Ca Core Research Articles

Low-lying bound and resonance states in Λ61Ca and ΛΛ62Ca

In this paper, the energy, and wavefunctions of the low-lying bound and resonance states of [Formula: see text]Ca and [Formula: see text]Ca are studied. For [Formula: see text]Ca we adopted [Formula: see text]Ca two-body cluster model while for [Formula: see text]Ca we adopted [Formula: see text]Ca three-body cluster model. Two models of potentials, namely SH: Hulthén type and WS: Woods–Saxon type potentials, each having a spin-orbit coupling term is chosen for the [Formula: see text]-nucleus pair while three-range Gaussian (TRG) Nijmegen hardcore and softcore potential models are chosen for [Formula: see text] pair. The resulting few-body (two- and three-body) Schrödinger equations are solved numerically to get the bound state energies and wavefunctions. For the three-body calculation, we used hyperspherical coordinates. The formalism of supersymmetric quantum mechanics is applied to construct a one-parameter family of isospectral potential to investigate the resonance states of the [Formula: see text]Ca ([Formula: see text]Ca) core-[Formula: see text] two-body system. To study the effect of replacement of the outer core valence nucleon(s) of [Formula: see text]Ca by [Formula: see text] hyperon(s), two- and three-body cluster model calculations for the bound states of [Formula: see text]Ca and [Formula: see text]Ca are also carried out using the same set of two-body potentials, as used for [Formula: see text]Ca and [Formula: see text]Ca respectively. And a clear enhancement in the one- and two-[Formula: see text] separation energies and a shrinking of the overall size of the nucleus is indicated. The computed results are compared with some of those found in the literature.

Density profiles near the nuclear surface of Ti44,52 : An indication of α clustering

We investigate the degree of $\alpha$ ($^4$He nucleus) clustering in the ground-state density profiles of $^{44}$Ti and $^{52}$Ti. Two types of density distributions, shell- and cluster-model configurations, are generated fully microscopically with the antisymmetrized quasi-cluster model, which can describe both the j-j coupling shell and $\alpha$-cluster configurations in a single scheme. Despite both the models reproducing measured charge radius data, we found that the $\alpha$ clustering significantly diffuses the density profiles near the nuclear surface compared to the ideal j-j coupling shell model configuration. The effect is most significant for $^{44}$Ti, while it is less for $^{52}$Ti due to the occupation of the $0f_{7/2}$ orbits in the $^{48}$Ca core. This difference can be detected by measuring proton-nucleus elastic scattering or the total reaction cross section on a carbon target at intermediate energies.

Charge Radii of ^{55,56}Ni Reveal a Surprisingly Similar Behavior at N=28 in Ca and Ni Isotopes.

Nuclear charge radii of ^{55,56}Ni were measured by collinear laser spectroscopy. The obtained information completes the behavior of the charge radii at the shell closure of the doubly magic nucleus ^{56}Ni. The trend of charge radii across the shell closures in calcium and nickel is surprisingly similar despite the fact that the ^{56}Ni core is supposed to be much softer than the ^{48}Ca core. The very low magnetic moment μ(^{55}Ni)=-1.108(20) μ_{N} indicates the impact of M1 excitations between spin-orbit partners across the N,Z=28 shell gaps. Our charge-radii results are compared to abinitio and nuclear density functional theory calculations, showing good agreement within theoretical uncertainties.

