Neighboring Nuclei Research Articles

Tyrosine hydroxylase afferents to the interstitial nucleus of the posterior limb of the anterior commissure are neurochemically distinct from those projecting to neighboring nuclei

The interstitial nucleus of the posterior limb of the anterior commissure (IPAC) is exclusively innervated by tyrosine hydroxylase-immunoreactive (TH-IR) fibers as observed in the other nuclei of the rat forebrain such as the striatum and nucleus accumbens. Distinguishing TH-IR afferents to the IPAC from those projecting to neighboring nuclei has been difficult. However, we previously showed that the TH-IR fibers projecting to the IPAC were invulnerable to neurodegeneration in zitter mutant rats, whereas almost all TH-IR afferents fibers to the dorsolateral striatum were lost, indicating that these two groups of TH-IR afferents have distinct neurochemical properties. Here, to explore this observation further, we injected Fluorogold (FG) retrograde tracers to identify neurons projecting to the IPAC or dorsal striatum. We also determined the distribution of attractin mRNA and protein, causative factors for the pathological phenotypes of zitter mutant rats, within the normal rat midbrain. In rats injected with FG into the dorsal striatum, we detected many FG-positive neurons in the ventral aspect of the substantia nigra pars compacta (SNC). In contrast, many FG-positive neurons were observed in the dorsal aspect of the SNC of rats injected with FG into the IPAC. Immunohistochemistry and in situ hybridization studies of intact animals revealed that both attractin mRNA and protein were expressed at higher levels in the ventral aspect of the SNC, whereas both attractin mRNA and protein were expressed at lower levels in the dorsal aspect of the SNC. Taken together, these results indicate that TH-IR afferents to the IPAC have distinct neurochemical properties from those to the striatum and may account for the differential vulnerability to neurodegeneration observed in zitter mutant rats.

ENDOR investigations of the Ce3+ ions in YAG: Transferred hyperfine interaction with nearest aluminum ions

The transferred hyperfine interactions of Ce3+ centers with 27Al neighbor nuclei in heavily cerium doped yttrium aluminum garnet (YAG) are resolved using Pulsed-Electron Nuclear Double Resonance (Pulsed-ENDOR). It is demonstrated that substitution of Ce3+ for Y3+ in YAG crystals leads to the strong reduction of the nuclear quadrupole coupling at the tetrahedral aluminum d-sites (e2qQ/h ≈ 4.67 MHz).

Characterizing the First and Second 27Al Neighbors of Brønsted and Lewis Acid Protons in Zeolites and the Distribution of 27Al Quadrupolar Couplings by 1H{27Al} Offset REAPDOR

The application of 1H{27Al} offset rotational-echo adiabatic-passage double-resonance (REAPDOR) NMR experiments enables the indirect observation of the first-order quadrupolar lineshapes for 27Al nuclei in acidic zeolites H-beta and H,Na-A by observing the neighboring 1H nuclei under the influence of dipolar coupling between them. The technique allows one to resolve the contribution of different Al environments, provided that these are characterized by different quadrupolar broadenings, reflecting different structural distortions. Therefore, Bronsted acid sites that typically show large quadrupolar coupling constants (CQ) can be distinguished from extra-framework Lewis sites, which often have considerably smaller quadrupolar couplings. The 1H{27Al} offset REAPDOR patterns can be simulated employing a Gaussian probability distribution using a library of reference offset REAPDOR curves (depending on quadrupolar coupling constant and asymmetry parameter). Monomodal and bimodal probability distributions of CQ...

Heavy particle decay studies using different versions of nuclear potentials

The heavy particle decay from 212-240Pa , 219-245Np , 228-246Pu , 230-249Am , and 232-252Cm leading to doubly magic 208Pb and its neighboring nuclei have been studied using fourteen versions of nuclear potentials. The study has shown that the barrier penetrability as well as the decay half-lives are found to vary with the nuclear potential used. The investigated decay events of the emission of the clusters 22Ne , 24Ne , 26Mg , 28Mg , 32Si and 33Si are not experimentally detected yet but may be detectable in the future. As most of the half-lives predicted are found to lie within the experimental upper limit, T 1/2 < 1030 s, our predictions will be a guide to future experimental design. The GN plots studied are linear for different cluster emissions from different parents with varying slopes and intercepts. Also, it is to be noted that the linearity of the GN plots is unaltered using different nuclear potentials. The universal curve studied ( log10 T 1/2 vs. -ln P for various clusters emitted from various parents shows a linear behavior with the same slope and intercept irrespective of the nuclear potential used.

