2,297 research outputs found
ROLE OF THE INDUSTRIAL ENTERPRISE FOR AN INCREASED EFFECTIVENESS OF THE WORKERS`DISPENSARIZATION
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New Measurement of the Direct 3α Decay from the 12C Hoyle State
Excited states in certain atomic nuclei possess an unusual structure, where the dominant degrees of freedom are those of α clusters rather than individual nucleons. It has been proposed that the diffuse 3α system of the 12C Hoyle state may behave like a Bose-Einstein condensate, where the α clusters maintain their bosonic identities. By measuring the decay of the Hoyle state into three α particles, we obtained an upper limit for the rare direct 3α decay branch of 0.047%. This value is now at a level comparable with theoretical predictions and could be a sensitive probe of the structure of this state
DYNAMICS OF THE RADIOACTIVE POLLUTION IN THE SURFACE LAYER OF SOILS IN BULGARIA TWENTY YEARS AFTER THE CHERNOBYL NUCLEAR POWER PLANT ACCIDENT
The twenty years period past after the contamination with radionuclides in 1986, as a result of the accident in the Chernobyl’s NPP, allowed the accumulation of rich data base for the radiation status of the soils in Bulgaria. Objective of many years studies were virgin soils from high mountain areas, hilly and flat (the region of Kozlodouy NPP and the Danube river valley). Ceasium-137 and strontium-90 were the main men-made radionuclides detected in
the examined Bulgarian soils, few years after the accident. The content of ceasium-137 and strontium-90 in the soils from high mountain areas (Rodopa and Rila mountains) is several times higher then that in the soils from Northern Bulgaria and Sofia field. High non-homogeneity in the pollution within small areas (scores of square meters even) was determined. No significant horizontal redistribution was observed for the period after 1986. The tendency of changes
in the radioactive status of the soils in Bulgaria after the accident at the Chernobyl Nuclear Power Plant is not due to trans-border transfer of radioactive materials or to any breakdown at the Kosloduy Nuclear Power Plant.Изминалият двадесетгодишен период след масираното отлагане на радионуклиди през 1986 година, като резултат от аварията в Чернобилската АЕЦ, даде възможност да бъде натрупана богата база данни за радиационния статус на почвите в България.
Обект на дългогодишни изследвания бяха целинни почви от високопланински райони, полупланински и равнинни (района на АЕЦ “Козлодуй” и поречието на р. Дунав. Няколко години след инцидента цезий- 137 и стронций-90 са основните техногенни радионуклиди се детектират в изследваните български почви.
Съдържанието на цезий-137 и стронций-90 в почвите от високопланинските райони (Родопите и Рила планина) е неколкократно по-високо от това в Северна България и Софийското поле. Установенеа бе силна нехомогенност на замърсяването, дори в рамките на малки площи (десетки квадратни метра). За периода след 1986 година не се наблюдав значимо хоризонтално преразпределение. Тенденциите в изменението на радиационния статус на почвите в България след авариятав Чернобилската АЕЦ не се дължат на трансграничен
пренос на радиоактивни материали или някакво нарушение в дейността на АЕЦ Козлодуй
CD80 on Human T Cells Is Associated With FoxP3 Expression and Supports Treg Homeostasis
CD80 and CD86 are expressed on antigen presenting cells (APCs) and their role in providing costimulation to T cells is well established. However, it has been shown that these molecules can also be expressed by T cells, but the significance of this observation remains unknown. We have investigated stimuli that control CD80 and CD86 expression on T cells and show that in APC-free conditions around 40% of activated, proliferating CD4+ T cells express either CD80, CD86 or both. Expression of CD80 and CD86 was strongly dependent upon provision of CD28 costimulation as ligands were not expressed following TCR stimulation alone. Furthermore, we observed that CD80+ T cells possessed the hallmarks of induced regulatory T cells (iTreg), expressing Foxp3 and high levels of CTLA-4 whilst proliferating less extensively. In contrast, CD86 was preferentially expressed on INF-γ producing cells, which proliferated more extensively and had characteristics of effector T cells. Finally, we demonstrated that CD80 expressed on T cells inhibits CTLA-4 function and facilitates the growth of iTreg. Together these data establish endogenous expression of CD80 and CD86 by activated T cells is not due to ligand capture by transendocytosis and highlight clear differences in their expression patterns and associated functions
Binary reaction decays from 24Mg+12C
Charged particle and gamma decays in 24Mg* are investigated for excitation
energies where quasimolecular resonances appear in 12C+12C collisions. Various
theoretical predictions for the occurence of superdeformed and hyperdeformed
bands associated with resonance structures with low spin are discussed within
the measured 24Mg* excitation energy region. The inverse kinematics reaction
24Mg+12C is studied at E_lab(24Mg) = 130 MeV, an energy which enables the
population of 24Mg states decaying into 12C+12C resonant break-up states.
