312 research outputs found
Resonance phenomena in ultracold dipole-dipole scattering
Elastic scattering resonances occurring in ultracold collisions of either
bosonic or fermionic polar molecules are investigated. The Born-Oppenheimer
adiabatic representation of the two-bodydynamics provides both a qualitative
classification scheme and a quantitative WKB quantization condition that
predicts several sequences of resonant states. It is found that the
near-threshold energy dependence of ultracold collision cross sections varies
significantly with the particle exchange symmetry, with bosonic systems showing
much smoother energy variations than their fermionic counterparts. Resonant
variations of the angular distributions in ultracold collisions are also
described.Comment: 19 pages, 6 figures, revtex4, submitted to J. Phys.
Detailed analysis of the cell-inactivation mechanism by accelerated protons and light ions
Published survival data for V79 cells irradiated by monoenergetic protons,
helium-3, carbon, and oxygen ions and for CHO cells irradiated by carbon ions
have been analyzed using the probabilistic two-stage model of cell
inactivation. Three different classes of DNA damages formed by traversing
particles have been distinguished, namely severe single-track damages which
might lead to cell inactivation directly, less severe damages where cell
inactivation is caused by their combinations, and damages of negligible
severity that can be repaired easily. Probabilities of single ions to form
these damages have been assessed in dependence on their linear energy transfer
(LET) values.
Damage induction probabilities increase with atomic number and LET. While
combined damages play crucial role at lower LET values, single-track damages
dominate in high-LET regions. The yields of single-track lethal damages for
protons have been compared with the Monte Carlo estimates of complex DNA
lesions, indicating that lethal events correlate well with complex DNA
double-strand breaks. The decrease in the single-track damage probability for
protons of LET above approx. 30 keV/m, suggested by limited experimental
evidence, is discussed, together with the consequent differences in the
mechanisms of biological effects between protons and heavier ions. Applications
of the results in hadrontherapy treatment planning are outlined.Comment: submitted to Physics in Medicine and Biolog
Cooling effect in emissions of 103mRh excited by bremsstrahlung
Nonlinear characteristic emissions of K alpha, K beta and gamma with a
significant triplet splitting at room temperature are observed from the
long-lived nuclear state of 103mRh excited by bremsstrahlung irradiation. A
pronounced phase-transition-like narrowing of the emission profiles occurs
immediately after the sample is cooled down to 77 K. The room temperature
profiles reappear again abruptly and almost reversibly as the temperature
drifts freely back to approximately the ice point after the filling of liquid
nitrogen is stopped. These emission properties at 300 K and at low temperature
may indicate that the 103mRh nuclei are in collective states
Tensorial form and matrix elements of the relativistic nuclear recoil operator
Within the lowest-order relativistic approximation () and to
first order in , the tensorial form of the relativistic corrections of
the nuclear recoil Hamiltonian is derived, opening interesting perspectives for
calculating isotope shifts in the multiconfiguration Dirac-Hartree-Fock
framework. Their calculation is illustrated for selected Li-, B- and C-like
ions. The present work underlines the fact that the relativistic corrections to
the nuclear recoil are definitively necessary for getting reliable isotope
shift values.Comment: 22 pages, no figures, submitted to J. Phys.
Preparation and thermal conductivity of CuO nanofluid via a wet chemical method
In this article, a wet chemical method was developed to prepare stable CuO nanofluids. The influences of synthesis parameters, such as kinds and amounts of copper salts, reaction time, were studied. The thermal conductivities of CuO nanofluids were also investigated. The results showed that different copper salts resulted in different particle morphology. The concentration of copper acetate and reaction time affected the size and shape of clusters of primary nanoparticles. Nanofluids with different microstructures could be obtained by changing the synthesis parameters. The thermal conductivities of CuO nanofluids increased with the increase of particle loading
A Set of 100 Chloroplast DNA Primer Pairs to Study Population Genetics and Phylogeny in Monocotyledons
Chloroplast DNA sequences are of great interest for population genetics and phylogenetic studies. However, only a small set of markers are commonly used. Most of them have been designed for amplification in a large range of Angiosperms and are located in the Large Single Copy (LSC). Here we developed a new set of 100 primer pairs optimized for amplification in Monocotyledons. Primer pairs amplify coding (exon) and non-coding regions (intron and intergenic spacer). They span the different chloroplast regions: 72 are located in the LSC, 13 in the Small Single Copy (SSC) and 15 in the Inverted Repeat region (IR). Amplification and sequencing were tested in 13 species of Monocotyledons: Dioscorea abyssinica, D. praehensilis, D. rotundata, D. dumetorum, D. bulbifera, Trichopus sempervirens (Dioscoreaceae), Phoenix canariensis, P. dactylifera, Astrocaryum scopatum, A. murumuru, Ceroxylon echinulatum (Arecaceae), Digitaria excilis and Pennisetum glaucum (Poaceae). The diversity found in Dioscorea, Digitaria and Pennisetum mainly corresponded to Single Nucleotide Polymorphism (SNP) while the diversity found in Arecaceae also comprises Variable Number Tandem Repeat (VNTR). We observed that the most variable loci (rps15-ycf1, rpl32-ccsA, ndhF-rpl32, ndhG-ndhI and ccsA) are located in the SSC. Through the analysis of the genetic structure of a wild-cultivated species complex in Dioscorea, we demonstrated that this new set of primers is of great interest for population genetics and we anticipate that it will also be useful for phylogeny and bar-coding studies
Analytical expressions for stopping-power ratios relevant for accurate dosimetry in particle therapy
In particle therapy, knowledge of the stopping-power ratios (STPRs) of the
ion beam for air and water is necessary for accurate ionization chamber
dosimetry. Earlier work has investigated the STPRs for pristine carbon ion
beams, but here we expand the calculations to a range of ions (1 <= z <= 18) as
well as spread out Bragg peaks (SOBPs) and provide a theoretical in-depth study
with a special focus on the parameter regime relevant for particle therapy. The
Monte Carlo transport code SHIELD-HIT is used to calculate complete
particle-fluence spectra which are required for determining STPRs according to
the recommendations of the International Atomic Energy Agency (IAEA).
We confirm that the STPR depends primarily on the current energy of the ions
rather than on their charge z or absolute position in the medium. However,
STPRs for different sets of stopping-power data for water and air recommended
by the International Commission on Radiation Units & Measurements (ICRU) are
compared, including also the recently revised data for water, yielding
deviations up to 2% in the plateau region. In comparison, the influence of the
secondary particle spectra on the STPR is about two orders of magnitude smaller
in the whole region up till the practical range. The gained insights enable us
to propose an analytic approximation for the STPR for both pristine and SOBPs
as a function of penetration depth, which parametrically depend only on the
initial energy and the residual range of the ion, respectively.Comment: 21 pages, 5 figures, fixed bug with figures in v
An Integrated Framework for Intersectorality: Nonprofitness and Its Influence on Society and Public Administration Programs
Cross-sector interactions have long occurred in the public delivery of goods, services, and interests. While scholars have often addressed cross-sector interactions using the dimensions of publicness (state) and privateness (market), an intersectoral framework necessitates the understanding and incorporation of nonprofitness to account for the dimensions of nonprofits along the public-private continuum. This article proposes a framework for identifying the dimensions of nonprofits in an intersectoral world and draws on relevant examples to illustrate the presence and influence of nonprofitness. The article then focuses on the future of education in the field of public administration and, in light of the proposed framework, makes and considers recommendations to help educational programs better equip students to appreciate work across sectors
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