Electron-capture decay rate of ⁷Be encapsulated in a C₇₀ fullerene cage

The decay rate of ⁷Be electron capture in C₇₀ and Be metal was measured employing a reference method. The half-life (T_{1/2}) of ⁷Be endohedral C₇₀ (⁷Be@C₇₀) was found to be T_{1/2} = 52.49±0.04 d at room temperature (T = 293 K) and T_{1/2} = 52.42±0.04 d at liquid helium temperature (T = 5 K). Furthermore, the T_{1/2} of ⁷Be in Be metal was T_{1/2} = 53.25±0.04 d at room temperature (T = 293 K) and T_{1/2} = 53.39±0.03 d at liquid helium temperature (T = 5 K). These values for ⁷Be@C₇₀ at T = 5 K are approximately 1.6%(1.8%) smaller than those for ⁷Be in Be metal at T = 293 K (T = 5 K), indicating the difference in the electron wave functions for ⁷Be inside C₇₀ and ⁷Be in C60 and Be metal. The average charge transfer from the L(2s) electrons of the ⁷Be atom influences such variations in the decay constant (λ = ln2/T_{1/2}) in the environment. The experimental and theoretical investigations revealed that the change in the EC-decay rate of ⁷Be could be largely related to the potential configurations and the environment inside C60 and/or C₇₀ cages. The motion of ⁷Be inside cages was found to be restricted according to temperature

Effects of nuclear orientation on fusion and fission in the reaction using 238U target nucleus

Fission fragment mass distributions in the reaction of 30Si+238U were measured around the Coulomb barrier. At the above-barrier energies, the mass distribution showed a Gaussian shape. At the subbarrier energies, triple-humped distribution was observed, which consists of symmetric fission and asymmetric fission peaked at AL/AH ~ 90/178. The asymmetric fission should be attributed to quasifission from the results of the measured evaporation residue (ER) cross-sections for 30Si+238U. The cross-section for 263Sg at the abovebarrier energy agree with the statistical model calculation which assumes that the measured fission cross-section originates from fusion-fission, whereas the one for 264 Sg measured at the sub-barrier energy is smaller than the calculation, which suggests the presence of quasifission

Life-time measurement of ^7Be in beryllium metal(II. Radiochemistry)

The decay rate of ^7Be (nucleus of electron-capture decay) was measured in Be metal. The half life of ^7Be in Be metal (Be metal (^7Be)) is found to be 53.12±0.05 days. We have found that the decay rate of ^7Be in Be metal is almost corresponding to that in graphite host, Lithium fluoride host etc. reported within the errors

Creation of Mo/Tc@C60 and Au@C60 and molecular-dynamics simulations

The formation of middle- and/or high-weight atom (Mo, Au)-incorporated fullerenes was investigated using radionuclides produced by nuclear reactions. From the trace radioactivities of ⁹⁹Mo/⁹⁹mTc or ¹⁹⁴Au after high-performance liquid chromatography, it was found that the formation of endohedral and/or heterofullerene fullerenes in ⁹⁹Mo/⁹⁹mTc and ¹⁹⁴Au atoms could occur by a recoil process following the nuclear reactions. Furthermore, the ⁹⁹mTc (and ¹⁹⁴Au) atoms recoiled against β-decay remained present inside these cages. To confirm the produced materials experimentally, ab initio molecular dynamics (MD) simulations based on an all-electron mixed-basis approach were performed. The possibility of the formation of endohedral fullerenes containing Mo/Tc and Au atoms is verified; here, the formation of heterofullerenes is excluded by MD simulations. These findings suggest that radionuclides stably encapsulated by fullerenes could potentially play a valuable role in diagnostic nuclear medicine

Observation of α-decay of ^<229m>Th produced from ^<229>Ac(II. Radiochemistry)

We produced ^Th in the nuclear reaction ^Th(γ, p2n)^ Ac, followed by disintegration to ^Th. The α-decay signals from ^Th were searched for and the alpha-particle events of the energy region between 4.93MeV and 5.05MeV were observed in the separated thorium fraction from an actinium source highly purified from the ^Th+γ reaction products. The energy values of the α-particles coincide with those expected for ^Th

