Bilinear and quadratic Hamiltonians in two-mode cavity quantum electrodynamics

In this work we show how to engineer bilinear and quadratic Hamiltonians in cavity quantum electrodynamics (QED) through the interaction of a single driven two-level atom with cavity modes. The validity of the engineered Hamiltonians is numerically analyzed even considering the effects of both dissipative mechanisms, the cavity field and the atom. The present scheme can be used, in both optical and microwave regimes, for quantum state preparation, the implementation of quantum logical operations, and fundamental tests of quantum theory.Comment: 11 pages, 3 figure

Nonadiabatic coherent evolution of two-level systems under spontaneous decay

In this paper we extend current perspectives in engineering reservoirs by producing a time-dependent master equation leading to a nonstationary superposition equilibrium state that can be nonadiabatically controlled by the system-reservoir parameters. Working with an ion trapped inside a nonindeal cavity we first engineer effective Hamiltonians that couple the electronic states of the ion with the cavity mode. Subsequently, two classes of decoherence-free evolution of the superposition of the ground and decaying excited levels are achieved: those with time-dependent azimuthal or polar angle. As an application, we generalise the purpose of an earlier study [Phys. Rev. Lett. 96, 150403 (2006)], showing how to observe the geometric phases acquired by the protected nonstationary states even under a nonadiabatic evolution.Comment: 5 pages, no figure

Incidência de aflatoxinas em milho (Zea mays L.) com diferentes níveis de umidade após tratamento com fungicida, armazenado em atmosfera com e sem aeração.

Foi verificada a produção de aflatoxinas em amostras de milho, cultivar BR 201, plantada em 1994, no Centro Nacional de Pesquisa de Milho e Sorgo (EMBRAPA), em Sete Lagoas, Minas Gerais. As amostras, coletadas em duplicata, apresentando diferentes níveis de umidade, foram tratadas com solução aquosa e oleosa de Iprodiona (20ppm), seguido de um armazenamento em tambores metálicos, com e sem aeração, proporcionando uma temperatura de 18-20o e 35-40oC, respectivamente. Os resultados encontrados mostraram uma redução dos níveis de aflatoxinas nas amostras tratadas com Iprodiona e armazenadas em amostras aerada. Quando o acondicionamento foi realizado em atmosfera sem aeração (temperatura 35-40o), o decréscimo dos teores de aflatoxinas não foi significativo, principalmente nos níveis de umidade mais elevados, indicando que temperaturas e umidade são fatores importantes no biossíntese de aflatoxinas

Controlled nucleation of topological defects in the stripe domain patterns of Lateral multilayers with Perpendicular Magnetic Anisotropy: competition between magnetostatic, exchange and misfit interactions

Magnetic lateral multilayers have been fabricated on weak perpendicular magnetic anisotropy amorphous Nd-Co films in order to perform a systematic study on the conditions for controlled nucleation of topological defects within their magnetic stripe domain pattern. A lateral thickness modulation of period $w$ is defined on the nanostructured samples that, in turn, induces a lateral modulation of both magnetic stripe domain periods $\lambda$ and average in-plane magnetization component $M_{inplane}$. Depending on lateral multilayer period and in-plane applied field, thin and thick regions switch independently during in-plane magnetization reversal and domain walls are created within the in-plane magnetization configuration coupled to variable angle grain boundaries and disclinations within the magnetic stripe domain patterns. This process is mainly driven by the competition between rotatable anisotropy (that couples the magnetic stripe pattern to in-plane magnetization) and in-plane shape anisotropy induced by the periodic thickness modulation. However, as the structural period $w$ becomes comparable to magnetic stripe period $\lambda$, the nucleation of topological defects at the interfaces between thin and thick regions is hindered by a size effect and stripe domains in the different thickness regions become strongly coupled.Comment: 10 pages, 7 figures, submitted to Physical Review

Proteção química e biológica de grãos de milho úmidos contra fungos de armazenagem e produção de aflatoxinas.

Grãos de milho da cultivar HD 9486, com 19,7% de umidade, foram tratados, imediatamente após a colheita, com soluções de extrato bruto de Eucalyptus citriodora (40%), essência de Eucalyptus citriodora (20%), ácido acético (5%), uréia (5%), cetato de sódio (5%), com os fungicidas benomyl (25g i.a.100kg-1 de grãos), thiabendazole (45g) e fludioxonil (3g); óleo de girassol, óleo mineral e com suspensão de 106 UFC.ml-1 de Sacharomyces cerevisiae. Aos grãos da testemunha foi adicionada água, obedecendo à mesma relação utilizada nos demais tratamentos (0,75% peso de grãos/volume do produto). A seguir, esses grãos foram armazenados em sistema com aeração contínua, constituído de tambores metálicos de 200 litros de capacidade, com fundo de tela de aço e sobre dutos de aeração, e em sistema sem aeração, constituído de tambores com fundo de metal, sobre estrados de madeira. O delineamento experimental foi o inteiramente casualizado, com 24 tratamentos (parcelas com 80kg de grãos), em três repetições. A eficiência dos produtos no controle de Aspergillus flavus e Penicillium spp. foi avaliada quantificando-se a porcentagem de grãos visualmente mofados, aos 17 dias de armazenagem. No sistema sem aeração, os fungicidas benomyl, thiabendazole e fludioxonil apresentaram controles desses fungos a níveis abaixo do limite de tolerância, que é de 3%. A testemunha apresentou 49,6% de grãos mofados. As médias da umidade e da temperatura intergranular foram de 15,5% e 35,5 oC, respectivamente. No sistema aerado, todos os tratamentos apresentaram baixo nível de mofamento dos grãos (1,2% na testemunha). Provavelmente, nesse período de armazenagem, a temperatura intergranular e a umidade dos grãos foram desfavoráveis ao desenvolvimento desses fungos. Nessa época, foram determinados os níveis (mg.kg-1 ou ppb) de aflatoxinas, sendo utilizado o métodos ELISA e cromatografia em camada delgada. Na condição aerada, os grãos de milho apresentaram os menores níveis de aflatoxinas e foram significativamente diferentes (P<0,05), quando comparados aos valores encontrados na condição não aerada. Na condição aerada, a maior eficiência na proteção dos grãos de milho em relação à biossíntese de aflatoxinas (2,1 mg.kg-1 de B1 + B2 + G1+G2) foi verificada no tratamento com thiabendazole. Do exposto, conclui-se que a aeração contínua e a proteção dos grãos com os fungicidas benomyl, thiabendazole e fludioxonil são eficientes contra o mofamento causado por Aspergillus flavus e Penicillium spp. e na redução da biossíntese de aflatoxinas

