Alpha Cluster Research Articles

Extreme nuclear shapes examined via giant dipole resonance lineshapes in hot light-mass systems

The influence of alpha clustering on nuclear reaction dynamics is investigated using the giant dipole resonance (GDR) lineshape studies in the reactions 20Ne (Elab=145,160 MeV) + 12C and 20Ne (Elab=160 MeV) + 27Al, populating 32S and 47V, respectively. The GDR lineshapes from the two systems are remarkably different from each other. Whereas, the non alpha-like 47V undergoes Jacobi shape transition and matches exceptionally well with the theoretical GDR lineshape estimated under the framework rotating liquid drop model (RLDM) and thermal shape fluctuation model (TSFM) signifying shape equilibration, for alpha cluster 32S an extended prolate kind of shape is observed. This unusual deformation, seen directly via -decay for the first time, is predicted to be due to the formation of orbiting di-nuclear configuration or molecular structure of 16O+ 16O in 32S superdeformed band.

Alpha cluster states and molecular orbitals in sd-shell nuclei

The α-clustering and molecular-orbitals of 22Ne and F isotopes are investigated based on antisymmetrized molecular dynamics (AMD). The observed candidates for the α cluster state of 22Ne are understood as the molecular-orbital states and α+ 18O di-nuclei states. The presence of the molecular-orbital states in the O and F isotopes and the drastic reduction of their excitation energy near the neutron-drip line are predicted.

Concepts of nuclearα-particle condensation

Certain aspects of the recently proposed antisymmetrised alpha particle product state wave function, or THSR alpha cluster wave function, for the description of the ground state in 8Be, the Hoyle state in 12C, and analogous states in heavier nuclei, are elaborated in detail. For instance, the influence of antisymmetrisation in the Hoyle state on the bosonic character of the alpha particles is studied carefully. It is shown to be weak, so that bosonic aspects are predominant. The de Broglie wave length of alpha particles in the Hoyle state is shown to be much larger than the inter-alpha distance. It is pointed out that the bosonic features of low density alpha gas states have measurable consequences, one of which, that is enhanced multi-alpha decay properties, likely already have been detected. Consistent with experiment, the width of the proposed analogue to the Hoyle state in 16O at the excitation energy of E_x=15.1 MeV is estimated to be very small (34 keV), lending credit to the existence of heavier Hoyle-like states. The intrinsic single boson density matrix of a self-bound Bose system can, under physically desirable boundary conditions, be defined unambiguously. One eigenvalue then separates out, being close to the number of alpha's in the system. Differences between Brink and THSR alpha cluster wave functions are worked out. No cluster model of the Brink type can describe the Hoyle state with a single configuration. On the contrary, many superpositions of the Brink type are necessary, implying delocalisation towards an alpha product state. It is shown that single alpha particle orbits in condensates of different nuclei are almost the same. It is thus argued that alpha particle antisymmetrised product states of the THSR type are a very promising novel and useful concept in nuclear physics.

Stability of 244–260Fm isotopes against alpha and cluster radioactivity

Taking Coulomb and proximity potentials as the interacting barrier we have studied the cold valley in the radioactive decay of 244–260Fm isotopes. It is found that in addition to alpha particle minima, other minima occur at S, Ar and Ca clusters. We have computed the half-lives and other characteristics of different clusters emitted from these parents treating parent, daughter and emitted cluster as spheres. Our study reveals that most of these parents are unstable against alpha and heavy cluster (46Ar, 48,50Ca) emissions and stable against light cluster emission, except 8Be from 244–248Fm isotopes. The most probable clusters from these parents are predicted to be 46Ar, 48,50Ca which indicate the role of doubly or near doubly magic clusters (Z = 20, N = 28) and also stress the role of doubly magic 208Pb daughter. The computed half-lives for alpha decay are in good agreement with the experimental data. It is found that the presence of neutron excess in the parent nuclei slows down the cluster decay process. The effect of quadrupole (β 2) and hexadecapole (β 4) deformations of parent and fragments on half-lives are also studied. It is found that inclusion of β 2 and β 4 reduces the height and shape of the barrier (increases barrier penetrability) and hence the half-life decreases.