Role of tensor interaction as salvation of cluster structure in Ti44

Background: The $^{44}$Ti nucleus has been known to have a $^{40}$Ca+$\alpha$ cluster structure, and inversion doublet structure has been observed; however, $\alpha$ cluster structure tends to be washed out when the breaking of the $\alpha$ cluster is allowed due to the spin-orbit interaction. Nevertheless, $\alpha$ clustering in medium-heavy nuclei is quite a hot subject recently. Purpose: The tensor interaction has been known to play an essential role in the strong binding of the $^4$He nucleus, which induces the two-particle-two-hole (2p2h) excitation. Since this excitation is blocked when another nucleus approaches, it is worthwhile to show whether the tensor effect works to keep the distance between $^4$He and $^{40}$Ca and becomes the salvation of the clustering in $^{44}$Ti. Methods: The spin-orbit effect is included in the cluster model by using the antisymmetrized quasi cluster model (AQCM) developed by the authors. We have also developed an improved version of the simplified method to include the tensor contribution ($i$SMT), which allows us to estimate the tensor effect within the cluster model. The competition of these two is investigated in the medium-heavy mass region for the first time. Results: According to AQCM, the spin-orbit interaction completely breaks the $\alpha$ cluster and restores the symmetry of $jj$-coupling shell model when the $\alpha$ cluster approaches the $^{40}$Ca core. On the other hand, $i$SMT gives a large distance between $\alpha$ and $^{40}$Ca due to the tensor effect. Conclusions: In $^{44}$Ti, because of the strong spin-orbit and tensor contributions, two completely different configurations ($jj$-coupling shell model and cluster states) almost degenerate, and their mixing becomes important.

Existence of higher nodal band states withα+Ca48cluster structure inTi52

It is shown that recently observed $\alpha$ cluster states a few MeV above the $\alpha$ threshold energy in $^{52}$Ti correspond to the higher nodal band states with the $\alpha$+$^{48}$Ca cluster structure, i.e. a vibrational mode in which the intercluster relative motion is excited. The existence of the higher nodal states in the $^{48}$Ca core region in addition to the well-known higher nodal states in $^{20}$Ne and $^{44}$Ti reinforces the importance of the concept of vibrational motion due to clustering even in medium-weight nuclei with a $jj$-shell closed core. The higher nodal band and the shell-like ground band in $^{52}$Ti are described in a unified way by a Luneburg lens-like deep local potential due to the Pauli principle, which explains the emergence of backward angle anomaly (anomalous large angle scattering (ALAS)) at low energies, prerainbows at intermediate energies and nuclear rainbows at high energies in $\alpha$+$^{48}$Ca scattering. The existence of a $K=0^-$ $\alpha$ cluster band analog to $^{44}$Ti midway between the ground band and the higher nodal band is inevitably predicted.

Swelling of Doubly Magic ^{48}Ca Core in Ca Isotopes beyond N=28.

Interaction cross sections for ^{42-51}Ca on a carbon target at 280 MeV/nucleon have been measured for the first time. The neutron number dependence of derived root-mean-square matter radii shows a significant increase beyond the neutron magic number N=28. Furthermore, this enhancement of matter radii is much larger than that of the previously measured charge radii, indicating a novel growth in neutron skin thickness. A simple examination based on the Fermi-type distribution, and mean field calculations point out that this anomalous enhancement of the nuclear size beyond N=28 results from an enlargement of the core by a sudden increase in the surface diffuseness of the neutron density distribution, which implies the swelling of the bare ^{48}Ca core in Ca isotopes beyond N=28.

Organophosphate esters in sediment cores from coastal Laizhou Bay of the Bohai Sea, China

Concentrations and vertical distributions of organophosphate esters (OPEs) were investigated in the sediment cores collected from the Laizhou Bay, Bohai Sea of China. The total concentrations of OPEs in the sediment core (CA) collected near the Yellow River Estuary were in the range of 11.8–102ng/g, while the total concentrations in the sediment core (CB) near a mariculture area were 6.65–41.5ng/g. Significantly high concentrations of OPEs were found in the sediments near the Yellow River Estuary than those in the mariculture area. Vertical distributions in the sediment cores demonstrated a recent increase of OPE emissions, especially for tri-n-butyl phosphate (TnBP), tris (2-chloroethyl) phosphate (TCEP), and tris (2-chloroisopropyl) phosphate (TCPP). Generally, TCEP and TCPP were the dominant congeners in the sediment cores, while the profiles of TnBP were increase in the surface 0–20cm layers of the CA core. OPEs in the CA core may be remarkably influenced by the discharge of Yellow River, whereas OPEs in the CB core may originate from the transport through seawater. The remarkable increase of OPE flame retardants in the surface sediments raises the concern about their emissions and risks to the environment and indicates the need for further monitoring.

