764 research outputs found
Distribuição espacial das necessidades hÃdricas das culturas do feijão, milho e soja na bacia do rio Tibaji, PR.
bitstream/item/89786/1/BOP-16.pd
Imaging the essential role of spin-fluctuations in high-Tc superconductivity
We have used scanning tunneling spectroscopy to investigate short-length
electronic correlations in three-layer Bi2Sr2Ca2Cu3O(10+d) (Bi-2223). We show
that the superconducting gap and the energy Omega_dip, defined as the
difference between the dip minimum and the gap, are both modulated in space
following the lattice superstructure, and are locally anti-correlated. Based on
fits of our data to a microscopic strong-coupling model we show that Omega_dip
is an accurate measure of the collective mode energy in Bi-2223. We conclude
that the collective mode responsible for the dip is a local excitation with a
doping dependent energy, and is most likely the (pi,pi) spin resonance.Comment: 4 pages, 4 figure
The Density of States in High-Tc Superconductors Vortices
We calculated the electronic structure of a vortex in a pseudogapped
superconductor within a model featuring strong correlations. With increasing
strength of the correlations, the BCS core states are suppressed and the
spectra in and outside the core become similar. If the correlations are
short-range, we find new core states in agreement with the observations in
YBaCuO and BiSrCaCuO. Our results point to a common phenomenology for these two
systems and indicate that normal-state correlations survive below Tc without
taking part in the overall phase coherence.Comment: REVTeX 4, 5 pages, 2 EPS figures. Some changes to the text; new
figures; references update
Human anti-CD30 recombinant antibodies by guided phage antibody selection using cell panning
In various clinical studies, Hodgkin’s patients have been treated with anti-CD30 immunotherapeutic agents and have shown promising responses. One of the problems that appeared from these studies is the development of an immune response against the non-human therapeutics, which limits repeated administration and reduces efficacy. We have set out to make a recombinant, human anti-CD30 single-chain variable fragment (scFv) antibody, which may serve as a targeting moiety with reduced immunogenicity and more rapid tumour penetration in similar clinical applications. Rather than selecting a naive phage antibody library on recombinant CD30 antigen, we used guided selection of a murine antibody in combination with panning on the CD30-positive cell line L540. The murine monoclonal antibody Ki-4 was chosen as starting antibody, because it inhibits the shedding of the extracellular part of the CD30 antigen. This makes the antibody better suited for CD30-targeting than most other anti-CD30 antibodies. We have previously isolated the murine Ki-4 scFv by selecting a mini-library of hybridoma-derived phage scFv-antibodies via panning on L540 cells. Here, we report that phage display technology was successfully used to obtain a human Ki-4 scFv version by guided selection. The murine variable heavy (VH) and light (VL) chain genes of the Ki-4 scFv were sequentially replaced by human V gene repertoires, while retaining only the major determinant for epitope-specificity: the heavy-chain complementarity determining region 3 (CDR3) of murine Ki-4. After two rounds of chain shuffling and selection by panning on L540 cells, a fully human anti-CD30 scFv was selected. It competes with the parental monoclonal antibody Ki-4 for binding to CD30, inhibits the shedding of the extracellular part of the CD30 receptor from L540 cells and is thus a promising candidate for the generation of anti-CD30 immunotherapeutics. © 2000 Cancer Research Campaig
Utilização do modelo Ceres-Maize como ferramenta na definição de estratégias de semeadura de milho: 1-sistema de produção de sequeiro.
