An extended pair tunneling model: studies on bilayer splitting and some superconducting state properties

We consider an extended version of the pair tunneling model including interlayer single particle hopping (ISPH) as a complementary process to pair tunneling. The normal state gap, as found in cuprates, is taken to suppress the effective ISPH in conformity with the experimental observations, and this in turn enhances the pair tunneling process. The effective ISPH involves a probability factor P for which we consider two choices and provide phenomenological arguments in favour of them. We address the issue of bilayer splitting by calculating the spectral density function and corresponding photoemission intensity curves and show that our calculations conform with the absence of bilayer splitting observed in ARPES experiments on Bi2212. We have also studied the temperature variation of the superconducting gap and ratio of the superconducting gap to T_c. Our results, obtained for both the choices of P, are reasonably in good agreement with those from experiments on cuprate superconductors. A linear T-dependent choice of P, however, yields a precise match to the experimantal data of the temperature varying superconducting gap.Comment: Latex file, 17 pages, 5 figures (postscript files) include

The Multidimensional Study of Viral Campaigns as Branching Processes

Viral campaigns on the Internet may follow variety of models, depending on the content, incentives, personal attitudes of sender and recipient to the content and other factors. Due to the fact that the knowledge of the campaign specifics is essential for the campaign managers, researchers are constantly evaluating models and real-world data. The goal of this article is to present the new knowledge obtained from studying two viral campaigns that took place in a virtual world which followed the branching process. The results show that it is possible to reduce the time needed to estimate the model parameters of the campaign and, moreover, some important aspects of time-generations relationship are presented.Comment: In proceedings of the 4th International Conference on Social Informatics, SocInfo 201

c-Axis Transport and Resistivity Anisotropy of Lightly- to Moderately-Doped La_{2-x}Sr_{x}CuO_{4} Single Crystals: Implications on the Charge Transport Mechanism

Both the in-plane and the out-of-plane resistivities (\rho_{ab} and \rho_{c}) are measured in high-quality La_{2-x}Sr_{x}CuO_{4} (LSCO) single crystals in the lightly- to moderately-doped region, x = 0.01 to 0.10, and the resistivity anisotropy is determined. In all the samples studied, the anisotropy ratio \rho _{c}/\rho_{ab} quickly increases with decreasing temperature, although in non-superconducting samples the strong localization effect causes \rho _{c}/\rho_{ab} to decrease at low temperatures. Most notably, it is found that \rho_{c}/\rho_{ab} at moderate temperatures (100 - 300 K) is almost completely independent of doping in the non-superconducting regime (x = 0.01 to 0.05); this indicates that the same charge confinement mechanism that renormalizes the c-axis hopping rate is at work down to x = 0.01. It is discussed that this striking x-independence of \rho_{c}/\rho_{ab} is consistent with the idea that holes form a self-organized network of hole-rich regions, which also explains the unusually metallic in-plane transport of the holes in the lightly-doped region. Furthermore, the data for x > 0.05 suggest that the emergence of the superconductivity is related to an increase in the c-axis coupling.Comment: 7 pages, 5 figures, submitted to Phys. Rev.

Behavioural change techniques in health coaching-based interventions for Type 2 Diabetes: a systematic review and meta-analysis

Background Given the high rates globally of Type 2 Diabetes Mellitus (T2DM), there is a clear need to target health behaviours through person-centred interventions. Health coaching is one strategy that has been widely recognised as a tool to foster positive behaviour change. However, it has been used inconsistently and has produced mixed results. This systematic review sought to explore the use of behaviour change techniques (BCTs) in health coaching interventions and identify which BCTs are linked with increased effectiveness in relation to HbA1C reductions. Methods In line with the PICO framework, the review focused on people with T2DM, who received health coaching and were compared with a usual care or active control group on HbA1c levels. Studies were systematically identified through different databases including Medline, Web of science, and PsycINFO searches for relevant randomised controlled trials (RCTs) in papers published between January 1950 and April 2022. The Cochrane collaboration tool was used to evaluate the quality of the studies. Included papers were screened on the reported use of BCTs based on the BCT taxonomy. The effect sizes obtained in included interventions were assessed by using Cohen’s d and meta-analysis was used to estimate sample-weighted average effect sizes (Hedges’ g). Results Twenty RCTs with a total sample size of 3222 were identified. Random effects meta-analysis estimated a small-sized statistically significant effect of health coaching interventions on HbA1c reduction (g+ = 0.29, 95% CI: 0.18 to 0.40). A clinically significant HbA1c decrease of ≥5 mmol/mol was seen in eight studies. Twenty-three unique BCTs were identified in the reported interventions, with a mean of 4.5 (SD = 2.4) BCTs used in each study. Of these, Goal setting (behaviour) and Problem solving were the most frequently identified BCTs. The number of BCTs used was not related to intervention effectiveness. In addition, there was little evidence to link the use of specific BCTs to larger reductions in HbA1c across the studies included in the review; instead, the use of Credible source and Social reward in interventions were associated with smaller reductions in HbA1c. Conclusion A relatively small number of BCTs have been used in RCTs of health coaching interventions for T2DM. Inadequate, imprecise descriptions of interventions and the lack of theory were the main limitations of the studies included in this review. Moreover, other possible BCTs directly related to the theoretical underpinnings of health coaching were absent. It is recommended that key BCTs are identified at an early stage of intervention development, although further research is needed to examine the most effective BCTs to use in health coaching interventions