Observation of a γ-decaying millisecond isomeric state in 128Cd80

A new high-spin isomer in the neutron-rich nucleus 128Cd was populated in the projectile fission of a 238U beam at the Radioactive Isotope Beam Factory at RIKEN. A half-life of T1/2=6.3(8) ms was measured for the new state which was tentatively assigned a spin/parity of (15−). The experimental results are compared to shell model calculations performed using state-of-the-art realistic effective interactions and to the neighbouring nucleus 129Cd. In the present experiment no evidence was found for the decay of a 18+E6 spin-trap isomer, based on the complete alignment of the two-neutron and two-proton holes in the 0h11/2 and the 0g9/2 orbit, respectively, which is predicted to exist by the shell model.

Local mass relations and the NpNn scheme

In this paper we show that $ip\ensuremath{-}jn$ relations for nuclear masses and charge radii of four neighboring nuclei reconcile with Casten's ${N}_{p}{N}_{n}$ scheme.

Nucleation and Growth Mechanism of Barium Titanate Nanoblocks in Hydrothermal Process Using Aqueous Titanium Compound

Barium titanate (BT) nanoblocks were synthesized by using aqueous sources of barium and titanium. To analyze the growth mechanism of nanoblocks, a kind of sampling hydrothermal vessel was employed to timely observe the reaction of precursor solution. During the nucleation and ripening process, intermediate of nanoblocks were taken out directly from reacting solution to analyze. BT nuclei grew directly in the Ti-based gel through an in situ growth mechanism. An oriented attachment phenomenon could be observed among neighboring nuclei. The Ostwald ripening process played a role in the growth of monodispersed BT nanoblocks. Diversified surface morphology of intermediate nanocrystals indicates that the chelating effect of oleate anions is unequal for all of the {100} crystal facets. After 24 h, agglomeration of nanoblocks occurred in Ti gel and formed BT meso-clusters with highly crystalline structure. The kinetics of the BT cluster was related with the oriented attachment mechanism. Nanoblocks overlapped wit...

Using "Functional" Target Coordinates of the Subthalamic Nucleus to Assess the Indirect and Direct Methods of the Preoperative Planning: Do the Anatomical and Functional Targets Coincide?

Objective: To answer the question of whether the anatomical center of the subthalamic nucleus (STN), as calculated indirectly from stereotactic atlases or by direct visualization on magnetic resonance imaging (MRI), corresponds to the best functional target. Since the neighboring red nucleus (RN) is well visualized on MRI, we studied the relationships of the final target to its different borders. Methods: We analyzed the data of 23 PD patients (46 targets) who underwent bilateral frame-based STN deep brain stimulation (DBS) procedure with microelectrode recording guidance. We calculated coordinates of the active contact on DBS electrode on postoperative MRI, which we referred to as the final “functional/optimal” target. The coordinates calculated by the atlas-based “indirect” and “direct” methods, as well as the coordinates of the different RN borders were compared to these final coordinates. Results: The mean ± SD of the final target coordinates was 11.7 ± 1.5 mm lateral (X), 2.4 ± 1.5 mm posterior (Y), and 6.1 ± 1.7 mm inferior to the mid-commissural point (Z). No significant differences were found between the “indirect” X, Z coordinates and those of the final targets. The “indirect” Y coordinate was significantly posterior to Y of the final target, with mean difference of 0.6 mm (p = 0.014). No significant differences were found between the “direct” X, Y, and Z coordinates and those of the final targets. Conclusions: The functional STN target is located in direct proximity to its anatomical center. During preoperative targeting, we recommend using the “direct” method, and taking into consideration the relationships of the final target to the mid-commissural point (MCP) and the different RN borders.

Multiple rescattering processes in high-order harmonic generation from molecular system.