THE STUDY OF α + 14C CLUSTER STATES OF 18O THROUGH THE RESONANT BREAKUP REACTION 12C(18O, 14Cα) AT E(18O) = 94.5 MeV

In this work, we study the alpha cluster structure of 18 O using resonant particle spectroscopy technique. Resonance breakup reaction of the projectile is studied experimentally to extract the excitation energy spectrum of the 18 O nucleus. The observed resonant states in the present work are 15.62, 15.82 (5-), 16.02, 16.22, 16.42, 16.92, 17.22, and 17.82 MeV.

Effect of projectile structure in incomplete fusion in 24Mg + 59Co reaction

Cross-sections for projectile-like fragments (PLFs) have been measured in the 24Mg$ + $59Co reaction at E lab = 93 , 100 and 108MeV to investigate the projectile structure effect in incomplete fusion (ICF) reactions. In this study, the cross-sections for ICF channels involving the emission of Ne, O and C were found to be higher than the other ICF channels involving the emission of odd Z PLFs. This observation was attributed to the alpha cluster structure of the 24Mg nucleus. Significant cross-sections for incomplete fusion reactions at these beam energies indicated that the collision trajectories with l < l crit are contributing to ICF.

Tumor Necrosis Factor Gene Variation and the Risk of Mortality After Burn Injury: A Cohort Study

Infection risk and mortality after burn trauma are primarily determined by patient age, burn size and depth, and associated inhalation injury. Whether genetic differences contribute to otherwise unexpected variability in outcomes is unknown. We sought to determine whether there was an association between genetic variation in inflammation-related genes and outcomes after burn trauma. We evaluated patients with burns >or=15% TBSA at a single regional burn center from October 2003 to December 2005. Blood was collected on admission and DNA genotyping was performed. We genotyped single nucleotide polymorphism (SNPs) in toll-like receptor 4 (TLR4) A896G, tumor necrosis factor alpha (TNF-alpha) G-308A, Interleukin-6 (IL-6) G-174C, interleukin-1beta (IL-1beta) T-31C, and cluster of differentiation marker 14 (CD14) C-159T. We compared SNP genotypes between survivors and nonsurvivors by chi analysis and logistic regression. Sixty-nine subjects with a median age of 38 years and mean TBSA of 34% were enrolled. The case fatality was 17%. Septic shock developed in 7 (10%) patients. After adjustment for age, percent full-thickness burns, and inhalation injury, carriage of the TNF-alpha -308 variant allele was associated with increased risk of mortality (OR 10.7, 95% CI = 1.2-95.5, P = .034). None of the other SNPs evaluated were associated with mortality. Mortality after burn trauma is primarily determined by clinical factors, but the TNF-alpha -308 A allele seems to contribute to an increased mortality risk.

ALPHA CLUSTERS IN MEDIUM LIGHT NUCLEI: RECENT RESULTS AND OPEN QUESTIONS

The presence of alpha cluster structures in light nuclei is well established. This paper concentrates on the medium light nuclei between 16 O and 44 Ti . Especially the nucleus 32 S has been examined in detail and new data is presented. The elastic scattering data of alpha particles on 28 Si forming 32 S shows a peculiar disappearance of cross section at 31 MeV excitation energy and above. Also, the energy versus J(J + 1) plot shows at least one clear rotational-like band of alpha cluster states, with the main energy levels split into many narrow and closely lying levels with the same spin. Furthermore, few experiments have been carried out investigating the alpha cluster structure of non-nα nuclei, especially on the proton rich side of stability. The evidence at hand indicates that adding neutrons retains some alpha cluster structures and in some cases might even enhance them, but adding protons seems to destroy the structures.