Ground-state electromagnetic moments of calcium isotopes

High-resolution bunched-beam collinear laser spectroscopy was used to measure the optical hyperfine spectra of the $^{43-51}$Ca isotopes. The ground state magnetic moments of $^{49,51}$Ca and quadrupole moments of $^{47,49,51}$Ca were measured for the first time, and the $^{51}$Ca ground state spin $I=3/2$ was determined in a model-independent way. Our results provide a critical test of modern nuclear theories based on shell-model calculations using phenomenological as well as microscopic interactions. The results for the neutron-rich isotopes are in excellent agreement with predictions using interactions derived from chiral effective field theory including three-nucleon forces, while lighter isotopes illustrate the presence of particle-hole excitations of the $^{40}$Ca core in their ground state.

The Comprehensive Approach — Doctrinal Overview and Swedish Leadership Implications at the Operative and Tactical Level

This article is built upon a doctrinal and literature review of comprehensive approach (ca) concepts and the larger international actors that currently use them, such as the un, eu and nato. It also focuses on how small actors, such as Sweden, can contribute within this collaborative framework. There is a focus on possible leadership challenges and suggestions of individual characteristics that would be desirable to handle these types of challenges. Examples of leadership challenges from Swedish informants were used to enrich the text from a Swedish perspective.The findings can be summarized with the following: (1) The un, eu and nato differ on how far they have developed ca core conceptual documents and to what levels they have implemented the approach within their international missions. (2) Sweden does not currently have a comprehensive approach of its own but seems to be headed in that direction. Small actors, such as Sweden, can mainly contribute to the larger actors with “plug-in” capabilities. (3) Possible challenges and competencies were identified and compared to the current leadership model used for the Swedish Armed Forces, Developmental Leadership. Our analysis indicates that although the current theoretical model of the Swedish Armed Forces holds up well to several ca factors, it could benefit to incorporate new concepts within the model that were identified as specific to a comprehensive approach context.

Thermodynamic Calculation on Calcium Treatment for 26CrMo4S/2 Steel

Because CaSi core wire was not fed in external refining process for 26CrMo4S/2 steel making, it was found that the molar ratio of calcium versus alumina was very low and subsequently resulted in generation of much more non-metallic inclusions. Hence, it was reasonable to sugguest feeding appropriate amount of Ca core wire. Before the performance, the thermodynamic calculation had been carried out to obtain the theoretical amount of Ca wire to be fed. According to the practical data from steel plant and the thermodynamic data, it was calculated that only when 1.38 × 10–4[%Al]T2/3 ≥ [%Ca]T ≥ 4.97×10–5[%Al]T2/3 in molten steel the Al2O3 inclusions could be properly modified.

STRUCTURE OF ODD 79,81,83Se ISOTOPES WITH PROTON AND NEUTRON EXCITATIONS ACROSS Z = 28 AND N = 40

The recently measured experimental data of 79,81,83 Se isotopes have been interpreted in terms of shell model (SM) calculations. The calculations have been performed in f5/2pg9/2 space with the recently derived interactions, namely JUN45 and jj44b. To study the importance of the proton excitations across the Z = 28 shell in this region, we have also performed calculation in fpg9/2 valence space using an fpg effective interaction with 48 Ca core and imposing a truncation. Excitation energies, B(2) values, quadrupole moments and magnetic moments are compared with the experimental data available. Present study reveals the importance of proton excitations across the Z = 28 shell for predicting quadrupole and magnetic moments.

