Improved Complexometric Determination of Calcium in Cheese

Accuracy and repeatability of complexometric methods for measuring calcium in cheese are limited by titration endpoints that are difficult to recognize. Much of this difficulty results from turbidity during titration. An alternative procedure is described in which 2 to 3 g of cheese are ashed, dissolved in dilute acid, and added calcium chloride is back titrated with ethylenediaminetetraacetic acid using hydroxy naphthol blue as indicator. Samples remain free of turbidity, and the titration endpoint is recognized easily.Recovery of calcium from solutions containing magnesium and phosphate was 100.9 ± .3%, indicating that a portion of sample magnesium (about 12%) also was measured. Error caused by magnesium recovery represented less than 1% of true calcium content.Analyses of 10 Cheddar cheese samples by the proposed method and by atomic emission differed by an average of .010% calcium. Mean values of the 10 samples did not differ significantly (P>.05) between methods. Duplicate analyses of 67 Cheddar cheese samples differed by an average of .008 ± .006% calcium. Similar repeatability was achieved by several inexperienced analysts. The method is applied readily to other dairy products.     

Gas Flow in a Plane Channel with Oscillating Walls

Gas oscillations occurring in a plane channel in excitation of elastic walls which is symmetric relative to the longitudinal axis are investigated by the methods of numerical modeling. The spatial localization of transverse and longitudinal waves has been revealed and the character of resonance oscillations of the gas in the vicinity of the excitation region for different velocities of the flow has been established.     

IBM's Linux watch, the challenge of miniaturization

Nearly four years in development, the IBM Linux watch contains a complete computer system that runs Linux, displays X11 graphics, and has wireless connectivity. The system fits in a case that could pass as a slightly unusual analog timepiece with a somewhat odd shape and an extraordinarily brilliant face. The developers have created two versions of the watch, one with an organic light-emitting diode display and the other with a liquid crystal display. Still considered a research prototype, the watch already runs some personal information management applications, and it can communicate with PCs, PDAs, and other wireless-enabled devices, viewing condensed e-mail and directly receiving pager-like messages. Eventually, users will be able to access various Internet-based services, such as up-to-the-minute information about weather, traffic conditions, the stock market, and sports     

Methods of Step-by-Step Modeling of Random Events

Calculation relations were obtained and step-by-step procedures were developed in order to model failures of given multiplicities in system elements and random sojourns of the semi-Markovian process in various states, as well as to construct variational series. These procedures can be used to design simulation systems of various destinations.     

Performance antecedents of voluntary and involuntary managerial turnover.

Examined the job performance of 420 credit managers (mean age at hiring 25 yrs) from a large finance company who either quit their job, were fired, or were promoted to a higher position in the company. Six biographical variables and 12 performance appraisal scores accumulated from data in employee files were used in a cross-validated multiple discriminant analysis to predict membership in the 3 classification groups. Results reveal a systematic relation between the performance appraisal variables and the classification groups: The performance of promoted Ss was significantly superior to that of Ss who quit, which in turn was significantly superior to the performance of the fired Ss. 18 discriminating variables accounted for a 46.7% hit rate in group membership. Findings are discussed in the context of research on performance antecedents of voluntary and involuntary turnover, as well as the feedback properties of performance appraisal information. It is suggested that no single performance–turnover relation exists. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

p,V, T and derived thermodynamic data for toluene,trichloromethane, dichloromethane,acetonitrile, aniline,and n-dodecane

Experimentally determined p,V,T data are reported for toluene, trichloromethane, dichloromethane, acetonitrile, aniline, and n-dodecane at 278, 288, 298, 313, and 323 K, except for dichloromethane, for which the highest temperature was 298 K. At each temperature, measurements were done at pressures up to about 280 MPa or (for aniline and n-dodecane) at a lower pressure slightly below the freezing pressure at the temperature of measurement. Values of the isobaric expansivity isothermal compressibility and (for toluene, trichloromethane, dichloromethane, and acetonitrile) internal pressure, derived from the p,V,T data, are presented.     

Towards the automatic generation of software diagrams

The authors formulate the criteria for drawing dataflow diagrams and describe the placement and routing algorithms used in a system called MONDRIAN. A generalized approach to the question of software diagrams is proposed based on the authors' experience with MONDRIAN and a metasystem approach to the creation of CASE (computer-aided software engineering) environments. A formal approach to the definition of software objects and their graphical representation is given. The use of location constraints as a basis for generalized layout algorithms is discussed     

Gamma sensitivity of ionization chambers

Translated from Atomnaya Énergiya, Vol. 66, No. 6, pp. 421–423, June, 1989.