Influence of nearest-neighbor Coulomb interactions on the phase diagram of the ferromagnetic Kondo model

The influence of a nearest-neighbor Coulomb repulsion of strength V on the properties of the ferromagnetic Kondo model is analyzed using computational techniques. The Hamiltonian studied here is defined on a chain using localized S = 1/2 spins, and one orbital per site. Special emphasis is given to the influence of the Coulomb repulsion on the regions of phase separation recently discovered in this family of models, as well as on the double-exchange-induced ferromagnetic ground state. When phase separation dominates at V= 0, the Coulomb interaction breaks the large domains of the two competing phases into small islands of one phase embedded into the other. This is in agreement with several experimental results, as discussed in the text. Vestiges of the original phase separation regime are found in the spin structure factor as incommensurate peaks, even at large values of V. In the ferromagnetic regime close to density n = 0.5, the Coulomb interaction induces tendencies to charge ordering without altering the fully polarized character of the state. This regime of charge-ordered ferromagnetism may be related with experimental observations of a similar phase by Chen and Cheong [Phys. Rev. Lett. 76, 4042 (1996)]. Our results reinforce the recently introduced notion [see, e.g., S. Yunoki et al., Phys. Rev. Lett. 80, 845 (1998)] that in realistic models for manganites analyzed with unbiased many-body techniques, the ground state properties arise from a competition between ferromagnetism and phase-separation - charge-ordering tendencies. ©1999 The American Physical Society.

Aspects of IFP for citrus production in Brazil

Brazilian citriculture represents about 25% of the total world citrus production with an area of 851,518 ha and a total production of more than 17 million tons in 1996. Besides its importance to the brazilian economy, represented by more than 1 billion US $ by year from FCOJ exportation, the citriculture has problems related to low productivity, due to several cultural practices and management. The productivity would be improved by an IFP system. The main problems are related to soil, as poor conservation, use of poor drained soils and bad preparation for planting; diseases-canker, CVC, leprosis, Phytophtora gummosis and other fungus diseases; pests - mites, scales, nematodes and others; the use of disease free and improved scion and rootstocks propagative material is usual; cultural practices - as nutrition, irrigation, wind breaks, weed control, pruning, replant and others, as density planting could be improved. Some possible solutions will be discussed for improving the brazilian citrus productivity and quality by IFP, based on research made.

Trabalhando com estratégias de ensino-aprendizado por descoberta na área da saúde: a problematização e a aprendizagem baseada em problemas.

Considering the changes in teaching in the health field and the demand for new ways of dealing with knowledge in higher learning, the article discusses two innovative methodological approaches: problem-based learning (PBL) and problematization. Describing the two methods' theoretical roots, the article attempts to identify their main foundations. As distinct proposals, both contribute to a review of the teaching and learning process: problematization, focused on knowledge construction in the context of the formation of a critical awareness; PBL, focused on cognitive aspects in the construction of concepts and appropriation of basic mechanisms in science. Both problematization and PBL lead to breaks with the traditional way of teaching and learning, stimulating participatory management by actors in the experience and reorganization of the relationship between theory and practice. The critique of each proposal's possibilities and limits using the analysis of their theoretical and methodological foundations leads us to conclude that pedagogical experiences based on PBL and/or problematization can represent an innovative trend in the context of health education, fostering breaks and more sweeping changes.

Efeito alelopático de extratos de parte aérea de barbatimão [Stryphnodendron adstringens (Mart.) Coville] na germinação e desenvolvimento da plântula de pepino

Stryphnodendron adstringens (Mart.) Coville (barbatimão), belonging to Mimosaceae family; it is used as ornamental and the wood is used in civil buildings, edification in wet places, lathe and joinery jobs, being very used also in home-made medicine against hemorrhage, diarrhea, hemorrhoids, conjunctivitis, injury cleaning, uterus hemorrhage, ulcerous hurt and excessive oily skin. The objective of this research was to determine the allelopathic potential of an aqueous extract, boiled or not of S. adstringens (Mart.) Coville, in the Cucumis sativus germination and initial development. Thus, the aqueous vegetable extract was extracted from the shoot, which was triturated in 1L of distilled water to 100g of leaf, being the extract filtrated and separated in boiled and not boiled. The treatments used were distilled water (0%) and boiled and not boiled extracts, in the concentrations of 50 and 100%. The cucumber seeds were put to germinate in Gerbox, having filter paper as substrate, which was wet with 25mL from different treatments, in constant temperature of 25°C. The reading germination was accomplished in breaks of 24 hours, for a period of five consequently days after the beginning of the experiment, considering germinated the seeds that showed 2mm of root, approximately. To dry matter determination, the seedlings with five days after the germination were separated in shoot and root, dried during three days to a constant weight in a 60°C forced draft oven. Through results, it can be concluded that the extract of S. adstringens affected more the Cucumis sativus seedling development than the germination, and it didn't show difference if boiled or not.