A data da semeadura é um dos fatores que mais afetam produtividade de milho de sequeiro. Utilizou-se o modelo Ceres-Maize para simular a produtividade de milho semedo em diferentes datas em Sete Lagoas, MG. Avaliou-se uma metodologia baseada em dados estatÃsticos, para auxiliar no estabelecimento do perÃodo adequado de semeadura de milho. Cabe ao tomador de decisão definir o nÃvel de quebra de produtividade que ele estaria disposto a aceitar. Tolerando-se uma redução de 10% na produtividade em relação ao valor médio máximo, o perÃodo de semeadura na região deve ser de 26 de setembro a sete de novembro, embora o risco para a semeadura de setembro seja alto devido à s instabilidades climáticas. Mesmo com semeaduras realizadas neste perÃodo, há uma probabilidade de cerca de 33% de que ocorram quebras de safra de até 10% em decorrência de déficit hÃdrico e de outros fatores como temperaturas noturnas altas
Responsive glyco-poly(2-oxazoline)s: synthesis, cloud point tuning, and lectin binding
A new sugar-substituted 2-oxazoline monomer was prepared using the copper-catalyzed alkyne-azide cycloaddition (CuAAC) reaction. Its copolymerization with 2-ethyl-2-oxazoline as well as 2-(dec-9-enyl)-2-oxazoline, yielding well-defined copolymers with the possibility to tune the properties by thiol-ene "click" reactions, is described. Extensive solubility studies on the corresponding glycocopolymers demonstrated that the lower critical solution temperature behavior and pH-responsiveness of these copolymers can be adjusted in water and phosphate-buffered saline (PBS) depending on the choice of the thiol. By conjugation of 2,3,4,6-tetra-O-acetyl-1-thio-beta-D-glucopyranose and subsequent deprotection of the sugar moieties, the hydrophilicity of the copolymer could be increased significantly, allowing a cloud-point tuning in the physiological range. Furthermore, the binding capability of the glycosylated copoly(2-oxazoline) to concanavalin A was investigated
Magnetic field induced charge and spin instabilities in cuprate superconductors
A d-wave superconductor, subject to strong phase fluctuations, is known to
suffer an antiferromagnetic instability closely related to the chiral symmetry
breaking in (2+1)-dimensional quantum electrodynamics (QED3). On the basis of
this idea we formulate a "QED3 in a box" theory of local instabilities of a
d-wave superconductor in the vicinity of a single pinned vortex undergoing
quantum fluctuations around its equilibrium position. As a generic outcome we
find an incommensurate 2D spin density wave forming in the neighborhood of a
vortex with a concomitant "checkerboard" pattern in the local electronic
density of states, in agreement with recent neutron scattering and tunneling
spectroscopy measurements.Comment: 4 pages REVTeX + 2 PostScript figures included in text. Version to
appear in PRL (minor stylistic changes, references updated). For related work
and info visit http://www.physics.ubc.ca/~fran
Utilização do modelo Ceres-Maize como ferramenta na definição de estratégias de semeadura de milho: 2-sistema de produção irrigado.
O uso da irrigação se constitui numa alternativa para alavancar a produção de milho na região central de Minas Gerais, que é carente de grãos. Modelos de simulação de culturas acoplados a ferramentas de apoio à decisão podem ser empregados para auxiliar na avaliação de estratégias de semeadura que possibilitem a obtenção de produtividades elevadas com o uso racional dos recurso hÃdricos. Utilizaram-se dados de produtividade de grãos de milho simulados e uma metodologia estatÃstica para desenvolver um critério de decisão para datas de semeadura em um sistema de produção de milho irrigado. Tolerando-se uma redução de 10% na produtividade, em relação ao valor médio máximo, o perÃodo de semeadura na região deve ser de 23 de janeiro a 27 de março
Determination of the Coherence Length and the Cooper-Pair Size in Unconventional Superconductors by Tunnelling Spectroscopy
The main purpose of the paper is to discuss a possibility of the
determination of the values of the coherence length and the Cooper-pair size in
unconventional superconductors by using tunnelling spectroscopy. In the mixed
state of type-II superconductors, an applied magnetic field penetrates the
superconductor in the form of vortices which form a regular lattice. In
unconventional superconductors, the inner structure of a vortex core has a
complex structure which is determined by the order parameter of the
superconducting state and by the pairing wavefunction of the Cooper pairs. In
clean superconductors, the spatial variations of the order parameter and the
pairing wavefunction occur over the distances of the order of the coherence
length and the Cooper-pair size, respectively. Therefore, by performing
tunnelling spectroscopy along a line passing through a vortex core, one is
able, in principle, to estimate the values of the coherent length and the
Cooper-pair size.Comment: 13 pages, including 17 figure
Nanoscale imaging reveals laterally expanding antimicrobial pores in lipid bilayers
Antimicrobial peptides are postulated to disrupt microbial phospholipid membranes. The prevailing molecular model is based on the formation of stable or transient pores although the direct observation of the fundamental processes is lacking. By combining rational peptide design with topographical (atomic force microscopy) and chemical (nanoscale secondary ion mass spectrometry) imaging on the same samples, we show that pores formed by antimicrobial peptides in supported lipid bilayers are not necessarily limited to a particular diameter, nor they are transient, but can expand laterally at the nano-to-micrometer scale to the point of complete membrane disintegration. The results offer a mechanistic basis for membrane poration as a generic physicochemical process of cooperative and continuous peptide recruitment in the available phospholipid matrix
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