Minimal complete sets of words

A characterization of minimal complete sets of words of a free monoid which are codes, is given.     

Balance between nutrients and anti-nutrients in nine Italian potato cultivars

Nine commercial potato cultivars have been analyzed in order to detect differences in nutritional quality, considering the balance between nutrients and anti-nutrient compounds present in each. The most important nutrients studied in this paper were: water, starch, free sugars, such as glucose, fructose and sucrose, malic acid, citric acid, ascorbic acid and chlorogenic acid. The anti-nutrients measured included α-solanine, α-chaconine and asparagine. This last compound was added to the anti-nutrient compounds because it is involved in the formation of acrylamide during thermal food processes. From this study, by considering the nutritional quality of each cultivar, we can divide the potato cultivars into three groups, each being suitable for a different technological processes.     

Simultaneous mass spectrometric measurement of prostaglandins E1 (PGE1) and PGE2 with a deuterated internal standard

The use of (3,3,4,4-²H₄)PGE₂ as internal standard for the quantitative measurement of PGE₁ by gas chromatography-mass spectrometry is reported. A method for the simultaneous analysis of PGE₁ and PGE₂ is also described. The prostaglandins were analyzed by selected ion monitoring as the methyl ester-trimethylsilyl ether (ME-TMS) derivatives of PGB₁ and PGB₂, respectively. In all cases, a linear response over the range 1 to 70 ng (2.8 to 198 pmoles) was demonstrated. The use of this procedure is exemplified by its application to the PG analysis of sheep seminal vesicles. Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may also be suitable.     

Co-metabolism of citrate and maltose byLactobacillus brevis subsp.lindneri CB1 citrate-negative strain: effect on growth,end-products and sourdough fermentation

Growth, substrates and end-product formation of the maltose and citrate co-metabolization byLactobacillus brevis subsp.lindneri CB1 citrate-negative strain were initially studied in synthetic medium. Compared to maltose (19 g/l) fermentation, the co-metabolization of maltose (10 g/l) plus citrate (9 g/l) caused faster cell growth, increased the concentrations of lactic acid and especially of acetic acid (from 0.7 g/l to 2.9 g/l), produced succinic acid (0.5 g/l) and reduced ethanol synthesis. Highest activities of acetate kinase, the same of lactate dehydrogenase and a reduced alcohol dehydrogenase activity were detected in cytoplasmic extracts of cells growing on maltose plus citrate. The breakdown of citrate depended upon the continuous presence of maltose in the growth medium. Upon depletion of citrate, the cells continued through the normal maltose fermentation, having a diauxic metabolic curve as shown by impedance measurements. Concentrations of citrate from 3 g/l to 15 g/l led to increases of acetic acid from 1.25 g/l to 5.55 g/l. Since maltose was naturally present during sourdough fermentation, the addition of 9 g citrate per kg wheat dough enabled the co-metabolization of maltose and citrate byL. brevis subsp.lindneri CB1. Compared with traditional sourdough fermentation, faster cell growth, a higher acetic acid concentration and a reduced quotient of fermentation were obtained by co-metabolism.     

On some properties of very pure codes

Some results on synchronization and maximality of very pure codes are given.     

Structure and ion dynamics in AgI : Ag2B4O7 vitreous electrolytes

Compounds of the system (AgI)_x(Ag₂B₄O₇)_1?x can be thought of as a network made by an equal number of BO₃ and BO₄ groups containing silver iodide polyhedra. Partially crystalline compounds are obtained when the AgI molar fraction, x, is more than two times the Ag₂B₄O₇ fraction. For the same iodine concentration, the ionic conductivities of the AgI : Ag₂B₄O₇ glasses are comparable with those of other AgI : Ag-oxysalt glasses. However, their glass transition temperatures are substantially higher. With increasing silver iodine content, the physical properties which have been investigated approach smoothly the corresponding values expected for α-AgI. However, it is shown that Ag⁺ within the iodide polyhedra is not the unique current carrier and that a wide distribution of barrier heights exists in these glasses.     

Ultrahigh molecular weight polyethylene as used in articular prostheses (a molecular weight distribution study)

Currently there is widespread use of ultrahigh molecular weight polyethylene (UHMWPE) acetabular components in total joint replacement prostheses. What has been most surprising about the wear of UHMWPE under such circumstances is the occurrence of brittle fracture. Such fracture had not been observed in the usual engineering tests done in the laboratory on UHMWPE. It was only when prosthese which had been removed from patients were examined or run in hip joint simulators with serum or synovial fluid as the lubricant, that brittle fracture was encountered. The problem of environment-enhanced brittle fracture in plastics dates back to 1946. Interestingly, the phenomenon was first described in polyethylene. The prime variables involved are polymer molecular weight, sensitizing environment, stress filed, and temperature. Other things being equal, brittle behavior in polyethylene is extremely sensitive to the amount of low molecular weight polymer present. In the light of the foregoing we have studied the molecular weight distribution in six commercially available UHMWPE components. These were obtained from six different manufacturers. The specimens were characterized both on their bearing (wear) surfaces and in their interior bulk. The results obtained indicate that:

• 1 The UHMWPE components contain substantial amounts of low molecular weight polymer.
• 2 The UHMWPE components differ significantly in molecular weight distribution.
• 3 The UHMWPE components contain substantial amounts of crosslinked polymer.