Assessment of DNA damage by extracts and fractions of Strychnos pseudoquina, a Brazilian medicinal plant with antiulcerogenic activity

Strychnos pseudoquina St. Hil. is a native plant of the Brazilian Savannah, used in popular medicine to treat a number of conditions. Since it contains large quantities of alkaloids with proven antiulcer activity, we tested the genotoxic potential of crude extracts and fractions containing alkaloids and flavonoids from the leaves of this plant, on Salmonella typhimurium and performed the micronucleus test on peripheral blood cells of mice treated in vivo. The results showed that the methanol extract of the leaves of S. pseudoquina is mutagenic to the TA98 (-S9) and TA100 (+S9, -S9) strains of Salmonella. The dichloromethane extract was not mutagenic to any of the tested strains. Fractions enriched with alkaloids or flavonoids were not mutagenic. In vivo tests were done on the crude methanol extract in albino Swiss mice, which were treated, by gavage, with three different doses of the extract. The highest dose tested (1800 mg/kg b.w.) induced micronuclei after acute treatment, confirming the mutagenic potential of the methanol extract of the leaves of S. pseudoquina. In high doses, constituents of S. pseudoquina compounds act on DNA, causing breaks and giving rise to micronuclei in the blood cells of treated animals. © 2006 Elsevier Ltd. All rights reserved.

In vitro cytotoxic and non-genotoxic effects of gutta-percha solvents on mouse lymphoma cells by single cell gel (comet) assay

Chloroform and eucalyptol are widely used in clinical dentistry as gutta-percha solvents. However, these compounds may represent a hazard to human health, especially by causing injury to genetic apparatus and/or inducing cellular death. In this study, the genotoxic and cytotoxic potentials associated with exposure to chloroform and eucalyptol were assessed on mouse lymphoma cells in vitro by the single cell gel (comet) assay and trypan blue exclusion test, respectively. Both gutta-percha solvents proved to be cytotoxic at the same levels in concentrations of 2.5, 5 and 10 μL/mL (p<0.05). On the other hand, neither of the solvents induced DNA breakage. Taken together, these results suggest that although both tested compounds (chloroform and eucalyptol) are strong cytotoxicants, it seems that they are not likely to increase the level of DNA damage on mammalian cells.

A proposed behavioral tool to assess sustained auditory attention

Sustained attention and vigilance are processeses that characterize attention, and are essential for the development of certain abilities Aim: a prospective study to propose a simple, easy and quick behavioral tool to support the assessment of sustained auditory attention. Material and methods: volunteer children aged between 6 and 11 years (139 female and 141 male) were selected. The test was named Sustained Auditory Attention Ability Test, and is based on the Continuous Performance Test. It consist of a binaural and diotic presentation of a list of 100 monosyllabic words in which a target monosyllable is included 20 times. This list was presented six times with no breaks. The test was carried out in a soundproofed room, using a CD player attached to a two-channel audiometer at 50 dBSL during 9 minutes. The test resulted in a total score and a vigilance decrement. Results: There was no statistically significant difference between genders, but a significant difference was found between ages. Conclusion: The proposed test had no discomfort for the participants, and was shown to be extremely promising to assess the sustained auditory attention ability in children. © Revista Brasileira de Otorrinolaringologia. All Rights reserved.

What's the signification of nuclear vacuoles in human sperm?

The aim of this study was to determine the extent of DNA fragmentation and the presence of single/denatured or double stranded of DNA in sperm with large nuclear vacuoles (LNV) selected by high-magnification. A total of 30 patients had fresh semen samples prepared by discontinuous concentration gradient. Sperm with normal nucleus (NN) and LNV were selected at 8400x magnification and placed in different slides. DNA fragmentation was determined by TUNEL assay. Denatured and double stranded DNA was identified by acridine orange fluorescence method. The percentage of DNA fragmentation in LNV sperm (29%) was significantly higher (P<0.001) than NN sperm (15.8%). Therefore, cleavage of genomic DNA in low molecular weight DNA fragments (mono and oligonucleosomes), and single strand breaks (nicks) in high molecular weight DNA occur more frequently in LNV. Identically, the percentage denatured stranded DNA in sperm with LNV (67.9%) was significantly higher (P <0.0001) than NN sperm (33%). The high level of denatured DNA in sperm with LNV suggests precocious decondensation and disaggregation of sperm chromatin fibers. Our results support an association between LNV sperm and DNA damage, and the routine selection and injection of morphological motile sperm at high magnification for ICSI. The adverse effect (DNA fragmentation or denaturation) leads to concern particularly about the possibility of iatrogenic transmission of genetic abnormalities. Copyright - SBRA - Sociedade Brasileira de Reprodução Assistida.

