RootSkin: From Soil to Soil

Food and architecture have always been intertwined. When humans started to build settlements, we began to dictate where the food would be grown. Simultaneously, natural resources such as water, light and nutrients dictate how a plant grows. When a climbing plant or vines are planted, humans begin to plan the route for the plant to grow, forcing it to take on certain forms. Is it possible to control the plant below the surface of the soil as it is above the soil? Plant roots seek out and grow towards the water source, posing the possibility to control the network of roots that are often hidden deep within the soil. Today architects are working with nature to create an architecture that is both responsive to and harmonious with nature. As resources, in particular land, become increasingly scarce and our human population continues to grow, we have to find new solutions for both food production and housing. Our cities provide us with new opportunities to reshape the urban fabric while responding to these current issues. While plants provide food, they can also potentially provide other resources that could be used in architectural applications. Plants already provide us with many benefits such as food, medicine, and cleaning the air, to name but a few. Often, once the fruit or seed is removed and the plant no longer fruits, the plant is removed from the soil and discarded - hopefully composted. This poses the question; is it possible to simultaneously harvest other elements of the plants and make use of them before they biodegrade and end up back in the soil? RootSkin is a research developed to explore the creation of biodegradable textiles made from the roots of plants as well as producing food during the “growth” of the textile. The aim being that these textiles can then form part of architectural installations such as skins for pavilions or buildings, for example. In addition, the natural biodegradation allows for an element of change to be incorporated into design

Finite-Difference Calculations for Atoms and Diatomic Molecules in Strong Magnetic and Static Electric Fields

Fully numerical mesh solutions of 2D quantum equations of Schroedinger and Hartree-Fock type allow us to work with wavefunctions which possess a very flexible geometry. This flexibility is especially important for calculations of atoms and molecules in strong external fields where neither the external field nor the internal interactions can be considered as a perturbation. The applications of the present approach include calculations of atoms and diatomic molecules in strong static electric and magnetic fields. For the latter we have carried out Hartree-Fock calculations for He, Li, C and several other atoms. This yields in particular the first comprehensive investigation of the ground state configurations of the Li and C atoms in the whole range of magnetic fields (0<B<10000 a.u.) and a study of the ground state electronic configurations of all the atoms with 1<Z<11 and their ions A^+ in the high-field fully spin-polarised regime. The results in a case of a strong electric field relate to single-electron systems including the correct solution of the Schroedinger equation for the H_2^+ ion (energies and decay rates) and the hydrogen atom in strong parallel electric and magnetic fields.Comment: 20 pages, 7 figure

The ground state of the carbon atom in strong magnetic fields

The ground and a few excited states of the carbon atom in external uniform magnetic fields are calculated by means of our 2D mesh Hartree-Fock method for field strengths ranging from zero up to 2.35 10^9 T. With increasing field strength the ground state undergoes six transitions involving seven different electronic configurations which belong to three groups with different spin projections S_z=-1,-2,-3. For weak fields the ground state configuration arises from the field-free 1s^2 2s^2 2p_0 2p_{-1}, S_z=-1 configuration. With increasing field strength the ground state involves the four S_z=-2 configurations 1s^22s2p_0 2p_{-1}2p_{+1}, 1s^22s2p_0 2p_{-1}3d_{-2}, 1s^22p_0 2p_{-1}3d_{-2}4f_{-3} and 1s^22p_{-1}3d_{-2}4f_{-3}5g_{-4}, followed by the two fully spin polarized S_z=-3 configurations 1s2p_02p_{-1}3d_{-2}4f_{-3}5g_{-4} and 1s2p_{-1}3d_{-2}4f_{-3}5g_{-4}6h_{-5}. The last configuration forms the ground state of the carbon atom in the high field regime \gamma>18.664. The above series of ground state configurations is extracted from the results of numerical calculations for more than twenty electronic configurations selected due to some general energetical arguments.Comment: 6 figures,acc. Phys.Rev.

