Stability of the Mokohydrate Crystal form of Cefazolin Sodium as a Function of Moisture

Moisture effects on the stability of the monohydrate crystal form of cefazolin sodium were investigated. Results show that increased moisture content of this compound adversely affects the microbiological and polarographic stability at elevated temperatures. In addition, butyl rubber stoppers provided more protection against moisture than natural rubber stoppers at higher humidity conditions.     

Specific associative unlearning in the AB-CD paradigm.

Since previous experiments have yielded conflicting results as to whether or not specific associative unlearning occurs in the different stimuli-different responses (AB-CD) paradigm, 2 experiments were directed at this problem. In Exp. I, with 96 undergraduates who were naive to verbal learning experiments, the response-form class of AB-CD lists was varied; no evidence of associative unlearning was found in any condition. In Exp. II, with 100 Ss, significant unlearning was found with similar and identical stimuli in both lists, but not when nonsense syllables and numbers were used as stimuli in successive lists, or when minimally related nonsense syllables were used as stimulus terms in the 2 lists. J. B. McGovern's (see record 2011-18733-001) analysis of unlearning was supported. (French summary) (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

A Material Handling System Selection Model

A technique is presented which can be used to design, or assist in the design of, an integrated materials handling system for a manufacturing facility or a major department of the facility. The developed procedure selects the materials handling equipment to be used to perform a given set of moves in order to miriimize the system's costs associated with the handling, assuming the plant arrangement remains fixed. To demonstrate the selection procedure, an example problem is presented. Since the method is heuristic, no claim of optimality is made.     

Gel in polyethylene

A quantitative test for the presence of gel (insoluble polymer) in polyethylene is described. A number of experiments were performed by using the test and on the polymers separated by the test. It is concluded that gel is crosslinked polyethylene in the form of discrete particles of significant size, the large ones, probably weighing up to at least 10 mg. Some crosslinks are broken by treatment with solvents above 200°C., and much of the gel is thus rendered permanently soluble. Gel is also insoluble in the reaction medium in which it is produced. Thus, even if the ethylene–polyethylene phase relationships would predict a homogeneous reaction, the reaction must be hetero-geneous if gel is present. Therefore, kinetic treatments of ethylene polymerization which do not consider phase separation when gel is found in the reaction product are oversimplified.     

Pore size analysis of fallow deer (<Emphasis Type="Italic">Dama dama</Emphasis>) antler bone

Deer antler is of interest to material scientists because it represents bone which can withstand applied stresses of over 300 MPa. In this work we demonstrate the presence of nanopores in this material by nuclear magnetic resonance (NMR) spectroscopy, and gas adsorption and mercury intrusion experiments. It is also shown that organic material in the antler influences observed pore sizes. Different modal groups of pores were observed when organic lipid material was removed from the sample and the sample saturated with water. The dominant organic phase associated with the small pores is protein.     

Lithographically fabricated nanopore-based electrodes for electrochemistry

We report a new technique for fabricating electrodes for electrochemical applications with lateral dimensions in the range 15-200 nm and a reproducible, well-defined geometry. This technique allows determining the electrode size by electron microscopy prior to electrochemical measurements and without contamination of the metal electrode. We measured the diffusion-limited current with stepped-current voltammetry and showed that its dependence on electrode size can be quantitatively understood if the known geometry of the electrodes is explicitly taken into account.     

Acousto-optic tunable filter sidelobe analysis and reduction with telecentric confocal optics

The acousto-optic tunable filter (AOTF) has optical sidelobes that are due to the acoustic field produced by the transducer. These sidelobes were analyzed by wave-vector phase matching between the optical and acoustic fields, which correlated with measurements made with a TeO2 AOTF. A white-light point source was filtered and imaged, showing reasonably large and slowly decreasing sidelobes covering a large spectral range. This effect reduces the image quality of an AOTF system by producing faint secondary images of bright objects. The image quality can be improved with a telecentric confocal optical arrangement in which the angular shift of the sidelobes is greatly reduced, producing a much sharper image. This effect was also demonstrated experimentally with the point source.     

Aligned carbon nanotube stacks by water-assisted selective etching

Well-aligned, high-purity carbon nanotube (CNT) stacks of up to 10 layers fabricated in one batch process have been formed by water-assisted selective etching of carbon atoms. Etching takes place at the CNT caps as well as at the interface between CNTs and metal catalyst particles. This simple process generates high-purity CNTs and opens the CNT ends by removing the nanotube caps. High-resolution transmission electron microscopy indicates that the process does not damage CNT wall structures. A mechanism for stacked growth of CNT layers is proposed.