Alpha decay, cluster decay and spontaneous fission in 294–326122 isotopes

The cluster decay half lives for 294–326122 isotopes are computed for various clusters ranging from an alpha particle to 70Ni within the Coulomb and proximity potential model. The computed alpha decay half lives agree with the values calculated using the Viola–Seaborg–Sobiczewski (VSS) systematic formulas. The half lives for spontaneous fission of these isotopes are carried out using the formula of Ren et al. It is found that the alpha emission is the dominant mode of decay for isotopes with mass number A < 306, and for those with A > 306 spontaneous fission is found to be dominant. The demarcation between alpha decay and spontaneous fission is at 306122, which shows the presence of a spherical neutron shell closure at N = 184.

Down‐regulation of protocadherin‐α A isoforms in mice changes contextual fear conditioning and spatial working memory

Diverse protocadherins (Pcdhs), which are encoded as a large cluster (composed of alpha, beta and gamma clusters) in the genome, are localized to axons and synapses. The Pcdhs have been proposed to contribute to the generation of sophisticated neural networks and to regulate brain function. To address the molecular roles of Pcdhs in regulating individual behavior, here we generated knockdown mice of Pcdh-alpha proteins and examined their behavioral abnormalities. There are two alternative splicing variants of the Pcdh-alpha constant region, Pcdh-alpha A and B isoforms, with different cytoplasmic tails. Pcdh-alpha(DeltaBneo/DeltaBneo) mice, in which the Pcdh-alpha B splicing variant was absent and the Pcdh-alpha A isoforms were down-regulated to approximately 20% of the wild-type level, exhibited enhanced contextual fear conditioning and disparities in an eight-arm radial maze. Similar abnormalities were found in Pcdh-alpha(DeltaAneo/DeltaAneo) mice, which lacked 57 amino acids of the Pcdh-alpha A cytoplasmic tail. These learning abnormalities were, however, not seen in Pcdh-alpha(DeltaB/DeltaB) mice [in which the neomycin-resistance (neo) gene cassette was removed from the Pcdh-alpha(DeltaBneo/DeltaBneo) alleles], in which the expression level of the Pcdh-alpha A isoforms was recovered, although the Pcdh-alpha B isoforms were still completely missing in the brain. In addition, the amount of 5-hydroxytryptamine increased in the hippocampus of the hypomorphic Pcdh-alpha A mutant mice but not in recovery Pcdh-alpha(DeltaB/DeltaB). These results suggested that the level of Pcdh-alpha A isoforms in the brain has an important role in regulating learning and memory functions and the amount of 5-hydroxytryptamine in the hippocampus.

History of cluster structure in nuclei

This contribution focuses on the history of clustering in nuclei. Elementary alpha models treat light 4-n nuclei as systems of alpha-particles obeying Bose Einstein statistics. These models neglect the internal structure of the alphas and effects of the Pauli principle between the nucleons in the alpha clusters are taken into account by introducing a short range repulsion between the clusters. The orthogonality condition model and excluded state model treat the alphas as elementary particles, but include effects of the Pauli principle in a more microscopic way. Wheeler's resonating group method is a fully microscopic theory for calculating properties of cluster systems. It makes simplifying assumptions about the internal structure of the clusters but takes the Pauli principle explicitly. Hartree-Fock theory can be used for a microscopic theory of nuclear structure but it is not suitable for light nuclei because there is no well defined mean field. Margenau's microscopic cluster model avoids this problem by using trial wave functions which are antisymmetrized products of parametrized single particle wave functions.

Long-range regulation of ?? globin gene expression during erythropoiesis

The analysis of globin gene expression during erythropoiesis has established many principles underlying normal mammalian gene expression. New aspects of gene regulation have been revealed by natural mutations that downregulate globin gene expression and cause thalassemia. Deletions involving sequences upstream of the alpha and beta clusters suggested that the globin genes might be controlled by remote regulatory elements. This was demonstrated experimentally and suggested that many mammalian genes may be controlled in a similar manner. Completion of the Human Genome Project and the associated encyclopaedia of DNA elements (ENCODE) project confirmed that human gene expression is commonly controlled by long-range, cis-acting elements. The development of chromatin immunoprecipitation has allowed us to identify binding of transcription factors and chromatin modifications at the key cis-acting sequences in vivo. In addition, chromosome conformation capture has enabled us to address the topological models proposed to mediate long-range interactions. Together, these methods have given us some insight into how long-range elements may influence gene expression and how this process may be subverted in thalassemia. The review asks how remote elements regulate alpha globin expression and how natural mutations interfere with this mechanism to cause alpha thalassemia. We also speculate as to why long-range control of gene expression may have evolved in higher organisms.

