EFFECT OF ELECTRICAL STIMULATION ON KILLING SALMONELLA TYPHIMURIUM IN VARIOUS SALT SOLUTIONS

Electrical stimulation was evaluated as a method to kill Salmonella typhimurium in various salt solutions at different concentration . Salmonella typhimurium at 2 × 10⁵ CFU/ml was treated at 22–24C for 60 min in each salt solution using electricity at 10 mA/cm² current, 1 kHz frequency, and 50% duty cycle. Samples taken at various times were serially diluted, plated on tryptic soy agar and xylose lysine desoxycholate agar, and incubated at 37C for 18–24 h. To detect injured cells, samples were also pre-enriched in buffered peptone water at 37C for 4–5h before being plated. Results indicated all salmonellae were electrically killed at 5 min in NaCl, at 30 min in NaNO₃, and at 45 min in NaC₂H₃O₂ at 0.15 and 0.015 M concentrations. Salmonellae were also killed at 45 min in Na₃PO₄ and at 60 min in Na₂CO₃ at 0.0015 M concentration by electricity in combination with high pH .     

ULTRASONICALLY ASSISTED EXTRACTION OF PHENOLIC COMPOUNDS FROM AROMATIC PLANTS: COMPARISON WITH CONVENTIONAL EXTRACTION TECHNICS

Extracts of aromatic plants contain bioactive substances such as phenolic compounds, which could be used as natural antioxidants. Conventional, as well as ultrasonically assisted extractions (UAEs ) of phenolic compounds from aromatic plants using different solvents, have been studied. Reversed phase high performance liquid chromatography (RP‐HPLC ) with ultraviolet detection was employed for the analysis of phenolic compounds. Total phenolic compounds were determined by the Folin–Ciocalteu assay. The amount of extractable phenolic substances for this method decreased with decreasing polarity of the solvent in the order water, 60% methanol, 60% acetone, and ethyl acetate/water (60:30, v/v). The HPLC results indicate that UAE is a more effective technic compared to the conventional method but was dependent on the solvent and the temperature employed. Increasing the temperature of sonication, the efficiency of extraction of phenolic compounds for all solvents is enhanced. However, water extraction was found to give reduced amounts of phenolic compounds when compared with the conventional method.     

ADAPTIVE CONTROL OF A HEAT EXCHANGER USING FUNCTION BLOCKS

Many adaptive control strategies require on-line identification, which implies that a digital computer is needed for implementation. The objective of the work presented in this paper is to demonstrate that adaptive process control can be accomplished by combining relatively simple digital control algorithms called function blocks. These function blocks are easily implemented in low-level microprocessor-based digital controllers without requiring a computer. The feasibility of these methods is illustrated through an industrial heat exchanger control example, and the performance benefits of this adaptive approach are illustrated by means of simulation results.     

Meter as Mechanism: A Neural Network Model that Learns Metrical Patterns

One kind of prosodic structure that apparently underlies both music and some examples of speech production is meter. Yet detailed measurements of the timing of both music and speech show that the nested periodicities that define metrical structure can be quite noisy in time. What kind of system could produce or perceive such variable metrical timing patterns? And what would it take to be able to store and reproduce particular metrical patterns from long-term memory? We have developed a network of coupled oscillators that both produces and perceives patterns of pulses that conform to particular meters. In addition, beginning with an initial state with no biases, it can learn to prefer the particular meter that it has been previously exposed to.     

A Text Creation Routine for Graphics on a Microcomputer

Placing text on the graphics screen in any size any angle is an important function of a graphics program. Some microcomputers, however, will not print characters on the graphics screen, and others have very limited ability, such as printing only in 40-character or 80-character mode. Characters are needed for dimensions and notes on the drawing as well as for prompts and messages. Alternate fonts, rotation of the text, and different sizes of text are needed for many applications, not to mention text that is scaled up and down as the user zooms in or out to magnify or reduce the size of the image. This article examines available techniques and discusses the advantages and disadvantages of each. A method is presented for producing stroke generated text by designing each character as a matrix of dots on a standard grid and storing the coordinates of the dots as endpoints of vectors to be used to draw the character. The standard grid is assumed to have its origin in the lower left corner and each coordinate is defined relative to that origin.     

MEASUREMENT OF FLUID FOOD VISCOSITY USING MICROFABRICATED RADIO FREQUENCY COILS

We report on the use and applicability of microfabricated radio frequency (r.f.) coils for viscosity measurements of fluid foods. The viscosity of fluid milk and milklike products was measured using nuclear magnetic resonance imaging based on microfabricated r.f. coils coupled to in‐line tubing with an inner diameter of 1.4 × 10^‐3 m. The fluid's apparent viscosity ranged from 0.002 to 0.08 Pa·s. The magnetic resonance‐based measurements were limited in shear rate range because of the small size of the coil. Magnetic resonance‐based measurements from 2 to 15 s^‐1 were obtained and were equivalent to off‐line rotational rheometry.     

Qualitative Methods Used in the Assessment of Engineering Education

This article clarifies key concepts that undergird qualitative research, which is being used increasingly as engineering educators improve classrooms, programs, and institutions. The paper compares quantitative and qualitative research, describes some qualitative data collection strategies used in engineering education, addresses methods for establishing trustworthiness, and discusses strategies for analyzing qualitative data. Also included are illustrative examples of recent engineering education research that features qualitative data analysis and mixed‐method (quantitative and qualitative) approaches.     

TORSION ANALYSIS OF FRESH AND AGED CHEESES1

Six cheese varieties encompassing a wide compositional and age range were analyzed fresh and after aging to determine correlations between casein proteolysis products, fat content, moisture content, and torsion results. Shear stress, a measure of the strength of the casein matrix, was dependent on the amount of intact α_sl‐casein. Shear strain, a measure of the cohesiveness of a structure, exhibited a negative correlation with fat content and a positive correlation with moisture content. Shear strain was also correlated with the ratio of moisture to protein, an indication of the interaction between casein particles. Torsion tests provide information on the level of degradation of the casein network in cheese, which can be used by manufacturers to alter storage conditions to optimize the quality of their aged cheese., April 10, 2003