Effects of non-universal large scales on conditional structure functions in turbulence

We report measurements of conditional Eulerian and Lagrangian structure functions in order to assess the effects of non-universal properties of the large scales on the small scales in turbulence. We study a 1m $\times$ 1m $\times$ 1.5m flow between oscillating grids which produces $R_\lambda=285$ while containing regions of nearly homogeneous and highly inhomogeneous turbulence. Large data sets of three-dimensional tracer particle velocities have been collected using stereoscopic high speed cameras with real-time image compression technology. Eulerian and Lagrangian structure functions are measured in both homogeneous and inhomogeneous regions of the flow. We condition the structure functions on the instantaneous large scale velocity or on the grid phase. At all scales, the structure functions depend strongly on the large scale velocity, but are independent of the grid phase. We see clear signatures of inhomogeneity near the oscillating grids, but even in the homogeneous region in the center we see a surprisingly strong dependence on the large scale velocity that remains at all scales. Previous work has shown that similar correlations extend to very high Reynolds numbers. Comprehensive measurements of these effects in a laboratory flow provide a powerful tool for assessing the effects of shear, inhomogeneity and intermittency of the large scales on the small scales in turbulence

Spin relaxation and anticrossing in quantum dots: Rashba versus Dresselhaus spin-orbit coupling

The spin-orbit splitting of the electron levels in a two-dimensional quantum dot in a perpendicular magnetic field is studied. It is shown that at the point of an accidental degeneracy of the two lowest levels above the ground state the Rashba spin-orbit coupling leads to a level anticrossing and to mixing of spin-up and spin-down states, whereas there is no mixing of these levels due to the Dresselhaus term. We calculate the relaxation and decoherence times of the three lowest levels due to phonons. We find that the spin relaxation rate as a function of a magnetic field exhibits a cusp-like structure for Rashba but not for Dresselhaus spin-orbit interaction.Comment: 6 pages, 1 figur

Measuring deliberate reflection in residents: validation and psychometric properties of a measurement tool

PURPOSE: Reflective capacity is the ability to understand critical analysis of knowledge and experience to achieve deeper meaning. In medicine, there is little provision for post-graduate medical education to teach deliberate reflection. The feasibility, scoring characteristics, reliability, validation, and adaptability of a modified previously validated instrument was examined for its usefulness assessing reflective capacity in residents as a step toward developing interventions for improvement. METHODS: Third-year residents and fellows from four anesthesia training programs were administered a slightly modified version of the Reflection Evaluation for Learners\u27 Enhanced Competencies Tool (REFLECT) in a prospective, observational study at the end of the 2019 academic year. Six written vignettes of imperfect anesthesia situations were created. Subjects recorded their perspectives on two randomly assigned vignettes. Responses were scored using a 5-element rubric; average scores were analyzed for psychometric properties. An independent self-report assessment method, the Cognitive Behavior Survey: Residency Level (rCBS) was used to examine construct validity. Internal consistency (ICR, Cronbach\u27s alpha) and interrater reliability (weighted kappa) were examined. Pearson correlations were used between the two measures of reflective capacity. RESULTS: 46/136 invited subjects completed 2/6 randomly assigned vignettes. Interrater agreement was high (k = 0.85). The overall average REFLECT score was 1.8 (1-4 scale) with good distribution across the range of scores. ICR for both the REFLECT score (mean 1.8, sd 0.5; α = 0.92) and the reflection scale of the rCBS (mean 4.5, sd 1.1; α = 0.94) were excellent. There was a significant correlation between REFLECT score and the rCBS reflection scale (r = .44, p \u3c 0.01). CONCLUSIONS: This study demonstrates feasibility, reliability, and sufficiently robust psychometric properties of a modified REFLECT rubric to assess graduate medical trainees\u27 reflective capacity and established construct/convergent validity to an independent measure. The instrument has the potential to assess the effectiveness of interventions intended to improve reflective capacity

Quantum Adiabatic Markovian Master Equations

We develop from first principles Markovian master equations suited for studying the time evolution of a system evolving adiabatically while coupled weakly to a thermal bath. We derive two sets of equations in the adiabatic limit, one using the rotating wave (secular) approximation that results in a master equation in Lindblad form, the other without the rotating wave approximation but not in Lindblad form. The two equations make markedly different predictions depending on whether or not the Lamb shift is included. Our analysis keeps track of the various time- and energy-scales associated with the various approximations we make, and thus allows for a systematic inclusion of higher order corrections, in particular beyond the adiabatic limit. We use our formalism to study the evolution of an Ising spin chain in a transverse field and coupled to a thermal bosonic bath, for which we identify four distinct evolution phases. While we do not expect this to be a generic feature, in one of these phases dissipation acts to increase the fidelity of the system state relative to the adiabatic ground state.Comment: 31 pages, 9 figures. v2: Generalized Markov approximation bound. Included a section on thermal equilibration. v3: Added text that appears in NJP version. Generalized Lindblad ME to include degenerate subspaces. v3. Corrections made to Appendix E and F. We thank Kabuki Takada and Hidetoshi Nishimori for pointing out the errors. v4: Corrected a typo in Eqt. B

Velocity correlations in dense granular gases

We report the statistical properties of spherical steel particles rolling on an inclined surface being driven by an oscillating wall. Strong dissipation occurs due to collisions between the particles and rolling and can be tuned by changing the number density. The velocities of the particles are observed to be correlated over large distances comparable to the system size. The distribution of velocities deviates strongly from a Gaussian. The degree of the deviation, as measured by the kurtosis of the distribution, is observed to be as much as four times the value corresponding to a Gaussian, signaling a significant breakdown of the assumption of negligible velocity correlations in a granular system.Comment: 4 pages, 4 Figure

MANEJO DO TOMBAMENTO EM PEPINO PELA ADIÇÃO AO SOLO DE CAMA DE AVIÁRIO E CASCA DE PINUS.

