A new cross section measurement of reactions induced by 3He-particles on a carbon target

International audienceThe production of intense beams of light radioactive nuclei can be achieved at the SPIRAL2 facility using intense stable beams accelerated by the driver accelerator and impinging on light targets. The isotope 14O is identied to be of high interest for future experiments. The excitation function of the production reaction 12C(3He, n)14O was measured between 7 and 35 MeV. Results are compared with literature data. As an additional result, we report the rst cross-section measurement for the 12C(3He, +n)10C reaction. Based on this new result, the potential in-target 14O yield at SPIRAL2 was estimated: 2.4x1011 pps, for 1 mA of 3He at 35 MeV. This is a factor 140 higher than the in-target yield at SPIRAL1

Asymptotic normalization coefficients from the (20)Ne((3)He, d)(21)Na reaction and astrophysical factor for (20)Ne(p,gamma)(21)Na

Journals published by the American Physical Society can be found at http://publish.aps.org/The (20)Ne(p,gamma)(21)Na reaction rate at stellar energies is dominated by capture to the ground state through the tail of a subthreshold resonance state at an excitation energy of 2425 keV in (21)Na. Both resonant and direct capture contribute to the reaction rate while direct captures to other bound states are negligible. The overall normalization of direct capture to the subthreshold state is determined by the asymptotic normalization coefficient (ANC). Simultaneously this ANC determines the proton partial width of the subthreshold resonance state. To determine the ANC, the (20)Ne((3)He,d)(21)Na proton transfer reaction has been measured, at an incident energy of 25.83 MeV. Angular distributions for proton transfer to the ground and first three excited states were measured, and ANCs were then extracted from comparison with distorted-wave Born approximation calculations. Using these ANCs, we calculated the astrophysical factor for (20)Ne(p,gamma)(21)Na. Our total astrophysical factor is S(0)=5900 +/- 1200 keV b. Our analysis confirms that only nonresonant and resonant captures through the subthreshold state are important

New astrophysical S factor for the (15)N(p,gamma)(16)O reaction via the asymptotic normalization coefficient (ANC) method

Journals published by the American Physical Society can be found at http://publish.aps.org/The (15)N(p,gamma)(16)O reaction provides a path from the CN cycle to the CNO bi-cycle and CNO tri-cycle. The measured astrophysical factor for this reaction is dominated by resonant capture through two strong J(pi) = 1(-) resonances at E(R) = 312 and 962 keV and direct capture to the ground state. Asymptotic normalization coefficients (ANCs) for the ground and seven excited states in (16)O were extracted from the comparison of experimental differential cross sections for the (15)N((3)He,d)(16)O reaction with distorted-wave Born approximation calculations. Using these ANCs and proton and alpha resonance widths determined from an R-matrix fit to the data from the (15)N(p,alpha)(12)C reaction, we carried out an R-matrix calculation to obtain the astrophysical factor for the (15)N(p,gamma)(16)O reaction. The results indicate that the direct capture contribution was previously overestimated. We find the astrophysical factor to be S(0) = 36.0 +/- 6.0 keV b, which is about a factor of 2 lower than the presently accepted value. We conclude that for every 2200 +/- 300 cycles of the main CN cycle one CN catalyst is lost due to this reaction

The role of the myosin ATPase activity in adaptive thermogenesis by skeletal muscle

Resting skeletal muscle is a major contributor to adaptive thermogenesis, i.e., the thermogenesis that changes in response to exposure to cold or to overfeeding. The identification of the “furnace” that is responsible for increased heat generation in resting muscle has been the subject of a number of investigations. A new state of myosin, the super relaxed state (SRX), with a very slow ATP turnover rate has recently been observed in skeletal muscle (Stewart et al. in Proc Natl Acad Sci USA 107:430–435, 2010). Inhibition of the myosin ATPase activity in the SRX was suggested to be caused by binding of the myosin head to the core of the thick filament in a structural motif identified earlier by electron microscopy. To be compatible with the basal metabolic rate observed in vivo for resting muscle, most myosin heads would have to be in the SRX. Modulation of the population of this state, relative to the normal relaxed state, was proposed to be a major contributor to adaptive thermogenesis in resting muscle. Transfer of only 20% of myosin heads from the SRX into the normal relaxed state would cause muscle thermogenesis to double. Phosphorylation of the myosin regulatory light chain was shown to transfer myosin heads from the SRX into the relaxed state, which would increase thermogenesis. In particular, thermogenesis by myosin has been proposed to play a role in the dissipation of calories during overfeeding. Up-regulation of muscle thermogenesis by pharmaceuticals that target the SRX would provide new approaches to the treatment of obesity or high blood sugar levels

