An already existing, sub-critical arrangement made of natural uranium and water moderator has been exposed to a low intensity (≈ 10
9 ppp) proton beam from CERN-PS at several kinetic energies from ...600 MeV to 2.75 GeV. The energy delivered by the hadronic cascade induced by the beam in the device has been measured by the temperature rise of small sampling blocks of uranium located in several different positions inside the device and counting the fissions in thin probe foils of natural uranium. We find typically
G ≈ 30 in reasonable agreement with calculations, where
G is the ratio of the energy produced in the device to the energy delivered by the beam. This result opens the way to the realisation of the so-called Energy Amplifier, a practical device to produce energy from thorium or depleted uranium targets exposed to an intense high energy proton beam. Results show that the optimal kinetic is ≥ 1 GeV, below which
G decreases but is still acceptable in the energy range explored
Energy and space distributions of spallation neutrons (from 2.5 and 3.57 GeV/
c CERN proton beams) slowing down in a 3.3 × 3.3 × 3 m
3 lead volume and neutron capture rates on long-lived fission ...fragments
99Tc and
129I demonstrate that Adiabatic Resonance Crossing (ARC) can be used to eliminate efficiently such nuclear waste and validate innovative simulation.
We summarize here the results of the TARC experiment whose main purpose is to demonstrate the possibility of using Adiabatic Resonance Crossing (ARC) to destroy efficiently Long-Lived Fission ...Fragments (LLFFs) in accelerator-driven systems and to validate a new simulation developed in the framework of the Energy Amplifier programme. An experimental set-up was installed in a CERN PS proton beam line to study how neutrons produced by spallation at relatively high energy ( E n ⩾1 MeV ) slow down quasi-adiabatically with almost flat isolethargic energy distribution and reach the capture resonance energy of an element to be transmuted where they will have a high probability of being captured. Precision measurements of energy and space distributions of spallation neutrons (using 2.5 and 3.5 GeV/ c protons) slowing down in a 3.3 m×3.3 m×3 m lead volume and of neutron capture rates on LLFFs 99 Tc, 129 I, and several other elements were performed. An appropriate formalism and appropriate computational tools necessary for the analysis and understanding of the data were developed and validated in detail. Our direct experimental observation of ARC demonstrates the possibility to destroy, in a parasitic mode, outside the Energy Amplifier core, large amounts of 99 Tc or 129 I at a rate exceeding the production rate, thereby making it practical to reduce correspondingly the existing stockpile of LLFFs. In addition, TARC opens up new possibilities for radioactive isotope production as an alternative to nuclear reactors, in particular for medical applications, as well as new possibilities for neutron research and industrial applications. (Elsevier)
The use of accelerator driven system (ADS) like for instance the Energy Amplifier concept (EA) proposed by C. Rubbia and his group might be one of the solutions to solve the energy problem and in ...particular to answer the question: what could we do with the nuclear waste produced by the present nuclear reactors? We present in this paper the EA concept, which is illustrated by two experiments performed at the CERN-PS facility. One of them is the TARC (Transmutation by Adiabatic Resonance crossing) experiment which is designed to demonstrate the high efficiency offered by the EA to destroy the long-lived fission fragments.
The Transmutation by Adiabatic Resonance Crossing (TARC) experiment was carried out as PS211 at the CERN PS from 1996 to 1999. Energy and space distributions of spallation neutrons (produced by 2.5 ...and 3.57
GeV/
c CERN proton beams) slowing down in a 3.3×3.3×3
m
3 lead volume and neutron capture rates on long-lived fission fragments
99Tc and
129I demonstrate that Adiabatic Resonance Crossing (ARC) can be used to eliminate efficiently such nuclear waste and validate innovative simulation.
The hypothesis that cancer is driven by tumour-initiating cells (popularly known as cancer stem cells) has recently attracted a great deal of attention, owing to the promise of a novel cellular ...target for the treatment of haematopoietic and solid malignancies. Furthermore, it seems that tumour-initiating cells might be resistant to many conventional cancer therapies, which might explain the limitations of these agents in curing human malignancies. Although much work is still needed to identify and characterize tumour-initiating cells, efforts are now being directed towards identifying therapeutic strategies that could target these cells. This Review considers recent advances in the cancer stem cell field, focusing on the challenges and opportunities for anticancer drug discovery.
The establishment and maintenance of spermatogenesis in mammals requires specialized networks of gene expression programs in the testis. The gonad-specific TAF4b component of TFIID (formerly ...TAF(II)105) is a transcriptional regulator enriched in the mouse testis. Herein we show that TAF4b is required for maintenance of spermatogenesis in the mouse. While young Taf4b-null males are initially fertile, Taf4b-null males become infertile by 3 mo of age and eventually exhibit seminiferous tubules devoid of germ cells. At birth, testes of Taf4b-null males appear histologically normal; however, at post-natal day 3 gonocyte proliferation is impaired and expression of spermatogonial stem cell markers c-Ret, Plzf, and Stra8 is reduced. Together, these data indicate that TAF4b is required for the precise expression of gene products essential for germ cell proliferation and suggest that TAF4b may be required for the regulation of spermatogonial stem cell specification and proliferation that is obligatory for normal spermatogenic maintenance in the adult.
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