123 research outputs found
5\u27-Nucleotidase and Thrombin-Like Activities of Selected Crotalid Venoms
Thrombin-like activities were not observed inCrotalus basiliscus, C. molossus and C. scutulatus scutulatus crude venoms. 5\u27-Nucleotidase specific activities of 0.863, 0.273 and 5.520 units/mg of crude venom protein were observed inC. basiliscus, C. molossus and C. s. scutulatus venoms, respectively. Concanavalin ASepharose 4 B (Con A)affinitychromatography yielded two fractions from each of the crude venoms. Ineach instance, both fractions exhibited 5\u27-nucleotidase activities and the Con A-binding proteins had higher activities than the Con A-nonbinding proteins. 5\u27-Nucleotidase activities inthe DEAESephadex A-50 chromatographic fractions were localized in the first elution fraction and the last fraction(s) to elute. EDTAhad no effect on the 5\u27-nucleotidase activities ofthe crude venoms
5\u27-Nucleotidase and Thrombin-Like Activities of Selected Crotalid Venoms
Thrombin-like activities were not observed inCrotalus basiliscus, C. molossus and C. scutulatus scutulatus crude venoms. 5\u27-Nucleotidase specific activities of 0.863, 0.273 and 5.520 units/mg of crude venom protein were observed inC. basiliscus, C. molossus and C. s. scutulatus venoms, respectively. Concanavalin ASepharose 4 B (Con A)affinitychromatography yielded two fractions from each of the crude venoms. Ineach instance, both fractions exhibited 5\u27-nucleotidase activities and the Con A-binding proteins had higher activities than the Con A-nonbinding proteins. 5\u27-Nucleotidase activities inthe DEAESephadex A-50 chromatographic fractions were localized in the first elution fraction and the last fraction(s) to elute. EDTAhad no effect on the 5\u27-nucleotidase activities ofthe crude venoms
An Absolute Measurement of Neutron Flux Using Calorimetry
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Measurement of the Neutron Lifetime by Counting Trapped Protons
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Measurement of the Neutron Lifetime by Counting Trapped Protons
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
A gamma- and X-ray detector for cryogenic, high magnetic field applications
As part of an experiment to measure the spectrum of photons emitted in
beta-decay of the free neutron, we developed and operated a detector consisting
of 12 bismuth germanate (BGO) crystals coupled to avalanche photodiodes (APDs).
The detector was operated near liquid nitrogen temperature in the bore of a
superconducting magnet and registered photons with energies from 5 keV to 1000
keV. To enlarge the detection range, we also directly detected soft X-rays with
energies between 0.2 keV and 20 keV with three large area APDs. The
construction and operation of the detector is presented, as well as information
on operation of APDs at cryogenic temperatures
Radiative β decay of the free neutron
The theory of quantum electrodynamics predicts that the β decay of the neutron into a proton, electron, and antineutrino is accompanied by a continuous spectrum of emitted photons described as inner bremsstrahlung. While this phenomenon has been observed in nuclear β decay and electron-capture decay for many years, it has only been recently observed in free-neutron decay. We present a detailed discussion of an experiment in which the radiative decay mode of the free neutron was observed. In this experiment, the branching ratio for this rare decay was determined by recording photons that were correlated with both the electron and proton emitted in neutron decay. We determined the branching ratio for photons with energy between 15 and 340 keV to be (3.09±0.32)×10-3 (68% level of confidence), where the uncertainty is dominated by systematic effects. This value for the branching ratio is consistent with theoretical predictions. The characteristic energy spectrum of the radiated photons, which differs from the uncorrelated background spectrum, is also consistent with the theoretical spectrum
From Lurker to Active Participant
The original publication is available from www.springerlink.com.
Sloep, P. B., & Kester, L. (2009). From Lurker to Active Participant. In R. Koper (Ed)., Learning Network Services for Professional Development (pp. 17-26). Berlin, Germany: Springer Verlag.In this chapter we will specifically go into the question of how prospective Learning Network users may be convinced of these benefits, for that is likely to be the necessary condition for their active participation in any Learning Network. Their question would be ‘Why should I participate?’, this chapter inventories an-swers to that question, which are then translated into a few guidelines for those contemplating to set up a particular, topic-bound Learning Network. Two kinds of answer are distinguished. Proximate answers, which affect the decision to partici-pate here and now; and ultimate answers, which motivate participation, but only in the long run, after the decision to participate has already been taken. Both are im-portant, the former to persuade people to participate, the latter to persuade people to keep participating. Before going into them, we’ll introduce a concrete example to add some realism to the discussion.The work on this publication has been sponsored in part by the TENCompetence Integrated Project that is funded by the European Commission's 6th Framework Programme, priority IST/Technology Enhanced Learning. Contract 027087 [http://www.tencompetence.org
Production of Medical Radioisotopes with High Specific Activity in Photonuclear Reactions with Beams of High Intensity and Large Brilliance
We study the production of radioisotopes for nuclear medicine in
photonuclear reactions or ()
photoexcitation reactions with high flux [()/s], small
diameter m and small band width () beams produced by Compton back-scattering of laser
light from relativistic brilliant electron beams. We compare them to (ion,np) reactions with (ion=p,d,) from particle accelerators like
cyclotrons and (n,) or (n,f) reactions from nuclear reactors. For
photonuclear reactions with a narrow beam the energy deposition in the
target can be managed by using a stack of thin target foils or wires, hence
avoiding direct stopping of the Compton and pair electrons (positrons).
isomer production via specially selected cascades
allows to produce high specific activity in multiple excitations, where no
back-pumping of the isomer to the ground state occurs. We discuss in detail
many specific radioisotopes for diagnostics and therapy applications.
Photonuclear reactions with beams allow to produce certain
radioisotopes, e.g. Sc, Ti, Cu, Pd, Sn,
Er, Pt or Ac, with higher specific activity and/or
more economically than with classical methods. This will open the way for
completely new clinical applications of radioisotopes. For example Pt
could be used to verify the patient's response to chemotherapy with platinum
compounds before a complete treatment is performed. Also innovative isotopes
like Sc, Cu and Ac could be produced for the first time
in sufficient quantities for large-scale application in targeted radionuclide
therapy.Comment: submitted to Appl. Phys.
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