312 research outputs found
Computer/PERT technique monitors actual versus allocated costs
A computer method measures the users performance in cost-type contracts utilizing the existing nasa program evaluation review technique without imposing any additional reporting requirements. progress is measured by comparing actual costs with a value of work performed in a specific period
High-spin states with seniority v=4,4,6 in 119-126Sn
The 119-126Sn nuclei have been produced as fission fragments in two reactions
induced by heavy ions: 12C+238U at 90 MeV bombarding energy, 18O+208Pb at 85
MeV. Their level schemes have been built from gamma rays detected using the
Euroball array. High-spin states located above the long-lived isomeric states
of the even- and odd-A 120-126Sn nuclei have been identified. Moreover isomeric
states lying around 4.5 MeV have been established in 120,122,124,126Sn from the
delayed coincidences between the fission fragment detector SAPhIR and the
Euroball array. The states located above 3-MeV excitation energy are ascribed
to several broken pairs of neutrons occupying the nu h11/2 orbit. The maximum
value of angular momentum available in such a high-j shell, i.e. for
mid-occupation and the breaking of the three neutron pairs, has been
identified. This process is observed for the first time in spherical nuclei.Comment: 20 pages, 22 figures, 12 tables, accepted for publication in Physical
Review
High-spin structures of 136Cs
Odd-odd 136Cs nuclei have been produced in the 18O + 208Pb and 12C + 238U
fusion-fission reactions and their gamma rays studied with the Euroball array.
The high-spin level scheme has been built up to ~ 4.7 MeV excitation energy and
spin I ~ 16 hbar from the triple gamma-ray coincidence data. The configurations
of the three structures observed above ~ 2 MeV excitation energy are first
discussed by analogy with the proton excitations identified in the semi-magic
137Cs nucleus, which involve the three high-j orbits lying above the Z=50 gap,
pi g_{7/2}, pi d_{5/2} and pi h_{11/2}. This is confirmed by the results of
shell-model calculations performed in this work.Comment: 6 pages, 4 figures, 3 table
Origins of Chevron Rollovers in Non-Two-State Protein Folding Kinetics
Chevron rollovers of some proteins imply that their logarithmic folding rates
are nonlinear in native stability. This is predicted by lattice and continuum
G\=o models to arise from diminished accessibilities of the ground state from
transiently populated compact conformations under strongly native conditions.
Despite these models' native-centric interactions, the slowdown is due partly
to kinetic trapping caused by some of the folding intermediates' nonnative
topologies. Notably, simple two-state folding kinetics of small single-domain
proteins are not reproduced by common G\=o-like schemes.Comment: 10 pages, 4 Postscript figures (will appear on PRL
Identification of evolutionary and kinetic drivers of NAD-dependent signaling
Nicotinamide adenine dinucleotide (NAD) provides an important link between metabolism and signal transduction and has emerged as central hub between bioenergetics and all major cellular events. NAD-dependent signaling (e.g., by sirtuins and poly-adenosine diphosphate [ADP] ribose polymerases [PARPs]) consumes considerable amounts of NAD. To maintain physiological functions, NAD consumption and biosynthesis need to be carefully balanced. Using extensive phylogenetic analyses, mathematical modeling of NAD metabolism, and experimental verification, we show that the diversification of NAD-dependent signaling in vertebrates depended on 3 critical evolutionary events: 1) the transition of NAD biosynthesis to exclusive usage of nicotinamide phosphoribosyltransferase (NamPT); 2) the occurrence of nicotinamide N-methyltransferase (NNMT), which diverts nicotinamide (Nam) from recycling into NAD, preventing Nam accumulation and inhibition of NAD-dependent signaling reactions; and 3) structural adaptation of NamPT, providing an unusually high affinity toward Nam, necessary to maintain NAD levels. Our results reveal an unexpected coevolution and kinetic interplay between NNMT and NamPT that enables extensive NAD signaling. This has implications for therapeutic strategies of NAD supplementation and the use of NNMT or NamPT inhibitors in disease treatment
Evaluating applicants to a new emergency medicine residency program: subjective assessment of applicant characteristics
New high-spin states of Ce and Ba from fusion-fission reactions: Proton excitations in the N = 84 isotones
High-spin states in the Ce and Ba nuclei have been populated in the C + U and O + Pb fusion-fission reactions at 90 MeV and 85 MeV bombarding energy, respectively. The emitted -radiation was detected using the Euroball III and IV arrays. The high-spin yrast and near-to-yrast structures of Ce have been considerably extended. The level scheme of Ba has been extended by six new levels. The newly observed structures in these N = 84 isotones are discussed by analogy with the neighbouring nuclei
High-spin structures of five N=82 isotones: 136Xe, 137Cs, 138Ba, 139La, and 140Ce
Five N=82 isotones have been produced in two fusion-fission reactions and
their gamma-rays studied with the Euroball array. The high-spin states of 139La
have been identified for the first time, while the high-spin yrast and
near-to-yrast structures of the four others have been greatly extended. From
angular correlation analysis,spin values have been assigned to some states of
136Xe and 137Cs. Several cascades involving gamma-rays of 139La have been found
to be delayed, they deexcite an isomeric state with T1/2= 315(35) ns located at
1800-keV excitation energy. The excited states of these five N=82 isotones are
expected to be due to various proton excitations involving the three high-j
subshells located above the Z=50 shell closure. This is confirmed by the
results of shell-model calculations performed in this work. In addition,
high-spin states corresponding to the excitation of the neutron core have been
unambiguously identified in 136Xe, 137Cs, and 138Ba.Comment: 18 pages, 18 figures, 10 tables, accepted for publication in Phys.
Rev.
The multiple facets of the Hsp90 machine
International audienceThe Ninth International Conference on the Hsp90 Chaperone Machine concluded in October 2018, in Leysin, Switzerland. The program highlighted findings in various areas, including integrated insight into molecular mechanism of Hsp90, cochaperones, and clients’ structure and function.Heat shock protein-90 (Hsp90) is a molecular chaperone critical for the folding, stability, and activity of client proteins 1. Hsp90 and its orthologs, including bacterial HtpG, mitochondrial TRAP1 and endoplasmic reticulum Grp94, exist as dimers, hydrolyze ATP, and cycle between distinct conformational states. Hsp90 preferentially binds proteins in near native states facilitating their remodeling for protein interactions and signaling. At the 9th International Conference on the Hsp90 Chaperone Machine approximately one-third of the attendees shared their data on Hsp90 structure and function through short talks (Figure 1). Here, we distill and summarize their finding
Observation of Positive-Parity Bands in Pd and Pd: Enhanced -Softness
The neutron-rich nuclei Pd and Pd were produced as fission
fragments following the Si + Er reaction at 142 MeV. Using the
identification based on the coincidences with the complementary fission
fragments, the only positive-parity bands observed so far in Pd and
Pd emerged from this work. A band, built on top of the 5/2 ground
state exhibiting = 1 energy-level staggering, was observed in each
of these nuclei. Both nuclei of interest, Pd and Pd, are
suggested to lie in the transitional region of Pd isotopes of maximum
-softness. The ground states of both nuclei are predicted by TRS
calculations to be extremely -soft with shallow triaxial minima. The
first crossing in the new bands is proposed to be due to an alignment of
neutrons
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