This contribution will focus on some of the advances that have been made since the last Cluster Conference in Debrecen, Hungary, and the challenges that remain for the subject before the next ...conference in Brazil. It addresses the question of cluster structure above and below the cluster decay threshold, dynamical symmetries, molecular structures and clustering at the neutron drip-line.
The relationship between the deformed harmonic oscillator and the formation of molecular cluster structures, whereby valence neutrons are exchanged between cluster cores, is examined. It is found ...that there is a strong connection between the properties of the valence orbitals associated with deformed structures in the deformed harmonic oscillator and the molecular orbitals created by linear combinations of single-centre orbitals around nuclear clusters. The conclusion is that in addition to the appearance of clustering in the deformed harmonic oscillator that every prolate deformed cluster structure should have molecular orbitals built on that structure. This is demonstrated through a series of examples that range from 13C to 57Ni.
After long-time exposure, protein adsorption at fluid/fluid interfaces is documented to produce interfacial, gellike networks. Formation of this network apparently results from adsorption-induced ...conformational changes and subsequent interprotein aggregation at the interface. We utilize interfacial shear and dilatational rheology to probe the structure of a globular protein, lysozyme, and a disordered protein, β-casein, and the kinetics of network formation at the hexadecane/water interface. For the first time, we present a detailed comparison of the interfacial shear and dilatational responses. For lysozyme, the shear moduli grow with interface age indicating a transition from fluidlike behavior at early times to network formation (solidlike behavior). Conversely, the interfacial shear moduli of β-casein change very little with interface age; in addition, both G ‘ and G ‘ ‘ for β-casein are an order of magnitude smaller than those of lysozyme. The strong protein intramolecular interactions that stabilize the native conformation of lysozyme act as kinetic barriers to conformational change and later become strong intermolecular interactions upon partial unfolding at the interface. Hence, interprotein linkages form (i.e., aggregation into an interfacial gel), resulting in the growth of G ‘ with time. We find that the interfacial dilatational storage modulus, E ‘, is comprised of a static response and a dynamic response. The static response corresponds to a change in the surface pressure upon interfacial-area change and is strain-rate independent. The dynamic contribution corresponds to rearrangement and reconfiguration of the protein molecules within the interface and is analogous to the shear storage response (i.e., a measure of the strength of interprotein linkages). The magnitudes of E ‘ and G ‘ for lysozyme and β-casein suggest that lysozyme initially adsorbs in a state similar to its native conformation. The native rigidity of the protein is linked to its kinetic stability at the interface. Globular lysozyme, once adsorbed, resists compression giving a high dilatational storage modulus. Contrastingly, native β-casein lacks tertiary structure, resulting in a small interfacial dilatational storage modulus relative to lysozyme. With increasing interface age, the static modulus of β-casein changes insignificantly, whereas it decreases substantially for lysozyme, indicating partial unfolding and loss of intrinsic rigidity. Upon unfolding, interprotein linkages form through hydrophobic peptide−peptide interactions. Correspondingly, G ‘ and the recoverable dilatational storage modulus, δE ‘, grow, signifying the onset of interfacial gelation.
This contribution reviews some of the challenges that nuclear cluster science has taken on focussing on those surrounding nuclear molecules for example in 24Mg. A view is taken that the most exciting ...challenges link to the structure of light nuclei, where they may be used to inform ab inito theories which attempt to utilise realistic nuclear forces. In some cases the limit of these theories is the nucleus 12C. The experimental progress in understanding this crucial nucleus is examined.
Proteins adsorbed at fluid/fluid interfaces influence many phenomena: food emulsion and foam stability (Murray et al. Langmuir 2002, 18, 9476 and Borbas et al. Colloids Surf., A 2003, 213, 93), ...two-phase enzyme catalysis (Cascao-Pereira et al. Biotechnol. Bioeng. 2003, 83, 498; 2002, 78, 595), human lung function (Lunkenheimer et al. Colloids Surf., A 1996, 114, 199; Wustneck et al.; and Banerjee et al. 2000, 15, 14), and cell membrane mechanical properties (Mohandas et al. 1994, 23, 787). Time scales important to these phenomena are broad, necessitating an understanding of the dynamics of biological macromolecules at interfaces. We utilize interfacial shear and dilatational deformations to study the rheology of a globular protein, lysozyme, and a disordered protein, β-casein, at the hexadecane/water interface. Linear viscoelastic properties are measured using small amplitude oscillatory flow, stress relaxation after a sudden dilatational displacement, and shear creep response to probe the rheological response over broad experimental time scales. Our studies of lysozyme and β-casein reveal that the interfacial dissipation mechanisms are strongly coupled to changes in the protein structure upon and after adsorption. For β-casein, the interfacial response is fluidlike in shear deformation and is dominated by interfacial viscous dissipation, particularly at low frequencies. Conversely, the dilatational response of β-casein is dominated by diffusion dissipation at low frequencies and viscous dissipation at higher frequencies (i.e., when the experimental time scale is faster than the characteristic time for diffusion). For lysozyme in shear deformation, the adsorbed protein layer is primarily elastic with only a weak frequency dependence. Similarly, the interfacial dilatational moduli change very little with frequency. In comparison to β-casein, the frequency response of lysozyme does not change substantially after washing the protein from the bulk solution. Apparently, it is the irreversibly adsorbed fraction that dominates the dynamic rheological response for lysozyme. Using stress relaxation after a sudden dilatational displacement and shear creep response, the characteristic time of relaxation was found to be 1000 s in both modes of deformation. The very long relaxation time for lysozyme likely results from the formation of a glassy interfacial network. This network develops at high interfacial concentrations where the molecules are highly constrained because of conformation changes that prevent desorption.
