Antipersistant Effects in the Dynamics of a Competing Population

We consider a population of agents competing for finite resources using strategies based on two channels of signals. The model is applicable to financial markets, ecosystems and computer networks. We find that the dynamics of the system is determined by the correlation between the two channels. In particular, occasional mismatches of the signals induce a series of transitions among numerous attractors. Surprisingly, in contrast to the effects of noises on dynamical systems normally resulting in a large number of attractors, the number of attractors due to the mismatched signals remains finite. Both simulations and analyses show that this can be explained by the antipersistent nature of the dynamics. Antipersistence refers to the response of the system to a given signal being opposite to that of the signal's previous occurrence, and is a consequence of the competition of the agents to make minority decisions. Thus, it is essential for stabilizing the dynamical systems.Comment: 4 pages, 6 figure

Yellow and green luminescence in a freestanding GaN template

We have studied a broad photoluminescence band in high-mobility freestanding 200-μm-thick GaN template prepared by hydride vapor-phase epitaxy. Variable-excitation intensity and energy experiments showed two defect-related bands: a yellow luminescence (YL) band at about 2.15 eV and a green luminescence (GL) band at about 2.43 eV. In contrast to epitaxial GaN samples prepared by both vapor-phase and molecular-beam epitaxy, the YL in the sample studied is weak and can be easily saturated. However, the GL is dominant. We attribute the GL to isolated defects involving galliumvacancies and the YL to the same defect, but bound to dislocations, or possibly to structuralsurface defects

Two charge states of dominant acceptor in unintentionally doped GaN: Evidence from photoluminescence study

Photoluminescence of the dominant deep-level acceptor in high-purity freestanding GaN is studied over a wide range of excitation intensities. A yellow luminescence (YL) band at about 2.2 eV saturates with increasing excitation intensity, whereas a green luminescence (GL) band at about 2.5 eV increases as a square of the excitation intensity. The YL and GL bands are attributed to two charge states of the same defect, presumably a gallium vacancy-oxygen complex

Transient photoluminescence of defect transitions in freestanding GaN

Deep level defects responsible for the 2.4 eV photoluminescence (PL) band in a freestanding GaN template were studied by transient photoluminescence. A nonexponential decay of PL intensity observed at low temperature is attributed to a donor–acceptor pair recombination involving a shallow donor and a deep acceptor. At room temperature, a single-exponential PL decay with a lifetime of 30 μs was observed at the high-energy side of the band, whereas the second component with a lifetime of about 750 μs was detected at the low-energy side of the band. The PL decay and transformation of the PL spectrum at room temperature can be explained by transitions from the conduction band to two deep acceptors. Electron-capture cross section has been estimated as 4×10−21 and 10−19 cm2 for the yellow and green bands, respectively, contributing to the broad 2.4 eV band

Mixing of scalar glueballs and flavour-singlet scalar mesons

We discuss in detail the extraction of hadronic mixing strengths from lattice studies. We apply this to the mixing of a scalar glueball and a scalar meson in the quenched approximation. We also measure correlations appropriate for flavour-singlet scalar mesons using dynamical quark configurations from UKQCD. This enables us to compare the results from the quenched study of the mixing with the direct determination of the mixed spectrum. Improved methods of evaluating the disconnected quark diagrams are also presented.Comment: 23 pages, 5 postscript figure

The flavour singlet mesons in QCD

We study the flavour singlet mesons from first principles using lattice QCD. We explore the splitting between flavour singlet and non-singlet for vector and axial mesons as well as the more commonly studied cases of the scalar and pseudoscalar mesons.Comment: 12 pages, LATEX, 4 ps figure

Long-lasting photoluminescence in freestanding GaN templates

We studied time-resolvedphotoluminescence(PL) over a temporal range 10−6–103 s in high-purity freestanding GaN templates. Red, yellow, green, blue, and shallow donor–acceptor emission bands can be resolved in the PLspectrum. Observation of luminescence long after the excitation is switched off is a striking feature of our study. The persistent PL observed for all above bands, except for the green band, is primarily attributed to the donor–acceptor-pair-type recombination. An unusually slow, nonexponential decay of radiative transitions from the conduction band to the shallow acceptor was also observed, pointing to some additional mechanism for the persistent PL. Possible role of the surface states in this effect is discussed

