7 research outputs found
The Kagome Heisenberg Antiferromagnet Revisited
We examine the perennial quantum spin-liquid candidate Heisenberg
antiferromagnet on the kagome lattice. Our study is based on achieving Lanczos
diagonalization of the Hamiltonian on a site cluster in sectors with
dimensions as a large as . The results reveal novel intricate
structures in the low-lying energy spectrum. These structures by no means
unambiguously support an emerging consensus of a spin liquid
ground state, but instead appear compatible with several scenarios, including
four-fold topological degeneracy, inversion symmetry breaking and a combination
thereof. We discuss finite-size effects, such as the apparent absence of ETH,
and note that while considerably reduced, some are still present for the
largest cluster. Finally, we observe that an XXZ model in the Ising limit
reproduces remarkably well the most striking features of finite-size spectra.Comment: 8 pages, 5 figure
Emergent multipolar spin correlations in a fluctuating spiral - The frustrated ferromagnetic S=1/2 Heisenberg chain in a magnetic field
We present the phase diagram of the frustrated ferromagnetic S=1/2 Heisenberg
J_1-J_2 chain in a magnetic field, obtained by large scale exact
diagonalizations and density matrix renormalization group simulations. A vector
chirally ordered state, metamagnetic behavior and a sequence of spin-multipolar
Luttinger liquid phases up to hexadecupolar kind are found. We provide
numerical evidence for a locking mechanism, which can drive spiral states
towards spin-multipolar phases, such as quadrupolar or octupolar phases. Our
results also shed light on previously discovered spin-multipolar phases in
two-dimensional quantum magnets in a magnetic field.Comment: 4+ pages, 4 figure
Isolation and cultivation of xylanolytic and cellulolytic Sarocladium kiliense and Trichoderma virens from the gut of the termite Reticulitermes santonensis
The purpose of this work was the isolation and cultivation of cellulolytic and xylanolytic microorganisms extracted from the gut of the lower termite Reticulitermes santonensis. Microcrystalline cellulose (with and without lignin) and beech wood xylan were used as diets instead of poplar wood in order to select cellulose and hemicellulose-degrading fungi. The strain Sarocladium kiliense (Acremonium kiliense) CTGxxyl was isolated from the termites fed on xylan, while the strain Trichoderma virens CTGxAviL was isolated from the termites fed on cellulose (with and without lignin). Both molds were cultivated in liquid media containing different substrates: agro-residues or purified polymers. S. kiliense produced maximal β-glucosidase, endo-1,4-β-D-glucanase, exo-1,4-β-D-glucanase and endo-1,4-β-D-xylanase activities of 0.103, 3.99, 0.53, and 40.8 IU/ml, respectively. T. virens produced maximal β-xylosidase, endo-1,4-β-D-glucanase, exo-1,4-β-D-glucanase, and endo-1,4-β-D-xylanase activities of 0.38, 1.48, 0.69, and 426 IU/ml. The cellulase and the xylanase of S. kiliense, less common than T. virens, were further investigated. The optimal activity of the xylanase was observed at pH 9–10 at 60 °C. The cellulase showed its maximal activity at pH 10, 70 °C. Zymography identified different xylanases produced by both molds, and some fragment sizes were highlighted: 35, 100, and 170 kDa for S. kiliense and 20, 40, 80, and 170 kDa for T. virens. In both cases, endo-1,4-β-D-xylanase activitieswere confirmed through mass spectrometry.Termitofue