The molecular multiple rescattering processes have been theoretically investigated via solving the time-dependent Schrödinger equation. Not only has the physical model been established, but also the related rescatterings originating from recombination with parent nucleus and with neighboring nucleus have been distinguished. Moreover, it has shown that the rescatterings originating from recombination with parent nucleus are similar with those atomic rescatterings, while those rescatterings from recombination with neighboring nucleus both before and after reversing the direction of the laser field are more sensitive to the internuclear distance. With time-frequency distribution and classical electron dynamics, the underlying mechanisms are revealed.

Re-evaluation of the thermal neutron capture cross section of 147Nd

In this paper we are proposing a re-evaluation of the thermal-neutron induced capture cross section of 147Nd. A unique measurement exists from which this cross section was calculated in 1974. This original calculation is based on an assumed value for a specific gamma-ray fraction (called F2), taken from the neighboring nucleus 145Nd. With the availability of reaction codes such as TALYS, such fraction can nowadays be calculated using specific reaction models and parameters. The new value of F2 indicates a decrease of the thermal cross section by 45%, leading to 243 barns, instead of the 440 barns previously reported. This new cross section impacts the calculation of the number density for the well-known burn-up indicator 148Nd, but as shown, the change is close to the usual experimental uncertainties for the 148Nd number densities, thus having a limited impact on burn-up calculation.

Decay of the compound nucleus118*297formed in the reactionCf249+Ca48using the dynamical cluster-decay model

The decay of the $Z=118$, $^{297}118^{*}$ compound system, formed in the $^{249}\mathrm{Cf}+^{48}\mathrm{Ca}$ reaction, is studied for $2n$, $3n$, and $4n$ emissions, by using the dynamical cluster-decay model (DCM) at compound-nucleus (CN) excitation energies ${E}_{\mathrm{CN}}^{*}=29.2$ and 34.4 MeV. A parallel attempt is made to analyze the $^{294}118$ residue nucleus synthesized in the $^{250}\mathrm{Cf}+^{48}\mathrm{Ca}$ reaction, subsequent to the $4n$ emission from the $^{298}118^{*}$ nucleus, to check the possibility of isotopic mixing in the $^{249}\mathrm{Cf}$ target used in the $^{249}\mathrm{Cf}+^{48}\mathrm{Ca}$ reaction. The possible role of deformations and orientations, together with different nuclear proximity potentials, is also investigated. In addition, an exclusive analysis of the mass distributions of $Z=113$ to 118 superheavy nuclei, formed in $^{48}\mathrm{Ca}$-induced reactions, is explored within the DCM. A comparative importance of Prox-1977 and Prox-2000 potentials on the $\ensuremath{\alpha}$-decay chains is also investigated, first by using the preformed cluster model (PCM) for spontaneous decays $(T=0)$, the $\mathrm{PCM}(T=0)$, and then analyzing the possible role of excitation energy in PCM, i.e., $\mathrm{PCM}(T\ensuremath{\ne}0)$, via the measured recoil energy of the residual $^{294}118$ nucleus left after $3n$ emission from $^{297}118^{*}$ CN. The branching of $\ensuremath{\alpha}$ decay to the most-probable clusters is also examined for $^{294}118^{*}$ and its subsequent $^{290}116^{*}$ and $^{286}114^{*}$ parents occurring in the $\ensuremath{\alpha}$-decay chain. Interestingly, the calculated decay half-lives for some clusters such as $^{86}\mathrm{Kr}$, $^{84}\mathrm{Se}$, and $^{80}\mathrm{Ge}$, referring to doubly magic $^{208}\mathrm{Pb}$ or its neighboring daughter nucleus, present themselves as exciting new possibilities, though to date difficult to observe, of heavy cluster emissions in superheavy mass region.

