Local controls on tree seedling growth following mounding on peatland seismic lines in Brazeau County and Lac La Biche, Alberta

Seismic lines in boreal peatlands are struggling to restore native canopy level vegetation. Mounding is a common restoration method that provides an advantageous growing environment for native tree seedlings. Although many mounding methodologies exist, it remains unclear how each unique mound type changes microsite conditions and influences seedling growth. This study compares five unique mounding and/or planting methods, and the influence of fertilization on black spruce and tamarack seedlings two years post-planting. This study was conducted the summer of 2021 in Alberta and observed seedling, mound microsite and seismic line variables for over 1500 samples. Data compared between mounding methods using ANOVA and characteristics supporting seedling growth were isolated using linear mixed effects models. The results of this study suggest that planted tree seedling survival and growth is heavily correlated with seismic line width, mound height, mound soil moisture and the diversity and density of surrounding vegetation. Comparing between mounding treatments, results indicate that traditional or 'Inverse' mounds are affected by heavy soil subsidence and have higher soil moisture content than any other treatment; they do not provide ideal habitat for black spruce seedlings. Non-traditional mounds like, Rip and Lift, Hummock Transfer and Inline, each had favourable microsite characteristics and support seedling growth. Regardless, Unmounded planting is a viable restoration technique if the seismic line has appropriate microtopographical variability and planting is targeted on the highest microsites. Tamarack seedlings had higher rates of growth than black spruce, but both species benefitted from fertilization with slow-release NPK (nitrogen-phosphorus-potassium) prills. Fertilizer was effective on all mounding treatments except Rip and Lift. The differences in seedling growth and ideal microsite characteristics identified in this study can be used to inform restoration planning. An effective landscape restoration plan can be tailored to existing seismic line characteristics and can build ideal mound microsites to support tree growth and the regrowth of forest canopies

Collective excitations of degenerate Fermi gases in anisotropic parabolic traps

The hydrodynamic low-frequency oscillations of highly degenerate Fermi gases trapped in anisotropic harmonic potentials are investigated. Despite the lack of an obvious spatial symmetry the wave-equation turns out to be separable in elliptical coordinates, similar to a corresponding result established earlier for Bose-condensates. This result is used to give the analytical solution of the anisotropic wave equation for the hydrodynamic modes.Comment: 11 pages, Revte

Occupational sitting behaviour and its relationship with back pain – A pilot study

AbstractNowadays, working in an office environment is ubiquitous. At the same time, progressively more people suffer from occupational musculoskeletal disorders. Therefore, the aim of this pilot study was to analyse the influence of back pain on sitting behaviour in the office environment.A textile pressure mat (64-sensor-matrix) placed on the seat pan was used to identify the adopted sitting positions of 20 office workers by means of random forest classification. Additionally, two standardised questionnaires (Korff, BPI) were used to assess short and long-term back pain in order to divide the subjects into two groups (with and without back pain). Independent t-test indicated that subjects who registered back pain within the last 24 h showed a clear trend towards a more static sitting behaviour. Therefore, the developed sensor system has successfully been introduced to characterise and compare sitting behaviour of subjects with and without back pain

Semiclassical Solution of the Quantum Hydrodynamic Equation for Trapped Bose-condensed Gas in the l=0 Case

In this paper the quantum hydrodynamic equation describing the collective, low energy excitations of a dilute atomic Bose gas in a given trapping potential is investigated with the JWKB semiclassical method. In the case of spherically symmetric harmonic confining potential a good agreement is shown between the semiclassical and the exact energy eigenvalues as well as wave functions. It is also demonstrated that for larger quantum numbers the calculation of the semiclassical wave function is numerically more stable than the exact polynomial with large alternating coefficients.Comment: 12 pages, 7 figure

Kinetic theory and dynamic structure factor of a condensate in the random phase approximation

We present the microscopic kinetic theory of a homogeneous dilute Bose condensed gas in the generalized random phase approximation (GRPA), which satisfies the following requirements: 1) the mass, momentum and energy conservation laws; 2) the H-theorem; 3) the superfluidity property and 4) the recovery of the Bogoliubov theory at zero temperature \cite{condenson}. In this approach, the condensate influences the binary collisional process between the two normal atoms, in the sense that their interaction force results from the mediation of a Bogoliubov collective excitation traveling throughout the condensate. Furthermore, as long as the Bose gas is stable, no collision happens between condensed and normal atoms. In this paper, we show how the kinetic theory in the GRPA allows to calculate the dynamic structure factor at finite temperature and when the normal and superfluid are in a relative motion. The obtained spectrum for this factor provides a prediction which, compared to the experimental results, allows to validate the GRPA. PACS numbers:03.75.Hh, 03.75.Kk, 05.30.-dComment: 6 pages, 1 figures, QFS2004 conferenc

The nonlinear damping of Bose-Einstein condensate oscillations at ultra-low temperatures

We analyze the damping of the transverse breathing mode in an elongated trap at ultralow temperatures. The damping occurs due to the parametric resonance entailing the energy transfer to the longitudinal degrees of freedom. It is found that the nonlinear coupling between the transverse and discrete longitudinal modes can result in an anomalous behavior of the damping as a function of time with the partially reversed pumping of the breathing mode. The picture revealed explains the results observed in [16]

Phases of a polar spin-1 Bose gas in a magnetic field

The two Bose--Einstein condensed phases of a polar spin-1 gas at nonzero magnetizations and temperatures are investigated. The Hugenholtz--Pines theorem is generalized to this system. Crossover to a quantum phase transition is also studied. Results are discussed in a mean field approximation.Comment: 6 pages, 3 figures, revised versio

Sound propagation in a cylindrical Bose-condensed gas

We study the normal modes of a cylindrical Bose condensate at $T = 0$ using the linearized time-dependent Gross-Pitaevskii equation in the Thomas-Fermi limit. These modes are relevant to the recent observation of pulse propagation in long, cigar-shaped traps. We find that pulses generated in a cylindrical condensate propagate with little spread at a speed $c = \sqrt{g\bar n /m}$, where $\bar n$ is the average density of the condensate over its cross-sectional area.Comment: 4 pages, 2 Postscript figure