Demonstration of the temporal matter-wave Talbot effect for trapped matter waves

We demonstrate the temporal Talbot effect for trapped matter waves using ultracold atoms in an optical lattice. We investigate the phase evolution of an array of essentially non-interacting matter waves and observe matter-wave collapse and revival in the form of a Talbot interference pattern. By using long expansion times, we image momentum space with sub-recoil resolution, allowing us to observe fractional Talbot fringes up to 10th order.Comment: 17 pages, 7 figure

Kaon Production and Kaon to Pion Ratio in Au+Au Collisions at \snn=130 GeV

Mid-rapidity transverse mass spectra and multiplicity densities of charged and neutral kaons are reported for Au+Au collisions at \snn=130 GeV at RHIC. The spectra are exponential in transverse mass, with an inverse slope of about 280 MeV in central collisions. The multiplicity densities for these particles scale with the negative hadron pseudo-rapidity density. The charged kaon to pion ratios are $K^+/\pi^- = 0.161 \pm 0.002 {\rm (stat)} \pm 0.024 {\rm (syst)}$ and $K^-/\pi^- = 0.146 \pm 0.002 {\rm (stat)} \pm 0.022 {\rm (syst)}$ for the most central collisions. The $K^+/\pi^-$ ratio is lower than the same ratio observed at the SPS while the $K^-/\pi^-$ is higher than the SPS result. Both ratios are enhanced by about 50% relative to p+p and $\bar{\rm p}$+p collision data at similar energies.Comment: 6 pages, 3 figures, 1 tabl

Azimuthal anisotropy and correlations in p+p, d+Au and Au+Au collisions at 200 GeV

We present the first measurement of directed flow ($v_1$) at RHIC. $v_1$ is found to be consistent with zero at pseudorapidities $\eta$ from -1.2 to 1.2, then rises to the level of a couple of percent over the range $2.4 < |\eta| < 4$. The latter observation is similar to data from NA49 if the SPS rapidities are shifted by the difference in beam rapidity between RHIC and SPS. Back-to-back jets emitted out-of-plane are found to be suppressed more if compared to those emitted in-plane, which is consistent with {\it jet quenching}. Using the scalar product method, we systematically compared azimuthal correlations from p+p, d+Au and Au+Au collisions. Flow and non-flow from these three different collision systems are discussed.Comment: Quark Matter 2004 proceeding, 4 pages, 3 figure

Azimuthal anisotropy: the higher harmonics

We report the first observations of the fourth harmonic (v_4) in the azimuthal distribution of particles at RHIC. The measurement was done taking advantage of the large elliptic flow generated at RHIC. The integrated v_4 is about a factor of 10 smaller than v_2. For the sixth (v_6) and eighth (v_8) harmonics upper limits on the magnitudes are reported.Comment: 4 pages, 6 figures, contribution to the Quark Matter 2004 proceeding

Strange Resonance Production in p+p and Au+Au Collisions at RHIC Energies

Resonance yields and spectra from elementary p+p and Au+Au collisions at $\sqrt{s_{\rm NN}} =$ 200 GeV from the STAR experiment at RHIC are presented and discussed in terms of chemical and thermal freeze-out conditions. Thermal models do not adequately describe the yields of the resonance production in central Au+Au collisions. The approach to include elastic hadronic interactions between chemical freeze-out and thermal freeze-out suggests a time of $\Delta \tau>$5 fm/c.Comment: 4 pages, 7 figures, proceedings of the Quark Matter 2004, in Oakland, California, to be published in Journal of Physics G: Nuclear and Particle Physic

Identified particles at large transverse momenta in STAR in Au+Au collisions @ sqrt(s_NN) = 200 GeV

We report measurements of the ratios of identified hadrons (pi,K,p,Lambda) in Au+Au collisions at sqrt(s_NN) = 200 GeV as a function of both collision centrality and transverse momentum (p_T). Ratios of anti-baryon to baryon yields are independent of p_T within 2<p_T <6 GeV/c indicating that, for such a range, our measurements are inconsistent with theoretical pQCD calculations predicting a decrease due to a stronger contribution from valence quark scattering. For both strange and non-strange species, a strong baryon enhancement relative to meson yields is observed as a function of collision centrality in this intermediate p_T region, leading to p/pi and Lambda/K ratios greater than unity. The nuclear modification factor, R_cp (central relative to peripheral collisions), is used to illustrate the interplay between jet quenching and hadron production. The physics implications of these measurements are discussed with reference to different theoretical models.Comment: 5 pages, 4 figures. Proceedings of Quark Matter 2004 Conference, Jan 2004, Oakland, USA. Submitted to Journal of Physics