow specialize in studying lattice dynamics, allowing them to determine how atoms in a crystal of a material vibrate. One of the basic tools they use is the PHONON program, created and developed by Prof. Krzysztof Parlinski (IFJ PAN). The VASP (Vienna Ab-initio Simulation Package) software was used to optimize the model. "Our model contains a layer of oxygen and iron with the thickness of a single atom deposited on a substrate made of platinum. The atoms in the monolayer are arranged in a hexagonal structure, like a honeycomb, a construction similar to the famous hexagonal two-dimensional graphene layers," describes Dr. Piekarz. He stresses that graphene creates a perfectly flat surface, entirely composed of carbon atoms. The modeled iron oxide layer, however turns out to be crimped: each iron atom was here surrounded by three oxygen atoms, located a little further from the substrate than the iron was. Calculations carried out for a single monolayer have established what types of vibrations are performed by atoms in the crystal lattice at different energies. The theoretical predictions were verified against the measurements thanks to a group headed by Prof. Jozef Korecki (IKiFP PAN and AGH). Not only have they developed a procedure for the preparation of samples with multiple monolayers of iron oxide on a platinum substrate, but over the past few years they have also been carrying out a series of measurements of their properties using the ESRF synchrotron in Grenoble. "In our laboratory the key to stabilizing materials of unnatural origin is the deposition of monocrystalline layers on the substrate - in this case it was properly oriented single-crystal platinum - which enforces the structure of the growing medium layer. In the laboratories scientists managed to produce a structure of stoichiometric FeO numbering no more than two monolayers of the oxide. Upon adding successive layers, the whole automatically transformed into magnetite Fe3O4. We were able to choose the parameters of the process so that the structure of FeO remained stable for a thickness of several atomic layers," says Prof. Korecki. Experiments at the synchrotron in Grenoble revealed that measurement data concerning vibrations of atoms in the crystal lattice of the new form of iron oxide perfectly agree with the theoretical model. Analysis of the results for samples with varying numbers of layers did more than just confirm the accuracy of the theoretical description. Iron oxide usually forms crystal lattices in which atoms are arranged at the corners of a cube (this is the structure of wustite, and among other substances, table salt). It was expected that after applying successive layers of FeO such a cubic structure would emerge automatically. But analysis of vibrations of atoms in the crystal lattice of the samples showed that the systems that count up to around a dozen monolayers still retain the hexagonal structure. This means that the researchers from Cracow were able to produce a new variety of iron oxide, different from the existing crystal structures. Subsequent measurements showed that for the monolayers number from six to ten, the iron atoms in the crystal have a long-range magnetic order. This is an unusual feature since a basic version of iron oxide is an antiferromagnet, wherein the magnetic moments of iron atoms at different locations are oriented in opposite directions, and therefore the substance as a whole is not magnetized. Meanwhile, the magnetic properties of a new phase of FeO are visible even at room temperature. "Spintronic materials for construction equipment have been sought after for many years. These instruments make use not only of the electrical current, but also the conduction of electron spin, which is responsible for its magnetic properties," relates Dr. Piekarz. "Our new material is not an insulator, like most oxides, but metal. So this combination of electrical and magnetic properties, rare for oxides, may be interesting for spintronics, as well as in the construction of various types of sensors and detectors." Of particular interest, however, was the analysis of the vibration of atoms depending on the number of layers of FeO on the platinum substrate. For one or two layers the movement of atoms is of a two-dimensional nature. When the number of layers reaches six or more, atoms vibrate as in a typical three-dimensional crystal. In the materials studied to date the nature of the vibration was closely associated with the dimensionality of the system. Meanwhile, a new variant of iron oxide at three, four and five layers of atoms proved to vibrate in an intermediate manner, corresponding to the fractional numbers of dimensions. "We're dealing with the first material in which the nature of vibration of atoms gradually passes from two-dimensional to three-dimensional. A similar effect, although expected in theory, has never before been observed in any other substance," claims Dr. Piekarz. Research on a new form of iron oxide, funded by grants from the Polish National Science Centre, are described in the renowned journal Physical Review Letters. About The Henryk Niewodniczanski Institute of Nuclear Physics The Henryk Niewodniczanski Institute of Nuclear Physics (IFJ PAN) is currently the largest research institute of the Polish Academy of Sciences. The broad range of studies and activities of IFJ PAN includes basic and applied research, ranging from particle physics and astrophysics, through