Comparative Developmental Expression Profiling of Two C. elegans Isolates

Gene expression is known to change during development and to vary among genetically diverse strains. Previous studies of temporal patterns of gene expression during C. elegans development were incomplete, and little is known about how these patterns change as a function of genetic background. We used microarrays that comprehensively cover known and predicted worm genes to compare the landscape of genetic variation over developmental time between two isolates of C. elegans. We show that most genes vary in expression during development from egg to young adult, many genes vary in expression between the two isolates, and a subset of these genes exhibit isolate-specific changes during some developmental stages. This subset is strongly enriched for genes with roles in innate immunity. We identify several novel motifs that appear to play a role in regulating gene expression during development, and we propose functional annotations for many previously unannotated genes. These results improve our understanding of gene expression and function during worm development and lay the foundation for linkage studies of the genetic basis of developmental variation in gene expression in this important model organism

Changes to the physical properties of the soil after the passage of an agricultural tractor

The effect of the passage of agricultural machinery on the soil is influenced by, for example, the inflation pressure in tyres. This article describes the effect of different tyre inflation pressures (200 and 100 kPa) on selected physical soil properties in the field experiment. The undisturbed samples were collected both in and between the tracks at depths of 0 to 0.5 m and subsequently processed according to a valid methodology in the laboratory. The results indicate that fewer negative changes were found in the variant with a lower inflation pressure for all of the observed soil properties (front wheels load 2 990 kg and rear wheels 11 760 kg). However, the differences between the pressures were not statistically significant. The impact of different tyre pressures at greater depths has also not been proven to date. This may be attributed to the creation of a plough pan due to the long-term use of the minimization technique because the values of individual properties were balanced at a depth of 0.2 to 0.3 m. These depths do not react to further tractor compaction due to the accumulation of compaction. Changes to the values of soil physical properties caused by the passage of the tractor were statistically significant for both tyre pressure variants only at depths ranging from 0 to 0.1 m

EINSTEIN AA-COEFFICIENTS AND STATISTICAL WEIGHTS FOR MOLECULAR ABSORPTION TRANSITIONS IN THE HITRANHITRAN DATABASE

Author Institution: Harvard-Smithsonian Center for Astrophysics, Atomic and Molecular Physics Division, Cambridge MA 02138-1516, USA; Laboratoire de Dynamiques, Interactions et Reactivites, Universite Pierre at Marie Curie, 4 place Jussieu, Paris 75252, France; University of Mass. Lowell, Department of Environmental, Earth \& Atmospheric Sciences, Lowell MA 01854, USA; University of Denver, Department of Physics, Denver CO 80208, USAThe weighted square of the transition moment presented in previous editions of $HITRAN$ has been replaced by the Einstein $A$-coefficient in $HITRAN$ 2004. The calculation has been performed using the $HITRAN$ line intensities $S_{HIT}$, the statistical weights $g_2$ of the upper levels and other related quantities \vspace{1em} $A_{21}=8{\pi}c{\nu}_0^2Q_{tot}(T_0)S_{HIT}/(e^{-c_2E_1/T_0}(1-e^{-c_2{\nu}_0/T_0})I_ag_2)$. \vspace{1em} The motivations and the corresponding theory, including the determination of the statistical weights for molecules of various symmetries, will be discussed

Asymptotic normalization coefficients for N-14 C-13+p from C-13(He-3,d)N-14

Journals published by the American Physical Society can be found at http://publish.aps.org/The C-13(He-3,d) N-14 proton transfer reaction has been measured at an incident energy of 26.3 MeV. Angular distributions for proton transfer to the ground state and excited states at 2.313 and 3.948 MeV in N-14 are analyzed within the framework of the modified DWBA. Asymptotic normalization coefficients (ANC's) defining the amplitude of the tails of the N-14 bound-state wave functions in the C-13+p channel are extracted that are in excellent agreement with values found previously with the C-13(N-14,C-13)N-14 reaction. We conclude that C-p1/2(2)=18.2(9) fm(-1) and C-p3/2(2) = 0.91(14) fm(-1) for the virtual decay N-14(g.s.) --> C-13+p. These are necessary for the analysis of the N-14(Be-7, B-8)C-13 and N-14( C-11, N-12) C-13 reactions to extract the ANC's far Be-7+p --> B-8 and C-11+p-->N-12, which determine the direct radiative capture cross sections Be-7(p,gamma)B-8 and C-11(p,gamma)N-12 at astrophysical energies