Patient-reported reasons for declining or discontinuing statin therapy: Insights from the PALM registry

Background: Many adults eligible for statin therapy for cardiovascular disease prevention are untreated. Our objective was to investigate patient‐reported reasons for statin underutilization, including noninitiation, refusal, and discontinuation.Methods and Results: This study included the 5693 adults recommended for statin therapy in the PALM (Patient and Provider Assessment of Lipid Management) registry. Patient surveys evaluated statin experience, reasons for declining or discontinuing statins, and beliefs about statins and cardiovascular disease risk. Overall, 1511 of 5693 adults (26.5%) were not on treatment. Of those not on a statin, 894 (59.2%) reported never being offered a statin, 153 (10.1%) declined a statin, and 464 (30.7%) had discontinued therapy. Women (relative risk: 1.22), black adults (relative risk: 1.48), and those without insurance (relative risk: 1.38) were most likely to report never being offered a statin. Fear of side effects and perceived side effects were the most common reasons cited for declining or discontinuing a statin. Compared with statin users, those who declined or discontinued statins were less likely to believe statins are safe (70.4% of current users vs. 36.9% of those who declined and 37.4% of those who discontinued) or effective (86.3%, 67.4%, and 69.1%, respectively). Willingness to take a statin was high; 67.7% of those never offered and 59.7% of patients who discontinued a statin would consider initiating or retrying a statin.Conclusions: More than half of patients eligible for statin therapy but not on treatment reported never being offered one by their doctor. Concern about side effects was the leading reason for statin refusal or discontinuation. Many patients were willing to reconsider statin therapy if offered

Overview of field operations during a 2013 research expedition to the southern Beaufort Sea on the RV Araon