Study of fission using multi-nucleon transfer reactions

Multi-nucleon transfer channels of the reactions of 18O+232Th, 18O+238U, 18O+248Cm were used to measure fission-fragment mass distribution for various nuclides and their excitation energy dependence. Predominantly asymmetric fission is observed at low excitation energies for all the studied cases, with an increase of the symmetric fission towards high excitation energies. Experimental data are compared with predictions of the fluctuation-dissipation model, where effects of multi-chance fission (neutron evaporation prior to fission) was introduced. It was shown that a reliable understanding of the observed fission fragment mass distributions can be obtained only invoking multi-chance fissions

Beneficial Effects of Estrogen in a Mouse Model of Cerebrovascular Insufficiency

BACKGROUND: The M(5) muscarinic acetylcholine receptor is known to play a crucial role in mediating acetylcholine dependent dilation of cerebral blood vessels. Previously, we reported that male M(5) muscarinic acetylcholine knockout mice (M5R(-/-) mice) suffer from a constitutive constriction of cerebral arteries, reduced cerebral blood flow, dendritic atrophy, and short-term memory loss, without necrosis and/or inflammation in the brain. METHODOLOGY/PRINCIPAL FINDINGS: We employed the Magnetic Resonance Angiography to study the area of the basilar artery in male and female M5R(-/-) mice. Here we show that female M5R(-/-) mice did not show the reduction in vascular area observed in male M5R(-/-) mice. However, ovariectomized female M5R(-/-) mice displayed phenotypic changes similar to male M5R(-/-) mice, strongly suggesting that estrogen plays a key role in the observed gender differences. We found that 17beta-estradiol (E2) induced nitric oxide release and ERK activation in a conditional immortalized mouse brain cerebrovascular endothelial cell line. Agonists of ERalpha, ERbeta, and GPR30 promoted ERK activation in this cell line. Moreover, in vivo magnetic resonance imaging studies showed that the cross section of the basilar artery was restored to normal in male M5R(-/-) mice treated with E2. Treatment with E2 also improved the performance of male M5R(-/-) mice in a cognitive test and reduced the atrophy of neural dendrites in the cerebral cortex and hippocampus. M5R(-/-) mice also showed astrocyte swelling in cortex and hippocampus using the three-dimensional reconstruction of electron microscope images. This phenotype was reversed by E2 treatment, similar to the observed deficits in dendrite morphology and the number of synapses. CONCLUSIONS/SIGNIFICANCE: Our findings indicate that M5R(-/-) mice represent an excellent novel model system to study the beneficial effects of estrogen on cerebrovascular function and cognition. E2 may offer new therapeutic perspectives for the treatment of cerebrovascular insufficiency related memory dysfunction

Tertiary network in mammalian mitochondrial tRNAAsp revealed by solution probing and phylogeny

Primary and secondary structures of mammalian mitochondrial (mt) tRNAs are divergent from canonical tRNA structures due to highly skewed nucleotide content and large size variability of D- and T-loops. The nonconservation of nucleotides involved in the expected network of tertiary interactions calls into question the rules governing a functional L-shaped three-dimensional (3D) structure. Here, we report the solution structure of human mt-tRNAAsp in its native post-transcriptionally modified form and as an in vitro transcript. Probing performed with nuclease S1, ribonuclease V1, dimethylsulfate, diethylpyrocarbonate and lead, revealed several secondary structures for the in vitro transcribed mt-tRNAAsp including predominantly the cloverleaf. On the contrary, the native tRNAAsp folds into a single cloverleaf structure, highlighting the contribution of the four newly identified post-transcriptional modifications to correct folding. Reactivities of nucleotides and phosphodiester bonds in the native tRNA favor existence of a full set of six classical tertiary interactions between the D-domain and the variable region, forming the core of the 3D structure. Reactivities of D- and T-loop nucleotides support an absence of interactions between these domains. According to multiple sequence alignments and search for conservation of Leontis–Westhof interactions, the tertiary network core building rules apply to all tRNAAsp from mammalian mitochondria