hadron physics, high-, medium-, and low-energy nuclear physics, condensed matter physics (including materials engineering), to various applications of methods of nuclear physics in interdisciplinary research, covering medical physics, dosimetry, radiation and environmental biology, environmental protection, and other related disciplines. The average yearly yield of the IFJ PAN encompasses more than 450 scientific papers in the Journal Citation Reports published by the Thomson Reuters. The part of the Institute is the Cyclotron Centre Bronowice (CCB) which is an infrastructure, unique in Central Europe, to serve as a clinical and research centre in the area of medical and nuclear physics. IFJ PAN is a member of the Marian Smoluchowski Krakow Research Consortium: "Matter-Energy-Future" which possesses the status of a Leading National Research Centre (KNOW) in physics for the years 2012-2017. The Institute is of A+ Category (leading level in Poland) in the field of sciences and engineering. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
Chopra A.,Drexel University |
Chopra A.,University of Pennsylvania |
Murray M.E.,University of Pennsylvania |
Byfield F.J.,University of Pennsylvania |
And 15 more authors.
Biomaterials | Year: 2014
Changes in tissue and organ stiffness occur during development and are frequently symptoms of disease. Many cell types respond to the stiffness of substrates and neighboring cells invitro and most cell types increase adherent area on stiffer substrates that are coated with ligands for integrins or cadherins. Invivo cells engage their extracellular matrix (ECM) by multiple mechanosensitive adhesion complexes and other surface receptors that potentially modify the mechanical signals transduced at the cell/ECM interface. Here we show that hyaluronic acid (also called hyaluronan or HA), a soft polymeric glycosaminoglycan matrix component prominent in embryonic tissue and upregulated during multiple pathologic states, augments or overrides mechanical signaling by some classes of integrins to produce a cellular phenotype otherwise observed only on very rigid substrates. The spread morphology of cells on soft HA-fibronectin coated substrates, characterized by formation of large actin bundles resembling stress fibers and large focal adhesions resembles that of cells on rigid substrates, but is activated by different signals and does not require or cause activation of the transcriptional regulator YAP. The fact that HA production is tightly regulated during development and injury and frequently upregulated in cancers characterized by uncontrolled growth and cell movement suggests that the interaction of signaling between HA receptors and specific integrins might be an important element in mechanical control of development and homeostasis. © 2013 Elsevier Ltd.
Matisoff G.,Case Western Reserve University |
Ketterer M.E.,Northern Arizona University |
Rosen K.,Swedish University of Agricultural Sciences |
Mietelski J.W.,The Henryk Niewodniczanski Institute of Nuclear Physics |
And 3 more authors.
Applied Geochemistry | Year: 2011
Vertical profiles of 137Cs and 239,240Pu were measured in soils collected from two sites in southern Sweden and three sites in southern Poland and were modeled using both a solute transport model and a bioturbation model to better understand their downward migration. A time series of measured 137Cs profiles indicates that 137Cs from Chernobyl was found at the soil surface in 1986 but it has migrated progressively downward into the soil 4.5-25.5cm since. However, because of dispersion during the migration and mixing following Chernobyl deposition and the much higher activities of 137Cs from Chernobyl, stratospheric fallout of 137Cs from the 1960s cannot be identified as a second 137Cs activity maximum lower in the soil column at any of the sites. Conversely, the 240Pu/239Pu ratio indicates that no Chernobyl-derived Pu is present in any of the cores with the exception of one sample in Sweden. This difference may be attributed to the nature of the release from Chernobyl. Cesium volatilized at the reactor temperature during the accident, and was released as a vapor whereas Pu was not volatile and was only released in the form of minute fuel particles that traveled regionally. Both the solute diffusion and the bioturbation models accurately simulate the downward migration of the radionuclides at some sites but poorly describe the distributions at other sites. The distribution coefficients required by the solute transport model are about 100 times lower than reported values from the literature indicating that even though the solute transport model can simulate the profile shapes, transport as a solute is not the primary mechanism governing the downward migration of either Cs or Pu. The bioturbation model uses reported values from the literature of the distribution coefficients and can simulate the downward migration because that model buries the fallout by placing soil from depth on top and mixing it slightly throughout the mixing zone (0.6-2% per year of mixing). However, mixing in that model predicts concentrations in the top parts of the soil profiles which are too high in many cases. Future progress at understanding the downward migration of radionuclides and other tracers will require a more comprehensive approach, combining solute transport with bioturbation and including other important soil processes. © 2010 Elsevier Ltd.