Research experiments conducted and preliminary findings The Expedition ARA04C is a multidisciplinary research program in the Beaufort Sea, carried out in collaboration between the Korea Polar Research Institute (KOPRI), Geological Survey of Canada (GSC), Department of Fisheries and Ocean (DFO), Monterey Bay Aquarium Research Institute (MBARI), and the Alfred Wegener Institute (AWI). The Expedition ARA04C on the IBRV Araon took place from September 6 to September 24, 2013 (Figure 0.1). Multiple research experiments were undertaken to study geological processes related to degrading permafrost, fluid flow and degassing, and associated geohazards, paleo-oceanography of the Beaufort shelf and slope region, as well as physical and chemical oceanography measurement of the Arctic Ocean linked with continuous atmospheric studies. The expedition focused on two main research areas: offshore Barrow, Alaska, from September 7 to September 9, 2013, and the Canadian Beaufort Sea from September 10 to September 24, 2013. Multichannel seismic data, in conjunction with an ocean-bottom-seismometer (OBS) study were collected to support drilling proposals especially IODP pre-proposal #806 (Dallimore et al., 2012), and to verify distribution and internal structures of the offshore permafrost occurrences (Figure 0.2). The multi-channel seismic data were acquired on the outer continental shelf of the Canadian Beaufort Sea, totaling 14 lines with ~435 line-kilometers and ~4,500 shot gathers (Chapter 3). The combined multichannel seismic and OBS data will be processed post-expedition at KOPRI and the GSC, and will allow detailed velocity analyses to investigate the permafrost signature and help mapping zones of high-velocity sediments indicative of the presence of ice (Chapter 4). Individual shot gathers collected during the multichannel seismic program show clear refraction arrivals with velocities around 2000m/s in areas of expected permafrost occurrence, and shot gathers lacked such arrivals in zones where the permafrost was predicted to be absent. It is therefore expected that the OBS data, once processed, will also show clear refracted arrivals for velocity analyses. Continuous sub-bottom profiler (SBP) and multibeam data were collected along all ship tracks for detailed subsurface imaging of sediment structures and permafrost, as well as for core-site location verification (Chapter 5 and 6). During Expedition ARA04C, more than 3000 line-kilometers of SBP data were collected, co-located with multibeam and backscatter data. These data are an essential part of the study of sub-seafloor permafrost distribution and provide insights into sediment dynamics at critical boundaries, such as the shelf edge. Along the shelf edge, the occurrence of pingo-like features (PLFs) result in a rugged landscape with thousands of PLFs piercing through the otherwise laminated sediments. More than 30 crossings of this critical shelf-edge boundary were made during this expedition, which complement data acquired in 2012 with the Huntec system and 3.5 kHz data provided by ArcticNet as part of the regional multibeam map of the study area. High resolution data provided critical new insights in deep-water fluid expulsion zones. Key new data were acquired over the area of the "Gary Knolls", where PLF structures occur at the shelf edge in water depth of only 50 to 60 m. All SBP data from this expedition will be post-processed and analyzed for the presence of sub-seafloor permafrost, occurrence of the PLF structures and indications for fluid and gas migration. Multibeam and backscatter data were collected along all ship tracks, adding to the database of existing information gathered through previous expeditions to the study region. Heat flow measurements were undertaken at eight stations (Figure 0.3) to study the thermal structure of fluid expulsion features, as well as degrading permafrost along a slope-shelf transect in the eastern Mackenzie Trough (Chapter 7). The data provide critical constraints on the distribution of sub-seafloor permafrost as well as the gas hydrate stability zone around fluid expulsion features. A very important finding is the observation made at the mud volcano in 420 m water depth, where seafloor temperatures are the highest in all observed stations, indicating active mud volcanism. Geological sampling using gravity coring and multi-coring tools was performed at strategic sites to support two research objectives. The first objective was to provide key data towards ongoing international research linked to IODP pre-proposals #753 (O'Regan et al., 2010) and #806 (Dallimore et al., 2012). The second objective was to collect core to define key seismo-stratigraphic horizons critical to the understanding of geohazards in the region (Chapter 8). In total, 21 gravity cores and 12 multi-cores were taken (Figure 0.4, Table 8.3). All cores were scanned with a multi-sensor core-logger to measure physical properties (Chapter 9). Most sediment analyses on the cores will be performed post-expedition at KOPRI, GSC, and laboratories of other University-based collaborators in Canada and Germany. Onboard, sub-samples were taken from all shallow multi-cores and selected gravity cores. On selected cores from the Canadian Beaufort study region pore-waters were extracted using rhizones. These samples will be analyzed postexpedition at MBARI. Water sampling and Conductivity-Temperature-Depth (CTD) profiling was undertaken at most core sites to study physical and chemical properties of the seawater (Figure 0.5). These station-measurements were complemented by continuous waterproperty and atmospheric measurements when the Araon was underway. Most samples taken will be analyzed post-expedition at KOPRI for DIC/TA, nutrients, DOC, and POC. The pH of seawater, underway data of pCO2, CH4, and N2O, as well as a variety of subsequent calculations is required for accurate estimates in the above listed parameters. Methane was also measured with a methane sensor attached to the CTD tool and at the mud volcano in 420 m water depth, methane concentrations of more than 100-times ocean background were seen. The methane plume was also acoustically imaged with the echo sounder systems on board the IBRV Araon. Further details on the water sampling and atmospheric measurements are given in Chapter 10 and 11

Seebeck Effect in Magnetic Tunnel Junctions

Creating temperature gradients in magnetic nanostructures has resulted in a new research direction, i.e., the combination of magneto- and thermoelectric effects. Here, we demonstrate the observation of one important effect of this class: the magneto-Seebeck effect. It is observed when a magnetic configuration changes the charge based Seebeck coefficient. In particular, the Seebeck coefficient changes during the transition from a parallel to an antiparallel magnetic configuration in a tunnel junction. In that respect, it is the analog to the tunneling magnetoresistance. The Seebeck coefficients in parallel and antiparallel configuration are in the order of the voltages known from the charge-Seebeck effect. The size and sign of the effect can be controlled by the composition of the electrodes' atomic layers adjacent to the barrier and the temperature. Experimentally, we realized 8.8 % magneto-Seebeck effect, which results from a voltage change of about -8.7 {\mu}V/K from the antiparallel to the parallel direction close to the predicted value of -12.1 {\mu}V/K.Comment: 16 pages, 7 figures, 2 table