Phytophthora capsici damping-off and fruit rot of cucurbits is a serious proble m on rainy warm summer seasons at the highlands of Santa Catarina State, Brazil. The main goal of this study was to evaluate the effects of chicken manure and pine bark as soil amendments on cucumber (Cucumis sativus cv. ‘Caipira’) damping-off. The experiments were conducted under greenhouse (CAV/UDESC, Lages/SC) conditions in a completely randomized block design with seven to eight replications. The doses of chicken manure used were 0, 5, 10, 20, 30, 40, 50, and 60 g/kg of soil (6 kg/m2), and the doses of pine bark were 0, 5, 10, 20, 30, 40, and 50 g/kg of soil. Chicken manure at the dose of 60 g/kg significantly decreased damping-off of cucumber and significantly increased: (a) the total population of bacteria 60 days after soil amendment; (b) the amounts of N, P, and K in soil 120 days after soil amendment; (c) the soil pH at 30 and 120 days after soil amendment; (d) the number of healthy plants 30 days after sowing; and (d) the fresh plant weight 30 days after sowing. Pine bark increased significantly: (a) the bacterial population 30 days after soil amendment in the soil; (b) the population of Trichoderma spp. in the soil 60 days after soil amendment; and (c) the soil pH 30 days after soil amendment. On the second cucumber planting, only chicken manure at the dose of 60 g/kg reduced the amount of damping-off.O tombamento e a podridão de frutos em cucurbitáceas causados por Phytophthora capsici é um sério problema, principalmente em verões quentes e chuvosos. O presente estudo visou avaliar o efeito da cama de aviário e da casca de pinus como resíduos orgânicos aplicados ao solo no tombamento em pepino (Cucumis sativus). Os experimentos foram delineados em blocos ao acaso e foram conduzidos em casa de vegetação utilizando-se a cv. ‘Caipira’. Testou-se 0, 5, 10, 20, 30, 40, 50 e 60 g de cama de aviário / kg de solo (6 kg/m2) e 0, 5, 10, 20, 30, 40, e 50 g de casca de pinus / kg de solo. Cama de aviário na dose de 60 g/kg de solo reduziu o tombamento de plântulas de pepino e aumentou significativamente: (a) a comunidade bacteriana total do solo aos 60 dias após a mistura; (b) os teores de nitrogênio, fósforo e potássio no solo aos 120 dias após a mistura; (c) o pH do solo aos 30 e 120 dias após a mistura; (d) a massa verde de plantas aos 30 dias após a semeadura; e (e) o número de plantas sadias aos 30 dias após a semeadura. A adição de casca de pinus na dose de 40-50 g/kg aumentou significativamente: (a) a população de bactérias do solo aos 30 dias após a incorporação de casca de pinus; (b) a população de Trichoderma spp. no solo aos 60 dias após a incorporação; e (c) o pH do solo aos 30 dias após a incorporação. Cama de aviário reduziu a incidência do tombamento em pepino, no segundo plantio, apenas na dose de 60 g/kg de solo

Spin Tunneling and Phonon-assisted Relaxation in Mn12-acetate

We present a comprehensive theory of the magnetization relaxation in a Mn12-acetate crystal in the high-temperature regime (T>1 K), which is based on phonon-assisted spin tunneling induced by quartic magnetic anisotropy and weak transverse magnetic fields. The overall relaxation rate as function of the longitudinal magnetic field is calculated and shown to agree well with experimental data including all resonance peaks measured so far. The Lorentzian shape of the resonances, which we obtain via a generalized master equation that includes spin tunneling, is also in good agreement with recent data. We derive a general formula for the tunnel splitting energy of these resonances. We show that fourth-order diagonal terms in the Hamiltonian lead to satellite peaks. A derivation of the effective linewidth of a resonance peak is given and shown to agree well with experimental data. In addition, previously unknown spin-phonon coupling constants are calculated explicitly. The values obtained for these constants and for the sound velocity are also in good agreement with recent data. We show that the spin relaxation in Mn12-acetate takes place via several transition paths of comparable weight. These transition paths are expressed in terms of intermediate relaxation times, which are calculated and which can be tested experimentally.Comment: 18 pages, 22 EPS figures, REVTe

Finite Temperature Transitions in Lattice QCD with Wilson Quarks --- Chiral Transitions and the Influence of the Strange Quark ---

The nature of finite temperature transitions in lattice QCD with Wilson quarks is studied near the chiral limit for the cases of 2, 3, and 6 flavors of degenerate quarks ($N_F=2$, 3, and 6) and also for the case of massless up and down quarks and a light strange quark ($N_F=2+1$). Our simulations mainly performed on lattices with the temporal direction extension $N_t=4$ indicate that the finite temperature transition in the chiral limit (chiral transition) is continuous for $N_F=2$, while it is of first order for $N_F=3$ and 6. We find that the transition is of first order for the case of massless up and down quarks and the physical strange quark where we obtain a value of $m_\phi/m_\rho$ consistent with the physical value. We also discuss the phase structure at zero temperature as well as that at finite temperatures.Comment: uuencoded compressed tar file, 70 pages, 32 figure

Accuracy of five algorithms to diagnose gambiense human African trypanosomiasis.

Algorithms to diagnose gambiense human African trypanosomiasis (HAT, sleeping sickness) are often complex due to the unsatisfactory sensitivity and/or specificity of available tests, and typically include a screening (serological), confirmation (parasitological) and staging component. There is insufficient evidence on the relative accuracy of these algorithms. This paper presents estimates of the accuracy of five algorithms used by past Médecins Sans Frontières programmes in the Republic of Congo, Southern Sudan and Uganda