Excitation and charged particle decay of the analogs of the dipole resonance in the alpha cluster of 6Li

Intrinsic excitation of α cluster in A = 6 nuclei were searched for by using the 6Li(3He, t) and 6Li(7Li,7Be) charge exchange reactions at the incident energy of 450 and 455 MeV at 0°. Charged particle decay from the dipole resonance at around 25 MeV in 6Be and 6He was measured. The dominant decay channels of the resonance are found to be d+3He+n for 6Be and d+t+p for 6He. The invariant mass spectra for 3He+n and 3H+p show clear enhancement in comparison with phase-space spectra, and suggests that α cluster in 6Be and 6He are excited to 4Li and 4H.

原子核のクラスター構造とα粒子移行反応 : fp殻領域でのα-クラスター構造の観測

原子核のクラスター構造とα粒子移行反応 : fp殻領域でのα-クラスター構造の観測

New candidate for an alpha cluster condensed state in [formula omitted] at 400 MeV

Inelastic α scattering on 16O is studied at 400 MeV using an ice target. Near the 4 α breakup threshold of 14.4 MeV, a broad peak is observed at an excitation energy of 13.6 ± 0.1 MeV with a width of 0.6 ± 0.2 MeV . The spin-parity is estimated to be 0 + from the momentum-transfer dependence. The observed width is significantly larger than that of the 0 + state at 12.0 MeV with the α + C 12 structure, indicating a well-developed α cluster structure. The magnitude of the cross section is sensitive to the density distribution of the constituent α clusters. The observed cross section is consistent with the theoretical prediction for the α cluster condensed state, characterized by its dilute density distribution with a large root-mean-square radius.

Molecular Evidence for the Ancient Origin of the Ribosomal Protection Protein That Mediates Tetracycline Resistance in Bacteria

The ribosomal protection proteins (RPPs) mediate the resistance to tetracycline (TC) in Gram-positive and Gram-negative bacteria. The RPPs display sequence similarity to translation elongation factors, EF-G/EF-2 and EF-Tu/EF-1alpha. To determine the evolutionary origin of the RPPs, we constructed a composite phylogenetic tree of the RPPs, EF-G/EF-2 and EF-Tu/EF-1alpha. This tree includes two universal trees for the EF-G/EF-2 and EF-Tu/EF-1alpha, which form clusters corresponding to the respective two groups of proteins from three superkingdoms. The cluster of RPPs was placed at a point between the EF-G/EF-2 and EF-Tu/EF-1alpha clusters. The branch length (substitutions/site) between the node for the RPP cluster and the primary divergence of the RPPs was statistically shorter than that between the node for this cluster and the primary divergence in the EF-G/EF-2 cluster. This indicates that the RPPs derived through duplication and divergence of the ancient GTPase before the divergence of the three superkingdoms. Furthermore, this suggests the RPPs' extant function occurred before the streptomycetes that include the TC-producing strains. Therefore, the RPPs evolved independent of the presence of TCs and serve a function other than antibiotic resistance. The RPPs may provide ribosomal protection against other chemical substances in the environment.

