8,409 research outputs found
Magneto-chiral scattering of light: a new optical manifestation of chirality
We have investigated multiple scattering of light in systems subject to
magneto-chiral (MC) effects. Our medium consists of magneto-optically active
dipoles placed in a chiral geometry under the influence of an external magnetic
field. We have calculated, for the first time, the total and the differential
scattering MC cross sections of this system, explicitely showing that they are
proportional to pseudoscalar quantities. This provides a new optical measure
for the degree of chirality, a pseudoscalar g, of an arbitrary geometrical
configuration of scatterers based on its scattering properties. We have
calculated g for some simple chiral systems and we have even used it to probe
the degree of optical chirality of random systems. Finally, we have compared
with other recently defined chiral measures in literature.Comment: 18 pages, 6 figures, RevTeX. Submitted to PR
Unavoidable Conflict Between Massive Gravity Models and Massive Topological Terms
Massive gravity models in 2+1 dimensions, such as those obtained by adding to
Einstein's gravity the usual Fierz-Pauli, or the more complicated Ricci scalar
squared (), terms, are tree level unitary. Interesting enough these
seemingly harmless systems have their unitarity spoiled when they are augmented
by a Chern-Simons term. Furthermore, if the massive topological term is added
to gravity, or to gravity
(higher-derivative gravity), which are nonunitary at the tree level, the
resulting models remain nonunitary. Therefore, unlike the common belief, as
well as the claims in the literature, the coexistence between three-dimensional
massive gravity models and massive topological terms is conflicting.Comment: 13 pages, no figure
Os desafios atuais da nematologia no contexto da olericultura: Meloidogyne enterolobii (sin. M. Mayaguensis) em hortaliças.
O emprego de cultivares resistentes traz a vantagem de requerer pequena ou nenhuma tecnologia adicional e, consequentemente, ser de baixo custo e de baixo impacto ambiental.bitstream/item/70337/1/coluna-jadir.pd
Structures of an apo and a binary complex of an evolved archeal b family DNA polymerase capable of synthesising highly cy-dye labelled DNA
Thermophilic DNA polymerases of the polB family are of great importance in biotechnological applications including high-fidelity PCR. Of particular interest is the relative promiscuity of engineered versions of the exo- form of polymerases from the Thermo- and Pyrococcales families towards non-canonical substrates, which enables key advances in Next-generation sequencing. Despite this there is a paucity of structural information to guide further engineering of this group of polymerases. Here we report two structures, of the apo form and of a binary complex of a previously described variant (E10) of Pyrococcus furiosus (Pfu) polymerase with an ability to fully replace dCTP with Cyanine dye-labeled dCTP (Cy3-dCTP or Cy5-dCTP) in PCR and synthesise highly fluorescent “CyDNA” densely decorated with cyanine dye heterocycles. The apo form of Pfu-E10 closely matches reported apo form structures of wild-type Pfu. In contrast, the binary complex (in the replicative state with a duplex DNA oligonucleotide) reveals a closing movement of the thumb domain, increasing the contact surface with the nascent DNA duplex strand. Modelling based on the binary complex suggests how bulky fluorophores may be accommodated during processive synthesis and has aided the identification of residues important for the synthesis of unnatural nucleic acid polymers
Biotechnology Tools Derived from the Bacteriophage/Bacteria Arms Race
The long association and intense competition between bacteria and their viruses have created a fertile ground for evolution to develop numerous tools for DNA modification, assembly and degradation. Many of these tools underpin the past 50 years of molecular biology, and others show great potential in shaping the next 50 years of the field. Here, I present some of the tools that have come out of the bacteria-bacteriophage arms race and discuss some of the concepts that may shape their future use. Molecular biology remains a fast-growing area increasingly limited solely by researcher ingenuity
Manejo integrado de doenças em hortaliças em cultivo orgânico.
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