Identification of native defects (vacancies and antisites) in CdSiP2 crystals

Electron paramagnetic resonance (EPR) is used to identify four native defects in single crystals of CdSiP2. This nonlinear optical material is used in optical parametric oscillators to generate tunable output in the mid-infrared. The performance of these frequency-conversion devices is limited when infrared absorption bands associated with native defects overlap a pump wavelength. Cadmium, silicon, and phosphorus vacancies and also silicon-on-cadmium antisites are present in the as-grown undoped CdSiP2 crystals. Using near-band-edge 632.8 nm light from a He-Ne laser, a paramagnetic charge state, and thus an EPR spectrum, is formed at liquid-helium temperatures for three of the four defects. The EPR spectrum from the singly ionized silicon vacancy (VSi−) is present without light and has five hyperfine lines due to equal interactions with the four neighboring 31P nuclei. In contrast, the photoinduced EPR spectrum from the singly ionized cadmium vacancy (VCd−) has a three-line hyperfine pattern due to equal interactions with only two of its four neighboring 31P nuclei. The light-induced spectrum from the singly ionized silicon-on-cadmium antisite (Si Cd+) also has a three-line hyperfine pattern, thus indicating that the unpaired spin interacts primarily with only two 31P neighbors. For the neutral phosphorus vacancy (VP 0), the unpaired spin is primarily localized on the nearest-neighbor silicon ions and the photoinduced EPR spectrum has no resolved 31P hyperfine interactions. The silicon and cadmium vacancies are acceptors, and the silicon-on-cadmium antisite and the phosphorus vacancy are donors.

Recent Advances in Theoretical and Physical Aspects of NMR Chemical Shifts

In the first part of this review, theoretical aspects of nuclear magnetic shielding include (a) general theory, for example, newly developed approaches in relativistic theory of nuclear shielding, the relation between the spin-rotation tensor and shielding in relativistic theory, ab initio methods for treating open shell systems and a complete theory of chemical shifts in paramagnetic systems, the link between the definitions of the elusive concepts aromaticity and anti-aromaticity and the magnetic properties: the magnetizability tensor and the nuclear magnetic shielding tensor via delocalized electron currents and electron current maps, (b) ab initio and DFT calculations, both relativistic and non-relativistic, for various nuclei in various molecular systems using various levels of theoretical treatment. Physical aspects include (a) anisotropy of the shielding tensor, usually from solid state measurements, and calculations to support these, (b) shielding surfaces and rovibrational averaging, paying special attention to the sensitive relationship between shielding and bond angles or torsion angles that makes shielding such a powerful tool for structural/conformational determination in macromolecules, (c) chemical shifts that arise from isotopic substitution of NMR nucleus or neighboring nuclei, (d) intermolecular effects on nuclear shielding, and (e) absolute shielding scales.

Concurrence of Fahr's disease and brain tumor: A case report and review of the literature.

Fahr's disease is a rare entity characterized by abnormal calcification in the bilateral basal ganglion regions and cerebellum. Concurrence of Fahr's disease with brain tumor is associated with an even lower incidence; the present study describes the fifth such case, in which a 32-year-old female presented with a 1-month history of headache and unsteady walking. Pathology and imaging studies resulted in a diagnosis of low-grade astrocytoma with calcified deposition. The patient recovered uneventfully. Following a review of the literature, several similarities among the reported cases were revealed. Patients were relatively young at the onset of the disease. The pathological diagnosis for all brain tumors was astrocytoma. The cerebellum was the predominant location of the brain tumor. The imaging studies of these cerebral astrocytomas were almost identical, with a cystic glioma occurring adjacent to a neighboring calcified dentate nucleus. Furthermore, the development of astrocytoma in the bilateral cerebellar hemisphere was not uncommon, which warrants close follow-up for these patients.

Positive-parity rotational band inTb158

Excited states of the odd-odd nucleus $^{158}\mathrm{Tb}$ have been studied via the $^{154}\mathrm{Sm}(^{7}\mathrm{Li},3n)^{158}\mathrm{Tb}$ reaction at a beam energy of 27 MeV. The new level scheme of $^{158}\mathrm{Tb}$ involving a positive parity rotational band is established up to excitation energy $\ensuremath{\sim}2.3\phantom{\rule{4.pt}{0ex}}\mathrm{MeV}$ and spin $\ensuremath{\sim}17\ensuremath{\hbar}$. By comparing with the rotational bands in the neighboring nuclei $^{157}\mathrm{Tb}$ and $^{157}\mathrm{Gd}$, the configuration was tentatively assigned as $\ensuremath{\pi}{d}_{5/2}\ensuremath{\bigotimes}\ensuremath{\nu}{i}_{13/2}$, and the phenomenon of signature inversion is discussed.

