Thermal energy storage in columns packed with crosslinked polyethylene tubes

An energy storage system based on solid-solid phase transition of crosslinked polyethylene was constructed and tested. The energy storage unit consisted of a column packed with crosslinked polyethylene tubes. The solid-solid phase transition enables heat transfer by direct contact between the form-stable polymer and the hot (cold) fluid. A theoretical model for the simulation of this system was developed. The heating-cooling characteristics of the energy storage system were simulated by the model, using measured thermodynamic properties of the crosslinked polyethylene. The potential of various crosslinked polyethylene materials for energy storage applications will depend on sufficient high-temperature stability.     

Alternative Modes of Addition of Electrophilic Olefins to the Vinylcyclopropane Systems in 2,2-Ethano-1-Methylene-1,2,3,4-Tetrahydronaphthalene and 1,1-Ethano-2-Methylene-1,2,3,4-Tetrahydronaphthalene

The title compounds 2,2-ethano-1-methylene and 1,1-ethano-2-methylene-1,2,3,4-tetrahydronaphthalene ( 13 and 14 respectively) were synthesized by the Wittig reaction from the corresponding ethano-tetralones ( 16 ) and ( 19 ) which were, in turn, prepared from the respective α- and β-tetralones ( 15 ) and ( 18 ). It is shown that the reaction of ( 13 ) with TCNE at 0° yields the corresponding [2 + 2] cycloaddition adduct ( 20 ), isomerizing thermally to the formal [2 + 5] cycloaddition adduct ( 21 ). Compound ( 13 ) reacts with N-tosylisocyanate (TIC) and with N-phenylsulfonylisocyanate (PSI) to a 4:1-isomeric mixture of (Z)- and (E)-acryloamides ( 24 ) and ( 26 ), respectively. The reaction of ( 14 ) with TCNE at 0° leads to the [2 + 5] cycloadduct ( 30 ), while with (TIC) and (PSI) the corresponding tricyclic adducts ( 28a ) and ( 28b ) result. Bromination of ( 16 ) with NBS yielded the respective 4-bromo-2,2-ethano-1-tetralone ( 31 ) which gave, upon dehydrobromination with the aid of DBU, the naphtho-dihydrofurane derivative ( 34 ). The latter was formed most likely via facile cyclopropylketone upon dihydrofurane rearrangement of an initially formed 2,2-ethano-1-oxo-1,2-dihydronaphthalene ( 32 ) which was desired for the formation of ( 33 ). Structures of all new compounds were assigned on basis of analytical and spectroscopic data (IR, UV, mass spectra, ¹H-NMR).     

Feeding Responses of Free-flying Honeybees to Secondary Compounds Mimicking Floral Nectars

The role of secondary compounds (SC) in deterring herbivores and pathogens from vegetative parts of plants is well established, whereas their role in plant reproductive organs such as floral nectar is unclear. The present study aimed to reveal the response of free-flying honeybees to naturally occurring concentrations of four SC in floral nectar. We selected nicotine, anabasine, caffeine, and amygdalin, all of which are found in nectar of various plants. In repeated paired-choice experiments, we offered 20% sucrose solution as control along with test solutions of 20% sucrose with various concentrations of the above SC. Except for anabasine, naturally occurring concentrations of SC did not have a deterring effect. Furthermore, low concentrations of nicotine and caffeine elicited a significant feeding preference. SC can, therefore, be regarded as postingestive stimulants to pollinators, indicating that the psychoactive alkaloids in nectar may be a part of their mutualistic reward. Further studies are needed to test our hypothesis that psychoactive alkaloids in nectar impose dependence or addiction effects on pollinators.     

The relation between limb dominance, acceptance of disability, and the phantom limb phenomenon.

