SHELF-LIFE MODELING OF SWEETENED CONDENSED MILK BASED ON KINETICS OF MAILLARD BROWNING

Nonenzymatic browning and related changes were monitored in commercial sweetened condensed milk stored at 7, 15, 30, 45 and 55C. Darkening of the color measured in terms of absorbance (100 - reflectance percent) followed zero-order kinetics, the apparent activation energy (E_a) being 45.2 kJ/mol at 7–30C and 139.9 kJ/mol at > 30–55C. Hydroxy-methyl-furfural (HMF) showed a first-order increase, the associated E_a values being smaller than those for absorbance. The pH exhibited a linear decline after a small initial rise at 30C and below. As browning progressed, the coffee whitening ability of the product decreased along zero-order kinetics. The Q₁₀ values for these variables ranged from 1.21 to 1.84 for temperatures up to 30C and were nearly 2–3 times higher above 30C. The sensory color score was negatively correlated with absorbance. The linear regression of color score on absorbance and the temperature dependence of the latter as expressed by Arrhenius relationship were combined into a mathematical model which could be useful in predicting the product's shelf-life.     

Experimental determination of thermal conductivity of apple and potato at different moisture contents

Thermal conductivity of apple and potato samples was measured by means of a specifically designed apparatus based on Fitch's method. The thermal conductivity was determined at various moisture contents at the sample mean temperature of 30 °C. As expected the conductivity decreases with the decrease in moisture content. Thermal conductivity data were correlated with moisture content using a straight line.     

Accuracy of patient recall of opportunistic smoking cessation advice in general practice

OBJECTIVE: To determine the accuracy of patient recall of a question about smoking in a specified consultation in general practice; the accuracy of smokers' recall of advice to stop smoking; and predictors of accurate recall. DESIGN: Analysis of 1075 audiotapes was compared blind with matching patient questionnaires administered after the consultation to calculate sensitivity and specificity for patient recall as a dichotomous variable. Predictors of recall were determined by logistic regression. SETTING: General practitioner training practices, New South Wales, Australia. SUBJECTS: Thirty-four trainees and consecutive samples of their patients 16-65 years of age. RESULTS: Patient recall of a question about smoking had a high false positive rate of 21% but a sensitivity of 93%. Smokers over-reported advice to stop smoking (specificity 82%; sensitivity 92%). Predictors of accuracy of a question about smoking included patient sex (women 1.58 times more likely than men to be accurate); smoking status (smokers 1.7 times as likely as non-smokers to be accurate); and interval since consultation (those who completed their questionnaires within a week were 1.84 times more likely to be accurate). CONCLUSIONS: Patient recall is systematically biased towards over-reporting of a question about smoking status and, among smokers, of advice to quit. Although we recommend its continued application in health services evaluation, findings should be interpreted with caution, particularly if subjects are male or the interval between recall of smoking cessation advice and the occasion of service in which it might have occurred is considerably delayed.


     

Detecting delaminations in a composite beam using anti-optimization

The present study proposes a detection technique for delaminations in a laminated beam. The proposed technique optimizes the spatial distribution of harmonic excitation so as to magnify the difference in response between the delaminated and intact beam. The technique is evaluated by numerical simulation of two-layered aluminum beams. Effects of measurement and geometric noise are included in the analysis. A finite element model for a delaminated composite, based on a layer-wise laminated plate theory is used in conjunction with a step function to simulate delaminations     

Epstein-Barr virus recombinants from overlapping cosmid fragments

Five overlapping type 1 Epstein-Barr virus (EBV) DNA fragments constituting a complete replication- and transformation-competent genome were cloned into cosmids and transfected together into P3HR-1 cells, along with a plasmid encoding the Z immediate-early activator of EBV replication. P3HR-1 cells harbor a type 2 EBV which is unable to transform primary B lymphocytes because of a deletion of DNA encoding EBNA LP and EBNA 2, but the P3HR-1 EBV can provide replication functions in trans and can recombine with the transfected cosmids. EBV recombinants which have the type 1 EBNA LP and 2 genes from the transfected EcoRI-A cosmid DNA were selectively and clonally recovered by exploiting the unique ability of the recombinants to transform primary B lymphocytes into lymphoblastoid cell lines. PCR and immunoblot analyses for seven distinguishing markers of the type 1 transfected DNAs identified cell lines infected with EBV recombinants which had incorporated EBV DNA fragments beyond the transformation marker-rescuing EcoRI-A fragment. Approximately 10% of the transforming virus recombinants had markers mapping at 7, 46 to 52, 93 to 100, 108 to 110, 122, and 152 kbp from the 172-kbp transfected genome. These recombinants probably result from recombination among the transfected cosmid-cloned EBV DNA fragments. The one recombinant virus examined in detail by Southern blot analysis has all the polymorphisms characteristic of the transfected type 1 cosmid DNA and none characteristic of the type 2 P3HR-1 EBV DNA. This recombinant was wild type in primary B-lymphocyte infection, growth transformation, and lytic replication. Overall, the type 1 EBNA 3A gene was incorporated into 26% of the transformation marker-rescued recombinants, a frequency which was considerably higher than that observed in previous experiments with two-cosmid EBV DNA cotransfections into P3HR-1 cells (B. Tomkinson and E. Kieff, J. Virol. 66:780-789, 1992). Of the recombinants which had incorporated the marker-rescuing cosmid DNA fragment and the fragment encoding the type 1 EBNA 3A gene, most had incorporated markers from at least two other transfected cosmid DNA fragments, indicating a propensity for multiple homologous recombinations. The frequency of incorporation of the nonselected transfected type 1 EBNA 3C gene, which is near the end of two of the transfected cosmids, was 26% overall, versus 3% in previous experiments using transfections with two EBV DNA cosmids. In contrast, the frequency of incorporation of a 12-kb EBV DNA deletion which was near the end of two of the transfected cosmids was only 13%.(ABSTRACT TRUNCATED AT 400 WORDS)     

On the dynamics of the electric field induced breakdown in lipidmembranes

Electric field methods are powerful tools for cell characterization and manipulation. Important biotechnological applications, e.g., electrofusion of cells or electroinjection of macromolecules into living cells, rely on membrane breakdown. Despite the widespread use of these techniques, the process of membrane breakdown is poorly understood: a better understanding can be expected to lead to higher efficiencies. The present study used planar lipid bilayers in order to limit the number of experimental parameters. Membrane rupture was induced by careful application of short electric field pulses: measurement of the subsequent increase in membrane conductivity with time permitted the underlying mechanism to be characterized. The initial process of pore formation starts a few μs after the onset of the pulse, and the ensuing breakdown of the entire lipid membrane occurs within about a millisecond (pore widening velocity of a few cm/s). The kinetics of the pore-opening process could be influenced qualitatively by adding surfactants and lipid-attached macromolecules, respectively. Changing the effective mass per unit area of membrane, which could be brought about by using known percentages of lipids with covalently bound, hydrophilic polymers, allowed a model for the pore widening process to be quantitatively tested     

Setting the record straight.

Replies to comments by H. W. Marsh and L. A. Roche (see record 1997-43129-003) on the author's article (Educational Policy Analysis Archives, 1997) on student evaluation and academic freedom. The author expresses his dismay that Marsh and Roche misrepresented (not misinterpreted) the article without documenting their misrepresentation. A documented response to this undocumented misrepresentation is provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved)