Solar-Powered Adsorption Icemaker With Double-Stage Mass Recovery Cycle

The performance of an adsorption icemaker prototype operating in a double-stage mass recovery cycle was experimentally investigated under the generation temperature of 75°C. The prototype was heated in the regeneration phase by an electric heater, and an analytical model was employed to assess the daily number of cycles and the ice production, if evacuated tube solar collectors were used to supply the regeneration heat. It was found that the parasitic heat consumed by the metallic part of the reactor greatly reduced the coefficient of performance (COP) and ice production per unit area of solar collector. A reduction of the parasitic heat by 60% would increase the COP in 54%, and the daily ice production per unit area of solar collector in 50 to 54%, depending on the insolation. The performance of the studied prototype was inferior to the performance of some prototypes presented in the literature, which were directly heated by solar energy and used methanol as refrigerant, but this type of prototype could be an alternative to avoid subatmospheric working pressures and to provide ice on rainy and low insolation days, if waste heat or another heat source is available.     

Benzodioxoles as alternative coinitiators for radical polymerization in a model‐dental adhesive resin

This study evaluated the effectiveness of benzodioxole derivatives as coinitiators of radical polymerization in a model‐dental adhesive resin. To compose the adhesive resin, a monomer mixture based on 50 wt % of Bis‐GMA, 25 wt % of TEGDMA, and 25 wt % of HEMA was used. Camphorquinone (CQ) 1 mol % was used as a photoinitiator to initiate polymerization. 1,3‐Benzodioxole (BDO) and piperonyl alcohol (PA) were used as coinitiators at 0.25, 0.5, 1, 2, 4, 8, and 16 mol % level. In addition, tertiary amine, ethyl 4‐dimethylamino benzoate (EDAB) was used as coinitiator in the control group. Some physical, chemical, and mechanical properties of the polymer formed in the experimental adhesives were evaluated using the kinetics of polymerization, sorption and solubility, flexural strength, and elastic modulus tests. The results indicated that BDO and PA were effective coinitiators in the photoinitiator system based on CQ. Comparisons between the benzodioxoles derivative coinitiators and EDAB showed similar performance in the kinetics of polymerization and flexural strength. For water sorption and solubility evaluation, BDO and PA demonstrated significantly more sorption of water and less solubility than the EDAB control group. The findings suggest that BDO and PA were feasible alternatives to conventional amine as coinitiator. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Failure analysis of two sets of aircraft blades

This paper describes the methodology employed for the failure analysis of aircraft blades and its application to two premature failed sets. The first one corresponds to the high pressure compressor manufactured in a 718 nickel base superalloy. The failure analysis carried out on this blade points towards foreign object damage (FOD). The second set belongs to the high pressure turbine of another engine. Scanning electron microscopy attributes the first fail to the premature failure by a thermo-mechanical fatigue mechanism of one blade with an inadequate microstructure. The remaining blades of this set, which possess a correct microstructure, failed due to the impacts of the debris generated by the fracture of the first one.     

Far-Infrared Laser Stark Spectroscopy of CH3OD

The high resolution Stark spectra of the singly deuterated methanol isotope, CH₃OD, have been studied using the HCN laser with Stark fields up to approximately 60 000 V/cm. Numerous families of absorption lines have been observed in both parallel and perpendicular polarizations, resulting in the following assignments: with the 311 μm line – J _K = 18₁ ← 18₀ E ₂, υ _t = 1; and with the 337 μm line – J _k = 6₄ ← 5₃ E ₂, υ _t = 0 and J _K = 14₆ ← 13₅ A, υ _t = 1. Zero-field frequencies for the assigned transitions are in agreement with Fourier transform measurements and those calculated from the available molecular constants.     

Coexistence in a chemostat: Application of a threshold policy

A well known result in chemostat theory states that two populations of microorganisms which compete for a single limiting nutrient cannot coexist under the condition of a spatially uniform environment and time invariant external influences. In this same setting, altering the dilution rate by means of a threshold policy can revert competitive exclusion to species coexistence in a vicinity of a previously chosen concentration.     

Esthetic preference of the frontal and profile views of the same smile

This study has shown that orthodontists and their patients share a common pool of diffuse esthetic values of the same smile. Profile and frontal views of the same smile were not similarly rated for esthetic pleasantness: the profile views were rated higher than the frontal views of the same smile. This finding suggests that orthodontists should consider both frontal and lateral views during evaluation of their patient when planning and assessing orthodontic treatment. More research is needed to determine the generalizability of the finding that orthodontists and patients have similar facial esthetic preferences. Future studies should expand the range of smiles that are evaluated by including both genders, people of different ethnic backgrounds, and people of a variety of ages. Research is also needed to evaluate facial esthetics and smiles in dynamic motion.     

Low cost measurement system for broadcast power amplifiers

For the fast prototyping, production, and delivery of commercial radio frequency products/systems, accurate and reliable test systems are necessary. These systems are usually product customized and thus expensive solutions, capable of performing all necessary measurements for a specific product. The purpose of this paper is to present a flexible cost‐effective test solution, capable of realizing all necessary measurement on a high output power amplifier system greater than 500 W, and to generate essential reports. These reports allow the system operator to (i) perform an analysis and a statistical comparison among various products, assuring that the quality is the same for all products; and (ii) retain products that present a performance poorer than other similar products, without a rigorous technical analysis, thus increasing efficiency in factory assembly line. Copyright © 2013 John Wiley & Sons, Ltd.     

Post-receptoral mechanisms of colour vision in New World primates

Diurnal platyrrhines, both di- and trichromats, have magnocellular (M-) and parvocellular (P-) retinal ganglion cells which are morphologically very similar to those found in catarrhines. Catarrhine central P ganglion cells contact single midget bipolar cells, which contact single cones. Physiological recordings of retinal ganglion cells of dichromatic Cebus monkeys showed very similar cell properties to the catarrhine macaque, except that P ganglion cells lacked colour-opponency. We describe the presence of single-headed midget bipolar cells in the Cebus retina. These midget bipolar cells have axon terminal sizes in the same range as the dendritic tree sizes of P ganglion cells as far as 2 mm of retinal eccentricity. This result supports the view that, as in catarrhines, central P ganglion cells of platyrrhines receive input from single midget bipolar cells which in turn, receive input from single cones. This finding is consistent with the idea that a P pathway with one-to-one connectivity was present in the anthropoid ancestor before the divergence between catarrhines and platyrrhines.     

Morphology of P and M retinal ganglion cells of the bush baby

P/midget ganglion cells mediate red-green color opponency in anthropoids. It has been proposed that these cells evolved as a specialization to subserve color vision in primates. If that is correct, they must have evolved about the same time as the long-wavelength ('red') and medium-wavelength ('green') pigment genes diverged, thirty million years ago. Strepsirhines are another group of primates that diverged from the ancestor of the anthropoids at least 55 million years ago. If P/midget ganglion cells evolved to subserve color vision, they should be absent in strepsirhines. We tested this hypothesis in a nocturnal strepsirhine, the greater bush baby Otolemur. The retinal ganglion cells were labeled with the lipophilic tracer Dil and the results show that bush babies have P/midget and M/parasol cells similar to those found in the peripheral retinas of anthropoids. A number of studies have shown that the P and M pathways of bush babies share many similarities with those of anthropoids, and our results show that the same is true for their retinal ganglion cells. These results support the hypothesis that the P system evolved prior to the emergence of red-green color opponency.