Using Seasonal Variation in Otolith Microchemical Composition to Indicate Largemouth Bass and Southern Flounder Residency Patterns across an Estuarine Salinity Gradient

AbstractEstuaries are transitional zones where salinity largely controls the distribution of both freshwater and marine species. However, the degree to which freshwater and marine species use these variable habitats as year‐round residents or transient migrants is largely unknown. We used otolith strontium: calcium ratios (Sr: Ca) as a marker for salinity exposure to reconstruct lifetime salinity exposure plots for individual Largemouth Bass Micropterus salmoides and Southern Flounder Paralichthys lethostigma collected across a seasonally variable estuarine salinity gradient. Initially, we determined that a definable relationship existed between salinity, water chemistry, and otolith Sr: Ca for both species. We then used otolith Sr: Ca profiles to indicate lifetime salinity exposure and subsequently classified each fish as either a freshwater resident, transient (combination of freshwater and estuarine signals in otolith), or estuarine resident. For Southern Flounder we also used Sr: Ca profiles from the otolith core to classify each individual as having either a freshwater core or estuarine or marine core. For Largemouth Bass, most (88%) individuals in the lower estuary were estuarine residents, whereas most (77%) individuals in the upper estuary were freshwater residents. These data support the hypothesis that adult Largemouth Bass in lower portions of the estuary do not migrate to avoid salinity, but rather remain in lower portions of the estuary throughout life. For Southern Flounder, 45% of individuals had estuarine or marine core Sr: Ca signals, while 55% had freshwater Sr: Ca core signals. Combining core and residency classification patterns revealed that three patterns described 95% of the Southern Flounder collected: (1) freshwater core and freshwater resident (16%), (2) freshwater core and estuarine resident (37%), and (3) estuarine or marine core and estuarine resident (42%). These data demonstrate that both tidal freshwater and low‐salinity estuarine habitats are important nursery areas for Southern Flounder.

The role of amphiboles in the metamorphic evolution of the UHP rocks: a case study from the Tso Morari Complex, northwest Himalayas

Amphiboles represent a crucial phase of the ultra-high-pressure (UHP) metamorphic rocks as their solid solution behavior reflects both bulk compositional and P–T changes. Three different types of amphibole have been reported from the UHP metamafic rocks of the Tso Morari Crystalline Complex, NW Himalayas: Na-rich (glaucophane); Na–Ca-rich (barroisite, taramite, winchite) and Ca-rich (tremolite, magnesio-hornblende, pargasite). The Na-amphibole is presented as a core of the zoned amphibole with Na–Ca-rich rim; Na–Ca-amphibole is presented as inclusion in garnets as well as in matrix, and Ca-amphibole is generally found in the matrix. The Na–Ca-amphibole is observed at two different stages of metamorphism. The first is pre-UHP, and the second is post-garnet–omphacite assemblage though with a significant difference in composition. The pressure–temperature estimations of the formation of these two sets of Na–Ca-amphiboles corroborate their textural associations. Ca-rich amphiboles are generally present in the matrix either as symplectite with plagioclase or as a pseudomorph after garnet along with other secondary minerals like chlorite and biotite. Two different types of zoning have been observed in the amphibole grains: (1) core is Na-rich followed by Na–Ca rim and (2) core of Na–Ca-amphibole is followed by Ca-rich rim. The pre-UHP (or the prograde P–T path) and post-UHP stages (or the retrograde P–T path) of Tso Morari eclogites are defined by characteristic amphibole compositions, viz. Na/Na–Ca-amphibole, Na–Ca-amphibole and Ca-amphibole and thus indicate their utility in inferring crustal evolution of this UHP terrain.

Structure of odd Ge isotopes with 40 < N < 50

We have interpreted recently measured experimental data of $^{77}$Ge, and also for $^{73,75,79,81}$Ge isotopes in terms of state-of-the-art shell model calculations. Excitation energies, B(2) values, quadrupole moments and magnetic moments are compared with experimental data when available. The calculations have been performed with the recently derived interactions, namely with JUN45 and jj44b for ${f_{5/2}pg_{9/2}}$ space. We have also performed calculation for ${fpg_{9/2}}$ valence space using an ${fpg}$ effective interaction with $^{48}$Ca core and imposing a truncation to study the importance of the proton excitations across the Z=28 shell in this region. The predicted results of jj44b interaction are in good agreement with experimental data.