진 제품 구매자의 추구혜택에 따른 평가기준 및 선호 이미지

The purpose of this study was to find differences in evaluation criteria and to find differences in preferred images based on benefits segmented groups of jeans products consumers. Male and female Korean university students participated in the study. Quota sampling method was used to collect the data based on gender and a residential area of the respondents. Data from 492 questionnaires were used in the analysis. Factor analysis, Cronbach`s alpha coefficient, cluster analysis, one-way ANOVA, and post-hoc test were conducted. As a result, respondents who seek multi-benefits considered aesthetic criteria(e.g., color, style, design, fit) and quality performance criteria(e.g., durability, ease of care, contractibility, flexibility) more importantly when evaluating and purchasing jeans products. Respondents who seek brand name considered extrinsic criteria(e.g., brand reputation, status symbol, country of origin, fashionability) more importantly than respondents who seek economic efciency. Respondents who seek multi-benefits such as attractiveness, fashion, individuality, and utility tend to prefer all the images: individual image, active image, sexual image, sophisticated image, and simple image when wearing jeans products. Respondents who seek fashion are likely to prefer individual image, and respondents who seek brand name more prefer both individual image and polished image. Mean while, respondents who seek economical efficiency less prefer sexual image and polished image.

Toward simpler and faster genome-wide mutagenesis in mice

Here we describe a practical Cre-loxP and piggyBac transposon-based mutagenesis strategy to systematically mutate coding sequences and/or the vast noncoding regions of the mouse genome for large-scale functional genomic analysis. To illustrate this approach, we first created loxP-containing loss-of-function alleles in the protocadherin alpha, beta and gamma gene clusters (Pcdha, Pcdhb and Pcdhg). Using these alleles, we show that, under proper guidance, Cre-loxP site-specific recombination can mediate efficient trans-allelic recombination in vivo, facilitating the generation of large germline deletions and duplications including deletions of Pcdha, and Pcdha to Pcdhb, simply by breeding (that is, at frequencies of 5.5%-21.6%). The same breeding method can also generate designed germline translocations between nonhomologous chromosomes at unexpected frequencies of greater than 1%. By incorporating a piggyBac transposon to insert and to distribute loxP sites randomly throughout the mouse genome, we present a simple but comprehensive method for generating genome-wide deletions and duplications, in addition to insertional loss-of-function and conditional rescue alleles, again simply by breeding.

Cluster Structures in Oxygen Isotopes

Cluster structure of 16O,18O and 20O is investigated by the antisymmettrized molecular dynamics (AMD) plus generator coordinate method (GCM). We have found the K^{\pi}=0$_2^+$ and 0$_1^-$ rotational bands of 18O that have the prominent 14C+\alpha cluster structure. Clustering systematics becomes richer in 20O. We suggest the K^{\pi}=0$_2^+$ band that is the mixture of the 12C+\alpha+4n and 14C+6He cluster structures, and the K^{\pi}=0$_1^-$ band that has the 14C+6He cluster structure. The K^{\pi}=0$_3^+$ and 0$_2^-$ bands that have the prominent 16C+\alpha cluster structure are also found.

Intranuclear mobility of estrogen receptor α and progesterone receptors in association with nuclear matrix dynamics

We analyzed the intranuclear dynamics of estrogen receptor alpha (ER alpha) and progesterone receptor (PR)-A/B labeled with different spectral variants of green fluorescent protein (GFP) in living cells. The distribution of ER alpha and PR-A/B were changed from a diffuse to discrete pattern after the addition of both ligands, but the extent of discrete cluster formation of PR-A/B was lower than that of ER alpha. The nuclear areas where PR-A/B were accumulated were colocalized with the cluster of ER alpha, suggesting that cross-talk in the transcriptional regulation occurred in the loci. Fluorescence recovery after photobleaching (FRAP) analysis revealed that the mobility of PR-A/B was hastened by the coexistence of ER alpha, while the mobility of ER alpha was not changed by the coexistence of PR-A/B. Cluster formation was correlated with the nuclear matrix binding, because nuclear matrix binding capacity was also lower in PR-A/B than ER alpha. By ATP-depletion from the cells, most of ER alpha and PR-A/B were bound to the nuclear matrix and their mobilities were extinguished both in the absence and presence of ligand. Fluorescent protein (FP) tagged nuclear matrix component protein (NuMA), which was colocalized with ER alpha and PR-A/B, showed ATP-dependent rapid exchange in the nucleus. These results indicate that the mobility of ER alpha and PR-A/B is associated with the dynamics of the nuclear matrix.