Thermal patterns in simple models of cylindrical reactors

The propagation of fronts and the emergence of spatiotemporal patterns on a cylindrically shaped thin catalytic reactor is simulated with a homogeneous model of a fixed catalytic bed, with characteristically large Lewis and Peclet numbers, and a first-order Arrhenius kinetics (i.e., thermokinetic model) which may be coupled with slow changes of catalytic activity (i.e., oscillatory kinetics). Planar fronts of the thermokinetic model may undergo symmetry breaking in the transversal direction only at relatively low Lewis number, but for high Le the front remains flat. Patterns due to oscillatory kinetics in reactors of high Le are shown, for the first time, to undergo symmetry breaking in the azimuthal direction when the perimeter is sufficiently large. The generic regular patterns simulated then are rotating multi-wave patterns of constant rotation-speed and oscillatory-‘firing’ ones, and theirs selection is highly sensitive to governing parameters and initial conditions. The results are organized in bifurcation diagrams showing the coexisting two-dimensional solutions with varying perimeter. Increasing convective velocity or reactor radius leads to symmetry breaking of regular patterns and the system may switch to chaos.     

Memory for context and its use in item memory: Comparisons of younger and older persons.

This study compared memory for words and the font in which they appeared (or the voice speaking them) in young and old participants, to explore whether age-related differences in episodic word memory are due to age-related differences in memory for perceptual–contextual information. In each of 3 experiments, young and older participants were presented with words to learn. The words were presented in either 1 of 2 font types, or in 1 of 2 male voices, and participants paid attention either to the fonts or voices or to the meaning of the words. Participants were then tested on both word and font or voice memory. Results showed that younger participants had better explicit memory for font and voice memory and for the words themselves but that older participants benefited at least as much as younger people when perceptual characteristics of the words were reinstated. There was no evidence of an age-related impairment in the encoding of perceptual–contextual information. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Adult age differences in episodic memory: Further support for an associative-deficit hypothesis.

This study further tested an associative-deficit hypothesis (ADH; M. Naveh-Benjamin, 2000), which attributes a substantial part of older adults' deficient episodic memory performance to their difficulty in merging unrelated attributes-units of an episode into a cohesive unit. First, the results of 2 experiments replicate those observed by M. Naveh-Benjamin (2000) showing that older adults are particularly deficient in memory tests requiring associations. Second, the results extend the type of stimuli (pictures) under which older adults show this associative deficit. Third, the results support an ADH in that older adults show less of an associative deficit when the components of the episodes used are already connected in memory, thereby facilitating their encoding and retrieval. Finally, a group of younger adults who encoded the information under divided-attention conditions did not show this associative deficit. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of flow-reversal, internal-recirculation and loop reactors

In this work, we compare the performance of flow-reversal, internal-recirculation and loop reactors. In the absence of analytical results we use asymptotic, approximate and simulated solutions and present some experimental results. As criteria for comparison we use the maximal temperature achieved and the robustness of solution.Experiments and simulations of ethylene oxidation in the flow-reversal and internal-recirculation reactor, showed that the technically simpler inner-outer internal-recycle reactor may operate better at low flow rates than that with flow reversal, but the conclusion is reversed at high flow rates. Using approximate solutions, we show the dependence of the maximal temperature on the inner-outer heat-transfer coefficient.Loop reactor can generate rotating pulse solution: we simulate such solutions for two asymptotic cases where the ratio of switching velocity (i.e., unit length/switching time) to pattern velocity is either around unity or very large. We compare them with solutions of 4-8 units reactors. The slow-switching regimes require a delicate control. The fast-switching solution is robust but its peak temperature depends on the kinetic parameters and reactor length, compared with that of the flow-reversal reactor where it depends mainly on bed conductivity.     

Dynamic stiffness analysis of laminated beams using a first order shear deformation theory

In this paper the exact vibration frequencies of generally laminated beams are found using a new method, including the effect of rotary inertia and shear deformations. The effect of shear in laminated beams is more significant than in homogenous beams, due to the fact that the ratio of extensional stiffness to the transverse shear stiffness is high. The exact dynamic stiffness matrix is derived, and then any set of boundary conditions including elastic connections, and assembly of members, can be solved as in the classical direct stiffness method for framed structures. The natural frequencies of vibration of a structure are those values of frequency that cause the dynamic stiffness matrix to become singular, and one can find as many frequencies as needed from the same matrix. In the paper several examples are given, and compared with results from the literature.     

Pairing Symmetry,Spin Gap,and More in HTSC Cuprates

This work is based on the double correlated linear aggregations of holes in checkerboard geometry. It is proved that the pairing function symmetry is ?d _{x2 ? y2}, as been observed experimentally. It is also shown that there is a “superconductive spin gap” for the observation of the magnetic incommensurate modulation peaks, in agreement with the experiment. In addition, the unperturbed Hamiltonian and its related propagator are reanalyzed and modified.     

Interpersonal and Print Nutrition Communication for a Spanish-Dominant Latino Population: Secretos de la Buena Vida.

Participants (N = 357) were randomly assigned to 1 of 3 conditions: lay health advisor (promotora) plus tailored print materials, tailored print materials only (tailored), or off-the-shelf print materials (control). The primary outcomes were calories from fat and daily grams of fiber. Secondary outcomes included total energy intake, total and saturated fat intake, and total carbohydrates. Adjusted for baseline values, calories from fat were 29%, 30%, and 30% for the promotora, tailored, and control conditions, respectively, and grams of fiber consumed were 16 g, 17 g, and 16 g. Significant Condition X Time interactions were not observed between baseline and 12-weeks postintervention. The LHA condition achieved significantly lower levels of energy intake, total fat and saturated fat, and total carbohydrates. The relative superiority of the promotora condition may derive from the personal touch achieved in the face-to-face interactions or from the women's use of print materials under the promotora's guidance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

New aspects of malaria imported from Ethiopia

We describe a high incidence of Plasmodium vivax malaria among travelers returning from Ethiopia, who all took the recommended prophylaxis. Three groups of 7-11 nonimmune travelers received mefloquine (250 mg weekly), beginning 1-2 weeks prior to departure and continuing for 4 weeks after their return. A fourth group mistakenly took inadequate prophylaxis and is presented for comparison. Vivax malaria occurred at a rate of up to 50% in the first three groups; nearly all patients became ill 3 months after exposure. In the fourth group, primary attacks of both falciparum and vivax malaria occurred within 1 month of return, at an incidence of 50%. The use of mefloquine prevented Plasmodium falciparum infection, but a very high rate of relapses of P. vivax infection occurred. The complexity of prophylaxis for malaria in an area with a high rate of both P. falciparum and P. vivax infections and the urgent need for effective causal prophylaxis are discussed.     

Cutting-tool management in computer-integrated manufacturing

The problem of cutting tool management has been brought to the forefront with the emergence of computer-integrated manufacturing (CIM) and, in particular, flexible manufacturing systems (FMSs). The financial and operational ramifications of effective tool management has spurred considerable research in this area during the past decade and many researchers are proposing sound solutions to various facets of this broad-ranging and difficult problem. This paper identifies critical areas of research for the development of tool management systems in CIM. To develop a framework for this, the paper examines and categorizes work in academia and in industry on the management of cutting-tools in CIM and describes some key implementations, particularly in the metal-cutting industry. The solution of manufacturing problems generally demands an eclectic approach, and for this reason, we have tried to taxonomize, describe, and critique the various research thrusts in an attempt to provide a synthesis of use in more unified approaches.