First identification of rotational band structures inRe9175166

Despite that it is more than 100 years since the atomic nucleus was first dis- covered by Ernest Rutherford and coworkers, many of its features still elude our understanding. The fact that the fundamental interactions between the nuclear constituents; nucleons, and ultimately quarks, are not yet known in detail, and the complexity of the nuclear many-body system compound the great challenges facing theoretical interpretations of experimental data. It is therefore important to focus on distinct phenomena where experimental mea- surements can be compared with theoretical predictions, providing stringent tests of theory. One such area is the nuclear phenomenology of collective excitations related to rotations and vibrations of the nucleus as a whole, and how such modes of excitation may develop from the interactions between a few nucleons occupying single-particle orbits outside closed shells.This thesis is devoted to experimental studies of excited states in the 99Tc, 162W, and 166Re nuclei. These nuclei lie in “transitional” regions of the Segre chart, where collective excitation mechanisms start becoming important when adding valence nucleons outside closed neutron and proton shells. Such nuclei are important for testing state-of-the-art theoretical models. The excited states of the nuclei studied in the present work were populated using heavy-ion fusion-evaporation reactions. Prior to the present work, high-spin data were still lacking in 99Tc since in the previous works [1–5] excited states were only populated up to around 3 MeV. Two collective bands have been extended to intermediate angular momentum states in the present work. The experimental results were compared with the systematics of other technetium isotopes, evaluating electromagnetic characteristics based on semiclassical calculations and the particle-rotor model. The 162W and 166Re nuclei are situated in the very neutron-deficient 160-170 mass region, requiring special techniques for identifying their excited-state structures. The level scheme of 162W was first reported by Dracoulis et al. in 1993 [6], where the first excited 2+ state was assigned to be 450 keV above the ground state. However, the lack of selectivity made the γ-ray identification for higher energy levels of 162W uncertain. In this work, the highly selective recoil-decay tagging technique was used to uniquely identify γ-ray transitions from excited states in 162W and to construct its level scheme. In addition, the experimental setup enabled a precise determination of the half-life of the α-decaying ground state of 162W. The α-formation probability for 162W was extracted from the measurement of the half-life and systematical comparisons with the neighboring nuclei were performed. Two rotational-like bands were identified in 166Re for the first time and the lifetimes of the lowest three excited states in band (1) were measured using the recoil distance Doppler shift method. The results were compared with theoretical calculations based on a semiclassical approach, the particle-rotor model, and the tilted axis cranking model in a relativistic mean field approach. The microscopic mechanisms (configuration and alignment, etc) of the rotational bands were interpreted under the framework of total Routhian surface predictions and cranked shell model calculations.

Evolution of quadrupole collectivity inN=80isotones toward theZ=64subshell gap: TheB(E2;21+→01+)value ofSm142

It was shown that the evolution of the $B(E2;{2}_{1}^{+}\ensuremath{\rightarrow}{0}_{1}^{+})$ values in $N$ = 80 isotones from Te to Nd is affected by the underlying subshell structure. This manifests itself in the observation of the local suppression of the $B(E2)$ value at $Z=58$ with respect to the neighboring nuclei $^{136}\mathrm{Ba}$ and $^{140}\mathrm{Nd}$. To investigate this shell sensitivity toward the $Z=64$ subshell gap, the $B(E2;{2}_{1}^{+}\ensuremath{\rightarrow}{0}_{1}^{+})$ value of the unstable nucleus $^{142}\mathrm{Sm}$ was measured utilizing the projectile Coulomb excitation technique. The radioactive ion beam (RIB) experiment was performed at the REX-ISOLDE facility at CERN. The $B(E2)$ value of $32\phantom{\rule{0.16em}{0ex}}(4)\phantom{\rule{0.16em}{0ex}}\mathrm{W}.\mathrm{u}.$ reflects the impact of the $\ensuremath{\pi}(1{g}_{7/2}\phantom{\rule{0.16em}{0ex}}2{d}_{5/2})$ subshell closure at $Z=64$ with respect to a linear scaling of collectivity with valence proton number.