From capital surges to drought: seeking stability for emerging economies

Includes bibliography

Arranjos configurados pelos nervos do plexo braquial no urubu (Coragyps atratus foetens - Linnaeus, 1758)

The anatomical study of the origin and distribution of brachial plexus in vulture (Coragyps atratus foetens) was performed in 14 animals, adults, males and females, deriving of the region of Araçatuba (SP). After fixed in watery solution of formaldehyde 10,00%, became dissected bilateral of the origin of the brachial plexus, and yours distribution. The analysis allowed verify that brachial plexus of vulture, four root possess, which originate from the ventral branches of cervical spinal nerves eleven (C11), twelve (C12) and thirteen (C13) and of the ventral branches of thoracic spinal nerve one (T1) and (T2) in both sides (100%). The first root part of C11 in the right and left side, and of the edge skull of the dorsal lace the nerves subescapular, subcoracoescapular e supracoracóide in both antímeros (100%). As the root originates from C12 in both sides, giving origin to the dorsal lace, giving the axilar, radial and anconeal nerves (100%). The third root of plexus originates solely from C13 (100%) and the root of T1 in both sides (100%). The roots of C12, C13 and T1 was united the ventral lace originates, which breaks the nerves to medianoulnar that divided in medium and to ulnar and the pectoral nerves (100%). T2 emits filaments that join it root nervous of T1, being one filament (35,55%) and two filaments (64,29%) in side right, while that in the left one filament (42,85%), two filaments (50%) and three filaments (7,15%).

The international competitiveness of the Costa Rican clothing industry

Includes bibliography

Cartografia geomorfológica como subsídio para a análise das interferências do uso da terra no desencadeamento dos processos erosivos: Um estudo em área canavieira

This study aimed at analyzing the geomorphologic dynamics and its relationship to human interference and ownership of relief, towards a systemic approach, through the interpretation, in an integrated manner, of cartographic documents made from techniques of geomorphologic cartography and of land use. By stereoscopic pairs of aerial photographs, it was prepared the Geomorphological Map and the Land Use Map, respectively based on Tricart's (1965) and Ceron and Diniz's (1966) technical procedures. The unit of the research analysis refers to the basin of Tijuco Preto Streamlet (SP) which is located at the Geomorphological Province of São Paulo state Peripheral Depression between latitudes 22°42'17 and 22°51'36 S, and longitudes 47°30'30 and 47°37'03. In general, it was possible to notice that this basin has been experiencing linear erosion processes, where it was mapped many erosion furrows, grooving and creeping, besides several slope breaks. These processes are associated with a conjunction of circumstances, and the anthropic one is mostly represented by sugarcane monoculture and by urbanization, which are crucial agents in activating erosion processes and in direct interfering on the dynamics of river and rain flow at the basin of Tijuco Preto Streamlet.

Multiferroicity in an organic charge-transfer salt that is suggestive of electric-dipole-driven magnetism

Multiferroics, showing simultaneous ordering of electrical and magnetic degrees of freedom, are remarkable materials as seen from both the academic and technological points of view. A prominent mechanism of multiferroicity is the spin-driven ferroelectricity, often found in frustrated antiferromagnets with helical spin order. There, as for conventional ferroelectrics, the electrical dipoles arise from an off-centre displacement of ions. However, recently a different mechanism, namely purely electronic ferroelectricity, where charge order breaks inversion symmetry, has attracted considerable interest. Here we provide evidence for ferroelectricity, accompanied by antiferromagnetic spin order, in a two-dimensional organic charge-transfer salt, thus representing a new class of multiferroics. We propose a charge-order-driven mechanism leading to electronic ferroelectricity in this material. Quite unexpectedly for electronic ferroelectrics, dipolar and spin order arise nearly simultaneously. This can be ascribed to the loss of spin frustration induced by the ferroelectric ordering. Hence, here the spin order is driven by the ferroelectricity, in marked contrast to the spin-driven ferroelectricity in helical magnets. © 2012 Macmillan Publishers Limited. All rights reserved.

Argentina: Dissemination of genetically modified cotton and its impact on the profitability of small-scale farmers in the Chaco province

Includes bibliography

Absence of mutagenicity of plants used to treat gastrointestinal disorders

The Brazilian Savanna (locally called Cerrado) is an important biome presenting several plants that are used in popular medicine. However, the risks associated with the consumption of derivatives from these plants are generally unknown. Studies with compounds obtained from different species have shown the risks of DNA damage. The present work assessed the in vivo mutagenicity of three plant species used in popular medicine to treat human gastrointestinal disorders (Mouriri pusa, Qualea grandiflora and Qualea multiflora). The micronucleus assay was performed in peripheral blood of mice submitted to acute treatments. Results showed that no assessed extracts were mutagenic in vivo. In fact, the absence of mutagenicity in the present study indicates that the extracts do not contain compounds capable of inducing DNA breaks or chromosomal loss. However, further analysis should be performed in others systems to guarantee their safety, mainly to human chronic use.