Migration and habitat use of the tropical eels Anguilla marmorata and A. bicolor pacifica in Vietnam

The patterns of use of marine and freshwater habitats by the tropical anguillid eels Anguilla marmorata and A. bicolor pacifica were examined by analysing the otolith strontium (Sr) and calcium (Ca) concentrations of yellow (immature) and silver (mature) stage eels collected in Vietnamese waters. In A. marmorata, the change in the Sr:Ca ratios outside the high Sr:Ca core was generally divided into three patterns: (1) typical catadromous life history pattern; (2) constant residence in brackish water; and (3) habitat shifting between sea and brackish waters with no freshwater life. In A. bicolor pacifica, no eels had a general life history as freshwater residents. The eels were also divided into three patterns: (1) constant residence in sea water; (2) constantly living in brackish water; and (3) habitat shifting from brackish to sea water with no freshwater residence. The mean Sr:Ca ratio value after recruitment to coastal waters ranged from 1.73 to 5.67 × 10−3 (mean 3.2 × 10−3) in A. marmorata and from 2.53 to 6.32 × 10−3 (mean 4.3 × 10−3) in A. bicolor pacifica. The wide range of otolith Sr:Ca ratios in both species indicated that the habitat use of these tropical eels was facultative among fresh, brackish, and marine waters during their growth phases after recruitment to coastal areas. Tropical eel species may have the same behavioural plasticity as temperate anguillid species regarding whether to enter freshwater or to remain in estuarine and marine environments.

Diverse mineral compositions, textures, and metamorphic P–T conditions of the glaucophane-bearing rocks in the Tamayen mélange, Yuli belt, eastern Taiwan

This paper presents new petrologic data for high-pressure, low-temperature (HP–LT) metamorphic rocks at Juisui. We reinterpret the so-called “Tamayen block” (Yang and Wang, 1985) or “Juisui block” (Liou, 1981; Beyssac et al., 2008) as a tectonic mélange. It is not a coherent sheet but rather a mixture dominated by greenschist and pelitic schist with pods of serpentinite, epidote amphibolite, and rare blueschist. Four types of glaucophane-bearing rocks are newly recognized in this mélange. Type I is in contact with greenschist lacking glaucophane and garnet. Glaucophane is present only as rare inclusions within pargasite. This type records metamorphic evolution from epidote blueschists-, epidote amphibolite-, to greenschist-facies. Type II contains characteristic zoned amphiboles from barroisite core to Mg-katophorite mantle and glaucophane rim, implying an epidote amphibolite-facies stage overprinted by an epidote blueschists-facies one. Type III includes winchite and indicates P–T conditions of about 6–8kbar, approaching 400°C. Type IV contains paragonite but lacks garnet; amphibole shows a Na–Ca core surrounded by a glaucophane rim. This type shows a high-pressure (?) epidote amphibolite-facies stage overprinted by an epidote blueschists-facies one. Amphibole zoning trends and mineral assemblages imply contradictory P–T paths for the four types of glaucophane-bearing rocks—consistent with the nature of a tectonic mélange. The new P–T constraints and petrologic findings differ from previous studies (Liou et al., 1975; Beyssac et al., 2008).

Spectroscopic Study of63Ni via Cold Neutron Capture Reaction: I. Nuclear Structure of63Ni

The γ-radiation has been investigated for 63 Ni produced by cold neutron capture in an enriched 62 Ni sample. The 315 γ-rays produced were placed in a 63 Ni level scheme, in which 272 placements are new. We determined the excitation energies with 0.2–0.8 keV error and the branching ratios of 62 bound levels in 63 Ni, including 30 new levels. The Q -value of the 62 Ni( n ,γ) 63 Ni reaction amounts to 6837.75±0.18 keV. A large-scale shell-model calculation was performed that included the four single-particle orbits of 0 f 7/2 , 1 p 3/2 , 0 f 5/2 , and 1 p 1/2 , assuming an inert 40 Ca core for negative-parity states, and those of 1 p 3/2 , 0 f 5/2 , 1 p 1/2 , and 0 g 9/2 , assuming a 56 Ni core for positive-parity states. The energies of the low-lying 63 Ni states were successfully reproduced. A mean-field statistical-model calculation was also performed by using a self-consistent interaction between the Hartree–Fock + Bardeen–Cooper–Schrieffer method and the statistical calculation. The calculation result is consistent with the experimental level density of 63 Ni.

