From an insulating to a superfluid pair-bond liquid

We study an exchange coupled system of itinerant electrons and localized fermion pairs resulting in a resonant pairing formation. This system inherently contains resonating fermion pairs on bonds which lead to a superconducting phase provided that long range phase coherence between their constituents can be established. The prerequisite is that the resonating fermion pairs can become itinerant. This is rendered possible through the emergence of two kinds of bond-fermions: individual and composite fermions made of one individual electron attached to a bound pair on a bond. If the strength of the exchange coupling exceeds a certain value, the superconducting ground state undergoes a quantum phase transition into an insulating pair-bond liquid state. The gap of the superfluid phase thereby goes over continuously into a charge gap of the insulator. The change-over from the superconducting to the insulating phase is accompanied by a corresponding qualitative modification of the dispersion of the two kinds of fermionic excitations. Using a bond operator formalism, we derive the phase diagram of such a scenario together with the elementary excitations characterizing the various phases as a function of the exchange coupling and the temperature.Comment: 10 pages, 5 figure

Microscopic thickness determination of thin graphite films formed on SiC from quantized oscillation in reflectivity of low-energy electrons

Low-energy electron microscopy (LEEM) was used to measure the reflectivity of low-energy electrons from graphitized SiC(0001). The reflectivity shows distinct quantized oscillations as a function of the electron energy and graphite thickness. Conduction bands in thin graphite films form discrete energy levels whose wave vectors are normal to the surface. Resonance of the incident electrons with these quantized conduction band states enhances electrons to transmit through the film into the SiC substrate, resulting in dips in the reflectivity. The dip positions are well explained using tight-binding and first-principles calculations. The graphite thickness distribution can be determined microscopically from LEEM reflectivity measurements.Comment: 7 pages, 3 figure

Oscillating Superfluidity of Bosons in Optical Lattices

We follow up on a recent suggestion by C. Orzel et. al., Science, 291, 2386 (2001), whereby bosons in an optical lattice would be subjected to a sudden parameter change from the Mott to the superfluid phase. We analyze the Bose Hubbard model with a modified coherent states path integral which can escribe - both - phases. The saddle point theory yields collective oscillations of the uniform superfluid order parameter. These would be seen in time resolved interference patterns made by the released gas. We calculate the collective oscillation's damping rate by phason pair emission. In two dimensions the overdamped region largely overlaps with the quantum critical region. Measurements of critical dynamics on the Mott side are proposed.Comment: 4 pages 1 eps figures; Final version as appears in PRL. Added discussion on spontaneous generation of vortice

Native title and Indigenous Australian utilisation of wildlife: Policy perspectives

The Native Title Act 1993 specifically recognises Indigenous property rights in Indigenous species; if there is one legislative event that could alter Indigenous utilisation of wildlife in the future it is provisions in this statute. This legal framework means that Indigenous people may in the future hold property or resource rights not just over currently vacant Crown land, but also in national parks or pastoral leasehold land. Some threshold legal issues, currently before the Federal Court, will clarify the significance of native title for Indigenous utilisation of wildlife. In this paper the use of wildlife by Indigenous Australians is assessed from an economic perspective using a standard production function framework in which output is determined by the variable combination of three input factors - land, labour and capital. The assessment shows that wildlife use for subsistence purposes is clearly of economic importance. Although inequalities exist in relation to the allocation of land between States, under the Native Title Act 1993 and the operations of the Indigenous Land Corporation it is possible there will be a significant increase in the amount of land owned or available for use by Indigenous people. This may not only increase access to wildlife resources and provide opportunities for Indigenous people to add to their incomes, but also add to the growing recognition of their ability and right to participate in environmental management. However, Indigenous people will need continuing access to cash to underwrite a subsistence lifestyle. Informed debate is needed to decide whether Indigenous use of wildlife is an economic option worth supporting and what benefits and costs might accrue from such facilitation both for Indigenous people and the wider Australian community

Indigenous participation in commercial fisheries in Torres Strait: A preliminary discussion

The Torres Strait Treaty between Australia and Papua New Guinea, ratified in 1985, recognised customary, and limited commercial, Indigenous rights in marine resources in Torres Strait. Since the High Court's Mabo vs Queensland decision in June 1992, and the establishment of the Torres Strait Regional Authority (TSRA), effectively from July 1994, the issue of rights in marine resources has become central to the development of a sustainable regional economic base for Indigenous people in Torres Strait. This paper describes the regulatory framework for managing marine resources in Torres Strait, the current value of the commercial fishing sector, and the potential for expansion of the industry. Attention is then focused on current Islander participation in the industry, and especially on barriers and incentives affecting participation. Options for creating well-defined Islander property rights in commercial fisheries are examined, and the policy implications of these options are discussed. Finally, the importance of further research is put in the context of the TSRA's responsibility for a Torres Strait Development Plan and the goals of increased Indigenous participation in commercial fisheries and greater economic self-sufficiency for the region

