Semiclassical Tunneling of Wavepackets with Real Trajectories

Semiclassical approximations for tunneling processes usually involve complex trajectories or complex times. In this paper we use a previously derived approximation involving only real trajectories propagating in real time to describe the scattering of a Gaussian wavepacket by a finite square potential barrier. We show that the approximation describes both tunneling and interferences very accurately in the limit of small Plank's constant. We use these results to estimate the tunneling time of the wavepacket and find that, for high energies, the barrier slows down the wavepacket but that it speeds it up at energies comparable to the barrier height.Comment: 23 pages, 7 figures Revised text and figure

Viabilidade do pólen de Eucalyptus benthamii Maiden et. Cambage.

Resumo

Penetrability of chloride ions in concrete protected by an acrylic painting

In order do decrease the penetrability of chloride ions in concrete the use of paintings based on polymers can be a good solution. The use of acrylic paintings is recommended because they have good resistance to ultraviolet radiation. It is important to quantify the decrease of chloride ions penetrability obtained by the use of this kind of paintings. The durability of the polymeric paintings is another aspect that needs to be analysed. In this study an acrylic painting was used to protect the concrete and decrease the penetrability of chloride ions. The concrete used was a C12/15, with a cement content of 280 kg/m3 and a water-cement ratio of 0.60. The acrylic painting was applied in concrete specimens 28 days after casting. In order to have a better protection we applied two coats separated by 5 hours. The penetrability of chloride ions was measured following the ASTM standard C 1202 – 94. Before the penetrability tests, some specimens were exposed to UV radiation. The exposition to the light occurred by cycles consisting of alternating periods of 8 hours of UV radiation at 60 ºC and 16 hours without UV radiation at 50 ºC. Three kinds of exposition were made consisting on 5, 10 and 15 cycles. The results showed always a high penetrability of chloride ions. This occurred because a poor concrete was used. The protection by an acrylic painting decreases the penetrability of chloride ions. The charge passed decreased about 32 %. However, is not possible to achieve low chloride ions penetrability only with the use of acrylic paintings. It is necessary also the use of a good concrete with low porosity. After the exposition to the UV radiation the penetrability of chlorides ions did not increase. It seems that the UV radiation does not affect the properties of the acrylic painting

Turing Patterns And Apparent Competition In Predator-prey Food Webs On Networks.

Reaction-diffusion systems may lead to the formation of steady-state heterogeneous spatial patterns, known as Turing patterns. Their mathematical formulation is important for the study of pattern formation in general and plays central roles in many fields of biology, such as ecology and morphogenesis. Here we show that Turing patterns may have a decisive role in shaping the abundance distribution of predators and prey living in patchy landscapes. We extend the original model proposed by Nakao and Mikhailov [Nat. Phys. 6, 544 (2010)] by considering food chains with several interacting pairs of prey and predators distributed on a scale-free network of patches. We identify patterns of species distribution displaying high degrees of apparent competition driven by Turing instabilities. Our results provide further indication that differences in abundance distribution among patches can be generated dynamically by self organized Turing patterns and not only by intrinsic environmental heterogeneity.8605620

Semiclassical coherent state propagator for systems with spin

We derive the semiclassical limit of the coherent state propagator for systems with two degrees of freedom of which one degree of freedom is canonical and the other a spin. Systems in this category include those involving spin-orbit interactions and the Jaynes-Cummings model in which a single electromagnetic mode interacts with many independent two-level atoms. We construct a path integral representation for the propagator of such systems and derive its semiclassical limit. As special cases we consider separable systems, the limit of very large spins and the case of spin 1/2.Comment: 19 pages, no figure

Variação de procedências para a produção de sementes de Araucaria angustifolia Bert. O. Ktze.

Resumo

Comparison of two rapid descriptive sensory techniques for profiling and screening of drivers of liking of sorghum breads.

Rapid descriptive methods have emerged as a relatively simple alternative for screening the sensory attributes of products that drive their liking, and may contribute to identify sorghum genotypes with potential for development of gluten-free breads with higher consumer acceptance. Two rapid techniques, Check-All-That-Apply (CATA) and Optimized Descriptive Profile (ODP), were herein compared on their ability to describe, discriminate and identify the drivers of liking of sorghum breads. Gluten-free bread formulations were developed using flours from selected sorghum genotypes (CMSS005, BR 501, BRS 332, BRS 330, BRS 305 and 1167048), besides commercial sorghum and rice flours. A semi-trained panel (n = 18) evaluated the samples using the ODP method, whereas consumers (n = 124) completed the CATA questionnaire and rated the liking in a 9-point hedonic scale. A total of 24 and 11 sensory descriptors were perceived by assessors as different among samples for CATA and ODP, respectively, with color and appearance-related attributes critical to discriminate samples in CATA, whereas flavor and texture descriptors had also prominent contribution in ODP. A similar pattern of sample distribution was noticed for both methods, which were shown to be highly and positively correlated (RV = 0.92, p < 0.002). Genotypes influenced the consumer perception of sorghum breads, being the BRS 332 and the CMSS005 breads among the most and the least accepted samples for either consumer segment, respectively. While 10 drivers of liking were identified by CATA, including ?appearance of whole flour breads?, ?uniform alveoli?, ?neutral flavor? and ?soft aroma?, in ODP 'crumb color', 'crust color', 'spots' and traditional bread aroma? drove bread acceptance. In summary, both methods were successfully applied and provided similar pattern of sample discrimination, whereas the attributes used for sample characterization, as well as those identified as drivers of liking were generally different. The ODP offers a simpler option for a quantitative perspective, while CATA remains as an easy method considering qualitative aspects, being clearly faster than ODP

Zoneamento de Pinus maximinoi para o estado do Paraná.

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