Coherent and Incoherent Dynamic Structure Function of the Free Fermi Gas

A detailed calculation of the coherent and incoherent dynamic structure functions of the free Fermi gas, starting from their expressions in terms of the one- and semi-diagonal two-body density matrices, is derived and discussed. Their behavior and evolution with the momentum transfer is analyzed, and particular attention is devoted to the contributions that both functions present at negative energies. Finally, an analysis of the energy weighted sum rules satisfied by both responses is also performed. Despite of the simplicity of the model, some of the conclusions can be extended to realistic systems.Comment: LaTeX, 3 figure

Intrinsic Mean Square Displacements in Proteins

The thermal mean square displacement (MSD) of hydrogen in proteins and its associated hydration water is measured by neutron scattering experiments and used an indicator of protein function. The observed MSD as currently determined depends on the energy resolution width of the neutron scattering instrument employed. We propose a method for obtaining the intrinsic MSD of H in the proteins, one that is independent of the instrument resolution width. The intrinsic MSD is defined as the infinite time value of that appears in the Debye-Waller factor. The method consists of fitting a model to the resolution broadened elastic incoherent structure factor or to the resolution dependent MSD. The model contains the intrinsic MSD, the instrument resolution width and a rate constant characterizing the motions of H in the protein. The method is illustrated by obtaining the intrinsic MSD of heparan sulphate (HS-0.4), Ribonuclease A and Staphysloccal Nuclase (SNase) from data in the literature

Excitations of amorphous solid helium

We present neutron scattering measurements of the dynamic structure factor, $S(Q,\omega)$, of amorphous solid helium confined in 47 $\AA$ pore diameter MCM-41 at pressure 48.6 bar. At low temperature, $T$ = 0.05 K, we observe $S(Q,\omega)$ of the confined quantum amorphous solid plus the bulk polycrystalline solid between the MCM-41 powder grains. No liquid-like phonon-roton modes, other sharply defined modes at low energy ($\omega<$ 1.0 meV) or modes unique to a quantum amorphous solid that might suggest superflow are observed. Rather the $S(Q,\omega)$ of confined amorphous and bulk polycrystalline solid appear to be very similar. At higher temperature ($T>$ 1 K), the amorphous solid in the MCM-41 pores melts to a liquid which has a broad $S(Q,\omega)$ peaked near $\omega \simeq$ 0 characteristic of normal liquid $^4$He under pressure. Expressions for the $S(Q,\omega)$ of amorphous and polycrystalline solid helium are presented and compared. In previous measurements of liquid $^4$He confined in MCM-41 at lower pressure the intensity in the liquid roton mode decreases with increasing pressure until the roton vanishes at the solidification pressure (38 bars), consistent with no roton in the solid observed here

Some phases of narrative art

Submitted in partial fulfillment of the requirements for the degree of Master of ArtsText from page 76: "The progress of narrative art, especially in its relation to naturalism, has been traced. Though it cannot be maintained that narrative art is characteristic cf naturalistic periods, it has been shown that naturalism is favorable to the development of such a style. The scarcity of narration in the present period of naturalistic tendenocies is due, probably, to two reasons: the presence of interests other than the human element, which must dominate narrative art, and the symbolical and allegorical treatment of the human element when it is retained by the modern artist."Includes bibliographical references (pages 78-82

Condensate fraction in liquid 4He at zero temperature

We present results of the one-body density matrix (OBDM) and the condensate fraction n_0 of liquid 4He calculated at zero temperature by means of the Path Integral Ground State Monte Carlo method. This technique allows to generate a highly accurate approximation for the ground state wave function Psi_0 in a totally model-independent way, that depends only on the Hamiltonian of the system and on the symmetry properties of Psi_0. With this unbiased estimation of the OBDM, we obtain precise results for the condensate fraction n_0 and the kinetic energy K of the system. The dependence of n_0 with the pressure shows an excellent agreement of our results with recent experimental measurements. Above the melting pressure, overpressurized liquid 4He shows a small condensate fraction that has dropped to 0.8% at the highest pressure of p = 87 bar.Comment: 12 pages. 4 figures. Accepted for publication on "Journal of Low Temperature Physics

From Research to Practice Change–Achieving Adoption through Regionally Packaged Technology and Farm Systems

The rate and extent of adoption of grazing systems technology is limited by the relevance of recommendations and the complexity of integrating new practices into farming systems. This paper describes how, through development of regional information packages, a national project is enhancing adoption of the outputs from research investment. Every farm has unique goals, soils, landscape, enterprise setup and existing practices. When making investment decisions, farmers consider the cost and potential impact of each option compared to other competing options, the fit into their existing management philosophy and other changes necessary to realise the potential benefit. Overlaying this, farmers consider whether the innovation applies to their region, and commonly cite lack of regional applicability as a reason not to adopt. We argue that development of regional packages is a powerful means of targeting the needs unique to each region. Such packages can include recommendations from whole-farm system experiments, modelling and case studies which tell the full story around profit, risk, natural resource management and lifestyle impacts of change options, and adviser training for supporting farmer adoption decision processes. By focusing on communicating how research outputs are relevant to local farming systems, utilising local input, regional packages have the capacity to change the way R,D & E is conducted and delivered, accelerating delivery of industry and environmental benefits