Exchange bias and interface electronic structure in Ni/Co3O4(011)

A detailed study of the exchange bias effect and the interfacial electronic structure in Ni/Co3O4(011) is reported. Large exchange anisotropies are observed at low temperatures, and the exchange bias effect persists to temperatures well above the Neel temperature of bulk Co3O4, of about 40 K: to ~80 K for Ni films deposited on well ordered oxide surfaces, and ~150 K for Ni films deposited on rougher Co3O4 surfaces. Photoelectron spectroscopy measurements as a function of Ni thickness show that Co reduction and Ni oxidation occur over an extended interfacial region. We conclude that the exchange bias observed in Ni/Co3O4, and in similar ferromagnetic metallic/Co3O4 systems, is not intrinsic to Co3O4 but rather due to the formation of CoO at the interface.Comment: 8 pages, 6 figures. Accepted for publication in Physical Review B

In the Era of Systematic Reviews, Does the Size of an Individual Trial Still Matter?

Background to the debate: Systematic reviews that combine high-quality evidence from several trials are now widely considered to be at the top of the hierarchy of clinical evidence. Given the primacy of systematic reviews—and the fact that individual clinical trials rarely provide definitive answers to a clinical research question—some commentators question whether the sample size calculation for an individual trial still matters. Others point out that small trials can still be potentially misleading

Safety of the Deferral of Coronary Revascularization on the Basis of Instantaneous Wave-Free Ratio and Fractional Flow Reserve Measurements in Stable Coronary Artery Disease and Acute Coronary Syndromes.

OBJECTIVES: The aim of this study was to investigate the clinical outcomes of patients deferred from coronary revascularization on the basis of instantaneous wave-free ratio (iFR) or fractional flow reserve (FFR) measurements in stable angina pectoris (SAP) and acute coronary syndromes (ACS). BACKGROUND: Assessment of coronary stenosis severity with pressure guidewires is recommended to determine the need for myocardial revascularization. METHODS: The safety of deferral of coronary revascularization in the pooled per-protocol population (n = 4,486) of the DEFINE-FLAIR (Functional Lesion Assessment of Intermediate Stenosis to Guide Revascularisation) and iFR-SWEDEHEART (Instantaneous Wave-Free Ratio Versus Fractional Flow Reserve in Patients With Stable Angina Pectoris or Acute Coronary Syndrome) randomized clinical trials was investigated. Patients were stratified according to revascularization decision making on the basis of iFR or FFR and to clinical presentation (SAP or ACS). The primary endpoint was major adverse cardiac events (MACE), defined as the composite of all-cause death, nonfatal myocardial infarction, or unplanned revascularization at 1 year. RESULTS: Coronary revascularization was deferred in 2,130 patients. Deferral was performed in 1,117 patients (50%) in the iFR group and 1,013 patients (45%) in the FFR group (p < 0.01). At 1 year, the MACE rate in the deferred population was similar between the iFR and FFR groups (4.12% vs. 4.05%; fully adjusted hazard ratio: 1.13; 95% confidence interval: 0.72 to 1.79; p = 0.60). A clinical presentation with ACS was associated with a higher MACE rate compared with SAP in deferred patients (5.91% vs. 3.64% in ACS and SAP, respectively; fully adjusted hazard ratio: 0.61 in favor of SAP; 95% confidence interval: 0.38 to 0.99; p = 0.04). CONCLUSIONS: Overall, deferral of revascularization is equally safe with both iFR and FFR, with a low MACE rate of about 4%. Lesions were more frequently deferred when iFR was used to assess physiological significance. In deferred patients presenting with ACS, the event rate was significantly increased compared with SAP at 1 year.info:eu-repo/semantics/publishedVersio

Dynamical properties of ultracold bosons in an optical lattice

We study the excitation spectrum of strongly correlated lattice bosons for the Mott-insulating phase and for the superfluid phase close to localization. Within a Schwinger-boson mean-field approach we find two gapped modes in the Mott insulator and the combination of a sound mode (Goldstone) and a gapped (Higgs) mode in the superfluid. To make our findings comparable with experimental results, we calculate the dynamic structure factor as well as the linear response to the optical lattice modulation introduced by Stoeferle et al. [Phys. Rev. Lett. 92, 130403 (2004)]. We find that the puzzling finite frequency absorption observed in the superfluid phase could be explained via the excitation of the gapped (Higgs) mode. We check the consistency of our results with an adapted f-sum-rule and propose an extension of the experimental technique by Stoeferle et al. to further verify our findings.Comment: 13 pages, 5 figure