Regular–chaos transition of the energy spectrum and electromagnetic transition intensities in 44V nucleus using the framework of the nuclear shell model

Abstract The spectral fluctuations and the statistics of electromagnetic transition intensities and electromagnetic moments in 44 V nucleus are studied by the framework of the interacting shell model, using the FPD 6 as a realistic effective interaction in the isospin formalism for 4 particles move in the fp -model space with a 40 Ca core. To look for a regular–chaos transition in 44 V nucleus, we perform shell model calculations using various interaction strengths β to the off-diagonal matrix elements of the FPD 6. The nearest-neighbors level spacing distribution P ( s ) and the distribution of electromagnetic transition intensities [such as, B ( M 1 ) and B ( E 2 ) transitions] are found to have a regular dynamic at β = 0 , a chaotic dynamic at β ⩾ 0.3 and an intermediate situation at 0 β 0.3 . For the Δ 3 statistic we have found a regular dynamic at β = 0 , a chaotic dynamic at β ⩾ 0.4 and an intermediate situation at 0 β 0.4 . It is also found that the statistics of the squares of M 1 and E 2 moments, which are consistent with a Porter–Thomas distribution, have no dependence on the interaction strength β .

The interaction of His337 with the Mn4Ca cluster of photosystem II

The most recent XRD studies of Photosystem II (PS II) reveal that the His337 residue is sufficiently close to the Mn(4)Ca core of the Water Oxidising Complex (WOC) to engage in H-bonding interactions with the μ(3)-oxo bridge connecting Mn(1), Mn(2) and Mn(3). Such interactions may account for the lengthening of the Mn-Mn distances observed in the most recent and highest resolution (1.9 Å) crystal structure of PS II compared to earlier, lower-resolution (2.9 Å or greater) XRD structures and EXAFS studies on functional PS II. Density functional theory is used to examine the influence on Mn-Mn distances of H-bonding interactions, mediated by the proximate His337 residue, which may lead to either partial or complete protonation of the μ(3)-oxo bridge on models of the WOC. Calculations were performed on a set of minimal-complexity models (in which WOC-ligating amino acid residues are represented as formate and imidazole ligands), and also on extended models in which a 13-peptide sequence (from His332 to Ala344) is treated explicitly. These calculations demonstrate that while the 2.9 Å structure is best described by models in which the μ(3)-oxo bridge is neither protonated nor involved in significant H-bonding, the 1.9 Å XRD structure is better reproduced by models in which the μ(3)-oxo bridge undergoes H-bonding interactions with the His337 residue leading to expansion of the 'close' Mn-Mn distances well known from EXAFS studies at ∼ 2.7 Å. Furthermore, full μ(3)-oxo-bridge protonation remains a distinct possibility during the process of water oxidation, as evidenced by the lengthening of the Mn-Mn vectors observed in EXAFS studies of the higher oxidation states of PS II. In this context, the Mn-Mn distances calculated in the protonated μ(3)-oxo bridge structures, particularly for the peptide extended models, are in close agreement with the EXAFS data.

Ab Initio Adiabatic and Diabatic Energies and Dipole Moments of the CaH+ Molecular Ion

The diabatic and adiabatic potential-energy curves and permanent and transition dipole moments of the highly excited states of the CaH(+) molecular ion have been computed as a function of the internuclear distance R for a large and dense grid varying from 2.5 to 240 au. The adiabatic results are determined by an ab initio approach involving a nonempirical pseudopotential for the Ca core, operatorial core-valence correlation, and full valence configuration interaction. The molecule is thus treated as a two-electron system. The diabatic potential energy curves have been calculated using an effective metric combined to the effective Hamiltonian theory. The diabatic potential-energy curves and their permanent dipole moments for the (1)∑(+) symmetry are examined and corroborate the high imprint of the ionic state in the adiabatic representation. Taking the benefit of the diabatization approach, correction of hydrogen electron affinity was taken into account leading to improved results for the adiabatic potentials but also the permanent and transition electric dipole moments.