Examined 2 hypotheses regarding the phantom limb sensation (PLS). One predicted that the frequency of PLS would be greater for the dominant than the nondominant limb. The 2nd hypothesized that there is an inverse relation between acceptance of the disability and frequency of PLS. 18 double-amputees who had lost 2 homologous limbs while in military service were administered questionnaires examining limb dominance, frequency of the PLS, and acceptance of disability. Results confirm only the 1st hypothesis. The PLS is discussed in light of the present findings, and it is concluded that the role of physiological factors seems to be clearer than that of psychological ones. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Water binding and irreversible dehydration processes in cellulose acetate membranes

The relative amounts of freezing and nonfreezing water in various water-wet cellulose acetate (CA) membranes were determined by NMR techniques, from the initial heights of the water component in the free induction decay (MNR intensity). The results suggest that (1) a significant fraction of the water in various wet CA membranes does not freeze, probably because of strong interaction with the polymer; (2) the relaxation times T₂ of the nonfreezing water are of the order of milliseconds indicating that they are still highly mobile compared with ice; (3) all the water contained in dense CA films or in membranes equilibrated at relative humidity of 0.93 does not freeze upon cooling the membranes from room temperature to ?60°C; (4) the amounts of nonfreezing bound water in membranes is higher than the total amount of water absorbed from liquid water by a dense film of the same polymer. However, the amounts of nonfreezing water in various CA membranes as calculated from the “relative NMR intensities” is substantially lower than those calculated from DSC melting endotherms by assuming the heat of fusion of water in membranes to be identical to that of pure water. Various possible reasons for this discrepancy are discussed. Measurements on the first desorption-adsorption cycle of wet CA membranes have also been performed. They suggest that during the first dehydration process, irreversible changes are induced in the structure of the membrane which result in a significantly lower accessibility of the polymer to interact with water. The extent of these irreversible changes in membrane structure is dependent on the details of the dehydration process being more pronounced at higher temperatures.     

An Industrial Software Engineering Retraining Course: Development Considerations and Lessons Learned

Israel Aircraft Industries has recently been conducting a novel six-month intensive course to retrain practicing engineers to become software engineers working on embedded computer systems. The first course was concluded in January 1982 and the second course began in November 1982. This paper describes the objectives, educational philosophy, course content, and practical experience of the first course. It also describes how the second course was modified as a result of the lessons learned from the successes and failures of the first course.     

Explicit stiffness matrices for non-prismatic members

Explicit terms for the stiffness matrices of several common non-prismatic members are derived. The stiffnesses are formulated from the flexibilities of the element. Fortran subroutines which generate the stiffness matrices for use with analysis programs are given. Comparison fo the values derived by the suggested formulation with known results is made. The formulation is highly recommended for small in-house computers which are short on memory.     

Magnetic resonance imaging (MRI) and relaxation spectrum analysis as methods to investigate swelling in whey protein gels

Effective means for controlled delivery of nutrients and nutraceuticals are needed. Whey protein-based gels, as a model system and as a potential delivery system, exhibit pH-dependent swelling when placed in aqueous solutions. Understanding the physics that govern gel swelling is thus important when designing gel-based delivery platforms. The extent of swelling over time was monitored gravimetrically. In addition to gravimetric measurements, magnetic resonance imaging (MRI) a real-time noninvasive imaging technique that quantified changes in geometry and water content of these gels was utilized. Heat-set whey protein gels were prepared at pH 7 and swelling was monitored in aqueous solutions with pH values of 2.5, 7, and 10. Changes in dimension over time, as characterized by the number of voxels in an image, were correlated to gravimetric measurements. Excellent correlations between mass uptake and volume change (R(2)= 0.99) were obtained for the gels in aqueous solutions at pH 7 and 10, but not for gels in the aqueous solution at pH 2.5. To provide insight into the mechanisms for water uptake, nuclear magnetic resonance (NMR) relaxation times were measured in independent experiments. The relaxation spectrum for the spin-spin relaxation time (T(2)) showed the presence of 3 proton pools for pH 7 and 10 trials and 4 proton pools for pH 2.5 trials. Results demonstrate that MRI and NMR relaxation measurements provided information about swelling in whey protein gels that can constitute a new means for investigating and developing effective delivery systems for foods.