Dworak D.,The Henryk Niewodniczanski Institute of Nuclear Physics |
Woznicka U.,The Henryk Niewodniczanski Institute of Nuclear Physics |
Zorski T.,AGH University of Science and Technology |
Wicek U.,The Henryk Niewodniczanski Institute of Nuclear Physics
Applied Radiation and Isotopes | Year: 2011
A signal of a spectrometric gamma-gamma density tool in specific borehole conditions has been numerically calculated. Transport of gamma rays, from a point 137Cs gamma source situated in a borehole tool, through rock media to detectors, has been simulated using a Monte Carlo code. The influence of heterogeneity of the rock medium surrounding the borehole on the signal of the detectors has been examined. This heterogeneity results from the presence of an interface between two different geological layers, parallel to the borehole wall. The above conditions may occur in horizontal logging, when the borehole is drilled along the boundary of geological layers. It is possible to assess the distance from the boundary on the basis of the responses of the gamma-gamma density tool, using the classic interpretation "spine & ribs" procedure. The effect of different densities of the bordered layers on the tool response has been analyzed. The presented calculations show the wide possibilities of numerical modeling of the complex borehole geometry and solving difficult interpretation problems in nuclear well logging. © 2010 Elsevier Ltd.
Lokas E.,The Henryk Niewodniczanski Institute of Nuclear Physics |
Mietelski J.W.,The Henryk Niewodniczanski Institute of Nuclear Physics |
Ketterer M.E.,Northern Arizona University |
Kleszcz K.,The Henryk Niewodniczanski Institute of Nuclear Physics |
And 4 more authors.
Applied Geochemistry | Year: 2013
This paper presents a detailed survey of the activities of selected man-made radionuclides in peat deposits located in SW Spitsbergen. Peat cores from the High Arctic (SW Spitsbergen) were analyzed by gamma spectrometry (137Cs), alpha spectrometry (238Pu, 239,240Pu, 241Am activities) and by ICPMS (240Pu/239Pu atom ratios). Maximum activities evident in the peats correspond to the 1963/1964 global maximum fallout from atmospheric testing of nuclear weapons; some of the activity profiles have been altered post-deposition by water infiltration. Activity ratios of 238Pu/239+240Pu, 241Am/239+240Pu, 239+240Pu/137Cs and 240Pu/239Pu atom ratios indicate mixing between global (stratospheric) and regional (tropospheric) sources of these radionuclides in the Svalbard area. The 238Pu/239+240Pu activity ratios varied from 0.02±0.01 to 0.09±0.03, suggesting global fallout as the dominant source of Pu. The 239+240Pu/137Cs activity ratios varied from 0.01±0.01 to 0.42±0.11, which apparently arises from the post-depositional mobility of 137Cs. The 241Am/239+240Pu activity ratios ranged between 0.10±0.02 and 1.5±0.3 and exceed the published global fallout ratio for Svalbard of 0.37 due to the relatively higher geochemical mobility of Pu vs. Am and/or ingrowth of Am from the decay of 241Pu. The atom ratio 240Pu/239Pu ranged from 0.142±0.006 to 0.241±0.027; however, the vast majority of peat samples exhibited 240Pu/239Pu atom ratios similar to the stratospheric fallout (∼0.18). © 2012 Elsevier Ltd.