Cross sections of α-induced reactions for targets with masses A ≈ 20–50 at low energies

A simple reduction scheme using so-called reduced energies $E_{\rm{red}}$ and reduced cross sections $\sigma_{\rm{red}}$ allows the comparison of heavy-ion induced reaction cross sections for a broad range of masses of projectile and target and over a wide energy range. A global behavior has been found for strongly bound projectiles whereas much larger reduced cross sections have been observed for weakly bound and halo projectiles. It has been shown that this simple reduction scheme works also well for $\alpha$-particle induced reactions on heavy target nuclei, but very recently significant deviations have been seen for $\alpha$+$^{33}$S and $\alpha$+$^{23}$Na. Motivated by these unexpected discrepancies, the present study analyses $\alpha$-induced reaction cross sections for targets with masses $A \approx 20-50$. The study shows that the experimental data for $\alpha$-induced reactions on nuclei with $A \approx 20-50$ deviate slightly from the global behavior of reduced cross sections. However, in general the deviations evolve smoothly towards lower masses. The only significant outliers are the recent data for $^{33}$S and $^{23}$Na which are far above the general systematics, and some very old data may indicate that $^{36}$Ar and $^{40}$Ar are below the general trend. As expected, also the doubly-magic $^{40}$Ca nucleus lies slightly below the results for its neighboring nuclei. Overall, the experimental data are nicely reproduced by a statistical model calculation utilizing the simple $\alpha$-nucleus potential by McFadden and Satchler. Simultaneously with the deviation of reduced cross sections $\sigma_{\rm{red}}$ from the general behavior, the outliers $^{23}$Na, $^{33}$S, $^{36}$Ar, and $^{40}$Ar also show significant disagreement between experiment and statistical model calculation.

Nucleon pairing correlations and theαcluster preformation probability inside heavy and superheavy nuclei

The presence of paired or unpaired protons and neutrons in the open-shell radioactive \ensuremath{\alpha} emitter affects the preformation probability of the \ensuremath{\alpha} cluster inside it. The \ensuremath{\alpha}-preformation probability inside the $\mathrm{odd}(Z)\text{\ensuremath{-}}\mathrm{even}(N)$, $\mathrm{even}(Z)\text{\ensuremath{-}}\mathrm{odd}(N)$, and $\mathrm{odd}(Z)\text{\ensuremath{-}}\mathrm{odd}(N)$ \ensuremath{\alpha} emitters is investigated. The study is restricted to those decays with no angular momentum transfer to make a precise prediction about the mere pairing effect. The extended cluster model of \ensuremath{\alpha} decay and the WKB approximation are used by taking into account the deformation degrees of freedom to carry out the calculations for 105 parent nuclei in the mass region of $A=175--289.$ The $\ensuremath{\alpha}$ + daughter interaction potential is calculated by using the Hamiltonian energy-density approach in terms of the SLy4 Skyrme-like interaction, then it is implemented to find the average decay width over the different orientations. The half-life of the decay is then estimated and employed in turn to extract the \ensuremath{\alpha}-preformation probability by taking account of errors on both the released energy and the experimental half-life time. According to the present calculations, it is found that the \ensuremath{\alpha} cluster preformation probability inside the nuclei which have unpaired nucleons is less than it would be in the neighboring nuclei of the same shell and subshell closures but have no unpaired nucleons. In particular, the effect of the single unpaired neutron in the $\mathrm{even}(Z)\text{\ensuremath{-}}\mathrm{odd}(N)$ nuclei is slightly larger than that of the single unpaired proton in the $\mathrm{odd}(Z)\text{\ensuremath{-}}\mathrm{even}(N)$ ones. The effect of the unpaired nucleons appears more clearly in the $\mathrm{odd}(Z)\text{\ensuremath{-}}\mathrm{odd}(N)$ nuclei which have both an unpaired neutron and an unpaired proton. Based on the obtained results, an empirical pairing term is added to the empirical formula [J. Phys. G 40, 105102 (2013)] that relates the \ensuremath{\alpha} cluster preformation probability to the proton and neutron numbers outside the closed shells of the parent nucleus.

Reconstitution of local mass relations

In this paper we show that double differences of separation energies for four neighboring nuclei cancel out with remarkable accuracy. The well-known Garvey-Kelson relations (GKs) and their generalizations are reduced to special cases of our reconstituted relations. Some of the new relations given in this paper are found to be in competitive or even better agreement with experimental data than the GKs.