Knowledge of the low-lying monopole strength in C12—the Hoyle state in particular—is crucial for our understanding of both the astrophysically important 3α reaction and of α-particle clustering. ...Multiple theoretical models have predicted a breathing mode of the Hoyle State at Ex≈9 MeV, corresponding to a radial in-phase oscillation of the underlying α clusters. The C12(α,α′)C12 and C14(p,t)C12 reactions were employed to populate states in 12C in order to search for this predicted breathing mode. A self-consistent, simultaneous analysis of the inclusive spectra with R-matrix lineshapes, together with angular distributions of charged-particle decay, yielded clear evidence for excess monopole strength at Ex≈9 MeV which is highly collective. Reproduction of the experimentally observed inclusive yields using a fit, with consistent population ratios for the various broad states, required an additional source of monopole strength. The interpretation of this additional monopole resonance as the breathing-mode excitation of the Hoyle state would provide evidence supporting a D3h symmetry for the Hoyle state itself. The excess monopole strength may complicate analysis of the properties of the Hoyle state, modifying the temperature dependence of the 3α rate at T9≳2 and ultimately, the predicted nucleosynthesis in explosive stars.
Abstract
Investigations of neutron-rich nuclei, particularly those that lie in regions of the nuclear chart known for a high probability of isomeric states forming, are of vital importance to the ...understanding of nuclear astrophysical processes. Studies of these nuclei, such as
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Re, can be used to validate and improve theoretical models of such processes. A polarised-beam experiment has been performed using the Munich Q3D magnetic spectrograph in order to investigate the energy-level structure of
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Re. An excitation-energy spectrum has been produced, allowing for energies to be assigned to observed states. Through comparison between measured and calculated differential cross-sections and vector analysing powers, the process of assigning spin and parity to newly observed states, and confirming the assignments for previously observed states, is underway.
Improvements in Radio-Isotope IDentification (RIID) algorithms have always been a continuous research focus. However, significant developments in machine learning have recently sparked renewed ...interest. To provide a rapid development environment for this, a generalised gamma simulator has been built using the GEANT4 toolkit. This enables consideration of a diverse range of radiation sources and shielding scenarios. The simulator currently provides training data for the development of neural network based RIID models.
Single-crystal nanowire transistors and other nanowire-based devices could have applications in large-area and flexible electronics if conventional top-down fabrication techniques can be integrated ...with high-precision bottom-up nanowire assembly. Here, we extend dielectrophoretic nanowire assembly to achieve a 98.5% yield of single nanowires assembled over 16,000 patterned electrode sites with submicrometre alignment precision. The balancing of surface, hydrodynamic and dielectrophoretic forces makes the self-assembly process controllable, and a hydrodynamic force component makes it self-limiting. Our approach represents a methodology to quantify nanowire assembly, and makes single nanowire assembly possible over an area limited only by the ability to reproduce process conditions uniformly.
Abstract Objectives In the present study we explore the effects of androgens and anti-androgens on primary cultures of EOC cells. We also investigate the effects of chemotherapy on AR expression. ...Epithelial ovarian cancer (EOC) arises from ovarian surface epithelial cells (OSE), which express the androgen receptor (AR). Androgen stimulation of OSE cells results in increased proliferation and protection from apoptosis. Nevertheless, in clinical trials anti-androgens have had a low objective response rate in relapsed ovarian cancer. Methods 1. Androgen receptor (AR) expression and response to androgenic stimulation were correlated in primary ovarian cancer cells derived from ascitic fluid from patients with advanced ovarian cancer, 2. AR expression in primary epithelial ovarian cancer was investigated before and after chemotherapy using paired histological samples which had been incorporated into a tissue microarray. Results Eleven primary ovarian cancer cultures were established from ascitic fluid. There was wide variation of expression of androgen receptor mRNA between cultures. Cell division increased after dihydro-testosterone (DHT) stimulation in 6 out of 11 primary cultures. The fraction of cells in S-phase increased from 4.4% in cells grown in serum-free medium to 8.3% in cells stimulated with 100 nM of DHT (P < 0.001). The increase in S-phase fraction was abrogated after treatment with the anti-androgen, bicalutamide in 4 out of 5 responsive cultures. There was a strong correlation (r2 = 0.7) between nuclear AR expression by immunohistochemistry and S-phase fraction changes in primary cultures. Paired pre- and post-chemotherapy histological samples from 29 patients were incorporated into a tissue microarray (TMA). Nuclear and cytoplasmic AR expression by immunohistochemistry (IHC) decreased significantly after chemotherapy (P < 0.01). Conclusion AR expression correlates with increased S-phase fraction in response to androgenic stimulation. Immunohistochemical analysis of AR expression needs to be further tested in clinical trials to select AR positive EOC for anti-androgen therapy. Anti-androgen use early in the course of ovarian cancer is more likely to be effective as these data suggest that androgen receptor expression decreases with exposure to chemotherapy and this may explain the low response rates seen in clinical trials of patients heavily pre-treated with multiple courses of chemotherapy.
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