An assessment of the remodelling of bifurcations in hazel (Corylus avellana L.) in response to bracing, drilling and splitting

This paper provides an insight into the ability of bifurcations in hazel trees to remodel themselves after bracing, drilling and splitting. The study uses evidence from field observations and testing the strength of these bifurcations using a universal testing machine alongside wood density tests. This work highlights the importance of the centrally-placed xylem at the apex of hazel forks in supplying tensile strength to the bifurcation. Additionally, it provides evidence that rod-braced bifurcations can atrophy in terms of their tensile strength, growth rate and wood density, suggesting that thigmomorphogenesis plays an important role in the development of a strong bifurcation

Sequential evacuation strategy for multiple rooms toward the same means of egress

This paper examines different evacuation strategies for systems where several rooms evacuate trough the same means of egress, using microscopic pedestrian simulation.As a case study, a medium-rise office building is considered. It was found that the standard strategy, whereby the simultaneous evacuation of all levels is performed, can be improved by a sequential evacuation, beginning with the lowest floor and continuing successively with each one of the upper floors after a certain delay. The importance of the present research is that it provides the basis for the design and implementation of new evacuation strategies and alarm systems that could significantly improve the evacuation of multiple rooms trough a common means of escape.Comment: 8 pages, 4 figure

Impulse approximation in nuclear pion production reactions: absence of a one-body operator

The impulse approximation of pion production reactions is studied by developing a relativistic formalism, consistent with that used to define the nucleon-nucleon potential. For plane wave initial states we find that the usual one-body (1B) expression O_1B is replaced by O_2B=-iK(m_pi/2)O_1B/m_pi, where K(m_pi/2) is the sum of all irreducible contributions to nucleon-nucleon scattering with energy transfer of m_pi/2. We show that O_2B is approximately O_1B for plane wave initial states. For distorted waves, we find that the usual operator is replaced with a sum of two-body operators that are well approximated by the operator O_2B. Our new formalism solves the (previously ignored) problem of energy transfer forbidding a one-body impulse operator. Using a purely one pion exchange deuteron, the net result is that the impulse amplitude for np --> d pi^0 at threshold is enhanced by a factor of approximately two. This amplitude is added to the larger "rescattering" amplitude and, although experimental data remain in disagreement, the theoretical prediction of the threshold cross section is brought closer to (and in agreement with) the data.Comment: 31 pages, 14 figures, final published versio

The level of occlusion of included bark affects the strength of bifurcations in hazel (Corylus avellana L.)

Bark-included junctions in trees are considered a defect as the bark weakens the union between the branches. To more accurately assess this weakening effect, 241 bifurcations from young specimens of hazel (Corylus avellana L.), of which 106 had bark inclusions, were harvested and subjected to rupture tests. Three-point bending of the smaller branches acted as a benchmark for the relative strength of the bifurcations. Bifurcations with included bark failed at higher displacements, and their modulus of rupture was 24% lower than normally formed bifurcations, while stepwise regression showed that the best predictors of strength in these bark-included bifurcations were the diameter ratio and width of the bark inclusion, which explained 16.6% and 8.1% of the variability, respectively. Cup-shaped, bark-included bifurcations where included bark was partially occluded by xylem were found, on average, to be 36% stronger than those, where included bark was situated at the bifurcation apex. These findings show that there are significant gradations in the strength of bark-included bifurcations in juvenile hazel trees that relate directly to the level of occlusion of the bark into the bifurcation. It therefore may be possible to assess the extent of the defect that a bark-included bifurcation represents in a tree by assessing the relative level of occlusion of the included bark

Improved transfer of quantum information using a local memory

We demonstrate that the quantum communication between two parties can be significantly improved if the receiver is allowed to store the received signals in a quantum memory before decoding them. In the limit of an infinite memory, the transfer is perfect. We prove that this scheme allows the transfer of arbitrary multipartite states along Heisenberg chains of spin-1/2 particles with random coupling strengths.Comment: 4 pages, 1 figure; added references to homogenization and asymptotic completenes

Full control by locally induced relaxation

We demonstrate a scheme for controlling a large quantum system by acting on a small subsystem only. The local control is mediated to the larger system by some fixed coupling Hamiltonian. The scheme allows to transfer arbitrary and unknown quantum states from a memory on the large system (``upload access'') as well as the inverse (``download access''). We study sufficient conditions of the coupling Hamiltonian and give lower bounds on the fidelities for downloading and uploading.Comment: 4 pages, 2 figure