Ionization and dissociation equilibrium in strongly-magnetized helium atmosphere

Recent observations and theoretical investigations of neutron stars indicate that their atmospheres consist not of hydrogen or iron but possibly other elements such as helium. We calculate the ionization and dissociation equilibrium of helium in the conditions found in the atmospheres of magnetized neutron stars. For the first time this investigation includes the internal degrees of freedom of the helium molecule. We found that at the temperatures and densities of neutron star atmospheres the rotovibrational excitations of helium molecules are populated. Including these excitations increases the expected abundance of molecules by up to two orders of magnitude relative to calculations that ignore the internal states of the molecule; therefore, if the atmospheres of neutron stars indeed consist of helium, helium molecules and possibly polymers will make the bulk of the atmosphere and leave signatures on the observed spectra from neutron stars. We applied our calculation to nearby radio-quiet neutron stars with B_{dipole}~10^{13}-10^{14} G. If helium comprises their atmospheres, our study indicates that isolated neutron stars with T_{BB}~10^6 K such as RXJ0720.4-3125 and RXJ1605.3+3249 will have He^+ ions predominantly, while isolated neutron stars with lower temperature (T_{BB}~5x10^5 K) such as RXJ1856.5-3754 and RXJ0420.0-5022 will have some fraction of helium molecules. If helium molecules are abundant, their spectroscopic signatures may be detected in the optical, UV and X-ray band. (Abridged)Comment: 12 pages, 12 figures, accepted for publication in MNRA

Matter in Strong Magnetic Fields

The properties of matter are significantly modified by strong magnetic fields, $B>>2.35\times 10^9$ Gauss ($1 G =10^{-4} Tesla$), as are typically found on the surfaces of neutron stars. In such strong magnetic fields, the Coulomb force on an electron acts as a small perturbation compared to the magnetic force. The strong field condition can also be mimicked in laboratory semiconductors. Because of the strong magnetic confinement of electrons perpendicular to the field, atoms attain a much greater binding energy compared to the zero-field case, and various other bound states become possible, including molecular chains and three-dimensional condensed matter. This article reviews the electronic structure of atoms, molecules and bulk matter, as well as the thermodynamic properties of dense plasma, in strong magnetic fields, $10^9G << B < 10^{16}G$. The focus is on the basic physical pictures and approximate scaling relations, although various theoretical approaches and numerical results are also discussed. For the neutron star surface composed of light elements such as hydrogen or helium, the outermost layer constitutes a nondegenerate, partially ionized Coulomb plasma if $B<<10^{14}G$, and may be in the form of a condensed liquid if the magnetic field is stronger (and temperature $<10^6$ K). For the iron surface, the outermost layer of the neutron star can be in a gaseous or a condensed phase depending on the cohesive property of the iron condensate.Comment: 45 pages with 9 figures. Many small additions/changes. Accepted for publication in Rev. Mod. Phy

Diffusion Rutherford en présence d'un champ magnétique, II

Exteraal Coulomb excitation of a fixed distribution of charges by a charged particle moving in a magnetic field has been studied as a first order perturbation problem. Adiabatic switching off of the magnetic field leads to the results of first Born approximation. When the magnetic field is continuously increased the scattering function behaves as a one-dimensional one but a selection rule governs the back-scattering.Le phénomène d'excitation coulombienne extérieure dont le projectile est plongé dans un champ magnétique est traité au premier ordre du calcul des perturbations. Cette étude qui généralise la diffusion monopolaire (Rutherford) a été menée au moyen de la fonction de Green du problème. L'extinction adiabatique du champ magnétique fait tendre la fonction de diffusion vers celle de l'approximation de Born. A la limite d'un champ magnétique très intense la fonction de diffusion se comporte comme celle d'un phénomène à une dimension (dans la direction du champ) soumis cependant à une règle de sélection dépendante des nombres quantiques du multipole.Demeur Marcel. Diffusion Rutherford en présence d'un champ magnétique, II. In: Bulletin de la Classe des sciences, tome 71, 1985. pp. 213-224

Jules Géhéniau (1909-1991)

Demeur Marcel. Jules Géhéniau (1909-1991). In: Bulletin de la Classe des sciences, tome 3, n°10-11, 1992. pp. 165-172

Jules Géhéniau (1909-1991)

Demeur Marcel. Jules Géhéniau (1909-1991). In: Bulletin de la Classe des sciences, tome 3, n°10-11, 1992. pp. 165-172