Cationic exchange in nanosized ZnFe2O4 spinel revealed by experimental and simulated near-edge absorption structure

The non-equilibrium cation site occupancy in nanosized zinc ferrites (6-13 nm) with different degree of inversion (0.2 to 0.4) was investigated using Fe and Zn K-edge x-ray absorption spectroscopy XANES and EXAFS, and magnetic measurements. The very good agreement between experimental and ab-initio calculations on the Zn K-edge XANES region clearly show the large Zn2+(A)--Zn2+[B] transference that takes place in addition to the well-identified Fe3+[B]--Fe3+(A) one, without altering the long-range structural order. XANES spectra features as a function of the spinel inversion were shown to depend on the configuration of the ligand shells surrounding the absorbing atom. This XANES approach provides a direct way to sense cationic inversion in these spinel compounds. We also demonstrated that a mechanical crystallization takes place on nanocrystalline spinel that causes an increase of both grain and magnetic sizes and, simultaneously, generates a significant augment of the inversion.Comment: 5 pages, 5 eps figures, uses revtex4, corrected table

Physiological changes in serum glucidic and nitrogenic analytes from captive Argentine authoctonous caimans

The purpose of this study was to establish reference intervals for serum glucidic and nitrogenic analytes from captive northeastern Argentinean caimans, as well as to detect physiological variations related to species, sex, age, feeding and season. Serum samples from 223 healthy sub–adults specimens of Caiman latirostris (n = 109) and Caiman yacare (n = 114), 50% each sex, were obtained. Values for glucose (4.18 ± 0.82 versus 4.01 ± 0.66 mmol/l), fructosamine (179 ± 33 versus 162 ± 29 umol/l), urea (1.11 ± 0.25 versus 1.06 ± 0.22 mmol/l), creatinine (56.1 ± 12.4 versus 52.5 ± 10.6 umol/l), and uric acid (127 ± 23 versus 156 ± 26 umol/l), were obtained by spectrophotometric methods for C. latirostris and C. yacare, respectively. Uric acid was significantly lower (p &lt; 0.05) in C. latirostris. Glucose and urea were higher in females from both species. Progress of age (increment of liveweight and dimensions) correlated with increases of all biochemical parameters, significantly for glucose. Values were lower in winter, except for uric acid. The feeding system used in a hatchery resulted in glucose, urea and creatinine values higher than those registered in zoo specimens. Data obtained are applicable for caiman nutritional control, as well as for the diagnosis and prevention of diseases

Interviews with farmers suggest negative direct and indirect effects of the invasive green iguana (Iguana iguana) on agriculture in Puerto Rico

Agricultural communities and crop production are negatively impacted by invasive species, with the effects of pathogenic fungi, parasitic insects and weedy plants being well studied. Mammals and birds are also recognized as impacting crops, but reptiles, such as non-native green iguanas (Iguana iguana), are typically not considered agricultural pests. Research on non-native green iguanas has largely focused on the lizard’s interactions with native species with little attention given to its impact in the agricultural landscape. We conducted semi-structured interviews with farmers from 20 farms in Puerto Rico to explore the effect of the invasive green iguana on the production of crops and how farmers manage impacts, if any. A total of 34 of 55 crop species reported by farmers were negatively affected by the green iguana. We found that green iguanas were absent from 20% of farms, did not consume crops in 10% of the farms and caused negative impacts in 70% of the remaining farms. Negative impacts included crop loss and infrastructural damage, which had behavioral, emotional, and economic effects on farmers. Specific outcomes of these effects were revenue loss, refurbishing costs, changes in crop selection, management costs and emotional stress. Farmers considered management strategies as mitigation measures that needed to be constant to produce any positive effects on crop yield. They reported use of mesh fencing, hunting, and domestic animals as attempts to reduce negative effects of green iguanas on crop production. Recognition of this species as an agricultural pest is warranted in Puerto Rico and perhaps elsewhere in its introduced range. Agricultural extension agents should consider providing guidance on strategies to reduce negative impacts of green iguanas including cultivating less susceptible crops when possible