Exclusive data were collected with the Binary Reaction Spectrometer in
coincidence with EUROBALL IV installed at the VIVITRON Tandem facility at
Strasbourg. Specific structures with large deformation were selectively
populated in binary reactions and their associated gamma decays studied.
Coincident events associated with inelastic and alpha-transfer channels have
been selected by choosing the excitation energy or the entry point via the
two-body Q-values. The analysis of the binary reaction channels is presented
with a particular emphasis on 24Mg-gamma, 20Ne-gamma and 16O-gamma
coincidences. New information (spin and branching ratios) is deduced on
high-energy states in 24Mg and 16O, respectively.Comment: 27 pages, 8 figures, 1 tabl
Clusters in Light Nuclei
A great deal of research work has been undertaken in the alpha-clustering
study since the pioneering discovery, half a century ago, of 12C+12C molecular
resonances. Our knowledge of the field of the physics of nuclear molecules has
increased considerably and nuclear clustering remains one of the most fruitful
domains of nuclear physics, facing some of the greatest challenges and
opportunities in the years ahead. In this work, the occurence of "exotic"
shapes in light N=Z alpha-like nuclei is investigated. Various approaches of
superdeformed and hyperdeformed bands associated with quasimolecular resonant
structures are presented. Results on clustering aspects are also discussed for
light neutron-rich Oxygen isotopes.Comment: 12 pages, 5 figures. Invited Talk presented by C. Beck at the
Zakopane Conference on Nuclear Physics "Extremes of the Nuclear Landscape"
XLV in the series of Zakopane Schools of Physics - International Symposium -
Zakopane, Poland, August 30 - September 5, 2010.To be publihed in Acta
Physica Polonica B42 no 3, March 201
Reaction mechanisms in 24Mg+12C and 32S+24Mg
The occurence of "exotic" shapes in light N=Z alpha-like nuclei is
investigated for 24Mg+12C and 32S+24Mg. Various approaches of superdeformed and
hyperdeformed bands associated with quasimolecular resonant structures with low
spin are presented. For both reactions, exclusive data were collected with the
Binary Reaction Spectrometer in coincidence with EUROBALL IV installed at the
VIVITRON Tandem facility of Strasbourg. Specific structures with large
deformation were selectively populated in binary reactions and their associated
-decays studied. The analysis of the binary and ternary reaction
channels is discussed.Comment: 7 pages, 4 figures, Paper presented at the Fusion08 International
Conference on New Aspects of Heavy Ion Collisions Near the Coulomb Barrier,
Chicago. Proceedings to be published by AIP Conference Proceedings Illinois,
USA, September 22-26, 200
Free energy for parameterized Polyakov loops in SU(2) and SU(3) lattice gauge theory
We present a study of the free energy of parameterized Polyakov loops P in
SU(2) and SU(3) lattice gauge theory as a function of the parameters that
characterize P. We explore temperatures below and above the deconfinement
transition, and for our highest temperatures T > 5 T_c we compare the free
energy to perturbative results.Comment: Minor changes. Final version to appear in JHE
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